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Sample records for plate driving crustal

  1. 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...... (lithosphere) recycling. The processes of crust–mantle interaction have created very dissimilar crustal styles in Europe, as seen by its seismic structure, crustal thickness, and average seismic velocities in the basement. Our special focus is on processes responsible for the formation of the thin crust...

  2. Crustal thickness controlled by plate tectonics

    DEFF Research Database (Denmark)

    Artemieva, Irina M.; Meissner, Rolf

    2012-01-01

    The continental crust on Earth cannot be extracted directly from the mantle, and the primary crust extracted directly from an early magma ocean is not preserved on Earth. We review geophysical and geochemical aspects of global crust–mantle material exchange processes and examine the processes which...... magmatism. While both subduction and delamination recycle crustal material into the mantle, mafic magmatism transports mantle material upward and participates in growth of newoceanic and continental crusts and significant structural and chemicalmodification of the latter. We discuss the role of basalt....../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...

  3. How mantle slabs drive plate tectonics.

    Science.gov (United States)

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-04

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  4. Plate tectonics and crustal deformation around the Japanese Islands

    Science.gov (United States)

    Hashimoto, Manabu; Jackson, David D.

    1993-01-01

    We analyze over a century of geodetic data to study crustal deformation and plate motion around the Japanese Islands, using the block-fault model for crustal deformation developed by Matsu'ura et al. (1986). We model the area including the Japanese Islands with 19 crustal blocks and 104 faults based on the distribution of active faults and seismicity. Geodetic data are used to obtain block motions and average slip rates of faults. This geodetic model predicts that the Pacific plate moves N deg 69 +/- 2 deg W at about 80 +/- 3 mm/yr relative to the Eurasian plate which is much lower than that predicted in geologic models. Substantial aseismic slip occurs on the subduction boundaries. The block containing the Izu Peninsula may be separated from the rigid part of the Philippine Sea plate. The faults on the coast of Japan Sea and the western part of the Median Tectonic Line have slip rates exceeding 4 mm/yr, while the Fossa Magna does not play an important role in the tectonics of the central Japan. The geodetic model requires the division of northeastern Japan, contrary to the hypothesis that northeastern Japan is a part of the North American plate. Owing to rapid convergence, the seismic risk in the Nankai trough may be larger than that of the Tokai gap.

  5. Plate tectonics and crustal deformation around the Japanese Islands

    Science.gov (United States)

    Hashimoto, Manabu; Jackson, David D.

    1993-01-01

    We analyze over a century of geodetic data to study crustal deformation and plate motion around the Japanese Islands, using the block-fault model for crustal deformation developed by Matsu'ura et al. (1986). We model the area including the Japanese Islands with 19 crustal blocks and 104 faults based on the distribution of active faults and seismicity. Geodetic data are used to obtain block motions and average slip rates of faults. This geodetic model predicts that the Pacific plate moves N deg 69 +/- 2 deg W at about 80 +/- 3 mm/yr relative to the Eurasian plate which is much lower than that predicted in geologic models. Substantial aseismic slip occurs on the subduction boundaries. The block containing the Izu Peninsula may be separated from the rigid part of the Philippine Sea plate. The faults on the coast of Japan Sea and the western part of the Median Tectonic Line have slip rates exceeding 4 mm/yr, while the Fossa Magna does not play an important role in the tectonics of the central Japan. The geodetic model requires the division of northeastern Japan, contrary to the hypothesis that northeastern Japan is a part of the North American plate. Owing to rapid convergence, the seismic risk in the Nankai trough may be larger than that of the Tokai gap.

  6. Global Plate Driving Forces at 50Ma

    Science.gov (United States)

    Butterworth, N. P.; Quevedo, L. E.; Müller, R. D.

    2011-12-01

    We apply a novel workflow utilising the BEM-Earth geodynamic software to analyse the global coupled plate-mantle dynamics at 50 Ma. A subduction history model based on kinematic data going as far back as 80 Ma was developed using the GPlates software. Advection of the plates into the mantle takes into account the absolute plate motions and lithospheric thickness derived from its age to produce an estimated density heterogeneity initial model condition in the upper mantle. The resulting global model consists of regions of a mantle viscosity and density structure that is post-processed to ensure smooth non-overlapping 3D surfaces. BEM-Earth is then free to evolve the model toward the 50 Ma solution. The evolution of the model is driven by self-consistent buoyancy driven mantle dynamics. We use the model velocity output to quantify changes in forces driving the plates before and after 50 Ma. We analyse the rapid change in plate motion of India, Africa and plates in the Pacific Ocean basin by considering slab-pull, ridge-push and mantle drag/suction forces that naturally result from such top-down driven mantle flow. We compare the results with plate kinematic reconstructions and other geological observations.

  7. Plate tectonics drive tropical reef biodiversity dynamics.

    Science.gov (United States)

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J; de Santana, Charles N; Heine, Christian; Mouillot, David; Bellwood, David R; Pellissier, Loïc

    2016-05-06

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics.

  8. Plate tectonics drive tropical reef biodiversity dynamics

    Science.gov (United States)

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F.; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J.; de Santana, Charles N.; Heine, Christian; Mouillot, David; Bellwood, David R.; Pellissier, Loïc

    2016-01-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics. PMID:27151103

  9. Plate tectonics drive tropical reef biodiversity dynamics

    Science.gov (United States)

    Leprieur, Fabien; Descombes, Patrice; Gaboriau, Théo; Cowman, Peter F.; Parravicini, Valeriano; Kulbicki, Michel; Melián, Carlos J.; de Santana, Charles N.; Heine, Christian; Mouillot, David; Bellwood, David R.; Pellissier, Loïc

    2016-05-01

    The Cretaceous breakup of Gondwana strongly modified the global distribution of shallow tropical seas reshaping the geographic configuration of marine basins. However, the links between tropical reef availability, plate tectonic processes and marine biodiversity distribution patterns are still unknown. Here, we show that a spatial diversification model constrained by absolute plate motions for the past 140 million years predicts the emergence and movement of diversity hotspots on tropical reefs. The spatial dynamics of tropical reefs explains marine fauna diversification in the Tethyan Ocean during the Cretaceous and early Cenozoic, and identifies an eastward movement of ancestral marine lineages towards the Indo-Australian Archipelago in the Miocene. A mechanistic model based only on habitat-driven diversification and dispersal yields realistic predictions of current biodiversity patterns for both corals and fishes. As in terrestrial systems, we demonstrate that plate tectonics played a major role in driving tropical marine shallow reef biodiversity dynamics.

  10. Contemporary Crustal Motion and Deformation of South America Plate

    Institute of Scientific and Technical Information of China (English)

    JIN Shuanggen; ZHU Wenyao

    2003-01-01

    This paper presents the contemporary motion and active deformation of South America plate and relative motion of Nazca-South America plate using space geodetic data. The South America plate is moving at average 14.5 mm/a with an azimuth of 15.2° and shrinking in the west-east at 10. 9 mm/a. The geodetic deformations of sites with respect to the South America plate are in quite good agreement with the estimated deformations from NNR-NUVEL1A, but the deformation of the western South America regions is very large.

  11. Inversion for the driving forces of plate tectonics

    Science.gov (United States)

    Richardson, R. M.

    1983-01-01

    Inverse modeling techniques have been applied to the problem of determining the roles of various forces that may drive and resist plate tectonic motions. Separate linear inverse problems have been solved to find the best fitting pole of rotation for finite element grid point velocities and to find the best combination of force models to fit the observed relative plate velocities for the earth's twelve major plates using the generalized inverse operator. Variance-covariance data on plate motion have also been included. Results emphasize the relative importance of ridge push forces in the driving mechanism. Convergent margin forces are smaller by at least a factor of two, and perhaps by as much as a factor of twenty. Slab pull, apparently, is poorly transmitted to the surface plate as a driving force. Drag forces at the base of the plate are smaller than ridge push forces, although the sign of the force remains in question.

  12. Inversion for the driving forces of plate tectonics

    Science.gov (United States)

    Richardson, R. M.

    1983-01-01

    Inverse modeling techniques have been applied to the problem of determining the roles of various forces that may drive and resist plate tectonic motions. Separate linear inverse problems have been solved to find the best fitting pole of rotation for finite element grid point velocities and to find the best combination of force models to fit the observed relative plate velocities for the earth's twelve major plates using the generalized inverse operator. Variance-covariance data on plate motion have also been included. Results emphasize the relative importance of ridge push forces in the driving mechanism. Convergent margin forces are smaller by at least a factor of two, and perhaps by as much as a factor of twenty. Slab pull, apparently, is poorly transmitted to the surface plate as a driving force. Drag forces at the base of the plate are smaller than ridge push forces, although the sign of the force remains in question.

  13. Earthquake stress drops, ambient tectonic stresses and stresses that drive plate motions

    Science.gov (United States)

    Hanks, T.C.

    1977-01-01

    A variety of geophysical observations suggests that the upper portion of the lithosphere, herein referred to as the elastic plate, has long-term material properties and frictional strength significantly greater than the lower lithosphere. If the average frictional stress along the non-ridge margin of the elastic plate is of the order of a kilobar, as suggested by the many observations of the frictional strength of rocks at mid-crustal conditions of pressure and temperature, the only viable mechanism for driving the motion of the elastic plate is a basal shear stress of several tens of bars. Kilobars of tectonic stress are then an ambient, steady condition of the earth's crust and uppermost mantle. The approximate equality of the basal shear stress and the average crustal earthquake stress drop, the localization of strain release for major plate margin earthquakes, and the rough equivalence of plate margin slip rates and gross plate motion rates suggest that the stress drops of major plate margin earthquakes are controlled by the elastic release of the basal shear stress in the vicinity of the plate margin, despite the existence of kilobars of tectonic stress existing across vertical planes parallel to the plate margin. If the stress differences available to be released at the time of faulting are distributed in a random, white fasbion with a mean-square value determined by the average earthquake stress drop, the frequency of occurrence of constant stress drop earthquakes will be proportional to reciprocal faulting area, in accordance with empirically known frequency of occurrence statistics. ?? 1977 Birkha??user Verlag.

  14. 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.

  15. Crustal Structure across Rivera Plate and Jalisco Block (MEXICO): TsuJal Project

    Science.gov (United States)

    Nuñez-Cornu, F. J.; Nunez, D.; Barba, D. C., Sr.; Trejo, E.; Escalona, F.; Danobeitia, J.; Gutierrez Pena, Q. J.

    2015-12-01

    Located on the western margin of Mexico, the collision zone between Rivera, Cocos and North American plates is a complex tectonic collage with high seismic hazards and potential tsunamigenic sources. During the spring of 2014, within the framework of TSUJAL project, Spanish and Mexican scientists investigated this region with the main objective of defining the crustal architecture of this active margin and recognizing potential structural sources that can trigger earthquakes and tsunamis at the convergence between Rivera plate-Jalisco block with the North American Plate. To achieve these goals, a wide-ranging of geophysical data was acquired in this region both offshore and onshore. In this paper, we present the preliminary results obtained from this project about bathymetric, structural geology and wide-angle seismic data of the southern coast of Bahía de Banderas. A crustal P-wave velocity model for the southern coast of Bahía de Banderas was obtained using WAS data recorded by OBS and land seismic stations for more than 150 km across Rivera Plate and Jalisco Block. The thickness of the slab in this area is about 10 km and presents a dip angle about 8º. Continental crustal thickness below Puerto Vallarta is about 20 km, no evidence of continental Moho was found in this study. This model support that due to the convergence of Rivera Plate against Jalisco Block, the region of Bahía de Banderas is under strong crustal stresses that generate structural lineaments and have the same trends offshore and inland. Most of the seismicity reported can be associated to the main structural lineaments. The Banderas Canyon apparently is in an opening process from west to east, which seems to continue through the Rio Pitillal river valley. There is no seismic or morphological evidence to consider that the Banderas Canyon is a continuation of Vallarta Graben.South of María Cleofas Island, the SC marks the limit between RP and JB, possibly being the result of the RP against JB

  16. Plate Tectonics 2.0: Using GPS to Refine Global Crustal Kinematics and Rewrite Textbooks

    Science.gov (United States)

    Kreemer, C.; Blewitt, G.; Stamps, D. S.; Saria, E.

    2015-12-01

    Any model of the Earth's inner workings should be consistent with the observed motion and deformation at its surface. The whole idea that the entire Earth's surface comprises of a dozen or so tectonic plates with no deformation in between them (as most textbooks will tell you) is embarrassingly outdated. The advent of high-precision GNSS measurements of crustal motion has led to the direct observation of plate motion, the confirmation of plate rigidity, and the refinement of crustal kinematics in diffuse plate boundary zones. With the rapidly growing number of continuous GPS (cGPS) stations (as well as campaign-style measurements) some of the earlier results can now be reassessed while at the same time we can continue to quantify the motion and deformation of a large part of the Earth's surface. We present the latest version (v. 2.2) of the Global Strain Rate Model (GSRM), which is almost entirely constrained by horizontal GPS velocities. The model contains the rigid-body rotations of 50 plates as well as strain rate and vorticity estimates at a high spatial resolution for the ~14% of the Earth's surface that is caught up in between the plates. Resulting global or regional maps of dilatation, vorticity, and strain tensor amplitude and style, are poised to augment standard textbook images of plate motions, and we anticipate that they will foster further scientific and educational inquiry. GSRM v2.2 is constrained by >24,000 velocities. Of those ~7900 were determined by us from time-series that we obtained through a routine processing of all globally available RINEX data. Many of these stations were not installed with the intention to track crustal motions, but often are very usable. This station category is currently the biggest contributor to the data explosion; our solution has >1100 more stations compared with the previous solution of just 18 months ago. We transform to our solution GPS velocities from >250 published studies, >30 more than in the previous

  17. Crustal and upper mantle seismic structure of the Australian Plate, South Island, New Zealand

    Science.gov (United States)

    Melhuish, Anne; Holbrook, W. Steven; Davey, Fred; Okaya, David A.; Stern, Tim

    2005-01-01

    Seismic reflection and refraction data were collected west of New Zealand's South Island parallel to the Pacific-Australian Plate boundary. The obliquely convergent plate boundary is marked at the surface by the Alpine Fault, which juxtaposes continental crust of each plate. The data are used to study the crustal and uppermost mantle structure and provide a link between other seismic transects which cross the plate boundary. Arrival times of wide-angle reflected and refracted events from 13 recording stations are used to construct a 380-km long crustal velocity model. The model shows that, beneath a 2-4-km thick sedimentary veneer, the crust consists of two layers. The upper layer velocities increase from 5.4-5.9 km/s at the top of the layer to 6.3 km/s at the base of the layer. The base of the layer is mainly about 20 km deep but deepens to 25 km at its southern end. The lower layer velocities range from 6.3 to 7.1 km/s, and are commonly around 6.5 km/s at the top of the layer and 6.7 km/s at the base. Beneath the lower layer, the model has velocities of 8.2-8.5 km/s, typical of mantle material. The Mohorovicic discontinuity (Moho) therefore lies at the base of the second layer. It is at a depth of around 30 km but shallows over the south-central third of the profile to about 26 km, possibly associated with a southwest dipping detachment fault. The high, variable sub-Moho velocities of 8.2 km/s to 8.5 km/s are inferred to result from strong upper mantle anisotropy. Multichannel seismic reflection data cover about 220 km of the southern part of the modelled section. Beneath the well-layered Oligocene to recent sedimentary section, the crustal section is broadly divided into two zones, which correspond to the two layers of the velocity model. The upper layer (down to about 7-9 s two-way travel time) has few reflections. The lower layer (down to about 11 s two-way time) contains many strong, subparallel reflections. The base of this reflective zone is the Moho. Bi

  18. The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

    Science.gov (United States)

    Solomon, Sean C.

    During our participation in the NASA Crustal Dynamics Project under NASA contract NAS-27339 and grant NAG5-814 for the period 1982-1991, we published or submitted for publication 30 research papers and 52 abstracts of presentations at scientific meetings. In addition, five M.I.T. Ph.D. students (Eric Bergman, Steven Bratt, Dan Davis, Jeanne Sauber, Anne Sheehan) were supported wholly or in part by this project during their thesis research. Highlights of our research progress during this period include the following: application of geodetic data to determine rates of strain in the Mojave block and in central California and to clarify the relation of such strain to the San Andreas fault and Pacific-North American plate motions; application of geodetic data to infer post seismic deformation associated with large earthquakes in the Imperial Valley, Hebgen Lake, Argentina, and Chile; determination of the state of stress in oceanic lithosphere from a systematic study of the centroid depths and source mechanisms of oceanic intraplate earthquakes; development of models for the state of stress in young oceanic regions arising from the differential cooling of the lithosphere; determination of the depth extent and rupture characteristics of oceanic transform earthquakes; improved determination of earthquake slip vectors in the Gulf of California, an important data set for the estimation of Pacific-North American plate motions; development of models for the state of stress and mechanics of fold-and-thrust belts and accretionary wedges; development of procedures to invert geoid height, residual bathymetry, and differential body wave travel time residuals for lateral variations in the characteristic temperature and bulk composition of the oceanic upper mantle; and initial GPS measurements of crustal deformation associated with the Imperial-Cerro Prieto fault system in southern California and northern Mexico. Full descriptions of the research conducted on these topics may be

  19. The World Stress Map Database Release 2016 - Global Crustal Stress Pattern vs. Absolute Plate Motion

    Science.gov (United States)

    Heidbach, Oliver; Rajabi, Mojtaba; Ziegler, Moritz; Reiter, Karsten

    2016-04-01

    The World Stress Map (WSM) Project was initiated in 1986 under the auspices of the International Lithosphere Program in order to compile the global information on the contemporary crustal stress state. The data come from a wide range of stress indicators such as borehole data (e.g. hydraulic fracturing, borehole breakouts), earthquake focal mechanism solutions, engineering methods (e.g. overcoring), and geological data (e.g. inversion of fault slip measurements). To guarantee the comparability of the different data sources each data record is assessed with the WSM quality ranking scheme. For the 30th anniversary we compiled a new WSM database with 42,410 data records which is an increase by >20,000 data records compared to the WSM 2008 database. In particular we added new data from more than 3,500 deep boreholes and put special emphasis on regions which previously had sparse or no published stress data such as China, Australia, Brazil, Southern Africa, Middle East and Iceland. Furthermore, we fully integrated the Chinese stress database and the Australian stress database. The resulting data increase reveals several areas with regional and local variability of the stress pattern. In particular we re-visited the question whether the plate boundary forces are the key control of the plate-wide stress pattern as indicated by the first release of the WSM in 1989 [Zoback et al, 1989]. As the WSM has now more than 10 times data records and thus a better spatial coverage we first filter the long-wave length stress pattern on a regular grid. We determine at these grid points the difference between absolute plate motion azimuth using the global plate model HS3-NUVEL1A [Gripp and Gordon, 2002] and the mean orientation of the maximum horizontal stress. The preliminary results show that the earlier findings are still valid in principal. However, all plates show in some parts significant deviations from this general trend; some plates such as the Australian Plate show hardly any

  20. A New Comprehensive Model for Crustal and Upper Mantle Structure of the European Plate

    Science.gov (United States)

    Morelli, A.; Danecek, P.; Molinari, I.; Postpischl, L.; Schivardi, R.; Serretti, P.; Tondi, M. R.

    2009-12-01

    We present a new comprehensive model of crustal and upper mantle structure of the whole European Plate — from the North Atlantic ridge to Urals, and from North Africa to the North Pole — describing seismic speeds (P and S) and density. Our description of crustal structure merges information from previous studies: large-scale compilations, seismic prospection, receiver functions, inversion of surface wave dispersion measurements and Green functions from noise correlation. We use a simple description of crustal structure, with laterally-varying sediment and cristalline layers thickness and seismic parameters. Most original information refers to P-wave speed, from which we derive S speed and density from scaling relations. This a priori crustal model by itself improves the overall fit to observed Bouguer anomaly maps, as derived from GRACE satellite data, over CRUST2.0. The new crustal model is then used as a constraint in the inversion for mantle shear wave speed, based on fitting Love and Rayleigh surface wave dispersion. In the inversion for transversely isotropic mantle structure, we use group speed measurements made on European event-to-station paths, and use a global a priori model (S20RTS) to ensure fair rendition of earth structure at depth and in border areas with little coverage from our data. The new mantle model sensibly improves over global S models in the imaging of shallow asthenospheric (slow) anomalies beneath the Alpine mobile belt, and fast lithospheric signatures under the two main Mediterranean subduction systems (Aegean and Tyrrhenian). We map compressional wave speed inverting ISC travel times (reprocessed by Engdahl et al.) with a non linear inversion scheme making use of finite-difference travel time calculation. The inversion is based on an a priori model obtained by scaling the 3D mantle S-wave speed to P. The new model substantially confirms images of descending lithospheric slabs and back-arc shallow asthenospheric regions, shown in

  1. Crustal structure of the Eurasia-Africa plate boundary across the Gloria Fault, North Atlantic Ocean

    Science.gov (United States)

    Batista, Luis; Hübscher, Christian; Terrinha, Pedro; Matias, Luis; Afilhado, Alexandra; Lüdmann, Thomas

    2017-05-01

    The oceanic crustal and uppermost lithospheric mantle structure across the Gloria Fault (GF) transcurrent plate boundary between Africa and Eurasia in the Northeast Atlantic is investigated based on seismic reflection, seismic refraction and wide-angle reflection data. This experiment used 18 ocean bottom stations along an N-S 150 km long traverse together with acquisition of a multichannel seismic reflection profile. Modeling of P and S seismic waves and gravimetric anomalies allowed estimation of P- and S-wave velocities, density, Poisson's ratio and discussion of a compositional model. A five-layer model is proposed in which layers 1-3 correspond to normal sediments through typical oceanic crust layers 2 and 3. Layer 5 yielded mantle velocities above 7.9 km s-1. Layer 4 with 4 km of thickness has Vp velocities between 7.1 and 7.4 km s-1 and is clearly separated from typical oceanic crust and mantle layers. Comparison with natural analogues and published lab measurements suggest that layer 4 can be a mix of lithologies that comply with the estimated P and S velocities and computed Poisson's ratio and densities, such as, olivine cumulates, peridotite, gabbro and hydrated mantle. We favour the tectonic process that produces secondary porosity from which results serpentinization due to sea water circulation in fractures. Structural and seismic stratigraphic interpretation of the reflection profile shows that Neogene to recent tectonic deformation on this segment of the plate boundary concentrated on the southern side of the GF, that is, the Africa plate.

  2. Crustal deformation evidences for viscous coupling and fragmented lithosphere at the Nubia-Iberia plate boundary (Western Mediterranean)

    Science.gov (United States)

    Palano, Mimmo; González, Pablo J.; Fernández, José

    2016-04-01

    A spatially dense crustal velocity field, based on up to 15 years of GNSS observations at more than 380 sites and extensively covering the Iberian Peninsula and Northern Africa, allow us to provide new insights into two main tectonic processes currently occurring in this area. We detected a slow large-scale clockwise rotation of the Iberian Peninsula with respect to a local pole located closely to the northwestern sector of the Pyrenean mountain range (Palano et al., 2015). Although this crustal deformation pattern could suggest a rigid rotating lithosphere block, this model would predict significant shortening along the Western (off-shore Lisbon) and North Iberian margin which cannot totally ruled out but currently is not clearly observed. Conversely, we favour the interpretation that this pattern reflects the quasi-continuous straining of the ductile lithosphere in some sectors of South and Western Iberia in response to viscous coupling of the NW Nubia and Iberian plate boundary in the Gulf of Cádiz. Furthermore, the western Mediterranean basin appears fragmented into independent crustal tectonic blocks, which delimited by inherited lithospheric shear structures and trapped within the Nubia-Eurasia collision, are currently accommodating most of the plate convergence rate. Among these blocks, an (oceanic-like western) Algerian one is currently transferring a significant fraction of the Nubia-Eurasia convergence rate into the Eastern Betics (SE Iberia) and likely causing the eastward motion of the Baleares Promontory. Most of the observed crustal ground deformation can be attributed to processes driven by spatially variable lithospheric plate forces imposed along the Nubia-Eurasia convergence boundary. Nevertheless, the observed deformation field infers a very low convergence rates as observed also at the eastern side of the western Mediterranean, along the Calabro Peloritan Arc, by space geodesy (e.g. Palano, 2015). References Palano M. (2015). On the present

  3. The role of harzburgite layers in the morphology of subducting plates and the behavior of oceanic crustal layers

    Science.gov (United States)

    Yoshida, Masaki

    2014-05-01

    Previous numerical studies of mantle convection focusing on subduction dynamics have indicated that the viscosity contrast between the subducting plate and the surrounding mantle have a primary effect on the behavior of subducting plates. The seismically observed plate stagnation at the base of the mantle transition zone (MTZ) under the Western Pacific and Eastern Eurasia is considered to mainly result from a viscosity increase at the ringwoodite to perovskite + magnesiowüstite (Rw→Pv+Mw) phase decomposition boundary, i.e., the boundary between the upper and lower mantle. The harzburgite layer, which is sandwiched between basaltic crust and depleted peridotite (lherzolite) layers, is a key component of highly viscous, cold oceanic plates. However, the possible sensitivity of the effective viscosity of harzburgite layers in the morphology of subducting plates that are flattened in the MTZ and/or penetrated in the lower mantle has not been examined systematically in previous three-dimensional (3D) numerical modeling studies that consider the viscosity increase at the boundary between the upper and lower mantle. In this study, in order to investigate the role of harzburgite layers in the morphology of subducting plates and the behavior of oceanic crustal layers, I performed a series of numerical simulations of mantle convection with semi-dynamic plate subduction in 3D regional spherical-shell geometry. The results show that a buckled crustal layer is observed under the "heel" of the stagnant slab that begins to penetrate into the lower mantle, regardless of the magnitude of the viscosity contrast between the harzburgite layer and the underlying mantle, when the factor of viscosity increase at the boundary of the upper and lower mantle is larger than 60-100. As the viscosity contrast between the harzburgite layer and the underlying mantle increases, the curvature of buckling is larger. When the viscosity increase at the boundary of the upper and lower mantle and the

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

    Science.gov (United States)

    Liu, Ming-Qi; Li, Zhong-Hai; Yang, Shao-Hua

    2017-09-01

    Subduction channel processes are crucial for understanding the material and energy exchange between the Earth's crust and mantle. 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. In addition, the crustal rocks generally 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 channels; 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. The thick overriding continental plate and the 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, the thin overriding lithosphere and the 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

  5. 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.

  6. The SOUTHERN PUNA Seismic Experiment: Shape of the Subducting Nazca Plate, Areas of Concentrated Mantle and Crustal Earthquakes, and Crustal Focal Mechanisms

    Science.gov (United States)

    Mulcahy, P.; Chen, C.; Kay, S. M.; Brown, L. D.; Alvarado, P. M.; Sandvol, E. A.; Heit, B.; Yuan, X.

    2010-12-01

    The SOUTHERN PUNA Seismic Experiment in the Central Andes between 25° - 28°S and 70° - 65°W recorded data in a 74-instrument array from Dec 07 to Nov 09 with the purpose of evaluating the structure and seismic character of the mantle and crust at the southern end of the Puna-Antiplano Plateau. Hypocenter locations for local and regional mantle earthquakes from 16 months of continuous recording confirm the persistence of the backarc teleseismic Antofalla Gap in intermediate depth mantle seismicity between 25.5° and 27.5°S consistent with the interpretation of a hot mantle wedge under this region. The best located Wadati Benioff Zone events agree with the subducting Nazca Plate contours of Cahill and Isacks (1992) north of 27°S, but show a more abrupt southward shallowing of contours in agreement with the Anderson et al. (2007) contours outlining the projected path of the already subducted Juan Fernandez Ridge. Another prominent feature in the data is the concentration of hypocenters in the Pipanaco nest to the south of the Antofalla Gap between 27° and 29°S. New PUNA results together with available HCMT solutions indicate NW oriented normal and strike-slip faulting in three general clusters within this nest at ~130km, 150km and 180km depth. Hypocenter locations and fault solutions for the Pipanaco Nest suggest flexure associated with steepening of the subducting slab consistent with the revised Wadati Benioff Zone contours. In an area of little to no crustal seismicity in global catalogs over the same time period, hundreds of well-located crustal earthquakes at depths less than 15km were recorded by the PUNA array. Among these earthquakes are three distinct clusters near relatively young volcanic centers. One cluster defines a nest northeast of the < 1 Ma Cerro Blanco caldera. The other two clusters are characterized by large quantities of earthquakes within 24-36 hours (swarms) near the Cerro Galan caldera that last erupted at ~2 Ma and near a ~1 Ma or

  7. Crustal Architecture at the Collision Zone Between Rivera and North American Plates at the Jalisco Block: Tsujal Project

    Science.gov (United States)

    Dañobeitia, Juanjo; Bartolomé, Rafael; Prada, Manel; Nuñez-Cornú, Francisco; Córdoba, Diego; Bandy, William L.; Estrada, F.; Cameselle, Alejandra L.; Nuñez, Diana; Castellón, Arturo; Alonso, José Luis; Mortera, Carlos; Ortiz, Modesto

    2016-09-01

    Processing and analysis of new multichannel seismic records, coincident with wide-angle seismic profiles, acquired in the framework of the TsuJal project allow us to investigate in detail the complex structure of the oceanic domain in the collision zone between Rivera Plate and Block Jalisco at its northern termination. The subducting Rivera Plate, which is overridden by the North American Plate-Jalisco Block, is clearly identified up to 21.5°N (just south of Maria Magdalena Island) as a two clear reflections that we interpret as the interplate and Moho discontinuities. North of the Tres Marias Islands the seismic images display a different tectonic scenario with structures that are consistent with large faulting and rifted margin. A two-dimensional velocity approach for the crustal geometry is achieved using joint refraction/reflection travel time tomography, the uncertainty of the results is assessed by means of Monte Carlo analysis. Our results show an average oceanic crustal thickness of 6-7 km with a moderate increase towards the Jalisco Block, an anomalous thick layers (~3.0 km) displaying a relatively low velocity (~5.5 km/s) underneath Maria Magdalena Rise, and an estimated Moho depth deeper than 15 km in the collision zone between Rivera Plate and Jalisco Block. We have also determined an anomalous crust on the western flank of the Tres Marias Islands, which may be related to the initial phases of continental breakup of the Baja California Peninsula and Mexico mainland. High-resolution bathymetry provides remarkable images of intensive slope instabilities marked by relatively large slides scars of more than 40 km2 extent, and mass-wasting deposits probably triggered by the intense seismicity in the area.

  8. Crustal Architecture at the Collision Zone Between Rivera and North American Plates at the Jalisco Block: Tsujal Project

    Science.gov (United States)

    Dañobeitia, Juanjo; Bartolomé, Rafael; Prada, Manel; Nuñez-Cornú, Francisco; Córdoba, Diego; Bandy, William L.; Estrada, F.; Cameselle, Alejandra L.; Nuñez, Diana; Castellón, Arturo; Alonso, José Luis; Mortera, Carlos; Ortiz, Modesto

    2016-10-01

    Processing and analysis of new multichannel seismic records, coincident with wide-angle seismic profiles, acquired in the framework of the TsuJal project allow us to investigate in detail the complex structure of the oceanic domain in the collision zone between Rivera Plate and Block Jalisco at its northern termination. The subducting Rivera Plate, which is overridden by the North American Plate-Jalisco Block, is clearly identified up to 21.5°N (just south of Maria Magdalena Island) as a two clear reflections that we interpret as the interplate and Moho discontinuities. North of the Tres Marias Islands the seismic images display a different tectonic scenario with structures that are consistent with large faulting and rifted margin. A two-dimensional velocity approach for the crustal geometry is achieved using joint refraction/reflection travel time tomography, the uncertainty of the results is assessed by means of Monte Carlo analysis. Our results show an average oceanic crustal thickness of 6-7 km with a moderate increase towards the Jalisco Block, an anomalous thick layers (~3.0 km) displaying a relatively low velocity (~5.5 km/s) underneath Maria Magdalena Rise, and an estimated Moho depth deeper than 15 km in the collision zone between Rivera Plate and Jalisco Block. We have also determined an anomalous crust on the western flank of the Tres Marias Islands, which may be related to the initial phases of continental breakup of the Baja California Peninsula and Mexico mainland. High-resolution bathymetry provides remarkable images of intensive slope instabilities marked by relatively large slides scars of more than 40 km2 extent, and mass-wasting deposits probably triggered by the intense seismicity in the area.

  9. Crustal motion studies in the southwest Pacific: Geodetic measurements of plate convergence in Tonga, Vanuatu and the Solomon Islands

    Science.gov (United States)

    Phillips, David A.

    The southwest Pacific is one of the most tectonically dynamic regions on Earth. This research focused on crustal motion studies in three regions of active Pacific-Australia plate convergence in the southwest Pacific: Tonga, the New Hebrides (Vanuatu) and the Solomons Islands. In Tonga, new and refined velocity estimates based on more than a decade of Global Positioning System (GPS) measurements and advanced analysis techniques are much more accurate than previously reported values. Convergence rates of 80 to 165 mm/yr at the Tonga trench represent the fastest plate motions observed on Earth. For the first time, rotation of the Fiji platform relative to the Australian plate is observed, and anomalous deformation of the Tonga ridge was also detected. In the New Hebrides, a combined GPS dataset with a total time series of more than ten years led to new and refined velocity estimates throughout the island arc. Impingement of large bathymetric features has led to arc fragmentation, and four distinct tectonic segments are identified. The central New Hebrides arc segment is being shoved eastward relative to the rest of the arc as convergence is partitioned between the forearc (Australian plate) and the backarc (North Fiji Basin) boundaries due to impingement of the d'Entrecasteaux Ridge and associated Bougainville seamount. The southern New Hebrides arc converges with the Australian plate more rapidly than predicted due to backarc extension. The first measurements of convergence in the northern and southernmost arc segments were also made. In the Solomon Islands, a four-year GPS time series was used to generate the first geodetic estimates of crustal velocity in the New Georgia Group, with 57--84 mm/yr of Australia-Solomon motion and 19--39 mm/yr of Pacific-Solomon motion being observed. These velocities are 20--40% lower than predicted Australia-Pacific velocities. Two-dimensional dislocation models suggest that most of this discrepancy can be attributed to locking of

  10. Application of Laser Ranging and VLBI Data to a Study of Plate Tectonic Driving Forces

    Science.gov (United States)

    Solomon, S. C.

    1980-01-01

    The conditions under which changes in plate driving or resistive forces associated with plate boundary earthquakes are measurable with laser ranging or very long base interferometry were investigated. Aspects of plate forces that can be characterized by such measurements were identified. Analytic solutions for two dimensional stress diffusion in a viscoelastic plate following earthquake faulting on a finite fault, finite element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting, and quantitative constraints from modeling of global intraplate stress on the magnitude of deviatoric stress in the lithosphere are among the topics discussed.

  11. Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

    Science.gov (United States)

    Marone, Federica; van der Meijde, Mark; van der Lee, Suzan; Giardini, Domenico

    2003-08-01

    A new map for the Moho discontinuity (EAM02) in the Eurasia-Africa plate boundary region is presented. Reliable results have also been obtained for the southern and eastern Mediterranean Basin, the northern African coasts and the eastern Atlantic Ocean, regions only occasionally considered in studies on the Mediterranean region. The Moho topography model is derived from two independent sets of constraints. Information contained in the fundamental and higher-mode Rayleigh waves obtained from waveform modelling is used to constrain the Moho depth between estimates of crustal thickness taken from published reflection and refraction surveys, gravity studies and receiver function analysis. Strong lateral variations in the Moho topography have been observed in the Mediterranean Sea, confirming the complex evolution of this plate boundary region. In the west, the Moho discontinuity has been found at 15-20 km depth, suggesting extended and, at least in some locations, oceanic crust, while in the east the crust is on average 25-30 km thick. There it is interpreted either as Mesozoic oceanic or thinned Precambrian continental crust covered by thick sedimentary deposits. Standard continental crust (30-35 km) is observed along the eastern part of the northern African coast, while to the west a rapid change from a relatively deep Moho (down to 42 km) below the Atlas Mountain Range to the thin crust of the southwestern Mediterranean Sea has been found. The crust beneath the eastern North Atlantic Ocean can be up to 5 km thicker compared with standard oceanic crust (6 km). The crust has been interpreted to be heterogeneous as a consequence of irregular magma supply at the Mid-Atlantic ridge. In addition, serpentinization of the sub-Moho mantle could contribute to the imaging of apparently anomalous thick oceanic crust. In Europe, the presence of crustal roots (>45 km) beneath the major mountain belts has been confirmed, while thin crust (isostatic compensation at 60 km depth

  12. Crustal Structure at the North Eastern Tip of Rivera Plate, Nayarit- Marias Islands Region: Scenarios and Tectonic Implications. Tsujal Project

    Science.gov (United States)

    Danobeitia, J.; Bartolome, R.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Bandy, W. L.; Prada, M.; Cameselle, A. L.; Nunez, D.; Espindola, J. M.; Estrada, F.; Zamora, A.; Gomez, A.; Ortiz, M.

    2014-12-01

    A primarily analysis of marine geophysical data acquired aboard the RRS James Cook in the framework of the project "Characterization of seismic hazard and tsunami associated with cortical contact structure Rivera Jalisco Block Plate (TSUJAL)" is presented. This survey was held in the region of Nayarit-Tres Marias Islands between February and March 2014. The examination of data recorded by 16 OBS 's, deployed along 4 wide angle seismic profiles is presented, using an airgun-array seismic source of 6800 c.i., which allows sampling the crustal structure to the Moho. The profiles are located along the margin off the Marias Islands: a profile of over 200 km NNW-SSE direction and parallel to the western flank of the Islas Marias Islands and three orthogonal thereto. These perpendicular sections sample the lithosphere from the north of Maria Madre Island with a profile of 100 km length, across Maria Magdalena and Mari Cleofas Islands, with a profile of 50 km long, till south of Maria Cleofas with a profile of 100 km long. Coincident multichannel seismic profiles with refraction ones are also surveyed, although shooting with a source of 3,540 c. i., and acquired with a digital "streamer" of 6.0 km long. Simultaneously, multibeam, parametric and potential field data were recorded during seismic acquisition A first analysis shows an anomalously thickened crust in the western flank of the Marias Islands, as indicated by relatively short pre-critical distances of 30-35 km. While the moderate dip of 7 ° of the subduction of the Pacific oceanic plate favors somehow this effect, the existence of a remnant crustal fragment is also likely. Moreover, the images provided by the parametric sounding show abundant mass wasting deposits suggesting of recent active tectonics, possibly generated by earthquakes with moderate magnitude as those reported in the Marias Islands. This set of geophysical data, not only provide valuable information for the seismogenic characterization and

  13. Deep crustal structure of the northeastern margin of the Arabian plate from seismic and gravity data

    Science.gov (United States)

    Pilia, Simone; Ali, Mohammed; Watts, Anthony; Keats, Brook; Searle, Mike

    2017-04-01

    The United Arab Emirates-Oman mountains constitute a 700 km long, 50 km wide compressional orogenic belt that developed during the Cainozoic on an underlying extensional Tethyan rifted margin. It contains the world's largest and best-exposed thrust sheet of oceanic crust and upper mantle (Semail Ophiolite), which was obducted onto the Arabian rifted continental margin during the Late Cretaceous. Although the shallow structure of the UAE-Oman mountain belt is reasonably well known through the exploitation of a diverse range of techniques, information on deeper structure remains little. Moreover, the mechanisms by which dense oceanic crustal and mantle rocks are emplaced onto less dense and more buoyant continental crust are still controversial and remain poorly understood. The focus here is on an active-source seismic and gravity E-W transect extending from the UAE-mountain belt to the offshore. Seismic refraction data were acquired using the survey ship M/V Hawk Explorer, which was equipped with a large-volume airgun array (7060 cubic inches, 116 liters). About 400 air gun shots at 50-second time interval were recorded on land by eight broadband seismometers. In addition, reflection data were acquired at 20 seconds interval and recorded by a 5-km-long multichannel streamer. Results presented here include an approximately 85 km long (stretching about 35 km onshore and 50 km offshore) P-wave velocity crustal profile derived by a combination of forward modelling and inversion of both diving and reflected wave traveltimes using RAYINVR software. We employ a new robust algorithm based on a Monte Carlo approach (VMONTECARLO) to address the velocity model uncertainties. We find ophiolite seismic velocities of about 5.5 km/s and a thick sedimentary package in the offshore. Furthermore, the velocity model reveals a highly stretched crust with the Moho discontinuity lying at about 20 km. A prestack depth-migrated profile (about 50 km long) coincident with the offshore part

  14. EFFICIENCY ANALYSIS OF DOUBLE CRANK RING-PLATE-TYPE PIN-CYCLOIDAL GEAR PLANETARY DRIVE

    Institute of Scientific and Technical Information of China (English)

    Li Xin; He Weidong; Linda Schmidt; Li Lixing

    2003-01-01

    From the general formula for calculating the efficiency of planetary gear trains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive is derived. To prove the theory, an experimental study has been conducted. The tested value of the efficiency of a sample set of the new-type drive in the experiment agrees with the calculated one. It shows that the new-type drive is of not merely high bearing capacity, but also quite high efficiency.

  15. Zinc Plating Industry Drives Zinc Consumption by Power Grids, Railways and Highways

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>On the afternoon of June 30, at the Chengdu Lead and Zinc Summit, more than 150 partici-pants voted for the product they felt drives zinc consumption the most. 48% went for zinc plat-ing products, 16% voted for zinc oxide,

  16. Performance improvement of rectangular-plate linear ultrasonic motors using dual-frequency drive.

    Science.gov (United States)

    Ming, Yang; Richardson, Robert C; Levesley, Martin C; Walker, Peter G; Watterson, Kevin

    2004-12-01

    To improve the performances of a rectangular-plate linear ultrasonic motor for specific applications, a dual-frequency drive has been proposed and investigated. Through careful design of the rectangular piezoelectric ceramic plate, its first longitudinal resonant frequency coincides with its second lateral bending resonant frequency and is one-third of its higher lateral bending resonant frequency. When a square-wave voltage is used to drive the motor, its first longitudinal and second bending and the higher bending vibration modes are excited. Experimental results show that the maximum thrust force and maximum velocity of the motor are over 170% of those obtained from the single-frequency sine-wave drive when the voltage performance of the motor becomes saturated.

  17. Application of laser ranging and VLBI data to a study of plate tectonic driving forces. [finite element method

    Science.gov (United States)

    Solomon, S. C.

    1980-01-01

    The measurability of changes in plate driving or resistive forces associated with plate boundary earthquakes by laser rangefinding or VLBI is considered with emphasis on those aspects of plate forces that can be characterized by such measurements. Topics covered include: (1) analytic solutions for two dimensional stress diffusion in a plate following earthquake faulting on a finite fault; (2) two dimensional finite-element solutions for the global state of stress at the Earth's surface for possible plate driving forces; and (3) finite-element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting.

  18. Crustal structure and evolution of the southern Juan de Fuca plate from wide-angle seismic data: Insights into the hydration state of the incoming plate off Cascadia subduction zone

    Science.gov (United States)

    Horning, G.; Canales, J. P.; Carbotte, S. M.; Nedimovic, M. R.; Carton, H. D.

    2014-12-01

    A multi-channel seismic reflection and wide-angle refraction seismic experiment was conducted on the Juan de Fuca (JdF) plate to investigate the evolution of the plate from accretion to its subduction at the Cascadia margin. Hydration of the upper crust (UC) of the JdF Plate is well documented, but the state of hydration of the lower crust (LC) and upper mantle (UM] remains to be investigated. A 2D P-wave velocity model of the plate is derived from a joint reflection-refraction travel-time inversion of wide-angle seismic data. Stacked MCS reflection images together with modeled sedimentary velocities define an increasing thickness of sedimentary cover of up to 2.7km. Evidence for bending-related faulting is identified in coincident MCS images both indirectly as faulting in the sedimentary layer [Gibson, et al., this meeting] and directly as dipping crustal reflectors [Han et al., this meeting]. Three first order features are evident in the patterns of crustal velocity variations along the profile. 1: Crustal velocities at 150-250 km landward of the spreading ridge (~5 Ma age) show reduced velocities up to -0.20 km/s in comparison to velocities in younger crust (~3 Ma) 100-150 km from the ridge. This decrease in velocities is coincident with a propagator wake. 2: Upper crustal velocities begin to increase at 170km from the deformation front (DF), which coincides with the first evidence of faulting from sedimentary offsets. Crustal velocities start a decreasing trend at 80km from the DF where fault throws are seen to begin increasing trend landward. 3: UC velocities in the region of directly imaged crustal faulting (40km from trench) increase ~0.5km/s at the DF, while LC velocities decrease ~0.3km/s. The contrasting behavior in the upper and lower crust may indicate that bending promotes hydrothermal circulation in the outer rise. Circulation may be vigorous enough within the sediments/UC so that any residual shallow porosity is clogged with alteration products

  19. Performance evaluation of dual-frequency driving plate ultrasonic motor based on an analytical model.

    Science.gov (United States)

    Pang, Yafei; Yang, Ming; Chen, Xuying; He, Wei; Li, Shiyang; Li, Chaodong

    2011-08-01

    An analytical model is presented to explain the effects of dual-frequency drive on the plate ultrasonic motor in this paper. The experimental prototype is a plate ultrasonic motor using single-phase asymmetric excitation, which can work under a single vibration or multiple vibration modes. Based on the linear superposition of vibrations with two different excitation frequencies, an analytical model is established using the classic Coulomb friction model, and the non-load rotation speed and maximum stall torque are deduced. Moreover, some crucial parameters such as preload and dead-zone in dual-frequency superposition model are identified or modified automatically by searching for the maximum correlation coefficient between simulation and experimental data using single-frequency drive. It is found that simulation and experiment results agree well when no excitation frequency component is at resonance.

  20. Investigating crustal deformation associated with the North America-Pacific plate boundary in southern California with GPS geodesy

    Science.gov (United States)

    Spinler, Joshua C.

    The three largest earthquakes in the last 25 years in southern California occurred on faults located adjacent to the southern San Andreas fault, with the M7.3 1992 Landers and M7.1 1999 Hector Mine earthquakes occurring in the eastern California shear zone (ECSZ) in the Mojave Desert, and the M7.2 2010 El Mayor-Cucapah earthquake occurring along the Laguna Salada fault in northern Baja California, Mexico. The locations of these events near to but not along the southern San Andreas fault (SSAF) is unusual in that the last major event on the SSAF occurred more than 300 years ago, with an estimated recurrence interval of 215 +/- 25 years. The focus of this dissertation is to address the present-day deformation field along the North America-Pacific plate boundary in southern California and northern Baja California, through the analysis of GPS data, and elastic block and viscoelastic earthquake models to determine fault slip rates and rheological properties of the lithosphere in the plate boundary zone. We accomplish this in three separate studies. The first study looks at how strain is partitioned northwards along-strike from the southern San Andreas fault near the Salton Sea. We find that estimates for slip-rates on the southern San Andreas decrease from ~23 mm/yr in the south to ~8 mm/yr as the fault passes through San Gorgonio Pass to the northwest, while ~13-18 mm/yr of slip is partitioned onto NW-SE trending faults of the ECSZ where the Landers and Hector Mine earthquakes occurred. This speaks directly to San Andreas earthquake hazards, as a reduction in the slip rate would require greater time between events to build up enough slip deficit in order to generate a large magnitude earthquake. The second study focuses on inferring the rheological structure beneath the Salton Trough region. This is accomplished through analysis of postseismic deformation observed using a set of the GPS data collected before and after the 2010 El Mayor-Cucapah earthquake. By

  1. Modelling and Simulation of Three Level Inverters for Main Drive of the Plate Mill Rolling Stand

    Directory of Open Access Journals (Sweden)

    Gasiyarov Vadim R.

    2016-01-01

    Full Text Available This paper addresses a modelling and a simulation of three level inverters for main drive of the plate mill rolling stand. The main purpose of the article is to develop of a mathematical description of the three level voltage source inverter based on a space vector pulse width modulation and to simulate a consumption current by the main electric drive based on 18-pulse rectification circuit. A twelve-megawatt synchronous motor as a load has been used. The modelling results were simulated at the Matlab/Simulink program. It can allow us to estimate an electromagnetic compatibility of the main electric drive based on transients of the consumption current. The research results can be used to assess the electromagnetic compatibility of powerful three level natural point clamped converters with different types of the space vector pulse width modulation on a load or a grid.

  2. Crustal Structure of the Caribbean-South American Diffuse Plate Boundary: Subduction Zone Migration and Polarity Reversal Along BOLIVAR Profile 64W

    Science.gov (United States)

    Clark, S. A.; Levander, A.; Magnani, M.; Zelt, C. A.; Sawyer, D. S.; Ave Lallemant, H. G.

    2005-12-01

    The BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) project is an NSF funded, collaborative seismic experiment in the southeast Caribbean region. The purpose of the project is to understand the diffuse plate boundary created by the oblique collision between the Caribbean and South American plates. Profile 64W of the BOLIVAR experiment, a 450 km-long, N-S transect onshore and offshore Venezuela located at ~64°W longitude, images the deep crustal structures formed by this collision. The active source components of profile 64W include 300 km of MCS reflection data, 33 coincident OBSs, and 344 land seismic stations which recorded 7500 offshore airgun shots and 2 explosive land shots. Results from the reflection and refraction seismic data along 64W show complex crustal structure across the entire span of the diffuse plate boundary. The onshore portion of 64W crosses the fold and thrust belt of the Serrania del Interior, which formed at ~16 Ma by collision of the Caribbean forearc with the northern South American passive margin. Underlying the Serrania del Interior is a south-vergent, remnant Lesser Antillean subduction zone. As this Lesser Antilles subduction impinged on continental crust, it caused a polarity reversal and jump offshore to the north. Convergence was initially localized in the closure and inversion of the Grenada Basin. However, subduction could not develop because of the ~20-km-thick crust of the Aves Ridge; instead, north-vergent subduction initiated further to the north, where ~12-km-thick Caribbean oceanic crust of the Venezuela Basin began to subduct beneath the Aves Ridge in the Pliocene (~4 Ma) and appears to continue subducting today. Between the remnant subduction zone and the modern one, the El Pilar and Coche dextral strike-slip faults accommodate most of the transform motion of the plate boundary. From the Serrania del Interior to the Aves Ridge, ~260 km of accreted orogenic float comprises the diffuse

  3. DRIVING VEHICLES SUBJECT TO A CUSTOMS RESTRICTIONS AGREEMENT WITH ORDINARY SWISS NUMBER PLATES

    CERN Multimedia

    Relations with the Host States Service

    2001-01-01

    The Swiss Permanent Mission to the International Organisations in Geneva has just confirmed to CERN that it is not necessary to hold a carte de légitimation or an attestation de fonctions issued by the Swiss Federal Department of Foreign Affairs to drive a vehicle subject to a customs restrictions agreement (engagement douanier), i.e. purchased or imported free of tax and customs duty, provided that the vehicle concerned is registered on ordinary Swiss number plates and not on diplomatic plates. We should like to remind you that the documents published by the Relations with the Host States Service since 1996 can be consulted on the Service's Web pages (http://www.cern.ch/relations/), which are updated as soon as new information is received from the Authorities of the Host States.

  4. Intraplate deformation, stress in the lithosphere and the driving mechanism for plate motions

    Science.gov (United States)

    Albee, Arden L.

    1993-01-01

    The initial research proposed was to use the predictions of geodynamical models of mantle flow, combined with geodetic observations of intraplate strain and stress, to better constrain mantle convection and the driving mechanism for plate motions and deformation. It is only now that geodetic observations of intraplate strain are becoming sufficiently well resolved to make them useful for substantial geodynamical inference to be made. A model of flow in the mantle that explains almost 90 percent of the variance in the observed longwavelength nonhydrostatic geoid was developed.

  5. Application of GPS in Crustal Deformation and Plate Motion Monitoring%GPS在地壳形变和板块运动监测中的应用

    Institute of Scientific and Technical Information of China (English)

    钱进; 韩志云; 林学峰; 吴星

    2013-01-01

    简要介绍了GPS在现代板块构造运动中的应用及其进展:GPS对于地球参考框架的建立和维持发挥着重要的作用;大量地壳运动监测网的建立使得GPS成为监测地壳运动强有力的工具;全球性、全天候的GPS卫星测高将在现代板块构造运动的监测中发挥重要作用;高精度的IGS产品为国际动力学服务提供坚实的数据基础.%In this paper,a brief introduction of GPS in modem plate tectonics and its progress is presented-the role GPS plays in the establishment and maintenance of the Earth's frame of reference,establishment of large crustal movement monitoring network which makes GPS monitoring crustal movement the strong tool,the important role the global and all-weather GPS satellite altimetry plays in the modern plate tectonic movement monitoring,and the solid data base the highly precise IGS products provide for the international dynamics services.

  6. Plate convergence, crustal delamination, extrusion tectonics and minimization of shortening work as main controlling factors of the recent Mediterranean deformation pattern

    Directory of Open Access Journals (Sweden)

    D. Babbucci

    1997-06-01

    Full Text Available It is argued that the time-space distribution of major post middle Miocene deformation events in the Central-Eastern Mediterranean region, deduced from the relevant literature, can be coherently explained as a consequence of the convergence between the Africa/Arabia and Eurasia blocks. This plate convergence has mainly been accommodated by the consumption of the thinnest parts of the Northern African (Ionian and Levantine basins and peri-Adriatic margins. During each evolutionary phase the space distribution of trench zones is controlled by the basic physical requirement of minimizing the work of horizontal forces, induced by plate convergence, against the resisting forces, i.e., the cohesion of the upper brittle crustal layer and the buoyancy forces at the consuming boundaries. The significant changes of tectonic styles which determined the transition from one phase to the next, like those which occurred around the Messinian and the late Pliocene-early Pleistocene, were determined by the suture of consuming boundaries. When such an event occurs, the system must activate alternative consuming processes to accommodate the convergence of the major confining blocks. The observed deformations in the study area suggest that this tectonic reorganization mostly developed by the lateral extrusion of crustal wedges away from the sutured borders. This mechanism allowed the translation of maximum horizontal stresses from the locked collisional fronts to the zones where consumable lithosphere was still present, in order to activate the next consuming processes. The extensional episodes which led to the formation of basins and troughs in the Tyrrhenian and Aegean zones are interpreted as secondary effects of the outward escape of crustal wedges, like those which occurred in response to longitudinal compressional regimes in the Apennines and Aegean regions.

  7. A Review of the Isotopic and Trace Element Evidence for Mantle and Crustal Processes in the Hadean and Archean: implications for the Onset of Plate Tectonic Subduction

    Science.gov (United States)

    Smart, Katie A.; Tappe, Sebastian; Stern, Richard A.; Webb, Susan J.; Ashwal, Lewis D.

    2016-03-01

    Plate tectonics plays a vital role in the evolution of our planet. Geochemical analysis of Earth’s oldest continental crust suggests that subduction may have begun episodically about 3.8 to 3.2 billion years ago, during the early Archaean or perhaps more than 3.8 billion years ago, during the Hadean. Yet, mantle rocks record evidence for modern-style plate tectonics beginning only in the late Archaean, about 3 billion years ago. Here we analyse the nitrogen abundance, as well as the nitrogen and carbon isotopic signatures of Archaean placer diamonds from the Kaapvaal craton, South Africa, which formed in the upper mantle 3.1 to 3.5 billion years ago. We find that the diamonds have enriched nitrogen contents and isotopic compositions compared with typical mantle values. This nitrogen geochemical fingerprint could have been caused by contamination of the mantle by nitrogen-rich Archaean sediments. Furthermore, the carbon isotopic signature suggests that the diamonds formed by reduction of an oxidized fluid or melt. Assuming that the Archaean mantle was more reduced than the modern mantle, we argue that the oxidized components were introduced to the mantle by crustal recycling at subduction zones. We conclude, on the basis of evidence from mantle-derived diamonds, that modern-style plate tectonics operated as early as 3.5 billion years ago.

  8. The interpretation of crustal dynamics data in terms of plate interactions and active tectonics of the Anatolian plate and surrounding regions in the Middle East

    Science.gov (United States)

    Toksoz, M. Nafi; Reilinger, Robert

    1992-01-01

    A detailed study was made of the consequences of the Arabian plate convergence against Eurasia and its effects on the tectonics of Anatolia and surrounding regions of the eastern Mediterranean. A primary source of information is time rates of change of baseline lengths and relative heights determined by repeated SLR measurements. These SLR observations are augmented by a network of GPS stations in Anatolia, Aegea, and Greece, established and twice surveyed since 1988. The existing SLR and GPS networks provide the spatial resolution necessary to reveal the details of ongoing tectonic processes in this area of continental collision. The effort has involved examining the state of stress in the lithosphere and relative plate motions as revealed by these space based geodetic measurements, seismicity, and earthquake mechanisms as well as the aseismic deformations of the plates from conventional geodetic data and geological evidence. These observations are used to constrain theoretical calculations of the relative effects of: (1) the push of the Arabian plate; (2) high topography of Eastern Anatolia; (3) the geometry and properties of African-Eurasian plate boundary; (4) subduction under the Hellenic Arc and southwestern Turkey; and (5) internal deformation and rotation of the Anatolian plate.

  9. Tsujal Marine Survey: Crustal Characterization of the Rivera Plate-Jalisco Block Boundary and its Implications for Seismic and Tsunami Hazard Assessment

    Science.gov (United States)

    Bartolome, R.; Danobeitia, J.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Cameselle, A. L.; Estrada, F.; Prada, M.; Bandy, W. L.

    2014-12-01

    During the spring of 2014, a team of Spanish and Mexican scientists explored the western margin of Mexico in the frame of the TSUJAL project. The two main objectives were to characterize the nature and structure of the lithosphere and to identify potential sources triggering earthquakes and tsunamis at the contact between Rivera plate-Jalisco block with the North American Plate. With these purposes a set of marine geophysical data were acquired aboard the RRS James Cook. This work is focus in the southern part of the TSUJAL survey, where we obtain seismic images from the oceanic domain up to the continental shelf. Thus, more than 800 km of MCS data, divided in 7 profiles, have been acquired with a 6km long streamer and using an air-gun sources ranging from 5800 c.i. to 3540 c.i. Furthermore, a wide-angle seismic profile of 190 km length was recorded in 16 OBS deployed perpendicular to the coast of Manzanillo. Gravity and magnetic, multibeam bathymetry and sub-bottom profiler data were recorded simultaneously with seismic data in the offshore area. Preliminary stacked MCS seismic sections reveal the crustal structure in the different domains of the Mexican margin. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate boundary between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define the subduction plane (TS06b). These strong reflections which we interpret as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Another clear pattern observed within the first second of the MCS data shows evidences of a bottom

  10. Mixing in mantle convection models with self-consistent plate tectonics and melting and crustal production: Application to mixing in the early Earth

    Science.gov (United States)

    Tackley, Paul

    2016-04-01

    It is generally thought that the early Earth's mantle was hotter than today, which using conventional convective scalings should have led to vigorous convection and mixing. Geochemical observations, however, suggest that mixing was not as rapid as would be expected, leading to the suggestion that early Earth had stagnant lid convection (Debaille et al., EPSL 2013). Additionally, the mantle's thermal evolution is difficult to explain using conventional scalings because early heat loss would have been too rapid, which has led to the hypothesis that plate tectonics convection does not follow the conventional convective scalings (Korenaga, GRL 2003). One physical process that could be important in this context is partial melting leading to crustal production, which has been shown to have the major effects of buffering mantle temperature and carrying a significant fraction of the heat from hot mantle (Nakagawa and Tackley, EPSL 2012), making plate tectonics easier (Lourenco et al., submitted), and causing compositional differentiation of the mantle that can buffer core heat loss (Nakagawa and Tackley, GCubed 2010). Here, the influence of this process on mantle mixing is examined, using secular thermo-chemical models that simulate Earth's evolution over 4.5 billion years. Mixing is quantified both in terms of how rapidly stretching occurs, and in terms of dispersion: how rapidly initially close heterogeneities are dispersed horizontally and vertically through the mantle. These measures are quantified as a function of time through Earth's evolution. The results will then be related to geochemically-inferred mixing rates.

