Calculation and Analysis of Permanent Magnet Eddy Current Loss Fault with Magnet Segmentation

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Bing Li

2016-01-01

Full Text Available This paper investigates the problem of calculating and analyzing the effect of the permanent magnet eddy current loss fault due to magnet segmentation. Taking an interior permanent magnet synchronous motor with inverter supplied as an example, the rated power of motor was 2.2 kW. Three-dimensional finite-element model was firstly established based on finite-element software. Then, the model mesh and boundary conditions were handled specially; permanent magnet eddy current loss fault was calculated and analyzed theoretically with magnet segmentation from space harmonic and time harmonic, respectively. Finally, calculation results were compared and explained. A useful conclusion for permanent magnet synchronous motor design has been obtained.

Resistivity structure of Sumatran Fault (Aceh segment) derived from 1-D magnetotelluric modeling

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Nurhasan, Sutarno, D.; Bachtiar, H.; Sugiyanto, D.; Ogawa, Y.; Kimata, F.; Fitriani, D.

2012-06-01

Sumatran Fault Zone is the most active fault in Indonesia as a result of strike-slip component of Indo-Australian oblique convergence. With the length of 1900 km, Sumatran fault was divided into 20 segments starting from the southernmost Sumatra Island having small slip rate and increasing to the north end of Sumatra Island. There are several geophysical methods to analyze fault structure depending on physical parameter used in these methods, such as seismology, geodesy and electromagnetic. Magnetotelluric method which is one of geophysical methods has been widely used in mapping and sounding resistivity distribution because it does not only has the ability for detecting contras resistivity but also has a penetration range up to hundreds of kilometers. Magnetotelluric survey was carried out in Aceh region with the 12 total sites crossing Sumatran Fault on Aceh and Seulimeum segments. Two components of electric and magnetic fields were recorded during 10 hours in average with the frequency range from 320 Hz to 0,01 Hz. Analysis of the pseudosection of phase and apparent resistivity exhibit vertical low phase flanked on the west and east by high phase describing the existence of resistivity contras in this region. Having rotated the data to N45°E direction, interpretation of the result has been performed using three different methods of 1D MT modeling i.e. Bostick inversion, 1D MT inversion of TM data, and 1D MT inversion of the impedance determinant. By comparison, we concluded that the use of TM data only and the impedance determinant in 1D inversion yield the more reliable resistivity structure of the fault compare to other methods. Based on this result, it has been shown clearly that Sumatra Fault is characterized by vertical contras resistivity indicating the existence of Aceh and Seulimeum faults which has a good agreement with the geological data.

Earthquake cycle modeling of multi-segmented faults: dynamic rupture and ground motion simulation of the 1992 Mw 7.3 Landers earthquake.

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Petukhin, A.; Galvez, P.; Somerville, P.; Ampuero, J. P.

2017-12-01

We perform earthquake cycle simulations to study the characteristics of source scaling relations and strong ground motions and in multi-segmented fault ruptures. For earthquake cycle modeling, a quasi-dynamic solver (QDYN, Luo et al, 2016) is used to nucleate events and the fully dynamic solver (SPECFEM3D, Galvez et al., 2014, 2016) is used to simulate earthquake ruptures. The Mw 7.3 Landers earthquake has been chosen as a target earthquake to validate our methodology. The SCEC fault geometry for the three-segmented Landers rupture is included and extended at both ends to a total length of 200 km. We followed the 2-D spatial correlated Dc distributions based on Hillers et. al. (2007) that associates Dc distribution with different degrees of fault maturity. The fault maturity is related to the variability of Dc on a microscopic scale. Large variations of Dc represents immature faults and lower variations of Dc represents mature faults. Moreover we impose a taper (a-b) at the fault edges and limit the fault depth to 15 km. Using these settings, earthquake cycle simulations are performed to nucleate seismic events on different sections of the fault, and dynamic rupture modeling is used to propagate the ruptures. The fault segmentation brings complexity into the rupture process. For instance, the change of strike between fault segments enhances strong variations of stress. In fact, Oglesby and Mai (2012) show the normal stress varies from positive (clamping) to negative (unclamping) between fault segments, which leads to favorable or unfavorable conditions for rupture growth. To replicate these complexities and the effect of fault segmentation in the rupture process, we perform earthquake cycles with dynamic rupture modeling and generate events similar to the Mw 7.3 Landers earthquake. We extract the asperities of these events and analyze the scaling relations between rupture area, average slip and combined area of asperities versus moment magnitude. Finally, the

Self-constrained inversion of microgravity data along a segment of the Irpinia fault

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Lo Re, Davide; Florio, Giovanni; Ferranti, Luigi; Ialongo, Simone; Castiello, Gabriella

2016-01-01

A microgravity survey was completed to precisely locate and better characterize the near-surface geometry of a recent fault with small throw in a mountainous area in the Southern Apennines (Italy). The site is on a segment of the Irpinia fault, which is the source of the M6.9 1980 earthquake. This fault cuts a few meter of Mesozoic carbonate bedrock and its younger, mostly Holocene continental deposits cover. The amplitude of the complete Bouguer anomaly along two profiles across the fault is about 50 μGal. The data were analyzed and interpreted according to a self-constrained strategy, where some rapid estimation of source parameters was later used as constraint for the inversion. The fault has been clearly identified and localized in its horizontal position and depth. Interesting features in the overburden have been identified and their interpretation has allowed us to estimate the fault slip-rate, which is consistent with independent geological estimates.

A summary of the active fault investigation in the extension sea area of Kikugawa fault and the Nishiyama fault , N-S direction fault in south west Japan

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Abe, S.

2010-12-01

In this study, we carried out two sets of active fault investigation by the request from Ministry of Education, Culture, Sports, Science and Technology in the sea area of the extension of Kikugawa fault and the Nishiyama fault. We want to clarify the five following matters about both active faults based on those results. (1)Fault continuity of the land and the sea. (2) The length of the active fault. (3) The division of the segment. (4) Activity characteristics. In this investigation, we carried out a digital single channel seismic reflection survey in the whole area of both active faults. In addition, a high-resolution multichannel seismic reflection survey was carried out to recognize the detailed structure of a shallow stratum. Furthermore, the sampling with the vibrocoring to get information of the sedimentation age was carried out. The reflection profile of both active faults was extremely clear. The characteristics of the lateral fault such as flower structure, the dispersion of the active fault were recognized. In addition, from analysis of the age of the stratum, it was recognized that the thickness of the sediment was extremely thin in Holocene epoch on the continental shelf in this sea area. It was confirmed that the Kikugawa fault extended to the offing than the existing results of research by a result of this investigation. In addition, the width of the active fault seems to become wide toward the offing while dispersing. At present, we think that we can divide Kikugawa fault into some segments based on the distribution form of the segment. About the Nishiyama fault, reflection profiles to show the existence of the active fault was acquired in the sea between Ooshima and Kyushu. From this result and topographical existing results of research in Ooshima, it is thought that Nishiyama fault and the Ooshima offing active fault are a series of structure. As for Ooshima offing active fault, the upheaval side changes, and a direction changes too. Therefore, we

Faulting at Mormon Point, Death Valley, California: A low-angle normal fault cut by high-angle faults

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Keener, Charles; Serpa, Laura; Pavlis, Terry L.

1993-04-01

New geophysical and fault kinematic studies indicate that late Cenozoic basin development in the Mormon Point area of Death Valley, California, was accommodated by fault rotations. Three of six fault segments recognized at Mormon Point are now inactive and have been rotated to low dips during extension. The remaining three segments are now active and moderately to steeply dipping. From the geophysical data, one active segment appears to offset the low-angle faults in the subsurface of Death Valley.

Paleoseismic analysis of the San Vicente segment of the El Salvador Fault Zone, El Salvador, Central America

OpenAIRE

Canora Catalán, Carolina; Villamor Pérez, María Pilar; Martínez Díaz, José J.; Berryman, K.R.; Álvarez Gómez, José Antonio; Capote del Villar, Ramón; Hernández, Walter

2012-01-01

The El Salvador earthquake of February 13th 2001 (Mw 6.6) was associated with the tectonic rupture of the El Salvador Fault Zone. Paleoseismic studies of the El Salvador Fault Zone undertaken after this earthquake provide a basis for examining the longer history of surface rupturing earthquakes on the fault. Trenching at five sites along the San Vicente segment, a 21km-long and up to 2km-wide central section of the El Salvador Fault Zone, shows that surface fault rupture has occurred at least...

Impulsive radon emanation on a creeping segment of the San Andreas fault, California

International Nuclear Information System (INIS)

King, C.-Y.

1984-01-01

Radon emanation was continuously monitored for several months at two locations along a creeping segment of the San Andreas fault in central California. The recorded emanations showed several impulsive increases that lasted as much as five hours with amplitudes considerably larger than meteorologically induced diurnal variations. Some of the radon increases were accompanied or followed by earthquakes or fault-creep events. They were possibly the result of some sudden outbursts of relatively radon-rich ground gas, sometimes triggered by crustal deformation or vibration. (Auth.)

Glacially induced faulting along the NW segment of the Sorgenfrei-Tornquist Zone, northern Denmark: Implications for neotectonics and Lateglacial fault-bound basin formation

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Brandes, Christian; Steffen, Holger; Sandersen, Peter B. E.; Wu, Patrick; Winsemann, Jutta

2018-06-01

The Sorgenfrei-Tornquist Zone (STZ) is the northwestern segment of the Tornquist Zone and extends from Bornholm across the Baltic Sea and northern Denmark into the North Sea. It represents a major lithospheric structure with a significant increase in lithosphere thickness from south to north. A series of meter-scale normal faults and soft-sediment deformation structures (SSDS) are developed in Lateglacial marine and lacustrine sediments, which are exposed along the Lønstrup Klint cliff at the North Sea coast of northern Denmark. These deformed deposits occur in the local Nørre Lyngby basin that forms part of the STZ. Most of the SSDS are postdepositional, implying major tectonic activity between the Allerød and Younger Dryas (∼14 ka to 12 ka). The occurrence of some syn- and metadepositional SSDS point to an onset of tectonic activity at around 14.5 ka. The formation of normal faults is probably the effect of neotectonic movements along the Børglum fault, which represents the northern boundary fault of the STZ in the study area. The narrow and elongated Nørre Lyngby basin can be interpreted as a strike-slip basin that developed due to right-lateral movements at the Børglum fault. As indicated by the SSDS, these movements were most likely accompanied by earthquake(s). Based on the association of SSDS these earthquake(s) had magnitudes of at least Ms ≥ 4.2 or even up to magnitude ∼ 7 as indicated by a fault with 3 m displacement. The outcrop data are supported by a topographic analysis of the terrain that points to a strong impact from the fault activity on the topography, characterized by a highly regular erosional pattern, the evolution of fault-parallel sag ponds and a potential fault scarp with a height of 1-2 m. With finite-element simulations, we test the impact of Late Pleistocene (Weichselian) glaciation-induced Coulomb stress change on the reactivation potential of the Børglum fault. The numerical simulations of deglaciation-related lithospheric

Holocene Paleoearthquake History on the Qingchuan Fault in the Northeastern Segment of the Longmenshan Thrust Zone and Its Implications

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Sun, H.; He, H.; Ikeda, Y.; Kano, K.; Shi, F.; Gao, W.; Echigo, T.; Okada, S.

2017-12-01

Although much work has been performed for faults with high slip-rates, little attention has been paid to low slip-rate faults, such as the Longmenshan Thrust Zone (LTZ). The LTZ is a long and matured fault that evolved during the Mesozoic as a structural boundary, but its Quaternary activity had been considered insignificant. The Wenchuan earthquake and the following Lushan earthquake on the central and southwestern segments of the LTZ not only demonstrate its capability for strong earthquakes but also illustrate the necessity of assessing the regional seismic potential around its northeastern extension. The sparse seismicity along the northeastern segment of the LTZ relative to the very seismically active Minshan Uplift seems to have suggested that the slip on the central LTZ transfers northeastward to the Minshan Uplift, so that its northeastern segment is inactive. However, the Wenchuan earthquake surface rupture and aftershocks extended beyond the Minshan Uplift, and revealed that the break both at and below the ground surface may have reached the northeastern segment of the LTZ raising a question that whether or not this fault segment is active. Although several studies had been carried out on the northeastern segment of the LTZ, little is known about its activity and seismic potential. To solve these problems, we conducted paleoseismological trench excavations on the Qingchuan fault (QF) in the northeastern LTZ and identified one (and the latest) event occurred in the Holocene. Based on radiocarbon dating, the event is constrained to occur between 4115-3820 B.C., and a long recurrence interval is thus estimated. Judging from the matured fault structure of the QF, the latest event was likely to have ruptured the full length of the QF, and was estimated to be Mw 7.6-7.9 according to empirical scaling laws. Using the slip rate and the elapsed time since the last event, it is estimated an accumulated seismic moment equivalent to Mw 7.5 on the QF. Considering the

Which Fault Segments Ruptured in the 2008 Wenchuan Earthquake and Which Did Not? New Evidence from Near‐Fault 3D Surface Displacements Derived from SAR Image Offsets

KAUST Repository

Feng, Guangcai

2017-03-15

The 2008 Mw 7.9 Wenchuan earthquake ruptured a complex thrust‐faulting system at the eastern edge of the Tibetan plateau and west of Sichuan basin. Though the earthquake has been extensively studied, several details about the earthquake, such as which fault segments were activated in the earthquake, are still not clear. This is in part due to difficult field access to the fault zone and in part due to limited near‐fault observations in Interferometric Synthetic Aperture Radar (InSAR) observations because of decorrelation. In this study, we address this problem by estimating SAR image offsets that provide near‐fault ground displacement information and exhibit clear displacement discontinuities across activated fault segments. We begin by reanalyzing the coseismic InSAR observations of the earthquake and then mostly eliminate the strong ionospheric signals that were plaguing previous studies by using additional postevent images. We also estimate the SAR image offsets and use their results to retrieve the full 3D coseismic surface displacement field. The coseismic deformation from the InSAR and image‐offset measurements are compared with both Global Positioning System and field observations. The results indicate that our observations provide significantly better information than previous InSAR studies that were affected by ionospheric disturbances. We use the results to present details of the surface‐faulting offsets along the Beichuan fault from the southwest to the northeast and find that there is an obvious right‐lateral strike‐slip component (as well as thrust faulting) along the southern Beichuan fault (in Yingxiu County), which was strongly underestimated in earlier studies. Based on the results, we provide new evidence to show that the Qingchuan fault was not ruptured in the 2008 Wenchuan earthquake, a topic debated in field observation studies, but show instead that surface faulting occurred on a northward extension of the Beichuan fault during

Which Fault Segments Ruptured in the 2008 Wenchuan Earthquake and Which Did Not? New Evidence from Near‐Fault 3D Surface Displacements Derived from SAR Image Offsets

KAUST Repository

Feng, Guangcai; Jonsson, Sigurjon; Klinger, Yann

2017-01-01

The 2008 Mw 7.9 Wenchuan earthquake ruptured a complex thrust‐faulting system at the eastern edge of the Tibetan plateau and west of Sichuan basin. Though the earthquake has been extensively studied, several details about the earthquake, such as which fault segments were activated in the earthquake, are still not clear. This is in part due to difficult field access to the fault zone and in part due to limited near‐fault observations in Interferometric Synthetic Aperture Radar (InSAR) observations because of decorrelation. In this study, we address this problem by estimating SAR image offsets that provide near‐fault ground displacement information and exhibit clear displacement discontinuities across activated fault segments. We begin by reanalyzing the coseismic InSAR observations of the earthquake and then mostly eliminate the strong ionospheric signals that were plaguing previous studies by using additional postevent images. We also estimate the SAR image offsets and use their results to retrieve the full 3D coseismic surface displacement field. The coseismic deformation from the InSAR and image‐offset measurements are compared with both Global Positioning System and field observations. The results indicate that our observations provide significantly better information than previous InSAR studies that were affected by ionospheric disturbances. We use the results to present details of the surface‐faulting offsets along the Beichuan fault from the southwest to the northeast and find that there is an obvious right‐lateral strike‐slip component (as well as thrust faulting) along the southern Beichuan fault (in Yingxiu County), which was strongly underestimated in earlier studies. Based on the results, we provide new evidence to show that the Qingchuan fault was not ruptured in the 2008 Wenchuan earthquake, a topic debated in field observation studies, but show instead that surface faulting occurred on a northward extension of the Beichuan fault during

Shallow high-resolution geophysical investigation along the western segment of the Victoria Lines Fault (island of Malta)

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Villani, Fabio; D'Amico, Sebastiano; Panzera, Francesco; Vassallo, Maurizio; Bozionelos, George; Farrugia, Daniela; Galea, Pauline

2018-01-01

The Victoria Lines Fault (island of Malta) is a >15 km-long and N260°-striking segmented normal fault-system, which is probably inactive since the late Pliocene. In the westernmost part, the Fomm Ir-Rih segment displays comparable geologic throw and escarpment height ( 150-170 m), moreover its hangingwall hosts thin patches of Middle Pleistocene clastic continental deposits (red beds), which are poorly preserved elsewhere. We acquired two seismic transects, by collecting ambient vibration recordings, processed by using horizontal-to-vertical spectral ratios, complemented by one high-resolution 2-D refraction tomography survey crossing this fault where it is locally covered by red beds and recent colluvial deposits. We found a resonance peak at 1.0 Hz in the hangingwall block, whereas clear peaks in the range 5.0-10.0 Hz appear when approaching the subsurface fault, and we relate them to the fractured bedrock within the fault zone. The best-fit tomographic model shows a relatively high-Vp shallow body (Vp 2200-2400 m/s) that we relate to the weathered top of the Miocene Upper Coralline Limestone Fm., bounded on both sides by low-Vp regions (230 m/s above the weathered top-bedrock. Our results depict a clear seismic signature of the Victoria Lines Fault, characterized by low seismic velocity and high amplification of ground motion. We hypothesize that, during the Middle Pleistocene, faulting may have affected the basal part of the red beds, so that this part of the investigated complex fault-system may be considered inactive since 0.6 Myr ago.

An L-band interferometric synthetic aperture radar study on the Ganos section of the north Anatolian fault zone between 2007 and 2011: Evidence for along strike segmentation and creep in a shallow fault patch.

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de Michele, Marcello; Ergintav, Semih; Aochi, Hideo; Raucoules, Daniel

2017-01-01

We utilize L-band interferometric synthetic aperture radar (InSAR) data in this study to retrieve a ground velocity map for the near field of the Ganos section of the north Anatolian fault (NAF) zone. The segmentation and creep distribution of this section, which last ruptured in 1912 to generate a moment magnitude (Mw)7.3 earthquake, remains incompletely understood. Because InSAR processing removes the mean orbital plane, we do not investigate large scale displacements due to regional tectonics in this study as these can be determined using global positioning system (GPS) data, instead concentrating on the close-to-the-fault displacement field. Our aim is to determine whether, or not, it is possible to retrieve robust near field velocity maps from stacking L-band interferograms, combining both single and dual polarization SAR data. In addition, we discuss whether a crustal velocity map can be used to complement GPS observations in an attempt to discriminate the present-day surface displacement of the Ganos fault (GF) across multiple segments. Finally, we characterize the spatial distribution of creep on shallow patches along multiple along-strike segments at shallow depths. Our results suggest the presence of fault segmentation along strike as well as creep on the shallow part of the fault (i.e. the existence of a shallow creeping patch) or the presence of a smoother section on the fault plane. Data imply a heterogeneous fault plane with more complex mechanics than previously thought. Because this study improves our knowledge of the mechanisms underlying the GF, our results have implications for local seismic hazard assessment.

Kinematics and strain analyses of the eastern segment of the Pernicana Fault (Mt. Etna, Italy derived from geodetic techniques (1997-2005

Directory of Open Access Journals (Sweden)

M. Mattia

2006-06-01

Full Text Available This paper analyses the ground deformations occurring on the eastern part of the Pernicana Fault from 1997 to 2005. This segment of the fault was monitored with three local networks based on GPS and EDM techniques. More than seventy GPS and EDM surveys were carried out during the considered period, in order to achieve a higher temporal detail of ground deformation affecting the structure. We report the comparisons among GPS and EDM surveys in terms of absolute horizontal displacements of each GPS benchmark and in terms of strain parameters for each GPS and EDM network. Ground deformation measurements detected a continuous left-lateral movement of the Pernicana Fault. We conclude that, on the easternmost part of the Pernicana Fault, where it branches out into two segments, the deformation is transferred entirely SE-wards by a splay fault.

A novel Lagrangian approach for the stable numerical simulation of fault and fracture mechanics

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Franceschini, Andrea; Ferronato, Massimiliano, E-mail: massimiliano.ferronato@unipd.it; Janna, Carlo; Teatini, Pietro

2016-06-01

The simulation of the mechanics of geological faults and fractures is of paramount importance in several applications, such as ensuring the safety of the underground storage of wastes and hydrocarbons or predicting the possible seismicity triggered by the production and injection of subsurface fluids. However, the stable numerical modeling of ground ruptures is still an open issue. The present work introduces a novel formulation based on the use of the Lagrange multipliers to prescribe the constraints on the contact surfaces. The variational formulation is modified in order to take into account the frictional work along the activated fault portion according to the principle of maximum plastic dissipation. The numerical model, developed in the framework of the Finite Element method, provides stable solutions with a fast convergence of the non-linear problem. The stabilizing properties of the proposed model are emphasized with the aid of a realistic numerical example dealing with the generation of ground fractures due to groundwater withdrawal in arid regions. - Highlights: • A numerical model is developed for the simulation of fault and fracture mechanics. • The model is implemented in the framework of the Finite Element method and with the aid of Lagrange multipliers. • The proposed formulation introduces a new contribution due to the frictional work on the portion of activated fault. • The resulting algorithm is highly non-linear as the portion of activated fault is itself unknown. • The numerical solution is validated against analytical results and proves to be stable also in realistic applications.

A novel Lagrangian approach for the stable numerical simulation of fault and fracture mechanics

International Nuclear Information System (INIS)

Franceschini, Andrea; Ferronato, Massimiliano; Janna, Carlo; Teatini, Pietro

2016-01-01

The simulation of the mechanics of geological faults and fractures is of paramount importance in several applications, such as ensuring the safety of the underground storage of wastes and hydrocarbons or predicting the possible seismicity triggered by the production and injection of subsurface fluids. However, the stable numerical modeling of ground ruptures is still an open issue. The present work introduces a novel formulation based on the use of the Lagrange multipliers to prescribe the constraints on the contact surfaces. The variational formulation is modified in order to take into account the frictional work along the activated fault portion according to the principle of maximum plastic dissipation. The numerical model, developed in the framework of the Finite Element method, provides stable solutions with a fast convergence of the non-linear problem. The stabilizing properties of the proposed model are emphasized with the aid of a realistic numerical example dealing with the generation of ground fractures due to groundwater withdrawal in arid regions. - Highlights: • A numerical model is developed for the simulation of fault and fracture mechanics. • The model is implemented in the framework of the Finite Element method and with the aid of Lagrange multipliers. • The proposed formulation introduces a new contribution due to the frictional work on the portion of activated fault. • The resulting algorithm is highly non-linear as the portion of activated fault is itself unknown. • The numerical solution is validated against analytical results and proves to be stable also in realistic applications.

Preliminary Results on Earthquake Recurrence Intervals, Rupture Segmentation, and Potential Earthquake Moment Magnitudes along the Tahoe-Sierra Frontal Fault Zone, Lake Tahoe, California

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Howle, J.; Bawden, G. W.; Schweickert, R. A.; Hunter, L. E.; Rose, R.

2012-12-01

Utilizing high-resolution bare-earth LiDAR topography, field observations, and earlier results of Howle et al. (2012), we estimate latest Pleistocene/Holocene earthquake-recurrence intervals, propose scenarios for earthquake-rupture segmentation, and estimate potential earthquake moment magnitudes for the Tahoe-Sierra frontal fault zone (TSFFZ), west of Lake Tahoe, California. We have developed a new technique to estimate the vertical separation for the most recent and the previous ground-rupturing earthquakes at five sites along the Echo Peak and Mt. Tallac segments of the TSFFZ. At these sites are fault scarps with two bevels separated by an inflection point (compound fault scarps), indicating that the cumulative vertical separation (VS) across the scarp resulted from two events. This technique, modified from the modeling methods of Howle et al. (2012), uses the far-field plunge of the best-fit footwall vector and the fault-scarp morphology from high-resolution LiDAR profiles to estimate the per-event VS. From this data, we conclude that the adjacent and overlapping Echo Peak and Mt. Tallac segments have ruptured coseismically twice during the Holocene. The right-stepping, en echelon range-front segments of the TSFFZ show progressively greater VS rates and shorter earthquake-recurrence intervals from southeast to northwest. Our preliminary estimates suggest latest Pleistocene/ Holocene earthquake-recurrence intervals of 4.8±0.9x103 years for a coseismic rupture of the Echo Peak and Mt. Tallac segments, located at the southeastern end of the TSFFZ. For the Rubicon Peak segment, northwest of the Echo Peak and Mt. Tallac segments, our preliminary estimate of the maximum earthquake-recurrence interval is 2.8±1.0x103 years, based on data from two sites. The correspondence between high VS rates and short recurrence intervals suggests that earthquake sequences along the TSFFZ may initiate in the northwest part of the zone and then occur to the southeast with a lower

Structural character of the northern segment of the Paintbrush Canyon fault, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Dickerson, R.P.; Spengler, R.W.

