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Sample records for constrain gabbroic crustal

  1. Seismically constrained two-dimentional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    Cambay basin; P-wave velocity; heat flow; heat generation; 2-D modelling; crustal thermal structure; Mohodepth; Curie isotherm. ... This work deals with the two-dimensional thermal modelling to delineate the crustal thermal structure along a 230 km long Deep Seismic Sounding (DSS) profile in the north Cambay basin.

  2. Crustal evolution at mantle depths constrained from Pamir xenoliths

    Science.gov (United States)

    Kooijman, E.; Hacker, B. R.; Smit, M. A.; Kylander-Clark, A. R.; Ratschbacher, L.

    2012-12-01

    Lower crustal xenoliths erupted in the Pamir at ~11 Ma provide an exclusive opportunity to study the evolution of crust at mantle depths during a continent-continent collision. To investigate, and constrain the timing of, the petrologic processes that occurred during burial to the peak conditions (2.5-2.8 GPa, 1000-1100 °C; [1]), we performed chemical- and isotope analyses of accessory minerals in 10 xenoliths, ranging from eclogites to grt-ky-qtz granulites. In situ laser ablation split-stream ICPMS yielded 1) U-Pb ages, Ti concentrations and REE in zircon, 2) U/Th-Pb ages and REE in monazite, and 3) U-Pb ages and trace elements in rutile. In addition, garnet, and biotite and K-feldspar were dated using Lu-Hf and 40Ar/39Ar geochronology, respectively. Zircon and monazite U-(Th-)Pb ages are 101.9±1.8, 53.7±1.0, 39.1±0.8, 21.7±0.4, 18.2±0.5, 16.9±0.8, 15.1±0.3 (2σ) and 12.5-11.1 Ma; most samples showed several or all of these populations. The 53.7 Ma and older ages are xenocrystic or detrital. For younger ages, zircon and monazite in individual samples recorded different ages-although zircon in one rock and monazite in another can be the same age. The 39.1 Ma zircon and monazite mostly occur as inclusions in minerals of the garnet-bearing assemblage that represents the early, low-P stages of burial. Garnet Lu-Hf ages of 37.8±0.3 Ma support garnet growth at this time. Spinifex-like textures containing 21.7-11.1 Ma zircon and monazite record short-lived partial melting events during burial. Aligned kyanite near these patches indicates associated deformation. Zircons yielding ≤12.5 Ma exhibit increased Eu/Eu* and markedly decreased HREE concentrations, interpreted to record feldspar breakdown and omphacite growth during increasing pressure. Rutile U-Pb cooling ages are 10.8±0.3 Ma in all samples. This agrees with the weighted mean 40Ar/39Ar age of eight biotite, K-feldspar and whole rock separates of 11.00+0.16/-0.09 Ma. Rutile in eclogites provides Zr

  3. Seismically constrained two-dimensional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to ...

  4. Seasonal Mass Changes and Crustal Vertical Deformations Constrained by GPS and GRACE in Northeastern Tibet

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    Yuanjin Pan

    2016-08-01

    Full Text Available Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs, in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet.

  5. Contemporary Crustal Deformation Within the Pamir Plateau Constrained by Geodetic Observations and Focal Mechanism Solutions

    Science.gov (United States)

    Pan, Zhengyang; He, Jiankun; Li, Jun

    2018-04-01

    We used an updated data set of 192 GPS-derived surface velocities and 393 earthquake focal mechanisms (Mw > 3.0, hypocenter depths https://doi.org/10.1029/2005jb004144, 2006). The results show that the crustal stress field around the Pamir Plateau is predominantly characterized by NNW-SSE compression and E-W extension, which is consistent with the principal orientations of the two-dimensional surface strain rate tensor. This agreement supports the notion that the Pamir and southwestern Tien Shan are uniformly strained blocks. In particular, the fan-shaped rotational pattern between {Shmax} and the strain rate from the western Pamir to the Tajik Basin shows that the counterclockwise rotation of the {Shmax} orientation is associated with vertical deformation, which is consistent with the idea of Schurr et al. (Tectonics 33(8):2014TC003576, 2014) concerning the gravitational collapse and westward extrusion of the crust in the western Pamir. We propose that such a stress-strain pattern, dominated by NNW-ESE oriented compression and E-W trending extension, originated from a combination of the northward push of the Indian continent and the southward subduction of the Tien Shan.

  6. Postseismic deformation associated with the 2015 Mw 7.8 Gorkha earthquake, Nepal: Investigating ongoing afterslip and constraining crustal rheology

    Science.gov (United States)

    Jiang, Zhongshan; Yuan, Linguo; Huang, Dingfa; Yang, Zhongrong; Hassan, Abubakr

    2018-05-01

    The 2015 Mw 7.8 Gorkha earthquake has not only imposed effective constraints on the geometrical structures, friction behaviours and seismogenic patterns of the Nepal Himalaya thrust systems but has also provided valuable insights into the uplift mechanism and lithosphere rheology of the Tibetan Plateau. Here, ∼1.6-year GPS observations are used to reveal the postseismic deformation characteristics following the Gorkha earthquake, investigate the ongoing aseismic afterslip on the Main Himalayan Thrust (MHT) fault and constrain the crustal rheology of the Southern Tibetan Plateau. First, afterslip is considered to be solely responsible for the postseismic deformation (afterslip-only model). The results show that afterslip is anticorrelated with peak coseismic slip areas. One high-afterslip-concentration area, with a peak of ∼24 cm, is distributed downdip of the coseismic rupture, as well as in two other regions: one partially overlapping the mainshock rupture, and the other next to the Mw 7.3 aftershock area. Second, the GPS postseismic observations are inverted to jointly investigate afterslip and viscoelastic deformation (multiple-mechanism model). The afterslip inversion results of the above two models are highly consistent, indicating the dominant contribution of afterslip to surface deformation during the ∼1.6-year postseismic period. Considering the interseismic fault coupling and historical seismicity, no appreciable fault slip associated with the Gorkha earthquake is found to occur both updip and west of the mainshock rupture areas. This reveals that the Gorkha earthquake only unzipped the lower edge of the locked portion of the MHT, leaving the shallow portion and western segment of the seismogenic zone still locked and the Nepal region under high seismic risk. The viscoelastic mechanism contributes minorly to surface deformation during the ∼1.6-year postseismic period. The middle-lower crust is assumed to comprise Maxwell material beneath an elastic

  7. The physical behaviour of gabbroic crystal mush

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    Humphreys, M.; Namur, O.; Holness, M. B.

    2012-12-01

    Crystal mushes form at the boundary layers of all magma bodies, from lava flows to volcanic conduits to batholiths. The physical behaviour of a crystal mush is important in controlling a number of physical processes, from the origin of crystal-poor rhyolites, and the migration and ascent of granitic magmas, to compaction and differentiation processes in large mafic bodies. As well as strain-rate, the grain-scale microstructure of the mush is an important factor in controlling its physical behaviour, with porosity (amount of residual liquid) being particularly important. One might therefore expect to see a range of different behaviours during the crystallisation of a magma body, depending on the porosity and strain rate at any given point in the crystallisation history. We describe evidence for three different mechanical regimes affecting a gabbroic crystal mush at different scales and residual liquid contents. We focus on the Marginal Border Series of the Skaergaard Intrusion, east Greenland, which crystallised on the steeply dipping sidewalls of the intrusion. It has the advantage that, unlike in most mushes that developed on the chamber floor, thermal gradients and the effects of gravity act in orthogonal directions, allowing shear-related features to be identified and distinguished from thermal effects. The largest-scale effects are evident at the contact between the Marginal Border Series (MBS) and the Layered Series, which crystallised on the floor of the intrusion. The contact is characterised by slumping and faulting of semi-consolidated crystal mush, resulting in slippage and rotation of large packets of relatively coherent igneous 'sediment' down-slope. This process may be analogous to the formation of slumps or rotational landslides in sedimentary systems. At a smaller scale, gravitational instability of the sidewalls caused localised sagging of the crystal mush and resulted in small ductile cracks or tears that filled with interstitial liquid. Finally

  8. Diapir versus along-channel ascent of crustal material during plate convergence: constrained by the thermal structure of subduction zones

    Science.gov (United States)

    Liu, M. Q.; Li, Z. H.

    2017-12-01

    Crustal rocks can be subducted to mantle depths, interact with the mantle wedge, and then exhume to the crustal depth again, which is generally considered as the mechanism for the formation of ultrahigh-pressure metamorphic rocks in nature. The crustal rocks undergo dehydration and melting at subarc depths, giving rise to fluids that metasomatize and weaken the overlying mantle wedge. There are generally two ways for the material ascent from subarc depths: one is along subduction channel; the other is through the mantle wedge by diapir. In order to study the conditions and dynamics of these contrasting material ascent modes, systematic petrological-thermo-mechanical numerical models are constructed with variable thicknesses of the overriding and subducting continental plates, ages of the subducting oceanic plate, as well as the plate convergence rates. The model results suggest that the thermal structures of subduction zones control the thermal condition and fluid/melt activity at the slab-mantle interface in subcontinental subduction channels, which further strongly affect the material transportation and ascent mode. Thick overriding continental plate and low-angle subduction style induced by young subducting oceanic plate both contribute to the formation of relatively cold subduction channels with strong overriding mantle wedge, where the along-channel exhumation occurs exclusively to result in the exhumation of HP-UHP metamorphic rocks. In contrast, thin overriding lithosphere and steep subduction style induced by old subducting oceanic plate are the favorable conditions for hot subduction channels, which lead to significant hydration and metasomatism, melting and weakening of the overriding mantle wedge and thus cause the ascent of mantle wedge-derived melts by diapir through the mantle wedge. This may corresponds to the origination of continental arc volcanism from mafic to ultramafic metasomatites in the bottom of the mantle wedge. In addition, the plate

  9. Using crustal thickness and subsidence history on the Iberia-Newfoundland margins to constrain lithosphere deformation modes during continental breakup

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    Jeanniot, Ludovic; Kusznir, Nick; Manatschal, Gianreto; Mohn, Geoffroy

    2014-05-01

    Observations at magma-poor rifted margins such as Iberia-Newfoundland show a complex lithosphere deformation history during continental breakup and seafloor spreading initiation leading to complex OCT architecture with hyper-extended continental crust and lithosphere, exhumed mantle and scattered embryonic oceanic crust and continental slivers. Initiation of seafloor spreading requires both the rupture of the continental crust and lithospheric mantle, and the onset of decompressional melting. Their relative timing controls when mantle exhumation may occur; the presence or absence of exhumed mantle provides useful information on the timing of these events and constraints on lithosphere deformation modes. A single lithosphere deformation mode leading to continental breakup and sea-floor spreading cannot explain observations. We have determined the sequence of lithosphere deformation events for two profiles across the present-day conjugate Iberia-Newfoundland margins, using forward modelling of continental breakup and seafloor spreading initiation calibrated against observations of crustal basement thickness and subsidence. Flow fields, representing a sequence of lithosphere deformation modes, are generated by a 2D finite element viscous flow model (FeMargin), and used to advect lithosphere and asthenosphere temperature and material. FeMargin is kinematically driven by divergent deformation in the upper 15-20 km of the lithosphere inducing passive upwelling beneath that layer; extensional faulting and magmatic intrusions deform the topmost upper lithosphere, consistent with observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996). Buoyancy enhanced upwelling, as predicted by Braun et al. (2000) is also kinematically included in the lithosphere deformation model. Melt generation by decompressional melting is predicted using the parameterization and methodology of Katz et al. (2003). The distribution of lithosphere deformation, the

  10. Lithospheric strength in the active boundary between the Pacific Plate and Baja California microplate constrained from lower crustal and upper mantle xenoliths

    Science.gov (United States)

    Chatzaras, Vasileios; van der Werf, Thomas; Kriegsman, Leo M.; Kronenberg, Andreas; Tikoff, Basil; Drury, Martyn R.

    2017-04-01

    The lower crust is the most poorly understood of the lithospheric layers in terms of its rheology, particularly at active plate boundaries. We studied naturally deformed lower crustal xenoliths within an active plate boundary, in order to link their microstructures and rheological parameters to the well-defined active tectonic context. The Baja California shear zone (BCSZ), located at the western boundary of the Baja California microplate, comprises the active boundary accommodating the relative motion between the Pacific plate and Baja California microplate. The basalts of the Holocene San Quintin volcanic field carry lower crustal and upper mantle xenoliths, which sample the Baja California microplate lithosphere in the vicinity of the BCSZ. The lower crustal xenoliths range from undeformed gabbros to granoblastic two-pyroxene granulites. Two-pyroxene geothermometry shows that the granulites equilibrated at temperatures of 690-920 oC. Phase equilibria (P-T pseudosections using Perple_X) indicate that symplectites with intergrown pyroxenes, plagioclase, olivine and spinel formed at 3.6-5.4 kbar, following decompression from pressures exceeding 6 kbar. FTIR spectroscopy shows that the water content of plagioclase varies among the analyzed xenoliths; plagioclase is relatively dry in two xenoliths while one xenolith contains hydrated plagioclase grains. Microstructural observations and analysis of the crystallographic texture provide evidence for deformation of plagioclase by a combination of dislocation creep and grain boundary sliding. To constrain the strength of the lower crust and upper mantle near the BCSZ we estimated the differential stress using plagioclase and olivine grain size paleopiezomtery, respectively. Differential stress estimates for plagioclase range from 10 to 32 MPa and for olivine are 30 MPa. Thus the active microplate boundary records elevated crustal temperatures, heterogeneous levels of hydration, and low strength in both the lower crust and

  11. Magmatism and crustal extension: Constraining activation of the ductile shearing along the Gediz detachment, Menderes Massif (western Turkey)

    Science.gov (United States)

    Rossetti, Federico; Asti, Riccardo; Faccenna, Claudio; Gerdes, Axel; Lucci, Federico; Theye, Thomas

    2017-06-01

    The Menderes Massif of western Turkey is a key area to study feedback relationships between magma generation/emplacement and activation of extensional detachment tectonics. Here, we present new textural analysis and in situ U-(Th)-Pb titanite dating from selected samples collected in the transition from the undeformed to the mylonitized zones of the Salihli granodiorite at the footwall of the Neogene, ductile-to-brittle, top-to-the-NNE Gediz-Alaşheir (GDF) detachment fault. Ductile shearing was accompanied by the fluid-mediated sub-solidus transformation of the granodiorite to orthogneiss, which occurred at shallower crustal levels and temperatures compatible with the upper greenschist-to-amphibolite facies metamorphic conditions (530-580 °C and P system ages during fluid-assisted syn-tectonic re-crystallisation in the transition from magma crystallization and emplacement (at 16-17 Ma) to the syn-tectonic, solid-state shearing (at 14-15 Ma). A minimum time lapse of ca. 1-2 Ma is then inferred between the crustal emplacement of the Salihli granodiorite and nucleation of the ductile extensional shearing along the Gediz detachment. The reconstruction of the cooling history of the Salihli granodiorite documents a punctuated evolution dominated by two episodes of rapid cooling, between 14 Ma and 12 Ma ( 100 °C/Ma) and between 3 and 2 Ma ( 105 °C/Ma). We relate the first episode to nucleation and development of post-emplacement of ductile shearing along the GDF and the second to brittle high-angle faulting, respectively. Our dataset suggests that in the Menderes Massif the activation of ductile extension was a consequence, rather than the cause, of magma emplacement in the extending crust.

  12. Experimental and geochemical evidence for derivation of the El Capitan Granite, California, by partial melting of hydrous gabbroic lower crust

    Science.gov (United States)

    Ratajeski, K.; Sisson, T.W.; Glazner, A.F.

    2005-01-01

    Partial melting of mafic intrusions recently emplaced into the lower crust can produce voluminous silicic magmas with isotopic ratios similar to their mafic sources. Low-temperature (825 and 850??C) partial melts synthesized at 700 MPa in biotite-hornblende gabbros from the central Sierra Nevada batholith (Sisson et al. in Contrib Mineral Petrol 148:635-661, 2005) have major-element and modeled trace-element (REE, Rb, Ba, Sr, Th, U) compositions matching those of the Cretaceous El Capitan Granite, a prominent granite and silicic granodiorite pluton in the central part of the Sierra Nevada batholith (Yosemite, CA, USA) locally mingled with coeval, isotopically similar quartz diorite through gabbro intrusions (Ratajeski et al. in Geol Soc Am Bull 113:1486-1502, 2001). These results are evidence that the El Capitan Granite, and perhaps similar intrusions in the Sierra Nevada batholith with lithospheric-mantle-like isotopic values, were extracted from LILE-enriched, hydrous (hornblende-bearing) gabbroic rocks in the Sierran lower crust. Granitic partial melts derived by this process may also be silicic end members for mixing events leading to large-volume intermediate composition Sierran plutons such as the Cretaceous Lamarck Granodiorite. Voluminous gabbroic residues of partial melting may be lost to the mantle by their conversion to garnet-pyroxene assemblages during batholithic magmatic crustal thickening. ?? Springer-Verlag 2005.

  13. Using crustal thickness, subsidence and P-T-t history on the Iberia-Newfoundland & Alpine Tethys margins to constrain lithosphere deformation modes during continental breakup

    Science.gov (United States)

    Jeanniot, L.; Kusznir, N. J.; Manatschal, G.; Mohn, G.; Beltrando, M.

    2013-12-01

    Observations at magma-poor rifted margins such as Iberia-Newfoundland show a complex lithosphere deformation history and OCT architecture, resulting in hyper-extended continental crust and lithosphere, exhumed mantle and scattered embryonic oceanic crust before continental breakup and seafloor spreading. Initiation of seafloor spreading requires both the rupture of the continental crust and lithospheric mantle, and the onset of decompressional melting. Their relative timing controls when mantle exhumation may occur; the presence or absence of exhumed mantle provides useful information on the timing of these events and constraints on lithosphere deformation modes. A single kinematic lithosphere deformation mode leading to continental breakup and sea-floor spreading cannot explain observations. We have determined the sequence of lithosphere deformation events, using forward modelling of crustal thickness, subsidence and P-T-t history calibrated against observations on the present-day Iberia-Newfoundland and the fossil analogue Alpine Tethys margins. Lithosphere deformation modes, represented by flow fields, are generated by a 2D finite element viscous flow model (FeMargin), and used to advect lithosphere and asthenosphere temperature and material. FeMargin is kinematically driven by divergent deformation in the topmost upper lithosphere inducing passive upwelling beneath that layer; the upper lithosphere is assumed to deform by extensional faulting and magmatic intrusions, consistent with observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996). Buoyancy enhanced upwelling is also included in the kinematic model as predicted by Braun et al (2000). We predict melt generation by decompressional melting using the parameterization and methodology of Katz et al., 2003. We use a series of numerical experiments, tested and calibrated against crustal thicknesses and subsidence observations, to determine the distribution of lithosphere

  14. Coupling Thermal and Chemical Signatures of Crustal Magma Bodies: Energy-Constrained Eruption, Recharge, Assimilation, and Fractional Crystallization (E'RAχFC)

    Science.gov (United States)

    Bohrson, W. A.; Spera, F. J.

    2004-12-01

    Energy-Constrained Eruption, Recharge, Assimilation and Fractional Crystallization (E'RAχFC) tracks the evolution of an open-system magmatic system by coupling conservation equations governing energy, mass and species (isotopes and trace elements). By linking the compositional characteristics of a composite magmatic system (host magma, recharge magma, wallrock, eruptive reservoir) to its mass and energy fluxes, predictions can be made about the chemical evolution of systems characterized by distinct compositional and thermal characteristics. An interesting application of E'RAχFC involves documenting the influence distinct thermal regimes have on the chemical evolution of magmatic systems. Heat transfer between a magma-country rock system at epizonal depths can be viewed as a conjugate heat transfer problem in which the average country rock-magma boundary temperature, Tb, is governed by the relative vigor of hydrothermal convection in the country rock vs. magma convection. For cases where hydrothermal circulation is vigorous and magmatic heat is efficiently transported away from the boundary, contact aureole temperatures (~Tb) are low. In cases where magmatic heat can not be efficiently transported away from the boundary and hydrothermal cells are absent or poorly developed, Tb is relatively high. Simultaneous solution of the differential equations governing momentum and energy conservation and continuity for the coupled hydrothermal-magmatic conjugate heat transfer system enables calculation of the characteristic timescale for EC-RAFC evolution and development of hydrothermal deposits as a function of material and medium properties, sizes of systems and relative efficiency of hydrothermal vs. magmatic heat transfer. Characteristic timescales lie in the range 102-106 yr depending on system size, magma properties and permeability among other parameters. In E'RAχFC, Tb is approximated by the user-defined equilibration temperature, Teq, which is the temperature at

  15. Compositional stratigraphy of crustal material from near-infrared spectra

    International Nuclear Information System (INIS)

    Pieters, C.M.

    1987-01-01

    An Earth-based telescopic program to acquire near-infrared spectra of freshly exposed lunar material now contains data for 17 large impact craters with central peaks. Noritic, gabbroic, anorthositic and troctolitic rock types can be distinguished for areas within these large craters from characteristic absorptions in individual spectra of their walls and central peaks. Norites dominate the upper lunar crust while the deeper crustal zones also contain significant amounts of gabbros and anorthosites. Data for material associated with large craters indicate that not only is the lunar crust highly heterogeneous across the nearside, but that the compositional stratigraphy of the lunar crust is nonuniform. Crustal complexity should be expected for other planetary bodies, which should be studied using high spatial and spectral resolution data in and around large impact craters

  16. Compositional stratigraphy of crustal material from near-infrared spectra

    Science.gov (United States)

    Pieters, Carle M.

    1987-01-01

    An Earth-based telescopic program to acquire near-infrared spectra of freshly exposed lunar material now contains data for 17 large impact craters with central peaks. Noritic, gabbroic, anorthositic and troctolitic rock types can be distinguished for areas within these large craters from characteristic absorptions in individual spectra of their walls and central peaks. Norites dominate the upper lunar crust while the deeper crustal zones also contain significant amounts of gabbros and anorthosites. Data for material associated with large craters indicate that not only is the lunar crust highly heterogeneous across the nearside, but that the compositional stratigraphy of the lunar crust is nonuniform. Crustal complexity should be expected for other planetary bodies, which should be studied using high spatial and spectral resolution data in and around large impact craters.

  17. Crustal permeability

    Science.gov (United States)

    Gleeson, Tom; Ingebritsen, Steven E.

    2016-01-01

    Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures.  The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration.  Although there are thousands of research papers on crustal permeability, this is the first book-length treatment.  This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. 

  18. Metasedimentary, granitoid, and gabbroic rocks from central Stewart Island, New Zealand

    International Nuclear Information System (INIS)

    Allibone, A.H.; Tulloch, A.J.

    1997-01-01

    A NNE-NE trending strip, 3-8 km wide, extending from the Freshwater valley across Mt Rakeahua Table Hill, and Mt Allen to the northern end or the Tin Range was mapped at a scale of 1:12,500 to locate and investigate the boundary between the Median Tectonic Zone (MTZ) and Western Province on Stewart Island. A NNE-trending fault, herein termed the Escarpment Fault, separates predominantly ductily deformed rocks on its south side from essentially undeformed rocks to the north. North of the Escarpment Fault, a small (2-3 km 2 ) pluton of alkali-feldspar granite (Freds Camp) intruded gabbroic rocks tentatively considered to be associated with gabbro/anorthosite/diorite of the Rakeahua pluton, centred on Mt Rakeahua. Both units were subsequently intruded by I-type biotite granite of the South West Arm pluton. South of the Escarpment Fault the oldest intrusions are biotite tonalite-granite orthogneisses (Ridge and Table Hill plutons) intercalated with the sillimanite-cordierite-bearing Pegasus Group metasedimentary rocks, considered to represent the Western Province. They contain titanite, allanite, and magmatic epidote-bearing assemblages, implying affinities with I-type granitoids. These older granitoids have been affected by at least three phases of ductile deformation. Immediately south of the Escarpment Fault, the Escarpment pluton (hornblende, biotite, quartz, monzonite-quartz monzodiorite) only exhibit effects of the third phase of deformation. Minor gabbroic intrusives concordant with the S 3 fabric intrude the Pegasus Group and intercalated orthogneisses. Plutons of two-mica, garnet ±cordierite granite (Blaikies and Knob) and younger biotite-titanite-magmatic epidote granite (Campsite) cut fabrics associated with the third phase of ductile deformation. Preliminary U-Pb dating indicate Devonian-Carboniferous, Jurassic, and Early Cretaceous emplacement ages for Ridge Orthogneiss, Freds Camp pluton, South West Arm pluton, and Blaikies pluton, respectively. South

  19. Recent crustal movements

    Science.gov (United States)

    Maelzer, H.

    Calculation of temporal height changes for the determination of recent vertical crustal movements in northern, western, and southern Germany is described. Precise geodetic measurements and their analysis for the determination of recent crustal movements in north-eastern Iceland, western Venezuela, and central Peru are described. Determination of recent vertical crustal movements by leveling and gravity data; geodetic modeling of deformations and recent crustal movements; geodetic modeling of plate motions; and instrumental developments in geodetic measuring are discussed.

  20. Crustal Seismic Anisotropy: Implications for Understanding Crustal Dynamics

    Science.gov (United States)

    Meltzer, A.; Christensen, N.; Okaya, D.

    2003-12-01

    variation in % anisotropy, changes in orientation of the regional foliation within the massif, and velocity (splitting) variance due to non-axial propagation through a wide range of event-station azimuths. Because the composition of the massif is basically homogeneous, the rock fabric is well developed, and the structure well constrained, this data set is ideal for studying and quantifying the affect of non-axial propagation through regional foliation. This type of analysis has important implications for understanding crustal dynamics. Vp, Vs, and Vp/Vs ratios are typically used to infer both lithology and rheology of subsurface materials and to provide constraints for thermo-mechanical models of deformation. Current tomography codes do not generally account for anisotropic effects and may potentially under or over estimate velocity structure in the crust. At Nanga Parbat, a prominent low-velocity zone is mapped beneath the core of the massif. The magnitude and extent of this zone constrains crustal flow paths focusing crustal strain, exhumation, and potential zones of partial melting in the crust. Accurate determination of velocity structure is clearly important to understand crustal structure and modification during orogenesis.

  1. Geochemistry and mineral chemistry of Shahabad gabbroic intrusion, NW Nourabad, Lorestan province

    Directory of Open Access Journals (Sweden)

    Reza Zarei Sahamieh

    2013-10-01

    Full Text Available The Shahabad gabbroic intrusion, with NW-SE trend cropped out at the boundary of Zagros and Sanandaj-Sirjan zones is composed of olivine gabbro, orthogabbro and troctolite. Plagioclase, clinopyroxene and olivine are the main minerals; and magnetite, titanomagnetite and serpentine are minor and secondary minerals. Microprobe analyses of the minerals show that plagioclase is labradorite, pyroxene diopsidic augite and olivine, chrysolite. The rocks appear to have calc-alkaline and metaluminous nature. The plots of some trace elements and composition of clinopyroxenes in the tectonic discrimination diagrams indicate a volcanic arc environment. In addition, spider diagram pattern of elements shows Sr enrichment and Ti, Nb, Zr and P depletion, typical characteristics of volcanic arc subduction related magmas. Furthermore, close similarity between the patterns of spider diagram for the Shahabad pluton with those of Andean basic rocks suggests that the Shahabad calc-alkaline basic magma may have formed in a subduction environment. Based on geological, geochemical and mineralogical features, formation of the gabbros, as a part of ophiolite mélange, is attributed to a suprasubduction system.

  2. Gabbroic lithologies of the dike-gabbro transition, Hole GT3A, Oman Drilling Project

    Science.gov (United States)

    Jesus, A. P. M.; Koepke, J.; Morishita, T.; Beinlich, A.; Johnson, K. T. M.; Greenberger, R. N.; Harris, M.; Michibayashi, K.; de Obeso, J. C.

    2017-12-01

    Hole GT3A intersects 400 m of oceanic crust providing unique insight into the dike-gabbro transition and the variability of the high level gabbros in the Samail ophiolite. Olivine gabbro and olivine bearing gabbro occur exclusively within the Upper Gabbro Sequence (16 % thickness; 111.02 m - 127.89 m) whereas oxide gabbro and disseminated oxide gabbro represent ca 5 % of the Lower Gabbro Sequence (233.84 m - 398.21 m). Gabbro with less than 1 vol. % olivine and oxide is the most common lithology in both Gabbro Sequences (10-13 %). Most gabbroic rocks were classified as "varitextured" due to textural and grain size macroscopic variations forming irregular domains/patches. Varitextured gabbros are medium-grained (1-5 mm), with seriate grain size distribution and subophitic/poikilitic to granular textural domains. Poikilitic domains comprise clinopyroxene with plagioclase chadacrysts, whereas in granular domains plagioclase interstices are filled by green-brown magmatic hornblende; plagioclase is zoned in both domains. Olivine (bearing) gabbros have 4-8 mm skeletal olivine pseudomorphs with roundish inclusions of chromite and plagioclase. Oxide (disseminated) gabbros comprise variable amounts of plagioclase, clinopyroxene, Oman paleo ridge.

  3. Constraints on the origin of gabbroic rocks from the Moldanubian-Moravian units boundary (Bohemian Massif, Czech Republic and Austria)

    Czech Academy of Sciences Publication Activity Database

    Ulrych, Jaromír; Ackerman, Lukáš; Kachlík, V.; Hegner, E.; Balogh, K.; Langrová, Anna; Luna, J.; Fediuk, F.; Lang, M.; Filip, Jiří

    2010-01-01

    Roč. 61, č. 3 (2010), s. 175-191 ISSN 1335-0552 R&D Projects: GA AV ČR IAA3013403; GA AV ČR IAA300130902 Institutional research plan: CEZ:AV0Z30130516 Keywords : gabbroic rocks * geochemistry * Sr-Nd isotopes * K-Ar ages * Moravian Unit * Moldanubian Unit * Bohemian Massif Subject RIV: DD - Geochemistry Impact factor: 0.909, year: 2010

  4. Constraints on the formation of the Martian crustal dichotomy from remnant crustal magnetism

    Science.gov (United States)

    Citron, Robert I.; Zhong, Shijie

    2012-12-01

    The Martian crustal dichotomy characterizing the topographic difference between the northern and southern hemispheres is one of the most important features on Mars. However, the formation mechanism for the dichotomy remains controversial with two competing proposals: exogenic (e.g., a giant impact) and endogenic (e.g., degree-1 mantle convection) mechanisms. Another important observation is the Martian crustal remnant magnetism, which shows a much stronger field in the southern hemisphere than in the northern hemisphere and also magnetic lineations. In this study, we examine how exogenic and endogenic mechanisms for the crustal dichotomy are constrained by the crustal remnant magnetism. Assuming that the dichotomy is caused by a giant impact in the northern hemisphere, we estimate that the average thickness of ejecta in the southern hemisphere is 20-25 km. While such a giant impact may cause crustal demagnetization in the northern hemisphere, we suggest that the impact could also demagnetize the southern hemisphere via ejecta thermal blanketing, impact demagnetization, and heat transfer from the hot layer of ejecta, thus posing a challenge for the giant impact model. We explore how the pattern of magnetic lineations relates to endogenic theories of dichotomy formation, specifically crustal production via degree-1 mantle convection. We observe that the pattern of lineations roughly corresponds to concentric circles about a single pole, and determine the pole for the concentric circles at 76.5° E and 84.5° S, which nearly overlaps with the centroid of the thickened crust in the southern hemisphere. We suggest that the crustal magnetization pattern, magnetic lineations, and crustal dichotomy (i.e., thickened crust in the highlands) can be explained by a simple endogenic process; one-plume convection causes melting and crustal production above the plume in the southern hemisphere, and strong crustal magnetization and magnetic lineations are formed in the southern

  5. Nd isotopes and crustal growth rate

    International Nuclear Information System (INIS)

    Albarede, F.

    1988-01-01

    Sm/Nd isotopic constraints on crustal growth is discussed. In order to constrain Sm/Nd fractionation between continental crust and depleted mantle, an extensive data base of isotopic measurements (assumed to be adequately representative of continental crust) was compiled. The results imply that the evolution of depleted mantles was roughly linear, with no major discontinuities over the course of geologic time. This is different from other determinations of depleting mantle evolution, which show nonlinear behavior. The Sm/Nd evolution lines for continental crust and depleted mantle intersect between 3.8 to 4.0 Ga, which may indicate that the onset of continental growth was later than 4.5 Ga. A mathematical model is described, the results of which imply that time integrated crustal additions from the mantle are about 1.8 to 2.5 cu km/a, whereas crustal subtractions by sediment recycling are about 0.6 to 1.5 cu km/a. This results in a net time integrated crustal growth rate of about 1 cu km/a, which is similar to present day rates determined, for example, by Reymer and Schubert

  6. Crustal structure and tectonic model of the Arctic region

    DEFF Research Database (Denmark)

    Petrov, Oleg; Morozov, Andrey; Shokalsky, Sergey

    2016-01-01

    We present a new model of the crustal and tectonic structure of the Arctic region north of 60° N latitude, constrained as a part of the international Atlas of Geological Maps of the Circumpolar Arctic under the aegis of the Commission for the Geological Map of the World. The region is largely...... formed by (i) Archean-Paleoproterozoic shields and platforms, (ii) orogenic belts of the Neoproterozoic to the Late Mesozoic ages overlain by platform and basin sediments, (iii) Cenozoic rift structures formed in part as a consequence of seafloor spreading in the North East Atlantic Ocean...... and thickness of the sedimentary cover and presents tectonic regionalization based on 18 major crustal types (oceanic, transitional, and continental) recognized in the Arctic. A 7600. km-long crustal geotransect across the region illustrates the details of its crustal and tectonic structure. We discuss...

  7. Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

    Science.gov (United States)

    Arakawa, Yoji; Endo, Daisuke; Ikehata, Kei; Oshika, Junya; Shinmura, Taro; Mori, Yasushi

    2017-03-01

    We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths) in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899-955°C) and pressures (3.6-5.9 kbar) than the B-type gabbro (687-824°C and 0.8-3.6 kbar). These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic) magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.

  8. Two types of gabbroic xenoliths from rhyolite dominated Niijima volcano, northern part of Izu-Bonin arc: petrological and geochemical constraints

    Directory of Open Access Journals (Sweden)

    Arakawa Yoji

    2017-03-01

    Full Text Available We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899–955°C and pressures (3.6–5.9 kbar than the B-type gabbro (687–824°C and 0.8–3.6 kbar. These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.

  9. Global variations in gravity-derived oceanic crustal thickness: Implications on oceanic crustal accretion and hotspot-lithosphere interactions

    Science.gov (United States)

    Lin, J.; Zhu, J.

    2012-12-01

    We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness 8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic emplacements on the plate. (2) In contrast, crustal thickness near fast and intermediately fast spreading ridges typically does not exceed 7-8 km. The relatively weak lithosphere at fast and intermediately fast ridges might make it harder for excess magmatism to accrete. We further speculate that

  10. Geochemistry and tectonomagmatic setting of the Kharaju gabbroic intrusions (South Azarshahr, East Azerbaijan province

    Directory of Open Access Journals (Sweden)

    Abdolnaser Fazlnia

    2016-12-01

    Full Text Available Kharaju mafic intrusions (south Azarshahr; East Azarbaijan are gabbro in composition. The rocks with Eocene age intruded the northwest part of Urumieh -Dokhtar magmatic belt with a trend of NW-SE. These rocks contain mostly of minerals such as plagioclase, quartz, pyroxene, titanite, apatite and magnetite. The rocks are moderate to high calc-alkaline. The gabbros were produced as a result of the partial melting of mantle wedge with spinel lherzolite and after emplacement into the crustal magma chamber underwent fractional crystallization. Injection of the Kharaju intrusions is in relation to the last stages of Neotethys subduction activity under Central Iran. Negative anomaly in the high ionic strength elements (HFSE like, Nb, Ta, P, Hf and Zr and mild positive anomalies of Eu and Sr with moderate increases in values of K, Sr, Rb, Ba, Pb and U show oblique subduction beneath Central Iran might be willing to make the appropriate space on the edge of central Iran and as a result, partial melting in the mantle wedge occurred due to reduce the pressure as decompression.

  11. Simulations of tremor-related creep reveal a weak crustal root of the San Andreas Fault

    Science.gov (United States)

    Shelly, David R.; Bradley, Andrew M.; Johnson, Kaj M.

    2013-01-01

    Deep aseismic roots of faults play a critical role in transferring tectonic loads to shallower, brittle crustal faults that rupture in large earthquakes. Yet, until the recent discovery of deep tremor and creep, direct inference of the physical properties of lower-crustal fault roots has remained elusive. Observations of tremor near Parkfield, CA provide the first evidence for present-day localized slip on the deep extension of the San Andreas Fault and triggered transient creep events. We develop numerical simulations of fault slip to show that the spatiotemporal evolution of triggered tremor near Parkfield is consistent with triggered fault creep governed by laboratory-derived friction laws between depths of 20–35 km on the fault. Simulated creep and observed tremor northwest of Parkfield nearly ceased for 20–30 days in response to small coseismic stress changes of order 104 Pa from the 2003 M6.5 San Simeon Earthquake. Simulated afterslip and observed tremor following the 2004 M6.0 Parkfield earthquake show a coseismically induced pulse of rapid creep and tremor lasting for 1 day followed by a longer 30 day period of sustained accelerated rates due to propagation of shallow afterslip into the lower crust. These creep responses require very low effective normal stress of ~1 MPa on the deep San Andreas Fault and near-neutral-stability frictional properties expected for gabbroic lower-crustal rock.

  12. Seismically constrained two-dimensional crustal thermal structure of ...

    Indian Academy of Sciences (India)

    oil bearing sedimentary basins of India is situated at ... related to the evolution of the western margin of India ... of approximately 46 mW/m2 for stable continental areas. This makes the region interesting from ... for hydrocarbon accumulation.

  13. Crustal Structure beneath Alaska from Receiver Functions

    Science.gov (United States)

    Zhang, Y.; Li, A.

    2017-12-01

    The crustal structure in Alaska has not been well resolved due to the remote nature of much of the state. The USArray Transportable Array (TA), which is operating in Alaska and northwestern Canada, significantly increases the coverage of broadband seismic stations in the region and allows for a more comprehensive study of the crust. We have analyzed P-receiver functions from earthquake data recorded by 76 stations of the TA and AK networks. Both common conversion point (CCP) and H-K methods are used to estimate the mean crustal thickness. The results from the CCP stacking method show that the Denali fault marks a sharp transition from thick crust in the south to thin crust in the north. The thickest crust up to 52 km is located in the St. Elias Range, which has been formed by oblique collision between the Yakutat microplate and North America. A thick crust of 48 km is also observed beneath the eastern Alaska Range. These observations suggest that high topography in Alaska is largely compensated by the thick crust root. The Moho depth ranges from 28 km to 35 km beneath the northern lowlands and increases to 40-45 km under the Books Range. The preliminary crustal thickness from the H-K method generally agrees with that from the CCP stacking with thicker crust beneath high mountain ranges and thinner crust beneath lowlands and basins. However, the offshore part is not well constrained due to the limited coverage of stations. The mean Vp/Vs ratio is around 1.7 in the Yukon-Tanana terrane and central-northern Alaska. The ratio is about 1.9 in central and southern Alaska with higher values at the Alaska Range, Wrangell Mountains, and St. Elias Range. Further data analyses are needed for obtaining more details of the crustal structure in Alaska to decipher the origin and development of different tectonic terranes.

  14. Constrained consequence

    CSIR Research Space (South Africa)

    Britz, K

    2011-09-01

    Full Text Available their basic properties and relationship. In Section 3 we present a modal instance of these constructions which also illustrates with an example how to reason abductively with constrained entailment in a causal or action oriented context. In Section 4 we... of models with the former approach, whereas in Section 3.3 we give an example illustrating ways in which C can be de ned with both. Here we employ the following versions of local consequence: De nition 3.4. Given a model M = hW;R;Vi and formulas...

  15. K, Rb and Sr abundances and Sr isotopic composition of the Tanzawa granitic and associated gabbroic rocks, Japan: low-potash island arc plutonic complex

    International Nuclear Information System (INIS)

    Ishizaka, K.; Yanagi, T.

    1977-01-01

    The granitic and associated gabbroic rocks of the Tanzawa plutonic complex of Miocene age occurring in the northern part of the Izu-Bonin arc are characterized by low abundances of K (229-6790 ppm) and Rb (0.414-12.1 ppm), low K 2 O/Na 2 O ratios (0.037-0.21), moderately high K/Rb ratios (541-630), low Rb/Sr ratios (0.00137-0.0579) and low initial 87 Sr/ 86 Sr ratios (0.70332-0.70372). This indicates that acid to intermediate plutonic rocks with these geochemical characteristics also occur in island arc environments besides mid-oceanic ridge environments. They represent, together with associated gabbroic rocks, a low-potash island arc plutonic complex and are expected to occur beneath young island arcs, although now unexposed. The Tanzawa plutonic complex may have been formed by differentiation of low-K calc-alkaline magma. (Auth.)

  16. Crustal response to lithosphere evolution

    DEFF Research Database (Denmark)

    Artemieva, Irina; Thybo, Hans; Cherepanova, Yulia

    2012-01-01

    We present a new model for the structure of the crust in an area which stretches from the North Atlantic region in the west to the Verkhoyansk Ridge in the east and encompasses Greenland, Iceland, most of Europe, West Siberian basin, and the Siberian cratons. The model is based on critically asse......, thicknesses of different crustal layers, and Pn seismic velocities....... assessed results from various seismic studies, including reflection and refraction profiles and receiver function studies. The region includes a nearly continuous age record for crustal evolution over ca. 3.6-3.8 billion years. We present an analysis of the crustal structure heterogeneity in relation...

  17. Petrology, geochemistry, and geochronology of the Chah-Bazargan gabbroic intrusions in the south Sanandaj-Sirjan zone, Neyriz, Iran

    Science.gov (United States)

    Fazlnia, Abdolnaser; Schenk, Volker; Appel, Peter; Alizade, Abouzar

    2013-07-01

    The Chah-Bazargan gabbroic intrusions are located in the south of Sanandaj-Sirjan zone. Precise U-Pb zircon SHRIMP ages of the intrusions show magmatic ages of 170.5 ± 1.9 Ma. These intrusions consist primarily of gabbros, interspersed with lenticular bodies of anorthosite, troctolite, clinopyroxenite, and wehrlite. The lenticular bodies show gradational or sharp boundaries with the gabbros. In the gradational boundaries, gabbros are mineralogically transformed into anorthosites, wehrlites, and/or clinopyroxenites. On the other hand, where the boundaries are sharp, the mineral assemblages change abruptly. There is no obvious deformation in the intrusions. Hence, the changes in mineral compositions are interpreted as the result of crystallization processes, such as fractionation in the magma chamber. Rock types with sharp boundaries show abrupt chemical changes, but the changes exhibit the same patterns of increasing and decreasing elements, especially of rare earth elements, as the gradational boundaries. Therefore, it is possible that all parts of the intrusions were formed from the same parental magma. Parts showing signs of nonequilibrium crystallization, such as cumulate features and sub-solidification, underwent fracturing and were interspersed throughout the magma chamber by late injection pulses or mechanical movements under mush conditions. The geological and age data show that the intrusions were formed from an Al-, Sr-, Fe-enriched and K-, Nb-depleted tholeiitic magma. The magma resulted from the partial melting of a metasomatized spinel demonstrated by negative Nb, P, Hf, and Ti, and positive Ba, Sr, and U anomalies typical of subduction-related magmas.

  18. Fault offsets and lateral crustal movement on Europa - Evidence for a mobile ice shell

    International Nuclear Information System (INIS)

    Schenk, P.M.; Mckinnon, W.B.

    1989-01-01

    An examination is conducted of Europa's cross-cutting structural relationships between various lineament types, in order to constrain the type of structure involved in each such case and, where possible, to also constrain the degree of extension across the lineaments. Evidence is adduced for significant lateral crustal movement, allowing alternative models and mechanisms for lineament formation to be discussed, as well as plausible lithospheric and crustal models. The question as to whether any of the water-ice layer has been, or currently is, liquid, is also treated in light of the evidence obtained. 53 refs

  19. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf

    2012-01-01

    /gabbro–eclogite phase transition in crustal evolution and the links between lithosphere recycling, mafic magmatism, and crustal underplating. We advocate that plate tectonics processes, togetherwith basalt/gabbro–eclogite transition, limit crustal thickness worldwide by providing effective mechanisms of crustal...

  20. Crustal Viscosity Structure Estimated from Multi-Phase Mixing Theory

    Science.gov (United States)

    Shinevar, W. J.; Behn, M. D.; Hirth, G.

    2014-12-01

    Estimates of lower crustal viscosity are typically constrained by analyses of isostatic rebound, post seismic creep, and laboratory-derived flow laws for crustal rocks and minerals. Here we follow a new approach for calculating the viscosity structure of the lower continental crust. We use Perple_X to calculate mineral assemblages for different crustal compositions. Effective viscosity is then calculated using the rheologic mixing model of Huet et al. (2014) incorporating flow laws for each mineral phase. Calculations are performed along geotherms appropriate for the Basin and Range, Tibetan Plateau, Colorado Plateau, and the San Andreas Fault. To assess the role of crustal composition on viscosity, we examined two compositional gradients extending from an upper crust with ~67 wt% SiO2 to a lower crust that is either: (i) basaltic with ~53 wt% SiO2 (Rudnick and Gao, 2003), or (ii) andesitic with ~64% SiO2 (Hacker et al., 2011). In all cases, the middle continental crust has a viscosity that is 2-3 orders of magnitude greater than that inferred for wet quartz, a common proxy for mid-crustal viscosities. An andesitic lower crust results in viscosities of 1020-1021 Pa-s and 1021-1022 Pa-s for hotter and colder crustal geotherms, respectively. A mafic lower crust predicts viscosities that are an order of magnitude higher for the same geotherm. In all cases, the viscosity calculated from the mixing model decreases less with depth compared to single-phase estimates. Lastly, for anhydrous conditions in which alpha quartz is stable, we find that there is a strong correlation between Vp/Vs and bulk viscosity; in contrast, little to no correlation exists for hydrous conditions.

  1. Magma Supply of Southwest Indian Ocean: Implication from Crustal Thickness Anomalies

    Science.gov (United States)

    Chiheng, L.; Jianghai, L.; Huatian, Z.; Qingkai, F.

    2017-12-01

    The Southwest Indian Ridge (SWIR) is one of the world's slowest spreading ridges with a full spreading rate of 14mm a-1, belonging to ultraslow spreading ridge, which are a novel class of spreading centers symbolized by non-uniform magma supply and crustal accretion. Therefore, the crustal thickness of Southwest Indian Ocean is a way to explore the magmatic and tectonic process of SWIR and the hotspots around it. Our paper uses Residual Mantle Bouguer Anomaly processed with the latest global public data to invert the relative crustal thickness and correct it according to seismic achievements. Gravity-derived crustal thickness model reveals a huge range of crustal thickness in Southwest Indian Ocean from 0.04km to 24km, 7.5km of average crustal thickness, and 3.5km of standard deviation. In addition, statistics data of crustal thickness reveal the frequency has a bimodal mixed skewed distribution, which indicates the crustal accretion by ridge and ridge-plume interaction. Base on the crustal thickness model, we divide three types of crustal thickness in Southwest Indian Ocean. About 20.31% of oceanic crust is 9.8km thick as thick crust. Furthermore, Prominent thin crust anomalies are associated with the trend of most transform faults, but thick crust anomalies presents to northeast of Andrew Bain transform fault. Cold and depleted mantle are also the key factors to form the thin crust. The thick crust anomalies are constrained by hotspots, which provide abundant heat to the mantle beneath mid-ocean ridge or ocean basin. Finally, we roughly delineate the range of ridge-plume interaction and transform fault effect.

  2. Crustal Ages of the Ocean Floor - Poster

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Crustal Ages of the Ocean Floor Poster was created at NGDC using the Crustal Ages of the Ocean Floor database draped digitally over a relief of the ocean floor...

  3. Along-Axis Structure and Crustal Construction Processes of Spreading Segments in Iceland: Implications for Magmatic Rifts

    Science.gov (United States)

    Siler, D. L.; Karson, J. A.

    2017-10-01

    Magmatic rift systems are composed of discrete spreading segments defined by morphologic, structural, and volcanic features that vary systematically along strike. In Iceland, structural features mapped in the glaciated and exhumed Miocene age upper crust correlate with analogous features in the seismically and volcanically active neovolcanic zone. Integrating information from both the active rift zones and ancient crust provides a three-dimensional perspective of crustal structure and the volcanic and tectonic processes that construct crust along spreading segments. Crustal exposures in the Skagi region of northern Iceland reveal significant along-strike variations in geologic structure. The upper crust at exhumed magmatic centers (segment centers) is characterized by a variety of intrusive rocks, high-temperature hydrothermal alteration, and geologic evidence for kilometer-scale subsidence. In contrast, the upper crust along segment limbs, which extend along strike from magmatic centers, is characterized by thick sections of gently dipping lava flows, cut by varying proportions of subvertical dikes. This structure implies relatively minor upper crustal subsidence and lateral dike intrusion. The differing modes of subsidence beneath segment centers and segment limbs require along-axis mass redistribution in the underlying upper, middle, and lower crust during crustal construction. This along-axis material transport is accomplished through lateral dike intrusion in the upper crust and by along-axis flow of magmatic to high-temperature solid-state gabbroic material in the middle and lower crust. These processes, inferred from outcrop evidence in Skagi, are consistent with processes inferred to be important during active rifting in Iceland and at analogous magmatic oceanic and continental rifts.

  4. The crustal thickness of Australia

    Science.gov (United States)

    Clitheroe, G.; Gudmundsson, O.; Kennett, B.L.N.

    2000-01-01

    We investigate the crustal structure of the Australian continent using the temporary broadband stations of the Skippy and Kimba projects and permanent broadband stations. We isolate near-receiver information, in the form of crustal P-to-S conversions, using the receiver function technique. Stacked receiver functions are inverted for S velocity structure using a Genetic Algorithm approach to Receiver Function Inversion (GARFI). From the resulting velocity models we are able to determine the Moho depth and to classify the width of the crust-mantle transition for 65 broadband stations. Using these results and 51 independent estimates of crustal thickness from refraction and reflection profiles, we present a new, improved, map of Moho depth for the Australian continent. The thinnest crust (25 km) occurs in the Archean Yilgarn Craton in Western Australia; the thickest crust (61 km) occurs in Proterozoic central Australia. The average crustal thickness is 38.8 km (standard deviation 6.2 km). Interpolation error estimates are made using kriging and fall into the range 2.5-7.0 km. We find generally good agreement between the depth to the seismologically defined Moho and xenolith-derived estimates of crustal thickness beneath northeastern Australia. However, beneath the Lachlan Fold Belt the estimates are not in agreement, and it is possible that the two techniques are mapping differing parts of a broad Moho transition zone. The Archean cratons of Western Australia appear to have remained largely stable since cratonization, reflected in only slight variation of Moho depth. The largely Proterozoic center of Australia shows relatively thicker crust overall as well as major Moho offsets. We see evidence of the margin of the contact between the Precambrian craton and the Tasman Orogen, referred to as the Tasman Line. Copyright 2000 by the American Geophysical Union.

  5. Glacial rebound and crustal stress in Finland

    International Nuclear Information System (INIS)

    Lambeck, K.; Purcell, A.

    2003-11-01

    The last ice age of Fennoscandinavia continues to have geological repercussions across Finland despite the last ice having retreated almost 10,000 years ago: land uplift, shoreline retreat, and the stress state of the crust continues to evolve. This report focusses on the glacial rebound signals for Finland and the Gulf of Bothnia and explores the consequences of the ongoing deformation. The rebound signals include the geological evidence as well as instrumental observations: the tide gauge and lake-level measurements of the past century, the changes in geodetic levels recorded in the repeat levelling surveys of the region and the direct measurement of crustal deformation (radial and horizontal) using high-precision space-geodesy measurements. These signals provide constraints on the Earth's rheology, its elasticity and viscosity, and the glacial history of the region. Once observationally constrained, the rebound models are used to predict both the ongoing evolution of shorelines and the changing state of stress within the crust. This report covers: (i) A review of glacial rebound modelling for Scandinavia (Sections 2 and 3). (ii) Review of observational evidence relating to sea-level change and crustal rebound (Section 4). (iii) New earth and ice-sheet model results from the inversion of the geological evidence for sea-level change, including models of shoreline evolution (Sections 5 and 6). (iv) Earth-model results from the inversion of the geodetic evidence for sea-level change (Section 7). (v) Development of crustal stress models for past and present stress states (Section 8). (vi) Conclusions and recommendations (Section 9). Specific conclusions reached pertain to: (i) Thickness of ice cover over Scandinavia since the Last Glacial Maximum, particularly for the Lateglacial period. (ii) Sea-level change and shoreline evolution for the Baltic area since the time the region became ice-free for the last time. (iii) The predicted rates of present-day crustal

  6. Chemical compositions and Sr, Nd isotope ratios of gabbroic xenoliths in calc-alkali andesites of Naeba and Torikabuto volcanoes, North Fossa Magna, central Japan

    International Nuclear Information System (INIS)

    Shimazu, Mitsuo; Kawano, Yoshinobu; Kaji, Kiyoshi; Igarashi, Satoshi.

    1991-01-01

    Gabbroic, doleritic and basaltic xenoliths found in calc-alkali andesites of Naeba and Torikabuto volcanoes are geochemically divided into three groups. Gabbro A of the group 1 from Naeba is rich in MgO and Ni, poor in alkalis, and shows depleted REE pattern resembling those of Ichinomegata (Sp. No.2232) and Hakone (HKG1, HKG2) volcanoes. On the basis the REE pattern and high Al IV contents in clinopyroxenes, gabbro A is interpreted to have been cumulate from a primary magma generated by partial melting of upper mantle. From REE pattern, gabbros of the group 2 from Ichinomegata (Sp. No.2218) may have derived from low alkali tholeiite magma which have been formed by removal of material such as the group 1 gabbro at shallow depth. Doleritic and basaltic xenoliths of the group 3 from Naeba, gabbroic xenoliths from Torikabuto and Umikawa are poorer in MgO and richer in alkalis than those of the group 1 and show enriched pattern in REE resembling that of high alkali tholeiite and contain clinopyroxenes having low Al IV . Therefore, these rocks are considered to be differentiates of high alkali tholeiite magma at shallow depth. On εNd- 87 Sr/ 86 Sr diagram, isotope data of gabbro A of the group 1 plot near those of andesites from Asama and Myoko volcanoes of the North Fossa Magna. It is interpreted that these rocks have derived from the same mantle source as the Asama and Myoko volcanoes which are richer in incompatible elements than those of MORB. (author)

  7. Crustal structure of Central Sicily

    Science.gov (United States)

    Giustiniani, Michela; Tinivella, Umberta; Nicolich, Rinaldo

    2018-01-01

    We processed crustal seismic profile SIRIPRO, acquired across Central Sicily. To improve the seismic image we utilized the wave equation datuming technique, a process of upward or downward continuation of the wave-field between two arbitrarily shaped surfaces. Wave equation datuming was applied to move shots and receivers to a given datum plane, removing time shifts related to topography and to near-surface velocity variations. The datuming procedure largely contributed to attenuate ground roll, enhance higher frequencies, increase resolution and improve the signal/noise ratio. Processed data allow recognizing geometries of crust structures differentiating seismic facies and offering a direct image of ongoing tectonic setting within variable lithologies characterizing the crust of Central Sicily. Migrated sections underline distinctive features of Hyblean Plateau foreland and above all a crustal thinning towards the Caltanissetta trough, to the contact with a likely deep Permo-Triassic rifted basin or rather a zone of a continent to oceanic transition. Inhomogeneity and fragmentation of Sicily crust, with a distinct separation of Central Sicily basin from western and eastern blocks, appear to have guided the tectonic transport inside the Caltanissetta crustal scale syncline and the accumulation of allochthonous terrains with south and north-verging thrusts. Major tectonic stack operated on the construction of a wide anticline of the Maghrebian chain in northern Sicily. Sequential south-verging imbrications of deep elements forming the anticline core denote a crust wedge indenting foreland structures. Deformation processes involved multiple detachment planes down to decoupling levels located near crust/mantle transition, supporting a presence of high-density lenses beneath the chain, interrelated to a southwards push of Tyrrhenian mantle and asthenosphere.

  8. Inferring regional vertical crustal velocities from averaged relative sea level trends: A proof of concept

    Directory of Open Access Journals (Sweden)

    Bâki Iz H.

    2017-02-01

    Full Text Available This study demonstrates that relative sea level trends calculated from long-term tide gauge records can be used to estimate relative vertical crustal velocities in a region with high accuracy. A comparison of the weighted averages of the relative sea level trends estimated at six tide gauge stations in two clusters along the Eastern coast of United States, in Florida and in Maryland, reveals a statistically significant regional vertical crustal motion of Maryland with respect to Florida with a subsidence rate of −1.15±0.15 mm/yr identified predominantly due to the ongoing glacial isostatic adjustment process. The estimate is a consilience value to validate vertical crustal velocities calculated from GPS time series as well as towards constraining predictive GIA models in these regions.

  9. Amphibole and felsic veins from the gabbroic oceanic core complex of Atlantis Bank (Southwest Indian Ridge, IODP Hole U1473A): when the fluids meets the melts

    Science.gov (United States)

    Sanfilippo, A.; Tribuzio, R.; Antonicelli, M.; Zanetti, A.

    2017-12-01

    We present a petrological/geochemical investigation of brown amphibole and felsic veins drilled during IODP 360 expedition at Atlantis Bank, a gabbroic oceanic core complex from Southwest Indian Ridge. The main purpose of this study is to unravel the role of seawater and magmatic components in the origin of these veins. Brown amphibole veins were collected at 90-170 mbsf. These veins typically include minor modal amounts of plagioclase and are associated with alteration halos made up of brown amphibole and whitish milky plagioclase in host gabbros. Two sets of late magmatic felsic veins, which mostly consist of plagioclase and minor brown amphibole, were selected. Amphibole-plagioclase geothermometry (Holland and Blundy, 1994) documents that crystallization of brown amphibole and felsic veins occurred in the 850-700 °C interval. In the brown amphibole veins, amphibole and plagioclase have relatively low concentrations of incompatible trace elements and significant Cl (0.2-0.3 wt%). The development of these veins at near surface levels is therefore attributed to seawater-derived fluids migrating downward through cracks developing in the exhuming gabbro. To explain the high temperature estimates for the development of these shallow veins, however, the seawater-derived fluids must have interacted not only with the gabbros, but also with a high temperature magmatic component. This petrogenetic hypothesis is consistent with oxygen and hydrogen isotopic compositions of amphiboles from shallow veins in adjacent Hole 735B gabbros (Alt and Bach, 2006). Trace element compositions of amphibole and plagioclase from the felsic veins show formation by silicate melts rich in incompatible elements. In addition, Cl concentrations in amphibole from the felsic veins are low, thereby indicating that the melts feeding these veins had low or no seawater component. We cautiously propose that: (i) the felsic veins were generated by SiO2-rich melts residual after crystallization of Fe

  10. New constraints on the crustal structure beneath northern Tyrrhenian Sea

    Science.gov (United States)

    Levin, V. L.; Park, J. J.

    2009-12-01

    We present new seismological data on the seismic structure beneath the Tyrrhenian Sea between Corsica and the coast of Italy. Teleseismic receiver functions from two Tyrrhenian islands (Elba and Gorgona) identify clear P-to-S mode-converted waves from two distinct interfaces, at ~20 and ~45 km depth. Both interfaces are characterized by an increase of seismic wavespeed with depth. Using a summation of direct and multiply-reflected body waves within the P wave coda we estimate the mean ratio of compressional and shear wave speeds above the 45 km interface to be 1.75-1.80. Using reflectivity computations in 1D layered models we develop a model of seismic wavespeed distribution that yields synthetic seismograms very similar to those observed. We apply a Ps-multiple summation procedure to the synthetic waveforms to further verify the match between observed and predicted wavefields. The lower layer of our model, between 20 and 45 km, has Vp ~ 7.5 km/sec, a value that can be ascribed to either very fast crustal rocks or very slow upper mantle rocks. The Vp/Vs ratio is ~1.8 in this intermediate layer. On the basis of a well-constrained downward increase in seismic wave speed beneath this second layer, we interpret it as the magmatically reworked lower crust, a lithology that has been proposed to explain high-Vp layers in the crustal roots of island-arc terranes and volcanically altered continental margins, as well as lower-crustal high-Vp features sometimes seen beneath continental rifts. The presence of a thick layer of high-Vp, but crustal, lithology beneath the Tyrrhenian Sea differs considerably from previous estimates that interpreted the interface at ~20 km as the Moho. Our new interpretation obviates a need for a crustal thickness change of over 20 km at the crest of the Apennines orogen. We propose an alteration in the properties of the lower crust instead. We argue that ongoing convergent subduction of the Adriatic lithospehre is not required beneath northern

  11. Obtaining Crustal Properties From the P Coda Without Deconvolution: an Example From the Dakotas

    Science.gov (United States)

    Frederiksen, A. W.; Delaney, C.

    2013-12-01

    Receiver functions are a popular technique for mapping variations in crustal thickness and bulk properties, as the travel times of Ps conversions and multiples from the Moho constrain both Moho depth (h) and the Vp/Vs ratio (k) of the crust. The established approach is to generate a suite of receiver functions, which are then stacked along arrival-time curves for a set of (h,k) values (the h-k stacking approach of Zhu and Kanamori, 2000). However, this approach is sensitive to noise issues with the receiver functions, deconvolution artifacts, and the effects of strong crustal layering (such as in sedimentary basins). In principle, however, the deconvolution is unnecessary; for any given crustal model, we can derive a transfer function allowing us to predict the radial component of the P coda from the vertical, and so determine a misfit value for a particular crustal model. We apply this idea to an Earthscope Transportable Array data set from North and South Dakota and western Minnesota, for which we already have measurements obtained using conventional h-k stacking, and so examine the possibility of crustal thinning and modification by a possible failed branch of the Mid-Continent Rift.

  12. Crustal anisotropy from Moho converted Ps wave splitting and geodynamic implications in Northeastern margin of Tibetan Plateau

    Science.gov (United States)

    Xie, Z.; Wu, Q.; Zhang, R.

    2017-12-01

    Collision between Indian and Eurasian result in intense deformation and crustal shortening in the Tibetan Plateau. NE margin of Tibetan Plateau experienced complex deformation between Qilian orogen and its adjacent blocks, Alxa Block in the north and Ordos Block in the east. We focus on if there any evidences exist in the NE margin of Tibetan Plateau, which can support crustal channel flow model. China Earthquake Administration had deployed temporary seismic array which is called ChinaArray Phase Ⅱ, dense seismic stations covered NE margin of Tibetan Plateau. Seismic data recorded by 81 seismic stations is applied in this research. We calculated receiver functions with time-domain deconvolution. We selected RFs which have clear Ps phase both in radial and transverse components to measure Ps splitting owing to crustal anisotropy, and 130 pairs of anisotropy parameters of 51 seismic stations were obtained. We would like to discuss about dynamic mechanism of this area using crustal anisotropy associated with the result of SKS-splitting and surface constrains like GPS velocity. The result can be summarized as follows. The large scale of delay time imply that the crustal anisotropy mainly derives from middle to lower crust rather than upper crust. In the southeastern part of the research area, crustal anisotropy is well agree with the result computed form SKS-splitting and GPS velocity directions trending NWW-SEE or E-W direction. This result imply a vertically coherent deformation in the area as the directions of crustal anisotropy trend to be perpendicular to the direction of normal stress. In the middle and north part of the research area, the fast polarization direction of crustal anisotropy is NEE-SWW or E-W direction, parallels with direction of GPS velocity, but differ to the direction of the result of SKS-splitting. This result may imply that decoupled deformation in this area associated with middle to lower crustal flow.

  13. Glacio-Seismotectonics: Ice Sheets, Crustal Deformation and Seismicity

    Science.gov (United States)

    Sauber, Jeanne; Stewart, Iain S.; Rose, James

    2000-01-01

    The last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity. This growth has been driven largely by the emergence of postglacial rebound models (PGM) constrained by new field observations that incorporate increasingly realistic rheological, mechanical, and glacial parameters. In this paper, we highlight some of these recent field-based investigations and new PGMs, and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation. The emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern Canada and Fennoscandia. However, many of these models neglect important parameters, such as topography, lateral variations in lithospheric strength and tectonic strain built up during glaciation. In glaciated mountainous terrains, glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism. Such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields.

  14. Correlation of Crustal Structures and Seismicity Patterns in Northern Appalachians

    Science.gov (United States)

    Yang, X.; Gao, H.

    2017-12-01

    The earthquake distributions in northern Appalachians are bounded by major geologically-defined terrane boundaries. There is a distinct seismic gap within Taconic Belt between the Western Quebec Seismic Zone (WQSZ) to the west and the seismically active Ganderia terrane to the east. It is not clear, however, what crustal structures control the characteristics of earthquake clustering in this region. Here we present a newly constructed crustal shear velocity model for the northern Appalachians using Rayleigh wave data extracted from ambient noises. Our tomographic model reveals strongly heterogeneous seismic structures in the crust. We observe multiple NW-dipping patches of high-velocity anomalies in the upper crust beneath the southeastern WQSZ. The upper crust shear velocities in the Ganderia and Avalonia region are generally lower than those beneath the WQSZ. The middle crust has relatively lower velocities in the study area. The earthquakes in the study area are constrained within the upper crust. Most of the earthquake hypocenters within the WQSZ are concentrated along the NW-dipping boundaries separating the high-velocity anomalies. In contrast, most of the earthquake hypocenters in the Ganderia and Avalonia region are diffusely distributed without clear vertical lineaments. The orientations of maximum compressive stresses change from W-E in the Ganderia and Avalonia region to SW-NE in the WQSZ. The contrasts in seismicity, velocity, and stress field across the Taconic Belt indicate that the Taconic Belt terrane may act as a seismically inactive buffer zone in northern Appalachians.

  15. Evolutionary constrained optimization

    CERN Document Server

    Deb, Kalyanmoy

    2015-01-01

    This book makes available a self-contained collection of modern research addressing the general constrained optimization problems using evolutionary algorithms. Broadly the topics covered include constraint handling for single and multi-objective optimizations; penalty function based methodology; multi-objective based methodology; new constraint handling mechanism; hybrid methodology; scaling issues in constrained optimization; design of scalable test problems; parameter adaptation in constrained optimization; handling of integer, discrete and mix variables in addition to continuous variables; application of constraint handling techniques to real-world problems; and constrained optimization in dynamic environment. There is also a separate chapter on hybrid optimization, which is gaining lots of popularity nowadays due to its capability of bridging the gap between evolutionary and classical optimization. The material in the book is useful to researchers, novice, and experts alike. The book will also be useful...

  16. Spatial Relationship Between Crustal Structure and Mantle Seismicity in the Vrancea Seismogenic Zone of Romania

    Science.gov (United States)

    Knapp, C. C.; Enciu, D. M.; Knapp, J. H.