  11. Investigating the deformation of upper crustal faults at the N-Chilean convergent plate boundary at different scales using high-resolution topography datasets and creepmeter measurements

    Science.gov (United States)

    Ewiak, O.; Victor, P.; Ziegenhagen, T.; Oncken, O.

    2012-04-01

    The Chilean convergent plate boundary is one of the tectonically most active regions on earth and prone to large megathrust earthquakes as e. g. the 2010 Mw 8.8 Maule earthquake which ruptured a mature seismic gap in south-central Chile. In northern Chile historical data suggests the existence of a seismic gap between Arica and Mejillones Peninsula (MP), which has not ruptured since 1877. Further south, the 1995 Mw 8.0 Antofagasta earthquake ruptured the subduction interface between MP and Taltal. In this study we investigate the deformation at four active upper plate faults (dip-slip and strike-slip) located above the coupling zone of the subduction interface. The target faults (Mejillones Fault - MF, Salar del Carmen Fault - SCF, Cerro Fortuna Fault - CFF, Chomache Fault - CF) are situated in forearc segments, which are in different stages of the megathrust seismic cycle. The main question of this study is how strain is accumulated in the overriding plate, what is the response of the target faults to the megathrust seismic cycle and what are the mechanisms / processes involved. The hyper arid conditions of the Atacama desert and the extremely low erosion rates enable us to investigate geomorphic markers, e .g. fault scarps and knickpoints, which serve as a record for upper crustal deformation and fault activity about ten thousands years into the past. Fault scarp data has been acquired with Differential-GPS by measuring high-resolution topographic profiles perpendicular to the fault scarps and along incised gullies. The topographic data show clear variations between the target faults which possibly result from their position within the forearc. The surveyed faults, e. g. the SCF, exhibit clear along strike variations in the morphology of surface ruptures attributed to seismic events and can be subdivided into individual segments. The data allows us to distinguish single, composite and multiple fault scarps and thus to detect differences in fault growth initiated

  12. GPS Measurements of Crustal Deformation in Lebanon: Implication for Current Kinematics of the Sinaï Plate.

    Science.gov (United States)

    Vergnolle, M.; Jomaa, R.; Brax, M.; Menut, J. L.; Sursock, A.; Elias, A. R.; Mariscal, A.; Vidal, M.; Cotte, N.

    2016-12-01

    The Levant fault is a major strike-slip fault bounding the Arabia and the Sinaï plates. Its kinematics, although understood in its main characteristics, remains partly unresolved in its quantification, especially in the Lebanese restraining bend. We present a GPS velocity field based on survey GPS data acquired in Lebanon (1999, 2002, 2010) and on continuous GPS data publicly available in the Levant area. To complete the measurements along the Levant fault, we combine our velocity field with previously published velocity fields. First, from our velocity field, we derive two velocity profiles, across the Lebanese fault system, which we analyze in terms of elastic strain accumulation. Despite the uncertainty on the locking depth of the main strand of the Levant fault, small lateral fault slip rates (2-4mm/yr) are detected on each profile, with a slight slip rate decrease (Lebanon. Small compression (Lebanon, is also suggested. Second, we analyze the combined GPS velocity field in the Sinaï tectonic framework. We evaluate how well the Sinaï plate motion is described with an Euler pole. Due to heterogeneous velocity errors (5 times smaller for cGPS velocities wrt sGPS velocities), a unique pole estimation using all the data provides good statistical results. However, the residuals show systematic deviations at central and northern sGPS stations. Using only the velocities at these stations, the estimated pole is significantly different from the unique pole at 95% confidence level. This analysis highlights the difficulty to robustly resolve the rigid Sinaï plate motion while the uncertainties on the velocities are heterogeneous. New sGPS measurements on existing sites should improve the solution and help to conclude.

  13. Crustal structure and seismicity distribution adjacent to the Pacific and North American plate boundary in southern California

    OpenAIRE

    Hauksson, Egill

    2000-01-01

    New three-dimensional (3-D) V_P and V_P/V_S models are determined for southern California using P and S-P travel times from local earthquakes and controlled sources. These models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the Pacific-North America plate boundary. The models extend from the U.S.-Mexico border in the south to the southernmost Coast Ranges and Sierra Nevada in the north and have a 15-km horizontal grid sp...

  14. Four-plate piezoelectric actuator driving a large-diameter special optical fiber for nonlinear optical microendoscopy.

    Science.gov (United States)

    Wang, Ying; Li, Zhi; Liang, Xiaobao; Fu, Ling

    2016-08-22

    In nonlinear optical microendoscope (NOME), a fiber with excellent optical characteristics and a miniature scanning mechanism at the distal end are two key components. Double-clad fibers (DCFs) and double-clad photonic crystal fibers (DCPCFs) have shown great optical characteristics but limited vibration amplitude due to large diameter. Besides reducing the damping of fiber cantilever, optimizing the structural of the actuator for lower energy dissipation also contributes to better driving capability. This paper presented an optimized actuator for driving a particular fiber cantilever in the view point of energy. Firstly, deformation energy of a bending fiber cantilever operating in resonant mode is investigated. Secondly, strain and stress analyses revealed that the four-plate actuator achieved lower energy dissipation. Then, finite-element simulations showed that the large-diameter fiber yielded an adequate vibration amplitude driven by a four-plate actuator, which was confirmed by experiments of our home-made four-plate actuator prototypes. Additionally, a NOME based on a DCPCF with a diameter of 350 μm driven by four-plate piezoelectric actuator has been developed. The NOME can excite and collect intrinsic second-harmonic and two-photon fluorescence signals with the excitation power of 10-30 mW and an adequate field of view of 200 μm, which suggest great potential applications in neuroscience and clinical diagnoses.

  15. A Comparative Analysis of Seismological and Gravimetric Crustal Thicknesses below the Andean Region with Flat Subduction of the Nazca Plate

    Directory of Open Access Journals (Sweden)

    Mario E. Gimenez

    2009-01-01

    Full Text Available A gravimetric study was carried out in a region of the Central Andean Range between 28∘ and 32∘ south latitudes and from 72∘ and 66∘ west longitudes. The seismological and gravimetrical Moho models were compared in a sector which coincides with the seismological stations of the CHARGE project. The comparison reveals discrepancies between the gravity Moho depths and those obtained from seismological investigations (CHARGE project, the latter giving deeper values than those resulting from the gravimetric inversion. These discrepancies are attenuated when the positive gravimetric effect of the Nazca plate is considered. Nonetheless, a small residuum of about 5 km remains beneath the Cuyania terrane region, to the east of the main Andean chain. This residuum could be gravimetrically justified if the existence of a high density or eclogitized portion of the lower crust is considered. This result differed from the interpretations from Project “CHARGE” which revealed that the entire inferior crust extending from the Precordillera to the occidental “Sierras Pampeanas” could be “eclogitized”. In this same sector, we calculated the effective elastic thickness (Te of the crust. These results indicated an anomalous value of Te = 30 km below the Cuyania terrane. This is further conclusive evidence of the fact that the Cuyania terrane is allochthonous, for which also geological evidences exist.

  16. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NARCIS (Netherlands)

    van Benthem, S.A.C.|info:eu-repo/dai/nl/304833657; Govers, R.|info:eu-repo/dai/nl/108173836; Wortel, R.|info:eu-repo/dai/nl/068439202

    2014-01-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second

  17. What drives microplate motion and deformation in the northeastern Caribbean plate boundary region?

    NARCIS (Netherlands)

    van Benthem, S.A.C.|info:eu-repo/dai/nl/304833657; Govers, R.|info:eu-repo/dai/nl/108173836; Wortel, R.|info:eu-repo/dai/nl/068439202

    2014-01-01

    The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second dr

  18. Plate tectonics: Crustal recycling evolution

    Science.gov (United States)

    Magni, Valentina

    2017-09-01

    The processes that form and recycle continental crust have changed through time. Numerical models reveal an evolution from extensive recycling on early Earth as the lower crust peeled away, to limited recycling via slab break-off today.

  19. Is subduction really in the plate tectonics driving seat, or do two other global mechanisms do the driving? A review in the 'deep-keeled cratons' frame for global dynamics

    Science.gov (United States)

    Osmaston, M. F.

    2012-04-01

    mantle boundary layer habitually assumed, but its LVZ content gives it (i) residual heat content, (ii) corresponding buoyancy, and (iii) a flexural strength which demands a reconsideration of its mode of downbend, hitherto widely regarded as flexural, but still be able to explain outer rises and their differences. Solutions for (ii) and (iii) are convincingly supported by widespread exposure of the resulting rocks in the Alps, telling us how they and other UHP metamorphic mountain belts have been built [11]. I will illustrate the essential points. In particular, the buoyancy (ii) provides the upward mechanical contact essential for the shallow basal subduction tectonic erosion of the upper plate as preparation of thin imbricate crustal slices to subduct to UHP. And a seismologically supported through-plate step-faulting mode of downbend copes with the flexure problem (iii) and provides the tectonic erosion mechanism. In tackling these matters, important intrinsic properties of the materials are, notably:- (1) the thermal conductivity of non-migrating interstitial melt is >20 times less than its parent rock, so the LVZ heat is effectively trapped during the plate's journey across the ocean, only to be released when subduction raises the pressure and the melt freezes; (2) the garnet-to-spinel peridotite phase change, typically at 50 to 90 km depth, gives some 50 times more volume change per joule than pure expansivity, and it does so with the big force of solid-state recrystallization. This force is the crack-wall push-apart force provided by our thick-plate MOR model, which thereby develops at least an order more ridge push than the divergent flow model. We now consider the post-downbend evolution of the subducting plate, recognizing both the heat content of its ex-LVZ material and that, within the 2-layer mantle picture established by the plate dynamics of 'deep-keeled cratons' [2 - 5], there is no substantial mantle transport across the 660 km level. Examination of

  20. A novel plate type linear piezoelectric actuator using dual-frequency drive

    Science.gov (United States)

    Liu, Zhen; Yao, Zhiyuan; Jian, Yue; Li, Xiang

    2017-09-01

    In this paper, a novel rectangular structure linear piezoelectric actuator that utilizes two lower order decoupled vibration modes is developed and investigated. A noticeable trait of the linear piezoelectric actuator is that it can realize bi-directional motion by changing the vibration mode of the stator with different exciting frequencies. Modal and harmonic analysis of the stator are performed by the finite element method to determine the actuator structure and dimensions and stablished that the driving tip trajectories are diagonal lines. The direction of the actuator is controlled by the orientation of the diagonal motion generated at the driving tip. When the diagonal motion is inclined right as the driving tip approaches the linear guide, it will move the linear guide right. Correspondingly, the linear guide will move to the left, if the diagonal motion inclines left. In addition, a prototype linear piezoelectric actuator is fabricated and experimented. The results of the experiments indicate that the actuator has good mechanical output characteristics. Typical output of the prototype is no-load speed of 504 mm s-1 and maximum mechanical load of 6.5 kg.

  1. Operando lithium plating quantification and early detection of a commercial LiFePO4 cell cycled under dynamic driving schedule

    Science.gov (United States)

    Anseán, D.; Dubarry, M.; Devie, A.; Liaw, B. Y.; García, V. M.; Viera, J. C.; González, M.

    2017-07-01

    Lithium plating is considered one of the most detrimental phenomenon in lithium ion batteries (LIBs), as it increases cell degradation and might lead to safety issues. Plating induced LIB failure presents a major concern for emerging applications in transportation and electrical energy storage. Hence, the necessity to operando monitor, detect and analyze lithium plating becomes critical for safe and reliable usage of LIB systems. Here, we report in situ lithium plating analyses for a commercial graphite||LiFePO4 cell cycled under dynamic stress test (DST) driving schedule. We designed a framework based on incremental capacity (IC) analysis and mechanistic model simulations to quantify degradation modes, relate their effects to lithium plating occurrence and assess cell degradation. The results show that lithium plating was induced by large loss of active material on the negative electrode that eventually led the electrode to over-lithiate. Moreover, when lithium plating emerged, we quantified that the loss of lithium inventory pace was increased by a factor of four. This study illustrates the benefits of the proposed framework to improve lithium plating analysis. It also discloses the symptoms of lithium plating formation, which prove valuable for novel, online strategies on early lithium plating detection.

  2. Temperature gradients drive radial fluid flow in Petri dishes and multiwell plates.

    Science.gov (United States)

    Lindsay, Stephen M; Yin, John

    2016-06-01

    Liquid in a Petri dish spontaneously circulates in a radial pattern, even when the dish is at rest. These fluid flows have been observed and utilized for biological research, but their origins have not been well-studied. Here we used particle-tracking to measure velocities of radial fluid flows, which are shown to be linked to evaporation. Infrared thermal imaging was used to identify thermal gradients at the air-liquid interface and at the bottom of the dish. Two-color ratiometric fluorescence confocal imaging was used to measure thermal gradients in the vertical direction within the fluid. A finite-element model of the fluid, incorporating the measured temperature profiles, shows that buoyancy forces are sufficient to produce flows consistent with the measured particle velocity results. Such flows may arise in other dish or plate formats, and may impact biological research in positive or negative ways.

  3. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    ’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through......Copenhagen Business School (CBS) finds itself needing to address the issue of English-medium instruction for its increasing number of foreign exchange and full degree students. With internationalisation as a main pillar of the institution’s agenda, there are concerns whether the teaching faculty...... the Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature...

  4. PLATE

    DEFF Research Database (Denmark)

    Kling, Joyce; Hjulmand, Lise-Lotte

    2008-01-01

    Copenhagen Business School (CBS) finds itself needing to address the issue of English-medium instruction for its increasing number of foreign exchange and full degree students. With internationalisation as a main pillar of the institution’s agenda, there are concerns whether the teaching faculty......’s level of English is sufficient for the increasing number of courses offered in English each semester. This paper addresses these concerns and describes a pilot project initiated in 2003 at CBS to gauge the overall English language proficiency of those teaching content courses in English. Through...... the Project in Language Assessment for Teaching in English (PLATE) language professionals from CBS’s Language Center observe teachers and provide feedback using evaluation criteria from the Common European Framework for Reference (CEFR) supplemented by some additional criteria which take the LSP nature...

  5. Determination of recent horizontal crustal movements and deformations of African and Eurasian plates in western Mediterranean region using geodetic-GPS computations extended to 2006 (from 1997) related to NAFREF and AFREF frames.

    Science.gov (United States)

    Azzouzi, R.

    2009-04-01

    Determination of recent horizontal crustal movements and deformations of African and Eurasian plates in western Mediterranean region using geodetic-GPS computations extended to 2006 (from 1997) related to NAFREF and AFREF frames. By: R. Azzouzi*, M. Ettarid*, El H. Semlali*, et A. Rimi+ * Filière de Formation en Topographie Institut Agronomique et Vétérinaire Hassan II B.P. 6202 Rabat-Instituts MAROC + Département de la Physique du Globe Université Mohammed V Rabat MAROC This study focus on the use of the geodetic spatial technique GPS for geodynamic purposes generally in the Western Mediterranean area and particularly in Morocco. It aims to exploit this technique first to determine the geodetic coordinates on some western Mediterranean sites. And also this technique is used to detect and to determine movements cross the boundary line between the two African and Eurasian crustal plates on some well chosen GPS-Geodynamics sites. It will allow us also to estimate crustal dynamic parameters of tension that results. These parameters are linked to deformations of terrestrial crust in the region. They are also associated with tectonic constraints of the study area. The usefulness of repeated measurements of these elements, the estimate of displacements and the determination of their temporal rates is indisputable. Indeed, sismo-tectonique studies allow a good knowledge of the of earthquake processes, their frequency their amplitude and even of their prediction in the world in general and in Moroccan area especially. They allow also contributing to guarantee more security for all most important management projects, as projects of building great works (dams, bridges, nuclear centrals). And also as preliminary study, for the most important joint-project between Europe and Africa through the Strait of Gibraltar. For our application, 23 GPS monitoring stations under the ITRF2000 reference frame are chosen in Eurasian and African plates. The sites are located around the

  6. Monitoring Crustal Movement of the Coastal Zone in Eastern China with GPS Technique

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    In this paper, various dominating factors affecting crustal movement of the coastal zone in eastern China are analyzed, and major characteristics of crustal movement are summarized. Subduction of the pacific plate and Philippine plate and southeastward "escape" of Qinghai-Tibet plateau are believed to be dominating factors affecting crustal movement of that zone. Undoubtedly, it is a best way to monitor this kind of large-scale crustal movement with GPS technique. The feasibility of monitoring crustal m...

  7. Geological evidence for the geographical pattern of mantle return flow and the driving mechanism of plate tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, W.

    1982-08-10

    Tectonic features at the earth's surface can be used to test models for mantle return flow and to determine the geographic pattern of this flow. A model with shallow return and deep continental roots places the strongest constraints on the geographical pattern of return flow and predicts recognizable surface manifestations. Because of the progressive shrinkage of the Pacific (averaging 0.5 km/sup 2//yr over the last 180 m.y.) this model predicts upper mantle outflow through the three gaps in the chain of continents rimming the Pacific (Carribbean, Drake Passage, Australian-Antartic gap). In this model, upper mantle return flow streams originating at the western Pacific trenches and at the Java Trench meet south of Australia, filling in behind this rapidly northward-moving continent and provding an explanation for the negative bathymetric and gravity anomalies of the 'Australian-Antarctic-Discordance'. The long-continued tectonic movements toward the east that characterize the Caribbean and the eastenmost Scotia Sea may be produced by viscous coupling to the predicted Pacific outflow through the gaps, and the Caribbean floor slopes in the predicted direction. If mantle outflow does not pass through the gaps in the Pacific perimeter, it must pass beneath three seismic zones (Central America, Lesser Antiles, Scotia Sea); none of these seismic zones shows foci below 200 km. Mantle material flowing through the Caribbean and Drake Passage gaps would supply the Mid-Atlantic Ridge, while the Java Trench supplies the Indian Ocean ridges, so that deep-mantle upwellings need not be centered under spreading ridges and therefore are not required to move laterally to follow ridge migrations. The analysis up to this point suggests that upper mantle return flow is a response to the motion of the continents. The second part of the paper suggest driving mechanism for the plate tectonic process which may explain why the continents move.

  8. Reports on crustal movements and deformations

    Science.gov (United States)

    Cohen, S. C.; Peck, T.

    1981-01-01

    Studies of tectonic plate motions, regional crustal deformations, strain accumulation and release, deformations associated with earthquakes and fault motion, and micro-plate motion, were collected and are summarized. To a limited extent, papers dealing with global models of current plate motions and crustal stress are included. The data base is restricted to articles appearing in reveiwed technical journals during the years 1970-1980. The major journals searched include: Journal of Geophysical Research (solid earth), Tectonophysics, Bulletin of the Seismological Society of America, Geological Society of America Bulletin, Geophysical Journal of the Royal Astronomical Society, and the Journal of Geology.

  9. Geochemical and zircon isotopic evidence for extensive high level crustal contamination in Miocene to mid-Pleistocene intra-plate volcanic rocks from the Tengchong field, western Yunnan, China

    Science.gov (United States)

    Li, Linlin; Shi, Yuruo; Williams, Ian S.; Anderson, J. Lawford; Wu, Zhonghai; Wang, Shubing

    2017-08-01

    SHRIMP zircon Pb/U dating of Cenozoic volcanic rocks in the Tengchong area, western Yunnan Province, China, shows that the dacite and andesitic breccia lavas from Qushi village were intruded at 480 ± 10 ka and 800 ± 40 ka, respectively. Moreover, Pb/U dating of trachyandesite from Tuantian village and olivine basalt from Wuhe village give weighted mean 206Pb/238U ages of 2.82 ± 0.08 Ma and 12.28 ± 0.30 Ma. Corrections for initial 230Th disequilibrium of zircon were used for the former two younger ages. The Tengchong volcanic rocks have a large range of SiO2 (48.6-66.9 wt.%) and mostly belong to a high-K calc-alkaline series. The lavas originated from heterogeneous sources and were modified by subsequent fractional crystallization. The REE and other trace element patterns of the Tengchong volcanic rocks resemble magmas having a large component of continental crust. All have similar degrees of LREE and HREE fractionation and are enriched in LILE, La, Ce and Pb, with depletions in Nb, Ta, Ti, Sr and P relative to primitive mantle. Zircon δ18O values of 6.96 ± 0.17 and 7.01 ± 0.24‰ and highly varied negative εHf(t) values of - 1.5 to - 11.0 and - 10.3 to - 13.7, as well as the presence of inherited zircon grains in the studied samples, indicate that the magmas contain crustal material on a large scale. The Tengchong volcanic rocks have HFSE ratios (e.g., Nb/Ta, La/Nb, Zr/Y) similar to continental flood basalts, indicative of an intra-plate extensional tectonic setting. Widespread distributed faults might have facilitated upwelling of mantle-derived melts and eruptions from shallow crustal magma chambers to form the large volcanic field.

  10. Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm.

    Science.gov (United States)

    Ming, Yang; Hanson, Ben; Levesley, Martin C; Walker, Peter G; Watterson, Kevin G

    2006-12-01

    In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).

  11. On crustal movement in Mt. Qomolangma area

    Institute of Scientific and Technical Information of China (English)

    陈俊勇; 王泽民; 庞尚益; 张骥; 张全德

    2002-01-01

    Mt. Qomolangma lies in the collision zone between the fringe of Eurasia plate and Indian plate. The crustal movement there is still very active so far. In the past three decades China carried out five geodetic campaigns in Mt. Qomolangma and its north vicinal area, independently or cooperatively with other countries, including triangulation, leveling, GPS positioning, atmospheric, astronomical and gravity measurements. On the basis of the observation results achieved in the campaigns the crustal movements in the area were studied and explored. A non-stationary phenomenon both in time and space of the crustal vertical movement in the area is found. There seems to be some relevance between the phenomenon of non-stationary in time and seismic episode in China. The phenomenon of non-stationary in space is possibly relevant to the no-homo- geneity of crustal medium and non-uniform absorption of terrestrial stress. The horizontal crustal movement in the area is in the direction of NEE at a speed of 6—7 cm per year, and the trend of strike slip movement is manifested evidently in the collision fringe of Indian plate and Qinghai-Xizang block.

  12. A review of structural patterns and melting processes in the Archean craton of West Greenland: Evidence for crustal growth at convergent plate margins as opposed to non-uniformitarian models

    Science.gov (United States)

    Polat, Ali; Wang, Lu; Appel, Peter W. U.

    2015-11-01

    The Archean craton of West Greenland consists of many fault-bounded Eoarchean to Neoarchean tectonic terranes (crustal blocks). These tectonic terranes are composed mainly of tonalite-trondhjemite-granodiorite (TTG) gneisses, granitic gneisses, metavolcanic-dominated supracrustal belts, layered anorthositic complexes, and late- to post-tectonic granites. Rock assemblages and geochemical signatures in these terranes suggest that they represent fragments of dismembered oceanic island arcs, consisting mainly of TTG plutons, tholeiitic to calc-alkaline basalts, boninites, picrites, and cumulate layers of ultramafic rocks, gabbros, leucogabbros and anorthosites, with minor sedimentary rocks. The structural characteristics of the terrane boundaries are consistent with the assembly of these island arcs through modern style of horizontal tectonics, suggesting that the Archean craton of West Greenland grew at convergent plate margins. Several supracrustal belts that occur at or near the terrane boundaries are interpreted as relict accretionary prisms. The terranes display fold and thrust structures and contain numerous 10 cm to 20 m wide bifurcating, ductile shear zones that are characterized by a variety of structures including transposed and redistributed isoclinal folds. Geometrically these structures are similar to those occurring on regional scales, suggesting that the Archean craton of West Greenland can be interpreted as a continental scale accretionary complex, such as the Paleozoic Altaids. Melting of metavolcanic rocks during tectonic thickening in the arcs played an important role in the generation of TTGs. Non-uniformitarian models proposed for the origin of Archean terranes have no analogs in the geologic record and are inconsistent with structural, lithological, petrological and geochemical data collected from Archean terranes over the last four decades. The style of deformation and generation of felsic rocks on outcrop scales in the Archean craton of West

  13. Geodynamical basis for crustal deformation under the Tibetan Plateau

    Science.gov (United States)

    Liu, H.-S.

    1985-01-01

    Plate tectonics and satellite-derived gravity data are used to examine crustal deformation under the Tibetan Plateau. A spherical harmonic analysis is given for the global plate boundary system, and the crustal stresses in Tibet are calculated from satellite gravity data. A superimposed stress system is constructed. The stress patterns reveal that the cold downwelling mantle convection flow beneath southern Tibet pulls the Indian plate down but applies a bending moment on the end of the plate to uplift and support the mass of the Himalayas.

  14. The Study on the Block Boundary's Driving Forces and Tectonic Stress Field of China Mainland and Its Adjacent Areas Using GPS Data

    Institute of Scientific and Technical Information of China (English)

    Du Zhi-xing; Qu Ji-kun; Han Bao-min; Jin Feng-xiang; Chai Yan-ju

    2003-01-01

    After reviewing the inversion study on the driving forces of China mainland and its adjacent areas, the inversion computation is made by means of genetic finite element method and covering complex method based on the displacement observations of the Crustal Movement Observation Network of China. The whole procedures of inversion study, including parameter selection, computation conditions, inversion analysis and interpretation, are given out in details. Then some conclusions are drawn:(1)the main driving forces acting on China mainland are still from the collision of Indian plate with Eurasian plate;(2)the driving forces of Pacific plate and Philippine plate are significant to the eastern China;(3)the back basin of Japan sea arc is continuously extending;(4)the forces from north prevent the northern motion of China.

  15. 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.

  16. Crustal growth in subduction zones

    Science.gov (United States)

    Vogt, Katharina; Castro, Antonio; Gerya, Taras

    2015-04-01

    There is a broad interest in understanding the physical principles leading to arc magmatisim at active continental margins and different mechanisms have been proposed to account for the composition and evolution of the continental crust. It is widely accepted that water released from the subducting plate lowers the melting temperature of the overlying mantle allowing for "flux melting" of the hydrated mantle. However, relamination of subducted crustal material to the base of the continental crust has been recently suggested to account for the growth and composition of the continental crust. We use petrological-thermo-mechanical models of active subduction zones to demonstrate that subduction of crustal material to sublithospheric depth may result in the formation of a tectonic rock mélange composed of basalt, sediment and hydrated /serpentinized mantle. This rock mélange may evolve into a partially molten diapir at asthenospheric depth and rise through the mantle because of its intrinsic buoyancy prior to emplacement at crustal levels (relamination). This process can be episodic and long-lived, forming successive diapirs that represent multiple magma pulses. Recent laboratory experiments of Castro et al. (2013) have demonstrated that reactions between these crustal components (i.e. basalt and sediment) produce andesitic melt typical for rocks of the continental crust. However, melt derived from a composite diapir will inherit the geochemical characteristics of its source and show distinct temporal variations of radiogenic isotopes based on the proportions of basalt and sediment in the source (Vogt et al., 2013). Hence, partial melting of a composite diapir is expected to produce melt with a constant major element composition, but substantial changes in terms of radiogenic isotopes. However, crustal growth at active continental margins may also involve accretionary processes by which new material is added to the continental crust. Oceanic plateaus and other

  17. Flat-slab subduction, whole crustal faulting, and geohazards in Alaska: Targets for Earthscope

    Science.gov (United States)

    Gulick, S. P.; Pavlis, T. L.; Bruhn, R. L.; Christeson, G. L.; Freymueller, J. T.; Hansen, R. A.; Koons, P. O.; Pavlis, G. L.; Roeske, S.; Reece, R.; van Avendonk, H. J.; Worthington, L. L.

    2010-12-01

    Crustal structure and evolution illuminated by the Continental Dynamics ST. Elias Erosion and tectonics Project (STEEP) highlights some fundamental questions about active tectonics processes in Alaska including: 1) what are the controls on far field deformation and lithospheric stabilization, 2) do strike slip faults extend through the entire crust and upper mantle and how does this influence mantle flow, and 3) how does the transition from “normal” subduction of the Pacific along the Aleutians to flat slab subduction of the Yakutat Terrane beneath southeast and central Alaska to translation of the Yakutat Terrane past North American in eastern Alaska affect geohazard assessment for the north Pacific? Active and passive seismic studies and geologic fieldwork focusing on the Yakutat Terrane show that the Terrane ranges from 15-35 km thick and is underthrusting the North American plate from the St. Elias Mountains to the Alaska Range (~500 km). Deformation of the upper plate occurs within the offshore Pamplona Zone fold and thrust belt, and onshore throughout the Robinson Mountains. Deformation patterns, structural evolution, and the sedimentary products of orogenesis are fundamentally influenced by feedbacks with glacial erosion. The Yakutat megathrust extends beneath Prince William Sound such that the 1964 Mw 9.2 great earthquake epicenter was on this plate boundary and jumped to the adjacent Aleutian megathrust coseismically; this event illuminates the potential for transitional tectonic systems to enhance geohazards. The northern, southern, and eastern limits of the Yakutat microplate are strike-slip faults that, where imaged, appear to cut the entire crustal section and may allow for crustal extrusion towards the Bering Sea. Yakutat Terrane effects on mantle flow, however, have been suggested to cross these crustal features to allow for far-field deformation in the Yukon, Brooks Range, and Amerasia Basin. From the STEEP results it is clear that the Yakutat

  18. SAHKE geophysical transect reveals crustal and subduction zone structure at the southern Hikurangi margin, New Zealand

    Science.gov (United States)

    Henrys, S.; Wech, A.; Sutherland, R.; Stern, T.; Savage, M.; Sato, H.; Mochizuki, K.; Iwasaki, T.; Okaya, D.; Seward, A.; Tozer, B.; Townend, J.; Kurashimo, E.; Iidaka, T.; Ishiyama, T.

    2013-07-01

    The Seismic Array Hikurangi Experiment (SAHKE) investigated the structure of the forearc and subduction plate boundary beneath the southern North Island along a 350 km transect. Tomographic inversion of first-arrival travel times was used to derive a well-resolved 15-20 km deep P wave image of the crust. The refracted phases and migrated reflection events image subducting slab geometry and crustal structure. In the west, Australian Plate Moho depth decreases westward across the Taranaki Fault system from 35 to ˜28-30 km. In the east, subducted Pacific Plate oceanic crust is recognized to have a positive velocity gradient, but becomes less distinct beneath the Tararua Ranges, where the interface increases in dip at about 15 km depth from 15°. This bend in the subducted plate is associated with vertical clusters in seismicity, splay fault branching, and low-velocity high-attenuation material that we interpret to be an underplated subduction sedimentary channel. We infer that a step down in the decollément transfers slip on the plate interface at the top of a subduction channel to the oceanic crust and drives local uplift of the Tararua Ranges. Reflections from the Wairarapa Fault show that it is listric and soles into the top of underplated sediments, which in turn abut the Moho of the overriding plate at ˜32 km depth, near the downdip end of the strongly locked zone. The change in dip of the Hikurangi subduction interface is spatially correlated with the transition from geodetically determined locked to unlocked areas of the plate interface.

  19. Research on Rare Earth Permanent Magnet Electromagnetic Drive in Tobacco Leaf Spring Plate Vibration Sieve System%基于稀土永磁电磁驱动的烟叶簧板式振筛系统的研究

    Institute of Scientific and Technical Information of China (English)

    林河; 祝荣壮; 袁兴

    2016-01-01

    烟草企业在用的烟叶簧板式振筛多为电机驱动,噪声大、能耗高、维护成本大、维护难度高;分析了直线电机原理,引入稀土永磁电磁驱动理论,通过控制器驱动电磁线圈,吸合永磁机构带动簧板往复运动;电磁驱动方式可实现无摩擦、低噪声、低耗能等绿色环保新理念振筛驱动方式,实际运行效果也很好。%The most of tobacco leaf spring plate vibration sieves are driven by motors in the current tobacco factories, such that op-erating noise, high energy consumption, high maintenance cost and maintenance difficulty exist in it. This paper analyses the princi-ple of the linear motor and introduces the theory of rare earth permanent magnet electromagnetic drive into it. The control er electro-magnetic coil and permanent magnetic actuator are used to drive the spring plate reciprocating movement; Electromagnetic drive mode withno friction, low noise, low energy consumption can be realized. It meets the new idea of green environmental protection such as the drive mode of the vibration sieve, its running effect is very good.

  20. Reports on crustal movements and deformations. [bibliography

    Science.gov (United States)

    Cohen, S. C.; Peck, T.

    1983-01-01

    This Catalog of Reports on Crustal Movements and Deformation is a structured bibliography of scientific papers on the movements of the Earth crust. The catalog summarizes by various subjects papers containing data on the movement of the Earth's surface due to tectonic processes. In preparing the catalog we have included studies of tectonic plate motions, spreading and convergence, microplate rotation, regional crustal deformation strain accumulation and deformations associated with the earthquake cycle, and fault motion. We have also included several papers dealing with models of tectonic plate motion and with crustal stress. Papers which discuss tectonic and geologic history but which do not present rates of movements or deformations and papers which are primarily theoretical analyses have been excluded from the catalog. An index of authors cross-referenced to their publications also appears in the catalog. The catalog covers articles appearing in reviewed technical journals during the years 1970-1981. Although there are citations from about twenty journals most of the items come from the following publications: Journal of Geophysical Research, Tectonophysics, Geological Society of America Bulletin of the Seismological Society of America, Nature, Science, Geophysical Journal of the Royal Astronomical Society, Earth and Planetary Science Letters, and Geology.

  1. Current crustal movement in Chinese mainland

    Institute of Scientific and Technical Information of China (English)

    王琪

    2003-01-01

    The quantification of tectonic deformation in the Eastern and Central Asia is of great significance for the study on global plate motion and lithospheric dynamics. In the past four years, the velocity field of horizontal crustal movement for the Chinese mainland has been established for the first time thanks to the intensified GPS measurements and its improved accuracy. The velocity field derived from GPS measurements delineates the patterns of tectonic deformation in the Chinese mainland in the unprecedented detail, and thus reveals the new features of the ongoing tectonic process resulted from the collision of Indian plate to Eurasian plate. Meanwhile, the surface offset induced by two strong earthquakes occurred in Chinese mainland was sampled precisely using InSAR technique.

  2. Crustal structure and active tectonics in the Eastern Alps

    DEFF Research Database (Denmark)

    Brückl, E.; Behm, M.; Decker, K.

    2010-01-01

    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...... 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...... and underthusting of AD mantle below PA from southwest to northeast. The Moho fragmentation correlates well with major upper crustal structures and is supported by gravity, seismic, and geodetic data. An analysis of crustal thickening suggests that active convergence is associated with continued thrusting...

  3. Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

    Science.gov (United States)

    Regalla, Christine; Fisher, Donald M.; Kirby, Eric; Furlong, Kevin P.

    2013-12-01

    Tectonic erosion along convergent plate boundaries, whereby removal of upper plate material along the subduction zone interface drives kilometer-scale outer forearc subsidence, has been purported to explain the evolution of nearly half the world's subduction margins, including part of the history of northeast Japan. Here, we evaluate the role of plate boundary dynamics in driving forearc subsidence in northeastern Japan. A synthesis of newly updated analyses of outer forearc subsidence, the timing and kinematics of upper plate deformation, and the history of plate convergence along the Japan trench demonstrate that the onset of rapid fore-arc tectonic subsidence is contemporaneous with upper plate extension during the opening of the Sea of Japan and with an acceleration in convergence rate at the trench. In Plio-Quaternary time, relative uplift of the outer forearc is contemporaneous with contraction across the arc and a decrease in plate convergence rate. The coincidence of these changes across the forearc, arc, backarc system appears to require an explanation at the scale of the entire plate boundary. Similar observations along other western Pacific margins suggest that correlations between forearc subsidence and major changes in plate kinematics are the rule, rather than the exception. We suggest that a significant component of forearc subsidence at the northeast Japan margin is not the consequence of basal tectonic erosion, but instead reflects dynamic changes in plate boundary geometry driven by temporal variations in plate kinematics. If correct, this model requires a reconsideration of the mass balance and crustal recycling of continental crust at nonaccretionary margins.

  4. Crustal deformation across the Southern Patagonian Icefield observed by GNSS

    Science.gov (United States)

    Richter, A.; Ivins, E.; Lange, H.; Mendoza, L.; Schröder, L.; Hormaechea, J. L.; Casassa, G.; Marderwald, E.; Fritsche, M.; Perdomo, R.; Horwath, M.; Dietrich, R.

    2016-10-01

    Geodetic GNSS observations at 43 sites well distributed over the Southern Patagonian Icefield region yield site velocities with a mean accuracy of 1 mm/a and 6 mm/a for the horizontal and vertical components, respectively. These velocities are analyzed to reveal the magnitudes and patterns of vertical and horizontal present-day crustal deformation as well as their primary driving processes. The observed vertical velocities confirm a rapid uplift, with rates peaking at 41 mm/a, causally related to glacial-isostatic adjustment (GIA). They yield now an unambiguous preference between two competing GIA models. Remaining discrepancies between the preferred model and our observations point toward an effective upper mantle viscosity even lower than 1.6 ṡ1018 Pas and effects of lateral rheological heterogeneities. An analysis of the horizontal strain and strain-rate fields reveals some complex superposition, with compression dominating in the west and extension in the east. This deformation field suggests significant contributions from three processes: GIA, a western interseismic tectonic deformation field related to plate subduction, and an extensional strain-rate field related to active Patagonian slab window tectonics.

  5. Evolution of crustal thickening in the central Andes, Bolivia

    Science.gov (United States)

    Eichelberger, Nathan; McQuarrie, Nadine; Ryan, Jamie; Karimi, Bobak; Beck, Susan; Zandt, George

    2015-09-01

    Paleoelevation histories from the central Andes in Bolivia have suggested that the geodynamic evolution of the region has been punctuated by periods of large-scale lithospheric removal that drive rapid increases in elevation at the surface. Here, we evaluate viable times and locations of material loss using a map-view reconstruction of the Bolivian orocline displacement field to forward-model predicted crustal thicknesses. Two volumetric models are presented that test assumed pre-deformation crustal thicknesses of 35 km and 40 km. Both models predict that modern crustal thicknesses were achieved first in the northern Eastern Cordillera (EC) by 30-20 Ma but remained below modern in the southern EC until ≤10 Ma. The Altiplano is predicted to have achieved modern crustal thickness after 10 Ma but only with a pre-deformation thickness of 50 km, including 10 km of sediment. At the final stage, the models predict 8-25% regional excess crustal volume compared to modern thickness, largely concentrated in the northern EC. The excess predicted volume from 20 to 0 Ma can be accounted for by: 1) crustal flow to the WC and/or Peru, 2) localized removal of the lower crust, or 3) a combination of the two. Only models with initial crustal thicknesses >35 km predict excess volumes sufficient to account for potential crustal thickness deficits in Peru and allow for lower crustal loss. However, both initial thickness models predict that modern crustal thicknesses were achieved over the same time periods that paleoelevation histories indicate the development of modern elevations. Localized removal of lower crust is only necessary in the northern EC where crustal thickness exceeds modern by 20 Ma, prior to paleoelevation estimates of modern elevations by 15 Ma. In the Altiplano, crustal thicknesses match modern values at 10 Ma and can only exceed modern values by 5 Ma, post-dating when modern elevations were thought to have been established. Collectively, these models predict that

  6. Obliquity along plate boundaries

    Science.gov (United States)

    Philippon, Mélody; Corti, Giacomo

    2016-12-01

    Most of the plate boundaries are activated obliquely with respect to the direction of far field stresses, as roughly only 8% of the plate boundaries total length shows a very low obliquity (ranging from 0 to 10°, sub-orthogonal to the plate displacement). The obliquity along plate boundaries is controlled by (i) lateral rheological variations within the lithosphere and (ii) consistency with the global plate circuit. Indeed, plate tectonics and magmatism drive rheological changes within the lithosphere and consequently influence strain localization. Geodynamical evolution controls large-scale mantle convection and plate formation, consumption, and re-organization, thus triggering plate kinematics variations, and the adjustment and re-orientation of far field stresses. These geological processes may thus result in plate boundaries that are not perpendicular but oblique to the direction of far field stresses. This paper reviews the global patterns of obliquity along plate boundaries. Using GPlate, we provide a statistical analysis of present-day obliquity along plate boundaries. Within this framework, by comparing natural examples and geological models, we discuss deformation patterns and kinematics recorded along oblique plate boundaries.

  7. Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates

    Science.gov (United States)

    Mahatsente, Rezene

    2017-08-01

    An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (tectonics. In this case, the ridge-push related stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.

  8. Crustal-thickness variations in the central Andes

    Science.gov (United States)

    Beck, Susan L.; Zandt, George; Myers, Stephen C.; Wallace, Terry C.; Silver, Paul G.; Drake, Lawrence

    1996-05-01

    We estimated the crustal thickness along an east-west transect across the Andes at lat 20°S and along a north-south transect along the eastern edge of the Altiplano from data recorded on two arrays of portable broadband seismic stations (BANJO and SEDA). Waveforms of deep regional events in the downgoing Nazca slab and teleseismic earthquakes were processed to isolate the P-to-S converted phases from the Moho in order to compute the crustal thickness. We found crustal-thickness variations of nearly 40 km across the Andes. Maximum crustal thicknesses of 70 74 km under the Western Cordillera and the Eastern Cordillera thin to 32 38 km 200 km east of the Andes in the Chaco Plain. The central Altiplano at 20°S has crustal thicknesses of 60 to 65 km. The crust also appears to thicken from north (16°S, 55 60 km) to south (20°S, 70 74 km) along the Eastern Cordillera. The Subandean zone crust has intermediate thicknesses of 43 to 47 km. Crustal-thickness predictions for the Andes based on Airy-type isostatic behavior show remarkable overall correlation with observed crustal thickness in the regions of high elevation. In contrast, at the boundary between the Eastern Cordillera and the Subandean zone and in the Chaco Plain, the crust is thinner than predicted, suggesting that the crust in these regions is supported in part by the flexural rigidity of a strong lithosphere. With additional constraints, we conclude that the observation of Airy-type isostasy is consistent with thickening associated with compressional shortening of a weak lithosphere squeezed between the stronger lithosphere of the subducting Nazca plate and the cratonic lithosphere of the Brazilian craton.

  9. GPS derived Crustal Deformation and Strain determination in India

    Directory of Open Access Journals (Sweden)

    Abhay P. Singh,

    2011-06-01

    Full Text Available The theory of Plate tectonics has revolutionized the way thinking about the processes of Earth. According to this theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The edges of these plates, where they move against each other, are sites of intense tectonic activity, suchas earthquakes, volcanism, and mountain building. It is well known that Indian Plate is currently moving in the northeast direction, while the Eurasian Plate is moving north. This is causing the Indian and Eurasian Plate to deform at the point of contact besides its interior. Modern geophysical and space geodetic techniques such asseismology and GPS (Global Positioning system, have become important tools in the study of the deformation in the Earth due to tectonic processes, leading to earthquakes. Geodesy has provided an important role for plate tectonics study with high temporal resolution of the plate movements, particular from space technologies such as GPS and VLBI. The Global Positioning System (GPS provides accurate measurements of the rate of displacement of crustal. Indeed, the GPS velocity field can only be compared to finite strain if one assumes adeformation mechanism and that the style of deformation has been the same over long periods of geological time. For study of crustal deformation National Center of Mineralogy and Petrology, University of Allahabad, Allahabad installed highly efficient and accurate LEICA GRX1200 Pro receiver at Ghoorpur near to Allahabad. This instrument is also equipped withMET3A sensor to record pressure, temperature, humidity at regular interval of 30 second. The Latitude and longitude of the GPS sites is 25.21N, 81.28E.

  10. 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...... such as lower crust/lithospheric mantle delamination in the Variscan Europe and large-scale rifting across the entire West Siberian basin. The results are summarized in a series of maps of lateral variations in crustal properties, including the depth to the basement and to the Moho, average crustal velocity......, thicknesses of different crustal layers, and Pn seismic velocities....

  11. Continental tectonics in the aftermath of plate tectonics

    Science.gov (United States)

    Molnar, Peter

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

  12. Continental tectonics in the aftermath of plate tectonics

    Science.gov (United States)

    Molnar, Peter

    1988-01-01

    It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

  13. THE CRUSTAL STRUCTURE OF ELLESMERE ISLAND FROM RECEIVER FUNCTION MODELLING

    DEFF Research Database (Denmark)

    Schiffer, Christian; Stephenson, Randell Alexander; Oakey, Gordon

    Atlantic region. The intraplate Eurekan orogeny in the Cenozoic caused additional crustal shortening in the area, related to the opening of Baffin Bay, the North Atlantic and the Arctic Ocean basins and the complex plate tectonic responses to these plate boundary reconfigurations. Geophysically Ellesmere...... stations was installed and maintained from 2010 to 2012 with the support of the Geological Survey of Canada and SEIS-UK. The two closest permanent stations (Eureka and Alert) in the area as well as two wide angle seismic profiles across the Canadian Arctic margin have been included to the interpretation...

  14. Tectonic implications of Mars crustal magnetism.

    Science.gov (United States)

    Connerney, J E P; Acuña, M H; Ness, N F; Kletetschka, G; Mitchell, D L; Lin, R P; Reme, H

    2005-10-18

    Mars currently has no global magnetic field of internal origin but must have had one in the past, when the crust acquired intense magnetization, presumably by cooling in the presence of an Earth-like magnetic field (thermoremanent magnetization). A new map of the magnetic field of Mars, compiled by using measurements acquired at an approximately 400-km mapping altitude by the Mars Global Surveyor spacecraft, is presented here. The increased spatial resolution and sensitivity of this map provide new insight into the origin and evolution of the Mars crust. Variations in the crustal magnetic field appear in association with major faults, some previously identified in imagery and topography (Cerberus Rupes and Valles Marineris). Two parallel great faults are identified in Terra Meridiani by offset magnetic field contours. They appear similar to transform faults that occur in oceanic crust on Earth, and support the notion that the Mars crust formed during an early era of plate tectonics.

  15. Crustal evolution in Asia: Correlations and connections

    Science.gov (United States)

    Tsunogae, Toshiaki; Kwon, Sanghoon; Santosh, M.

    2016-11-01

    The Asian region records multiple subduction, accretion and collision processes related to the breakup of Gondwana and Pangea, and the ongoing formation of the future supercontinent Amasia. The oldest geological record of Asia is preserved in Archean crustal fragments which were welded together by later collisional events related to the assembly of several supercontinents. The Asian region also records recent geological events such as volcanic activities and mega-earthquakes related to subduction of oceanic plates along active continental margins and collision of microplates. This region is thus regarded as an excellent field laboratory for examining the evolution of continental crust and cratons, formation and destruction of continents and supercontinents, and related metallogenic and surface environmental processes.

  16. 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

  17. Central Andean crustal structure from receiver function analysis

    Science.gov (United States)

    Ryan, Jamie; Beck, Susan; Zandt, George; Wagner, Lara; Minaya, Estela; Tavera, Hernado

    2016-07-01

    The Central Andean Plateau (15°-27°S) is a high plateau in excess of 3 km elevation, associated with thickened crust along the western edge of the South America plate, in the convergent margin between the subducting Nazca plate and the Brazilian craton. We have calculated receiver functions using seismic data from a recent portable deployment of broadband seismometers in the Bolivian orocline (12°-21°S) region and combined them with waveforms from 38 other stations in the region to investigate crustal thickness and crust and mantle structures. Results from the receiver functions provide a more detailed map of crustal thickness than previously existed, and highlight mid-crustal features that match well with prior studies. The active volcanic arc and Altiplano have thick crust with Moho depths increasing from the central Altiplano (65 km) to the northern Altiplano (75 km). The Eastern Cordillera shows large along strike variations in crustal thickness. Along a densely sampled SW-NE profile through the Bolivian orocline there is a small region of thin crust beneath the high peaks of the Cordillera Real where the average elevations are near 4 km, and the Moho depth varies from 55 to 60 km, implying the crust is undercompensated by 5 km. In comparison, a broader region of high elevations in the Eastern Cordillera to the southeast near 20°S has a deeper Moho at 65-70 km and appears close to isostatic equilibrium at the Moho. Assuming the modern-day pattern of high precipitation on the flanks of the Andean plateau has existed since the late Miocene, we suggest that climate induced exhumation can explain some of the variations in present day crustal structure across the Bolivian orocline. We also suggest that south of the orocline at 20°S, the thicker and isostatically compensated crust is due to the absence of erosional exhumation and the occurrence of lithospheric delamination.

  18. Beyond plate tectonics - Looking at plate deformation with space geodesy

    Science.gov (United States)

    Jordan, Thomas H.; Minster, J. Bernard

    1988-01-01

    The requirements that must be met by space-geodetic systems in order to constrain the horizontal secular motions associated with the geological deformation of the earth's surface are explored. It is suggested that in order to improve existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of less than 3 mm/yr. Results indicate that measuring the velocities between crustal blocks to + or - 5 mm/yr on 100-km to 1000-km scales can produce geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States.

  19. Beyond plate tectonics - Looking at plate deformation with space geodesy

    Science.gov (United States)

    Jordan, Thomas H.; Minster, J. Bernard

    1988-01-01

    The requirements that must be met by space-geodetic systems in order to constrain the horizontal secular motions associated with the geological deformation of the earth's surface are explored. It is suggested that in order to improve existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of less than 3 mm/yr. Results indicate that measuring the velocities between crustal blocks to + or - 5 mm/yr on 100-km to 1000-km scales can produce geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States.

  20. 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

  1. Drive Stands

    Data.gov (United States)

    Federal Laboratory Consortium — The Electrical Systems Laboratory (ESL)houses numerous electrically driven drive stands. A drive stand consists of an electric motor driving a gearbox and a mounting...

  2. Lateral variations of crustal structure beneath the Indochina Peninsula

    Science.gov (United States)

    Yu, Youqiang; Hung, Tran D.; Yang, Ting; Xue, Mei; Liu, Kelly H.; Gao, Stephen S.

    2017-08-01

    Crustal thickness (H) and Vp/Vs (κ) measurements obtained by stacking P-to-S receiver functions recorded at 32 broadband seismic stations covering the Indochina Peninsula reveal systematic spatial variations in crustal properties. Mafic bulk crustal composition as indicated by high κ (>1.81) observations is found to exist along major strike-slip faults and the southern part of the Peninsula, where pervasive basaltic magmatism is found and is believed to be the results of lithospheric thinning associated with the indentation of the Indian into the Eurasian plates. In contrast, crust beneath the Khorat Plateau, which occupies the core of the Indochina Block, has relatively large H values with a mean of 36.9 ± 3 km and small κ measurements with an average of 1.74 ± 0.04, which indicates an overall felsic bulk composition. Those observations for the Khorat Plateau are comparable to the undeformed part of the South China Block. The laterally heterogeneous distribution of crustal properties and its correspondence with indentation-related tectonic features suggest that the Indochina lithosphere is extruded as rigid blocks rather than as a viscous flow.

  3. The crustal and upper mantle structure around the Gulf of California, inferred from surface wave data and receiver functions

    NARCIS (Netherlands)

    de Vos, D.

    2016-01-01

    This thesis reports on studies that have been carried out to better image the crustal and upper mantle shear velocity structure around the Gulf of California, Mexico. The Gulf of California forms a part of the plate boundary between the Pacific and North-American plates, where transform motion in th

  4. Crustal response to lithosphere evolution

    DEFF Research Database (Denmark)

    Artemieva, Irina; Thybo, Hans; Cherepanova, Yulia;

    2012-01-01

    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...... to geological and tectono-thermal ages of the crust, and the tectonic setting. The results indicate that the Precambrian crust is as heterogeneous as Phanerozoic, and we do not observe any evidence for thickening from the Archean to Proterozoic crust. If anything, our analysis rather suggests the opposite trend...

  5. 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...

  6. Crustal structure of the Eastern Alps and their foreland

    DEFF Research Database (Denmark)

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

    2009-01-01

    plate, Adriatic microplate and the recently identified Pannonian fragment. The seismic data along the presented profile originate from two large experiments: CELEBRATION 2000 and ALP 2002. The wavefield observed in the Eastern Alps is more complex than in the Bohemian Massif. Strong first arrivals (Pg......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...

  7. Geoid, topography, and convection-driven crustal deformation on Venus

    Science.gov (United States)

    Simons, Mark; Hager, Bradford H.; Solomon, Sean C.

    1993-01-01

    High-resolution Magellan images and altimetry of Venus reveal a wide range of styles and scales of surface deformation that cannot readily be explained within the classical terrestrial plate tectonic paradigm. The high correlation of long-wavelength topography and gravity and the large apparent depths of compensation suggest that Venus lacks an upper-mantle low-viscosity zone. A key difference between Earth and Venus may be the degree of coupling between the convecting mantle and the overlying lithosphere. Mantle flow should then have recognizable signatures in the relationships between the observed surface topography, crustal deformation, and the gravity field. Therefore, comparison of model results with observational data can help to constrain such parameters as crustal and thermal boundary layer thicknesses as well as the character of mantle flow below different Venusian features. We explore in this paper the effects of this coupling by means of a finite element modelling technique.

  8. Constraints on Crustal Viscosity from Geodetic Observations

    Science.gov (United States)

    Houseman, Gregory

    2015-04-01

    Laboratory measurements of the ductile deformation of crustal rocks demonstrate a range of crystal deformation mechanisms that may be represented by a viscous deformation law, albeit one in which the effective viscosity may vary by orders of magnitude, depending on temperature, stress, grain size, water content and other factors. In such measurements these factors can be separately controlled and effective viscosities can be estimated more or less accurately, though the measured deformation occurs on much shorter time scales and length scales than are typical of geological deformation. To obtain bulk measures of the in situ crustal viscosity law for actual geological processes, estimated stress differences are balanced against measured surface displacement or strain rates: at the continental scale, surface displacement and strain rates can be effectively measured using GPS, and stress differences can be estimated from the distribution of gravitational potential energy; this method has provided constraints on a depth-averaged effective viscosity for the lithosphere as a whole in regions that are actively deforming. Another technique measures the post-seismic displacements that are interpreted to occur in the aftermath of a large crustal earthquake. Stress-differences here are basically constrained by the co-seismic deformation and the elastic rigidity (obtained from seismic velocity) and the strain rates are again provided by GPS. In this technique the strain is a strong function of position relative to the fault, so in general the interpretation of this type of data depends on a complex calculation in which various simplifying assumptions must be made. The spatial variation of displacement history on the surface in this case contains information about the spatial variation of viscosity within the crust. Recent post-seismic studies have shown the potential for obtaining measurements of both depth variation and lateral variation of viscosity in the crust beneath

  9. Crustal structure beneath Eastern Greenland

    DEFF Research Database (Denmark)

    Reiche, Sönke; Thybo, H.; Kaip, G.

    2011-01-01

    these mountain belts is needed for assessing the isostatic balance of the crust and to gain insight into possible links between crustal composition, rifting history and present-day topography of the North Atlantic Region. However, the acquisition of geophysical data onshore Greenland is logistically complicated...

  10. Thin plate neotectonic models of the Australian plate

    Science.gov (United States)

    Burbidge, D. R.

    2004-10-01

    Thin plate finite element models of the neotectonic deformation of the Australian plate have been calculated in order to estimate the stress and strain rate within the plate, specifically concentrating on the Australian continent. The model includes plate-bounding faults, an anelastic brittle-ductile layered rheology and the option of laterally varying elevation and heat flow. The results of the models are compared to (1) the velocity of geodetic benchmarks on the Australian plate, (2) the spreading rate of the mid-oceanic ridges along the Australian plate's margins, (3) the direction of the maximum horizontal principal stress, (4) the stress regime within the plate, and (5) the crustal thickness estimated from the depth to the base of Mohorovicic discontinuity's transition zone. A variety of models are tested with a wide range of input parameters. The model with the smallest misfit with observations predicts that the strain rate for most of the Australian continent is approximately 10-17 s-1. This model has a slightly lower strain rate in the central Australia and is higher off the northern coast of Australia than for the rest of the continent. Strain rates of this magnitude would be difficult to observe from geodetic or geologic data for most parts of Australia but would be enough to generate much of the seismicity that has been observed over the last century.

  11. Crustal deformation across the Southern Patagonian Icefield: GNSS observations and GIA models

    Science.gov (United States)

    Mendoza, Luciano; Richter, Andreas; Marderwald, Eric; Hormaechea, José Luis; Ivins, Erik; Perdomo, Raúl; Lange, Heiner; Schröder, Ludwig; Dietrich, Reinhard

    2017-04-01

    We present the geodetic observation and geodynamic interpretation of crustal deformation rates in a network of 43 GNSS sites covering the region of the Southern Patagonian Icefield (Argentina and Chile). Repeated and semi-permanent GNSS observations initiated in 1996 yield 3D site velocities within a terrestrial reference frame with mean accuracies of 1 mm/a and 6 mm/a for the horizontal and vertical components, respectively. These site velocities are interpreted with regard to the magnitude, patterns and primary driving processes of vertical and horizontal present-day crustal deformation (Richter et al. 2016). The vertical site velocities document a rapid uplift causally related to glacial-isostatic adjustment (GIA) reaching 4 cm/a. They yield now an unambiguous preference between two competing regional GIA models (Lange et al. 2014). Remaining discrepancies between the preferred model and our observations point toward an exceptionally low effective upper mantle viscosity and effects of lateral rheological heterogeneities. The extension and geometry of our network allow, for the first time, also a detailed analysis of the horizontal velocity components. An analysis of the horizontal strain-rate field reveals a complex composite, with compression dominating in the west and extension in the east. The observed velocities suggest significant contributions from three processes: GIA, a western interseismic tectonic deformation field related to plate subduction, and an extensional strain-rate field related to active Patagonian slab window tectonics. They document a dual interaction between the peculiar tectonic situation and the visco-elastic response to ice-load changes: First, a mechanical superposition of the characteristic patterns of each of the three processes, which results in the complex superposition of horizontal deformation revealed by our strain analysis. And second, the lateral differentiation of the glacial-isostatic response imposed by the three

  12. Petroleum and natural gas geology and plate tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, B.

    1984-01-01

    Several processes of oil and gas geology are studied in connection with plate-tectonical processes. Thus it becomes clear, that there is a distinct difference between the Paleozoic development of the European plate and the Mesozoic development. One can state, that the Paleozoic development is essentially influenced by the positions of the mobile belts and the cratonized parts of the plates. The development during Meso-Caenozoic is mainly characterized by crustal processes in the result of the disintegration of Pangaea.

  13. Drugged Driving

    Science.gov (United States)

    ... Parents & Educators Children & Teens Search Connect with NIDA : Google Plus Facebook LinkedIn Twitter YouTube Flickr RSS Menu ... misuse of prescription drugs can make driving a car unsafe—just like driving after drinking alcohol. Drugged ...