1994-01-01

Detailed mapping of exposed features along the northern part of the Paintbrush Canyon fault was initiated to aid in construction of the computer-assisted three-dimensional lithostratigraphic model of Yucca Mountain, to contribute to kinematic reconstruction of the tectonic history of the Paintbrush Canyon fault, and to assist in the interpretation of geophysical data from Midway Valley. Yucca Mountain is segmented into relatively intact blocks of east-dipping Miocene volcanic strata, bounded by north-striking, west-dipping high-angle normal faults. The Paintbrush Canyon fault, representing the easternmost block-bounding normal fault, separates Fran Ridge from Midway Valley and continues northward across Yucca Wash to at least the southern margin of the Timber Mountain Caldera complex. South of Yucca Wash, the Paintbrush Canyon Fault is largely concealed beneath thick Quaternary deposits. Bedrock exposures to the north reveal a complex fault, zone, displaying local north- and west-trending grabens, and rhombic pull-apart features. The fault scarp, discontinuously exposed along a mapped length of 8 km north of Yucca Wash, dips westward by 41 degrees to 74 degrees. Maximum vertical offset of the Rhyolite of Comb Peak along the fault measures about 210 m in Paintbrush Canyon and, on the basis of drill hole information, vertical offset of the Topopoah Spring Tuff is about 360 m near the northern part of Fran Ridge. Observed displacement along the fault in Paintbrush Canyon is down to the west with a component of left-lateral oblique slip. Unlike previously proposed tectonic models, strata adjacent to the fault dip to the east. Quaternary deposits do not appear displaced along the fault scarp north of Yucca Wash, but are displaced in trenches south of Yucca Wash

Numerical analysis of the effects induced by normal faults and dip angles on rock bursts

Science.gov (United States)

Jiang, Lishuai; Wang, Pu; Zhang, Peipeng; Zheng, Pengqiang; Xu, Bin

2017-10-01

The study of mining effects under the influences of a normal fault and its dip angle is significant for the prediction and prevention of rock bursts. Based on the geological conditions of panel 2301N in a coalmine, the evolution laws of the strata behaviors of the working face affected by a fault and the instability of the fault induced by mining operations with the working face of the footwall and hanging wall advancing towards a normal fault are studied using UDEC numerical simulation. The mechanism that induces rock burst is revealed, and the influence characteristics of the fault dip angle are analyzed. The results of the numerical simulation are verified by conducting a case study regarding the microseismic events. The results of this study serve as a reference for the prediction of rock bursts and their classification into hazardous areas under similar conditions.

Fault morphology of the lyo Fault, the Median Tectonic Line Active Fault System

OpenAIRE

後藤, 秀昭

1996-01-01

In this paper, we investigated the various fault features of the lyo fault and depicted fault lines or detailed topographic map. The results of this paper are summarized as follows; 1) Distinct evidence of the right-lateral movement is continuously discernible along the lyo fault. 2) Active fault traces are remarkably linear suggesting that the angle of fault plane is high. 3) The lyo fault can be divided into four segments by jogs between left-stepping traces. 4) The mean slip rate is 1.3 ～ ...

Segmentation pattern and structural complexities in seismogenic extensional settings: The North Matese Fault System (Central Italy)

Science.gov (United States)

Ferrarini, Federica; Boncio, Paolo; de Nardis, Rita; Pappone, Gerardo; Cesarano, Massimo; Aucelli, Pietro P. C.; Lavecchia, Giusy

2017-02-01

We investigated the northern slope of the Matese Mts. (Molise, Central Italy) with the aim of characterizing the N- to NE-dipping active normal fault system in the Bojano basin, a sector of primary importance from a seismic hazard perspective. We collected field data to define the geometry and segmentation pattern of two sub-systems (Patalecchia-Colle di Mezzo and Bojano-Campochiaro). New evidence of late Quaternary faulting was obtained by exploiting well log interpretations. Kinematic analysis revealed the interaction of pre-Quaternary inherited (mainly E-W-striking) and newly formed (NW-SE-striking) normal faults. Slip accommodation through linkage was clearly noted in the case of the Patalecchia-Colle di Mezzo sub-system. Detailed topographic profiles across the active fault segments provided post-LGM (15 ± 3 kyr) slip rates up to ∼2 mm/yr which agree with the high deformation rates based on different approaches in the literature. Finally, the instrumental seismicity analysis constrained the bottom of the seismogenic layer to depths of 13-14 km, and the gathered information allowed us to reconstruct the North Matese seismogenic source. Its 3D geometry and dimensions agree with both the dimension-magnitude relationships and macroseismic information available for the 1805 earthquake (Mw 6.6), the main historical earthquake to have struck the Bojano basin.

Analysis of Fault Spacing in Thrust-Belt Wedges Using Numerical Modeling

Science.gov (United States)

Regensburger, P. V.; Ito, G.

2017-12-01

Numerical modeling is invaluable in studying the mechanical processes governing the evolution of geologic features such as thrust-belt wedges. The mechanisms controlling thrust fault spacing in wedges is not well understood. Our numerical model treats the thrust belt as a visco-elastic-plastic continuum and uses a finite-difference, marker-in-cell method to solve for conservation of mass and momentum. From these conservation laws, stress is calculated and Byerlee's law is used to determine the shear stress required for a fault to form. Each model consists of a layer of crust, initially 3-km-thick, carried on top of a basal décollement, which moves at a constant speed towards a rigid backstop. A series of models were run with varied material properties, focusing on the angle of basal friction at the décollement, the angle of friction within the crust, and the cohesion of the crust. We investigate how these properties affected the spacing between thrusts that have the most time-integrated history of slip and therefore have the greatest effect on the large-scale undulations in surface topography. The surface position of these faults, which extend through most of the crustal layer, are identifiable as local maxima in positive curvature of surface topography. Tracking the temporal evolution of faults, we find that thrust blocks are widest when they first form at the front of the wedge and then they tend to contract over time as more crustal material is carried to the wedge. Within each model, thrust blocks form with similar initial widths, but individual thrust blocks develop differently and may approach an asymptotic width over time. The median of thrust block widths across the whole wedge tends to decrease with time. Median fault spacing shows a positive correlation with both wedge cohesion and internal friction. In contrast, median fault spacing exhibits a negative correlation at small angles of basal friction (laws that can be used to predict fault spacing in

Long term fault system reorganization of convergent and strike-slip systems

Science.gov (United States)

Cooke, M. L.; McBeck, J.; Hatem, A. E.; Toeneboehn, K.; Beyer, J. L.

2017-12-01

Laboratory and numerical experiments representing deformation over many earthquake cycles demonstrate that fault evolution includes episodes of fault reorganization that optimize work on the fault system. Consequently, the mechanical and kinematic efficiencies of fault systems do not increase monotonically through their evolution. New fault configurations can optimize the external work required to accommodate deformation, suggesting that changes in system efficiency can drive fault reorganization. Laboratory evidence and numerical results show that fault reorganization within accretion, strike-slip and oblique convergent systems is associated with increasing efficiency due to increased fault slip (frictional work and seismic energy) and commensurate decreased off-fault deformation (internal work and work against gravity). Between episodes of fault reorganization, fault systems may become less efficient as they produce increasing off fault deformation. For example, laboratory and numerical experiments show that the interference and interaction between different fault segments may increase local internal work or that increasing convergence can increase work against gravity produced by a fault system. This accumulation of work triggers fault reorganization as stored work provides the energy required to grow new faults that reorganize the system to a more efficient configuration. The results of laboratory and numerical experiments reveal that we should expect crustal fault systems to reorganize following periods of increasing inefficiency, even in the absence of changes to the tectonic regime. In other words, fault reorganization doesn't require a change in tectonic loading. The time frame of fault reorganization depends on fault system configuration, strain rate and processes that relax stresses within the crust. For example, stress relaxation may keep pace with stress accumulation, which would limit the increase in the internal work and gravitational work so that

On the numerical solution of fault trees

International Nuclear Information System (INIS)

Demichela, M.; Piccinini, N.; Ciarambino, I.; Contini, S.

2003-01-01

In this paper an account will be given of the numerical solution of the logic trees directly extracted from the Recursive Operability Analysis. Particular attention will be devoted to the use of the NOT and INH logic gates for correct logical representation of Fault Trees prior to their quantitative resolution. The NOT gate is needed for correct logical representation of events when both non-intervention and correct intervention of a protective system may lead to a Top Event. The INH gate must be used to correctly represent the time link between two events that are both necessary, but must occur in sequence. Some numerical examples will be employed to show both the correct identification of the events entering the INH gates and how use of the AND gate instead of the INH gate leads to overestimation of the probability of occurrence of a Top Event

Hanging-wall deformation above a normal fault: sequential limit analyses

Science.gov (United States)

Yuan, Xiaoping; Leroy, Yves M.; Maillot, Bertrand

2015-04-01

The deformation in the hanging wall above a segmented normal fault is analysed with the sequential limit analysis (SLA). The method combines some predictions on the dip and position of the active fault and axial surface, with geometrical evolution à la Suppe (Groshong, 1989). Two problems are considered. The first followed the prototype proposed by Patton (2005) with a pre-defined convex, segmented fault. The orientation of the upper segment of the normal fault is an unknown in the second problem. The loading in both problems consists of the retreat of the back wall and the sedimentation. This sedimentation starts from the lowest point of the topography and acts at the rate rs relative to the wall retreat rate. For the first problem, the normal fault either has a zero friction or a friction value set to 25o or 30o to fit the experimental results (Patton, 2005). In the zero friction case, a hanging wall anticline develops much like in the experiments. In the 25o friction case, slip on the upper segment is accompanied by rotation of the axial plane producing a broad shear zone rooted at the fault bend. The same observation is made in the 30o case, but without slip on the upper segment. Experimental outcomes show a behaviour in between these two latter cases. For the second problem, mechanics predicts a concave fault bend with an upper segment dip decreasing during extension. The axial surface rooting at the normal fault bend sees its dips increasing during extension resulting in a curved roll-over. Softening on the normal fault leads to a stepwise rotation responsible for strain partitioning into small blocks in the hanging wall. The rotation is due to the subsidence of the topography above the hanging wall. Sedimentation in the lowest region thus reduces the rotations. Note that these rotations predicted by mechanics are not accounted for in most geometrical approaches (Xiao and Suppe, 1992) and are observed in sand box experiments (Egholm et al., 2007, referring

Insights into the 3D architecture of an active caldera ring-fault at Tendürek volcano through modeling of geodetic data

KAUST Repository

Vasyura-Bathke, Hannes

2015-04-28

The three-dimensional assessment of ring-fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field, geodetic or seismological data, or by only partial ring-fault rupture or slip. Here we use a novel combination of spatially dense InSAR time-series data, numerical models and sand-box experiments to determine the three-dimensional geometry and kinematics of a sub-surface ring-fault at Tendürek volcano in Turkey. The InSAR data reveal that the area within the ring-fault not only subsides, but also shows substantial westward-directed lateral movement. The models and experiments explain this as a consequence of a ‘sliding-trapdoor’ ring-fault architecture that is mostly composed of outward-inclined reverse segments, most markedly so on the volcano\\'s western flanks but includes inward-inclined normal segments on its eastern flanks. Furthermore, the model ring-fault exhibits dextral and sinistral strike-slip components that are roughly bilaterally distributed onto its northern and southern segments, respectively. Our more complex numerical model describes the deformation at Tendürek better than an analytical solution for a single rectangular dislocation in a half-space. Comparison to ring-faults defined at Glen Coe, Fernandina and Bárðarbunga calderas suggests that ‘sliding-trapdoor’ ring-fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring-faults at different scales worldwide.

Ring-fault activity at subsiding calderas studied from analogue experiments and numerical modeling

Science.gov (United States)

Liu, Y. K.; Ruch, J.; Vasyura-Bathke, H.; Jonsson, S.

2017-12-01

Several subsiding calderas, such as the ones in the Galápagos archipelago and the Axial seamount in the Pacific Ocean have shown a complex but similar ground deformation pattern, composed of a broad deflation signal affecting the entire volcanic edifice and of a localized subsidence signal focused within the caldera. However, it is still debated how deep processes at subsiding calderas, including magmatic pressure changes, source locations and ring-faulting, relate to this observed surface deformation pattern. We combine analogue sandbox experiments with numerical modeling to study processes involved from initial subsidence to later collapse of calderas. The sandbox apparatus is composed of a motor driven subsiding half-piston connected to the bottom of a glass box. During the experiments the observation is done by five digital cameras photographing from various perspectives. We use Photoscan, a photogrammetry software and PIVLab, a time-resolved digital image correlation tool, to retrieve time-series of digital elevation models and velocity fields from acquired photographs. This setup allows tracking the processes acting both at depth and at the surface, and to assess their relative importance as the subsidence evolves to a collapse. We also use the Boundary Element Method to build a numerical model of the experiment setup, which comprises contracting sill-like source in interaction with a ring-fault in elastic half-space. We then compare our results from these two approaches with the examples observed in nature. Our preliminary experimental and numerical results show that at the initial stage of magmatic withdrawal, when the ring-fault is not yet well formed, broad and smooth deflation dominates at the surface. As the withdrawal increases, narrower subsidence bowl develops accompanied by the upward propagation of the ring-faulting. This indicates that the broad deflation, affecting the entire volcano edifice, is primarily driven by the contraction of the

Quaternay faulting along the southern Lemhi fault near the Idaho National Engineering Laboratory Southeastern Idaho

International Nuclear Information System (INIS)

Hemphill-Haley, M.A.; Sawyer, T.L.; Wong, I.G.; Kneupfer, P.L.K.; Forman, S.L.; Smith, R.P.

1991-01-01

Four exploratory trenches excavated across the Howe and Fallen Springs segments of the southern Lemhi fault in southeastern Idaho provide data to characterize these potential seismic sources. Evidence for up to three surface faulting events is exposed in each trench. Thermoluminescence (TL) and radiocarbon analyses were performed to provide estimates of the timing of each faulting event. The most recent event (MRE) occurred at: (1) about 15,000 to 19,000 years B.P. at the East Canyon trench (southern Howe segment); (2) approximately 17,000 to 24,000 years. B.P. at the Black Canyon site (northern Howe segment); and (3) about 19,000 to 24,000 years B.P. at the Camp Creek trench (southern Fallen Springs segment). A Holocene event is estimated for the Coyote Springs trench (central Fallert Springs segment) based on degree of soil development and correlation of faulted and unfaulted deposits. The oldest Black Canyon event is constrained by a buried soil (Av) horizons with a TL age of 24,700 +/- 3,100 years B.P. Possibly three events occurred at this site between about 17,000 and 24,000 years ago followed by quiescence. Stratigraphic and soil relationships, and TL and 14 C dates are consistent with the following preliminary interpretations: (1) the MRE's for the southern segments are older than those for the central Lemhi fault; (2) the Black Canyon site may share rupture events with sites to the north and south as a result of a open-quotes leakyclose quotes segment boundary; (3) temporal clustering of seismic events separated by a long period of quiescence may be evident along the southern Lemhi fault; and (4) Holocene surface rupture is evident along the central part of the Fallert Springs segment but not at its southern end; and (5) the present segmentation model may need to be revised

Relaxation on the Ismetpasa segment of the North Anatolian Fault after the Golcuk Mw = 7.4 and Duzce Mw = 7.2 shocks

Directory of Open Access Journals (Sweden)

E. Koksal

2010-12-01

Full Text Available The Ismetpasa segment of the North Anatolian Fault (NAF is a rare place where aseismic fault slip (creep has been observed. Its creep behaviour has been monitored using different observation methods since the 1950s. The findings obtained from the studies until 1990s showed that the creep rate exponentially decreased before the major shocks in 1999, Golcuk (Mw = 7.4 and Duzce (Mw = 7.2. After these shocks, three GPS periods observation in 2002, 2007 and 2008 were carried out on the geodetic network established around the segment. The evaluations of these observations showed that the creep behaviour relaxed after the major earthquakes. This result demonstrates that the creep behaviour of the Ismetpasa segment might be a warning before future major earthquakes.

Need for denser geodetic network to get real constrain on the fault behavior along the Main Marmara Sea segments of the NAF, toward an optimized GPS network.

Science.gov (United States)

Klein, E.; Masson, F.; Duputel, Z.; Yavasoglu, H.; Agram, P. S.

2016-12-01

Over the last two decades, the densification of GPS networks and the development of new radar satellites offered an unprecedented opportunity to study crustal deformation due to faulting. Yet, submarine strike slip fault segments remain a major issue, especially when the landscape appears unfavorable to the use of SAR measurements. It is the case of the North Anatolian fault segments located in the Main Marmara Sea, that remain unbroken ever since the Mw7.4 earthquake of Izmit in 1999, which ended a eastward migrating seismic sequence of Mw > 7 earthquakes. Located directly offshore Istanbul, evaluation of seismic hazard appears capital. But a strong controversy remains over whether these segments are accumulating strain and are likely to experience a major earthquake, or are creeping, resulting both from the simplicity of current geodetic models and the scarcity of geodetic data. We indeed show that 2D infinite fault models cannot account for the complexity of the Marmara fault segments. But current geodetic data in the western region of Istanbul are also insufficient to invert for the coupling using a 3D geometry of the fault. Therefore, we implement a global optimization procedure aiming at identifying the most favorable distribution of GPS stations to explore the strain accumulation. We present here the results of this procedure that allows to determine both the optimal number and location of the new stations. We show that a denser terrestrial survey network can indeed locally improve the resolution on the shallower part of the fault, even more efficiently with permanent stations. But data closer from the fault, only possible by submarine measurements, remain necessary to properly constrain the fault behavior and its potential along strike coupling variations.

Structural Mapping Along the Central San Andreas Fault-zone Using Airborne Electromagnetics

Science.gov (United States)

Zamudio, K. D.; Bedrosian, P.; Ball, L. B.

2017-12-01

Investigations of active fault zones typically focus on either surface expressions or the associated seismogenic zones. However, the largely aseismic upper kilometer can hold significant insight into fault-zone architecture, strain partitioning, and fault-zone permeability. Geophysical imaging of the first kilometer provides a link between surface fault mapping and seismically-defined fault zones and is particularly important in geologically complex regions with limited surface exposure. Additionally, near surface imaging can provide insight into the impact of faulting on the hydrogeology of the critical zone. Airborne electromagnetic (AEM) methods offer a unique opportunity to collect a spatially-large, detailed dataset in a matter of days, and are used to constrain subsurface resistivity to depths of 500 meters or more. We present initial results from an AEM survey flown over a 60 kilometer long segment of the central San Andreas Fault (SAF). The survey is centered near Parkfield, California, the site of the SAFOD drillhole, which marks the transition between a creeping fault segment to the north and a locked zone to the south. Cross sections with a depth of investigation up to approximately 500 meters highlight the complex Tertiary and Mesozoic geology that is dismembered by the SAF system. Numerous fault-parallel structures are imaged across a more than 10 kilometer wide zone centered on the surface trace. Many of these features can be related to faults and folds within Plio-Miocene sedimentary rocks found on both sides of the fault. Northeast of the fault, rocks of the Mesozoic Franciscan and Great Valley complexes are extremely heterogeneous, with highly resistive volcanic rocks within a more conductive background. The upper 300 meters of a prominent fault-zone conductor, previously imaged to 1-3 kilometers depth by magnetotellurics, is restricted to a 20 kilometer long segment of the fault, but is up to 4 kilometers wide in places. Elevated fault

Coseismic Slip Deficit of the 2017 Mw 6.5 Ormoc Earthquake That Occurred Along a Creeping Segment and Geothermal Field of the Philippine Fault

Science.gov (United States)

Yang, Ying-Hui; Tsai, Min-Chien; Hu, Jyr-Ching; Aurelio, Mario A.; Hashimoto, Manabu; Escudero, John Agustin P.; Su, Zhe; Chen, Qiang

2018-03-01

Coseismic surface deformation imaged through interferometric synthetic aperture radar (InSAR) measurements was used to estimate the fault geometry and slip distribution of the 2017 Mw 6.5 Ormoc earthquake along a creeping segment of the Philippine Fault on Leyte Island. Our best fitting faulting model suggests that the coseismic rupture occurred on a fault plane with high dip angle of 78.5° and strike angle of 325.8°, and the estimated maximum fault slip of 2.3 m is located at 6.5 km east-northeast of the town of Kananga. The recognized insignificant slip in the Tongonan geothermal field zone implies that the plastic behavior caused by high geothermal gradient underneath the Tongonan geothermal field could prevent the coseismic failure in heated rock mass in this zone. The predicted Coulomb failure stress change shows that a significant positive Coulomb failure stress change occurred along the SE segment of central Philippine Fault with insignificant coseismic slip and infrequent aftershocks, which suggests an increasing risk for future seismic hazard.

Near-fault earthquake ground motion prediction by a high-performance spectral element numerical code

International Nuclear Information System (INIS)

Paolucci, Roberto; Stupazzini, Marco

2008-01-01

Near-fault effects have been widely recognised to produce specific features of earthquake ground motion, that cannot be reliably predicted by 1D seismic wave propagation modelling, used as a standard in engineering applications. These features may have a relevant impact on the structural response, especially in the nonlinear range, that is hard to predict and to be put in a design format, due to the scarcity of significant earthquake records and of reliable numerical simulations. In this contribution a pilot study is presented for the evaluation of seismic ground-motions in the near-fault region, based on a high-performance numerical code for 3D seismic wave propagation analyses, including the seismic fault, the wave propagation path and the near-surface geological or topographical irregularity. For this purpose, the software package GeoELSE is adopted, based on the spectral element method. The set-up of the numerical benchmark of 3D ground motion simulation in the valley of Grenoble (French Alps) is chosen to study the effect of the complex interaction between basin geometry and radiation mechanism on the variability of earthquake ground motion

Numerical Methods for the Analysis of Power Transformer Tank Deformation and Rupture Due to Internal Arcing Faults.

Science.gov (United States)

Yan, Chenguang; Hao, Zhiguo; Zhang, Song; Zhang, Baohui; Zheng, Tao

2015-01-01

Power transformer rupture and fire resulting from an arcing fault inside the tank usually leads to significant security risks and serious economic loss. In order to reveal the essence of tank deformation or explosion, this paper presents a 3-D numerical computational tool to simulate the structural dynamic behavior due to overpressure inside transformer tank. To illustrate the effectiveness of the proposed method, a 17.3 MJ and a 6.3 MJ arcing fault were simulated on a real full-scale 360MVA/220kV oil-immersed transformer model, respectively. By employing the finite element method, the transformer internal overpressure distribution, wave propagation and von-Mises stress were solved. The numerical results indicate that the increase of pressure and mechanical stress distribution are non-uniform and the stress tends to concentrate on connecting parts of the tank as the fault time evolves. Given this feature, it becomes possible to reduce the risk of transformer tank rupture through limiting the fault energy and enhancing the mechanical strength of the local stress concentrative areas. The theoretical model and numerical simulation method proposed in this paper can be used as a substitute for risky and costly field tests in fault overpressure analysis and tank mitigation design of transformers.