    2007-12-01

    Active crustal deformation and subsidence in the Southeast Carpathian foreland has previously been attributed to active foundering of thickened continental lithosphere beneath the Carpathian bend region (Knapp et al, 2005). The present study involves integration of active and passive-source seismic data in order to place constraints on the duration, timing, and scale of crustal deformation in the Carpathian foreland, and in particular to assess the genetic relationship with the Vrancea intermediate-depth seismogenic zone (VSZ). Relocated crustal earthquakes and focal mechanisms were correlated with four deep industry seismic profiles, the reprocessed DACIA PLAN deep seismic profile, and the DRACULA (Deep Reflection Acquisition Constraining Unusual Lithospheric Activity) II and III profiles. Projection of foreland crustal hypocenters onto the deep seismic lines correlates well with previously identified crustal faults such as the Trotus and Sinaia, as well as the newly identified Ialomita Fault. Specifically, results of this study (1) image the full crustal and uppermost mantle structure of the Focsani Basin in the close proximity of the VSZ, (2) show evidence for a sub-horizontal, slightly east-dipping Moho in the vicinity of the VSZ and thinning of the crust towards the Carpathian orogen, (3) illustrate the conspicuous absence of west-dipping fabrics or structures in the crust and across the Moho, (4) present evidence that the Trotus Fault is a crustal-scale active fault with a dextral sense of motion, (5) suggest that the Paleozoic age Peceneaga-Camena and Capidava-Ovidiu Faults have not been active in post-Paleozoic time, and (6) show evidence for a new active crustal scale sinistral fault, named the Ialomita fault. Both the seismogenic Vrancea body and deformation in the Focsani Basin appear to be concentrically bound by the Trotus Fault in the north and east and the Sinaia-Ialomita Fault in the south, suggesting a coupled deformation between the VSZ and the

  17. NASA plan for international crustal dynamics studies

    Science.gov (United States)

    1979-01-01

    The international activities being planned as part of the NASA geodynamics program are described. Methods of studying the Earth's crustal movements and deformation characteristics are discussed. The significance of the eventual formalations of earthquake predictions methods is also discussed.

  18. Estimating crustal thickness and Vp/Vs ratio with joint constraints of receiver function and gravity data

    Science.gov (United States)

    Shi, Lei; Guo, Lianghui; Ma, Yawei; Li, Yonghua; Wang, Weilai

    2018-05-01

    The technique of teleseismic receiver function H-κ stacking is popular for estimating the crustal thickness and Vp/Vs ratio. However, it has large uncertainty or ambiguity when the Moho multiples in receiver function are not easy to be identified. We present an improved technique to estimate the crustal thickness and Vp/Vs ratio by joint constraints of receiver function and gravity data. The complete Bouguer gravity anomalies, composed of the anomalies due to the relief of the Moho interface and the heterogeneous density distribution within the crust, are associated with the crustal thickness, density and Vp/Vs ratio. According to their relationship formulae presented by Lowry and Pérez-Gussinyé, we invert the complete Bouguer gravity anomalies by using a common algorithm of likelihood estimation to obtain the crustal thickness and Vp/Vs ratio, and then utilize them to constrain the receiver function H-κ stacking result. We verified the improved technique on three synthetic crustal models and evaluated the influence of selected parameters, the results of which demonstrated that the novel technique could reduce the ambiguity and enhance the accuracy of estimation. Real data test at two given stations in the NE margin of Tibetan Plateau illustrated that the improved technique provided reliable estimations of crustal thickness and Vp/Vs ratio.

  19. Crustal balance and crustal flux from shortening estimates in the Central Andes

    Science.gov (United States)

    Hindle, David; Kley, Jonas; Oncken, Onno; Sobolev, Stephan

    2005-01-01

    The Central Andes of South America form the second largest high elevation plateau on earth. Extreme elevations have formed on a noncollisional margin with abundant associated arc magmatism. It has long been thought that the crustal thickness necessary to support Andean topography was not accounted for by known crustal shortening alone. We show that this may in part be due to a two-dimensional treatment of the problem. A three-dimensional analysis of crustal shortening and crustal thickness shows that displacement of material towards the axis of the bend in the Central Andes has added a significant volume of crust not accounted for in previous comparisons. We find that present-day crustal thickness between 12°S and 25°S is accounted for (∼-10% to ∼+3%)with the same shortening estimates, and the same assumed initial crustal thickness as had previously led to the conclusion of a ∼25-35% deficit in shortening relative to volume of crustal material. We suggest that the present-day measured crustal thickness distribution may not match that predicted due to shortening, and substantial redistribution of crust may have occurred by both erosion and deposition at the surface and lower crustal flow in regions of the thermally weakened middle and lower crust.

  20. Seismic crustal structure of the North China Craton and surrounding area: Synthesis and analysis

    Science.gov (United States)

    Xia, B.; Thybo, H.; Artemieva, I. M.

    2017-07-01

    We present a new digital model (NCcrust) of the seismic crustal structure of the Neoarchean North China Craton (NCC) and its surrounding Paleozoic-Mesozoic orogenic belts (30°-45°N, 100°-130°E). All available seismic profiles, complemented by receiver function interpretations of crustal thickness, are used to constrain a new comprehensive crustal model NCcrust. The model, presented on a 0.25° × 0.25°grid, includes the Moho depth and the internal structure (thickness and velocity) of the crust specified for four layers (the sedimentary cover, upper, middle, and lower crust) and the Pn velocity in the uppermost mantle. The crust is thin (30-32 km) in the east, while the Moho depth in the western part of the NCC is 38-44 km. The Moho depth of the Sulu-Dabie-Qinling-Qilian orogenic belt ranges from 31 km to 51 km, with a general westward increase in crustal thickness. The sedimentary cover is 2-5 km thick in most of the region, and typical thicknesses of the upper crust, middle crust, and lower crust are 16-24 km, 6-24 km, and 0-6 km, respectively. We document a general trend of westward increase in the thickness of all crustal layers of the crystalline basement and as a consequence, the depth of the Moho. There is no systematic regional pattern in the average crustal Vp velocity and the Pn velocity. We examine correlation between the Moho depth and topography for seven tectonic provinces in the North China Craton and speculate on mechanisms of isostatic compensation.

  1. Exploring Constrained Creative Communication

    DEFF Research Database (Denmark)

    Sørensen, Jannick Kirk

    2017-01-01

    Creative collaboration via online tools offers a less ‘media rich’ exchange of information between participants than face-to-face collaboration. The participants’ freedom to communicate is restricted in means of communication, and rectified in terms of possibilities offered in the interface. How do...... these constrains influence the creative process and the outcome? In order to isolate the communication problem from the interface- and technology problem, we examine via a design game the creative communication on an open-ended task in a highly constrained setting, a design game. Via an experiment the relation...... between communicative constrains and participants’ perception of dialogue and creativity is examined. Four batches of students preparing for forming semester project groups were conducted and documented. Students were asked to create an unspecified object without any exchange of communication except...

  2. Choosing health, constrained choices.

    Science.gov (United States)

    Chee Khoon Chan

    2009-12-01

    In parallel with the neo-liberal retrenchment of the welfarist state, an increasing emphasis on the responsibility of individuals in managing their own affairs and their well-being has been evident. In the health arena for instance, this was a major theme permeating the UK government's White Paper Choosing Health: Making Healthy Choices Easier (2004), which appealed to an ethos of autonomy and self-actualization through activity and consumption which merited esteem. As a counterpoint to this growing trend of informed responsibilization, constrained choices (constrained agency) provides a useful framework for a judicious balance and sense of proportion between an individual behavioural focus and a focus on societal, systemic, and structural determinants of health and well-being. Constrained choices is also a conceptual bridge between responsibilization and population health which could be further developed within an integrative biosocial perspective one might refer to as the social ecology of health and disease.

  3. Thinned crustal structure and tectonic boundary of the Nansha Block, southern South China Sea

    Science.gov (United States)

    Dong, Miao; Wu, Shi-Guo; Zhang, Jian

    2016-12-01

    The southern South China Sea margin consists of the thinned crustal Nansha Block and a compressional collision zone. The Nansha Block's deep structure and tectonic evolution contains critical information about the South China Sea's rifting. Multiple geophysical data sets, including regional magnetic, gravity and reflection seismic data, reveal the deep structure and rifting processes. Curie point depth (CPD), estimated from magnetic anomalies using a windowed wavenumber-domain algorithm, enables us to image thermal structures. To derive a 3D Moho topography and crustal thickness model, we apply Oldenburg algorithm to the gravity anomaly, which was extracted from the observed free air gravity anomaly data after removing the gravity effect of density variations of sediments, and temperature and pressure variations of the lithospheric mantle. We found that the Moho depth (20 km) is shallower than the CPD (24 km) in the Northwest Borneo Trough, possibly caused by thinned crust, low heat flow and a low vertical geothermal gradient. The Nansha Block's northern boundary is a narrow continent-ocean transition zone constrained by magnetic anomalies, reflection seismic data, gravity anomalies and an interpretation of Moho depth (about 13 km). The block extends southward beneath a gravity-driven deformed sediment wedge caused by uplift on land after a collision, with a contribution from deep crustal flow. Its southwestern boundary is close to the Lupar Line defined by a significant negative reduction to the pole (RTP) of magnetic anomaly and short-length-scale variation in crustal thickness, increasing from 18 to 26 km.

  4. Revised crustal architecture of the southeastern Carpathian foreland from active and passive seismic data

    Science.gov (United States)

    Enciu, Dana M.; Knapp, Camelia C.; Knapp, James H.

    2009-08-01

    Integration of active and passive source seismic data is employed in order to study the nature of the relationships between crustal seismicity and geologic structures in the southeastern (SE) Carpathian foreland of Romania and the possible connection with the Vrancea Seismogenic Zone (VSZ) of intermediate-depth seismicity, one of the most active earthquake-prone areas in Europe. Crustal epicenters and focal mechanisms are correlated with four deep industry seismic profiles, the reprocessed Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics (DACIA PLAN) profile and the Deep Reflection Acquisition Constraining Unusual Lithospheric Activity II and III (DRACULA) profiles in order to understand the link between neotectonic foreland deformation and Vrancea mantle seismicity. Projection of crustal foreland hypocenters onto deep seismic profiles identifies several active crustal faults in the SE Carpathian foreland and suggests a mechanical coupling between the mantle located VSZ and the overlying foreland crust. The coupled associated deformation appears to take place on the Trotus Fault, the Sinaia Fault, and the newly detected Ialomita Fault. Seismic reflection imaging reveals the absence of west dipping reflectors in the crystalline crust and a slightly east dipping to horizontal Moho in the proximity of the Vrancea area. These findings argue against previously purported mechanisms to generate mantle seismicity in the VSZ including oceanic lithosphere subduction in place and oceanic slab break off, furthermore suggesting that the Vrancea seismogenic body is undetached from the overlying crust in the foreland.

  5. Constrained superfields in supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Dall’Agata, Gianguido; Farakos, Fotis [Dipartimento di Fisica ed Astronomia “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)

    2016-02-16

    We analyze constrained superfields in supergravity. We investigate the consistency and solve all known constraints, presenting a new class that may have interesting applications in the construction of inflationary models. We provide the superspace Lagrangians for minimal supergravity models based on them and write the corresponding theories in component form using a simplifying gauge for the goldstino couplings.

  6. Minimal constrained supergravity

    Energy Technology Data Exchange (ETDEWEB)

    Cribiori, N. [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Dall' Agata, G., E-mail: dallagat@pd.infn.it [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Farakos, F. [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, 35131 Padova (Italy); Porrati, M. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

    2017-01-10

    We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  7. Minimal constrained supergravity

    Directory of Open Access Journals (Sweden)

    N. Cribiori

    2017-01-01

    Full Text Available We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  8. Minimal constrained supergravity

    International Nuclear Information System (INIS)

    Cribiori, N.; Dall'Agata, G.; Farakos, F.; Porrati, M.

    2017-01-01

    We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.

  9. Thickening the outer margins of the Tibetan Plateau: The role of crustal shortening

    Science.gov (United States)

    Lease, R. O.; Burbank, D. W.

    2012-12-01

    One of the most direct consequences of the collision of two buoyant continents is large-scale crustal thickening that results in the upward and outward growth of high terrain. As the stronger Indian continent has collided with weaker Asia over at least the past 50 Myr, widespread crustal thickening has occurred over an area that is approximately 2.5 million km^2 at present. The resultant Tibetan crust is the thickest observed on Earth today with an average thickness of 65 km and a maximum that may reach 90 km in places. The mechanisms by which Tibetan crust has thickened, however, as well as the timing and distribution of these mechanisms across the plateau, remain debatable. Two of the most popular mechanisms for thickening the crust beneath the margins of the Tibetan Plateau are: 1) pure shear with faulting and folding in the upper crust and horizontal shortening below; and 2) flow and inflation of lower or middle crust without significant shortening of the upper crust. To help discriminate between the relative contributions of these two mechanisms, well-constrained estimates of upper crustal shortening are needed. Here we document the Cenozoic shortening budget across the northeastern Tibetan Plateau margin near 36°N 102.5°E with several 100- to 145-km-long balanced cross sections. Thermochronological and magnetostratigraphic data indicate that modest NNE-SSW shortening began in middle Eocene time, shortly after initial India-Asia collision. Accelerated east-west shortening, however, did not commence until ~35 Myr later. A five-fold acceleration in shortening rates in middle Miocene-to-Recent time accounts for more than half of the total Cenozoic crustal shortening and thickening in this region. Overall, the balanced cross sections indicate 11 ± 2 % east-west shortening since middle Miocene time, and ~9 ± 2 % NNE-SSW shortening between middle Eocene and middle Miocene times. Given the present-day crustal thickness of 56 ± 4 km in northeastern Tibet, crustal

  10. Constrained Vapor Bubble Experiment

    Science.gov (United States)

    Gokhale, Shripad; Plawsky, Joel; Wayner, Peter C., Jr.; Zheng, Ling; Wang, Ying-Xi

    2002-11-01

    Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ PC (personal computer)-based LabView data acquisition system via thermocouples. Film thickness profiles were measured using interferometry. A theoretical model was developed to predict the curvature profile of the stable film in the evaporator. The concept of the total amount of evaporation, which can be obtained directly by integrating the experimental temperature profile, was introduced. Experimentally measured curvature profiles are in good agreement with modeling results. For microgravity conditions, an analytical expression, which reveals an inherent relation between temperature and curvature profiles, was derived.

  11. Constrained noninformative priors

    International Nuclear Information System (INIS)

    Atwood, C.L.

    1994-10-01

    The Jeffreys noninformative prior distribution for a single unknown parameter is the distribution corresponding to a uniform distribution in the transformed model where the unknown parameter is approximately a location parameter. To obtain a prior distribution with a specified mean but with diffusion reflecting great uncertainty, a natural generalization of the noninformative prior is the distribution corresponding to the constrained maximum entropy distribution in the transformed model. Examples are given

  12. Combined Gravimetric-Seismic Crustal Model for Antarctica

    Science.gov (United States)

    Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad

    2018-01-01

    The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24

  13. Crustal insights from gravity and aeromagnetic analysis: Central North Slope, Alaska

    Science.gov (United States)

    Saltus, R.W.; Potter, C.J.; Phillips, J.D.

    2006-01-01

    Aeromagnetic and gravity data are processed and interpreted to reveal deep and shallow information about the crustal structure of the central North Slope, Alaska. Regional aeromagnetic anomalies primarily reflect deep crustal features. Regional gravity anomalies are more complex and require detailed analysis. We constrain our geophysical models with seismic data and interpretations along two transects including the Trans-Alaska Crustal Transect. Combined geophysical analysis reveals a remarkable heterogeneity of the pre-Mississippian basement. In the central North Slope, pre-Mississippian basement consists of two distinct geophysical domains. To the southwest, the basement is dense and highly magnetic; this basement is likely mafic and mechanically strong, possibly acting as a buttress to basement involvement in Brooks Range thrusting. To the northeast, the central North Slope basement consists of lower density, moderately magnetic rocks with several discrete regions (intrusions?) of more magnetic rocks. A conjugate set of geophysical trends, northwest-southeast and southwest-northeast, may be a factor in the crustal response to tectonic compression in this domain. High-resolution gravity and aeromagnetic data, where available, reflect details of shallow fault and fold structure. The maps and profile models in this report should provide useful guidelines and complementary information for regional structural studies, particularly in combination with detailed seismic reflection interpretations. Future challenges include collection of high-resolution gravity and aeromagnetic data for the entire North Slope as well as additional deep crustal information from seismic, drilling, and other complementary methods. Copyrights ?? 2006. The American Association of Petroleum Geologists. All rights reserved.

  14. Spatial relationships between crustal structures and mantle seismicity in the Vrancea Seismogenic Zone of Romania: Implications for geodynamic evolution

    Science.gov (United States)

    Enciu, Dana-Mihaela

    Integration of active and passive-source seismic data is employed to study the relationships between crustal structures and seismicity in the SE Carpathian foreland of Romania, and the connection with the Vrancea Seismogenic Zone. Relocated crustal epicenters and focal mechanisms are correlated with industry seismic profiles Comanesti, Ramnicu Sarat, Braila and Buzau, the reprocessed DACIA PLAN profile and the DRACULA (Deep Reflection Acquisition Constraining Unusual Lithospheric Activity) II and III profiles in order to understand the link between neo-tectonic foreland deformation and Vrancea mantle seismicity. Projection of crustal foreland hypocenters onto deep seismic profiles identified active crustal faults suggesting a mechanical coupling between sedimentary, crustal and upper mantle structures on the Trotus, Sinaia and newly observed Ialomita Faults. Seismic reflection imaging revealed the absence of west dipping reflectors in the crust and an east dipping to horizontal Moho in the proximity of the Vrancea area. These findings argue against both 'subduction-in-place' and 'slab break-off' as viable mechanisms for generating Vrancea mantle seismicity.

  15. Crustal structure of the Khartoum Basin, Sudan

    CSIR Research Space (South Africa)

    El Tahir, N

    2013-05-01

    Full Text Available Basin ranges between 33 and 37 km, with an average of 35 km, and that the crustal Vp/Vs ratio ranges from 1.74 to 1.81, with an average of 1.78. From the joint inversion of receiver functions and Rayleigh wave group velocities,we obtained similar results...

  16. Estimating the Crustal Power Spectrum From Vector Magsat Data: Crustal Power Spectrum

    Science.gov (United States)

    Lowe, David A. J.; Parker, Robert L.; Purucker, Michael E.; Constable, Catherine G.

    2000-01-01

    The Earth's magnetic field can be subdivided into core and crustal components and we seek to characterize the crustal part through its spatial power spectrum (R(sub l)). We process vector Magsat data to isolate the crustal field and then invert power spectral densities of flight-local components along-track for R(sub l) following O'Brien et al. [1999]. Our model (LPPC) is accurate up to approximately degree 45 (lambda=900 km) - this is the resolution limit of our data and suggests that global crustal anomaly maps constructed from vector Magsat data should not contain features with wavelengths less than 900 km. We find continental power spectra to be greater than oceanic ones and attribute this to the relative thicknesses of continental and oceanic crust.

  17. Modeling of periodic great earthquakes on the San Andreas fault: Effects of nonlinear crustal rheology

    Science.gov (United States)

    Reches, Ze'ev; Schubert, Gerald; Anderson, Charles

    1994-01-01

    We analyze the cycle of great earthquakes along the San Andreas fault with a finite element numerical model of deformation in a crust with a nonlinear viscoelastic rheology. The viscous component of deformation has an effective viscosity that depends exponentially on the inverse absolute temperature and nonlinearity on the shear stress; the elastic deformation is linear. Crustal thickness and temperature are constrained by seismic and heat flow data for California. The models are for anti plane strain in a 25-km-thick crustal layer having a very long, vertical strike-slip fault; the crustal block extends 250 km to either side of the fault. During the earthquake cycle that lasts 160 years, a constant plate velocity v(sub p)/2 = 17.5 mm yr is applied to the base of the crust and to the vertical end of the crustal block 250 km away from the fault. The upper half of the fault is locked during the interseismic period, while its lower half slips at the constant plate velocity. The locked part of the fault is moved abruptly 2.8 m every 160 years to simulate great earthquakes. The results are sensitive to crustal rheology. Models with quartzite-like rheology display profound transient stages in the velocity, displacement, and stress fields. The predicted transient zone extends about 3-4 times the crustal thickness on each side of the fault, significantly wider than the zone of deformation in elastic models. Models with diabase-like rheology behave similarly to elastic models and exhibit no transient stages. The model predictions are compared with geodetic observations of fault-parallel velocities in northern and central California and local rates of shear strain along the San Andreas fault. The observations are best fit by models which are 10-100 times less viscous than a quartzite-like rheology. Since the lower crust in California is composed of intermediate to mafic rocks, the present result suggests that the in situ viscosity of the crustal rock is orders of magnitude

  18. Global crustal movement and tectonic plate boundary deformation constrained by the ITRF2008

    Directory of Open Access Journals (Sweden)

    Zhu Ze

    2012-08-01

    Full Text Available On the basis of the newly released International Terrestrial Reference Frame(ITRF2008 by the International Earth Rotation Service (IERS, a new global plate model ITRF2008 plate for the major plates is established. This ITRF2008-derived model is analyzed in comparison with NNR-NUVEL1A model, which is mainly based on geological and geophysical data. The Eurasia and Pacific plates display obvious differences in terms of the velocity fields derived from the two plate motion models. Plate acceleration is also introduced to characterize the differences of the two velocity fields which obtained from ITRF2008 -plate and NNR-NUVEL1A models for major individual plates. The results show that the Africa, South America and Eurasia plates are undergoing acceleration, while the North America and Australia plates are in the state of deceleration motion.

  19. Crustal parameters in the Iberian Peninsula

    Science.gov (United States)

    Banda, E.

    1988-06-01

    The structure of the crust in the Iberian Peninsula has been investigated for the last 15 years by Spanish and Portuguese groups in close collaboration with other European institutions. The first experiments were carried out in Portugal (Mueller et al., 1973) with the aim of investigating the crustal structure of the Hercynian belt in the southwest corner of the Iberian peninsula. Other experiments have been subsequently realized to study different aspects of the crust in various regions of Portugal. In Spain the main effort has been focused in Alpine areas, with the first experiments in the Alboran Sea and the Betic Cordilleras (Working Group for Deep Seismic Sounding in Spain, 1974-1975, 1977; Working Group for Deep Seismic Sounding in the Alboran Sea, 1974-1975, 1978). Follow-up experiments until 1981 completed the work in the Betic Cordillera. Extensive experiments were carried out in the Pyrenees in 1978. Further surveys covered the Balearic Islands in 1976, the Valencia Trough in 1976 and 1983, and the Celtiberian Chain (or Iberic system) in 1981. The Hercynian belt has only been studied in detail in the northwest corner of Spain in 1982, with smaller studies in the central Iberian Massif in 1976 and 1986. Mostaanpour (1984) has compiled some crustal parameters (crustal thickness, average crustal velocity and Pn velocity) for western Europe. Meanwhile, more complete data are available for the Iberian Peninsula. The results presented here were derived from a large number of seismic refraction experiments which have been carried out mostly along or close to coastal areas of the Iberian Peninsula. Offshore explosions of various sizes were used as the energy source in most cases, in addition to some quarry blasts. Unfortunately this leaves most of the inner part of the Iberian Peninsula unsurveyed. Our purpose is to summarize some of the crustal parameters obtained so far and to detail the appropriate literature for the interested reader.

  20. Ring-constrained Join

    DEFF Research Database (Denmark)

    Yiu, Man Lung; Karras, Panagiotis; Mamoulis, Nikos

    2008-01-01

    . This new operation has important applications in decision support, e.g., placing recycling stations at fair locations between restaurants and residential complexes. Clearly, RCJ is defined based on a geometric constraint but not on distances between points. Thus, our operation is fundamentally different......We introduce a novel spatial join operator, the ring-constrained join (RCJ). Given two sets P and Q of spatial points, the result of RCJ consists of pairs (p, q) (where p ε P, q ε Q) satisfying an intuitive geometric constraint: the smallest circle enclosing p and q contains no other points in P, Q...

  1. Origin of primitive ocean island basalts by crustal gabbro assimilation and multiple recharge of plume-derived melts

    Science.gov (United States)

    Borisova, Anastassia Y.; Bohrson, Wendy A.; Grégoire, Michel

    2017-07-01

    Chemical Geodynamics relies on a paradigm that the isotopic composition of ocean island basalt (OIB) represents equilibrium with its primary mantle sources. However, the discovery of huge isotopic heterogeneity within olivine-hosted melt inclusions in primitive basalts from Kerguelen, Iceland, Hawaii and South Pacific Polynesia islands implies open-system behavior of OIBs, where during magma residence and transport, basaltic melts are contaminated by surrounding lithosphere. To constrain the processes of crustal assimilation by OIBs, we employed the Magma Chamber Simulator (MCS), an energy-constrained thermodynamic model of recharge, assimilation and fractional crystallization. For a case study of the 21-19 Ma basaltic series, the most primitive series ever found among the Kerguelen OIBs, we performed sixty-seven simulations in the pressure range from 0.2 to 1.0 GPa using compositions of olivine-hosted melt inclusions as parental magmas, and metagabbro xenoliths from the Kerguelen Archipelago as wallrock. MCS modeling requires that the assimilant is anatectic crustal melts (P2O5 ≤ 0.4 wt.% contents) derived from the Kerguelen oceanic metagabbro wallrock. To best fit the phenocryst assemblage observed in the investigated basaltic series, recharge of relatively large masses of hydrous primitive basaltic melts (H2O = 2-3 wt%; MgO = 7-10 wt.%) into a middle crustal chamber at 0.2 to 0.3 GPa is required. Our results thus highlight the important impact that crustal gabbro assimilation and mantle recharge can have on the geochemistry of mantle-derived olivine-phyric OIBs. The importance of crustal assimilation affecting primitive plume-derived basaltic melts underscores that isotopic and chemical equilibrium between ocean island basalts and associated deep plume mantle source(s) may be the exception rather than the rule.

  2. Sharp spatially constrained inversion

    DEFF Research Database (Denmark)

    Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.

    2013-01-01

    We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....

  3. MAGNETAR FIELD EVOLUTION AND CRUSTAL PLASTICITY

    International Nuclear Information System (INIS)

    Lander, S. K.

    2016-01-01

    The activity of magnetars is believed to be powered by colossal magnetic energy reservoirs. We sketch an evolutionary picture in which internal field evolution in magnetars generates a twisted corona, from which energy may be released suddenly in a single giant flare, or more gradually through smaller outbursts and persistent emission. Given the ages of magnetars and the energy of their giant flares, we suggest that their evolution is driven by a novel mechanism: magnetic flux transport/decay due to persistent plastic flow in the crust, which would invalidate the common assumption that the crustal lattice is static and evolves only under Hall drift and Ohmic decay. We estimate the field strength required to induce plastic flow as a function of crustal depth, and the viscosity of the plastic phase. The star’s superconducting core may also play a role in magnetar field evolution, depending on the star’s spindown history and how rotational vortices and magnetic fluxtubes interact.

  4. Crustal Magnetic Field Anomalies and Global Tectonics

    Science.gov (United States)

    Storetvedt, Karsten

    2014-05-01

    A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents

  5. Crustal structure along the DESERT 2000 Transect inferred from 3-D gravity modelling

    Science.gov (United States)

    El-Kelani, R.; Goetze, H.; Rybakov, M.; Hassouneh, M.; Schmidt, S.

    2003-12-01

    A three-dimensional interpretation of the newly compiled Bouguer anomaly map is part of the DESERT 2000 Transect. That is multi-disciplinary and multinational project studying for first time the Dead Sea Transform (DST) fault system (DST) from the Mediterranean Sea to Saudi Arabia across the international border in the NW-SE direction. The negative Bouguer anomalies (with magnitude reached "C130 mGal), located into transform valley, are caused by the internal sedimentary basins filled by the light density young sediments (­Y10 km). A high-resolution 3-D model constrained with the seismic results reveals a possible crustal thickness and density distribution beneath the DST valley. The inferred zone of intrusion coincides with the maximum gravity anomaly over the eastern flank of the DST. The intrusion is displaced at different sectors along the NW-SE direction. The zone of the maximum crustal thinning (­30 km) is attained in the western sector at the Mediterranean. The southeastern plateau, on the other hand, shows by far the largest crustal thickness in the region (38-42 km). Linked to the left lateral movement of ~ 105 km at the boundary between the African and Arabian plate, and constrained with the DESERT 2000 seismic data, a small asymmetric topography of the Moho beneath the DST was modelled. The thickness and density of the crust suggest that a continental crust underlies the DST. The deep basins, the relatively large nature of the intrusion and the asymmetric topography of the Moho lead to the conclusion that a small-scale asthenospheric upwelling(?) might be responsible for the thinning of the crust and subsequent rifting of the Dead Sea graben during the left lateral movement.

  6. Early cosmology constrained

    Energy Technology Data Exchange (ETDEWEB)

    Verde, Licia; Jimenez, Raul [Institute of Cosmos Sciences, University of Barcelona, IEEC-UB, Martí Franquès, 1, E08028 Barcelona (Spain); Bellini, Emilio [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Pigozzo, Cassio [Instituto de Física, Universidade Federal da Bahia, Salvador, BA (Brazil); Heavens, Alan F., E-mail: liciaverde@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: cpigozzo@ufba.br, E-mail: a.heavens@imperial.ac.uk, E-mail: raul.jimenez@icc.ub.edu [Imperial Centre for Inference and Cosmology (ICIC), Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2017-04-01

    We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter Ω{sub MR} < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < N {sub eff} < 3.2 when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is r {sub s} = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to r {sub s} = 150 ± 5 Mpc.

  7. Constraining neutrinoless double beta decay

    International Nuclear Information System (INIS)

    Dorame, L.; Meloni, D.; Morisi, S.; Peinado, E.; Valle, J.W.F.

    2012-01-01

    A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum-rules (MSR). We show how these theories may constrain the absolute scale of neutrino mass, leading in most of the cases to a lower bound on the neutrinoless double beta decay effective amplitude.

  8. Modes of continental extension in a crustal wedge

    KAUST Repository

    Wu, Guangliang

    2015-07-01

    © 2015 Elsevier B.V. We ran numerical experiments of the extension of a crustal wedge as an approximation to extension in an orogenic belt or a continental margin. We study the effects of the strength of the lower crust and of a weak mid-crustal shear zone on the resulting extension styles. A weak mid-crustal shear zone effectively decouples upper crustal extension from lower crustal flow. Without the mid-crustal shear zone, the degree of coupling between the upper and the lower crust increases and extension of the whole crust tends to focus on the thickest part of the wedge. We identify three distinct modes of extension determined by the strength of the lower crust, which are characterized by 1) localized, asymmetric crustal exhumation in a single massif when the lower crust is weak, 2) the formation of rolling-hinge normal faults and the exhumation of lower crust in multiple core complexes with an intermediate strength lower crust, and 3) distributed domino faulting over the weak mid-crustal shear zone when the lower crust is strong. A frictionally stronger mid-crustal shear zone does not change the overall model behaviors but extension occurred over multiple rolling-hinges. The 3 modes of extension share characteristics similar to geological models proposed to explain the formation of metamorphic core complexes: 1) the crustal flow model for the weak lower crust, 2) the rolling-hinge and crustal flow models when the lower crust is intermediate and 3) the flexural uplift model when the lower crust is strong. Finally we show that the intensity of decoupling between the far field extension and lower crustal flow driven by the regional pressure gradient in the wedge control the overall style of extension in the models.

  9. Modes of continental extension in a crustal wedge

    KAUST Repository

    Wu, Guangliang; Lavier, Luc L.; Choi, Eunseo

    2015-01-01

    © 2015 Elsevier B.V. We ran numerical experiments of the extension of a crustal wedge as an approximation to extension in an orogenic belt or a continental margin. We study the effects of the strength of the lower crust and of a weak mid-crustal shear zone on the resulting extension styles. A weak mid-crustal shear zone effectively decouples upper crustal extension from lower crustal flow. Without the mid-crustal shear zone, the degree of coupling between the upper and the lower crust increases and extension of the whole crust tends to focus on the thickest part of the wedge. We identify three distinct modes of extension determined by the strength of the lower crust, which are characterized by 1) localized, asymmetric crustal exhumation in a single massif when the lower crust is weak, 2) the formation of rolling-hinge normal faults and the exhumation of lower crust in multiple core complexes with an intermediate strength lower crust, and 3) distributed domino faulting over the weak mid-crustal shear zone when the lower crust is strong. A frictionally stronger mid-crustal shear zone does not change the overall model behaviors but extension occurred over multiple rolling-hinges. The 3 modes of extension share characteristics similar to geological models proposed to explain the formation of metamorphic core complexes: 1) the crustal flow model for the weak lower crust, 2) the rolling-hinge and crustal flow models when the lower crust is intermediate and 3) the flexural uplift model when the lower crust is strong. Finally we show that the intensity of decoupling between the far field extension and lower crustal flow driven by the regional pressure gradient in the wedge control the overall style of extension in the models.

  10. A tomographic image of upper crustal structure using P and S wave seismic refraction data in the southern granulite terrain (SGT), India

    Science.gov (United States)

    Rajendra Prasad, B.; Behera, Laxmidhar; Rao, P. Koteswara

    2006-07-01

    We present a 2-D tomographic P and S wave velocity (Vp and Vs) image with Vp/Vs ratios along N-S trending 220 km long deep seismic profile acquired in 2005, which traverses across major shear and tectonically disturbed zones in southern granulite terrain (SGT), India. The 2-D velocity model constrained down to maximum 8 km depth shows velocity anomalies (>0.2 km/s) beneath major shear zones with good spatial resolution (>0.05 km/s). The presence of high Vp (6.3-6.5 km/s), Vs (3.5-3.8 km/s), Vp/Vs (>1.75) and Poisson's ratio (0.25-0.29) indicate significant compositional changes of rocks at shallow depths (0.5 to 8 km) reveal rapid crustal exhumation of mid to lower crustal rocks. This crustal exhumation could be responsible due to Pan-African tectonothermal activity during Neoproterozoic period.

  11. Crustal Growth: In Defense of the Dogma

    Science.gov (United States)

    Albarede, F.; Blichert-Toft, J.; Guitreau, M.

    2012-12-01

    Plate tectonics was not even in its teens when Armstrong suggested that mantle and crust have interacted at steady-state over Earth's history. With the help of new geochemical tools and large-scale compilations, the concept of steady-state crust (as opposed to continuous crustal growth) is being revived with the implications that the equivalent of several volumes of present-day crust (PDCV) may have been subducted through geological times. Here we argue --or recall-- that four different lines of evidence invalidate this model. (i) The subduction filter must be particularly efficient for argon, even more so than for LILE and most other volatile elements. Atmosphere collects 40Ar degassed from both the extant crust and the crust dragged down at subduction zones over geological time. Regardless of the residence time of the crust at the surface, the amount of atmospheric 40Ar limits subduction of continental crust into the mantle to < 30% of the PDCV [1]. (ii) EM II, the only component that undoubtedly represents subducted continental crust in oceanic basalts, is extremely uncommon. (iii) Crustal age histograms are irrepressibly episodic. It has been argued that erosion selectively removes the crust with the elusive ages [2]. Ages of detrital zircons, which in the selective erosion conjecture should fill the voids, do not support this view [3]. Episodicity is difficult to reconcile with a continental protolith isolated by the common geological processes working either at mid-ocean ridges or subduction zones. A role may be recognized for Wilson cycles, if they can be shown to have prevailed for the entire history of the Earth. Geochemistry demonstrates that superplume material makes up the crustal protolith of all the major juvenile provinces. (iv) The residence time in the mantle of the elements distinctive of the crust is similar to the age of the Earth or even longer [4]. Continental crust finds its source in the instabilities of the lower mantle and the irreversible

  12. Pb isotopes during crustal melting and magma mingling - A cautionary tale from the Miki Fjord macrodike, central east Greenland

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Lesher, Charles

    2010-01-01

    Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... grain boundaries during disequilibrium melting of the host rock by the mafic magma. The crustal melt involved in magma interactions was therefore heterogeneous with respect to Pb isotopes on a metre-scale. These results illustrate the difficulties inherent in interpreting isotopic variations...... in contaminated mafic magmas even when the end-members are well constrained by field relations. We show that the Pb isotopic composition of the crustal contaminants and contamination trajectories for the Miki Fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated...

  13. Constrained evolution in numerical relativity

    Science.gov (United States)

    Anderson, Matthew William

    The strongest potential source of gravitational radiation for current and future detectors is the merger of binary black holes. Full numerical simulation of such mergers can provide realistic signal predictions and enhance the probability of detection. Numerical simulation of the Einstein equations, however, is fraught with difficulty. Stability even in static test cases of single black holes has proven elusive. Common to unstable simulations is the growth of constraint violations. This work examines the effect of controlling the growth of constraint violations by solving the constraints periodically during a simulation, an approach called constrained evolution. The effects of constrained evolution are contrasted with the results of unconstrained evolution, evolution where the constraints are not solved during the course of a simulation. Two different formulations of the Einstein equations are examined: the standard ADM formulation and the generalized Frittelli-Reula formulation. In most cases constrained evolution vastly improves the stability of a simulation at minimal computational cost when compared with unconstrained evolution. However, in the more demanding test cases examined, constrained evolution fails to produce simulations with long-term stability in spite of producing improvements in simulation lifetime when compared with unconstrained evolution. Constrained evolution is also examined in conjunction with a wide variety of promising numerical techniques, including mesh refinement and overlapping Cartesian and spherical computational grids. Constrained evolution in boosted black hole spacetimes is investigated using overlapping grids. Constrained evolution proves to be central to the host of innovations required in carrying out such intensive simulations.

  14. Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

    Science.gov (United States)

    Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

    2016-04-01

    The Porcupine Basin is a tongue-shaped offshore basin SW of Ireland that formed during the opening of the North Atlantic Ocean. Its history of development involved several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on subsidence analysis, showed that stretching factors (β) in the northern part of the basin are 6. However, recent studies based on seismic reflection and refraction profiles concluded that β in places along the basin axis were significantly higher, and suggested the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Constraining β and the processes related to the formation of the basin will provide insights into aspects such as the tectonic response to lithospheric extension and the thermal evolution of the basin. Here we present the tomography results of five wide-angle seismic (WAS) profiles acquired across and along the basin axis. We used a travel time inversion method to model the WAS data and obtain P-wave velocity (Vp) models of the crust and uppermost mantle, together with the geometry of the main geological interfaces along each of these lines. Coincident seismic reflection profiles to each WAS line were also used to integrate the tectonic structure with the Vp model. These results improved constrains on the location of the base of the crust and allow to estimate maximum β (βmax) along each profile. The analysis shows that βmax values in the northern part of the basin are 5-6 times larger than estimates based on subsidence analysis. Towards the south, βmax increases up to 10, but then rapidly decreases to 3.3 southwards. These values are well within the range of crustal extension at which the crust becomes entirely brittle at magma-poor margins allowing the formation of major crustal faulting and serpentinization of the mantle. In agreement with this observation, Vp

  15. Crustal permeability: Introduction to the special issue

    Science.gov (United States)

    Ingebritsen, Steven E.; Gleeson, Tom

    2015-01-01

    The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

  16. Shallow Crustal Thermal Structures of Central Taiwan Foothills Region

    Directory of Open Access Journals (Sweden)

    Shao-Kai Wu

    2013-01-01

    Full Text Available Crustal thermal structures are closely related to metamorphism, rock rheology, exhumation processes, hydrocarbon maturation levels, frictional faulting and other processes. Drilling is the most direct way to access the temperature fields in the shallow crust. However, a regional drilling program for geological investigation is usually very expensive. Recently, a large-scale in-situ investigation program in the Western Foothills of Central Taiwan was carried out, providing a rare opportunity to conduct heat flow measurements in this region where there are debates as to whether previous measured heat flows are representative of the thermal state in this region. We successfully collected 28 geothermal gradients from these wells and converted them into heat flows. The new heat flow dataset is consistent with previous heat flows, which shows that the thermal structures of Central Taiwan are different from that of other subduction accretionary prisms. We then combine all the available heat flow information to analyze the frictional parameters of the Chelungpu fault zone that ruptured during the 1999, Chi-Chi, Taiwan, earthquake. The heat flow dataset gave consistent results compared with the frictional parameters derived from another independent study that used cores recovered from the Chelungpu fault zone at depth. This study also shows that it is suitable for using heat-flow data obtained from shallow subsurface to constrain thrusting faulting parameters, similar to what had been done for the strike-slip San Andreas Fault in California. Additional fieldworks are planned to study heat flows in other mountainous regions of Taiwan for more advanced geodynamic modeling efforts.

  17. Mechanism of crustal extension in the Laxmi Basin, Arabian Sea

    Directory of Open Access Journals (Sweden)

    Anju Pandey

    2015-11-01

    Full Text Available Continental rifting and magmatism has been extensively studied worldwide as it is believed that continental rifting, break up of continents and associated magmatism lead to genesis of new oceanic crust. However, various regions of the world show that these processes may lead to genesis of other types of crust than the oceanic crust. Laxmi Basin in the western continental margin of the India is one such region with an enigmatic crust. Due to its extreme strategic significance for the palaeogeographic reconstruction of continents during Cretaceous continental breakup of India, this basin has attracted various workers for more than two decades. However, still the issue of nature of crust in the basin remains controversial. In this contribution, in order to identify nature of crust, mechanism of continental extension in the Laxmi Basin has been studied for the first time through newly acquired seismic data from the basin. Here, we propose a plausible mechanism of crustal extension in the Laxmi Basin which eventually constrains the nature of crust of the Laxmi Basin. We have demonstrated that the crust in the Laxmi Basin can be categorised in two zones of stretched and transitional crust. In the stretched zone several fault bounded horst and graben structures are identified which preserve syn- and post-rift sediments along with different periods of hiatus in sedimentations as unconformities. These faults are identified as listric faults in the upper crust which sole out in the detachment faults. Detachment faults decouples the upper brittle and lower ductile crust. The transitional crust is identified as heavily intruded by sills and basaltic volcanic which were emplaced due to melting of subcontinental mantle (SCM after hyper-stretching of crust and serpentinisation of the SCM. Panikkar Ridge is proposed to be one such basaltic volcanic body derived from melting of lower part of the SCM.

  18. Thin Crust and High Crustal Vp/Vs beneath the Central Armenia Plateau of the Lesser Caucasus

    Science.gov (United States)

    Tseng, T. L.; Lin, C. M.; Huang, B. S.; Karakhanyan, A.

    2017-12-01

    Armenia volcanic highland is part of the Lesser Caucasus directly connected with the East Anatolian Plateau to the west and Iranian Plateau to the east. Abundant Quaternary volcanoes in Armenia are the youngest among those associated with post-collision of Arabia-Eurasian since Miocene ( 11 Ma). In this study, teleseismic receiver functions were analyzed from a temporary array to constrain the crustal structures under Armenia and the vicinity. The results show that the Moho depth is shallowest beneath central Armenia where the estimated crustal thickness is 32 km with high averaged crustal Vp/Vs of 1.8-2.0 using H-κ technique. The high crustal Vp/Vs is distributed in a wider area but thin crust is confined more locally around stratovolcano Aragats, whose last eruption was about 0.5 Ma. High crustal Vp/Vs value approaching to 2.1 is found near East of volcano Ghegam complex and NW of volcano Ararat with last dated ages of 0.5 and <0.1 Ma, respectively. Such high Vp/Vs (2.0) cannot be explained without high mafic content and the presence of partial melt in the crust. The 1-D velocity models inverted demonstrate that the partial melt is more likely in the low-velocity layer of the lower crust. To support the unusually thin crust in central Armenia, it requires additional thermal buoyancy in the uppermost mantle which is consistent with regionally low Pn velocity found in previous studies. We propose that the volcanism here is facilitated by the stretches of lithosphere.

  19. Lightweight cryptography for constrained devices

    DEFF Research Database (Denmark)

    Alippi, Cesare; Bogdanov, Andrey; Regazzoni, Francesco

    2014-01-01

    Lightweight cryptography is a rapidly evolving research field that responds to the request for security in resource constrained devices. This need arises from crucial pervasive IT applications, such as those based on RFID tags where cost and energy constraints drastically limit the solution...... complexity, with the consequence that traditional cryptography solutions become too costly to be implemented. In this paper, we survey design strategies and techniques suitable for implementing security primitives in constrained devices....

  20. Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data: The SIMA experiment

    Science.gov (United States)

    Ayarza, P.; Carbonell, R.; Teixell, A.; Palomeras, I.; Martí, D.; Kchikach, A.; Harnafi, M.; Levander, A.; Gallart, J.; Arboleya, M. L.; Alcalde, J.; Fernández, M.; Charroud, M.; Amrhar, M.

    2014-05-01

    The crustal structure and topography of the Moho boundary beneath the Atlas Mountains of Morocco has been constrained by a controlled source, wide-angle seismic reflection transect: the SIMA experiment. This paper presents the first results of this project, consisting of an almost 700 km long, high-resolution seismic profile acquired from the Sahara craton across the High and the Middle Atlas and the Rif Mountains. The interpretation of this seismic data set is based on forward modeling by raytracing, and has resulted in a detailed crustal structure and velocity model for the Atlas Mountains. Results indicate that the High Atlas features a moderate crustal thickness, with the Moho located at a minimum depth of 35 km to the S and at around 31 km to the N, in the Middle Atlas. Upper crustal shortening is resolved at depth through a crustal root where the Saharan crust underthrusts the northern Moroccan crust. This feature defines a lower crust imbrication that, locally, places the Moho boundary at ˜40-41 km depth in the northern part of the High Atlas. The P-wave velocity model is characterized by relatively low velocities, mostly in the lower crust and upper mantle, when compared to other active orogens and continental regions. These low deep crustal velocities together with other geophysical observables such as conductivity estimates derived from MT measurements, moderate Bouguer gravity anomaly, high heat flow, and surface exposures of recent alkaline volcanism lead to a model where partial melts are currently emplaced at deep crustal levels and in the upper mantle. The resulting model supports the existence of a mantle upwelling as mechanism that would contribute significantly to sustain the High Atlas topography. However, the detailed Moho geometry deduced in this work should lead to a revision of the exact geometry and position of this mantle feature and will require new modeling efforts.

  1. Oblique reactivation of lithosphere-scale lineaments controls rift physiography - the upper-crustal expression of the Sorgenfrei-Tornquist Zone, offshore southern Norway

    Science.gov (United States)

    Phillips, Thomas B.; Jackson, Christopher A.-L.; Bell, Rebecca E.; Duffy, Oliver B.

    2018-04-01

    Pre-existing structures within sub-crustal lithosphere may localise stresses during subsequent tectonic events, resulting in complex fault systems at upper-crustal levels. As these sub-crustal structures are difficult to resolve at great depths, the evolution of kinematically and perhaps geometrically linked upper-crustal fault populations can offer insights into their deformation history, including when and how they reactivate and accommodate stresses during later tectonic events. In this study, we use borehole-constrained 2-D and 3-D seismic reflection data to investigate the structural development of the Farsund Basin, offshore southern Norway. We use throw-length (T-x) analysis and fault displacement backstripping techniques to determine the geometric and kinematic evolution of N-S- and E-W-striking upper-crustal fault populations during the multiphase evolution of the Farsund Basin. N-S-striking faults were active during the Triassic, prior to a period of sinistral strike-slip activity along E-W-striking faults during the Early Jurassic, which represented a hitherto undocumented phase of activity in this area. These E-W-striking upper-crustal faults are later obliquely reactivated under a dextral stress regime during the Early Cretaceous, with new faults also propagating away from pre-existing ones, representing a switch to a predominantly dextral sense of motion. The E-W faults within the Farsund Basin are interpreted to extend through the crust to the Moho and link with the Sorgenfrei-Tornquist Zone, a lithosphere-scale lineament, identified within the sub-crustal lithosphere, that extends > 1000 km across central Europe. Based on this geometric linkage, we infer that the E-W-striking faults represent the upper-crustal component of the Sorgenfrei-Tornquist Zone and that the Sorgenfrei-Tornquist Zone represents a long-lived lithosphere-scale lineament that is periodically reactivated throughout its protracted geological history. The upper-crustal component of

  2. Crustal evolution inferred from apollo magnetic measurements

    International Nuclear Information System (INIS)

    Dyal, P.; Daily, W.D.; Vanyan, L.L.

    1978-09-01

    Magnetic field and solar wind plasma density measurements were analyzed to determine the scale size characteristics of remanent fields at the Apollo 12, 15, and 16 landing sites. Theoretical model calculations of the field-plasma interaction, involving diffusion of the remanent field into the solar plasma, were compared to the data. The information provided by all these experiments shows that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized during early crustal evolution. Bombardment and subsequent gardening of the upper layers of these magnetized regions left randomly oriented, smaller scale (5 to 10 km) magnetic sources close to the surface. The larger scale size fields of magnitude approximately 0.1 gammas are measured by the orbiting subsatellite experiments and the small scale sized remanent fields of magnitude approximately 100 gammas are measured by the surface experiments

  3. GPS-derived crustal deformation in Azerbaijan

    Science.gov (United States)

    Safarov, Rafig; Mammadov, Samir; Kadirov, Fakhraddin

    2017-04-01

    Crustal deformations of the Earth's crust in Azerbaijan were studied based on GPS measurements. The GPS velocity vectors for Azerbaijan, Iran, Georgia, and Armenia were used in order to estimate the deformation rates. It is found that compression is observable along the Greater Caucasus, in Gobustan, the Kura depression, Nakhchyvan Autonomous Republic, and adjacent areas of Iran. The axes of compression/contraction of the crust in the Greater Caucasus region are oriented in the S-NE direction. The maximum strain rate is observed in the zone of mud volcanism at the SHIK site (Shykhlar), which is marked by a sharp change in the direction of the compression axes (SW-NE). It is revealed that the deformation field also includes the zones where strain rates are very low. These zones include the Caspian-Guba and northern Gobustan areas, characterized by extensive development of mud volcanism. The extension zones are confined to the Lesser Caucasus and are revealed in the Gyadabei (GEDA) and Shusha (SHOU) areas. The analysis of GPS data for the territory of Azerbaijan and neighboring countries reveals the heterogeneous patterns of strain field in the region. This fact suggests that the block model is most adequate for describing the structure of the studied region. The increase in the number of GPS stations would promote increasing the degree of detail in the reconstructions of the deformation field and identifying the microplate boundaries.It is concluded that the predominant factor responsible for the eruption of mud volcanoes is the intensity of gasgeneration processes in the earth's interior, while deformation processes play the role of a trigger. The zone of the epicenters of strong earthquakes is correlated to the gradient zone in the crustal strain rates.

  4. Fractal behavior in continental crustal heat production

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    N. Vedanti

    2011-02-01

    Full Text Available The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India, Kaapvaal craton (South Africa, Baltic shield (Kola, Russia, Hidaka metamorphic belt (Japan, Nissho pluton (Japan and Continental Deep Drilling site (KTB, Germany. The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  5. Fractal behavior in continental crustal heat production

    Science.gov (United States)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  6. The Glacial BuzzSaw, Isostasy, and Global Crustal Models

    Science.gov (United States)

    Levander, A.; Oncken, O.; Niu, F.

    2015-12-01

    The glacial buzzsaw hypothesis predicts that maximum elevations in orogens at high latitudes are depressed relative to temperate latitudes, as maximum elevation and hypsography of glaciated orogens are functions of the glacial equilibrium line altitude (ELA) and the modern and last glacial maximum (LGM) snowlines. As a consequence crustal thickness, density, or both must change with increasing latitude to maintain isostatic balance. For Airy compensation crustal thickness should decrease toward polar latitudes, whereas for Pratt compensation crustal densities should increase. For similar convergence rates, higher latitude orogens should have higher grade, and presumably higher density rocks in the crustal column due to more efficient glacial erosion. We have examined a number of global and regional crustal models to see if these predictions appear in the models. Crustal thickness is straightforward to examine, crustal density less so. The different crustal models generally agree with one another, but do show some major differences. We used a standard tectonic classification scheme of the crust for data selection. The globally averaged orogens show crustal thicknesses that decrease toward high latitudes, almost reflecting topography, in both the individual crustal models and the models averaged together. The most convincing is the western hemisphere cordillera, where elevations and crustal thicknesses decrease toward the poles, and also toward lower latitudes (the equatorial minimum is at ~12oN). The elevation differences and Airy prediction of crustal thickness changes are in reasonable agreement in the North American Cordillera, but in South America the observed crustal thickness change is larger than the Airy prediction. The Alpine-Himalayan chain shows similar trends, however the strike of the chain makes interpretation ambiguous. We also examined cratons with ice sheets during the last glacial period to see if continental glaciation also thins the crust toward

  7. Variation in Crustal Structure of the Lesser Caucasus Region from Teleseismic Receiver Functions

    Science.gov (United States)

    Lin, C. M.; Tseng, T. L.; Huang, B. S.; Legendre, C. P.; Karakhanian, A.

    2016-12-01

    The Caucasus, including the mountains of Greater and Lesser Caucasus, is formed by the continental collision between Arabia and Eurasia. The crustal thickness for this region was mostly constrained by joint analysis of receiver functions and surface waves. Although the thickest value of 52 km was reported under the Lesser Caucasus, the resolution of earlier studies were often limited by sparse array. Large gradient across Moho also makes the definition of Moho difficult. Moreover, higher value of the Vp/Vs ratio is commonly reported in the northeastern Turkey but no estimates had been made for the Caucasus. To further investigate the detail structure around the Lesser Caucasus, we constructed a new seismic network in Georgia and Armenia. We also include other broadband stations to enhance the coverage. The average interval in the Lesser Caucasus is roughly 30 km, much denser than any previous experiments. We selected P-waveforms from teleseismic earthquakes during the operation (January 2012 - June 2016) to calculate receiver functions and then estimate the crustal thickness (H) and Vp/Vs ratio (k) with the H-k stacking technique. Our preliminary results show that Moho depth increases from 40 km under the northeastern Turkey to 50 km beneath northern Georgia, no station with Moho deeper than 50 km under the Lesser Caucasus. The Vp/Vs ratios in the northeastern Anatolian plateau are around 1.8, which is slightly higher than the average of global continents but consistent with the previous estimates. Further to the east, some stations show anomalously higher Vp/Vs ratio in central & southern Armenia that may be associated with Holocene volcanism. In the future, we plan to join locally measured dispersion curves to invert the velocity model without velocity-depth trade-off. We expect to resolve the velocity variations of the crust beneath this region in small scale that may be tied to the continental collision and surface volcanism. Keywords: Caucasus, receiver

  8. Crustal Stretching Style and Lower Crust Flow of the South China Sea Northern Margin

    Science.gov (United States)

    Bai, Y.; Dong, D.; Runlin, D.

    2017-12-01

    There is a controversy about crustal stretching style of the South China Sea (SCS) northern margin mainly due to considerable uncertainty of stretching factor estimation, for example, as much as 40% of upper crust extension (Walsh et al., 1991) would be lost by seismic profiles due to poor resolution. To discover and understand crustal stretching style and lower crustal flow on the whole, we map the Moho and Conrad geometries based on gravity inversion constrained by deep seismic profiles, then according to the assumption of upper and lower crust initial thickness, upper and lower crust stretching factors are estimated. According to the comparison between upper and lower crust stretching factors, the SCS northern margin could be segmented into three parts, (1) sediment basins where upper crust is stretched more than lower crust, (2) COT regions where lower crust is stretched more than upper crust, (3) other regions where the two layers have similar stretching factors. Stretching factor map shows that lower crust flow happened in both of COT and sediment basin regions where upper crust decouples with lower crust due to high temperature. Pressure contrast by sediment loading in basins and erosion in sediment-source regions will lead to lower crust flow away from sediment sink to source. Decoupled and fractured upper crust is stretched further by sediment loading and the following compensation would result in relatively thick lower crust than upper crust. In COT regions with thin sediment coverage, low-viscosity lower crust is easier to thin in extensional environment, also the lower crust tends to flow away induced by magma upwelling. Therefore, continental crust on the margin is not stretching in a constant way but varies with the tectonic setting changes. This work is supported by National Natural Science Foundation of China (Grant No. 41506055, 41476042) and Fundamental Research Funds for the Central Universities China (No.17CX02003A).

  9. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    Science.gov (United States)

    Rudnick, R. L.; Liu, X. M.

    2012-04-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  10. Quantitative tectonic reconstructions of Zealandia based on crustal thickness estimates

    Science.gov (United States)

    Grobys, Jan W. G.; Gohl, Karsten; Eagles, Graeme

    2008-01-01

    Zealandia is a key piece in the plate reconstruction of Gondwana. The positions of its submarine plateaus are major constraints on the best fit and breakup involving New Zealand, Australia, Antarctica, and associated microplates. As the submarine plateaus surrounding New Zealand consist of extended and highly extended continental crust, classic plate tectonic reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly. However, if the early breakup history shall be reconstructed, it is crucial to consider crustal stretching in a plate-tectonic reconstruction. We present a reconstruction of the basins around New Zealand (Great South Basin, Bounty Trough, and New Caledonia Basin) based on crustal balancing, an approach that takes into account the rifting and thinning processes affecting continental crust. In a first step, we computed a crustal thickness map of Zealandia using seismic, seismological, and gravity data. The crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20-24 km and the basins to have a thickness of 12-16 km. We assumed that a reconstruction of Zealandia should close the basins and lead to a most uniform crustal thickness. We used the standard deviation of the reconstructed crustal thickness as a measure of uniformity. The reconstruction of the Campbell Plateau area shows that the amount of extension in the Bounty Trough and the Great South Basin is far smaller than previously thought. Our results indicate that the extension of the Bounty Trough and Great South Basin occurred simultaneously.

  11. Crustal structure of the Murray Ridge, northwest Indian Ocean, from wide-angle seismic data

    Science.gov (United States)

    Minshull, T. A.; Edwards, R. A.; Flueh, E. R.

    2015-07-01

    The Murray Ridge/Dalrymple Trough system forms the boundary between the Indian and Arabian plates in the northern Arabian Sea. Geodetic constraints from the surrounding continents suggest that this plate boundary is undergoing oblique extension at a rate of a few millimetres per year. We present wide-angle seismic data that constrains the composition of the Ridge and of adjacent lithosphere beneath the Indus Fan. We infer that Murray Ridge, like the adjacent Dalrymple Trough, is underlain by continental crust, while a thin crustal section beneath the Indus Fan represents thinned continental crust or exhumed serpentinized mantle that forms part of a magma-poor rifted margin. Changes in crustal structure across the Murray Ridge and Dalrymple Trough can explain short-wavelength gravity anomalies, but a long-wavelength anomaly must be attributed to deeper density contrasts that may result from a large age contrast across the plate boundary. The origin of this fragment of continental crust remains enigmatic, but the presence of basement fabrics to the south that are roughly parallel to Murray Ridge suggests that it separated from the India/Seychelles/Madagascar block by extension during early breakup of Gondwana.

  12. Application of SAR interferometry to low-rate crustal deformation fields

    Science.gov (United States)

    Vincent, Paul

    Differential SAR interferometry is applied to the study of low-rate interseismic crustal deformation fields along three regions of the San Adreas fault system: Salton Sea (southernmost region), Pinto Mountain fault (south-central region), and San Francisco Bay (northern region). New techniques are developed to analyze and model these low-rate deformation fields including constrained horizontal-vertical component deconvolution, deformation phase pattern analysis and strain field evolution modeling. Several new active faults were discovered as well as unmeasured activity on existing faults in the process of this SAR interferometry study. The feasibility and limitations of InSAR as a tool to study low-rate deformation fields is also addressed.

  13. Satellite measurements of the earth's crustal magnetic field

    Science.gov (United States)

    Schnetzler, C. C.

    1989-01-01

    The literature associated with the Magsat mission has evaluated the capabilities and limitations of satellite measurements of the earth's crustal magnetic field, and demonstrated that there exists a 300-3000 km magnetic field, related to major features in the earth's crust, which is primarily caused by induction. Due to its scale and sensitivity, satellite data have been useful in the development of models for such large crustal features as subduction zones, submarine platforms, continental accretion boundaries, and rifts. Attention is presently given to the lack of agreement between laboratory and satellite estimates of lower crustal magnetization.

  14. Crustal tracers in the atmosphere and ocean: Relating their concentrations, fluxes, and ages

    Science.gov (United States)

    Han, Qin

    Crustal tracers are important sources of key limiting nutrients (e.g., iron) in remote ocean regions where they have a large impact on global biogeochemical cycles. However, the atmospheric delivery of bio-available iron to oceans via mineral dust aerosol deposition is poorly constrained. This dissertation aims to improve understanding and model representation of oceanic dust deposition and to provide soluble iron flux maps by testing observations of crustal tracer concentrations and solubilities against predictions from two conceptual solubility models. First, we assemble a database of ocean surface dissolved Al and incorporate Al cycling into the global Biogeochemical Elemental Cycling (BEC) model. The observed Al concentrations show clear basin-scale differences that are useful for constraining dust deposition. The dynamic mixed layer depth and Al residence time in the BEC model significantly improve the simulated dissolved Al field. Some of the remaining model-data discrepancies appear related to the neglect of aerosol size, age, and air mass characteristics in estimating tracer solubility. Next, we develop the Mass-Age Tracking method (MAT) to efficiently and accurately estimate the mass-weighted age of tracers. We apply MAT to four sizes of desert dust aerosol and simulate, for the first time, global distributions of aerosol age in the atmosphere and at deposition. These dust size and age distributions at deposition, together with independent information on air mass acidity, allow us to test two simple yet plausible models for predicting the dissolution of mineral dust iron and aluminum during atmospheric transport. These models represent aerosol solubility as controlled (1) by a diffusive process leaching nutrients from the dust into equilibrium with the liquid water coating or (2) by a process that continually dissolves nutrients in proportion to the particle surface area. The surface-controlled model better captures the spatial pattern of observed

  15. Crustal structure beneath the Paleozoic Parnaíba Basin revealed by airborne gravity and magnetic data, Brazil

    Science.gov (United States)

    de Castroa, David L.; Fuck, Reinhardt A.; Phillips, Jeffrey D.; Vidotti, Roberta M.; Bezerra, Francisco H. R.; Dantas, Elton L.

    2014-01-01

    The Parnaíba Basin is a large Paleozoic syneclise in northeastern Brazil underlain by Precambrian crystalline basement, which comprises a complex lithostructural and tectonic framework formed during the Neoproterozoic–Eopaleozoic Brasiliano–Pan African orogenic collage. A sag basin up to 3.5 km thick and 1000 km long formed after the collage. The lithologic composition, structure, and role in the basin evolution of the underlying basement are the focus of this study. Airborne gravity and magnetic data were modeled to reveal the general crustal structure underneath the Parnaíba Basin. Results indicate that gravity and magnetic signatures delineate the main boundaries and structural trends of three cratonic areas and surrounding Neoproterozoic fold belts in the basement. Triangular-shaped basement inliers are geophysically defined in the central region of this continental-scale Neoproterozoic convergence zone. A 3-D gravity inversion constrained by seismological data reveals that basement inliers exhibit a 36–40.5 km deep crustal root, with borders defined by a high-density and thinner crust. Forward modeling of gravity and magnetic data indicates that lateral boundaries between crustal units are limited by Brasiliano shear zones, representing lithospheric sutures of the Amazonian and São Francisco Cratons, Tocantins Province and Parnaíba Block. In addition, coincident residual gravity, residual magnetic, and pseudo-gravity lows indicate two complex systems of Eopaleozoic rifts related to the initial phase of the sag deposition, which follow basement trends in several directions.

  16. Crustal seismic anisotropy beneath Shillong plateau - Assam valley in North East India: Shear-wave splitting analysis using local earthquakes

    Science.gov (United States)

    Sharma, Antara; Baruah, Santanu; Piccinini, Davide; Saikia, Sowrav; Phukan, Manoj K.; Chetia, Monisha; Kayal, J. R.

    2017-10-01

    We present crustal anisotropy estimates constrained by shear wave splitting (SWS) analysis using local earthquakes in the Shillong plateau and Assam valley area, North East India (NE India) region. Splitting parameters are determined using an automated cross-correlation (CC) method. We located 330 earthquakes recorded by 17 broadband seismic stations during 2001-2014 in the study area. Out of these 330 events, seismograms of 163 events are selected for the SWS analysis. Relatively small average delay times (0.039-0.084 s) indicate existence of moderate crack density in the crust below the study area. It is found that fast polarization directions vary from station to station depending on the regional stress system as well as geological conditions. The spatial pattern of crustal anisotropy in the area is controlled mostly by tectonic movement of the Indian plate towards NE. Presence of several E-W and N-S trending active faults in the area also play an important role on the observed pattern of crustal anisotropy.

  17. Constraining walking and custodial technicolor

    DEFF Research Database (Denmark)

    Foadi, Roshan; Frandsen, Mads Toudal; Sannino, Francesco

    2008-01-01

    We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level-custodial technicolor-and argue that these models...

  18. Early Neoarchaean A-type granitic magmatism by crustal reworking ...

    Indian Academy of Sciences (India)

    29

    marginal part of the Singhbhum craton whose origin and role in crustal evolution are poorly ...... Lu-Hf and Sm-Nd isotope systematics of Archean komatiites; Earth Planet. ..... Association Commission on New Minerals and Mineral Names; Can.

  19. Early Neoarchaean A-type granitic magmatism by crustal reworking ...

    Indian Academy of Sciences (India)

    29

    understand their petrogenesis and tectonic setting. .... crystallize from magmas with temperatures significantly higher than those of other intracrustal ...... blanketing by greenstone belt volcanic rocks, crustal thickening and hot subduction or a. 1.

  20. Continental crustal formation and recycling: Evidence from oceanic basalts

    Science.gov (United States)

    Saunders, A. D.; Tarney, J.; Norry, M. J.

    1988-01-01

    Despite the wealth of geochemical data for subduction-related magma types, and the clear importance of such magmas in the creation of continental crust, there is still no concensus about the relative magnitudes of crustal creation versus crustal destruction (i.e., recycling of crust into the mantle). The role of subducted sediment in the formation of the arc magmas is now well documented; but what proportion of sediment is taken into the deeper mantle? Integrated isotopic and trace element studies of magmas erupted far from presently active subduction zones, in particular basaltic rocks erupted in the ocean basins, are providing important information about the role of crustal recycling. By identifying potential chemical tracers, it is impossible to monitor the effects of crustal recycling, and produce models predicting the mass of material recycled into the mantle throughout long periods of geological time.

  1. Viscoelastic crustal deformation by magmatic intrusion: A case study in the Kutcharo caldera, eastern Hokkaido, Japan

    Science.gov (United States)

    Yamasaki, Tadashi; Kobayashi, Tomokazu; Wright, Tim J.; Fukahata, Yukitoshi

    2018-01-01

    Geodetic signals observed at volcanoes, particularly their temporal patterns, have required us to make the correlation between the surface displacement and magmatic process at depth in terms of viscoelastic crustal rheology. Here we use a parallelized 3-D finite element model to examine the response of the linear Maxwell viscoelastic crust and mantle to the inflation of a sill in order to show the characteristics of a long-term volcano deformation. In the model, an oblate-spheroidal sill is instantaneously or gradually inflated in a two-layered medium that consists of an elastic layer underlain by a viscoelastic layer. Our numerical experiments show that syn-inflation surface uplift is followed by post-inflation surface subsidence as the viscoelastic substrate relaxes. For gradual inflation events, the magnitude of inflation-induced uplift is reduced by the relaxation, through which the volume of a magma inferred by matching the prediction of an elastic model with observed surface uplift could be underestimated. For a given crustal viscosity, sill depth is the principal factor controlling subsidence caused by viscoelastic relaxation. The subsidence rate is highest when the inflation occurs at the boundary between the elastic and the viscoelastic layers. The mantle viscosity has an insignificant impact unless the depth of the inflation is greater than a half the crustal thickness. We apply the viscoelastic model to the interferometric synthetic aperture radar (InSAR) data in the Kutcharo caldera, eastern Hokkaido, Japan, where the surface has slowly subsided over a period of approximately three years following about a two-year period of inflation. The emplacement of a magmatic sill is constrained to occur at a depth of 4.5 km, which is significantly shallower than the geophysically imaged large-scale magma chamber. The geodetically detected deformation in the caldera reflects the small-scale emplacement of a magma that ascended from the deeper chamber, but not the

  2. The global chemical systematics of arc front stratovolcanoes: Evaluating the role of crustal processes

    Science.gov (United States)

    Turner, Stephen J.; Langmuir, Charles H.

    2015-07-01

    , but the required composition of the theoretical enriched end-member is not similar to compositions expected in the deep crust or to any known rock composition. The large-scale chemical variations among volcanic arcs are therefore likely to be generated by processes in the subducting slab or mantle wedge, rather than the crust. While crustal processes are important in the differentiation of convergent margin magmas, they do not account for the systematics presented here. Models that attribute the chemical variability of arc magmas to slab or wedge processes are also constrained to be consistent with the global chemical systematics, and are discussed in Turner and Langmuir (2015).