  14. Crustal Seismic Anisotropy: Implications for Understanding Crustal Dynamics

    Science.gov (United States)

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

    2003-12-01

    The Nanga Parbat - Haramosh massif, in the core of the western syntaxis of the Himalaya, represents a unique exposure of mid-lower continental crust from beneath a collisional orogen. The exhumed core of the massif forms a large scale antiformal structure with axial orientation of N10E and associated lineation directed north-south with near-vertical dips. Laboratory measurements of seismic velocity on a suite of quartzofeldspathic gneisses from the massif show a relatively strong degree of anisotropy, up to 12.5% for compressional waves and up to 21% for shear waves. The degree of velocity anisotropy is primarily a function of mica content and rock fabric strength. The strong anisotropy measured in these rocks should be observable in recorded seismic field data and provides a means of mapping rock fabric at depth provided the rock fabric is coherent over appropriate length scales. An IRIS/PASSCAL deployment of 50 short period instruments recorded local and regional earthquakes to characterize seismicity and determine crustal structure beneath the massif as part of a multidisciplinary NSF Continental Dynamics study investigating the active tectonic processes responsible for exhumation and crustal reworking at Nanga Parbat. Microseismicity at Nanga Parbat is distributed along strike beneath the massif but exhibits a sharp drop-off laterally into adjacent terranes and with depth. This data set is ideal for studying crustal seismic anisotropy because the raypaths are restricted to the crust, sharp onsets in P and S allow for clear identification of arrivals, and source-receiver geometries sample a range of azimuths with respect to structure. Preliminary analysis indicates that the majority of local events exhibit some degree of splitting and that splitting patterns, while complicated, are coherent. While splitting delay normally increases with distance traveled through anisotropic material, the range of delay times can be due to heterogeneity in composition, lateral

  15. The dynamics of Cenozoic and Mesozoic plate motions

    OpenAIRE

    Lithgow-Bertelloni, C.; Richards, M. A.

    1998-01-01

    Our understanding of the dynamics of plate motions is based almost entirely upon modeling of present-day plate motions. A fuller understanding, however, can be derived from consideration of the history of plate motions. Here we investigate the kinematics of the last 120 Myr of plate motions and the dynamics of Cenozoic motions, paying special attention to changes in the character of plate motions and plate-driving forces. We analyze the partitioning of the observed surface velocity field into...

  16. Crustal fingering: solidification on a moving interface

    Science.gov (United States)

    Fu, Xiaojing; Jimenez-Martinez, Joaquin; Porter, Mark; Cueto-Felgueroso, Luis; Juanes, Ruben

    2016-11-01

    Viscous fingering-the hydrodynamic instability that takes place when a less viscous fluid displaces a more viscous fluid-is a well known phenomenon. Motivated by the formation of gas hydrates in seafloor sediments and during the ascent of gas bubbles through ocean water, here we study the interplay of immiscible viscous fingering with solidification of the evolving unstable interface. We present experimental observations of the dynamics of a bubble of Xenon in a water-filled and pressurized Hele-Shaw cell. The evolution is controlled by two processes: (1) the formation of a hydrate "crust" around the bubble, and (2) viscous fingering from bubble expansion. To reproduce the experimental observations, we propose a phase-field model that describes the nucleation and thickening of a porous solid shell on a moving gas-liquid interface. We design the free energy of the three-phase system (gas-liquid-hydrate) to rigorously account for interfacial effects, mutual solubility, and phase transformations (hydrate formation and disappearance). We introduce a pseudo-plasticity model with large variations in viscosity to describe the plate-like rheology of the hydrate shell. We present high-resolution numerical simulations of the model, which illustrate the emergence of complex "crustal fingering" patterns as a result of gas fingering dynamics modulated by hydrate growth at the interface.

  17. Electric drives

    CERN Document Server

    Boldea, Ion

    2005-01-01

    ENERGY CONVERSION IN ELECTRIC DRIVESElectric Drives: A DefinitionApplication Range of Electric DrivesEnergy Savings Pay Off RapidlyGlobal Energy Savings Through PEC DrivesMotor/Mechanical Load MatchMotion/Time Profile MatchLoad Dynamics and StabilityMultiquadrant OperationPerformance IndexesProblemsELECTRIC MOTORS FOR DRIVESElectric Drives: A Typical ConfigurationElectric Motors for DrivesDC Brush MotorsConventional AC MotorsPower Electronic Converter Dependent MotorsEnergy Conversion in Electric Motors/GeneratorsPOWER ELECTRONIC CONVERTERS (PECs) FOR DRIVESPower Electronic Switches (PESs)The

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

    Directory of Open Access Journals (Sweden)

    Robert Tenzer and Pavel Novák

    2013-01-01

    Full Text Available We investigate the gravity gradient components corrected for major known anomalous density structures within the _ 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 _ 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.

  19. Continent-scale strike-slip on a low-angle fault beneath New Zealand's Southern Alps: Implications for crustal thickening in oblique collision zones

    Science.gov (United States)

    Lamb, Simon; Smith, Euan; Stern, Tim; Warren-Smith, Emily

    2015-09-01

    New Zealand's Southern Alps lie adjacent to the continent-scale dextral strike-slip Alpine Fault, on the boundary between the Pacific and Australian plates. We show with a simple 2-D model of crustal balancing that the observed crustal root and erosion (expressed as equivalent crustal shortening) is up to twice that predicted by the orthogonal plate convergence since ˜11 Ma, and even since ˜23 Ma when the Alpine Fault formed. We consider two explanations for this, involving a strong component of motion along the length of the plate-boundary zone. Geophysical data indicate that the Alpine Fault has a listric geometry, flattening at mid crustal levels, and has accommodated sideways underthrusting of Australian plate crust beneath Pacific plate crust. The geometry of the crustal root, together with plate reconstructions, requires the underthrust crust to be the hyperextended part of an asymmetric rift system which formed over 500 km farther south during the Eocene—the narrow remnant part today forms the western margin of the Campbell Plateau. At ˜10 Ma, the hyperextended margin underwent shallow subduction in the Puysegur subduction zone, and then was dragged over 300 km along the length of the Southern Alps beneath a low-angle (plate boundary zone, providing a mechanism for clockwise rotation of the Hikurangi margin.

  20. Establishment and analyses on the unified horizontal crustal velocity fields in the Chinese mainland

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The related data of GPS networks in the Chinese mainland and its peripheral areas are collected from internet sites in the paper. And various data fusion methods are presented based on the collected GPS data. Thus the unified horizontal crustal velocity fields can be established in the Chinese mainland and its peripheral areas. The available data of 423 GPS sites are applied to the velocity fields and its area gets to 1.2′107 km2. By analyzing the velocity fields, the basic spatial distribution feature of the horizontal crustal motion in the Chinese mainland and its peripheral area can be obtained preliminarily. Meanwhile, the range of the velocity fields in the Chinese mainland affected by the collision force of India plate to Eurasia plate and the problem of principal direction of the force from India plate are discussed.

  1. Crustal Thickness Along the Central American Volcanic Front

    Science.gov (United States)

    MacKenzie, L. S.; Abers, G. A.; Rondenay, S.; Fischer, K. M.; Syracuse, E. M.; Protti, J. M.; Gonzalez, V.; Strauch, W.

    2007-12-01

    Subduction zone processes alter the upper plate in a number of ways, including accretion, magmatic addition, serpentinization of the mantle wedge and formation of mafic cumulates in the lower crust. All of these changes affect seismic velocities, and characterizing the structure of underlying terranes in Central America establishes a baseline for composition and continental growth. Tomography Under Costa Rica and Nicaragua (TUCAN) is a PASSCAL deployment of broadband seismometers over an 18-month period. The network has two dense cross arc lines and two along arc lines that cross terrane boundaries. Teleseismic P and PP arrivals recorded on the TUCAN network have been used to estimate crustal thickness and Vp/Vs, and to develop receiver function images. Surface reflected mode conversions (Ppms and Psms) enhance resolution. Crustal thickness ranges from 25 to 44 km with formal errors ranging 1.6-9.2 km. The thinnest crust (24.6 +/- 3.5 km) lies directly beneath the arc in Nicaragua, whereas the thickest crust (43.5 +/- 2.5 km) lies in the backarc in Nicaragua and beneath the Costa Rican arc (37.9 +/- 5.2). Changes in crustal thickness and Vp/Vs show two distinct terrane boundaries crossing the arc. Vp/Vs indicate continental crust (Vp/Vs=1.71-1.77) in Nicaragua, with a transition to gabbroic crust (Vp/Vs=1.82-1.88) in Costa Rica where fragments of the Caribbean large Igneous Province have been found. Crustal thickness beneath the arc in Costa Rica yields a crustal growth rate of 16-36 km3/km/Ma, assuming a base crustal thickness of 30-32 km with 6-14 Ma of magmatism. The Moho shows strong velocity contrasts throughout the study area, and is the only interface seen in the backarc, but it is complicated by interferences caused by shallow structure beneath the arc and forearc. Forward modeling indicates that reverberations in sediment layers interfere with the Ps arrival, however surface reflected arrivals (Ppms) require a velocity contrast on the order of 0.5-1.0 km

  2. History of crustal recycling recorded in transition zone diamonds

    Science.gov (United States)

    Pearson, D. G.; Stachel, T.; Palot, M.; Ickert, R. B.

    2015-12-01

    The Earth's transition zone (TZ) is a key region within the Earth that, from seismology, may be composed of a mixture of relatively primitive material together with the products of crustal recycling throughout the history of plate tectonics. The only samples of the TZ come in the form of inclusions in diamonds, that, for the most-part are retrogressed lower pressure equivalents of their precursor phases that formed at depth. Recent work by our group and others [1] on transition zone diamonds indicate that both peridotite and eclogitic paragenesis diamonds may record the products of crustal recycling. In-situ ion probe nitrogen and carbon isotopic measurements indicate the crystallisation of TZ diamonds from fluids bearing crustal signatures, of both oxidised and reduced forms. At the same time, majoritic garnets record extreme oxygen isotope compositions that track the interaction of oceanic crust with seawater at low temperature [2]. Such an origin is consistent with the few measured Sr-Nd isotope compositions of majorite garnet inclusions which resemble depleted MORB [3]. We have found considerably more enriched Sr isotope compositions (87Sr/86S ranging to > 0.8) in CaSiO3 inclusions that are from deep asthenosphere to TZ depths, supporting an origin that includes incorporation of recycled crustal sediment, in addition to the basaltic oceanic crust required to explain the phase equilibria [4]. Lastly, the discovery of hydrous ringwoodite in a diamond [5] containing more water than is soluble at the lower TZ adiabat indicates the possible role of recycling in transporting water as well as carbon into the TZ via a cool thermally unequilibrated slab. [1] Thomson et al (2014) CMP, 168, 1081. [2] Ickert et al (2015) Geochemical perspectives Letters, 1, 65-74. [3] Harte & Richardson (2011) Gondwana Research, 21, 236-235. [4] Walter et al. (2011) Science, 334, 54-57.[Pearson et al. (2014) Nature, 507, 221-224.

  3. Plate tectonics conserves angular momentum

    Directory of Open Access Journals (Sweden)

    C. Bowin

    2009-03-01

    features, and fracture zones (and wedge-shaped sites of seafloor spreading are adjustment zones that accommodate strains in the lithosphere. Further, the interlocked pattern of the Australian and Pacific plates the past 42 Million years (with their absolute plate motions near 90° to each other is taken as strong evidence that large thermally driven "roller" convection cells previously inferred as the driving mechanism in earlier interpretations of continental drift and plate tectonics, have not been active in the Earth's mantle the past 42 Million years, if ever. This report also presents estimates of the changes in location and magnitude of the Earth's axis of total plate tectonic angular momentum for the past 62 million years.

  4. Plate tectonics, damage and inheritance.

    Science.gov (United States)

    Bercovici, David; Ricard, Yanick

    2014-04-24

    The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto-subduction (about 4 billion years ago) and global tectonics (approximately 3 billion years ago) suggests that plates and plate boundaries became widespread over a period of 1 billion years. The reason for this time lag is unknown but fundamental to understanding the origin of plate tectonics. Here we suggest that when sufficient lithospheric damage (which promotes shear localization and long-lived weak zones) combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of weak plate boundaries and eventually to fully formed tectonic plates driven by subduction alone. We simulate this process using a grain evolution and damage mechanism with a composite rheology (which is compatible with field and laboratory observations of polycrystalline rocks), coupled to an idealized model of pressure-driven lithospheric flow in which a low-pressure zone is equivalent to the suction of convective downwellings. In the simplest case, for Earth-like conditions, a few successive rotations of the driving pressure field yield relic damaged weak zones that are inherited by the lithospheric flow to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even though flow is driven only by subduction. But for hotter surface conditions, such as those on Venus, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which corresponds to observations. After plates have developed, continued changes in driving forces, combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor plates.

  5. Analysis the 1978–2008 crustal and sub-crustal earthquake catalog of Vrancea region

    Directory of Open Access Journals (Sweden)

    L. Telesca

    2012-05-01

    Full Text Available The crustal and sub-crustal seismicity that occurred in the Vrancea area from 1978 to 2008 is investigated. Due to quarry blast contamination, the analysis of the crustal seismicity was restricted to events that occurred between 20 km and 60 km, considering sub-crustal events as all those that occurred at depths larger than 60 km. The completeness magnitude was estimated between 2.3 and 2.5 for the crustal seismicity and between 2.9 and 3.1 for the sub-crustal one. The Gutenberg-Richter b-values show clear differences between crustal and sub-crustal seismicity, with values around 0.9 and 1.3–1.4, respectively. The analysis performed in this study represents a preliminary issue for the seismic hazard assessment of surrounding regions like Moldova, for which the earthquakes generated in Vrancea represent an important threat.

  6. Crustal structure beneath Eastern Greenland

    DEFF Research Database (Denmark)

    Reiche, Sönke; Thybo, H.; Kaip, G.

    2011-01-01

    is recorded by 350 Reftek Texan receivers for 10 equidistant shot points along the profile. We use forward ray tracing modelling to construct a two-dimensional velocity model from the observed travel times. These results show the first images of the subsurface velocity structure beneath the Greenland ice...... these mountain belts is needed for assessing the isostatic balance of the crust and to gain insight into possible links between crustal composition, rifting history and present-day topography of the North Atlantic Region. However, the acquisition of geophysical data onshore Greenland is logistically complicated...

  7. 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, Karen M.; Tong, Xiaopeng; Sandwell, David T.; Brooks, Benjamin A.; Bevis, Michael G.

    2011-11-01

    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.

  8. Pile Driving

    Science.gov (United States)

    1987-01-01

    Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.

  9. SAMI Automated Plug Plate Configuration

    CERN Document Server

    Lorente, Nuria P F; Goodwin, Michael

    2012-01-01

    The Sydney-AAO Multi-object Integral field spectrograph (SAMI) is a prototype wide-field system at the Anglo-Australian Telescope (AAT) which uses a plug-plate to mount its 13 x 61-core imaging fibre bundles (hexabundles) in the optical path at the telescope's prime focus. In this paper we describe the process of determining the positions of the plug-plate holes, where plates contain three or more stacked observation configurations. The process, which up until now has involved several separate processes and has required significant manual configuration and checking, is now being automated to increase efficiency and reduce error. This is carried out by means of a thin Java controller layer which drives the configuration cycle. This layer controls the user interface and the C++ algorithm layer where the plate configuration and optimisation is carried out. Additionally, through the Aladin display package, it provides visualisation and facilitates user verification of the resulting plates.

  10. Crustal thinning between the Ethiopian and East African Plateaus from modeling Rayleigh wave dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Benoit, M H; Nyblade, A A; Pasyanos, M E

    2006-01-17

    The East African and Ethiopian Plateaus have long been recognized to be part of a much larger topographic anomaly on the African Plate called the African Superswell. One of the few places within the African Superswell that exhibit elevations of less than 1 km is southeastern Sudan and northern Kenya, an area containing both Mesozoic and Cenozoic rift basins. Crustal structure and uppermost mantle velocities are investigated in this area by modeling Rayleigh wave dispersion. Modeling results indicate an average crustal thickness of 25 {+-} 5 km, some 10-15 km thinner than the crust beneath the adjacent East African and Ethiopian Plateaus. The low elevations can therefore be readily attributed to an isostatic response from crustal thinning. Low Sn velocities of 4.1-4.3 km/s also characterize this region.

  11. Crustal structure of western Hispaniola (Haiti) from a teleseismic receiver function study

    Science.gov (United States)

    Corbeau, J.; Rolandone, F.; Leroy, S.; Guerrier, K.; Keir, D.; Stuart, G.; Clouard, V.; Gallacher, R.; Ulysse, S.; Boisson, D.; Bien-aimé Momplaisir, R.; Saint Preux, F.; Prépetit, C.; Saurel, J.-M.; Mercier de Lépinay, B.; Meyer, B.

    2017-07-01

    Haiti, located at the northern Caribbean plate boundary, records a geological history of terrane accretion from Cretaceous island arc formations to the Eocene to Recent oblique collision with the Bahamas platform. Little is presently known about the underlying crustal structure of the island. We analyze P-waveforms arriving at 27 temporary broadband seismic stations deployed over a distance of 200 km across the major terrane boundaries in Haiti to determine the crustal structure of western Hispaniola. We compute teleseismic receiver functions using the Extended-Time Multi-Taper method and determine crustal thickness and bulk composition (Vp/Vs) using the H-k stacking method. Three distinctive and fault-bounded crustal domains, defined by their characteristic Moho depth distributions and bulk crustal Vp/Vs, are imaged across Haiti. We relate these domains to three crustal terranes that have been accreted along the plate boundary during the northeastwards displacement of the Caribbean plate and are presently being deformed in a localized fold and thrust belt. In the northern domain, made up of volcanic arc facies, the crust has a thickness of 23 km and Vp/Vs of 1.75 ± 0.1 typical of average continental crust. The crust in the southern domain is part of the Caribbean Large Igneous Province (Caribbean LIP), and is 22 km thick with Vp/Vs of 1.80 ± 0.03 consistent with plume-related rocks of late Cretaceous age. Significantly thicker, the crust in central Haiti has values of Moho depths averaging 41 km and with Vp/Vs of 1.80 ± 0.05. We propose that the central domain is likely constructed of an island arc upper crust with fragments of dense material originating from mafic lavas or LIP material. We produce a crustal profile along a N-S transect across Haiti accounting for the surface geology, shallow structural history, and new seismological constraints provided by variations of crustal thickness and bulk composition.

  12. Crustal deformation in the Kumano Basin along the Nankai Trough inferred from repeated seafloor geodetic observations

    Science.gov (United States)

    Watanabe, T.; Tadokoro, K.; Sugimoto, S.; Okuda, T.; Muto, D.; Kimoto, A.; Miyata, K.; Kuno, M.

    2008-12-01

    At the Nankai Trough (NT), the Philippine Sea plate (PH) subducts beneath the southwest Japan at a rate of about 4-6 cm/yr, where great interplate earthquakes have repeatedly occurred every 100-200 years. A number of researchers have investigated crustal deformation caused by subduction of the PH based on geodetic measurements as represented by GPS observation. However it is difficult to infer the plate coupling strength in offshore areas, due to the poverty of offshore geodetic data. From a viewpoint of disaster mitigation, it is important to know the updip and downdip limit of the plate locking depth. For this issue, we have conducted observations of the seafloor crustal deformations around the NT using a GPS/Acoustic technique since 2004. In this system, we estimate the position of a surveying vessel by Kinematic GPS analysis and measure the distance between the vessel and the benchmark on the sea floor by Acoustic measurements. Next we determine the location of the benchmark. For the repeatability of observation, the location of benchmark is determined within a precision of 2-3 cm at horizontal components (Tadokoro et al., 2006). In the Kumano Basin, we have two seafloor benchmarks, which are located about 60 and 80 km away from the deformation front of the NT. The observations from 2005 to 2008 have illustrated that these benchmarks are moving at rates of about 5-6 cm/yr with velocity uncertainties of 1-3 cm/yr relative to the Amurian plate. In this study, in order to estimate interplate coupling at the NT, we calculated surface deformations accompanied with plate subduction in an elastic half-space and compared them with on- and offshore GPS velocities. Then, we investigated the effect of observation for the seafloor crustal deformations on slip resolution on the plate interface. We conclude that offshore crustal deformation data provide good constraints for the estimation of fault slips at the shallower part of the plate interface, especially at the depths

  13. High Amplitude Secondary Mass Drive

    Energy Technology Data Exchange (ETDEWEB)

    DYCK,CHRISTOPHER WILLIAM; ALLEN,JAMES J.; HUBER,ROBERT JOHN; SNIEGOWSKI,JEFFRY J.

    2000-07-06

    In this paper we describe a high amplitude electrostatic drive for surface micromachined mechanical oscillators that may be suitable for vibratory gyroscopes. It is an advanced design of a previously reported dual mass oscillator (Dyck, et. al., 1999). The structure is a 2 degree-of-freedom, parallel-plate driven motion amplifier, termed the secondary mass drive oscillator (SMD oscillator). During each cycle the device contacts the drive plates, generating large electrostatic forces. Peak-to-peak amplitudes of 54 {micro}m have been obtained by operating the structure in air with an applied voltage of 11 V. We describe the structure, present the analysis and design equations, and show recent results that have been obtained, including frequency response data, power dissipation, and out-of- plane motion.

  14. Seismological study on the crustal structure of Tengchong volcanic-geothermal area

    Institute of Scientific and Technical Information of China (English)

    王椿镛; 楼海; 吴建平; 白志明; 皇甫岗; 秦嘉政

    2002-01-01

    Based upon the deep seismic sounding profile conducted in the Tengchong volcanic-geothermal area, a two-dimensional crustal P velocity structure is obtained by use of the finite-difference inversion and the forward travel-time fitting method. The crustal model shows that there is a low velocity zone in upper crust in the Tengchong area, which may be related to the volcanic-geothermal activities, and two intracrustal faults (the Longling-Ruili fault and Tengchong fault) exist on the profile, where the Tengchong fault may extend to the Moho discontinuity. Meanwhile, based on teleseismic data recorded by a temporary seismic network, we obtained the S-wave velocity structures beneath the Rehai-Retian region in the Tengchong area, which show the low S-wave velocity anomaly in upper crust. The authors discuss the causes of Tengchong volcanic eruption based on the deep crustal structure. The crustal structure in the Tengchong volcanic-geothermal area is characterized by low P-wave and S-wave velocity, low resistivity, high heat-flow value and low Q value. The P-wave velocity in the upper mantle is also low. For this information, it can be induced that the magma in the crust is derived from the upper mantle, and the low velocity anomaly in upper crust in the Tengchong area may be related to the differentiation of magma. The Tengchong volcanoes are close to an active plate boundary and belong to "plate boundary" volcanoes.

  15. Distracted Driving

    Science.gov (United States)

    ... What's this? Submit What's this? Submit Button Distracted Driving Recommend on Facebook Tweet Share Compartir Each day in the United States, over 8 people are killed and 1,161 injured in crashes ...

  16. DRIVING GREEN

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    China is promoting environmentally friendly cars to save energy and protect the environment While people enjoy the pleasure and convenience of driving, they are also creating and breathing more and more toxic

  17. Seismological constraints on the crustal structures generated by continental rejuvenation in northeastern China.

    Science.gov (United States)

    Zheng, Tian-Yu; He, Yu-Mei; Yang, Jin-Hui; Zhao, Liang

    2015-10-07

    Crustal rejuvenation is a key process that has shaped the characteristics of current continental structures and components in tectonic active continental regions. Geological and geochemical observations have provided insights into crustal rejuvenation, although the crustal structural fabrics have not been well constrained. Here, we present a seismic image across the North China Craton (NCC) and Central Asian Orogenic Belt (CAOB) using a velocity structure imaging technique for receiver functions from a dense array. The crustal evolution of the eastern NCC was delineated during the Mesozoic by a dominant low seismic wave velocity with velocity inversion, a relatively shallow Moho discontinuity, and a Moho offset beneath the Tanlu Fault Zone. The imaged structures and geochemical evidence, including changes in the components and ages of continental crusts and significant continental crustal growth during the Mesozoic, provide insight into the rejuvenation processes of the evolving crust in the eastern NCC caused by structural, magmatic and metamorphic processes in an extensional setting. The fossil structural fabric of the convergent boundary in the eastern CAOB indicates that the back-arc action of the Paleo-Pacific Plate subduction did not reach the hinterland of Asia.

  18. Surface effects of Rayleigh-Taylor instability: Feedback between drip dynamics and crustal deformation

    Science.gov (United States)

    Wang, H.; Currie, C. A.

    2013-12-01

    For many continental plates, significant vertical motion of Earth's surface has occurred within the plate interior which can not be clearly linked to plate tectonic processes. For example, several craton areas exhibit anomalous basins, e.g., the Williston basin, Illinois basin and Michigan basin in North America. In orogenic belts, there are examples of local areas (~100 km wide) where the surface has undergone subsidence and then uplift of >1 km, such as the Arizaro basin (central Andes) and Wallowa Mountains (northeast Oregon). Given the near-circular shape of the surface deflection, it has been suggested that they may be related to gravitational foundering of dense lower lithosphere, i.e., Rayleigh-Taylor instability (or 'RT drip'). In order to investigate the surface effects of an RT drip, we use two methods: (1) 2D thermal-mechanical numerical models to study links between drip dynamics and crustal deformation and (2) a theoretical analysis of the crustal deformation induced by stresses from the RT drip. The numerical models consist of a continental lithosphere overlying a sublithospheric mantle. A high-density material is placed in the mantle lithosphere or lower crust to initiate a drip event, and a stress-free boundary condition allows the development of surface topography during model evolution. A reasonable range of crustal viscosity and thickness is tested to study the RT drip in different tectonic settings, from a cold craton to a hot orogen with thick crust. Four types of surface deflection are observed: (1) subsidence; (2) subsidence followed by uplift; (3) uplift; and (4) little deflection. When the crust is relatively strong or thin, the surface has a negative elevation, forming a basin. For a weak or thick crust, the RT drip induces crustal flow, leading to crustal thickening that can uplift the surface; an extremely weak crust decouples the surface and RT drip and the surface is unperturbed. Our theoretical analysis considers the surface

  19. Re-examination of geophysical data off Northwest India: Implications to the Late Cretaceous plate tectonics between India and Africa.

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Desa, M.; Ramprasad, T.

    processes. Late Cretaceous seafloor spreading between India and Africa formed the Mascarene Basin, and the plate reconstruction models depict unequal crustal accretion in this basin. Re-interpretation of magnetic data in the Gop and Laxmi Basins suggests...

  20. Magma production rate along the Ninetyeast Ridge and its relationship to Indian plate motion and Kerguelen hot spot activity

    Digital Repository Service at National Institute of Oceanography (India)

    Sreejith, K.M.; Krishna, K.S.

    The Ninetyeast Ridge, a linear trace of the Kerguelen hot spot in the Indian Ocean, was emplaced on a rapidly drifting Indian plate. Magma production rates along the ridge track are computed using gravity-derived excess crustal thickness data...

  1. Crustal architecture and deep structure of the Namibian passive continental margin around Walvis Ridge from wide-angle seismic data

    Science.gov (United States)

    Behrmann, Jan H.; Planert, Lars; Jokat, Wilfried; Ryberg, Trond; Bialas, Jörg; Jegen, Marion

    2013-04-01

    The opening of the South Atlantic ocean basin was accompanied by voluminous magmatism on the conjugate continental margins of Africa and South America, including the formation of the Parana and Entendeka large igneous provinces (LIP), the build-up of up to 100 km wide volcanic wedges characterized by seaward dipping reflector sequences (SDR), as well as the formation of paired hotspot tracks on the rifted African and South American plates, the Walvis Ridge and the Rio Grande Rise. The area is considered as type example for hotspot or plume-related continental break-up. However, SDR, and LIP-related features on land are concentrated south of the hotspot tracks. The segmentation of the margins offers a prime opportunity to study the magmatic signal in space and time, and investigate the interrelation with rift-related deformation. A globally significant question we address here is whether magmatism drives continental break-up, or whether even rifting accompanied by abundant magmatism is in response to crustal and lithospheric stretching governed by large-scale plate kinematics. In 2010/11, an amphibious set of wide-angle seismic data was acquired around the landfall of Walvis Ridge at the Namibian passive continental margin. The experiments were designed to provide crustal velocity information and to investigate the structure of the upper mantle. In particular, we aimed at identifying deep fault zones and variations in Moho depth, constrain the velocity signature of SDR sequences, as well as the extent of magmatic addition to the lower crust near the continent-ocean transition. Sediment cover down to the igneous basement was additionally constrained by reflection seismic data. Here, we present tomographic analysis of the seismic data of one long NNW oriented profile parallel to the continental margin across Walvis Ridge, and a second amphibious profile from the Angola Basin across Walvis Ridge and into the continental interior, crossing the area of the Etendeka

  2. 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.

  3. The Precambrian crustal structure of East Africa

    Science.gov (United States)

    Tugume, Fred Alex

    In this thesis, the Precambrian crustal structure of East African is investigated along with the crustal structures of three Cenozoic rift basins located in the western branch of the East African Rift System (EARS). In the first part of the thesis, P-wave receiver functions are modeled using the H-k method to obtain new insights about the bulk composition and thickness of the crust for Precambrian terrains throughout East Africa. The average crustal thickness for all but one of the terrains is between 37 and 39 km. An exception is the Ubendian terrain, which has an average crustal thickness 42 km. In all terrains, the average Poisson's ratio is similar, ranging from 0.25 to 0.26, indicating a bulk crustal composition that is felsic to intermediate. The main finding of this study is that crustal structure is similar across all terrains, which span more than 4.0 Ga of earth history. There is no discernable difference in the crustal thicknesses and Poisson's ratios between the Archean and Proterozoic terrains, or between the Proterozoic terrains, unlike the variability in Precambrian crustal structure found in many other continents. In the second part of the thesis, a joint inversion of Rayleigh wave phase and group velocities and receiver functions was used to investigate the shear wave velocity structure of the crust and uppermost mantle beneath the Precambrian terrains of East Africa. In comparison with other areas of similar age in southern and western Africa where the same joint inversion method has been applied, I find that while there is little difference in the mean shear wave velocities for the entire crust across all of the Precambrian terrains, and also few differences in the thickness of the crust, there exists substantial variability in lower crustal structure. This variability is reflected primarily in the thickness of the lower crustal layers with shear wave velocities ≥ 4.0 km/s. This variability is found both within terrains of the same age (i

  4. 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.

  5. Lower crustal intrusions beneath the southern Baikal Rift Zone

    DEFF Research Database (Denmark)

    Nielsen, Christoffer; Thybo, Hans

    2009-01-01

    The Cenozoic Baikal Rift Zone (BRZ) is situated in south-central Siberia in the suture between the Precambrian Siberian Platform and the Amurian plate. This more than 2000-km long rift zone is composed of several individual basement depressions and half-grabens with the deep Lake Baikal at its...... 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...... of the crust and uppermost mantle. Previous interpretation and velocity modelling of P-wave arrivals in the BEST data has revealed a multi layered crust with smooth variation in Moho depth between the Siberian Platform (41 km) and the Sayan-Baikal fold belt (46 km). The lower crust exhibits normal seismic...

  6. Robot Arm with Tendon Connector Plate and Linear Actuator

    Science.gov (United States)

    Ihrke, Chris A. (Inventor); Diftler, Myron A. (Inventor); Bridgwater, Lyndon (Inventor); Nguyen, Vienny (Inventor); Millerman, Alexander (Inventor)

    2014-01-01

    A robotic system includes a tendon-driven end effector, a linear actuator, a flexible tendon, and a plate assembly. The linear actuator assembly has a servo motor and a drive mechanism, the latter of which translates linearly with respect to a drive axis of the servo motor in response to output torque from the servo motor. The tendon connects to the end effector and drive mechanism. The plate assembly is disposed between the linear actuator assembly and the tendon-driven end effector and includes first and second plates. The first plate has a first side that defines a boss with a center opening. The second plate defines an accurate through-slot having tendon guide channels. The first plate defines a through passage for the tendon between the center opening and a second side of the first plate. A looped end of the flexible tendon is received within the tendon guide channels.

  7. Lower crustal mush generation and evolution

    Science.gov (United States)

    Karakas, Ozge; Bachmann, Olivier; Dufek, Josef; Wright, Heather; Mangan, Margaret

    2016-04-01

    Recent seismic, field, and petrologic studies on several active and fossil volcanic settings provide important constraints on the time, volume, and melt fraction of their lower crustal magma bodies. However, these studies provide an incomplete picture of the time and length scales involved during their thermal and compositional evolution. What has been lacking is a thermal model that explains the temporal evolution and state of the lower crustal magma bodies during their growth. Here we use a two-dimensional thermal model and quantify the time and length scales involved in the long-term thermal and compositional evolution of the lower crustal mush regions underlying the Salton Sea Geothermal Field (USA), Mt St Helens (USA), and the Ivrea-Verbano Zone (North Italy). Although a number of seismic, tectonic, petrologic, and field studies explained the tectonic and magmatic evolution of these regions, controversy remains on their lower crustal heat sources, melt fraction, and origin of erupted magmas. Our thermal modeling results suggest that given a geologically reasonable range of basalt fluxes (~10^-3 to 10^-4 km3/yr), a long-lived (>105 yr) crystalline mush is formed in the lower crust. The state of the lower crustal mush is strongly influenced by the magma flux, crustal thickness, and water content of intruded basalt, giving an average melt fraction of mush is mainly evolving through fractional crystallization of basalt with minor crustal assimilation in all regions, in agreement with isotopic studies. Quantification of the lower crustal mush regions is key to understanding the mass and heat balance in the crust, evolution of magma plumbing systems, and geothermal energy exploration.

  8. Current knowledge on the crustal properties of Italy

    Directory of Open Access Journals (Sweden)

    C. Morelli

    1994-06-01

    Full Text Available The recent advances in experimental petrography together with the information derived from the super-deep drilling projects have provided additional constraints for the interpretation of refraction and reflection seismic data. These constraints can also be used in the interpretation of magnetic and gravity data to resolve nonuniqueness. In this study, we re-interpret the magnetic and gravity data of the Italian peninsula and neighbouring areas. In view of the constraints mentioned above, it is now possible to find an agreement between the seismic and gravity models of the Central Alps. By taking into account the overall crustal thickness, we have recognized the existence of three types of Moho: 1 European which extends to the north and west of the peninsula and in the Corsican-Sardinian block. Its margin was the foreland in the Alpine Orogeny and it was the ramp on which European and Adriatic mantle and crustal slices were overthrusted. This additional load caused bending and deepening and the Moho which now lies beneath the Adriatic plate reaching a maximum depth of approximately 75 km. 2 Adriatic (or African which lies beneath the Po plain, the Apennines and the Adriatic Sea. The average depth of the Moho is about 30-35 km below the Po plain and the Adriatic Sea and it increases toward the Alps and the Tyrrhenian Sea (acting as foreland along this margin. The maximum depth (50 km is reached in Calabria. 3 Pery-Tyrrhenian. This is an oceanic or thinned continental crust type of Moho. It borders the oceanic Moho of the Tyrrhenian Sea and it acquires a transitional character in the Ligurian and Provençal basins (<15 km thickness while further thickening occurs toward the East where the Adriatic plate is overthrusted. In addition, the interpretation of the heat flow data appears to confirm the origin of this Moho and its geodynamic allocation.

  9. Arctic and N Atlantic Crustal Thickness and Oceanic Lithosphere Distribution from Gravity Inversion

    Science.gov (United States)

    Kusznir, Nick; Alvey, Andy

    2014-05-01

    The ocean basins of the Arctic and N. Atlantic formed during the Mesozoic and Cenozoic as a series of distinct ocean basins, both small and large, leading to a complex distribution of oceanic crust, thinned continental crust and rifted continental margins. The plate tectonic framework of this region was demonstrated by the pioneering work of Peter Ziegler in AAPG Memoir 43 " Evolution of the Arctic-North Atlantic and the Western Tethys" published in 1988. The spatial evolution of Arctic Ocean and N Atlantic ocean basin geometry and bathymetry are critical not only for hydrocarbon exploration but also for understanding regional palaeo-oceanography and ocean gateway connectivity, and its influence on global climate. Mapping crustal thickness and oceanic lithosphere distribution represents a substantial challenge for the Polar Regions. Using gravity anomaly inversion we have produced comprehensive maps of crustal thickness and oceanic lithosphere distribution for the Arctic and N Atlantic region, We determine Moho depth, crustal basement thickness, continental lithosphere thinning and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). Gravity anomaly and bathymetry data used in the gravity inversion are from the NGA (U) Arctic Gravity Project and IBCAO respectively; sediment thickness is from a new regional compilation. The resulting maps of crustal thickness and continental lithosphere thinning factor are used to determine continent-ocean boundary location and the distribution of oceanic lithosphere. Crustal cross-sections using Moho depth from the gravity inversion allow continent-ocean transition structure to be determined and magmatic type (magma poor, "normal" or magma rich). Our gravity inversion predicts thin crust and high continental lithosphere thinning factors in the Eurasia, Canada, Makarov, Podvodnikov and Baffin Basins

  10. A Simulation of crustal deformation around sourthwest Japan using 3D Finite Element Method

    Science.gov (United States)

    Oma, T.; Ito, T.; Sasajima, R.

    2015-12-01

    In southwest Japan, the Philippine Sea plate is subducting beneath the Amurian plate at the Nankai Trough. Megathrust earthquakes have been occurred with recurrence intervals of about 100-150 years. Previous studies have estimated co-seismic slip distribution at the 1944 Tokankai and the 1946 Nankai earthquakes and interplate plate coupling along the Nankai Trough. Many of previous studies employed a homogeneous elastic half space or elastic and viscoelastic layers structure. However, these assumptions as mentioned above are inadequate, since inhomogeneous structure is exceled in the real earth result from subducting plate. Therefore, in order to estimate the effect of inhomogeneous structure on the crustal deformation, we calculate crustal deformation due to Megathrust earthquake using 3-dimensional Finite Element Method (FEM). We use FEM software PyLith v2.1. In this study, we construct a finite element mesh with the region of 3000km(SW) × 2300km(NS) × 400km(depth) cover Japanese Islands, using Cubit 13.0. This mesh is considered topography, the Philippine Sea plate, the Pacific plate, Moho discontinuity, and curvature of the earth. In order to examine differences of surface displacement between inhomogeneous and homogeneous structures, we use co-seismic slip distribution of the 1944 and 1946 earthquakes estimated by Sagiya and Thatcher (1999). In result, surface elastic response under inhomogeneous structure becomes 30% larger than it's homogeneous structure at the Muroto cape. This difference indicates that co-seismic slip or plate coupling distribution estimated from Green's function under an assumption of homogeneous structure is overestimated. Then, we calculate viscoelastic response assuming Maxwell rheology model and viscosity as 1×1019. As a result, predicted horizontal velocity of viscoelastic response due to the events corresponds to 10 % of observed present deformation. It suggest that spatial pattern of plate coupling might be change when we

  11. Seismicity and crustal structure at the Mendocino triple junction, Northern California

    Energy Technology Data Exchange (ETDEWEB)

    Dicke, M.

    1998-12-01

    A high level of seismicity at the Mendocino triple junction in Northern California reflects the complex active tectonics associated with the junction of the Pacific, North America, and Gorda plates. To investigate seismicity patterns and crustal structure, 6193 earthquakes recorded by the Northern California Seismic Network (NCSN) are relocated using a one-dimensional crustal velocity model. A near vertical truncation of the intense seismic activity offshore Cape Mendocino follows the strike of the Mattole Canyon fault and is interpreted to define the Pacific plate boundary. Seismicity along this boundary displays a double seismogenic layer that is attributed to interplate activity with the North America plate and Gorda plate. The interpretation of the shallow seismogenic zone as the North America - Pacific plate boundary implies that the Mendocino triple junction is situated offshore at present. Seismicity patterns and focal mechanisms for events located within the subducting Gorda pl ate are consistent with internal deformation on NE-SW and NW-SE trending rupture planes in response to north-south compression. Seismic sections indicate that the top of the Gorda plate locates at a depth of about 18 Km beneath Cape Mendocino and dips gently east-and southward. Earthquakes that are located in the Wadati-Benioff zone east of 236{sup o}E show a change to an extensional stress regime indicative of a slab pull force. This slab pull force and scattered seismicity within the contractional forearc region of the Cascadia subduction zone suggest that the subducting Gorda plate and the overriding North America plate are strongly coupled. The 1992 Cape Mendocino thrust earthquake is believed to have ruptured a blind thrust fault in the forearc region, suggesting that strain is accumulating that must ultimately be released in a potential M 8+ subduction earthquake.

  12. Lower crustal flow and the role of shear in basin subsidence: An example from the Dead Sea basin

    Science.gov (United States)

    Al-Zoubi, A.; ten Brink, U.

    2002-01-01

    We interpret large-scale subsidence (5-6 km depth) with little attendant brittle deformation in the southern Dead Sea basin, a large pull-apart basin along the Dead Sea transform plate boundary, to indicate lower crustal thinning due to lower crustal flow. Along-axis flow within the lower crust could be induced by the reduction of overburden pressure in the central Dead Sea basin, where brittle extensional deformation is observed. Using a channel flow approximation, we estimate that lower crustal flow would occur within the time frame of basin subsidence if the viscosity is ??? 7 ?? 1019 - 1 ?? 1021 Pa s, a value compatible with the normal heat flow in the region. Lower crustal viscosity due to the strain rate associated with basin extension is estimated to be similar to or smaller than the viscosity required for a channel flow. However, the viscosity under the basin may be reduced to 5 ?? 1017 - 5 ?? 1019 Pa s by the enhanced strain rate due to lateral shear along the transform plate boundary. Thus, lower crustal flow facilitated by shear may be a viable mechanism to enlarge basins and modify other topographic features even in the absence of underlying thermal anomalies. ?? 2002 Elsevier Science B.V. All rights reserved.

  13. Death Drive

    OpenAIRE

    Stühler, Rebekka Hellstrøm

    2012-01-01

    The aim of this project is to investigate why the Freudian term Death Drive is not acknowledged in modern psychological therapy. On basis of psychoanalytical theory and through a literary analysis, the project will present a discussion of the significance and presence of the term within these practises.

  14. Foreland shortening and crustal balancing in the Andes at 30°S latitude

    Science.gov (United States)

    Allmendinger, R. W.; Figueroa, D.; Synder, D.; Beer, J.; Mpodozis, C.; Isaacks, B. L.

    1990-08-01

    Excellent surface exposures, known Benioff zone geometry, a dynamic morphology, and the availability of industry seismic reflection data all make the Andes at 30°S an excellent transect for investigating crustal-scale balanced sections. 150-170 km of horizontal shortening has occurred in three major belts located between the trench and the foreland. The thin-skinned, east-verging Precordillera of western Argentina accounts for 60-75% of the total shortening and formed mostly since major volcanism ceased at ˜10 Ma. Industry seismic reflection data show that the décollement of the Precordillera belt is located anomalously deep at ˜15 km. The belt is dominated by fault propagation folds and contains several prominent out-of-sequence thrust faults. Seismic stratigraphie analysis shows that Miocene strata in the Iglesia Valley, located between the Precordillera and the crest of the Andes, accumulated in a piggy-back basin. Onlap relations on the western side indicate that the High Cordillera was uplifted as a major fault bend fold over a buried ramp. Thrusting in the two western belts, both in the High Cordillera of Chile, formed during the waning stages of arc volcanism, 11-16 Ma. and account for 25-40% of the shortening. The observed shortening is probably greater than can be accounted for with reasonable crustal thicknesses, indicating the possibility of continental truncation or erosion along the plate margin or an anomalously thick root held down by the nearly flat subducted Nazca Plate. Our preferred crustal geometry puts the ramp between upper and lower crustal deformation west of the high topography, requiring crustal scale tectonic wedging to thicken the crust beneath the crest of the Andes. This non-unique model provides a simple explanation of the first order morphology of the Andes at this latitude.

  15. Slab detachment during continental collision: Influence of crustal rheology and interaction with lithospheric delamination

    Science.gov (United States)

    Duretz, T.; Gerya, T. V.

    2013-08-01

    Collision between continents can lead to the subduction of continental material. If the crust remains coupled to the downgoing slab, a large buoyancy force is generated. This force slows down convergence and promotes slab detachment. If the crust resists to subduction, it may decouple from the downgoing slab and be subjected to buoyant extrusion. We employ two-dimensional thermo-mechanical modelling to study the importance of crustal rheology on the evolution of subduction-collision systems. We propose simple quantifications of the mechanical decoupling between lithospheric levels (σ*) and the potential for buoyant extrusion of the crust (ξ*). The modelling results indicate that a variable crustal rheological structure results in slab detachment, delamination, or the combination of both mechanisms. A strong crust provides coupling at the Moho (low σ*) and remains coherent during subduction (low ξ). It promotes deep subduction of the crust (180 km) and slab detachment. Exhumation occurs in coherent manners via eduction and thrusting. Slab detachment triggers the development of topography (> 4.5 km) close to the suture. A contrasting style of collision occurs using a weak crustal rheology. Mechanical decoupling at the Moho (high σ*) promotes the extrusion of the crust (high ξ), disabling slab detachment. Ongoing shortening leads to buckling of the crust and development of topography on the lower plate. Collisions involving rheologically layered crust allow decoupling at mid-crustal depths. This structure favours both the extrusion of upper crust and the subduction of the lower crust. Such collisions are successively affected by delamination and slab detachment. Topography develops together with the buoyant extrusion of crust onto the foreland and is further amplified by slab detachment. Our results suggest that the occurrence of both delamination (Apennines) and slab detachment (Himalayas) in orogens may indicate differences in the initial crustal structure of

  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. 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.

  18. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics

    Science.gov (United States)

    Tackley, P. J.; Xie, S.

    2001-12-01

    The thermal and chemical evolution of Earth's mantle and plates are inextricably coupled by the plate tectonic - mantle convective system. Convection causes chemical differentiation, recycling and mixing, while chemical variations affect the convection through physical properties such as density and viscosity which depend on composition. It is now possible to construct numerical mantle convection models that track the thermo-chemical evolution of major and minor elements, and which can be used to test prospective models and hypotheses regarding Earth's chemical and thermal evolution. Model thermal and chemical structures can be compared to results from seismic tomography, while geochemical signatures (e.g., trace element ratios) can be compared to geochemical observations. The presented, two-dimensional model combines a simplified 2-component major element model with tracking of the most important trace elements, using a tracer method. Melting is self-consistently treated using a solidus, with melt placed on the surface as crust. Partitioning of trace elements occurs between melt and residue. Decaying heat-producing elements and secular cooling of the mantle and core provide the driving heat sources. Pseudo-plastic yielding of the lithosphere gives a first-order approximation of plate tectonics, and also allows planets with a rigid lid or intermittent plate tectonics to be modeled simply by increasing the yield strength. Preliminary models with an initially homogeneous mantle show that regions with a HIMU-like signature can be generated by crustal recycling, and regions with high 3He/4He ratios can be generated by residuum recycling. Outgassing of Argon is within the observed range. Models with initially layered mantles will also be investigated. In future it will be important to include a more realistic bulk compositional model that allows continental crust as well as oceanic crust to form, and to extend the model to three dimensions since toroidal flow may alter

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

    DEFF Research Database (Denmark)

    Schiffer, Christian; Stephenson, Randell Alexander; Oakey, Gordon

    2016-01-01

    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...

  20. Long-term exhumation of landscapes along the Pacific-North American plate boundary as inferred from apatite (U-Th)/He and ArcGIS analyses

    OpenAIRE

    Buscher, Jamie Todd

    2007-01-01

    The Pacific-North American plate boundary is typified by transpression and convergence, yet the relationship between interplate deformation and long-term crustal shortening is not fully understood. The continuous belt of rugged topography that extends along the entire plate boundary is generally associated with oblique tectonic plate motion, strong interplate coupling, and terrane accretion, but relating plate boundary orogenesis to variations in plate geometry and behavior requires detailed ...

  1. Episodic plate tectonics on Venus

    Science.gov (United States)

    Turcotte, Donald

    1992-01-01

    Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

  2. Crustal Thickness in Northern Andes Using pP and sS Precursors at Teleseismic Distances

    Science.gov (United States)

    Aranda Camacho, N. M.; Assumpcao, M.

    2013-12-01

    The Andean belt is a result of the subduction of the Nazca plate beneath the South American continental plate. It has an extension of 8000 km from Venezuela to Tierra del Fuego. While the crustal-thickness is a well-known property in Southern and Central Andes, it is still poorly known in the Northern Andes (between 10°N and 4° S). The crustal thickness is a very important property to understand the crustal evolution such as in geodynamic models and in modeling wave-propagation in global and regional seismic studies. Due to the high seismic activity at intermediate depths in the Northern Andes, it is possible to use the teleseismic P-wave and S-wave trains to find the crustal-thickness. In this study, we analyze the reflections from the underside of the Moho for intermediate and deep earthquakes in the northern Andes recorded at teleseismic distances (between 40°- 85°), and estimate the crustal-thickness at the bounce points of the pP and sS wave by converting the delay time between the phases pP and pmP and also between sS and smS into crustal thickness. This method can be applied in zones with earthquakes having magnitude larger than 6 for that reason the Northern Andes is a favorable area to develop it. We analyzed five events from the Northern Andes with magnitude larger than 6 and deeper than 100 km. The crustal thickness was calculated using the P wave with the vertical component and the S wave using both transverse SH and radial SV components. We find that the crustal-thickness in this area varied from 27.9 × 2.4 km at (76.48 W, 4.82 N) to 55.7 × 5.2 km at (77.92 W, 2 S). Our results show a crustal-thickness consistent with a compilation made for a larger region that includes our research area, showing residuals between -4 km and 4 km in most of the bounce points . We are getting results in areas that have not been studied previously so it will help to increase the database of crustal-thicknesses for the Northern Andes.

  3. The Alps 2: Controls on crustal subduction and (ultra)high-pressure rock exhumation in Alpine-type orogens

    Science.gov (United States)

    Butler, Jared P.; Beaumont, Christopher; Jamieson, Rebecca A.

    2014-07-01

    Building on our previous results, we use 2-D upper mantle-scale thermomechanical numerical models to explore key controls on the evolution of Alpine-type orogens and the Alps per se, focusing on (ultra)high-pressure ((U)HP) metamorphic rocks. The models show that UHP rocks form and exhume by burial and subsequent buoyant ascent of continental crust in the subduction conduit. Here we test the sensitivity of the models to surface erosion rate, crustal heat production, plate convergence/divergence rates, geometry of the subducting continental margin, and strength of the retrocontinent. Surface erosion affects crustal exhumation but not early buoyant exhumation. Metamorphic temperatures increase with crustal radioactive heat production. Maximum burial depth prior to exhumation increases with plate convergence rates, but exhumation rates are only weakly dependent on subduction rates. Onset of absolute plate divergence does not trigger exhumation in these models. We conclude that contrasting peak pressures, exhumation rates, and volumes of (U)HP crust exhumed in the Alps orogen primarily reflect along-strike contrasts in the geometry, thermal structure, and/or strength of the subducting microcontinent (Briançonnais) and continental (European margin) crust. The experiments also support the interpretation that the Western Alps (U)HP Internal Crystalline Massifs exhumed as composite, stacked plumes and that these plumes drove local crustal extension during orogen-scale shortening. For weak upper plate retrocrusts, postexhumation retrothrusting forms a retrowedge. Overall, these results are consistent with predictions using the exhumation number (ratio of buoyancy to side traction forces in the conduit), which expresses the combined parameter control of the depth/volume of crustal subduction and the transition to buoyant exhumation.

  4. The fluid budget of a continental plate boundary fault: Quantification from the Alpine Fault, New Zealand

    Science.gov (United States)

    Menzies, Catriona D.; Teagle, Damon A. H.; Niedermann, Samuel; Cox, Simon C.; Craw, Dave; Zimmer, Martin; Cooper, Matthew J.; Erzinger, Jörg

    2016-07-01

    Fluids play a key role in modifying the chemical and physical properties of fault zones, which may prime them for repeated rupture by the generation of high pore fluid pressures and precipitation of commonly weak, secondary minerals. Fluid flow paths, sources and fluxes, and the permeability evolution of fault zones throughout their seismic cycles remain poorly constrained, despite their importance to understanding fault zone behaviour. Here we use geochemical tracers of fluid-rock exchange to determine budgets for meteoric, metamorphic and mantle fluids on a major compressional tectonic plate boundary. The Alpine Fault marks the transpressional Pacific-Australian plate boundary through South Island, New Zealand and appears to fail in regular (329 ± 68 yrs) large earthquakes (Mw ∼ 8) with the most recent event in 1717 AD. Significant convergent motion has formed the Southern Alps and elevated geothermal gradients in the hangingwall, which drive crustal fluid flow. Along the Alpine Fault the Alpine Schist of the Pacific Plate is thrust over radiogenic metasedimentary rocks on the Australian plate. The absence of highly radiogenic (87Sr/86Sr > 0.7200) strontium isotope ratios of hangingwall hot springs and hydrothermal minerals formed at a range of depths in the Alpine Fault damage zone indicates that the fluid flow is restricted to the hangingwall by a cross-fault fluid flow barrier throughout the seismogenic crust. Helium isotope ratios measured in hot springs near to the Alpine Fault (0.15-0.81 RA) indicate the fault is a crustal-scale feature that acts as a conduit for fluids from the mantle. Rock-exchanged oxygen, but meteoric water-like hydrogen isotope signatures of hydrothermal veins indicate that partially rock-exchanged meteoric fluids dominate down to the top of the brittle to ductile transition zone at ∼6 km. Geochemical tracer transport modelling suggests only ∼0.02 to 0.05% of total rainfall west of the Main Divide penetrates to depth, yet this

  5. Create Your Plate

    Medline Plus

    Full Text Available ... A A A Listen En Español Create Your Plate Create Your Plate is a simple and effective ... and that your options are endless. Create Your Plate! Click on the plate sections below to add ...

  6. Crustal Structure of Iraq from Receiver Functions and Surface Wave Dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Gok, R; Mahdi, H; Al-Shukri, H; Rodgers, A J

    2006-08-31

    We report the crustal structure of Iraq, located in the northeastern Arabian plate, estimated by joint inversion of P-wave receiver functions and surface wave group velocity dispersion. Receiver functions were computed from teleseismic recordings at two temporary broadband seismic stations in Mosul (MSL) and Baghdad (BHD), separated by approximately 360 km. Group velocity dispersion curves at the sites were derived from continental-scale tomography of Pasyanos (2006). The inversion results show that the crustal thicknesses are 39 km at MSL and 43 km at BHD. Both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km at station MSL and 7 km at BHD, agreeing well with the existing models. Ignoring the sediments, the crustal velocities and thicknesses are remarkably similar between the two stations, suggesting that the crustal structure of the proto-Arabian Platform in northern Iraq was uniform before subsidence and deposition of the sediments in the Cenozoic. Deeper low velocity sediments at BHD are expected to result in higher ground motions for earthquakes.

  7. Excitation and Characterization of Chladni Plate Patterns

    Science.gov (United States)

    Bourke, Shannon; Behringer, Ernest

    2011-04-01

    When a thin metal plate with a small amount of sand on it is made to vibrate, aesthetically pleasing sand patterns can form along the nodal lines of the plate. These symmetric patterns are called Chladni Patterns. Students taking PHY 101 Physical Science in the Arts at Eastern Michigan University create these patterns by pulling a violin bow across the edge of a plate, or by using a mechanical oscillator to drive the center of a plate. These two methods only allow a small subset of all possible points on the plate to be excited. We designed and built an electronic device that allows its user to excite the plate at any point. We present patterns created with this electronic device and other methods, and describe ways to model the observed patterns.

  8. 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.

  9. Trace element differences between Archean, Proterozoic and Phanerozoic crustal components: Implications for crustal growth processes

    Science.gov (United States)

    Tarney, J.; Wyborn, L. E. A.; Sheraton, J. W.; Wyborn, D.

    1988-01-01

    Critical to models for continental crust growth and recycling are the processes through which crustal growth takes place. In particular, it is important to know whether these processes have changed fundamentally with time in response to the earth's thermal evolution, and whether the crustal compositions generated are compatible with crustal remobilization, crustal recycling, or represent primary additions. There are some significant and consistent differences in the major and trace element compositions of crustal components with time which have important implications for crustal growth processes. These will be illustrated with reference to Archean rocks from a number of shield areas, Proterozoic granitoids from Australia and elsewhere, Palaeozoic granitoids from Australia and Scotland, and Mesozoic - recent granitoids from present continental margin belts. Surprisingly some rather simple and consistent patterns energy using this technique. There are then significant differences in compositions of granitoid crustal additions throughout geological time, with a particular type of granitoid apparently dominating a particular time period. This implies that the tectonic processes giving rise to granite generation have changed in response to the earth's thermal evolution.

  10. Crustal structure of the Khartoum Basin, Sudan

    CSIR Research Space (South Africa)

    El Tahir, N

    2013-05-01

    Full Text Available Tectonophysics Vol. 593 (2013) 151–160 Crustal structure of the Khartoum Basin, Sudan Nada El Tahir a,b,*, Andrew Nyblade a,b, Jordi Julià c, Raymond Durrheim a,d a School of Geosciences, The University of the Witwatersrand, Johannesburg, South... Centre for Mining Innovation, Johannesburg, South Africa *Corresponding author: nada_ahmed99@hotmail.com Abstract The crustal structure of the northern part of the Khartoum Basin has been investigated using data from 3 permanent seismic stations...

  11. Crustal accretion at high temperature spreading centres: Rheological control of crustal thickness

    Science.gov (United States)

    Schmeling, Harro

    2010-12-01

    New determinations of lateral crustal thickness variations at anomalous oceanic spreading centres such as Iceland have shown that the crust may be thinner at the ridge axis above the plume thickening towards the sides ( Bjarnason and Schmeling, 2009). To understand this behaviour crustal accretion models have been carried out solving the conservation equations of mass, momentum and energy with melting, melt extraction, and feedback of extracted material as newly formed crust for an extending lithosphere system underlain by a hot mantle plume. The dynamics of rifting are thermally and rheologically controlled by the feedback due to accreted new crust. Four accretional modes with characteristic crustal thickness variations are identified depending on the width of the volcanic emplacement zone, the accretional heating rate, which can be associated with the thickness of the surface layer in which magmatic emplacement takes place, and the spreading rate. Mode 1: zero crustal thickness at the spreading axis develops for cool accretion and a wide emplacement zone. Mode 2: strongly or moderately crustal thickening away from the axis develops in case of warm (deep reaching) accretion and wide emplacement zones. Mode 3: nearly constant crustal thickness develops in case of warm (deep reaching) accretion but narrow emplacement zones. Dynamic topography of mode 3 shows only a weak or no regional minimum at all near the axis. Modes 2 or 3 may be identified with the situation in Iceland. Mode 4: a stagnating central crustal block evolves for cool accretion and narrow emplacement. This mode disappears for increasing spreading rates. No accretional mode with maximum crustal thickness above the plume at the rift axis has been found. The absence of mode 1 accretion (with zero crust at ridge axis) on earth may be an indication that in general crustal accretion is not cold (and shallow). The model is also applied to other hotspot-ridge settings (Azores, Galapagos) and suggests modes 2

  12. Contemporary vertical crustal motion in the Pacific Northwest

    Science.gov (United States)

    Holdahl, Sandford R.; Faucher, Francois; Dragert, Herb

    A map of recent vertical crustal motion has been compiled for coastal Washington and southwest British Columbia. Average velocities over the past 80 years were determined by least squares adjustment of repeated precise levelings and mean sea-level observations from 21 tide gauges. Annual variations in mean sea level were determined directly within the adjustment model under the assumption that they were identical at all tide gauges in a given year. The derived vertical velocities range from -2.0±0.9 mm/yr near Seattle, to 2.5±0.8 mm/yr at the northwest tip of the Olympic Peninsula, and over 3 mm/yr in the region to the north of Campbell River on Vancouver Island. Determination of a constant velocity in this latter region is complicated by about 10 cm of coseismic subsidence associated with a magnitude 7.3 earthquake in 1946, and an apparent increase in uplift rate over the past decade. Qualitatively, the regional velocity pattern is consistent with features of the current plate convergence model: 1) the rapid uplift of the region north of central Vancouver Island is consistent with the overriding of the young (Explorer Plate which may be underplating the coastal margin in this area; and 2) the ridge of uplift extending from the Neah Bay area north across Vancouver Island to Campbell River is consistent with a pattern expected from a locked subduction zone underlying this coastal region. The large-scale subsidence to the southwest of Puget Sound is more difficult to explain in the context of plate convergence.