Numerical Methods for the Analysis of Power Transformer Tank Deformation and Rupture Due to Internal Arcing Faults

Science.gov (United States)

Yan, Chenguang; Hao, Zhiguo; Zhang, Song; Zhang, Baohui; Zheng, Tao

2015-01-01

Power transformer rupture and fire resulting from an arcing fault inside the tank usually leads to significant security risks and serious economic loss. In order to reveal the essence of tank deformation or explosion, this paper presents a 3-D numerical computational tool to simulate the structural dynamic behavior due to overpressure inside transformer tank. To illustrate the effectiveness of the proposed method, a 17.3MJ and a 6.3MJ arcing fault were simulated on a real full-scale 360MVA/220kV oil-immersed transformer model, respectively. By employing the finite element method, the transformer internal overpressure distribution, wave propagation and von-Mises stress were solved. The numerical results indicate that the increase of pressure and mechanical stress distribution are non-uniform and the stress tends to concentrate on connecting parts of the tank as the fault time evolves. Given this feature, it becomes possible to reduce the risk of transformer tank rupture through limiting the fault energy and enhancing the mechanical strength of the local stress concentrative areas. The theoretical model and numerical simulation method proposed in this paper can be used as a substitute for risky and costly field tests in fault overpressure analysis and tank mitigation design of transformers. PMID:26230392

Fault Gauge Numerical Simulation : Dynamic Rupture Propagation and Local Energy Partitioning

Science.gov (United States)

Mollon, G.

2017-12-01

In this communication, we present dynamic simulations of the local (centimetric) behaviour of a fault filled with a granular gauge submitted to dynamic rupture. The numerical tool (Fig. 1) combines classical Discrete Element Modelling (albeit with the ability to deal with arbitrary grain shapes) for the simualtion of the gauge, and continuous modelling for the simulation of the acoustic waves emission and propagation. In a first part, the model is applied to the simulation of steady-state shearing of the fault under remote displacement boudary conditions, in order to observe the shear accomodation at the interface (R1 cracks, localization, wear, etc.). It also makes it possible to fit to desired values the Rate and State Friction properties of the granular gauge by adapting the contact laws between grains. Such simulations provide quantitative insight in the steady-state energy partitionning between fracture, friction and acoustic emissions as a function of the shear rate. In a second part, the model is submitted to dynamic rupture. For that purpose, the fault is elastically preloaded just below rupture, and a displacement pulse is applied at one end of the sample (and on only one side of the fault). This allows to observe the propagation of the instability along the fault and the interplay between this propagation and the local granular phenomena. Energy partitionning is then observed both in space and time.

Deeper penetration of large earthquakes on seismically quiescent faults.

Science.gov (United States)

Jiang, Junle; Lapusta, Nadia

2016-06-10

Why many major strike-slip faults known to have had large earthquakes are silent in the interseismic period is a long-standing enigma. One would expect small earthquakes to occur at least at the bottom of the seismogenic zone, where deeper aseismic deformation concentrates loading. We suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes. We support this conclusion with numerical simulations of fault behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas Fault in Southern California penetrated below the seismogenic zone by at least 3 to 5 kilometers. Our findings suggest that such deeper ruptures may occur on other major fault segments, potentially increasing the associated seismic hazard. Copyright © 2016, American Association for the Advancement of Science.

Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

Science.gov (United States)

Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

2008-07-01

The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent

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.|info:eu-repo/dai/nl/413306674; 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

Structural setting and kinematics of Nubian fault system, SE Western Desert, Egypt: An example of multi-reactivated intraplate strike-slip faults

Science.gov (United States)

Sakran, Shawky; Said, Said Mohamed

2018-02-01

Detailed surface geological mapping and subsurface seismic interpretation have been integrated to unravel the structural style and kinematic history of the Nubian Fault System (NFS). The NFS consists of several E-W Principal Deformation Zones (PDZs) (e.g. Kalabsha fault). Each PDZ is defined by spectacular E-W, WNW and ENE dextral strike-slip faults, NNE sinistral strike-slip faults, NE to ENE folds, and NNW normal faults. Each fault zone has typical self-similar strike-slip architecture comprising multi-scale fault segments. Several multi-scale uplifts and basins were developed at the step-over zones between parallel strike-slip fault segments as a result of local extension or contraction. The NNE faults consist of right-stepping sinistral strike-slip fault segments (e.g. Sin El Kiddab fault). The NNE sinistral faults extend for long distances ranging from 30 to 100 kms and cut one or two E-W PDZs. Two nearly perpendicular strike-slip tectonic regimes are recognized in the NFS; an inactive E-W Late Cretaceous - Early Cenozoic dextral transpression and an active NNE sinistral shear.

A novel Lagrangian approach for the stable numerical simulation of fault and fracture mechanics

Science.gov (United States)

Franceschini, Andrea; Ferronato, Massimiliano; Janna, Carlo; Teatini, Pietro

2016-06-01

The simulation of the mechanics of geological faults and fractures is of paramount importance in several applications, such as ensuring the safety of the underground storage of wastes and hydrocarbons or predicting the possible seismicity triggered by the production and injection of subsurface fluids. However, the stable numerical modeling of ground ruptures is still an open issue. The present work introduces a novel formulation based on the use of the Lagrange multipliers to prescribe the constraints on the contact surfaces. The variational formulation is modified in order to take into account the frictional work along the activated fault portion according to the principle of maximum plastic dissipation. The numerical model, developed in the framework of the Finite Element method, provides stable solutions with a fast convergence of the non-linear problem. The stabilizing properties of the proposed model are emphasized with the aid of a realistic numerical example dealing with the generation of ground fractures due to groundwater withdrawal in arid regions.

Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France

Directory of Open Access Journals (Sweden)

Audrey Taillefer

2017-01-01

Full Text Available The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29°C to 73°C, along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro- and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1 in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2 in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.

Synthetic seismicity for the San Andreas fault

Directory of Open Access Journals (Sweden)

S. N. Ward

1994-06-01

Full Text Available Because historical catalogs generally span only a few repetition intervals of major earthquakes, they do not provide much constraint on how regularly earthquakes recur. In order to obtain better recurrence statistics and long-term probability estimates for events M ? 6 on the San Andreas fault, we apply a seismicity model to this fault. The model is based on the concept of fault segmentation and the physics of static dislocations which allow for stress transfer between segments. Constraints are provided by geological and seismological observations of segment lengths, characteristic magnitudes and long-term slip rates. Segment parameters slightly modified from the Working Group on California Earthquake Probabilities allow us to reproduce observed seismicity over four orders of magnitude. The model yields quite irregular earthquake recurrence patterns. Only the largest events (M ? 7.5 are quasi-periodic; small events cluster. Both the average recurrence time and the aperiodicity are also a function of position along the fault. The model results are consistent with paleoseismic data for the San Andreas fault as well as a global set of historical and paleoseismic recurrence data. Thus irregular earthquake recurrence resulting from segment interaction is consistent with a large range of observations.

Fault zone processes in mechanically layered mudrock and chalk

Science.gov (United States)

Ferrill, David A.; Evans, Mark A.; McGinnis, Ronald N.; Morris, Alan P.; Smart, Kevin J.; Wigginton, Sarah S.; Gulliver, Kirk D. H.; Lehrmann, Daniel; de Zoeten, Erich; Sickmann, Zach

2017-04-01

A 1.5 km long natural cliff outcrop of nearly horizontal Eagle Ford Formation in south Texas exposes northwest and southeast dipping normal faults with displacements of 0.01-7 m cutting mudrock, chalk, limestone, and volcanic ash. These faults provide analogs for both natural and hydraulically-induced deformation in the productive Eagle Ford Formation - a major unconventional oil and gas reservoir in south Texas, U.S.A. - and other mechanically layered hydrocarbon reservoirs. Fault dips are steep to vertical through chalk and limestone beds, and moderate through mudrock and clay-rich ash, resulting in refracted fault profiles. Steeply dipping fault segments contain rhombohedral calcite veins that cross the fault zone obliquely, parallel to shear segments in mudrock. The vertical dimensions of the calcite veins correspond to the thickness of offset competent beds with which they are contiguous, and the slip parallel dimension is proportional to fault displacement. Failure surface characteristics, including mixed tensile and shear segments, indicate hybrid failure in chalk and limestone, whereas shear failure predominates in mudrock and ash beds - these changes in failure mode contribute to variation in fault dip. Slip on the shear segments caused dilation of the steeper hybrid segments. Tabular sheets of calcite grew by repeated fault slip, dilation, and cementation. Fluid inclusion and stable isotope geochemistry analyses of fault zone cements indicate episodic reactivation at 1.4-4.2 km depths. The results of these analyses document a dramatic bed-scale lithologic control on fault zone architecture that is directly relevant to the development of porosity and permeability anisotropy along faults.

Dynamic Models of Earthquake Rupture along branch faults of the Eastern San Gorgonio Pass Region in CA using Complex Fault Structure

Science.gov (United States)

Douilly, R.; Oglesby, D. D.; Cooke, M. L.; Beyer, J. L.

2017-12-01

Compilation of geomorphic and paleoseismic data have illustrated that the right-lateral Coachella segment of the southern San Andreas Fault is past its average recurrence time period. On its western edge, this fault segment is split into two branches: the Mission Creek strand, and the Banning fault strand, of the San Andreas. Depending on how rupture propagates through this region, there is the possibility of a through-going rupture that could lead to the channeling of damaging seismic energy into the Los Angeles Basin. The fault structures and rupture scenarios on these two strands are potentially very different, so it is important to determine which strand is a more likely rupture path, and under which circumstances rupture will take either one. In this study, we focus on the effect of different assumptions about fault geometry and stress pattern on the rupture process to test those scenarios and thus investigate the most likely path of a rupture that starts on the Coachella segment. We consider two types of fault geometry based on the SCEC Community Fault Model and create a 3D finite element mesh. These two meshes are then incorporated into the finite element method code FaultMod to compute a physical model for the rupture dynamics. We use the slip-weakening friction law, and we consider different assumptions of background stress such as constant tractions, regional stress regimes of different orientations, heterogeneous off-fault stresses and the results of long-term stressing rates from quasi-static crustal deformation models that consider time since last event on each fault segment. Both the constant and regional stress distribution show that it is more likely for the rupture to branch from the Coachella segment to the Mission Creek compared to the Banning fault segment. For the regional stress distribution, we encounter cases of super-shear rupture for one type of fault geometry and sub-shear rupture for the other one. The fault connectivity at this branch

Geomorphological and structural characterization of the southern Weihe Graben, central China: Implications for fault segmentation

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Cheng, Yali; He, Chuanqi; Rao, Gang; Yan, Bing; Lin, Aiming; Hu, Jianmin; Yu, Yangli; Yao, Qi

2018-01-01

The Cenozoic graben systems around the tectonically stable Ordos Block, central China, have been considered as ideal places for investigating active deformation within continental rifts, such as the Weihe Graben at the southern margin with high historical seismicity (e.g., 1556 M 8.5 Huaxian great earthquake). However, previous investigations have mostly focused on the active structures in the eastern and northern parts of this graben. By contrast, in the southwest, tectonic activity along the northern margin of the Qinling Mountains has not been systematically investigated yet. In this study, based on digital elevation models (DEMs), we carried out geomorphological analysis to evaluate the relative tectonic activity along the whole South Border Fault (SBF). On the basis of field observations, high resolution DEMs acquired by small unmanned aerial vehicles (sUVA) using structure-for-motion techniques, radiocarbon (14C) age dating, we demonstrate that: 1) Tectonic activity along the SBF changes along strike, being higher in the eastern sector. 2) Seven major segment boundaries have been assigned, where the fault changes its strike and has lower tectonic activity. 3) The fault segment between the cities of Huaxian and Huayin characterized by almost pure normal slip has been active during the Holocene. We suggest that these findings would provide a basis for further investigating on the seismic risk in densely-populated Weihe Graben. Table S2. The values and classification of geomorphic indices obtained in this study. Fig. S1. Morphological features of the stream long profiles (Nos. 1-75) and corresponding SLK values. Fig. S2. Comparison of geomorphological parameters acquired from different DEMs (90-m SRTM and 30-m ASTER GDEM): (a) HI values; (b) HI linear regression; (c) mean slope of drainage basin; (d) mean slope linear regression.

Geometric-kinematic characteristics of the main faults in the W-SW of the Lut Block (SE Iran)

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Rashidi Boshrabadi, Ahmad; Khatib, Mohamad Mahdi; Raeesi, Mohamad; Mousavi, Seyed Morteza; Djamour, Yahya

2018-03-01

The area to the W-SW of the Lut Block in Iran has experienced numerous historical and recent destructive earthquakes. We examined a number of faults in this area that have high potential for generating destructive earthquakes. In this study a number of faults are introduced and named for the first time. These new faults are Takdar, Dehno, Suru, Hojat Abad, North Faryab, North Kahnoj, Heydarabad, Khatun Abad and South Faryab. For a group of previously known faults, their mechanism and geological offsets are investigated for the first time. This group of faults include East Nayband, West Nayband, Sardueiyeh, Dalfard, Khordum, South Jabal-e-Barez, and North Jabal-e-Barez. The N-S fault systems of Sabzevaran, Gowk, and Nayband induce slip on the E-W, NE-SW and NW-SE fault systems. The faulting patterns appear to preserve different stages of fault development. We investigated the distribution of active faults and the role that they play in accommodating tectonic strain in the SW-Lut. In the study area, the fault systems with en-echelon arrangement create structures such as restraining and releasing stepover, fault bend and pullapart basin. The main mechanism for fault growth in the region seems to be 'segment linkage of preexisting weaknesses' and also for a limited area through 'process zone'. Estimations are made for the likely magnitudes of separate or combined failure of the fault segments. Such magnitudes are used in hazard analysis of the region.

Motion in the north Iceland volcanic rift zone accommodated by bookshelf faulting

Science.gov (United States)

Green, Robert G.; White, Robert S.; Greenfield, Tim

2014-01-01

Along mid-ocean ridges the extending crust is segmented on length scales of 10-1,000km. Where rift segments are offset from one another, motion between segments is accommodated by transform faults that are oriented orthogonally to the main rift axis. Where segments overlap, non-transform offsets with a variety of geometries accommodate shear motions. Here we use micro-seismic data to analyse the geometries of faults at two overlapping rift segments exposed on land in north Iceland. Between the rift segments, we identify a series of faults that are aligned sub-parallel to the orientation of the main rift. These faults slip through left-lateral strike-slip motion. Yet, movement between the overlapping rift segments is through right-lateral motion. Together, these motions induce a clockwise rotation of the faults and intervening crustal blocks in a motion that is consistent with a bookshelf-faulting mechanism, named after its resemblance to a tilting row of books on a shelf. The faults probably reactivated existing crustal weaknesses, such as dyke intrusions, that were originally oriented parallel to the main rift and have since rotated about 15° clockwise. Reactivation of pre-existing, rift-parallel weaknesses contrasts with typical mid-ocean ridge transform faults and is an important illustration of a non-transform offset accommodating shear motion between overlapping rift segments.

Lateral Offset Quality Rating along Low Slip Rate Faults: Application to the Alhama de Murcia Fault (SE Iberian Peninsula

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Marta Ferrater

2015-11-01

Full Text Available Seismic hazard assessment of strike-slip faults is based partly on the identification and mapping of landforms laterally offset due to fault activity. The characterization of these features affected by slow-moving faults is challenging relative to studies emphasizing rapidly slipping faults. We propose a methodology for scoring fault offsets based on subjective and objective qualities. We apply this methodology to the Alhama de Murcia fault (SE Iberian Peninsula where we identify 138 offset features that we mapped on a high-resolution (0.5 × 0.5 m pixel size Digital Elevation Model (DEM. The amount of offset, the uncertainty of the measurement, the subjective and objective qualities, and the parameters that affect objective quality are independent variables, suggesting that our methodological scoring approach is good. Based on the offset measurements and qualifications we calculate the Cumulative Offset Probability Density (COPD for the entire fault and for each fault segment. The COPD for the segments differ from each other. Tentative interpretation of the COPDs implies that the slip rate varies from one segment to the other (we assume that channels with the same amount of offset were incised synchronously. We compare the COPD with climate proxy curves (aligning using the very limited age control to test if entrenchment events are coincident with climatic changes. Channel incision along one of the traces in Lorca-Totana segment may be related to transitions from glacial to interglacial periods.

Radon concentration distributions in shallow and deep groundwater around the Tachikawa fault zone.

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Tsunomori, Fumiaki; Shimodate, Tomoya; Ide, Tomoki; Tanaka, Hidemi

2017-06-01

Groundwater radon concentrations around the Tachikawa fault zone were surveyed. The radon concentrations in shallow groundwater samples around the Tachikawa fault segment are comparable to previous studies. The characteristics of the radon concentrations on both sides of the segment are considered to have changed in response to the decrease in groundwater recharge caused by urbanization on the eastern side of the segment. The radon concentrations in deep groundwater samples collected around the Naguri and the Tachikawa fault segments are the same as those of shallow groundwater samples. However, the radon concentrations in deep groundwater samples collected from the bedrock beside the Naguri and Tachikawa fault segments are markedly higher than the radon concentrations expected from the geology on the Kanto plane. This disparity can be explained by the development of fracture zones spreading on both sides of the two segments. The radon concentration distribution for deep groundwater samples from the Naguri and the Tachikawa fault segments suggests that a fault exists even at the southern part of the Tachikawa fault line. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extension parallel to the rift zone during segmented fault growth: application to the evolution of the NE Atlantic

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A. Bubeck

2017-11-01

Full Text Available The mechanical interaction of propagating normal faults is known to influence the linkage geometry of first-order faults, and the development of second-order faults and fractures, which transfer displacement within relay zones. Here we use natural examples of growth faults from two active volcanic rift zones (Koa`e, island of Hawai`i, and Krafla, northern Iceland to illustrate the importance of horizontal-plane extension (heave gradients, and associated vertical axis rotations, in evolving continental rift systems. Second-order extension and extensional-shear faults within the relay zones variably resolve components of regional extension, and components of extension and/or shortening parallel to the rift zone, to accommodate the inherently three-dimensional (3-D strains associated with relay zone development and rotation. Such a configuration involves volume increase, which is accommodated at the surface by open fractures; in the subsurface this may be accommodated by veins or dikes oriented obliquely and normal to the rift axis. To consider the scalability of the effects of relay zone rotations, we compare the geometry and kinematics of fault and fracture sets in the Koa`e and Krafla rift zones with data from exhumed contemporaneous fault and dike systems developed within a > 5×104 km2 relay system that developed during formation of the NE Atlantic margins. Based on the findings presented here we propose a new conceptual model for the evolution of segmented continental rift basins on the NE Atlantic margins.

Is lithostatic loading important for the slip behavior and evolution of normal faults in the Earth's crust?

International Nuclear Information System (INIS)

Kattenhorn, Simon A.; Pollard, David D.

1999-01-01

Normal faults growing in the Earth's crust are subject to the effects of an increasing frictional resistance to slip caused by the increasing lithostatic load with depth. We use three-dimensional (3-D) boundary element method numerical models to evaluate these effects on planar normal faults with variable elliptical tip line shapes in an elastic solid. As a result of increasing friction with depth, normal fault slip maxima for a single slip event are skewed away from the fault center toward the upper fault tip. There is a correspondingly greater propagation tendency at the upper tip. However, the tall faults that would result from such a propagation tendency are generally not observed in nature. We show how mechanical interaction between laterally stepping fault segments significantly competes with the lithostatic loading effect in the evolution of a normal fault system, promoting lateral propagation and possibly segment linkage. Resultant composite faults are wider than they are tall, resembling both 3-D seismic data interpretations and previously documented characteristics of normal fault systems. However, this effect may be greatly complemented by the influence of a heterogeneous stratigraphy, which can control fault nucleation depth and inhibit fault propagation across the mechanical layering. Our models demonstrate that although lithostatic loading may be an important control on fault evolution in relatively homogeneous rocks, the contribution of lithologic influences and mechanical interaction between closely spaced, laterally stepping faults may predominate in determining the slip behavior and propagation tendency of normal faults in the Earth's crust. (c) 1999 American Geophysical Union

Evolution of the Puente Hills Thrust Fault

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Bergen, K. J.; Shaw, J. H.; Dolan, J. F.

2013-12-01

This study aims to assess the evolution of the blind Puente Hills thrust fault system (PHT) by determining its age of initiation, lateral propagation history, and changes in slip rate over time. The PHT presents one of the largest seismic hazards in the United States, given its location beneath downtown Los Angeles. The PHT is comprised of three fault segments: the Los Angeles (LA), Santa Fe Springs (SFS), and Coyote Hills (CH). The LA and SFS segments are characterized by growth stratigraphy where folds formed by uplift on the fault segments have been continually buried by sediment from the Los Angeles and San Gabriel rivers. The CH segment has developed topography and is characterized by onlapping growth stratigraphy. This depositional setting gives us the unique opportunity to measure uplift on the LA and SFS fault segments, and minimum uplift on the CH fault segment, as the difference in sediment thicknesses across the buried folds. We utilize depth converted oil industry seismic reflection data to image the fold geometries. Identifying time-correlative stratigraphic markers for slip rate determination in the basin has been a problem for researchers in the past, however, as the faunal assemblages observed in wells are time-transgressive by nature. To overcome this, we utilize the sequence stratigraphic model and well picks of Ponti et al. (2007) as a basis for mapping time-correlative sequence boundaries throughout our industry seismic reflection data from the present to the Pleistocene. From the Pleistocene to Miocene we identify additional sequence boundaries in our seismic reflection data from imaged sequence geometries and by correlating industry well formation tops. The sequence and formation top picks are then used to build 3-dimensional surfaces in the modeling program Gocad. From these surfaces we measure the change in thicknesses across the folds to obtain uplift rates between each sequence boundary. Our results show three distinct phases of

Paleoearthquake rupture behavior and recurrence of great earthquakes along the Haiyuan fault, northwestern China

Institute of Scientific and Technical Information of China (English)

ZHANG Peizhen; MIN Wei; DENG Qidong; MAO Fengying

2005-01-01

The Haiyuan fault is a major seismogenic fault in north-central China where the1920 Haiyuan earthquake of magnitude 8.5 occurred, resulting in more than 220000 deaths. The fault zone can be divided into three segments based on their geometric patterns and associated geomorphology. To study paleoseismology and recurrent history of devastating earthquakes along the fault, we dug 17 trenches along different segments of the fault zone. Although only 10of them allow the paleoearthquake event to be dated, together with the 8 trenches dug previously they still provide adequate information that enables us to capture major paleoearthquakes occurring along the fault during the past geological time. We discovered 3 events along the eastern segment during the past 14000 a, 7 events along the middle segment during the past 9000 a, and 6 events along the western segment during the past 10000 a. These events clearly depict two temporal clusters. The first cluster occurs from 4600 to 6400 a, and the second occurs from 1000to 2800 a, approximately. Each cluster lasts about 2000 a. Time period between these two clusters is also about 2000 a. Based on fault geometry, segmentation pattern, and paleoearthquake events along the Haiyuan fault we can identify three scales of earthquake rupture: rupture of one segment, cascade rupture of two segments, and cascade rupture of entire fault (three segments).Interactions of slip patches on the surface of the fault may cause rupture on one patch or ruptures of more than two to three patchs to form the complex patterns of cascade rupture events.

Searching for geodetic transient slip signals along the Parkfield segment of the San Andreas Fault

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Rousset, B.; Burgmann, R.

2017-12-01

The Parkfield section of the San Andreas fault is at the transition between a segment locked since the 1857 Mw 7.9 Fort Tejon earthquake to its south and a creeping segment to the north. It is particularly well instrumented since it is the many previous studies have focused on studying the coseismic and postseismic phases of the two most recent earthquake cycles, the interseismic phase is exhibiting interesting dynamics at the down-dip edge of the seismogenic zone, characterized by a very large number of low frequency earthquakes (LFE) with different behaviors depending on location. Interseismic fault creep rates appear to vary over a wide range of spatial and temporal scales, from the Earth's surface to the base of crust. In this study, we take advantage of the dense Global Positioning System (GPS) network, with 77 continuous stations located within a circle of radius 80 km centered on Parkfield. We correct these time series for the co- and postseismic signals of the 2003 Mw 6.3 San Simeon and 2004 Mw 6.0 Parkfield earthquakes. We then cross-correlate the residual time series with synthetic slow-slip templates following the approach of Rousset et al. (2017). Synthetic tests with transient events contained in GPS time series with realistic noise show the limit of detection of the method. In the application with real GPS time series, the highest correlation amplitudes are compared with micro-seismicity rates, as well as tremor and LFE observations.