  3. Crustal Structure of Active Deformation Zones in Africa: Implications for Global Crustal Processes

    Science.gov (United States)

    Ebinger, C. J.; Keir, D.; Bastow, I. D.; Whaler, K.; Hammond, J. O. S.; Ayele, A.; Miller, M. S.; Tiberi, C.; Hautot, S.

    2017-12-01

    The Cenozoic East African rift (EAR), Cameroon Volcanic Line (CVL), and Atlas Mountains formed on the slow-moving African continent, which last experienced orogeny during the Pan-African. We synthesize primarily geophysical data to evaluate the role of magmatism in shaping Africa's crust. In young magmatic rift zones, melt and volatiles migrate from the asthenosphere to gas-rich magma reservoirs at the Moho, altering crustal composition and reducing strength. Within the southernmost Eastern rift, the crust comprises 20% new magmatic material ponded in the lower crust and intruded as sills and dikes at shallower depths. In the Main Ethiopian Rift, intrusions comprise 30% of the crust below axial zones of dike-dominated extension. In the incipient rupture zones of the Afar rift, magma intrusions fed from crustal magma chambers beneath segment centers create new columns of mafic crust, as along slow-spreading ridges. Our comparisons suggest that transitional crust, including seaward dipping sequences, is created as progressively smaller screens of continental crust are heated and weakened by magma intrusion into 15-20 km thick crust. In the 30 Ma Recent CVL, which lacks a hot spot age progression, extensional forces are small, inhibiting the creation and rise of magma into the crust. In the Atlas orogen, localized magmatism follows the strike of the Atlas Mountains from the Canary Islands hot spot toward the Alboran Sea. CVL and Atlas magmatism has had minimal impact on crustal structure. Our syntheses show that magma and volatiles are migrating from the asthenosphere through the plates, modifying rheology, and contributing significantly to global carbon and water fluxes.

  4. Ionospheric precursors for crustal earthquakes in Italy

    Directory of Open Access Journals (Sweden)

    L. Perrone

    2010-04-01

    Full Text Available Crustal earthquakes with magnitude 6.0>M≥5.5 observed in Italy for the period 1979–2009 including the last one at L'Aquila on 6 April 2009 were considered to check if the earlier obtained relationships for ionospheric precursors for strong Japanese earthquakes are valid for the Italian moderate earthquakes. The ionospheric precursors are based on the observed variations of the sporadic E-layer parameters (h'Es, fbEs and foF2 at the ionospheric station Rome. Empirical dependencies for the seismo-ionospheric disturbances relating the earthquake magnitude and the epicenter distance are obtained and they have been shown to be similar to those obtained earlier for Japanese earthquakes. The dependences indicate the process of spreading the disturbance from the epicenter towards periphery during the earthquake preparation process. Large lead times for the precursor occurrence (up to 34 days for M=5.8–5.9 tells about a prolong preparation period. A possibility of using the obtained relationships for the earthquakes prediction is discussed.

  5. The crustal dynamics intelligent user interface anthology

    Science.gov (United States)

    Short, Nicholas M., Jr.; Campbell, William J.; Roelofs, Larry H.; Wattawa, Scott L.

    1987-01-01

    The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has, as one of its components, the development of an Intelligent User Interface (IUI). The intent of the IUI is to develop a friendly and intelligent user interface service based on expert systems and natural language processing technologies. The purpose of such a service is to support the large number of potential scientific and engineering users that have need of space and land-related research and technical data, but have little or no experience in query languages or understanding of the information content or architecture of the databases of interest. This document presents the design concepts, development approach and evaluation of the performance of a prototype IUI system for the Crustal Dynamics Project Database, which was developed using a microcomputer-based expert system tool (M. 1), the natural language query processor THEMIS, and the graphics software system GSS. The IUI design is based on a multiple view representation of a database from both the user and database perspective, with intelligent processes to translate between the views.

  6. Cooperative research in space geodesy and crustal dynamics

    Science.gov (United States)

    1994-01-01

    This research grant, which covered the period of July 1991 to August 1994, was concerned with a variety of topics within the geodesy and crustal dynamics fields. The specific topics of this grant included satellite tracking and gravity field determinations and crustal dynamics (this concentrated of space geodetic site stability for VLBI sites). Summaries of the specific research projects are included along with a list of publications and presentations supported by this research grant.

  7. Lower crustal earthquakes in the North China Basin and implications for crustal rheology

    Science.gov (United States)

    Yuen, D. A.; Dong, Y.; Ni, S.; LI, Z.

    2017-12-01

    The North China Basin is a Mesozoic-Cenozoic continental rift basin on the eastern North China Craton. It is the central region of craton destruction, also a very seismically active area suffering severely from devastating earthquakes, such as the 1966 Xingtai M7.2 earthquake, the 1967 Hejian M6.3 earthquake, and the 1976 Tangshan M7.8 earthquake. We found remarkable discrepancies of depth distribution among the three earthquakes, for instance, the Xingtai and Tangshan earthquakes are both upper-crustal earthquakes occurring between 9 and 15 km on depth, but the depth of the Hejian earthquake was reported of about 30 72 km, ranging from lowermost crust to upper mantle. In order to investigate the focal depth of earthquakes near Hejian area, we developed a method to resolve focal depth for local earthquakes occurring beneath sedimentary regions by P and S converted waves. With this method, we obtained well-resolved depths of 44 local events with magnitudes between M1.0 and M3.0 during 2008 to 2016 at the Hejian seismic zone, with a mean depth uncertainty of about 2 km. The depth distribution shows abundant earthquakes at depth of 20 km, with some events in the lower crust, but absence of seismicity deeper than 25 km. In particular, we aimed at deducing some constraints on the local crustal rheology from depth-frequency distribution. Therefore, we performed a comparison between the depth-frequency distribution and the crustal strength envelop, and found a good fit between the depth profile in the Hejian seismic zone and the yield strength envelop in the Baikal Rift Systems. As a conclusion, we infer that the seismogenic thickness is 25 km and the main deformation mechanism is brittle fracture in the North China Basin . And we made two hypotheses: (1) the rheological layering of dominant rheology in the North China Basin is similar to that of the Baikal Rift Systems, which can be explained with a quartz rheology at 0 10 km depth and a diabase rheology at 10 35 km

  8. Mechanisms of unsteady shallow creep on major crustal faults

    Science.gov (United States)

    Jiang, J.; Fialko, Y. A.

    2017-12-01

    A number of active crustal faults are associated with geodetically detectable shallow creep, while other faults appear to be locked all the way to the surface over the interseismic period. Faults that exhibit shallow creep also often host episodic accelerated creep events. Examples include the Ismetpasa segment of the North Anatolian Fault (NAF) in Turkey and the Southern San Andreas and Superstition Hills (SHF) faults in Southern California. Recent geodetic observations indicate that shallow creep events can involve large fault sections (tens of km long) and persist throughout different stages of a seismic cycle. A traditional interpretation of shallow creep in terms of a velocity-strengthening (VS) layer atop the seismogenic velocity-weakening (VW) zone fails to explain episodic creep events. Wei et al. (2013) proposed that such events can be due to a thin VW layer within the VS shallow crust, implying rather special structural and lithologic conditions. We explore the rheologic controls on aseismic episodic slip and its implications for seismic faulting in the framework of laboratory rate-and-state friction. Observations of co-, post- and inter-seismic slip from the NAF and SHF are used to infer depth-dependent frictional properties in a 2D fault model. In particular, creep events with displacements on the order of millimeters and periods of months are reproduced in a model having monotonic depth variations in rate-and-state parameters. Such a model includes a velocity-neutral (VN) layer sandwiched between the surface layer with VS frictional properties, constrained by observed postseismic afterslip, and a deeper VW layer that largely controls the recurrence of major earthquakes. With the presence of the VN layer, the amount of surface-breaching coseismic slip critically depends on how dynamic weakening varies with depth in the seismogenic layer. Observations of limited surface slip during prior events on the NAF and SHF suggest that coseismic fault weakening is

  9. Geochemical Relationships between Volcanic and Plutonic Upper to Mid Crustal Exposures of the Rosario Segment, Alisitos Arc (Baja California, Mexico): An Outstanding Field Analog to the Izu-Bonin-Mariana Arc

    Science.gov (United States)

    Morris, R.; DeBari, S. M.; Busby, C. J.; Medynski, S.

    2015-12-01

    Exposed paleo-arcs, such as the Rosario segment of the Cretaceous Alisitos Arc in Baja California, Mexico, provide an opportunity to explore the evolution of arc crust through time. Remarkable 3-D exposures of the Rosario segment record crustal generation processes in the volcanic rocks and underlying plutonic rocks. In this study, we explore the physical and geochemical connection between the plutonic and volcanic sections of the extensional Alisitos Arc, and elucidate differentiation processes responsible for generating them. These results provide an outstanding analog for extensional active arc systems, such as the Izu-Bonin-Mariana (IBM) Arc. Upper crustal volcanic rocks have a coherent stratigraphy that is 3-5 km thick and ranges in composition from basalt to dacite. The most felsic compositions (70.9% SiO2) are from a welded ignimbrite unit. The most mafic compositions (51.5% SiO2, 3.2% MgO) are found in basaltic sill-like units. Phenocrysts in the volcanic units include plagioclase +/- amphibole and clinopyroxene. The transition to deeper plutonic rocks is clearly an intrusive boundary, where plutonic units intrude the volcanic units. Plutonic rocks are dominantly a quartz diorite main phase with a more mafic, gabbroic margin. A transitional zone is observed along the contact between the plutonic and volcanic rocks, where volcanics have coarsely recrystallized textures. Mineral assemblages in the plutonic units include plagioclase +/- quartz, biotite, amphibole, clinopyroxene and orthopyroxene. Most, but not all, samples are low K. REE patterns are relatively flat with limited enrichment. Normalization diagrams show LILE enrichment and HFSE depletion, where trends are similar to average IBM values. We interpret plutonic and volcanic units to have similar geochemical relationships, where liquid lines of descent show the evolution of least to most evolved magma types. We provide a model for the formation and magmatic evolution of the Alisitos Arc.

  10. Magnetotelluric evidence for a deep-crustal mineralizing system beneath the Olympic Dam iron oxide copper-gold deposit, southern Australia

    Science.gov (United States)

    Heinson, Graham S.; Direen, Nicholas G.; Gill, Rob M.

    2006-07-01

    The iron oxide copper-gold Olympic Dam deposit, situated along the margin of the Proterozoic Gawler craton, South Australia, is the world's largest uranium deposit and sixth-largest copper deposit; it also contains significant reserves of gold, silver, and rare earth elements. Gaining a better understanding of the mechanisms for genesis of the economic liberalization is fundamental for defining exploration models in similar crustal settings. To delineate crustal structures that may constrain mineral system fluid pathways, coincident deep crustal seismic and magnetotelluric (MT) transects were obtained along a 220 km section that crosses Olympic Dam and the major crustal boundaries. In this paper we present results from 58 long-period (10 104 s) MT sites, with site spacing of 5 10 km. A two-dimensional inversion of MT data from 33 sites to a depth of 100 km shows four notable features: (1) sedimentary cover sequences with low resistivity (1000 Ω·m) Archean crustal core from a more conductive crust and mantle to the north (typically Olympic Dam, the upper-middle crust to ˜20 km is quite resistive (˜1000 Ω·m), but the lower crust is much more conductive (Olympic Dam, we image a low-resistivity region (Olympic Dam may be due to the upward movement of CO2-bearing volatiles near the time of deposit formation that precipitated conductive graphite liberalization along grain boundaries, simultaneously annihilating acoustic impedance boundaries. The source of the volatiles may be from the mantle degassing or retrograde metamorphism of the lower crust associated with Proterozoic crustal deformation.

  11. CRUSTAL THICKNESS VARIATIONS AND SEISMICITY OF NORTHWESTERN SOUTH AMERICA

    Directory of Open Access Journals (Sweden)

    Woo Kim Jeong

    2007-06-01

    Full Text Available Any uncompensated mass of the northern Andes Mountains is presumably under pressure to adjust within the Earth to its ideal state of isostatic equilibrium. Isostasy is the ideal state that any
    uncompensated mass seeks to achieve in time. These pressures interact with the relative motions between adjacent plates that give rise to earthquakes along the plate boundaries. By combining the
    gravity MOHO estimates and crustal discontinuities with historical and instrumental seismological catalogs the correlation between isostatically disturbed terrains and seismicity has been established.
    The thinner and thicker crustal regions were mapped from the zero horizontal curvature of the crustal thickness estimates. These boundaries or edges of crustal thickness variations were compared to
    crustal discontinuities inferred from gravity and magnetic anomalies and the patterns of seismicity that have been catalogued for the last 363 years. The seismicity is very intense along the Nazca-North
    Andes, Caribbean-North American and North Andes-South American collision zones and associated with regional tectonic compressional stresses that have locally increased and/or diminished by
    compressional and tensional stress, respectively, due to crustal thickness variations. High seismicity is also associated with the Nazca-Cocos diverging plate boundary whereas low seismicity is associated with the Panama-Nazca Transform Fault and the South American Plate.

  12. Crustal Accretion at Subduction Initiation Along Izu-Bonin-Mariana Arc and the Link to SSZ Ophiolites

    Science.gov (United States)

    Ishizuka, O.; Tani, K.; Reagan, M. K.; Kanayama, K.; Umino, S.; Harigane, Y.; Sakamoto, I.

    2014-12-01

    The Izu-Bonin-Mariana (IBM) forearc preserves the earliest arc magmatic history from subduction initiation to the establishment of the arc. Recent investigations have established a bottom to top igneous stratigraphy of: 1) mantle peridotite, 2) gabbroic rocks, 3) a sheeted dyke complex, 4) basaltic pillow lavas (forearc basalts: FAB), 5) boninites and magnesian andesites, 6) tholeiites and calcalkaline arc lavas. This stratigraphy has many similarities to supra-subduction zone (SSZ) ophiolites. One of the most important common characteristics between the SSZ ophiolites and the forearc crust is the occurrence of MORB-like basaltic lavas underlying or accompanying boninites and early arc volcanic suites. A key observation from the IBM forearc is that FAB differs from nearby back-arc lavas in chemical characteristics, including a depletion in moderately incompatible elements. This indicates that FAB is not a pre-existing oceanic basement of the arc, but the first magmatic product after subduction initiation. Sheeted dikes of FAB composition imply that this magmatism was associated with seafloor spreading, possibly triggered by onset of slab sinking. Recognition of lavas with transitional geochemical characteristics between the FAB and the boninites strongly implies genetic linkage between these two magma types. The close similarity of the igneous stratigraphy of SSZ ophiolites to the IBM forearc section strongly implies a common magmatic evolutionary path, i.e., decompressional melting of a depleted MORB-type mantle is followed by melting of an even more depleted mantle with the addition of slab-derived fluid/melt to produce boninite magma. Similarity of magmatic process between IBM forearc and Tethyan ophiolites appears to be reflected on common characteristics of upper mantle section. Peridotite from both sections show more depleted characteristics compared to upper mantle rocks from mid-ocean ridges. Age determinations reveal that first magmatism at the IBM arc

  13. The crustal structure of Ellesmere Island, Arctic Canada—teleseismic mapping across a remote intraplate orogenic belt

    Science.gov (United States)

    Schiffer, Christian; Stephenson, Randell; Oakey, Gordon N.; Jacobsen, Bo H.

    2016-03-01

    Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affected by two distinct orogenies, the Palaeozoic Ellesmerian orogeny (the Caledonian equivalent in Arctic Canada and Northern Greenland) and the Palaeogene Eurekan orogeny, related to the opening of Baffin Bay and the consequent convergence of the Greenland plate. The details of this complex evolution and the present-day deep structure are poorly constrained in this remote area and deep geophysical data are sparse. Receiver function analysis of seven temporary broad-band seismometers of the Ellesmere Island Lithosphere Experiment complemented by two permanent stations provides important data on the crustal velocity structure of Ellesmere Island. The crustal expression of the northernmost tectonic block of Ellesmere Island (˜82°-83°N), Pearya, which was accreted during the Ellesmerian orogeny, is similar to that at the southernmost part, which is part of the Precambrian Laurentian (North America-Greenland) craton. Both segments have thick crystalline crust (˜35-36 km) and comparable velocity-depth profiles. In contrast, crustal thickness in central Ellesmere Island decreases from ˜24-30 km in the Eurekan fold and thrust belt (˜79.7°-80.6°N) to ˜16-20 km in the Hazen Stable Block (HSB; ˜80.6°-81.4°N) and is covered by a thick succession of metasediments. A deep crustal root (˜48 km) at ˜79.6°N is interpreted as cratonic crust flexed beneath the Eurekan fold and thrust belt. The Carboniferous to Palaeogene sedimentary succession of the Sverdrup Basin is inferred to be up to 1-4 km thick, comparable to geologically-based estimates, near the western margin of the HSB.

  14. A frozen record of density-driven crustal overturn in lava lakes: The example of Kilauea Iki 1959

    Science.gov (United States)

    Stovall, W.K.; Houghton, Bruce F.; Harris, A.J.L.; Swanson, D.A.

    2009-01-01

    Lava lakes are found at basaltic volcanoes on Earth and other planetary bodies. Density-driven crustal foundering leading to surface renewal occurs repeatedly throughout the life of a lava lake. This process has been observed and described in a qualitative sense, but due to dangerous conditions, no data has been acquired to evaluate the densities of the units involved. Kilauea Iki pit crater in Hawai'i houses a lava lake erupted during a 2 month period in 1959. Part of the surface of the Kilauea Iki lake now preserves the frozen record of a final, incomplete, crustal-overturn cycle. We mapped this region and sampled portions of the foundering crust, as well as overriding and underlying lava, to constrain the density of the units involved in the overturn process. Overturn is driven by the advance of a flow front of fresh, low-density lava over an older, higher density surface crust. The advance of the front causes the older crust to break up, founder, and dive downwards into the lake to expose new, hot, low-density lava. We find density differences of 200 to 740 kg/m3 between the foundering crust and over-riding and under-lying lava respectively. In this case, crustal overturn is driven by large density differences between the foundering and resurfacing units. These differences lead, inevitably, to frequent crustal renewal: simple density differences between the surface crust and underlying lake lava make the upper layers of the lake highly unstable. ?? Springer-Verlag 2008.

  15. A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production

    Science.gov (United States)

    Burton-Johnson, A.; Halpin, J.; Whittaker, J. M.; Graham, F. S.; Watson, S. J.

    2017-12-01

    We present recently published findings (Burton-Johnson et al., 2017) on the variability of Antarctic sub-glacial heat flux and the impact from upper crustal geology. Our new method reveals that the upper crust contributes up to 70% of the Antarctic Peninsula's subglacial heat flux, and that heat flux values are more variable at smaller spatial resolutions than geophysical methods can resolve. Results indicate a higher heat flux on the east and south of the Peninsula (mean 81 mWm-2) where silicic rocks predominate, than on the west and north (mean 67 mWm-2) where volcanic arc and quartzose sediments are dominant. Whilst the data supports the contribution of HPE-enriched granitic rocks to high heat flux values, sedimentary rocks can be of comparative importance dependent on their provenance and petrography. Models of subglacial heat flux must utilize a heterogeneous upper crust with variable radioactive heat production if they are to accurately predict basal conditions of the ice sheet. Our new methodology and dataset facilitate improved numerical model simulations of ice sheet dynamics. The most significant challenge faced remains accurate determination of crustal structure, particularly the depths of the HPE-enriched sedimentary basins and the sub-glacial geology away from exposed outcrops. Continuing research (particularly detailed geophysical interpretation) will better constrain these unknowns and the effect of upper crustal geology on the Antarctic ice sheet. Burton-Johnson, A., Halpin, J.A., Whittaker, J.M., Graham, F.S., and Watson, S.J., 2017, A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production: Geophysical Research Letters, v. 44, doi: 10.1002/2017GL073596.

  16. The Damage and Geochemical Signature of a Crustal Scale Strike-Slip Fault Zone

    Science.gov (United States)

    Gomila, R.; Mitchell, T. M.; Arancibia, G.; Jensen Siles, E.; Rempe, M.; Cembrano, J. M.; Faulkner, D. R.

    2013-12-01

    Fluid-flow migration in the upper crust is strongly controlled by fracture network permeability and connectivity within fault zones, which can lead to fluid-rock chemical interaction represented as mineral precipitation in mesh veins and/or mineralogical changes (alteration) of the host rock. While the dimensions of fault damage zones defined by fracture intensity is beginning to be better understood, how such dimensions compare to the size of alteration zones is less well known. Here, we show quantitative structural and chemical analyses as a function of distance from a crustal-scale strike-slip fault in the Atacama Fault System, Northern Chile, to compare fault damage zone characteristics with its geochemical signature. The Jorgillo Fault (JF) is a ca. 18 km long NNW striking strike-slip fault cutting Mesozoic rocks with sinistral displacement of ca. 4 km. In the study area, the JF cuts through orthogranulitic and gabbroic rocks at the west (JFW) and the east side (JFE), respectively. A 200 m fault perpendicular transect was mapped and sampled for structural and XRF analyses of the core, damage zone and protolith. The core zone consists of a ca. 1 m wide cataclasite zone bounded by two fault gouge zones ca. 40 cm. The damage zone width defined by fracture density is ca. 50 m wide each side of the core. The damage zone in JFW is characterized by NW-striking subvertical 2 cm wide cataclastic rocks and NE-striking milimetric open fractures. In JFE, 1-20 mm wide chlorite, quartz-epidote and quartz-calcite veins, cut the gabbro. Microfracture analysis in JFW reveal mm-wide cataclasitic/ultracataclasitic bands with clasts of protolith and chlorite orientated subparallel to the JF in the matrix, calcite veins in a T-fractures orientation, and minor polidirectional chlorite veins. In JFE, chlorite filled conjugate fractures with syntaxial growth textures and evidence for dilational fracturing processes are seen. Closest to the core, calcite veins crosscut chlorite veins

  17. Anomalous Structure of Oceanic Lithosphere in the North Atlantic and Arctic Oceans: A Preliminary Analysis Based on Bathymetry, Gravity and Crustal Structure

    Science.gov (United States)

    Barantsrva, O.

    2014-12-01

    We present a preliminary analysis of the crustal and upper mantle structure for off-shore regions in the North Atlantic and Arctic oceans. These regions have anomalous oceanic lithosphere: the upper mantle of the North Atlantic ocean is affected by the Iceland plume, while the Arctic ocean has some of the slowest spreading rates. Our specific goal is to constrain the density structure of the upper mantle in order to understand the links between the deep lithosphere dynamics, ocean spreading, ocean floor bathymetry, heat flow and structure of the oceanic lithosphere in the regions where classical models of evolution of the oceanic lithosphere may not be valid. The major focus is on the oceanic lithosphere, but the Arctic shelves with a sufficient data coverage are also included into the analysis. Out major interest is the density structure of the upper mantle, and the analysis is based on the interpretation of GOCE satellite gravity data. To separate gravity anomalies caused by subcrustal anomalous masses, the gravitational effect of water, crust and the deep mantle is removed from the observed gravity field. For bathymetry we use the global NOAA database ETOPO1. The crustal correction to gravity is based on two crustal models: (1) global model CRUST1.0 (Laske, 2013) and, for a comparison, (2) a regional seismic model EUNAseis (Artemieva and Thybo, 2013). The crustal density structure required for the crustal correction is constrained from Vp data. Previous studies have shown that a large range of density values corresponds to any Vp value. To overcome this problem and to reduce uncertainty associated with the velocity-density conversion, we account for regional tectonic variations in the Northern Atlantics as constrained by numerous published seismic profiles and potential-field models across the Norwegian off-shore crust (e.g. Breivik et al., 2005, 2007), and apply different Vp-density conversions for different parts of the region. We present preliminary results

  18. Trends in PDE constrained optimization

    CERN Document Server

    Benner, Peter; Engell, Sebastian; Griewank, Andreas; Harbrecht, Helmut; Hinze, Michael; Rannacher, Rolf; Ulbrich, Stefan

    2014-01-01

    Optimization problems subject to constraints governed by partial differential equations (PDEs) are among the most challenging problems in the context of industrial, economical and medical applications. Almost the entire range of problems in this field of research was studied and further explored as part of the Deutsche Forschungsgemeinschaft (DFG) priority program 1253 on “Optimization with Partial Differential Equations” from 2006 to 2013. The investigations were motivated by the fascinating potential applications and challenging mathematical problems that arise in the field of PDE constrained optimization. New analytic and algorithmic paradigms have been developed, implemented and validated in the context of real-world applications. In this special volume, contributions from more than fifteen German universities combine the results of this interdisciplinary program with a focus on applied mathematics.   The book is divided into five sections on “Constrained Optimization, Identification and Control”...

  19. Effective stress, friction and deep crustal faulting

    Science.gov (United States)

    Beeler, N.M.; Hirth, Greg; Thomas, Amanda M.; Burgmann, Roland

    2016-01-01

    Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid contact area across the fault. αf varies with depth and is only near 1 when the yield strength of asperity contacts greatly exceeds the applied normal stress. For a vertical strike-slip quartz fault zone at hydrostatic pore pressure and assuming 1 mm and 1 km shear zone widths for friction and ductile shear, respectively, the BDT is at ~13 km. αf near 1 is restricted to depths where the shear zone is narrow. Below the BDT αf = 0 is due to a dramatically decreased strain rate. Under these circumstances friction cannot be reactivated below the BDT by increasing the pore pressure alone and requires localization. If pore pressure increases and the fault localizes back to 1 mm, then brittle behavior can occur to a depth of around 35 km. The interdependencies among effective stress, contact-scale strain rate, and pore pressure allow estimates of the conditions necessary for deep low-frequency seismicity seen on the San Andreas near Parkfield and in some subduction zones. Among the implications are that shear in the region separating shallow earthquakes and deep low-frequency seismicity is distributed and that the deeper zone involves both elevated pore fluid pressure and localization.

  20. Intensity attenuation for active crustal regions

    Science.gov (United States)

    Allen, Trevor I.; Wald, David J.; Worden, C. Bruce

    2012-07-01

    We develop globally applicable macroseismic intensity prediction equations (IPEs) for earthquakes of moment magnitude M W 5.0-7.9 and intensities of degree II and greater for distances less than 300 km for active crustal regions. The IPEs are developed for two distance metrics: closest distance to rupture ( R rup) and hypocentral distance ( R hyp). The key objective for developing the model based on hypocentral distance—in addition to more rigorous and standard measure R rup—is to provide an IPE which can be used in near real-time earthquake response systems for earthquakes anywhere in the world, where information regarding the rupture dimensions of a fault may not be known in the immediate aftermath of the event. We observe that our models, particularly the model for the R rup distance metric, generally have low median residuals with magnitude and distance. In particular, we address whether the direct use of IPEs leads to a reduction in overall uncertainties when compared with methods which use a combination of ground-motion prediction equations and ground motion to intensity conversion equations. Finally, using topographic gradient as a proxy and median model predictions, we derive intensity-based site amplification factors. These factors lead to a small reduction of residuals at shallow gradients at strong shaking levels. However, the overall effect on total median residuals is relatively small. This is in part due to the observation that the median site condition for intensity observations used to develop these IPEs is approximately near the National Earthquake Hazard Reduction Program CD site-class boundary.

  1. Present day crustal deformation of the Italian peninsula observed by permanent GPS stations

    Science.gov (United States)

    Devoti, Roberto; Esposito, Alessandra; Galvani, Alessandro; Pietrantonio, Grazia; Pisani, Anna Rita; Riguzzi, Federica; Sepe, Vincenzo

    2010-05-01

    Italian penisula is a crucial area in the Mediterranean region to understand the active deformation processes along Nubia-Eurasia plate boundary. We present the velocity and strain rate fields of the Italian area derived from continuous GPS observations of more than 300 sites in the time span 1998-2009. The GPS networks were installed and managed by different institutions and for different purposes; altogether they cover the whole country with a mean inter-site distance of about 50 km and provide a valuable source of data to map the present day kinematics of the region. The data processing is performed by BERNESE software ver. 5.0, adopting a distributed session approach, with more than 10 clusters, sharing common stations, each of them consisting of about 40 stations. Daily loosely constrained solutions are routinely produced for each cluster and then combined into a network daily loose solution. Subsequently daily solutions are transformed on the chosen reference frame and the constrained time series are fitted using the complete covariance matrix, simultaneously estimating site velocities together with annual signals and sporadic offsets at epochs of instrumental changes. In this work we provide an updated detailed picture of the horizontal and vertical kinematics (velocity maps) and deformation pattern (strain rate maps) of the Italian area. The results show several crustal domains characterized by different velocity rates and styles of deformation.

  2. New Crustal Thickness for Djibouti, Afar, Using Seismic Techniques

    Science.gov (United States)

    Dugda, Mulugeta; Bililign, Solomon

    2008-10-01

    Crustal thickness and Poisson's ratio for the seismic station ATD in Djibouti, Afar, has been investigated using two seismic techniques (H-κ stacking of receiver functions and a joint inversion of receiver functions and surface wave group velocities). Both techniques give consistent results of crustal thickness 23±1.5 km and Poisson's ratio 0.31±0.02. We also determined a mean P-wave velocity (Vp) of ˜6.2 km/s but ˜6.9-7.0 km/s below a 2 - 5 km thick low velocity layer at the surface. Previous studies of crustal structure for Djibouti reported that the crust is 6 to 11 km thick while our study shows that the crust beneath Djibouti is between 20 and 25 km. This study argues that the crustal thickness values reported for Djibouti for the last 3 decades were not consistent with the reports for the other neighboring region in central and eastern Afar. Our results for ATD in Djibouti, however, are consistent with the reports of crustal thickness in many other parts of central and eastern Afar. We attribute this difference to how the Moho (the crust-mantle discontinuity) is defined (an increase of Vp to 7.4 km/s in this study vs. 6.9 km/s in previous studies).

  3. Crustal structure of northern Italy from the ellipticity of Rayleigh waves

    Science.gov (United States)

    Berbellini, Andrea; Morelli, Andrea; G. Ferreira, Ana M.

    2017-04-01

    Northern Italy is a diverse geological region, including the wide and thick Po Plain sedimentary basin, which is bounded by the Alps and the Apennines. The seismically slow shallow structure of the Po Plain is difficult to retrieve with classical seismic measurements such as surface wave dispersion, yet the detailed structure of the region greatly affects seismic wave propagation and hence seismic ground shaking. Here we invert Rayleigh wave ellipticity measurements in the period range 10-60 s for 95 stations in northern Italy using a fully non linear approach to constrain vertical vS,vP and density profiles of the crust beneath each station. The ellipticity of Rayleigh wave ground motion is primarily sensitive to shear-wave velocity beneath the recording station, which reduces along-path contamination effects. We use the 3D layering structure in MAMBo, a previous model based on a compilation of geological and geophysical information for the Po Plain and surrounding regions of northern Italy, and employ ellipticity data to constrain vS,vP and density within its layers. We show that ellipticity data from ballistic teleseismic wave trains alone constrain the crustal structure well. This leads to MAMBo-E, an updated seismic model of the region's crust that inherits information available from previous seismic prospection and geological studies, while fitting new seismic data well. MAMBo-E brings new insights into lateral heterogeneity in the region's subsurface. Compared to MAMBo, it shows overall faster seismic anomalies in the region's Quaternary, Pliocene and Oligo-Miocene layers and better delineates the seismic structures of the Po Plain at depth. Two low velocity regions are mapped in the Mesozoic layer in the western and eastern parts of the Plain, which seem to correspond to the Monferrato sedimentary basin and to the Ferrara-Romagna thrust system, respectively.

  4. Nested Sampling with Constrained Hamiltonian Monte Carlo

    OpenAIRE

    Betancourt, M. J.

    2010-01-01

    Nested sampling is a powerful approach to Bayesian inference ultimately limited by the computationally demanding task of sampling from a heavily constrained probability distribution. An effective algorithm in its own right, Hamiltonian Monte Carlo is readily adapted to efficiently sample from any smooth, constrained distribution. Utilizing this constrained Hamiltonian Monte Carlo, I introduce a general implementation of the nested sampling algorithm.

  5. Constrained minimization in C ++ environment

    International Nuclear Information System (INIS)

    Dymov, S.N.; Kurbatov, V.S.; Silin, I.N.; Yashchenko, S.V.

    1998-01-01

    Based on the ideas, proposed by one of the authors (I.N.Silin), the suitable software was developed for constrained data fitting. Constraints may be of the arbitrary type: equalities and inequalities. The simplest of possible ways was used. Widely known program FUMILI was realized to the C ++ language. Constraints in the form of inequalities φ (θ i ) ≥ a were taken into account by change into equalities φ (θ i ) = t and simple inequalities of type t ≥ a. The equalities were taken into account by means of quadratic penalty functions. The suitable software was tested on the model data of the ANKE setup (COSY accelerator, Forschungszentrum Juelich, Germany)

  6. Coherent states in constrained systems

    International Nuclear Information System (INIS)

    Nakamura, M.; Kojima, K.

    2001-01-01

    When quantizing the constrained systems, there often arise the quantum corrections due to the non-commutativity in the re-ordering of constraint operators in the products of operators. In the bosonic second-class constraints, furthermore, the quantum corrections caused by the uncertainty principle should be taken into account. In order to treat these corrections simultaneously, the alternative projection technique of operators is proposed by introducing the available minimal uncertainty states of the constraint operators. Using this projection technique together with the projection operator method (POM), these two kinds of quantum corrections were investigated

  7. Constraining formation of the Eggvin Bank (West of Jan Mayen, N. Atlantic) from OBS data

    Science.gov (United States)

    Tan, P.; Breivik, A. J.; Mjelde, R.; Azuma, R.

    2015-12-01

    The anomalously high magma flux in the Eggvin Bank area has triggered new research efforts to better understand the crustal development in this area. The Eggvin Bank is located between the Jan Mayen Island and the west coast of Greenland. Some proposed origins of the Eggvin Bank are: a distinct plume located beneath Jan Mayen; an extension of the Iceland plume; minor spreading or leakage along West Jan Mayen Fracture Zone (WJMFZ); intruded continental crust extending from Jan Mayen Microcontinent (JMMC); and rifted Greenland sub-continental lithospheric mantle. In this first modern refraction seismic study of the Eggvin Bank, we present a 2D velocity model based on OBS data. The OBSs were deployed approx. N-S over the Eggvin Bank with good data quality constrained by 4 OBSs. The air-gun array used during OBS shooting produced good quality reflection data. Three distinct seamounts are observed along the profile: the northern seamount (water depth 730m), has a flat top with a thin sedimentary veneer on top, which indicates it has been eroded at sea surface; while the southern two seamounts, one (water depth 550m) is less flat with around 100m thick sedimentary units on top, another one is rounded with tiny sedimentary veneer on top having the shallowest water depth (460m). This could suggest that the southern seamounts are younger, since they are shallower but without obvious signs that they were subaerially exposed. However, increased cooling of the lithosphere across the WJMFZ in the north may also contribute to depth differences. A normal fault offsetting sedimentary strata (~300 m) in the Greenland Basin indicates recent tectonic activity north of the Eggvin Bank. The velocity modeling shows crustal thickness with large variations, ranging from 8 km to 14 km, where crustal thickness changes of 4-5 km are associated with 20-30 km wide segments with thick crust under the seamounts. The crust consists of three oceanic crustal layers: upper crust (2.8km/s-4.8km

  8. Petrology and geochemistry of charnockites (felsic ortho-granulites) from the Kerala Khondalite Belt, Southern India: Evidence for intra-crustal melting, magmatic differentiation and episodic crustal growth

    Science.gov (United States)

    Ravindra Kumar, G. R.; Sreejith, C.

    2016-10-01

    contents of Y (71-99 ppm; average 87), and low Sr/Y (average 2) ratios with significant negative Eu anomalies (Eu/Eu* = 0.03-0.31; average 0.23) and low Sr (average 160 ppm) contents. The protoliths of the TC are interpreted as being derived from partial melting of thickened oceanic-arc crust composed of Archaean mafic composite source rocks (i.e., eclogite and/or garnet amphibolite) with a garnet amphibolite residue. Geochemical features of the GC, such as high Rb/Sr (average 1.80) and Ba/Sr ratios (average values > 6), are considered as evidence for crustal reworking in their genesis, suggesting remelting of a quartzo-feldspathic (TTG) source, within the plagioclase stability fields. The geochemical features of the felsic ortho-granulite suite, substantiated with published geochronological data on members of the TC, GC, and AC suites, suggest a four-stage crustal evolution of the KKB. The first stage is marked by the formation of an over-thickened oceanic-arc. Zircon Hfc model ages of the TC and GC suites constrain the time of this juvenile magmatic crust-forming event as Meso- to Neoarchaean (2.8 to 2.6 Ga). The second stage corresponds to the production of TTG magmas by melting of the over-thickened oceanic-arc crust, subsequent to basaltic underplating during Palaeoproterozoic (ca. 2.1 Ga). The third stage was initiated by a transition in subduction style from shallow to steep due to continent-arc accretion. This stage is marked by the formation of granitic magmas through partial melting of the TTG crust and their differentiation into GC and TC. The zircon crystallization ages (1.89 and 1.85 Ga) of the GC indicate arc accretion occurred during the Palaeoproterozoic. The fourth stage of crustal evolution is correlated with the Mesoproterozoic ( 1.5 Ga) emplacement of megacrystic K-feldspar granites (protoliths to the AC and augen gneisses). The distinct petrography, geochemistry and crystallization ages of the AC suggests recurrence of megacrystic, high-K calc

  9. The geophysical character of southern Alaska - Implications for crustal evolution

    Science.gov (United States)

    Saltus, R.W.; Hudson, T.L.; Wilson, Frederic H.

    2007-01-01

    The southern Alaska continental margin has undergone a long and complicated history of plate convergence, subduction, accretion, and margin-parallel displacements. The crustal character of this continental margin is discernible through combined analysis of aeromagnetic and gravity data with key constraints from previous seismic interpretation. Regional magnetic data are particularly useful in defining broad geophysical domains. One of these domains, the south Alaska magnetic high, is the focus of this study. It is an intense and continuous magnetic high up to 200 km wide and ∼1500 km long extending from the Canadian border in the Wrangell Mountains west and southwest through Cook Inlet to the Bering Sea shelf. Crustal thickness beneath the south Alaska magnetic high is commonly 40–50 km. Gravity analysis indicates that the south Alaska magnetic high crust is dense. The south Alaska magnetic high spatially coincides with the Peninsular and Wrangellia terranes. The thick, dense, and magnetic character of this domain requires significant amounts of mafic rocks at intermediate to deep crustal levels. In Wrangellia these mafic rocks are likely to have been emplaced during Middle and (or) Late Triassic Nikolai Greenstone volcanism. In the Peninsular terrane, the most extensive period of mafic magmatism now known was associated with the Early Jurassic Talkeetna Formation volcanic arc. Thus the thick, dense, and magnetic character of the south Alaska magnetic high crust apparently developed as the response to mafic magmatism in both extensional (Wrangellia) and subduction-related arc (Peninsular terrane) settings. The south Alaska magnetic high is therefore a composite crustal feature. At least in Wrangellia, the crust was probably of average thickness (30 km) or greater prior to Triassic mafic magmatism. Up to 20 km (40%) of its present thickness may be due to the addition of Triassic mafic magmas. Throughout the south Alaska magnetic high, significant crustal growth

  10. A Geodynamic Study of Active Crustal Deformation and Earthquakes in North China

    Science.gov (United States)

    Yang, Y.; Liu, M.

    2005-12-01

    North China is part of the Archaean Sino-Korean craton, yet today it is a region of intense crustal deformation and earthquakes, including 21 M >=7.0 events since 512 AD. More than half of the large events occurred within the Fen-Wei rift system surrounding the stable Ordos plateau; the largest events (M >=7.3) show a sequential southward migration along the rift. However, since 1695 the Fen-Wei rift has became seismically dormant, while seismicity seems having shifted eastward to the North China plain, marked by the 1996 Tangshan earthquake (M=7.8). We have developed a 3D viscoelastic geodynamic model to study the cause of seismicity and its spatial-temporal pattern in North China. Constrained by crustal kinematics from GPS and neotectonic data, the model shows high deviatoric stress in the North China crust, resulting mainly from compression of the expanding Tibetan Plateau and resistance from the stable Siberian block. Within North China seismicity is largely controlled by lateral heterogeneity of lithospheric structures, which explains the concentration of seismicity in the Fen-Wei rift. Our results show that stress triggering may have contributed to the sequential migration of large events along the rift, and the release and migration of stress and strain energy from these large events may partially explain the intense seismicity in the North China plain in the past 300 years. Comparing the predicted long-term spatial pattern of strain energy with seismic energy release provides some insights of potential earthquake risks in North China.

  11. Crustal structure of the Arabian plate: new constraints of receiver functions

    Science.gov (United States)

    Cui, Z.; Mai, P. M.; Pei, S.

    2013-12-01

    We perform P-wave receiver function analysis across Saudi Arabia to constrain crustal thickness and Poisson's ratio to investigate the role of Afar super plume, on-going sea-floor spreading and mechanical crustal thinning during continental breakup. We include analysis of data from 132 stations, many of them new stations to improve upon previous analysis from a sparse array (30 stations). We first select 201 earthquakes with high signal-to-noise seismogram, using IRIS-station RAYN as reference to pick the events, recorded on 101 stations operated by the Saudi Geological Survey (SGS) during 2007-2011. SGS continually deploys stations every year and we added a second data set of 96 earthquakes on 30 newly deployed stations in 2012, again station RAYN is used as reference for picking high quality recordings. Two way, 4th order band-pass Butterworth filter with pass band of 0.01 - 3 Hz is applied to eliminate low-frequency noise, then deconvolution is performed in time-domain. We deploy the slant stack method to determine both the Moho depth and Poisson's ratio at each station; this method combines the later multiples (PpPs and PpSs+PsPs) with the Moho Ps converted phase to mitigate the trade-off between the Moho depth and crustal Poisson's ratio. Average crustal P wave velocities of 6.5km/s for Arabian Shield and 6.1 km/s for Arabian Platform are assigned, respectively. In addition, we add the semblance parameter through semblance analysis into the objective function of the slant stack method to suppress the incoherent noise. Our results show that Moho depth is 38-42 km at the central boundary between the Arabian Shield and the Arabian Platform, where the crust is not extended and there is little sediment deposited. To the east beneath the Arabian Platform the crust thickens to 43-46 km, then decreases to 37-41km against the Persian Gulf. To the west the crust gradually thins to 33-35 km over a distance of approximately 400-500 km. Farther east, toward the Red Sea

  12. Crustal fraction of moment of inertia in pulsars

    International Nuclear Information System (INIS)

    Atta, Debasis; Mukhopadhyay, Somnath; Basu, D.N.

    2015-01-01

    In the present work, stability of the β-equilibrated dense nuclear matter is analyzed with respect to the thermodynamic stability conditions. Based on the density dependent M3Y (DDM3Y) effective nucleon-nucleon (NN) interaction, the location of the inner edge of neutron star crusts and core-crust transition density and pressure are calculated and crustal fraction of moment of inertia is determined. These results for pressure and density at core-crust transition together with the observed minimum crustal fraction of the total moment of inertia provide a new limit for the radius of the Vela pulsar

  13. Crustal structure and active tectonics in the Eastern Alps

    DEFF Research Database (Denmark)

    Brückl, E.; Behm, M.; Decker, K.

    2010-01-01

    fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south......During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian...

  14. High resolution 2D numerical models from rift to break-up: Crustal hyper-extension, Margin asymmetry, Sequential faulting

    Science.gov (United States)

    Brune, Sascha; Heine, Christian; Pérez-Gussinyé, Marta; Sobolev, Stephan

    2013-04-01

    Numerical modelling is a powerful tool to integrate a multitude of geological and geophysical data while addressing fundamental questions of passive margin formation such as the occurrence of crustal hyper-extension, (a-)symmetries between conjugate margin pairs, and the sometimes significant structural differences between adjacent margin segments. This study utilises knowledge gathered from two key examples of non-magmatic, asymmetric, conjugate margin pairs, i.e. Iberia-New Foundland and Southern Africa-Brazil, where many published seismic lines provide solid knowledge on individual margin geometry. While both margins involve crustal hyper-extension, it is much more pronounced in the South Atlantic. We investigate the evolution of these two margin pairs by carefully constraining our models with detailed plate kinematic history, laboratory-based rheology, and melt fraction evaluation of mantle upwelling. Our experiments are consistent with observed fault patterns, crustal thickness, and basin stratigraphy. We conduct 2D thermomechanical rift models using the finite element code SLIM3D that operates with nonlinear stress- and temperature-dependent elasto-visco-plastic rheology, with parameters provided by laboratory experiments on major crustal and upper mantle rocks. In our models we also calculate the melt fraction within the upwelling asthenosphere, which allows us to control whether the model indeed corresponds to the non-magmatic margin type or not. Our modelling highlights two processes as fundamental for the formation of hyper-extension and margin asymmetry at non-magmatic margins: (1) Strain hardening in the rift center due to cooling of upwelling mantle material (2) The formation of a weak crustal domain adjacent to the rift center caused by localized viscous strain softening and heat transfer from the mantle. Simultaneous activity of both processes promotes lateral rift migration in a continuous way that generates a wide layer of hyper-extended crust on

  15. Geochemistry and geochronology of the ∼0.82 Ga high-Mg gabbroic dykes from the Quanji Massif, southeast Tarim Block, NW China: Implications for the Rodinia supercontinent assembly

    Science.gov (United States)

    Liao, Fanxi; Wang, Qinyan; Chen, Nengsong; Santosh, M.; Xu, Yixian; Mustafa, Hassan Abdelsalam

    2018-05-01

    The role of the Tarim Block in the reconstruction of the Neoproterozoic supercontinent Rodinia remains contentious. Here we report a suite of high-Mg gabbroic dykes from the Yingfeng area in northwestern Quanji Massif, which is considered as a fragment of the Tarim Block in NW China. Magmatic zircons from these dykes yield to have a weighted mean 206Pb/238U age of 822.2 ± 5.3 Ma, recording the timing of their emplacement. The gabbros have high MgO (9.91-13.09 wt%), Mg numbers (69.89-75.73) and CaO (8.41-13.55 wt%), medium FeOt (8.50-9.67 wt%) and TiO2 (0.67-0.93 wt%), variable Al2O3 (13.04-16.07 wt%), and high Cr (346.14-675.25 ppm), but relatively low Ni (138.72-212.94 ppm), suggestive of derivation from a primary magma. The rocks display chondrite-normalized LREE patterns with weak fractionation but flat HREE patterns relative to those of the N-MORB. Their primitive mantle normalized trace elemental patterns show positive Rb, Ba and U but negative Th, Nb, Ti and Zr anomalies, carrying characteristics of both mid-ocean ridge basalts and arc basalts. The εHf(t) values of the zircons from these rocks vary from +4.7 to +13.5 with depleted mantle model ages (TDM) of 1.23-0.85 Ga, and the youngest value nearly approaching that for the coeval depleted mantle, suggesting significant addition of juvenile materials. Our data suggest that the strongly depleted basaltic magma was probably sourced from a depleted mantle source that had undergone metasomatism by subduction-related components in a back-arc setting. Accordingly we postulate that a subduction-related tectonic regime possibly prevailed at ∼0.8 Ga along the southeastern margin of the Tarim Block. Combining with available information from the northern Tarim Block, we propose an opposite verging double-sided subduction model for coeval subduction of the oceanic crust beneath both the southern and northern margins of the Tarim Block during early Neoproterozoic.

  16. Avalonian crustal controls on basin evolution: implications for the Mesozoic basins of the southern North Sea

    Science.gov (United States)

    Smit, Jeroen; van Wees, Jan-Diederik; Cloetingh, Sierd

    2015-04-01

    Little is known of the Southern North Sea Basin's (SNSB) Pre-Permian basement due to a lack of outcrop and cores. The nature and structure of the East Avalonian crust and lithosphere remain even less constrained in the absence of deep seismic (refraction) lines. However, various studies have hinted at the importance of the Reactivation of the Early Carboniferous fault network during each consecutive Mesozoic and Cenozoic tectonic phase, demonstrating the key role of weak zones from the Early Carboniferous structural grain in partitioning of structural deformation and vertical basin motions at various scales. Although the older basin history and the basement attract increasing attention, the Pre-Permian tectonics of the SNSB remains little studied with most attention focused on the Permian and younger history. The strong dispersal of existing constraints requires a comprehensive study from Denmark to the UK, i.e. the East Avalonian microplate, bordered by the Variscan Rheïc suture, the Atlantic and Baltica. Based on an extensive literature study and the reinterpretation of publicly available data, linking constraints from the crust and mantle to stratigraphic-sedimentological information, we complement the map of Early Carboniferous rifting of East Avalonia and propose a new tectonic scenario. From the reinterpretation of the boundary between Avalonia and Baltica we propose a new outline for the Avalonian microplate with implications for the tectonics of the North German Basin. Furthermore, we highlight the nature and extent of the major crustal/lithospheric domains with contrasting structural behaviour and the major boundaries that separate them. Results shed light on the effects of long lived differences in crustal fabric that are responsible for spatial heterogeneity in stress and strain magnitudes and zonations of fracturing, burial history and temperature history. The geomechanical control of large crustal-scale fault structures will provide the constraints

  17. Role of crustal assimilation and basement compositions in the petrogenesis of differentiated intraplate volcanic rocks: a case study from the Siebengebirge Volcanic Field, Germany

    Science.gov (United States)

    Schneider, K. P.; Kirchenbaur, M.; Fonseca, R. O. C.; Kasper, H. U.; Münker, C.; Froitzheim, N.

    2016-06-01

    The Siebengebirge Volcanic Field (SVF) in western Germany is part of the Cenozoic Central European Volcanic Province. Amongst these volcanic fields, the relatively small SVF comprises the entire range from silica-undersaturated mafic lavas to both silica-undersaturated and silica-saturated differentiated lavas. Owing to this circumstance, the SVF represents a valuable study area representative of intraplate volcanism in Europe. Compositions of the felsic lavas can shed some new light on differentiation of intraplate magmas and on the extent and composition of potential crustal assimilation processes. In this study, we provide detailed petrographic and geochemical data for various differentiated SVF lavas, including major and trace element concentrations as well as Sr-Nd-Hf-Pb isotope compositions. Samples include tephriphonolites, latites, and trachytes with SiO2 contents ranging between 53 and 66 wt%. If compared to previously published compositions of mafic SVF lavas, relatively unradiogenic 143Nd/144Nd and 176Hf/177Hf coupled with radiogenic 87Sr/86Sr and 207Pb/204Pb lead to the interpretation that the differentiated volcanic rocks have assimilated significant amounts of lower crustal mafic granulites like the ones found as xenoliths in the nearby Eifel volcanic field. These crustal contaminants should possess unradiogenic 143Nd/144Nd and 176Hf/177Hf, radiogenic 87Sr/86Sr, and highly radiogenic 207Pb/204Pb compositions requiring the presence of ancient components in the central European lower crust that are not sampled on the surface. Using energy-constrained assimilation-fractional crystallisation (EC-AFC) model calculations, differentiation of the SVF lithologies can be modelled by approximately 39-47 % fractional crystallisation and 6-15 % crustal assimilation. Notably, the transition from silica-undersaturated to silica-saturated compositions of many felsic lavas in the SVF that is difficult to account for in closed-system models is also well explained by

  18. Crustal Gravitational Potential Energy Change and Subduction Earthquakes

    Science.gov (United States)

    Zhu, P. P.

    2017-05-01

    Crustal gravitational potential energy (GPE) change induced by earthquakes is an important subject in geophysics and seismology. For the past forty years the research on this subject stayed in the stage of qualitative estimate. In recent few years the 3D dynamic faulting theory provided a quantitative solution of this subject. The theory deduced a quantitative calculating formula for the crustal GPE change using the mathematic method of tensor analysis under the principal stresses system. This formula contains only the vertical principal stress, rupture area, slip, dip, and rake; it does not include the horizontal principal stresses. It is just involved in simple mathematical operations and does not hold complicated surface or volume integrals. Moreover, the hanging wall vertical moving (up or down) height has a very simple expression containing only slip, dip, and rake. The above results are significant to investigate crustal GPE change. Commonly, the vertical principal stress is related to the gravitational field, substituting the relationship between the vertical principal stress and gravitational force into the above formula yields an alternative formula of crustal GPE change. The alternative formula indicates that even with lack of in situ borehole measured stress data, scientists can still quantitatively calculate crustal GPE change. The 3D dynamic faulting theory can be used for research on continental fault earthquakes; it also can be applied to investigate subduction earthquakes between oceanic and continental plates. Subduction earthquakes hold three types: (a) crust only on the vertical up side of the rupture area; (b) crust and seawater both on the vertical up side of the rupture area; (c) crust only on the vertical up side of the partial rupture area, and crust and seawater both on the vertical up side of the remaining rupture area. For each type we provide its quantitative formula of the crustal GPE change. We also establish a simplified model (called

  19. Formal language constrained path problems

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, C.; Jacob, R.; Marathe, M.

    1997-07-08

    In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

  20. Upper mantle and crustal structure of the East Greenland Caledonides

    DEFF Research Database (Denmark)

    Schiffer, Christian; Balling, N.; Jacobsen, B. H.

    The East Greenland and Scandinavian Caledonides once formed a major coherent mountain range, as a consequence of the collision of the continents of Laurentia and Baltica. The crustal and upper mantle structure was furthermore influenced by several geodynamic processes leading to the formation of ...

  1. Mars - Crustal structure inferred from Bouguer gravity anomalies.

    Science.gov (United States)

    Phillips, R. J.; Saunders, R. S.; Conel, J. E.

    1973-01-01

    Bouguer gravity has been computed for the equatorial region of Mars by differencing free air gravity and the gravity predicted from topographic variations. The free air gravity was generated from an eighth-order set of spherical harmonic coefficients. The gravity from topographic variations was generated by integrating a two-dimensional Green's function over each contour level. The Bouguer gravity indicates crustal inhomogeneities on Mars that are postulated to be variations in crustal thickness. The Tharsis ridge is a region of thick continental type crust. The gravity data, structural patterns, topography, and surface geology of this region lead to the interpretation of the Tharsis topographic high as a broad crustal upwarp possibly associated with local formation of lower-density crustal material and subsequent rise of a thicker crust. The Amazonis region is one of several basins of relatively thin crust, analogous to terrestrial ocean basins. The Libya and Hellas basins, which are probable impact features, are also underlain by thin crust and are possible regions of mantle upwelling.

  2. Deep Crustal Melting and the Survival of Continental Crust

    Science.gov (United States)

    Whitney, D.; Teyssier, C. P.; Rey, P. F.; Korchinski, M.

    2017-12-01

    Plate convergence involving continental lithosphere leads to crustal melting, which ultimately stabilizes the crust because it drives rapid upward flow of hot deep crust, followed by rapid cooling at shallow levels. Collision drives partial melting during crustal thickening (at 40-75 km) and/or continental subduction (at 75-100 km). These depths are not typically exceeded by crustal rocks that are exhumed in each setting because partial melting significantly decreases viscosity, facilitating upward flow of deep crust. Results from numerical models and nature indicate that deep crust moves laterally and then vertically, crystallizing at depths as shallow as 2 km. Deep crust flows en masse, without significant segregation of melt into magmatic bodies, over 10s of kms of vertical transport. This is a major mechanism by which deep crust is exhumed and is therefore a significant process of heat and mass transfer in continental evolution. The result of vertical flow of deep, partially molten crust is a migmatite dome. When lithosphere is under extension or transtension, the deep crust is solicited by faulting of the brittle upper crust, and the flow of deep crust in migmatite domes traverses nearly the entire thickness of orogenic crust in Recognition of the importance of migmatite (gneiss) domes as archives of orogenic deep crust is applicable to determining the chemical and physical properties of continental crust, as well as mechanisms and timescales of crustal differentiation.

  3. An Approach to the Crustal Thickness Inversion Problem

    Science.gov (United States)

    De Marchi, F.; Di Achille, G.

    2017-12-01

    We describe a method to estimate the crustal thickness of a planet and we apply it to Venus. As in the method of (Parker, 1972), modified by (Wieczorek & Phillips, 1998), the gravity field anomalies of a planet are assumed to be due to the combined effect of topography and relief on the crust-mantle interface. No assumptions on isostasy are necessary. In our case, rather than using the expansion of the powers of the relief in Taylor series, we model the gravitational field of topography/relief by means of a large number of prism-shaped masses covering the whole surface of the planet. Under the hypothesis that crustal and mantle densities are the same everywhere, we solve for the relief depths on the crust-mantle interface by imposing that observed and modeled gravity field at a certain reference spherical surface (external to the planet) must be equal. This method can be extended to the case of non-uniform densities. Finally, we calculate a map of the crustal thickness of Venus and compare our results with those predicted by previous work and with the global distribution of main geological features (e.g. rift zones, tesserae, coronae). We discuss the agremeent between our results and the main geodynamical and crustal models put forth to explain the origin of such features and the applicability of this method in the context of the mission VOX (Venus Origins Explore), proposed for NASA's NF4 call.

  4. Magnetic anomaly patterns over crustal blocks of the King Edward VII Peninsula, Marie Byrd Land, West Antarctica

    Directory of Open Access Journals (Sweden)

    M. Spano

    2000-06-01

    Full Text Available Within the framework of the GITARA II project an aeromagnetic survey was performed during the GANOVEXVII expedition (1992/1993 over the King Edward VII Peninsula in northwestern Marie Byrd Land (West Antarctica. This region which may represent the eastern flank of the Ross Sea rift system had previously been explored only at reconnaissance level. New total field and upward continued (10 km magnetic anomaly maps are produced and interpreted here to map and discuss the crustal structure of the Edward VII Peninsula. Tworound-shaped, high-amplitude magnetic anomalies are recognised over the Alexandra Mountains block. The anomalies are difficult to interpret since susceptibility data indicate the prevalence of non-magnetic rocks at the surface. A possible interpretation is that the anomalies are due to Cretaceous mafic intrusives distinct from weakly magnetic Byrd Coast Granite of the adjacent Rockefeller Mountains block. Alternatively the anomalies could be related to buried pluton-sized Devonian Ford Granodiorite intruded by dikes. If Cretaceous in age, the former intrusives revealed from the magnetics could also be responsible for contact metamorphism of the adjacent Alexandra Mountains migmatites. Lower amplitude circular anomalies over the Central Plateau and Prestrud Inlet are likely to be caused by unexposed Devonian Ford Granodiorite which crops out in the Ford Ranges. Elongated high-frequency anomalies of the Sulzberger Bay are similar to those recognised over seismically constrained Cenozoic rift-related volcanics of the Ross Sea. A broad magnetic low over the Sulzberger Ice Shelf may be indicative of a fault bounded graben-like basin with sedimentary infill. Overall recognition of magnetic anomaly patterns and trends reveals segmentation of the Edward VII Peninsula and of the adjacent marine areas in distinct crustal blocks. Faults may separate these blocks and they are interpreted to reflect multiple Cretaceous and maybe Cenozoic crustal

  5. Wavelet library for constrained devices

    Science.gov (United States)

    Ehlers, Johan Hendrik; Jassim, Sabah A.

    2007-04-01

    The wavelet transform is a powerful tool for image and video processing, useful in a range of applications. This paper is concerned with the efficiency of a certain fast-wavelet-transform (FWT) implementation and several wavelet filters, more suitable for constrained devices. Such constraints are typically found on mobile (cell) phones or personal digital assistants (PDA). These constraints can be a combination of; limited memory, slow floating point operations (compared to integer operations, most often as a result of no hardware support) and limited local storage. Yet these devices are burdened with demanding tasks such as processing a live video or audio signal through on-board capturing sensors. In this paper we present a new wavelet software library, HeatWave, that can be used efficiently for image/video processing/analysis tasks on mobile phones and PDA's. We will demonstrate that HeatWave is suitable for realtime applications with fine control and range to suit transform demands. We shall present experimental results to substantiate these claims. Finally this library is intended to be of real use and applied, hence we considered several well known and common embedded operating system platform differences; such as a lack of common routines or functions, stack limitations, etc. This makes HeatWave suitable for a range of applications and research projects.

  6. Estimates of stress drop and crustal tectonic stress from the 27 February 2010 Maule, Chile, earthquake: Implications for fault strength

    Science.gov (United States)

    Luttrell, K.M.; Tong, X.; Sandwell, D.T.; Brooks, B.A.; Bevis, M.G.

    2011-01-01

    The great 27 February 2010 Mw 8.8 earthquake off the coast of southern Chile ruptured a ???600 km length of subduction zone. In this paper, we make two independent estimates of shear stress in the crust in the region of the Chile earthquake. First, we use a coseismic slip model constrained by geodetic observations from interferometric synthetic aperture radar (InSAR) and GPS to derive a spatially variable estimate of the change in static shear stress along the ruptured fault. Second, we use a static force balance model to constrain the crustal shear stress required to simultaneously support observed fore-arc topography and the stress orientation indicated by the earthquake focal mechanism. This includes the derivation of a semianalytic solution for the stress field exerted by surface and Moho topography loading the crust. We find that the deviatoric stress exerted by topography is minimized in the limit when the crust is considered an incompressible elastic solid, with a Poisson ratio of 0.5, and is independent of Young's modulus. This places a strict lower bound on the critical stress state maintained by the crust supporting plastically deformed accretionary wedge topography. We estimate the coseismic shear stress change from the Maule event ranged from-6 MPa (stress increase) to 17 MPa (stress drop), with a maximum depth-averaged crustal shear-stress drop of 4 MPa. We separately estimate that the plate-driving forces acting in the region, regardless of their exact mechanism, must contribute at least 27 MPa trench-perpendicular compression and 15 MPa trench-parallel compression. This corresponds to a depth-averaged shear stress of at least 7 MPa. The comparable magnitude of these two independent shear stress estimates is consistent with the interpretation that the section of the megathrust fault ruptured in the Maule earthquake is weak, with the seismic cycle relieving much of the total sustained shear stress in the crust. Copyright 2011 by the American

  7. The Crustal Structure and Seismicity of Eastern Venezuela

    Science.gov (United States)

    Schmitz, M.; Martins, A.; Sobiesiak, M.; Alvarado, L.; Vasquez, R.

    2001-12-01

    Eastern Venezuela is characterized by a moderate to high seismicity, evidenced recently by the 1997 Cariaco earthquake located on the El Pilar Fault, a right lateral strike slip fault which marks the plate boundary between the Caribbean and South-American plates in this region. Recently, the seismic activity seems to migrate towards the zone of subduction of the Lesser Antilles in the northeast, where a mb 6.0 earthquake occurred in October 2000 at 120 km of depth. Periodical changes in the seismic activity are related to the interaction of the stress fields of the strike-slip and the subduction regimes. The seismic activity decreases rapidly towards to the south with some disperse events on the northern edge of the Guayana Shield, related to the Guri fault system. The crustal models used in the region are derived from the information generated by the national seismological network since 1982 and by microseismicity studies in northeastern Venezuela, coinciding in a crustal thickness of about 35 km in depth. Results of seismic refraction measurements for the region were obtained during field campains in 1998 (ECOGUAY) for the Guayana Shield and the Cariaco sedimentary basin and in 2001 (ECCO) for the Oriental Basin. The total crustal thickness decreases from about 45 km on the northern edge of the Guayana Shield to some 36 km close to El Tigre in the center of the Oriental Basin. The average crustal velocity decreases in the same sense from 6.5 to 5.8 km/s. In the Cariaco sedimentary basin a young sedimentary cover of 1 km thickness with a seismic velocity of 2 km/s was derived. Towards the northern limit of the South-American plate, no deep seismic refraction data are available up to now. The improvement of the crustal models used in that region would constitute a step forward in the analysis of the seismic hazard. Seismic refraction studies funded by CONICIT S1-97002996 and S1-2000000685 projects and PDVSA (additional drilling and blasting), recording equipment

  8. Crustal Structure Within the Southeastern Carpathian Arc, Transylvanian Basin, Romania from Teleseismic Receiver Functions

    Science.gov (United States)

    Stanciu, A. C.; Russo, R. M.; Mocanu, V. I.; Munteanu, L.

    2013-05-01

    We present new measurements of receiver functions at 4 broadband stations temporarily deployed in the Transylvanian Basin within the Carpathian Arc, Romania. Receiver functions can reveal depths to sharp crustal seismic velocity boundaries, which in complex tectonic environments such as the study area provide a good diagnostic for the regional tectonics. As a result of Africa (Adria) collision with Europe and subduction of a part of Tethys Ocean, Tisza-Dacia and Alcapa blocks escaped the collision and were emplaced in an embayment of this ocean, and form today the basement of the Transylvanian Basin. The collision of these terranes with the European continent culminated in the formation, in the Romanian part, of the Eastern Carpathians at the contact between the Transylvanian Basin and the East European Platform along the Tornquist-Teisseyre Suture zone, and of Southern Carpathians at the contact with Moesian Platform. In the foreland of the Carpathian Bend Zone, connecting the two mountain chains, in a very constrained area, a high velocity seismic body was contoured by hypocenters between 70 and 200 km depth. We constructed receiver functions using teleseismic P waves generated by events located between 30 and 95 degrees epicentral angle using the method of Ligorria and Ammon (1999) for individual measurements. We used the H-K method of Zhu and Kanamori (2000) to derive boundary interfaces depths and receiver function complexity from binned stacks. Preliminary results show a relatively shallow Moho depth beneath the Transylvanian Basin.

  9. Order-constrained linear optimization.

    Science.gov (United States)

    Tidwell, Joe W; Dougherty, Michael R; Chrabaszcz, Jeffrey S; Thomas, Rick P

    2017-11-01

    Despite the fact that data and theories in the social, behavioural, and health sciences are often represented on an ordinal scale, there has been relatively little emphasis on modelling ordinal properties. The most common analytic framework used in psychological science is the general linear model, whose variants include ANOVA, MANOVA, and ordinary linear regression. While these methods are designed to provide the best fit to the metric properties of the data, they are not designed to maximally model ordinal properties. In this paper, we develop an order-constrained linear least-squares (OCLO) optimization algorithm that maximizes the linear least-squares fit to the data conditional on maximizing the ordinal fit based on Kendall's τ. The algorithm builds on the maximum rank correlation estimator (Han, 1987, Journal of Econometrics, 35, 303) and the general monotone model (Dougherty & Thomas, 2012, Psychological Review, 119, 321). Analyses of simulated data indicate that when modelling data that adhere to the assumptions of ordinary least squares, OCLO shows minimal bias, little increase in variance, and almost no loss in out-of-sample predictive accuracy. In contrast, under conditions in which data include a small number of extreme scores (fat-tailed distributions), OCLO shows less bias and variance, and substantially better out-of-sample predictive accuracy, even when the outliers are removed. We show that the advantages of OCLO over ordinary least squares in predicting new observations hold across a variety of scenarios in which researchers must decide to retain or eliminate extreme scores when fitting data. © 2017 The British Psychological Society.

  10. A new model of crustal structure of Siberia

    DEFF Research Database (Denmark)

    Cherepanova, Yulia; Artemieva, Irina; Thybo, Hans

    2010-01-01

    to the Verkoyansk Ridge/Lena river in the east, and from the Arctic shelf in the north to the Tien Shan and Altay-Sayans mountains in the south. The new crustal model is based on our new ("from scratch") compilation of all available reliable seismic data and includes the results of seismic reflection, refraction...... orientation. Low surface heat flow (on average around 20-22 microW/m3) and the absence of the high-velocity (Vp>7.2 km/s) lowercrustal layer in the block with the thick crust suggest that eclogitization in the crustal root was subdued, thus allowing preservation of the ultra thick, seismically distinguishable...

  11. The nature of crustal reflectivity at the southwest Iberian margin

    Science.gov (United States)

    Buffett, G. G.; Torne, M.; Carbonell, R.; Melchiorre, M.; Vergés, J.; Fernàndez, M.