  13. A view into crustal evolution at mantle depths

    Science.gov (United States)

    Kooijman, Ellen; Smit, Matthijs A.; Ratschbacher, Lothar; Kylander-Clark, Andrew R. C.

    2017-05-01

    melted, densified, and buried to 80-90 km depth - 20 km deeper than the present-day Moho - at 930 ± 35°C. The material descended rapidly, accelerating from 0.9-1.7 mm yr-1 to 4.7-5.8 mm yr-1 within 10-12 Myr, and continued descending after reaching mantle depth at 14-13 Ma. The data reflect the foundering of differentiated deep-crustal fragments (2.9-3.5 g cm-3) into a metasomatized and less dense mantle wedge. Through our new approach in constraining the burial history of rocks, we provided the first time-resolved record of this crustal-recycling process. Foundering introduced vestiges of old evolved crust into the mantle wedge over a relatively short period (c. 10 Myr). The recycling process could explain the variability in the degree of crustal contamination of mantle-derived magmatic rocks in the Pamir and neighboring Tibet during the Cenozoic without requiring a change in plate dynamics or source region.

  14. Crustal rheology controls on the Tibetan plateau formation during India-Asia convergence

    Science.gov (United States)

    Chen, Lin; Capitanio, Fabio A.; Liu, Lijun; Gerya, Taras V.

    2017-07-01

    The formation of the Tibetan plateau during the India-Asia collision remains an outstanding issue. Proposed models mostly focus on the different styles of Tibetan crustal deformation, yet these do not readily explain the observed variation of deformation and deep structures along the collisional zone. Here we use three-dimensional numerical models to evaluate the effects of crustal rheology on the formation of the Himalayan-Tibetan orogenic system. During convergence, a weaker Asian crust allows strain far north within the upper plate, where a wide continental plateau forms behind the orogeny. In contrast, a stronger Asian crust suppresses the plateau formation, while the orogeny accommodates most of the shortening. The stronger Asian lithosphere is also forced beneath the Indian lithosphere, forming a reversed-polarity underthrusting. Our results demonstrate that the observed variations in lithosphere deformation and structures along the India-Asia collision zone are primarily controlled by the strength heterogeneity of the Asian continental crust.

  15. A COMPARISON OF TWO METHODS FADING MEMORY FILTER AND ADAPTIVE KALMAN FILTER IN MONITORING CRUSTAL MOVEMENT

    Directory of Open Access Journals (Sweden)

    Cahit Tağı ÇELİK

    2004-01-01

    Full Text Available Monitoring the Crustal Movement in Geodesy is performed by the deformation survey and analysis. If monitoring the crustal movements involves more than two epochs of survey campaign then from the plate tectonic theory, stations do not move randomly from one epoch to the other, therefore Kalman Filter may be suitable to use. However, if sudden movements happened in the crust in particular earthquake happened, the crust moves very fast in a very short period of time. When Kalman Filter used for monitoring these movements, from associated epoch, for a number of epochs the results may be biased. In the paper, comparison of two methods for elimination of the above mentioned biases have been performed. These methods are Fading Memory Filter and Adaptive Kalman Filter for an unknown bias.

  16. 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.

  17. Distribution of crustal types in Canada Basin, Arctic Ocean

    Science.gov (United States)

    Chian, D.; Jackson, H. R.; Hutchinson, D. R.; Shimeld, J. W.; Oakey, G. N.; Lebedeva-Ivanova, N.; Li, Q.; Saltus, R. W.; Mosher, D. C.

    2016-11-01

    Seismic velocities determined from 70 sonobuoys widely distributed in Canada Basin were used to discriminate crustal types. Velocities of oceanic layer 3 (6.7-7.1 km/s), transitional (7.2-7.6 km/s) and continental crust (5.5-6.6 km/s) were used to distinguish crustal types. Potential field data supports the distribution of oceanic crust as a polygon with maximum dimensions of 340 km (east-west) by 590 km (north-south) and identification of the ocean-continent boundary (OCB). Paired magnetic anomalies are associated only with crust that has oceanic velocities. Furthermore, the interpreted top of oceanic crust on seismic reflection profiles is more irregular and sometimes shallower than adjacent transitional crust. The northern segment of the narrow Canada Basin Gravity Low (CBGL), often interpreted as a spreading center, bisects this zone of oceanic crust and coincides with the location of a prominent valley in seismic reflection profiles. Data coverage near the southern segment of CBGL is sparse. Velocities typical of transitional crust are determined east of it. Extension in this region, close to the inferred pole of rotation, may have been amagmatic. Offshore Alaska is a wide zone of thinned continental crust up to 300 km across. Published longer offset refraction experiments in the Basin confirm the depth to Moho and the lack of oceanic layer 3 velocities. Further north, toward Alpha Ridge and along Northwind Ridge, transitional crust is interpreted to be underplated or intruded by magmatism related to the emplacement of the High Arctic Large Igneous Province (HALIP). Although a rotational plate tectonic model is consistent with the extent of the conjugate magnetic anomalies that occupy only a portion of Canada Basin, it does not explain the asymmetrical configuration of the oceanic crust in the deep water portion of Canada Basin, and the unequal distribution of transitional and continental crust around the basin.

  18. The role of crustal quartz in controlling Cordilleran deformation.

    Science.gov (United States)

    Lowry, Anthony R; Pérez-Gussinyé, Marta

    2011-03-17

    Large-scale deformation of continents remains poorly understood more than 40 years after the plate tectonic revolution. Rock flow strength and mass density variations both contribute to stress, so both are certain to be important, but these depend (somewhat nebulously) on rock type, temperature and whether or not unbound water is present. Hence, it is unclear precisely how Earth material properties translate to continental deformation zones ranging from tens to thousands of kilometres in width, why deforming zones are sometimes interspersed with non-deforming blocks and why large earthquakes occasionally rupture in otherwise stable continental interiors. An important clue comes from observations that mountain belts and rift zones cyclically form at the same locations despite separation across vast gulfs of time (dubbed the Wilson tectonic cycle), accompanied by inversion of extensional basins and reactivation of faults and other structures formed in previous deformation events. Here we show that the abundance of crustal quartz, the weakest mineral in continental rocks, may strongly condition continental temperature and deformation. We use EarthScope seismic receiver functions, gravity and surface heat flow measurements to estimate thickness and seismic velocity ratio, v(P)/v(S), of continental crust in the western United States. The ratio v(P)/v(S) is relatively insensitive to temperature but very sensitive to quartz abundance. Our results demonstrate a surprising correlation of low crustal v(P)/v(S) with both higher lithospheric temperature and deformation of the Cordillera, the mountainous region of the western United States. The most plausible explanation for the relationship to temperature is a robust dynamical feedback, in which ductile strain first localizes in relatively weak, quartz-rich crust, and then initiates processes that promote advective warming, hydration and further weakening. The feedback mechanism proposed here would not only explain

  19. Crustal stress regime in Italy

    Directory of Open Access Journals (Sweden)

    M. Cesaro

    1997-06-01

    Full Text Available In order to obtain a reliable map of the present-day stress field in Italy, needed to better understand the active tectonic processes and to contribute to the assessment of seismic hazard, in 1992 we started to collect and analyze new data from borehole breakouts in deep oil and geothermal wells and focal mechanisms of earthquakes (2.5 < M <5 occurred in Italy between 1988 and 1995. From about 200 deep wells and 300 focal mechanisms analyzed to date, we infer that: the internal (SW sector of the Northern Apenninic arc is extending with minimum compressional stress (Shmin oriented ? ENE, while the external front is thrusting over the Adriatic foreland (Shmin ? NW-SE. The entire Southern Apennine is extending in NE direction (from the Tyrrhenian margin to the Apulian foreland and compression (in the foredeep is no longer active at the outer (NE thrust front. Between these two arcs, an abrupt change in the tectonic regime is detected with directions of horizontal stress changing by as much as 90º in the external front, around latitude 430N. Along the Ionian side of the Calabrian arc the stress directions inferred from breakouts and focal mechanisms are scattered with a hint of rotation from N-S Shmin close to the Southern Apennines, to ~ E-W directions in the Messina Strait. In Sicily, a NW-SE direction of SHmax is evident in the Hyblean foreland, parallel to the direction of plate motion between Africa and Europe. A more complex pattern of stress directions is observed in the thrust belt zone, with rotations from the regional trend (NW í directed SHmax to NE oriented SHmax. A predominant NW direction of SHmax is also detected in mainland Sicily from earthquake focal mechanisms, but no well data are available in this region. In the northern part of Sicily (Aeolian Islands a ~N-S direction of SHmax is observed.

  20. Kinematics of the crustal velocity field in the western US

    Science.gov (United States)

    Pollitz, F. F.

    2008-12-01

    GPS measurements embodied in PBO and PBO Nucleus allow the crustal velocity field of the western US to be constructed in unprecedented detail. Velocity and strain fields span the entire San Andreas fault system and Cascadia subduction zone from Baja California to northern Washington as well as the continental interior including the Great Basin and Wasatch Front. Rationalizing the GPS velocity field over the several tectonic regimes provides key tests of prevailing notions of interseismic crustal deformation. In our interpretation, we begin with the premise that the load-carrying portion of the lithosphere coincides with the (seismogenic) upper crust with an effective elastic thickness of ~20 km at the time scales of interseimic motions (Thatcher and Pollitz, 2008). End member kinematic models include (1) viscoelastic relaxation of the ductile lower crust and upper mantle following large earthquakes, and (2) slip in the lower elastic lithosphere, each of which serves to localize strain around major faults during interseismic periods. More detailed kinematic models emphasize the roles of lateral variations in rigidity and/or effective elastic plate thickness as well as distributed deformation. Our modeling of western US kinematics shows that the GPS velocity field is well explained with a range of models involving a combination of all of the above components; no single endmember suffices. Zones of inferred distributed deformation in the continental interior coincide with well-known seismic belts (Eastern California Shear Zone; Walker Lane; Interseismic Mountain Belt). Continued acquisition of vector constraints on crustal motions and study of available geodetic data are needed to clarify active deformation patterns in several areas. Some outstanding issues are: The nature of distributed faulting at the margins of the Great Basin (southern Nevada Transverse Zone, northern Walker Lane); understanding how dextral shear from the eastern boundary of the Sierra Nevada

  1. Nd Isotope Constraint on Crustal Replacement Induced by Subduction of Paleo-Pacific Plate in the Yanbian Area, NE China%古太平洋板块俯冲对延边地区深部地壳的置换作用:显生宙花岗岩的 Nd 同位素制约

    Institute of Scientific and Technical Information of China (English)

    黄秘伟; 郭锋; 赵亮; 李竞妍

    2015-01-01

    延边地区晚古生代–早白垩世花岗岩的 Nd 同位素研究显示,该区可以富尔河–古洞河断裂为界划分为南北两个岩区。北区显示亏损、年轻的源区特征(εNd(t)=-0.7~+3.8, tDM2=691~976 Ma),南区可能继承了古老富集端元组分(εNd(t)=–13.6~–0.6, tDM2=1004~2166 Ma)。从二叠纪到白垩纪,北区花岗岩的εNd(t)值随着年龄变新递减,南区的εNd(t)值则随着年龄变新递增,并在早白垩世时两区花岗岩的εNd(t)值达到基本相同。这种 Nd 同位素组成的变化趋势,说明南北两区深部地壳物质组成随时间变新而趋于均一化,反映了北区和南区先前存在的古亚洲洋型增生地壳和华北克拉通古老再循环地壳,在中生代期间遭受了古太平洋板块俯冲形成的新增生弧地壳的强烈改造和置换,使得两区深部地壳组成在白垩纪时基本一致。该研究结果为深入理解中生代古太平洋俯冲作用对东北地区深部地壳的改造过程提供了可靠的同位素地球化学制约。%A detailed Nd isotopic study on the Late Paleozoic-Early Cretaceous granitoids from the Yanbian area, NE China, is presented in this paper. The new results show that there are two granite zones in the area, i.e., the North and South Granite Zones separated by the Fu’erhe-Gudonghe Fault. Most of the granitoids in the Northern Zone are characterized by positive εNd(t) values (-0.7–+3.8) and younger tDM2 model ages (691–976 Ma), suggesting a significant contribution of juvenile crustal material. In contrasting, the granitoids in the South Zone show negative εNd(t) values, ranging from –13.6 to –0.6, and older tDM2 ages of 1004–2166 Ma, implying that the Precambrian old recycled crust of North China Craton played a significant role in the generation of these rocks. Following the youthening of the emplacement age, the εNd(t) value of the granitoids in the North Zone decreases gradually, whereas it increases in the

  2. Crustal Movement Patterns of China Continent Measured by GPS

    Institute of Scientific and Technical Information of China (English)

    YAO Yibin

    2003-01-01

    This paper uses multi-quadric equations interpolation to es-tablish a widely covered and valuablespeed field model of China, withwhich the horizontal crustal movementpatterns are obtained. The present-dayvertical crustal movement velocity im-age of China is also expressed by GPSobservations, from which we canknow the vertical crustal movementpatterns.

  3. 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.

  4. Rheological and geodynamic controls on the mechanisms of subduction and HP/UHP exhumation of crustal rocks during continental collision : Insights from numerical models

    NARCIS (Netherlands)

    Burov, Evgene; Francois, Thomas; Agard, Philippe; Le Pourhiet, Laetitia; Meyer, Bertrand; Tirel, C.|info:eu-repo/dai/nl/304838209; Lebedev, Sergei; Yamato, Philippe; Brun, Jean Pierre

    2014-01-01

    While subduction of crustal rocks is increasingly accepted as a common scenario inherent to convergent processes involving continental plates and micro-continents, its occurrence in each particular context, as well as its specific mechanisms and conditions is still debated. The presence of

  5. Rheological and geodynamic controls on the mechanisms of subduction and HP/UHP exhumation of crustal rocks during continental collision : Insights from numerical models

    NARCIS (Netherlands)

    Burov, Evgene; Francois, Thomas; Agard, Philippe; Le Pourhiet, Laetitia; Meyer, Bertrand; Tirel, C.; Lebedev, Sergei; Yamato, Philippe; Brun, Jean Pierre

    2014-01-01

    While subduction of crustal rocks is increasingly accepted as a common scenario inherent to convergent processes involving continental plates and micro-continents, its occurrence in each particular context, as well as its specific mechanisms and conditions is still debated. The presence of ultra-hig

  6. Outer rise seismicity of the subducting Nazca Plate: Plate stress distribution, fault orientation and plate hydration

    Science.gov (United States)

    Barama, Louisa

    Subduction of the Nazca plate beneath the South American plate drives frequent and sometimes large magnitude earthquakes. During the past 40 years, significant numbers of outer rise earthquakes have occurred in the offshore regions of Colombia and Chile. In this study, we investigate the distribution of stress due to lithospheric bending and the extent of faults within the subducting plate. To calculate more accurate epicenters and to constrain which earthquakes occurred within the outer rise, we use hypocentroidal decomposition to relocate earthquakes with Global Centroid Moment Tensor (GCMT) solutions occurring after 1976 offshore Colombia and Chile. We determine centroid depths of outer rise earthquakes by inverting teleseismic P-, SH-, and SV- waveforms for earthquakes occurring from 1993 to 2014 with Mw ≥ 5.5. In order to further constrain the results of the waveform inversion, we estimate depths by comparing earthquake duration, amplitude, and arrival times for select stations with waveforms with good signal to noise ratios. Our results indicate that tensional earthquakes occur at depths down to 13 km and 24 km depth beneath the surface in the Colombia and Chile regions, respectively. Since faulting within the outer rise can make the plate susceptible to hydration and mantle serpentinization, we therefore infer the extent of possible hydration of the Nazca plate to extend no deeper than the extent of tensional outer rise earthquakes.

  7. Investigation of the Crustal Structure in the Middle East from Body-Wave Analysis (POSTPRINT). Annual Report 2

    Science.gov (United States)

    2012-06-05

    this region. The Zagros Mountains exhibit tectonic features resulting from the collision of the Arabian and Eurasian plates . Investigations of Pn and Pg...study encompasses crustal studies obtained with seismic waveform data from stations throughout the Middle East. This effort generates an...unprecedented dataset for this region consisting of 173 seismic stations, including 53 high-quality broadband stations and over 58,000 local and regional events

  8. Is South-eastward Crustal Flow Possible around East Himalayan Syntax? - New Insights from SINOPROBE Magnetotellurics Array Data

    Science.gov (United States)

    Dong, H.; Wei, W.; Ye, G.; Jin, S.; Jing, J.; Jones, A. G.; Zhang, L.; Xie, C.; Yin, Y.; Wang, G.

    2015-12-01

    The south-eastward expansion of Tibet plateau in eastern Tibet is considered a key process for understanding the large scale uplift and crustal thickening without significant concomitant crustal shortening. However, the geodynamic processes creating this iconic process is still unclear and hotly debated. Two popular geodynamic models, namely crustal flow at mid-to-lower crustal depths and coherent deformation between the crust and lithospheric mantle, are commonly appealed to as the expansion's driving mechanism. However, neither of these mechanisms is able to reconcile all of the abundant geological and geophysical data. In this study we present a three-dimensional (3D) geo-electrical model, derived from SINOPROBE magnetotelluric (MT) array data, which reveals the geo-electrical and rheological structure in southeast Tibet that brings new insights into the region. Instead of continuous NW-SE conductive channels proposed in previous two-dimensional (2D) MT studies, a large-scale N-S directed resistive structure is revealed to disconnect the conductors from the crust to the upper mantle, arguing against the model of south-eastward (downslope) channel flow. Furthermore, distinct NNE directed conductive anomalies, which are perpendicular to the surface structures, are identified in the mid-to-lower crust. We interpret these anomalies as distributed NNE oriented crustal flow channels, which might cause the azimuthal clockwise extension around East Himalayan Syntax and partly contributed to the south-eastward expansion of eastern Tibet.

  9. Crustal deformation in northern Central America

    Science.gov (United States)

    Cáceres, Diego; Monterroso, David; Tavakoli, Behrooz

    2005-07-01

    Evaluation of the seismic moment tensor for earthquakes on plate boundary is a standard procedure to determine the relative velocity of plates, which controls the seismic deformation rate predicted from the slip on a single fault. The moment tensor is also decomposed into an isotropic and a deviatoric part to discover the relationship between the average strain rate and the relative velocity between two plates. We utilize this procedure to estimate the rates of deformation in northern Central America where plate boundaries are seismically well defined. Four different tectonic environments are considered for modelling of the plate motions. The deformation rates obtained here compare well with those predicted from the plate motions models and are in good agreement with actual observations. Deformation rates on faults are increasingly being used to estimate earthquake recurrence from information on fault slip rate and more on how we can incorporate our current understanding into seismic hazard analyses.

  10. How plume-ridge interaction shapes the crustal thickness pattern of the Réunion hotspot track

    Science.gov (United States)

    Bredow, Eva; Steinberger, Bernhard; Gassmöller, Rene; Dannberg, Juliane

    2017-08-01

    The Réunion mantle plume has shaped a large area of the Earth's surface over the past 65 million years: from the Deccan Traps in India along the hotspot track comprising the island chains of the Laccadives, Maldives, and Chagos Bank on the Indian plate and the Mascarene Plateau on the African plate up to the currently active volcanism at La Réunion Island. This study addresses the question how the Réunion plume, especially in interaction with the Central Indian Ridge, created the complex crustal thickness pattern of the hotspot track. For this purpose, the mantle convection code ASPECT was used to design three-dimensional numerical models, which consider the specific location of the plume underneath moving plates and surrounded by large-scale mantle flow. The results show the crustal thickness pattern produced by the plume, which altogether agrees well with topographic maps. Especially two features are consistently reproduced by the models: the distinctive gap in the hotspot track between the Maldives and Chagos is created by the combination of the ridge geometry and plume-ridge interaction; and the Rodrigues Ridge, a narrow crustal structure which connects the hotspot track and the Central Indian Ridge, appears as the surface expression of a long-distance sublithospheric flow channel. This study therefore provides further insight how small-scale surface features are generated by the complex interplay between mantle and lithospheric processes.

  11. When Did Plate Tectonics Begin

    Science.gov (United States)

    Brown, M.

    2015-12-01

    Present-day plate tectonics on Earth is characterized by asymmetric (one-sided) subduction, but how do we recognize the imprint of subduction in the geologic record? How do we weigh global (commonly younger) vs local (commonly older) datasets or distinguish initiation from episodic from continuous subduction? How reliable are data gaps? Characteristics of the Paleozoic record of subduction include calc-alkaline magmatism, blueschist/UHP metamorphism and collisional orogenesis, and ophiolites as representatives of former ocean lithosphere. Are these characteristic rocks preserved in Proterozoic, Archean and Hadean crust? Does a hotter mantle, higher heat production and weaker lithosphere modify or eliminate these features? What preceded subduction and how do we recognize that regime? Are rock associations or geochemical fingerprints reliable? Does reworking and overprinting modify geochemical fingerprints? Proposals for the start of plate tectonics have been based on: persistence of isotope anomalies/fractionated chemical domains in the mantle; changes in chemistry of magmatic rocks, rates of crustal growth vs reworking, and sites of growth; the metamorphic record, particularly the first appearance of contrasting thermal gradients or eclogite (including evidence from mineral inclusions in diamonds) or UHP metamorphic rocks; stabilization of cratonic lithosphere and formation of supercratons, and the beginning of the Proterozoic supercontinent cycle; the end of the flat Earth, emergence of continents, development of significant topography, changes in the style of orogeny and the rise in atmospheric oxygen; and, the appearance of passive margins and changes in the style of sedimentation. Estimates of the timing have varied from the Hadean to Neoproterozoic. I will summarize evidence for a growing consensus that the late Mesoarchean to early Paleoproterozoic was a 700 Myr long period of transition to continuous (?) subduction and global (?) mobile-lid plate tectonics.

  12. Two opposed subduction modes at the southern Caribbean plate margin of Colombia

    Science.gov (United States)

    Kammer, Andreas; Piraquive, Alejandro

    2014-05-01

    Cretaceous to Paleogene convergence at the southern Caribbean plate margin is still little deciphered and a generalized interpretation is hindered by the absence of regionally correlatable tectonic elements, like magmatic arcs, time constraints and an intense crustal fragmentation brought about by Neogene strike-slip tectonics. In order to illustrate the diversity of these subduction settings and discuss possible tectonic controls on their subsequent collisional evolution, we outline the structural evolution along a thickened and a thinned continental segment. The first case is exemplified by the Sierra Nevada de Santa Marta, a triangular block that exposes an imbricated lower crustal section capped by nested plutons and a volcanic sequence of a Jurassic to Early Cretaceous arc. This exceptionally thick crustal section forms the upper plate of a continent-ward dipping main suture that is underlain by strongly sheared platform sediments and transitional basement rocks of a lower plate. Penetrative deformation developed under medium-grade conditions with a uniform top-to-the NE shear attests to a stable subduction interval of a still unknown duration. Onset of a collisional phase is marked by a crustal imbrication further inboard of the main suture, leading to a further crustal thickening, and links in the Paleogene to the emplacement of the dome-like Santa Marta batholith within the lower plate. It is likely that the juxtaposition of thickened continental Southamerican and thinner oceanic Caribbean crust triggered a crustal channel flow that fed the magmatic dome in the transitional part of these crustal realms, leading thus to some gravitational collapse of the continental crust. The opposite case of the juxtaposition of a continental platform, previously thinned by Jurassic to Early Cretaceous rifting and a relatively thick Caribbean crust is documented in the northwestern Guajira Peninsula. Here platform sequences and their corresponding basement were subducted

  13. Magnetar Field Evolution and Crustal Plasticity

    Science.gov (United States)

    Lander, S. K.

    2016-06-01

    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.

  14. Crustal kinematics of the Colorado Plateau from GPS geodesy

    Science.gov (United States)

    Holland, A. A.; Broermann, J.; Bennett, R. A.; Kreemer, C.; Blewitt, G.

    2013-12-01

    We present results from new continuous and campaign GPS networks spanning the state of Arizona and the southern portion of Utah. The 33 station continuous GPS network, funded by the NSF EarthScope Program, supplements a sparse distribution of continuous GPS stations that comprise the NSF EarthScope Plate Boundary Observatory network. The campaign network originally established by the National Geodetic survey in the mid-1990's, has been reoccupied two or more times over the past five years with support from the Arizona Geological Survey. The data from the continuous GPS stations are analyzed independently with the GIPSY and GAMIT software. The new horizontal velocity data set provides an improved image of deformation in the transition zone between the Colorado Plateau and the Northern and Southern Basin and Ranges Provinces. Preliminary modeling of the crustal kinematics reveals that only a very limited part of the region can be modeled as a rigid-body rotation. Most of the area is part of a broad zone of diffuse east-west directed extension from the Rio Grande Rift in the East to the Mojave Desert in the west. Only near the transition from the northern Colorado Plateau to the northern Basin and Range Province is the extension more localized. Besides a discussion of the regional kinematics, we will also discuss the affect the 2010 El Mayor-Cucapah earthquake had on the geodetic data in the southern Basin and Range.

  15. Quantitative restoration the Gulf of Mexico continental margins based on a newly-derived, basin-wide, crustal thickness map

    Science.gov (United States)

    Nguyen, L. C.; Mann, P.

    2016-12-01

    For decades, one of the main difficulties for understanding the tectonic evolution of the Gulf of Mexico (GOM) is quantifying the amount of crustal thinning of its deeply-buried and salt-covered continental margins formed during the Triassic-Jurassic rifting. In this study, we present a new crustal thickness map for the entire GOM and its surrounding areas based on integration of: 1) depth to basement compilation of previous seismic refraction and well data; and 2) regional estimation of Moho depths from 3D gravity inversion. Gravity modeling of salt thickness and Moho depth provide new constraints on crustal thickness in areas where refraction and well data are not available from both the US and Mexican GOM. Our derived crustal thickness map shows a zone of stretched continental crust with an average thickness of 20 km extending 700 km from the Ouachita foldbelt to the Sigsbee escarpment and in a 200-km-wide zone along the north and NW edge of the Yucatan block. To fully reconstruct the GOM to its pre-rift stage, we first close the late Jurassic oceanic part of the deep GOM using the traces of oceanic transform faults mapped from satellite gravity data. We then use our crustal thickness map to restore the thinned continental crust of the conjugate margins. Restoring the Yucatan block in a NW-SE direction produces the optimal, closed-fit model which supports a two-phase, GOM opening concept with early asymmetrical rifting across a broader, more extended, North American lower plate ( 250 km) in the northern, US GOM and a narrower, less extended, Yucatan upper plate ( 100 km) in the southern, Mexican GOM. Our full-fit reconstruction shows a single, post-rift Louann-Campeche salt-filled sag basin and re-aligned Paleozoic magnetic trends between the Yucatan block and Florida.

  16. Magmatic and crustal differentiation history of granitic rocks from Hf-O isotopes in zircon.

    Science.gov (United States)

    Kemp, A I S; Hawkesworth, C J; Foster, G L; Paterson, B A; Woodhead, J D; Hergt, J M; Gray, C M; Whitehouse, M J

    2007-02-16

    Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.

  17. Antarctic Crustal Thickness from Gravity Inversion

    Science.gov (United States)

    Vaughan, A. P.; Kusznir, N. J.; Ferraccioli, F.; Jordan, T. A.

    2013-12-01

    Using gravity anomaly inversion, we have produced the first comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information. The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the most recent Bedmap2 ice thickness and bedrock topography compilation south of 60 degrees south (Fretwell et al., 2013) and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica penetrated by narrow continental rifts that feature relatively thinner crust. The East Antarctic Rift System (EARS) is a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. Intermediate crustal thickness with an inferred linear rift fabric is predicted under Coates Land. An extensive region of either thick oceanic crust or highly thinned continental crust is predicted offshore Oates Land and north Victoria Land, and also off West Antarctica

  18. Introduction to Special Section: The Trans-Alaska Crustal Transect (TACT) Across Arctic Alaska

    Science.gov (United States)

    Plafker, George; Mooney, Walter D.

    1997-01-01

    This special section of the Journal of Geophysical Research addresses the composition and structural evolution of the lithosphere in northern Alaska. Investigations reported in this section were mainly undertaken as part of the Trans-Alaska Crustal Transect (TACT), an integrated geological and geophysical transect of the entire Alaskan lithosphere along a north-south corridor undertaken from 1984 to 1992 (Figure 1). The onshore segment of the transect approximately follows along the route of the trans-Alaskan pipeline; the offshore segment extends across the continental margin in the Gulf of Alaska to the Pacific plate. The TACT line is unique in that it provides a coordinated onshore/offshore geological and geophysical traverse of the North American plate in Alaska from the active convergent Pacific margin to the passive Arctic margin of the continent.

  19. A thermo-mechanical model of horizontal subduction below an overriding plate

    NARCIS (Netherlands)

    Hunen, Jeroen van; Berg, A.P. van den; Vlaar, N.J.

    2000-01-01

    Subduction of young oceanic lithosphere cannot be explained by the gravitational driving mechanisms of slab pull and ridge push. This deficiency of driving forces can be overcome by obduction of an actively overriding plate, which forces the young plate either to subduct or to collide. This

  20. A thermo-mechanical model of horizontal subduction below an overriding plate

    NARCIS (Netherlands)

    Hunen, Jeroen van; Berg, A.P. van den; Vlaar, N.J.

    2001-01-01

    Subduction of young oceanic lithosphere cannot be explained by the gravitational driving mechanisms of slab pull and ridge push. This deficiency of driving forces can be overcome by obduction of an actively overriding plate, which forces the young plate either to subduct or to collide. This mechanis

  1. Processless offset printing plates

    Directory of Open Access Journals (Sweden)

    Sanja Mahović Poljaček

    2015-06-01

    Full Text Available With the implementation of platesetters in the offset printing plate making process, imaging of the printing plate became more stable and ensured increase of the printing plate quality. But as the chemical processing of the printing plates still highly influences the plate making process and the graphic reproduction workflow, development of printing plates that do not require chemical processing for offset printing technique has been one of the top interests in graphic technology in the last few years. The main reason for that came from the user experience, where majority of the problems with plate making process could be connected with the chemical processing of the printing plate. Furthermore, increased environmental standards lead to reducing of the chemicals used in the industrial processes. Considering these facts, different types of offset printing plates have been introduced to the market today. This paper presents some of the processless printing plates.

  2. Crustal and upper mantle structure of central Qiangtang terrane (Tibet Plateau) imaged with magnetotelluric data

    Science.gov (United States)

    Zeng, S.; Hu, X.; Li, J.

    2013-12-01

    Since the Tethys Ocean closed, the ongoing collision between India and Aisa continents has created the Tibet Plateau, which is the most spectacular topographic feature on the surface of the earth. In the last decades, a large number of geological and geophysical studies have been undertaken in the Tibet Plateau, but most of these studies were focused on southern Tibet, where the collision of the Indian tectonic plate with Eurasia was occurred, and southeast Tibet, where lateral extrusion of crustal material may be occurred, absent in the central Tibet. As research continues, it has become clear that a complete understanding of the formation and deformation of the Tibet Plateau requires a study of the entire plateau. The Qiangtang terrane is located in the central Tibet Plateau. In 1993-1994, three profiles of broadband MT data (320 Hz to 2000 s) along N-S trending ranges from 86°E to 91°E were collected by China University of Geoscience in central Qiangtang terrane for the purpose of oil and gas exploration, the previous interpretation was focused on the shallow structures. In this study, we reanalyze the three MT profiles to produce more detailed images of the deep electrical structure of the Qiangtang terrane. Dimensionality analysis and geoelectric strike analysis of these data show that they appear to be two dimensional. 2-D inversion model show that there is a pervasive conductivity layer in the mid- to lower crustal and upper mantle, especially in the north Qiangtang terrane, which was considered to be the result of partial melt. The partial melt fraction is sufficient for crustal flow to occur. The similarity of the inversion models of the three profiles show that there is west-east crustal flow along the Jinsha River suture in central Qiangtang terrane, which seems to be western extension of the crustal flow observed in southeast Tibet by Bai et al. (2010). The inversion results also show difference of the electrical structure between the west and east

  3. Relation between relief and crustal structure in the Cantabrian Mountains (Spain) using DEM-GIS analysis

    Science.gov (United States)

    Llana-Fúnez, Sergio; Rodríguez-Rodríguez, Laura; Ballesteros, Daniel; María Díaz-Díaz, Luis; Valenzuela, Pablo; López-Fernández, Carlos; José Domínguez-Cuesta, María; Meléndez, Mónica; Jiménez-Sánchez, Montserrat; Fernández-Viejo, Gabriela

    2017-04-01

    The Cantabrian Mountains show a linear E-W trend parallel to the northern coast of Iberia peninsula, from the Pyrenees to Galicia, where it looses its trend and linearity. The western end of the linear segment of the orogen coincides with a change in the style of structures, accommodating the N-S shortening during the convergence between Europe and Iberia plates. We study the relief of the 230 km-long segment of the linear range between the Cantabria and Galicia re- gions, up to 2,650 m altitude. The bulk trend of the orogeny is controlled by the orientation of alpine thrusts that accommodate the shortening in relation to plate convergence. The Alpine Orogeny produced crustal thickening and the present day topography. Crustal thickness varies from 30 km in Eastern Cantabrian Mountains to 45-55 km at the Middle part of these mountains. The collision between European and African plates localized in northern Iberia from the Eocene to Oligocene and later migrated to southern Iberia during the Miocene. No major tectonic convergence was accommodated in the Cantabrians Mountains since the Oligocene, entering the orogen an erosional phase since then. The GIS-analysis present here, using 5 and 25 m-resolution DEMs by the Spanish National Geographical Institute, aims to identify the major features and to characterize the overall relief of the Cantabrians Mountains. In our preliminary approach, we present swath profiles, major river basins, watershed, longitudinal profiles of major rivers and hypsometric curves from selected areas that cover the studied orogen segment. Major tectonic structures control the location and orientation of the main watershed of the mountain range, but also the orientation of some local watersheds, e.g. associated to the Llanera thrust or the Ventaniella (strike-slip) fault. An unexpected result is that the average altitude along the water divide is 1,500 m, regardless of the large differences in crustal thickness along the study area. Most

  4. Crustal structure of the Dead Sea Basin (DSB) from a receiver function analysis

    Science.gov (United States)

    Mohsen, A.; Asch, G.; Mechie, J.; Kind, R.; Hofstetter, R.; Weber, M.; Stiller, M.; Abu-Ayyash, K.

    2011-01-01

    The Dead Sea Transform (DST) is a major left-lateral strike-slip fault that accommodates the relative motion between the African and Arabian plates, connecting a region of extension in the Red Sea to the Taurus collision zone in Turkey over a length of about 1100 km. The Dead Sea Basin (DSB) is one of the largest basins along the DST. The DSB is a morphotectonic depression along the DST, divided into a northern and a southern sub-basin, separated by the Lisan salt diapir. We report on a receiver function study of the crust within the multidisciplinary geophysical project, DEad Sea Integrated REsearch (DESIRE), to study the crustal structure of the DSB. A temporary seismic network was operated on both sides of the DSB between 2006 October and 2008 April. The aperture of the network is approximately 60 km in the E-W direction crossing the DSB on the Lisan peninsula and about 100 km in the N-S direction. Analysis of receiver functions from the DESIRE temporary network indicates that Moho depths vary between 30 and 38 km beneath the area. These Moho depth estimates are consistent with results of near-vertical incidence and wide-angle controlled-source techniques. Receiver functions reveal an additional discontinuity in the lower crust, but only in the DSB and west of it. This leads to the conclusion that the internal crustal structure east and west of the DSB is different at the present-day. However, if the 107 km left-lateral movement along the DST is taken into account, then the region beneath the DESIRE array where no lower crustal discontinuity is observed would have lain about 18 Ma ago immediately adjacent to the region under the previous DESERT array west of the DST where no lower crustal discontinuity is recognized.

  5. 对3F 机组调速器推拉杆压板上定位销扭断的分析--以水布垭电站为例%Analysis of Twist-off Fault of Upper Location Pins for Binder Plates of Driving Rod in Governor of 3F Generator Unit in Shuibuya Hydropower Station

    Institute of Scientific and Technical Information of China (English)

    赵公杰; 陈赞

    2014-01-01

    3F机组调速器推拉杆压板上定位销扭断分析是机组运行中的常见问题,原因比较复杂,有时可能是好几种原因综合的结果。对3F机组调速器接力器推拉杆压板上定位销扭断的原因进行了分析,提出了一系列的技术改进措施,并针对水布垭机组提出了解决方案。%It is a common problem that the upper location pins for binder plates of driving rod in governors of 3F genera-tor unit twist off in the operation .While the causes are complex , it is possibly due to a combined effect of different rea-sons.In this paper, the possible reasons are analyzed and technical improvement measures are proposed .Specifically, solutions are provided for generator units in the Shuibuya hydropower station .

  6. 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.

  7. Modes of continental extension in a crustal wedge

    Science.gov (United States)

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

    2015-07-01

    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.

  8. Trans-Alaska Crustal Transect and continental evolution involving subduction underplating and synchronous foreland thrusting

    Science.gov (United States)

    Fuis, G.S.; Moore, T.E.; Plafker, G.; Brocher, T.M.; Fisher, M.A.; Mooney, W.D.; Nokleberg, W.J.; Page, R.A.; Beaudoin, B.C.; Christensen, N.I.; Levander, A.R.; Lutter, W.J.; Saltus, R.W.; Ruppert, N.A.

    2008-01-01

    We investigate the crustal structure and tectonic evolution of the North American continent in Alaska, where the continent has grown through magmatism, accretion, and tectonic underplating. In the 1980s and early 1990s, we conducted a geological and geophysical investigation, known as the Trans-Alaska Crustal Transect (TACT), along a 1350-km-long corridor from the Aleutian Trench to the Arctic coast. The most distinctive crustal structures and the deepest Moho along the transect are located near the Pacific and Arctic margins. Near the Pacific margin, we infer a stack of tectonically underplated oceanic layers interpreted as remnants of the extinct Kula (or Resurrection) plate. Continental Moho just north of this underplated stack is more than 55 km deep. Near the Arctic margin, the Brooks Range is underlain by large-scale duplex structures that overlie a tectonic wedge of North Slope crust and mantle. There, the Moho has been depressed to nearly 50 km depth. In contrast, the Moho of central Alaska is on average 32 km deep. In the Paleogene, tectonic underplating of Kula (or Resurrection) plate fragments overlapped in time with duplexing in the Brooks Range. Possible tectonic models linking these two regions include flat-slab subduction and an orogenic-float model. In the Neogene, the tectonics of the accreting Yakutat terrane have differed across a newly interpreted tear in the subducting Pacific oceanic lithosphere. East of the tear, Pacific oceanic lithosphere subducts steeply and alone beneath the Wrangell volcanoes, because the overlying Yakutat terrane has been left behind as underplated rocks beneath the rising St. Elias Range, in the coastal region. West of the tear, the Yakutat terrane and Pacific oceanic lithosphere subduct together at a gentle angle, and this thickened package inhibits volcanism. ?? 2008 The Geological Society of America.

  9. HARMONIC DRIVE SELECTION

    Directory of Open Access Journals (Sweden)

    Piotr FOLĘGA

    2014-03-01

    Full Text Available The variety of types and sizes currently in production harmonic drive is a problem in their rational choice. Properly selected harmonic drive must meet certain requirements during operation, and achieve the anticipated service life. The paper discusses the problems associated with the selection of the harmonic drive. It also presents the algorithm correct choice of harmonic drive. The main objective of this study was to develop a computer program that allows the correct choice of harmonic drive by developed algorithm.

  10. 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.

  11. Modeling and Simulation of Nonlinear Micro-electromechanical Circular Plate

    Directory of Open Access Journals (Sweden)

    Chin-Chia Liu

    2013-09-01

    Full Text Available In the present study, the hybrid differential transformation and finite difference method is applied to analyze the dynamic behavior of the nonlinear micro-electromechanical circular plate actuated by combined DC / AC loading schemes. The analysis takes account of the axial residual stress and hydrostatic pressure acting on micro circular plate upper surface. The dynamic response of the plate as a function of the magnitude of the AC driving voltage is explored. Moreover, the effect of the initial gap height on the pull-in voltage of the plate is systematically explored.

  12. Creation of the Cocos and Nazca plates by fission of the Farallon plate

    Science.gov (United States)

    Lonsdale, Peter

    2005-08-01

    -Nazca spreading was a linear feature that, at least through the 680 km of ruptured Oligocene lithosphere known to have avoided subduction, did not follow any pre-existing feature on the Farallon plate, e.g., a "fracture zone" trail of a transform fault. (iv) The margins of surviving parts of the plate-splitting fracture have narrow shoulders raised by uplift of unloaded footwalls, and partially buried by fissural volcanism. (v) Cocos-Nazca spreading began at 23 Ma; reports of older Cocos-Nazca crust in the eastern Panama Basin were based on misidentified magnetic anomalies. There is increased evidence that the driving force for the 23 Ma fission of the Farallon plate was the divergence of slab-pull stresses at the Middle America and South America subduction zones. The timing and location of the split may have been influenced by (i) the increasingly divergent northeast slab pull at the Middle America subduction zone, which lengthened and reoriented because of motion between the North America and Caribbean plates; (ii) the slightly earlier detachment of a northern part of the plate that had been entering the California subduction zone, contributing a less divergent plate-driving stress; and (iii) weakening of older parts of the plate by the Galapagos hotspot, which had come to underlie the equatorial region, midway between the risecrest and the two subduction zones, by the Late Oligocene.

  13. Energy of plate tectonics calculation and projection

    Directory of Open Access Journals (Sweden)

    N. H. Swedan

    2013-02-01

    Full Text Available Mathematics and observations suggest that the energy of the geological activities resulting from plate tectonics is equal to the latent heat of melting, calculated at mantle's pressure, of the new ocean crust created at midocean ridges following sea floor spreading. This energy varies with the temperature of ocean floor, which is correlated with surface temperature. The objective of this manuscript is to calculate the force that drives plate tectonics, estimate the energy released, verify the calculations based on experiments and observations, and project the increase of geological activities with surface temperature rise caused by climate change.

  14. Create Your Plate

    Medline Plus

    Full Text Available ... steps to get started: Using your dinner plate, put a line down the middle of the plate. ... vegetables . Now in one of the small sections, put grains and starchy foods. See this list of ...

  15. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets ... 2016 Articles from Diabetes Forecast® magazine: wcie-meal-planning, In this section Food Planning Meals Diabetes Meal ...

  16. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal ... Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook ...

  17. Food guide plate

    Science.gov (United States)

    ... chips or cookies. VEGETABLES: MAKE HALF OF YOUR PLATE FRUITS AND VEGETABLES Vegetables can be raw, fresh, ... as a snack. FRUITS: MAKE HALF OF YOUR PLATE FRUITS AND VEGETABLES Fruits can be fresh, canned, ...

  18. Growth Plate Fractures

    Science.gov (United States)

    ... the most widely used by doctors is the Salter-Harris system, described below. Type I Fractures These ... incidence of growth plate fractures peaks in adolescence. Salter-Harris classification of growth plate fractures. AAOS does ...

  19. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart- ...

  20. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook ... Create Your Plate Meal Planning for Vegetarian Diets Gluten Free Diets Holiday Meal Planning Cook with Heart- ...

  1. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets you still choose the foods you want, but changes the portion sizes so you are getting larger ...

  2. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate It's simple and effective for both managing diabetes and losing weight. Creating your plate lets ... Sleeve Custom jerseys for your Tour de Cure team benefits the cause. Ask the Experts: Learn to ...

  3. Strain Accumulation Estimated from Seafloor Crustal Deformation at the Nankai Trough, Japan

    Science.gov (United States)

    Tadokoro, K.; Watanabe, T.; Nagai, S.; Ikuta, R.; Okuda, T.; Kenji, Y.; Sakata, T.

    2012-12-01

    Our research has developed an observation system for seafloor crustal deformation composed of the kinematic GPS and acoustic ranging techniques [Tadokoro et al., 2006; Ikuta et al., 2008]. We monitored crustal deformation at the Nankai Trough, Japan, where the Philippine Sea Plate subducts beneath the Amurian Plate. The convergence rate is predicted at 60 mm/y in the N59W direction by the Euler vector of REVEL [Sella et al., 2002]. We installed three monitoring sites (named KMN, KMS, and KME) on the seafloor at depths of about 1920-2030 m. The sites KMN and KMS are installed perpendicular to the trough axis with a spacing of 20 km; the site KME is 50 km from KMN and KMS in the direction parallel to the trough axis. The monitoring was started in 2004, 2005, and 2008 at KMS, KMN, and KME, respectively. The numbers of measurements are 16, 20, and 5 times at KMN, KMS, and KME, respectively. We obtained 3-7 years averaged horizontal site velocities within ITRF2000 adopting a robust estimation method with Tukey's biweight function to the time series of site position measured until the end of 2011. Substituting the synthetic rigid block motions of the Amurian Plate from the velocities within ITRF2000, we obtained the following site velocities with respect to the Amurian Plate [Tadokoro et al., 2012]: KMN 41±4 mm/y, N77±7W KMS 43±5 mm/y, N80±6W KME 42±5 mm/y, N80±7W In contrast, the on-land GPS horizontal velocities along the coast is 23-33 mm/y toward N74-80W. The present observational results show: (1) the velocity vectors are all the same length and direction, which indicates no internal deformation in this region; (2) the back-slip model predicts that the plate interface beneath the region is uniformly locked with coupling ratios of 60-80 %, indicating strain accumulation that will be released during the anticipated mega-thrust Tonankai earthquake; and (3) the directions of site velocities differ from that of convergence vector by 20 degrees, which is affected by

  4. Reports on block rotations, fault domains and crustal deformation

    Science.gov (United States)

    Nur, Amos

    1990-01-01

    Studies of block rotations, fault domains and crustal deformation in the western United States, Israel, and China are discussed. Topics include a three-dimensional model of crustal fracture by distributed fault sets, distributed deformation and block rotation in 3D, stress field rotation, and multiple strike slip fault sets.

  5. THE CRUSTAL STRUCTURE OF ELLESMERE ISLAND FROM RECEIVER FUNCTION MODELLING

    DEFF Research Database (Denmark)

    Schiffer, Christian; Stephenson, Randell Alexander; Oakey, Gordon

    . Preliminary results give estimates of Moho depths and crustal velocity structure and these are discussed with a focus on the relationship to topography, regional geological units and fault zones. The receiver functions reveal crustal roots underneath the Victoria and Albert Mountains (45km) and the Grantland...

  6. Accelerated plate tectonics.

    Science.gov (United States)

    Anderson, D L

    1975-03-21

    The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence.

  7. Active Crustal Faults in the Forearc Region, Guerrero Sector of the Mexican Subduction Zone

    Science.gov (United States)

    Gaidzik, Krzysztof; Ramírez-Herrera, Maria Teresa; Kostoglodov, Vladimir

    2016-10-01

    This work explores the characteristics and the seismogenic potential of crustal faults on the overriding plate in an area of high seismic hazard associated with the occurrence of subduction earthquakes and shallow earthquakes of the overriding plate. We present the results of geomorphic, structural, and fault kinematic analyses conducted on the convergent margin between the Cocos plate and the forearc region of the overriding North American plate, within the Guerrero sector of the Mexican subduction zone. We aim to determine the active tectonic processes in the forearc region of the subduction zone, using the river network pattern, topography, and structural data. We suggest that in the studied forearc region, both strike-slip and normal crustal faults sub-parallel to the subduction zone show evidence of activity. The left-lateral offsets of the main stream courses of the largest river basins, GPS measurements, and obliquity of plate convergence along the Cocos subduction zone in the Guerrero sector suggest the activity of sub-latitudinal left-lateral strike-slip faults. Notably, the regional left-lateral strike-slip fault that offsets the Papagayo River near the town of La Venta named "La Venta Fault" shows evidence of recent activity, corroborated also by GPS measurements (4-5 mm/year of sinistral motion). Assuming that during a probable earthquake the whole mapped length of this fault would rupture, it would produce an event of maximum moment magnitude Mw = 7.7. Even though only a few focal mechanism solutions indicate a stress regime relevant for reactivation of these strike-slip structures, we hypothesize that these faults are active and suggest two probable explanations: (1) these faults are characterized by long recurrence period, i.e., beyond the instrumental record, or (2) they experience slow slip events and/or associated fault creep. The analysis of focal mechanism solutions of small magnitude earthquakes in the upper plate, for the period between 1995

  8. Create Your Plate

    Medline Plus

    Full Text Available ... Reset Plate Share Create Your Plate ! Share: Seven Simple Steps to Create Your Plate It's simple and effective for both managing diabetes and losing ... en.html Have Type 2 Diabetes? Our free program will help you live well. More from diabetes. ...

  9. Horizontal crustal movement in Chinese mainland from 1999 to 2001

    Institute of Scientific and Technical Information of China (English)

    顾国华; 符养; 王武星

    2004-01-01

    The paper introduces the horizontal crustal movement obtained from GPS observations in the regional networks(including the basic network and the fiducial network) of the Crustal Movement Observation Network of China(CMONOC) carried out in 1999 and 2001. This paper is characterized by the acquisition of the horizontal dis-placement velocities during the period from 1999 to 2001 at the observation stations in the regional networks withdatum definition of a group of stable stations with small mutual displacements in east China. Based on the mostdetailed map of horizontal crustal movement in Chinese mainland, the division of blocks, their displacements anddeformations are studied. An approach to analysis of the intensity of the horizontal crustal deformation is proposed.The general characteristics of the recent horizontal crustal movement in Chinese mainland and that before theKunlunshan earthquake of M=8.1 on November 14, 2001 are analyzed.

  10. Long wavelength gravity anomalies over India: Crustal and lithospheric structures and its flexure

    Science.gov (United States)

    Tiwari, V. M.; Ravi Kumar, M.; Mishra, D. C.

    2013-07-01

    crustal thicknesses under the Vindhyan and the Ganga basins are attributed to the lithospheric flexure of the Indian plate due to Himalaya. Crustal bulge due to lithospheric flexure is well reflected in isostatic Moho based on flexural model of average effective elastic thickness of ˜40 km. Lithospheric flexure causes high heat flow that is aided by large crustal scale fault system of mobile belts and their extensions northwards in this section, which may be responsible for lower crustal bulk density in the northern part. A low density and high thermal regime in north India north of the SMB compared to south India, however does not conform to the high S-wave velocity in the northern part and thus it is attributed to changes in composition between the northern and the southern parts indicating a reworked lithosphere. Some of the long wavelength gravity anomalies along the east and the west coasts of India are attributed to the intrusives that caused the breakup of India from Antarctica, and Africa, Madagascar and Seychelles along the east and the west coasts of India, respectively.

  11. Crustal structure using receiver function in the east part of A'nyêmaqên suture belt

    Institute of Scientific and Technical Information of China (English)

    DUAN Yong-hong; ZHANG Xian-kang; LIU Zhi; XU Zhao-fan; WANG Fu-yun; PAN Ji-shun; LIANG Guo-jing

    2007-01-01

    Twenty broadband seismographs were deployed along Hongyuan, Sichuan to Wuwei, Gansu. 81 teleseismic events were recorded in one year. We computed receiver functions from teleseismic waveform data and obtained S wave velocity structure beneath each station along the profile by using receiver function inversion method. The results revealed that the crustal structure is very complex and crustal average S wave velocity is to be on the low side. Low velocity structure generally exists in the depth range of 10~40 km in the crust between Aba arc fault and northern edge fault of Qinling earth's axis and it is a tectonic feature of complex geological process such as ancient A'nyêmaqên Tethys ocean from closing and side colliding to subducted plate exhumed or thrust rock slice lifted. The Moho is about 50 km depth along the profile and is slightly deeper in the south than in the north.

  12. INVESTIGATION OF CRUSTAL MOTION IN THE TIEN SHAN USING INSAR

    Energy Technology Data Exchange (ETDEWEB)

    Mellors, R J

    2011-02-25

    The northern Tien Shan of Central Asia is an area of active mid-continent deformation. Although far from a plate boundary, this region has experienced 5 earthquakes larger than magnitude 7 in the past century and includes one event that may as be as large as Mw 8.0. Previous studies based on GPS measurements indicate on the order of 23 mm/yr of shortening across the entire Tien Shan and up to 15 mm/year in the northern Tien Shan (Figure 1). The seismic moment release rate appears comparable with the geodetic measured slip, at least to first order, suggesting that geodetic rates can be considered a proxy for accumulation rates of stress for seismic hazard estimation. Interferometric synthetic aperture radar may provide a means to make detailed spatial measurements and hence in identifying block boundaries and assisting in seismic hazard. Therefore, we hoped to define block boundaries by direct measurement and by identifying and resolving earthquake slip. Due to political instability in Kyrgzystan, the existing seismic network has not performed as well as required to precisely determine earthquake hypocenters in remote areas and hence InSAR is highly useful. In this paper we present the result of three earthquake studies and show that InSAR is useful for refining locations of teleseismically located earthquakes. ALOS PALSAR data is used to investigate crustal motion in the Tien Shan mountains of Central Asia. As part of the work, considerable software development was undertaken to process PALSAR data. This software has been made freely available. Two damaging earthquakes have been imaged in the Tien Shan and the locations provided by ALOS InSAR have helped to refine seismological velocity models. A third earthquake south of Kyrgyzstan was also imaged. The use of InSAR data and especially L band is therefore very useful in providing groundtruth for earthquake locations.

  13. Crustal Structure of Salton Trough using Deformable Layer Tomography

    Science.gov (United States)

    Yuan, F.

    2012-12-01

    Salton Trough is an important geologic structure to understand the active rift between Imperial Fault and San Andreas Fault. To determine the underground geometry of Salton Trough and its nearby faults, we analyzed seismic phase data recorded by Southern California Earthquake Data Center (SCEDC). Both 2-D and 3-D models have been made to refine the velocity model so as to determine the basin and moho geometry beneath Salton Trough region. Here three inline and five cross-line velocity profiles were built by using 2D Deformable Layer Tomography (DLT) method. From these 2D profiles, we can see that the velocity gradient is very small in the low velocity zone. The low velocity anomaly can be detected beneath the axis of the Salton Trough around the depth of 19-21 km, and the relatively high velocity can be seen beneath the San Andreas faults. Within 100*150*40 km3 model volume, 90,180 P-wave and S-wave first arrival picks from 27,663 local events (from 2001 to 2012), which were obtained from 44 stations, were used to build 3D seismic velocity model of the crust. During the iterations of velocity updating, full 3-D ray tracing is implemented. From these 3-D velocity models with different sizes of grids, low velocity anomalies are present under the southwest of Salton Sea, while high velocity zone is present across Southern San Andreas Fault throughout all the depths. Profiles from 2-D velocity models compared to 3-D velocity models show similar geometry. 3-D crustal structure, which is determined from 3-D DLT, helps to better understand the divergent boundary between the North American and the Pacific tectonic plates

  14. The crustal composition of the Falkland Plateau

    Science.gov (United States)

    Klemt, Claudia; Jokat, Wilfried

    2015-04-01

    The Falkland Islands are situated in the South Atlantic Ocean 500 km east of Patagonia, South America. The islands are part of the Falkland Plateau, which stretches eastward for more than 1500 km. A bathymetric high, the Maurice Ewing Bank, terminates the plateau in the east. Until Late Jurassic the Falkland Islands were part of Gondwana and were located adjacent to the east coast of South Africa. While the Falkland Islands and Maurice Ewing Bank are proved to be of continental composition, the nature and structure of the Falkland Plateau's basement in between is debatable. The first crustal model derived from sonobuoy data contradicts an only recently published 3D-gravity model. To enhance the understanding of Gondwana break-up considering timing, geometry and amount of volcanism, further knowledge about the structure and thickness of the crust is inevitable. During the ANT-XXIX/5 Polarstern cruise seismic refraction measurements were conducted using Ocean Bottom Seismometers (OBS) and Reftek land stations onshore of East Falkland. The OBS were deployed at 78 locations along an approximately 1500 km east-west stretching profile. For the western transect a P-wave velocity model is calculated using 2D-raytracing techniques. The results are presented in combination with potential field data showing the extension of the Falkland Islands basement, the continent-ocean transition zone and the crustal structure of the plateau. On the Falkland Plateau Basin sediment thickness is about 6 km with velocities ranging from 1.7 to 4.1 km/s in the upper part and about 4.7 km/s above basement. The crust is of oceanic composition with an igneous section that is considerably thicker than average oceanic crust (up to 17 km). The velocity structure in the upper crustal part is typical for layer 2 with a velocity gradient ranging from 5.4 km/s to 6.5 km/s and thicknesses between 1.5 km and 4 km. Layer 3 is about 14 km thick with a velocity gradient from 6.6 km/s to 7.6 km/s, which is

  15. The kinematics of crustal deformation in Java from GPS observations: Implications for fault slip partitioning

    Science.gov (United States)

    Koulali, A.; McClusky, S.; Susilo, S.; Leonard, Y.; Cummins, P.; Tregoning, P.; Meilano, I.; Efendi, J.; Wijanarto, A. B.

    2017-01-01

    Our understanding of seismic risk in Java has been focused primarily on the subduction zone, where the seismic records during the last century have shown the occurrence of a number of tsunami earthquakes. However, the potential of the existence of active crustal structures within the island of Java itself is less well known. Historical archives show the occurrence of several devastating earthquake ruptures north of the volcanic arc in west Java during the 18th and the 19th centuries, suggesting the existence of active faults that need to be identified in order to guide seismic hazard assessment. Here we use geodetic constraints from the Global Positioning System (GPS) to quantify the present day crustal deformation in Java. The GPS velocities reveal a homogeneous counterclockwise rotation of the Java Block independent of Sunda Block, consistent with a NE-SW convergence between the Australian Plate and southeast Asia. Continuous GPS observations show a time-dependent change in the linear rate of surface motion in west Java, which we interpret as an ongoing long-term post-seismic deformation following the 2006 Mw 7.7 Java earthquake. We use an elastic block model in combination with a viscoelastic model to correct for this post-seismic transient and derive the long-term inter-seismic velocity, which we interpret as a combination of tectonic block motions and crustal faults strain related deformation. There is a north-south gradient in the resulting velocity field with a decrease in the magnitude towards the North across the Kendeng Thrust in the east and the Baribis Thrust in the west. We suggest that the Baribis Thrust is active and accommodating a slow relative motion between Java and the Sunda Block at about 5 ± 0.2 mm /yr. We propose a kinematic model of convergence of the Australian Plate and the Sunda Block, involving a slip partitioning between the Java Trench and a left-lateral structure extending E-W along Java with most of the convergence being

  16. Extraction of crustal deformations and oceanic fluctuations from ocean bottom pressures

    Science.gov (United States)

    Ariyoshi, Keisuke; Nagano, Akira; Hasegawa, Takuya; Matsumoto, Hiroyuki; Kido, Motoyuki; Igarashi, Toshihiro; Uchida, Naoki; Iinuma, Takeshi; Yamashita, Yusuke

    2017-04-01

    It has been well known that megathrust earthquakes such as the 2004 Sumatra-Andaman Earthquake (Mw 9.1) and the 2011 the Pacific Coast of Tohoku Earthquake (Mw 9.0) had devastated the coastal areas in the western of Indonesia and in the north-eastern of Japan, respectively. To mitigate the disaster of those forthcoming megathrust earthquakes along Nankai Trough, the Japanese government has established seafloor networks of cable-linked observatories around Japan: DONET (Dense Oceanfloor Network system for Earthquakes and Tsunamis along the Nankai Trough) and S-net (Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench). The advantage of the cable-linked network is to monitor the propagation process of tsunami and seismic waves as well as seismic activity in real time. DONET contains pressure gauges as well as seismometers, which are expected to detect crustal deformations driven by peeling off subduction plate coupling process. From our simulation results, leveling changes are different sense among the DONET points even in the same science node. On the other hand, oceanic fluctuations such as melting ice masses through the global warming have so large scale as to cause ocean bottom pressure change coherently for all of DONET points especially in the same node. This difference suggests the possibility of extracting crustal deformations component from ocean bottom pressure data by differential of stacking data. However, this operation cannot be applied to local-scale fluctuations related to ocean mesoscale eddies and current fluctuations, which affect ocean bottom pressure through water density changes in the water column (from the sea surface to the bottom). Therefore, we need integral analysis by combining seismology, ocean physics and tsunami engineering so as to decompose into crustal deformation, oceanic fluctuations and instrumental drift, which will bring about high precision data enough to find geophysical phenomena. In this study

  17. Visualization and dissemination of global crustal models on virtual globes

    Science.gov (United States)

    Zhu, Liang-feng; Pan, Xin; Sun, Jian-zhong

    2016-05-01

    Global crustal models, such as CRUST 5.1 and its descendants, are very useful in a broad range of geoscience applications. The current method for representing the existing global crustal models relies heavily on dedicated computer programs to read and work with those models. Therefore, it is not suited to visualize and disseminate global crustal information to non-geological users. This shortcoming is becoming obvious as more and more people from both academic and non-academic institutions are interested in understanding the structure and composition of the crust. There is a pressing need to provide a modern, universal and user-friendly method to represent and visualize the existing global crustal models. In this paper, we present a systematic framework to easily visualize and disseminate the global crustal structure on virtual globes. Based on crustal information exported from the existing global crustal models, we first create a variety of KML-formatted crustal models with different levels of detail (LODs). And then the KML-formatted models can be loaded into a virtual globe for 3D visualization and model dissemination. A Keyhole Markup Language (KML) generator (Crust2KML) is developed to automatically convert crustal information obtained from the CRUST 1.0 model into KML-formatted global crustal models, and a web application (VisualCrust) is designed to disseminate and visualize those models over the Internet. The presented framework and associated implementations can be conveniently exported to other applications to support visualizing and analyzing the Earth's internal structure on both regional and global scales in a 3D virtual-globe environment.