Paleoseismic evidence in the segment of fault Sopetran or San Jeronimo Network 5

International Nuclear Information System (INIS)

Lalinde, Claudia; Gonzalez, Adriana; Caballero, Humberto

2009-01-01

The area Metropolitana did a seismic Hazard study of Barbosa, Girardota, Copacabana, Sabaneta, La Estrella, Caldas y Envigado towns additional to Studies did in years 1999 and 2002. Solingral, Integral, Inteinsa, Universidad Nacional y Universidad Eafit, did the study for Area Metropolitana. This work present the paleoseismic evidence found in the road Conexion Vial Aburra Cauca in the south side of the pike site in the west side of the tunnel. This evidence is associated with the Sopetran Fault or Segment 5 San Jeronimo Fault, which has 25km length. The paleoseismic interpretation identifies two seismic events in the last 10.000 years. The oldest is an event of Mw 6.4 magnitude that displaced the last volcanic ash layer between 10.000 and 5.000 years considering that the last volcanic ash layer fallow 10.000 year ago, they appear reworking, it is width and is covered by paleosoil. The most recent event is an event of Mw 6.7 magnitude and displaced the paleosoil which was dated by 1830±40BP C14 so the last event occurs in the last 1800 years.

Loading of the San Andreas fault by flood-induced rupture of faults beneath the Salton Sea

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Brothers, Daniel; Kilb, Debi; Luttrell, Karen; Driscoll, Neal W.; Kent, Graham

2011-01-01

The southern San Andreas fault has not experienced a large earthquake for approximately 300 years, yet the previous five earthquakes occurred at ~180-year intervals. Large strike-slip faults are often segmented by lateral stepover zones. Movement on smaller faults within a stepover zone could perturb the main fault segments and potentially trigger a large earthquake. The southern San Andreas fault terminates in an extensional stepover zone beneath the Salton Sea—a lake that has experienced periodic flooding and desiccation since the late Holocene. Here we reconstruct the magnitude and timing of fault activity beneath the Salton Sea over several earthquake cycles. We observe coincident timing between flooding events, stepover fault displacement and ruptures on the San Andreas fault. Using Coulomb stress models, we show that the combined effect of lake loading, stepover fault movement and increased pore pressure could increase stress on the southern San Andreas fault to levels sufficient to induce failure. We conclude that rupture of the stepover faults, caused by periodic flooding of the palaeo-Salton Sea and by tectonic forcing, had the potential to trigger earthquake rupture on the southern San Andreas fault. Extensional stepover zones are highly susceptible to rapid stress loading and thus the Salton Sea may be a nucleation point for large ruptures on the southern San Andreas fault.

3D Dynamic Rupture Simulations along Dipping Faults, with a focus on the Wasatch Fault Zone, Utah

Science.gov (United States)

Withers, K.; Moschetti, M. P.

2017-12-01

We study dynamic rupture and ground motion from dip-slip faults in regions that have high-seismic hazard, such as the Wasatch fault zone, Utah. Previous numerical simulations have modeled deterministic ground motion along segments of this fault in the heavily populated regions near Salt Lake City but were restricted to low frequencies ( 1 Hz). We seek to better understand the rupture process and assess broadband ground motions and variability from the Wasatch Fault Zone by extending deterministic ground motion prediction to higher frequencies (up to 5 Hz). We perform simulations along a dipping normal fault (40 x 20 km along strike and width, respectively) with characteristics derived from geologic observations to generate a suite of ruptures > Mw 6.5. This approach utilizes dynamic simulations (fully physics-based models, where the initial stress drop and friction law are imposed) using a summation by parts (SBP) method. The simulations include rough-fault topography following a self-similar fractal distribution (over length scales from 100 m to the size of the fault) in addition to off-fault plasticity. Energy losses from heat and other mechanisms, modeled as anelastic attenuation, are also included, as well as free-surface topography, which can significantly affect ground motion patterns. We compare the effect of material structure and both rate and state and slip-weakening friction laws have on rupture propagation. The simulations show reduced slip and moment release in the near surface with the inclusion of plasticity, better agreeing with observations of shallow slip deficit. Long-wavelength fault geometry imparts a non-uniform stress distribution along both dip and strike, influencing the preferred rupture direction and hypocenter location, potentially important for seismic hazard estimation.

Style of the surface deformation by the 1999 Chichi earthquake at the central segment of Chelungpu fault, Taiwan, with special reference to the presence of the main and subsidiary faults and their progressive deformation in the Tsauton area

Science.gov (United States)

Ota, Y.; Watanabe, M.; Suzuki, Y.; Yanagida, M.; Miyawaki, A.; Sawa, H.

2007-11-01

We describe the style of surface deformation in the 1999 Chichi earthquake in the central segment of the Chelungpu Fault. The study covers the Kung-fu village, north of Han River, to the south of Tsauton area. A characteristic style of the surface deformation is a convex scarp in profile and sinuous plan view, due to the low angle thrust fault. Two subparallel faults, including the west facing Tsauton West fault, and the east facing Tsauton East fault, limit the western and eastern margin of the Tsauton terraced area. The Tsauton West fault is the continuation of the main Chelungpu fault and the Tsauton East fault is located about 2 km apart. Both faults record larger amounts of vertical displacement on the older terraces. The 1999 surface rupture occurred exactly on a pre-existing fault scarp of the Tsauton West and East faults. Thus, repeated activities of these two faults during the Holocene, possibly since the late Quaternary, are confirmed. The amount of vertical offset of the Tsauton East fault is smaller, and about 40-50% of that of the Tsauton West fault for the pre-existing fault. This indicates that the Tsauton East fault is a subsidiary fault and moved together with the main fault, but accommodated less amount.

Eigenvector of gravity gradient tensor for estimating fault dips considering fault type

Science.gov (United States)

Kusumoto, Shigekazu

2017-12-01

The dips of boundaries in faults and caldera walls play an important role in understanding their formation mechanisms. The fault dip is a particularly important parameter in numerical simulations for hazard map creation as the fault dip affects estimations of the area of disaster occurrence. In this study, I introduce a technique for estimating the fault dip using the eigenvector of the observed or calculated gravity gradient tensor on a profile and investigating its properties through numerical simulations. From numerical simulations, it was found that the maximum eigenvector of the tensor points to the high-density causative body, and the dip of the maximum eigenvector closely follows the dip of the normal fault. It was also found that the minimum eigenvector of the tensor points to the low-density causative body and that the dip of the minimum eigenvector closely follows the dip of the reverse fault. It was shown that the eigenvector of the gravity gradient tensor for estimating fault dips is determined by fault type. As an application of this technique, I estimated the dip of the Kurehayama Fault located in Toyama, Japan, and obtained a result that corresponded to conventional fault dip estimations by geology and geomorphology. Because the gravity gradient tensor is required for this analysis, I present a technique that estimates the gravity gradient tensor from the gravity anomaly on a profile.

Source characterization and dynamic fault modeling of induced seismicity

Science.gov (United States)

Lui, S. K. Y.; Young, R. P.

2017-12-01

In recent years there are increasing concerns worldwide that industrial activities in the sub-surface can cause or trigger damaging earthquakes. In order to effectively mitigate the damaging effects of induced seismicity, the key is to better understand the source physics of induced earthquakes, which still remain elusive at present. Furthermore, an improved understanding of induced earthquake physics is pivotal to assess large-magnitude earthquake triggering. A better quantification of the possible causes of induced earthquakes can be achieved through numerical simulations. The fault model used in this study is governed by the empirically-derived rate-and-state friction laws, featuring a velocity-weakening (VW) patch embedded into a large velocity-strengthening (VS) region. Outside of that, the fault is slipping at the background loading rate. The model is fully dynamic, with all wave effects resolved, and is able to resolve spontaneous long-term slip history on a fault segment at all stages of seismic cycles. An earlier study using this model has established that aseismic slip plays a major role in the triggering of small repeating earthquakes. This study presents a series of cases with earthquakes occurring on faults with different fault frictional properties and fluid-induced stress perturbations. The effects to both the overall seismicity rate and fault slip behavior are investigated, and the causal relationship between the pre-slip pattern prior to the event and the induced source characteristics is discussed. Based on simulation results, the subsequent step is to select specific cases for laboratory experiments which allow well controlled variables and fault parameters. Ultimately, the aim is to provide better constraints on important parameters for induced earthquakes based on numerical modeling and laboratory data, and hence to contribute to a physics-based induced earthquake hazard assessment.

Paleoseismology of the Nephi Segment of the Wasatch Fault Zone, Juab County, Utah - Preliminary Results From Two Large Exploratory Trenches at Willow Creek

Science.gov (United States)

Machette, Michael N.; Crone, Anthony J.; Personius, Stephen F.; Mahan, Shannon; Dart, Richard L.; Lidke, David J.; Olig, Susan S.

2007-01-01

In 2004, we identified a small parcel of U.S. Forest Service land at the mouth of Willow Creek (about 5 km west of Mona, Utah) that was suitable for trenching. At the Willow Creek site, which is near the middle of the southern strand of the Nephi segment, the WFZ has vertically displaced alluvial-fan deposits >6-7 m, forming large, steep, multiple-event scarps. In May 2005, we dug two 4- to 5-m-deep backhoe trenches at the Willow Creek site, identified three colluvial wedges in each trench, and collected samples of charcoal and A-horizon organic material for AMS (acceleration mass spectrometry) radiocarbon dating, and sampled fine-grained eolian and colluvial sediment for luminescence dating. The trenches yielded a stratigraphic assemblage composed of moderately coarse-grained fluvial and debris-flow deposits and discrete colluvial wedges associated with three faulting events (P1, P2, and P3). About one-half of the net vertical displacement is accommodated by monoclinal tilting of fan deposits on the hanging-wall block, possibly related to massive ductile landslide deposits that are present beneath the Willow Creek fan. The timing of the three surface-faulting events is bracketed by radiocarbon dates and results in a much different fault chronology and higher slip rates than previously considered for this segment of the Wasatch fault zone.

Numerical seismic modelling of fault-fold structures in a mountainous setting

Energy Technology Data Exchange (ETDEWEB)

Kirtland Grech, M.G.; Lawton, D.C.; Spratt, D.A. (Calgary Univ., AB (Canada))

1999-01-01

Experiments were conducted to determine the performance of different prestack migration algorithms in complex structural areas, particularly in the presence of rugged topography and thrust faults that result in severe lateral and vertical velocity changes, using a series of numerical seismic models. The numerical model used was based on a cross section through the Rocky Mountains Front Ranges of Western Canada and is 33 km wide and 11 km deep. The best migrated section was obtained with FD shot migration in depth and from topography, using the known velocity model. This result was superior to Kirchhoff depth migration from topography and from a flat datum. As the velocities departed from their true value, the deeper events were most affected, because of the accumulation of velocity errors with depth. The small-scale features of Target A, in the shallower part of the section, could still be interpreted even when the velocities were inaccurate. In the presence of velocity errors, the different structures could still be interpreted, but were at the wrong depth and had the wrong structural shape and size. Layers that were of the order of 1 km in width and 500 km in thickness, such as Layer 4, were the most poorly imaged and focussed, both with time migration and with depth migration. Fault planes were not imaged in the absence of a velocity contrast across them, making some FW cutoffs difficult to interpret. 2 refs.

Numerical seismic modelling of fault-fold structures in a mountainous setting

Energy Technology Data Exchange (ETDEWEB)

Kirtland Grech, M.G.; Lawton, D.C.; Spratt, D.A. [Calgary Univ., AB (Canada)

1999-11-01

Experiments were conducted to determine the performance of different prestack migration algorithms in complex structural areas, particularly in the presence of rugged topography and thrust faults that result in severe lateral and vertical velocity changes, using a series of numerical seismic models. The numerical model used was based on a cross section through the Rocky Mountains Front Ranges of Western Canada and is 33 km wide and 11 km deep. The best migrated section was obtained with FD shot migration in depth and from topography, using the known velocity model. This result was superior to Kirchhoff depth migration from topography and from a flat datum. As the velocities departed from their true value, the deeper events were most affected, because of the accumulation of velocity errors with depth. The small-scale features of Target A, in the shallower part of the section, could still be interpreted even when the velocities were inaccurate. In the presence of velocity errors, the different structures could still be interpreted, but were at the wrong depth and had the wrong structural shape and size. Layers that were of the order of 1 km in width and 500 km in thickness, such as Layer 4, were the most poorly imaged and focussed, both with time migration and with depth migration. Fault planes were not imaged in the absence of a velocity contrast across them, making some FW cutoffs difficult to interpret. 2 refs.

The role of bed-parallel slip in the development of complex normal fault zones

Science.gov (United States)

Delogkos, Efstratios; Childs, Conrad; Manzocchi, Tom; Walsh, John J.; Pavlides, Spyros

2017-04-01

Normal faults exposed in Kardia lignite mine, Ptolemais Basin, NW Greece formed at the same time as bed-parallel slip-surfaces, so that while the normal faults grew they were intermittently offset by bed-parallel slip. Following offset by a bed-parallel slip-surface, further fault growth is accommodated by reactivation on one or both of the offset fault segments. Where one fault is reactivated the site of bed-parallel slip is a bypassed asperity. Where both faults are reactivated, they propagate past each other to form a volume between overlapping fault segments that displays many of the characteristics of relay zones, including elevated strains and transfer of displacement between segments. Unlike conventional relay zones, however, these structures contain either a repeated or a missing section of stratigraphy which has a thickness equal to the throw of the fault at the time of the bed-parallel slip event, and the displacement profiles along the relay-bounding fault segments have discrete steps at their intersections with bed-parallel slip-surfaces. With further increase in displacement, the overlapping fault segments connect to form a fault-bound lens. Conventional relay zones form during initial fault propagation, but with coeval bed-parallel slip, relay-like structures can form later in the growth of a fault. Geometrical restoration of cross-sections through selected faults shows that repeated bed-parallel slip events during fault growth can lead to complex internal fault zone structure that masks its origin. Bed-parallel slip, in this case, is attributed to flexural-slip arising from hanging-wall rollover associated with a basin-bounding fault outside the study area.

Frictional Properties of Shionohira Fault Gouge (Part 2) -A Comparison with Kuruma Fault Gouge at the Southern Extension of Shionohira Fault-

Science.gov (United States)

Seshimo, K.; Kazuhiro, A.; Yukumo, T.; Masakazu, N.; Shimamoto, T.; Ma, S.; Yao, L.; Kametaka, M.

2016-12-01

The April 11, 2011 Fukushima-ken Hamadori Earthquake (the largest aftershock of the 2011 off the Pacific coast of Tohoku Earthquake) formed co-seismic surface ruptures in NNW-SSE direction in Iwaki City, Fukushima Prefecture, Japan, named Shionohira Fault (hereafter called "active segment"). A N-S trending geological fault with lineaments (Kuruma Fault) along the southern extension of Shionohira Fault showed no surface ruptures (hereafter called "non-active segment"). The current report discusses differences of active and non-active segments by conducting low to high-velocity friction experiments on the gouge from shallow borehole cores. All experiments used a rotary-shear low to high-velocity frictional testing apparatus at the State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. The apparatus can produce slip rates of 0.2 microns/s to 2.1 mm/s under dry and wet conditions at room temperature and at normal stresses of mostly 1.38MPa. Experiments were performed under drained condition using gouges sealed by teflon sleeves. Non-active segment samples were taken from shallow borehole cores at depths 20.90 20.95m of Minakami-kita outcrop, and those for active segment at depths 12.82 12.87m of Shionohira outcrop and 5.96 6.00m of Betto outcrop. Three slip behaviors were recognized based on velocity dependence of steady-state friction coefficient: almost no velocity dependence for low velocity-regime of below 10 to 100 microns/s; clear velocity strengthening for intermediate velocity-regime of 100 microns/s to 1 mm/s; and significant velocity weakening for high velocity-regime of above 1 to 10 mm/s. Steady-state friction coefficients of dry gouges were 0.6 to 1.0 at low to intermediate slip velocity, and about 0.1 at high slip velocity. Wet gouges, however, of both Betto and Shionohira outcrop samples and Betto borehole core sample measured below 0.2 at low slip velocity although core samples of Shionohira and Minakami

Secondary Fault Activity of the North Anatolian Fault near Avcilar, Southwest of Istanbul: Evidence from SAR Interferometry Observations

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Faqi Diao

2016-10-01

Full Text Available Strike-slip faults may be traced along thousands of kilometers, e.g., the San Andreas Fault (USA or the North Anatolian Fault (Turkey. A closer look at such continental-scale strike faults reveals localized complexities in fault geometry, associated with fault segmentation, secondary faults and a change of related hazards. The North Anatolian Fault displays such complexities nearby the mega city Istanbul, which is a place where earthquake risks are high, but secondary processes are not well understood. In this paper, long-term persistent scatterer interferometry (PSI analysis of synthetic aperture radar (SAR data time series was used to precisely identify the surface deformation pattern associated with the faulting complexity at the prominent bend of the North Anatolian Fault near Istanbul city. We elaborate the relevance of local faulting activity and estimate the fault status (slip rate and locking depth for the first time using satellite SAR interferometry (InSAR technology. The studied NW-SE-oriented fault on land is subject to strike-slip movement at a mean slip rate of ~5.0 mm/year and a shallow locking depth of <1.0 km and thought to be directly interacting with the main fault branch, with important implications for tectonic coupling. Our results provide the first geodetic evidence on the segmentation of a major crustal fault with a structural complexity and associated multi-hazards near the inhabited regions of Istanbul, with similarities also to other major strike-slip faults that display changes in fault traces and mechanisms.

A microstructural study of fault rocks from the SAFOD: Implications for the deformation mechanisms and strength of the creeping segment of the San Andreas Fault

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Hadizadeh, Jafar; Mittempergher, Silvia; Gratier, Jean-Pierre; Renard, Francois; Di Toro, Giulio; Richard, Julie; Babaie, Hassan A.

2012-09-01

The San Andreas Fault zone in central California accommodates tectonic strain by stable slip and microseismic activity. We study microstructural controls of strength and deformation in the fault using core samples provided by the San Andreas Fault Observatory at Depth (SAFOD) including gouge corresponding to presently active shearing intervals in the main borehole. The methods of study include high-resolution optical and electron microscopy, X-ray fluorescence mapping, X-ray powder diffraction, energy dispersive X-ray spectroscopy, white light interferometry, and image processing. The fault zone at the SAFOD site consists of a strongly deformed and foliated core zone that includes 2-3 m thick active shear zones, surrounded by less deformed rocks. Results suggest deformation and foliation of the core zone outside the active shear zones by alternating cataclasis and pressure solution mechanisms. The active shear zones, considered zones of large-scale shear localization, appear to be associated with an abundance of weak phases including smectite clays, serpentinite alteration products, and amorphous material. We suggest that deformation along the active shear zones is by a granular-type flow mechanism that involves frictional sliding of microlithons along phyllosilicate-rich Riedel shear surfaces as well as stress-driven diffusive mass transfer. The microstructural data may be interpreted to suggest that deformation in the active shear zones is strongly displacement-weakening. The fault creeps because the velocity strengthening weak gouge in the active shear zones is being sheared without strong restrengthening mechanisms such as cementation or fracture sealing. Possible mechanisms for the observed microseismicity in the creeping segment of the SAF include local high fluid pressure build-ups, hard asperity development by fracture-and-seal cycles, and stress build-up due to slip zone undulations.

The 2016-2017 central Italy coseismic surface ruptures and their meaning with respect to foreseen active fault systems segmentation

Science.gov (United States)

De Martini, P. M.; Pucci, S.; Villani, F.; Civico, R.; Del Rio, L.; Cinti, F. R.; Pantosti, D.

2017-12-01

In 2016-2017 a series of moderate to large normal faulting earthquakes struck central Italy producing severe damage in many towns including Amatrice, Norcia and Visso and resulting in 299 casualties and >20,000 homeless. The complex seismic sequence depicts a multiple activation of the Mt. Vettore-Mt. Bove (VBFS) and the Laga Mts. fault systems, which were considered in literature as independent segments characterizing a recent seismic gap in the region comprised between two modern seismic sequences: the 1997-1998 Colfiorito and the 2009 L'Aquila. We mapped in detail the coseismic surface ruptures following three mainshocks (Mw 6.0 on 24th August, Mw 5.9 and Mw 6.5 on 26th and 30th October, 2016, respectively). Primary surface ruptures were observed and recorded for a total length of 5.2 km, ≅10 km and ≅25 km, respectively, along closely-spaced, parallel or subparallel, overlapping or step-like synthetic and antithetic fault splays of the activated fault systems, in some cases rupturing repeatedly the same location. Some coseismic ruptures were mapped also along the Norcia Fault System, paralleling the VBFS about 10 km westward. We recorded geometric and kinematic characteristics of the normal faulting ruptures with an unprecedented detail thanks to almost 11,000 oblique photographs taken from helicopter flights soon after the mainshocks, verified and integrated with field data (more than 7000 measurements). We analyze the along-strike coseismic slip and slip vectors distribution to be observed in the context of the geomorphic expression of the disrupted slopes and their depositional and erosive processes. Moreover, we constructed 1:10.000 scale geologic cross-sections based on updated maps, and we reconstructed the net offset distribution of the activated fault system to be compared with the morphologic throws and to test a cause-effect relationship between faulting and first-order landforms. We provide a reconstruction of the 2016 coseismic rupture pattern as

Numerical modelling of the mechanical and fluid flow properties of fault zones - Implications for fault seal analysis

NARCIS (Netherlands)

Heege, J.H. ter; Wassing, B.B.T.; Giger, S.B.; Clennell, M.B.

2009-01-01

Existing fault seal algorithms are based on fault zone composition and fault slip (e.g., shale gouge ratio), or on fault orientations within the contemporary stress field (e.g., slip tendency). In this study, we aim to develop improved fault seal algorithms that account for differences in fault zone

Fault zone hydrogeology

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Bense, V. F.; Gleeson, T.; Loveless, S. E.; Bour, O.; Scibek, J.

2013-12-01

Deformation along faults in the shallow crust (research effort of structural geologists and hydrogeologists. However, we find that these disciplines often use different methods with little interaction between them. In this review, we document the current multi-disciplinary understanding of fault zone hydrogeology. We discuss surface- and subsurface observations from diverse rock types from unlithified and lithified clastic sediments through to carbonate, crystalline, and volcanic rocks. For each rock type, we evaluate geological deformation mechanisms, hydrogeologic observations and conceptual models of fault zone hydrogeology. Outcrop observations indicate that fault zones commonly have a permeability structure suggesting they should act as complex conduit-barrier systems in which along-fault flow is encouraged and across-fault flow is impeded. Hydrogeological observations of fault zones reported in the literature show a broad qualitative agreement with outcrop-based conceptual models of fault zone hydrogeology. Nevertheless, the specific impact of a particular fault permeability structure on fault zone hydrogeology can only be assessed when the hydrogeological context of the fault zone is considered and not from outcrop observations alone. To gain a more integrated, comprehensive understanding of fault zone hydrogeology, we foresee numerous synergistic opportunities and challenges for the discipline of structural geology and hydrogeology to co-evolve and address remaining challenges by co-locating study areas, sharing approaches and fusing data, developing conceptual models from hydrogeologic data, numerical modeling, and training interdisciplinary scientists.

Numerical modeling of fracking fluid and methane migration through fault zones in shale gas reservoirs

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Taherdangkoo, Reza; Tatomir, Alexandru; Sauter, Martin

2017-04-01

Hydraulic fracturing operation in shale gas reservoir has gained growing interest over the last few years. Groundwater contamination is one of the most important environmental concerns that have emerged surrounding shale gas development (Reagan et al., 2015). The potential impacts of hydraulic fracturing could be studied through the possible pathways for subsurface migration of contaminants towards overlying aquifers (Kissinger et al., 2013; Myers, 2012). The intent of this study is to investigate, by means of numerical simulation, two failure scenarios which are based on the presence of a fault zone that penetrates the full thickness of overburden and connect shale gas reservoir to aquifer. Scenario 1 addresses the potential transport of fracturing fluid from the shale into the subsurface. This scenario was modeled with COMSOL Multiphysics software. Scenario 2 deals with the leakage of methane from the reservoir into the overburden. The numerical modeling of this scenario was implemented in DuMux (free and open-source software), discrete fracture model (DFM) simulator (Tatomir, 2012). The modeling results are used to evaluate the influence of several important parameters (reservoir pressure, aquifer-reservoir separation thickness, fault zone inclination, porosity, permeability, etc.) that could affect the fluid transport through the fault zone. Furthermore, we determined the main transport mechanisms and circumstances in which would allow frack fluid or methane migrate through the fault zone into geological layers. The results show that presence of a conductive fault could reduce the contaminant travel time and a significant contaminant leakage, under certain hydraulic conditions, is most likely to occur. Bibliography Kissinger, A., Helmig, R., Ebigbo, A., Class, H., Lange, T., Sauter, M., Heitfeld, M., Klünker, J., Jahnke, W., 2013. Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2. Environ Earth Sci 70, 3855

Three-dimensional numerical modeling of the influence of faults on groundwater flow at Yucca Mountain, Nevada

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Cohen, Andrew J.B. [Univ. of California, Berkeley, CA (United States)

1999-06-01

Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how the faulted hydrogeologic structure influences groundwater flow from a proposed high-level nuclear waste repository. Simulations are performed using a 3-D model that has a unique grid block discretization to accurately represent the faulted geologic units, which have variable thicknesses and orientations. Irregular grid blocks enable explicit representation of these features. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. The model has 23 layers and 11 faults, and approximately 57,000 grid blocks and 200,000 grid block connections. In the past, field measurement of upward vertical head gradients and high water table temperatures near faults were interpreted as indicators of upwelling from a deep carbonate aquifer. Simulations show, however, that these features can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities and thermal conductivities, and by the presence of permeable fault zones or faults with displacement only. In addition, a moderate water table gradient can result from fault displacement or a laterally continuous low permeability fault zone, but not from a high permeability fault zone, as others postulated earlier. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high and low permeability layers at faults, and from upward flow within high permeability fault zones. Conversely, large-scale channeling can occur due to groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different than that of the water table gradient, and isolated

Three-dimensional numerical modeling of the influence of faults on groundwater flow at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Cohen, Andrew J.B.