    2017-11-01

    Reprocessing of multi-channel seismic reflection data acquired over the northern margin of the Gulf of Cádiz (SW Iberian margin) places new constraints on the upper crustal structure of the Guadalquivir-Portimão Bank. The data presented have been processed with optimized stacking and interval velocity models, a better approach to multiple attenuation, preserved amplitude information to derive the nature of seismic reflectivity, and accurate time-to-depth conversion after migration. The reprocessed data reveal a bright upper crustal reflector just underneath the Paleozoic basement that spatially coincides with the local positive free-air gravity high called the Gulf of Cádiz Gravity High. To investigate the nature of this reflector and to decipher whether it could be associated with pieces of mantle material emplaced at upper crustal levels, we calculated its reflection coefficient and compared it to a buried high-density ultramafic body (serpentinized peridotite) at the Gorringe Bank. Its reflection coefficient ratio with respect to the sea floor differs by only 4.6% with that calculated for the high-density ultramafic body of the Gorringe Bank, while it differs by 35.8% compared to a drilled Miocene limestone unconformity. This means that the Gulf of Cádiz reflector has a velocity and/or density contrast similar to the peridotite at the Gorringe Bank. However, considering the depth at which it is found (between 2.0 and 4.0 km) and the available geological information, it seems unlikely that the estimated shortening from the Oligocene to present is sufficient to emplace pieces of mantle material at these shallow levels. Therefore, and despite the similarity in its reflection coefficient with the peridotites of the Gorringe Bank, our preferred interpretation is that the upper crustal Gulf of Cádiz reflector represents the seismic response of high-density intracrustal magmatic intrusions that may partially contribute to the Gulf of Cádiz Gravity High.

  12. Investigating Microbial Biofilm Formations on Crustal Rock Substrates

    Science.gov (United States)

    Weiser, M.; D'Angelo, T.; Carr, S. A.; Orcutt, B.

    2017-12-01

    Ocean crust hosts microbial life that, in some cases, alter the component rocks as a means of obtaining energy. Variations in crust lithology, included trace metal and mineral content, as well as the chemistry of the fluids circulating through them, provide substrates for some microbes to metabolize, leading to formation of biofilm community structures. Microbes have different parameters for the situations in which they will form biofilms, but they must have some source of energy in excess at the site of biofilm formation for them to become stationary and form the carbohydrate-rich structures connecting the cells to one another and the substrate. Generally, the requirements for microbes to form biofilms on crustal minerals are unclear. We designed two experiments to test (1) mineral preference and biofilm formation rates by natural seawater microbial communities, and (2) biofilm development as a function of phosphate availability for an organism isolated from subseafloor ocean crust. In Experiment 1, we observed that phyric basalt groundmass is preferentially colonized over aphyric basalt or metal sulfides in a shallow water and oxic seawater environment. In experiment 2, tests of the anaerobic heterotroph Thalassospira bacteria isolated from oceanic crustal fluids showed that they preferentially form biofilms, lose motility, and increase exponentially in number over time in higher-PO4 treatments (50 micromolar), including with phosphate-doped basalts, than in treatments with low phosphate concentrations (0.5 micromolar) often found in crustal fluids. These observations suggest phosphate as a main driver of biofilm formation in subsurface crust. Overall, these data suggest that the drivers of microbial biofilm formation on crustal substrates are selective to the substrate conditions, which has important implications for estimating the global biomass of life harbored in oceanic crust.

  13. Parallel Fast Multipole Boundary Element Method for crustal dynamics

    International Nuclear Information System (INIS)

    Quevedo, Leonardo; Morra, Gabriele; Mueller, R Dietmar

    2010-01-01

    Crustal faults and sharp material transitions in the crust are usually represented as triangulated surfaces in structural geological models. The complex range of volumes separating such surfaces is typically three-dimensionally meshed in order to solve equations that describe crustal deformation with the finite-difference (FD) or finite-element (FEM) methods. We show here how the Boundary Element Method, combined with the Multipole approach, can revolutionise the calculation of stress and strain, solving the problem of computational scalability from reservoir to basin scales. The Fast Multipole Boundary Element Method (Fast BEM) tackles the difficulty of handling the intricate volume meshes and high resolution of crustal data that has put classical Finite 3D approaches in a performance crisis. The two main performance enhancements of this method: the reduction of required mesh elements from cubic to quadratic with linear size and linear-logarithmic runtime; achieve a reduction of memory and runtime requirements allowing the treatment of a new scale of geodynamic models. This approach was recently tested and applied in a series of papers by [1, 2, 3] for regional and global geodynamics, using KD trees for fast identification of near and far-field interacting elements, and MPI parallelised code on distributed memory architectures, and is now in active development for crustal dynamics. As the method is based on a free-surface, it allows easy data transfer to geological visualisation tools where only changes in boundaries and material properties are required as input parameters. In addition, easy volume mesh sampling of physical quantities enables direct integration with existing FD/FEM code.

  14. Crustal thickness of Antarctica estimated using data from gravimetric satellites

    Science.gov (United States)

    Llubes, Muriel; Seoane, Lucia; Bruinsma, Sean; Rémy, Frédérique

    2018-04-01

    Computing a better crustal thickness model is still a necessary improvement in Antarctica. In this remote continent where almost all the bedrock is covered by the ice sheet, seismic investigations do not reach a sufficient spatial resolution for geological and geophysical purposes. Here, we present a global map of Antarctic crustal thickness computed from space gravity observations. The DIR5 gravity field model, built from GOCE and GRACE gravimetric data, is inverted with the Parker-Oldenburg iterative algorithm. The BEDMAP products are used to estimate the gravity effect of the ice and the rocky surface. Our result is compared to crustal thickness calculated from seismological studies and the CRUST1.0 and AN1 models. Although the CRUST1.0 model shows a very good agreement with ours, its spatial resolution is larger than the one we obtain with gravimetric data. Finally, we compute a model in which the crust-mantle density contrast is adjusted to fit the Moho depth from the CRUST1.0 model. In East Antarctica, the resulting density contrast clearly shows higher values than in West Antarctica.

  15. Crustal thickness of Antarctica estimated using data from gravimetric satellites

    Directory of Open Access Journals (Sweden)

    M. Llubes

    2018-04-01

    Full Text Available Computing a better crustal thickness model is still a necessary improvement in Antarctica. In this remote continent where almost all the bedrock is covered by the ice sheet, seismic investigations do not reach a sufficient spatial resolution for geological and geophysical purposes. Here, we present a global map of Antarctic crustal thickness computed from space gravity observations. The DIR5 gravity field model, built from GOCE and GRACE gravimetric data, is inverted with the Parker–Oldenburg iterative algorithm. The BEDMAP products are used to estimate the gravity effect of the ice and the rocky surface. Our result is compared to crustal thickness calculated from seismological studies and the CRUST1.0 and AN1 models. Although the CRUST1.0 model shows a very good agreement with ours, its spatial resolution is larger than the one we obtain with gravimetric data. Finally, we compute a model in which the crust–mantle density contrast is adjusted to fit the Moho depth from the CRUST1.0 model. In East Antarctica, the resulting density contrast clearly shows higher values than in West Antarctica.

  16. Boron isotope fractionation in magma via crustal carbonate dissolution.

    Science.gov (United States)

    Deegan, Frances M; Troll, Valentin R; Whitehouse, Martin J; Jolis, Ester M; Freda, Carmela

    2016-08-04

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ(11)B values down to -41.5‰, reflecting preferential partitioning of (10)B into the assimilating melt. Loss of (11)B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports (11)B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ(11)B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  17. Precambrian crustal history of the Nimrod Group, central Transantarctic Mountains

    International Nuclear Information System (INIS)

    Goodge, J.W.; Fanning, C.M.

    2002-01-01

    High-grade metamorphic and igneous rocks of the Nimrod Group represent crystalline basement to the central Transantarctic Mountains. Despite metamorphism and penetrative deformation during the Ross Orogeny, they preserve a deep record of Precambrian geologic history in this sector of the East Antarctic shield. A review of available U-Pb geochronometric data reveals multiple geologic events spanning 2.5 b.y. of Archean to Early Paleozoic time, including: (1) juvenile Archean crust production by magmatism between 3150 and 3000 Ma; (2) crustal stabilisation and metamorphism between 2955 and 2900 Ma; (3) ultra-metamorphism or anatexis at c. 2500 Ma; (4) deep-crustal metamorphism and magmatism between 1720 and 1730 Ma, redefining the Nimrod Orogeny; (5) post-1700 Ma sedimentation; and (6) basement reactivation involving high-grade metamorphism, magmatism, and penetrative deformation during the Ross Orogeny between 540 and 515 Ma. A strong regional metamorphic and deformational Ross overprint, dated by U-Pb and Ar thermochronology, had pronounced thermomechanical effects on the basement assemblage, yet rocks of the Nimrod Group retain robust evidence of their Precambrian ancestry. The zircon U-Pb record therefore demonstrates that primary crustal lithosphere of the East Antarctic shield extends to the central Transantarctic Mountains, and that it has undergone multiple episodes of reactivation culminating in the Ross Orogeny. (author). 48 refs., 2 figs., 1 tab

  18. Boron isotope fractionation in magma via crustal carbonate dissolution

    Science.gov (United States)

    Deegan, Frances M.; Troll, Valentin R.; Whitehouse, Martin J.; Jolis, Ester M.; Freda, Carmela

    2016-08-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to -41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  19. Developing Tools to Test the Thermo-Mechanical Models, Examples at Crustal and Upper Mantle Scale

    Science.gov (United States)

    Le Pourhiet, L.; Yamato, P.; Burov, E.; Gurnis, M.

    2005-12-01

    Testing geodynamical model is never an easy task. Depending on the spatio-temporal scale of the model, different testable predictions are needed and no magic reciepe exist. This contribution first presents different methods that have been used to test themo-mechanical modeling results at upper crustal, lithospheric and upper mantle scale using three geodynamical examples : the Gulf of Corinth (Greece), the Western Alps, and the Sierra Nevada. At short spatio-temporal scale (e.g. Gulf of Corinth). The resolution of the numerical models is usually sufficient to catch the timing and kinematics of the faults precisely enough to be tested by tectono-stratigraphic arguments. In active deforming area, microseismicity can be compared to the effective rheology and P and T axes of the focal mechanism can be compared with local orientation of the major component of the stress tensor. At lithospheric scale the resolution of the models doesn't permit anymore to constrain the models by direct observations (i.e. structural data from field or seismic reflection). Instead, synthetic P-T-t path may be computed and compared to natural ones in term of rate of exhumation for ancient orogens. Topography may also help but on continent it mainly depends on erosion laws that are complicated to constrain. Deeper in the mantle, the only available constrain are long wave length topographic data and tomographic "data". The major problem to overcome now at lithospheric and upper mantle scale, is that the so called "data" results actually from inverse models of the real data and that those inverse model are based on synthetic models. Post processing P and S wave velocities is not sufficient to be able to make testable prediction at upper mantle scale. Instead of that, direct wave propagations model must be computed. This allows checking if the differences between two models constitute a testable prediction or not. On longer term, we may be able to use those synthetic models to reduce the residue

  20. Crustal and mantle structure of the greater Jan Mayen-East Greenland region (NE Atlantic) from combined 3D structural, S-wave velocity, and gravity modeling

    Science.gov (United States)

    Tan, P.; Sippel, J.; Scheck-Wenderoth, M.; Meeßen, C.; Breivik, A. J.

    2016-12-01

    The study area is located between the Jan Mayen Ridge and the east coast of Greenland. It has a complex geological setting with the ultraslow Kolbeinsey and Mohn's spreading ridges, the anomalously shallow Eggvin Bank, the Jan Mayen Microcontinent (JMMC), and the tectonically active West Jan Mayen Fracture Zone (WJMFZ). In this study, we present the results of forward 3D structural, S-wave velocity, and gravity modeling which provide new insights into the deep crust and mantle structure and the wide-ranging influence of the Iceland Plume. The crustal parts of the presented 3D structural model are mainly constrained by local seismic refraction and reflection data. Accordingly, greatest crustal thicknesses (24 km) are observed on the northern boundary of the JMMC, while the average crustal thickness is 8.5 km and 4 km in the Kolbeinsey and Mohn's Ridge, respectively. The densities of the crustal parts are from previous studies. Additionally, the mantle density is derived from S-wave velocity data (between 50 and 250 km depth), while densities of the lithospheric mantle between the Moho and 50 km are calculated assuming isostatic equilibrium at 250 km depth. This is used as a starting density model which is further developed to obtain a reasonable fit between the calculated and measured (free-air) gravity fields. The observed S-wave tomographic data and the gravity modeling prove that the Iceland plume anomaly in the asthenosphere affects the lithospheric thickness and temperature, from the strongly influenced Middle Kolbeinsey Ridge, to the less affected North Kolbeinsey Ridge (Eggvin Bank), and to the little impacted Mohn's Ridge. Thus, the age-temperature relations of the different mid-ocean ridges of the study area are perturbed to different degrees controlled by the distance from the Iceland Plume. Furthermore, we find that the upper 50 km of lithospheric mantle are thermally affected by the plume only in the southwestern parts of the study area.

  1. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...... to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number...

  2. "Storms of crustal stress" and AE earthquake precursors

    Directory of Open Access Journals (Sweden)

    G. P. Gregori

    2010-02-01

    Full Text Available Acoustic emission (AE displays violent paroxysms preceding strong earthquakes, observed within some large area (several hundred kilometres wide around the epicentre. We call them "storms of crustal stress" or, briefly "crustal storms". A few case histories are discussed, all dealing with the Italian peninsula, and with the different behaviour shown by the AE records in the Cephalonia island (Greece, which is characterized by a different tectonic setting.

    AE is an effective tool for diagnosing the state of some wide slab of the Earth's crust, and for monitoring its evolution, by means of AE of different frequencies. The same effect ought to be detected being time-delayed, when referring to progressively lower frequencies. This results to be an effective check for validating the physical interpretation.

    Unlike a seismic event, which involves a much limited focal volume and therefore affects a restricted area on the Earth's surface, a "crustal storm" typically involves some large slab of lithosphere and crust. In general, it cannot be easily reckoned to any specific seismic event. An earthquake responds to strictly local rheological features of the crust, which are eventually activated, and become crucial, on the occasion of a "crustal storm". A "crustal storm" lasts typically few years, eventually involving several destructive earthquakes that hit at different times, at different sites, within that given lithospheric slab.

    Concerning the case histories that are here discussed, the lithospheric slab is identified with the Italian peninsula. During 1996–1997 a "crustal storm" was on, maybe elapsing until 2002 (we lack information for the period 1998–2001. Then, a quiet period occurred from 2002 until 26 May 2008, when a new "crustal storm" started, and by the end of 2009 it is still on. During the 1996–1997 "storm" two strong earthquakes occurred (Potenza and

  3. Complex, multilayered azimuthal anisotropy beneath Tibet: evidence for co-existing channel flow and pure-shear crustal thickening

    Science.gov (United States)

    Agius, Matthew R.; Lebedev, Sergei

    2017-09-01

    Of the two debated, end-member models for the late-Cenozoic thickening of Tibetan crust, one invokes 'channel flow' (rapid viscous flow of the mid-lower crust, driven by topography-induced pressure gradients and transporting crustal rocks eastward) and the other 'pure shear' (faulting and folding in the upper crust, with viscous shortening in the mid-lower crust). Deep-crustal deformation implied by each model is different and would produce different anisotropic rock fabric. Observations of seismic anisotropy can thus offer a discriminant. We use broad-band phase-velocity curves-each a robust average of tens to hundreds of measurements-to determine azimuthal anisotropy in the entire lithosphere-asthenosphere depth range and constrain its amplitude. Inversions of the differential dispersion from path pairs, region-average inversions and phase-velocity tomography yield mutually consistent results, defining two highly anisotropic layers with different fast-propagation directions within each: the middle crust and the asthenosphere. In the asthenosphere beneath central and eastern Tibet, anisotropy is 2-4 per cent and has an NNE-SSW fast-propagation azimuth, indicating flow probably driven by the NNE-ward, shallow-angle subduction of India. The distribution and complexity of published shear wave splitting measurements can be accounted for by the different anisotropy in the mid-lower crust and asthenosphere. The estimated splitting times that would be accumulated in the crust alone are 0.25-0.8 s; in the upper mantle-0.5-1.2 s, depending on location. In the middle crust (20-45 km depth) beneath southern and central Tibet, azimuthal anisotropy is 3-5 and 4-6 per cent, respectively, and its E-W fast-propagation directions are parallel to the current extension at the surface. The rate of the extension is relatively low, however, whereas the large radial anisotropy observed in the middle crust requires strong alignment of mica crystals, implying large finite strain and

  4. Near-surface compressional and shear wave speeds constrained by body-wave polarization analysis

    Science.gov (United States)

    Park, Sunyoung; Ishii, Miaki

    2018-06-01

    A new technique to constrain near-surface seismic structure that relates body-wave polarization direction to the wave speed immediately beneath a seismic station is presented. The P-wave polarization direction is only sensitive to shear wave speed but not to compressional wave speed, while the S-wave polarization direction is sensitive to both wave speeds. The technique is applied to data from the High-Sensitivity Seismograph Network in Japan, and the results show that the wave speed estimates obtained from polarization analysis are compatible with those from borehole measurements. The lateral variations in wave speeds correlate with geological and physical features such as topography and volcanoes. The technique requires minimal computation resources, and can be used on any number of three-component teleseismic recordings, opening opportunities for non-invasive and inexpensive study of the shallowest (˜100 m) crustal structures.

  5. Barents Sea Crustal and Upper Mantle Structure from Deep Seismic and Potential Field Data

    Science.gov (United States)

    Aarseth, I.; Mjelde, R.; Breivik, A. J.; Minakov, A.; Huismans, R. S.; Faleide, J. I.

    2016-12-01

    The Barents Sea basement comprises at least two different domains; the Caledonian in the west and the Timanian in the east. Contrasting interpretations have been published recently, as the transition between these two domains is not well constrained. Interpretations of new high-quality magnetic data covering most of the SW Barents Sea challenged previous studies of the Late Paleozoic basin configurations in the western and central Barents Sea. Two major directions of Caledonian structures have been proposed by different authors: N-S and SW-NE. Two regional ocean bottom seismic (OBS) profiles, crossing these two major directions, were acquired in 2014.The primary goal in this project is to locate the main Caledonian suture in the western Barents Sea, as well as the possible Barentsia-Baltica suture postulated further eastwards. High velocity anomalies associated with Caledonian eclogites are particularly interesting as they may be related to Caledonian suture zones. The collapse of the Caledonian mountain range predominantly along these suture zones is expected to be closely linked to the deposition of Devonian erosional products, and subsequent rifting is likely to be influenced by inheritance of Caledonian trends. P-wave travel-time modelling is done by use of a combined ray-tracing and inversion scheme, and gravity modelling has been used to support the seismic model. The results indicate high P-wave velocities (mostly over 4 km/s) close to the seafloor as well as high velocity (around 6 km/s) zones at shallow depths which are interpreted as volcanic sills. The crustal transect reveals areas of complex geology and velocity inversions. Strong reflections from within the crystalline crust indicate a heterogeneous basement terrain. Gravity modelling agrees with this, as several blocks with variable densities had to be introduced in order to reproduce the observed gravity anomalies. Refractions from the top of the crystalline basement together with reflections from

  6. Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography

    Science.gov (United States)

    Korenaga, J.; Holbrook, W. S.; Kent, G. M.; Kelemen, P. B.; Detrick, R. S.; Larsen, H.-C.; Hopper, J. R.; Dahl-Jensen, T.

    2000-09-01

    We present results from a combined multichannel seismic reflection (MCS) and wideangle onshore/offshore seismic experiment conducted in 1996 across the southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure. We employ a hybrid ray-tracing scheme based on the graph method and the local ray-bending refinement to efficiently obtain an accurate forward solution, and we employ smoothing and optional damping constraints to regularize an iterative inversion. We invert 2318 Pg and 2078 PmP travel times to construct a compressional velocity model for the 350-km-long transect, and a long-wavelength structure with strong lateral heterogeneity is recovered, including (1) ˜30-km-thick, undeformed continental crust with a velocity of 6.0 to 7.0 km/s near the landward end, (2) 30- to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone, and (3) 15- to 9-km-thick oceanic crust toward the seaward end. The thickness of the igneous upper crust characterized by a high-velocity gradient also varies from 6 km within the transition zone to ˜3 km seaward. The bottom half of the lower crust generally has a velocity higher than 7.0 km/s, reaching a maximum of 7.2 to 7.5 km/s at the Moho. A nonlinear Monte Carlo uncertainty analysis is performed to estimate the a posteriori model variance, showing that most velocity and depth nodes are well determined with one standard deviation of 0.05-0.10 km/s and 0.25-1.5 km, respectively. Despite significant variation in crustal thickness, the mean velocity of the igneous crust, which serves as a proxy for the bulk crustal composition, is surprisingly constant (˜7.0 km/s) along the transect. On the basis of a mantle melting model incorporating the effect of active mantle upwelling, this velocity-thickness relationship is used to constrain the mantle melting process during the breakup of Greenland

  7. Asymptotic Likelihood Distribution for Correlated & Constrained Systems

    CERN Document Server

    Agarwal, Ujjwal

    2016-01-01

    It describes my work as summer student at CERN. The report discusses the asymptotic distribution of the likelihood ratio for total no. of parameters being h and 2 out of these being are constrained and correlated.

  8. Constrained bidirectional propagation and stroke segmentation

    Energy Technology Data Exchange (ETDEWEB)

    Mori, S; Gillespie, W; Suen, C Y

    1983-03-01

    A new method for decomposing a complex figure into its constituent strokes is described. This method, based on constrained bidirectional propagation, is suitable for parallel processing. Examples of its application to the segmentation of Chinese characters are presented. 9 references.

  9. Mathematical Modeling of Constrained Hamiltonian Systems

    NARCIS (Netherlands)

    Schaft, A.J. van der; Maschke, B.M.

    1995-01-01

    Network modelling of unconstrained energy conserving physical systems leads to an intrinsic generalized Hamiltonian formulation of the dynamics. Constrained energy conserving physical systems are directly modelled as implicit Hamiltonian systems with regard to a generalized Dirac structure on the

  10. Client's Constraining Factors to Construction Project Management

    African Journals Online (AJOL)

    factors as a significant system that constrains project management success of public and ... finance for the project and prompt payment for work executed; clients .... consideration of the loading patterns of these variables, the major factor is ...

  11. On the origin of constrained superfields

    Energy Technology Data Exchange (ETDEWEB)

    Dall’Agata, G. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy); Dudas, E. [Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay,F-91128 Palaiseau (France); Farakos, F. [Dipartimento di Fisica “Galileo Galilei”, Università di Padova,Via Marzolo 8, 35131 Padova (Italy); INFN, Sezione di Padova,Via Marzolo 8, 35131 Padova (Italy)

    2016-05-06

    In this work we analyze constrained superfields in supersymmetry and supergravity. We propose a constraint that, in combination with the constrained goldstino multiplet, consistently removes any selected component from a generic superfield. We also describe its origin, providing the operators whose equations of motion lead to the decoupling of such components. We illustrate our proposal by means of various examples and show how known constraints can be reproduced by our method.

  12. Crustal contamination and crystal entrapment during polybaric magma evolution at Mt. Somma-Vesuvius volcano, Italy: Geochemical and Sr isotope evidence

    Science.gov (United States)

    Piochi, M.; Ayuso, R.A.; de Vivo, B.; Somma, R.

    2006-01-01

    New major and trace element analyses and Sr-isotope determinations of rocks from Mt. Somma-Vesuvius volcano produced from 25 ky BP to 1944 AD are part of an extensive database documenting the geochemical evolution of this classic region. Volcanic rocks include silica undersaturated, potassic and ultrapotassic lavas and tephras characterized by variable mineralogy and different crystal abundance, as well as by wide ranges of trace element contents and a wide span of initial Sr-isotopic compositions. Both the degree of undersaturation in silica and the crystal content increase through time, being higher in rocks produced after the eruption at 472 AD (Pollena eruption). Compositional variations have been generally thought to reflect contributions from diverse types of mantle and crust. Magma mixing is commonly invoked as a fundamental process affecting the magmas, in addition to crystal fractionation. Our assessment of geochemical and Sr-isotopic data indicates that compositional variability also reflects the influence of crustal contamination during magma evolution during upward migration to shallow crustal levels and/or by entrapment of crystal mush generated during previous magma storage in the crust. Using a variant of the assimilation fractional crystallization model (Energy Conservation-Assimilation Fractional Crystallization; [Spera and Bohrson, 2001. Energy-constrained open-system magmatic processes I: General model and energy-constrained assimilation and fractional crystallization (EC-AFC) formulation. J. Petrol. 999-1018]; [Bohrson, W.A. and Spera, F.J., 2001. Energy-constrained open-system magmatic process II: application of energy-constrained assimilation-fractional crystallization (EC-AFC) model to magmatic systems. J. Petrol. 1019-1041]) we estimated the contributions from the crust and suggest that contamination by carbonate rocks that underlie the volcano (2 km down to 9-10 km) is a fundamental process controlling magma compositions at Mt. Somma

  13. Crustal heterogeneity and seismotectonics of the region around Beijing, China

    Science.gov (United States)

    Huang, Jinli; Zhao, Dapeng

    2004-07-01

    A detailed three-dimensional (3-D) P-wave velocity model of the crust and uppermost mantle under the Chinese capital (Beijing) region is determined with a spatial resolution of 25 km in the horizontal direction and 4-17 km in depth. We used 48,750 precise P-wave arrival times from 2973 events of local crustal earthquakes, controlled seismic explosions and quarry blasts. These events were recorded by a new digital seismic network consisting of 101 seismic stations equipped with high-sensitivity seismometers. The data are analyzed by using a 3-D seismic tomography method. Our tomographic model provides new insights into the geological structure and tectonics of the region, such as the lithological variations and large fault zones across the major geological terranes like the North China Basin, the Taihangshan and the Yanshan mountainous areas. The velocity images of the upper crust reflect well the surface geological and topographic features. In the North China Basin, the depression and uplift areas are imaged as slow and fast velocities, respectively. The Taihangshan and Yanshan mountainous regions are generally imaged as broad high-velocity zones, while the Quaternary intermountain basins show up as small low-velocity anomalies. Velocity changes are visible across some of the large fault zones. Large crustal earthquakes, such as the 1976 Tangshan earthquake ( M=7.8) and the 1679 Sanhe earthquake ( M=8.0), generally occurred in high-velocity areas in the upper to middle crust. In the lower crust to the uppermost mantle under the source zones of the large earthquakes, however, low-velocity and high-conductivity anomalies exist, which are considered to be associated with fluids. The fluids in the lower crust may cause the weakening of the seismogenic layer in the upper and middle crust and thus contribute to the initiation of the large crustal earthquakes.

  14. Effect of Crustal Density Structures on GOCE Gravity Gradient Observables

    Directory of Open Access Journals (Sweden)

    Robert Tenzer Pavel Novák

    2013-01-01

    Full Text Available We investigate the gravity gradient components corrected for major known anomalous density structures within the Earth¡¦s crust. Heterogeneous mantle density structures are disregarded. The gravimetric forward modeling technique is utilized to compute the gravity gradients based on methods for a spherical harmonic analysis and synthesis of a gravity field. The Earth¡¦s gravity gradient components are generated using the global geopotential model GOCO-03s. The topographic and stripping gravity corrections due to the density contrasts of the ocean and ice are computed from the global topographic/bathymetric model DTM2006.0 (which also includes the ice-thickness dataset. The discrete data of sediments and crust layers taken from the CRUST2.0 global crustal model are then used to apply the additional stripping corrections for sediments and remaining anomalous crustal density structures. All computations are realized globally on a one arc-deg geographical grid at a mean satellite elevation of 255 km. The global map of the consolidated crust-stripped gravity gradients reveals distinctive features which are attributed to global tectonics, lithospheric plate configuration, lithosphere structure and mantle dynamics (e.g., glacial isostatic adjustment, mantle convection. The Moho signature, which is the most pronounced signal in these refined gravity gradients, is superimposed over a weaker gravity signal of the lithospheric mantle. An interpretational quality of the computed (refined gravity gradient components is mainly limited by a low accuracy and resolution of the CRUST2.0 sediment and crustal layer data and unmodeled mantle structures.

  15. Improved H-κ Method by Harmonic Analysis on Ps and Crustal Multiples in Receiver Functions with respect to Dipping Moho and Crustal Anisotropy

    Science.gov (United States)

    Li, J.; Song, X.; Wang, P.; Zhu, L.

    2017-12-01

    The H-κ method (Zhu and Kanamori, 2000) has been widely used to estimate the crustal thickness and Vp/Vs ratio with receiver functions. However, in regions where the crustal structure is complicated, the method may produce uncertain or even unrealistic results, arising particularly from dipping Moho and/or crustal anisotropy. Here, we propose an improved H-κ method, which corrects for these effects first before stacking. The effect of dipping Moho and crustal anisotropy on Ps receiver function has been well studied, but not as much on crustal multiples (PpPs and PpSs+PsPs). Synthetic tests show that the effect of crustal anisotropy on the multiples are similar to Ps, while the effect of dipping Moho on the multiples is 5 times that on Ps (same cosine trend but 5 times in time shift). A Harmonic Analysis (HA) method for dipping/anisotropy was developed by Wang et al. (2017) for crustal Ps receiver functions to extract parameters of dipping Moho and crustal azimuthal anisotropy. In real data, the crustal multiples are much more complicated than the Ps. Therefore, we use the HA method (Wang et al., 2017), but apply separately to Ps and the multiples. It shows that although complicated, the trend of multiples can still be reasonably well represented by the HA. We then perform separate azimuthal corrections for Ps and the multiples and stack to obtain a combined receiver function. Lastly, the traditional H-κ procedure is applied to the stacked receiver function. We apply the improved H-κ method on 40 CNDSN (Chinese National Digital Seismic Network) stations distributed in a variety of geological setting across the Chinese continent. The results show apparent improvement compared to the traditional H-κ method, with clearer traces of multiples and stronger stacking energy in the grid search, as well as more reliable H-κ values.

  16. Testing Predictions of Continental Insulation using Oceanic Crustal Thicknesses

    Science.gov (United States)

    Hoggard, Mark; Shorttle, Oliver; White, Nicky

    2016-04-01

    The thermal blanketing effect of continental crust has been predicted to lead to elevated temperatures within the upper mantle beneath supercontinents. Initial break-up is associated with increased magmatism and the generation of flood basalts. Continued rifting and sea-floor spreading lead to a steady reduction of this thermal anomaly. Recently, evidence in support of this behaviour has come from the major element geochemistry of mid-ocean ridge basalts, which suggest excess rifting temperatures of ˜ 150 °C that decay over ˜ 100 Ma. We have collated a global inventory of ˜ 1000 seismic reflection profiles and ˜ 500 wide-angle refraction experiments from the oceanic realm. Data are predominantly located along passive margins, but there are also multiple surveys in the centres of the major oceanic basins. Oceanic crustal thickness has been mapped, taking care to avoid areas of secondary magmatic thickening near seamounts or later thinning such as across transform faults. These crustal thicknesses are a proxy for mantle potential temperature at the time of melt formation beneath a mid-ocean ridge system, allowing us to quantify the amplitude and duration of thermal anomalies generated beneath supercontinents. The Jurassic break-up of the Central Atlantic and the Cretaceous rifting that formed the South Atlantic Ocean are both associated with excess temperatures of ˜ 50 °C that have e-folding times of ˜ 50 Ma. In addition to this background trend, excess temperatures reach > 150 °C around the region of the Rio Grande Rise, associated with the present-day Tristan hotspot. The e-folding time of this more local event is ˜ 10 Ma, which mirrors results obtained for the North Atlantic Ocean south of Iceland. In contrast, crustal thicknesses from the Pacific Ocean reveal approximately constant potential temperature through time. This observation is in agreement with predictions, as the western Pacific was formed by rifting of an oceanic plate. In summary

  17. Lower crustal intrusions beneath the southern Baikal Rift Zone

    DEFF Research Database (Denmark)

    Nielsen, Christoffer; Thybo, Hans

    2009-01-01

    centre. The BEST (Baikal Explosion Seismic Transect) project acquired a 360-km long, deep seismic, refraction/wide-angle reflection profile in 2002 across southern Lake Baikal. The data from this project is used for identification of large-scale crustal structures and modelling of the seismic velocities....../s and 7.9 km/s. We interpret this feature as resulting from mafic to ultra-mafic intrusions in the form of sills. Petrological interpretation of the velocity values suggests that the intrusions are sorted by fractional crystallization into plagioclase-rich low-velocity layers and pyroxene- and olivine...

  18. Co-Seismic Effect of the 2011 Japan Earthquake on the Crustal Movement Observation Network of China

    Directory of Open Access Journals (Sweden)

    Shaomin Yang

    2013-01-01

    Full Text Available Great earthquakes introduce measurable co-seismic displacements over regions of hundreds and thousands of kilometers in width, which, if not accounted for, may significantly bias the long-term surface velocity field constrained by GPS observations performed during a period encompassing that event. Here, we first present an estimation of the far-field co-seismic off-sets associated with the 2011 Japan Mw 9.0 earthquake using GPS measurements from the Crustal Movement Observation Network of China (CMONOC in North China. The uncertainties of co-seismic off-set, either at cGPS stations or at campaign sites, are better than 5 - 6 mm on average. We compare three methods to constrain the co-seismic off-sets at the campaign sites in northeastern China 1 interpolating cGPS coseismic offsets, 2 estimating in terms of sparsely sampled time-series, and 3 predicting by using a well-constrained slip model. We show that the interpolation of cGPS co-seismic off-sets onto the campaign sites yield the best co-seismic off-set solution for these sites. The source model gives a consistent prediction based on finite dislocation in a layered spherical Earth, which agrees with the best prediction with discrepancies of 2 - 10 mm for 32 campaign sites. Thus, the co-seismic off-set model prediction is still a reasonable choice if a good coverage cGPS network is not available for a very active region like the Tibetan Plateau in which numerous campaign GPS sites were displaced by the recent large earthquakes.

  19. The Roles of the Yellowstone Hotspot and Crustal Assimilation in Generating Pleistocene-Holocene Basalts on the Eastern Snake River Plain

    Science.gov (United States)

    Mintz, H.; Chadwick, J.

    2017-12-01

    The southwest motion of the North American plate across the Yellowstone hotspot created a chain of age-progressive rhyolitic calderas over the past 16 myr. in southern Idaho, U.S. The focus of Yellowstone activity now resides in northwest Wyoming, but basaltic volcanism has continued in its wake in southern Idaho on the eastern Snake River Plain (ESRP). These younger basaltic lavas are not age progressive and have buried the Yellowstone rhyolites on the ESRP. The ultimate source of the basalts is commonly ascribed to the passage or presence of the hotspot. However, the mechanisms involved, and the relative roles of the hotspot, other mantle sources, and the North American crust in generating the ESRP basalts remain unclear and have been the subject of recent geochemical and isotopic studies. In this study, the role of crustal assimilation is addressed by analyzing the chemical and isotopic characteristics of some of the youngest Pleistocene-Holocene tholeiitic volcanic fields on the ESRP, which were erupted through varying thicknesses of continental crust. Samples were analyzed from the Hell's Half Acre flow (5,200 years old; all dates Kuntz et al., 1986, 1994), Cerro Grande flow (13,380 years), and Black Butte Crater (a.k.a. Shoshone) flow (10,130 years), which were erupted at distances from between about 200 to 300 km from the current location of the hotspot. The crust of the ESRP thins from northeast to southwest, from about 47 km at the Hells Half Acre flow to 40 km at the Black Butte Crater flow, a thickness difference of about 15%. The apparently similar tectonic and magmatic environments of the three sampled flows suggest the crustal thickness variation may be a primary influence on the magnitude of assimilation and therefore the isotopic characteristics of the lavas. The goal of this work is to constrain the relative role of assimilation and to understand the source(s) of the magmas and the Yellowstone hotspot contribution. Major elements, trace elements

  20. Crustal Structure of the Tengchong Intra-plate Volcanic Area

    Science.gov (United States)

    Qian, Rongyi; Tong, Vincent C. H.

    2015-09-01

    We here provide an overview of our current understanding of the crustal structure of Tengchong in southwest China, a key intra-plate volcanic area along the Himalayan geothermal belt. Given that there is hitherto a lack of information about the near-surface structure of intra-plate volcanic areas, we present the first seismic reflection and velocity constraints on the shallow crust between intra-plate volcanoes. Our near-surface seismic images reveal the existence of dome-shaped seismic reflectors (DSRs) in the shallow crust between intra-plate volcanic clusters in Tengchong. The two DSRs are both ~2 km wide, and the shallowest parts of the DSRs are found at the depth of 200-300 m. The velocity model shows that the shallow low-velocity layer (<4 km/s) is anomalously thick (~1 km) in the region where the DSRs are observed. The presence of DSRs indicates significant levels of intra-plate magmatism beneath the along-axis gap separating two volcano clusters. Along-axis gaps between volcano clusters are therefore not necessarily an indicator of lower levels of magmatism. The seismic images obtained in this technically challenging area for controlled-source seismology allow us to conclude that shallow crustal structures are crucial for understanding the along-axis variations of magmatism and hydrothermal activities in intra-plate volcanic areas.

  1. Seismotectonics and Crustal Thickness of Northwest Mindoro, Philippines

    Science.gov (United States)

    Chen, P. F.; Olavere, E. A.; Lee, K. M.; Bautista, B.; Solidum, R., Jr.; Huang, B. S.

    2015-12-01

    Mindoro Island locates where the Palawan Continental Block (PCB) indented into the Philippine Mobile Belt (PMB) during the Early Miocene and where the Manila Trench terminates, having ceased convergence due to collision. On the transition from subduction to collision, Northwest Mindoro exhibits vigorous seismic activity and has been debated about its affiliation being PCB or PMB. Here, we use data from both the EHB and Global Centroid Moment Tensor catalogues to study the regional seismotectonics. We also deployed five broadband stations to probe the crustal thickness beneath NW Mindoro using receiver function analysis. Results show that, following the southeasterly reduction of convergence rates at the southern termination of the Manila Trench, the slab dipping angles steepen, were initiated at depth (~200 km) and propagate upwards. The horizontal distances of the trench and slab, as measured from the Wadati-Benioff zone at 200 km depth, also reduce in a southeasterly direction. Observations of intermediate-depth earthquakes that exhibit predominantly down-dip extensional stress patterns attest that the steepening of slab dipping angles is due to the negative buoyancy of the slab. Preliminary results of receiver function analysis suggest that the crustal thickness beneath NW Mindoro is about 40 km and is probably PCB affiliated.

  2. Crustal structure of the Eastern Alps and their foreland

    DEFF Research Database (Denmark)

    Grad, M.; Brückl, E.; Majdanski, M.

    2009-01-01

    The subject of this paper concerns the seismic modelling of the crustal structure in the transition zone from the Bohemian Massif, across the Molasse basin and the Eastern Alps to the Southern Alps, mainly on the territory of Austria. The CEL10/Alp04 profile crosses the triple point of the European......) are distinct up to 60-90 km offset and are characterized by large variations in apparent velocity and amplitude. The contact between the Molasse basin and the Eastern Alps represents a barrier for seismic waves. Mid-crustal reflections (Pc) are usually recorded at short distance intervals (20-50 km......, was undertaken using a ray-tracing technique. The P-wave velocity in the crystalline upper crust of the Bohemian Massif and Molasse basin is about 6.15 km s-1, which is slightly higher than in the Alpine area (about 6.0 km s-1). Below the northern accretionary wedge of the Eastern Alps low-velocity sediments...

  3. Lower crustal xenoliths, Chinese Peak lava flow, central Sierra Nevada.

    Science.gov (United States)

    Dodge, F.C.W.; Calk, L.C.; Kistler, R.W.

    1986-01-01

    This assemblage of pyroxenite, peridotite and mafic granulite xenoliths in the toe of a 10 m.y. trachybasalt flow remnant overlying late Cretaceous granitic rocks, indicates the presence of a mafic-ultramafic complex beneath this part of central California; orthopyroxenites, websterites and clinopyroxenites are dominant. A few of the xenoliths contain ovoid opaque patches that are apparently pseudomorphs after garnet and have pyralspite garnet compositions; using a garnet-orthopyroxene geobarometer, they indicate a lower crustal depth of approx 40 km. Abundant mafic granulites can be subdivided into those with Al2O3 = or 15% and showing considerable scatter on oxide variation diagrams. The high-alumina granulite xenoliths have relatively low 87Rb/86Sr but high 87Sr/86Sr, whereas the low-alumina and ultramafic xenoliths have a wide range of 87Rb/86Sr, but lower 87Sr/86Sr; the isotopic data indicate roughly the same age as that of overlying granitic plutons (approx 100 m.y.). However, the granitic rocks have initial 87Sr/86Sr ratios intermediate between those of the high-alumina and ultramafic xenoliths, suggesting that they result from the mixing of basaltic magma (represented by the ultramafic rocks) and crustal materials, with subsequent crystal fractionation.-R.A.H.

  4. ADMAP-2: The second generation Antarctic crustal magnetic anomaly map.

    Science.gov (United States)

    Ferraccioli, F.; Golynsky, A.; Golynsky, D.; Young, D. A.; Eagles, G.; Damaske, D.; Finn, C.; Aitken, A.; von Frese, R. R. B.; Ghidella, M. E.; Kim, H. R.; Hong, J.

    2017-12-01

    ADMAP-2 is the second generation crustal magnetic anomaly compilation for the Antarctic region south of 60°S. It was produced from more than 3.5 million line-km of near-surface terrestrial, airborne and marine magnetic observations collected since the International Geophysical Year 1957/58 through 2013. The data were edited, IGRF corrected, profile levelled and gridded at a 1.5-km interval on a polar stereographic projection using the minimum curvature technique. Given the ubiquitous polar cover of snow, ice and sea water, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies, and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and break-up of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice-probing radar and gravity information greatly facilitate understanding the evolution of fundamental large-scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.

  5. Nanocalorimetric characterization of microbial activity in deep subsurface oceanic crustal fluids

    Directory of Open Access Journals (Sweden)

    Alberto eRobador

    2016-04-01

    Full Text Available Although fluids within the upper oceanic basaltic crust harbor a substantial fraction of the total prokaryotic cells on Earth, the energy needs of this microbial population are unknown. In this study, a nanocalorimeter (sensitivity down to 4.3 x 10-3 mJ h-1 ml-1 was used to measure the enthalpy of microbially catalyzed reactions as a function of temperature in samples from two distinct crustal fluid aquifers. Microorganisms in unamended, warm (63 °C and geochemically altered anoxic fluids taken from 292 meters sub-basement (msb near the Juan de Fuca Ridge produced 267.3 mJ of heat over the course of 97 hours during a step-wise isothermal scan from 35.5 to 85.0 °C. Most of this heat signal likely stems from the germination of thermophilic endospores (6.66 x 104 cells ml-1FLUID and their subsequent metabolic activity at temperatures greater than 50 °C. The average cellular energy consumption (1.79 x 10-7 kJ h-1 cell-1 reveals the high metabolic potential of a dormant community transported by fluids circulating through the ocean crust. By contrast, samples taken from 293 msb from cooler (3.8 °C, relatively unaltered oxic fluids, produced 12.8 mJ of heat over the course of 14 hours as temperature ramped from 34.8 to 43.0 °C. Corresponding cell-specific energy turnover rates (0.18 pW cell-1 were converted to oxygen uptake rates of 24.5 nmol O2 ml-1FLUID d-1, validating previous model predictions of microbial activity in this environment. Given that the investigated fluids are characteristic of expansive areas of the upper oceanic crust, the measured metabolic heat rates can be used to constrain boundaries of habitability and microbial activity in the oceanic crust.

  6. Physical and chemical consequences of crustal melting in fossil mature intra-oceanic arcs

    Science.gov (United States)

    Berger, J.; Burg, J.-P.

    2012-04-01

    Seismic velocity models of active intra-oceanic arcs show roots with densities and P-wave velocities intermediate to classical lower oceanic crust (density; ~3.0, Vp: ~7.0 km/s) and uppermost harzburgitic mantle (density: 3.2-3.3, Vp: 7.9-8.0 km/s). Most studies on active and fossil exhumed island arcs interpret the petrological nature of this root as ultramafic cumulates crystallized from primitive melts and/or as pyroxenites formed via basalt-peridotite reactions. Igneous cumulates and pyroxenites have densities close to or above that of uppermost mantle rocks; they can consequently undergo gravity-driven delamination, a process thought to drive the bulk composition of the arc toward an andesitic, continental crust-like composition. Dehydration and melting reactions are reported from exposed arc roots (Jijal complex in Kohistan; Amalaoulaou arc in Mali; Fiordland arc in New-Zealand). Intense influx of mantle-derived basaltic magmas at high pressure in a thickening island arc can enable lower crustal rocks to locally cross the dehydration-melting solidus of hydrous subalkaline basalts. Thermodynamic modeling using Perple_X, geochemical analysis and compilation of experimental and field data have been combined to constrain processes, conditions and consequences of intra-arc melting. The position of the solidus in a P-T grid is strongly dependent of the bulk water content: at 1 GPa, it is as low as 750 °C for water saturated hornblende-gabbros (>1 wt% H2O) and 830°C for gabbros with 0.1 wt% H2O. Incipient melting (F conditions to trigger gravity-driven delamination of the root and could lead to introduction of fertile arc garnet pyroxenites within the upper mantle. However, in Kohistan and at Amalaoulaou, the dense garnet-clinopyroxene residues are dispersed in the arc roots; they are intermingled with hornblendite and pyroxenite bodies. The small density contrast between garnet granulites and the harzburgitic mantle, and the low volumes of garnet

  7. Towards weakly constrained double field theory

    Directory of Open Access Journals (Sweden)

    Kanghoon Lee

    2016-08-01

    Full Text Available We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  8. Continuation of Sets of Constrained Orbit Segments

    DEFF Research Database (Denmark)

    Schilder, Frank; Brøns, Morten; Chamoun, George Chaouki

    Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajectory...... that starts close and returns close to this fixed point within finite time. More complicated examples are hybrid periodic orbits of piecewise smooth systems or quasi-periodic invariant tori. Even though it is possible to define generalised two-point boundary value problems for computing sets of constrained...... orbit segments, this is very disadvantageous in practice. In this talk we will present an algorithm that allows the efficient continuation of sets of constrained orbit segments together with the solution of the full variational problem....

  9. Variable crustal thickness beneath Thwaites Glacier revealed from airborne gravimetry, possible implications for geothermal heat flux in West Antarctica

    Science.gov (United States)

    Damiani, Theresa M.; Jordan, Tom A.; Ferraccioli, Fausto; Young, Duncan A.; Blankenship, Donald D.

    2014-12-01

    Thwaites Glacier has one of the largest glacial catchments in West Antarctica. The future stability of Thwaites Glacier's catchment is of great concern, as this part of the West Antarctic Ice Sheet has recently been hypothesized to already be en route towards collapse. Although an oceanic trigger is thought to be responsible for current change at the grounding line of Thwaites Glacier, in order to determine the effects of this coastal change further in the interior of the West Antarctic Ice Sheet it is essential to also better constrain basal conditions that control the dynamics of fast glacial flow within the catchment itself. One major contributor to fast glacial flow is the presence of subglacial water, the production of which is a result of both glaciological shear heating and geothermal heat flux. The primary goal of our study is to investigate the crustal thickness beneath Thwaites Glacier, which is an important contributor to regional-scale geothermal heat flux patterns. Crustal structure is an indicator of past tectonic events and hence provides a geophysical proxy for the thermal status of the crust and mantle. Terrain-corrected Bouguer gravity disturbances are used here to estimate depths to the Moho and mid-crustal boundary. The thin continental crust we reveal beneath Thwaites Glacier supports the hypothesis that the West Antarctic Rift System underlies the region and is expressed topographically as the Byrd Subglacial Basin. This rifted crust is of similar thickness to that calculated from airborne gravity data beneath neighboring Pine Island Glacier, and is more extended than crust in the adjacent Siple Coast sector of the Ross Sea Embayment. A zone of thinner crust is also identified near the area's subaerial volcanoes lending support to a recent interpretation predicting that this part of Marie Byrd Land is a major volcanic dome, likely within the West Antarctic Rift System itself. Near-zero Bouguer gravity disturbances for the subglacial highlands

  10. Constrained principal component analysis and related techniques

    CERN Document Server

    Takane, Yoshio

    2013-01-01

    In multivariate data analysis, regression techniques predict one set of variables from another while principal component analysis (PCA) finds a subspace of minimal dimensionality that captures the largest variability in the data. How can regression analysis and PCA be combined in a beneficial way? Why and when is it a good idea to combine them? What kind of benefits are we getting from them? Addressing these questions, Constrained Principal Component Analysis and Related Techniques shows how constrained PCA (CPCA) offers a unified framework for these approaches.The book begins with four concre

  11. Crustal structure of the rifted volcanic margins and uplifted plateau of Western Yemen from receiver function analysis

    Science.gov (United States)

    Ahmed, Abdulhakim; Tiberi, Christel; Leroy, Sylvie; Stuart, Graham W.; Keir, Derek; Sholan, Jamal; Khanbari, Khaled; Al-Ganad, Ismael; Basuyau, Clémence

    2013-06-01

    We analyse P-wave receiver functions across the western Gulf of Aden and southern Red Sea continental margins in Western Yemen to constrain crustal thickness, internal crustal structure and the bulk seismic velocity characteristics in order to address the role of magmatism, faulting and mechanical crustal thinning during continental breakup. We analyse teleseismic data from 21 stations forming the temporary Young Conjugate Margins Laboratory (YOCMAL) network together with GFZ and Yemeni permanent stations. Analysis of computed receiver functions shows that (1) the thickness of unextended crust on the Yemen plateau is ˜35 km; (2) this thins to ˜22 km in coastal areas and reaches less than 14 km on the Red Sea coast, where presence of a high-velocity lower crust is evident. The average Vp/Vs ratio for the western Yemen Plateau is 1.79, increasing to ˜1.92 near the Red Sea coast and decreasing to 1.68 for those stations located on or near the granitic rocks. Thinning of the crust, and by inference extension, occurs over a ˜130-km-wide transition zone from the Red Sea and Gulf of Aden coasts to the edges of the Yemen plateau. Thinning of continental crust is particularly localized in a <30-km-wide zone near the coastline, spatially co-incident with addition of magmatic underplate to the lower crust, above which on the surface we observe the presence of seaward dipping reflectors (SDRs) and thickened Oligo-Miocene syn-rift basaltic flows. Our results strongly suggest the presence of high-velocity mafic intrusions in the lower crust, which are likely either synrift magmatic intrusion into continental lower crust or alternatively depleted upper mantle underplated to the base of the crust during the eruption of the SDRs. Our results also point towards a regional breakup history in which the onset of rifting was synchronous along the western Gulf of Aden and southern Red Sea volcanic margins followed by a second phase of extension along the Red Sea margin.

  12. Crustal deformation mechanism in southeastern Tibetan Plateau: Insights from numerical modeling

    Science.gov (United States)

    Li, Y.; Liu, S.; Chen, L.

    2017-12-01

    The Indo-Asian collision developed the complicated crustal deformation around the southeastern Tibetan plateau. Numerous models have proposed to explain the crustal deformation, but the mechanism remains controversial, especially the increasing multi-geophysics data, which demonstrate the existence of lower velocity, lower resistivity and high conductivity, implying that lower crustal flow is responsible for the crustal deformation, arguing for the lower crust flow model. To address the relations between the crust flow and the surface deformation, we employ a three-dimensional viscoelastic finite model to investigate the possible influence on the surface deformation, and discuss the stress field distribution under the model. Our preliminary results suggest that lower crustal flow plays an important role in crustal deformation in southeastern Tibetan plateau. The best fitting is achieved when the flow velocity of the lower crust is approximately 10-11 mm/a faster than that of the upper crust. Crustal rheological properties affect regional crustal deformation, when the viscosity of the middle and lower crust in the South China block reaches 1022 and 1023 Pa.s, respectively; the predicted match observations well, especially for the magnitude within the South China block. The maximum principal stress field exhibits clear zoning, gradually shifting from an approximately east-west orientation in the northern Bayan Har block to southeast in the South China block, southwest in the western Yunnan block, and a radially divergent distribution in the Middle Yunnan and Southern Yunnan blocks.

  13. Density heterogeneity of the upper mantle beneath Siberia from satellite gravity and a new regional crustal model

    DEFF Research Database (Denmark)

    Herceg, Matija; Thybo, Hans; Artemieva, Irina

    2013-01-01

    We present a new regional model for the density structure of the upper mantle below Siberia. The residual mantle gravity anomalies are based on gravity data derived from the GOCE gravity gradients and geopotential models, with crustal correction to the gravity field being calculated from a new...... on regional and global crustal models. We analyze how uncertainties and errors in the crustal model propagate from crustal densities to mantle residual gravity anomalies and the density model of the upper mantle. The new regional density model for the Siberian craton and the West Siberian Basin complements...... regional crustal model. This newly compiled database on the crustal seismic structure, complemented by additional constraints from petrological analysis of near-surface rocks and lower crustal xenoliths, allows for a high-resolution correction of the crustal effects as compared to previous studies based...

  14. On Tree-Constrained Matchings and Generalizations

    NARCIS (Netherlands)

    S. Canzar (Stefan); K. Elbassioni; G.W. Klau (Gunnar); J. Mestre

    2011-01-01

    htmlabstractWe consider the following \\textsc{Tree-Constrained Bipartite Matching} problem: Given two rooted trees $T_1=(V_1,E_1)$, $T_2=(V_2,E_2)$ and a weight function $w: V_1\\times V_2 \\mapsto \\mathbb{R}_+$, find a maximum weight matching $\\mathcal{M}$ between nodes of the two trees, such that

  15. Constrained systems described by Nambu mechanics

    International Nuclear Information System (INIS)

    Lassig, C.C.; Joshi, G.C.

    1996-01-01

    Using the framework of Nambu's generalised mechanics, we obtain a new description of constrained Hamiltonian dynamics, involving the introduction of another degree of freedom in phase space, and the necessity of defining the action integral on a world sheet. We also discuss the problem of quantizing Nambu mechanics. (authors). 5 refs

  16. Client's constraining factors to construction project management ...

    African Journals Online (AJOL)

    This study analyzed client's related factors that constrain project management success of public and private sector construction in Nigeria. Issues that concern clients in any project can not be undermined as they are the owners and the initiators of project proposals. It is assumed that success, failure or abandonment of ...

  17. Hyperbolicity and constrained evolution in linearized gravity

    International Nuclear Information System (INIS)

    Matzner, Richard A.

    2005-01-01

    Solving the 4-d Einstein equations as evolution in time requires solving equations of two types: the four elliptic initial data (constraint) equations, followed by the six second order evolution equations. Analytically the constraint equations remain solved under the action of the evolution, and one approach is to simply monitor them (unconstrained evolution). Since computational solution of differential equations introduces almost inevitable errors, it is clearly 'more correct' to introduce a scheme which actively maintains the constraints by solution (constrained evolution). This has shown promise in computational settings, but the analysis of the resulting mixed elliptic hyperbolic method has not been completely carried out. We present such an analysis for one method of constrained evolution, applied to a simple vacuum system, linearized gravitational waves. We begin with a study of the hyperbolicity of the unconstrained Einstein equations. (Because the study of hyperbolicity deals only with the highest derivative order in the equations, linearization loses no essential details.) We then give explicit analytical construction of the effect of initial data setting and constrained evolution for linearized gravitational waves. While this is clearly a toy model with regard to constrained evolution, certain interesting features are found which have relevance to the full nonlinear Einstein equations

  18. A Dynamic Programming Approach to Constrained Portfolios

    DEFF Research Database (Denmark)

    Kraft, Holger; Steffensen, Mogens

    2013-01-01

    This paper studies constrained portfolio problems that may involve constraints on the probability or the expected size of a shortfall of wealth or consumption. Our first contribution is that we solve the problems by dynamic programming, which is in contrast to the existing literature that applies...

  19. A model for optimal constrained adaptive testing

    NARCIS (Netherlands)

    van der Linden, Willem J.; Reese, Lynda M.

    2001-01-01

    A model for constrained computerized adaptive testing is proposed in which the information on the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum

  20. A model for optimal constrained adaptive testing

    NARCIS (Netherlands)

    van der Linden, Willem J.; Reese, Lynda M.

    1997-01-01

    A model for constrained computerized adaptive testing is proposed in which the information in the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum

  1. Neutron Powder Diffraction and Constrained Refinement

    DEFF Research Database (Denmark)

    Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.

    1977-01-01

    The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement is...

  2. Terrestrial Sagnac delay constraining modified gravity models

    Science.gov (United States)

    Karimov, R. Kh.; Izmailov, R. N.; Potapov, A. A.; Nandi, K. K.

    2018-04-01

    Modified gravity theories include f(R)-gravity models that are usually constrained by the cosmological evolutionary scenario. However, it has been recently shown that they can also be constrained by the signatures of accretion disk around constant Ricci curvature Kerr-f(R0) stellar sized black holes. Our aim here is to use another experimental fact, viz., the terrestrial Sagnac delay to constrain the parameters of specific f(R)-gravity prescriptions. We shall assume that a Kerr-f(R0) solution asymptotically describes Earth's weak gravity near its surface. In this spacetime, we shall study oppositely directed light beams from source/observer moving on non-geodesic and geodesic circular trajectories and calculate the time gap, when the beams re-unite. We obtain the exact time gap called Sagnac delay in both cases and expand it to show how the flat space value is corrected by the Ricci curvature, the mass and the spin of the gravitating source. Under the assumption that the magnitude of corrections are of the order of residual uncertainties in the delay measurement, we derive the allowed intervals for Ricci curvature. We conclude that the terrestrial Sagnac delay can be used to constrain the parameters of specific f(R) prescriptions. Despite using the weak field gravity near Earth's surface, it turns out that the model parameter ranges still remain the same as those obtained from the strong field accretion disk phenomenon.

  3. Chance constrained uncertain classification via robust optimization

    NARCIS (Netherlands)

    Ben-Tal, A.; Bhadra, S.; Bhattacharayya, C.; Saketha Nat, J.

    2011-01-01

    This paper studies the problem of constructing robust classifiers when the training is plagued with uncertainty. The problem is posed as a Chance-Constrained Program (CCP) which ensures that the uncertain data points are classified correctly with high probability. Unfortunately such a CCP turns out

  4. Integrating job scheduling and constrained network routing

    DEFF Research Database (Denmark)

    Gamst, Mette

    2010-01-01

    This paper examines the NP-hard problem of scheduling jobs on resources such that the overall profit of executed jobs is maximized. Job demand must be sent through a constrained network to the resource before execution can begin. The problem has application in grid computing, where a number...

  5. Neuroevolutionary Constrained Optimization for Content Creation

    DEFF Research Database (Denmark)

    Liapis, Antonios; Yannakakis, Georgios N.; Togelius, Julian

    2011-01-01

    and thruster types and topologies) independently of game physics and steering strategies. According to the proposed framework, the designer picks a set of requirements for the spaceship that a constrained optimizer attempts to satisfy. The constraint satisfaction approach followed is based on neuroevolution...... and survival tasks and are also visually appealing....

  6. Models of Flux Tubes from Constrained Relaxation

    Indian Academy of Sciences (India)

    tribpo

    J. Astrophys. Astr. (2000) 21, 299 302. Models of Flux Tubes from Constrained Relaxation. Α. Mangalam* & V. Krishan†, Indian Institute of Astrophysics, Koramangala,. Bangalore 560 034, India. *e mail: mangalam @ iiap. ernet. in. † e mail: vinod@iiap.ernet.in. Abstract. We study the relaxation of a compressible plasma to ...

  7. Physics of Earthquake Disaster: From Crustal Rupture to Building Collapse

    Science.gov (United States)

    Uenishi, Koji

    2018-05-01

    Earthquakes of relatively greater magnitude may cause serious, sometimes unexpected failures of natural and human-made structures, either on the surface, underground, or even at sea. In this review, by treating several examples of extraordinary earthquake-related failures that range from the collapse of every second building in a commune to the initiation of spontaneous crustal rupture at depth, we consider the physical background behind the apparently abnormal earthquake disaster. Simple but rigorous dynamic analyses reveal that such seemingly unusual failures actually occurred for obvious reasons, which may remain unrecognized in part because in conventional seismic analyses only kinematic aspects of the effects of lower-frequency seismic waves below 1 Hz are normally considered. Instead of kinematics, some dynamic approach that takes into account the influence of higher-frequency components of waves over 1 Hz will be needed to anticipate and explain such extraordinary phenomena and mitigate the impact of earthquake disaster in the future.

  8. PIXEL: Japanese InSAR community for crustal deformation research

    Science.gov (United States)

    Furuya, M.; Shimada, M.; Ozawa, T.; Fukushima, Y.; Aoki, Y.; Miyagi, Y.; Kitagawa, S.

    2007-12-01

    In anticipation of the launch of ALOS (Advanced Land Observation Satellite) by JAXA (Japan Aerospace eXploration Agency), and in order to expand and bolster the InSAR community for crustal deformation research in Japan, a couple of scientists established a consortium, PIXEL, in November 2005 in a completely bottom-up fashion. PIXEL stands for Palsar Interferometry Consortium to Study our Evolving Land. Formally, it is a research contract between JAXA and Earthquake Research Institute (ERI), University of Tokyo. As ERI is a shared institute of the Japanese universities and research institutes, every scientist at all Japanese universities and institutes can participate in this consortium. The activity of PIXEL includes information exchange by mailing list, tutorial workshop for InSAR software, research workshop, and PALSAR data sharing. After the launch of ALOS, we have already witnessed several earthquakes and volcanic activities using PALSAR interferometry. We will briefly show and digest some of those observation results.

  9. Investigation of lunar crustal structure and isostasy. Final technical report

    International Nuclear Information System (INIS)

    Thurber, C.H.

    1987-07-01

    The lunar mascon basins have strongly free air gravity anomalies, generally exceeding 100 milligals at an elevation of 100 km. The source of the anomalies is a combination of mantle uplift beneath the impact basins and subsequent infilling by high-density mare basalts. The relative contribution of these two components is still somewhat uncertain, although it is generally accepted that the amount of mantle uplift greatly exceeds the thickness of the basalts. Extensive studies have been carried out of the crustal structure of mare basins, based on gravity data, and their tectonic evolution, based on compressive and extensional tectonic features. The present study endeavored to develop a unified, self-consistent model of the lunar crust and lithosphere incorporating both gravity and tectonic constraints

  10. Sub-crustal seismic activity beneath Klyuchevskoy Volcano

    Science.gov (United States)

    Carr, M. J.; Droznina, S.; Levin, V. L.; Senyukov, S.

    2013-12-01

    Seismic activity is extremely vigorous beneath the Klyuchevskoy Volcanic Group (KVG). The unique aspect is the distribution in depth. In addition to upper-crustal seismicity, earthquakes take place at depths in excess of 20 km. Similar observations are known in other volcanic regions, however the KVG is unique in both the number of earthquakes and that they occur continuously. Most other instances of deep seismicity beneath volcanoes appear to be episodic or transient. Digital recording of seismic signals started at the KVG in early 2000s.The dense local network reliably locates earthquakes as small as ML~1. We selected records of 20 earthquakes located at depths over 20 km. Selection was based on the quality of the routine locations and the visual clarity of the records. Arrivals of P and S waves were re-picked, and hypocentral parameters re-established. Newl locations fell within the ranges outlined by historical seismicity, confirming the existence of two distinct seismically active regions. A shallower zone is at ~20 km depth, and all hypocenters are to the northeast of KVG, in a region between KVG and Shiveluch volcano. A deeper zone is at ~30 km, and all hypocenters cluster directly beneath the edifice of the Kyuchevskoy volcano. Examination of individual records shows that earthquakes in both zones are tectonic, with well-defined P and S waves - another distinction of the deep seismicity beneath KVG. While the upper seismic zone is unquestionably within the crust, the provenance of the deeper earthquakes is enigmatic. The crustal structure beneath KVG is highly complex, with no agreed-upon definition of the crust-mantle boundary. Rather, a range of values, from under 30 to over 40 km, exists in the literature. Similarly, a range of velocity structures has been reported. Teleseismic receiver functions (RFs) provide a way to position the earthquakes with respect to the crust-mantle boundary. We compare the differential travel times of S and P waves from deep

  11. Crustal structure of Australia from ambient seismic noise tomography

    Science.gov (United States)

    Saygin, Erdinc; Kennett, B. L. N.

    2012-01-01

    Surface wave tomography for Australian crustal structure has been carried out using group velocity measurements in the period range 1-32 s extracted from stacked correlations of ambient noise between station pairs. Both Rayleigh wave and Love wave group velocity maps are constructed for each period using the vertical and transverse component of the Green's function estimates from the ambient noise. The full suite of portable broadband deployments and permanent stations on the continent have been used with over 250 stations in all and up to 7500 paths. The permanent stations provide a useful link between the various shorter-term portable deployments. At each period the group velocity maps are constructed with a fully nonlinear tomographic inversion exploiting a subspace technique and the Fast Marching Method for wavefront tracking. For Rayleigh waves the continental coverage is good enough to allow the construction of a 3D shear wavespeed model in a two stage approach. Local group dispersion information is collated for a distribution of points across the continent and inverted for a 1D SV wavespeed profile using a Neighbourhood Algorithm method. The resulting set of 1D models are then interpolated to produce the final 3D wavespeed model. The group velocity maps show the strong influence of thick sediments at shorter periods, and distinct fast zones associated with cratonic regions. Below the sediments the 3D shear wavespeed model displays significant heterogeneity with only moderate correlation with surface tectonic features. For example, there is no evident expression of the Tasman Line marking the eastern edge of Precambrian outcrop. The large number of available inter-station paths extracted from the ambient noise analysis provide detailed shear wavespeed information for crustal structure across the Australian continent for the first time, including regions where there was no prior sampling because of difficult logistics.

  12. Shallow and deep crustal velocity models of Northeast Tibet

    Science.gov (United States)

    Karplus, M.; Klemperer, S. L.; Mechie, J.; Shi, D.; Zhao, W.; Brown, L. D.; Wu, Z.

    2009-12-01

    The INDEPTH IV seismic profile in Northeast Tibet is the highest resolution wide-angle refraction experiment imaging the Qaidam Basin, North Kunlun Thrusts (NKT), Kunlun Mountains, North and South Kunlun Faults (NKT, SKT), and Songpan-Ganzi terrane (SG). First arrival refraction modeling using ray tracing and least squares inversion has yielded a crustal p-wave velocity model, best resolved for the top 20 km. Ray tracing of deeper reflections shows considerable differences between the Qaidam Basin and the SG, in agreement with previous studies of those areas. The Moho ranges from about 52 km beneath the Qaidam Basin to 63 km with a slight northward dip beneath the SG. The 11-km change must occur between the SKF and the southern edge of the Qaidam Basin, just north of the NKT, allowing the possibility of a Moho step across the NKT. The Qaidam Basin velocity-versus-depth profile is more similar to the global average than the SG profile, which bears resemblance to previously determined “Tibet-type” velocity profiles with mid to lower crustal velocities of 6.5 to 7.0 km/s appearing at greater depths. The highest resolution portion of the profile (100-m instrument spacing) features two distinct, apparently south-dipping low-velocity zones reaching about 2-3 km depth that we infer to be the locations of the NKF and SKF. A strong reflector at 35 km, located entirely south of the SKF and truncated just south of it, may be cut by a steeply south-dipping SKF. Elevated velocities at depth beneath the surface location of the NKF may indicate the south-dipping NKF meets the SKF between depths of 5 and 10 km. Undulating regions of high and low velocity extending about 1-2 km in depth near the southern border of the Qaidam Basin likely represent north-verging thrust sheets of the NKT.

  13. Electrical imaging of deep crustal features of Kutch, India

    Science.gov (United States)

    Sastry, R. S.; Nagarajan, Nandini; Sarma, S. V. S.