  18. Crustal structure and tectonic history of the Kermadec arc inferred from MANGO seismic refraction profiles

    Science.gov (United States)

    Bassett, D.; Kopp, H.; Sutherland, R.; Henrys, S.; Watts, A. B.; Timm, C.; Scherwath, M.; Grevemeyer, I.; de Ronde, C. E. J.

    2016-12-01

    We have analyzed three wide-angle seismic reflection and refraction profiles and applied spectral averaging techniques to regional grids of bathymetry and free-air gravity anomaly to place the first regional constraints on the crustal structure of the Kermadec arc. These observations are used to test contrasting tectonic models for an along-strike transition in margin structure, across which, 1) the remnant Lau-Colville and active Kermadec arc ridges narrow by >50%; 2) the backarc and forearc deepen by 1 km, and 3) the active volcanic arc is deflected west into the deepest known backarc basin. We use residual bathymetric anomalies to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the forearc with VP 6.5-7.3 km s-1 and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110±20 km) and strike ( 005° south of 25°S). South of the CKD the forearc is structurally homogeneous down-dip with VP 5.7-7.3 km s-1. Lower crustal velocities are similar to the northern Kermadec forearc, but there is no seismic or gravimetric evidence for an extinct arc ridge within the forearc. In the Havre Trough backarc, crustal thickness south of the CKD is 8-9 km, which is up-to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. The northern Kermadec/Tonga arc preserves a substrate of the Eocene arc, the southern Kermadec forearc preserves Mesozoic forearc rocks accreted at the Gondwana margin, and the central Kermadec arc may have fomed in the Kupe Abyssal Plain. The oldest arc related rocks recovered north and south of the CKD are 52 Ma and 16.7 Ma respectively, and plate tectonic reconstruction suggest the Eocene arc was originally conjoined with the Three Kings Ridge. The separation of these ridges during the early Oligocene likely formed the CKD. In contrast to previous interpretations, we

  19. Crustal recycling by subduction erosion in the central Mexican Volcanic Belt

    Science.gov (United States)

    Straub, Susanne M.; Gómez-Tuena, Arturo; Bindeman, Ilya N.; Bolge, Louise L.; Brandl, Philipp A.; Espinasa-Perena, Ramón; Solari, Luigi; Stuart, Finlay M.; Vannucchi, Paola; Zellmer, Georg F.

    2015-10-01

    Recycling of upper plate crust in subduction zones, or 'subduction erosion', is a major mechanism of crustal destruction at convergent margins. However, assessing the impact of eroded crust on arc magmas is difficult owing to the compositional similarity between the eroded crust, trench sediment and arc crustal basement that may all contribute to arc magma formation. Here we compare Sr-Nd-Pb-Hf and trace element data of crustal input material to Sr-Nd-Pb-Hf-He-O isotope chemistry of a well-characterized series of olivine-phyric, high-Mg# basalts to dacites in the central Mexican Volcanic Belt (MVB). Basaltic to andesitic magmas crystallize high-Ni olivines that have high mantle-like 3He/4He = 7-8 Ra and high crustal δ18Omelt = +6.3-8.5‰ implying their host magmas to be near-primary melts from a mantle infiltrated by slab-derived crustal components. Remarkably, their Hf-Nd isotope and Nd/Hf trace element systematics rule out the trench sediment as the recycled crust end member, and imply that the coastal and offshore granodiorites are the dominant recycled crust component. Sr-Nd-Pb-Hf isotope modeling shows that the granodiorites control the highly to moderately incompatible elements in the calc-alkaline arc magmas, together with lesser additions of Pb- and Sr-rich fluids from subducted mid-oceanic ridge basalt (MORB)-type altered oceanic crust (AOC). Nd-Hf mass balance suggests that the granodiorite exceeds the flux of the trench sediment by at least 9-10 times, corresponding to a flux of ⩾79-88 km3/km/Myr into the subduction zone. At an estimated thickness of 1500-1700 m, the granodiorite may buoyantly rise as bulk 'slab diapirs' into the mantle melt region and impose its trace element signature (e.g., Th/La, Nb/Ta) on the prevalent calc-alkaline arc magmas. Deep slab melting and local recycling of other slab components such as oceanic seamounts further diversify the MVB magmas by producing rare, strongly fractionated high-La magmas and a minor population of

  20. Transition on the Geometry of the Cocos Plate in Central-Southern Mexico.

    Science.gov (United States)

    Rodríguez-Domínguez, M. Á.; Perez-Campos, X.; Valencia-Cabrera, D.; Clayton, R. W.; Cordoba-Montiel, F.; Valdes-Gonzales, C. M.; Brudzinski, M. R.; Cabral-Cano, E.; Arciniega-Ceballos, A.

    2014-12-01

    The tectonic setting, produced by the interaction between the Cocos and North American plates, follows complex geometries along the Pacific coast. Previous studies in central Mexico showed that the slab dips nearly horizontally before steeply subducting into the continental mantle; in contrast, in southern Mexico, the slabs dips under the continental plate at a constant angle. Receiver functions from four seismic networks: GECO (Geometry of Cocos), SSN (Servicio Sismológico Nacional), OxNet (Oaxaca Network) and UV (Universidad Veracruzana) are used to study the crustal structure underneath the stations, and image the subducting Cocos plate in order to define the geometry and the transition angle in central-southern Mexico.

  1. Detailed crustal thickness variations beneath the Illinois Basin area: Implications for crustal evolution of the midcontinent

    Science.gov (United States)

    Yang, Xiaotao; Pavlis, Gary L.; Hamburger, Michael W.; Marshak, Stephen; Gilbert, Hersh; Rupp, John; Larson, Timothy H.; Chen, Chen; Carpenter, N. Seth

    2017-08-01

    We present high-resolution imaging results of crustal and upper mantle velocity discontinuities across the Illinois Basin area using both common conversion point stacking and plane wave migration methods applied to P wave receiver functions from the EarthScope Ozark, Illinois, Indiana, and Kentucky experiment. The images reveal unusually thick crust (up to 62 km) throughout the central and southeastern Illinois Basin area. A significant Moho gradient underlies the NW trending Ste. Genevieve Fault Zone, which delineates the boundary between the Illinois Basin and Ozark Dome. Relatively thinner crust (convergent margin tectonics around 1.55-1.35 Ga; (3) by Late Precambrian magmatic underplating at the base of older crust, associated with the creation of the Eastern Granite-Rhyolite Province around 1.3 Ga; and (4) through crustal "relamination" during an episode of Proterozoic flat-slab subduction beneath the Illinois Basin, possibly associated with the Grenville Orogeny.

  2. Angular shear plate

    Science.gov (United States)

    Ruda, Mitchell C [Tucson, AZ; Greynolds, Alan W [Tucson, AZ; Stuhlinger, Tilman W [Tucson, AZ

    2009-07-14

    One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.

  3. Moroccan crustal response to continental drift.

    Science.gov (United States)

    Kanes, W H; Saadi, M; Ehrlich, E; Alem, A

    1973-06-01

    The formation and development of a zone of spreading beneath the continental crust resulted in the breakup of Pangea and formation of the Atlantic Ocean. The crust of Morocco bears an extremely complete record of the crustal response to this episode of mantle dynamics. Structural and related depositional patterns indicate that the African margin had stabilized by the Middle Jurassic as a marine carbonate environment; that it was dominated by tensile stresses in the early Mesozoic, resulting in two fault systems paralleling the Atlantic and Mediterranean margins and a basin and range structural-depositional style; and that it was affected by late Paleozoic metamorphism and intrusion. Mesozoic events record the latter portion of African involvement in the spreading episode; late Paleozoic thermal orogenesis might reflect the earlier events in the initiation of the spreading center and its development beneath significant continental crust. In that case, more than 100 million years were required for mantle dynamics to break up Pangea.

  4. Fractal behavior in continental crustal heat production

    Directory of Open Access Journals (Sweden)

    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. Crustal structure beneath two seismic stations in the Sunda-Banda arc transition zone derived from receiver function analysis

    Energy Technology Data Exchange (ETDEWEB)

    Syuhada, E-mail: hadda9@gmail.com [Graduate Research on Earthquake and Active Tectonics (GREAT), Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132 (Indonesia); Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Kompleks Puspiptek Serpong, Tangsel 15314, Banten Indonesia (Indonesia); Hananto, Nugroho D.; Handayani, Lina [Research Centre for Geotechnology - Indonesian Institute of Sciences (LIPI), Jl. Sangkuriang (Kompleks LIPI) Bandung 40135 (Indonesia); Puspito, Nanang T; Yudistira, Tedi [Faculty of Mining and Petroleum Engineering ITB, Jalan Ganesha 10, Bandung 40132 (Indonesia); Anggono, Titi [Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Kompleks Puspiptek Serpong, Tangsel 15314, Banten Indonesia (Indonesia)

    2015-04-24

    We analyzed receiver functions to estimate the crustal thickness and velocity structure beneath two stations of Geofon (GE) network in the Sunda-Banda arc transition zone. The stations are located in two different tectonic regimes: Sumbawa Island (station PLAI) and Timor Island (station SOEI) representing the oceanic and continental characters, respectively. We analyzed teleseismic events of 80 earthquakes to calculate the receiver functions using the time-domain iterative deconvolution technique. We employed 2D grid search (H-κ) algorithm based on the Moho interaction phases to estimate crustal thickness and Vp/Vs ratio. We also derived the S-wave velocity variation with depth beneath both stations by inverting the receiver functions. We obtained that beneath station PLAI the crustal thickness is about 27.8 km with Vp/Vs ratio 2.01. As station SOEI is covered by very thick low-velocity sediment causing unstable solution for the inversion, we modified the initial velocity model by adding the sediment thickness estimated using high frequency content of receiver functions in H-κ stacking process. We obtained the crustal thickness is about 37 km with VP/Vs ratio 2.2 beneath station SOEI. We suggest that the high Vp/Vs in station PLAI may indicate the presence of fluid ascending from the subducted plate to the volcanic arc, whereas the high Vp/Vs in station SOEI could be due to the presence of sediment and rich mafic composition in the upper crust and possibly related to the serpentinization process in the lower crust. We also suggest that the difference in velocity models and crustal thicknesses between stations PLAI and SOEI are consistent with their contrasting tectonic environments.

  6. Crustal structure beneath two seismic stations in the Sunda-Banda arc transition zone derived from receiver function analysis

    Science.gov (United States)

    Syuhada, Hananto, Nugroho D.; Puspito, Nanang T.; Anggono, Titi; Handayani, Lina; Yudistira, Tedi

    2015-04-01

    We analyzed receiver functions to estimate the crustal thickness and velocity structure beneath two stations of Geofon (GE) network in the Sunda-Banda arc transition zone. The stations are located in two different tectonic regimes: Sumbawa Island (station PLAI) and Timor Island (station SOEI) representing the oceanic and continental characters, respectively. We analyzed teleseismic events of 80 earthquakes to calculate the receiver functions using the time-domain iterative deconvolution technique. We employed 2D grid search (H-κ) algorithm based on the Moho interaction phases to estimate crustal thickness and Vp/Vs ratio. We also derived the S-wave velocity variation with depth beneath both stations by inverting the receiver functions. We obtained that beneath station PLAI the crustal thickness is about 27.8 km with Vp/Vs ratio 2.01. As station SOEI is covered by very thick low-velocity sediment causing unstable solution for the inversion, we modified the initial velocity model by adding the sediment thickness estimated using high frequency content of receiver functions in H-κ stacking process. We obtained the crustal thickness is about 37 km with VP/Vs ratio 2.2 beneath station SOEI. We suggest that the high Vp/Vs in station PLAI may indicate the presence of fluid ascending from the subducted plate to the volcanic arc, whereas the high Vp/Vs in station SOEI could be due to the presence of sediment and rich mafic composition in the upper crust and possibly related to the serpentinization process in the lower crust. We also suggest that the difference in velocity models and crustal thicknesses between stations PLAI and SOEI are consistent with their contrasting tectonic environments.

  7. Apparatus and method for explosive bonding to edge of flyer plate

    Science.gov (United States)

    Bement, Laurence J.; Kushnick, Anne C.

    1991-09-01

    The invention is an apparatus and a process for the explosive joining of a flyer plate and a base plate. The apparatus consists of a flyer plate positioned over a base plate. The flyer plate has a notch containing a filler material in intimate contact with the flyer plate. An adhesive means holds a ribbon explosive partially overlapping the notch in the flyer plate. A detonating means initiates the ribbon explosive that drives the flyer plate to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and effacing bonding, resulting in electron sharing linkups between the plates. An unbonded tab fractures at a base of the notch leaving a bond to an edge of the attached flyer plate.

  8. Hidden Earthquake Potential in Plate Boundary Transition Zones

    Science.gov (United States)

    Furlong, Kevin P.; Herman, Matthew; Govers, Rob

    2017-04-01

    Plate boundaries can exhibit spatially abrupt changes in their long-term tectonic deformation (and associated kinematics) at triple junctions and other sites of changes in plate boundary structure. How earthquake behavior responds to these abrupt tectonic changes is unclear. The situation may be additionally obscured by the effects of superimposed deformational signals - juxtaposed short-term (earthquake cycle) kinematics may combine to produce a net deformational signal that does not reflect intuition about the actual strain accumulation in the region. Two examples of this effect are in the vicinity of the Mendocino triple junction (MTJ) along the west coast of North America, and at the southern end of the Hikurangi subduction zone, New Zealand. In the region immediately north of the MTJ, GPS-based observed crustal displacements (relative to North America (NAm)) are intermediate between Pacific and Juan de Fuca (JdF) motions. With distance north, these displacements rotate to become more aligned with JdF - NAm displacements, i.e. to motions expected along a coupled subduction interface. The deviation of GPS motions from the coupled subduction interface signal near the MTJ has been previously interpreted to reflect clock-wise rotation of a coastal, crustal block and/or reduced coupling at the southern Cascadia margin. The geologic record of crustal deformation near the MTJ reflects the combined effects of northward crustal shortening (on geologic time scales) associated with the MTJ Crustal Conveyor (Furlong and Govers, 1999) overprinted onto the subduction earthquake cycle signal. With this interpretation, the Cascadia subduction margin appears to be well-coupled along its entire length, consistent with paleo-seismic records of large earthquake ruptures extending to its southern limit. At the Hikurangi to Alpine Fault transition in New Zealand, plate interactions switch from subduction to oblique translation as a consequence of changes in lithospheric structure of

  9. 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

  10. Driving After a Stroke

    Science.gov (United States)

    ... Inspirational Stories Stroke Heroes Among Us Driving After Stroke Updated:Jul 23,2015 Can I drive after ... more tips for daily living . Let's Talk About Stroke Fact Sheets Our stroke fact sheets cover treatments, ...

  11. Electric Vehicle - Economical driving

    DEFF Research Database (Denmark)

    Jensen, VCE, Steen V.; Schøn, Henriette

    1999-01-01

    Instruct the reader in getting most satisfaction out of an EV, especially concerning driving and loading.......Instruct the reader in getting most satisfaction out of an EV, especially concerning driving and loading....

  12. Dementia and driving

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000028.htm Dementia and driving To use the sharing features on ... please enable JavaScript. If your loved one has dementia , deciding when they can no longer drive may ...

  13. Abrupt plate accelerations shape rifted continental margins

    Science.gov (United States)

    Brune, Sascha; Williams, Simon E.; Butterworth, Nathaniel P.; Müller, R. Dietmar

    2016-08-01

    Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth’s major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength-velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.

  14. Abrupt plate accelerations shape rifted continental margins.

    Science.gov (United States)

    Brune, Sascha; Williams, Simon E; Butterworth, Nathaniel P; Müller, R Dietmar

    2016-08-11

    Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth's major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength--velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.

  15. Intra Plate Stresses Using Finite Element Modelling

    Directory of Open Access Journals (Sweden)

    Jayalakshmi S.

    2016-10-01

    Full Text Available One of the most challenging problems in the estimation of seismic hazard is the ability to quantify seismic activity. Empirical models based on the available earthquake catalogue are often used to obtain activity of source regions. The major limitation with this approach is the lack of sufficient data near a specified source. The non-availability of data poses difficulties in obtaining distribution of earthquakes with large return periods. Such events recur over geological time scales during which tectonic processes, including mantle convection, formation of faults and new plate boundaries, are likely to take place. The availability of geometries of plate boundaries, plate driving forces, lithospheric stress field and GPS measurements has provided numerous insights on the mechanics of tectonic plates. In this article, a 2D finite element model of Indo-Australian plate is developed with the focus of representing seismic activity in India. The effect of large scale geological features including sedimentary basins, fold belts and cratons on the stress field in India is explored in this study. In order to address long term behaviour, the orientation of stress field and tectonic faults of the present Indo-Australian plate are compared with a reconstructed stress field from the early Miocene (20 Ma.

  16. Measurement of sediment and crustal thickness corrected RDA for 2D profiles at rifted continental margins: Applications to the Iberian, Gulf of Aden and S Angolan margins

    Science.gov (United States)

    Cowie, Leanne; Kusznir, Nick

    2014-05-01

    Subsidence analysis of sedimentary basins and rifted continental margins requires a correction for the anomalous uplift or subsidence arising from mantle dynamic topography. Whilst different global model predictions of mantle dynamic topography may give a broadly similar pattern at long wavelengths, they differ substantially in the predicted amplitude and at shorter wavelengths. As a consequence the accuracy of predicted mantle dynamic topography is not sufficiently good to provide corrections for subsidence analysis. Measurements of present day anomalous subsidence, which we attribute to mantle dynamic topography, have been made for three rifted continental margins; offshore Iberia, the Gulf of Aden and southern Angola. We determine residual depth anomaly (RDA), corrected for sediment loading and crustal thickness variation for 2D profiles running from unequivocal oceanic crust across the continental ocean boundary onto thinned continental crust. Residual depth anomalies (RDA), corrected for sediment loading using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average or from anomalous uplift or subsidence. Gravity anomaly inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic reflection data has been used to determine Moho depth, calibrated using seismic refraction, and oceanic crustal basement thickness. Crustal basement thicknesses derived from gravity inversion together with Airy isostasy have been used to correct for variations of crustal thickness from a standard oceanic thickness of 7km. The 2D profiles of RDA corrected for both sediment loading and non-standard crustal

  17. Layer-block tectonics of Cenozoic basements and formation of intra-plate basins in Nansha micro-plate,southern South China Sea

    Institute of Scientific and Technical Information of China (English)

    LIU Hailing; XIE Guofa; LIN Qiujin; ZHENG Hongbo; LIU Yingchun

    2009-01-01

    Layer-block tectonics (LBT) concept, with the core of pluralistic geodynamic outlook and multi-layer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea (SCS). Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei (Rifleman bank)-Andu (Ardasier bank) and Liyue (Reed bank)-North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei-Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip-detachment of basemental layer-block and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei-Andu and Liyue-North Palawan intra-plate basin groups, respectively.

  18. Gear bearing drive

    Science.gov (United States)

    Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  19. Crustal architecture and deep structure of the Namibian continental shelf and adjacent oceanic basins around the landfall of Walvis Ridge from wide-angle seismic and marine magnetotelluric data

    Science.gov (United States)

    Planert, L.; Behrmann, J.; Jegen, M.; Heincke, B.; Jokat, W.; Bialas, J.; Marti, A.

    2012-12-01

    The opening of the South Atlantic ocean basin resulted in voluminous magmatism on the conjugate continental margins of Africa and South America, including the formation of the Parana and Entendeka large igneous provinces (LIPs), the formation of up to 100 km wide volcanic wedges characterized by seaward dipping reflector sequences (SDRs), as well as the formation of paired hotspot tracks on the rifted African and South American plates, the Walvis Ridge and the Rio Grande Rise. Hence, the passive margins bordering the South Atlantic are today considered as type examples for models involving hotspot related continental break-up. However, the presence of volcanic features (SDRs, LIPs) appears to be limited south of the hotspot trails. The resulting segmentation of the margins offers a prime opportunity to study the magmatic signal in space and time, and investigate the interrelation with rift-related deformation. A globally significant question to be adressed here is whether magmatism is the driving force for continental break-up, or whether even rifting with abundant hotspot related magmatism is in principle in response to crustal and lithospheric stretching. In 2010/11, a combination of on-/offshore wide-angle seismic, marine magnetotelluric and on-/offshore seismological data were acquired around the landfall of Walvis Ridge at the Namibian passive continental margin. The set of experiments was designed to provide crustal velocity and conductivity information and to investigate the structure of the upper mantle. In particular, we aimed at identifying deep fault zones and variations in Moho depth, the presence of interleaved sediment layers in SDR sequences as well as magmatic intrusions and underplated material near the continent-ocean transition. The sedimentary portions down to the igneous basement were additionally constrained by coincident single-channel reflection seismic data. Here, we present preliminary results for two wide-angle seismic transects and first

  20. Simple Driving Techniques

    DEFF Research Database (Denmark)

    Rosendahl, Mads

    2002-01-01

    -like language. Our aim is to extract a simple notion of driving and show that even in this tamed form it has much of the power of more general notions of driving. Our driving technique may be used to simplify functional programs which use function composition and will often be able to remove intermediate data......Driving was introduced as a program transformation technique by Valentin Turchin in some papers around 1980. It was intended for the programming language REFAL and used in metasystem transitions based on super compilation. In this paper we present one version of driving for a more conventional lisp...

  1. High performance AC drives

    CERN Document Server

    Ahmad, Mukhtar

    2010-01-01

    This book presents a comprehensive view of high performance ac drives. It may be considered as both a text book for graduate students and as an up-to-date monograph. It may also be used by R & D professionals involved in the improvement of performance of drives in the industries. The book will also be beneficial to the researchers pursuing work on multiphase drives as well as sensorless and direct torque control of electric drives since up-to date references in these topics are provided. It will also provide few examples of modeling, analysis and control of electric drives using MATLAB/SIMULIN

  2. Crustal density structure in northwestern South America derived from analysis and 3-D modeling of gravity and seismicity data

    Science.gov (United States)

    Sanchez-Rojas, J.; Palma, M.

    2014-11-01

    This paper presents a three-dimensional (3-D) interpretation of new gravity and seismicity datasets for northern South America. A 3-D forward density model was constructed on the basis of deep wide-angle seismic refraction sections, Moho depth from receiver functions, and surface geology. Density values were estimated from published borehole data for sediments by using empirical velocity-density functions and considering mineralogical-chemical composition variations under typical pressure-temperature conditions for upper and lower crustal rocks. The modeled 3-D density structure was kept as simple as possible. The continental and oceanic plates were formed by two sedimentary bodies, one crustal body, and one mantle lithosphere body overlying a sub-lithospheric mantle. The Caribbean plate was modeled with an atypical crustal thickness of ~ 18 km (including sediments). The geometry of the Caribbean plate was modeled using a combination of gravity modeling and analyses of the seismicity and focal-mechanism solutions. Intermediate seismicity and the orientation of the T-axes appeared aligned along the predicted position of the slab. As a result, the estimated slab dip angle under Maracaibo and the Mérida Andes was ~ 15° and increases up to ~ 20° after 100 km depth. The model shows two orientations in the slab strike: ~ N150°E ± 5 in western Colombia and southward underneath the Maracaibo block. The modeling results suggest that the northern South American upper and lower crusts are relatively light and the density of the Caribbean crust is typical for an oceanic crust.

  3. Application of global positioning system to determination of tectonic plate movements and crustal deformations

    Science.gov (United States)

    Anderle, R. J.

    1978-01-01

    It is shown that pseudo-range measurements to four GPS satellites based on correlation of the pseudo random code transmissions from the satellites can be used to determine the relative position of ground stations which are separated by several hundred kilometers to a precision at the centimeter level. Carrier signal measurements during the course of passage of satellites over a pair of stations also yield centimeter precision in the relative position, but oscillator instabilities limit the accuracy. The accuracy of solutions based on either type of data is limited by unmodeled tropospheric refraction effects which would reach 5 centimeters at low elevation angles for widely separated stations.

  4. 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.

  5. Crustal structure and tectonics of the northern part of the Southern Granulite Terrane, India

    Science.gov (United States)

    Rao, V.V.; Sain, K.; Reddy, P.R.; Mooney, W.D.

    2006-01-01

    Deep seismic reflection studies investigating the exposed Archean lower continental crust of the Southern Granulite Terrane, India, yield important constraints on the nature and evolution of the deep crust, including the formation and exhumation of granulites. Seismic reflection images along the Kuppam-Bhavani profile reveal a band of reflections that dip southward from 10.5 to 15.0??s two-way-time (TWT), across a distance of 50??km. The bottom of these reflections beneath the Dharwar craton is interpreted as the Moho. Further south, another reflection band dipping northward is observed. These bands of reflectivity constitute a divergent reflection fabric that converges at the Moho boundary observed at the Mettur shear zone. Reflection fabrics that intersect at a steep angle are interpreted as a collisional signature due to the convergence of crustal blocks, which we infer resulted in crustal thickening and the formation of granulites. Anomalous gravity and magnetic signatures are also observed across the Mettur shear zone. The gravity model derived from the Bouguer gravity data corroborates seismic results. The tectonic regime and seismic reflection profiles are combined in a 3-D representation that illustrates our evidence for paleo-subduction at a collision zone. The structural dissimilarities and geophysical anomalies suggest that the Mettur shear zone is a suture between the Dharwar craton in the north and another crustal block in the south. This study contributes significantly to our understanding of the operation of Archean plate tectonics, here inferred to involve collision and subduction. Furthermore, it provides an important link between the Gondwanaland and global granulite evolution occurring throughout the late Archean. ?? 2006 Elsevier B.V. All rights reserved.

  6. ERF Based Precision Linear Drive System

    Science.gov (United States)

    Tönshoff, Hans Kurt; Stegmann, Axel

    The design of clutches using electrorheological fluids (ERF) or magnetorheological suspensions (MRS) offers a new approach to precision linear drive systems based on the ‘inch-worm’ principle. This principle needs two clutches or controllable clamps and one (or more) elements to vary the distance between these clamps. To perform a caterpillar-like motion the actuators are controlled in a cyclic mode. This paper presents design elements, system structure and first results of motion performance of a prototype drive system. The presented linear drive combines the high resolution of piezo actuators, the unlimited travel of the ‘inch-worm’ principle and the clutch effect of ERF without a substantial mechanical excitation. The motion of the two clamps is controlled to move a stage in point to point mode or to follow a given velocity profile. Using two piezo actuators the stage can move continuously. Pre-loaded piezo actuators control the distances between the two clamps and the central slide. Each ERF clamp is designed as a set of thin parallel steel plate electrodes which interlock with a set of ground plates. Drive force limits are given by the maximum yield force of the clamps as well as by the relation of the actuator expansion and the ERF/MRS shear stiffness in “solid” mode.

  7. Seismic imaging of deep low-velocity zone beneath the Dead Sea basin and transform fault: Implications for strain localization and crustal rigidity

    Science.gov (United States)

    ten Brink, U.S.; Al-Zoubi, A. S.; Flores, C.H.; Rotstein, Y.; Qabbani, I.; Harder, S.H.; Keller, Gordon R.

    2006-01-01

    New seismic observations from the Dead Sea basin (DSB), a large pull-apart basin along the Dead Sea transform (DST) plate boundary, show a low velocity zone extending to a depth of 18 km under the basin. The lower crust and Moho are not perturbed. These observations are incompatible with the current view of mid-crustal strength at low temperatures and with support of the basin's negative load by a rigid elastic plate. Strain softening in the middle crust is invoked to explain the isostatic compensation and the rapid subsidence of the basin during the Pleistocene. Whether the deformation is influenced by the presence of fluids and by a long history of seismic activity on the DST, and what the exact softening mechanism is, remain open questions. The uplift surrounding the DST also appears to be an upper crustal phenomenon but its relationship to a mid-crustal strength minimum is less clear. The shear deformation associated with the transform plate boundary motion appears, on the other hand, to cut throughout the entire crust. Copyright 2006 by the American Geophysical Union.

  8. Crustal Thickness and Lower Crustal Velocity Structure Beneath the Endeavour Segment of the Juan de Fuca Ridge

    Science.gov (United States)

    Hill, R.; Soule, D. C.; Wilcock, W. S. D.; Toomey, D. R.; Hooft, E. E. E.; Weekly, R. T.

    2014-12-01

    In 2009, a multi-scale seismic tomography experiment was conducted on the Endeavour segment of the Juan de Fuca Ridge aboard the R/V Marcus G. Langseth. Ocean bottom seismometers were deployed at 64 sites and recorded 5567 shots of a 36-element, 6600 in.3 airgun array. The experiment extended 100 km along-axis and 60 km cross-axis. Two crustal tomographic analyses have previously been completed using data from the experiment. First, 93,000 manually picked crustal refraction arrivals (Pg) were used to develop a three-dimensional model of crustal velocity and thickness in the upper crust (Weekly et al. 2014). Second, this model was used as the starting model in an analysis that incorporated ~19,000 Moho reflection arrivals (PmP) for non-ridge crossing paths to image lower crustal velocity structure and crustal thickness off-axis. A key feature of this model is a ~0.5-1 km increase in crustal thickness beneath a bathymetric plateau that extends to either side of the central portion of the Endeavour segment. We present a tomographic inversions that incorporates ridge-crossing paths to examine spatial variations in lower crustal velocity and crustal thickness beneath the ridge axis. The preliminary results from an inversion that incorporates ~8700 manually picked ridge-crossing PmP arrival times reveals a ~10-km-wide low velocity zone extending throughout the lower crust with a velocity anomaly of -0.3 to -0.5 km/s at ≥4 km depth. This low velocity zone extends both to the north and south of the axial magma chamber reflector imaged previously beneath the central Endeavour. The inversion also shows significant variations in apparent crustal thickness along axis but additional analysis is required to understand whether these variations are well resolved.

  9. Computation of Capacitance for MEMS Comb-Drive Structures

    Institute of Scientific and Technical Information of China (English)

    LI Ming-hui; GAO Shi-qiao; LIU Hai-peng; LIANG Xin-jian

    2009-01-01

    According to the characteristics of comb-drive structures,the electrical potential field is analyzed;the model based on corner capacitor is presented and solved with the capacitance characteristic formula of nonlinear capacitor.Compared with the results of finite element method simulation,the model based on corner capacitor is more accurate than the models based on infinite parallel plate capacitor and parallel plate capacitor with edge effects,

  10. Crustal seismicity of the Black Sea areal

    Science.gov (United States)

    Diaconescu, Mihail; Moldovan, Iren-Adelina; Petruta Constantin, Angela

    2014-05-01

    The main target of the study is to decipher the seismicity of the Black Sea areal from the tsunami-genetic potential. From the seismotectonical point of view the earthquakes which are responsible for tsunami are those associated with thrust faults (subduction zones), normal and inverse faults and less strike slip faults (only if the oblique-slip and deep slip components are predominant), with magnitude higher than 6.5 (even the USGS cited tsunami at 5.1 magnitude) and depth, a shallow one, less than 20 km depth. In order to delimit the seismic sources from Black Sea and to discrimate among them the tsunamigenic ones, the following elements have been taken into account: - depth of the earthquakes foci, that allow separation of two major categories: deeper than 40 km depth and crustal, normal, (less than 40 km deep); - development of the earthquakes epicenters in the orogen zone or in zones with active tectonics (fault systems); - establishment of the areas of active faults along which the earthquakes epicenters are aligned; - the absence of a recent or actual tectonic activity; the epicenters recorded in these tectonically stable zones are considered as the result of a diffuse, accidental seismicity. The studies on active tectonics have clearly shown the position of the seismic sources (connected to well define active fault) which do not interfere and do not result in alternatives of other seismotectonic model constructions. According to the distribution map of earthquakes and as well as to the map of the areas with active tectonics, ten seismic sources were established: Central Dobrogea(S1), Shabla(S2), Istanbul(S3), North Anatolian Fault(S4), Georgia(S5), Novorossjsk(S6), Crimea(S7), West Black Sea Fault(S8) and Mid Black Sea Ridge(S9). The maximum possible magnitude of each seismic source was obtained through three aproaches: (i) using seismotectonics and geological database (the length of the faults, possible apparition on surface, geomorphology, etc

  11. Evidence for Moho-lower crustal transition depth diking and rifting of the Sierra Nevada microplate

    Science.gov (United States)

    Smith, Kenneth D.; Kent, Graham M.; Seggern, David P.; Driscoll, Neal W.; Eisses, Amy

    2016-10-01

    Lithospheric rifting most often initiates in continental extensional settings where "breaking of a plate" may or may not progress to sea floor spreading. Generally, the strength of the lithosphere is greater than the tectonic forces required for rupture (i.e., the "tectonic force paradox"), and it has been proposed that rifting requires basaltic magmatism (e.g., dike emplacement) to reduce the strength and cause failure, except for the case of a thin lithosphere (structure, each striking N45°W and dipping 50°NE. A single event at 30 km depth that locates on the implied dipping feature between the two swarms is further evidence for a single Moho-transition depth structure. We propose that basaltic or fluid emplacement at or near Moho depths weakens the upper mantle lid, facilitating lithospheric rupture of the Sierra Microplate. Similar to the LT sequence, the SV event is also associated with increased upper crustal seismicity. An 27 October 2011, Mw 4.7 earthquake occurred directly above the deep SV sequence at the base of the upper crustal seismogenic zone ( 15 km depth).

  12. GPS Crustal deformation in the Eastern Betics and the Lorca earthquake of 2011

    Science.gov (United States)

    Khazaradze, Giorgi; Echeverria, Anna; Asensio, Eva; Gárate, Jorge; Suriñach, Emma

    2013-04-01

    We present an updated crustal deformation field in the Eastern Betics, based on GPS observations of the CuaTeNeo network. This non-permanent network was established in 1996 to quantify the current tectonic deformation of the SE Betics. The network consists of 15 stable monuments distributed between Murcia and Almeria, which were observed five times (1997, 2002, 2006, 2009 and 2011). In general, the results show a velocity field lower than 2 mm/yr with a dominant trend oriented parallel to the Eurasia and Nubia relative plate convergence. Stations located farther inland exhibit lower velocity vectors. The calculated crustal deformation field presents clear evidence that the tectonic faults forming the Eastern Betic Shear Zone remain active. As it was evidenced by the May 11th 2011 Lorca earthquake of magnitude Mw5.2, which was caused by a reverse and sinistral slip of the Alhama de Murcia Fault. Our GPS observations, preceding the occurrence of the earthquake, are in agreement with this type of focal mechanism. Co-seismic deformation related to the earthquake was relatively small: offset of ~5mm to the North was detected at the continuous GPS station LORC located within the city.

  13. DEEP CRUSTAL STRUCTURE AND ESTIMATION OF MOHO IN THE LHASA TERRANE OF CENTRAL TIBET

    Directory of Open Access Journals (Sweden)

    Ul-Islam Md. Sultan

    2008-12-01

    Full Text Available Seismic attributes analysis is applied to INDEPTH II seismic profiles to develop a better understanding of the deep crustal structure and geodynamics of the Lhasa Terrane in the central Tibet area. Analyses indicate that the frequency anomalies are obtained over the range in between 0-30 Hz. Some area of the analyzed traces of the seismic profiles have shown dominated frequency anomaly approximately 10 Hz with little amount of other frequencies. The variation of frequency anomaly is shown to be the indication of theMoho depth of the area. EstimatedMoho depths are found very irregular and varying from20 kmto more than 136 km. The crust is thinner in southern, northern and eastern parts of the area while it is thicker in the western part having asymmetric nature in the central part. This variation might be the result of the complicated tectonic process of the Indian and Eurasian plates. Vertically downward pocket like frequency distributions and similar type frequency distributions at near and far depth are also observed in one of the analyzed sections. It might be indication of uprised asthenospheric matter which exchanged with lithosphere in subduction zones related to the multiple crustal uprising.

  14. Carpathian Shear Corridor - A strike-slip boundary of an extruded crustal segment

    Science.gov (United States)

    Marko, František; Andriessen, Paul A. M.; Tomek, Čestmír; Bezák, Vladimír; Fojtíková, Lucia; Bošanský, Marián; Piovarči, Milan; Reichwalder, Peter

    2017-04-01

    The Carpathian Shear Corridor (CSC), a morphostructurally distinctive ENE-WSW brittle shear zone, is a prominent dynamic interface of crustal fragments shifted during an oblique collision process combined with lateral extrusions in the Late stages of the Western Carpathians tectonic evolution. This tectonics was due to convection in the upper mantle, driven mainly by slab-pull forces related to a subductional process in front of prograding Carpathians. The CSC separates the marginal segment of the Western Carpathians, already firmly attached to the European plate, from the southern still eastwardly moving block. This process led to structural transpositions, anomalous rotation of small blocks and tilting and uplift/subsidence events, resulting in a tectonic style of horst and intramountaine basin alternations within the corridor. Preliminary paleomagnetic data indicate anomalous CCW block rotations within this corridor, and AFT ages indicate Early and Late Miocene (ca 24-22 Ma and ca 10-7 Ma) fault controlled exhumation events triggered by increased shear zone activity. Deep seismic sections, magnetotelluric and gravity data show that CSC follows a frontal ramp of the Western Carpathians thrust over the foreland. The CSC remains an active strike-slip shear zone, and therefore the most important earthquake risk-zone in the Slovakian portion of the Western Carpathians. It presents a lateral ramp transform boundary of eastwardly extruding crustal segment during the Miocene and up to the recent time.

  15. Regional Geophysical Surveys and Crustal Structure of the Gulf of Mexico

    Science.gov (United States)

    Rodríguez-Chavez, F.; Fucugauchi, J. U.

    2007-05-01

    Results of processing and modeling of anomaly data from regional geophysical surveys in the southern sector of the Gulf of Mexico are presented. The Gulf of Mexico has been intensively studied for several years, mainly because of the economic potential of the oil and gas resources. The basin may have formed by sea-floor spreading, rifting and lateral translation/rotation of continental slivers ssociated with major break-up and drifting apart of North and South America continental plates in the mid Mesozoic. Major structural features and crustal structure, including the continent-ocean transition and Gulf coastal passive margin are relatively poorly understood. Aerogeophysical gravity and magnetic surveys have been conducted and data are processed and modeled to investigate on the Gulf crustal structure. Spectral statistical estimates of regional basement depths derived from aeromagnetics give mean depths of 8000 m. Estimates derived from gravity anomalies are in the order of 10000 m. Depths derived from 2D and 3D seismic reflection surveys conducted for oil exploration purposes in selected areas indicate average depths to basement from 6000 m to values grater than those derived from potential field data.

  16. 3-D simulation for the tectonic evolution around the Kanto Region of Japan using the kinematic plate subduction model

    Science.gov (United States)

    Hashima, A.; Sato, T.; Ito, T.; Miyauchi, T.; Kameo, K.; Yamamoto, S.

    2011-12-01

    In the Kanto region of Japan, we can observe one of the most active crustal deformations on the earth. In the southern part of the Boso peninsula to the south, the uplift rate is estimated to be 5 mm/yr from the height of marine terraces. From geological evidence, the Kanto mountains to the west are considered to uplift at 1mm/yr. In contrast, the center part of the Kanto region is stable or subsiding, covered by the Holocene sediments. The depth of the basement reaches 3 km at the deepest. Vertical deformation in the timescale of 1 Myr is being revealed by the analysis of the recent seismic reflection experiments compared with the heights of the dated sediment layers exposed on land. These crustal deformation occurs in a highly complex tectonic setting with four plates interacting with each other: beneath Kanto, situated on the Eurasian and North American plates, the Philippine sea plate subducts and the Pacific plate further descends beneath the North American and Philippine sea plates, forming the unique trench-trench-trench triple junction on the earth. In addition, the Izu-Bonin (Ogasawara) arc on the Philippine sea plate is colliding with the Japan islands due to the buoyancy of the arc crust. At the plate boundaries near the Izu-Bonin arc, large interplate earthquakes occurred at the Sagami trough in 1703 and 1923 (Kanto earthquake) and at the Nankai trough in 1707, 1854 and 1944. To reveal the crustal deformation under these plate-to-plate interactions, we use the kinematic plate subduction model based on the elastic dislocation theory. This model is based on the idea that mechanical interaction between plates can rationally be represented by the increase of the displacement discontinuity (dislocation) across plate interfaces. Given the 3-D geometry of plate interfaces, the distribution of slip rate vectors for simple plate subduction can be obtained directly from relative plate velocities. In collision zones, the plate with arc crust cannot easily descend

  17. Generalized Fibonacci zone plates

    CERN Document Server

    Ke, Jie; Zhu, Jianqiang

    2015-01-01

    We propose a family of zone plates which are produced by the generalized Fibonacci sequences and their axial focusing properties are analyzed in detail. Compared with traditional Fresnel zone plates, the generalized Fibonacci zone plates present two axial foci with equal intensity. Besides, we propose an approach to adjust the axial locations of the two foci by means of different optical path difference, and further give the deterministic ratio of the two focal distances which attributes to their own generalized Fibonacci sequences. The generalized Fibonacci zone plates may allow for new applications in micro and nanophotonics.

  18. The Ionian and Alfeo-Etna fault zones : New segments of an evolving plate boundary in the central Mediterranean Sea?

    NARCIS (Netherlands)

    Polonia, A.; Torelli, L.; Artoni, A.; Carlini, M.; Faccenna, C.; Ferranti, L.; Gasperini, L.; Govers, R.; Klaeschen, D.; Monaco, C.; Neri, G.; Nijholt, N.; Orecchio, B.; Wortel, R.

    2016-01-01

    The Calabrian Arc is a narrow subduction-rollback system resulting from Africa/Eurasia plate convergence. While crustal shortening is taken up in the accretionary wedge, transtensive deformation accounts for margin segmentation along transverse lithospheric faults. One of these structures is the NNW

  19. The Ionian and Alfeo-Etna fault zones : New segments of an evolving plate boundary in the central Mediterranean Sea?

    NARCIS (Netherlands)

    Polonia, A.; Torelli, L.; Artoni, A.; Carlini, M.; Faccenna, C.; Ferranti, L.; Gasperini, L.; Govers, R.|info:eu-repo/dai/nl/108173836; Klaeschen, D.; Monaco, C.; Neri, G.; Nijholt, N.; Orecchio, B.; Wortel, R.|info:eu-repo/dai/nl/068439202

    2016-01-01

    The Calabrian Arc is a narrow subduction-rollback system resulting from Africa/Eurasia plate convergence. While crustal shortening is taken up in the accretionary wedge, transtensive deformation accounts for margin segmentation along transverse lithospheric faults. One of these structures is the NNW

  20. Measuring crustal convergence using rock exhumation along the complex glaciated Chugach Mountains, southeast Alaska

    Science.gov (United States)

    Spotila, J. A.; Buscher, J.

    2002-12-01

    Rates of rock uplift often constrain magnitudes of convergent plate motion in collisional settings. In complex orogenic belts, however, these rates can be difficult to measure. In southeast Alaska, a rapidly-evolving mountain system is centered at a syntaxial bend in the Pacific-North American plate boundary. Rugged topography of the Chugach Mountains stretches for more than 500 km along the hanging wall of the Aleutian Trench, above a colliding microplate, and as coast ranges along the Queen Charlotte-Fairweather transform fault. At each segment of the plate boundary, crustal convergence within North America should vary according to the obliquity of plate motion and the degree of underthrusting. Geodetic and neotectonic studies of rapidly-eroding structures have yet to define rates of horizontal plate motion partitioning. Surface uplift studies, based on short term geodesy or Holocene motion of coastal landforms, are also complicated by megathrust elastic strain accumulation cycles and the viscoelastic response to recent glacial ice thinning. It is thus important to measure exhumation and the erosional transfer of mass as a proxy for the degree of upper crustal convergence accommodated by rock uplift. We have attempted to determine exhumation pattern where the highly-deformed, oceanic and continental rocks of the Yakutat microplate collide with North America. Although the total shortening rate between this microplate and North America is of the order ~3-5 cm/yr, an unconstrained magnitude of shortening is absorbed by imbricate thrust faults within it, the suture between it and North America, and within the previously accreted terranes that form the edge of the continent. We have constrained rock cooling histories as a proxy for exhumation on samples along a dense grid that spans major structural elements, including the Pamplona and Chugach-St. Elias fault systems. Apatite and zircon radiogenic helium ages provide a range in temperature sensitivity that can be used

  1. Oligocene crustal anatexis in the Tethyan Himalaya, southern Tibet

    Science.gov (United States)

    Gao, Li-E.; Zeng, Lingsen; Gao, Jiahao; Shang, Zhen; Hou, Kejun; Wang, Qian

    2016-11-01

    Recent studies in the Xiaru and Malashan gneiss dome of the Tethyan Himalaya, southern Tibet identify that Xiaru and Paiku tourmaline-bearing leucogranite dike formed at 28-29 Ma. Together with 28 Ma Kuday garnet-bearing leucogranites, it is demonstrated that the Himalayan orogenic belt experienced a major episode of crustal melting in the Mid-Oligocene. Geochemical data indicate that three suites of leucogranite are characterized by large variations in the major and trace element compositions as well as Sr-Nd isotope systematics, which could be explained by combined fractional crystallization and relative contributions of micas and accessory phases dissolved into a crustal melt during decompressional melting of metapelitic rocks. Documentation of Oligocene partial melting of crustal rocks could indicate that the exhumation of deep crustal rocks in the Himalayan orogenic belt could have started as early as Oligocene.

  2. Slip Partitioning, Crustal Tectonics and Deformation of the Queen Charlotte Margin and Northern Vancouver Island

    Science.gov (United States)

    Hippchen, Sabine

    Part I of this thesis investigates current deformation in western British Columbia from northern Vancouver Island in the south to Haida Gwaii in the north. The area is characterized by transition from the Cascadia subduction zone to the Queen Charlotte transform fault. The tectonic setting involves interactions between the Pacific, North America, Juan de Fuca, and Explorer plates, and the Winona block, involving a number of plate boundaries: the mainly strike-slip Queen Charlotte, Revere-Dellwood-Wilson and Nootka faults, the Explorer ridge, and the Cascadia subduction zone. Using GPS campaign data from 1993 to 2008 I derive a new crustal velocity field for Northern Vancouver Island and the adjacent mainland, and integrate it with previous velocity fields developed for Haida Gwaii, southern Vancouver Island and the adjacent mainland. The northern limit of the subduction zone is confirmed to be at Brooks Peninsula, where the direction of the crustal motion changes abruptly from ENE to NNE. I use viscoelastic models to explore what percentage of the observed deformation is transient, related to the earthquake cycle, and how much is permanent ongoing deformation, distributed off the continental margin. Previous authors have developed two competing end-member models that can each explain how the Pacific/North America plate convergence is accommodated off Haida Gwaii. These models assume either internal crustal shortening or underthrusting of the Pacific plate. These new GPS data allow me to conclude that underthrusting does occur, and that a small component (Haida Gwaii the distinction between transient and long-term deformation is not as clear; however, I conclude that transient deformation alone cannot fully explain the observed velocities, and so long-term deformation likely must also occur. Part II of the thesis investigates the updip and downdip limits of the seismogenic zone of the Sumatra megathrust fault. Temperature and downdip changes in formation composition

  3. Plate tectonics on Venus

    Science.gov (United States)

    Anderson, D. L.

    1981-01-01

    The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

  4. Plate tectonics on Venus

    Science.gov (United States)

    Anderson, D. L.

    1981-01-01

    The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

  5. 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.

  6. Pb isotopic geochemical study on the crustal structure of Tongbaishan

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Pb isotopic composition of the Tongbai complex, distributed in the Tongbaishan to the west of the Dabieshan, ranges between the Dabie core complex and the Dabie ultral-high pressure (UHP) metamorphic complex, the latter having more radiogenic Pb isotopic composition than the former. Granites from the Jigongshan pluton, which intruded mainly into the Tongbai complex, are distinct from the Tongbai complex but similar to the Dabie core complex in Pb isotopic composition, showing that the magma of the Jigongshan granites was derived from the partial melting of the Dabie core complex. According to Pb isotopic compositional variation model in the vertical crustal section and magma source from the Jigongshan pluton, it is suggested that the Tongbai complex was an upper rock serial of the Dabie core complex, which is beneath the Dabie UHP metamorphic complex in the crustal structure of the Tongbai-Dabie orogenic belt. The Tongbai complex was not well preserved in the Dabie area due to the high exhumed crustal section. However, the crustal section in the Tongbai area was exhumed less than that in the Dabie area, and the deep crust in the Tongbai area still contains the basement composition similar to the Dabie core complex. Therefore, the crustal basements from the Dabie to Tongbai areas are united. The present distribution of the basement blocks in different locations of the Tongbai-Dabie orogenic belt reflects different exposure of the crustal section.

  7. Lectures on magnetohydrodynamical drives

    Science.gov (United States)

    Loigom, Villem

    The paper deals with nonconventional types of electrical machines and drives - magnetohydrodynamical (MHD) machines and drives. In cardinal it is based on the research conducted with participation of the author in Tallinn Technical University at the Institute of Electrical Drives and Power Electronics, where the use of magnetohydrodynamical motors and drives in the metallurgical and casting industries have been studied for a long time. Major research interests include the qualities and applications of the induction MHD-drives for set in the motion (pumping, turning, dosing, mixing, etc.) non-ferrous molten metals like Al, Mg, Sn, Pb, Na, K, and their alloys. The first part of the paper describes induction MHD motors and their electrohydraulical qualities. In the second part energy conversion problems are described. Also, on the basis of the analogy between electromechanical and electrohydraulical phenomenas, static and dynamic qualities of MHD drives with induction MHD machines are discussed.

  8. Mechanical design of multiple zone plates precision alignment apparatus for hard X-ray focusing in twenty-nanometer scale

    Energy Technology Data Exchange (ETDEWEB)

    Shu, Deming; Liu, Jie; Gleber, Sophie C.; Vila-Comamala, Joan; Lai, Barry; Maser, Jorg M.; Roehrig, Christian; Wojcik, Michael J.; Vogt, Franz Stefan

    2017-04-04

    An enhanced mechanical design of multiple zone plates precision alignment apparatus for hard x-ray focusing in a twenty-nanometer scale is provided. The precision alignment apparatus includes a zone plate alignment base frame; a plurality of zone plates; and a plurality of zone plate holders, each said zone plate holder for mounting and aligning a respective zone plate for hard x-ray focusing. At least one respective positioning stage drives and positions each respective zone plate holder. Each respective positioning stage is mounted on the zone plate alignment base frame. A respective linkage component connects each respective positioning stage and the respective zone plate holder. The zone plate alignment base frame, each zone plate holder and each linkage component is formed of a selected material for providing thermal expansion stability and positioning stability for the precision alignment apparatus.

  9. Mechanical design of multiple zone plates precision alignment apparatus for hard X-ray focusing in twenty-nanometer scale

    Science.gov (United States)

    Shu, Deming; Liu, Jie; Gleber, Sophie C.; Vila-Comamala, Joan; Lai, Barry; Maser, Jorg M.; Roehrig, Christian; Wojcik, Michael J.; Vogt, Franz Stefan

    2017-04-04

    An enhanced mechanical design of multiple zone plates precision alignment apparatus for hard x-ray focusing in a twenty-nanometer scale is provided. The precision alignment apparatus includes a zone plate alignment base frame; a plurality of zone plates; and a plurality of zone plate holders, each said zone plate holder for mounting and aligning a respective zone plate for hard x-ray focusing. At least one respective positioning stage drives and positions each respective zone plate holder. Each respective positioning stage is mounted on the zone plate alignment base frame. A respective linkage component connects each respective positioning stage and the respective zone plate holder. The zone plate alignment base frame, each zone plate holder and each linkage component is formed of a selected material for providing thermal expansion stability and positioning stability for the precision alignment apparatus.

  10. Climate modulated erosion and sediment flux control offshore crustal structure at South China Sea continental margin

    Science.gov (United States)

    Clift, P. D.; Brune, S.; Quinteros, J.

    2015-12-01

    Rifted continental lithosphere subsides as a consequence of combined crustal thinning and mantle lithosphere cooling yet basins on some continental margins experience anomalous subsidence events that postdate active extension. Deep basins on the northern margin of the South China Sea, notably the Baiyun Sag, show basement subsidence accelerating after ~21 Ma, postdating extension by several million years. Similar subsidence events are seen after 5 Ma in the Song Hong Basin and after 11 Ma in the Qiongdongnan Basin. We combine geophysical observations and numerical forward modeling to show that loading of the offshore basins by increased sediment flux caused by faster onshore erosion following Early Miocene monsoon intensification is a viable trigger for ductile flow after the cessation of active extension. Loading works in conjunction with onshore uplift to drive flow of the lower crust away from the rift axis. As well as sediment supply rates distribution patterns and drainage capture can be significant in controlling crustal flow and thinning. This illustrates that offshore basin dynamics at continental margins with weak crust can be controlled by onshore surface processes in a newly recognized form of climate-tectonic coupling.

  11. Blue Willow Story Plates

    Science.gov (United States)

    Fontes, Kris

    2009-01-01

    In the December 1997 issue of "SchoolArts" is a lesson titled "Blue Willow Story Plates" by Susan Striker. In this article, the author shares how she used this lesson with her middle-school students many times over the years. Here, she describes a Blue Willow plate painting project that her students made.

  12. Create Your Plate

    Medline Plus

    Full Text Available ... In Memory In Honor Become a Member En Español Type 1 Type 2 About Us Online Community ... Page Text Size: A A A Listen En Español Create Your Plate Create Your Plate is a ...

  13. Create Your Plate

    Medline Plus

    Full Text Available ... Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning ... Planning Meals Diabetes Meal Plans and a Healthy Diet Create Your Plate Meal Planning for Vegetarian Diets ...

  14. 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.

  15. Crustal structure in the Falcón Basin area, northwestern Venezuela, from seismic and gravimetric evidence

    Science.gov (United States)

    Bezada, Maximiliano J.; Schmitz, Michael; Jácome, María Inés; Rodríguez, Josmat; Audemard, Franck; Izarra, Carlos; The Bolivar Active Seismic Working Group

    2008-05-01

    The Falcón Basin in northwestern Venezuela has a complex geological history driven by the interactions between the South American and Caribbean plates. Igneous intrusive bodies that outcrop along the axis of the basin have been associated with crustal thinning, and gravity modeling has shown evidence for a significantly thinned crust beneath the basin. In this study, crustal scale seismic refraction/wide-angle reflection data derived from onshore/offshore active seismic experiments are interpreted and forward-modeled to generate a P-wave velocity model for a ˜450 km long profile. The final model shows thinning of the crust beneath the Falcón Basin where depth to Moho decreases to 27 km from a value of 40 km about 100 km to the south. A deeper reflected phase on the offshore section is interpreted to be derived from the downgoing Caribbean slab. Velocity values were converted to density and the resulting gravimetric response was shown to be consistent with the regional gravity anomaly. The crustal thinning proposed here supports a rift origin for the Falcón Basin.

  16. Estimation of interplate coupling at the Nankai Trough based on observation of ocean bottom crustal deformation at the Kumano Basin

    Science.gov (United States)

    Watanabe, T.; Tadokoro, K.; Sugimoto, S.; Okuda, T.; Muto, D.; Kimoto, A.; Kuno, M.

    2007-12-01

    At the Nankai Trough, the Philippine Sea plate (PH) subducts beneath the southwest Japan with a rate of about 4- 6 cm/yr, where great interplate earthquakes have repeatedly occurred every 100-200 years. A number of researchers have investigated crustal deformation caused by subduction of the PH based on geodetic measurements as represented by GPS observation. However it is difficult to infer the strength of the plate coupling in offshore areas, due to the poverty of offshore geodetic data. For this issue, we have conducted seafloor geodetic observation using GPS/Acoustic techniques around the Nankai Trough since 2004. In this system, we estimate the position of a surveying vessel by Kinematic GPS analysis and measure the distance between the vessel and the benchmark on the seafloor by Acoustic measurements. Next we determine the location of the benchmark and detected crustal movement of the seafloor. There are three seafloor sites in this region, and then the location of benchmark is determined within a precision of 2-3 cm at horizontal components for each observation (Tadokoro et al., 2006). As a result of observations from November 2005 to February 2007, one of the seafloor sites is moving at a rate of 6.96 +/- 4.03 cm/yr in the WNW direction with respect to the Amurian plate (AM). In this study, we investigate interplate coupling at the Nankai Trough using onshore GPS velocities derived from Geophysical Survey Institute of Japan and our estimated offshore GPS site velocity. We assume that observed GPS velocities are represented by the superposition of elastic deformation associated with subduction of the PH, rigid block motion of the overriding plate, and error. The plate interface along the Nankai Trough is represented by multiple rectangular faults. The strength of the plate coupling for each fault segment varies with depth according to a thermal model (Hyndman et al., 1995). Moreover relative plate motion of the PH-AM (Miyazaki and Heki, 2001) is assigned to

  17. Universal Drive Train Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This vehicle drive train research facility is capable of evaluating helicopter and ground vehicle power transmission technologies in a system level environment. The...