1999-01-01

Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how the faulted hydrogeologic structure influences groundwater flow from a proposed high-level nuclear waste repository. Simulations are performed using a 3-D model that has a unique grid block discretization to accurately represent the faulted geologic units, which have variable thicknesses and orientations. Irregular grid blocks enable explicit representation of these features. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. The model has 23 layers and 11 faults, and approximately 57,000 grid blocks and 200,000 grid block connections. In the past, field measurement of upward vertical head gradients and high water table temperatures near faults were interpreted as indicators of upwelling from a deep carbonate aquifer. Simulations show, however, that these features can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities and thermal conductivities, and by the presence of permeable fault zones or faults with displacement only. In addition, a moderate water table gradient can result from fault displacement or a laterally continuous low permeability fault zone, but not from a high permeability fault zone, as others postulated earlier. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high and low permeability layers at faults, and from upward flow within high permeability fault zones. Conversely, large-scale channeling can occur due to groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different than that of the water table gradient, and isolated

Spatial and Temporal Variations in Earthquake Stress Drop on Gofar Transform Fault, East Pacific Rise: Implications for Fault Strength

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Moyer, P. A.; Boettcher, M. S.; McGuire, J. J.; Collins, J. A.

2017-12-01

During the last five seismic cycles on Gofar transform fault on the East Pacific Rise, the largest earthquakes (6.0 ≤ Mw ≤ 6.2) have repeatedly ruptured the same fault segment (rupture asperity), while intervening fault segments host swarms of microearthquakes. Previous studies on Gofar have shown that these segments of low (≤10%) seismic coupling contain diffuse zones of seismicity and P-wave velocity reduction compared with the rupture asperity; suggesting heterogeneous fault properties control earthquake behavior. We investigate the role systematic differences in material properties have on earthquake rupture along Gofar using waveforms from ocean bottom seismometers that recorded the end of the 2008 Mw 6.0 seismic cycle.We determine stress drop for 117 earthquakes (2.4 ≤ Mw ≤ 4.2) that occurred in and between rupture asperities from corner frequency derived using an empirical Green's function spectral ratio method and seismic moment obtained by fitting the omega-square source model to the low frequency amplitude of earthquake spectra. We find stress drops from 0.03 to 2.7 MPa with significant spatial variation, including 2 times higher average stress drop in the rupture asperity compared to fault segments with low seismic coupling. We interpret an inverse correlation between stress drop and P-wave velocity reduction as the effect of damage on earthquake rupture. Earthquakes with higher stress drops occur in more intact crust of the rupture asperity, while earthquakes with lower stress drops occur in regions of low seismic coupling and reflect lower strength, highly fractured fault zone material. We also observe a temporal control on stress drop consistent with log-time healing following the Mw 6.0 mainshock, suggesting a decrease in stress drop as a result of fault zone damage caused by the large earthquake.

Faults architecture and growth in clay-limestone alternation. Examples in the S-E Basin alternations (France) and numerical modeling

International Nuclear Information System (INIS)

Roche, Vincent

2011-01-01

The following work has been carried out in the framework of the studies conducted by IRSN in support of its safety evaluation of the geological disposal programme of high and intermediate level, long-lived radioactive waste. Such a disposal is planned to be hosted by the Callovian-Oxfordian indurate clay formation between two limestone formations in eastern Paris basin, France. Hypothetical faults may cross-cut this layered section, decreasing the clay containment ability by creating preferential pathways for radioactive solute towards limestones. This study aims at characterising the fault architecture and the normal fault growth in clay/limestone layered sections. Structural analysis and displacement profiles have been carried out in normal faults crossing several decimetres to metre thick sedimentary alternations in the South-Eastern Basin (France) and petrophysical properties have been determined for each layer. The studied faults are simple fault planes or complex fault zones showing are significantly controlled by the layering. The analysis of the fault characteristics and the results obtained on numerical models enlighten several processes such as fault nucleation, fault restriction, and fault growth through layered section. Some studied faults nucleated in the limestone layers, without using pre-existing fractures such as joints, and according to our numerical analysis, a strong stiffness, a low strength contrast between the limestone and the clay layer, and/or s a greater thickness of the clay layer are conditions which favour nucleation of faults in limestone. The range of mechanical properties leading to the fault nucleation in one layer type or another was investigated using a 3D modelling approach. After its nucleation, the fault propagates within a homogeneous medium with a constant displacement gradient until its vertical propagation is stopped by a restrictor. The evidenced restrictors are limestone-clay interfaces or faults in clays, sub

How is tectonic slip partitioned from the Alpine Fault to the Marlborough Fault System? : results from the Hope Fault

International Nuclear Information System (INIS)

Langridge, R.M.

2004-01-01

This report contains data from research undertaken by the author on the Hope Fault from 2000-2004. This report provides an opportunity to include data that was additional to or newer than work that was published in other places. New results from studies along the Hurunui section of the Hope Fault, additional to that published in Langridge and Berryman (2005) are presented here. This data includes tabulated data of fault location and description measurements, a graphical representation of this data in diagrammatic form along the length of the fault and new radiocarbon dates from the current EQC funded project. The new data show that the Hurunui section of the Hope Fault has the capability to yield further data on fault slip rate, earthquake displacements, and paleoseismicity. New results from studies at the Greenburn Stream paleoseismic site additional to that published in Langridge et al. (2003) are presented here. This includes a new log of the deepened west wall of Trench 2, a log of the west wall of Trench 1, and new radiocarbon dates from the second phase of dating undertaken at the Greenburn Stream site. The new data show that this site has the capability to yield further data on the paleoseismicity of the Conway segment of the Hope Fault. Through a detailed analysis of all three logged walls at the site and the new radiocarbon dates, it may, in combination with data from the nearby Clarence Reserve site of Pope (1994), be possible to develop a good record of the last 5 events on the Conway segment. (author). 12 refs., 12 figs

Fault rocks from the SAFOD core samples : implications for weakening at shallow depths along the San Andreas Fault, California

NARCIS (Netherlands)

Holdsworth, R.E.; van Diggelen, E.W.E.; Spiers, C.J.; Bresser, J.H.P. de; Walker, R.J.; Bown, L.

2011-01-01

The drilling of a deep borehole across the actively creeping Parkfield segment of the San Andreas Fault Zone (SAFZ), California, and collection of core materials permit direct geological study of fault zone processes at 2–3 km depth. The three drill cores sample both host and fault rocks and pass

Why the 2002 Denali fault rupture propagated onto the Totschunda fault: implications for fault branching and seismic hazards

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Schwartz, David P.; Haeussler, Peter J.; Seitz, Gordon G.; Dawson, Timothy E.

2012-01-01

The propagation of the rupture of the Mw7.9 Denali fault earthquake from the central Denali fault onto the Totschunda fault has provided a basis for dynamic models of fault branching in which the angle of the regional or local prestress relative to the orientation of the main fault and branch plays a principal role in determining which fault branch is taken. GeoEarthScope LiDAR and paleoseismic data allow us to map the structure of the Denali-Totschunda fault intersection and evaluate controls of fault branching from a geological perspective. LiDAR data reveal the Denali-Totschunda fault intersection is structurally simple with the two faults directly connected. At the branch point, 227.2 km east of the 2002 epicenter, the 2002 rupture diverges southeast to become the Totschunda fault. We use paleoseismic data to propose that differences in the accumulated strain on each fault segment, which express differences in the elapsed time since the most recent event, was one important control of the branching direction. We suggest that data on event history, slip rate, paleo offsets, fault geometry and structure, and connectivity, especially on high slip rate-short recurrence interval faults, can be used to assess the likelihood of branching and its direction. Analysis of the Denali-Totschunda fault intersection has implications for evaluating the potential for a rupture to propagate across other types of fault intersections and for characterizing sources of future large earthquakes.

Robust Fault Diagnosis Design for Linear Multiagent Systems with Incipient Faults

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Jingping Xia

2015-01-01

Full Text Available The design of a robust fault estimation observer is studied for linear multiagent systems subject to incipient faults. By considering the fact that incipient faults are in low-frequency domain, the fault estimation of such faults is proposed for discrete-time multiagent systems based on finite-frequency technique. Moreover, using the decomposition design, an equivalent conclusion is given. Simulation results of a numerical example are presented to demonstrate the effectiveness of the proposed techniques.

Active strike-slip faulting in El Salvador, Central America

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Corti, Giacomo; Carminati, Eugenio; Mazzarini, Francesco; Oziel Garcia, Marvyn

2005-12-01

Several major earthquakes have affected El Salvador, Central America, during the Past 100 yr as a consequence of oblique subduction of the Cocos plate under the Caribbean plate, which is partitioned between trench-orthogonal compression and strike-slip deformation parallel to the volcanic arc. Focal mechanisms and the distribution of the most destructive earthquakes, together with geomorphologic evidence, suggest that this transcurrent component of motion may be accommodated by a major strike-slip fault (El Salvador fault zone). We present field geological, structural, and geomorphological data collected in central El Salvador that allow the constraint of the kinematics and the Quaternary activity of this major seismogenic strike-slip fault system. Data suggest that the El Salvador fault zone consists of at least two main ˜E-W fault segments (San Vicente and Berlin segments), with associated secondary synthetic (WNW-ESE) and antithetic (NNW-SSE) Riedel shears and NW-SE tensional structures. The two main fault segments overlap in a dextral en echelon style with the formation of an intervening pull-apart basin. Our original geological and geomorphologic data suggest a late Pleistocene Holocene slip rate of ˜11 mm/yr along the Berlin segment, in contrast with low historical seismicity. The kinematics and rates of deformation suggested by our new data are consistent with models involving slip partitioning during oblique subduction, and support the notion that a trench-parallel component of motion between the Caribbean and Cocos plates is concentrated along E-W dextral strike-slip faults parallel to the volcanic arc.

A numerical model for modeling microstructure and THM couplings in fault gouges

Science.gov (United States)

Veveakis, M.; Rattez, H.; Stefanou, I.; Sulem, J.; Poulet, T.

2017-12-01

When materials are subjected to large deformations, most of them experience inelastic deformations, accompanied by a localization of these deformations into a narrow zone leading to failure. Localization is seen as an instability from the homogeneous state of deformation. Therefore a first approach to study it consists at looking at the possible critical conditions for which the constitutive equations of the material allow a bifurcation point (Rudnicki & Rice 1975). But in some cases, we would like to know the evolution of the material after the onset of localization. For example, a fault in the crustal part of the lithosphere is a shear band and the study of this localized zone enables to extract information about seismic slip. For that, we need to approximate the solution of a nonlinear boundary value problem numerically. It is a challenging task due to the complications that arise while dealing with a softening behavior. Indeed, the classical continuum theory cannot be used because the governing system of equations is ill-posed (Vardoulakis 1985). This ill-posedness can be tracked back to the fact that constitutive models don't contain material parameters with the dimension of a length. It leads to what is called "mesh dependency" for numerical simulations, as the deformations localize in only one element of the mesh and the behavior of the system depends thus on the mesh size. A way to regularize the problem is to resort to continuum models with microstructure, such as Cosserat continua (Sulem et al. 2011). Cosserat theory is particularly interesting as it can explicitly take into account the size of the microstructure in a fault gouge. Basically, it introduces 3 degrees of freedom of rotation on top of the 3 translations (Godio et al. 2016). The original work of (Mühlhaus & Vardoulakis 1987) is extended in 3D and thermo-hydro mechanical couplings are added to the model to study fault system in the crustal part of the lithosphere. The system of equations is

Late Holocene earthquake history of the Brigham City segment of the Wasatch fault zone at the Hansen Canyon, Kotter Canyon, and Pearsons Canyon trench sites, Box Elder County, Utah

Science.gov (United States)

DuRoss, Christopher B.; Personius, Stephen F.; Crone, Anthony J.; McDonald, Greg N.; Briggs, Richard W.

2012-01-01

Of the five central segments of the Wasatch fault zone (WFZ) having evidence of recurrent Holocene surface-faulting earthquakes, the Brigham City segment (BCS) has the longest elapsed time since its most recent surface-faulting event (~2.1 kyr) compared to its mean recurrence time between events (~1.3 kyr). Thus, the BCS has the highest time-dependent earthquake probability of the central WFZ. We excavated trenches at three sites––the Kotter Canyon and Hansen Canyon sites on the north-central BCS and Pearsons Canyon site on the southern BCS––to determine whether a surface-faulting earthquake younger than 2.1 ka occurred on the BCS. Paleoseismic data for Hansen Canyon and Kotter Canyon confirm that the youngest earthquake on the north-central BCS occurred before 2 ka, consistent with previous north-central BCS investigations at Bowden Canyon and Box Elder Canyon. At Hansen Canyon, the most recent earthquake is constrained to 2.1–4.2 ka and had 0.6–2.5 m of vertical displacement. At Kotter Canyon, we found evidence for two events at 2.5 ± 0.3 ka and 3.5 ± 0.3 ka, with an average displacement per event of 1.9–2.3 m. Paleoseismic data from Pearsons Canyon, on the previously unstudied southern BCS, indicate that a post-2 ka earthquake ruptured this part of the segment. The Pearsons Canyon earthquake occurred at 1.2 ± 0.04 ka and had 0.1–0.8 m of vertical displacement, consistent with our observation of continuous, youthful scarps on the southern 9 km of the BCS having 1–2 m of late Holocene(?) surface offset. The 1.2-ka earthquake on the southern BCS likely represents rupture across the Weber–Brigham City segment boundary from the penultimate Weber-segment earthquake at about 1.1 ka. The Pearsons Canyon data result in a revised length of the BCS that has not ruptured since 2 ka (with time-dependent probability implications), and provide compelling evidence of at least one segment-boundary failure and multi-segment rupture on the central WFZ. Our

Mathematical modeling and numerical simulation of unilateral dynamic rupture propagation along very-long reverse faults

Science.gov (United States)

Hirano, S.

2017-12-01

For some great earthquakes, dynamic rupture propagates unilaterally along a horizontal direction of very-long reverse faults (e.g., the Mw9.1 Sumatra earthquake in 2004, the Mw8.0 Wenchuan earthquake in 2008, and the Mw8.8 Maule earthquake in 2010, etc.). It seems that barriers or creeping sections may not lay along the opposite region of the co-seismically ruptured direction. In fact, in the case of Sumatra, the Mw8.6 earthquake occurred in the opposite region only three months after the mainshock. Mechanism of unilateral mode-II rupture along a material interface has been investigated theoretically and numerically. For mode-II rupture propagating along a material interface, an analytical solution implies that co-seismic stress perturbation depends on the rupture direction (Weertman, 1980 JGR; Hirano & Yamashita, 2016 BSSA), and numerical modeling of plastic yielding contributes to simulating the unilateral rupture (DeDonteny et al., 2011 JGR). However, mode-III rupture may dominate for the very-long reverse faults, and it can be shown that stress perturbation due to mode-III rupture does not depend on the rupture direction. Hence, an effect of the material interface is insufficient to understand the mechanism of unilateral rupture along the very-long reverse faults. In this study, I consider a two-dimensional bimaterial system with interfacial dynamic mode-III rupture under an obliquely pre-stressed configuration (i.e., the maximum shear direction of the background stress is inclined from the interfacial fault). First, I derived an analytical solution of regularized elastic stress field around a steady-state interfacial slip pulse using the method of Rice et al. (2005 BSSA). Then I found that the total stress, which is the sum of the background stress and co-seismic stress perturbation, depends on the rupture direction even in the mode-III case. Second, I executed a finite difference numerical simulation with a plastic yielding model of Andrews (1978 JGR; 2005

A bottom-driven mechanism for distributed faulting: Insights from the Gulf of California Rift

Science.gov (United States)

Persaud, P.; Tan, E.; Choi, E.; Contreras, J.; Lavier, L. L.

2017-12-01

The Gulf of California is a young oblique rift that displays a variation in rifting style along strike. Despite the rapid localization of strain in the Gulf at 6 Ma, the northern rift segment has the characteristics of a wide rift, with broadly distributed extensional strain and small gradients in topography and crustal thinning. Observations of active faulting in the continent-ocean transition of the Northern Gulf show multiple oblique-slip faults distributed in a 200 x 70 km2area developed some time after a westward relocation of the plate boundary at 2 Ma. In contrast, north and south of this broad pull-apart structure, major transform faults accommodate Pacific-North America plate motion. Here we propose that the mechanism for distributed brittle deformation results from the boundary conditions present in the Northern Gulf, where basal shear is distributed between the Cerro Prieto strike-slip fault (southernmost fault of the San Andreas fault system) and the Ballenas Transform fault. We hypothesize that in oblique-extensional settings whether deformation is partitioned in a few dip-slip and strike-slip faults, or in numerous oblique-slip faults may depend on (1) bottom-driven, distributed extension and shear deformation of the lower crust or upper mantle, and (2) the rift obliquity. To test this idea, we explore the effects of bottom-driven shear on the deformation of a brittle elastic-plastic layer with pseudo-three dimensional numerical models that include side forces. Strain localization results when the basal shear is a step-function while oblique-slip on numerous faults dominates when basal shear is distributed. We further investigate how the style of faulting varies with obliquity and demonstrate that the style of faulting observed in the Northern Gulf of California is reproduced in models with an obliquity of 0.7 and distributed basal shear boundary conditions, consistent with the interpreted obliquity and boundary conditions of the study area. Our

Spreading rate dependence of gravity anomalies along oceanic transform faults.

Science.gov (United States)

Gregg, Patricia M; Lin, Jian; Behn, Mark D; Montési, Laurent G J

2007-07-12

Mid-ocean ridge morphology and crustal accretion are known to depend on the spreading rate of the ridge. Slow-spreading mid-ocean-ridge segments exhibit significant crustal thinning towards transform and non-transform offsets, which is thought to arise from a three-dimensional process of buoyant mantle upwelling and melt migration focused beneath the centres of ridge segments. In contrast, fast-spreading mid-ocean ridges are characterized by smaller, segment-scale variations in crustal thickness, which reflect more uniform mantle upwelling beneath the ridge axis. Here we present a systematic study of the residual mantle Bouguer gravity anomaly of 19 oceanic transform faults that reveals a strong correlation between gravity signature and spreading rate. Previous studies have shown that slow-slipping transform faults are marked by more positive gravity anomalies than their adjacent ridge segments, but our analysis reveals that intermediate and fast-slipping transform faults exhibit more negative gravity anomalies than their adjacent ridge segments. This finding indicates that there is a mass deficit at intermediate- and fast-slipping transform faults, which could reflect increased rock porosity, serpentinization of mantle peridotite, and/or crustal thickening. The most negative anomalies correspond to topographic highs flanking the transform faults, rather than to transform troughs (where deformation is probably focused and porosity and alteration are expected to be greatest), indicating that crustal thickening could be an important contributor to the negative gravity anomalies observed. This finding in turn suggests that three-dimensional magma accretion may occur near intermediate- and fast-slipping transform faults.

Late Cenozoic thrusting of major faults along the central segment of Longmen Shan, eastern Tibet: Evidence from low-temperature thermochronology

Science.gov (United States)

Tan, Xi-Bin; Xu, Xi-Wei; Lee, Yuan-Hsi; Lu, Ren-Qi; Liu, Yiduo; Xu, Chong; Li, Kang; Yu, Gui-Hua; Kang, Wen-Jun

2017-08-01

The Cenozoic orogenic process of the Longmen Shan (LMS) and the kinematics of major faults along the LMS are crucial for understanding the growth history and mechanism of the eastern Tibetan Plateau. Three major faults, from west to east, are present in the central segment of the LMS: the Wenchuan-Maoxian Fault (WMF), the Beichuan-Yingxiu Fault (BYF), and the Jiangyou-Guanxian Fault (JGF). Previous researchers have placed great impetus on the Pengguan Massif, between the WMF and BYF. However, limited low-temperature thermochronology data coverage in other areas prevents us from fully delineating the tectonic history of the LMS. In this study, we collect 22 samples from vertical profiles in the Xuelongbao Massif and the range frontal area located at the hanging walls of the WMF and JGF respectively, and conduct apatite and zircon fission track analyses. New fission track data reveal that the Xuelongbao Massif has been undergoing rapid exhumation with an average rate of 0.7-0.9 mm/yr since 11 Ma, and the range frontal area began rapid exhumation at 7.5 Ma with total exhumation of 2.5-4.5 km. The exhumation histories indicate that the three major faults (WMF, BYF and JGF) in the central LMS are all reverse faults, and show a basinward in-sequence propagation from middle Miocene to present-day. Such a pattern further implies that upper crustal shortening is the primary driver for the LMS' uplift during the Late Cenozoic. Nevertheless, middle-lower crustal deformation is difficult to be constrained by the exhumation histories, and its contribution to LMS' uplift cannot be ruled out.

Spatial distribution correlation of soil-gas radon (222Rn) and mercury with leveling deformation in northern margin fault zone of West Qinling, China.

Science.gov (United States)

Li, Chenhua; Zhang, Hui; Su, Hejun; Zhou, Huiling; Wang, Yanhong

2017-11-01

This study concerns measurement of 222 Rn and mercury concentrations in soil-gas in the northern margin fault zone of West Qinling, Tibet (China). Based on profiles crossing perpendicularly the different segments of the fault at six different locations, the relations between the gas measurements, fault deformation, and seismic activity in each segment of the studied fault were analyzed, determining seismic risks in the fault zone. Soil-gas data are heterogeneous, but appear relatively organized along the three segments of the fault. The detailed multidisciplinary analysis reveals complex interactions between the structural setting, uprising fluids, leveling and seismic activity in different fault segments. The results for both fault soil gas and deformation indicated relatively stronger fault activity in the Wushan segment in the middle-eastern segment of the northern margin fault zone of West Qinling and lower activity in the Zhangxian segment, whereas the fault in the Tianshui segment was relatively locked. Additionally, in the Wushan strike-slip pull-apart area, the active influence of fluid activities facilitated the occurrence of small to medium-sized seismic events, which prevented the occurrence of larger events; in contrast, in the Tianshui segment, the west Zhangxian segment, the weak fluid activities and the corresponding strain rate will probably lead to strong earthquake buildup. Copyright © 2017 Elsevier Ltd. All rights reserved.

Numerical simulations of earthquakes and the dynamics of fault systems using the Finite Element method.

Science.gov (United States)

Kettle, L. M.; Mora, P.; Weatherley, D.; Gross, L.; Xing, H.

2006-12-01

Simulations using the Finite Element method are widely used in many engineering applications and for the solution of partial differential equations (PDEs). Computational models based on the solution of PDEs play a key role in earth systems simulations. We present numerical modelling of crustal fault systems where the dynamic elastic wave equation is solved using the Finite Element method. This is achieved using a high level computational modelling language, escript, available as open source software from ACcESS (Australian Computational Earth Systems Simulator), the University of Queensland. Escript is an advanced geophysical simulation software package developed at ACcESS which includes parallel equation solvers, data visualisation and data analysis software. The escript library was implemented to develop a flexible Finite Element model which reliably simulates the mechanism of faulting and the physics of earthquakes. Both 2D and 3D elastodynamic models are being developed to study the dynamics of crustal fault systems. Our final goal is to build a flexible model which can be applied to any fault system with user-defined geometry and input parameters. To study the physics of earthquake processes, two different time scales must be modelled, firstly the quasi-static loading phase which gradually increases stress in the system (~100years), and secondly the dynamic rupture process which rapidly redistributes stress in the system (~100secs). We will discuss the solution of the time-dependent elastic wave equation for an arbitrary fault system using escript. This involves prescribing the correct initial stress distribution in the system to simulate the quasi-static loading of faults to failure; determining a suitable frictional constitutive law which accurately reproduces the dynamics of the stick/slip instability at the faults; and using a robust time integration scheme. These dynamic models generate data and information that can be used for earthquake forecasting.