    2008-03-01

    A regional Magnetotelluric (MT) study, was carried out with 55 MT soundings, distributed along five traverses, across the Kutch Mainland Unit (KMU), on the west coast of India, a region characterized by a series of successive uplifts and intervening depressions in the form of half graben, bounded by master faults. We obtain the deeper electrical structure of the crust beneath Kutch, from 2-D modelling of MT data along the 5 traverses, in order to evaluate the geo-electrical signatures, if any, of the known primary tectonic structures in this region. The results show that the deeper electrical structure in the Kutch region presents a mosaic of high resistive crustal blocks separated by deep-rooted conductive features. Two such crustal conductive features spatially correlate with the known tectonic features, viz., the Kutch Mainland Fault (KMF), and the Katrol Hill Fault (KHF). An impressive feature of the geo-electrical sections is an additional, well-defined conductive feature, running between Jakhau and Mundra, located at the southern end of each of the five MT traverses and interpreted to be the electrical signature of yet another hidden fault at the southern margin of the KMU. This new feature is named as Jakhau-Mundra Fault (JMF). It is inferred that the presence of JMF together with the Kathiawar Fault (NKF), further south, located at the northern boundary of the Saurashtra Horst, would enhance the possibility of occurrence of a thick sedimentary column in the Gulf of Kutch. The region between the newly delineated fault (JMF) and the Kathiawar fault (NKF) could thus be significant for Hydrocarbon Exploration.

  14. Chemical cycles and health risks of some crustal nuclides

    International Nuclear Information System (INIS)

    McKone, T.E.

    1981-01-01

    This dissertation describes and utilizes an approach for assessing long term health risks due to dispersion of naturally occurring radionuclide series and chemical toxins by normal and altered landscape chemical cycles. In particular, the health risks resulting from geochemical mobilizations of arsenic, lead, uranium and radium are considered. Based on a review of toxic waste hazard-measures and risk assessment studies, a general expression is developed for quantifying health risks imposed by the introduction of toxic materials to components of the total environment. This general measure deals with long term interactions within and between the internal human environment and the external biogeochemical environment. Health hazards are expressed as dose factors which convert environmental concentrations into a corresponding dose field (organ doses in rad for radionuclides; daily intake for toxic elements). The dose field is translated into population health risk expressed as lifetime cancer risk for carcinogens and average blood levels for other toxins. The landscape cell (or prism) is presented as a tool for visualizing and mapping toxic material cycles near the crustal surface. The overall process is incorporated in the GEOTOX code which is a geochemical systems model for describing the dynamics of crustal toxins within a landscape and the resulting health risks. GEOTOX is used to investigate the response of regional landscapes to increased soil and rock inventories of 238 U, 226 Ra, arsenic and lead. It is found that each decay series of element imposes a hazard by its behavior in the total environment that can not be quantified by a similar measure of toxicity

  15. Variation in the crustal structure across central Iceland

    Science.gov (United States)

    Du, Zhijun; Foulger, G. R.

    2001-04-01

    We determine the crustal structures beneath 12 broad-band seismic stations deployed in a swath across central Iceland along and around the ICEMELT explosion seismic profile by combining teleseismic receiver functions, surface wave dispersion curves and the waveforms of a large, local event in Iceland. By using teleseisms that approach from different backazimuths, we study lateral structural variability out of the line of the ICEMELT profile. Beneath Tertiary areas, the thickness of the upper crust, as defined by the 6.5kms-1 velocity horizon, is ~8km and the depth to the base of the lower crust, as defined by the 7.2kms-1 velocity horizon, is ~29-32km. Beneath the currently active rift zone the upper crust thins to ~6.0km and the depth to the base of the lower crust increases to ~35-40km. A substantial low-velocity zone underlies the Middle Volcanic Zone in the lower crust, which may indicate anomalously high geothermal gradients there. This suggests that the large-scale thermal centre of the hotspot may be more westerly than northwest Vatnajokull, where it is generally assumed to lie. Simplified description of the results notwithstanding, there is substantial variability in the overall style of crustal structure throughout Iceland, and a clear, tripartite division into upper and lower crusts and a sharp Moho is poorly supported by many of our results. The nature, distinctiveness and continuity of the Moho is variable and in many areas the crust-mantle transition is a zone with enhanced velocity gradients several kilometres thick.

  16. Self-constrained inversion of potential fields

    Science.gov (United States)

    Paoletti, V.; Ialongo, S.; Florio, G.; Fedi, M.; Cella, F.

    2013-11-01

    We present a potential-field-constrained inversion procedure based on a priori information derived exclusively from the analysis of the gravity and magnetic data (self-constrained inversion). The procedure is designed to be applied to underdetermined problems and involves scenarios where the source distribution can be assumed to be of simple character. To set up effective constraints, we first estimate through the analysis of the gravity or magnetic field some or all of the following source parameters: the source depth-to-the-top, the structural index, the horizontal position of the source body edges and their dip. The second step is incorporating the information related to these constraints in the objective function as depth and spatial weighting functions. We show, through 2-D and 3-D synthetic and real data examples, that potential field-based constraints, for example, structural index, source boundaries and others, are usually enough to obtain substantial improvement in the density and magnetization models.

  17. Cosmogenic photons strongly constrain UHECR source models

    Directory of Open Access Journals (Sweden)

    van Vliet Arjen

    2017-01-01

    Full Text Available With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT’s IGRB, as long as their number density is not strongly peaked at recent times.

  18. A constrained supersymmetric left-right model

    Energy Technology Data Exchange (ETDEWEB)

    Hirsch, Martin [AHEP Group, Instituto de Física Corpuscular - C.S.I.C./Universitat de València, Edificio de Institutos de Paterna, Apartado 22085, E-46071 València (Spain); Krauss, Manuel E. [Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Institut für Theoretische Physik und Astronomie, Universität Würzburg,Emil-Hilb-Weg 22, 97074 Wuerzburg (Germany); Opferkuch, Toby [Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Porod, Werner [Institut für Theoretische Physik und Astronomie, Universität Würzburg,Emil-Hilb-Weg 22, 97074 Wuerzburg (Germany); Staub, Florian [Theory Division, CERN,1211 Geneva 23 (Switzerland)

    2016-03-02

    We present a supersymmetric left-right model which predicts gauge coupling unification close to the string scale and extra vector bosons at the TeV scale. The subtleties in constructing a model which is in agreement with the measured quark masses and mixing for such a low left-right breaking scale are discussed. It is shown that in the constrained version of this model radiative breaking of the gauge symmetries is possible and a SM-like Higgs is obtained. Additional CP-even scalars of a similar mass or even much lighter are possible. The expected mass hierarchies for the supersymmetric states differ clearly from those of the constrained MSSM. In particular, the lightest down-type squark, which is a mixture of the sbottom and extra vector-like states, is always lighter than the stop. We also comment on the model’s capability to explain current anomalies observed at the LHC.

  19. Coding for Two Dimensional Constrained Fields

    DEFF Research Database (Denmark)

    Laursen, Torben Vaarbye

    2006-01-01

    a first order model to model higher order constraints by the use of an alphabet extension. We present an iterative method that based on a set of conditional probabilities can help in choosing the large numbers of parameters of the model in order to obtain a stationary model. Explicit results are given...... for the No Isolated Bits constraint. Finally we present a variation of the encoding scheme of bit-stuffing that is applicable to the class of checkerboard constrained fields. It is possible to calculate the entropy of the coding scheme thus obtaining lower bounds on the entropy of the fields considered. These lower...... bounds are very tight for the Run-Length limited fields. Explicit bounds are given for the diamond constrained field as well....

  20. Communication Schemes with Constrained Reordering of Resources

    DEFF Research Database (Denmark)

    Popovski, Petar; Utkovski, Zoran; Trillingsgaard, Kasper Fløe

    2013-01-01

    This paper introduces a communication model inspired by two practical scenarios. The first scenario is related to the concept of protocol coding, where information is encoded in the actions taken by an existing communication protocol. We investigate strategies for protocol coding via combinatorial...... reordering of the labelled user resources (packets, channels) in an existing, primary system. However, the degrees of freedom of the reordering are constrained by the operation of the primary system. The second scenario is related to communication systems with energy harvesting, where the transmitted signals...... are constrained by the energy that is available through the harvesting process. We have introduced a communication model that covers both scenarios and elicits their key feature, namely the constraints of the primary system or the harvesting process. We have shown how to compute the capacity of the channels...

  1. Q-deformed systems and constrained dynamics

    International Nuclear Information System (INIS)

    Shabanov, S.V.

    1993-01-01

    It is shown that quantum theories of the q-deformed harmonic oscillator and one-dimensional free q-particle (a free particle on the 'quantum' line) can be obtained by the canonical quantization of classical Hamiltonian systems with commutative phase-space variables and a non-trivial symplectic structure. In the framework of this approach, classical dynamics of a particle on the q-line coincides with the one of a free particle with friction. It is argued that q-deformed systems can be treated as ordinary mechanical systems with the second-class constraints. In particular, second-class constrained systems corresponding to the q-oscillator and q-particle are given. A possibility of formulating q-deformed systems via gauge theories (first-class constrained systems) is briefly discussed. (orig.)

  2. Online constrained model-based reinforcement learning

    CSIR Research Space (South Africa)

    Van Niekerk, B

    2017-08-01

    Full Text Available Constrained Model-based Reinforcement Learning Benjamin van Niekerk School of Computer Science University of the Witwatersrand South Africa Andreas Damianou∗ Amazon.com Cambridge, UK Benjamin Rosman Council for Scientific and Industrial Research, and School... MULTIPLE SHOOTING Using direct multiple shooting (Bock and Plitt, 1984), problem (1) can be transformed into a structured non- linear program (NLP). First, the time horizon [t0, t0 + T ] is partitioned into N equal subintervals [tk, tk+1] for k = 0...

  3. Constraining supergravity models from gluino production

    International Nuclear Information System (INIS)

    Barbieri, R.; Gamberini, G.; Giudice, G.F.; Ridolfi, G.

    1988-01-01

    The branching ratios for gluino decays g tilde → qanti qΧ, g tilde → gΧ into a stable undetected neutralino are computed as functions of the relevant parameters of the underlying supergravity theory. A simple way of constraining supergravity models from gluino production emerges. The effectiveness of hadronic versus e + e - colliders in the search for supersymmetry can be directly compared. (orig.)

  4. Cosmicflows Constrained Local UniversE Simulations

    Science.gov (United States)

    Sorce, Jenny G.; Gottlöber, Stefan; Yepes, Gustavo; Hoffman, Yehuda; Courtois, Helene M.; Steinmetz, Matthias; Tully, R. Brent; Pomarède, Daniel; Carlesi, Edoardo

    2016-01-01

    This paper combines observational data sets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. The latter are excellent laboratories for studies of the non-linear process of structure formation in our neighbourhood. With measurements of radial peculiar velocities in the local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor of 2 to 3 on a 5 h-1 Mpc scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observation-reconstructed velocity fields is only 104 ± 4 km s-1, I.e. the linear theory threshold. These two results demonstrate that these simulations are in agreement with each other and with the observations of our neighbourhood. For the first time, simulations constrained with observational radial peculiar velocities resemble the local Universe up to a distance of 150 h-1 Mpc on a scale of a few tens of megaparsecs. When focusing on the inner part of the box, the resemblance with our cosmic neighbourhood extends to a few megaparsecs (<5 h-1 Mpc). The simulations provide a proper large-scale environment for studies of the formation of nearby objects.

  5. Dynamic Convex Duality in Constrained Utility Maximization

    OpenAIRE

    Li, Yusong; Zheng, Harry

    2016-01-01

    In this paper, we study a constrained utility maximization problem following the convex duality approach. After formulating the primal and dual problems, we construct the necessary and sufficient conditions for both the primal and dual problems in terms of FBSDEs plus additional conditions. Such formulation then allows us to explicitly characterize the primal optimal control as a function of the adjoint process coming from the dual FBSDEs in a dynamic fashion and vice versa. Moreover, we also...

  6. Statistical mechanics of budget-constrained auctions

    OpenAIRE

    Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.

    2009-01-01

    Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). Based on the cavity method of statistical mechanics, we introduce a message passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution,...

  7. Constraining neutron star matter with Quantum Chromodynamics

    CERN Document Server

    Kurkela, Aleksi; Schaffner-Bielich, Jurgen; Vuorinen, Aleksi

    2014-01-01

    In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount --- or even presence --- of quark matter inside the stars.

  8. Density heterogeneity of the North American upper mantle from satellite gravity and a regional crustal model

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2014-01-01

    -density conversion and (ii) uncertainties in knowledge of the crustal structure (thickness and average Vp velocities of individual crustal layers, including the sedimentary cover). In this study, we address both sources of possible uncertainties by applying different conversions from velocity to density...... and by introducing variations into the crustal structure which corresponds to the uncertainty of its resolution by highquality and low-quality seismic models. We examine the propagation of these uncertainties into determinations of lithospheric mantle density. Given a relatively small range of expected density...

  9. Crustal nature and origin of the Russian Altai: Implications for the continental evolution and growth of the Central Asian Orogenic Belt (CAOB)

    Science.gov (United States)

    Cai, Keda; Sun, Min; Buslov, M. M.; Jahn, Bor-ming; Xiao, Wenjiao; Long, Xiaoping; Chen, Huayong; Wan, Bo; Chen, Ming; Rubanova, E. S.; Kulikova, A. V.; Voytishek, E. E.

    2016-04-01

    The Central Asian Orogenic Belt is a gigantic tectonic collage of numerous accreted terranes. However, its geodynamic evolution has been hotly debated primarily due to incomplete knowledge on the nature of these enigmatic terranes. This work presents new detrital zircon U-Pb and Hf isotopic data to constrain the crustal nature and origin of the Russian Altai, a critical segment of Altai-Mongolian terrane. The youngest zircon 206Pb/238U ages of 470 Ma constrain that the Terekta Formation, previously envisaged as Precambrian basement, was actually deposited after the Middle Ordovician. As for the three more sedimentary sequences above the Terekta Formation, they have youngest zircon 206Pb/238U ages of 425 Ma, 440 Ma and 380 Ma, respectively, indicating their depositions likely in the Late Silurian to Devonian. From all analyses, it is noted that many zircon U-Pb ages cluster at ca. 520 Ma and ca. 800 Ma, and these zircons display oscillatory zoning and have subhedral to euhedral morphology, which, collectively, suggests that adjacent Neoproterozoic to Paleozoic igneous rocks were possibly dominant in the sedimentary provenance. Additionally, a few rounded Archean to Mesoproterozoic zircon grains are characterized by complex texture, which are interpreted as recycling materials probably derived from the Tuva-Mongolian microcontinent. Precambrian rocks have not been identified in the Russian Altai, Chinese Altai and Mongolian Altai so far, therefore, Precambrian basement may not exist in the Altai-Mongolian terrane, but this terrane probably represents a large subduction-accretion complex built on the margin of the Tuva-Mongolian microcontinent in the Early Paleozoic. Multiple episodes of ridge-trench interaction may have caused inputs of mantle-derived magmas to trigger partial melting of the newly accreted crustal materials, which contributed to the accretionary complex. During accretionary orogenesis of the CAOB, formation of such subduction-accretion complex is

  10. Constraining the mass of the Local Group

    Science.gov (United States)

    Carlesi, Edoardo; Hoffman, Yehuda; Sorce, Jenny G.; Gottlöber, Stefan

    2017-03-01

    The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging - its mass budget is dominated by dark matter that cannot be directly observed. To meet this end, the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed - the Λ cold dark matter model that is used to set up the simulations, and an LG model that encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted on to the Cosmicflows-2 data base of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different vtan choices affect the peak mass values up to a factor of 2, and change mass ratios of MM31 to MMW by up to 20 per cent; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred Milky Way masses lie in the range of (0.6-0.8) × 1012 M⊙; whereas (e) MM31 is found to vary between (1.0-2.0) × 1012 M⊙, with a strong dependence on the vtan values used.

  11. Experimental determination of liquidus H2O contents of haplogranite at deep-crustal conditions

    Science.gov (United States)

    Makhluf, A. R.; Newton, R. C.; Manning, C. E.

    2017-09-01

    The liquidus water content of a haplogranite melt at high pressure ( P) and temperature ( T) is important, because it is a key parameter for constraining the volume of granite that could be produced by melting of the deep crust. Previous estimates based on melting experiments at low P (≤0.5 GPa) show substantial scatter when extrapolated to deep crustal P and T (700-1000 °C, 0.6-1.5 GPa). To improve the high-P constraints on H2O concentration at the granite liquidus, we performed experiments in a piston-cylinder apparatus at 1.0 GPa using a range of haplogranite compositions in the albite (Ab: NaAlSi3O8)—orthoclase (Or: KAlSi3O8)—quartz (Qz: SiO2)—H2O system. We used equal weight fractions of the feldspar components and varied the Qz between 20 and 30 wt%. In each experiment, synthetic granitic composition glass + H2O was homogenized well above the liquidus T, and T was lowered by increments until quartz and alkali feldspar crystalized from the liquid. To establish reversed equilibrium, we crystallized the homogenized melt at the lower T and then raised T until we found that the crystalline phases were completely resorbed into the liquid. The reversed liquidus minimum temperatures at 3.0, 4.1, 5.8, 8.0, and 12.0 wt% H2O are 935-985, 875-900, 775-800, 725-775, and 650-675 °C, respectively. Quenched charges were analyzed by petrographic microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), and electron microprobe analysis (EMPA). The equation for the reversed haplogranite liquidus minimum curve for Ab36.25Or36.25Qz27.5 (wt% basis) at 1.0 GPa is T = - 0.0995 w_{{{H}_{ 2} {O}}}^{ 3} + 5.0242w_{{{H}_{ 2} {O}}}^{ 2} - 88.183 w_{{{H}_{ 2} {O}}} + 1171.0 for 0 ≤ w_{{{H}_{ 2} {O}}} ≤ 17 wt% and T is in °C. We present a revised P - T diagram of liquidus minimum H2O isopleths which integrates data from previous determinations of vapor-saturated melting and the lower pressure vapor-undersaturated melting studies conducted by other workers on

  12. Constraints on fault and crustal strength of the Main Ethiopian Rift from formal inversion of earthquake focal mechanism data

    Science.gov (United States)

    Muluneh, Ameha A.; Kidane, Tesfaye; Corti, Giacomo; Keir, Derek

    2018-04-01

    We evaluate the frictional strength of seismogenic faults in the Main Ethiopian Rift (MER) by inverting the available, well-constrained earthquake focal mechanisms. The regional stress field is given by - 119.6°/77.2°, 6.2°/7.6°, and 97.5°/10.2° for trend/plunge of σ1, σ2 and σ3, respectively agrees well with previous fault kinematic and focal mechanism inversions. We determine the coefficient of friction, μ, for 44 seismogenic faults by assuming the pore pressure to be at hydrostatic conditions. Slip on 36 seismogenic faults occurs with μ ≥ 0.4. Slip on the remaining eight faults is possible with low μ. In general, the coefficient of friction in the MER is compatible with a value of μ of 0.59 ± 0.16 (2σ standard deviation). The shear stresses range from 16 to 129 MPa, is similar to crustal shear stress observed in extensional tectonic regimes and global compilations of shear stresses from major fault zones. The maximum shear stress is observed in the ductile crust, below the seismologically determined brittle-ductile transition (BDT) zone. Below the BDT, the crust is assumed to be weak due to thermal modification and/or high pore fluid pressure. Our results indicate linearly increasing μ and shear stress with depth. We argue that in the MER upper crust is strong and deforms according to Coulomb frictional-failure criterion.

  13. Crustal imaging of western Michoacán and the Jalisco Block, Mexico, from Ambient Seismic Noise

    Science.gov (United States)

    Spica, Zack; Cruz-Atienza, Víctor M.; Reyes-Alfaro, Gabriel; Legrand, Denis; Iglesias-Mendoza, Arturo

    2014-12-01

    Detailed crustal imaging of western Michoacán and the Jalisco Block is obtained from ambient noise tomography. Results show a deep and well-delineated volcanic system below the Colima volcano complex, rooting up to ~ 22 km depth, with a shallow magmatic chamber constrained to the first ~ 7 km. A shallow low-velocity system to the south of the Chapala rift and west of the Michoacán-Guanajuato volcanic field merges, underneath the Colima rift, with the Colima volcano system at about 20 km depth, honoring the geometry of the Trans-Mexican Volcanic Belt. For depths greater than ~30 km, low-velocity features become parallel to the slab strike, right beneath the Mascota, Ayutla and Tapalpa volcanic fields, suggesting the presence of the mantle wedge above the Rivera plate. All mentioned low-velocity bodies are spatially correlated with the superficial volcanic activity suggesting their magmatic origin so that, the shallower these bodies, the younger are the associated volcanic deposits. Along the coast, different depths of the uppermost layer of the Rivera and the Cocos plates suggest that the latter plate subducts with an angle ~ 9° steeper than the former.

  14. Fluvial archives, a valuable record of vertical crustal deformation

    Science.gov (United States)

    Demoulin, A.; Mather, A.; Whittaker, A.

    2017-06-01

    The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes. As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace

  15. Regional Crustal Deformation and Lithosphere Thickness Observed with Geodetic Techniques

    Science.gov (United States)

    Vermeer, M.; Poutanen, M.; Kollo, K.; Koivula, H.; Ahola, J.

    2009-04-01

    The solid Earth, including the lithosphere, interacts in many ways with other components of the Earth system, oceans, atmosphere and climate. Geodesy is a key provider of data needed for global and environmental research. Geodesy provides methods and accurate measurements of contemporary deformation, sea level and gravity change. The importance of the decades-long stability and availability of reference frames must be stressed for such studies. In the future, the need to accurately monitor 3-D crustal motions will grow, both together with increasingly precise GNSS (Global Navigation Satellite System) positioning, demands for better follow-up of global change, and local needs for crustal motions, especially in coastal areas. These demands cannot yet be satisfied. The project described here is a part of a larger entity: Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas, DynaQlim, an International Lithosphere Project (ILP) -sponsored initiative. The aims of DynaQlim are to understand the relations between upper mantle dynamics, mantle composition, physical properties, temperature and rheology, to study the postglacial uplift and ice thickness models, sea level change and isostatic response, Quaternary climate variations and Weichselian (Laurentian and other) glaciations during the late Quaternary. We aim at studying various aspects of lithospheric motion within the Finnish and Fennoscandian area, but within a global perspective, by the newest geodetic techniques in a multidisciplinary setting. The studies involve observations of three-dimensional motions and gravity change in a multidisciplinary context on a range of spatial scales: the whole of Fennoscandia, Finland, a regional test area of Satakunta, and the local test site Olkiluoto. Objectives of the research include improving our insight into the 3-D motion of a thick lithosphere, and into the gravity effect of the uplift, using novel approaches; improving the kinematic 3-D models in the

  16. Crustal and deep seismicity in Italy (30 years after

    Directory of Open Access Journals (Sweden)

    G. Selvaggi

    1997-06-01

    Full Text Available The first modern studies of seismicity in Italy date back to the late 60's and early 70's. Although with a sparse seismic network available and only a few telemetered short-period stations, significant studies were carried out that outlined the main features of Italian seismicity (see, e.g., Boschi et al., 1969. Among these studies, one of the most important achievements was the reconnaissance of a Wadati-Benioff zone in Southern Tyrrhenian, described for the first time in detail in the papers of Caputo et al.(1970, 1973. Today, after three decades of more and more detailed seismological monitoring of the Italian region and tens of thousands earthquakes located since then, the knowledge of the earthquake generation processes in our country is much improved, although some of the conclusions reached in these early papers still hold. These improvements were made possible by the efforts of many institutions and seismologists who have been working hard to bring seismological research in Italy to standards of absolute quality, under the pivoting role of the Istituto Nazionale di Geofisica (ING. From the relocation of about 30000 crustal earthquakes and detailed studies on intermediate and deep shocks carried out in the last few years, we show that seismic release in peninsular Italy is only weakly related to the Africa-Eurasia convergence, but rather is best explained by the existence of two separate subduction/collision arcs (Northern Apennines and Southern Apennines-Calabria-Sicily. The width of the deforming belt running along peninsular Italy is 30 to 60 km, it is broader in the north than in the south, and the two arcs are separated by a region of more distributed deformation and stress rotations in the Central Apennines. Along the belt, the reconnaissance of regions of continuous and weak release of seismic energy, adjacent to fault areas which are currently «locked» (and therefore are the best candidates for future earthquakes is another

  17. A numerical model for dynamic crustal-scale fluid flow

    Science.gov (United States)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel

    2015-04-01

    Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude

  18. Constraining the timescale of magma stagnation beneath Mauna Kea volcano, Hawaii,using diffusion profiles in olivine phenocrysts

    Science.gov (United States)

    Bloch, E. M.; Ganguly, J.

    2009-12-01

    Fe-Mg diffusion profiles have been measured in olivine xenocrysts within alkalic basalts in order to constrain the timescales of magma stagnation beneath Mauna Kea volcano, Hawaii. It has been suggested that during the main tholeiitic shield-building stage, and postshield eruptive stages of Mauna Kea, magmas were stalled and stagnated near the Moho, at a depth of ~15 km. Evidence in support of this hypothesis comes from cumulates formed by gravity-settling and in situ crystallization within magma chambers (Fodor and Galar, 1997), and from clinopyroxene-wholerock thermobarometry on Hamakua basalts (Putirka, in press). The cumulates represent a ‘fossil’ magma chamber which formed primarily from tholeiitic basalts; during the later capping-lava stage of Mauna Kea, alkalic basalts tore off chunks of these cumulates during ascent to the surface. We have measured several diffusion profiles in olivine xenocrysts from a single basalt sample. Because these xenocrysts have homogenous core compositions identical to a neighboring dunite cumulate, and because they are much larger and texturally distinct from compositionally dissimilar olivine phenocrysts, they are interpreted to be cumulate olivines which were dislodged during magma recharge/mixing in the stagnation zone. Although the orientations of the phenocrysts are not yet known, the diffusion profiles have been fit using diffusion coefficients parallel to the c and a crystallographic axes (i.e. minimum and maximum values). Modeling diffusion profiles yields ∫Ddt ≤4.5 x 10-5 cm2. Assuming that the xenocrysts were broken off from the cumulate immediately when the magma chamber was recharged, it is possible to calculate the maximum stagnation time of the basalts. Thus, the retrieved ∫Ddt value yields a maximum stagnation time of ~0.7 years. References: Fodor RV, Galar, PA (1997). A View into the Subsurface of Mauna Kea Volcano, Hawaii: Crystallization Processes Interpreted through the Petrology and Petrography of

  19. Crustal volumes of the continents and of oceanic and continental submarine plateaus

    Science.gov (United States)

    Schubert, G.; Sandwell, D.

    1989-01-01

    Using global topographic data and the assumption of Airy isostasy, it is estimated that the crustal volume of the continents is 7182 X 10 to the 6th cu km. The crustal volumes of the oceanic and continental submarine plateaus are calculated at 369 X 10 to the 6th cu km and 242 X 10 to the 6th cu km, respectively. The total continental crustal volume is found to be 7581 X 10 to the 6th cu km, 3.2 percent of which is comprised of continental submarine plateaus on the seafloor. An upper bound on the contintental crust addition rate by the accretion of oceanic plateaus is set at 3.7 cu km/yr. Subduction of continental submarine plateaus with the oceanic lithosphere on a 100 Myr time scale yields an upper bound to the continental crustal subtraction rate of 2.4 cu km/yr.

  20. Crustal seismicity and active fault system in the SE of Romania

    International Nuclear Information System (INIS)

    Raileanu, V; Bala, A.; Radulian, M.; Popescu, E.; Mateciuc, D.; Popa, M.; Dinu, C.; Diaconescu, V.

    2007-01-01

    Romania is known as a country with a high seismicity located in the Vrancea region where 2-3 strong intermediate depth earthquakes/century generate great damages and casualties. A moderate crustal seismicity is also observed in other zones of the country, with events having a moderate magnitude but sometimes with important economic and social effects on the locale scale. The crustal seismogenic zones are located in front of the Eastern Carpathian Bend, South Carpathians, Dobrogea, Banat, Crisana and Maramures regions. The SE part of Romania comprises some of the most active crustal seismic sources that generated earthquakes up to Mw=6.5 concentrated in more zones, namely: Vrancea crustal domain, E Vrancea zone that is overlapped on the Focsani basin, Barlad and Predobrogean depressions along with the North Dobrogea Orogen, Intramoesian and Shabla (Bulgaria) zones and Fagaras-Campulung-Sinaia zone. (authors)

  1. 2-D Crustal thermal structure along Thuadara–Sindad DSS profile ...

    Indian Academy of Sciences (India)

    Thuadara–Sindad Deep Seismic Sounding (DSS) profile which runs almost in the N–S direction ... These studies include four Deep Seis- ... Geology and tectonic frame work ..... alous high-velocity layer at shallow crustal depths in the.

  2. Crustal structure and tectonics of the Ninetyeast Ridge from seismic and gravity studies

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Neprochnov, Y.P.; Rao, D.G.; Grinko, B.N.

    Seismic reflection and refraction, gravity, and bathymetric data across and along the central part of the Ninetyeast Ridge were analyzed to determine the crustal structure of the ridge and to understand its tectonics. The ridge in the study area...

  3. Crustal and upper mantle structure of Siberia from teleseismic receiver functions

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Thybo, Hans; Artemieva, Irina

    2015-01-01

    ). With this method, we determine seismic P- and S-velocities that are comparable to the results of teleseismic body wave and surface wave tomography techniques. The RF model shows variations in the crustal thickness between 35 and 55 km. Intracrustal structures are identified, in particular using the high......This study presents seismic images of the crustal and lithospheric structure in Siberia based on the available broadband seismic data using teleseismic receiver functions (RFs). We invert P- and S-RFs jointly. The inversion technique is carried out by approach described by Vinnik et al. (2004....... The current results of RF analysis of the crustal and mantle structure will help to build a model for tectonic and geodynamic evolution of different provinces of Siberia. We compare our results to the recent detailed models of crustal structure in the area and with seismic models for similar geodynamic...

  4. The Chaotic Terrains of Mercury: A History of Large-Scale Crustal Devolatilization

    Science.gov (United States)

    Rodriguez, J. A. P.; Domingue, D. L.; Berman, D. C.; Kargel, J. S.; Baker, V. R.; Teodoro, L. F.; Banks, M.; Leonard, G.

    2018-05-01

    Approximately 400 million years after the Caloris basin impact, extensive collapse formed Mercury's chaotic terrains. Collapse likely resulted from regionally elevated heat flow devolatilizing crustal materials along NE and NW extensional faults.

  5. Further Mapping of Mercury's Crustal Magnetic Field Using MESSENGER Magnetometer Data

    Science.gov (United States)

    Hood, L. L.; Oliveira, J. S.; Spudis, P. D.; Galluzzi, V.

    2018-05-01

    Further mapping of Mercury's crustal magnetic field shows that anomalies are associated with some impact craters but not others. Differences in impactor composition (e.g., iron content) may be indicated by this new observation.

  6. Ophiolitic basement to the Great Valley forearc basin, California, from seismic and gravity data: Implications for crustal growth at the North American continental margin

    Science.gov (United States)

    Godfrey, N.J.; Beaudoin, B.C.; Klemperer, S.L.; Levander, A.; Luetgert, J.; Meltzer, A.; Mooney, W.; Tréhu, A.

    1997-01-01

    The nature of the Great Valley basement, whether oceanic or continental, has long been a source of controversy. A velocity model (derived from a 200-km-long east-west reflection-refraction profile collected south of the Mendocino triple junction, northern California, in 1993), further constrained by density and magnetic models, reveals an ophiolite underlying the Great Valley (Great Valley ophiolite), which in turn is underlain by a westward extension of lower-density continental crust (Sierran affinity material). We used an integrated modeling philosophy, first modeling the seismic-refraction data to obtain a final velocity model, and then modeling the long-wavelength features of the gravity data to obtain a final density model that is constrained in the upper crust by our velocity model. The crustal section of Great Valley ophiolite is 7-8 km thick, and the Great Valley ophiolite relict oceanic Moho is at 11-16 km depth. The Great Valley ophiolite does not extend west beneath the Coast Ranges, but only as far as the western margin of the Great Valley, where the 5-7-km-thick Great Valley ophiolite mantle section dips west into the present-day mantle. There are 16-18 km of lower-density Sierran affinity material beneath the Great Valley ophiolite mantle section, such that a second, deeper, "present-day" continental Moho is at about 34 km depth. At mid-crustal depths, the boundary between the eastern extent of the Great Valley ophiolite and the western extent of Sierran affinity material is a near-vertical velocity and density discontinuity about 80 km east of the western margin of the Great Valley. Our model has important implications for crustal growth at the North American continental margin. We suggest that a thick ophiolite sequence was obducted onto continental material, probably during the Jurassic Nevadan orogeny, so that the Great Valley basement is oceanic crust above oceanic mantle vertically stacked above continental crust and continental mantle.

  7. A preliminary investigation of vertical crustal movements in the United Kingdom in the context of subsurface nuclear waste isolation for the Department of the Environment

    International Nuclear Information System (INIS)

    1981-03-01

    The report falls under the headings: vertical crustal movements - a manifestation of intraplate geological processes (reports of vertical crustal movements observed by geodetic levelling in intraplate environments; vertical crustal movements and the geological record; possible causes of vertical crustal movements); an investigation of recent crustal movements in a test area of the United Kingdom by comparison of geodetic levelling records; vertical crustal movements and the isolation of nuclear waste in intraplate geological systems (conventional methods of site appraisal - a perspective of geological hazard assessment; the role of vertical crustal movements as a tool for rationalisation of hazard assessment, site selection and the assessment of future geological change); research options. (U.K.)

  8. Seismic cycle feedbacks in a mid-crustal shear zone

    Science.gov (United States)

    Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Smit, Louis; Macey, Paul

    2018-07-01

    Mid-crustal fault rheology is controlled by alternating brittle and plastic deformation mechanisms, which cause feedback cycles that influence earthquake behavior. Detailed mapping and microstructural observations in the Pofadder Shear Zone (Namibia and South Africa) reveal a lithologically heterogeneous shear zone core with quartz-rich mylonites and ultramylonites, plastically overprinted pseudotachylyte and active shear folds. We present evidence for a positive feedback cycle in which coseismic grain size reduction facilitates active shear folding by enhancing competency contrasts and promoting crystal plastic flow. Shear folding strengthens a portion of a shear zone by limb rotation, focusing deformation and promoting plastic flow or brittle slip in resulting areas of localized high stress. Using quartz paleopiezometry, we estimate strain and slip rates consistent with other studies of exhumed shear zones and modern plate boundary faults, helping establish the Pofadder Shear Zone as an ancient analogue to modern, continental-scale, strike-slip faults. This feedback cycle influences seismicity patterns at the scale of study (10s of meters) and possibly larger scales as well, and contributes to bulk strengthening of the brittle-plastic transition on modern plate boundary faults.

  9. Decrease in oceanic crustal thickness since the breakup of Pangaea

    Science.gov (United States)

    van Avendonk, Harm J. A.; Davis, Joshua K.; Harding, Jennifer L.; Lawver, Lawrence A.

    2017-01-01

    Earth's mantle has cooled by 6-11 °C every 100 million years since the Archaean, 2.5 billion years ago. In more recent times, the surface heat loss that led to this temperature drop may have been enhanced by plate-tectonic processes, such as continental breakup, the continuous creation of oceanic lithosphere at mid-ocean ridges and subduction at deep-sea trenches. Here we use a compilation of marine seismic refraction data from ocean basins globally to analyse changes in the thickness of oceanic crust over time. We find that oceanic crust formed in the mid-Jurassic, about 170 million years ago, is 1.7 km thicker on average than crust produced along the present-day mid-ocean ridge system. If a higher mantle temperature is the cause of thicker Jurassic ocean crust, the upper mantle may have cooled by 15-20 °C per 100 million years over this time period. The difference between this and the long-term mantle cooling rate indeed suggests that modern plate tectonics coincide with greater mantle heat loss. We also find that the increase of ocean crustal thickness with plate age is stronger in the Indian and Atlantic oceans compared with the Pacific Ocean. This observation supports the idea that upper mantle temperature in the Jurassic was higher in the wake of the fragmented supercontinent Pangaea due to the effect of continental insulation.

  10. Cascading Constrained 2-D Arrays using Periodic Merging Arrays

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Laursen, Torben Vaarby

    2003-01-01

    We consider a method for designing 2-D constrained codes by cascading finite width arrays using predefined finite width periodic merging arrays. This provides a constructive lower bound on the capacity of the 2-D constrained code. Examples include symmetric RLL and density constrained codes...

  11. Operator approach to solutions of the constrained BKP hierarchy

    International Nuclear Information System (INIS)

    Shen, Hsin-Fu; Lee, Niann-Chern; Tu, Ming-Hsien

    2011-01-01

    The operator formalism to the vector k-constrained BKP hierarchy is presented. We solve the Hirota bilinear equations of the vector k-constrained BKP hierarchy via the method of neutral free fermion. In particular, by choosing suitable group element of O(∞), we construct rational and soliton solutions of the vector k-constrained BKP hierarchy.

  12. Barents Sea Paleozoic basement and basin configurations: Crustal structure from deep seismic and potential field data

    Science.gov (United States)

    Aarseth, Iselin; Mjelde, Rolf; Breivik, Asbjørn Johan; Huismans, Ritske; Faleide, Jan Inge

    2016-04-01

    The Barents Sea is underlain by at least two different basement domains; the Caledonian in the west and the Timanian in the east. The transition between these two domains is not well constrained and contrasting interpretations have been published recently. Interpretations of new high-quality magnetic data covering most of the SW Barents Sea has challenged the Late Paleozoic basin configurations in the western and central Barents Sea as outlined in previous studies. Two regional ocean bottom seismic (OBS) profiles were acquired in 2014. This new dataset crosses the two major directions of Caledonian deformation proposed by different authors: N-S direction and SW-NE direction. Of particular importance are the high velocity anomalies related to Caledonian eclogites, revealing the location of Caledonian suture zones in the northern Barents Sea. One of the main objectives with this project is to locate the main Caledonian suture in the western Barents Sea, as well as the possible Barentsia-Baltica suture postulated further eastwards. The collapse of the Caledonian mountain range predominantly along these suture zones is expected to be tightly linked to the deposition of large thicknesses of Devonian erosional products, and later rifting is expected to be influenced by inheritance of Caledonian trends. The P-wave travel-time modelling is done by use of a combined ray-tracing and inversion scheme, and gravity- and magnetic modelling will be used to augment the seismic model. The preliminary results indicate high P-wave velocities (mostly over 4 km/s) close to the seafloor as well as high velocity (around 6 km/s) zones at shallow depths which are interpreted as volcanic sills. The crustal transects reveal areas of complex geology and velocity inversions. A low seismic impedance contrast between the sedimentary section and top crystalline basement makes identification of this interface uncertain. Depth to Moho mostly lies around 30 km, except in an area of rapid change in

  13. Combining deterministic and stochastic velocity fields in the analysis of deep crustal seismic data

    Science.gov (United States)

    Larkin, Steven Paul

    Standard crustal seismic modeling obtains deterministic velocity models which ignore the effects of wavelength-scale heterogeneity, known to exist within the Earth's crust. Stochastic velocity models are a means to include wavelength-scale heterogeneity in the modeling. These models are defined by statistical parameters obtained from geologic maps of exposed crystalline rock, and are thus tied to actual geologic structures. Combining both deterministic and stochastic velocity models into a single model allows a realistic full wavefield (2-D) to be computed. By comparing these simulations to recorded seismic data, the effects of wavelength-scale heterogeneity can be investigated. Combined deterministic and stochastic velocity models are created for two datasets, the 1992 RISC seismic experiment in southeastern California and the 1986 PASSCAL seismic experiment in northern Nevada. The RISC experiment was located in the transition zone between the Salton Trough and the southern Basin and Range province. A high-velocity body previously identified beneath the Salton Trough is constrained to pinch out beneath the Chocolate Mountains to the northeast. The lateral extent of this body is evidence for the ephemeral nature of rifting loci as a continent is initially rifted. Stochastic modeling of wavelength-scale structures above this body indicate that little more than 5% mafic intrusion into a more felsic continental crust is responsible for the observed reflectivity. Modeling of the wide-angle RISC data indicates that coda waves following PmP are initially dominated by diffusion of energy out of the near-surface basin as the wavefield reverberates within this low-velocity layer. At later times, this coda consists of scattered body waves and P to S conversions. Surface waves do not play a significant role in this coda. Modeling of the PASSCAL dataset indicates that a high-gradient crust-mantle transition zone or a rough Moho interface is necessary to reduce precritical Pm

  14. Nd isotopes in French Phanerzoic shales: external vs. internal aspects of crustal evolution

    International Nuclear Information System (INIS)

    Michard, A.; Gurriet, P.; Soudant, M.; Alberede, F.; Ecole Nationale Superieure de Geologie Appliquee et de Prospection Miniere, 54 - Nancy

    1985-01-01

    Nd isotopic composition has been determined on shales of Paleozoic (Brittany and Languedoc) and Mesozoic (Lorraine) age. epsilonsub(Nd)(T) values range from -6 to -12 while Nd crustal residence ages are typically in excess over their stratigraphic ages by some 1.4 Ga. Exceptions to this rule are the sediments coeval with Hercynian, Caledonian and Cadomian orogenic events, the epsilonsub(Nd)(T) values of which suggest addition of mantle material to the sediment in the form of volcanoclastic detritus. In Brittany, this is confirmed by the local zircon chronology which provides upper intercepts of Concordia up to 800 m.y. in excess of Nd crustal residence ages. Comparison of crustal residence ages with stratigraphic ages through geologic time suggests a three stage history: a) for rocks older than 2 Ga, stratigraphic and crustal residence ages coincide, b) from 2 to 1 Ga, crustal residence ages level off at ca. 2 Ga and then c) decrease down to 1.4 Ga in recent sediments. Two extreme models can account for the observed variations: an internally driven model, in which variable quantities of mantle material are added to the crust, and an externally driven model, in which the rate of crustal recycling is low in the Archean but increases rapidly at the onset of the atmospheric oxygen buildup. (author)

  15. Feature and Pose Constrained Visual Aided Inertial Navigation for Computationally Constrained Aerial Vehicles

    Science.gov (United States)

    Williams, Brian; Hudson, Nicolas; Tweddle, Brent; Brockers, Roland; Matthies, Larry

    2011-01-01

    A Feature and Pose Constrained Extended Kalman Filter (FPC-EKF) is developed for highly dynamic computationally constrained micro aerial vehicles. Vehicle localization is achieved using only a low performance inertial measurement unit and a single camera. The FPC-EKF framework augments the vehicle's state with both previous vehicle poses and critical environmental features, including vertical edges. This filter framework efficiently incorporates measurements from hundreds of opportunistic visual features to constrain the motion estimate, while allowing navigating and sustained tracking with respect to a few persistent features. In addition, vertical features in the environment are opportunistically used to provide global attitude references. Accurate pose estimation is demonstrated on a sequence including fast traversing, where visual features enter and exit the field-of-view quickly, as well as hover and ingress maneuvers where drift free navigation is achieved with respect to the environment.

  16. Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Core, Central Snake River Plain, Idaho: A 5.5-million-year Highlight Reel of Petrogenetic processes in a Mid-Crustal Sill Complex

    Science.gov (United States)

    Potter, Katherine E.; Shervais, John W.; Christiansen, Eric H.; Vetter, Scott K.

    2018-02-01

    Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5-10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319 m, 1045 m, 1078 m, and 1189 m, evolved and high K

  17. Incomplete Dirac reduction of constrained Hamiltonian systems

    Energy Technology Data Exchange (ETDEWEB)

    Chandre, C., E-mail: chandre@cpt.univ-mrs.fr

    2015-10-15

    First-class constraints constitute a potential obstacle to the computation of a Poisson bracket in Dirac’s theory of constrained Hamiltonian systems. Using the pseudoinverse instead of the inverse of the matrix defined by the Poisson brackets between the constraints, we show that a Dirac–Poisson bracket can be constructed, even if it corresponds to an incomplete reduction of the original Hamiltonian system. The uniqueness of Dirac brackets is discussed. The relevance of this procedure for infinite dimensional Hamiltonian systems is exemplified.

  18. Capturing Hotspots For Constrained Indoor Movement

    DEFF Research Database (Denmark)

    Ahmed, Tanvir; Pedersen, Torben Bach; Lu, Hua

    2013-01-01

    Finding the hotspots in large indoor spaces is very important for getting overloaded locations, security, crowd management, indoor navigation and guidance. The tracking data coming from indoor tracking are huge in volume and not readily available for finding hotspots. This paper presents a graph......-based model for constrained indoor movement that can map the tracking records into mapping records which represent the entry and exit times of an object in a particular location. Then it discusses the hotspots extraction technique from the mapping records....

  19. Quantization of soluble classical constrained systems

    International Nuclear Information System (INIS)

    Belhadi, Z.; Menas, F.; Bérard, A.; Mohrbach, H.

    2014-01-01

    The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way

  20. Quantization of soluble classical constrained systems

    Energy Technology Data Exchange (ETDEWEB)

    Belhadi, Z. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Laboratoire de physique théorique, Faculté des sciences exactes, Université de Bejaia, 06000 Bejaia (Algeria); Menas, F. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Ecole Nationale Préparatoire aux Etudes d’ingéniorat, Laboratoire de physique, RN 5 Rouiba, Alger (Algeria); Bérard, A. [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France); Mohrbach, H., E-mail: herve.mohrbach@univ-lorraine.fr [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France)

    2014-12-15

    The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way.

  1. Pole shifting with constrained output feedback

    International Nuclear Information System (INIS)

    Hamel, D.; Mensah, S.; Boisvert, J.

    1984-03-01

    The concept of pole placement plays an important role in linear, multi-variable, control theory. It has received much attention since its introduction, and several pole shifting algorithms are now available. This work presents a new method which allows practical and engineering constraints such as gain limitation and controller structure to be introduced right into the pole shifting design strategy. This is achieved by formulating the pole placement problem as a constrained optimization problem. Explicit constraints (controller structure and gain limits) are defined to identify an admissible region for the feedback gain matrix. The desired pole configuration is translated into an appropriate cost function which must be closed-loop minimized. The resulting constrained optimization problem can thus be solved with optimization algorithms. The method has been implemented as an algorithmic interactive module in a computer-aided control system design package, MVPACK. The application of the method is illustrated to design controllers for an aircraft and an evaporator. The results illustrate the importance of controller structure on overall performance of a control system

  2. Changes in epistemic frameworks: Random or constrained?

    Directory of Open Access Journals (Sweden)

    Ananka Loubser

    2012-11-01

    Full Text Available Since the emergence of a solid anti-positivist approach in the philosophy of science, an important question has been to understand how and why epistemic frameworks change in time, are modified or even substituted. In contemporary philosophy of science three main approaches to framework-change were detected in the humanist tradition:1. In both the pre-theoretical and theoretical domains changes occur according to a rather constrained, predictable or even pre-determined pattern (e.g. Holton.2. Changes occur in a way that is more random or unpredictable and free from constraints (e.g. Kuhn, Feyerabend, Rorty, Lyotard.3. Between these approaches, a middle position can be found, attempting some kind of synthesis (e.g. Popper, Lakatos.Because this situation calls for clarification and systematisation, this article in fact tried to achieve more clarity on how changes in pre-scientific frameworks occur, as well as provided transcendental criticism of the above positions. This article suggested that the above-mentioned positions are not fully satisfactory, as change and constancy are not sufficiently integrated. An alternative model was suggested in which changes in epistemic frameworks occur according to a pattern, neither completely random nor rigidly constrained, which results in change being dynamic but not arbitrary. This alternative model is integral, rather than dialectical and therefore does not correspond to position three. 

  3. Fringe instability in constrained soft elastic layers.

    Science.gov (United States)

    Lin, Shaoting; Cohen, Tal; Zhang, Teng; Yuk, Hyunwoo; Abeyaratne, Rohan; Zhao, Xuanhe

    2016-11-04

    Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer's thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width. In this case, the middle portion along the layer's thickness elongates nearly uniformly while the constrained fringe portions of the layer deform nonuniformly. When the applied stretch reaches a critical value, the exposed free surfaces of the fringe portions begin to undulate periodically without debonding from the rigid bodies, giving the fringe instability. We use experiments, theory and numerical simulations to quantitatively explain the fringe instability and derive scaling laws for its critical stress, critical strain and wavelength. We show that in a force controlled setting the elastic fingering instability is associated with a snap-through buckling that does not exist for the fringe instability. The discovery of the fringe instability will not only advance the understanding of mechanical instabilities in soft materials but also have implications for biological and engineered adhesives and joints.

  4. Tracing crustal contamination along the Java segment of the Sunda Arc, Indonesia

    Science.gov (United States)

    Jolis, E. M.; Troll, V.; Deegan, F.; Blythe, L.; Harris, C.; Freda, C.; Hilton, D.; Chadwick, J.; Van Helden, M.

    2012-04-01

    Arc magmas typically display chemical and petrographic characteristics indicative of crustal input. Crustal contamination can take place either in the mantle source region or as magma traverses the upper crust (e.g. [1]). While source contamination is generally considered the dominant process (e.g. [2]), late-stage crustal contamination has been recognised at volcanic arcs too (e.g. [3]). In light of this, we aim to test the extent of upper crustal versus source contamination along the Java segment of the Sunda arc, which, due its variable upper crustal structure, is an exemplary natural laboratory. We present a detailed geochemical study of 7 volcanoes along a traverse from Anak-Krakatau in the Sunda strait through Java and Bali, to characterise the impact of the overlying crust on arc magma composition. Using rock and mineral elemental geochemistry, radiogenic (Sr, Nd and Pb) and, stable (O) isotopes, we show a correlation between upper crustal composition and the degree of upper crustal contamination. We find an increase in 87Sr/86Sr and δ18O values, and a decrease in 143Nd/144Nd values from Krakatau towards Merapi, indicating substantial crustal input from the thick continental basement present. Volcanoes to the east of Merapi and the Progo-Muria fault transition zone, where the upper crust is thinner, in turn, show considerably less crustal input in their isotopic signatures, indicating a stronger influence of the mantle source. Our new data represent a systematic and high-resolution arc-wide sampling effort that allows us to distinguish the effects of the upper crust on the compositional spectrum of individual volcanic systems along the Sunda arc. [1] Davidson, J.P, Hora, J.M, Garrison, J.M & Dungan, M.A 2005. Crustal Forensics in Arc Magmas. J. Geotherm. Res. 140, 157-170; [2] Debaille, V., Doucelance, R., Weis, D., & Schiano, P. 2005. Geochim. Cosmochim. Acta, 70,723-741; [3] Gasparon, M., Hilton, D.R., & Varne, R. 1994. Earth Planet. Sci. Lett., 126, 15-22.

  5. Crustal deformation and volcanism at active plate boundaries

    Science.gov (United States)

    Geirsson, Halldor

    Most of Earth's volcanoes are located near active tectonic plate boundaries, where the tectonic plates move relative to each other resulting in deformation. Likewise, subsurface magma movement and pressure changes in magmatic systems can cause measurable deformation of the Earth's surface. The study of the shape of Earth and therefore studies of surface deformation is called geodesy. Modern geodetic techniques allow precise measurements (˜1 mm accuracy) of deformation of tectonic and magmatic systems. Because of the spatial correlation between tectonic boundaries and volcanism, the tectonic and volcanic deformation signals can become intertwined. Thus it is often important to study both tectonic and volcanic deformation processes simultaneously, when one is trying to study one of the systems individually. In this thesis, I present research on crustal deformation and magmatic processes at active plate boundaries. The study areas cover divergent and transform plate boundaries in south Iceland and convergent and transform plate boundaries in Central America, specifically Nicaragua and El Salvador. The study is composed of four main chapters: two of the chapters focus on the magma plumbing system of Hekla volcano, Iceland and the plate boundary in south Iceland; one chapter focuses on shallow controls of explosive volcanism at Telica volcano, Nicaragua; and the fourth chapter focuses on co- and post-seismic deformation from a Mw = 7.3 earthquake which occurred offshore El Salvador in 2012. Hekla volcano is located at the intersection of a transform zone and a rift zone in Iceland and thus is affected by a combination of shear and extensional strains, in addition to co-seismic and co-rifting deformation. The inter-eruptive deformation signal from Hekla is subtle, as observed by a decade (2000-2010) of GPS data in south Iceland. A simultaneous inversion of this data for parameters describing the geometry and source characteristics of the magma chamber at Hekla, and

  6. Does Aspartic Acid Racemization Constrain the Depth Limit of the Subsurface Biosphere?

    Science.gov (United States)

    Onstott, T C.; Magnabosco, C.; Aubrey, A. D.; Burton, A. S.; Dworkin, J. P.; Elsila, J. E.; Grunsfeld, S.; Cao, B. H.; Hein, J. E.; Glavin, D. P.; hide

    2013-01-01

    Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of approximately 89 years for 1 km depth and 27 C and 1-2 years for 3 km depth and 54 C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

  7. Data base and seismicity studies for Fagaras, Romania crustal earthquakes

    International Nuclear Information System (INIS)

    Moldovan, I.-A.; Enescu, B. D.; Pantea, A.; Constantin, A.; Bazacliu, O.; Malita, Z.; Moldoveanu, T.

    2002-01-01

    Besides the major impact of the Vrancea seismic region, one of the most important intermediate earthquake sources of Europe, the Romanian crustal earthquake sources, from Fagaras, Banat, Crisana, Bucovina or Dobrogea regions, have to be taken into consideration for seismicity studies or seismic hazard assessment. To determine the characteristics of the seismicity for Fagaras seismogenic region, a revised and updated catalogue of the Romanian earthquakes, recently compiled by Oncescu et al. (1999) is used. The catalogue contains 471 tectonic earthquakes and 338 induced earthquakes and is homogenous starting with 1471 for I>VIII and for I>VII starting with 1801. The catalogue is complete for magnitudes larger than 3 starting with 1982. In the studied zone only normal earthquakes occur, related to intracrustal fractures situated from 5 to 30 km depth. Most of them are of low energy, but once in a century a large destructive event occurs with epicentral intensity larger than VIII. The maximum expected magnitude is M GR = 6.5 and the epicenter distribution outlines significant clustering in the zones and on the lines mentioned in the tectonic studies. Taking into account the date of the last major earthquake (1916) and the return periods of severe damaging shocks of over 85 years it is to be expected very soon a large shock in the area. That's why a seismicity and hazard study for this zone is necessary. In the paper there are studied the b parameter variation (the mean value is 0.69), the activity value, the return periods, and seismicity maps and different histograms are plotted. At the same time there are excluded from the catalogue the explosions due to Campulung quarry. Because the catalogue contains the aftershocks for the 1916 earthquake for the seismicity studies we have excluded these shocks. (authors)

  8. Solitary Waves of Ice Loss Detected in Greenland Crustal Motion

    Science.gov (United States)

    Adhikari, S.; Ivins, E. R.; Larour, E. Y.

    2017-12-01

    The annual cycle and secular trend of Greenland mass loading are well recorded in measurements of solid Earth deformation. While bedrock vertical displacements are in phase with loading as inferred from space observations, horizontal motions have received almost no attention. The horizontal bedrock displacements can potentially track the spatiotemporal detail of mass changes with great fidelity. Our analysis of Greenland crustal motion data reveals that a significant excitation of horizontal amplitudes occurs during the intense Greenland melting. A suite of space geodetic observations and climate reanalysis data cannot explain these large horizontal displacements. We discover that solitary seasonal waves of substantial mass transport traveled through Rink Glacier in 2010 and 2012. We deduce that intense summer melting enhanced either basal lubrication or shear softening, or both, causing the glacier to thin dynamically. The newly routed upstream sublglacial water was likely to be both retarded and inefficient, thus providing a causal mechanism for the prolonged ice transport to continue well into the winter months. As the climate continues to produce increasingly warmer spring and summer, amplified seasonal waves of mass transport may become ever more present in years of future observations. Increased frequency of amplified seasonal mass transport may ultimately strengthen the Greenland's dynamic ice mass loss, a component of the balance that will have important ramifications for sea level rise. This animation shows a solitary wave passing through Rink Glacier, Greenland, in 2012, recorded by the motion of a GPS station (circle with arrow). Darker blue colors within the flow indicate mass loss, red colors show mass gain. The star marks the center of the wave. Credit: NASA/JPL-Caltech

  9. Crustal anisotropy across northern Japan from receiver functions.

    Science.gov (United States)

    Bianchi, I; Bokelmann, G; Shiomi, K

    2015-07-01

    Northern Japan is a tectonically active area, with the presence of several volcanoes, and with frequent earthquakes among which the destructive M w  = 8.9-9.0 Tohoku-oki occurred on 11 March 2011. Tectonic activity leaves an imprint on the crustal structures, on both the upper and the lower layers. To investigate the crust in northern Japan, we construct a receiver function data set using teleseismic events recorded at 58 seismic stations belonging to the Japanese National (Hi-net) network. We isolate the signals, in the receiver function wavelet, that witness the presence of anisotropic structures at depth, with the aim of mapping the variation of anisotropy across the northern part of the island. This study focuses on the relation among anisotropy detected in the crust, stresses induced by plate convergence across the subduction zone, and the intrinsic characteristics of the rocks. Our results show how a simple velocity model with two anisotropic layers reproduces the observed data at the stations. We observe a negligible or small amount of signal related to anisotropy in the eastern part of the study area (i.e., the outer arc) for both upper and lower crust. Distinct anisotropic features are observed at the stations on the western part of the study area (i.e., the inner arc) for both upper and lower crust. The symmetry axes are mostly E-W oriented. Deviation from the E-W orientation is observed close to the volcanic areas, where the higher geothermal gradient might influence the deformation processes.

  10. Cumulate xenoliths from St. Vincent, Lesser Antilles Island Arc: a window into upper crustal differentiation of mantle-derived basalts

    Science.gov (United States)

    Tollan, P. M. E.; Bindeman, I.; Blundy, J. D.

    2012-02-01

    In order to shed light on upper crustal differentiation of mantle-derived basaltic magmas in a subduction zone setting, we have determined the mineral chemistry and oxygen and hydrogen isotope composition of individual cumulus minerals in plutonic blocks from St. Vincent, Lesser Antilles. Plutonic rock types display great variation in mineralogy, from olivine-gabbros to troctolites and hornblendites, with a corresponding variety of cumulate textures. Mineral compositions differ from those in erupted basaltic lavas from St. Vincent and in published high-pressure (4-10 kb) experimental run products of a St. Vincent high-Mg basalt in having higher An plagioclase coexisting with lower Fo olivine. The oxygen isotope compositions (δ18O) of cumulus olivine (4.89-5.18‰), plagioclase (5.84-6.28‰), clinopyroxene (5.17-5.47‰) and hornblende (5.48-5.61‰) and hydrogen isotope composition of hornblende (δD = -35.5 to -49.9‰) are all consistent with closed system magmatic differentiation of a mantle-derived basaltic melt. We employed a number of modelling exercises to constrain the origin of the chemical and isotopic compositions reported. δ18OOlivine is up to 0.2‰ higher than modelled values for closed system fractional crystallisation of a primary melt. We attribute this to isotopic disequilibria between cumulus minerals crystallising at different temperatures, with equilibration retarded by slow oxygen diffusion in olivine during prolonged crustal storage. We used melt inclusion and plagioclase compositions to determine parental magmatic water contents (water saturated, 4.6 ± 0.5 wt% H2O) and crystallisation pressures (173 ± 50 MPa). Applying these values to previously reported basaltic and basaltic andesite lava compositions, we can reproduce the cumulus plagioclase and olivine compositions and their associated trend. We conclude that differentiation of primitive hydrous basalts on St. Vincent involves crystallisation of olivine and Cr-rich spinel at depth

  11. The Origin of the Compositional Diversity of Mercury's Surface Constrained From Experimental Melting of Enstatite Chondrites

    Science.gov (United States)

    Boujibar, A.; Righter, K.; Pando, K.; Danielson, L.

    2015-01-01

    Mercury is known as an endmember planet as it is the most reduced terrestrial planet with the highest core/mantle ratio. MESSENGER spacecraft has shown that its surface is FeO-poor (2-4 wt%) and Srich (up to 6-7 wt%), which confirms the reducing nature of its silicate mantle. Moreover, high resolution images revealed large volcanic plains and abundant pyroclastic deposits, suggesting important melting stages of the Mercurian mantle. This interpretation was confirmed by the high crustal thickness (up to 100 km) derived from Mercury's gravity field. This is also corroborated by a recent experimental result that showed that Mercurian partial melts are expected to be highly buoyant within the Mercurian mantle and could have risen from depths as high as the core-mantle boundary. In addition MESSENGER spacecraft provided relatively precise data on major elemental compositions of Mercury's surface. These results revealed important chemical and mineralogical heterogeneities that suggested several stages of differentiation and re-melting processes. However, the extent and nature of compositional variations produced by partial melting remains poorly constrained for the particular compositions of Mercury (very reducing conditions, low FeO-contents and high sulfur-contents). Therefore, in this study, we investigated the processes that lead to the various compositions of Mercury's surface. Melting experiments with bulk Mercury-analogue compositions were performed and compared to the compositions measured by MESSENGER.

  12. Scheduling of resource-constrained projects

    CERN Document Server

    Klein, Robert

    2000-01-01

    Project management has become a widespread instrument enabling organizations to efficiently master the challenges of steadily shortening product life cycles, global markets and decreasing profit margins. With projects increasing in size and complexity, their planning and control represents one of the most crucial management tasks. This is especially true for scheduling, which is concerned with establishing execution dates for the sub-activities to be performed in order to complete the project. The ability to manage projects where resources must be allocated between concurrent projects or even sub-activities of a single project requires the use of commercial project management software packages. However, the results yielded by the solution procedures included are often rather unsatisfactory. Scheduling of Resource-Constrained Projects develops more efficient procedures, which can easily be integrated into software packages by incorporated programming languages, and thus should be of great interest for practiti...

  13. Constrained mathematics evaluation in probabilistic logic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Arlin Cooper, J

    1998-06-01

    A challenging problem in mathematically processing uncertain operands is that constraints inherent in the problem definition can require computations that are difficult to implement. Examples of possible constraints are that the sum of the probabilities of partitioned possible outcomes must be one, and repeated appearances of the same variable must all have the identical value. The latter, called the 'repeated variable problem', will be addressed in this paper in order to show how interval-based probabilistic evaluation of Boolean logic expressions, such as those describing the outcomes of fault trees and event trees, can be facilitated in a way that can be readily implemented in software. We will illustrate techniques that can be used to transform complex constrained problems into trivial problems in most tree logic expressions, and into tractable problems in most other cases.

  14. Constraining dark sectors with monojets and dijets

    International Nuclear Information System (INIS)

    Chala, Mikael; Kahlhoefer, Felix; Nardini, Germano; Schmidt-Hoberg, Kai; McCullough, Matthew

    2015-03-01

    We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.

  15. Constrained KP models as integrable matrix hierarchies

    International Nuclear Information System (INIS)

    Aratyn, H.; Ferreira, L.A.; Gomes, J.F.; Zimerman, A.H.

    1997-01-01

    We formulate the constrained KP hierarchy (denoted by cKP K+1,M ) as an affine [cflx sl](M+K+1) matrix integrable hierarchy generalizing the Drinfeld endash Sokolov hierarchy. Using an algebraic approach, including the graded structure of the generalized Drinfeld endash Sokolov hierarchy, we are able to find several new universal results valid for the cKP hierarchy. In particular, our method yields a closed expression for the second bracket obtained through Dirac reduction of any untwisted affine Kac endash Moody current algebra. An explicit example is given for the case [cflx sl](M+K+1), for which a closed expression for the general recursion operator is also obtained. We show how isospectral flows are characterized and grouped according to the semisimple non-regular element E of sl(M+K+1) and the content of the center of the kernel of E. copyright 1997 American Institute of Physics

  16. Quantum cosmology of classically constrained gravity

    International Nuclear Information System (INIS)

    Gabadadze, Gregory; Shang Yanwen

    2006-01-01

    In [G. Gabadadze, Y. Shang, hep-th/0506040] we discussed a classically constrained model of gravity. This theory contains known solutions of General Relativity (GR), and admits solutions that are absent in GR. Here we study cosmological implications of some of these new solutions. We show that a spatially-flat de Sitter universe can be created from 'nothing'. This universe has boundaries, and its total energy equals to zero. Although the probability to create such a universe is exponentially suppressed, it favors initial conditions suitable for inflation. Then we discuss a finite-energy solution with a nonzero cosmological constant and zero space-time curvature. There is no tunneling suppression to fluctuate into this state. We show that for a positive cosmological constant this state is unstable-it can rapidly transition to a de Sitter universe providing a new unsuppressed channel for inflation. For a negative cosmological constant the space-time flat solutions is stable.

  17. Multiple Clustering Views via Constrained Projections

    DEFF Research Database (Denmark)

    Dang, Xuan-Hong; Assent, Ira; Bailey, James

    2012-01-01

    Clustering, the grouping of data based on mutual similarity, is often used as one of principal tools to analyze and understand data. Unfortunately, most conventional techniques aim at finding only a single clustering over the data. For many practical applications, especially those being described...... in high dimensional data, it is common to see that the data can be grouped into different yet meaningful ways. This gives rise to the recently emerging research area of discovering alternative clusterings. In this preliminary work, we propose a novel framework to generate multiple clustering views....... The framework relies on a constrained data projection approach by which we ensure that a novel alternative clustering being found is not only qualitatively strong but also distinctively different from a reference clustering solution. We demonstrate the potential of the proposed framework using both synthetic...

  18. Shape space exploration of constrained meshes

    KAUST Repository

    Yang, Yongliang

    2011-12-12

    We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.

  19. Shape space exploration of constrained meshes

    KAUST Repository

    Yang, Yongliang; Yang, Yijun; Pottmann, Helmut; Mitra, Niloy J.

    2011-01-01

    We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.

  20. Constrained vertebrate evolution by pleiotropic genes.

    Science.gov (United States)

    Hu, Haiyang; Uesaka, Masahiro; Guo, Song; Shimai, Kotaro; Lu, Tsai-Ming; Li, Fang; Fujimoto, Satoko; Ishikawa, Masato; Liu, Shiping; Sasagawa, Yohei; Zhang, Guojie; Kuratani, Shigeru; Yu, Jr-Kai; Kusakabe, Takehiro G; Khaitovich, Philipp; Irie, Naoki

    2017-11-01

    Despite morphological diversification of chordates over 550 million years of evolution, their shared basic anatomical pattern (or 'bodyplan') remains conserved by unknown mechanisms. The developmental hourglass model attributes this to phylum-wide conserved, constrained organogenesis stages that pattern the bodyplan (the phylotype hypothesis); however, there has been no quantitative testing of this idea with a phylum-wide comparison of species. Here, based on data from early-to-late embryonic transcriptomes collected from eight chordates, we suggest that the phylotype hypothesis would be better applied to vertebrates than chordates. Furthermore, we found that vertebrates' conserved mid-embryonic developmental programmes are intensively recruited to other developmental processes, and the degree of the recruitment positively correlates with their evolutionary conservation and essentiality for normal development. Thus, we propose that the intensively recruited genetic system during vertebrates' organogenesis period imposed constraints on its diversification through pleiotropic constraints, which ultimately led to the common anatomical pattern observed in vertebrates.

  1. Constraining Lyman continuum escape using Machine Learning

    Science.gov (United States)

    Giri, Sambit K.; Zackrisson, Erik; Binggeli, Christian; Pelckmans, Kristiaan; Cubo, Rubén; Mellema, Garrelt

    2018-05-01

    The James Webb Space Telescope (JWST) will observe the rest-frame ultraviolet/optical spectra of galaxies from the epoch of reionization (EoR) in unprecedented detail. While escaping into the intergalactic medium, hydrogen-ionizing (Lyman continuum; LyC) photons from the galaxies will contribute to the bluer end of the UV slope and make nebular emission lines less prominent. We present a method to constrain leakage of the LyC photons using the spectra of high redshift (z >~ 6) galaxies. We simulate JWST/NIRSpec observations of galaxies at z =6-9 by matching the fluxes of galaxies observed in the Frontier Fields observations of galaxy cluster MACS-J0416. Our method predicts the escape fraction fesc with a mean absolute error Δfesc ~ 0.14. The method also predicts the redshifts of the galaxies with an error .