  18. Contemporary crustal deformation of the Chinese continent and tectonic block model

    Institute of Scientific and Technical Information of China (English)

    王敏; 沈正康; 牛之俊; 张祖胜; 孙汉荣; 甘卫军; 王琪; 任群

    2003-01-01

    We obtain the preliminary result of crustal deformation velocity field for the Chinese con-tinent by analyzing GPS data from the Crustal Motion Observation Network of China (CMONOC), particularly the data from the regional networks of CMONOC observed in 1999 and 2001. We de-lineate 9 tectonically active blocks and 2 broadly distributed deformation zones out of a denseGPS velocity field, and derive block motion Euler poles for the blocks and their relative motionrates. Our result reveals that there are 3 categories of deformation patterns in the Chinese conti-nent. The first category, associated with the interior of the Tibetan Plateau and the Tianshan oro-genic belt, shows broadly distributed deformation within the regions. The third category, associatedwith the Tarim Basin and the region east of the north-south seismic belt of China, shows block-likemotion, with deformation accommodated along the block boundaries only. The second category, mainly associated with the borderland of the Tibetan Plateau, such as the Qaidam, Qilian, Xining(in eastern Qinghai), and the Diamond-shaped (in western Sichuan and Yunnan) blocks, has thedeformation pattern between the first and the third, i.e. these regions appear to deform block-like,but with smaller sizes and less strength for the blocks. Based on the analysis of the lithosphericstructures and the deformation patterns of the regions above, we come to the inference that thedeformation modes of the Chinese continental crust are mainly controlled by the crustal structure.The crust of the eastern China and the Tarim Basin is mechanically strong, and its deformationtakes the form of relative motion between rigid blocks. On the other hand, the northward indentation of the Indian plate into the Asia continent has created the uplift of the Tibetan Plateau and the Tianshan Mountains, thickened their crust, and raised the temperature in the crust. The lower crust thus has become ductile, evidenced in low seismic velocity and high

  19. Co- and post-seismic crustal deformation of the 2014 Iquique-Pisagua Earthquake observed with InSAR and GPS data

    Science.gov (United States)

    Eckelmann, Felix; Moreno, Marcos; Metzger, Sabrina; Bartsch, Mitja; Oncken, Onno; Baez, Juan Carlos; Klotz, Jürgen

    2015-04-01

    The western margin of South America is dominated by a 6000 km long subduction zone that drives the seismogenic processes of megathrust earthquakes along the Chilean coast. Almost all seismotectonic segments at this highly active plate boundary have broken within the last decades producing great earthquakes (MW>8.5). The only segment that has not ruptured since 1877 is known as Northern Chile-Southern Peru seismic gap. It is located between 18°-22°S latitude and has the potential of generating a Mw=9+ earthquake. On 1 April 2014, the Iquique-Pisagua earthquake (MW>8.5) affected the north-central part of this gap. This earthquake was proceeded by a transient deformation 15 days before the main shock and followed by a MW=7.6 aftershock. In this study, we analyze and model the co- and postseismic crustal deformation related to the Iquique-Pisagua earthquake by means of InSAR and GPS measurements. In the modeling, we perform a joint inversion of InSAR and GPS data by applying principle component analysis and the decomposition of displacement vectors in an elastic half-space. Our InSAR observations include three TerraSAR-X images from three years before the earthquake and one, resp. 79 days after the event. This dataset allows us to separate deformation caused by the main event and the aftershock two days later. Moreover, we present five Radarsat-2 scenes from four days before and three, 19, 44 and 76 days after the earthquake. Our GPS data include time-series of more than 40 continuous stations of the Integrated Plate Boundary Observatory Chile (IPOC) and 60 survey-mode GPS data. The co-seismic interferograms show a circular deformation pattern centered at the North Chilean coast near the city of Iquique. The cGPS recorded a maximum horizontal displacement of 80 cm trenchward. In the post-seismic interferograms the deformation is much smaller and somewhat less symmetric. The first two month of postseismic deformation show a cumulative GPS displacement up to 10 cm

  20. IODP Expedition 301 Installs Three Borehole Crustal Observatories, Prepares for Three-Dimensional, Cross-Hole Experiments in the Northeastern Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Adam Klaus

    2005-09-01

    Full Text Available Introduction and Goals The basaltic upper oceanic crust comprises the largestaquifer on Earth, containing a volume of water about equalto that currently stored in ice sheets and glaciers. Annualfluid fluxes through the upper oceanic crust are at leastas large as the global river flux to the ocean. Much of theseafloor is hydrogeologically active, but the majority ofthe fluid flow within oceanic crust occurs on ridge flanks,regions located kilometers or more from active seafloorspreading centers. Fluid circulation in these areas is drivenmainly by lithospheric heat rising from deep within theplate but is influenced by seafloor and basement topography,seismic and tectonic events, and tides.Subseaf loor f luid f low on ridge f lanks inf luences adiverse array of processes and properties, including thethermal state and evolution of oceanic plates, alteration ofthe lithosphere and crustal pore waters, establishment andmaintenance of vast subseaf loor microbial ecosystems,and diagenetic, seismic, and magmatic activity along plateboundaryfaults. Although numerous drilling expeditionsand surface and submersible surveys over the last severaldecades have focused on hydrogeologic phenomena, we stillknow relatively little about driving forces, property distributions,scales of flow, rates of flow, extent of compartmentalizationor isolation of distinct fluid-rock systems, or linksbetween hydrogeologic, geochemical, microbiological, andgeophysical processes. Progress through drilling has beenlimited in the past by the perturbing effects of boreholecreation on subseafloor thermal, pressure, chemical, andbiological conditions. Subseafloor observatories addressthis challenge by allowing the formation to recover fromdrilling perturbations, and also allow scientists to runpassive and active experiments for years to decades.IODP Expedition 301 was part of a multi-disciplinaryprogram designed to evaluate the formation-scale hydrogeologicproperties within oceanic crust

  1. History and Evolution of Precambrian plate tectonics

    Science.gov (United States)

    Fischer, Ria; Gerya, Taras

    2014-05-01

    Plate tectonics is a global self-organising process driven by negative buoyancy at thermal boundary layers. Phanerozoic plate tectonics with its typical subduction and orogeny is relatively well understood and can be traced back in the geological records of the continents. Interpretations of geological, petrological and geochemical observations from Proterozoic and Archean orogenic belts however (e.g., Brown, 2006), suggest a different tectonic regime in the Precambrian. Due to higher radioactive heat production the Precambrian lithosphere shows lower internal strength and is strongly weakened by percolating melts. The fundamental difference between Precambrian and Phanerozoic tectonics is therefore the upper-mantle temperature, which determines the strength of the upper mantle (Brun, 2002) and the further tectonic history. 3D petrological-thermomechanical numerical modelling experiments of oceanic subduction at an active plate at different upper-mantle temperatures show these different subduction regimes. For upper-mantle temperatures buckling and also lithospheric delamination and drip-offs. For upper-mantle temperatures > 250 K above the present day value no subduction occurs any more. The whole lithosphere is delaminating and due to strong volcanism and formation of a thicker crust subduction is inhibited. This stage of 200-250 K higher upper mantle temperature which corresponds roughly to the early Archean (Abbott, 1994) is marked by strong volcanism due to sublithospheric decompression melting which leads to an equal thickness for both oceanic and continental plates. As a consequence subduction is inhibited, but a compressional setup instead will lead to orogeny between a continental or felsic terrain and an oceanic or mafic terrain as well as internal crustal convection. Small-scale convection with plume shaped cold downwellings also in the upper mantle is of increased importance compared to the large-scale subduction cycle observed for present temperature

  2. A proposal of monitoring and forecasting system for crustal activity in and around Japan using a large-scale high-fidelity finite element simulation codes

    Science.gov (United States)

    Hori, T.; Ichimura, T.

    2015-12-01

    Here we propose a system for monitoring and forecasting of crustal activity, especially great interplate earthquake generation and its preparation processes in subduction zone. Basically, we model great earthquake generation as frictional instability on the subjecting plate boundary. So, spatio-temporal variation in slip velocity on the plate interface should be monitored and forecasted. Although, we can obtain continuous dense surface deformation data on land and partly at the sea bottom, the data obtained are not fully utilized for monitoring and forecasting. It is necessary to develop a physics-based data analysis system including (1) a structural model with the 3D geometry of the plate interface and the material property such as elasticity and viscosity, (2) calculation code for crustal deformation and seismic wave propagation using (1), (3) inverse analysis or data assimilation code both for structure and fault slip using (1)&(2). To accomplish this, it is at least necessary to develop highly reliable large-scale simulation code to calculate crustal deformation and seismic wave propagation for 3D heterogeneous structure. Actually, Ichimura et al. (2014, SC14) has developed unstructured FE non-linear seismic wave simulation code, which achieved physics-based urban earthquake simulation enhanced by 10.7 BlnDOF x 30 K time-step. Ichimura et al. (2013, GJI) has developed high fidelity FEM simulation code with mesh generator to calculate crustal deformation in and around Japan with complicated surface topography and subducting plate geometry for 1km mesh. Further, for inverse analyses, Errol et al. (2012, BSSA) has developed waveform inversion code for modeling 3D crustal structure, and Agata et al. (2015, this meeting) has improved the high fidelity FEM code to apply an adjoint method for estimating fault slip and asthenosphere viscosity. Hence, we have large-scale simulation and analysis tools for monitoring. Furthermore, we are developing the methods for

  3. Tectonic history of the Ordos Block and Qinling Orogen inferred from crustal thickness

    Science.gov (United States)

    Feng, Mei; An, Meijian; Dong, Shuwen

    2017-07-01

    The Ordos Block and the Qinling Orogen in central China are key regions that have been affected by Indo-Eurasian collision, convergence of the North China, South China and Siberian cratons, and subduction of the Pacific oceanic plate during the Phanerozoic. Investigation of the crustal structure in this area can therefore provide significant insights into the interactions among these tectonic blocks and plates. The Chinese Academy of Geological Sciences deployed ca. 249 portable broad-band seismic stations in this area from 2011 to 2016, and we retrieved P-wave receiver functions (RFs) from these new stations, and also from all other available permanent and portable seismic stations in China. Crustal thicknesses beneath the stations were retrieved using 1-D S-wave velocity models, which were obtained by linearized inversion of the RFs with initial reference models from regionalized S-wave velocities of surface wave inversions. We demonstrate with synthetic tests that this inversion scheme is superior to a jointly linearized inversion of RFs and surface waves. The results show that crustal thicknesses generally correlate with tectonic domains in the study region. Thus, thick crust is present beneath the Daba Shan region and the area close to the northeastern Tibetan Plateau, intermediate-thickness crust is present beneath the Ordos Block and the central North China Craton, and thin crust exists beneath the North China Plain. However, some notable exceptions exist. The crust beneath the central Qinling is thinner than that beneath the neighbouring Daba Shan region and even the Weihe Basin, implying that subduction and collision of the North China and South China cratons in the Palaeozoic did not produce a thick crust beneath the suture. The relatively thin crust beneath the eastern and central Qinling must be denser than that beneath neighbouring areas. All the basins around the Ordos Block have been considered to be graben. However, our results show that the crust

  4. Estimation of crustal movements using the Global Positioning System (GPS measurements along Nile Valley area, Egypt from 2007 to 2012

    Directory of Open Access Journals (Sweden)

    Kamal Sakr

    2015-06-01

    The present study aimed to determine the recent crustal movement parameters along the Nile Valley using the Global Positioning System (GPS measurements. To achieve this mission, a GPS network consisting of ten geodetic stations has been established on both sides along the Nile Valley area. GPS measurements have been collected from 2007 to 2012. The collected data were processed using Bernese 5.0 Software. The result of the data analysis indicates that the rate of local velocity is small ranging from 1 to 4 mm/year. This rate is consistent with the low rate of occurrence of recent earthquakes activity along the Nile Valley area. But, the results obtained from the calculation of the regional velocity indicated that the velocity of the GPS stations including the African Plate motion is about 25 mm/year in the northeast direction which is consistent with the African Plate motion direction.

  5. Crustal structure of seismic velocity in southern Tibet and east-westward escape of the crustal material--An example by wide-angle seismic profile from Peigu Tso to Pumoyong Tso

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Zhongjie; TENG; Jiwen; LI; Yingkang; S.Klemperer

    2004-01-01

    The reflecting events from Moho and other interfaces within the crust are recognized from the wavefield characteristics of P- and S-wave for the 480km long wide-angle seismic profile between Peigu Tso and Pumoyong Tso. Then, seismic crustal structures of P- and S-wave velocities and Poisson ratio under the nearly east-west profile in southern Tibet are interpreted by fitting the observed traveltimes with the calculated ones by forward modelling. Our interpreting results demonstrate that the crustal thickness varies remarkably in the east-west direction, showing a pattern that the crust could be divided into three parts bounded by the west of Dingri and the east of Dinggyê, respectively, where the depth of Moho is about 71km for the western part, about 76km for the middle and about 74km for the eastern. There is one lower velocity layer (LVL) at the bottom of the upper crust with depth of 20-30 km. One of the distinct features is that the thickness of LVL abruptly thins from 24km on the west to 6km on the east. The other is that the velocity variation in the crust along east-west direction for both P- and S-wave displays a feature as quasi-periodic variation. The lower velocity (compared to the average value for the continent of the globe) in the lower crust and three sets of north-southward active normal faults are probably attributed to the coupling process of material delamination in the lower crust, crustal thicking and east-westward escape of the crustal material accompanied with the continental collision between India and Eurasia Plate.

  6. Nitrogen speciation in mantle and crustal fluids

    Science.gov (United States)

    Li, Yuan; Keppler, Hans

    2014-03-01

    Seventy-nine experiments have been carried out at 600-1400 °C, 2-35 kbar, and oxygen fugacities ranging from the Fe-FeO to the Re-ReO2 buffer to investigate the nitrogen speciation in mantle and crustal N-H-O fluids. Laser Raman analyses of fluid inclusions trapped in situ in quartz and olivine crystals show that N2 and/or NH3 are the only detectable nitrogen species in the fluids at the conditions of the present study. The results further show that in the fluids of the oxidized shallow upper mantle, nitrogen is mostly present as N2, while in the deep reduced upper mantle, NH3 is the dominant nitrogen species. Nitrogen speciation in subduction zone fluids is also calculated from the experimental data to constrain the efficiency of nitrogen recycling. The data show that a hot, oxidized slab is an efficient barrier for deep nitrogen subduction, while a cold, reduced slab would favor recycling nitrogen into the deep mantle. The nitrogen species in magmatic fluids of mid-ocean ridge basalt and arc magmas are predominantly N2, but a significant fraction of nitrogen can be NH3 at certain conditions. The nitrogen species in fluids released from the solidifying magma ocean and the reduced young mantle may have been mostly NH3. The release of such fluids may have created a reduced atmosphere on the every early Earth, with an elevated concentration of NH3. This may not only resolve the faint young Sun paradox but may also have created favorable conditions for the formation of biomolecules through Miller-Urey type reactions.

  7. Piezoelectric drive circuit

    Science.gov (United States)

    Treu, Jr., Charles A.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

  8. Fundamentals of electrical drives

    CERN Document Server

    Veltman, André; De Doncker, Rik W

    2007-01-01

    Provides a comprehensive introduction to various aspects of electrical drive systems. This volume provides a presentation of dynamic generic models that cover all major electrical machine types and modulation/control components of a drive as well as dynamic and steady state analysis of transformers and electrical machines.

  9. Electric vehicles: Driving range

    Science.gov (United States)

    Kempton, Willett

    2016-09-01

    For uptake of electric vehicles to increase, consumers' driving-range needs must be fulfilled. Analysis of the driving patterns of personal vehicles in the US now shows that today's electric vehicles can meet all travel needs on almost 90% of days from a single overnight charge.

  10. Recognizing driving in haste

    NARCIS (Netherlands)

    Rendón-Vélez, E.

    2014-01-01

    One can often hear people discussing the reasons why a road accident has happened: “She had to pick up her kids in the school before four o’clock and she was driving in haste and careless”, “He was stressed, he wanted to reach the beginning of the football match, tried to drive faster and didn't app

  11. Drive Around the World

    Institute of Scientific and Technical Information of China (English)

    Yang Wei

    2008-01-01

    @@ "It's so cool that I can drive on my own,and my own car,"Cao Gang,WOrking for a private company in Changsha,capital city of Hunan Province,mid-south China,said in excitement when he newly bought Ben Ben,a Chinese local auto brand of Chang'an,with his freshly-passed driving license.

  12. Recognizing driving in haste

    NARCIS (Netherlands)

    Rendón-Vélez, E.

    2014-01-01

    One can often hear people discussing the reasons why a road accident has happened: “She had to pick up her kids in the school before four o’clock and she was driving in haste and careless”, “He was stressed, he wanted to reach the beginning of the football match, tried to drive faster and didn't app

  13. Electric Vehicle - Economical driving

    DEFF Research Database (Denmark)

    Jensen, VCE, Steen V.; Schøn, Henriette

    1999-01-01

    How do you reduce the energy-wast when driving and loading EV's - or rather: How do I get more km/l out of an EV......How do you reduce the energy-wast when driving and loading EV's - or rather: How do I get more km/l out of an EV...

  14. Recognizing driving in haste

    NARCIS (Netherlands)

    Rendón-Vélez, E.

    2014-01-01

    One can often hear people discussing the reasons why a road accident has happened: “She had to pick up her kids in the school before four o’clock and she was driving in haste and careless”, “He was stressed, he wanted to reach the beginning of the football match, tried to drive faster and didn't

  15. Pixelated neutron image plates

    Science.gov (United States)

    Schlapp, M.; Conrad, H.; von Seggern, H.

    2004-09-01

    Neutron image plates (NIPs) have found widespread application as neutron detectors for single-crystal and powder diffraction, small-angle scattering and tomography. After neutron exposure, the image plate can be read out by scanning with a laser. Commercially available NIPs consist of a powder mixture of BaFBr : Eu2+ and Gd2O3 dispersed in a polymer matrix and supported by a flexible polymer sheet. Since BaFBr : Eu2+ is an excellent x-ray storage phosphor, these NIPs are particularly sensitive to ggr-radiation, which is always present as a background radiation in neutron experiments. In this work we present results on NIPs consisting of KCl : Eu2+ and LiF that were fabricated into ceramic image plates in which the alkali halides act as a self-supporting matrix without the necessity for using a polymeric binder. An advantage of this type of NIP is the significantly reduced ggr-sensitivity. However, the much lower neutron absorption cross section of LiF compared with Gd2O3 demands a thicker image plate for obtaining comparable neutron absorption. The greater thickness of the NIP inevitably leads to a loss in spatial resolution of the image plate. However, this reduction in resolution can be restricted by a novel image plate concept in which a ceramic structure with square cells (referred to as a 'honeycomb') is embedded in the NIP, resulting in a pixelated image plate. In such a NIP the read-out light is confined to the particular illuminated pixel, decoupling the spatial resolution from the optical properties of the image plate material and morphology. In this work, a comparison of experimentally determined and simulated spatial resolutions of pixelated and unstructured image plates for a fixed read-out laser intensity is presented, as well as simulations of the properties of these NIPs at higher laser powers.

  16. Plate removal following orthognathic surgery.

    Science.gov (United States)

    Little, Mhairi; Langford, Richard Julian; Bhanji, Adam; Farr, David

    2015-11-01

    The objectives of this study are to determine the removal rates of orthognathic plates used during orthognathic surgery at James Cook University Hospital and describe the reasons for plate removal. 202 consecutive orthognathic cases were identified between July 2004 and July 2012. Demographics and procedure details were collected for these patients. Patients from this group who returned to theatre for plate removal between July 2004 and November 2012 were identified and their notes were analysed for data including reason for plate removal, age, smoking status, sex and time to plate removal. 3.2% of plates were removed with proportionally more plates removed from the mandible than the maxilla. 10.4% of patients required removal of one or more plate. Most plates were removed within the first post-operative year. The commonest reasons for plate removal were plate exposure and infection. The plate removal rates in our study are comparable to those seen in the literature.

  17. Anisotropic elastic plates

    CERN Document Server

    Hwu, Chyanbin

    2010-01-01

    As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a

  18. Plating in Top Agar

    OpenAIRE

    sprotocols

    2014-01-01

    1. Warm plates to room temperature before use. Cold plates causes the top agar to solidify irregularly. DO not warm plates to 37° as the top agar will take forever to solidify. - Prepare top agar as the appropriate liquid medium with 0.7% agar. Keeping 100 mL bottles is convenient. For phages, use λ top agar, which is less rich and yields bigger plaques. - Melt top agar in the microwave completely. Allow the agar to boil after liquification; incompletely melted agar looks liquid, but is...

  19. Long-range Receiver Function Profile of Crustal and Mantle Discontinuities From the Aleutian Arc to Tierra del Fuego

    Science.gov (United States)

    Spieker, Kathrin; Rondenay, Stéphane; Sawade, Lucas

    2016-04-01

    The Circum-Pacific belt, also called the Pacific Ring of Fire, is the most seismically active region on Earth. Multiple plate boundaries form a zone characterized by frequent volcanic eruptions and seismicity. While convergent plate boundaries such as the Peru-Chile trench dominate the Circum-Pacific belt, divergent and transform boundaries are present as well. The eastern section of the Circum-Pacific belt extends from the Aleutian arc, through the Cascadia subduction zone, San Andreas Fault, middle America trench and the Andean margin down to Tierra del Fuego. Due to the significant hazards posed by this tectonic activity, the region has been densely instrumented by thousands of seismic stations deployed across fifteen countries, over a distance of more than 15000 km. Various seismological studies, including receiver function analyses, have been carried out to investigate the crustal and mantle structure beneath local segments of the eastern Circum-Pacific belt (i.e., at ~100-500 km scale). However, to the best of our knowledge, no study to date has ever attempted to combine all available seismic data from the eastern Circum-Pacific belt to generate a continuous profile of seismic discontinuities extending from the Aleutians to Tierra del Fuego. Here, we use results from the "Global Imaging using Earthquake Records" (GLImER) P-wave receiver function database to create a long-range profile of crustal and upper mantle discontinuities across the entire eastern portion of the Circum-Pacific belt. We image intermittent crustal and mantle discontinuities along the profile, and examine them with regard to their behaviour and properties across transitions between different tectonic regimes.

  20. Design Modification & Failure Analysis of a Driven Plate/Friction Plate of a Clutch using FEA.

    Directory of Open Access Journals (Sweden)

    Marella. Veerendra

    2014-10-01

    Full Text Available Clutch is device which is used to transmit power one component to another. It is a device used to connect the driving shaft to a driven shaft, so that the driven shaft may be started or stopped at will, without stopping the driving shaft. A clutch thus provides an interruptible connection between two rotating shafts Clutches allow a high inertia load to be stated with a small power. The engine power transmitted to the system through the clutch. The failure of such a critical component during service can stall the whole application. The objective of present project is to do analysis on driven plate of a clutch which is often fails during the operation. In this present research work analysis is conducted on driven plate of a clutch used in TATA Vehicle. There are so many complaints are noted against the failure of clutch during heavy loads. The driven main plate failed normally during its operation due to cyclic loading. For this reason we designed the driven plate and modeled in Pro-E and analyzed using FEA package in the process of designing and analyzing the actual design is changed to lower down the failure values. And the design may suggest to the company.

  1. Torque exerted on the side of crustal blocks controls the kinematics of Ethiopian Rift

    Science.gov (United States)

    Muluneh, Ameha A.; Kidane, Tesfaye; Cuffaro, Marco; Doglioni, Carlo

    2016-04-01

    Plate tectonic stress at active plate boundary can arises from 1) a torque applied on the side of lithospheric blocks and 2) a torque at the base of the lithosphere due to the flow of the underlying mantle. In this paper we use a simple force balance analysis to compare side and basal shear stresses and their contribution in driving kinematics and deformation in the Ethiopian Rift (ER), in the northern part of the East African Rift System (EARS). Assuming the constraints of the ER given by the dimension of the lithospheric blocks, the strain rate, the viscosity of the low velocity zone (LVZ) and the depth of the brittle-ductile transition zone, the lateral torque is several orders of magnitude higher than the basal torque. The minor contribution of basal torque might be due to low viscosity in the LVZ. Both Africa and Somalia plates are moving to the "west" relative to the mantle and there are not slabs that can justify this pull and consequent motion. Therefore, we invoke that westerly oriented tidal torque on Africa and Somalia plates in providing the necessary side torque in the region. This plate motion predicts significant sinistral transtension along the ER and rift parallel strike-slip faulting similar to the estimated angular velocity vector for tectonic blocks and GPS observations. Vertical axis block rotations are observed in areas where the lithospheric mantle is removed and strain is widely distributed.

  2. Subduction zone and crustal dynamics of western Washington; a tectonic model for earthquake hazards evaluation

    Science.gov (United States)

    Stanley, Dal; Villaseñor, Antonio; Benz, Harley

    1999-01-01

    The Cascadia subduction zone is extremely complex in the western Washington region, involving local deformation of the subducting Juan de Fuca plate and complicated block structures in the crust. It has been postulated that the Cascadia subduction zone could be the source for a large thrust earthquake, possibly as large as M9.0. Large intraplate earthquakes from within the subducting Juan de Fuca plate beneath the Puget Sound region have accounted for most of the energy release in this century and future such large earthquakes are expected. Added to these possible hazards is clear evidence for strong crustal deformation events in the Puget Sound region near faults such as the Seattle fault, which passes through the southern Seattle metropolitan area. In order to understand the nature of these individual earthquake sources and their possible interrelationship, we have conducted an extensive seismotectonic study of the region. We have employed P-wave velocity models developed using local earthquake tomography as a key tool in this research. Other information utilized includes geological, paleoseismic, gravity, magnetic, magnetotelluric, deformation, seismicity, focal mechanism and geodetic data. Neotectonic concepts were tested and augmented through use of anelastic (creep) deformation models based on thin-plate, finite-element techniques developed by Peter Bird, UCLA. These programs model anelastic strain rate, stress, and velocity fields for given rheological parameters, variable crust and lithosphere thicknesses, heat flow, and elevation. Known faults in western Washington and the main Cascadia subduction thrust were incorporated in the modeling process. Significant results from the velocity models include delineation of a previously studied arch in the subducting Juan de Fuca plate. The axis of the arch is oriented in the direction of current subduction and asymmetrically deformed due to the effects of a northern buttress mapped in the velocity models. This

  3. Rheology of Melt-bearing Crustal Rocks

    Science.gov (United States)

    Rosenberg, C. L.; Medvedev, S.; Handy, M. R.

    2006-12-01

    A review and reinterpretation of previous experimental data on the deformation of melt-bearing crustal rocks (Rosenberg and Handy, 2005) revealed that the relationship of aggregate strength to melt fraction is non-linear, even if plotted on a linear ordinate and abscissa. At melt fractions, Φ 0.07, the dependence of aggregate strength on Φ is significantly greater than at Φ > 0.07. This melt fraction (Φ= 0.07) marks the transition from a significant increase in the proportion of melt-bearing grain boundaries up to this point to a minor increase thereafter. Therefore, we suggest that the increase of melt-interconnectivity causes the dramatic strength drop between the solidus and a melt fraction of 0.07. A second strength drop occurs at higher melt fractions and corresponds to the breakdown of the solid (crystal) framework, corresponding to the well-known "rheologically critical melt percentage" (RCMP; Arzi, 1978). Although the strength drop at the RCMP is about 4 orders of magnitude, the absolute value of this drop is small compared to the absolute strength of the unmelted aggregate, rendering the RCMP invisible in a linear aggregate strength vs. melt fraction diagram. Predicting the rheological properties and thresholds of melt-bearing crust on the basis of the results and interpretations above is very difficult, because the rheological data base was obtained from experiments performed at undrained conditions in the brittle field. These conditions are unlikely to represent the flow of partially melted crust. The measured strength of most of the experimentally deformed, partially-melted samples corresponds to their maximum differential stress, before the onset of brittle failure, not to their viscous strength during "ductile" (viscous) flow. To overcome these problems, we extrapolated a theoretically-derived flow law for partially melted granite deforming by diffusion-accommodated grain-boundary sliding (Paterson, 2001) and an experimentally-derived flow law for

  4. Spatio-temporal mapping of plate boundary faults in California using geodetic imaging

    Science.gov (United States)

    Donnellan, Andrea; Arrowsmith, Ramon; DeLong, Stephen B.

    2017-01-01

    The Pacific–North American plate boundary in California is composed of a 400-km-wide network of faults and zones of distributed deformation. Earthquakes, even large ones, can occur along individual or combinations of faults within the larger plate boundary system. While research often focuses on the primary and secondary faults, holistic study of the plate boundary is required to answer several fundamental questions. How do plate boundary motions partition across California faults? How do faults within the plate boundary interact during earthquakes? What fraction of strain accumulation is relieved aseismically and does this provide limits on fault rupture propagation? Geodetic imaging, broadly defined as measurement of crustal deformation and topography of the Earth’s surface, enables assessment of topographic characteristics and the spatio-temporal behavior of the Earth’s crust. We focus here on crustal deformation observed with continuous Global Positioning System (GPS) data and Interferometric Synthetic Aperture Radar (InSAR) from NASA’s airborne UAVSAR platform, and on high-resolution topography acquired from lidar and Structure from Motion (SfM) methods. Combined, these measurements are used to identify active structures, past ruptures, transient motions, and distribution of deformation. The observations inform estimates of the mechanical and geometric properties of faults. We discuss five areas in California as examples of different fault behavior, fault maturity and times within the earthquake cycle: the M6.0 2014 South Napa earthquake rupture, the San Jacinto fault, the creeping and locked Carrizo sections of the San Andreas fault, the Landers rupture in the Eastern California Shear Zone, and the convergence of the Eastern California Shear Zone and San Andreas fault in southern California. These examples indicate that distribution of crustal deformation can be measured using interferometric synthetic aperture radar (InSAR), Global Navigation

  5. Create Your Plate

    Medline Plus

    Full Text Available ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ... but changes the portion sizes so you are getting larger portions of non-starchy vegetables and a ...

  6. Create Your Plate

    Medline Plus

    Full Text Available ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ... 4/Box) Taking the guesswork out of portion control has never been easier. It can be a ...

  7. Tectonic Plate Movement.

    Science.gov (United States)

    Landalf, Helen

    1998-01-01

    Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

  8. MyPlate

    Science.gov (United States)

    ... our stage of life, situations, preferences, access to food, culture, traditions, and the personal decisions we make over time. All your food and beverage choices count. MyPlate offers ideas and ...

  9. Create Your Plate

    Medline Plus

    Full Text Available ... blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ... you have an easy portion control solution that works. Last Reviewed: October 8, 2015 Last Edited: September ...

  10. Designing Assemblies Of Plates

    Science.gov (United States)

    Williams, F. W.; Kennedy, D.; Butler, R.; Aston, G.; Anderson, M. S.

    1992-01-01

    VICONOPT calculates vibrations and instabilities of assemblies of prismatic plates. Designed for efficient, accurate analysis of buckling and vibration, and for optimum design of panels of composite materials. Written in FORTRAN 77.

  11. Create Your Plate

    Medline Plus

    Full Text Available ... Your Plate Gluten Free Diets Meal Planning for Vegetarian Diets Cook with Heart-Healthy Foods Holiday Meal Planning What Can I Eat? Making Healthy Food Choices Diabetes Superfoods Non-starchy Vegetables Grains and Starchy Vegetables ...

  12. Create Your Plate

    Medline Plus

    Full Text Available ... Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten Free Diets Meal Planning ... serving of dairy or both as your meal plan allows. Choose healthy fats in small amounts. For ...

  13. Create Your Plate

    Medline Plus

    Full Text Available ... 1 Diabetes Get Started Safely Get And Stay Fit Types of Activity Weight Loss Assess Your Lifestyle ... manage portion control wherever you are. Now, our best-selling, sectioned to-go plate with easy-sealing ...

  14. Create Your Plate

    Medline Plus

    Full Text Available ... Plate is a simple and effective way to manage your blood glucose levels and lose weight. With ... been easier. It can be a challenge to manage portion control wherever you are. Now, our best- ...

  15. Tectonic Plate Movement.

    Science.gov (United States)

    Landalf, Helen

    1998-01-01

    Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)

  16. Create Your Plate

    Medline Plus

    Full Text Available ... Carbohydrates Carbohydrate Counting Make Your Carbs Count Glycemic ... to manage portion control wherever you are. Now, our best-selling, sectioned to-go plate with easy-sealing ...

  17. Crustal Structure Linked to Ultra-High-Pressure Rock Exhumation: A Model for the Tso Morari Complex

    Science.gov (United States)

    Jamieson, R. A.; Beaumont, C.; Butler, J. P.; Warren, C. J.

    2009-05-01

    Many syn-collisional ultra-high-pressure (UHP) complexes display an array of upper-crustal structures suggesting that doming accompanied by coeval normal and thrust faulting is closely linked to UHP exhumation processes. We present a geodynamical model that accounts for structural, metamorphic, and geochronological data from UHP terranes in terms of crustal burial and exhumation in a subduction channel below an accretionary wedge. Competition between down-channel shear traction and up-channel buoyancy forces, expressed as the exhumation number, E, controls crustal subduction and exhumation, leading to rapid up-channel flow when E > 1. In some cases, transient slab rollback can lead to incorporation of deep mantle peridotite into the subduction channel. Exhuming UHP material forms a nappe stack and structural dome as it penetrates and destabilises the overlying wedge, driving thrusting and extension. The Tso Morari complex, Ladakh, is a structural dome cored by UHP rocks that were metamorphosed and exhumed during the early stages of the Himalayan collision (ca. 55-45 Ma). Results from a high-resolution numerical model, in which convergence velocity decreases from 15 cm/a to 5 cm/a during the early stages of collision, are consistent with a wide range of structural, metamorphic, and geochronological data from Tso Morari. We conclude that the model offers a viable explanation for the geological evolution of syn-collisional UHP complexes. Moreover, the model demonstrates that buoyant exhumation from deep in the subduction channel is responsible for observed upper-crustal structures, which therefore hold important (but commonly overlooked) clues to UHP exhumation processes.

  18. Origami - Folded Plate Structures

    OpenAIRE

    Buri, Hans Ulrich

    2010-01-01

    This research investigates new methods of designing folded plate structures that can be built with cross-laminated timber panels. Folded plate structures are attractive to both architects and engineers for their structural, spatial, and plastic qualities. Thin surfaces can be stiffened by a series of folds, and thus not only cover space, but also act as load bearing elements. The variation of light and shadow along the folded faces emphasizes the plas...

  19. Fractal multifiber microchannel plates

    Science.gov (United States)

    Cook, Lee M.; Feller, W. B.; Kenter, Almus T.; Chappell, Jon H.

    1992-01-01

    The construction and performance of microchannel plates (MCPs) made using fractal tiling mehtods are reviewed. MCPs with 40 mm active areas having near-perfect channel ordering were produced. These plates demonstrated electrical performance characteristics equivalent to conventionally constructed MCPs. These apparently are the first MCPs which have a sufficiently high degree of order to permit single channel addressability. Potential applications for these devices and the prospects for further development are discussed.

  20. Crustal structure of southern Madagascar from receiver functions and ambient noise correlation: Implications for crustal evolution

    Science.gov (United States)

    Rindraharisaona, E. J.; Tilmann, F.; Yuan, X.; Rümpker, G.; Giese, J.; Rambolamanana, G.; Barruol, G.

    2017-02-01

    The Precambrian rocks of Madagascar were formed and/or modified during continental collision known as the Pan-African orogeny. Aborted Permo-Triassic Karoo rifting and the subsequent separation from Africa and India resulted in the formation of sedimentary basins in the west and volcanic activity predominantly along the margins. Many geological studies have documented the imprint of these processes, but little was known about the deeper structure. We therefore deployed seismic stations along an SE-NW trending profile spanning nearly all geological domains of southern Madagascar. Here we focus on the crustal structure, which we determined based on joint analysis of receiver functions and surface waves derived from ambient noise measurements. For the sedimentary basin we document a thinning of the underlying crystalline basement by up to ˜60% to 13 km. The crustal velocity structure demonstrates that the thinning was accomplished by removal or exhumation of the lower crust. Both the Proterozoic and Archean crust have a 10 km thick upper crust and 10-12 km thick midcrust. However, in contrast to the typical structure of Proterozoic and Archean aged crust, the Archean lower crust is thicker and faster than the Proterozoic one, indicating possible magmatic intrusions; an underplated layer of 2-8 km thickness is present only below the Archean crust. The Proterozoic mafic lower crust might have been lost during continental collision by delamination or subduction or thinned as a result of extensional collapse. Finally, the Cretaceous volcanics along the east coast are characterized by thin crust (30 km) and very large VP/VS ratios.

  1. The Cause of the Republic Day Earthquake of India: Intraplate or Plate Boundary Process?

    Science.gov (United States)

    Li, Q.

    2001-12-01

    The Mw 7.6 Republic Day (1/26/2001) earthquake of India killed at least 14,000 people and destroyed tens of thousands of homes. The cause of this earthquake and other historic earthquakes in the surrounding region, all thrust faults with roughly N-S compression, has been the subject of intensive debate. Some workers argued that this earthquake, located ~400 km from the plate boundary, is an intraplate event that may bear important implications for other intraplate earthquakes such as those in the New Madrid seismic zone. Others, however, recognize the diffuse plate boundary in western India and regard this earthquake as part of the plate boundary activity. We have developed a viscoelastic finite element model to address the question of why this and other historic earthquakes concentrated in this part of the India plate. The computer model includes relevant boundary conditions and first-order rheologic variations as indicated by geological and seismic data. We calculated the stresses within the India plate using displacement boundary conditions as indicated by the GPS data and compared the predicted stresses with the theoretical crustal strengths. Our results indicate that the change of plate boundary conditions (from transform fault along the Owen Fracture zone in the India ocean to continental thrusting and shearing along northwestern India) causes stress to accumulate in a broad zone near the junction of the Indian, the Arabian, and the Eurasian plates. Crustal weakening by diffuse seismicity along the northwestern Indian plate boundary may cause further inland migration of stress accumulation. With additional factors, including the contrasts of the crustal strength between the continental and oceanic Indian plate, the presence of the Kachchh rift zone, and the pronounced thinning of the lithosphere in this region as indicated by seismic tomography, the model predict an earthquake-prone belt extending hundreds of kilometers into the interior of the India plate

  2. Consideration of optimum site distribution for detecting seafloor crustal deformation at the Nankai subduction zone

    Science.gov (United States)

    Watanabe, T.; Tadokoro, K.; Sugimoto, S.; Okuda, T.; Miyata, K.; Kuno, M.

    2009-12-01

    The Philippine Sea plate subducts beneath the southwest Japan from the Nankai Trough with a rate of about 4-6 cm/yr, where great interplate earthquakes have repeatedly occurred every 100-150 years. To clarify the mechanism of earthquake occurrence at such subduction zones, we require the geodetic data obtained from not only onshore area but also offshore area. However it is difficult to estimate the strength of interplate coupling in offshore areas, due to the poverty of those data. For this issue, we have conducted seafloor geodetic observation using GPS/Acoustic techniques around the Nankai Trough since 2004. In this system, we estimate the position of a surveying vessel by Kinematic GPS analysis and measure the distance between the vessel and the benchmark on the seafloor by Acoustic measurements. Next, we determine the location of the benchmark and detected crustal movement on the seafloor. In the Kumano Basin, we have two seafloor benchmarks, which are located about 60 and 80 km away from the deformation front of the Nankai Trough. The observations from 2005 to 2008 have illustrated that those benchmarks are moving at rates of about 5-6 cm/yr toward west-northwest with velocity uncertainties of about 2 cm/yr relative to the Amurian plate. In this study, in order to estimate infer coupling at the Nankai Trough, we calculated surface deformations accompanied with subduction of the Philippine Sea plate in an elastic half-space and compared them with on- and offshore GPS velocities. Then, we checked the effect of seafloor geodetic observation on slip resolution on the plate interface. Moreover, we investigated optimum seafloor site distribution at the Nankai Trough using numerical simulation, because we require more seafloor sites to understand spatial variation of the slip and strain accumulation on the plate interface. We conclude that seafloor geodetic observation data provide good constraints for the estimation of slips at the shallower part of the plate

  3. The crustal evolution of the west-central Pyrenees revisited: Inferences from a new kinematic scenario

    Science.gov (United States)

    Teixell, Antonio; Labaume, Pierre; Lagabrielle, Yves

    2016-03-01

    New evolutionary models for the Pyrenean orogeny must consider feedbacks between the Mid-Cretaceous hyperextension postulated recently and the Pyrenean inversion. We present a new crustal section of the Pyrenees through the Jaca Basin, the western Axial Zone and the Chaînons Béarnais, which allows identifying the ancient continental margins of the Iberian and European plates and a suture. A sequential restoration allows a reassessment of the style of convergence through time. Restoration leads to a progressively thinned crust in narrow continental margins separated by a domain of exhumed mantle peridotite and overlain by a detached sedimentary lid. Early convergence during the Late Cretaceous and the Earliest Paleogene was accommodated by subduction of the peridotite domain. This was followed in the Eocene by initial collision involving overriding of the Iberian margin onto the European margin along the deep ramp of the North-Pyrenean Frontal thrust, which defines the suture. Subsequent full collision and strong relief generation from the late-Mid or Late Eocene to the Early Miocene were associated with thrust accretion of the Iberian plate, underlain by wedging and northward subduction of the decoupled Iberian lower crust.

  4. Turbulent current drive mechanisms

    Science.gov (United States)

    McDevitt, Christopher J.; Tang, Xian-Zhu; Guo, Zehua

    2017-08-01

    Mechanisms through which plasma microturbulence can drive a mean electron plasma current are derived. The efficiency through which these turbulent contributions can drive deviations from neoclassical predictions of the electron current profile is computed by employing a linearized Coulomb collision operator. It is found that a non-diffusive contribution to the electron momentum flux as well as an anomalous electron-ion momentum exchange term provide the most efficient means through which turbulence can modify the mean electron current for the cases considered. Such turbulent contributions appear as an effective EMF within Ohm's law and hence provide an ideal means for driving deviations from neoclassical predictions.

  5. Polar Direct Drive

    Science.gov (United States)

    Skupsky, S.

    2003-10-01

    Direct drive offers the potential of higher target gain on the National Ignition Facility (NIF) than x-ray drive: The initial direct-drive target design had a 1-D gain of 45 and consisted primarily of a pure cryogenic DT shell. Using the expected levels of target and laser nonuniformities for the NIF, two-dimensional (2-D) hydrodynamic simulations predicted target gains around 30.(P.W. McKenty et al.), Phys. Plasmas 8, 2315 (2001). More-recent designs have shown that higher target gains could be obtained by replacing a portion of the DT shell with ``wetted'' CH foam and by using adiabat shaping: (1) Higher-Z material (C) in the foam increases laser absorption by about 40% (from 60% absorption to 85%).(S. Skupsky et al.), in Inertial Fusion Sciences and Applications 2001, edited by K. Tanaka et al. (Elsevier, Paris, 2002), p. 240. (2) Adiabat shaping allows the main portion of the fuel to be placed on a lower adiabat without compromising target stability.(V.N. Goncharov et al.), Phys. Plasmas 10, 1906 (2003). These direct-drive concepts can be tested on the NIF, long before that facility is converted to a direct-drive (spherically symmetric) irradiation configuration. Using the NIF x-ray-drive beam configuration, some of the near-polar beams could be pointed to better illuminate the target's equator. These more-oblique, equatorial beams will have lower absorption and reduced drive efficiency than the polar beams. One strategy to compensate for the difference in polar and equatorial drive is to reduce the irradiation at the poles and employ different pulse shapes to accommodate the time-dependent variations in drive and absorption. This concept of polar direct drive (PDD) has been studied using the 2-D hydrocode DRACO to determine the requirements for achieving ignition and moderate target gain for the NIF. Experiments on the OMEGA laser will examine the effects of oblique irradiation on target drive. Results of simulations for different direct-drive target designs

  6. Bright Soil Churned by Spirit's Sol 1861 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Spirit drove 22.7 meters (74 feet) toward the southwest on the 1,861st Martian day, or sol, of Spirit's mission on Mars (March 28, 2009). After the drive, the rover took this image with its front hazard-avoidance camera, looking back at the tracks from the drive. As usual since losing the use of its right-front wheel in 2006, Spirit drove backwards. The immobile right-front wheel churned up a long stripe of bright soil during this drive. Where Spirit has found such bright soil in the past, subsequent analysis of the composition found concentrations of sulfur or silica that testified to past action of water at the site. When members of the rover team saw the large quantity of bright soil exposed by the Sol 1861 drive, they quickly laid plans to investigate the composition with Spirit's alpha particle X-ray spectrometer. The Sol 1861 drive took the rover past the northwest corner of the low plateau called 'Home Plate,' making progress on a route around the western side of Home Plate. The edge of Home Plate forms the horizon on the right side of this image. Husband Hill is on the horizon on the left side. For scale, the parallel rover wheel tracks are about 1 meter (40 inches) apart. The rover's hazard-avoidance cameras take 'fisheye' wide-angle images.

  7. View Ahead After Spirit's Sol 1861 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Spirit used its navigation camera to take the images combined into this 210-degree view of the rover's surroundings during the 1,861st to 1,863rd Martian days, or sols, of Spirit's surface mission (March 28 to 30, 2009). The center of the scene is toward the south-southwest. East is on the left. West-northwest is on the right. The rover had driven 22.7 meters (74 feet) southwestward on Sol 1861 before beginning to take the frames in this view. The drive brought Spirit past the northwestern corner of Home Plate. In this view, the western edge of Home Plate is on the portion of the horizon farthest to the left. A mound in middle distance near the center of the view is called 'Tsiolkovsky' and is about 40 meters (about 130 feet) from the rover's position. This view is presented as a cylindrical projection with geometric seam correction.

  8. View Ahead After Spirit's Sol 1861 Drive

    Science.gov (United States)

    2009-01-01

    NASA's Mars Exploration Rover Spirit used its navigation camera to take the images combined into this 210-degree view of the rover's surroundings during the 1,861st to 1,863rd Martian days, or sols, of Spirit's surface mission (March 28 to 30, 2009). The center of the scene is toward the south-southwest. East is on the left. West-northwest is on the right. The rover had driven 22.7 meters (74 feet) southwestward on Sol 1861 before beginning to take the frames in this view. The drive brought Spirit past the northwestern corner of Home Plate. In this view, the western edge of Home Plate is on the portion of the horizon farthest to the left. A mound in middle distance near the center of the view is called 'Tsiolkovsky' and is about 40 meters (about 130 feet) from the rover's position. This view is presented as a cylindrical projection with geometric seam correction.

  9. Geomorphological effects of plate movemen during Quaternary in China's tropics

    Institute of Scientific and Technical Information of China (English)

    ZHANGWeiqiang; HUANGZhenguo

    2004-01-01

    The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China's tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 110°E.

  10. Vibration and Buckling of Web Plate of the Plate Girder

    OpenAIRE

    高橋, 和雄; 呉, 明強; 中澤, 聡志; 筑紫, 宏之

    1998-01-01

    The vibration and buckling of the web of the plate girder are studied in this paper. The small deflection theory of the thin plate is used. The finite strip method is employed to solve vibration and buckling of the plate girder. Natural frequenies of buckling properties are shown for various plate girder bridges.

  11. Spreading continents kick-started plate tectonics.

    Science.gov (United States)

    Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

    2014-09-18

    Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.

  12. Crustal Heat Production and Mantle Heat Flow in Southeast China

    Institute of Scientific and Technical Information of China (English)

    胡圣标; 汪集旸

    1994-01-01

    The correlation between seismic velocity (vp) and radiogenic heat production (A) en-ables the distribution of crustal heat production to be evaluated,from which the mantle heat flow for 21seismic velocity-depth profiles located along the two continental geotraverses in Southeast China can bededuced.Several approaches have been proposed to special problems connected with the conversion ofseismic velocities into heat production in orogenic areas.The results show that the crustal heat flow inSoutheast China is quite inhomogeneous,varying between 17.8 and 46 mW·m-2,which can be attribut-ed to the complicated crustal structure related to overthrusting and overlapping in the upper crust.The re-markable regional variation in the mantle heat flow,ranging from 23.2 to 41.6 mW·m-2,correspondsto the large-scale tectonothermal evolution of the orogenic belts.

  13. The Computation of Potential Harmonic Coefficients Using Global Crustal Information

    Science.gov (United States)

    Tsoulis, D.

    Topographic/isostatic potential harmonic coefficients can be computed from a global elevation model, when one accounts for the compensation of the upper crust according to a certain model of isostasy. The theory is based on a series expansion of the inverse distance function, which enables an efficient computation of the dimensionless poten- tial coefficients on the sphere. The availability of global crustal models permits the application of the same theory, with the exception that here the theoretically defined boundary between upper crust and mantle is replaced with crustal thickness informa- tion derived mainly from processing repeated seismic observations. The present paper deals with the spherical harmonic analysis of such a model, namely the CRUST 2.0 global crustal model, and compares the derived spectrum with the respective coeffi- cient sets delivered by the application of idealized isostatic models such as those of Airy/Heiskanen or Pratt/Hayford.

  14. Assessment: A Driving Force.

    Science.gov (United States)

    Rakow, Steven J.

    1992-01-01

    Asserts that educational assessment drives the curriculum. Thus, assessment is very important in contemplating reform in science education. Assessment should be an integral part of the instructional process, utilizing diagnostic testing, monitoring, and summative evaluations. (PR)

  15. Driving in a womb

    NARCIS (Netherlands)

    Anonymous

    Drive thousands of kilometres on just a litre of fuel? During the annual Shell eco-marathon at the end of May, schoolchildren and students – including a team from TU Delft – demonstrated that it can indeed be done.

  16. Instant Google Drive starter

    CERN Document Server

    Procopio, Mike

    2013-01-01

    This book is a Starter which teaches you how to use Google Drive practically. This book is perfect for people of all skill levels who want to enjoy the benefits of using Google Drive to safely store their files online and in the cloud. It's also great for anyone looking to learn more about cloud computing in general. Readers are expected to have an Internet connection and basic knowledge of using the internet.

  17. Marine winch drive systems

    Energy Technology Data Exchange (ETDEWEB)

    Clifford, M.; Smith, P.M.

    1983-12-01

    In the design of marine winch drive systems, efficiency, controllability, compactness and component layout flexibility are major considerations. This paper discusses design concepts aimed at achieving the above considerations in the design of variable speed, hydrostatic, marine winch drive systems. These concepts utilize a high pressure, load sensing pump, and a low-speed, high-torque (LSHT), radial-piston, hydraulic motor. These components are then shown applied in several open circuit hydrostatic power transmission systems.

  18. Scaling behaviour in temporal fluctuations of crustal seismicity in Taiwan

    Directory of Open Access Journals (Sweden)

    L. Telesca

    2009-12-01

    Full Text Available The crustal seismicity of Taiwan was investigated by means of the Allan Factor analysis and Count-based Periodogram, which allow to identify scaling behaviour in point processes and to quantify their temporal fluctuations by means of the estimate of the scaling exponent. Our findings point out to the presence of two time-scaling regions in the crustal Taiwanese seismicity. The first region, involving the intermediate timescales can be probably linked with aftershock activity, while the second region, involving the large timescales could be related with the background seismicity.

  19. Monitoring Crustal Deformations with Radar Interferometry:A Review

    Institute of Scientific and Technical Information of China (English)

    刘国祥; 丁晓利; 黄丁发

    2004-01-01

    The crustal movements, probably motivating earthquakes, are considered as one of the main geodynamic sources. The quantitative measurements of ground surface deformations are vital for studying mechanisms of the buried faults or even estimating earthquake potential. A new space-geodetic technology, synthetic aperture radar interferometry (InSAR), can be applied to detect such large-area deformations, and has demonstrated some prominent advantages. This paper reviews the capacity and limitations of InSAR, and summarises the existing applications including some of our results in studying the earthquake-related crustal motions.Finally it gives the outlook for the future development of InSAR.

  20. Dementia and driving.

    Science.gov (United States)

    O'Neill, D; Neubauer, K; Boyle, M; Gerrard, J; Surmon, D; Wilcock, G K

    1992-04-01

    Many European countries test cars, but not their drivers, as they age. There is evidence to suggest that human factors are more important than vehicular factors as causes of motor crashes. The elderly also are involved in more accidents per distance travelled than middle-aged drivers. As the UK relies on self-certification of health by drivers over the age of 70 years, we examined the driving practices of patients with dementia attending a Memory Clinic. Nearly one-fifth of 329 patients with documented dementia continued to drive after the onset of dementia, and impaired driving ability was noted in two-thirds of these. Their families experienced great difficulty in persuading patients to stop driving, and had to invoke outside help in many cases. Neuropsychological tests did not help to identify those who drove badly while activity of daily living scores were related to driving ability. These findings suggest that many patients with dementia drive in an unsafe fashion after the onset of the illness. The present system of self-certification of health by the elderly for driver-licensing purposes needs to be reassessed.

  1. Self-driving carsickness.

    Science.gov (United States)

    Diels, Cyriel; Bos, Jelte E

    2016-03-01

    This paper discusses the predicted increase in the occurrence and severity of motion sickness in self-driving cars. Self-driving cars have the potential to lead to significant benefits. From the driver's perspective, the direct benefits of this technology are considered increased comfort and productivity. However, we here show that the envisaged scenarios all lead to an increased risk of motion sickness. As such, the benefits this technology is assumed to bring may not be capitalised on, in particular by those already susceptible to motion sickness. This can negatively affect user acceptance and uptake and, in turn, limit the potential socioeconomic benefits that this emerging technology may provide. Following a discussion on the causes of motion sickness in the context of self-driving cars, we present guidelines to steer the design and development of automated vehicle technologies. The aim is to limit or avoid the impact of motion sickness and ultimately promote the uptake of self-driving cars. Attention is also given to less well known consequences of motion sickness, in particular negative aftereffects such as postural instability, and detrimental effects on task performance and how this may impact the use and design of self-driving cars. We conclude that basic perceptual mechanisms need to be considered in the design process whereby self-driving cars cannot simply be thought of as living rooms, offices, or entertainment venues on wheels.

  2. Linear ultrasonic motor using quadrate plate transducer

    Institute of Scientific and Technical Information of China (English)

    Jiamei JIN; Chunsheng ZHAO

    2009-01-01

    A linear ultrasonic motor using a quadrate plate transducer was developed for precision positioning. This motor consists of two pairs of Pb(Zr, Ti)O3 piezo-electric ceramic elements, which are piezoelectrically excited into the second-bending mode of the motor stator's neutral surface in two orthogonal directions, on which the tops of four projections move along an elliptical trajectory, which in turn drives a contacted slider into linear motion via frictional forces. The coincident frequency of the stator is easily obtained for its coincident characteristic dimen-sion in two orthogonal directions. The performance characteristics achieved by the motor are: 1) a maximum linear speed of more than 60 mm/s; 2) a stroke of more than 150 mm; 3) a driving force of more than 5.0 N; and 4) a response time of about 2 ms.

  3. Create Your Plate

    Medline Plus

    Full Text Available ... Events Wellness Lives Here Drive to Stop Diabetes Awareness Programs Hispanic Heritage Month African American Programs Latino ... Offices Volunteer Opportunities Signature Events Camps Diabetes EXPOs Awareness Programs Wellness Lives Here Become a Member American ...

  4. Create Your Plate

    Medline Plus

    Full Text Available ... Find Your Local Office Find your local diabetes education program Calendar of Events Wellness Lives Here Drive ... We Support Your Doctor Clinical Practice Guidelines Patient Education Materials Scientific Sessions Journals for Professionals Professional Books ...

  5. Create Your Plate

    Medline Plus

    Full Text Available ... Find your local diabetes education program Calendar of Events Wellness Lives Here Drive to Stop Diabetes Awareness ... Camp Learning at Camp Find a Camp Fundraising Events Step Out Walk to Stop Diabetes Tour de ...

  6. Create Your Plate

    Medline Plus

    Full Text Available ... Children and Type 2 Diabetes Know Your Rights Employment Discrimination Health Care Professionals Law Enforcement Driver's License ... Find Your Local Office Find your local diabetes education program Calendar of Events Wellness Lives Here Drive ...

  7. Create Your Plate

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  11. Bending and stretching of plates

    CERN Document Server

    Mansfield, E H; Hemp, W S

    1964-01-01

    The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

  12. Subsidence history, crustal structure, and evolution of the Somaliland-Yemen conjugate margin

    Science.gov (United States)

    Ali, M. Y.; Watts, A. B.

    2013-04-01

    We have used biostratigraphic data from deep exploration wells to determine the tectonic subsidence history of the Somaliland (northwestern Somalia)-Yemen conjugate margin, a poorly known margin in the central part of the Gulf of Aden. Bathymetry and magnetic anomaly data suggest the Gulf of Aden is a young feature that formed following the rifting apart and breakup of the African and Arabian plates ~32 Ma. Our tectonic subsidence data suggest, however, that the present-day Gulf of Aden developed on an earlier Mesozoic rift system. The oldest episode of rifting initiated at ~156 Ma and lasted for ~10 Ma and had a NW-SE trend. We interpret the rift as a late stage event associated with the breakup of Gondwana and the separation of Africa and Madagascar. At ~80 Ma, there is evidence of an intermediate rift event which correlates with a rapid increase in spreading rate on the ridges separating the African and Indian and African and Antarctica plates and a contemporaneous slowing down of Africa's plate motion. The combined effect of all three rifting events has been to thin the crust and upper mantle by up to a factor of 2. The amount of thinning deduced from the wells is in accord with the crustal structure inferred from available seismic refraction data and process-oriented gravity and flexure modeling. The margin is asymmetric with a steeper gradient in the Moho on the Yemen side than the Somaliland side. The main discrepancy is on the Yemen side where the gravity-derived Moho is 10 km deeper than the well-derived Moho. We attribute the discrepancy to the addition of material at the base of the crust since rifting, possibly magma sourced from the Afar plume.

  13. The Palaeoproterozoic crustal evolution: evidences from granulite-gneiss belts, collisional and accretionary orogens

    Science.gov (United States)

    Mints, M. V.; Konilov, A. N.

    2003-04-01

    The Palaeoproterozoic juvenile assemblages were emplaced within two types of mobile belts: (1) high-grade or "granulite-gneiss" belts; (2) low- and medium-grade volcano-sedimentary and volcano-plutonic belts. Type (1) belts resulted from plume-induced heating, magmatism, emergence of riftogenic basins and volcano-tectonic depressions, their filling with rift-type sediments and juvenile but strongly contaminated lavas and ash-flow deposits, high-grade recrystallization of the lower- and mid-crustal assemblages including the filling of the basins and depressions that followed in intraplate and back-arc settings, and final thrusting and exhumation caused by collision-related tectonism. Type (2) belts represent sutures containing MORB- and arc-related assemblages, together with initial rift-related assemblages formed during evolution of the short-lived, mainly Red Sea-type oceans (intracontinental collisional orogens) and systems of oceanic, island-arc and back-arc terranes amalgamated along continent margins (peripheral accretionary orogens). Palaeoproterozoic history can be subdivided into five periods: (1) 2.51-2.44 Ga superplume activity and displacement of Fennoscandia; (2) 2.44-2.0 (2.11) Ga quiescent within-plate development complicated by local plume- and plate tectonics-related processes; (3) a 2.0-1.95 Ga superplume event; (4) 1.95-1.75 (1.71) Ga combined plume- and plate tectonics-related evolution, resulting in the partial disruption of the continental crust, and formation of accretionary orogens along some margins of the supercontinent and rebirth of the supercontinent entity, and (5) grade recrystallization of both juvenile and old rocks, it did not lead to the wholesale breakup and general reorganization of the Neoarchaen supercontinent. The work has been supported by the RFBR (00-05-64241 and 01-05-64373).

  14. Impact Melt Cover on Central Peaks of Complex Craters: Implications for Deriving Crustal Composition

    Science.gov (United States)

    Dhingra, D.; Pieters, C. M.

    2017-05-01

    The use of impact crater central peaks for deriving crustal mineralogy at depth assumes pristine nature of the peaks. Impact melt on several central peaks is evidence for contamination. Central-peaks-derived crustal mineralogy may be affected.

  15. Along-Strike Variations in Focal Mechanisms of Central Andean Crustal Earthquakes: Northern Peru through the Argentina Sierras Pampeanas

    Science.gov (United States)

    Devlin, S.; Isacks, B. L.