Subsurface structures of the active reverse fault zones in Japan inferred from gravity anomalies.

Science.gov (United States)

Matsumoto, N.; Sawada, A.; Hiramatsu, Y.; Okada, S.; Tanaka, T.; Honda, R.

2016-12-01

The object of our study is to examine subsurface features such as continuity, segmentation and faulting type, of the active reverse fault zones. We use the gravity data published by the Gravity Research Group in Southwest Japan (2001), the Geographical Survey Institute (2006), Yamamoto et al. (2011), Honda et al. (2012), and the Geological Survey of Japan, AIST (2013) in this study. We obtained the Bouguer anomalies through terrain corrections with 10 m DEM (Sawada et al. 2015) under the assumed density of 2670 kg/m3, a band-pass filtering, and removal of linear trend. Several derivatives and structural parameters calculated from a gravity gradient tensor are applied to highlight the features, such as a first horizontal derivatives (HD), a first vertical derivatives (VD), a normalized total horizontal derivative (TDX), a dip angle (β), and a dimensionality index (Di). We analyzed 43 reverse fault zones in northeast Japan and the northern part of southwest Japan among major active fault zones selected by Headquarters for Earthquake Research Promotion. As the results, the subsurface structural boundaries clearly appear along the faults at 21 faults zones. The weak correlations appear at 13 fault zones, and no correlations are recognized at 9 fault zones. For example, in the Itoigawa-Shizuoka tectonic line, the subsurface structure boundary seems to extend further north than the surface trace. Also, a left stepping structure of the fault around Hakuba is more clearly observed with HD. The subsurface structures, which detected as the higher values of HD, are distributed on the east side of the surface rupture in the north segments and on the west side in the south segments, indicating a change of the dip direction, the east dipping to the west dipping, from north to south. In the Yokote basin fault zone, the subsurface structural boundary are clearly detected with HD, VD and TDX along the fault zone in the north segment, but less clearly in the south segment. Also, Di

Numerical simulation of faulting in the Sunda Trench shows that seamounts may generate megathrust earthquakes

Science.gov (United States)

Jiao, L.; Chan, C. H.; Tapponnier, P.

2017-12-01

The role of seamounts in generating earthquakes has been debated, with some studies suggesting that seamounts could be truncated to generate megathrust events, while other studies indicate that the maximum size of megathrust earthquakes could be reduced as subducting seamounts could lead to segmentation. The debate is highly relevant for the seamounts discovered along the Mentawai patch of the Sunda Trench, where previous studies have suggested that a megathrust earthquake will likely occur within decades. In order to model the dynamic behavior of the Mentawai patch, we simulated forearc faulting caused by seamount subducting using the Discrete Element Method. Our models show that rupture behavior in the subduction system is dominated by stiffness of the overriding plate. When stiffness is low, a seamount can be a barrier to rupture propagation, resulting in several smaller (M≤8.0) events. If, however, stiffness is high, a seamount can cause a megathrust earthquake (M8 class). In addition, we show that a splay fault in the subduction environment could only develop when a seamount is present, and a larger offset along a splay fault is expected when stiffness of the overriding plate is higher. Our dynamic models are not only consistent with previous findings from seismic profiles and earthquake activities, but the models also better constrain the rupture behavior of the Mentawai patch, thus contributing to subsequent seismic hazard assessment.

Segmentation of Slow Slip Events in South Central Alaska Possibly Controlled by a Subducted Oceanic Plateau

Science.gov (United States)

Li, Haotian; Wei, Meng; Li, Duo; Liu, Yajing; Kim, YoungHee; Zhou, Shiyong

2018-01-01

Recent GPS observations show that slow slip events in south central Alaska are segmented along strike. Here we review several mechanisms that might contribute to this segmentation and focus on two: along-strike variation of slab geometry and effective normal stress. We then test them by running numerical simulations in the framework of rate-and-state friction with a nonplanar fault geometry. Results show that the segmentation is most likely related to the along-strike variation of the effective normal stress on the fault plane caused by the Yakutat Plateau. The Yakutat Plateau could affect the effective normal stress by either lowering the pore pressure in Upper Cook Inlet due to less fluids release or increasing the normal stress due to the extra buoyancy caused by the subducted Yakutat Plateau. We prefer the latter explanation because it is consistent with the relative amplitudes of the effective normal stress in Upper and Lower Cook Inlet and there is very little along-strike variation in Vp/Vs ratio in the fault zone from receiver function analysis. However, we cannot exclude the possibility that the difference in effective normal stress results from along-strike variation of pore pressure due to the uncertainties in the Vp/Vs estimates. Our work implies that a structural anomaly can have a long-lived effect on the subduction zone slip behavior and might be a driving factor on along-strike segmentation of slow slip events.

Elemental Geochemistry of Samples From Fault Segments of the San Andreas Fault Observatory at Depth (SAFOD) Drill Hole

Science.gov (United States)

Tourscher, S. N.; Schleicher, A. M.; van der Pluijm, B. A.; Warr, L. N.

2006-12-01

Elemental geochemistry of mudrock samples from phase 2 drilling of the San Andreas Fault Observatory at Depth (SAFOD) is presented from bore hole depths of 3066 m to 3169 m and from 3292 m to 3368 m, which contain a creeping section and main trace of the fault, respectively. In addition to preparation and analysis of whole rock sample, fault grains with neomineralized, polished surfaces were hand picked from well-washed whole rock samples, minimizing the potential contamination from drilling mud and steel shavings. The separated fractions were washed in deionized water, powdered using a mortar and pestle, and analyzed using an Inductively Coupled Plasma- Optical Emission Spectrometer for major and minor elements. Based on oxide data results, systematic differences in element concentrations are observed between the whole rock and fault rock. Two groupings of data points are distinguishable in the regions containing the main trace of the fault, a shallow part (3292- 3316 m) and a deeper section (3320-3368 m). Applying the isocon method, assuming Zr and Ti to be immobile elements in these samples, indicates a volume loss of more than 30 percent in the shallow part and about 23 percent in the deep part of the main trace. These changes are minimum estimates of fault-related volume loss, because the whole rock from drilling samples contains variable amount of fault rock as well. Minimum estimates for volume loss in the creeping section of the fault are more than 50 percent when using the isocon method, comparing whole rock to plucked fault rock. The majority of the volume loss in the fault rocks is due to the dissolution and loss of silica, potassium, aluminum, sodium and calcium, whereas (based on oxide data) the mineralized surfaces of fractures appear to be enriched in Fe and Mg. The large amount of element mobility within these fault traces suggests extensive circulation of hydrous fluids along fractures that was responsible for progressive dissolution and leaching

Mapping of the surface rupture induced by the M 7.3 Kumamoto Earthquake along the Eastern segment of Futagawa fault using image correlation techniques

Science.gov (United States)

Ekhtari, N.; Glennie, C. L.; Fielding, E. J.; Liang, C.

2016-12-01

Near field surface deformation is vital to understanding the shallow fault physics of earthquakes but near-field deformation measurements are often sparse or not reliable. In this study, we use the Co-seismic Image Correlation (COSI-Corr) technique to map the near-field surface deformation caused by the M 7.3 April 16, 2016 Kumamoto Earthquake, Kyushu, Japan. The surface rupture around the Eastern segment of Futagawa fault is mapped using a pair of panchromatic 1.5 meter resolution SPOT 7 images. These images were acquired on January 16 and April 29, 2016 (3 months before and 13 days after the earthquake respectively) with close to nadir (less than 1.5 degree off nadir) viewing angle. The two images are ortho-rectified using SRTM Digital Elevation Model and further co-registered using tie points far away from the rupture field. Then the COSI-Corr technique is utilized to produce an estimated surface displacement map, and a horizontal displacement vector field is calculated which supplies a seamless estimate of near field displacement measurements along the Eastern segment of the Futagawa fault. The COSI-Corr estimated displacements are then compared to other existing displacement observations from InSAR, GPS and field observations.

Transpressive mantle uplift at large offset oceanic transform faults

Science.gov (United States)

Maia, M.; Briais, A.; Brunelli, D.; Ligi, M.; Sichel, S. E.; Campos, T.

2017-12-01

Large-offset transform faults deform due to changes in plate motions and local processes. At the St. Paul transform, in the Equatorial Atlantic, a large body of ultramafic rocks composed of variably serpentinized and mylonitized peridotites is presently being tectonically uplifted. We recently discovered that the origin of the regional mantle uplift is linked to long-standing compressive stresses along the transform fault (1). A positive flower structure, mainly made of mylonitized mantle rocks, can be recognized on the 200 km large push-up ridge. Compressive earthquakes mechanisms reveal seismically active thrust faults on the southern flank of the ridge . The regional transpressive stress field affects a large portion of the ridge segment south of the transform, as revealed by the presence of faults and dykes striking obliquely to the direction of the central ridge axis. A smaller thrust, affecting recent sediments, was mapped south of this segment, suggesting a regional active compressive stress field. The transpressive stress field is interpreted to derive from the propagation of the Mid-Atlantic Ridge (MAR) segment into the transform domain as a response to the enhanced melt supply at the ridge axis. The propagation forced the migration and segmentation of the transform fault southward and the formation of restraining step-overs. The process started after a counterclockwise change in plate motion at 11 Ma initially resulting in extensive stress of the transform domain. A flexural transverse ridge formed in response. Shortly after plate reorganization, the MAR segment started to propagate southwards due to the interaction of the ridge and the Sierra Leone thermal anomaly. 1- Maia et al., 2016. Extreme mantle uplift and exhumation along a transpressive transform fault Nat. Geo. doi:10.1038/ngeo2759

Modeling earthquake sequences along the Manila subduction zone: Effects of three-dimensional fault geometry

Science.gov (United States)

Yu, Hongyu; Liu, Yajing; Yang, Hongfeng; Ning, Jieyuan

2018-05-01

To assess the potential of catastrophic megathrust earthquakes (MW > 8) along the Manila Trench, the eastern boundary of the South China Sea, we incorporate a 3D non-planar fault geometry in the framework of rate-state friction to simulate earthquake rupture sequences along the fault segment between 15°N-19°N of northern Luzon. Our simulation results demonstrate that the first-order fault geometry heterogeneity, the transitional-segment (possibly related to the subducting Scarborough seamount chain) connecting the steeper south segment and the flatter north segment, controls earthquake rupture behaviors. The strong along-strike curvature at the transitional-segment typically leads to partial ruptures of MW 8.3 and MW 7.8 along the southern and northern segments respectively. The entire fault occasionally ruptures in MW 8.8 events when the cumulative stress in the transitional-segment is sufficiently high to overcome the geometrical inhibition. Fault shear stress evolution, represented by the S-ratio, is clearly modulated by the width of seismogenic zone (W). At a constant plate convergence rate, a larger W indicates on average lower interseismic stress loading rate and longer rupture recurrence period, and could slow down or sometimes stop ruptures that initiated from a narrower portion. Moreover, the modeled interseismic slip rate before whole-fault rupture events is comparable with the coupling state that was inferred from the interplate seismicity distribution, suggesting the Manila trench could potentially rupture in a M8+ earthquake.

Comparison of maximum runup through analytical and numerical approaches for different fault parameters estimates

Science.gov (United States)

Kanoglu, U.; Wronna, M.; Baptista, M. A.; Miranda, J. M. A.

2017-12-01

The one-dimensional analytical runup theory in combination with near shore synthetic waveforms is a promising tool for tsunami rapid early warning systems. Its application in realistic cases with complex bathymetry and initial wave condition from inverse modelling have shown that maximum runup values can be estimated reasonably well. In this study we generate a simplistic bathymetry domains which resemble realistic near-shore features. We investigate the accuracy of the analytical runup formulae to the variation of fault source parameters and near-shore bathymetric features. To do this we systematically vary the fault plane parameters to compute the initial tsunami wave condition. Subsequently, we use the initial conditions to run the numerical tsunami model using coupled system of four nested grids and compare the results to the analytical estimates. Variation of the dip angle of the fault plane showed that analytical estimates have less than 10% difference for angles 5-45 degrees in a simple bathymetric domain. These results shows that the use of analytical formulae for fast run up estimates constitutes a very promising approach in a simple bathymetric domain and might be implemented in Hazard Mapping and Early Warning.

Structure of the 1906 near-surface rupture zone of the San Andreas Fault, San Francisco Peninsula segment, near Woodside, California

Science.gov (United States)

Rosa, C.M.; Catchings, R.D.; Rymer, M.J.; Grove, Karen; Goldman, M.R.

2016-07-08

nearby sites. Multiple fault strands in the area of the 1906 surface rupture may account for variations in geologic slip rates calculated from several paleoseismic sites along the Peninsula segment of the San Andreas Fault.t.

Deformation around basin scale normal faults

International Nuclear Information System (INIS)

Spahic, D.

2010-01-01

in the central Vienna Basin from commercial 3D seismic data. In addition to detailed conventional fault analysis (displacement and fault shape), syn-and anticlinal structures of sedimentary horizons occurring both in hanging wall and footwall are assessed. Reverse drag geometries of variable magnitudes are found to correlate with local displacement maxima along the fault. In contrast, normal drag is observed along segment boundaries and relay zones. Thus, the detailed documentation of the distribution, type and magnitude of fault drag provides additional information on the fault evolution, as initial fault segments as well as linkage or relay zones can be identified. (author) [de

Luminescence dating of paleoseismic events associated with the Muzaffarnagar fault in the Western Gangetic Plain

International Nuclear Information System (INIS)

Bhosle, Balaji; Parkash, B.; Awasthi, A.K.

2006-01-01

Using remote sensing and GIS techniques of satellite data processing, Muzaffarnagar fault is identified in western Gangetic Plain. Activity along the fault has resulted in deposition of colluvial deposits (alluvial fans) on the downthrown block. Luminescence dating of colluvial deposits suggests that the fault is segmented. The last activity which took place along the eastern segment was at 3.5 ka and middle and western segment were active during 2.5-2.8 ka. (author)

Domain decomposition method for dynamic faulting under slip-dependent friction

International Nuclear Information System (INIS)

Badea, Lori; Ionescu, Ioan R.; Wolf, Sylvie

2004-01-01

The anti-plane shearing problem on a system of finite faults under a slip-dependent friction in a linear elastic domain is considered. Using a Newmark method for the time discretization of the problem, we have obtained an elliptic variational inequality at each time step. An upper bound for the time step size, which is not a CFL condition, is deduced from the solution uniqueness criterion using the first eigenvalue of the tangent problem. Finite element form of the variational inequality is solved by a Schwarz method assuming that the inner nodes of the domain lie in one subdomain and the nodes on the fault lie in other subdomains. Two decompositions of the domain are analyzed, one made up of two subdomains and another one with three subdomains. Numerical experiments are performed to illustrate convergence for a single time step (convergence of the Schwarz algorithm, influence of the mesh size, influence of the time step), convergence in time (instability capturing, energy dissipation, optimal time step) and an application to a relevant physical problem (interacting parallel fault segments)

GPS measurements along the North Anatolian fault zone ont he Mid-Anatolia segment

Science.gov (United States)

Yavasoglu, H.; Team

2003-04-01

features of the NAF is seen in the central part. Here NAF consists of southward spliting concave branches. These splines have generally right-lateral slip compared these splays with the Riedel fractures. One of the biggest splays is known as Sungurlu fault. The other important splays are Merzifon and Lacin faults. Recent palaeomagnetic data indicated that the main Anatolian Block to the south of the Sungurlu fault rotated anticlockwise and the other blocks rotated clockwise and anticlockwise according to the orientation and the geometry of the faults bounding the blocks. In contrast to the other parts of the NAF, central part has not been studied in detail yet. The data, which will be produced in this project, are expected to add an important contribution to the present knowledge on the NAF. 3. THE GPS MEASUREMENTS 3.1 The Design of The Mid-NAF GPS Network The estimated lateral movement on the LVKI segment of NAF is approximately 2-3cm per year. In order to determine approximately 2-3 centimeters of movements, point marks in the network should be built with forced centering instruments (pillars or steel rods etc.). At first a study in advance is carried out in the study area to find out convenient old pillars. At the end of the study, useful already established 25 pillar points are determined on the region. However, it is decided that the network can consist of 16 station points, because of the reasons such as financial limitations and the number of GPS receivers. The network consists of 16 point. The points are given name with the four letter abbreviations of the nearest settlement. The GPS sites mainly were chosen as representative of the fault-bounded continental blocks. Although there are lots of faults in the area, active and recently earthquake produced faults and continental blocks that are bounded by these faults were taken into consideration. 3.2 GPS Measurements The number and features of receivers are Measurements were performed in six days at two stages. For

Magmatic controls on axial relief and faulting at mid-ocean ridges

Science.gov (United States)

Liu, Zhonglan; Buck, W. Roger

2018-06-01

Previous models do not simultaneously reproduce the observed range of axial relief and fault patterns at plate spreading centers. We suggest that this failure is due to the approximation that magmatic dikes open continuously rather than in discrete events. During short - lived events, dikes open not only in the strong axial lithosphere but also some distance into the underlying weaker asthenosphere. Axial valley relief affects the partitioning of magma between the lithosphere and asthenosphere during diking events. The deeper the valley, the more magma goes into lithospheric dikes in each event and so the greater the average opening rate of those dikes. The long-term rate of lithospheric dike opening controls faulting rate and axial depth. The feedback between axial valley depth D and lithospheric dike opening rate allows us to analytically relate steady-state values of D to lithospheric thickness HL and crustal thickness HC. A two-dimensional model numerical model with a fixed axial lithospheric structure illustrates the analytic model implications for axial faulting. The predictions of this new model are broadly consistent with global and segment-scale trends of axial depth and fault patterns with HL and HC.

Changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992.

Science.gov (United States)

Jaumé, S C; Sykes, L R

1992-11-20

The April to June 1992 Landers earthquake sequence in southern California modified the state of stress along nearby segments of the San Andreas fault, causing a 50-kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near San Gorgonio Pass. The decrease in compressive normal stress may also have reduced fluid pressures along that fault segment. As pressures are reequilibrated by diffusion, that fault segment should move closer to failure with time. That fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years.

GONAF - A Deep Geophysical Observatory at the North Anatolian Fault

International Nuclear Information System (INIS)

Bohnhoff, Marco

2014-01-01

An outline was given of the GONAF (Deep Geophysical Observatory at the North Anatolian Fault Zone) project operating at the Marmara seismic gap of the North Anatolian Fault Zone. The Princes Island Segment is a part of the North Anatolian Fault Zone in Marmara seismic gap. This segment is a remaining part of the recent rupture of the North Anatolian Fault. Further, the rupture of this part is predicted to occur in the near future. The primary objectives of the project are to collect seismograms of small earthquakes with magnitudes less than zero using borehole observations with low noise, to gain new insight into the physical states of critically stressed fault segments during and after large earthquakes, and to monitor progressive damage evolution at fault asperities. There were explanations about the seismic network in the region, the recent micro-earthquake observation, and the project's PIRES (Princes Islands Real time Permanent Seismic Network). For the GONAF project, a network of eight borehole arrays with five-level seismometers, including a ground surface of 300-m boreholes, is planned. Horizontal arrays on the surface of an island in the Marmara Sea have also been deployed. In addition, deployment of a permanent ocean bottom seismometer is planned as part of the GONAF+ plan in 2014. (author)

Timing of initiation and fault rates of the Yushu-Xianshuihe-Xiaojiang fault system around the eastern Himalayan syntaxis.

Science.gov (United States)

Hervé Leloup, Philippe; Replumaz, Anne; Chevalier, Marie-Luce; Zhang, Yuan-Ze; Paquette, Jean-Louis; Wang, Guo-Can; Bernet, Matthias; van der Beek, Peter; Pan, Jiawei; Metois, Marianne; Li, Haibing

2017-04-01

In eastern Tibet, the left-lateral strike-slip Yushu-Xianshuihe-Xiaojiang fault system (YXX-FS) is 1400 km long, veering from N100° to N175° broadly following a small circle whose pole is located in the eastern Himalayan syntaxis. Several competing models are proposed to explain the geological evolution of eastern Tibet, and in particular of the YXX-FS: fault following slip-lines in a plastic media, book-shelf fault in a large right-lateral shear zone, or fault bounding a lower channel flow veering around the syntaxis. In this contribution we document the timing of onset of the YXX-FS, its propagation through time, its rate at various time-scales; and discuss how these relate to the deformation models. The YXX-FS comprises four segments from east (Tibetan Plateau) to west (Yunnan): Yushu-Ganzi, Xianshuihe, Anninghe, and Zemuhe-Xiaojiang. It is one of the most tectonically active intra-continental fault system in China along which more than 20 M>6.5 earthquakes occurred since 1700. Slip-rates of 3.5 to 30 mm/yr along the YXX-FS have been suggested by matching geological offsets of 60-100 km with initiation ages of 2 to 17 Ma. Late Quaternary rates deduced from morphological offsets, InSAR, paleoseismology and GPS also show a large range: between 3 and 20 mm/yr. The timing of initiation of the Yushu-Ganzi segment has been constrained at 12.6±1 Ma and its total offset to 76 - 90 km (Wang et al., 2009) yielding a rate of 6.6+0.8-0.7 mm/yr. By measuring the offsets of moraine crests and fan edges across the fault using LiDAR and kinematic GPS, and dating their surfaces using 10Be, we determined slip-rates of 7+1.1-1.0 mm/yr, 3 - 11.2 mm/yr and 8.5+0.8-0.7 mm/yr at three different sites. This suggests a constant rate of 6-8 mm/yr along the fault segment since 13Ma. The timing of initiation of the Xianshuihe segment was thought to be prior to 12.8±1.4 Ma (Roger et al., 1995), but new field studies and geochronological ages suggest that the fault initiated later. Using

Seismic Hazard Analysis on a Complex, Interconnected Fault Network

Science.gov (United States)

Page, M. T.; Field, E. H.; Milner, K. R.

2017-12-01

In California, seismic hazard models have evolved from simple, segmented prescriptive models to much more complex representations of multi-fault and multi-segment earthquakes on an interconnected fault network. During the development of the 3rd Uniform California Earthquake Rupture Forecast (UCERF3), the prevalence of multi-fault ruptures in the modeling was controversial. Yet recent earthquakes, for example, the Kaikora earthquake - as well as new research on the potential of multi-fault ruptures (e.g., Nissen et al., 2016; Sahakian et al. 2017) - have validated this approach. For large crustal earthquakes, multi-fault ruptures may be the norm rather than the exception. As datasets improve and we can view the rupture process at a finer scale, the interconnected, fractal nature of faults is revealed even by individual earthquakes. What is the proper way to model earthquakes on a fractal fault network? We show multiple lines of evidence that connectivity even in modern models such as UCERF3 may be underestimated, although clustering in UCERF3 mitigates some modeling simplifications. We need a methodology that can be applied equally well where the fault network is well-mapped and where it is not - an extendable methodology that allows us to "fill in" gaps in the fault network and in our knowledge.

Holocene paleoearthquakes on the strike-slip Porters Pass Fault, Canterbury, New Zealand

International Nuclear Information System (INIS)

Howard, M.; Nicol, A.; Campbell, J.; Pettinga, J.R.