  2. Statistical mechanics of budget-constrained auctions

    International Nuclear Information System (INIS)

    Altarelli, F; Braunstein, A; Realpe-Gomez, J; Zecchina, R

    2009-01-01

    Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise

  3. Constraining Dark Sectors with Monojets and Dijets

    CERN Document Server

    Chala, Mikael; McCullough, Matthew; Nardini, Germano; Schmidt-Hoberg, Kai

    2015-01-01

    We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simpli...

  4. Statistical mechanics of budget-constrained auctions

    Science.gov (United States)

    Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.

    2009-07-01

    Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise.

  5. Constrained least squares regularization in PET

    International Nuclear Information System (INIS)

    Choudhury, K.R.; O'Sullivan, F.O.

    1996-01-01

    Standard reconstruction methods used in tomography produce images with undesirable negative artifacts in background and in areas of high local contrast. While sophisticated statistical reconstruction methods can be devised to correct for these artifacts, their computational implementation is excessive for routine operational use. This work describes a technique for rapid computation of approximate constrained least squares regularization estimates. The unique feature of the approach is that it involves no iterative projection or backprojection steps. This contrasts with the familiar computationally intensive algorithms based on algebraic reconstruction (ART) or expectation-maximization (EM) methods. Experimentation with the new approach for deconvolution and mixture analysis shows that the root mean square error quality of estimators based on the proposed algorithm matches and usually dominates that of more elaborate maximum likelihood, at a fraction of the computational effort

  6. Constraining dark sectors with monojets and dijets

    Energy Technology Data Exchange (ETDEWEB)

    Chala, Mikael; Kahlhoefer, Felix; Nardini, Germano; Schmidt-Hoberg, Kai [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); McCullough, Matthew [European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theory Div.

    2015-03-15

    We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.

  7. Constraining the dark side with observations

    International Nuclear Information System (INIS)

    Diez-Tejedor, Alberto

    2007-01-01

    The main purpose of this talk is to use the observational evidences pointing out to the existence of a dark side in the universe in order to infer some of the properties of the unseen material. We will work within the Unified Dark Matter models, in which both, Dark Matter and Dark Energy appear as the result of one unknown component. By modeling effectively this component with a classical scalar field minimally coupled to gravity, we will use the observations to constrain the form of the dark action. Using the flat rotation curves of spiral galaxies we will see that we are restringed to the use of purely kinetic actions, previously studied in cosmology by Scherrer. Finally we arrive to a simple action which fits both cosmological and astrophysical observations

  8. Constraining the dark side with observations

    Energy Technology Data Exchange (ETDEWEB)

    Diez-Tejedor, Alberto [Dpto. de Fisica Teorica, Universidad del PaIs Vasco, Apdo. 644, 48080, Bilbao (Spain)

    2007-05-15

    The main purpose of this talk is to use the observational evidences pointing out to the existence of a dark side in the universe in order to infer some of the properties of the unseen material. We will work within the Unified Dark Matter models, in which both, Dark Matter and Dark Energy appear as the result of one unknown component. By modeling effectively this component with a classical scalar field minimally coupled to gravity, we will use the observations to constrain the form of the dark action. Using the flat rotation curves of spiral galaxies we will see that we are restringed to the use of purely kinetic actions, previously studied in cosmology by Scherrer. Finally we arrive to a simple action which fits both cosmological and astrophysical observations.

  9. Hard exclusive meson production to constrain GPDs

    Energy Technology Data Exchange (ETDEWEB)

    Wolbeek, Johannes ter; Fischer, Horst; Gorzellik, Matthias; Gross, Arne; Joerg, Philipp; Koenigsmann, Kay; Malm, Pasquale; Regali, Christopher; Schmidt, Katharina; Sirtl, Stefan; Szameitat, Tobias [Physikalisches Institut, Albert-Ludwigs-Universitaet Freiburg, Freiburg im Breisgau (Germany); Collaboration: COMPASS Collaboration

    2014-07-01

    The concept of Generalized Parton Distributions (GPDs) combines the two-dimensional spatial information, given by form factors, with the longitudinal momentum information from the PDFs. Thus, GPDs provide a three-dimensional 'tomography' of the nucleon. Furthermore, according to Ji's sum rule, the GPDs H and E enable access to the total angular momenta of quarks, antiquarks and gluons. While H can be approached using electroproduction cross section, hard exclusive meson production off a transversely polarized target can help to constrain the GPD E. At the COMPASS experiment at CERN, two periods of data taking were performed in 2007 and 2010, using a longitudinally polarized 160 GeV/c muon beam and a transversely polarized NH{sub 3} target. This talk introduces the data analysis of the process μ + p → μ' + p' + V, and recent results are presented.

  10. Qinghai-Tibet Plateau crustal thickness derived from EGM2008 and CRSUT2.0

    Directory of Open Access Journals (Sweden)

    Zhou Hao

    2014-11-01

    Full Text Available Qinghai-Tibet Plateau is the most complex region for crustal thickness inversion, while high-resolution earth gravity model (EGM makes it possible to obtain high precision gravity anomaly, which is a key parameter to depict the Earth’s inner structure in geodesy domain. On the basis of this principle, we calculated the Bouguer gravity anomalies in Qinghai-Tibet Plateau with EGM2008 and SRTM6. 0 by efficient high-degree spherical harmonic synthesis algorithm. In order to obtain the gravity anomaly caused by Moho density mutant, the noises caused by the topography was removed by wavelet details. Then, the crustal thickness was corrected on the basis of CRUST 2. 0 with the deep-large-scale single density interface formula. The inversion result indicates that the crustal thickness in Qinghai-Tibet Plateau is between 50 km and 75 km, which is in correspondence with the recent science research result. Compared with the 2 degree CRUST 2. 0 model, the spatial resolution of crustal thickness in our research can reach 40 arc minutes. In addition, there is a positive relationship between the inversed crustal thickness and topography, which can prove the effectiveness of Airy-Heiskanen isostatic model in gravity reduction.

  11. Influence of crustal layering and thickness on co-seismic effects of Wenchuan earthquake

    Directory of Open Access Journals (Sweden)

    Tan Hongbo

    2011-02-01

    Full Text Available Using the PSGRN/PSCMP software and the fault model offered by USGS and on the basis of finite rectangular dislocation theory and the local layered wave velocity structures of the crust-upper-mantle, the influences of crustal layering and thickness on co-seismic gravity changes and deformation of Wenchuan earthquake have been simulated. The results indicate that; the influences have a relationship with the attitude of faults and the relative position between calculated points and fault. The difference distribution form of simulated results between the two models is similar to that of co-seismic effect. For the per centum distribution, it’s restricted by the zero line of the co-seismic effects obviously. Its positive is far away from the zero line. For the crustal thickness, the effect is about 10% – 20%. The negative and the effect over 30% focus around the zero line. The average influences of crustal layering and thickness for the E-W displacement, N-S displacement, vertical displacement and gravity changes are 18.4%,18.0%, 15.8% and 16.2% respectively, When the crustal thickness is 40 km, they are 4.6%, 5.3%, 3.8% and 3.8%. Then the crustal thickness is 70 km, the average influences are 3.5%, 4.6%, 3.0% and 2.5% respectively.

  12. Seismotectonics of Taiwan Shoal region in northeastern SCS: Insights from crustal structure

    Science.gov (United States)

    Kuiyuan, Wan; Jinlong, Sun; Shaohong, Xia; Xiaoling, Xie; Xiang, Zhang; Huilong, Xu; Jinghe, Cao

    2017-04-01

    A seismicity cluster and a great 16 September 1994 earthquake occur in the Taiwan Shoal region, outer rise of the Manila subduction zone. To understand what mechanisms control and generate the earthquake cluster, it is important to investigate the deep crustal structure of the Taiwan Shoal region. We present a 2-D seismic tomographic image of the crustal structure along the OBS2012 profile based on ocean bottom seismographic (OBS) data. The structure exhibits that a high velocity anomaly in the upper crust beneath the Taiwan Shoal is flanked by lower velocity anomalies. Based on the crustal structure, we study the 765 earthquakes, which occurred in the period 1991-2015. These epicenters, combined with the regional faults, and crustal structure, allow us to better understand the nature of the active tectonics in this region. The high velocity area is interpreted as representing stronger, defining major asperities where stress is concentrated corresponding to the location of the earthquake cluster. The earthquake cluster is influenced by the fault interactions. However, the 16 September 1994 earthquake is independents of the seismic activities but associated with the reactivation of the preexisting fault. In Taiwan region, the slab-pull was resisted by the exposed pre-collision accretionary prism and the resistive force caused the in-plane compressive stress accumulation. This condition may favor the triggering of future damaging earthquakes in this region. Key words: earthquake cluster; crustal structure; fault interactions; outer rise; Taiwan Shoal

  13. Crustal moment of inertia of glitching pulsars with the KDE0v1 Skyrme interaction

    Energy Technology Data Exchange (ETDEWEB)

    Madhuri, K.; Routray, T.R.; Pattnaik, S.P. [Sambalpur University, School of Physics, Jyotivihar (India); Basu, D.N. [Variable Energy Cyclotron Center, Kolkata (India)

    2017-07-15

    The mass, radius and crustal fraction of moment of inertia in neutron stars are calculated using β-equilibrated nuclear matter obtained from the Skyrme effective interaction. The transition density, pressure and proton fraction at the inner edge separating the liquid core from the solid crust of the neutron stars are determined from the thermodynamic stability conditions using the KDE0v1 set. The neutron star masses obtained by solving the Tolman-Oppenheimer-Volkoff equations using neutron star matter obtained from this set are able to describe highly massive compact stars ∝ 2M {sub CircleDot}. The crustal fraction of the moment of inertia can be extracted from studying pulsar glitches. This fraction is highly dependent on the core-crust transition pressure and corresponding density. These results for pressure and density at core-crust transition together with the observed minimum crustal fraction of the total moment of inertia provide a limit for the radius of the Vela pulsar, R ≥ 3.69 + 3.44M/M {sub CircleDot}. Present calculations suggest that the crustal fraction of the total moment of inertia can be ∝ 6.3% due to crustal entrainment caused by the Bragg reflection of unbound neutrons by lattice ions. (orig.)

  14. Crustal CO2 liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia

    Science.gov (United States)

    Troll, Valentin R.; Hilton, David R.; Jolis, Ester M.; Chadwick, Jane P.; Blythe, Lara S.; Deegan, Frances M.; Schwarzkopf, Lothar M.; Zimmer, Martin

    2012-06-01

    High-temperature volcanic gas is widely considered to originate from ascending, mantle-derived magma. In volcanic arc systems, crustal inputs to magmatic gases mainly occur via subducted sediments in the mantle source region. Our data from Merapi volcano, Indonesia imply, however, that during the April-October 2006 eruption significant quantities of CO2 were added from shallow crustal sources. We show that prior to the 2006 events, summit fumarole gas δ13C(CO2) is virtually constant (δ13C1994-2005 = -4.1 ± 0.3‰), but during the 2006 eruption and after the shallow Yogyakarta earthquake of late May, 2006 (M6.4; hypocentres at 10-15 km depth), carbon isotope ratios increased to -2.4 ± 0.2‰. This rise in δ13C is consistent with considerable addition of crustal CO2 and coincided with an increase in eruptive intensity by a factor of ˜3 to 5. We postulate that this shallow crustal volatile input supplemented the mantle-derived volatile flux at Merapi, intensifying and sustaining the 2006 eruption. Late-stage volatile additions from crustal contamination may thus provide a trigger for explosive eruptions independently of conventional magmatic processes.

  15. New Interpretation of Crustal Extension Evidences on Mars

    Science.gov (United States)

    Grin, E. A.

    The record of early evolution of life on Earth has been obscured by extensive surface activity. On the opposite, large fractions of the martian surface date back to an early clement epoch favorable to the needs of biological systems [1]. The upper martian surface reflects a wide variety of modifying processes which destroy the geological context. However, due to endogenic causes acting after the end of the primordial bombardment, abundant extensional structures display vertical sequences of stratigraphic units from late Noachian to early Hesperian periods [2]. Deep structural incisions in the upper crust provide unaltered strata, open flanks, and slope deposits that favor the use of an autonomous lander-rover-penetrator The strategy for an exobiology search of such an optimum site should be guided by the recent attention devoted to extensional structures and their global significance [4]. Geological evidence supporting the martian crustal extension is suggested by abundant fractures associated with the dichotomy boundary northland-south upland, i.e., Aeolis Region, and peak igneous activity (Elysium bulge). As pointed out by [5], the system of fractures correlates with the endogenic origin of the dichotomy, as related to a major difference in the thicknessof the crust. Perpendicular to this boundary, fractures of deep graben testify to a general tectonic crust relaxation. The opening of the graben, joined with compressive wrinkles, is the signature of a dynamical pervasive stress regime that implies a large scale roll-over of the upper crust over the ductile interface of a more dense mantle. This general motion is not a transport of material, as there is no thickening on the boundary of the dichotomy. The horizontal movement is due to the gravitational mechanism and differential thermal convection cells in the upper crust over the slope of the anti-flexure rigid interface consequential to Elysium bulge. The fracturation occurs as the neutral zone of the crust rises

  16. Crustal processes of the Mid-Ocean Ridge

    Science.gov (United States)

    Ballard, Richard D.; Craig, H.; Edmond, J.; Einaudi, M.; Holcomb, R.; Holland, H.D.; Hopson, C.A.; Luyendyk, B.P.; Macdonald, K.; Morton, J.; Orcutt, J.; Sleep, N.

    1981-01-01

    Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21 ??N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0

  17. Crustal Structure of Khövsgöl, Mongolia

    Science.gov (United States)

    Scott, A. M.; Meltzer, A.; Stachnik, J.; Russo, R.; Munkhuu, U.; Tsagaan, B.

    2017-12-01

    Mongolia is part of the Central Asian Orogenic Belt, an accretionary event that spanned 800 million years from the mid-Proterozoic to mid-Phanerozoic. As a result of the past collisional and rifting events, the modern Khövsgöl rift system of northern Mongolia contains a heterogeneous lithospheric structure. The current rift system has three parallel N-S trending basins that roughly align with terrane boundaries. Structures inherited during the accretionary events may be a factor influencing regional deformation. The forces that drive local deformation are not well understood, but varying processes have been proposed: far-field effects of India-Eurasian plate convergence, westward subduction of the Pacific plate, magmatic underplating at the base of the crust, mantle plume activity, and asthenospheric mantle convection. Determining the nature of crustal features within this poorly understood region may illuminate processes that control rifting within intracontinental settings. A network of 26 broadband seismic stations encompassing 200 square kilometers of the Khövsgöl rift system were deployed from August 2014 to June 2016. More than 2100 events were detected, and most earthquakes were concentrated near rift structures. Events between Busiin-Gol and Darkhad, the westernmost and central basins of the Khövsgöl rift system, are distributed within the crust. An active fault is outlined along the eastern border of the Darkhad basin. Khövsgöl earthquakes bound both sides of the rift. Along the northern border of Lake Khövsgöl, seismic events define a shallow active fault orthogonal to the basin. The largest event recorded within the network was a magnitude ml=5.2 located near the northeastern border of Lake Khövsgöl on 12-05-2014. The focal mechanism of this earthquake is predominantly strike-slip, but also includes an extensional component. This work focuses on earthquake relocation and calculating moment tensors and focal mechanisms of larger regional

  18. Crustal processes of the mid-ocean ridge.

    Science.gov (United States)

    1981-07-03

    Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21 degrees N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0

  19. Constrained optimization via simulation models for new product innovation

    Science.gov (United States)

    Pujowidianto, Nugroho A.

    2017-11-01

    We consider the problem of constrained optimization where the decision makers aim to optimize the primary performance measure while constraining the secondary performance measures. This paper provides a brief overview of stochastically constrained optimization via discrete event simulation. Most review papers tend to be methodology-based. This review attempts to be problem-based as decision makers may have already decided on the problem formulation. We consider constrained optimization models as there are usually constraints on secondary performance measures as trade-off in new product development. It starts by laying out different possible methods and the reasons using constrained optimization via simulation models. It is then followed by the review of different simulation optimization approach to address constrained optimization depending on the number of decision variables, the type of constraints, and the risk preferences of the decision makers in handling uncertainties.

  20. Crustal evolution of South American Platform based on Sm-Nd isotope geochemistry; Evolucao crustal da plataforma sul americana com base na geoquimica isotopica Sm-Nd

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Kei

    1998-07-01

    Sm-Nd isotopic systematics is relevant to the topics of origin and evolution the of continental crust, where model ages refer to the time when crustal material was differentiated from the upper mantle. Alternative interpretations are due to a lack of adequate information on crustal processes and the variable composition of the mantle sources. The Sm-Nd methods are presented, and applied on rock materials from the South American Platform. The main conclusions indicate juvenile accretion with higher growth rates (peaks), around 3.7-3.5 Ga ({approx} 0.5% in volume), 3.1 - 2.9 Ga ({approx}16%), 2.7 - 2.6 ({approx} 9%), 2.2 - 1.9 (35%) and 1.3-1.0 (7%). The continental growth curve indicates that about 35 % of the crust was formed by 2.5 Ga, 88% by 1.8 Ga and 99% by 1.0 Ga, and the remaining {approx} 1 % was added in the Phanerozoic. Rapid crustal growth occurred between 2.2 and 1.9 Ga. The main period of continental crust formation occurred during the Paleoproterozoic, corresponding to 54 % in volume. Sm-Nd model ages, when compared with the crystallisation ages of granitoid rocks, furnish a rough estimate of juvenile vs. reworked material. Within the South American Platform about 45% of juvenile continental crust is still preserved within tectonic provinces of different ages. The remainder represents continental crust reworked in younger tectono-thermal events. In particular crustal reworking was predominating over juvenile accretion during Meso-Neoproterozoic. The Transbrasiliano Lineament is a megasuture, active in the Neoproterozoic, which separates a large northwestern mass, including the Amazonian and Sao Luis Cratons, from a southeastern mass, formed by a collage of cratonic fragments, of which the Sao Francisco and Rio de La Plata are the largest. The crustal evolutions of these two large continental masses are considered individually, and can be resumed following form: I - Old Archean rocks (>3.4 Ga) are found only within the south-eastern part (Gaviao Block

  1. Reflected stochastic differential equation models for constrained animal movement

    Science.gov (United States)

    Hanks, Ephraim M.; Johnson, Devin S.; Hooten, Mevin B.

    2017-01-01

    Movement for many animal species is constrained in space by barriers such as rivers, shorelines, or impassable cliffs. We develop an approach for modeling animal movement constrained in space by considering a class of constrained stochastic processes, reflected stochastic differential equations. Our approach generalizes existing methods for modeling unconstrained animal movement. We present methods for simulation and inference based on augmenting the constrained movement path with a latent unconstrained path and illustrate this augmentation with a simulation example and an analysis of telemetry data from a Steller sea lion (Eumatopias jubatus) in southeast Alaska.

  2. Resource Management in Constrained Dynamic Situations

    Science.gov (United States)

    Seok, Jinwoo

    Resource management is considered in this dissertation for systems with limited resources, possibly combined with other system constraints, in unpredictably dynamic environments. Resources may represent fuel, power, capabilities, energy, and so on. Resource management is important for many practical systems; usually, resources are limited, and their use must be optimized. Furthermore, systems are often constrained, and constraints must be satisfied for safe operation. Simplistic resource management can result in poor use of resources and failure of the system. Furthermore, many real-world situations involve dynamic environments. Many traditional problems are formulated based on the assumptions of given probabilities or perfect knowledge of future events. However, in many cases, the future is completely unknown, and information on or probabilities about future events are not available. In other words, we operate in unpredictably dynamic situations. Thus, a method is needed to handle dynamic situations without knowledge of the future, but few formal methods have been developed to address them. Thus, the goal is to design resource management methods for constrained systems, with limited resources, in unpredictably dynamic environments. To this end, resource management is organized hierarchically into two levels: 1) planning, and 2) control. In the planning level, the set of tasks to be performed is scheduled based on limited resources to maximize resource usage in unpredictably dynamic environments. In the control level, the system controller is designed to follow the schedule by considering all the system constraints for safe and efficient operation. Consequently, this dissertation is mainly divided into two parts: 1) planning level design, based on finite state machines, and 2) control level methods, based on model predictive control. We define a recomposable restricted finite state machine to handle limited resource situations and unpredictably dynamic environments

  3. Sensitivity analysis of crustal correction for calculation of lithospheric mantle density from gravity data

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2016-01-01

    for the crust and (ii) uncertainties in the seismic crustal structure (thickness and average VP velocities of individual crustal layers, including the sedimentary cover). We examine the propagation of these uncertainties into determinations of lithospheric mantle density and analyse both sources of possible......We investigate how uncertainties in seismic and density structure of the crust propagate to uncertainties in mantle density structure. The analysis is based on interpretation of residual upper-mantle gravity anomalies which are calculated by subtracting (stripping) the gravitational effect...... mantle, knowledge on uncertainties associated with incomplete information on crustal structure is of utmost importance for progress in gravity modelling. Uncertainties in the residual upper-mantle gravity anomalies result chiefly from uncertainties in (i) seismic VP velocity-density conversion...

  4. Modelling of crustal rock mechanics for radioactive waste storage in Fennoscandia - problem definition

    International Nuclear Information System (INIS)

    Stephansson, O.

    1987-05-01

    Existing knowledge of crustal stresses for Fennoscandia is presented. Generic, two-dimensional models are proposed for vertical and planar sections of a traverse having a direction NW-SE in Northern Fennoscandia. The proposed traverse will include the major neotectonic structures at Lansjaerv and Paervie, respectively, and also the study site for storage of spent nuclear fuel at Kamlunge. The influence of glaciation, deglaciation, glacial rebound on crustal rock mechanics and stability is studied for the modelling work. Global models, with a length of roughly 100 km, will increase our over all understanding of the change in stresses and deformations. These can provide boundary conditions for regional and near-field models. Properties of strength and stiffness of intact granitic rock masses, faults and joints are considered in the modelling of the crustal rock mechanics for any of the three models described. (orig./HP)

  5. Influence of mid-crustal rheology on the deformation behavior of continental crust in the continental subduction zone

    Science.gov (United States)

    Li, Fucheng; Sun, Zhen; Zhang, Jiangyang

    2018-06-01

    Although the presence of low-viscosity middle crustal layer in the continental crust has been detected by both geophysical and geochemical studies, its influence on the deformation behavior of continental crust during subduction remains poorly investigated. To illustrate the crustal deformation associated with layered crust during continental subduction, we conducted a suite of 2-D thermo-mechanical numerical studies with visco-brittle/plastic rheology based on finite-differences and marker-in-cell techniques. In the experiments, we established a three-layer crustal model with a quartz-rich middle crustal layer embedded between the upper and lower continental crust. Results show that the middle crustal layer determines the amount of the accreted upper crust, maximum subduction depth, and exhumation path of the subducted upper crust. By varying the initial effective viscosity and thickness of the middle crustal layer, the further effects can be summarized as: (1) a rheologically weaker and/or thicker middle crustal layer results in a larger percentage of the upper crust detaching from the underlying slab and accreting at the trench zone, thereby leading to more serious crustal deformation. The rest of the upper crust only subducts into the depths of high pressure (HP) conditions, causing the absence of ultra-high pressure (UHP) metamorphic rocks; (2) a rheologically stronger and/or thinner middle crustal layer favors the stable subduction of the continental crust, dragging the upper crust to a maximum depth of ∼100 km and forming UHP rocks; (3) the middle crustal layer flows in a ductile way and acts as an exhumation channel for the HP-UHP rocks in both situations. In addition, the higher convergence velocity decreases the amount of subducted upper crust. A detailed comparison of our modeling results with the Himalayan collisional belt are conducted. Our work suggests that the presence of low-viscosity middle crustal layer may be another possible mechanism for

  6. Sequential unconstrained minimization algorithms for constrained optimization

    International Nuclear Information System (INIS)

    Byrne, Charles

    2008-01-01

    The problem of minimizing a function f(x):R J → R, subject to constraints on the vector variable x, occurs frequently in inverse problems. Even without constraints, finding a minimizer of f(x) may require iterative methods. We consider here a general class of iterative algorithms that find a solution to the constrained minimization problem as the limit of a sequence of vectors, each solving an unconstrained minimization problem. Our sequential unconstrained minimization algorithm (SUMMA) is an iterative procedure for constrained minimization. At the kth step we minimize the function G k (x)=f(x)+g k (x), to obtain x k . The auxiliary functions g k (x):D subset of R J → R + are nonnegative on the set D, each x k is assumed to lie within D, and the objective is to minimize the continuous function f:R J → R over x in the set C = D-bar, the closure of D. We assume that such minimizers exist, and denote one such by x-circumflex. We assume that the functions g k (x) satisfy the inequalities 0≤g k (x)≤G k-1 (x)-G k-1 (x k-1 ), for k = 2, 3, .... Using this assumption, we show that the sequence {(x k )} is decreasing and converges to f(x-circumflex). If the restriction of f(x) to D has bounded level sets, which happens if x-circumflex is unique and f(x) is closed, proper and convex, then the sequence {x k } is bounded, and f(x*)=f(x-circumflex), for any cluster point x*. Therefore, if x-circumflex is unique, x* = x-circumflex and {x k } → x-circumflex. When x-circumflex is not unique, convergence can still be obtained, in particular cases. The SUMMA includes, as particular cases, the well-known barrier- and penalty-function methods, the simultaneous multiplicative algebraic reconstruction technique (SMART), the proximal minimization algorithm of Censor and Zenios, the entropic proximal methods of Teboulle, as well as certain cases of gradient descent and the Newton–Raphson method. The proof techniques used for SUMMA can be extended to obtain related results

  7. Explaining evolution via constrained persistent perfect phylogeny

    Science.gov (United States)

    2014-01-01

    Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to

  8. Crustal structure of north Peru from analysis of teleseismic receiver functions

    Science.gov (United States)

    Condori, Cristobal; França, George S.; Tavera, Hernando J.; Albuquerque, Diogo F.; Bishop, Brandon T.; Beck, Susan L.

    2017-07-01

    In this study, we present results from teleseismic receiver functions, in order to investigate the crustal thickness and Vp/Vs ratio beneath northern Peru. A total number of 981 receiver functions were analyzed, from data recorded by 28 broadband seismic stations from the Peruvian permanent seismic network, the regional temporary SisNort network and one CTBTO station. The Moho depth and average crustal Vp/Vs ratio were determined at each station using the H-k stacking technique to identify the arrival times of primary P to S conversion and crustal reverberations (PpPms, PpSs + PsPms). The results show that the Moho depth correlates well with the surface topography and varies significantly from west to east, showing a shallow depth of around 25 km near the coast, a maximum depth of 55-60 km beneath the Andean Cordillera, and a depth of 35-40 km further to the east in the Amazonian Basin. The bulk crustal Vp/Vs ratio ranges between 1.60 and 1.88 with the mean of 1.75. Higher values between 1.75 and 1.88 are found beneath the Eastern and Western Cordilleras, consistent with a mafic composition in the lower crust. In contrast values vary from 1.60 to 1.75 in the extreme flanks of the Eastern and Western Cordillera indicating a felsic composition. We find a positive relationship between crustal thickness, Vp/Vs ratio, the Bouguer anomaly, and topography. These results are consistent with previous studies in other parts of Peru (central and southern regions) and provide the first crustal thickness estimates for the high cordillera in northern Peru.

  9. Developing a Crustal and Upper Mantle Velocity Model for the Brazilian Northeast

    Science.gov (United States)

    Julia, J.; Nascimento, R.

    2013-05-01

    Development of 3D models for the earth's crust and upper mantle is important for accurately predicting travel times for regional phases and to improve seismic event location. The Brazilian Northeast is a tectonically active area within stable South America and displays one of the highest levels of seismicity in Brazil, with earthquake swarms containing events up to mb 5.2. Since 2011, seismic activity is routinely monitored through the Rede Sismográfica do Nordeste (RSisNE), a permanent network supported by the national oil company PETROBRAS and consisting of 15 broadband stations with an average spacing of ~200 km. Accurate event locations are required to correctly characterize and identify seismogenic areas in the region and assess seismic hazard. Yet, no 3D model of crustal thickness and crustal and upper mantle velocity variation exists. The first step in developing such models is to refine crustal thickness and depths to major seismic velocity boundaries in the crust and improve on seismic velocity estimates for the upper mantle and crustal layers. We present recent results in crustal and uppermost mantle structure in NE Brazil that will contribute to the development of a 3D model of velocity variation. Our approach has consisted of: (i) computing receiver functions to obtain point estimates of crustal thickness and Vp/Vs ratio and (ii) jointly inverting receiver functions and surface-wave dispersion velocities from an independent tomography study to obtain S-velocity profiles at each station. This approach has been used at all the broadband stations of the monitoring network plus 15 temporary, short-period stations that reduced the inter-station spacing to ~100 km. We expect our contributions will provide the basis to produce full 3D velocity models for the Brazilian Northeast and help determine accurate locations for seismic events in the region.

  10. Reworked crustal of early Paleozoic WuYi Orogen revealed by receiver function data

    Science.gov (United States)

    Wei, Y.; Duan, Y.; Tian, X.; Zhao, Y.

    2017-12-01

    Intraplate orogenic belt, which occurs at the rigid and undeformable plate interiors, is a distinct new type of orogen rather than an interplate or plate marginal orogenic belt, whose deformation occurs exclusively at plate margins. Therefore, intraplate orogenic belts are the most obvious exception to the plate-tectonic paradigm, they are uncommon in Earth's history. The early Paleozoic Wuyi orogen in South China is one of the few examples of intraplate orogen, and is a key to understanding the process of intraplate orogenesis and global early Paleozoic geodynamics. In this study, we select teleseismic records from 45 mobile linear seismic stations deployed in Wuyi Mountain and 58 permanent stations setting in Jiangxi and Fujian provinces, from January 2011 to December 2012, and calculate the crustal thickness and average crustal Vp/Vs ratio using the H-κ stacking method. The main results include the following: 1) the crustal average Poission's ratio shows an increase tendency from land to sea, the interior of Wuyi orogen belt with an low ration less than 0.23, and the coastline with high ration which is up to 0.28, which indicate a very heterogeneous crustal structure and composition in Wuyi orogen and coast belt. 2) the crustal thickness ranges 28-34 km and shows a tendency of thinning from inland to coast in the region of SE China margin, which maight mean the eastern Eurasia lithospheric is extension and thinning induced by the subducted paleo-Pacific slab. To conclusion, we assume that Wuyi orogen experienced upper crustal thickening, lower crust and lithosphere delamination during the early Paleozoic orogeny, and lithosphere extension in Mesozoic. This research is founded by the Natural Science Foundation of China (41174052 and 41604048).

  11. Crustal thickness and Vp/Vs beneath the southeastern United States: Constraints from receiver function stacking

    Science.gov (United States)

    Yang, Q.; Gao, S. S.; Liu, K. H.

    2017-12-01

    To provide new constraints on crustal structure and evolution models beneath a collage of tectonic provinces in the southeastern United States, a total of 10,753 teleseismic receiver functions recorded by 125 USArray and other seismic stations are used to compute crustal thickness and Vp/Vs values. The resulting crustal thicknesses range from 25 km at the coast to 51 km beneath the peak of the southern Appalachians with an average of 36.2 km ± 5.5 km. The resulting crustal thicknesses correlate well with surface elevation and Bouguer gravity anomalies. Beneath the Atlantic Coastal Plain, the crustal thicknesses show a clear eastward thinning with a magnitude of 10 km, from about 40 km beneath the western margin to 30 km beneath the coast. The Vp/Vs values for the entire study area range from 1.71 to 1.90 with a mean value of 1.80 ± 0.04. The mean Vp/Vs value is 1.82±0.035 in the southern Appalachian Mountain. The slightly larger than normal crustal Vp/Vs for this area might be the result of significant erosion of the felsic upper crust over the past 300 million years. Alternatively, it could also suggest the existence of pervasive magmatic intrusion into the Appalachian crust. The Vp/Vs measurements in the Atlantic Coastal Plain increase toward the east, ranging from 1.75 to 1.82, probably indicating a gradual increase of mafic magmatic intrusion into thinner crust during the development of the passive continental margin.

  12. Orphan Basin crustal structure from a dense wide-angle seismic profile - Tomographic inversion

    Science.gov (United States)

    Watremez, Louise; Lau, K. W. Helen; Nedimović, Mladen R.; Louden, Keith E.; Karner, Garry D.

    2014-05-01

    Orphan Basin is located on the eastern margin of Canada, offshore of Newfoundland and East of Flemish Cap. It is an aborted continental rift formed by multiple episodes of rifting. The crustal structure across the basin has been determined by an earlier refraction study using 15 instruments on a 550 km long line. It shows that the continental crust was extended over an unusually wide region but did not break apart. The crustal structure of the basin thus documents stages in the formation of a magma-poor rifted margin up to crustal breakup. The OBWAVE (Orphan Basin Wide-Angle Velocity Experiment) survey was carried out to image crustal structures across the basin and better understand the processes of formation of this margin. The spacing of the 89 recording stations varies from 3 to 5 km along this 500-km-long line, which was acquired along a pre-existing reflection line. The highest resolution section corresponds to the part of the profile where the crust was expected to be the thinnest. We present the results from a joint tomography inversion of first and Moho reflected arrival times. The high data density allows us to define crustal structures with greater detail than for typical studies and to improve the understanding of the processes leading to the extreme stretching of continental crust. The final model was computed following a detailed parametric study to determine the optimal parameters controlling the ray-tracing and the inversion processes. The final model shows very good resolution. In particular, Monte Carlo standard deviations of crustal velocities and Moho depths are generally Orphan Basin is the result of rifting of a non-homogeneous Avalon terrane where the lower crust is primarily ductile.

  13. Monitoring Vertical Crustal Deformation and Gravity Variations during Water Level Changes at the Three Gorges Reservoir

    Directory of Open Access Journals (Sweden)

    WANG Wei

    2017-06-01

    Full Text Available Monitoring vertical crustal deformation and gravity changes during water level changes at the Three Gorges reservoir is important for the safe operation of the Three Gorges Dam and for the monitoring and prevention of a regional geological disaster. In this study, we determined vertical crustal deformation and gravity changes during water level variations of the Three Gorges reservoir from direct calculations and actual measurements and a comprehensive solution. We used water areas extracted image data from the ZY-3 satellite and water level data to calculate gravity changes and vertical crustal deformation caused by every 5 m change in the water level due to storage and drainage of the Three Gorges reservoir from 145 m to 175 m. The vertical crustal deformation was up to 30 mm. The location of gravity change above 20 μ Gal(1 Gal=10-2 m/s2 was less than 2 km from the centerline of the Yangtze River. The CORS ES13 in Badong, near the reservoir, measured the vertical crustal deformation during water level changes. Because of the small number of CORS and gravity stations in the Three Gorges reservoir area, monitoring deformation and gravity related to changes in the Three Gorges reservoir water level cannot be closely followed. Using 26 CORS and some of the gravity stations in the Three Gorges area and based on loading deformation and the spherical harmonic analysis method, an integrated solution of vertical deformation and gravity variations during water level changes of the reservoir was determined, which is consistent with the actual CORS monitoring results. By comparison, we found that an integrated solution based on a CORS network can effectively enhance the capability of monitoring vertical crustal deformation and gravity changes during water level variations of the reservoir.

  14. Modeling the blockage of Lg waves from 3-D variations in crustal structure

    Science.gov (United States)

    Sanborn, Christopher J.; Cormier, Vernon F.

    2018-05-01

    Comprised of S waves trapped in Earth's crust, the high frequency (2-10 Hz) Lg wave is important to discriminating earthquakes from explosions by comparing its amplitude and waveform to those of Pg and Pn waves. Lateral variations in crustal structure, including variations in crustal thickness, intrinsic attenuation, and scattering, affect the efficiency of Lg propagation and its consistency as a source discriminant at regional (200-1500 km) distances. To investigate the effects of laterally varying Earth structure on the efficiency of propagation of Lg and Pg, we apply a radiative transport algorithm to model complete, high-frequency (2-4 Hz), regional coda envelopes. The algorithm propagates packets of energy with ray theory through large-scale 3-D structure, and includes stochastic effects of multiple-scattering by small-scale heterogeneities within the large-scale structure. Source-radiation patterns are described by moment tensors. Seismograms of explosion and earthquake sources are synthesized in canonical models to predict effects on waveforms of paths crossing regions of crustal thinning (pull-apart basins and ocean/continent transitions) and thickening (collisional mountain belts), For paths crossing crustal thinning regions, Lg is amplified at receivers within the thinned region but strongly disrupted and attenuated at receivers beyond the thinned region. For paths crossing regions of crustal thickening, Lg amplitude is attenuated at receivers within the thickened region, but experiences little or no reduction in amplitude at receivers beyond the thickened region. The length of the Lg propagation within a thickened region and the complexity of over- and under-thrust crustal layers, can produce localized zones of Lg amplification or attenuation. Regions of intense scattering within laterally homogeneous models of the crust increase Lg attenuation but do not disrupt its coda shape.

  15. A hybrid origin of the Martian crustal dichotomy: Degree-1 convection antipodal to a giant impact

    Science.gov (United States)

    Citron, Robert I.; Manga, Michael; Tan, Eh

    2018-06-01

    The Martian crustal dichotomy is the stark ∼5 km difference in surface elevation and ∼26 km difference in crustal thickness between the northern lowlands and southern highlands that originated within 100s of Myr of Mars' formation. The origin of the dichotomy has broad implications for the geodynamic history of Mars, but purely exogenic or endogenic theories so far cannot explain all of the large scale geophysical observations associated with dichotomy formation. A giant impact can produce the shape and slope of the dichotomy boundary, but struggles to explain Mars' remanent crustal magnetic signatures and the ultimate formation of Tharsis. Degree-1 mantle convection can relate the crustal dichotomy to the formation of Tharsis, but does not explain the elliptical dichotomy shape and must be initiated by a large pre-existing viscosity jump in the mantle. We propose a hybrid model of dichotomy formation in which a giant impact induces degree-1 convection with an upwelling antipodal to the impact site. In this scenario, a giant impact in the northern hemisphere excavates crust, creating an initial difference in crustal thickness and possibly composition between the two hemispheres. Over 10s to 100s of Myr, the dominant upwelling(s) would migrate to be under the thicker, insulating crust in the southern hemisphere, generating melt that further thickens the southern crust. We examine this process using 3-D mantle convection simulations, and find that a hemispherical difference in crustal thickness and composition caused by a giant impact can induce degree-1 convection with the upwelling(s) antipodal to the impact site in <100 Myr.

  16. Evidences of Episodic Crustal Magmatic Diapir and Shallow Volcanic Activity at Uturuncu, Central Andes, from Geodetic Observations between 2014 - 2017

    Science.gov (United States)

    Lau, H. N.; Tymofyeyeva, E.; Fialko, Y. A.

    2017-12-01

    Previous space geodetic studies using ERS-1/2 and Envisat Interferometric Synthetic Aperture Radar (InSAR) data revealed a broad uplift of 10 mm/yr within the Altiplano-Puna Volcanic Complex (APVC), centered at the Uturuncu volcano, surrounded by a ring of subsidence at a rate of a few millimeters per year. This pattern was attributed to formation of a diapir in the middle of the Altiplano-Puna Magma Body (APMB), at depth of 15-19 km. We use new data from the Sentinel-1 InSAR mission, collected between 2014-2017, to produce high-resolution maps of surface displacements in the satellite's line of sight (LOS) from 4 satellite tracks. We estimated random propagation effects (e.g. due to atmospheric turbulence) using a common-point stacking method by Tymofyeyeva and Fialko [2015] and estimated temporally-correlated propagation effects (e.g. due to seasonal variations in atmospheric moisture) using a regression of the residual phase against topography. The estimated atmospheric artifacts were removed from the interferograms prior to computing the time series of the LOS displacements. The data indicate that the uplift above the APMB has considerably slowed down compared to the 1992-2010 epoch. The observed variations in the uplift rate suggest that the "ballooning" of the mid-crustal diapir is episodic on time scales of year to decades, possibly due to variations in melt supply from the partially molten APMB to the incipient diapir. We also find a previously undiscovered localized uplift 11 km south of Uturuncu's peak with maximum LOS velocities of 10 - 15 mm/yr. Joint inversions of data from different satellite tracks for a point source of inflation in an elastic half space constrain the source depth to be at 2 km, suggestive of a shallow magma chamber or a hydrothermal system.

  17. The temporal and spatial distribution of upper crustal faulting and magmatism in the south Lake Turkana rift, East Africa

    Science.gov (United States)

    Muirhead, J.; Scholz, C. A.

    2017-12-01

    During continental breakup extension is accommodated in the upper crust largely through dike intrusion and normal faulting. The Eastern branch of the East African Rift arguably represents the premier example of active continental breakup in the presence magma. Constraining how faulting is distributed in both time and space in these regions is challenging, yet can elucidate how extensional strain localizes within basins as rifting progresses to sea-floor spreading. Studies of active rifts, such as the Turkana Rift, reveal important links between faulting and active magmatic processes. We utilized over 1100 km of high-resolution Compressed High Intensity Radar Pulse (CHIRP) 2D seismic reflection data, integrated with a suite of radiocarbon-dated sediment cores (3 in total), to constrain a 17,000 year history of fault activity in south Lake Turkana. Here, a set of N-S-striking intra-rift faults exhibit time-averaged slip-rates as high as 1.6 mm/yr, with the highest slip-rates occurring along faults within 3 km of the rift axis. Results show that strain has localized into a zone of intra-rift faults along the rift axis, forming an approximately 20 km-wide graben in central parts of the basin. Subsurface structural mapping and fault throw profile analyses reveal increasing basin subsidence and fault-related strain as this faulted graben approaches a volcanic island in the center of the basin (South Island). The long-axis of this island trends north-south, and it contains a number of elongate cones that support recent emplacement of N-S-striking dike intrusions, which parallel recently active intra-rift faults. Overall, these observations suggest strain localization into intra-rift faults in the rift center is likely a product of both volcanic loading and the mechanical and thermal effects of diking along the rift axis. These results support the establishment of magmatic segmentation in southern Lake Turkana, and highlight the importance of magmatism for focusing upper

  18. REE, Sm-Nd and U-Pb zircon study of eclogites from the Alpine External Massifs (Western Alps): Evidence for crustal contamination

    International Nuclear Information System (INIS)

    Paquette, J.L.; Eidgenoessische Technische Hochschule, Zurich; Menot, R.P.; Peucat, J.J.

    1989-01-01

    A geochemical and geochronological study of the Alpine External Crystalline Massifs (AECM) of Aiguilles Rouges, Belledonne and Argentera was undertaken in order to constrain the geodynamic evolution of this segment of the Variscan foldbelt. Another aim of the study is to characterize the behaviour of isotopic markers, in particular the U-Pb zircon system, under high-grade metamorphic conditions. The whole-rock geochemistry of eclogites and amphibolites was investigated using major and trace element (including the REE) analytical techniques; isotopic studies were performed by application of the Sm-Nd whole-rock and U-Pb zircon methods. In terms of regional geological history, the early development of metamorphic and magmatic activity in the AECM is typical of the extensional tectonic regime observed throughout the Variscan foldbelt during the Cambro-Ordovician (i.e. basic magmatism dated at 475-450 Ma). The composition of the metabasic rocks is closely similar to tholeiites emplaced into thinned continental crust which are generally associated with the initial stages of oceanic rifting. The source regions for these metabasics are characterized by initial ε Nd values between +6 and +8, suggesting depleted mantle sources influenced by a weak crustal component and/or the existence of a metasomatised lithosphere. The multi-stage eclogite-facies metamorphism is dated at 425-395 Ma (i.e. Silurian). An application of the U-Pb method, associated with the artificial abrasion of zircon grains, has led to the recognition of a weak crustal contamination in the metabasic protoliths. This is implied by the Archaean and Lower Proterozoic upper intercepts on Concordia - devoid of geological significance - which reflect the presence of a pre-existing basement to the AECM. (orig./WL)

  19. Using aerogravity and seismic data to model the bathymetry and upper crustal structure beneath the Pine Island Glacier ice shelf, West Antarctica

    Science.gov (United States)

    Muto, A.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.; Riverman, K. L.

    2013-12-01

    Recent estimates indicate that ice shelves along the Amundsen Sea coast in West Antarctica are losing substantial mass through sub-ice-shelf melting and contributing to the accelerating mass loss of the grounded ice buttressed by them. For Pine Island Glacier (PIG), relatively warm Circumpolar Deep Water has been identified as the key driver of the sub-ice-shelf melting although poor constraints on PIG sub-ice shelf have restricted thorough understanding of these ice-ocean interactions. Aerogravity data from NASA's Operation IceBridge (OIB) have been useful in identifying large-scale (on the order of ten kilometers) features but the results have relatively large uncertainties due to the inherent non-uniqueness of the gravity inversion. Seismic methods offer the most direct means of providing water thickness and upper crustal geological constraints, but availability of such data sets over the PIG ice shelf has been limited due to logistical constraints. Here we present a comparative analysis of the bathymetry and upper crustal structure beneath the ice shelf of PIG through joint inversion of OIB aerogravity data and in situ active-source seismic measurements collected in the 2012-13 austral summer. Preliminary results indicate improved resolution of the ocean cavity, particularly in the interior and sides of the PIG ice shelf, and sedimentary drape across the region. Seismically derived variations in ice and ocean water densities are also applied to the gravity inversion to produce a more robust model of PIG sub-ice shelf structure, as opposed to commonly used single ice and water densities across the entire study region. Misfits between the seismically-constrained gravity inversion and that estimated previously from aerogravity alone provide insights on the sensitivity of gravity measurements to model perturbations and highlight the limitations of employing gravity data to model ice shelf environments when no other sub-ice constraints are available.

  20. Fine-scale crustal structure of the Azores Islands from teleseismic receiver functions

    Science.gov (United States)

    Spieker, K.; Rondenay, S.; Ramalho, R. S.; Thomas, C.; Helffrich, G. R.

    2016-12-01

    The Azores plateau is located near the Mid-Atlantic Ridge (MAR) and consists of nine islands, most of which lie east of the MAR. Various methods including seismic reflection, gravity, and passive seismic imaging have been used to investigate the crustal thickness beneath the islands. They have yielded thickness estimates that range between roughly 10 km and 30 km, but until now models of the fine-scale crustal structure have been lacking. A comparison of the crustal structure beneath the islands that lie west and east of the MAR might give further constraints on the evolution of the islands. For example, geochemical studies carried out across the region predict the existence of volcanic interfaces that should be detected seismically within the shallow crust of some of the islands. In this study, we use data from ten seismic stations located on the Azores Islands to investigate the crustal structure with teleseismic P-wave receiver functions. We query our resulting receiver functions for signals associated with the volcanic edifice, the crust-mantle boundary, and potential underplated layers beneath the various islands. The islands west of the MAR have a crustal structure comprising two discontinuities - an upper one at 1-2 km depth marking the base of the volcanic edifice, and a lower one at 10 km depth that we interpret as crust-mantle boundary. The islands east of the MAR can be subdivided into two groups. The central islands that are closer to the MAR exhibit a crustal structure similar to that of the western islands, with a volcanic edifice reaching a depth of 2 km and an average crust-mantle boundary at around 12 km depth. The easternmost islands, located on the oldest lithosphere, exhibit a more complex crustal structure with evidence for a mid-crustal interface and an underplated layer, yielding an effective crust-mantle boundary at >15 km depth. The difference in structure between proximal and distal islands might be related to the age of the plate at the

  1. Prediction of long-term crustal movement for geological disposal of radioactive waste

    International Nuclear Information System (INIS)

    Sasaki, Takeshi; Morikawa, Seiji; Tabei, Kazuto; Koide, Hitoshi; Tashiro, Toshiharu

    2000-01-01

    Long-term stability of the geological environment is essential for the safe geological disposal of radioactive waste, for which it is necessary to predict the crustal movement during an assessment period. As a case study, a numerical analysis method for the prediction of crustal movement in Japan is proposed. A three-dimensional elastic analysis by FEM for the geological block structure of the Kinki region and the Awaji-Rokko area is presented. Stability analysis for a disposal cavern is also investigated. (author)

  2. Terrestrial spreading centers under Venus conditions - Evaluation of a crustal spreading model for Western Aphrodite Terra

    Science.gov (United States)

    Sotin, C.; Senske, D. A.; Head, J. W.; Parmentier, E. M.

    1989-01-01

    The model of Reid and Jackson (1981) for terrestrial spreading centers is applied to Venus conditions. On the basis of spreading rate, mantle temperature, and surface temperature, the model predicts both isostatic topography and crustal thickness. The model and Pioneer Venus altimetry and gravity data are used to test the hypothesis of Head and Crumpler (1987) that Western Aphrodite Terra is the location of crustal spreading on Venus. It is concluded that a spreading center model for Ovda Regio in Western Aphrodite Terra could account for the observed topography and line-of-sight gravity anomalies found in the Pioneer data.

  3. On the geographical distribution of induced time-varying crustal magnetic fields

    DEFF Research Database (Denmark)

    Thebault, E.; Hemant, K.; Hulot, G.

    2009-01-01

    A long standing question in geomagnetism is whether the time variation of the induced crustal field is a detectable quantity and, if so, at which spatial wavelengths. We tackle this problem with the help of a forward modeling approach using a vertically integrated susceptibility (VIS) grid...... of the Earth's crust. For spherical harmonic degrees 15-90, we estimate the root mean square of the crustal magnetic field secular variation to amount 0.06-0.12 nT/yr at the terrestrial surface between epochs 1960-2002.5. The geographical distribution of the signal shows absolute values reaching 0.65-1.30 n...

  4. Crustal growth of the Izu-Ogasawara arc estimated from structural characteristics of Oligocene arc

    Science.gov (United States)

    Takahashi, N.; Yamashita, M.; Kodaira, S.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.

    2011-12-01

    Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out seismic surveys using a multichannel reflection system and ocean bottom seismographs, and we have clarified crustal structures of whole Izu-Ogasawara (Bonin)-Marina (IBM) arc since 2002. These refection images and velocity structures suggest that the crustal evolution in the intra-oceanic island arc accompanies with much interaction of materials between crust and mantle. Slow mantle velocity identified beneath the thick arc crusts suggests that dense crustal materials transformed into the mantle. On the other hand, high velocity lower crust can be seen around the bottom of the crust beneath the rifted region, and it suggests that underplating of mafic materials occurs there. Average crustal production rate of the entire arc is larger than expected one and approximately 200 km3/km/Ma. The production rate of basaltic magmas corresponds to that of oceanic ridge. Repeated crustal differentiation is indispensable to produce much light materials like continental materials, however, the real process cannot still be resolved yet. We, therefore, submitted drilling proposals to obtain in-situ middle crust with P-wave velocity of 6 km/s. In the growth history of the IBM arc, it is known by many papers that boninitic volcanisms preceded current bimodal volcanisms based on basaltic magmas. The current volcanisms accompanied with basaltic magmas have been occurred since Oligocene age, however, the tectonic differences to develop crustal architecture between Oligocene and present are not understood yet. We obtained new refraction/reflection data along an arc strike of N-S in fore-arc region. Then, we estimate crustal structure with severe change of the crustal thickness from refraction data, which are similar to that along the volcanic front. Interval for location of the thick arc crust along N-S is very similar to that along the volcanic front. The refection image indicates that the basement of the fore

  5. Constrained Sypersymmetric Flipped SU (5) GUT Phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John; /CERN /King' s Coll. London; Mustafayev, Azar; /Minnesota U., Theor. Phys. Inst.; Olive, Keith A.; /Minnesota U., Theor. Phys. Inst. /Minnesota U. /Stanford U., Phys. Dept. /SLAC

    2011-08-12

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, Min, above the GUT scale, M{sub GUT}. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino {chi} and the lighter stau {tilde {tau}}{sub 1} is sensitive to M{sub in}, as is the relationship between m{sub {chi}} and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m{sub 1/2}, m{sub 0}) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to Min, as we illustrate for several cases with tan {beta} = 10 and 55. However, these features do not necessarily disappear at large Min, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses.

  6. Constrained supersymmetric flipped SU(5) GUT phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John [CERN, TH Division, PH Department, Geneva 23 (Switzerland); King' s College London, Theoretical Physics and Cosmology Group, Department of Physics, London (United Kingdom); Mustafayev, Azar [University of Minnesota, William I. Fine Theoretical Physics Institute, Minneapolis, MN (United States); Olive, Keith A. [University of Minnesota, William I. Fine Theoretical Physics Institute, Minneapolis, MN (United States); Stanford University, Department of Physics and SLAC, Palo Alto, CA (United States)

    2011-07-15

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, M{sub in}, above the GUT scale, M{sub GUT}. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino {chi} and the lighter stau {tau}{sub 1} is sensitive to M{sub in}, as is the relationship between m{sub {chi}} and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m{sub 1/2},m{sub 0}) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to M{sub in}, as we illustrate for several cases with tan {beta}=10 and 55. However, these features do not necessarily disappear at large M{sub in}, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses. (orig.)

  7. Joint Chance-Constrained Dynamic Programming

    Science.gov (United States)

    Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J. Bob

    2012-01-01

    This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.

  8. Constraining the roughness degree of slip heterogeneity

    KAUST Repository

    Causse, Mathieu

    2010-05-07

    This article investigates different approaches for assessing the degree of roughness of the slip distribution of future earthquakes. First, we analyze a database of slip images extracted from a suite of 152 finite-source rupture models from 80 events (Mw = 4.1–8.9). This results in an empirical model defining the distribution of the slip spectrum corner wave numbers (kc) as a function of moment magnitude. To reduce the “epistemic” uncertainty, we select a single slip model per event and screen out poorly resolved models. The number of remaining models (30) is thus rather small. In addition, the robustness of the empirical model rests on a reliable estimation of kc by kinematic inversion methods. We address this issue by performing tests on synthetic data with a frequency domain inversion method. These tests reveal that due to smoothing constraints used to stabilize the inversion process, kc tends to be underestimated. We then develop an alternative approach: (1) we establish a proportionality relationship between kc and the peak ground acceleration (PGA), using a k−2 kinematic source model, and (2) we analyze the PGA distribution, which is believed to be better constrained than slip images. These two methods reveal that kc follows a lognormal distribution, with similar standard deviations for both methods.

  9. Technologies for a greenhouse-constrained society

    International Nuclear Information System (INIS)

    Kuliasha, M.A.; Zucker, A.; Ballew, K.J.

    1992-01-01

    This conference explored how three technologies might help society adjust to life in a greenhouse-constrained environment. Technology experts and policy makers from around the world met June 11--13, 1991, in Oak Ridge, Tennessee, to address questions about how energy efficiency, biomass, and nuclear technologies can mitigate the greenhouse effect and to explore energy production and use in countries in various stages of development. The conference was organized by Oak Ridge National Laboratory and sponsored by the US Department of Energy. Energy efficiency biomass, and nuclear energy are potential substitutes for fossil fuels that might help slow or even reverse the global warming changes that may result from mankind's thirst for energy. Many other conferences have questioned whether the greenhouse effect is real and what reductions in greenhouse gas emissions might be necessary to avoid serious ecological consequences; this conference studied how these reductions might actually be achieved. For these conference proceedings, individuals papers are processed separately for the Energy Data Base

  10. Constrained Supersymmetric Flipped SU(5) GUT Phenomenology

    CERN Document Server

    Ellis, John; Olive, Keith A

    2011-01-01

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, $M_{in}$, above the GUT scale, $M_{GUT}$. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino and the lighter stau is sensitive to $M_{in}$, as is the relationship between the neutralino mass and the masses of the heavier Higgs bosons. For these reasons, prominent features in generic $(m_{1/2}, m_0)$ planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to $M_{in}$, as we illustrate for several cases with tan(beta)...

  11. Constrained supersymmetric flipped SU(5) GUT phenomenology

    International Nuclear Information System (INIS)

    Ellis, John; Mustafayev, Azar; Olive, Keith A.

    2011-01-01

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, M in , above the GUT scale, M GUT . We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino χ and the lighter stau τ 1 is sensitive to M in , as is the relationship between m χ and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m 1/2 ,m 0 ) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to M in , as we illustrate for several cases with tan β=10 and 55. However, these features do not necessarily disappear at large M in , unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses. (orig.)

  12. Scheduling Aircraft Landings under Constrained Position Shifting

    Science.gov (United States)

    Balakrishnan, Hamsa; Chandran, Bala

    2006-01-01

    Optimal scheduling of airport runway operations can play an important role in improving the safety and efficiency of the National Airspace System (NAS). Methods that compute the optimal landing sequence and landing times of aircraft must accommodate practical issues that affect the implementation of the schedule. One such practical consideration, known as Constrained Position Shifting (CPS), is the restriction that each aircraft must land within a pre-specified number of positions of its place in the First-Come-First-Served (FCFS) sequence. We consider the problem of scheduling landings of aircraft in a CPS environment in order to maximize runway throughput (minimize the completion time of the landing sequence), subject to operational constraints such as FAA-specified minimum inter-arrival spacing restrictions, precedence relationships among aircraft that arise either from airline preferences or air traffic control procedures that prevent overtaking, and time windows (representing possible control actions) during which each aircraft landing can occur. We present a Dynamic Programming-based approach that scales linearly in the number of aircraft, and describe our computational experience with a prototype implementation on realistic data for Denver International Airport.

  13. Should we still believe in constrained supersymmetry?

    International Nuclear Information System (INIS)

    Balazs, Csaba; Buckley, Andy; Carter, Daniel; Farmer, Benjamin; White, Martin

    2013-01-01

    We calculate partial Bayes factors to quantify how the feasibility of the constrained minimal supersymmetric standard model (CMSSM) has changed in the light of a series of observations. This is done in the Bayesian spirit where probability reflects a degree of belief in a proposition and Bayes' theorem tells us how to update it after acquiring new information. Our experimental baseline is the approximate knowledge that was available before LEP, and our comparison model is the Standard Model with a simple dark matter candidate. To quantify the amount by which experiments have altered our relative belief in the CMSSM since the baseline data we compute the partial Bayes factors that arise from learning in sequence the LEP Higgs constraints, the XENON100 dark matter constraints, the 2011 LHC supersymmetry search results, and the early 2012 LHC Higgs search results. We find that LEP and the LHC strongly shatter our trust in the CMSSM (with M 0 and M 1/2 below 2 TeV), reducing its posterior odds by approximately two orders of magnitude. This reduction is largely due to substantial Occam factors induced by the LEP and LHC Higgs searches. (orig.)

  14. Electricity in a Climate-Constrained World

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    After experiencing a historic drop in 2009, electricity generation reached a record high in 2010, confirming the close linkage between economic growth and electricity usage. Unfortunately, CO2 emissions from electricity have also resumed their growth: Electricity remains the single-largest source of CO2 emissions from energy, with 11.7 billion tonnes of CO2 released in 2010. The imperative to 'decarbonise' electricity and improve end-use efficiency remains essential to the global fight against climate change. The IEA’s Electricity in a Climate-Constrained World provides an authoritative resource on progress to date in this area, including statistics related to CO2 and the electricity sector across ten regions of the world (supply, end-use and capacity additions). It also presents topical analyses on the challenge of rapidly curbing CO2 emissions from electricity. Looking at policy instruments, it focuses on emissions trading in China, using energy efficiency to manage electricity supply crises and combining policy instruments for effective CO2 reductions. On regulatory issues, it asks whether deregulation can deliver decarbonisation and assesses the role of state-owned enterprises in emerging economies. And from technology perspectives, it explores the rise of new end-uses, the role of electricity storage, biomass use in Brazil, and the potential of carbon capture and storage for ‘negative emissions’ electricity supply.

  15. Vertical crustal movements in Southern California, 1974 to 1978

    Science.gov (United States)

    Burford, R.O.; Gilmore, Thomas D.

    1984-01-01

    An extensive resurvey of most of the first-order leveling network in southern California, known as the Southern California Releveling Program (SCRP), was carried out during the first 5 months of 1978. The primary scientific purpose of these measurements was to rapidly update the vertical control record throughout a recently uplifted region of southern California in order to more thoroughly document the vertical component of tectonic movement and to provide a reliable base for comparison with future levelings. Analyses of historic first-order leveling results have clearly demonstrated that a broad crustal upwarping, largely contained within a region consisting of the Transverse Ranges province and an area along the intervening section of the San Andreas fault system, had developed between about 1959 and 1974. Unfortunately, there is strong evidence that parts of the 1978 SCRP data are contaminated by the effects of intrasurvey tectonic deformation, limited surficial failures, and, less certainly, magnetically induced systematic error associated with the use of automatic levels. However, any distortions in leveling results caused by these or other factors are not so serious as to render the SCRP data useless. In fact, the bulk of these data can be accepted at face value, and most of the remaining data can be incorporated with some caution to augment the more reliable parts of the network. The evaluation of the 1978 leveling is based on a combination of circuit-misclosures, local timing of the field observations, analysis of profiles of apparent height changes derived from comparisons with previous levelings, and an analysis of the position and orientation of the various routes in relation to the regional structural grain and the gradients of differential vertical motion established by previous investigations. Comparisons of the 1978 SCRP results with the latest of the previous surveys along each route retained in the analysis show that all but about one-third of the

  16. New aeromagnetic data of eastern Dronning Maud Land: implications for the spatial extent of a major Early Neoproterozoic juvenile crustal province

    Science.gov (United States)

    Ruppel, A. S.; Jacobs, J.; Eagles, G.; Läufer, A.; Jokat, W.

    2017-12-01

    A long-standing collaboration between Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the Federal Institute for Geosciences and Natural Resources (BGR) aims to investigate the sub-ice crustal architecture and tectonic evolution of East Antarctica. Its main emphasis is on Dronning Maud Land (DML). During the austral summers 2014 and 2015, ca. 40.000 line kilometre of new magnetic, gravity and ice-penetrating radar data were collected with 10 km line spacing. Here, we report on magnetic anomaly data to the east and south of Sør Rondane (eastern DML), analysed with several filtering techniques. These data are integrated with exposure information from Sør Rondane, the Belgica Mts., and the Yamato Mts.. The study area covers the eastern part of a major, recently revealed Early Neoproterozoic juvenile crustal block, the Tonian Oceanic Arc Super Terrane (TOAST). The western extent of the TOAST is well defined by the Forster Magnetic Anomaly and characterized by a province of subdued SE-striking parallel positive magnetic anomalies in the mostly ice-covered region of south-eastern DML (the SE DML province). Geological investigations showed that this area can be correlated with exposures in Sør Rondane and scattered nunataks west of it. U-Pb ages of ca. 1000-900 Ma, are documented from zircons of gabbro-trondhjemite-tonalite-granodiorite (GTTG) suites in both areas. Further, geochemical analyses prove a juvenile character of the GTTGs, which are interpreted as oceanic arc complexes. Glacial drift from southern Sør Rondane points to an inland continuation of the TOAST, so far of unknown dimensions. The new magnetic data constrain the southern and eastern minimum extent of the TOAST, which we think has a minimum area of 450.000 km2. The spatial extent of this major juvenile crustal province has major significance for the tectonic reconstruction of East Antarctica and its involvement in Rodinia since it is suggested having evolved

  17. Crustal and mantle structure and anisotropy beneath the incipient segments of the East African Rift System: Preliminary results from the ongoing SAFARI

    Science.gov (United States)

    Yu, Y.; Reed, C. A.; Gao, S. S.; Liu, K. H.; Massinque, B.; Mdala, H. S.; moidaki, M.; Mutamina, D. M.; Atekwana, E. A.; Ingate, S. F.; Reusch, A.; Barstow, N.

    2013-12-01

    Despite the vast wealth of research conducted toward understanding processes associated with continental rifting, the extent of our knowledge is derived primarily from studies focused on mature rift systems, such as the well-developed portions of the East African Rift System (EARS) north of Lake Malawi. To explore the dynamics of early rift evolution, the SAFARI (Seismic Arrays for African Rift Initiation) team deployed 50 PASSCAL broadband seismic stations across the Malawi, Luangwa, and Okavango rifts of the EARS during the summer of 2012. The cumulative length of the profiles is about 2500 km and the planned recording duration is 2 years. Here we present the preliminary results of systematic analyses of data obtained from the first year of acquisition for all 50 stations. A total of 446 high-quality shear-wave splitting measurements using PKS, SKKS, and SKS phases from 84 teleseismic events were used to constrain fast polarization directions and splitting times throughout the region. The Malawi and Okavango rifts are characterized by mostly NE trending fast directions with a mean splitting time of about 1 s. The fast directions on the west side of the Luangwa Rift Zone are parallel to the rift valley, and those on the east side are more N-S oriented. Stacking of approximately 1900 radial receiver functions reveals significant spatial variations of both crustal thickness and the ratio of crustal P and S wave velocities, as well as the thickness of the mantle transition zone. Stations situated within the Malawi rift demonstrate a southward increase in observed crustal thickness, which is consistent with the hypothesis that the Malawi rift originated at the northern end of the rift system and propagated southward. Both the Okavango and Luangwa rifts are associated with thinned crust and increased Vp/Vs, although additional data is required at some stations to enhance the reliability of the observations. Teleseismic P-wave travel-time residuals show a delay of about

  18. Crustal deformation characteristics of Sichuan-Yunnan region in China on the constraint of multi-periods of GPS velocity fields

    Science.gov (United States)

    Yue, Caiya; Dang, Yamin; Dai, Huayang; Yang, Qiang; Wang, Xiankai

    2018-04-01

    In order to obtain deformation parameters in each block of Sichuan-Yunnan Region (SYG) in China by stages and establish a dynamic model about the variation of the strain rate fields and the surface expansion in this area, we taken the Global Positioning System (GPS) sites velocity in the region as constrained condition and taken advantage of the block strain calculation model based on spherical surface. We also analyzed the deformation of the active blocks in the whole SYG before and after the Wenchuan earthquake, and analyzed the deformation of active blocks near the epicenter of the Wenchuan earthquake in detail. The results show that, (1) Under the effects of the carving from India plate and the crimping from the potential energy of Tibetan Plateau for a long time, there is a certain periodicity in crustal deformation in SYG. And the period change and the earthquake occurrence have a good agreement. (2) The differences in GPS velocity fields relative Eurasian reference frame shows that the Wenchuan earthquake and the Ya'an earthquake mainly affect the crustal movement in the central and southern part of SYG, and the average velocity difference is about 4-8 mm/a for the Wenchuan earthquake and 2-4 mm/a for the Ya'an earthquake. (3) For the Wenchuan earthquake, the average strain changed from 10 to 20 nanostrian/a before earthquake to 40-50 nanostrian/a after the earthquake, but before and after the Ya'an earthquake, the strain value increased from about 15 nanostrian/a to about 30 nanostrian/a. (4) The Wenchuan earthquake has changed the strain parameter of each active block more or less. Especially, the Longmen block and Chengdu block near the epicenter. The research provides fundamental material for the study of the dynamic mechanism of the push extrusion from the north-east of the India plate and the crimp from Qinghai Tibet Plateau, and it also provides support for the study of crustal stress variation and earthquake prediction in Sichuan Yunnan region.

  19. Bouguer gravity trends and crustal structure of the Palmyride Mountain belt and surrounding northern Arabian platform in Syria

    Science.gov (United States)

    Best, John A.; Barazangi, Muawia; Al-Saad, Damen; Sawaf, Tarif; Gebran, Ali

    1990-12-01

    This study examines the crustal structure of the Palmyrides and the northern Arabian platform in Syria by two- and three-dimensional modeling of the Bouguer gravity anomalies. Results of the gravity modeling indicate that (1) western Syria is composed of at least two different crustal blocks, (2) the southern crustal block is penetrated by a series of crustal-scale, high-density intrusive complexes, and (3) short-wavelength gravity anomalies in the southwest part of the mountain belt are clearly related to basement structure. The crustal thickness in Syria, as modeled on the gravity profiles, is approximately 40 ±4 km, which is similar to crustal thicknesses interpreted from refraction data in Jordan and Saudi Arabia. The different crustal blocks and large-scale mafic intrusions are best explained, though not uniquely, by Proterozoic convergence and suturing and early Paleozoic rifting, as interpreted in the exposed rocks of the Arabian shield. These two processes, combined with documented Mesozoic rifting and Cenozoic transpression, compose the crustal evolution of the northern Arabian platform beneath Syria.