    2003-12-01

    120 shallow focal mechanisms in the crust above the subducted Nazca plate were assembled from the Harvard CMT catalog and published studies covering over 40 years of seismicity. The study area included the Andes crust above three major segments of the subducted plate, the Peruvian and Argentinean flat-slab segments and the intervening segment where the subducted Nazca plate dips more steeply. The most seismically active regions continue to be the thick-skinned foreland thrust belts in the eastern Andes of Peru and the Sierras Pampeanas. The earthquakes there are clearly associated with youthful tectonic structures with strong topographic signatures as revealed by the new 90 m SRTM digital elevation models. The mechanisms are dominantly of the thrust type but include a minority of strike-slip orientations. However the P axes remain consistent. The thin-skinned thrust belts east of the central Andean Plateau show significant activity only near Santa Cruz, Bolivia and northern Argentina; most of the Sub-Andean thrust belt of Bolivia and southern Peru remains aseismic. The central Andean plateau itself also remains aseismic except for the region of southern Peru and two earthquakes in the Puna. The crustal seismicity in southern Peru is largely concentrated on the western side of the plateau. The focal mechanisms show a strong grouping of T axes in a horizontal, north-south orientation. Both normal and strike-slip mechanisms occur in this region, with no obvious correlation with elevation or surface structures. Remarkably, with the exception of one normal fault type mechanism near the Cusco basin, the earthquakes occur in regions of the western parts of the Altiplano that do not exhibit topographic evidence of substantial crustal deformation. These results are consistent with a model in which the Altiplano of southern Peru, with a trend most oblique to the overall direction of convergence, manifests a left-lateral shearing component across the orogen.

  16. Subduction controls the distribution and fragmentation of Earth’s tectonic plates.

    Science.gov (United States)

    Mallard, Claire; Coltice, Nicolas; Seton, Maria; Müller, R Dietmar; Tackley, Paul J

    2016-07-07

    The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

  17. Subduction controls the distribution and fragmentation of Earth’s tectonic plates

    Science.gov (United States)

    Mallard, Claire; Coltice, Nicolas; Seton, Maria; Müller, R. Dietmar; Tackley, Paul J.

    2016-07-01

    The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size-frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

  18. Anterior cervical plating

    Directory of Open Access Journals (Sweden)

    Gonugunta V

    2005-01-01

    Full Text Available Although anterior cervical instrumentation was initially used in cervical trauma, because of obvious benefits, indications for its use have been expanded over time to degenerative cases as well as tumor and infection of the cervical spine. Along with a threefold increase in incidence of cervical fusion surgery, implant designs have evolved over the last three decades. Observation of graft subsidence and phenomenon of stress shielding led to the development of the new generation dynamic anterior cervical plating systems. Anterior cervical plating does not conclusively improve clinical outcome of the patients, but certainly enhances the efficacy of autograft and allograft fusion and lessens the rate of pseudoarthrosis and kyphosis after multilevel discectomy and fusions. A review of biomechanics, surgical technique, indications, complications and results of various anterior cervical plating systems is presented here to enable clinicians to select the appropriate construct design.

  19. Geophysical Modeling of Tectonostratigraphic Terrane Boundaries and Crustal Structure Across a Pacific Ocean-Gulf of Mexico Transect, Southern Mexico

    Science.gov (United States)

    Urrutia-Fucugauchi, J.; Flores-Ruiz, J. H.; Spranger, M.

    2006-12-01

    Geophysical models of terrane boundaries and lithospheric structure beneath southern Mexico derived from gravity and aeromagnetic surveys are presented. The transect crosses southern Mexico from the active Pacific margin to the passive Gulf of Mexico margin, across four distinct terranes (Xolapa, Oaxaca, Juarez and Maya) with Precambrian, Paleozoic and Mesozoic basements and contrasting tectonostratigraphic records. The crust/mantle boundary displays a smooth large amplitude variation along the transect from Puerto Escondido at the Pacific margin to Los Tuxtlas-Alvarado at the Gulf of Mexico, roughly between 28 km and 44 km deep. Crustal thickness variations correspond well with inferred terrane distribution and major surface discontinuities. Suture zones are complex as a result of the kinematics of terrane accretion, contrasting crustal rheological properties, shallow level detachments, post-accretion deformation, thermal conditions and characteristics of relative terrane/plate motions. Pre-suturing characteristics of terranes including crustal structure are difficult to document because of deformation resulting from suturing and any subsequent post-accretion processes. In a simplified way, gravity anomalies from the Pacific margin to the Gulf of Mexico show: large positive 50 mgal anomaly above the continental slope units and the intrusive and metamorphic rocks of the Xolapa complex, then anomalies increasingly negative (with minimum values of -180 mgal over the Acatlan and Oaxaca metamorphics. The Juchatengo mylonitic zone is characterized by a gradient change, while minimum gravity values approximately coincide with the wide mylonitic zone north of Oaxaca city. The Juarez terrane and the region over the Sierra de Juarez is characterized by positive gradient. Finally, the Gulf coastal plain is marked by a positive anomaly in the order of -40 mgal. Geophysical models are combined with the seismic models of the Geolimex profile and used to evaluate the crustal

  20. Crustal structure of the Newer Volcanics Province, SE Australia, from ambient noise tomography

    Science.gov (United States)

    Jiang, Chengxin; Yang, Yingjie; Rawlinson, Nicholas; Griffin, William L.

    2016-06-01

    Intraplate volcanism is a widespread phenomenon, and is generally regarded to be independent of plate tectonics. The Newer Volcanics Province (NVP) of SE Australia represents the most recent (and arguably still active) intraplate volcanism on the Australian continent, and has been postulated to originate from the combined effect of localized shear flow and edge-driven convection. In this study, we adopt ambient noise tomography and Monte-Carlo inversion methods to construct the first local-scale 3D crustal Vs model of the NVP region with a resolution of 35 km. The model displays distinct crustal velocity features near the eastern and western margins of the NVP, which may point to the existence of a lithosphere-scale plumbing system for the migration of melt associated with the boundary between the Delamerian Orogen and the Lachlan Orogen, which underlies the NVP. In particular, exceptionally high velocities are observed in the middle crust of the Delamerian Orogen, and are best explained by buried magmatic arcs. This interpretation is consistent with a subduction-accretion origin for the Delamerian Orogen. Trans-lithospheric faults might have developed during the accretion processes, providing possible pathways for the migration of NVP magmas to the crust and surface. Our 3D model also images small localized velocity reductions in the lower crust at the region where the two distinct lithospheric units meet. The low velocity zone is spatially correlated with the top of a prominent lithosphere-scale low-resistivity zone (10-30 Ωm), which we interpret to represent intruded magmatic sills with small proportions of melt remaining.

  1. Current regional stress field and the resultant crustal deformation in SE Korea and their tectonic implication

    Science.gov (United States)

    Kim, M. C.; Cho, H.; Son, M.

    2014-12-01

    To determine current regional stress field and to characterize the resultant crustal deformation in SE Korea, Quaternary fault, focal mechanism, and geotechnical in-situ stress data were synthetically analyzed. The Quaternary faults are extensively observed along major inherited fault zones and show compatible orientations with general trends of the inherited faults. Most of the Quaternary faults have a top-to-the-west thrust geometry and kinematics and show a tendency of upward-decreasing dip angle and upward-narrowing gouge zone. Slip-sense indicators and paleo-stress field reconstructions indicate that the faults resulted from reverse or transpressional faulting under an E-W compression. All the magnetic fabrics (AMS) of the fault gouges also indicate the prevailing reverse-slip faulting under an ENE-WNW compression. The dominant oblate magnetic fabrics parallel to fault plane and the degrees of anisotropy increasing in proportion to their oblatenesses indicate that the fabrics have formed by a progressive deformation due to continuous simple shear during the last reactivation stage as reverse faulting. The focal mechanism study in and around the Korean Peninsula show the horizontally clustered P-axes in ENE-WSW direction and the girdle-distributed T-axes in NNW trend. The geotechnical in-situ stress data in south Korea also show NE- or ENE-trending maximum horizontal stress. The current crustal deformation in Korea thus can be characterized by contractional structures produced under a regional E-W or ENE-WSW compression stress field, and most of the Quaternary faults resulted from the local re-activation of appropriately oriented inherited major faults. Considering the tectonic setting and structural features in Asia during the Neogene, the current stress regime is interpreted to have been caused by the cooperation of westward shallow subduction of Pacific Plate and collision of Indian and Eurasian continents since about 5-3.5 Ma.

  2. Multi-stage crustal growth and cratonization of the North China Craton

    Directory of Open Access Journals (Sweden)

    Mingguo Zhai

    2014-07-01

    The ∼2.5 Ga metamorphic-magmatic event is stronger than in most other cratons in the world. How to understand the geological significance of the 2.5 Ga event? The following points are emphasized: (1 nearly all old rocks >2.5 Ga underwent metamorphism at ∼2.52–2.5 Ga; (2 Archean basement rocks in the NCC experienced strong partial melting and migmatization; (3 granitoid rocks derived from partial melting include potassium granites, TTG granites and monzonites. These granitoids rocks intruded both the Archean greenstone belts and micro-blocks; (4 ∼2.5 Ga mafic dikes (amphibolites, granitic dikes (veins and syenitic-ultramafic dykes are also developed. Therefore, we suggest an assembly model that all micro-blocks in the NCC were welded together by late Archean greenstone belts at the end of the late Neoarchean. We also propose that the various micro-blocks were surrounded by small ocean basins, and the old continental crust and the oceanic crust were hotter than today. Subduction and collision were on much smaller scales as compared to the Phanerozoic plate tectonic regime, although the tectonic style and mechanisms were more or less similar. The formation of crustal melt granites is one of the processes of cratonization, inducing generation of stable upper and lower crustal layers. This process also generated an upper crust of more felsic composition and a lower crust of more mafic composition, due to molten residual materials and some underplated gabbros.

  3. Impact of Inert Metal Particles Flow on Aluminium Plate

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongqi; LIU Yi; CHEN Yahong; BAI Chunhua

    2008-01-01

    Inert metal explosive, a new kind of explosive, is a mixture of high explosive and inert metal particle.When this kind of explosive is detonated, an inert metal particle flow will be formed by the explosive product driving.To determine the characteristics of the movement of the metal particle flow, a series of aluminium plates were designed to be the targets on which the metal particle flow impacted.The test result was presented and a numerical model was set up to analyze the impact of the high speed inert metal particles on aluminium plate.Based on the numerical analysis, the relationship between the characteristic of the mark on the target plate and the initial condition of the inert metal particles was proposed.From the analysis of the impact on target plates, more information about the movement of the metal particles could be reconstructed.

  4. Non-equilibrium Casimir force between vibrating plates.

    Directory of Open Access Journals (Sweden)

    Andreas Hanke

    Full Text Available We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed.

  5. Plate Margin Deformation and Active Tectonics Along the Northern Edge of the Yakutat Terrane in the Saint Elias Orogen, Alaska and Yukon, Canada

    Science.gov (United States)

    Bruhn, Ronald L.; Sauber, Jeanne; Cotton, Michele M.; Pavlis, Terry L.; Burgess, Evan; Ruppert, Natalia; Forster, Richard R.

    2012-01-01

    The northwest directed motion of the Pacific plate is accompanied by migration and collision of the Yakutat terrane into the cusp of southern Alaska. The nature and magnitude of accretion and translation on upper crustal faults and folds is poorly constrained, however, due to pervasive glaciation. In this study we used high-resolution topography, geodetic imaging, seismic, and geologic data to advance understanding of the transition from strike-slip motion on the Fairweather fault to plate margin deformation on the Bagley fault, which cuts through the upper plate of the collisional suture above the subduction megathrust. The Fairweather fault terminates by oblique-extensional splay faulting within a structural syntaxis, allowing rapid tectonic upwelling of rocks driven by thrust faulting and crustal contraction. Plate motion is partly transferred from the Fairweather to the Bagley fault, which extends 125 km farther west as a dextral shear zone that is partly reactivated by reverse faulting. The Bagley fault dips steeply through the upper plate to intersect the subduction megathrust at depth, forming a narrow fault-bounded crustal sliver in the obliquely convergent plate margin. Since . 20 Ma the Bagley fault has accommodated more than 50 km of dextral shearing and several kilometers of reverse motion along its southern flank during terrane accretion. The fault is considered capable of generating earthquakes because it is linked to faults that generated large historic earthquakes, suitably oriented for reactivation in the contemporary stress field, and locally marked by seismicity. The fault may generate earthquakes of Mw <= 7.5.

  6. License plate detection algorithm

    Science.gov (United States)

    Broitman, Michael; Klopovsky, Yuri; Silinskis, Normunds

    2013-12-01

    A novel algorithm for vehicle license plates localization is proposed. The algorithm is based on pixel intensity transition gradient analysis. Near to 2500 natural-scene gray-level vehicle images of different backgrounds and ambient illumination was tested. The best set of algorithm's parameters produces detection rate up to 0.94. Taking into account abnormal camera location during our tests and therefore geometrical distortion and troubles from trees this result could be considered as passable. Correlation between source data, such as license Plate dimensions and texture, cameras location and others, and parameters of algorithm were also defined.

  7. Crustal thickness and images of the lithospheric discontinuities in the Gibraltar arc and surrounding areas

    Science.gov (United States)

    Mancilla, Flor de Lis; Stich, Daniel; Morales, José; Martín, Rosa; Diaz, Jordi; Pazos, Antonio; Córdoba, Diego; Pulgar, Javier A.; Ibarra, Pedro; Harnafi, Mimoun; Gonzalez-Lodeiro, Francisco

    2015-12-01

    The Gibraltar arc and surrounding areas are a complex tectonic region and its tectonic evolution since Miocene is still under debate. Knowledge of its lithospheric structure will help to understand the mechanisms that produced extension and westward motion of the Alboran domain, simultaneously with NW-SE compression driven by Africa-Europe plates convergence. We perform a P-wave receiver function analysis in which we analyse new data recorded at 83 permanent and temporary seismic broad-band stations located in the South of the Iberian peninsula. These data are stacked and combined with data from a previous study in northern Morocco to build maps of thickness and average vP/vS ratio for the crust, and cross-sections to image the lithospheric discontinuities beneath the Gibraltar arc, the Betic and Rif Ranges and their Iberian and Moroccan forelands. Crustal thickness values show strong lateral variations in the southern Iberia peninsula, ranging from ˜19 to ˜46 km. The Variscan foreland is characterized by a relatively flat Moho at ˜31 km depth, and an average vP/vS ratio of ˜1.72, similar to other Variscan terranes, which may indicate that part of the lower crustal orogenic root was lost. The thickest crust is found at the contact between the Alboran domain and the External Zones of the Betic Range, while crustal thinning is observed southeastern Iberia (down to 19 km) and in the Guadalquivir basin where the thinning at the Iberian paleomargin could be still preserved. In the cross-sections, we see a strong change between the eastern Betics, where the Iberian crust underthrusts and couples to the Alboran crust, and the western Betics, where the underthrusting Iberian crust becomes partially delaminated and enters into the mantle. The structures largely mirror those on the Moroccan side where a similar detachment was observed in northern Morocco. We attribute a relatively shallow strong negative-polarity discontinuity to the lithosphere-asthenosphere boundary

  8. Contrasted terrace systems of the lower Moulouya valley as indicator of crustal deformation in NE Morocco

    Science.gov (United States)

    Rixhon, Gilles; Bartz, Melanie; El Ouahabi, Meriam; Szemkus, Nina; Brueckner, Helmut

    2016-04-01

    The Moulouya river has the largest catchment in Morocco and drains an area which is characterized by active crustal deformation during the Late Cenozoic due to the convergence between the African and Eurasian plates. As yet, its Pleistocene terrace sequence remains poorly documented. Our study focuses on the lowermost reach of the river in NE Morocco, which drains the Triffa sedimentary basin directly upstream of the estuary. New field observations, measurements and sedimentological data reveal contrasted fluvial environments on either side of a newly identified thrust zone, which disrupts the whole sedimentary basin and is associated with N-S compressive shortening in this region (Barcos et al., 2014). Long-lasting fluvial aggradation, materialized by ≥37 m-thick stacked fill terraces, and the development of a well-preserved terrace staircase, with (at least) three Pleistocene terrace levels, occur in the footwall and the hanging wall of the thrust, respectively. Same as for the Pleistocene terrace sediments of the middle Moulouya, a recurrent sedimentary pattern, characterized by fining-upward sequences was observed in the studied terrace profiles. Assessing the rates of crustal deformation along this main thrust zone requires age estimations for these Pleistocene terrace deposits of the lower Moulouya on each side of the thrust. Samples for luminescence (OSL/IRSL), electron spin resonance (ESR, on quartz) and cosmogenic nuclide dating (26Al/10Be, burial dating) were collected in terrace deposits located both in the foot- and hanging walls. Sample preparation and analysis as well as age determination are in progress. The preliminary data mentioned above, soon to be completed by chronological data, agree well with morphometric indicators stating that the whole Moulouya catchment is at disequilibrium state (Barcos et al., 2014). This is confirmed by several knickpoints in its longitudinal profile. Late Cenozoic uplift associated with crustal shortening, which

  9. Crustal Thickness Across Alaska via Ps Receiver Functions and Gravity Data and Comparison to Lithospheric Structure

    Science.gov (United States)

    O'Driscoll, L.; Saltus, R. W.; Miller, M. S.; Porritt, R. W.

    2015-12-01

    The geologic mosaic of terranes, adjacent multi-phase plate boundary, rapid lateral topographic variations, and heterogeneous distribution of strain throughout Alaska all suggest strong heterogeneity of crustal architecture. We present a model of crustal thickness across the state is primarily constrained where seismic instrumentation has been deployed - dense coverage in the south-central region and sparse coverage in the north, west, and arc regions. P receiver functions (PRF) were calculated using an upgraded version of Funclab, a software module that retrieves data, calculates receiver functions, facilitates quality control, and calculates H-k stacking, depth mapping via binned Common Conversion Point stacking, and other backend products. 1,678 events and 262 stations yielded 102,000 preliminary PRF that were culled to 21,000 total RFs. Iterative time-domain deconvolution was performed about a 1 Hz central frequency for ZRT traces. Our model reproduces many of the Moho depth variations previously modeled by receiver functions and gravity. Thick (>60 km) crust below the Chugach and St. Elias Ranges transitions to ~40 km thick crust south of the Denali Fault. Immediately to the north, thin (29-35) crust is observed in central Alaska between the Alaska and Brooks Ranges. The central Brooks Range is observed to have a thick crustal root below its topographic high axis. Stations scattered throughout western Alaska and the Bering Sea regions generally show average (~35 km) thickness crust while displaying inter-station uniqueness in the form of stacked RFs. Below the forearc and central Alaska Range, the Yakutat slab Moho is also observed. To complete coverage for the state we use a gravity Moho model calibrated to our receiver function solutions. The resolution of gravity-derived Moho models is limited and can only produce a smoothed approximation of the actual Moho. Where receiver function results are dense we observe significant complexity to the Moho, consistent

  10. Effects of humidity on the interaction between a fused silica test mass and an electrostatic drive

    Energy Technology Data Exchange (ETDEWEB)

    Koptsov, D.V., E-mail: kopcov@physics.msu.ru; Prokhorov, L.G.; Mitrofanov, V.P.

    2015-10-23

    Interaction of a fused silica test mass with electric field of an electrostatic drive with interdigitated electrodes and influence of ambient air humidity on this interaction are investigated. The key element of the experimental setup is the fused silica torsional oscillator. Time dependent increase of the torque acting on the oscillator's plate after application of DC voltage to the drive is demonstrated. The torque relaxation is presumably caused by the redistribution of electric charges on the fused silica plate. The numerical model has been developed to compute the time evolution of the plate's surface charge distribution and the corresponding torque. - Highlights: • Interaction between a fused silica plate and an electrostatic drive was investigated. • The interaction force is time and relative humidity dependent. • Numerical model of the interaction was developed. • Charge redistribution is shown to be the cause of the interaction force evolution.

  11. Along-strike variation in subducting plate velocity induced by along-strike variation in overriding plate structure: Insights from 3D numerical models

    Science.gov (United States)

    Rodríguez-González, Juan; Billen, Magali I.; Negredo, Ana M.; Montesi, Laurent G. J.

    2016-10-01

    Subduction dynamics can be understood as the result of the balance between driving and resisting forces. Previous work has traditionally regarded gravitational slab pull and viscous mantle drag as the main driving and resistive forces for plate motion respectively. However, this paradigm fails to explain many of the observations in subduction zones. For example, subducting plate velocity varies significantly along-strike in many subduction zones and this variation is not correlated to the age of subducting lithosphere. Here we present three-dimensional and time-dependent numerical models of subduction. We show that along-strike variations of the overriding plate thermal structure can lead to along-strike variations in subducting plate velocity. In turn, velocity variations lead to significant migration of the Euler pole over time. Our results show that the subducting plate is slower beneath the colder portion of the overriding plate due to two related mechanisms. First, the mantle wedge beneath the colder portion of the overriding plate is more viscous, which increases mantle drag. Second, where the mantle wedge is more viscous, hydrodynamic suction increases, leading to a lower slab dip. Both factors contribute to decreasing subducting plate velocity in the region; therefore, if the overriding plate is not uniform, the resulting velocity varies significantly along-strike, which causes the Euler pole to migrate closer to the subducting plate. We present a new mechanism to explain observations of subducting plate velocity in the Cocos and Nazca plates. These results shed new light on the balance of forces that control subduction dynamics and prove that future studies should take into consideration the three-dimensional structure of the overriding plate.

  12. Combined crustal-geological cross-section of Ellesmere Island

    DEFF Research Database (Denmark)

    Stephenson, Randell Alexander; Schiffer, Christian; Oakey, Gordon

    (Eurekan “Orogeny”). An almost complete absence of information about the crustal or lithosphere structure of Ellesmere Island has been addressed by the acquisition of teleseismic data between 2010 and 2012 on a passive seismological array called ELLITE (“Ellesmere Island Teleseismic Experiment...

  13. Crustal growth at active continental margins: Numerical modeling

    NARCIS (Netherlands)

    Vogt, Katharina|info:eu-repo/dai/nl/370618947; Gerya, Taras; Castro, Antonio

    2012-01-01

    The dynamics and melt sources for crustal growth at active continental margins are analyzed by using a 2D coupled petrological–thermomechanical numerical model of an oceanic-continental subduction zone. This model includes spontaneous slab retreat and bending, dehydration of subducted crust, aqueous

  14. Microbial Turnover of Fixed Nitrogen Compounds in Oceanic Crustal Fluids

    Science.gov (United States)

    Kraft, B.; Wankel, S. D.; Glazer, B. T.; Huber, J. A.; Girguis, P. R.

    2014-12-01

    Oceanic crust is the largest aquifer on Earth, with a massive volume of seawater advecting through the basaltic crust. The microbiome of this deep marine subsurface biosphere has been estimated to be substantial, and consequently their metabolic activity may have major influences on global biogeochemical cycles. While earlier and recent studies provide insight into the microbial community composition of oceanic crustal fluids, information on the microbial ecophysiology is broadly missing. Therefore, to investigate the microbial transformation of fixed nitrogen compounds in crustal aquifer fluids, fluids were sampled from different horizons of two neighbouring CORK (Circulation Obviation Retrofit Kit) observatories at the North Pond sediment pond. This site is located on the western flank of the Mid Atlantic Ridge and is characterized by relatively young oceanic crust and cold fluids. The crustal fluids contain oxygen and nitrate, which potentially both may serve as electron acceptor for respiration. In a multidisciplinary approach we combined stable isotope incubations, determination of the natural isotopic compositions and plan to analyse relevant functional genes from a metagenomic dataset to investigate the nitrogen cycling at North Pond. The turnover of fixed nitrogen in oceanic crustal fluids may have important implications for the understanding of the global nitrogen cycle.

  15. A proposed concept for a crustal dynamics information management network

    Science.gov (United States)

    Lohman, G. M.; Renfrow, J. T.

    1980-01-01

    The findings of a requirements and feasibility analysis of the present and potential producers, users, and repositories of space-derived geodetic information are summarized. A proposed concept is presented for a crustal dynamics information management network that would apply state of the art concepts of information management technology to meet the expanding needs of the producers, users, and archivists of this geodetic information.

  16. Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

    Science.gov (United States)

    Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

    2010-12-01

    We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian

  17. Driving anger in Malaysia.

    Science.gov (United States)

    Sullman, Mark J M; Stephens, Amanda N; Yong, Michelle

    2014-10-01

    The present study examined the types of situations that cause Malaysian drivers to become angry. The 33-item version of the driver anger scale (Deffenbacher et al., 1994) was used to investigate driver anger amongst a sample of 339 drivers. Confirmatory factor analysis showed that the fit of the original six-factor model (discourtesy, traffic obstructions, hostile gestures, slow driving, illegal driving and police presence), after removing one item and allowing three error pairs to covary, was satisfactory. Female drivers reported more anger, than males, caused by traffic obstruction and hostile gestures. Age was also negatively related to five (discourtesy, traffic obstructions, hostile gestures, slow driving and police presence) of the six factors and also to the total DAS score. Furthermore, although they were not directly related to crash involvement, several of the six forms of driving anger were significantly related to the crash-related conditions of: near misses, loss of concentration, having lost control of a vehicle and being ticketed. Overall the pattern of findings made in the present research were broadly similar to those from Western countries, indicating that the DAS is a valid measure of driving anger even among non-European based cultures.

  18. Crustal structure across the Filchner Ronne Shelf, Antarctica

    Science.gov (United States)

    Herter, U.; Jokat, W.

    2012-04-01

    Crustal structure across the Filchner Ronne Shelf, Antarctica U. Herter, W. Jokat One large gap in understanding the tectonic evolution of Antarctica beside the few rock outcrops on the continent is the missing information on crustal thickness along its margins but also in its interior. E.g., the few marine deep seismic lines are located mainly along the Antarctic Peninsula/Pacific margin, but for most of the East Antarctic margins such information is not available. In this contribution we concentrate on one of the most remote areas in Antarctica, the Filchner Ronne Shelf (FRS). The area is underlain by approximately 12 km of sediments, but its crustal fabric is questionable. Thus, some existing deep seismic sounding data were modeled and reinterpreted. Especially, data gathered in 1995 have been analyzed, and a more detailed 2D P-wave velocity model has been calculated. For the profiles in total 12 RefTek stations each with nine geophone chains were placed on the ice shelf and 3175 airgun shots along a 480 km transect were fired by two 32 l BOLT-Airguns each 60 s. Signals were recorded up to distances of 180 km. Due to the ice coverage it was not possible to acquire the data without gaps or along straight lines, which caused some difficulties in the modeling process. Furthermore, in the new model all data from older experiments of the AWI and Soviet Antarctic expeditions acquired with dynamite sources were incorporated. The model shows a sedimentary basin with a thickness up to 12 km and a large velocity inversion in a deeper sediment unit. The crustal thickness varies from 40 km beneath the Antarctic Peninsula, and 14 km of basement in the center part of the profile. Towards Berkner Island the crust thickens again, but the top of the basement is still 11 km deep. The lower crustal velocities range between 6.8 and 7.2 km/s. We interpret the crustal structure as clear evidence for the presence of a failed rift. The initial stretching of the continental crust

  19. Crustal Seismicity and Recent Faults in Southern Peru

    Science.gov (United States)

    David, C.; Comte, D.; Tavera, H.; Audin, L.; Herail, G.

    2004-12-01

    Most seismological studies in southern Peru have been focused on the downgoing slab seismicity in order to constrain the Wadati-Benioff zone. This study deals with the intra-continental seismicity of the southern Peru forearc (17,3° S - 18,5° S) in a post-seismic context (Arequipa thrust earthquake, Mw=8.4, 23 June, 2001). It is difficult to identify historical crustal earthquake from available catalogues, however some crustal events teleseismically recorded can be found since 1976; they exhibit normal focal mechanism solutions in the southern Peru volcanic arc and inverse focal mechanism solutions in the Central Depression. Following a notable increase of shallow crustal seismicity located close to the Western Cordillera after the 23 June 2001, a temporary seismic network was deployed between January and March 2003 in order to study the Wadati-Benioff zone and monitoring the crustal seismicity in southern Peru. From the about 1700 events locally recorded by the local network, 300 crustal earthquakes were identified in the Peruvian forearc between Tacna and Moquegua. This crustal seismicity is distributed along a lineament located at depths between 0 and 60 km, dipping at about 45° from the Western Cordillera towards the coast, almost perpendicular to the subducting slab; this behaviour was previously observed in northern Chile and in southern Peru, north of the study zone (16° S). In the Central Depression, seismic activity is not superficial occurring between 25-60 km depth and it is mostly characterized by inverse focal mechanism solutions. Superficial faults situated in the Central Depression and in the Coastal Cordillera can not be associated with the seismic activity observed in this area. However, in the Pre-Cordillera, crustal seismicity occurs at depths between 0-15 km and can be correlated with shallow fault systems recognized by satellite images and on the field. For examples, the Incapuquio fault system which was a transpressive system in Cretaceous

  20. Casimir force between metal plate and dielectric plate

    Institute of Scientific and Technical Information of China (English)

    刘中柱; 邵成刚; 罗俊

    1999-01-01

    The Casimir effect between metal plate and dielectric plate is discussed with 1+1-dimensional potential model without using cut-off method. Calculation shows that the Casimir force between metal plate and dielectric plate is determined not only by the potential V0, the dielectric thickness and the distance α between the metal plate and dielectric plate, but also by the dimension of the vessel. When α is far less than the dimension of the vessel, the Casimir force Fc∝α(-1); conversely Fc∝α-2. This result is significant for Casimir force experiment.

  1. U.S. DRIVE

    Energy Technology Data Exchange (ETDEWEB)

    None

    2012-03-16

    U.S. DRIVE, which stands for United States Driving Research and Innovation for Vehicle efficiency and Energy sustainability, is an expanded government-industry partnership among the U.S. Department of Energy; USCAR, representing Chrysler Group LLC, Ford Motor Company and General Motors; Tesla Motors; five energy companies – BP America, Chevron Corporation, ConocoPhillips, ExxonMobil Corporation, and Shell Oil Products US; two utilities – Southern California Edison and Michigan-based DTE Energy; and the Electric Power Research Institute (EPRI). The U.S. DRIVE mission is to accelerate the development of pre-competitive and innovative technologies to enable a full range of affordable and clean advanced light-duty vehicles, as well as related energy infrastructure.

  2. Filling in the juvenile magmatic gap: Evidence for uninterrupted Paleoproterozoic plate tectonics

    Science.gov (United States)

    Partin, C. A.; Bekker, A.; Sylvester, P. J.; Wodicka, N.; Stern, R. A.; Chacko, T.; Heaman, L. M.

    2014-02-01

    Despite several decades of research on growth of the continental crust, it remains unclear whether the production of juvenile continental crust has been continuous or episodic throughout the Precambrian. Models for episodic crustal growth have gained traction recently through compilations of global U-Pb zircon age frequency distributions interpreted to delineate peaks and lulls in crustal growth through geologic time. One such apparent trough in zircon age frequency distributions between ∼2.45 and 2.22 Ga is thought to represent a pause in crustal addition, resulting from a global shutdown of magmatic and tectonic processes. The ∼2.45-2.22 Ga magmatic shutdown model envisions a causal relationship between the cessation of plate tectonics and accumulation of atmospheric oxygen over the same period. Here, we present new coupled U-Pb, Hf, and O isotope data for detrital and magmatic zircon from the western Churchill Province and Trans-Hudson orogen of Canada, covering an area of approximately 1.3 million km2, that demonstrate significant juvenile crustal production during the ∼2.45-2.22 Ga time interval, and thereby argue against the magmatic shutdown hypothesis. Our data is corroborated by literature data showing an extensive 2.22-2.45 Ga record in both detrital and magmatic rocks on every continent, and suggests that the operation of plate tectonics continued throughout the early Paleoproterozoic, while atmospheric oxygen rose over the same time interval. We argue that uninterrupted plate tectonics between ∼2.45 and 2.22 Ga would have contributed to efficient burial of organic matter and sedimentary pyrite, and the consequent rise in atmospheric oxygen documented for this time interval.

  3. Effects of Martian crustal magnetic field on its ionosphere

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The effect of the Martian crustal magnetic field is one of the hot topics of the study of Martian ionosphere.The studies on this topic are summarized in this paper.Main data of the Martian ionosphere were resulted from radio occultation experiments.According to the observations,the electron density scale height and the peak electron density of the Martian ionosphere are influenced by its crustal magnetic field.The strong horizontal magnetic field prevents the vertical diffusion of the plasma and makes the electron density scale height in the topside ionosphere close to that in the photo equilibrium region.In the cusp-like regions with strong vertical magnetic field,the enhanced vertical diffusion leads to a larger electron density scale height in the diffusion equilibrium region.The observation of radio occultation experiment onboard Mars Global Surveyor (MGS) showed that the averaged peak electron density observed in the southern hemisphere with strong crustal magnetic field was slightly larger than that in the northern hemisphere with weak crustal magnetic field.The Mars advanced radar for subsurface and ionosphere sounding (MARSIS) onboard Mars Express (MEX) was the first topside sounder to be used to observe Martian ionosphere.The MARSIS results confirmed that the enhancement of the peak electron density occurred in cusp-like regions with open field lines,and the amount of the enhancement was much larger than that observed by the radio occultation experiment.There are two possible mechanisms for the peak electron density enhancement in the cusp-like crustal magnetic field regions:One is the precipitation of the energetic particles and the other is the heating by the waves excited by plasma instabilities.It’s difficult to determine which one is the key mechanism for the peak electron density enhancement.Based on these studies,several interesting problems on the Martian ionosphere and plasma environment are presented.

  4. Nuclear reactor alignment plate configuration

    Energy Technology Data Exchange (ETDEWEB)

    Altman, David A; Forsyth, David R; Smith, Richard E; Singleton, Norman R

    2014-01-28

    An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accomodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through with the dowel pins pass.

  5. Toyota hybrid synergy drive

    Energy Technology Data Exchange (ETDEWEB)

    Gautschi, H.

    2008-07-01

    This presentation made at the Swiss 2008 research conference on traffic by Hannes Gautschi, director of service and training at the Toyota company in Switzerland, takes a look at Toyota's hybrid drive vehicles. The construction of the vehicles and their combined combustion engines and electric generators and drives is presented and the combined operation of these components is described. Braking and energy recovery are discussed. Figures on the performance, fuel consumption and CO{sub 2} output of the hybrid vehicles are compared with those of conventional vehicles.

  6. Toyota hybrid synergy drive

    Energy Technology Data Exchange (ETDEWEB)

    Gautschi, H.

    2008-07-01

    This presentation made at the Swiss 2008 research conference on traffic by Hannes Gautschi, director of service and training at the Toyota company in Switzerland, takes a look at Toyota's hybrid drive vehicles. The construction of the vehicles and their combined combustion engines and electric generators and drives is presented and the combined operation of these components is described. Braking and energy recovery are discussed. Figures on the performance, fuel consumption and CO{sub 2} output of the hybrid vehicles are compared with those of conventional vehicles.

  7. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  8. Gears and gear drives

    CERN Document Server

    Jelaska, Damir T

    2012-01-01

    Understanding how gears are formed and how they interact or 'mesh' with each other is essential when designing equipment that uses gears or gear trains. The way in which gear teeth are formed and how they mesh is determined by their geometry and kinematics, which is the topic of this book.  Gears and Gear Drives provides the reader with comprehensive coverage of gears and gear drives. Spur, helical, bevel, worm and planetary gears are all covered, with consideration given to their classification, geometry, kinematics, accuracy control, load capacity and manufacturing. Cylindric

  9. Microlinear piezo drive experiments

    Science.gov (United States)

    Azin, A. V.; Bogdanov, E. P.; Rikkonen, S. V.; Ponomarev, S. V.; Khramtsov, A. M.

    2017-02-01

    The article embraces the experimental description of the micro linear piezo drive intended for the peripheral cord tensioner in the reflecting surface shape regulator system for large-sized transformable spacecraft antenna reflectors. The research target is the experimental investigation of the micro linear piezo drive to determine the stable oscillatory system operating modes which would include improved energy conversion parameters. The following points are briefly presented: test stand construction-design of the peripheral cord tensioner; the determined frequency characteristics and the identified resonant and actual frequencies of an oscillatory system under inertia load. A series of experiments has been conducted for both different preliminary voltages and inertia mass values.

  10. Create Your Plate

    Medline Plus

    Full Text Available ... 1 Type 2 About Us Online Community Meal Planning Sign In Search: Search More Sites Search ≡ Are ... Fitness Home Food MyFoodAdvisor Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten ...

  11. Create Your Plate

    Medline Plus

    Full Text Available ... Create Your Plate is a simple and effective way to manage your blood glucose levels and lose weight. With ... year of delicious meals to help prevent and manage diabetes. Healthy Recipes: ... to your day with this guide. Ways to Give: Wear Your Cause on Your Sleeve - ...

  12. The Plate Tectonics Project

    Science.gov (United States)

    Hein, Annamae J.

    2011-01-01

    The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…

  13. Create Your Plate

    Medline Plus

    Full Text Available ... tax-deductible gift today can fund critical diabetes research and support vital diabetes education services that improve the ... way to manage your blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  14. Create Your Plate

    Medline Plus

    Full Text Available ... 1 Type 2 About Us Online Community Meal Planning Sign In Search: Search More Sites Search ≡ Are ... Fitness Home Food MyFoodAdvisor Recipes Association Cookbook Recipes Planning Meals Diabetes Meal Plans Create Your Plate Gluten ...

  15. Create Your Plate

    Medline Plus

    Full Text Available ... tax-deductible gift today can fund critical diabetes research and support vital diabetes education services that improve the ... way to manage your blood glucose levels and lose weight. With this method, you fill your plate with more non-starchy ...

  16. Create Your Plate

    Medline Plus

    Full Text Available ... unsweetened tea or coffee. Featured Product Precise Portions® Go Healthy Travel Pack (4/Box) Taking the guesswork ... you are. Now, our best-selling, sectioned to-go plate with easy-sealing lid is offered in ...

  17. Create Your Plate

    Medline Plus

    Full Text Available ... manage portion control wherever you are. Now, our best-selling, sectioned to-go plate with easy-sealing lid is offered in a 4-pack. Whether ... Research & Practice We Are Research Leaders We Support Your Doctor ...

  18. INL HIP Plate Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    B. H. Park; C. R. Clark; J. F. Jue

    2010-02-01

    This document outlines the process used to bond monolithic fuel plates by Hot Isostatic Pressing (HIP). This method was developed at Idaho National Laboratory (INL) for the Reduced Enrichment for Research and Test Reactors (RERTR) program. These foils have been used in a number of irradiation experiments in support of the United States Global Threat Reduction Initiative (GTRI) program.

  19. The Plate Tectonics Project

    Science.gov (United States)

    Hein, Annamae J.

    2011-01-01

    The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…

  20. Create Your Plate

    Medline Plus

    Full Text Available ... Planning Meals > Create Your Plate Share: Print Page Text Size: A A A Listen En Español Create ... somewhere in between, you have an easy portion control solution that works. Last Reviewed: October 8, 2015 Last Edited: ... Cost of Diabetes Advocate Toolkit Call to Congress Research & ...

  1. Dangers of Texting While Driving

    Science.gov (United States)

    ... nhtsa.gov/risky-driving/distracted-driving . Print Out Texting While Driving Guide (pdf) File a Complaint with the FCC ... Office: Consumer and Governmental Affairs Tags: Consumers - Distracted Driving - Health and Safety - Texting Federal Communications Commission 445 12th Street SW, Washington, ...

  2. Three-Dimensional Numerical Modeling of Crustal Growth at Active Continental Margins

    Science.gov (United States)

    Zhu, G.; Gerya, T.; Tackley, P. J.

    2011-12-01

    Active margins are important sites of new continental crust formation by magmatic processes related to the subduction of oceanic plates. We investigate these phenomena using a three-dimensional coupled petrological-geochemical-thermomechanical numerical model, which combines a finite-difference flow solver with a non-diffusive marker-in-cell technique for advection (I3ELVIS code, Gerya and Yuen, PEPI,2007). The model includes mantle flow associated with the subducting plate, water release from the slab, fluid propagation that triggers partial melting at the slab surface, melt extraction and the resulting volcanic crustal growth at the surface. The model also accounts for variations in physical properties (mainly density and viscosity) of both fluids and rocks as a function of local conditions in temperature, pressure, deformation, nature of the rocks, and chemical exchanges. Our results show different patterns of crustal growth and surface topography, which are comparable to nature, during subduction at active continental margins. Often, two trench-parallel lines of magmatic activity, which reflect two maxima of melt production atop the slab, are formed on the surface. The melt extraction rate controls the patterns of new crust at different ages. Moving free water reflects the path of fluids, and the velocity of free water shows the trend of two parallel lines of magmatic activity. The formation of new crust in particular time intervals is distributed in finger-like shapes, corresponding to finger-like and ridge-like cold plumes developed atop the subducting slabs (Zhu et al., G-cubed,2009; PEPI,2011). Most of the new crust is basaltic, formed from peridotitic mantle. Granitic crust extracted from melted sediment and upper crust forms in a line closer to the trench, and its distribution reflects the finger-like cold plumes. Dacitic crust extracted from the melted lower crust forms in a line farther away from the trench, and its distribution is anticorrelated with

  3. Extensional crustal tectonics and crust-mantle coupling, a view from the geological record

    Science.gov (United States)

    Jolivet, Laurent; Menant, Armel; Clerc, Camille; Sternai, Pietro; Ringenbach, Jean-Claude; Bellahsen, Nicolas; Leroy, Sylvie; Faccenna, Claudio; Gorini, Christian

    2017-04-01

    In passive margins or back-arc regions, extensional deformation is often asymmetric, i.e. normal faults or extensional ductile shear zones dip in the same direction over large distances. We examine a number of geological examples in convergent or divergent contexts suggesting that this asymmetry results from a coupling between asthenospheric flow and crustal deformation. This is the case of the Mediterranean back-arc basins, such as the Aegean Sea, the northern Tyrrhenian Sea, the Alboran domain or the Gulf of Lion passive margin. Similar types of observation can be made on some of the Atlantic volcanic passive margins and the Afar region, which were all formed above a mantle plume. We discuss these contexts and search for the main controlling parameters for this asymmetric distributed deformation that imply a simple shear component at the scale of the lithosphere. The different geodynamic settings and tectonic histories of these different examples provide natural case-studies of the different controlling parameters, including a pre-existing heterogeneity of the crust and lithosphere (tectonic heritage) and the possible contribution of the underlying asthenospheric flow through basal drag or basal push. We show that mantle flow can induce deformation in the overlying crust in case of high heat flow and thin lithosphere. In back-arc regions, the cause of asymmetry resides in the relative motion between the asthenosphere below the overriding plate and the crust. When convergence and slab retreat work concurrently the asthenosphere flows faster than the crust toward the trench and the sense of shear is toward the upper plate. When slab retreat is the only cause of subduction, the sense of shear is opposite. In both cases, mantle flow is mostly the consequence of slab retreat and convergence. Mantle flow can however result also from larger-scale convection, controlling rifting dynamics prior to the formation of oceanic crust. In volcanic passive margins, in most cases

  4. Subsidence history, crustal structure and evolution of the Nogal Rift, Northern Somalia

    Science.gov (United States)

    Ali, M. Y.; Watts, A. B.

    2013-12-01

    Seismic reflection profile, gravity anomaly, and biostratigraphic data from deep exploration wells have been used to determine the tectonic subsidence, structure and evolution of the Nogal basin, Northern Somalia, one of a number of ENE-WSW trending early Mesozoic rifts that formed prior to opening of the Gulf of Aden. Backstripping of biostratigraphic data at the Nogal-1 and Kali-1 wells provides new constraints on the age of rifting, and the amount of crustal and mantle extension. The tectonic subsidence and uplift history at the wells can be generally explained as a consequence of two, possibly three, major rifting events. The first event initiated in the Late Jurassic (~156 Ma) and lasted for ~10 Myr. We interpret the rift as a late stage event associated with the break-up of Gondwana and the separation of Africa and Madagascar. The second event initiated in the Late Cretaceous (~80 Ma) and lasted for ~20 Myr. This event probably correlates with a rapid increase in spreading rate on the ridges separating the African and Indian and African and Antarctica plates and a contemporaneous slowing down of Africa's plate motion. The backstripped tectonic subsidence data can be explained by a multi-rift extensional model with a stretching factor, β, in the range 1.17-1.38. The third and most recent event occurred in the Oligocene (~32 Ma) and lasted for ~10 Myr. This rift only developed at the centre of the basin close to Nogal-1 well, and is related to the opening of the Gulf of Aden. The amount of crustal thinning inferred at the Kali-1 well is consistent with the results of Process-Oriented Gravity and Flexure (POGM) modelling, assuming an elastic thickness of ~30 km. The thinning at the Nogal-1 well, however, is greater by ~ 7 km than predicted suggesting that the basin may be locally underplated by magmatic material. Irrespective, POGM suggests the transition between thick crust beneath Northern Somalia to thin crust beneath the Indian Ocean forms a ~500 km wide

  5. Inside a Crustal Earthquake - the Rock Evidence

    Science.gov (United States)

    Sibson, R. H.

    2012-12-01

    Exhumed fault rock assemblages provide insights into fault zone structure, rupture processes and physical conditions of seismogenesis which can be melded with high-resolution geophysical information on modern earthquakes. The transition from dominantly cataclasite-series to mylonite-series fault rocks at greenschist and greater grades of metamorphism is the basis of fault zone models and rheological strength profiles defining the FR-VS (frictional-viscous) transition which governs the base of the microseismically defined seismogenic zone, within which larger ruptures are mostly contained. In areas of crust deforming under moderate-to-high heat flow (e.g. Japan, California) there is good correlation between geothermal gradient and the base of microseismic activity in the crust. However, compositional variations (e.g. quartz- vs. feldspar-dominant rheology) plus other factors such as water content locally perturb the base of the seismogenic zone, creating strength asperities which may affect the nucleation of large ruptures (e.g.1989 M6.9 Loma Prieta earthquake). The level of shear stress driving rupturing within the seismogenic zone remains problematic. While some estimates (e.g. those inferred from pseudotachylyte friction-melts) are broadly consistent with expectations for the frictional strength of optimally oriented faults with 'Byerlee friction' (τ ~ 80-240 MPa at 10 km depth, depending on faulting mode), others (e.g. faults with associated hydrothermal extension veins) appear to slip at much lower levels of shear stress (max. τ 90% of global seismic moment release) and areas of active compressional inversion (e.g. NE Honshu). However, while fault overpressuring is more easily generated and sustained in compressional regimes, it may be more widespread than once thought. The presence of incrementally deposited hydrothermal veins along fault slip surfaces (often associated with subsidiary extension vein arrays) is not uncommon in fault assemblages exhumed from

  6. Migrating Ignimbrite Flares in the Central Andes, Implications for Crustal Evolution Based on Chemical, Isotopic, Geochronological, and GIS-Based Volumetric Data

    Science.gov (United States)

    Worner, G.; Brandmeier, M.; Freymuth, H.; Heistek, R. M.

    2014-12-01

    Temporal and compositional patterns of Neogene ignimbrites in the Central Andes were analysed using GIS and geostatistical modelling based on 203 digitized ignimbrite sheets for which geochronological, geochemical, and Sr-Nd-Pb-isotopic data on pumices as well as Sr-O isotopes on minerals from selected samples were compiled and compared to compositional and isotopic data from andesite lavas. Composition, timing, volumes and sources of erupted ignimbrite deposits are thus constrained and magma volumes through space and time are calculated. The total erupted ignimbrite magma volume of 31,000 km3 (minimum value) in the past 30 Ma indicate an average magmatic addition of 20-30 km3*Ma/km, similar to the basaltic "base"-flux for arc magmatism. Ignimbrite flare-ups are, however, rather punctuated, short-lived events well separated in space and time. There is a clear N-S "younging" of ignimbrite pulses from N to S at 19-24 Ma, 13-14 Ma, 6-10 Ma and 3-6 Ma. Ignimbrite eruptions occurred in the wake of subduction of the Juan-Fernandez ridge on the Nazca Plate passing below the Central Andes from N to S. Low angle subduction caused compression and fluid release is followed by massive inflow and melting of asthenospheric mantle when the slab steepened again after the passing of the ridge. This in turn caused massive melting within the crust aided by advective heat transport. Differences in chemical and isotopic composition of the large-volume ignimbrites are related to changes in crustal thickness, and different "preconditioning" during the Andean orogeny at a given space in time. Isotope data and whole rock compositional data suggest a higher degree of crustal assimilation for the younger Altiplano ignimbrites in the S (c. 50%) compared to the older (22-19 Ma) ignimbrites in the N were the crustal component is significantly less (20%). REE compositions reflect changes in crustal thickness with a "transition" at c. 13-9 Ma that can be related to accelerated crustal shortening

  7. CSI: Hard Drive

    Science.gov (United States)

    Sturgeon, Julie

    2008-01-01

    Acting on information from students who reported seeing a classmate looking at inappropriate material on a school computer, school officials used forensics software to plunge the depths of the PC's hard drive, searching for evidence of improper activity. Images were found in a deleted Internet Explorer cache as well as deleted file space.…

  8. Chaos in drive systems

    Directory of Open Access Journals (Sweden)

    Kratochvíl C.

    2007-10-01

    Full Text Available The purpose of this article is to provide an elementary introduction to the subject of chaos in the electromechanical drive systems. In this article, we explore chaotic solutions of maps and continuous time systems. These solutions are also bounded like equilibrium, periodic and quasiperiodic solutions.

  9. Fresh Drive Against Corruption

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    China’s government is making efforts to prevent corruption by taking harsh measures against the illegal selection and appointment of cadres on the 10th anniversary of China’s anti-corruption drive,President Hu Jintao called fogreater efforts to carry it out.

  10. Driving with a Goat

    Institute of Scientific and Technical Information of China (English)

    高素菊

    2006-01-01

    <正>A highway patrol officer was sitting in his car beside the road one day when he noticed a man driving with a goat in the back seat of his car.Turning on the lights,he pulled out,sped up, and pulled the man over.

  11. Drugs and driving

    NARCIS (Netherlands)

    Walsh, J. Michael; De Gier, Johan J.; Christopherson, Asbjørg S.; Verstraete, Alain G.

    2004-01-01

    The authors present a global overview on the issue of drugs and driving covering four major areas: (1) Epidemiology and Prevalence-which reviews epidemiological research, summarizes available information, discusses the methodological shortcomings of extant studies, and makes recommendations for futu

  12. Drive-Through Training

    Science.gov (United States)

    Carter, Margie

    2010-01-01

    In this article, the author discusses how the early childhood field's approach to staff training reflects the drive-through, fast-food culture. Year after year directors send their teachers to workshops to get some quick refresher techniques. The author suggests that rather than focusing professional development on topics, focus on observing…

  13. The Drive to Influence

    Science.gov (United States)

    Rodriguez, Diego

    2017-01-01

    At the heart of the educational vocation is a drive to influence, to meaningfully affect the learning and development of others. For adult educators working in higher education, daily activities--from teaching classes to supervising student research to attending faculty meetings to sitting on advisory boards--are full of opportunities to…

  14. Driving While Intoxicated.

    Science.gov (United States)

    Brick, John

    Alcohol intoxication increases the risk of highway accidents, the relative risk of crash probability increasing as a function of blood alcohol content (BAC). Because alcohol use is more prevalent than use of other drugs, more is known about the relationship between alcohol use and driving. Most states presume a BAC of .10% to be evidence of drunk…

  15. Gaze-controlled Driving

    DEFF Research Database (Denmark)

    Tall, Martin; Alapetite, Alexandre; San Agustin, Javier

    2009-01-01

    We investigate if the gaze (point of regard) can control a remote vehicle driving on a racing track. Five different input devices (on-screen buttons, mouse-pointing low-cost webcam eye tracker and two commercial eye tracking systems) provide heading and speed control on the scene view transmitted...

  16. Electric-Drive Vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Septon, Kendall K [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-11

    Electric-drive vehicles use electricity as their primary fuel or to improve the efficiency of conventional vehicle designs. These vehicles can be divided into three categories: Hybrid electric vehicles (HEVs), Plug-in hybrid electric vehicles (PHEVs), All-electric vehicles (EVs). Together, PHEVs and EVs can also be referred to as plug-in electric vehicles (PEVs).

  17. Current Arabian Plate Motion From Campaign GPS Measurements in Saudi Arabia: Preliminary Results

    Science.gov (United States)

    Almuslmani, B.; Teferle, F. N.; Bingley, R. M.; Moore, T.

    2007-12-01

    Current investigations of the motions of the Arabian and its neighboring plates are primarily based on GPS measurements obtained in the surrounding areas of the Arabian plate, with few stations actually located on the Arabian plate itself in the Kingdom of Saudi Arabia. In order to advance the knowledge of the dynamics of the Arabian plate and its intra-plate deformations, the General Directorate of Military Survey (GDMS), through collaboration with the Institute of Engineering Surveying and Space Geodesy (IESSG), densified the GPS network in Saudi Arabia, covering nearly two thirds of the tectonic plate. Since July 2002, a network of 32 GPS stations has been established at locations of the Saudi Arabia geodetic network. At all of these GPS stations a concrete pillar has been used as the monument and the locations have been selected in order to give the broadest distribution of observing sites. During 2005, 27 additional GPS stations in the Hejaz and Asser Mountains, and the Farasan Islands, all in south-western Saudi Arabia, have been established, for which the past and future campaign GPS measurements will provide valuable data for investigations of crustal deformations close to the plate boundaries between the Nubia, Somalian and Arabian plates. In this presentation we will show results in the form of velocity field and plate motion estimates based on data from at least three campaigns occupying the initial 32 GDMS GPS network stations, but also from a number of IGS stations in the region. Our reference frame is aligned to ITRF2005 and uses approximately 40 IGS reference frame stations located on all major tectonic plates, e.g. Nubia and Somalia, surrounding the Arabian plate. Furthermore, we apply absolute satellite and receiver antenna phase center models together with newly available GPS products from a recent global re-processing effort.

  18. Comparative seismic and petrographic crustal study between the Western and Eastern Sierras Pampeanas region (31°S

    Directory of Open Access Journals (Sweden)

    P. Alvarado

    2005-12-01

    Full Text Available The ancient Sierras Pampeanas in the central west part of Argentina are a seismically active region in the back-arc of the Andes. Their crystalline basement cored uplifts extend up to 800 km east of the oceanic trench over the flat subduction segment of the Nazca plate. Approximately 40 felt crustal earthquakes, are reported per year for this region. Historic and modern seismicity indicates that the Western Sierras Pampeanas (WSP have more crustal earthquakes of greater-size than the Eastern Sierras Pampeanas (ESP. Remarkable changes in composition and structure also characterize the WSP and ESP basements. We have quantitatively compared both regions using seismological constrains. A recent regional study of moderate earthquakes shows reverse and thrust focal mechanisms occurring at depths down to 25 km in the WSP. In contrast, the ESP have reverse and strike-slip focal mechanisms of shallower depths (< 10 km. A seismic velocity structure of Vp 6.4 km/s, Vp/Vs ~1.80, and thickness 50 km, best represents the WSP crust. The ESP crust is characterized by Vp 6.0 km/s, Vp/Vs < 1.70, and thickness 30 km. These seismological determinations correlate with the interpretation of a different origin for the western and eastern terranes. The WSP show seismic properties indicative of a more mafic-ultramafic thick crust consistent with an oceanic island-arc and back-arc formation. The ESP show crustal seismic properties consistent with a higher silica content and with a formation by the collision of a continental terrane.

  19. Create Your Plate

    Medline Plus

    Full Text Available ... low-calorie drink like water, unsweetened tea or coffee. Featured Product Precise Portions® Go Healthy Travel Pack ( ... For Professionals En Español Online Community Walk Bike Shop Sign in American Diabetes Association 2451 Crystal Drive, ...

  20. 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.

  1. MyPlate Food Guide

    Science.gov (United States)

    ... Choosing the Right Sport for You Shyness MyPlate Food Guide KidsHealth > For Teens > MyPlate Food Guide Print ... other sugary drinks. Avoid oversized portions. continue Five Food Groups Different food groups meet different nutrition needs. ...

  2. What Are Growth Plate Injuries?

    Science.gov (United States)

    ... plate injuries are:  Falling down  Competitive sports (like football)  Recreational activities. Other reasons for growth plate injuries are:  Child abuse  Injury from extreme cold (for ...

  3. Controlling Laminate Plate Elastic Behavior

    OpenAIRE

    Mareš, T.

    2004-01-01

    This paper aims to express the relation of a measure of laminate plate stiffness with respect to the fiber orientation of its plies. The inverse of the scalar product of the lateral displacement of the central plane and lateral loading of the plate is the measure of laminate plate stiffness. In the case of a simply supported rectangular laminate plate this measure of stiffness is maximized, and the optimum orientation of its plies is searched.

  4. Microchannel plate streak camera

    Science.gov (United States)

    Wang, Ching L.

    1989-01-01

    An improved streak camera in which a microchannel plate electron multiplier is used in place of or in combination with the photocathode used in prior streak cameras. The improved streak camera is far more sensitive to photons (UV to gamma-rays) than the conventional x-ray streak camera which uses a photocathode. The improved streak camera offers gamma-ray detection with high temporal resolution. It also offers low-energy x-ray detection without attenuation inside the cathode. Using the microchannel plate in the improved camera has resulted in a time resolution of about 150 ps, and has provided a sensitivity sufficient for 1000 KeV x-rays.

  5. New geological evidence of crustal thickening in the Gangdese block prior to the Indo-Asian collision

    Institute of Scientific and Technical Information of China (English)

    DING Lin; LAI Qingzhou

    2003-01-01

    Recent mapping in the Gangdese block has revealed many leucogranites that are similar to those in the High Himalaya. These leucogranites formed at ~140 Ma as indicated by monazite Th-Pb ion-microprobe dating and cooled at ~130 Ma as indicated by muscovite 40Ar/39Ar dating. In conjunction with previous structural and paleogeographic studies, the new data indicate that the Gangdese block underwent crustal thickening and associated exhumation during ~140-130 Ma. In this regard, the southern margin of Eurasia continent was comparable to the modern South American Altiplano-Puna plateau, the prime example of active ocean-continent subduction and associated thickened crust. Specifically, the early stages of crustal thickening and uplifting of the Gangdese block may result from subduction of the Neo-Tethyan Ocean. If the Tibetan Plateau would form by accretion of a series of blocks with thickened crust, an elevated topographic plateau similar to the Altiplano- Puna plateau had formed before collision between the Indian and Eurasian plates. Then the Tibetan Plateau would have quickly thickened, uplifted, and begun to extend soon after onset of the collision. Thus, the deformational mechanism of the Tibetan Plateau is not distributed shortening, but rather concentrating deformation within regions of thin crust between the accreted blocks.