2005-01-01

The Porters Pass Fault comprises a series of discontinuous Holocene active traces which extend for c. 40 km between the Rakaia and Waimakariri Rivers in the foothills of the Southern Alps. There have been no historical earthquakes on the Porters Pass Fault (i.e., within the last 150 yr), and the purpose of this paper is to establish the timing and magnitudes of displacements on the fault at the ground surface during Holocene paleoearthquakes. Displaced geomorphic features (e.g., relict streams, stream channels, and ridge crests), measured using either tape measure (n = 20) or surveying equipment (n = 5), range from 5.5 to 33 m right lateral strike slip and are consistent with six earthquakes characterised by slip per event of c. 5-7 m. The timing of these earthquakes is constrained by radiocarbon dates from four trenches excavated across the fault and two auger sites from within swamps produced by ponding of drainage along the fault scarp. These data indicate markedly different Holocene earthquake histories along the fault length separated by a behavioural segment boundary near Lake Coleridge. On the eastern segment at least six Holocene earthquakes were identified at 8400-9000, 5700-6700, 4500-6000, 2300-2500, 800-1100, and 500-600 yr BP, producing an average recurrence interval of c. 1500 yr. On the western segment of the fault in the Rakaia River valley, a single surface-rupturing earthquake displaced Acheron Advance glacial deposits (c.10,000-14,000 yr in age) and may represent the southward continuation of the 2300-2500 yr event identified on the eastern segment. These data suggest Holocene slip rates of 3.2-4.1 mm/yr and 0.3-0.9 mm/yr on the eastern and western sections of the fault, respectively. Displacement and timing data suggest that earthquakes ruptured the western segment of the fault in no more than one-sixth of cases and that for a sample period of 10,000 yr the recurrence intervals were not characteristic. (auth). 45 refs., 10 figs., 3 tabs

Passive Fault-tolerant Control of Discrete-time Piecewise Affine Systems against Actuator Faults

DEFF Research Database (Denmark)

Tabatabaeipour, Seyed Mojtaba; Izadi-Zamanabadi, Roozbeh; Bak, Thomas

2012-01-01

In this paper, we propose a new method for passive fault-tolerant control of discrete time piecewise affine systems. Actuator faults are considered. A reliable piecewise linear quadratic regulator (LQR) state feedback is designed such that it can tolerate actuator faults. A sufficient condition f...... is illustrated on a numerical example and a two degree of freedom helicopter....

A double-panel active segmented partition module using decoupled analog feedback controllers: numerical model.

Science.gov (United States)

Sagers, Jason D; Leishman, Timothy W; Blotter, Jonathan D

2009-06-01

Low-frequency sound transmission has long plagued the sound isolation performance of lightweight partitions. Over the past 2 decades, researchers have investigated actively controlled structures to prevent sound transmission from a source space into a receiving space. An approach using active segmented partitions (ASPs) seeks to improve low-frequency sound isolation capabilities. An ASP is a partition which has been mechanically and acoustically segmented into a number of small individually controlled modules. This paper provides a theoretical and numerical development of a single ASP module configuration, wherein each panel of the double-panel structure is independently actuated and controlled by an analog feedback controller. A numerical model is developed to estimate frequency response functions for the purpose of controller design, to understand the effects of acoustic coupling between the panels, to predict the transmission loss of the module in both passive and active states, and to demonstrate that the proposed ASP module will produce bidirectional sound isolation.

Influence of fault steps on rupture termination of strike-slip earthquake faults

Science.gov (United States)

Li, Zhengfang; Zhou, Bengang

2018-03-01

A statistical analysis was completed on the rupture data of 29 historical strike-slip earthquakes across the world. The purpose of this study is to examine the effects of fault steps on the rupture termination of these events. The results show good correlations between the type and length of steps with the seismic rupture and a poor correlation between the step number and seismic rupture. For different magnitude intervals, the smallest widths of the fault steps (Lt) that can terminate the rupture propagation are variable: Lt = 3 km for Ms 6.5 6.9, Lt = 4 km for Ms 7.0 7.5, Lt = 6 km for Ms 7.5 8.0, and Lt = 8 km for Ms 8.0 8.5. The dilational fault step is easier to rupture through than the compression fault step. The smallest widths of the fault step for the rupture arrest can be used as an indicator to judge the scale of the rupture termination of seismic faults. This is helpful for research on fault segmentation, as well as estimating the magnitude of potential earthquakes, and is thus of significance for the assessment of seismic risks.

Active intra-basin faulting in the Northern Basin of Lake Malawi from seismic reflection data

Science.gov (United States)

Shillington, D. J.; Chindandali, P. R. N.; Scholz, C. A.; Ebinger, C. J.; Onyango, E. A.; Peterson, K.; Gaherty, J. B.; Nyblade, A.; Accardo, N. J.; McCartney, T.; Oliva, S. J.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

2016-12-01

Many questions remain about the development and evolution of fault systems in weakly extended rifts, including the relative roles of border faults and intra-basin faults, and segmentation at various scales. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined by 100-km-long border faults. The basins also contain a series of intrabasinal faults and associated synrift sediments. The occurrence of the 2009 Karonga Earthquake Sequence on one of these intrabasinal faults indicates that some of them are active. Here we present new multichannel seismic reflection data from the Northern Basin of the Malawi Rift collected in 2015 as a part of the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project. This rift basin is bound on its east side by the west-dipping Livingstone border fault. Over 650 km of seismic reflection profiles were acquired in the Northern Basin using a 500 to 1540 cu in air gun array and a 1200- to 1500-m seismic streamer. Dip lines image a series of north-south oriented west-dipping intra-basin faults and basement reflections up to 5 s twtt near the border fault. Cumulative offsets on intra-basin faults decrease to the west. The largest intra-basin fault has a vertical displacement of >2 s two-way travel time, indicating that it has accommodated significant total extension. Some of these intra-basin faults offset the lake bottom and the youngest sediments by up to 50 s twtt ( 37 m), demonstrating they are still active. The two largest intra-basin faults exhibit the largest offsets of young sediments and also correspond to the area of highest seismicity based on analysis of seismic data from the 89-station SEGMeNT onshore/offshore network (see Peterson et al, this session). Fault patterns in MCS profiles vary along the basin, suggesting a smaller scale of segmentation of faults within the basin; these variations in fault patterns

Fault slip and earthquake recurrence along strike-slip faults — Contributions of high-resolution geomorphic data

KAUST Repository

Zielke, Olaf

2015-01-01

Understanding earthquake (EQ) recurrence relies on information about the timing and size of past EQ ruptures along a given fault. Knowledge of a fault\\'s rupture history provides valuable information on its potential future behavior, enabling seismic hazard estimates and loss mitigation. Stratigraphic and geomorphic evidence of faulting is used to constrain the recurrence of surface rupturing EQs. Analysis of the latter data sets culminated during the mid-1980s in the formulation of now classical EQ recurrence models, now routinely used to assess seismic hazard. Within the last decade, Light Detection and Ranging (lidar) surveying technology and other high-resolution data sets became increasingly available to tectono-geomorphic studies, promising to contribute to better-informed models of EQ recurrence and slip-accumulation patterns. After reviewing motivation and background, we outline requirements to successfully reconstruct a fault\\'s offset accumulation pattern from geomorphic evidence. We address sources of uncertainty affecting offset measurement and advocate approaches to minimize them. A number of recent studies focus on single-EQ slip distributions and along-fault slip accumulation patterns. We put them in context with paleoseismic studies along the respective faults by comparing coefficients of variation CV for EQ inter-event time and slip-per-event and find that a) single-event offsets vary over a wide range of length-scales and the sources for offset variability differ with length-scale, b) at fault-segment length-scales, single-event offsets are essentially constant, c) along-fault offset accumulation as resolved in the geomorphic record is dominated by essentially same-size, large offset increments, and d) there is generally no one-to-one correlation between the offset accumulation pattern constrained in the geomorphic record and EQ occurrence as identified in the stratigraphic record, revealing the higher resolution and preservation potential of

A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

Science.gov (United States)

Kim, Jongchan; Archer, Rosalind

2017-04-01

In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

Fault geometry, rupture dynamics and ground motion from potential earthquakes on the North Anatolian Fault under the Sea of Marmara

KAUST Repository

Oglesby, David D.

2012-03-01

Using the 3-D finite-element method, we develop dynamic spontaneous rupture models of earthquakes on the North Anatolian Fault system in the Sea of Marmara, Turkey, considering the geometrical complexity of the fault system in this region. We find that the earthquake size, rupture propagation pattern and ground motion all strongly depend on the interplay between the initial (static) regional pre-stress field and the dynamic stress field radiated by the propagating rupture. By testing several nucleation locations, we observe that those far from an oblique normal fault stepover segment (near Istanbul) lead to large through-going rupture on the entire fault system, whereas nucleation locations closer to the stepover segment tend to produce ruptures that die out in the stepover. However, this pattern can change drastically with only a 10° rotation of the regional stress field. Our simulations also reveal that while dynamic unclamping near fault bends can produce a new mode of supershear rupture propagation, this unclamping has a much smaller effect on the speed of the peak in slip velocity along the fault. Finally, we find that the complex fault geometry leads to a very complex and asymmetric pattern of near-fault ground motion, including greatly amplified ground motion on the insides of fault bends. The ground-motion pattern can change significantly with different hypocentres, even beyond the typical effects of directivity. The results of this study may have implications for seismic hazard in this region, for the dynamics and ground motion of geometrically complex faults, and for the interpretation of kinematic inverse rupture models.

Fault geometry, rupture dynamics and ground motion from potential earthquakes on the North Anatolian Fault under the Sea of Marmara

KAUST Repository

Oglesby, David D.; Mai, Paul Martin

2012-01-01

Using the 3-D finite-element method, we develop dynamic spontaneous rupture models of earthquakes on the North Anatolian Fault system in the Sea of Marmara, Turkey, considering the geometrical complexity of the fault system in this region. We find that the earthquake size, rupture propagation pattern and ground motion all strongly depend on the interplay between the initial (static) regional pre-stress field and the dynamic stress field radiated by the propagating rupture. By testing several nucleation locations, we observe that those far from an oblique normal fault stepover segment (near Istanbul) lead to large through-going rupture on the entire fault system, whereas nucleation locations closer to the stepover segment tend to produce ruptures that die out in the stepover. However, this pattern can change drastically with only a 10° rotation of the regional stress field. Our simulations also reveal that while dynamic unclamping near fault bends can produce a new mode of supershear rupture propagation, this unclamping has a much smaller effect on the speed of the peak in slip velocity along the fault. Finally, we find that the complex fault geometry leads to a very complex and asymmetric pattern of near-fault ground motion, including greatly amplified ground motion on the insides of fault bends. The ground-motion pattern can change significantly with different hypocentres, even beyond the typical effects of directivity. The results of this study may have implications for seismic hazard in this region, for the dynamics and ground motion of geometrically complex faults, and for the interpretation of kinematic inverse rupture models.

The Morelia-Acambay Fault System

Science.gov (United States)

Velázquez Bucio, M.; Soria-Caballero, D.; Garduño-Monroy, V.; Mennella, L.

2013-05-01

The Trans-Mexican Volcanic Belt (TMVB) is one of the most actives and representative zones of Mexico geologically speaking. Research carried out in this area gives stratigraphic, seismologic and historical evidence of its recent activity during the quaternary (Martinez and Nieto, 1990). Specifically the Morelia-Acambay faults system (MAFS) consist in a series of normal faults of dominant direction E - W, ENE - WSW y NE - SW which is cut in center west of the Trans-Mexican Volcanic Belt. This fault system appeared during the early Miocene although the north-south oriented structures are older and have been related to the activity of the tectonism inherited from the "Basin and Range" system, but that were reactivated by the east- west faults. It is believed that the activity of these faults has contributed to the creation and evolution of the longed lacustrine depressions such as: Chapala, Zacapu, Cuitzeo, Maravatio y Acambay also the location of monogenetic volcanoes that conformed the Michoacan-Guanajuato volcanic field (MGVF) and tend to align in the direction of the SFMA dominant effort. In a historical time different segments of the MAFS have been the epicenter of earthquakes from moderated to strong magnitude like the events of 1858 in Patzcuaro, Acambay in 1912, 1979 in Maravatio and 2007 in Morelia, among others. Several detailed analysis and semi-detailed analysis through a GIS platform based in the vectorial archives and thematic charts 1:50 000 scaled from the data base of the INEGI which has allowed to remark the influence of the MAFS segments about the morphology of the landscape and the identification of other structures related to the movement of the existent faults like fractures, alignments, collapses and others from the zone comprehended by the northwest of Morelia in Michoacán to the East of Acambay, Estado de México. Such analysis suggests that the fault segments possess a normal displacement plus a left component. In addition it can be

Fault kinematics and localised inversion within the Troms-Finnmark Fault Complex, SW Barents Sea

Science.gov (United States)

Zervas, I.; Omosanya, K. O.; Lippard, S. J.; Johansen, S. E.

2018-04-01

The areas bounding the Troms-Finnmark Fault Complex are affected by complex tectonic evolution. In this work, the history of fault growth, reactivation, and inversion of major faults in the Troms-Finnmark Fault Complex and the Ringvassøy Loppa Fault Complex is interpreted from three-dimensional seismic data, structural maps and fault displacement plots. Our results reveal eight normal faults bounding rotated fault blocks in the Troms-Finnmark Fault Complex. Both the throw-depth and displacement-distance plots show that the faults exhibit complex configurations of lateral and vertical segmentation with varied profiles. Some of the faults were reactivated by dip-linkages during the Late Jurassic and exhibit polycyclic fault growth, including radial, syn-sedimentary, and hybrid propagation. Localised positive inversion is the main mechanism of fault reactivation occurring at the Troms-Finnmark Fault Complex. The observed structural styles include folds associated with extensional faults, folded growth wedges and inverted depocentres. Localised inversion was intermittent with rifting during the Middle Jurassic-Early Cretaceous at the boundaries of the Troms-Finnmark Fault Complex to the Finnmark Platform. Additionally, tectonic inversion was more intense at the boundaries of the two fault complexes, affecting Middle Triassic to Early Cretaceous strata. Our study shows that localised folding is either a product of compressional forces or of lateral movements in the Troms-Finnmark Fault Complex. Regional stresses due to the uplift in the Loppa High and halokinesis in the Tromsø Basin are likely additional causes of inversion in the Troms-Finnmark Fault Complex.

From tomographic images to fault heterogeneities

Directory of Open Access Journals (Sweden)

A. Amato

1994-06-01

Full Text Available Local Earthquake Tomography (LET is a useful tool for imaging lateral heterogeneities in the upper crust. The pattern of P- and S-wave velocity anomalies, in relation to the seismicity distribution along active fault zones. can shed light on the existence of discrete seismogenic patches. Recent tomographic studies in well monitored seismic areas have shown that the regions with large seismic moment release generally correspond to high velocity zones (HVZ's. In this paper, we discuss the relationship between the seismogenic behavior of faults and the velocity structure of fault zones as inferred from seismic tomography. First, we review some recent tomographic studies in active strike-slip faults. We show examples from different segments of the San Andreas fault system (Parkfield, Loma Prieta, where detailed studies have been carried out in recent years. We also show two applications of LET to thrust faults (Coalinga, Friuli. Then, we focus on the Irpinia normal fault zone (South-Central Italy, where a Ms = 6.9 earthquake occurred in 1980 and many thousands of attershock travel time data are available. We find that earthquake hypocenters concentrate in HVZ's, whereas low velocity zones (LVZ’ s appear to be relatively aseismic. The main HVZ's along which the mainshock rupture bas propagated may correspond to velocity weakening fault regions, whereas the LVZ's are probably related to weak materials undergoing stable slip (velocity strengthening. A correlation exists between this HVZ and the area with larger coseismic slip along the fault, according to both surface evidence (a fault scarp as high as 1 m and strong ground motion waveform modeling. Smaller wave-length, low-velocity anomalies detected along the fault may be the expression of velocity strengthening sections, where aseismic slip occurs. According to our results, the rupture at the nucleation depth (~ 10-12 km is continuous for the whole fault lenoth (~ 30 km, whereas at shallow depth

Spatial radon anomalies on active faults in California

International Nuclear Information System (INIS)

King, C.-Y.; King, B.-S.; Evans, W.C.; Wei Zhang

1996-01-01

Radon emanation has been observed to be anomalously high along active faults in many parts of the world. We tested this relationship by conducting and repeating soil-air radon surveys with a portable radon meter across several faults in California. The results confirm the existence of fault-associated radon anomalies, which show characteristic features that may be related to fault structures but vary in time due to other environmental changes, such as rainfall. Across two creeping faults in San Juan Bautista and Hollister, the radon anomalies showed prominent double peaks straddling the fault-gouge zone during dry summers, but the peak-to-background ratios diminished after significant rain fall during winter. Across a locked segment of the San Andreas fault near Olema, the anomaly has a single peak located several meters southwest of the slip zone associated with the 1906 San Francisco earthquake. Across two fault segments that ruptured during the magnitude 7.5 Landers earthquake in 1992, anomalously high radon concentration was found in the fractures three weeks after the earthquake. We attribute the fault-related anomalies to a slow vertical gas flow in or near the fault zones. Radon generated locally in subsurface soil has a concentration profile that increases three orders of magnitude from the surface to a depth of several meters; thus an upward flow that brings up deeper and radon-richer soil air to the detection level can cause a significantly higher concentration reading. This explanation is consistent with concentrations of carbon dioxide and oxygen, measured in soil-air samples collected during one of the surveys. (Author)

Identifiability of Additive Actuator and Sensor Faults by State Augmentation

Science.gov (United States)

Joshi, Suresh; Gonzalez, Oscar R.; Upchurch, Jason M.

2014-01-01

A class of fault detection and identification (FDI) methods for bias-type actuator and sensor faults is explored in detail from the point of view of fault identifiability. The methods use state augmentation along with banks of Kalman-Bucy filters for fault detection, fault pattern determination, and fault value estimation. A complete characterization of conditions for identifiability of bias-type actuator faults, sensor faults, and simultaneous actuator and sensor faults is presented. It is shown that FDI of simultaneous actuator and sensor faults is not possible using these methods when all sensors have unknown biases. The fault identifiability conditions are demonstrated via numerical examples. The analytical and numerical results indicate that caution must be exercised to ensure fault identifiability for different fault patterns when using such methods.

Geochemistry, geochronology, and tectonic setting of Early Cretaceous volcanic rocks in the northern segment of the Tan-Lu Fault region, northeast China

Science.gov (United States)

Ling, Yi-Yun; Zhang, Jin-Jiang; Liu, Kai; Ge, Mao-Hui; Wang, Meng; Wang, Jia-Min

2017-08-01

We present new geochemical and geochronological data for volcanic and related rocks in the regions of the Jia-Yi and Dun-Mi faults, in order to constrain the late Mesozoic tectonic evolution of the northern segment of the Tan-Lu Fault. Zircon U-Pb dating shows that rhyolite and intermediate-mafic rocks along the southern part of the Jia-Yi Fault formed at 124 and 113 Ma, respectively, whereas the volcanic rocks along the northern parts of the Jia-Yi and Dun-Mi faults formed at 100 Ma. The rhyolite has an A-type granitoid affinity, with high alkalis, low MgO, Ti, and P contents, high rare earth element (REE) contents and Ga/Al ratios, enrichments in large-ion lithophile (LILEs; e.g., Rb, Th, and U) and high-field-strength element (HFSEs; e.g., Nb, Ta, Zr, and Y), and marked negative Eu anomalies. These features indicate that the rhyolites were derived from partial melting of crustal material in an extensional environment. The basaltic rocks are enriched in light REEs and LILEs (e.g., Rb, K, Th, and U), and depleted in heavy REEs, HFSEs (e.g., Nb, Ta, Ti, and P), and Sr. These geochemical characteristics indicate that these rocks are calc-alkaline basalts that formed in an intraplate extensional tectonic setting. The dacite is a medium- to high-K, calc-alkaline, I-type granite that was derived from a mixed source involving both crustal and mantle components in a magmatic arc. Therefore, the volcanic rocks along the Jia-Yi and Dun-Mi faults were formed in an extensional regime at 124-100 Ma (Early Cretaceous), and these faults were extensional strike-slip faults at this time.

Numerical Investigation of Earthquake Nucleation on a Laboratory-Scale Heterogeneous Fault with Rate-and-State Friction

Science.gov (United States)

Higgins, N.; Lapusta, N.

2014-12-01

Many large earthquakes on natural faults are preceded by smaller events, often termed foreshocks, that occur close in time and space to the larger event that follows. Understanding the origin of such events is important for understanding earthquake physics. Unique laboratory experiments of earthquake nucleation in a meter-scale slab of granite (McLaskey and Kilgore, 2013; McLaskey et al., 2014) demonstrate that sample-scale nucleation processes are also accompanied by much smaller seismic events. One potential explanation for these foreshocks is that they occur on small asperities - or bumps - on the fault interface, which may also be the locations of smaller critical nucleation size. We explore this possibility through 3D numerical simulations of a heterogeneous 2D fault embedded in a homogeneous elastic half-space, in an attempt to qualitatively reproduce the laboratory observations of foreshocks. In our model, the simulated fault interface is governed by rate-and-state friction with laboratory-relevant frictional properties, fault loading, and fault size. To create favorable locations for foreshocks, the fault surface heterogeneity is represented as patches of increased normal stress, decreased characteristic slip distance L, or both. Our simulation results indicate that one can create a rate-and-state model of the experimental observations. Models with a combination of higher normal stress and lower L at the patches are closest to matching the laboratory observations of foreshocks in moment magnitude, source size, and stress drop. In particular, we find that, when the local compression is increased, foreshocks can occur on patches that are smaller than theoretical critical nucleation size estimates. The additional inclusion of lower L for these patches helps to keep stress drops within the range observed in experiments, and is compatible with the asperity model of foreshock sources, since one would expect more compressed spots to be smoother (and hence have

Heterogeneous slip and rupture models of the San Andreas fault zone based upon three-dimensional earthquake tomography

Energy Technology Data Exchange (ETDEWEB)

Foxall, William [Univ. of California, Berkeley, CA (United States)

1992-11-01

Crystal fault zones exhibit spatially heterogeneous slip behavior at all scales, slip being partitioned between stable frictional sliding, or fault creep, and unstable earthquake rupture. An understanding the mechanisms underlying slip segmentation is fundamental to research into fault dynamics and the physics of earthquake generation. This thesis investigates the influence that large-scale along-strike heterogeneity in fault zone lithology has on slip segmentation. Large-scale transitions from the stable block sliding of the Central 4D Creeping Section of the San Andreas, fault to the locked 1906 and 1857 earthquake segments takes place along the Loma Prieta and Parkfield sections of the fault, respectively, the transitions being accomplished in part by the generation of earthquakes in the magnitude range 6 (Parkfield) to 7 (Loma Prieta). Information on sub-surface lithology interpreted from the Loma Prieta and Parkfield three-dimensional crustal velocity models computed by Michelini (1991) is integrated with information on slip behavior provided by the distributions of earthquakes located using, the three-dimensional models and by surface creep data to study the relationships between large-scale lithological heterogeneity and slip segmentation along these two sections of the fault zone.

A comparison between rate-and-state friction and microphysical models, based on numerical simulations of fault slip

Science.gov (United States)

van den Ende, M. P. A.; Chen, J.; Ampuero, J.-P.; Niemeijer, A. R.

2018-05-01

Rate-and-state friction (RSF) is commonly used for the characterisation of laboratory friction experiments, such as velocity-step tests. However, the RSF framework provides little physical basis for the extrapolation of these results to the scales and conditions of natural fault systems, and so open questions remain regarding the applicability of the experimentally obtained RSF parameters for predicting seismic cycle transients. As an alternative to classical RSF, microphysics-based models offer means for interpreting laboratory and field observations, but are generally over-simplified with respect to heterogeneous natural systems. In order to bridge the temporal and spatial gap between the laboratory and nature, we have implemented existing microphysical model formulations into an earthquake cycle simulator. Through this numerical framework, we make a direct comparison between simulations exhibiting RSF-controlled fault rheology, and simulations in which the fault rheology is dictated by the microphysical model. Even though the input parameters for the RSF simulation are directly derived from the microphysical model, the microphysics-based simulations produce significantly smaller seismic event sizes than the RSF-based simulation, and suggest a more stable fault slip behaviour. Our results reveal fundamental limitations in using classical rate-and-state friction for the extrapolation of laboratory results. The microphysics-based approach offers a more complete framework in this respect, and may be used for a more detailed study of the seismic cycle in relation to material properties and fault zone pressure-temperature conditions.

Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

KAUST Repository

Metwally, Ahmed Mohsen Hassan

2017-05-31

We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

KAUST Repository

Metwally, Ahmed Mohsen Hassan; Hanafy, Sherif; Guo, Bowen; Kosmicki, Maximillian Sunflower

2017-01-01

We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

Characterization of the San Andreas Fault near Parkfield, California by fault-zone trapped waves

Science.gov (United States)

Li, Y.; Vidale, J.; Cochran, E.