  20. Bouguer gravity trends and crustal structure of the Palmyride Mountain belt and surrounding northern Arabian platform in Syria

    Energy Technology Data Exchange (ETDEWEB)

    Best, J.A.; Barazangi, M. (Cornell Univ., Ithaca, NY (USA)); Al-Saad, D.; Sawaf, T.; Gebran, A. (Syrian Petroleum Company, Damascus (Syria))

    1990-12-01

    This study examines the crustal structure of the Palmyrides and the northern Arabian platform in Syria by two- and three-dimensional modeling of the Bouguer gravity anomalies. Results of the gravity modeling indicate that (1) western Syria is composed of at least two different crustal blocks, (2) the southern crustal block is penetrated by a series of crustal-scale, high-density intrusive complexes, and (3) short-wavelength gravity anomalies in the southwest part of the mountain belt are clearly related to basement structure. The crustal thickness in Syria, as modeled on the gravity profiles, is approximately 40{plus minus}4 km, which is similar to crustal thicknesses interpreted from refraction data in Jordan and Saudi Arabia. The different crustal blocks and large-scale mafic intrusions are best explained, though not uniquely, by Proterozoic convergence and suturing and early Paleozoic rifting, as interpreted in the exposed rocks of the Arabian shield. These two processes, combined with documented Mesozoic rifting and Cenozoic transpression, compose the crustal evolution of the northern Arabian platform beneath Syria.

  1. Faults, fluids and friction : Effect of pressure solution and phyllosilicates on fault slip behaviour, with implications for crustal rheology

    NARCIS (Netherlands)

    Bos, B.

    2000-01-01

    In order to model the mechanics of motion and earthquake generation on large crustal fault zones, a quantitative description of the rheology of fault zones is prerequisite. In the past decades, crustal strength has been modeled using a brittle or frictional failure law to represent fault slip at

  2. Faults, fluids and friction : effect of pressure solution and phyllosilicates on fault slip behaviour, with implications for crustal rheology

    NARCIS (Netherlands)

    Bos, B.

    2000-01-01

    In order to model the mechanics of motion and earthquake generation on large crustal fault zones, a quantitative description of the rheology of fault zones is prerequisite. In the past decades, crustal strength has been modeled using a brittle or frictional failure law to represent fault slip

  3. A discretized algorithm for the solution of a constrained, continuous ...

    African Journals Online (AJOL)

    A discretized algorithm for the solution of a constrained, continuous quadratic control problem. ... The results obtained show that the Discretized constrained algorithm (DCA) is much more accurate and more efficient than some of these techniques, particularly the FSA. Journal of the Nigerian Association of Mathematical ...

  4. I/O-Efficient Construction of Constrained Delaunay Triangulations

    DEFF Research Database (Denmark)

    Agarwal, Pankaj Kumar; Arge, Lars; Yi, Ke

    2005-01-01

    In this paper, we designed and implemented an I/O-efficient algorithm for constructing constrained Delaunay triangulations. If the number of constraining segments is smaller than the memory size, our algorithm runs in expected O( N B logM/B NB ) I/Os for triangulating N points in the plane, where...

  5. Full 40 km crustal reflection seismic datasets in several Indonesian basins

    Science.gov (United States)

    Dinkelman, M. G.; Granath, J. W.; Christ, J. M.; Emmet, P. A.; Bird, D. E.

    2010-12-01

    Long offset, deep penetration regional 2D seismic data sets have been acquired since 2002 by GX Technology in a number of regions worldwide (www.iongeo.com/Data_Libraries/Spans/). Typical surveys consist of 10+ lines located to image specific critical aspects of basin structure. Early surveys were processed to 20 km, but more recent ones have extended to 40-45 km from 16 sec records. Pre-stack time migration is followed by pre-stack depth migration using gravity and in some cases magnetic modeling to constrain the velocity structure. We illustrate several cases in the SE Asian and Australasian area. In NatunaSPAN™ two generations of inversion can be distinguished, one involving Paleogene faults with Neogene inversion and one involving strike slip-related uplift in the West Natuna Basin. Crustal structure in the very deep Neogene East Natuna Basin has also been imaged. The JavaSPAN™ program traced Paleogene sediments onto oceanic crust of the Flores Sea, thus equating back arc spreading there to the widespread Eocene extension. It also imaged basement in the Makassar Strait beneath as much as 6 km of Cenozoic sedimentary rocks that accumulated Eocene rift basins (the North and South Makassar basins) on the edge of Sundaland, the core of SE Asia. The basement is seismically layered: a noisy upper crust overlies a prominent 10 km thick transparent zone, the base of which marks another change to slightly noisier reflectivity. Eocene normal faults responsible for the opening of extensional basins root in the top of the transparent layer which may be Moho or a brittle-ductile transition within the extended continental crust. Of particular significance is the first image of thick Precambrian basins comprising the bulk of continental crust under the Arafura Sea in the ArafuraSPAN™ program. Four lines some 1200 km long located between Australia and New Guinea on the Arafura platform image a thin Phanerozoic section overlying a striking Precambrian basement composed of

  6. Regional Responses to Constrained Water Availability

    Science.gov (United States)

    Cui, Y.; Calvin, K. V.; Hejazi, M. I.; Clarke, L.; Kim, S. H.; Patel, P.

    2017-12-01

    There have been many concerns about water as a constraint to agricultural production, electricity generation, and many other human activities in the coming decades. Nevertheless, how different countries/economies would respond to such constraints has not been explored. Here, we examine the responding mechanism of binding water availability constraints at the water basin level and across a wide range of socioeconomic, climate and energy technology scenarios. Specifically, we look at the change in water withdrawals between energy, land-use and other sectors within an integrated framework, by using the Global Change Assessment Model (GCAM) that also endogenizes water use and allocation decisions based on costs. We find that, when water is taken into account as part of the production decision-making, countries/basins in general fall into three different categories, depending on the change of water withdrawals and water re-allocation between sectors. First, water is not a constraining factor for most of the basins. Second, advancements in water-saving technologies of the electricity generation cooling systems are sufficient of reducing water withdrawals to meet binding water availability constraints, such as in China and the EU-15. Third, water-saving in the electricity sector alone is not sufficient and thus cannot make up the lowered water availability from the binding case; for example, many basins in Pakistan, Middle East and India have to largely reduce irrigated water withdrawals by either switching to rain-fed agriculture or reducing production. The dominant responding strategy for individual countries/basins is quite robust across the range of alternate scenarios that we test. The relative size of water withdrawals between energy and agriculture sectors is one of the most important factors that affect the dominant mechanism.

  7. Constraining Cosmic Evolution of Type Ia Supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A.C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Covarrubias, R.; Davis, T.M.; Garnavich, P.M.; Jha, S.; Kirshner, R.P.; Krisciunas, K.; Leibundgut, B.; Li, W.; Matheson, T.; Miceli, A.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A.G.; /UC, Berkeley, Astron. Dept. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Harvard-Smithsonian Ctr. Astrophys. /Chile U., Catolica /Bohr Inst. /Notre Dame U. /KIPAC, Menlo Park /Texas A-M /European Southern Observ. /NOAO, Tucson /Fermilab /Chile U., Santiago /Harvard U., Phys. Dept. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Res. Sch. Astron. Astrophys., Weston Creek /Stockholm U. /Hawaii U. /Illinois U., Urbana, Astron. Dept.

    2008-02-13

    We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 ultraviolet spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with similar slit widths, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be {approx}0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of {approx}3% in the optical and growing toward the ultraviolet. The difference between the maximum-light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.

  8. Laterally constrained inversion for CSAMT data interpretation

    Science.gov (United States)

    Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun

    2015-10-01

    Laterally constrained inversion (LCI) has been successfully applied to the inversion of dc resistivity, TEM and airborne EM data. However, it hasn't been yet applied to the interpretation of controlled-source audio-frequency magnetotelluric (CSAMT) data. In this paper, we apply the LCI method for CSAMT data inversion by preconditioning the Jacobian matrix. We apply a weighting matrix to Jacobian to balance the sensitivity of model parameters, so that the resolution with respect to different model parameters becomes more uniform. Numerical experiments confirm that this can improve the convergence of the inversion. We first invert a synthetic dataset with and without noise to investigate the effect of LCI applications to CSAMT data, for the noise free data, the results show that the LCI method can recover the true model better compared to the traditional single-station inversion; and for the noisy data, the true model is recovered even with a noise level of 8%, indicating that LCI inversions are to some extent noise insensitive. Then, we re-invert two CSAMT datasets collected respectively in a watershed and a coal mine area in Northern China and compare our results with those from previous inversions. The comparison with the previous inversion in a coal mine shows that LCI method delivers smoother layer interfaces that well correlate to seismic data, while comparison with a global searching algorithm of simulated annealing (SA) in a watershed shows that though both methods deliver very similar good results, however, LCI algorithm presented in this paper runs much faster. The inversion results for the coal mine CSAMT survey show that a conductive water-bearing zone that was not revealed by the previous inversions has been identified by the LCI. This further demonstrates that the method presented in this paper works for CSAMT data inversion.

  9. The cost-constrained traveling salesman problem

    Energy Technology Data Exchange (ETDEWEB)

    Sokkappa, P.R.

    1990-10-01

    The Cost-Constrained Traveling Salesman Problem (CCTSP) is a variant of the well-known Traveling Salesman Problem (TSP). In the TSP, the goal is to find a tour of a given set of cities such that the total cost of the tour is minimized. In the CCTSP, each city is given a value, and a fixed cost-constraint is specified. The objective is to find a subtour of the cities that achieves maximum value without exceeding the cost-constraint. Thus, unlike the TSP, the CCTSP requires both selection and sequencing. As a consequence, most results for the TSP cannot be extended to the CCTSP. We show that the CCTSP is NP-hard and that no K-approximation algorithm or fully polynomial approximation scheme exists, unless P = NP. We also show that several special cases are polynomially solvable. Algorithms for the CCTSP, which outperform previous methods, are developed in three areas: upper bounding methods, exact algorithms, and heuristics. We found that a bounding strategy based on the knapsack problem performs better, both in speed and in the quality of the bounds, than methods based on the assignment problem. Likewise, we found that a branch-and-bound approach using the knapsack bound was superior to a method based on a common branch-and-bound method for the TSP. In our study of heuristic algorithms, we found that, when selecting modes for inclusion in the subtour, it is important to consider the neighborhood'' of the nodes. A node with low value that brings the subtour near many other nodes may be more desirable than an isolated node of high value. We found two types of repetition to be desirable: repetitions based on randomization in the subtour buildings process, and repetitions encouraging the inclusion of different subsets of the nodes. By varying the number and type of repetitions, we can adjust the computation time required by our method to obtain algorithms that outperform previous methods.

  10. Crustal tomographic imaging and geodynamic implications toward south of Southern Granulite Terrain (SGT), India

    Science.gov (United States)

    Behera, Laxmidhar

    2011-09-01

    The crustal structure toward southern part of SGT is poorly defined leaving an opportunity to understand the tectonic and geodynamic evolution of this high-grade granulite terrain surrounded by major shear and tectonically disturbed zones like Achankovil Shear Zone (AKSZ) and Palghat Cauvery Shear Zone (PCSZ). To develop a geologically plausible crustal tectonic model depicting major structural elements, a comprehensive tomographic image was derived using deep-seismic-sounding data corroborated by Bouguer gravity modeling, coincident-reflection-seismic, heat-flow and available geological/geochronological informations along the N-S trending Vattalkundu-Kanyakumari geotransect. The final tectonic model represents large compositional changes of subsurface rocks accompanied by velocity heterogeneities with crustal thinning (44-36 km) and Moho upwarping from north to south. This study also reveals and successfully imaged anomalous zone of exhumation near AKSZ having transpression of exhumed rocks at mid-to-lower crustal level (20-30 km) with significant underplating and mantle upwelling forming a complex metamorphic province. The presence of shear zones with high-grade charnockite massifs in the upper-crust exposed in several places reveal large scale exhumation of granulites during the Pan-African rifting (~ 550 Ma) and provide important insights of plume-continental lithosphere interaction with reconstruction of the Gondwanaland.

  11. The Crustal Thickness of the Philippine Sea Plate Derived from Gravity Data

    Directory of Open Access Journals (Sweden)

    Horng-Yuan Yen

    2015-01-01

    Full Text Available We constructed a new free-air gravity anomaly map of the Philippine Sea Plate (PSP using ship-tracked gravity data from the National Geophysical Data Center (NGDC. Our results show that the isogals trend correlates well with the tectonic structures in the PSP. After removing the gravity induced by sea water from the free-air gravity data, we obtained the regional Bouguer gravity anomaly, which is later used to compute the Moho geometry in the PSP by applying the Parker-Oldenburg iterative method. Our results indicate that in the southern part of the West Philippine Basin (WPB the crustal thickness is nearly homogeneous with a value of about 5 km, which implies that the WPB is quite stable. The low-amplitude and near-zero free-air gravity anomalies clearly indicate that the whole WPB, except at trenches and island arcs, is nearly in a state of isostatic equilibrium. The average crustal thickness of the Palau Kyushu Ridge (PKR is more than 10 km. In the eastern PSP the crustal thickness gradually increases eastward. Our results also imply that a relatively thin and low density mantle exists beneath the Parece Vela Basin (PVB as a consequence of back-arc spreading and serpentinized upwells of the thin crustal thickness.

  12. Crustal structure under the central High Atlas Mountains (Morocco) from geological and gravity data

    Science.gov (United States)

    Ayarza, P.; Alvarez-Lobato, F.; Teixell, A.; Arboleya, M. L.; Tesón, E.; Julivert, M.; Charroud, M.

    2005-05-01

    Seismic wide angle and receiver function results together with geological data have been used as constraints to build a gravity-based crustal model of the central High Atlas of Morocco. Integration of a newly acquired set of gravity values with public data allowed us to undertake 2-2.5D gravity modelling along two profiles that cross the entire mountain chain. Modelling suggests moderate crustal thickening, and a general state of Airy isostatic undercompensation. Localized thickening appears restricted to the vicinity of a north-dipping crustal-scale thrust fault, that offsets the Moho discontinuity and defines a small crustal root which accounts for the minimum Bouguer gravity anomaly values. Gravity modelling indicates that this root has a northeasterly strike, slightly oblique to the ENE general orientation of the High Atlas belt. A consequence of the obliquity between the High Atlas borders and its internal and deep structure is the lack of correlation between Bouguer gravity anomaly values and topography. Active buckling affecting the crust, a highly elevated asthenosphere, or a combination of both are addressed as side mechanisms that help to maintain the high elevations of the Atlas mountains.

  13. Papers presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets

    Science.gov (United States)

    1985-01-01

    Several topics relative to heat and detachment in crustal extension on continents and planets are discussed. Rifting on Venus, heat flow and continental breakup, magnetism, the mountains and tectonic processes of Io, and the ductile extension of planetary lithospheres are among the topics covered.

  14. Millennia of magmatism recorded in crustal xenoliths from alkaline provinces in Southwest Greenland

    DEFF Research Database (Denmark)

    Smit, Matthijs; Waight, Tod Earle; Nielsen, Troels

    2016-01-01

    Neoproterozoic alkaline provinces in West Greenland: 1)Sarfartôq, which overlies Archean ultra-depleted SCLM and yielded ultra-deep mineral indicators, and 2)Sisimiut, where the SCLM is refertilized and deep xenoliths (>120km) are lacking. We focused on the rare and understudied crustal xenoliths, which preserve...

  15. Satellite gravity anomalies and crustal features of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, D.G.; Krishna, K.S.; Neprochnov, Y.P.; Grinko, B.N.

    -air anomalies due to volcanic constructs that trend in arcuate shape from north to south parallel to 82.5 degrees E are noted as southern continuity of the 85 degrees E Ridge, which terminates at the Afanasy Nikitin seamount. Change in rheology of the crustal...

  16. The crustal uplift determined at the Jakobshavn glacier (West Greenland) using ATM and GPS data

    DEFF Research Database (Denmark)

    Muresan, Ioana Stefania; Frumosu, Flavia Dalia; Khan, Shfaqat Abbas

    present both a predicted and observed crustal upliftfor the Jakobshavn glacier using ATM data (Airborne Topographic Mapper) from NASA ATM flights during 1997, 2005 and 2010 supplemented with data provided from continuous Global Positioning System (GPS), measurements made on bedrock between 2005...

  17. Tropics in Antarctica? Crustal Evaluation Education Project. Teacher's Guide [and] Student Investigation.

    Science.gov (United States)

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

  18. Existence of torsional surface waves in an earth's crustal layer lying ...

    Indian Academy of Sciences (India)

    This paper aims to study the dispersion of torsional surface waves in a crustal layer being sandwiched between a rigid boundary plane and a sandy mantle. In the mantle, rigidity and initial stress vary linearly while density remains constant. Dispersion relation has been deduced in a closed form by means of variable ...

  19. Magnetic crustal thickness in Greenland from CHAMP and Ørsted data

    DEFF Research Database (Denmark)

    Maule, Cathrine Fox; Purucker, Michael E.; Olsen, Nils

    2005-01-01

    and observatory data. After correcting for the remanent magnetization, we determine the vertically integrated magnetization of the crust. Making some simplifying assumptions about the susceptibility, the thickness of the magnetic crust is determined by iteratively improving an initial crustal thickness model...

  20. Drifting Continents and Wandering Poles. Crustal Evolution Education Project. Teacher's Guide [and] Student Investigation.

    Science.gov (United States)

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

  1. Drifting Continents and Magnetic Fields. Crustal Evolution Education Project. Teacher's Guide [and] Student Investigation.

    Science.gov (United States)

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

  2. Volcanoes: Where and Why? Crustal Evolution Education Project. Teacher's Guide [and] Student Investigation.

    Science.gov (United States)

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

  3. Hot Spots in the Earth's Crust. Crustal Evolution Education Project. Teacher's Guide [and] Student Investigation.

    Science.gov (United States)

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

  4. Geothermal modeling along a two-dimensional crustal profile in Southern Portugal

    Czech Academy of Sciences Publication Activity Database

    Correia, A.; Šafanda, Jan

    2002-01-01

    Roč. 34, č. 1 (2002), s. 47-61 ISSN 0264-3707. [Geothermics at the turn of the century. Evora, 03.04.2000-07.04.2000] Institutional research plan: CEZ:AV0Z3012916 Keywords : geothermal modeling * Southern Portugal * surface heat flow * crustal profile Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.058, year: 2002

  5. Global maps of the CRUST 2.0 crustal components stripped gravity disturbances

    NARCIS (Netherlands)

    Tenzer, R.; Hamayun, K.; Vajda, P.

    2009-01-01

    We use the CRUST 2.0 crustal model and the EGM08 geopotential model to compile global maps of the gravity disturbances corrected for the gravitational effects (attractions) of the topography and of the density contrasts of the oceans, sediments, ice, and the remaining crust down to the Moho

  6. Real-time and on-demand buoy observation system for tsunami and crustal displacement

    Science.gov (United States)

    Takahashi, N.; Imai, K.; Ishihara, Y.; Fukuda, T.; Ochi, H.; Suzuki, K.; Kido, M.; Ohta, Y.; Imano, M.; Hino, R.

    2017-12-01

    We develop real-time and on-demand buoy observation system for tsunami and crustal displacement. It is indispensable for observation of crustal displacement to understand changes of stress field related to future large earthquakes. The current status of the observation is carried out by using a vessel with an interval of a few times per a year. When a large earthquake occurs, however, we need dense or on-demand observation of the crustal displacement to grasp nature of the slow slip after the rupture. Therefore, we constructed buoy system with a buoy station, wire-end station, seafloor unit and acoustic transponders for crustal displacement, and we installed a pressure sensor on the seafloor unit and GNSS system on the buoy in addition to measurement of e distance between the buoy and the seafloor acoustic transponders. Tsunami is evaluated using GNSS data and pressure data sent from seafloor. Observation error of the GNSS is about 10 cm. The crustal displacement is estimated using pressure sensor for vertical and acoustic measurement for horizontal. Using current slack ratio of 1.58, the observation error for the measurement of the crustal displacement is about 10 cm. We repeated three times sea trials and confirmed the data acquisition with high data quality, mooring without dredging anchor in the strong sea current with a speed of 5.5 knots. Current issues to be resolved we face are removing noises on the acoustic data transmission, data transmission between the buoy and wire-end stations, electrical consumption on the buoy station and large observation error on the crustal displacement due to large slack ratio. We consider the change of the acoustic transmission for pressure data, replace of a GNSS data logger with large electrical consumption, and reduce of the slack ratio, and search method to reduce resistance of the buoy on the sea water. In this presentation, we introduce the current status of the technical development and tsunami waveforms recorded on our

  7. Crustal inheritance and arc magmatism: Magnetotelluric constraints from the Washington Cascades on top-down control

    Science.gov (United States)

    Bedrosian, P.; Peacock, J.; Bowles-martinez, E.; Schultz, A.; Hill, G.

    2017-12-01

    Worldwide, arc volcanism occurs along relatively narrow magmatic arcs, the locations of which are considered to mark the onset of dehydration reactions within the subducting slab. This `bottom-up' approach, in which the location of arc volcanism reflects where fluids and melt are generated, explains first-order differences in trench-to-arc distance and is consistent with known variations in the thermal structure and geometry of subducting slabs. At a finer scale, arc segmentation, magmatic gaps, and anomalous forearc and backarc magmatism are also frequently interpreted in terms of variations in slab geometry, composition, or thermal structure.The role of inherited crustal structure in controlling faulting and deformation is well documented; less well examined is the role of crustal structure in controlling magmatism. While the source distribution of melt and subduction fluids is critical to determining the location of arc magmatism, we argue that crustal structure provides `top-down' control on patterns or seismicity and deformation as well as the channeling and ascent of arc magmas. We present evidence within the Washington Cascades based upon correlation between a new three-dimensional resistivity model, potential-field data, seismicity, and Quaternary volcanism. We image a mid-Tertiary batholith, intruded within an Eocene crustal suture zone, and extending throughout much of the crustal column. This and neighboring plutons are interpreted to channel crustal fluids and melt along their margins within steeply dipping zones of marine to transitional metasedimentary rock. Mount St. Helens is interpreted to be fed by fluids and melt generated further east at greater slab depths, migrating laterally (underplating?) beneath the Spirit Lake batholith, and ascending through metasedimentary rocks within the brittle crust. At a regional scale, we argue that this concealed suture zone controls present-day deformation and seismicity as well as the distribution of forearc

  8. Estimating Crustal Properties Directly from Satellite Tracking Data by Using a Topography-based Constraint

    Science.gov (United States)

    Goossens, S. J.; Sabaka, T. J.; Genova, A.; Mazarico, E. M.; Nicholas, J. B.; Neumann, G. A.; Lemoine, F. G.

    2017-12-01

    The crust of a terrestrial planet is formed by differentiation processes in its early history, followed by magmatic evolution of the planetary surface. It is further modified through impact processes. Knowledge of the crustal structure can thus place constraints on the planet's formation and evolution. In particular, the average bulk density of the crust is a fundamental parameter in geophysical studies, such as the determination of crustal thickness, studies of the mechanisms of topography support, and the planet's thermo-chemical evolution. Yet even with in-situ samples available, the crustal density is difficult to determine unambiguously, as exemplified by the results for the Gravity and Recovery Interior Laboratory (GRAIL) mission, which found an average crustal density for the Moon that was lower than generally assumed. The GRAIL results were possible owing to the combination of its high-resolution gravity and high-resolution topography obtained by the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO), and high correlations between the two datasets. The crustal density can be determined by its contribution to the gravity field of a planet, but at long wavelengths flexure effects can dominate. On the other hand, short-wavelength gravity anomalies are difficult to measure, and either not determined well enough (other than at the Moon), or their power is suppressed by the standard `Kaula' regularization constraint applied during inversion of the gravity field from satellite tracking data. We introduce a new constraint that has infinite variance in one direction, called xa . For constraint damping factors that go to infinity, it can be shown that the solution x becomes equal to a scale factor times xa. This scale factor is completely determined by the data, and we call our constraint rank-minus-1 (RM1). If we choose xa to be topography-induced gravity, then we can estimate the average bulk crustal density directly from the data

  9. Chukchi Borderland | Crustal Complex of the Amerasia Basin, Arctic Ocean

    Science.gov (United States)

    Ilhan, I.; Coakley, B.; Houseknecht, D. W.

    2017-12-01

    In the Arctic Ocean, Chukchi Borderland separates the North Chukchi shelf and Toll deep basins to the west and Canada deep basin to the east. Existing plate reconstructions have attempted to restore this north-striking, fragments of the continental crust to all margins of the Amerasia Basin based on sparse geologic and geophysical measurements. Regional multi-channel seismic reflection and potential field geophysics, and geologic data indicate it is a high standing continental block, requiring special accommodation to create a restorable model of the formation of the Amerasia Basin. The Borderland is composed of the Chukchi Plateau, Northwind Basin, and Northwind Ridge divided by mostly north striking normal faults. These offset the basement and bound a sequence of syn-tectonic sediments. Equivalent strata are, locally, uplifted, deformed and eroded. Seaward dipping reflectors (SDRs) are observed in the juncture between the North Chukchi, Toll basins, and southern Chukchi Plateau underlying a regional angular unconformity. This reveals that this rifted margin was associated with volcanism. An inferred condensed section, which is believed to be Hauterivian-Aptian in age, synchronous with the composite pebble shale and gamma-ray zone of the Alaska North Slope forms the basal sediments in the North Chukchi Basin. Approximately 15 km of post-rift strata onlap the condensed section, SDRs and, in part, the wedge sequence on the Chukchi Plateau from west to east, thinning to the north. These post-Aptian sediments imply that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for the inferred pre-Cretaceous rifting in this region. The recognition of SDRs and Hauterivian—Aptian condensed section, and continuity of the Early—Late Cretaceous post-rift strata along the margins of the Borderland, strike variations of the normal faults, absence of observable deformation along the Northwind Escarpment substantially constrain

  10. Three-dimensional Crustal Structure beneath the Tibetan Plateau Revealed by Multi-scale Gravity Analysis

    Science.gov (United States)

    Xu, C.; Luo, Z.; Sun, R.; Li, Q.

    2017-12-01

    The Tibetan Plateau, the largest and highest plateau on Earth, was uplifted, shorten and thicken by the collision and continuous convergence of the Indian and Eurasian plates since 50 million years ago, the Eocene epoch. Fine three-dimensional crustal structure of the Tibetan Plateau is helpful in understanding the tectonic development. At present, the ordinary method used for revealing crustal structure is seismic method, which is inhibited by poor seismic station coverage, especially in the central and western plateau primarily due to the rugged terrain. Fortunately, with the implementation of satellite gravity missions, gravity field models have demonstrated unprecedented global-scale accuracy and spatial resolution, which can subsequently be employed to study the crustal structure of the entire Tibetan Plateau. This study inverts three-dimensional crustal density and Moho topography of the Tibetan Plateau from gravity data using multi-scale gravity analysis. The inverted results are in agreement with those provided by the previous works. Besides, they can reveal rich tectonic development of the Tibetan Plateau: (1) The low-density channel flow can be observed from the inverted crustal density; (2) The Moho depth in the west is deeper than that in the east, and the deepest Moho, which is approximately 77 km, is located beneath the western Qiangtang Block; (3) The Moho fold, the directions of which are in agreement with the results of surface movement velocities estimated from Global Positioning System, exists clearly on the Moho topography.This study is supported by the National Natural Science Foundation of China (Grant No. 41504015), the China Postdoctoral Science Foundation (Grant No. 2015M572146), and the Surveying and Mapping Basic Research Programme of the National Administration of Surveying, Mapping and Geoinformation (Grant No. 15-01-08).

  11. Detailed crustal structure of the North China and its implication for seismicity

    Science.gov (United States)

    Jiang, Wenliang; Wang, Xin; Tian, Tian; Zhang, Jingfa; Wang, Donglei

    2014-02-01

    Since the Mesozoic-Cenozoic era the North China Craton has experienced an important tectonic transition and it has given rise to complicated crustal structure and strong earthquake activity. Based on the large-scale surface gravity data, we studied the detailed crustal structure and seismogenic mechanism of the North China. The results indicate that the North China presents typical characteristics of adjoining depression and uplift, alternating basins and hills, inhomogeneous density and also great differences in crustal structure and Moho topography. The upper and middle crustal structures are dominated by the NNE-striking tectonic units, with many faults cut down to the middle crust. The lower crust is characterized by the folding-structure, with high and low-density placed alternately from west to east, presenting lateral heterogeneous feature. Adjusted by the gravity isostasy, Moho topography of the North China fluctuates greatly. Compared with the North China Basin, crustal thickness in the Western Taihang, northern Yanshan and Luzhong areas are much thicker while those densities are lower than the North China Basin. The dominating tectonic direction of the Moho topography strikes NE to NNE and undulates alternately from west to east. The epicenters are mostly concentrated in the upper and middle crust, especially the transitional areas between the high and low-gravity anomalies. The Tancheng earthquake in 1668, Sanhe earthquake in 1673, Tangshan earthquake in 1976, and all other seismic tectonic zones of the North China are all distributed in area where magma moves strongly beneath the crust, which is considered to be related to the movement of the high density, unstable and heat flows along the deep passage from the uppermost and asthenosphere due to the subduction of the Pacific slab towards the Eurasian plate.

  12. Strain transformation between tectonic extrusion and crustal thickening in the growth of the Tibetan Plateau

    Science.gov (United States)

    Liu, M.; Li, Y.; Sun, Y.; Shen, X.

    2017-12-01

    The Indo-Eurasian continental collision since 50 Ma has thickened the crust to raise the Himalayan-Tibetan Plateau and driven lateral extrusion of Asian lithospheric blocks to affect Cenozoic tectonics in central and east Asia. The relative roles of crustal thickening and tectonic extrusion, and the strain partitioning between them over time and space, remain controversial. We have analyzed the strain rates using GPS velocities, and correlated the results with vertical motion derived from precise leveling. We found that tectonic extrusion largely transforms to crustal thickening near the margins of the Tibetan Plateau. Near the NW margin of the Tibetan Plateau, the shear stain transforms to compressive strain, consistent with neotectonic studies that indicate crustal shortening and uplift. Around the SE margin, shear stain largely terminates in the southern Yunnan province of China. The present-day crustal motion in SE Tibetan Plateau can be well explained by gravitational spreading without invoking plate-edge push as envisioned in the tectonic extrusion model. Using data collected from local seismic arrays, we derived receiver functions to image the lithospheric structures across the Tibetan Plateau and the Alashan block to its north and the Ordos block to its east. Our results indicate that the mantle lithosphere of these bounding Asian blocks has not been reworked by Tibetan tectonics; instead they have acted as restrictive walls to the growing Tibetan Plateau. Our finite element modeling shows that crustal deformation along the margins of the Tibetan Plateau are consistent with the notion that the east- and southeastward extrusion of the Tibetan lithosphere is largely confined to the Tibetan Plateau because of the restrictive bounding blocks of the Asian lithosphere. Thus the tectonic impact of the Indo-Eurasian collision on the Cenozoic Asian tectonics may not be as extensive as previously thought.

  13. Topside ionosphere of Mars: Variability, transient layers, and the role of crustal magnetic fields

    Science.gov (United States)

    Gopika, P. G.; Venkateswara Rao, N.

    2018-04-01

    The topside ionosphere of Mars is known to show variability and transient topside layers. In this study, we analyzed the electron density profiles measured by the radio occultation technique aboard the Mars Global Surveyor spacecraft to study the topside ionosphere of Mars. The electron density profiles that we used in the present study span between 1998 and 2005. All the measurements are done from the northern high latitudes, except 220 profiles which were measured in the southern hemisphere, where strong crustal magnetic fields are present. We binned the observations into six measurement periods: 1998, 1999-north, 1999-south, 2000-2001, 2002-2003, and 2004-2005. We found that the topside ionosphere in the southern high latitudes is more variable than that from the northern hemisphere. This feature is clearly seen with fluctuations of wavelengths less than 20 km. Some of the electron density profiles show a transient topside layer with a local maximum in electron density between 160 km and 210 km. The topside layer is more prone to occur in the southern hemispheric crustal magnetic field regions than in the other regions. In addition, the peak density of the topside layer is greater in regions of strong crustal magnetic fields than in other regions. The variability of the topside ionosphere and the peak density of the topside layer, however, do not show one-to-one correlation with the strength of the crustal magnetic fields and magnetic field inclination. The results of the present study are discussed in the light of current understanding on the topside ionosphere, transient topside layers, and the role of crustal magnetic fields on plasma motions.

  14. Interaction between mantle and crustal detachments: a non-linear system controlling lithospheric extension

    Science.gov (United States)

    Rosenbaum, G.; Regenauer-Lieb, K.; Weinberg, R. F.

    2009-12-01

    We use numerical modelling to investigate the development of crustal and mantle detachment faults during lithospheric extension. Our models simulate a wide range of rift systems with varying values of crustal thickness and heat flow, showing how strain localization in the mantle interacts with localization in the upper crust and controls the evolution of extensional systems. Model results reveal a richness of structures and deformation styles, which grow in response to a self-organized mechanism that minimizes the internal stored energy of the system by localizing deformation at different levels of the lithosphere. Crustal detachment faults are well developed during extension of overthickened (60 km) continental crust, even when the initial heat flow is relatively low (50 mW/m2). In contrast, localized mantle deformation is most pronounced when the extended lithosphere has a normal crustal thickness (30-40 km) and an intermediate (60-70 mW/m2) heat flow. Results show a non-linear response to subtle changes in crustal thickness or heat flow, characterized by abrupt and sometime unexpected switches in extension modes (e.g. from diffuse rifting to effective lithospheric-scale rupturing) or from mantle- to crust-dominated strain localization. We interpret this non-linearity to result from the interference of doming wavelengths. Disharmony of crust and mantle doming wavelengths results in efficient communication between shear zones at different lithospheric levels, leading to rupturing of the whole lithosphere. In contrast, harmonious crust and mantle doming inhibits interaction of shear zones across the lithosphere and results in a prolonged rifting history prior to continental breakup.

  15. Interaction between mantle and crustal detachments: A nonlinear system controlling lithospheric extension

    Science.gov (United States)

    Rosenbaum, Gideon; Regenauer-Lieb, Klaus; Weinberg, Roberto F.

    2010-11-01

    We use numerical modeling to investigate the development of crustal and mantle detachments during lithospheric extension. Our models simulate a wide range of extensional systems with varying values of crustal thickness and heat flow, showing how strain localization in the mantle interacts with localization in the upper crust and controls the evolution of extensional systems. Model results reveal a richness of structures and deformation styles as a response to a self-organized mechanism that minimizes the internal stored energy of the system by localizing deformation. Crustal detachments, here referred as low-angle normal decoupling horizons, are well developed during extension of overthickened (60 km) continental crust, even when the initial heat flow is relatively low (50 mW m-2). In contrast, localized mantle deformation is most pronounced when the extended lithosphere has a normal crustal thickness (30-40 km) and an intermediate heat flow (60-70 mW m-2). Results show a nonlinear response to subtle changes in crustal thickness or heat flow, characterized by abrupt and sometimes unexpected switches in extension modes (e.g., from diffuse extensional deformation to effective lithospheric-scale rupturing) or from mantle- to crust-dominated strain localization. We interpret this nonlinearity to result from the interference of doming wavelengths in the presence of multiple necking instabilities. Disharmonic crust and mantle doming wavelengths results in efficient communication between shear zones at different lithospheric levels, leading to rupturing of the whole lithosphere. In contrast, harmonic crust and mantle doming inhibits interaction of shear zones across the lithosphere and results in a prolonged history of extension prior to continental breakup.

  16. KINETIC CONSEQUENCES OF CONSTRAINING RUNNING BEHAVIOR

    Directory of Open Access Journals (Sweden)

    John A. Mercer

    2005-06-01

    Full Text Available It is known that impact forces increase with running velocity as well as when stride length increases. Since stride length naturally changes with changes in submaximal running velocity, it was not clear which factor, running velocity or stride length, played a critical role in determining impact characteristics. The aim of the study was to investigate whether or not stride length influences the relationship between running velocity and impact characteristics. Eight volunteers (mass=72.4 ± 8.9 kg; height = 1.7 ± 0.1 m; age = 25 ± 3.4 years completed two running conditions: preferred stride length (PSL and stride length constrained at 2.5 m (SL2.5. During each condition, participants ran at a variety of speeds with the intent that the range of speeds would be similar between conditions. During PSL, participants were given no instructions regarding stride length. During SL2.5, participants were required to strike targets placed on the floor that resulted in a stride length of 2.5 m. Ground reaction forces were recorded (1080 Hz as well as leg and head accelerations (uni-axial accelerometers. Impact force and impact attenuation (calculated as the ratio of head and leg impact accelerations were recorded for each running trial. Scatter plots were generated plotting each parameter against running velocity. Lines of best fit were calculated with the slopes recorded for analysis. The slopes were compared between conditions using paired t-tests. Data from two subjects were dropped from analysis since the velocity ranges were not similar between conditions resulting in the analysis of six subjects. The slope of impact force vs. velocity relationship was different between conditions (PSL: 0.178 ± 0.16 BW/m·s-1; SL2.5: -0.003 ± 0.14 BW/m·s-1; p < 0.05. The slope of the impact attenuation vs. velocity relationship was different between conditions (PSL: 5.12 ± 2.88 %/m·s-1; SL2.5: 1.39 ± 1.51 %/m·s-1; p < 0.05. Stride length was an important factor

  17. Implications for the crustal Architecture in West Antarctica revealed by the means of depth-to-the-bottom of the magnetic source (DBMS) mapping and 3D FEM geothermal heat flux models

    Science.gov (United States)

    Dziadek, Ricarda; Gohl, Karsten; Kaul, Norbert

    2017-04-01

    The West Antarctic Rift System (WARS) is one of the largest rift systems in the world, which displays unique coupled relationships between tectonic processes and ice sheet dynamics. Palaeo-ice streams have eroded troughs across the Amundsen Sea Embayment (ASE) that today route warm ocean deep water to the West Antarctic Ice Sheet (WAIS) grounding zone and reinforce dynamic ice sheet thinning. Rift basins, which cut across West Antarctica's landward-sloping shelves, promote ice sheet instability. Young, continental rift systems are regions with significantly elevated geothermal heat flux (GHF), because the transient thermal perturbation to the lithosphere caused by rifting requires 100 m.y. to reach long-term thermal equilibrium. The GHF in this region is, especially on small scales, poorly constrained and suspected to be heterogeneous as a reflection of the distribution of tectonic and volcanic activity along the complex branching geometry of the WARS, which reflects its multi-stage history and structural inheritance. We investigate the crustal architecture and the possible effects of rifting history from the WARS on the ASE ice sheet dynamics, by the use of depth-to-the-bottom of the magnetic source (DBMS) estimates. These are based on airborne-magnetic anomaly data and provide an additional insight into the deeper crustal properties. With the DBMS estimates we reveal spatial changes at the bottom of the igneous crust and the thickness of the magnetic layer, which can be further incorporated into tectonic interpretations. The DBMS also marks an important temperature transition zone of approximately 580°C and therefore serves as a boundary condition for our numerical FEM models in 2D and 3D. On balance, and by comparison to global values, we find average GHF of 90 mWm-2 with spatial variations due to crustal heterogeneities and volcanic activities. This estimate is 30% more than commonly used in ice sheet models in the ASE region.

  18. Using 81Kr-age of groundwater in the Guarani Aquifer, Brazil, to constrain estimates of continental degassing flux of 4He

    Science.gov (United States)

    Aggarwal, P. K.; Matsumoto, T.; Sturchio, N. C.; Chang, H. K.; Gastmans, D.; Lu, Z.; Jiang, W.; Müller, P.; Yokochi, R.; Han, L.; Klaus, P.; Torgersen, T.

    2013-12-01

    Continental degassing flux of helium is the dominant component of dissolved helium in deep groundwater together with that produced in-situ in the aquifer. A reliable estimate of the degassing flux is critical to the use of 4He as a dating tool in groundwater studies. The degassing flux is also important for understanding fluid and heat transport in the mantle and the rust. An independent tracer of groundwater age is required in order to deconvolute the two signals of the external, degassing flux and in situ production. Estimates of degassing flux mostly have relied upon shorter-lived radionuclides such as 14C and tritium and the resulting flux estimates have a significant variability (Torgersen, 2010). In the Guarani Aquifer in Brazil, an effective crustal 4He degassing flux into the aquifer was estimated from 81Kr ages ranging from about 70 Ka to 570 Ka. We then used the model framework of Toregesen and Ivey (1985), modified to include a diffusive reduction of originally uniform crustal helium flux from basement rocks through a thick sedimentary layer beneath the aquifer, to calculate a distribution of radiogenic 4He within the aquifer. With this framework, we obtain 4He ages that are consistent with ages based on 81Kr and 14C, and with a crustal degassing flux equivalent to that estimated from U and Th contents in the crust. The model framework for the Guarani Aquifer is also applied to data from other deep aquifers in Africa and Australia and our results suggest that the continental flux of 4He may be uniform, at least in stable continental areas. Additionally, a reliable estimate of the 4He degassing flux also helps to constrain the surficial discharge of deep groundwater.

  19. Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation

    Science.gov (United States)

    Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito

    2014-02-01

    A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.

  20. Evaluation of six NEHRP B/C crustal amplification models proposed for use in western North America

    Science.gov (United States)

    Boore, David; Campbell, Kenneth W.

    2016-01-01

    We evaluate six crustal amplification models based on National Earthquake Hazards Reduction Program (NEHRP) B/C crustal profiles proposed for use in western North America (WNA) and often used in other active crustal regions where crustal properties are unknown. One of the models is based on an interpolation of generic rock velocity profiles previously proposed for WNA and central and eastern North America (CENA), in conjunction with material densities based on an updated velocity–density relationship. A second model is based on the velocity profile used to develop amplification factors for the Next Generation Attenuation (NGA)‐West2 project. A third model is based on a near‐surface velocity profile developed from the NGA‐West2 site database. A fourth model is based on velocity and density profiles originally proposed for use in CENA but recently used to represent crustal properties in California. We propose two alternatives to this latter model that more closely represent WNA crustal properties. We adopt a value of site attenuation (κ0) for each model that is either recommended by the author of the model or proposed by us. Stochastic simulation is used to evaluate the Fourier amplification factors and their impact on response spectra associated with each model. Based on this evaluation, we conclude that among the available models evaluated in this study the NEHRP B/C amplification model of Boore (2016) best represents median crustal amplification in WNA, although the amplification models based on the crustal profiles of Kamai et al. (2013, 2016, unpublished manuscript, see Data and Resources) and Yenier and Atkinson (2015), the latter adjusted to WNA crustal properties, can be used to represent epistemic uncertainty.

  1. Carbon-constrained scenarios. Final report

    International Nuclear Information System (INIS)

    2009-05-01

    This report provides the results of the study entitled 'Carbon-Constrained Scenarios' that was funded by FONDDRI from 2004 to 2008. The study was achieved in four steps: (i) Investigating the stakes of a strong carbon constraint for the industries participating in the study, not only looking at the internal decarbonization potential of each industry but also exploring the potential shifts of the demand for industrial products. (ii) Developing an hybrid modelling platform based on a tight dialog between the sectoral energy model POLES and the macro-economic model IMACLIM-R, in order to achieve a consistent assessment of the consequences of an economy-wide carbon constraint on energy-intensive industrial sectors, while taking into account technical constraints, barriers to the deployment of new technologies and general economic equilibrium effects. (iii) Producing several scenarios up to 2050 with different sets of hypotheses concerning the driving factors for emissions - in particular the development styles. (iv) Establishing an iterative dialog between researchers and industry representatives on the results of the scenarios so as to improve them, but also to facilitate the understanding and the appropriate use of these results by the industrial partners. This report provides the results of the different scenarios computed in the course of the project. It is a partial synthesis of the work that has been accomplished and of the numerous exchanges that this study has induced between modellers and stakeholders. The first part was written in April 2007 and describes the first reference scenario and the first mitigation scenario designed to achieve stabilization at 450 ppm CO 2 at the end of the 21. century. This scenario has been called 'mimetic' because it has been build on the assumption that the ambitious climate policy would coexist with a progressive convergence of development paths toward the current paradigm of industrialized countries: urban sprawl, general

  2. Sensitivity analysis of crustal correction and its error propagation to upper mantle residual gravity and density anomalies

    DEFF Research Database (Denmark)

    Herceg, Matija; Artemieva, Irina; Thybo, Hans

    2013-01-01

    ) uncertainties in the velocity-density conversion and (ii) uncertainties in knowledge of the crustal structure (thickness and average Vp velocities of individual crustal layers, including the sedimentary cover). In this study, we address both sources of possible uncertainties by applying different conversions...... from velocity to density and by introducing variations into the crustal structure which corresponds to the uncertainty of its resolution by high-quality and low-quality seismic models. We examine the propagation of these uncertainties into determinations of lithospheric mantle density. The residual...

  3. A preliminary investigation of vertical crustal movements in the United Kingdom in the context of subsurface nuclear waste isolation

    International Nuclear Information System (INIS)

    1981-03-01

    Two types of change will influence the environment of a subsurface nuclear waste isolation facility: natural geological changes and changes caused by the construction of the waste repository and introduction of the waste. This report is concerned with vertical crustal movements, which are an expression of natural geological changes. Vertical crustal movements observed outside the United Kingdom are reviewed, and vertical movements in a test region of the UK investigated by comparison of geodetic levellings. The implications of vertical crustal movement to waste isolation facilities and some potentially valuable lines of research are discussed. (author)

  4. FXR agonist activity of conformationally constrained analogs of GW 4064.

    Science.gov (United States)

    Akwabi-Ameyaw, Adwoa; Bass, Jonathan Y; Caldwell, Richard D; Caravella, Justin A; Chen, Lihong; Creech, Katrina L; Deaton, David N; Madauss, Kevin P; Marr, Harry B; McFadyen, Robert B; Miller, Aaron B; Navas, Frank; Parks, Derek J; Spearing, Paul K; Todd, Dan; Williams, Shawn P; Bruce Wisely, G

    2009-08-15

    Two series of conformationally constrained analogs of the FXR agonist GW 4064 1 were prepared. Replacement of the metabolically labile stilbene with either benzothiophene or naphthalene rings led to the identification of potent full agonists 2a and 2g.

  5. Automated Precision Maneuvering and Landing in Extreme and Constrained Environments

    Data.gov (United States)

    National Aeronautics and Space Administration — Autonomous, precise maneuvering and landing in extreme and constrained environments is a key enabler for future NASA missions. Missions to map the interior of a...

  6. Security constrained optimal power flow by modern optimization tools

    African Journals Online (AJOL)

    Security constrained optimal power flow by modern optimization tools. ... International Journal of Engineering, Science and Technology ... If you would like more information about how to print, save, and work with PDFs, Highwire Press ...

  7. Affine Lie algebraic origin of constrained KP hierarchies

    International Nuclear Information System (INIS)

    Aratyn, H.; Gomes, J.F.; Zimerman, A.H.

    1994-07-01

    It is presented an affine sl(n+1) algebraic construction of the basic constrained KP hierarchy. This hierarchy is analyzed using two approaches, namely linear matrix eigenvalue problem on hermitian symmetric space and constrained KP Lax formulation and we show that these approaches are equivalent. The model is recognized to be generalized non-linear Schroedinger (GNLS) hierarchy and it is used as a building block for a new class of constrained KP hierarchies. These constrained KP hierarchies are connected via similarity-Backlund transformations and interpolate between GNLS and multi-boson KP-Toda hierarchies. The construction uncovers origin of the Toda lattice structure behind the latter hierarchy. (author). 23 refs

  8. Slow logarithmic relaxation in models with hierarchically constrained dynamics

    OpenAIRE

    Brey, J. J.; Prados, A.

    2000-01-01

    A general kind of models with hierarchically constrained dynamics is shown to exhibit logarithmic anomalous relaxation, similarly to a variety of complex strongly interacting materials. The logarithmic behavior describes most of the decay of the response function.

  9. Synthesis of conformationally constrained peptidomimetics using multicomponent reactions

    NARCIS (Netherlands)

    Scheffelaar, R.; Klein Nijenhuis, R.A.; Paravidino, M.; Lutz, M.; Spek, A.L.; Ehlers, A.W.; de Kanter, F.J.J.; Groen, M.B.; Orru, R.V.A.; Ruijter, E.

    2009-01-01

    A novel modular synthetic approach toward constrained peptidomimetics is reported. The approach involves a highly efficient three-step sequence including two multicomponent reactions, thus allowing unprecedented diversification of both the peptide moieties and the turn-inducing scaffold. The

  10. Filter Pattern Search Algorithms for Mixed Variable Constrained Optimization Problems

    National Research Council Canada - National Science Library

    Abramson, Mark A; Audet, Charles; Dennis, Jr, J. E

    2004-01-01

    .... This class combines and extends the Audet-Dennis Generalized Pattern Search (GPS) algorithms for bound constrained mixed variable optimization, and their GPS-filter algorithms for general nonlinear constraints...

  11. Capacity Constrained Routing Algorithms for Evacuation Route Planning

    National Research Council Canada - National Science Library

    Lu, Qingsong; George, Betsy; Shekhar, Shashi

    2006-01-01

    .... In this paper, we propose a new approach, namely a capacity constrained routing planner which models capacity as a time series and generalizes shortest path algorithms to incorporate capacity constraints...

  12. Lithospheric rheology constrained from twenty-five years of postseismic deformation following the 1989 Mw 6.9 Loma Prieta earthquake

    Science.gov (United States)

    Huang, Mong-Han; Burgmann, Roland; Pollitz, Fred

    2016-01-01

    The October 17, 1989 Mw 6.9 Loma Prieta earthquake provides the first opportunity of probing the crustal and upper mantle rheology in the San Francisco Bay Area since the 1906 Mw 7.9 San Francisco earthquake. Here we use geodetic observations including GPS and InSAR to characterize the Loma Prieta earthquake postseismic displacements from 1989 to 2013. Pre-earthquake deformation rates are constrained by nearly 20 yr of USGS trilateration measurements and removed from the postseismic measurements prior to the analysis. We observe GPS horizontal displacements at mean rates of 1–4 mm/yr toward Loma Prieta Mountain until 2000, and ∼2 mm/yr surface subsidence of the northern Santa Cruz Mountains between 1992 and 2002 shown by InSAR, which is not associated with the seasonal and longer-term hydrological deformation in the adjoining Santa Clara Valley. Previous work indicates afterslip dominated in the early (1989–1994) postseismic period, so we focus on modeling the postseismic viscoelastic relaxation constrained by the geodetic observations after 1994. The best fitting model shows an elastic 19-km-thick upper crust above an 11-km-thick viscoelastic lower crust with viscosity of ∼6 × 1018 Pas, underlain by a viscous upper mantle with viscosity between 3 × 1018 and 2 × 1019 Pas. The millimeter-scale postseismic deformation does not resolve the viscosity in the different layers very well, and the lower-crustal relaxation may be localized in a narrow shear zone. However, the inferred lithospheric rheology is consistent with previous estimates based on post-1906 San Francisco earthquake measurements along the San Andreas fault system. The viscoelastic relaxation may also contribute to the enduring increase of aseismic slip and repeating earthquake activity on the San Andreas fault near San Juan Bautista, which continued for at least a decade after the Loma Prieta event.

  13. Constrained multi-degree reduction with respect to Jacobi norms

    KAUST Repository

    Ait-Haddou, Rachid; Barton, Michael

    2015-01-01

    We show that a weighted least squares approximation of Bézier coefficients with factored Hahn weights provides the best constrained polynomial degree reduction with respect to the Jacobi L2L2-norm. This result affords generalizations to many previous findings in the field of polynomial degree reduction. A solution method to the constrained multi-degree reduction with respect to the Jacobi L2L2-norm is presented.

  14. Clustering Using Boosted Constrained k-Means Algorithm

    Directory of Open Access Journals (Sweden)

    Masayuki Okabe

    2018-03-01

    Full Text Available This article proposes a constrained clustering algorithm with competitive performance and less computation time to the state-of-the-art methods, which consists of a constrained k-means algorithm enhanced by the boosting principle. Constrained k-means clustering using constraints as background knowledge, although easy to implement and quick, has insufficient performance compared with metric learning-based methods. Since it simply adds a function into the data assignment process of the k-means algorithm to check for constraint violations, it often exploits only a small number of constraints. Metric learning-based methods, which exploit constraints to create a new metric for data similarity, have shown promising results although the methods proposed so far are often slow depending on the amount of data or number of feature dimensions. We present a method that exploits the advantages of the constrained k-means and metric learning approaches. It incorporates a mechanism for accepting constraint priorities and a metric learning framework based on the boosting principle into a constrained k-means algorithm. In the framework, a metric is learned in the form of a kernel matrix that integrates weak cluster hypotheses produced by the constrained k-means algorithm, which works as a weak learner under the boosting principle. Experimental results for 12 data sets from 3 data sources demonstrated that our method has performance competitive to those of state-of-the-art constrained clustering methods for most data sets and that it takes much less computation time. Experimental evaluation demonstrated the effectiveness of controlling the constraint priorities by using the boosting principle and that our constrained k-means algorithm functions correctly as a weak learner of boosting.

  15. New Exact Penalty Functions for Nonlinear Constrained Optimization Problems

    Directory of Open Access Journals (Sweden)

    Bingzhuang Liu

    2014-01-01

    Full Text Available For two kinds of nonlinear constrained optimization problems, we propose two simple penalty functions, respectively, by augmenting the dimension of the primal problem with a variable that controls the weight of the penalty terms. Both of the penalty functions enjoy improved smoothness. Under mild conditions, it can be proved that our penalty functions are both exact in the sense that local minimizers of the associated penalty problem are precisely the local minimizers of the original constrained problem.

  16. Constrained multi-degree reduction with respect to Jacobi norms

    KAUST Repository

    Ait-Haddou, Rachid

    2015-12-31

    We show that a weighted least squares approximation of Bézier coefficients with factored Hahn weights provides the best constrained polynomial degree reduction with respect to the Jacobi L2L2-norm. This result affords generalizations to many previous findings in the field of polynomial degree reduction. A solution method to the constrained multi-degree reduction with respect to the Jacobi L2L2-norm is presented.

  17. Crustal structure, and topographic relief in the high southern Scandes, Norway

    Science.gov (United States)

    Stratford, W.; Thybo, H.; Frassetto, A.

    2010-05-01

    Resolving the uplift history of southern Norway is hindered by the lack of constraint available from the geologic record. Sediments that often contain information of burial and uplift history have long since been stripped from the onshore regions in southern Norway, and geophysical, dating methods and geomorphological studies are the remaining means of unraveling uplift history. New constraints on topographic evolution and uplift in southern Norway have been added by a recent crustal scale refraction project. Magnus-Rex (Mantle investigation of Norwegian uplift Structure, refraction experiment) recorded three ~400 km long active source seismic profiles across the high southern Scandes Mountains. The goal of the project is to determine crustal thickness and establish whether these mountains are supported at depth by a crustal root or by other processes. The southern Scandes Mountains were formed during the Caledonian Orogeny around 440 Ma. These mountains, which reach elevations of up to ~2.5 km, are comprised of one or more palaeic (denudation) surfaces of rolling relief that are incised by fluvial and glacial erosion. Extreme vertical glacial incision of up to 1000 m cuts into the surfaces in the western fjords, while the valleys of eastern Norway are more fluvial in character. Climatic controls on topography here are the Neogene - Recent effects of rebound due to removal of the Fennoscandian ice sheet and isostatic rebound due to incisional erosion. However, unknown tectonic uplift mechanisms may also be in effect, and separating the tectonic and climate-based vertical motions is often difficult. Sediment and rock has been removed by the formation of the palaeic surfaces and uplift measurements cannot be directly related to present elevations. Estimates so far have indicated that rebound due to incisional erosion has a small effect of ~500 m on surface elevation. Results from Magnus-Rex indicate the crust beneath the high mountains is up to 40 km thick. This

  18. Yellowstone-Snake River Plain seismic profilling experiment: Crustal structure of the eastern Snake River Plain

    International Nuclear Information System (INIS)

    Braile, L.W.; Smith, R.B.; Ansorge, J.; Baker, M.R.; Sparlin, M.A.; Prodehl, C.; Schilly, M.M.; Healy, J.H.; Mueller, S.; Olsen, K.H.

    1982-01-01

    Seismic refraction profiles recorded along the eastern Snake River Plain (ESRP) in southeastern Idaho during the 1978 Yellowstone-Snake River Plain cooperative seismic profiling experiment are interpreted to infer the crustal velocity and attenuation (Q-1) structure of the ESRP. Travel-time and synthetic seismogram modeling of a 250 km reversed refraction profile as well as a 100 km detailed profile indicate that the crust of the ESRP is highly anomalous. Approximately 3 to 6 km of volcanic rocks (with some interbedded sediments) overlie an upper-crustal layer (compressional velocity approx. =6.1 km/s) which thins southwestward along the ESRP from a thickness of 10 km near Island Park Caldera to 2 to 3 km beneath the central and southwestern portions of the ESRP. An intermediate-velocity (approx. =6.5 km/s) layer extends from approx. =10 to approx. =20 km depth. a thick (approx. =22 km) lower crust of compressional velocity 6.8 km/s, a total crustall thickness of approx. =42 km, and a P/sub n/ velocity of approx. =7.9 km/s is observed in the ESRP, similar to the western Snake River Plain and the Rocky Mountains Provinces. High attenuation is evident on the amplitude corrected seismic data due to low-Q values in the volcanic rocks (Q/sub p/ = 20 to 200) and throughout the crust (Q/sub p/ = 160 to 300). Based on these characteristics of the crustal structure and volcanic-age progression data, it is suggested that the ESRP has resulted from an intensitive period of intrusion of mantle-derived basaltic magma into the upper crust generating explosive silicic volcanism and associated regional uplift and caldera collapse. This activity began about 15 m.y. ago in southwestern Idaho and has migrated northeast to its present position at Yellowstone. Subsequent cooling of the intruded upper crust results in the 6.5 km/s velocity intermediate layer. Crustal subsidence and periodic basaltic volcanism as represented by the ESRP complete the sequence of crustal evolution

  19. Crustal evolution of South American Platform based on Sm-Nd isotope geochemistry

    International Nuclear Information System (INIS)

    Sato, Kei

    1998-01-01

    Sm-Nd isotopic systematics is relevant to the topics of origin and evolution the of continental crust, where model ages refer to the time when crustal material was differentiated from the upper mantle. Alternative interpretations are due to a lack of adequate information on crustal processes and the variable composition of the mantle sources. The Sm-Nd methods are presented, and applied on rock materials from the South American Platform. The main conclusions indicate juvenile accretion with higher growth rates (peaks), around 3.7-3.5 Ga (∼ 0.5% in volume), 3.1 - 2.9 Ga (∼16%), 2.7 - 2.6 (∼ 9%), 2.2 - 1.9 (35%) and 1.3-1.0 (7%). The continental growth curve indicates that about 35 % of the crust was formed by 2.5 Ga, 88% by 1.8 Ga and 99% by 1.0 Ga, and the remaining ∼ 1 % was added in the Phanerozoic. Rapid crustal growth occurred between 2.2 and 1.9 Ga. The main period of continental crust formation occurred during the Paleoproterozoic, corresponding to 54 % in volume. Sm-Nd model ages, when compared with the crystallisation ages of granitoid rocks, furnish a rough estimate of juvenile vs. reworked material. Within the South American Platform about 45% of juvenile continental crust is still preserved within tectonic provinces of different ages. The remainder represents continental crust reworked in younger tectono-thermal events. In particular crustal reworking was predominating over juvenile accretion during Meso-Neoproterozoic. The Transbrasiliano Lineament is a megasuture, active in the Neoproterozoic, which separates a large northwestern mass, including the Amazonian and Sao Luis Cratons, from a southeastern mass, formed by a collage of cratonic fragments, of which the Sao Francisco and Rio de La Plata are the largest. The crustal evolutions of these two large continental masses are considered individually, and can be resumed following form: I - Old Archean rocks (>3.4 Ga) are found only within the south-eastern part (Gaviao Block, Contendas

  20. TopoGreenland: crustal structure in central-eastern Greenland along a new refraction profile

    Science.gov (United States)

    Shulgin, Alexey; Thybo, Hans; Field Team TopoGreenland

    2013-04-01

    We present the seismic structure in the interior of Greenland based on the first measurements by the seismic refraction/wide angle reflection method. Previous seismic surveys have only been carried out offshore and near the coast of Greenland, where the crustal structure is affected by oceanic break-up and may not be representative of the interior of the island. Acquisition of geophysical data in onshore Greenland is logistically complicated by the presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The EW-trending profile extends 310 km inland from the approximate edge of the stable ice cap near Scoresby Sund across the center of the ice cap. The planned extension of the profile by use of OBSs and air gun shooting in Scoresbysund Fjord to the east coast of Greenland was unfortunately canceled, because navigation was prevented by ice drift. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about 125 kg at 35-85 m depth in individual boreholes. Two-dimensional velocity model based on tomographic inversion and forward ray tracing modeling shows a decrease of crustal thickness from 47 km below the center of Greenland in the western part to 40 km in the eastern part of the profile. Earlier studies show that crustal thickness further decreases eastward to ca. 30 km below the fjord system, but details of the changes are unknown. Relatively high lower crustal velocities (Vp 6.8 - 7.3) in the western part of the TopoGreenland profile may indicate past collision tectonics or may be related or to the passage of the Iceland mantle plume. The origin of the pronounced circum-Atlantic mountain ranges in Norway and eastern Greenland

  1. Crustal evolution derived from the Izu-Bonin-Mariana arc velocity images

    Science.gov (United States)

    Takahashi, N.; Kodaira, S.; Tatsumi, Y.; Miura, S.; Sato, T.; Yamashita, M.; No, T.; Takahashi, T.; Noguchi, N.; Takizawa, K.; Kaiho, Y.; Kaneda, Y.

    2010-12-01

    The Izu-Bonin-Mariana arc is known as one of typical oceanic island arcs, which has developed by subduction between oceanic crusts producing continental materials. Japan Agency for Marine-Earth Science and Technology has carried out seismic surveys using a multi-channel reflection survey system (MCS) and ocean bottom seismographs (OBSs) in the Izu-Bonin-Mariana (IBM) arc since 2002, and reported these crustal images. As the results, we identified the structural characteristics of whole Izu-Bonin-Mariana arc. Rough structural characteristics are, 1) middle crust with Vp of 6 km/s, 2) upper part of the lower crust with Vp of 6.5-6.8 km/s, 3) lower part of the lower crust with Vp of 6.8-7.5 km/s, and 4) lower mantle velocity beneath the arc crusts. In addition, structural variation along the volcanic front, for example, thickness variation of andesitic layers was imaged and the distributions is consistent with those of rhyolite volcanoes, that is, it suggested that the cause the structural variation is various degree of crustal growth (Kodaira et al., 2007). Moreover, crustal thinning with high velocity lower crust across arc was also imaged, and it is interpreted that such crust has been influenced backarc opening (Takahashi et al., 2009). According to Tatsumi et al. (2008), andesitic middle crust is produced by differentiation of basaltic lower crust and a part of the restites are transformed to the upper mantle. This means that region showing much crustal differentiation has large volume of transformation of dense crustal materials to the mantle. We calculated volume profiles of the lower crust along all seismic lines based on the petrologic model, and compared them with observed real volumes obtained by seismic images. If the real volume of the lower crust is large, it means that the underplating of dense materials to the crustal bottom is dominant rather than transformation of dense materials to the upper mantle. According to obtained profiles to judge if the

  2. Dissolution-precipitation creep at mid-crustal levels of the Scandian Caledonides: the COSC-1 case study

    Science.gov (United States)

    Giuntoli, Francesco; Menegon, Luca; Warren, Clare

    2017-04-01

    The thermo-mechanical properties of the middle and lower crust exert a fundamental control on the structure of orogenic belts, and on the amount and style of shortening during continental collision. By virtue of the deep erosional level, the internal parts of the Scandinavian Caledonides expose middle and lower crustal sections involved in subduction-exhumation history and nappe stacking. In this study we analysed the development of a mylonitic microstructure and the associated deformation mechanisms in amphibolites from the middle portion (1.5-2.2 km of depth) of the COSC-1 drill core, central Sweden. Mylonitic amphibolites are common in the drill core. They are composed of hornblende, plagioclase, chlorite, quartz, epidote, carbonate and ilmenite. The plagioclase displays two generations: (1) fractured millimetric porphyroclast cores (Plag1; Ab 99), which are wrapped by the foliation and are dark in the SEM-cathodoluminescence images, and (2) rims (Plag2; Ab 80-90), some tens of microns in size, are bright in the cathodoluminescence images, heal the fractures and overgrow the cores of Plag1. Plag2 grows syn-deformationally, as it is commonly found in strain shadows around Plag1 porphyroclasts. The hornblende preserves corroded cores (Amp1) with higher Mg number compared to the rims (Amp2). The Amp2 is lengthened as the foliation and shows intergrowths with Plag2 and chlorite in strain shadows. Amphibole crystals are commonly boudinaged parallel to the foliation, with chlorite filling the boudin necks. Preliminary pressure and temperature estimates, using Amp2 and Plag2 pairs, constrain their growth at 600°C and 1GPa. EBSD analysis indicates a homogeneous orientation of the porphyroclastic Plag1 without the development of low-angle boundaries, suggesting that Plag1 crystals are strain free. Furthermore, the fractures are sealed by the Plag2 with the same crystallographic orientation as the plagioclase core. The Plag2 grains have their [100] axes oriented

  3. Lower-crustal xenoliths from Jurassic kimberlite diatremes, upper Michigan (USA): Evidence for Proterozoic orogenesis and plume magmatism in the lower crust of the southern Superior Province

    Science.gov (United States)

    Zartman, Robert E.; Kempton, Pamela D.; Paces, James B.; Downes, Hilary; Williams, Ian S.; Dobosi, Gábor; Futa, Kiyoto

    2013-01-01

    Jurassic kimberlites in the southern Superior Province in northern Michigan contain a variety of possible lower-crustal xenoliths, including mafic garnet granulites, rare garnet-free granulites, amphibolites and eclogites. Whole-rock major-element data for the granulites suggest affinities with tholeiitic basalts. P–T estimates for granulites indicate peak temperatures of 690–730°C and pressures of 9–12 kbar, consistent with seismic estimates of crustal thickness in the region. The granulites can be divided into two groups based on trace-element characteristics. Group 1 granulites have trace-element signatures similar to average Archean lower crust; they are light rare earth element (LREE)-enriched, with high La/Nb ratios and positive Pb anomalies. Most plot to the left of the geochron on a 206Pb/€204Pb vs 207Pb/€204Pb diagram, and there was probably widespread incorporation of Proterozoic to Archean components into the magmatic protoliths of these rocks. Although the age of the Group 1 granulites is not well constrained, their protoliths appear to be have been emplaced during the Mesoproterozoic and to be older than those for Group 2 granulites. Group 2 granulites are also LREE-enriched, but have strong positive Nb and Ta anomalies and low La/Nb ratios, suggesting intraplate magmatic affinities. They have trace-element characteristics similar to those of some Mid-Continent Rift (Keweenawan) basalts. They yield a Sm–Nd whole-rock errorchron age of 1046 ± 140 Ma, similar to that of Mid-Continent Rift plume magmatism. These granulites have unusually radiogenic Pb isotope compositions that plot above the 207Pb/€204Pb vs 206Pb/€204Pb growth curve and to the right of the 4·55 Ga geochron, and closely resemble the Pb isotope array defined by Mid-Continent Rift basalts. These Pb isotope data indicate that ancient continental lower crust is not uniformly depleted in U (and Th) relative to Pb. One granulite xenolith, S69-5, contains quartz, and has a

  4. Free and constrained symplectic integrators for numerical general relativity

    International Nuclear Information System (INIS)

    Richter, Ronny; Lubich, Christian

    2008-01-01

    We consider symplectic time integrators in numerical general relativity and discuss both free and constrained evolution schemes. For free evolution of ADM-like equations we propose the use of the Stoermer-Verlet method, a standard symplectic integrator which here is explicit in the computationally expensive curvature terms. For the constrained evolution we give a formulation of the evolution equations that enforces the momentum constraints in a holonomically constrained Hamiltonian system and turns the Hamilton constraint function from a weak to a strong invariant of the system. This formulation permits the use of the constraint-preserving symplectic RATTLE integrator, a constrained version of the Stoermer-Verlet method. The behavior of the methods is illustrated on two effectively (1+1)-dimensional versions of Einstein's equations, which allow us to investigate a perturbed Minkowski problem and the Schwarzschild spacetime. We compare symplectic and non-symplectic integrators for free evolution, showing very different numerical behavior for nearly-conserved quantities in the perturbed Minkowski problem. Further we compare free and constrained evolution, demonstrating in our examples that enforcing the momentum constraints can turn an unstable free evolution into a stable constrained evolution. This is demonstrated in the stabilization of a perturbed Minkowski problem with Dirac gauge, and in the suppression of the propagation of boundary instabilities into the interior of the domain in Schwarzschild spacetime

  5. Implications for Crustal Structures and Heat Fluxes from Depth-to-the-Bottom of the Magnetic Source Estimates in West Antarctica, Amundsen Sea Sector

    Science.gov (United States)

    Dziadek, R.; Ferraccioli, F.; Gohl, K.; Spiegel, C.; Kaul, N. E.