  6. A study on crustal shear wave splitting in the western part of the Banda arc-continent collision

    Energy Technology Data Exchange (ETDEWEB)

    Syuhada, E-mail: hadda9@gmail.com [Graduate Research on Earthquake and Active Tectonics-ITB, Jl. Ganesha 10, Bandung 40132 (Indonesia); Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Puspiptek Serpong 15314,Indonesia (Indonesia); Hananto, Nugroho D. [Research Centre for Geotechnology -LIPI, Jl. Sangkuriang (Kompleks LIPI) Bandung 40135 (Indonesia); Puspito, Nanang T.; Yudistira, Tedi [Faculty of Mining and Petroleum Engineering ITB, Jalan Ganesha 10, Bandung 40132 (Indonesia); Anggono, Titi [Research Centre for Physics - Indonesian Institute of Sciences (LIPI), Puspiptek Serpong 15314,Indonesia (Indonesia)

    2016-03-11

    We analyzed shear wave splitting parameters from local shallow (< 30 km) earthquakes recorded at six seismic stations in the western part of the Banda arc-continent collision. We determined fast polarization and delay time for 195 event-stations pairs calculated from good signal-to-noise ratio waveforms. We observed that there is evidence for shear wave splitting at all stations with dominant fast polarization directions oriented about NE-SW, which are parallel to the collision direction of the Australian plate. However, minor fast polarization directions are oriented around NW-SE being perpendicular to the strike of Timor through. Furthermore, the changes in fast azimuths with the earthquake-station back azimuth suggest that the crustal anisotropy in the study area is not uniform. Splitting delay times are within the range of 0.05 s to 0.8 s, with a mean value of 0.29±0.18 s. Major seismic stations exhibit a weak tendency increasing of delay times with increasing hypocentral distance suggesting the main anisotropy contribution of the shallow crust. In addition, these variations in fast azimuths and delay times indicate that the crustal anisotropy in this region might not only be caused by extensive dilatancy anisotropy (EDA), but also by heterogeneity shallow structure such as the presence of foliations in the rock fabric and the fracture zones associated with active faults.

  7. Electronic Equipment Cold Plates

    Science.gov (United States)

    1976-04-01

    equations for such a flow regiae. For laainar flow and Moderate teaperature differwwe« between the well «nd coolant, a aodifled Sieder -Tate...con- figuration. The heat-transfer coefficients, therefore, were determined by using both the Sieder -Tate and McAdams equations and the coaputed...values used In the analytical predictions. As with th* previous cold Plates, the Sieder -Tate equation gave too low of values for the heat- transfer

  8. Elastic plate spallation

    Science.gov (United States)

    Oline, L.; Medaglia, J.

    1972-01-01

    The dynamic finite element method was used to investigate elastic stress waves in a plate. Strain displacement and stress strain relations are discussed along with the stiffness and mass matrix. The results of studying point load, and distributed load over small, intermediate, and large radii are reported. The derivation of finite element matrices, and the derivation of lumped and consistent matrices for one dimensional problems with Laplace transfer solutions are included. The computer program JMMSPALL is also included.

  9. Plate Tearing by a Cone

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup

    1997-01-01

    The present paper is concerned with steady-state plate tearing by a cone. This is a scenario where a cone is forced through a ductile metal plate with a constant lateral tip penetration in a motion in the plane of the plate. The considered process could be an idealisaton of the damage, which...

  10. Plate Tearing by a Cone

    DEFF Research Database (Denmark)

    Simonsen, Bo Cerup

    1998-01-01

    The present paper is concerned with steady-state plate tearing by a cone. This is a scenario where a cone is forced through a ductile metal plate with a constant lateral tip penetration in a motion in the plane of the plate. The considered process could be an idealisation of the damage, which...

  11. Vertical Crustal Displacements Due to Surface Fluid Changes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shiyu; ZHONG Min

    2007-01-01

    Using the model data for surface mass changes of the atmosphere, ocean, soil moisture and snow depth, the vertical crustal displacements of 25 ficual stations in China were calculated according to the loading theory. From the spectral analysis of the results, we can see that the periods of displacements are 12 months and the semi-periods are 6 months. The results also show that the maximum seasonal displacements can reach 20 mm and even larger. The covariance analyses and significance tests show that the coefficients of 96 percent of the stations are significant at the 0.1 significance level. The results show that one of the reasons of the vertical crustal displacements is the changing surface fluid loads.

  12. Efficacy of crustal superfluid neutrons in pulsar glitch models

    CERN Document Server

    Hooker, J; Li, Bao-An

    2013-01-01

    Within the framework of recent hydrodynamic models of pulsar glitches, we explore systematically the dependence on the stiffness of the nuclear symmetry energy at saturation density $L$, of the fractional moment of inertia of the pinned neutron superfluid in the crust $G$ and the initial post-glitch relative acceleration of the crust $K$, both of which are confronted with observational constraints from the Vela pulsar. We allow for a variable fraction of core superfluid neutrons coupled to the crust on glitch rise timescales, $Y_{\\rm g}$. We assess whether the crustal superfluid neutrons are still a tenable angular momentum source to explain the Vela glitches when crustal entrainment is included. The observed values $G$ and $K$ are found to provide nearly orthogonal constraints on the slope of the symmetry energy, and thus taken together offer potentially tight constraints on the equation of state. However, when entrainment is included at the level suggested by recent microscopic calculations, the model is un...

  13. Crustal displacements in Greenland caused by ice mass variability

    DEFF Research Database (Denmark)

    Nielsen, Karina

    The climate of the Earth is changing. A consequence of this is observed at the polar regions such as Greenland, where the ice sheet is melting with an increasing rate. The unloading of ice causes the Earth to respond elastically in terms of uplift and an outward horizontal deformation of the crust....... This motion can be measured by permanent Global Positioning System (GPS) receivers. Hence, the rates of crustal displacement are an indirect measure of the occurring mass changes. Currently, 55 GPS sites are located around the margin of the Greenland ice sheet, continuously providing information about...... the state of the ice sheet. However, the Earth is also adjusting viscoelastically to variations in the late Pleistocene ice sheets i.e. glacial isostatic adjustment (GIA). Observed rates of crustal displacement therefor contain signals from both past and present ice mass variations. Hence, to interpret...

  14. Crustal structure, seismicity and seismotectonics of the Trentino region (Southern Alps, Italy)

    Science.gov (United States)

    Viganò, Alfio; Scafidi, Davide; Martin, Silvana; Spallarossa, Daniele; Froner, Luca; Groaz, Oscar

    2013-04-01

    The Trentino region is located at the junction between the central and eastern Southern Alps (Italy), at the intersection between the Giudicarie, Schio-Vicenza and Valsugana fault systems. This area is characterized by relevant lithological and structural lateral heterogeneities, both at the crustal and lithospheric scales. A low-to-moderate seismicity is located in the upper crust, where faults are seismically active under a dominant compressive with variable strike-slip component regime. Here we study the crustal structure of this portion of the Southern Alps (Adria plate) from interpretation of local earthquake tomography images, in relation with distribution of relocated seismicity and regional tectonic patterns. Local earthquake tomography derives from a set of 476 selected earthquakes in the period 1994-2007, with local magnitudes comprised between 0.8 and 5.3. Hypocenter distribution, and number and quality of manually-repicked phases (6322 P and 5483 S) ensure optimal seismic ray coverage. Original recordings are principally from the Provincia Autonoma di Trento (PAT), that manages the Trentino seismic network since 1981, and from other networks (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - INOGS; Istituto Nazionale di Geofisica e Vulcanologia - INGV; others available via the European Integrated Data Archive). The code HYPOELLIPSE is used to perform initial earthquake relocations. The code VELEST is then used to calculate a new minimum 1-D velocity model, as input for tomography. The 3-D tomographic inversion (V P and V P-V S ratio) is obtained via the code SIMULPS, with the implementation of an accurate shooting ray-tracer. The crustal volume is discretized in order to have a regular grid with a homogenous horizontal spatial resolution of 7.5 km. The resolution in depth varies according to the obtained minimum 1-D velocity model. Reliability and accuracy of results are estimated by analyzing the Resolution Diagonal Elements of the

  15. The Iberian Plate: myth or reality?

    Energy Technology Data Exchange (ETDEWEB)

    Canerot, J.

    2016-10-01

    The plate tectonics theory generally leads us to consider that Iberia was an independent plate separated from Europe by the North Pyrenean Fault (NPF). The NPF has been commonly interpreted as a transform fault associated with a huge counterclockwise transverse and rotational movement that allowed the opening of the Bay of Biscay and the relative eastward motion of Iberia during the Mesozoic. According to some interpretations, this movement may have generated an interplate gap several hundreds of km wide, which led to the creation of an oceanic crust during the Late Jurassic and Early Cretaceous. However, field studies recently carried out in the Pyrenees do not support these interpretations. The North Pyrenean Fault (NPF) of Tertiary age is observed in the central and eastern Pyrenees, where pioneering researchers defined it as separating the North Pyrenean Zone from the Axial Zone.However, this fault cannot be identified in the western part of the range to the west of the Ossau valley. Consequently, the geodynamic evolution of Iberia has always been dependent on Europe, especially during the failed oceanic rifting in the Mid-Cretaceous. Indeed, during this period, a central zone of crustal thinning occupied by turbiditic basins separated the European from the Iberian continental crust, with a very localized mantle exhumation found only in the Mauleon basin. Therefore, far from being an interplate range, the Pyrenees can neither be considered as an intraplate unit. We can define this orogenic belt as resulting from the Tertiary tectonic inversion of a Mid-Cretaceous rift system. According to this new interpretation, Iberia would not have been an isolated plate but represented an unstable, outlying part of Europe. Rather than displaying the features of a rigid lithospheric unit with well-defined boundaries, Iberia grouped together different crustal blocks undergoing specific movements at particular times. During the Mesozoic, normal, reverse or strike

  16. Mechanisms of crustal deformation in the western US

    Science.gov (United States)

    Turcotte, Donald L.

    1986-01-01

    The deformation processes in the western United States were studied, considering both deterministic models and random or statistical models. The role of the intracrustal delamination and mechanisms of crustal thinning were also examined. The application of fractal techniques to understand how the crust is deforming was studied in complex regions. Work continued on the development of a fractal based model for deformation in the western United States. Fractal studies were also extended to the study of topography and the geoid.

  17. Crustal blocks and seismicity in the Central Apennines of Italy

    Energy Technology Data Exchange (ETDEWEB)

    Bella, F.; Della Monica, G. (Rome, Univ. ' Roma III' (Italy). Dip di Fisica ' E. Amaldi' ); Caputo, M. (Rome, Univ. ' La Sapienza' (Italy). Dip. di Fisica ' E. Fermi' )

    Kinematics and geo dynamics of crustal-block structures separated by compliant zones with viscoelastic rheology play an important role in defining the conditions for many deformation events such as ordinary seismic ruptures, silent and slow earthquakes and aseismic fault creep phenomena. New seismological data from the Latium-Abruzzi carbonatic platform of central Italy fit a block-tectonic modelling previously proposed for this area on the basis of structural and paleomagnetic evidences.

  18. Spatial variation of crustal coda Q in California

    Science.gov (United States)

    Philips, W.S.; Lee, W.H.K.; Newberry, J.T.

    1988-01-01

    Coda wave data from California microearthquakes were studied in order to delineate regional fluctuations of apparent crustal attenuation in the band 1.5 to 24 Hz. Apparent attenuation was estimated using a single back scattering model of coda waves. The coda wave data were restricted to ???30 s following the origin time; this insures that crustal effects dominate the results as the backscattered shear waves thought to form the coda would not have had time to penetrate much deeper. Results indicate a strong variation in apparent crustal attenuation at high frequencies between the Franciscan and Salinian regions of central California and the Long Valley area of the Sierra Nevada. Although the coda Q measurements coincide at 1.5 Hz (Qc=100), at 24 Hz there is a factor of four difference between the measurements made in Franciscan (Qc=525) and Long Valley (Qc=2100) with the Salinian midway between (Qc=900). These are extremely large variations compared to measures of seismic velocities of comparable resolution, demonstrating the exceptional sensitivity of the high frequency coda Q measurement to regional geology. In addition, the frequency trend of the results is opposite to that seen in a compilation of coda Q measurements made worldwide by other authors which tend to converge at high and diverge at low frequencies, however, the worldwide results generally were obtained without limiting the coda lengths and probably reflect upper mantle rather than crustal properties. Our results match those expected due to scattering in random media represented by Von Karman autocorrelation functions of orders 1/2 to 1/3. The Von Karman medium of order 1/3 corresponding to the Franciscan coda Q measurement contains greater amounts of high wavenumber fluctuations. This indicates relatively large medium fluctuations with wavelengths on the order of 100 m in the highly deformed crust associated with the Franciscan, however, the influence of scattering on the coda Q measurement is

  19. Topographic Expression of Deep Crustal and Mantle Processes

    Science.gov (United States)

    Whipple, K. X.; Ouimet, W. B.; Baldwin, J. A.

    2006-12-01

    The topography of mountain ranges records much information about the history of tectonic events and climatic conditions. Although this record is not easily read, as there are many imperfectly understood factors that influence landscape morphology, there is much encouraging evidence that the river steepness index (a cousin of the Hack gradient index) exhibits a robust correlation with rock uplift rate. Published, and soon to be published, examples span a wide range of field conditions from sites around the globe (e.g., Western US, Bolivia, Nepal, China, Taiwan). Differences in substrate rock properties can have a pronounced influence on channel steepness for a given rock uplift rate, however, and analyses are best limited to regional studies where climatic conditions and lithology are largely uniform. In such settings, careful analysis of river profiles and the relief structure of the landscape can reveal important information about the history of rock uplift, recording temporal changes in uplift/river incision rates. This potential adds considerably to the value of topographic analyses, especially where uplift is driven by deep crustal or mantle processes and not clearly expressed in upper crustal structures and geodetic shortening data. However, this potential comes at the price of complicating the interpretation of the relationship between topography and the modern snapshot of deep crustal/mantle conditions provided by geophysical imaging techniques. Over what timescales does topography retain a record of past events in earth's interior? Important questions remain unanswered about the age of topography in many landscapes where deep crustal or mantle dynamics have been invoked. We discuss the factors that control landscape response time, both to an increase in rock uplift rate and to the cessation of tectonic activity, and present constraints on the antiquity of topography in several field settings.

  20. Crustal radial anisotropy beneath Cameroon from ambient noise tomography

    Science.gov (United States)

    Ojo, Adebayo Oluwaseun; Ni, Sidao; Li, Zhiwei

    2017-01-01

    To increase the understanding of crustal deformation and crustal flow patterns due to tectonic processes in Cameroon, we study the lateral variability of the crustal isotropic velocity and radial anisotropy estimated using Ambient Noise Tomography (ANT). Rayleigh and Love wave Noise Correlation Functions (NCFs) were retrieved from the cross-correlation of seismic ambient noise data recorded in Cameroon, and phase velocities at periods of 8 to 30 s were measured to perform surface wave tomography. Joint inversion of Rayleigh and Love wave data for isotropic velocity models could not fit the observed dispersions simultaneously. We attribute the Love-Rayleigh discrepancy to the presence of radial anisotropy in the crust and estimated its magnitude. Our 3-D radial anisotropic model reveals the spatial variation of strong to weak positive (Vsh > Vsv) and negative (Vsv > Vsh) radial anisotropy in the crust. We observe negative radial anisotropy in the upper crust that is associated mainly with the location of a previously reported mantle plume. The anisotropy could be attributed to the vertical alignment of fossil microcracks or metamorphic foliations due to the upwelling of plume material. A strong positive radial anisotropy is centered at the location of an inferred boundary between the Congo Craton and the Oubanguides Belt that might be related to the preferred orientation of crustal anisotropic minerals associated with shearing in this fault zone. The middle crust is characterized by a widespread negative radial anisotropy that is likely caused by the flow-induced alignment of anisotropic minerals that crystallized during magma intrusion. The magnitude of the radial anisotropy varies systematically from predominantly negative in the middle crust to positive in the lower crust. The imaged patterns of the isotropic velocity and radial anisotropy are consistent with previous studies and agree with regional tectonics.

  1. Driving and engine cycles

    CERN Document Server

    Giakoumis, Evangelos G

    2017-01-01

    This book presents in detail the most important driving and engine cycles used for the certification and testing of new vehicles and engines around the world. It covers chassis and engine-dynamometer cycles for passenger cars, light-duty vans, heavy-duty engines, non-road engines and motorcycles, offering detailed historical information and critical review. The book also provides detailed examples from SI and diesel engines and vehicles operating during various cycles, with a focus on how the engine behaves during transients and how this is reflected in emitted pollutants, CO2 and after-treatment systems operation. It describes the measurement methods for the testing of new vehicles and essential information on the procedure for creating a driving cycle. Lastly, it presents detailed technical specifications on the most important chassis-dynamometer cycles around the world, together with a direct comparison of those cycles.

  2. Fore-arc structure, plate coupling and isostasy in the Central Andes: Insight from gravity data modelling

    Science.gov (United States)

    Rutledge, Sophia; Mahatsente, Rezene

    2017-02-01

    The central segment of the Peru-Chile subduction zone has not seen a major earthquake of similar scale to the megathrust Iquique event in 1877 (Magnitude ∼8.8). The plate interface between the subducting and overriding plates in the central segment of the subduction zone is highly coupled and is accumulating elastic energy. Here, we assessed the locking mechanism and isostatic state of the Central Andes based on gravity models of the crust and upper mantle structure. The density models are based on satellite gravity data and are constrained by velocity models and earthquake hypocenters. The gravity models indicate a high density batholithic structure in the fore-arc, overlying the subducting Nazca plate. This high density crustal structure is pressing downward into the slab and locking the plate interface. Thus, plate coupling in the Central Andes may result from pressure exerted by high density fore-arc structures and buoyancy force on the subducting Nazca plate. The increased compressive stress closer to the trench, due to the increased contact between the subducting and overriding plates, may increase the intraplate coupling in the Central Andes. To assess the isostatic state of the Central Andes, we determined the residual topography of the region (difference between observed and isostatic topography). There is a residual topography of ∼800 m in the western part of the Central Andes that cannot be explained by the observed crustal thicknesses. The residual topography may be attributed to mantle wedge flow and subduction of the Nazca plate. Thus, part of the observed topography in the western part of the Central Andes may be dynamically supported by mantle wedge flow below the overriding plate.

  3. Geophysical interpretation of satellite laser ranging measurements of crustal movement in California

    Science.gov (United States)

    Cohen, Steven C.

    1985-12-01

    As determined by satellite laser ranging the rate of contraction of a 900 km baseline between sites located near Quincy in northern California and San Diego in southern California is about 61-65 mm/yr with a formal uncertainty of about 10 mm/yr (Christodoulidis et al., 1985). The measured changes in baseline length are a manifestation of the relative motion between the North America and Pacific tectonic plates. This long baseline result is compared to measurements made by more conventional means on shorter baselines. Additional information based on seismiscity, geology, and theoretical modelling is also analyzed. Deformation lying within a few tens of kilometers about the major faults in southern California accounts for most, but not all, of the observed motion. Further motion is attributable to a broader-scale deformation in southern California. Data suggesting crustal movements north of the Garlock fault, in and near the southern Sierra Nevada and local motion at an observatory are also critically reviewed. The best estimates of overall motion indicated by ground observations lie between 40 and 60 mm/yr. This lies within one or two standard deviations of that deduced from satellite ranging but the possibility of some unresolved deficit cannot be entirely dismissed. The long time scale RM2 plate tectonic model of Minster and Jordan (1978) predicts a contraction between 47 and 53 mm/yr depending on the extension rate of the Basin and Range. Thus the ground based observations, SLR results, and RM2 rates differ at about the 10 mm/yr level but are not inconsistent with one another within the data and model uncertainties.

  4. Characteristics of Lower Crustal Granulite Xenoliths from the East Qinling Orogenic Belt and Their Tectonic Significance

    Institute of Scientific and Technical Information of China (English)

    1994-01-01

    The Tongbai granulites are present mainly as xenoliths in granodioritic gneisses. The xenoliths with a zircon age of 470Ma are older than host rocks of granoioritic gneisses which yield a zircon age of 435Ma. It is suggested that the granulites were transported from the lower crust to the upper level along with granodioritic magma. Geothermormetrical and geobarometrical strdies based on the coexisting minerals(Opx-Cpx and Opx-Gar) show that the granulites were crystallized at 818-840℃ and 9.5-9.8×108 Pa corresponding to the lower crust. Tectonically,the Shangdan suture zone constitutes the boundary between the North China and Yangtze plates.The zone is char-acterized by the occurrence of ophiolites in the western part and by that of granulites in the eastern part.So the western part marks the upper crustal level of the Qinling belt, while the eastern part represents the exposure of a deeper level.The results of isotopic dating and the geochemical character istics of the xenoliths are consistent with those of meta-tholeiites of the ophiolites in the western part. Therefore ,it is assumed that both ophiolites found in the west and granulites found in the east all represent the remnants of the ancient Qinling ocean plate .The difference is that the ophiolites are pieces of obducted fragments from the ocean floor during the subduction in the Early Palaeozoic. However,in the Tongbai area, when the ocean floor was subducting towards the lower crust, it underwent a granulite facies metamorphism.Subsequently, granodioritic magma formed by partial melting trapped some fragments of granulite upwards.

  5. Moho depth and crustal composition in Southern Africa

    DEFF Research Database (Denmark)

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

    2013-01-01

    heterogeneous crustal structure with short wavelength variations in thickness (H), Vp/Vs-ratio (composition), and Moho sharpness, which defines ~20 blocks that do not everywhere coincide with surface tectonic features. In the Zimbabwe Craton, the Tokwe block has H = 35–38 km and Vp/Vs = 1.74–1.79 whereas...... the thicker crust in the Tati block (H = 47–51 km)may be related to deformation of the Archean crust along the cratonicmargin. Two distinct crustal blocks with similar crustal thickness (42–46 km) but significantly different Vp/Vs-ratios are recognized in the Limpopo Belt. Extreme values of 1......-existing lower crust, which is further supported by a very sharp Moho transition. The exposed cross-section in the Vredefort impact crater is non-representative of cratonic crust due to shallowMoho (34 km) and high Vp/Vs ~ 1.80 attributed to shock metamorphism. High Vp/Vs = 1.76 is typical of the Witwatersrand...

  6. 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.

  7. Crustal structure of the Eastern Gulf of Mexico

    Science.gov (United States)

    Nwafor, Emeka

    The Gulf of Mexico initiated in the Late Triassic as South America and Africa separated from North America during the break up of Pangea. Previous studies indicate three models for the opening of the GOM. These include counter clockwise rotation of the Yucatan Block, rotation of the Yucatan Block about the same pole of rotation as those describing seafloor spreading in the central North Atlantic, and clockwise rotation of the Yucatan Block. There is much debate about the margin type and the crustal structure of the Eastern Gulf of Mexico (EGOM), especially below the depth of 6 km where crustal structure is poorly imaged on seismic reflection data. Two 2.5-D forward gravity and magnetic models across the margin are presented. These are constrained by basement picks from sparse seismic reflection and refraction data, spectral analysis of gravity data to determine the depth to source, magnetic susceptibility derived from results from other margins, the empirical relationship between P-wave velocity and density, and crustal scale isostatic modeling. The models, combined with a kinematic reconstruction of the GOM, show that: 1) it is a rifted margin; 2) the point where the Moho deepens downward from ˜17 km to ˜32 km is approximately 50 km outboard of the topographic shelf edge; 3) the carbonate bank retreated by several kilometers from its original termination due to the action of contourite currents; 4) extension and subsidence was accommodated with little shallow brittle faulting; 5) oceanic lithosphere is possibly outboard of the EGOM continental slope.

  8. Driving on the Descartes

    Science.gov (United States)

    1972-01-01

    Astronaut John W. Young, Apollo 16 mission commander, drives the 'Rover', Lunar Roving Vehicle (LRV) to its final parking place near the end of the third extravehicular activity (EVA-3) at the Descartes landing site. Astronaut Charles M. Duke Jr., Lunar Module pilot, took this photograph looking southward. The flank of Stone Mountain can be seen on the horizon at left. The shadow of the Lunar Module 'Orion' is visible in the foreground.

  9. Estimation of crustal movements using the Global Positioning System (GPS) measurements along Nile Valley area, Egypt from 2007 to 2012

    Science.gov (United States)

    Sakr, Kamal; Radwan, Ali M.; Rashwan, Mohamed; Gomaa, Mahmoud

    2015-06-01

    The Nile Valley in Egypt is located to the west of the Red Sea Rift and to the south of the Mediterranean Sea. Recently, some moderate earthquakes were occurred along the Nile Valley at the eastern and western side. Tectonically, the Nile Valley is controlled by NW-SE, NE-SW, E-W and N-S tectonic trends due to the exerted forces and stresses. A program of studying the recent crustal movements in Egypt has been started since 1984 to cover some areas which are characterized by the occurrence of felt Earthquakes. One of these areas is the Nile Valley. About 6 moderate earthquakes with magnitudes more than 4 were occurred on both sides of River Nile. The present study aimed to determine the recent crustal movement parameters along the Nile Valley using the Global Positioning System (GPS) measurements. To achieve this mission, a GPS network consisting of ten geodetic stations has been established on both sides along the Nile Valley area. GPS measurements have been collected from 2007 to 2012. The collected data were processed using Bernese 5.0 Software. The result of the data analysis indicates that the rate of local velocity is small ranging from 1 to 4 mm/year. This rate is consistent with the low rate of occurrence of recent earthquakes activity along the Nile Valley area. But, the results obtained from the calculation of the regional velocity indicated that the velocity of the GPS stations including the African Plate motion is about 25 mm/year in the northeast direction which is consistent with the African Plate motion direction.

  10. RECENT GEODYNAMICS OF INTRACONTINENTAL AREAS: INSTRUMENTAL AND GEOMORPHOLOGICAL ASSESSMENT OF CRUSTAL MOVEMENTS AND DEFORMATION IN CENTRAL ASIA

    Directory of Open Access Journals (Sweden)

    V. А. Sankov

    2015-09-01

    Full Text Available Studies of recent geodynamics have been conducted by the Institute of the Earth’s Crust, SB RAS since 1998. Present-day crustal deformations are monitored at the geodynamic GPS polygon established by the Laboratory of Recent Geodynamics in the Mongol-Baikal region. Original methods and techniques using specialized equipment are applied to research intra-continental tectonic deformation and have already provided original scientific results. Independent data are received concerning the onset and character of processes of neotectonic activation and the state of stresses and deformation of the crust in the southern part of Siberia and in Mongolia. A model of the Late Cenozoic and contemporary geodynamics of the Mongol-Siberian mobile area is proposed. With application of GPS geodesy methods, quantitative parameters of present-day horizontal movements and deformations are determined for Central Asia and a part of the Far East at different scale levels. Present-day velocities of extension of the Baikal rift are estimated, and parameters of rotation of the Amur plate relative to Eurasia are calculated. Data on long-term and contemporary deformation are subject to comparative analyses. The Laboratory develops studies of present-day and historical seismicity in relation to processes of contemporary faulting in active tectonic zones of inter-plate boundaries and diffusive activation of subactive intraplate territories. The first results are obtained in studies of local crustal deformation by methods of satellite radar interferometry and ground polygonometry. Jointly with other institutes of SB RAS, the Laboratory conducts instrumental studies of interaction between the lithosphere and the ionosphere. Looking further ahead, the main scientific fields and prospects of the Laboratory are highlighted.  

  11. Vehicle License Plate Recognition Syst

    Directory of Open Access Journals (Sweden)

    Meenakshi,R. B. Dubey

    2012-12-01

    Full Text Available The vehicle license plate recognition system has greater efficiency for vehicle monitoring in automatic zone access control. This Plate recognition system will avoid special tags, since all vehicles possess a unique registration number plate. A number of techniques have been used for car plate characters recognition. This system uses neural network character recognition and pattern matching of characters as two character recognition techniques. In this approach multilayer feed-forward back-propagation algorithm is used. The performance of the proposed algorithm has been tested on several car plates and provides very satisfactory results.

  12. Is plate tectonics needed to evolve technological species on exoplanets?

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2016-07-01

    tectonics for developing a technological species is examined via a thought experiment using two otherwise identical planets: one with plate tectonics and the other without. A planet with oceans, continents, and plate tectonics maximizes opportunities for speciation and natural selection, whereas a similar planet without plate tectonics provides fewer such opportunities. Plate tectonics exerts environmental pressures that drive evolution without being capable of extinguishing all life. Plate tectonic processes such as the redistribution of continents, growth of mountain ranges, formation of land bridges, and opening and closing of oceans provide a continuous but moderate environmental pressure that stimulates populations to adapt and evolve. Plate tectonics may not be needed in order for life to begin, but evolution of technological species is favored on planets with oceans, continents, plate tectonics, and intermittently clear night sky.

  13. Using plate mapping to examine portion size and plate composition for large and small divided plates.

    Science.gov (United States)

    Sharp, David E; Sobal, Jeffery; Wansink, Brian

    2014-12-01

    Does the size of a plate influence the serving of all items equally, or does it influence the serving of some foods - such as meat versus vegetables - differently? To examine this question, we used the new method of plate mapping, where people drew a meal on a paper plate to examine sensitivity to small versus large three-compartment divided plates in portion size and meal composition in a sample of 109 university students. The total drawn meal area was 37% bigger on large plates than small plates, which showed that the portion of plate coverage did not differ by plate size. Men and women drew bigger vegetable portions and men drew bigger meat portions on large plates when compared to small plates. These results suggest that men and women are differentially sensitive to plate size for overall meal size and for meal composition. Implications for decreasing portion size and improving meal balance are that plate size may influence portion size and change the proportions of foods served.

  14. Testing for Changes in Crustal Velocity at the Tocopilla Earthquake, Northern Chile

    Science.gov (United States)

    Richter, T.; Asch, G.; Kind, R.

    2011-12-01

    We use two different techniques to investigate the region between Antofagasta and Arica in northern Chile for crustal velocity changes. Data are taken from the 19 broadband stations of the IPOC project (Integrated Plate Boundary Observatory Chile) operating partly since 2006 by GFZ and Institut de Physique du Globe de Paris (IPGP). In the neighborhood of the seismic stations an M7.0 earthquake occurred near Tocopilla on 14 November 2007. Other studies have shown that in the course of such earthquakes seismic velocities may be changing (e.g. Brenguier et al. 2008). The first method is testing for phase shifts in receiver functions. To avoid varying travel paths of different events we compare events located in small source regions. Although temporal variations have been found in receiver functions for the Parkfield M6.0 and San Simeon M6.5 earthquakes (Audet 2006) we cannot find any variations exceeding the noise level of our dataset at the time of the M7.0 earthquake near Tocopilla. Therefore the data is analyzed with the help of cross-correlation technique of ambient seismic noise (Bensen et al. 2007). Compared to the first method it has the advantage of regularly available correlation functions (e.g. 1 per day). We report on first results.

  15. Efficient transport of droplet sandwiched between saw-tooth plates.

    Science.gov (United States)

    Wang, Liya; Wu, Hengan; Wang, Fengchao

    2016-01-15

    The transport of droplet sandwiched between smooth and saw-tooth plates was investigated using molecular dynamics method. The repeated opening and closing of the plates result in sequential stretching and squeezing of the droplet, which provide the driving force. The asymmetrical saw tooth obstructs the backward motion of the droplet, and gives rise to a net forward displacement of the droplet in every opening and closing cycle. This unidirectional motion facilitates the efficient droplet transport, which is referred to as the ratchet-like effect in this work. Our simulations also reveal that the influence of the surface wettability on the droplet transport is different for saw-tooth and smooth plates. Droplet transport efficiency exhibits monotonic decrease with the increase of the solid-liquid interactions for saw-tooth plates. While for smooth plates, unidirectional droplet movement was only observed for certain solid-liquid interactions. Taken together these simulation results and theoretical analysis, we demonstrate that hydrophobic saw-tooth plates can improve the transport efficiency significantly. These findings not only enhance our understanding of the droplet transport from atomistic scale, but also are beneficial to practical applications in designing of micro- and nano-fluidic systems.

  16. Near-Field Acoustic Holography of Chladni Plate

    Science.gov (United States)

    Kim, Hyunhee; Kim, Yunbog; Jeon, Dongryul

    2007-03-01

    Characteristic modes of a Chladni plate can be visualized by sand gathering along the nodal lines. Although one can view two-dimensional vibration patterns, the sand pattern does not show a bending of antinode. We used near-field acoustic holography to reconstruct a three-dimensional image of circular and rectangular Chladni plates. The sound pressure was measured using four scanning microphones located 3 mm above a Chladni plate. A reference microphone was placed close to a speaker which drives the plate. A total of 60x60 data were collected from 30x30 cm^2 area and processed using MATLAB in accordance with the algorithm of near-field acoustic holography. The three-dimensional graphic image of the vibrating plate reconstructed this way not only matched the sand pattern but also visualized the bending of the plate. Propagation of the sound pressure could be also visualized three-dimensionally. The plot of sound pressure against the distance showed the 1/distance^2 dependence as expected. Sound is a difficult subject in physics class because it is invisible. Our results demonstrate that near-field acoustic holography combined with computer graphic is an effective tool to visualize the generation of a sound.

  17. Early Archaean crustal collapse structures and sedimentary basin dynamics

    Science.gov (United States)

    Nijman, W.; de Vries, S. T.

    2003-04-01

    Observations in the Lower Archaean (>3.3 Ga) of the Pilbara and Kaapvaal Cratons point to a direct genetic relationship between the thickness and facies distribution of volcano-sedimentary basin fills and non-linear patterns of extensional faults in early Earth. The basin fills consist of mafic volcanic products, largely pillow basalts, with distinct phases of intermediate to felsic volcanism and concentration of silica, either primary or secondary, in sediments deposited near base-level. The extensional structures are listric growth-faults, arranged in superposed arrays, that migrated upwards with the growth of the Early Archaean stratigraphical column. The faults linked intermittently occurring shallow-level felsic intrusions via porphyry pipes, veins and hydrothermal circulations with the surficial sedimentary basin fill of cherty sediments, concurrent mineralisation and alteration products. The non-linear pattern of the fault systems is recorded by their restored facing directions over large areas and corresponds best with over 100 km-wide (semi)circular crustal collapse structures. Crustal collapse, and therefore basin formation, did not represent a reaction to compression and crustal thickening. It also had no relationship with the present-day distribution of granitoid domes and greenstone belts. Collapse followed crustal uplift recorded by shallowing of the basin fill from a general subaqueous level of deposition of pillow basalts towards zero water level for the sediments and low-relief emersion. Maxima of extension coincide with the appearance of intermediate or felsic volcanic rocks in the overall mafic environment. The geodynamical setting is most appropriately explained by crustal delamination and related plume activity. Although individual features may be compared to Phanerozoic and Recent geological phenomena, like calderas, for the collapse structures as a whole such younger counterparts cannot be found. Rather they have their equivalents in collapse

  18. Temperature field of steel plate cooling process after plate rolling

    Directory of Open Access Journals (Sweden)

    Huijun Feng, Lingen Chen, Fengrui Sun

    2015-01-01

    Full Text Available Based on numerical calculation with Matlab, the study on cooling process after plate rolling is carried out, and the temperature field distribution of the plate varying with the time is obtained. The effects of the plate thickness, final rolling temperature, cooling water temperature, average flow rate of the cooling water, carbon content of the plate and cooling method on the plate surface and central temperatures as well as final cooling temperature are discussed. For the same cooling time, the plate surface and central temperatures as well as their temperature difference increase; with the decrease in rolling temperature and the increase in average flow rate of the cooling water, the plate surface and central temperatures decrease. Compared with the single water cooling process, the temperature difference between the plate centre and surface based on intermittent cooling is lower. In this case, the temperature uniformity of the plate is better, and the corresponding thermal stress is lower. The fitting equation of the final cooling temperature with respect to plate thickness, final rolling temperature, cooling water temperature and average flow rate of the cooling water is obtained.

  19. Real Plates and Dubious Microplates

    Science.gov (United States)

    Kogan, M. G.; Steblov, G. M.

    2008-12-01

    From the onset of plate tectonics, the existence of most of the plates was never put in doubt, although the boundaries of some plates, like Africa, were later revised. There are however, two microplates in northeast Asia, the Amurian and Okhotsk, whose existence and the sense of rotation was revised several times. The rms value of plate-residual GPS velocities is 0.5-0.9 mm/a for sets of stations representing the motion of the following plates: Antarctic, Australian, Eurasian, North American, Nubian, Pacific, and South American. This value can be regarded as an upper bound on deviation of real plates from infinite stiffness. The rms value of plate-residual GPS velocities is 1.2-1.8 mm/a for the Indian, Nazca, and Somalian plates. Higher rms values for India and Nazca are attributed to the noisier data. The higher rms value for Somalia appears to arise from the distributed deformation to the east of the East African Rift; whether this statement is true can only be decided from observations of denser network in the future. From the analysis of plate-residual GPS velocities, the Canadian Arctic and northeastern Siberia belong to the North American plate. The detailed GPS survey on Sakhalin Island shows that the Sea of Okhotsk region also belongs to the North American plate while the region to the west of it belongs to the Eurasian plate. These results provide a constraint on the geometry of the North American plate and put in doubt the existence of smaller plates in northeast Asia.

  20. Global plate tectonics and the secular motion of the pole

    Science.gov (United States)

    Soler, T.

    1977-01-01

    Astronomical data compiled during the last 70 years by the international organizations providing the coordinates of the instantaneous pole clearly shows a persistent drift of the mean pole. The differential contributions to the earth's second-order tensor of inertia were obtained and applied, resulting in no significant displacement of the earth's principal axis. In view of the above, the effect that theoretical geophysical models for absolute plate velocities may have on an apparent displacement of the mean pole as a consequence of station drifting was analyzed. The investigation also reports new values for the crustal tensor of inertia (assuming an ellipsoidal earth) and the orientation of its axis of figure, reopening the old speculation of a possible sliding of the whole crustover the upper mantle, including the supporting geophysical and astronomic evidence.

  1. Developing the plate tectonics from oceanic subduction to continental collision

    Institute of Scientific and Technical Information of China (English)

    ZHENG YongFei; YE Kai; ZHANG LiFei

    2009-01-01

    The studies of continental deep subduction and ultrahigh-pressure metamorphism have not only promoted the development of solid earth science in China,but also provided an excellent opportunity to advance the plate tectonics theory.In view of the nature of subducted crust,two types of subduction and collision have been respectively recognized in nature.On one hand,the crustal subduction occurs due to underflow of either oceanic crust (Pacific type) or continental crust (Alpine type).On the other hand,the continental collision proceeds by arc-continent collision (Himalaya-Tibet type) or continent-continent collision (Dabie-Sulu type).The key issues in the future study of continental dynamics are the chemical changes and differential exhumation in continental deep subduction zones,and the temporal-spatial transition from oceanic subduction to continental subduction.

  2. Plate-wide stress relaxation explains European Palaeocene basin inversions

    DEFF Research Database (Denmark)

    Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.

    2005-01-01

    of compression, mainly from the Alpine orogen. Here we show that the main phases differed both in structural style and cause. The Cretaceous phase was characterized by narrow uplift zones, reverse activation of faults, crustal shortening, and the formation of asymmetric marginal troughs. In contrast, the Middle...... Paleocene phase was characterized by domal uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence related inversion upon relaxation...... of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe....

  3. Late Jurassic Crustal Thickening in the Mesozoic Arc of Ecuador and Colombia: Implications on the Evolution of Continental Arcs.

    Science.gov (United States)

    Vanegas, J.; Cardona, A.; Blanco-Quintero, I.; Valencia, V.

    2014-12-01

    The tectonic evolution of South America during the Jurassic is related to the subduction of the Farallon plate and the formation of a series of continental arcs. In the northern Andes such arcs have been considered as controlled by extensional dominated tectonics. Paleomagnetic constraints have also suggested that between the Early and Late Jurassic several crustal domains were translate along the continental margin in association with strain partitioning in the convergent margin. A review of the character of the Salado terrane in the Cordillera Real of Ecuador indicates that it includes extensively deformed and metamorphosed volcano-sedimentary rocks that have achieved a greenschist to amphibolite facies event with chloritoid and garnet. This rocks are tightly associated with a ca. 143 Ma syn-tectonic granodiorite to monzogranite batholith that is also extensively milonitized.A similar Late Jurassic crustal thickening event that apparently affected volcano-sedimentary rocks have been also recently suspected in the Central Cordillera of the Colombian Andes in association with Jurassic plutonic rocks (Blanco-Quintero et al., 2013) It is therefore suggested that during the Late Jurassic the Northern Andes experienced significant contractional tectonics. Such crustal thickening may be related to either the active subduction setting were the crustal slivers formed in relation to oblique convergence are transfered and re-accreted to the margin and triggered the deformational event or to a collisional event associated to the arrival of an allocthonous terrane. New geochronological constraints on the metamorphic evolution and precise understanding on the relations between magmatism and deformation are going to be obtain in the Salado Terrane to appropriately test this hypothesis and contribute to the understanding of the extensional to compressional tectonic switching in continental arcs. Blanco-Quintero, I. F., García-Casco, A., Ruíz, E. C., Toro, L. M., Moreno, M

  4. Magnetometer Data Tests Models for the Origin of the Martian Crustal Dichotomy; Dichotomy Models Constrain Timing of Martian Magnetic Field

    Science.gov (United States)

    Gilmore, M. S.

    1999-01-01

    Measurements recently supplied by the MGS Magnetometer/Electron Reflectometer (MAG/ER) on MGS can be applied to test theories of the origin of the martian crustal dichotomy. Strong (+/- 1500 nT) magnetic anomalies are observed in the Martian crust. The observations can be summarized as follows: 1) strong crustal magnetic sources are generally confined to the southern highlands, although weaker (approx. 40 nT) anomalies were observed during close periapsis; 2) strong magnetic anomalies are absent in the vicinity of Hellas and Argyre; 3) the anomalies in the region 0 deg to 90 deg S, 120 deg to 240 deg west have a linear geometry, strike generally east west for 1000s km, and show several reversals. This latter point has led to the suggestion that some form of lateral plate tectonics may have been operative in the southern highlands of Mars. These observations have led previous workers to hypothesize that the magnetic anomalies were present prior to and were destroyed by the formation of Hellas and Argyre. As such large impacts are confined to the era of heavy bombardment, this places the time of formation of large magnetic anomalies prior to approx. 3.9 Ga. One obvious extension of this is that the northern lowlands lack significant anomalies because they were erased by impacts and/or the northern lowlands represent crust completely reheated above the Curie temperature. Preliminary observations of the distributions of the large crustal magnetic anomalies show that many of them extend continuously over the highland lowland boundary. This occurs particularly north of the boundary between 30 deg W and 270 deg W, corresponding to northern Arabia, but also occurs in southern Elysium (approx. 10 deg S, 200 deg) and the SW portion of Tharsis (approx. 15 deg S, 140 deg). This suggests that, in these areas, Noachian crust containing the greater than 3.9 Ga magnetic signature, lies beneath the northern highlands. This geometry can be used to test models for the formation of

  5. "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

  6. A felsic MASH zone of crustal magmas - Feedback between granite magma intrusion and in situ crustal anatexis

    Science.gov (United States)

    Schwindinger, Martin; Weinberg, Roberto F.

    2017-07-01

    Magma mixing and mingling are described from different tectonic environments and are key mechanisms in the evolution of granitoids. The literature focuses on the interaction between mafic and felsic magmas with only limited research on the interaction between similar magmas. Here, we investigate instead hybridization processes between felsic magmas formed during the 500 Ma Delamerian Orogeny on the south coast of Kangaroo Island. Field relations suggest that a coarse, megacrystic granite intruded and interacted with a fine-grained diatexite that resulted from combined muscovite dehydration and water-fluxed melting of Kanmantoo Group turbidites. The two magmas hybridized during syn-magmatic deformation, explaining the complexity of relationships and variability of granitoids exposed. We suggest that granite intrusion enhanced melting of the turbidites by bringing in heat and H2O. With rising melt fraction, intrusive magmas became increasingly unable to traverse the partially molten terrane, creating a positive feedback between intrusion and anatexis. This feedback loop generated the exposed mid-crustal zone where magmas mixed and homogenized. Thus, the outcrops on Kangaroo Island represent a crustal and felsic melting-assimilation-storage-homogenization (felsic MASH) zone where, instead of having direct mantle magma involvement, as originally proposed, these processes developed in a purely crustal environment formed by felsic magmas.

  7. The dynamics of plate tectonics and mantle flow: from local to global scales.

    Science.gov (United States)

    Stadler, Georg; Gurnis, Michael; Burstedde, Carsten; Wilcox, Lucas C; Alisic, Laura; Ghattas, Omar

    2010-08-27

    Plate tectonics is regulated by driving and resisting forces concentrated at plate boundaries, but observationally constrained high-resolution models of global mantle flow remain a computational challenge. We capitalized on advances in adaptive mesh refinement algorithms on parallel computers to simulate global mantle flow by incorporating plate motions, with individual plate margins resolved down to a scale of 1 kilometer. Back-arc extension and slab rollback are emergent consequences of slab descent in the upper mantle. Cold thermal anomalies within the lower mantle couple into oceanic plates through narrow high-viscosity slabs, altering the velocity of oceanic plates. Viscous dissipation within the bending lithosphere at trenches amounts to approximately 5 to 20% of the total dissipation through the entire lithosphere and mantle.

  8. Drive system failure control for distributed drive electric vehicles

    Science.gov (United States)

    Liu, Tao; Tang, Yuan; Wang, Jianfeng; Li, Yaou; Yang, Na; Liu, Yiqun

    2017-09-01

    Aiming at the failure problem of distributed electric drive vehicle, the conventional control strategy of drive system failure is designed according to the characteristics of each wheel torque independent control and the redundant configuration of the power unit. On this basis, combined with the traditional body stability control technology, the direct yaw moment control method is used. The simulation results show that the conventional control method designed of the drive system failure can effectively improve the driving condition of the vehicle. The driving stability of the vehicle is further improved after the direct yaw torque control is applied.

  9. Plate Full of Color

    Centers for Disease Control (CDC) Podcasts

    2008-08-04

    The Eagle Books are a series of four books that are brought to life by wise animal characters - Mr. Eagle, Miss Rabbit, and Coyote - who engage Rain That Dances and his young friends in the joy of physical activity, eating healthy foods, and learning from their elders about health and diabetes prevention. Plate Full of Color teaches the value of eating a variety of colorful and healthy foods.  Created: 8/4/2008 by National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP).   Date Released: 8/5/2008.

  10. Dynamics of Tectonic Plates

    CERN Document Server

    Pechersky, E; Sadowski, G; Yambartsev, A

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend on features of resistant forces.

  11. Dynamics of Tectonic Plates

    OpenAIRE

    2014-01-01

    We suggest a model that describes a mutual dynamic of tectonic plates. The dynamic is a sort of stick-slip one which is modeled by a Markov random process. The process defines a microlevel of the dynamic. A macrolevel is obtained by a scaling limit which leads to a system of integro-differential equations which determines a kind of mean field systems. Conditions when Gutenberg-Richter empirical law are presented on the mean field level. These conditions are rather universal and do not depend ...

  12. Crustal Structure of the Central Anatolia - Eastern Mediterrenean, Turkey and Cyprus from Wide-Angle Seismic Data

    Science.gov (United States)

    Denli, Alper; Gürbüz, Cemil; Mechie, James; Weber, Michael

    2016-04-01

    As a part of the CyprusArc project, a seismic wide-angle reflection/refraction profiles were carried out in March 2010. The 300 km and 45 km long north-south trending profiles extended from Cihanbeyli in Central Anatolia to Anamur in eastern Mediterranean, Turkey and in southern Cyprus, respectively. The purpose of the project is to observe the impact of the transition from subduction to continent-continent collision of the African plate with the Anatolian plate. The field experiment comprised two land shots (1125 kg explosives) in Turkey and airguns (98 cubic liters) on the Mediterranean sea, beneath Cyprus. 244 stations were installed on land for data acquisition. 77 three-component sensors and 167 vertical-component sensors were installed along ~300 km distances between Cihanbeyli and Anamur with an average spacing of 1.25 km, on Turkey. 24 three-component sensors and 21 vertical component sensors were deployed along 45 km distances on land at southern Cyprus with an average spacing of 1.25 km. To reveal a good data quality, a visual quality check, frequency analysis and filtering were applied to the seismic data. Two land shots on Turkey (also recorded on Cyprus) and airgun shots on the Mediterranean sea beneath Cyprus, geological and previous seismic investigations provide information to derive a layered velocity models beneath from the Anatolian plateau to eastern Mediterranean, Turkey and for the ophiolite complex on Cyprus. After picking observed seismic phases, finite-differences ray tracing of the wide-angle data leads a 2-D crustal P-wave velocity models. The results show moho depth increases from 38 km to 45 km depth along north-south trending profile on Turkey and crustal thinning between south Turkey and Cyprus from 40 km to 36 km. Obtained models were further refined using forward modeling to generate synthetic seismograms for individual shot gathers. Thus, by varying the velocity structure, the theoretical times and amplitudes of the various

  13. Change in the pattern of crustal seismicity at the Southern Central Andes from a local seismic network

    Science.gov (United States)

    Nacif, Silvina; Lupari, Marianela; Triep, Enrique G.; Nacif, Andrés; Álvarez, Orlando; Folguera, Andrés; Gímenez, Mario

    2017-06-01

    Shallow seismicity in the Southern Central Andes is associated with interplate earthquakes due to the subduction of the Nazca plate beneath the South American plate and neotectonic activity, mainly located in the retro-arc region. However, this pattern changes drastically south of 34°S within the transition zone at the Southern Central Andes where crustal seismicity associated with mountain-building processes concentrates at the fore-arc and intra-arc region. In order to define more accurately this transition we used data from a high density-seismic network over the Chilean fore-arc and axial Andean sector ( 33-34.5°S). We obtained a constraint data set of 77 seismic events located mostly in the Principal Cordillera western flank in the first 10 km of the upper crust. This cluster implies an abrupt change in the pattern of seismicity at the Southern Central Andes with a set of structures in the fore-arc and intra-arc accommodating shortening. This change in the locus of crustal seismicity and particularly its location on the fore-arc and intra-arc south of 34°S is discussed on the light of different hypotheses among which changes in the precipitation pattern and erosion along the Andes were favored. Focalized erosion associated with direction of prevailing Pacific winds south of 34°S could determine subcritical conditions that could be adjusted by out-of-sequence deformation causing crustal earthquakes in the fore-arc region, becoming the retro-arc zone nearly fossilized from a deformational point of view. Additionally, trench sediments associated with this change in the precipitation pattern could also favor decoupling of the subduction zone inhibiting retro-arc seismicity, although it does not explain activation of fore-arc structures south of 34°S and their absence north of this latitude. Finally, inhomogeneous distribution of seismicity through the fore-arc zone south of 34°S is discussed on the light of variable elastic thicknesses.

  14. Evidence for a deep crustal hot zone beneath the Diamante Caldera-Maipo volcanic complex, Southern Volcanic Zone

    Science.gov (United States)

    Drew, D.; Murray, T.; Sruoga, P.; Feineman, M. D.

    2010-12-01

    Subduction zones at convergent continental margins are dynamic environments that control the long-term evolution and interaction of the crust and residual mantle. The Southern Volcanic Zone (SVZ) of the Andes formed as a result of volcanic activity and uplift due to the eastern subduction of the Nazca Plate beneath the South American Plate. Maipo and neighboring volcanoes in the northern SVZ are unique in that the continental crust is exceptionally thick (~50 km), causing the mantle-derived magma to stall and interact with the crust at multiple levels prior to eruption. Maipo is an andesite/dacite stratovolcano that lies within the Diamante Caldera, which formed approximately 450 Ka during an explosive eruption that produced 350 km3 of rhyolitic ignimbrite. Following post-caldera reactivation Maipo has undergone a complex evolution, first erupting 86 Ka and experiencing seven eruptive events extending to historic times. The Maipo lavas represent a unique geochemical evolution resulting from fractional crystallization, crustal assimilation, and magma mixing in the lower and upper crust. By analyzing trace element compositions, major element compositions, and 87Sr/86Sr ratios in sixteen samples, we have begun to constrain the complex geochemical processes that formed this volcano and contribute to the differentiation of Andean continental crust. The major element analysis of the samples reflects the extent of differentiation resulting in dacite to andesite volcanic rock, and was used to distinguish between the seven eruptive events. The trace elements and Sr isotope ratios reflect the composition of the source rock, the extent of crustal assimilation, and the crystallization of minerals from the resulting mantle derived magma. The SiO2 weight percent (ranging from 54.3 to 68.5%) and 87Sr/86Sr ratios (0.7048 to 0.7057) show a linear correlation nearly identical to that reported by Hildreth and Moorbath (1988, CMP 98, 455-489) for nearby Cerro Marmolejo, suggesting a

  15. ~55Ma Aged High Topography of the Lhasa Block From Stable and Clumped Isotope Paleoaltimetry: Implications for ~50±25% Crustal Mass Deficit in the India-Asia Collisional System

    Science.gov (United States)

    Rowley, D. B.; Ingalls, M.; Colman, A. S.; Currie, B.; Li, S.; Olack, G.; Lin, D.

    2015-12-01

    We reconstruct the ~55 Ma paleo-elevation of the pre- to syn-collisional Linzizong arc by coupling carbonate-derived oxygen stable isotope measurements (d18Oc) with paleotemperatures derived from the Δ47-'clumped' isotope paleothermometer (T(Δ47)). We estimate a pre- to early syn-collisional (~54 ± 2 Ma) paleo-elevation of the Penbo/Linzhou region of >4100 ± 550 meters. This provides the first well-constrained elevation estimate of the pre-collisional Linzizong Volcanic arc in the southern Tibetan Plateau. Our results indicate that high relief at low latitude did indeed prevail on the Asian "Andean" margin prior to collision. We use the most recent plate kinematic constraints to compute the mass flux associated with India-Asia convergence with uncertainty as a function of time. Integration of mass flux as a function of time, together with estimates of the diachronous collision age with uncertainty and corresponding suture zone length with uncertainty allow explicit estimates with uncertainties of pre-collisional crustal mass. Mass balance is estimated using estimates of pre-collisional elevation and crustal thickness with their associated uncertainties relative to the pre-collisional mass. We find that ~50±25% of the collision-related crustal mass cannot be accounted for by the mass preserved in excess crustal thickness (in Himalaya, Tibet, and adjacent Asia), southeast Asian tectonic escape, and exported eroded sediments. This implies large-scale subduction of continental crust, amounting to ~15% of the total oceanic subduction flux since 56 Ma during this continent-continent collision. Contamination of the mantle by direct input of continental crustal materials rather than crust-derived sediments may be more significant than previously thought and may be responsible for crustal geochemical anomalies in mantle-derived melts.

  16. Partial melting in one-plate planets: Implications for thermo-chemical and atmospheric evolution

    Science.gov (United States)

    Plesa, A.-C.; Breuer, D.

    2014-08-01

    In the present work, we investigate the influence of partial melting on mantle dynamics, crustal formation, and volcanic outgassing of a one-plate planet using a 2D mantle convection code. When melt is extracted to form crust, the mantle material left behind is more buoyant than its parent material and depleted in radioactive heat sources. The extracted heat-producing elements are then enriched in the crust, which also has an insulating effect due to its lower thermal conductivity compared to the mantle. In addition, partial melting can influence the mantle rheology through the dehydration (water depletion) of the mantle material by volcanic outgassing. As a consequence, the viscosity of water-depleted regions increases more than two orders of magnitude compared to water-saturated rocks resulting in slower cooling rates. The most important parameter influencing the thermo-chemical evolution is the assumed density difference between the primitive and the depleted mantle material (i.e., between peridotite and harzburgite). With small or negligible values of compositional buoyancy, crustal formation including crustal delamination is very efficient, also resulting in efficient processing and degassing of the mantle. The convecting mantle below the stagnant lid depletes continuously with time. In contrast, with increasing compositional buoyancy, crustal formation and mantle degassing are strongly suppressed although partial melting is substantially prolonged in the thermal evolution. The crust shows strong lateral variations in thickness, and crustal delamination is reduced and occurs only locally. Furthermore, two to four different mantle reservoirs can form depending on the initial temperature distribution. Two of these reservoirs can be sustained during the entire evolution - a scenario possibly valid for Mars as it may explain the isotope characteristic of the Martian meteorites.

  17. Offset Compound Gear Drive

    Science.gov (United States)

    Stevens, Mark A.; Handschuh, Robert F.; Lewicki, David G.

    2010-01-01

    The Offset Compound Gear Drive is an in-line, discrete, two-speed device utilizing a special offset compound gear that has both an internal tooth configuration on the input end and external tooth configuration on the output end, thus allowing it to mesh in series, simultaneously, with both a smaller external tooth input gear and a larger internal tooth output gear. This unique geometry and offset axis permits the compound gear to mesh with the smaller diameter input gear and the larger diameter output gear, both of which are on the same central, or primary, centerline. This configuration results in a compact in-line reduction gear set consisting of fewer gears and bearings than a conventional planetary gear train. Switching between the two output ratios is accomplished through a main control clutch and sprag. Power flow to the above is transmitted through concentric power paths. Low-speed operation is accomplished in two meshes. For the purpose of illustrating the low-speed output operation, the following example pitch diameters are given. A 5.0 pitch diameter (PD) input gear to 7.50 PD (internal tooth) intermediate gear (0.667 reduction mesh), and a 7.50 PD (external tooth) intermediate gear to a 10.00 PD output gear (0.750 reduction mesh). Note that it is not required that the intermediate gears on the offset axis be of the same diameter. For this example, the resultant low-speed ratio is 2:1 (output speed = 0.500; product of stage one 0.667 reduction and stage two 0.750 stage reduction). The design is not restricted to the example pitch diameters, or output ratio. From the output gear, power is transmitted through a hollow drive shaft, which, in turn, drives a sprag during which time the main clutch is disengaged.

  18. The effects of possibly buoyant flat slab segments on Nazca and South American plate motions

    Science.gov (United States)

    Lithgow-Bertelloni, C. R.; Shea, R.; Crameri, F.

    2014-12-01

    Flat slabs are ubiquitous today and in Earth's past, present in at least 10% of present-day subduction zones. The Nazca slab is a classic example with large dip variations along strike, including two prominent flat segments in Peru and Argentina that coincide with the subduction of aseismic ridges. The origin of flat segments remain enigmatic though much work has examined the consequences for upper plate deformation and continued subduction. In the case of the Argentinian flat segment, detailed seismic imaging has shown significantly increased crustal thickness in the flat part of the slab. Our present understanding of oceanic crust formation suggests that incrased crustal thickness forms in response to larger degrees of partial melt, which in turn decrease the water content of the formed crust. The residuum from this process is depleted. The resulting combined lithospheric column is buoyant with respect to the underlying mantle, and likely cold from its contact with the overlying plate and unlikely to undergo the basalt-eclogite transition due to kinetic hindrances. This has consequences for mantle flow and the shear stresses it exerts at the base of the lithosphere and hence to plate motions. Interestingly, the motion of the Nazca-South America pair is difficult to reproduce even in the most sophisticated models (Stadler et al. 2010) without invoking special coupling, rheology or forces. We examine the effects of the subduction of neutral and buoyant flat segments on mantle flow and plate motions, globally and locally for Nazca and South America. We construct high-resolution models of the morphology and density structure of the Nazca slab and embed them in an existing global slab model. We compute the global viscous flow induced and predict plate motions consistent with the density heterogeneity and plate geometry. As an end member we also examine a Nazca slab that dips uniformly with a 30 degree dip. We find, perhaps unsurprisingly, that the most important

  19. PURE DRIVE GT

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    在2004年奥林匹克赛事中,中国的李婷,孙甜甜取得了中国网球第一个金牌一女子双打冠军。忘记不了当时李婷挥动着她的BABOLAT(百保力)网拍Pure Drive Zylon 360°激动地拥抱着孙甜甜吵闹着,幸福地哭着的情景。

  20. Electric drive design methodology

    CERN Document Server

    Jufer, Marcel

    2013-01-01

    An electric drive that is designed or adapted to a specific application must take into account all the elements of the chain of constituent elements in its use and deployment. In addition to the motor, the transmission, power electronics, control, sensors, and electrical protection systems must be taken into account. The motor and the transmission can be optimized and designed to obtain the best energy efficiency assessment, in particular for dynamic nodes. An inventory and a characterization of these various components is proposed as part of this book's examination and explanation