    2017-12-01

    The West Antarctic Rift System is one of the least understood rift systems on earth, but displays a unique coupled relationship between tectonic processes and ice sheet dynamics. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Young, continental rift systems are regions with significantly elevated geothermal heat flux (GHF), because the transient thermal perturbation to the lithosphere caused by rifting requires 100 Ma to reach long-term thermal equilibrium. We discuss airborne, high-resolution magnetic anomaly data from the Amundsen Sea Sector, to provide additional insight into deeper crustal structures related to the West Antarctic Rift System in the Amundsen/Bellingshausen sector. With the depth-to-the-bottom of the magnetic source (DBMS) estimates we reveal spatial changes at the bottom of the igneous crust and the thickness of the magnetic layer, which can be further incorporated into tectonic interpretations. The DBMS also marks an important temperature transition zone of approximately 580°C and therefore serves as a boundary condition for our numerical FEM thermal models in 2D and 3D.

  6. Columbia River volcanism - The question of mantle heterogeneity or crustal contamination

    Science.gov (United States)

    Carlson, R. W.; Lugmair, G. W.; Macdougall, J. D.

    1981-01-01

    It is found that, although crystal fractionation played an important role in producing the chemical characteristics of Columbia River Province basalts displaying a wide range of chemical and isotopic compositions, the isotopic variability calls for the involvement of at least two isotopically distinct components. The major and trace element characteristics of the main volume of the basalts are not consistent with a metasomatized mantle source region, and the presence of a primordial mantel component is not supported by the chemical data. Models of simple binary mixing between a primary magma and Precambrian sialic crustal materials, while satisfying the observed Nd and Sr isotopic variations, fail to account for major trace element abundances. The combination of crustal assimilation and fractional crystalization is found to give a superior fit to the compositional data.

  7. The gravity field and crustal structure of the northwestern Arabian Platform in Jordan

    Science.gov (United States)

    Batayneh, A. T.; Al-Zoubi, A. S.

    2001-01-01

    The Bouguer gravity field over the northwestern Arabian Platform in Jordan is dominated by large variations, ranging from -132 to +4 mGal. A study of the Bouguer anomaly map shows that the gravity field maintains a general north-northeasterly trend in the Wadi Araba-Dead Sea-Jordan Riff, Northern Highlands and Northeast Jordanian Limestone Area, while the remainder of the area shows north-northwesterly-trending gravity anomalies. Results of 2-D gravity modeling of the Bouguer gravity field indicate that the crustal thickness in Jordan is ˜ 38 km, which is similar to crustal thicknesses obtained from refraction data in northern Jordan and Saudi Arabia, and from gravity data in Syria.

  8. Evidence for crustal recycling during the Archean: the parental magmas of the stillwater complex

    International Nuclear Information System (INIS)

    McCallum, I.S.

    1988-01-01

    The petrology and geochemistry of the Stillwater Complex, an Archean (2.7 Ga) layered mafic intrusion in the Beartooth Mountains of Montana, is discussed. Efforts to reconstruct the compositions of possible parental magmas and thereby place some constraints on the composition and history of their mantle source regions was studied. A high-Mg andesite or boninite magma best matches the crystallization sequences and mineral compositions of Stillwater cumulates, and represents either a primary magma composition or a secondary magma formed, for example, by assimilation of crustal material by a very Mg-rich melt such as komatiite. Isotopic data do not support the extensive amounts of assimilation required by the komatiite parent hypothesis, and it is argued that the Stillwater magma was generated from a mantle source that had been enriched by recycling and homogenization of older crustal material over a large area

  9. Crustal geomagnetic field - Two-dimensional intermediate-wavelength spatial power spectra

    Science.gov (United States)

    Mcleod, M. G.

    1983-01-01

    Two-dimensional Fourier spatial power spectra of equivalent magnetization values are presented for a region that includes a large portion of the western United States. The magnetization values were determined by inversion of POGO satellite data, assuming a magnetic crust 40 km thick, and were located on an 11 x 10 array with 300 km grid spacing. The spectra appear to be in good agreement with values of the crustal geomagnetic field spatial power spectra given by McLeod and Coleman (1980) and with the crustal field model given by Serson and Hannaford (1957). The spectra show evidence of noise at low frequencies in the direction along the satellite orbital track (N-S). indicating that for this particular data set additional filtering would probably be desirable. These findings illustrate the value of two-dimensional spatial power spectra both for describing the geomagnetic field statistically and as a guide for diagnosing possible noise sources.

  10. The use of satellite laser observations in studying the crustal movements

    Directory of Open Access Journals (Sweden)

    Gamal F. Attia

    2012-12-01

    Full Text Available The mutual tectonic displacements of the lithospheric blocks take place within the deep fracture dividing them into hundreds and thousands kilometers long. It is possible to suggest that the reason of the accumulation of considerable local shift deformations is the change of the velocity of the tectonic motion in some or other parts of fractures as a result of different physical, chemical and mechanical processes. Nowadays, the range precision of Satellite Laser Ranging (SLR technique reaches a few millimeters level. Therefore, the space geodesy technique becomes a very important tool in detecting and monitoring recent crustal movements. Regular repeated measurements of the baselines between some stations on different plates give the possibility to construct precise and detail models of crustal movements. In this paper, the length of four baselines between Helwan-SLR station and other four SLR stations are calculated using satellite geodetical technique.

  11. An evaluation of information on vertical crustal movements pertaining to deep disposal

    International Nuclear Information System (INIS)

    Gale, J.E.; Quinlan, G.; Rogerson, R.; Welhan, J.

    1986-03-01

    The geological and historical information on the magnitude and distribution of uplift and differential movements of rock masses as well as groundwater flow system transients that result from glacial unloading, erosion and tectonic stress have been reviewed. Data presented in the literature show that vertical crustal movements have occurred during the Cenozoic. In addition, the literature indicates significant transients exist in groundwater flow systems. The documented evidence of vertical crustal movements, plus supporting data on the stress-permeability constitutive relationships for discontinuities in fractured crystalline rocks, and three-dimensional modelling capability justifies a detailed analysis of the effects of vertical uplift on bedrock and on groundwater as they pertain to the deep disposal of radioactive waste. 159 annotated refs

  12. Crustal and Upper Mantle Structure from Joint Inversion of Body Wave and Gravity Data

    Science.gov (United States)

    2012-09-01

    We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity data provide...relocation analysis. We use both free-air and Bouguer gravity anomalies derived from the global gravity model of the GRACE satellite mission. The gravity...topographic relief this effect needs to be removed; thus, we converted free-air anomalies into Bouguer anomalies assuming a standard density for crustal rocks

  13. Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field

    Science.gov (United States)

    Voorhies, C.

    1998-01-01

    The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

  14. Basalt generation at the Apollo 12 site. Part 2: Source heterogeneity, multiple melts, and crustal contamination

    Science.gov (United States)

    Neal, Clive R.; Hacker, Matthew D.; Snyder, Gregory A.; Taylor, Lawrence A.; Liu, Yun-Gang; Schmitt, Roman A.

    1994-01-01

    The petrogenesis of Apollo 12 mare basalts has been examined with emphasis on trace-element ratios and abundances. Vitrophyric basalts were used as parental compositions for the modeling, and proportions of fractionating phases were determined using the MAGFOX prograqm of Longhi (1991). Crystal fractionation processes within crustal and sub-crustal magma chambers are evaluated as a function of pressure. Knowledge of the fractionating phases allows trace-element variations to be considered as either source related or as a product of post-magma-generation processes. For the ilmenite and olivine basalts, trace-element variations are inherited from the source, but the pigeonite basalt data have been interpreted with open-system evolution processes through crustal assimilation. Three groups of basalts have been examined: (1) Pigeonite basalts-produced by the assimilation of lunar crustal material by a parental melt (up to 3% assimilation and 10% crystal fractionation, with an 'r' value of 0.3). (2) Ilmenite basalts-produced by variable degrees of partial melting (4-8%) of a source of olivine, pigeonite, augite, and plagioclase, brought together by overturn of the Lunar Magma Ocean (LMO) cumulate pile. After generation, which did not exhaust any of the minerals in the source, these melts experienced closed-system crystal fractionation/accumulation. (3) Olivine basalts-produced by variable degrees of partial melting (5-10%) of a source of olivine, pigeonite, and augite. After generation, again without exhausting any of the minerals in the source, these melts evolved through crystal accumulation. The evolved liquid counterparts of these cumulates have not been sampled. The source compositions for the ilmenite and olivine basalts were calculated by assuming that the vitrophyric compositions were primary and the magmas were produced by non-modal batch melting. Although the magnitude is unclear, evaluation of these source regions indicates that both be composed of early- and

  15. Temperature and redox effect on mineral colonization in Juan de Fuca Ridge flank subsurface crustal fluids

    Directory of Open Access Journals (Sweden)

    Jean-Paul eBaquiran

    2016-03-01

    Full Text Available To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for one year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B. In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences and Gammaproteobacteria (29.3%. Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the one-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen.

  16. Crustal Structure and Mantle Transition Zone Thickness beneath the Central Mongolia from Teleseismic Receiver Functions

    Science.gov (United States)

    He, J.; Wu, Q.; Gao, M.; Munkhuu, U.; Demberel, S. G.

    2013-12-01

    The Mongolian Plateau (northern Asia) is situated between the Gobi-Altai range and the Siberian craton. In order to understand the crustal and mantle structure environmental characteristics, we use the teleseismic data recorded by 69 broadband stations located in the Central Mongolia(103.5°-111.5°E, 42°-50°N). The teleseismic events are selected from the global earthquakes between Aug. 2011 and Dec. 2013 with magnitude >5.5and the epicentral distance range from 30° to 95° to the center of the network. Lateral variations of the crustal thicknesses H and Vp/Vs ratios are obtained by using receiver function method. The crust thins gradually from northwest to southeast in the studying field. We found that the thinnest crust is ~37.5km in the southeast which is Gobi. The distribution of Vp/Vs ratios are between 1.68 and 1.84, which shows the heterogeneity. There are three high-anomaly areas: the Gobi range which is the Later Paleozoic Orogeny; the Khentei Mountains which is in the Jurassic-Cretaceous Reactive Continental Margin; the northwest area which is granite. Our research not only reveals the powerful evident of the crustal formation and evolution mechanism, but also provides some constraints on the mechanism of uplift of the Mongolian Plateau.This study was supported by the international cooperation project of the Ministry of Science and Technology of China (2011DFB20120).

  17. Present-day crustal deformation and strain transfer in northeastern Tibetan Plateau

    Science.gov (United States)

    Li, Yuhang; Liu, Mian; Wang, Qingliang; Cui, Duxin

    2018-04-01

    The three-dimensional present-day crustal deformation and strain partitioning in northeastern Tibetan Plateau are analyzed using available GPS and precise leveling data. We used the multi-scale wavelet method to analyze strain rates, and the elastic block model to estimate slip rates on the major faults and internal strain within each block. Our results show that shear strain is strongly localized along major strike-slip faults, as expected in the tectonic extrusion model. However, extrusion ends and transfers to crustal contraction near the eastern margin of the Tibetan Plateau. The strain transfer is abrupt along the Haiyuan Fault and diffusive along the East Kunlun Fault. Crustal contraction is spatially correlated with active uplifting. The present-day strain is concentrated along major fault zones; however, within many terranes bounded by these faults, intra-block strain is detectable. Terranes having high intra-block strain rates also show strong seismicity. On average the Ordos and Sichuan blocks show no intra-block strain, but localized strain on the southwestern corner of the Ordos block indicates tectonic encroachment.

  18. Crustal structure of the SW Iberian passive margin: The westernmost remnant of the Ligurian Tethys?

    Science.gov (United States)

    Ramos, A.; Fernández, O.; Torne, M.; Sánchez de la Muela, A.; Muñoz, J. A.; Terrinha, P.; Manatschal, G.; Salas, M. C.

    2017-05-01

    At present, the SW Iberian margin is located along the convergent Iberia-Nubia plate boundary. In Mesozoic times, the margin was located at the triple junction of the Ligurian Tethys, Central Atlantic and Northern Atlantic. The characterization of its crustal structure has allowed us to propose a configuration for this triple junction and to determine the role that this transform margin played within the plate kinematic system. In this paper we present an integrated study based on the interpretation of a 2D regional multichannel seismic survey consisting of 58 profiles, tied with onshore geology and exploratory wells, and on gravimetric modeling performed over four NW-SE trending profiles. Integrated interpretation of MCS data combined with 2D gravity modeling reveals a complex pattern in the southward crustal thinning of SW Iberia and supports the possible presence of oceanic crust under the Gulf of Cadiz. The tapering of Iberian crust is characterized by steps with rapid changes in the thickness of the crust, and thinning to Bank. Margin inversion and the pre-existing extensional crustal structure are responsible for the areal distribution and amplitude of the prominent positive gravity anomaly observed in the Gulf of Cadiz.

  19. Distinct crustal isostasy trends east and west of the Rocky Mountain Front

    KAUST Repository

    Schmandt, Brandon

    2015-12-14

    © 2015. American Geophysical Union. All Rights Reserved. Seismic structure beneath the contiguous U.S. was imaged with multimode receiver function stacking and inversion of Rayleigh wave dispersion and ellipticity measurements. Crust thickness and elevation are weakly correlated across the contiguous U.S., but the correlation is ∼3-4 times greater for separate areas east and west of the Rocky Mountain Front (RMF). Greater lower crustal shear velocities east of the RMF, particularly in low-elevation areas with thick crust, are consistent with deep crustal density as the primary cause of the contrasting crust thickness versus elevation trends. Separate eastern and western trends are best fit by Airy isostasy models that assume lower crust to uppermost mantle density increases of 0.18 g/cm3 and 0.40 g/cm3, respectively. The former value is near the minimum that is plausible for felsic lower crust. Location of the transition at the RMF suggests that Laramide to post-Laramide processes reduced western U.S. lower crustal density.

  20. Crustal thickness and Moho sharpness beneath the Midcontinent rift from receiver functions

    Directory of Open Access Journals (Sweden)

    Moikwathai Moidaki

    2013-02-01

    Full Text Available The Mesoproterozoic Midcontinent rift (MCR in the central US is an approximately 2000 km long, 100 km wide structure from Kansas to Michigan. During the 20-40 million years of rifting, a thick (up to 20 km layer of basaltic lava was deposited in the rift valleys. Quantifying the effects of the rifting and associated volcanic eruptions on the structure and composition of the crust and mantle beneath the MCR is important for the understanding of the evolution of continental lithosphere. In this study we measure the crustal thickness (H, and the sharpness of the Moho (R at about 24 portable and permanent stations in Iowa, Kansas, and South Dakota by stacking Pto- S converted waves (PmS and their multiples (PPmS and PSmS. Under the assumption that the crustal mean velocity in the study area is the same as the IASP91 earth model, we find a significantly thickened crust beneath the MCR of about 53 km. The crustal Vp/Vs ratios increases from about 1.80 off rift to as large as 1.95 within the rift, which corresponds to an increase of Poisson’s ratio from 0.28 to 0.32, suggesting a more mafic crust beneath the MCR. The R measurements are spatially variable and are relatively small in the vicinity of the MCR, indicating the disturbance of the original sharp Moho by the rifting and magmatic intrusion and volcanic eruption.

  1. Martian crustal dichotomy: product of accretion and not a specific event?

    International Nuclear Information System (INIS)

    Frey, H.; Schultz, R.A.; Maxwell, T.A.

    1987-01-01

    Attempts to explain the fundamental crustal dichotomy on Mars range from purely endogenic to extreme exogenic processes, but to date no satisfactory theory has evolved. What is accepted is: (1) the dichotomy is an ancient feature of the Martian crust, and (2) the boundary between the cratered highlands and northern plains which marks the dichotomy in parts of Mars has undergone significant and variable modification during the observable parts of Martian history. Some ascribe it to a single mega-impact event, essentially an instantaneous rearrangement of the crustal structures (topography and lithospheric thickness). Others prefer an internal mechanism: a period of vigorous convection subcrustally erodes the northern one third of Mars, causing foundering and isostatic lowering of that part of Mars. The evidence for each theory is reviewed, with the conclusion that there is little to recommend either. An alternative is suggested: the formation of the crustal dichotomy on Mars was not a specific tectonic event but a byproduct of the accretionary process and therefore a primordial characteristic of the Martian crust, predating the oldest recognizable landforms

  2. A Systematic Comparison of Vertical GPS Time Series Calculated by Five Processing Centers for Detecting Climatic-Induced Crustal Movements

    Science.gov (United States)

    Setti Junior, P. D. T.; Wdowinski, S.

    2016-12-01

    Vertical crustal movements, as observed by continuous GPS measurements, are sensitive to load changes induced by atmospheric and hydrological processes, as lake level fluctuations, ice melt, groundwater depletion, or drought. These movements are often dominated by a seasonal signal but also by year-to-year changes, which reflect a long-term climatic signal. Recently, we developed a new technique that extracts the climatic signal by removing the seasonal signal from vertical GPS time series (Wdowinski et al., 2016). However, the method's results, which are the climatic signals, are very sensitive to the quality of the time series and the choice of reference frame (RF). In this study, we conduct a systematic comparison between eight vertical GPS time series calculated by five processing centers and evaluate their suitability to extract the climatic signal. We use the solutions produced by Central Washington University (CWU), New Mexico Institute of Technology (NMT), Nevada Geodetic Laboratory (NGL), Scripps Orbit and Permanent Array Center (SOPAC) and Jet Propulsion Laboratory (JPL), as well as combined solution calculated by the Plate Boundary Observatory (PBO) and GPS Explorer. We use the solutions constrained in the IGS08 RF and in the case of NGL, we also use the NA12 solutions. Three of the processing centers, CWU, NGL and JPL use the GIPSY software, whereas the other two, NMT and SOPAC, use GAMIT. Both combined solutions integrate between GIPSY and GAMIT solutions. We conducted our comparative analysis in two study areas, one in western US taking advantage of the two decades long time series of the Basin and Range network, and the other in eastern U.S. and Canada (Washington DC area, Newfoundland, and Ottawa area). Preliminary results suggest that the three GIPSY solutions (CWU, NGL and JPL) are more consistent between one another compared with the GAMIT solutions. The GIPSY solutions also yield climatic signal that is more consistent with regional climatic

  3. Improved images of crustal structures in the Bergslagen, central Sweden, through seismic reprocessing of BABEL lines 1, 6 and 7

    Science.gov (United States)

    Buntin, Sebastian; Malehmir, Alireza; Malinowski, Michał; Högdahl, Karin; Juhlin, Christopher; Buske, Stefan

    2017-04-01

    In a joint effort through the BABEL project, geoscientists from five countries acquired marine seismic data in the Baltic Sea with a total length of 2268 km in the year 1989. These consisted of near-vertical reflection and wide-angle refraction seismic data, providing insights into the subsurface down to the Moho and suggesting the existence of plate tectonics already during the Paleoproterozoic. The seismic data were acquired using a receiver group interval of 50 m and a total cable length of 3 km. In total, 60 groups of 64 hydrophones at 15 m depth were used. An airgun array consisting of six equal subarrays towed at 7.5 m depth was used to generate the seismic signal. The shot interval and the corresponding record lengths were different among the lines. A record length of 25 s and 75 m shot spacing for lines 1 and 7, respectively and 23 s and 62.5 m for line 6, respectively was used. The sampling rate was 4 ms for all three profiles. Lines 1, 6 and 7 are located at the boundary to the world-class and historical Bergslagen mineral district, and are being revisited in this study. Improved images can be used to refine previous interpretations, particularly at shallower depths (stack deconvolutions and coherency enhancements were applied. The reprocessing revealed reflections in the shallow part of the profiles, likely from major deformation (multi-phase) zones extending down to the lower crust, which were not present in the previous images. Also the images of the reflections in the deeper parts are remarkably improved. This also includes a few sub-Moho reflections. The three reprocessed profiles help constrain the nature of the northern boundary of Bergslagen and associated crustal structures. Furthermore they should assist in the planning of an onshore refraction and reflection profile, to be acquired in 2017, crossing the northern boundary of the Bergslagen district. Acknowledgments: This work is supported by the Swedish Research Council (VR) grant number 2015

  4. Broadband Magnetotelluric Investigations of Crustal Resistivity Structure in North-Eastern Alberta: Implications for Engineered Geothermal Systems

    Science.gov (United States)

    Liddell, M. V.; Unsworth, M. J.; Nieuwenhuis, G.

    2013-12-01

    Greenhouse gas emissions from hydrocarbon consumption produce profound changes in the global climate, and the implementation of alternative energy sources is needed. The oilsands industry in Alberta (Canada) is a major producer of greenhouse gases as natural gas is burnt to produce the heat required to extract and process bitumen. Geothermal energy could be utilized to provide this necessary heat and has the potential to reduce both financial costs and environmental impacts of the oilsands industry. In order to determine the geothermal potential the details of the reservoir must be understood. Conventional hydrothermal reservoirs have been detected using geophysical techniques such as magnetotellurics (MT) which measures the electrical conductivity of the Earth. However, in Northern Alberta the geothermal gradient is relatively low, and heat must be extracted from deep inside the basement rocks using Engineered Geothermal Systems (EGS) and therefore an alternative exploration technique is required. MT can be useful in this context as it can detect fracture zones and regions of elevated porosity. MT data were recorded near Fort McMurray with the goal of determining the geothermal potential by understanding the crustal resistivity structure beneath the Athabasca Oilsands. The MT data are being used to locate targets of significance for geothermal exploration such as regions of low resistivity in the basement rocks which can relate to in situ fluids or fracture zones which can facilitate efficient heat extraction or het transport. A total of 93 stations were collected ~500m apart on two profiles stretching 30 and 20km respectively. Signals were recorded using Phoenix Geophysics V5-2000 systems over frequency bands from 1000 to 0.001 Hz, corresponding to depths of penetration approximately 50m to 50km. Groom-Bailey tensor decomposition and phase tensor analysis shows a well defined geoelectric strike direction that varied along the profile from N60°E to N45

  5. The Crustal Structure of the North-South Earthquake Belt in China Revealed from Deep Seismic Soundings and Gravity Data

    Science.gov (United States)

    Zhao, Yang; Guo, Lianghui; Shi, Lei; Li, Yonghua

    2018-01-01

    The North-South earthquake belt (NSEB) is one of the major earthquake regions in China. The studies of crustal structure play a great role in understanding tectonic evolution and in evaluating earthquake hazards in this region. However, some fundamental crustal parameters, especially crustal interface structure, are not clear in this region. In this paper, we reconstructed the crustal interface structure around the NSEB based on both the deep seismic sounding (DSS) data and the gravity data. We firstly reconstructed the crustal structure of crystalline basement (interface G), interface between upper and lower crusts (interface C) and Moho in the study area by compiling the results of 38 DSS profiles published previously. Then, we forwardly calculated the gravity anomalies caused by the interfaces G and C, and then subtracted them from the complete Bouguer gravity anomalies, yielding the regional gravity anomalies mainly due to the Moho interface. We then utilized a lateral-variable density interface inversion technique with constraints of the DSS data to invert the regional anomalies for the Moho depth model in the study area. The reliability of our Moho depth model was evaluated by comparing with other Moho depth models derived from other gravity inversion technique and receiver function analysis. Based on our Moho depth model, we mapped the crustal apparent density distribution in the study area for better understanding the geodynamics around the NSEB.

  6. Preliminary crustal deformation model deduced from GPS and earthquakes’ data at Abu-Dabbab area, Eastern Desert, Egypt

    Directory of Open Access Journals (Sweden)

    Abdel-Monem S. Mohamed

    2013-06-01

    From the seismic tomography study, the 3D Vp and Vp/Vs crustal models indicate high Vp/Vs values forms an elongated anomaly, in the central part of the study area, that extends from a depth of 12 km to about 1–2 km of depth is obtained. By using this crustal model in relocations all seismicity informed that most of the seismicity strongly tend to occur in a cluster manner exactly above the southern part of the study area. Based on the conducted source mechanism study, it is noticed that shallow earthquakes are associated by a high CLVD ratio (up to 40%. Furthermore, initiation of a high level seismic activity, without a large seismic main shock is observed in the Abu-Dabbab area. The distribution of micro-earthquakes tends to align in an ENE–WSW direction marking a zone of activity verse the Red Sea. The nucleation of the seismic activity beneath the southern part of the Abu-Dabbab crust is more consistent with the obtained crustal deformation result by increasing the crustal movement in the south part than the northern part. Then, based on the obtained results of the above mentioned studies; seismic tomography; source mechanisms, and crustal deformation we conclude that these seismic activities that are associated by crustal deformation are owing to some magma activity beneath the crust of the Abu-Dabbab area.

  7. Particle-In-Cell Simulations of the Solar Wind Interaction with Lunar Crustal Magnetic Anomalies: Magnetic Cusp Regions

    Science.gov (United States)

    Poppe, A. R.; Halekas, J. S.; Delory, G. T.; Farrell, W. M.

    2012-01-01

    As the solar wind is incident upon the lunar surface, it will occasionally encounter lunar crustal remanent magnetic fields. These magnetic fields are small-scale, highly non-dipolar, have strengths up to hundreds of nanotesla, and typically interact with the solar wind in a kinetic fashion. Simulations, theoretical analyses, and spacecraft observations have shown that crustal fields can reflect solar wind protons via a combination of magnetic and electrostatic reflection; however, analyses of surface properties have suggested that protons may still access the lunar surface in the cusp regions of crustal magnetic fields. In this first report from a planned series of studies, we use a 1 1/2-dimensional, electrostatic particle-in-cell code to model the self-consistent interaction between the solar wind, the cusp regions of lunar crustal remanent magnetic fields, and the lunar surface. We describe the self-consistent electrostatic environment within crustal cusp regions and discuss the implications of this work for the role that crustal fields may play regulating space weathering of the lunar surface via proton bombardment.

  8. Constrained Local UniversE Simulations: a Local Group factory

    Science.gov (United States)

    Carlesi, Edoardo; Sorce, Jenny G.; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo; Libeskind, Noam I.; Pilipenko, Sergey V.; Knebe, Alexander; Courtois, Hélène; Tully, R. Brent; Steinmetz, Matthias

    2016-05-01

    Near-field cosmology is practised by studying the Local Group (LG) and its neighbourhood. This paper describes a framework for simulating the `near field' on the computer. Assuming the Λ cold dark matter (ΛCDM) model as a prior and applying the Bayesian tools of the Wiener filter and constrained realizations of Gaussian fields to the Cosmicflows-2 (CF2) survey of peculiar velocities, constrained simulations of our cosmic environment are performed. The aim of these simulations is to reproduce the LG and its local environment. Our main result is that the LG is likely a robust outcome of the ΛCDMscenario when subjected to the constraint derived from CF2 data, emerging in an environment akin to the observed one. Three levels of criteria are used to define the simulated LGs. At the base level, pairs of haloes must obey specific isolation, mass and separation criteria. At the second level, the orbital angular momentum and energy are constrained, and on the third one the phase of the orbit is constrained. Out of the 300 constrained simulations, 146 LGs obey the first set of criteria, 51 the second and 6 the third. The robustness of our LG `factory' enables the construction of a large ensemble of simulated LGs. Suitable candidates for high-resolution hydrodynamical simulations of the LG can be drawn from this ensemble, which can be used to perform comprehensive studies of the formation of the LG.

  9. A deep crustal fluid channel into the San Andreas Fault system near Parkfield, California

    Science.gov (United States)

    Becken, M.; Ritter, O.; Park, S.K.; Bedrosian, P.A.; Weckmann, U.; Weber, M.

    2008-01-01

    Magnetotelluric (MT) data from 66 sites along a 45-km-long profile across the San Andreas Fault (SAF) were inverted to obtain the 2-D electrical resistivity structure of the crust near the San Andreas Fault Observatory at Depth (SAFOD). The most intriguing feature of the resistivity model is a steeply dipping upper crustal high-conductivity zone flanking the seismically defined SAF to the NE, that widens into the lower crust and appears to be connected to a broad conductivity anomaly in the upper mantle. Hypothesis tests of the inversion model suggest that upper and lower crustal and upper-mantle anomalies may be interconnected. We speculate that the high conductivities are caused by fluids and may represent a deep-rooted channel for crustal and/or mantle fluid ascent. Based on the chemical analysis of well waters, it was previously suggested that fluids can enter the brittle regime of the SAF system from the lower crust and mantle. At high pressures, these fluids can contribute to fault-weakening at seismogenic depths. These geochemical studies predicted the existence of a deep fluid source and a permeable pathway through the crust. Our resistivity model images a conductive pathway, which penetrates the entire crust, in agreement with the geochemical interpretation. However, the resistivity model also shows that the upper crustal branch of the high-conductivity zone is located NE of the seismically defined SAF, suggesting that the SAF does not itself act as a major fluid pathway. This interpretation is supported by both, the location of the upper crustal high-conductivity zone and recent studies within the SAFOD main hole, which indicate that pore pressures within the core of the SAF zone are not anomalously high, that mantle-derived fluids are minor constituents to the fault-zone fluid composition and that both the volume of mantle fluids and the fluid pressure increase to the NE of the SAF. We further infer from the MT model that the resistive Salinian block

  10. Magmatism at different crustal levels in the ancient North Cascades magmatic arc

    Science.gov (United States)

    Shea, E. K.; Bowring, S. A.; Miller, R. B.; Miller, J. S.

    2013-12-01

    The mechanisms of magma ascent and emplacement inferred from study of intrusive complexes have long been the subject of intense debate. Current models favor incremental construction based on integration of field, geochemical, geochronologic, and modeling studies. Much of this work has been focused on a single crustal level. However, study of magmatism throughout the crust is critical for understanding how magma ascends through and intrudes surrounding crustal material. Here, we present new geochronologic and geochemical work from intrusive complexes emplaced at a range of crustal depths in the Cretaceous North Cascades magmatic arc. These complexes were intruded between 92 and 87 Ma at depths of at ≤5 -10 km, ~20 km, and ~25 km during this time. U-Pb CA-TIMS geochronology in zircon can resolve Jack-Entiat intrusive complex, a highly elongate amalgamation of intrusions recording two episodes of magmatism between~92-88 Ma and ~80-77 Ma. Each of these complexes provides a window into crustal processes that occur at different depths. Our data suggest assembly of the Black Peak intrusive complex occurred via a series of small (0.5-2 km2) magmatic increments from ~92 Ma to ~87 Ma. Field relations and zircon trace element geochemistry indicate each of these increments were emplaced and crystallized as closed systems-we find no evidence for mixing between magmas in the complex. However, zircon inheritance becomes more common in younger intrusions, indicating assimilation of older plutonic material, possibly during magma production or transport. The Seven-Fingered Jack intrusive complex, emplaced around 15-20 km, preserves a much more discontinuous record of intrusion than the Black Peak. Our data indicate major magmatism in the complex occurred between ~92.1-91.1 Ma. Inheritance in the Seven-Fingered Jack is common, particularly along contacts between intrusions. The Tenpeak intrusive complex, assembled between ~92 Ma and 89 Ma, represents one of the deepest exhumed

  11. Continental Delamination of the Romanian Eastern Carpathians: A Lower Crustal Origin of the Vrancea Seismogenic Zone?

    Science.gov (United States)

    Fillerup, M. A.; Knapp, J. H.; Knapp, C. C.

    2006-12-01

    Two lithosphere-scale, explosive-source seismic reflection profiles (DRACULA I and DACIA PLAN), inclusive of the hinterland and foreland of the Romanian Eastern Carpathians, provide new evidence for the geodynamic origin of the Vrancea Seismogenic Zone (VSZ) of Romania. These data, collected to evaluate existing subduction-related and delamination geodynamic models proposed to explain the intermediate depth seismicity associated with the Vrancea zone, show evidence of continental crust extending continuously above the VSZ from the Carpathian foreland well into the Transylvanian hinterland. Crustal thicknesses inferred from these data based on reflectivity show a 40-45 km crust below the Transylvanian basin abruptly shallowing to 32 km for ~120 km beneath the fold and thrust belt of the main Carpathian orogen and thickening again to 38-42 km crust in the foreland. This thinned crust outlines an apparent lower crustal sub-orogenic cavity that is overlain by a relatively subhorizontal reflective fabric absent of dipping reflectivity. The northwest dipping Vrancea seismogenic body, a 30x70x200 km volume of intermediate depth earthquakes, is located on the eastern flank of the apparently thin crust beneath the Carpathian orogen. Amplitude decay curves show penetration of seismic energy to a depth of ~60 km in the vicinity of the sub-orogenic cavity, implying this non- reflective zone is a geologic signature. Rotation of the VSZ about a hinge beneath the foreland basin at a depth of ~50 km restores to fill the lower-crustal cavity under the orogen, suggesting the VSZ represents a portion of brittle lower crust delaminated during continental lithospheric delamination which may have caused regional uplift of the Transylvanian basin. The lack of through-going, dipping crustal-scale boundaries along this composite lithospheric transect would appear to preclude subduction as an explanation for seismicity in the VSZ, consistent with abundant surface geologic data. These

  12. Evaluation of Earth's Geobiosphere Emergy Baseline and the Emergy of Crustal Cycling

    Science.gov (United States)

    De Vilbiss, Chris

    This dissertation quantitatively analyzed the exergy supporting the nucleosynthesis of the heavy isotopes, Earth's geobiosphere, and its crustal cycling. Exergy is that portion of energy that is available to drive work. The exergy sources that drive the geobiosphere are sunlight, Earth's rotational kinetic energy and relic heat, and radionuclides in Earth's interior. These four exergy sources were used to compute the Earth's geobiosphere emergy baseline (GEB), expressed as a single unit, solar equivalent joules (seJ). The seJ of radionuclides were computed by determining the quantity of gravitational exergy that dissipated in the production of both sunlight and heavy isotopes. This is a new method of computing solar equivalences also was applied to Earth's relic heat and rotational energy. The equivalent quantities of these four exergy sources were then added to express the GEB. This new baseline was compared with several other contemporary GEB methods. The new GEB is modeled as the support to Earth's crustal cycle and ultimately to the economical mineral deposits used in the US economy. Given the average annual cycling of crustal material and its average composition, specific emergies were calculated to express the average emergy per mass of particular crustal minerals. Chemical exergies of the minerals were used to develop transformities and specific emergies of minerals at heightened concentrations, i.e. minable concentrations. The effect of these new mineral emergy values were examined using the US economy as an example. The final result is an 83% reduction in the emergy of limestone, a 91% reduction in the aggregated emergy of all other minerals, and a 23% reduction in the emergy of the US economy. This dissertation explored three unique and innovative methods to compute the emergy of Earth's exergy sources and resources. First was a method for computing the emergy of radionuclides. Second was a method to evaluate the Earth's relic heat and dissipation of

  13. How can we constrain the amount of heat producing elements in the interior of Mars?

    Science.gov (United States)

    Grott, M.; Plesa, A.; Breuer, D.

    2013-12-01

    The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to be launched in 2016 will study Mars' deep interior and help improving our knowledge about the interior structure and the thermal evolution of the planet - the latter is also directly linked to its volcanic history and atmospheric evolution. Measurements planned with the two main instruments, SEIS (Seismic Experiment for Interior Structure) and HP3 (Heat Flow and Physical Properties Package) aim to constrain the main structure of the planet, i.e. core, mantle and crust as well as the rate at which the planet loses the interior heat over its surface. Since the surface heat flow depends on the amount of radiogenic heat elements (HPE) present in the interior, it offers a measurable quantity which could constrain the heat budget. Being the principal agent regulating the heat budget which in turn influences partial melting in the interior, crustal and atmospheric evolution, the heat producing elements have a major impact on the entire the present temperature thermal history of the planet. To constrain the radiogenic heat elements of the planet from the surface heat flow is possible assuming that the urey number of the planet, which describes the contribution of internal heat production to the surface heat loss, is known. We have tested this assumption by calculating the thermal evolution of the planet with fully dynamical numerical simulations and by comparing the obtained present-day urey number for a set of different models/parameters (Fig. 1). For one-plate planets like Mars, numerical models show - in contrast to models for the Earth, where plate tectonics play a major role adding more complexity to the system - that the urey ratio is mainly sensitive to two effects: the efficiency of cooling due to the temperature-dependence of the viscosity and the mean half-life time of the long lived radiogenic isotopes. The temperature-dependence of the viscosity results in the

  14. In vitro transcription of a torsionally constrained template

    DEFF Research Database (Denmark)

    Bentin, Thomas; Nielsen, Peter E

    2002-01-01

    RNA polymerase (RNAP) and the DNA template must rotate relative to each other during transcription elongation. In the cell, however, the components of the transcription apparatus may be subject to rotary constraints. For instance, the DNA is divided into topological domains that are delineated...... of torsionally constrained DNA by free RNAP. We asked whether or not a newly synthesized RNA chain would limit transcription elongation. For this purpose we developed a method to immobilize covalently closed circular DNA to streptavidin-coated beads via a peptide nucleic acid (PNA)-biotin conjugate in principle...... constrained. We conclude that transcription of a natural bacterial gene may proceed with high efficiency despite the fact that newly synthesized RNA is entangled around the template in the narrow confines of torsionally constrained supercoiled DNA....

  15. The Impacts of 3-D Earth Structure on GIA-Induced Crustal Deformation and Future Sea-Level Change in the Antarctic

    Science.gov (United States)

    Powell, E. M.; Hay, C.; Latychev, K.; Gomez, N. A.; Mitrovica, J. X.

    2017-12-01

    Glacial Isostatic Adjustment (GIA) models used to constrain the extent of past ice sheets and viscoelastic Earth structure, or to correct geodetic and geological observables for ice age effects, generally only consider depth-dependent variations in Earth viscosity and lithospheric structure. A et al. [2013] argued that 3-D Earth structure could impact GIA observables in Antarctica, but concluded that the presence of such structure contributes less to GIA uncertainty than do differences in Antarctic deglaciation histories. New seismic and geological evidence, however, indicates the Antarctic is underlain by complex, high amplitude variability in viscoelastic structure, including a low viscosity zone (LVZ) under West Antarctica. Hay et al. [2016] showed that sea-level fingerprints of modern melting calculated using such Earth models differ from those based on elastic or 1-D viscoelastic Earth models within decades of melting. Our investigation is motivated by two questions: (1) How does 3-D Earth structure, especially this LVZ, impact observations of GIA-induced crustal deformation associated with the last deglaciation? (2) How will 3-D Earth structure affect predictions of future sea-level rise in Antarctica? We compute the gravitationally self-consistent sea level, uplift, and gravity changes using the finite volume treatment of Latychev et al. [2005]. We consider four viscoelastic Earth models: a global 1-D model; a regional, West Antarctic-like 1-D model; a 3-D model where the lithospheric thickness varies laterally; and a 3-D model where both viscosity and lithospheric thickness vary laterally. For our Last Glacial Maximum to present investigations we employ ICE6g [Peltier et al., 2015]. For our present-future investigations we consider a melt scenario consistent with GRACE satellite gravity derived solutions [Harig et al., 2015]. Our calculations indicate that predictions of crustal deformations due to both GIA and ongoing melting are strongly influenced by 3-D

  16. Node Discovery and Interpretation in Unstructured Resource-Constrained Environments

    DEFF Research Database (Denmark)

    Gechev, Miroslav; Kasabova, Slavyana; Mihovska, Albena D.

    2014-01-01

    for the discovery, linking and interpretation of nodes in unstructured and resource-constrained network environments and their interrelated and collective use for the delivery of smart services. The model is based on a basic mathematical approach, which describes and predicts the success of human interactions...... in the context of long-term relationships and identifies several key variables in the context of communications in resource-constrained environments. The general theoretical model is described and several algorithms are proposed as part of the node discovery, identification, and linking processes in relation...

  17. Value, Cost, and Sharing: Open Issues in Constrained Clustering

    Science.gov (United States)

    Wagstaff, Kiri L.

    2006-01-01

    Clustering is an important tool for data mining, since it can identify major patterns or trends without any supervision (labeled data). Over the past five years, semi-supervised (constrained) clustering methods have become very popular. These methods began with incorporating pairwise constraints and have developed into more general methods that can learn appropriate distance metrics. However, several important open questions have arisen about which constraints are most useful, how they can be actively acquired, and when and how they should be propagated to neighboring points. This position paper describes these open questions and suggests future directions for constrained clustering research.

  18. Magnetic Mineralogy of a Complete Oceanic Crustal Section (IODP hole 1256D)

    Science.gov (United States)

    Krasa, D.; Herrero-Bervera, E.; Acton, G.; Rodriguez Durand, S.

    2008-12-01

    lower part of the sheeted dykes witnesses the onset of hydrothermal alteration. In the gabbroic part of the section, grain sizes of TMs reach values of up to several mm. These findings lead to the conclusion that the different parts of the section had acquired their remanent magnetisation by different mechanisms: The extrusive part carries a TRM, the intensity of which was later influenced by LT oxidation and inversion. The sheeted dyke part is likely to carry a CRM acquired during hydrothermal alteration, and the underlying gabbro acquired a TCRM at a time significantly after emplacement due to slow cooling at this depth.

  19. Crustal structure of the Gulf of Aden southern margin: Evidence from receiver functions on Socotra Island (Yemen)

    Science.gov (United States)

    Ahmed, Abdulhakim; Leroy, Sylvie; Keir, Derek; Korostelev, Félicie; Khanbari, Khaled; Rolandone, Frédérique; Stuart, Graham; Obrebski, Mathias

    2014-12-01

    Breakup of continents in magma-poor setting occurs primarily by faulting and plate thinning. Spatial and temporal variations in these processes can be influenced by the pre-rift basement structure as well as by early syn-rift segmentation of the rift. In order to better understand crustal deformation and influence of pre-rift architecture on breakup we use receiver functions from teleseismic recordings from Socotra which is part of the subaerial Oligo-Miocene age southern margin of the Gulf of Aden. We determine variations in crustal thickness and elastic properties, from which we interpret the degree of extension related thinning and crustal composition. Our computed receiver functions show an average crustal thickness of ~ 28 km for central Socotra, which decreases westward along the margin to an average of ~ 21 km. In addition, the crust thins with proximity to the continent-ocean transition to ~ 16 km in the northwest. Assuming an initial pre-rift crustal thickness of 35 km (undeformed Arabian plate), we estimate a stretching factor in the range of ~ 2.1-2.4 beneath Socotra. Our results show considerable differences between the crustal structure of Socotra's eastern and western sides on either side of the Hadibo transfer zone; the east displays a clear intracrustal conversion phase and thick crust when compared with the western part. The majority of measurements across Socotra show Vp/Vs ratios of between 1.70 and 1.77 and are broadly consistent with the Vp/Vs values expected from the granitic and carbonate rock type exposed at the surface. Our results strongly suggest that intrusion of mafic rock is absent or minimal, providing evidence that mechanical thinning accommodated the majority of crustal extension. From our observations we interpret that the western part of Socotra corresponds to the necking zone of a classic magma-poor continental margin, while the eastern part corresponds to the proximal domain.

  20. Constraints on the crustal structure beneath the Sinai subplate, SE Mediterranean, from analysis of local and regional travel times

    Directory of Open Access Journals (Sweden)

    Mohamed K. Salah

    2013-03-01

    Full Text Available The Sinai Peninsula has been recognized as a subplate of the African Plate located at the triple junction of the Gulf of Suez rift, the Dead Sea Transform fault, and the Red Sea rift. The upper and lower crustal structures of this tectonically active, rapidly developing region are yet poorly understood because of many limitations. For this reason, a set of P- and S-wave travel times recorded at 14 seismic stations belonging to the Egyptian National Seismographic Network (ENSN from 111 local and regional events are analyzed to investigate the crustal structures and the locations of the seismogenic zones beneath central and southern Sinai. Because the velocity model used for routine earthquake location by ENSN is one-dimensional, the travel-time residuals will show lateral heterogeneity of the velocity structures and unmodeled vertical structures. Seismic activity is strong along the eastern and southern borders of the study area but low to moderate along the northern boundary and the Gulf of Suez to the west. The crustal Vp/Vs ratio is 1.74 from shallow (depth ≤ 10 km earthquakes and 1.76 from deeper (depth > 10 km crustal events. The majority of the regional and local travel-time residuals are positive relative to the Preliminary Reference Earth Model (PREM, implying that the seismic stations are located above widely distributed, tectonically-induced low-velocity zones. These low-velocity zones are mostly related to the local crustal faults affecting the sedimentary section and the basement complex as well as the rifting processes prevailing in the northern Red Sea region and the ascending of hot mantle materials along crustal fractures. The delineation of these low-velocity zones and the locations of big crustal earthquakes enable the identification of areas prone to intense seismotectonic activities, which should be excluded from major future development projects and large constructions in central and southern Sinai.

  1. Cratonic roots and lower crustal seismicity: Investigating the role of deep intrusion in the Western rift, Africa

    Science.gov (United States)

    Drooff, C.; Ebinger, C. J.; Lavayssiere, A.; Keir, D.; Oliva, S. J.; Tepp, G.; Gallacher, R. J.

    2017-12-01

    Improved seismic imaging beneath the African continent reveals lateral variations in lithospheric thickness, and crustal structure, complementing a growing crust and mantle xenolith data base. Border fault systems in the active cratonic rifts of East Africa are characterized by lower crustal seismicity, both in magmatic sectors and weakly magmatic sectors, providing constraints on crustal rheology and, in some areas, magmatic fluid migration. We report new seismicity data from magmatic and weakly magmatic sectors of the East African rift zone, and place the work in the context of independent geophysical and geochemical studies to models for strain localization during early rifting stages. Specifically, multidisciplinary studies in the Magadi Natron rift sectors reveal volumetrically large magmatic CO2 degassing along border faults with seismicity along projections of surface dips to the lower crust. The magmatic CO2 degassing and high Vp/Vs ratios and reflectivity of the lower crust implies that the border fault serves a conduit between the lower crustal underplating and the atmospheric. Crustal xenoliths in the Eastern rift sector indicate a granulitic lower crust, which is relatively weak in the presence of fluids, arguing against a strong lower crust. Within magmatic sectors, seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Within some weakly magmatic sectors, lower crustal earthquakes also occur along projections of border faults to the lower crust (>30 km), and they are prevalent in areas with high Vp/Vs in the lower crust. Within the southern Tanganyika rift, focal mechanisms are predominantly normal with steep nodal planes. Our comparative studies suggest that pervasive metasomatism above a mantle plume, and melt extraction in thin zones between cratonic roots, lead to

  2. Coherent Structures and Entropy in Constrained, Modulationally Unstable, Nonintegrable Systems

    International Nuclear Information System (INIS)

    Rumpf, Benno; Newell, Alan C.

    2001-01-01

    Many studies have shown that nonintegrable systems with modulational instabilities constrained by more than one conservation law exhibit universal long time behavior involving large coherent structures in a sea of small fluctuations. We show how this behavior can be explained in detail by simple thermodynamic arguments

  3. Invariant set computation for constrained uncertain discrete-time systems

    NARCIS (Netherlands)

    Athanasopoulos, N.; Bitsoris, G.

    2010-01-01

    In this article a novel approach to the determination of polytopic invariant sets for constrained discrete-time linear uncertain systems is presented. First, the problem of stabilizing a prespecified initial condition set in the presence of input and state constraints is addressed. Second, the

  4. Applications of a Constrained Mechanics Methodology in Economics

    Science.gov (United States)

    Janova, Jitka

    2011-01-01

    This paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for undergraduate physics education. The aim of the paper is (i) to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even at the…

  5. Excision technique in constrained formulations of Einstein equations: collapse scenario

    International Nuclear Information System (INIS)

    Cordero-Carrión, I; Vasset, N; Novak, J; Jaramillo, J L

    2015-01-01

    We present a new excision technique used in constrained formulations of Einstein equations to deal with black hole in numerical simulations. We show the applicability of this scheme in several scenarios. In particular, we present the dynamical evolution of the collapse of a neutron star to a black hole, using the CoCoNuT code and this excision technique. (paper)

  6. Constraining the evolution of the Hubble Parameter using cosmic chronometers

    Science.gov (United States)

    Dickinson, Hugh

    2017-08-01

    Substantial investment is being made in space- and ground-based missions with the goal of revealing the nature of the observed cosmic acceleration. This is one of the most important unsolved problems in cosmology today.We propose here to constrain the evolution of the Hubble parameter [H(z)] between 1.3 fundamental nature of dark energy.

  7. Nonmonotonic Skeptical Consequence Relation in Constrained Default Logic

    Directory of Open Access Journals (Sweden)

    Mihaiela Lupea

    2010-12-01

    Full Text Available This paper presents a study of the nonmonotonic consequence relation which models the skeptical reasoning formalised by constrained default logic. The nonmonotonic skeptical consequence relation is defined using the sequent calculus axiomatic system. We study the formal properties desirable for a good nonmonotonic relation: supraclassicality, cut, cautious monotony, cumulativity, absorption, distribution. 

  8. Extended shadow test approach for constrained adaptive testing

    NARCIS (Netherlands)

    Veldkamp, Bernard P.; Ariel, A.

    2002-01-01

    Several methods have been developed for use on constrained adaptive testing. Item pool partitioning, multistage testing, and testlet-based adaptive testing are methods that perform well for specific cases of adaptive testing. The weighted deviation model and the Shadow Test approach can be more

  9. Time-constrained project scheduling with adjacent resources

    NARCIS (Netherlands)

    Hurink, Johann L.; Kok, A.L.; Paulus, J.J.; Schutten, Johannes M.J.

    We develop a decomposition method for the Time-Constrained Project Scheduling Problem (TCPSP) with adjacent resources. For adjacent resources the resource units are ordered and the units assigned to a job have to be adjacent. On top of that, adjacent resources are not required by single jobs, but by

  10. Evaluation of constrained mobility for programmability in network management

    NARCIS (Netherlands)

    Bohoris, C.; Liotta, A.; Pavlou, G.; Ambler, A.P.; Calo, S.B.; Kar, G.

    2000-01-01

    In recent years, a significant amount of research work has addressed the use of code mobility in network management. In this paper, we introduce first three aspects of code mobility and argue that constrained mobility offers a natural and easy approach to network management programmability. While

  11. Testing a Constrained MPC Controller in a Process Control Laboratory

    Science.gov (United States)

    Ricardez-Sandoval, Luis A.; Blankespoor, Wesley; Budman, Hector M.

    2010-01-01

    This paper describes an experiment performed by the fourth year chemical engineering students in the process control laboratory at the University of Waterloo. The objective of this experiment is to test the capabilities of a constrained Model Predictive Controller (MPC) to control the operation of a Double Pipe Heat Exchanger (DPHE) in real time.…

  12. In vitro transcription of a torsionally constrained template

    DEFF Research Database (Denmark)

    Bentin, Thomas; Nielsen, Peter E

    2002-01-01

    of torsionally constrained DNA by free RNAP. We asked whether or not a newly synthesized RNA chain would limit transcription elongation. For this purpose we developed a method to immobilize covalently closed circular DNA to streptavidin-coated beads via a peptide nucleic acid (PNA)-biotin conjugate in principle...

  13. GPS-based ionospheric tomography with a constrained adaptive ...

    Indian Academy of Sciences (India)

    Gauss weighted function is introduced to constrain the tomography system in the new method. It can resolve the ... the research focus in the fields of space geodesy and ... ment of GNSS such as GPS, Glonass, Galileo and. Compass, as these ...

  14. Constrained variational calculus for higher order classical field theories

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Cedric M; De Leon, Manuel; De Diego, David MartIn, E-mail: cedricmc@icmat.e, E-mail: mdeleon@icmat.e, E-mail: david.martin@icmat.e [Instituto de Ciencias Matematicas, CSIC-UAM-UC3M-UCM, Serrano 123, 28006 Madrid (Spain)

    2010-11-12

    We develop an intrinsic geometrical setting for higher order constrained field theories. As a main tool we use an appropriate generalization of the classical Skinner-Rusk formalism. Some examples of applications are studied, in particular to the geometrical description of optimal control theory for partial differential equations.

  15. Identification of different geologic units using fuzzy constrained resistivity tomography

    Science.gov (United States)

    Singh, Anand; Sharma, S. P.

    2018-01-01

    Different geophysical inversion strategies are utilized as a component of an interpretation process that tries to separate geologic units based on the resistivity distribution. In the present study, we present the results of separating different geologic units using fuzzy constrained resistivity tomography. This was accomplished using fuzzy c means, a clustering procedure to improve the 2D resistivity image and geologic separation within the iterative minimization through inversion. First, we developed a Matlab-based inversion technique to obtain a reliable resistivity image using different geophysical data sets (electrical resistivity and electromagnetic data). Following this, the recovered resistivity model was converted into a fuzzy constrained resistivity model by assigning the highest probability value of each model cell to the cluster utilizing fuzzy c means clustering procedure during the iterative process. The efficacy of the algorithm is demonstrated using three synthetic plane wave electromagnetic data sets and one electrical resistivity field dataset. The presented approach shows improvement on the conventional inversion approach to differentiate between different geologic units if the correct number of geologic units will be identified. Further, fuzzy constrained resistivity tomography was performed to examine the augmentation of uranium mineralization in the Beldih open cast mine as a case study. We also compared geologic units identified by fuzzy constrained resistivity tomography with geologic units interpreted from the borehole information.

  16. Constrained variational calculus for higher order classical field theories

    International Nuclear Information System (INIS)

    Campos, Cedric M; De Leon, Manuel; De Diego, David MartIn

    2010-01-01

    We develop an intrinsic geometrical setting for higher order constrained field theories. As a main tool we use an appropriate generalization of the classical Skinner-Rusk formalism. Some examples of applications are studied, in particular to the geometrical description of optimal control theory for partial differential equations.

  17. Bounds on the capacity of constrained two-dimensional codes

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Justesen, Jørn

    2000-01-01

    Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run-l...

  18. The balance of payment-constrained economic growth in Ethiopia ...

    African Journals Online (AJOL)

    The objective of this paper is to empirically test the validity of the simplified version of the balance of payment-constrained economic growth model for Ethiopia during the period 1971-20082. According to the model, economies only grow at a pace allowed by the constraints imposed by the requirement of balance of payment ...

  19. Toward cognitively constrained models of language processing : A review

    NARCIS (Netherlands)

    Vogelzang, Margreet; Mills, Anne C.; Reitter, David; van Rij, Jacolien; Hendriks, Petra; van Rijn, Hedderik

    2017-01-01

    Language processing is not an isolated capacity, but is embedded in other aspects of our cognition. However, it is still largely unexplored to what extent and how language processing interacts with general cognitive resources. This question can be investigated with cognitively constrained

  20. The Balance of Payment-Constrained Economic Growth in Ethiopia ...

    African Journals Online (AJOL)

    Administrator

    Page 100 financial liberalization and export promotion strategy necessarily lead to better growth performance. Rather, one should consider not only exports of goods and services, but also the income elasticity of imports. The balance of payments-constrained growth model postulates that the rate of growth in any country is ...

  1. Evaluating potentialities and constrains of Problem Based Learning curriculum

    DEFF Research Database (Denmark)

    Guerra, Aida

    2013-01-01

    This paper presents a research design to evaluate Problem Based Learning (PBL) curriculum potentialities and constrains for future changes. PBL literature lacks examples of how to evaluate and analyse established PBL learning environments to address new challenges posed. The research design......) in the curriculum and a mean to choose cases for further case study (third phase)....

  2. Binary classification posed as a quadratically constrained quadratic ...

    Indian Academy of Sciences (India)

    Binary classification is posed as a quadratically constrained quadratic problem and solved using the proposed method. Each class in the binary classification problem is modeled as a multidimensional ellipsoid to forma quadratic constraint in the problem. Particle swarms help in determining the optimal hyperplane or ...

  3. GPS-based ionospheric tomography with a constrained adaptive ...

    Indian Academy of Sciences (India)

    According to the continuous smoothness of the variations of ionospheric electron density (IED) among neighbouring voxels, Gauss weighted function is introduced to constrain the tomography system in the new method. It can resolve the dependence on the initial values for those voxels without any GPS rays traversing them ...

  4. Time-constrained project scheduling with adjacent resources

    NARCIS (Netherlands)

    Hurink, Johann L.; Kok, A.L.; Paulus, J.J.; Schutten, Johannes M.J.

    2008-01-01

    We develop a decomposition method for the Time-Constrained Project Scheduling Problem (TCPSP) with Adjacent Resources. For adjacent resources the resource units are ordered and the units assigned to a job have to be adjacent. On top of that, adjacent resources are not required by single jobs, but by

  5. Constrained relationship agency as the risk factor for intimate ...

    African Journals Online (AJOL)

    We used structural equation modelling to identify and measure constrained relationship agency (CRA) as a latent variable, and then tested the hypothesis that CRA plays a significant role in the pathway between IPV and transactional sex. After controlling for CRA, receiving more material goods from a sexual partner was ...

  6. Chance-constrained optimization of demand response to price signals

    DEFF Research Database (Denmark)

    Dorini, Gianluca Fabio; Pinson, Pierre; Madsen, Henrik

    2013-01-01

    within a recursive least squares (RLS) framework using data measurable at the grid level, in an adaptive fashion. Optimal price signals are generated by embedding the FIR models within a chance-constrained optimization framework. The objective is to keep the price signal as unchanged as possible from...

  7. Solution of a Complex Least Squares Problem with Constrained Phase.

    Science.gov (United States)

    Bydder, Mark

    2010-12-30

    The least squares solution of a complex linear equation is in general a complex vector with independent real and imaginary parts. In certain applications in magnetic resonance imaging, a solution is desired such that each element has the same phase. A direct method for obtaining the least squares solution to the phase constrained problem is described.

  8. Dark matter, constrained minimal supersymmetric standard model, and lattice QCD.

    Science.gov (United States)

    Giedt, Joel; Thomas, Anthony W; Young, Ross D

    2009-11-13

    Recent lattice measurements have given accurate estimates of the quark condensates in the proton. We use these results to significantly improve the dark matter predictions in benchmark models within the constrained minimal supersymmetric standard model. The predicted spin-independent cross sections are at least an order of magnitude smaller than previously suggested and our results have significant consequences for dark matter searches.

  9. Constrained Quantum Mechanics: Chaos in Non-Planar Billiards

    Science.gov (United States)

    Salazar, R.; Tellez, G.

    2012-01-01

    We illustrate some of the techniques to identify chaos signatures at the quantum level using as guiding examples some systems where a particle is constrained to move on a radial symmetric, but non-planar, surface. In particular, two systems are studied: the case of a cone with an arbitrary contour or "dunce hat billiard" and the rectangular…

  10. Constrained control of a once-through boiler with recirculation

    DEFF Research Database (Denmark)

    Trangbæk, K

    2008-01-01

    There is an increasing need to operate power plants at low load for longer periods of time. When a once-through boiler operates at a sufficiently low load, recirculation is introduced, significantly altering the control structure. This paper illustrates the possibilities for using constrained con...

  11. On the Integrated Job Scheduling and Constrained Network Routing Problem

    DEFF Research Database (Denmark)

    Gamst, Mette

    This paper examines the NP-hard problem of scheduling a number of jobs on a finite set of machines such that the overall profit of executed jobs is maximized. Each job demands a number of resources, which must be sent to the executing machine via constrained paths. Furthermore, two resource demand...

  12. Effective Teaching of Economics: A Constrained Optimization Problem?

    Science.gov (United States)

    Hultberg, Patrik T.; Calonge, David Santandreu

    2017-01-01

    One of the fundamental tenets of economics is that decisions are often the result of optimization problems subject to resource constraints. Consumers optimize utility, subject to constraints imposed by prices and income. As economics faculty, instructors attempt to maximize student learning while being constrained by their own and students'…

  13. Vacuum expectation values in a scalar constrained theory

    International Nuclear Information System (INIS)

    Alonso, F.; Julve, J.; Tiemblo, A.

    1985-01-01

    A class of finite Green functions in the context of a scalar constrained theory is studied. In a particular model the one-point GFs show that the vacuum expectation values for some fields vanish while one of them remains finite, a feature exhibited by the Goldstone and Higgs fields respectively. (orig.)

  14. Lagrangian formalism for constrained systems. 2. Gauge symmetries

    International Nuclear Information System (INIS)

    Pyatov, P.N.

    1990-01-01

    Using the Lagrangian formalism for constrained systems all gauge symmetries peculiar for a given Lagrangian system and in establishing the relation between them and the constraints are constructed. Besides, the question about the possible dependence of gauge transformations on accelerations and other higher order time derivatives of coordinates is clarified. 14 refs

  15. Factors constraining accessibility and usage of information among ...

    African Journals Online (AJOL)

    Various factors may negatively impact on information acquisition and utilisation. To improve understanding of the determinants of information acquisition and utilisation, this study investigated the factors constraining accessibility and usage of poultry management information in three rural districts of Tanzania. The findings ...

  16. Constrained Geocast to Support Cooperative Adaptive Cruise Control (CACC) Merging

    NARCIS (Netherlands)

    Klein Wolterink, W.; Heijenk, Geert; Karagiannis, Georgios

    2010-01-01

    In this paper we introduce a new geocasting concept to target vehicles based on where they will be in the direct future, in stead of their current position. We refer to this concept as constrained geocast. This may be useful in situations where vehicles have interdependencies based on (future)

  17. Reconnaissance isotopic investigations in the Namaqua mobile belt and implications for proterozoic crustal evolution - Namaqualand geotraverse

    International Nuclear Information System (INIS)

    Barton, E.S.

    1983-01-01

    Fourteen rock units in the western portion of the Namaqua mobile belt were investigated by some or all of the following isotopic methods: Rb-Sr, Pb-Pb, Th-Pb total-rock and Rb-Sr mineral age measurements. Two major tectogenetic events are recongnised. The early Orange River event is represented by the emplacement and metamorphism of the volcanic rocks of the Haib Subgroup and the emplacement of granitoids of the Vioolsdrif and Gladkop suites in the regions of the Richtersveld Province and the Steinkopf domain. The later Namaqua event is represented mainly by extensive granitoid emplacement and high-grade granulite facies metamorphism in the Okiep Copper District, with minor granitoid and dyke emplacement taking place in the Steinkopf domain. The polymetamorphism associated with these tectonic events had far-reaching effects in the form of long continued isotopic resetting of rock and mineral systems. In the instances where the regression of the total-rock isotopic data define errorchron results, geological disturbance is inferred. The Sr-isotopic results indicate substrantial crustal reworking and two periods of mantle differentiation producing continental crust at approximately 2 000 and approximately 1 200 Ma ago. The Pb-isotopic data for these rocks indicate μ 2 values for the source regions that are compatible with crustal reworking for the felsic rocks or a significant amount of crustal recycling into the mantle for the mafic rocks. On this basis a magmatic arc environment is envisaged for the rocks generated during the Orange River event. The deformation fabrics associated with the Orange River and Namaqua tectogenetic episodes are dated by the time of emplacement of syn- and post-tectonic granitic rocks. The regional fabric observed in the Steinkopf domain and in the Okiep Copper District was not synchronously developed

  18. First-order control of syntectonic sedimentation on crustal-scale structure of mountain belts

    Science.gov (United States)

    Erdős, Zoltán.; Huismans, Ritske S.; van der Beek, Peter

    2015-07-01

    The first-order characteristics of collisional mountain belts and the potential feedback with surface processes are predicted by critical taper theory. While the feedback between erosion and mountain belt structure has been fairly extensively studied, less attention has been given to the potential role of synorogenic deposition. For thin-skinned fold-and-thrust belts, recent studies indicate a strong control of syntectonic deposition on structure, as sedimentation tends to stabilize the thin-skinned wedge. However, the factors controlling basement deformation below fold-and-thrust belts, as evident, for example, in the Zagros Mountains or in the Swiss Alps, remain largely unknown. Previous work has suggested that such variations in orogenic structure may be explained by the thermotectonic "age" of the deforming lithosphere and hence its rheology. Here we demonstrate that sediment loading of the foreland basin area provides an additional control and may explain the variable basement involvement in orogenic belts. When examining the role of sedimentation, we identify two end-members: (1) sediment-starved orogenic systems with thick-skinned basement deformation in an axial orogenic core and thin-skinned deformation in the bordering forelands and (2) sediment-loaded orogens with thick packages of synorogenic deposits, derived from the axial basement zone, deposited on the surrounding foreland fold-and-thrust belts, and characterized by basement deformation below the foreland. Using high-resolution thermomechanical models, we demonstrate a strong feedback between deposition and crustal-scale thick-skinned deformation. Our results show that the loading effects of syntectonic sediments lead to long crustal-scale thrust sheets beneath the orogenic foreland and explain the contrasting characteristics of sediment-starved and sediment-loaded orogens, showing for the first time how both thin- and thick-skinned crustal deformations are linked to sediment deposition in these

  19. Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

    Science.gov (United States)

    Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

    2015-01-01

    Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

  20. Lithospheric Structure, Crustal Kinematics, and Earthquakes in North China: An Integrated Study

    Science.gov (United States)

    Liu, M.; Yang, Y.; Sandvol, E.; Chen, Y.; Wang, L.; Zhou, S.; Shen, Z.; Wang, Q.

    2007-12-01

    The North China block (NCB) is geologically part of the Archaean Sino-Korean craton. But unusual for a craton, it was thermally rejuvenated since late Mesozoic, and experienced widespread extension and volcanism through much of the Cenozoic. Today, the NCB is characterized by strong internal deformation and seismicity, including the 1976 Tangshan earthquake that killed ~250,000 people. We have started a multidisciplinary study to image the lithospheric and upper mantle structure using seismological methods, to delineate crustal kinematics and deformation via studies of neotectonics and space geodesy, and to investigate the driving forces, the stress states and evolution, and seismicity using geodynamic modeling. Both seismic imaging and GPS results indicate that the Ordos plateau, which is the western part of the NCB and a relic of the Sino-Korean craton, has been encroached around its southern margins by mantle flow and thus is experiencing active cratonic destruction. Some of the mantle flow may be driven by the Indo-Asian collision, although the cause of the broad mantle upwelling responsible for the Mesozoic thinning of the NCB lithosphere remains uncertain. At present, crustal deformation in the NCB is largely driven by gravitational spreading of the expanding Tibetan Plateau. Internal deformation within the NCB is further facilitated by the particular tectonic boundary conditions around the NCB, and the large lateral contrasts of lithospheric strength and rheology. Based on the crustal kinematics and lithospheric structure, we have developed a preliminary geodynamic model for stress states and strain energy in the crust of the NCB. The predicted long-term strain energy distribution is comparable with the spatial pattern of seismic energy release in the past 2000 years. We are exploring the cause of the spatiotemporal occurrence of large earthquakes in the NCB, especially the apparent migration of seismicity from the Weihe-Shanxi grabens around the Ordos to