2003-04-01

In October, 2002, coordinated by the Pre-EarthScope/SAFOD, we conducted an extensive seismic experiment at the San Andreas fault (SAF), Parkfield to record fault-zone trapped waves generated by explosions and microearthquakes using dense linear seismic arrays of 52 PASSCAL 3-channel REFTEKs deployed across and along the fault zone. We detonated 3 explosions within and out of the fault zone during the experiment, and also recorded other 13 shots of PASO experiment of UWM/RPI (Thurber and Roecker) detonated around the SAFOD drilling site at the same time. We observed prominent fault-zone trapped waves with large amplitudes and long duration following S waves at stations close to the main fault trace for sources located within and close to the fault zone. Dominant frequencies of trapped waves are 2-3 Hz for near-surface explosions and 4-5 Hz for microearthquakes. Fault-zone trapped waves are relatively weak on the north strand of SAF for same sources. In contrast, seismograms registered for both the stations and shots far away from the fault zone show a brief S wave and lack of trapped waves. These observations are consistent with previous findings of fault-zone trapped waves at the SAF [Li et al., 1990; 1997], indicating the existence of a well-developed low-velocity waveguide along the main fault strand (principal slip plan) of the SAF. The data from denser arrays and 3-D finite-difference simulations of fault-zone trapped waves allowed us to delineate the internal structure, segmentation and physical properties of the SAF with higher resolution. The trapped-wave inferred waveguide on the SAF Parkfield segment is ~150 m wide at surface and tapers to ~100 m at seismogenic depth, in which Q is 20-50 and S velocities are reduced by 30-40% from wall-rock velocities, with the greater velocity reduction at the shallow depth and to southeast of the 1966 M6 epicenter. We interpret this low-velocity waveguide on the SAF main strand as being the remnant of damage zone caused

Coulomb Stress Accumulation along the San Andreas Fault System

Science.gov (United States)

Smith, Bridget; Sandwell, David

2003-01-01

Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 x 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1 - 10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

Frictional strengths of fault gouge from a creeping segment of the Bartlett Springs Fault, northern California

Science.gov (United States)

Swiatlowski, J. L.; Moore, D. E.; Lockner, D. A.

2017-12-01

The Bartlett Springs Fault (BSF) is a right-lateral strike-slip fault that is part of the San Andreas Fault System in Northern California with an estimated slip rate of 7 mm/yr. An exposure of the BSF near Lake Pillsbury, which creeps at a rate of 3.4 mm/yr, reveals a 1.5 m-wide zone of serpentinite-bearing gouge that has risen buoyantly to the surface in a manner similar to that documented for the San Andreas creeping section at SAFOD. The gouge is a heterogeneous mixture of the high-temperature serpentine mineral antigorite and the greenschist facies alteration assemblage talc + chlorite + tremolite, all of which are stable at temperatures >250°C, indicating that the gouge was tectonically entrained in the fault from depths near the base of the seismogenic zone. Antigorite has been shown to promote fault creep when sheared between crustal rocks at hydrothermal conditions. However, the effect of thorough metasomatism of antigorite on sliding stability are unknown. We conducted velocity-stepping strength experiments to explore the effect on frictional behavior if the serpentinite is completely replaced by the talc-chlorite-tremolite assemblage. The experiments were conducted at 290°C, 140 MPa effective normal stress, and 90 MPa fluid pressure to simulate conditions at 9 km depth. We tested mixtures of the three minerals in varying proportions (ternary mixing-law). The end-member samples show a four-fold variation in frictional strength: talc is the weakest (µ 0.12), tremolite the strongest (µ 0.55), and chlorite intermediate (µ 0.30). Talc and chlorite are velocity strengthening (a-b > 0) and tremolite velocity weakening (a-b 50% talc have coefficients of friction <0.2 with (a-b) ≥ 0. Talc would thus need to be concentrated in the sheared gouge matrix to promote creep in thoroughly altered serpentinite at depth.

Active tectonics of the Seattle fault and central Puget sound, Washington - Implications for earthquake hazards

Science.gov (United States)

Johnson, S.Y.; Dadisman, S.V.; Childs, J. R.; Stanley, W.D.

1999-01-01

We use an extensive network of marine high-resolution and conventional industry seismic-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle fault zone and crosscutting high-angle faults in the Puget Lowland of western Washington. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates that the west-trending Seattle fault comprises a broad (4-6 km) zone of three or more south-dipping reverse faults. Quaternary sediment has been folded and faulted along all faults in the zone but is clearly most pronounced along fault A, the northernmost fault, which forms the boundary between the Seattle uplift and Seattle basin. Analysis of growth strata deposited across fault A indicate minimum Quaternary slip rates of about 0.6 mm/yr. Slip rates across the entire zone are estimated to be 0.7-1.1 mm/yr. The Seattle fault is cut into two main segments by an active, north-trending, high-angle, strike-slip fault zone with cumulative dextral displacement of about 2.4 km. Faults in this zone truncate and warp reflections in Tertiary and Quaternary strata and locally coincide with bathymetric lineaments. Cumulative slip rates on these faults may exceed 0.2 mm/yr. Assuming no other crosscutting faults, this north-trending fault zone divides the Seattle fault into 30-40-km-long western and eastern segments. Although this geometry could limit the area ruptured in some Seattle fault earthquakes, a large event ca. A.D. 900 appears to have involved both segments. Regional seismic-hazard assessments must (1) incorporate new information on fault length, geometry, and displacement rates on the Seattle fault, and (2) consider the hazard presented by the previously unrecognized, north-trending fault zone.

Large-scale thermal convection of viscous fluids in a faulted system: 3D test case for numerical codes

Science.gov (United States)

Magri, Fabien; Cacace, Mauro; Fischer, Thomas; Kolditz, Olaf; Wang, Wenqing; Watanabe, Norihiro

2017-04-01

In contrast to simple homogeneous 1D and 2D systems, no appropriate analytical solutions exist to test onset of thermal convection against numerical models of complex 3D systems that account for variable fluid density and viscosity as well as permeability heterogeneity (e.g. presence of faults). Owing to the importance of thermal convection for the transport of energy and minerals, the development of a benchmark test for density/viscosity driven flow is crucial to ensure that the applied numerical models accurately simulate the physical processes at hands. The presented study proposes a 3D test case for the simulation of thermal convection in a faulted system that accounts for temperature dependent fluid density and viscosity. The linear stability analysis recently developed by Malkovsky and Magri (2016) is used to estimate the critical Rayleigh number above which thermal convection of viscous fluids is triggered. The numerical simulations are carried out using the finite element technique. OpenGeoSys (Kolditz et al., 2012) and Moose (Gaston et al., 2009) results are compared to those obtained using the commercial software FEFLOW (Diersch, 2014) to test the ability of widely applied codes in matching both the critical Rayleigh number and the dynamical features of convective processes. The methodology and Rayleigh expressions given in this study can be applied to any numerical model that deals with 3D geothermal processes in faulted basins as by example the Tiberas Basin (Magri et al., 2016). References Kolditz, O., Bauer, S., Bilke, L., Böttcher, N., Delfs, J. O., Fischer, T., U. J. Görke, T. Kalbacher, G. Kosakowski, McDermott, C. I., Park, C. H., Radu, F., Rink, K., Shao, H., Shao, H.B., Sun, F., Sun, Y., Sun, A., Singh, K., Taron, J., Walther, M., Wang,W., Watanabe, N., Wu, Y., Xie, M., Xu, W., Zehner, B., 2012. OpenGeoSys: an open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media. Environmental

Analysis of the growth of strike-slip faults using effective medium theory

Energy Technology Data Exchange (ETDEWEB)

Aydin, A.; Berryman, J.G.

2009-10-15

Increases in the dimensions of strike-slip faults including fault length, thickness of fault rock and the surrounding damage zone collectively provide quantitative definition of fault growth and are commonly measured in terms of the maximum fault slip. The field observations indicate that a common mechanism for fault growth in the brittle upper crust is fault lengthening by linkage and coalescence of neighboring fault segments or strands, and fault rock-zone widening into highly fractured inner damage zone via cataclastic deformation. The most important underlying mechanical reason in both cases is prior weakening of the rocks surrounding a fault's core and between neighboring fault segments by faulting-related fractures. In this paper, using field observations together with effective medium models, we analyze the reduction in the effective elastic properties of rock in terms of density of the fault-related brittle fractures and fracture intersection angles controlled primarily by the splay angles. Fracture densities or equivalent fracture spacing values corresponding to the vanishing Young's, shear, and quasi-pure shear moduli were obtained by extrapolation from the calculated range of these parameters. The fracture densities or the equivalent spacing values obtained using this method compare well with the field data measured along scan lines across the faults in the study area. These findings should be helpful for a better understanding of the fracture density/spacing distribution around faults and the transition from discrete fracturing to cataclastic deformation associated with fault growth and the related instabilities.

Geology and structure of the North Boqueron Bay-Punta Montalva Fault System

Science.gov (United States)

Roig Silva, Coral Marie

The North Boqueron Bay-Punta Montalva Fault Zone is an active fault system that cuts across the Lajas Valley in southwestern Puerto Rico. The fault zone has been recognized and mapped based upon detailed analysis of geophysical data, satellite images and field mapping. The fault zone consists of a series of Cretaceous bedrock faults that reactivated and deformed Miocene limestone and Quaternary alluvial fan sediments. The fault zone is seismically active (ML < 5.0) with numerous locally felt earthquakes. Focal mechanism solutions and structural field data suggest strain partitioning with predominantly east-west left-lateral displacements with small normal faults oriented mostly toward the northeast. Evidence for recent displacement consists of fractures and small normal faults oriented mostly northeast found in intermittent streams that cut through the Quaternary alluvial fan deposits along the southern margin of the Lajas Valley, Areas of preferred erosion, within the alluvial fan, trend toward the west-northwest parallel to the on-land projection of the North Boqueron Bay Fault. Beyond the faulted alluvial fan and southeast of the Lajas Valley, the Northern Boqueron Bay Fault joins with the Punta Montalva Fault. The Punta Montalva Fault is defined by a strong topographic WNW lineament along which stream channels are displaced left laterally 200 meters and Miocene strata are steeply tilted to the south. Along the western end of the fault zone in northern Boqueron Bay, the older strata are only tilted 3° south and are covered by flat lying Holocene sediments. Focal mechanisms solutions along the western end suggest NW-SE shortening, which is inconsistent with left lateral strain partitioning along the fault zone. The limited deformation of older strata and inconsistent strain partitioning may be explained by a westerly propagation of the fault system from the southwest end. The limited geomorphic structural expression along the North Boqueron Bay Fault segment

Empirical Relationships Among Magnitude and Surface Rupture Characteristics of Strike-Slip Faults: Effect of Fault (System) Geometry and Observation Location, Dervided From Numerical Modeling

Science.gov (United States)

Zielke, O.; Arrowsmith, J.

2007-12-01

In order to determine the magnitude of pre-historic earthquakes, surface rupture length, average and maximum surface displacement are utilized, assuming that an earthquake of a specific size will cause surface features of correlated size. The well known Wells and Coppersmith (1994) paper and other studies defined empirical relationships between these and other parameters, based on historic events with independently known magnitude and rupture characteristics. However, these relationships show relatively large standard deviations and they are based only on a small number of events. To improve these first-order empirical relationships, the observation location relative to the rupture extent within the regional tectonic framework should be accounted for. This however cannot be done based on natural seismicity because of the limited size of datasets on large earthquakes. We have developed the numerical model FIMozFric, based on derivations by Okada (1992) to create synthetic seismic records for a given fault or fault system under the influence of either slip- or stress boundary conditions. Our model features A) the introduction of an upper and lower aseismic zone, B) a simple Coulomb friction law, C) bulk parameters simulating fault heterogeneity, and D) a fault interaction algorithm handling the large number of fault patches (typically 5,000-10,000). The joint implementation of these features produces well behaved synthetic seismic catalogs and realistic relationships among magnitude and surface rupture characteristics which are well within the error of the results by Wells and Coppersmith (1994). Furthermore, we use the synthetic seismic records to show that the relationships between magntiude and rupture characteristics are a function of the observation location within the regional tectonic framework. The model presented here can to provide paleoseismologists with a tool to improve magnitude estimates from surface rupture characteristics, by incorporating the

A Framework For Evaluating Comprehensive Fault Resilience Mechanisms In Numerical Programs

Energy Technology Data Exchange (ETDEWEB)

Chen, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Peng, L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bronevetsky, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-01-09

As HPC systems approach Exascale, their circuit feature will shrink, while their overall size will grow, all at a fixed power limit. These trends imply that soft faults in electronic circuits will become an increasingly significant problem for applications that run on these systems, causing them to occasionally crash or worse, silently return incorrect results. This is motivating extensive work on application resilience to such faults, ranging from generic techniques such as replication or checkpoint/restart to algorithm-specific error detection and resilience techniques. Effective use of such techniques requires a detailed understanding of (1) which vulnerable parts of the application are most worth protecting (2) the performance and resilience impact of fault resilience mechanisms on the application. This paper presents FaultTelescope, a tool that combines these two and generates actionable insights by presenting in an intuitive way application vulnerabilities and impact of fault resilience mechanisms on applications.

Use of controlled dynamic impacts on hierarchically structured seismically hazardous faults for seismically safe relaxation of shear stresses

Science.gov (United States)

Ruzhich, Valery V.; Psakhie, Sergey G.; Levina, Elena A.; Shilko, Evgeny V.; Grigoriev, Alexandr S.

2017-12-01

In the paper we briefly outline the experience in forecasting catastrophic earthquakes and the general problems in ensuring seismic safety. The purpose of our long-term research is the development and improvement of the methods of man-caused impacts on large-scale fault segments to safely reduce the negative effect of seismodynamic failure. Various laboratory and large-scale field experiments were carried out in the segments of tectonic faults in Baikal rift zone and in main cracks in block-structured ice cove of Lake Baikal using the developed measuring systems and special software for identification and treatment of deformation response of faulty segments to man-caused impacts. The results of the study let us to ground the necessity of development of servo-controlled technologies, which are able to provide changing the shear resistance and deformation regime of fault zone segments by applying vibrational and pulse triggering impacts. We suppose that the use of triggering impacts in highly stressed segments of active faults will promote transferring the geodynamic state of these segments from a metastable to a more stable and safe state.

Static stress changes associated with normal faulting earthquakes in South Balkan area

Science.gov (United States)

Papadimitriou, E.; Karakostas, V.; Tranos, M.; Ranguelov, B.; Gospodinov, D.

2007-10-01

Activation of major faults in Bulgaria and northern Greece presents significant seismic hazard because of their proximity to populated centers. The long recurrence intervals, of the order of several hundred years as suggested by previous investigations, imply that the twentieth century activation along the southern boundary of the sub-Balkan graben system, is probably associated with stress transfer among neighbouring faults or fault segments. Fault interaction is investigated through elastic stress transfer among strong main shocks ( M ≥ 6.0), and in three cases their foreshocks, which ruptured distinct or adjacent normal fault segments. We compute stress perturbations caused by earthquake dislocations in a homogeneous half-space. The stress change calculations were performed for faults of strike, dip, and rake appropriate to the strong events. We explore the interaction between normal faults in the study area by resolving changes of Coulomb failure function ( ΔCFF) since 1904 and hence the evolution of the stress field in the area during the last 100 years. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account both the coseismic slip in strong earthquakes and the slow tectonic stress buildup associated with major fault segments. We evaluate if these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. Our modeling results show that the generation of each strong event enhanced the Coulomb stress on along-strike neighbors and reduced the stress on parallel normal faults. We extend the stress calculations up to present and provide an assessment for future seismic hazard by identifying possible sites of impending strong earthquakes.

Earthquake Rupture at Focal Depth, Part I: Structure and Rupture of the Pretorius Fault, TauTona Mine, South Africa

Science.gov (United States)

Heesakkers, V.; Murphy, S.; Reches, Z.

2011-12-01

We analyze the structure of the Archaean Pretorius fault in TauTona mine, South Africa, as well as the rupture-zone that recently reactivated it. The analysis is part of the Natural Earthquake Laboratory in South African Mines (NELSAM) project that utilizes the access to 3.6 km depth provided by the mining operations. The Pretorius fault is a ~10 km long, oblique-strike-slip fault with displacement of up to 200 m that crosscuts fine to very coarse grain quartzitic rocks in TauTona mine. We identify here three structural zones within the fault-zone: (1) an outer damage zone, ~100 m wide, of brittle deformation manifested by multiple, widely spaced fractures and faults with slip up to 3 m; (2) an inner damage zone, 25-30 m wide, with high density of anastomosing conjugate sets of fault segments and fractures, many of which carry cataclasite zones; and (3) a dominant segment, with a cataclasite zone up to 50 cm thick that accommodated most of the Archaean slip of the Pretorius fault, and is regarded as the `principal slip zone' (PSZ). This fault-zone structure indicates that during its Archaean activity, the Pretorius fault entered the mature fault stage in which many slip events were localized along a single, PSZ. The mining operations continuously induce earthquakes, including the 2004, M2.2 event that rejuvenated the Pretorius fault in the NELSAM project area. Our analysis of the M2.2 rupture-zone shows that (1) slip occurred exclusively along four, pre-existing large, quasi-planer segments of the ancient fault-zone; (2) the slipping segments contain brittle cataclasite zones up to 0.5 m thick; (3) these segments are not parallel to each other; (4) gouge zones, 1-5 mm thick, composed of white `rock-flour' formed almost exclusively along the cataclasite-host rock contacts of the slipping segments; (5) locally, new, fresh fractures branched from the slipping segments and propagated in mixed shear-tensile mode; (6) the maximum observed shear displacement is 25 mm in

Crustal structure across Tancheng-Lujiang fault belt in East China

Science.gov (United States)

Zhang, Zhongjie; Xu, Tao; Tian, Xiaobo; Teng, Jiwen; Bai, Zhiming

2013-04-01

Tancheng-Lujiang (T-L) fault extends more than 3,000km in the eastern China continent. T-L fault is closely related to strong earthquake occurrences such as Ms 7.8 Tangshan earthquake in 1976, basin development with rich oil/gas reserves and mineral resource concentration. The mechanism to form this fault is still in dispute. The proposed models include: post-collisional offset model (Okay and Sengor, 1992); indenter model (Yin and Nie, 1994); thrust model (Li, 1994); North China Craton penetration into South China model (Yokoyama et al., 2001) and Scissor collision model (Zhang et al., 2002, 2006). T-L fault is characterized with its segmentation, while the south segment is favored to understand the deep continental subduction and ultra-high pressure rocks extrusion from the collision between the convergence between Yangtze and North China Craton. In order to provide constraints on the evaluation of the proposed tectonic models, we carried out a 400-km-long wide-angle seismic profiling across the southern segment of the T-L fault. Here we present seismic P-wave data and the interpretation results. Seismic events of reflection and refraction from Moho discontinuity and other intracrustal reflections are remarkably observed with high signal/noise ratio. Crustal P-wave velocity model was reconstructed with forward modelling inversion, and T-L fault penetrates the whole crust, with gentle penetration angle in the upper crust, but very steep angle in the lower crust, which are probably seismic indicators of two phases of lateral escaping to accommodate the collision and extrusion of continental crust of the Yangtze block.

Numerical models of pore pressure and stress changes along basement faults due to wastewater injection: Applications to the 2014 Milan, Kansas Earthquake

Science.gov (United States)

Hearn, Elizabeth H.; Koltermann, Christine; Rubinstein, Justin R.

2018-01-01

We have developed groundwater flow models to explore the possible relationship between wastewater injection and the 12 November 2014 Mw 4.8 Milan, Kansas earthquake. We calculate pore pressure increases in the uppermost crust using a suite of models in which hydraulic properties of the Arbuckle Formation and the Milan earthquake fault zone, the Milan earthquake hypocenter depth, and fault zone geometry are varied. Given pre‐earthquake injection volumes and reasonable hydrogeologic properties, significantly increasing pore pressure at the Milan hypocenter requires that most flow occur through a conductive channel (i.e., the lower Arbuckle and the fault zone) rather than a conductive 3‐D volume. For a range of reasonable lower Arbuckle and fault zone hydraulic parameters, the modeled pore pressure increase at the Milan hypocenter exceeds a minimum triggering threshold of 0.01 MPa at the time of the earthquake. Critical factors include injection into the base of the Arbuckle Formation and proximity of the injection point to a narrow fault damage zone or conductive fracture in the pre‐Cambrian basement with a hydraulic diffusivity of about 3–30 m2/s. The maximum pore pressure increase we obtain at the Milan hypocenter before the earthquake is 0.06 MPa. This suggests that the Milan earthquake occurred on a fault segment that was critically stressed prior to significant wastewater injection in the area. Given continued wastewater injection into the upper Arbuckle in the Milan region, assessment of the middle Arbuckle as a hydraulic barrier remains an important research priority.

Off-fault plasticity in three-dimensional dynamic rupture simulations using a modal Discontinuous Galerkin method on unstructured meshes: Implementation, verification, and application

Science.gov (United States)

Wollherr, Stephanie; Gabriel, Alice-Agnes; Uphoff, Carsten

2018-05-01

The dynamics and potential size of earthquakes depend crucially on rupture transfers between adjacent fault segments. To accurately describe earthquake source dynamics, numerical models can account for realistic fault geometries and rheologies such as nonlinear inelastic processes off the slip interface. We present implementation, verification, and application of off-fault Drucker-Prager plasticity in the open source software SeisSol (www.seissol.org). SeisSol is based on an arbitrary high-order derivative modal Discontinuous Galerkin (ADER-DG) method using unstructured, tetrahedral meshes specifically suited for complex geometries. Two implementation approaches are detailed, modelling plastic failure either employing sub-elemental quadrature points or switching to nodal basis coefficients. At fine fault discretizations the nodal basis approach is up to 6 times more efficient in terms of computational costs while yielding comparable accuracy. Both methods are verified in community benchmark problems and by three dimensional numerical h- and p-refinement studies with heterogeneous initial stresses. We observe no spectral convergence for on-fault quantities with respect to a given reference solution, but rather discuss a limitation to low-order convergence for heterogeneous 3D dynamic rupture problems. For simulations including plasticity, a high fault resolution may be less crucial than commonly assumed, due to the regularization of peak slip rate and an increase of the minimum cohesive zone width. In large-scale dynamic rupture simulations based on the 1992 Landers earthquake, we observe high rupture complexity including reverse slip, direct branching, and dynamic triggering. The spatio-temporal distribution of rupture transfers are altered distinctively by plastic energy absorption, correlated with locations of geometrical fault complexity. Computational cost increases by 7% when accounting for off-fault plasticity in the demonstrating application. Our results

Spatial analysis of hypocenter to fault relationships for determining fault process zone width in Japan

International Nuclear Information System (INIS)

Arnold, Bill Walter; Roberts, Barry L.; McKenna, Sean Andrew; Coburn, Timothy C.

2004-01-01

Preliminary investigation areas (PIA) for a potential repository of high-level radioactive waste must be evaluated by NUMO with regard to a number of qualifying factors. One of these factors is related to earthquakes and fault activity. This study develops a spatial statistical assessment method that can be applied to the active faults in Japan to perform such screening evaluations. This analysis uses the distribution of seismicity near faults to define the width of the associated process zone. This concept is based on previous observations of aftershock earthquakes clustered near active faults and on the assumption that such seismic activity is indicative of fracturing and associated impacts on bedrock integrity. Preliminary analyses of aggregate data for all of Japan confirmed that the frequency of earthquakes is higher near active faults. Data used in the analysis were obtained from NUMO and consist of three primary sources: (1) active fault attributes compiled in a spreadsheet, (2) earthquake hypocenter data, and (3) active fault locations. Examination of these data revealed several limitations with regard to the ability to associate fault attributes from the spreadsheet to locations of individual fault trace segments. In particular, there was no direct link between attributes of the active faults in the spreadsheet and the active fault locations in the GIS database. In addition, the hypocenter location resolution in the pre-1983 data was less accurate than for later data. These pre-1983 hypocenters were eliminated from further analysis

Spatial analysis of hypocenter to fault relationships for determining fault process zone width in Japan.

Energy Technology Data Exchange (ETDEWEB)

Arnold, Bill Walter; Roberts, Barry L.; McKenna, Sean Andrew; Coburn, Timothy C. (Abilene Christian University, Abilene, TX)

2004-09-01

Preliminary investigation areas (PIA) for a potential repository of high-level radioactive waste must be evaluated by NUMO with regard to a number of qualifying factors. One of these factors is related to earthquakes and fault activity. This study develops a spatial statistical assessment method that can be applied to the active faults in Japan to perform such screening evaluations. This analysis uses the distribution of seismicity near faults to define the width of the associated process zone. This concept is based on previous observations of aftershock earthquakes clustered near active faults and on the assumption that such seismic activity is indicative of fracturing and associated impacts on bedrock integrity. Preliminary analyses of aggregate data for all of Japan confirmed that the frequency of earthquakes is higher near active faults. Data used in the analysis were obtained from NUMO and consist of three primary sources: (1) active fault attributes compiled in a spreadsheet, (2) earthquake hypocenter data, and (3) active fault locations. Examination of these data revealed several limitations with regard to the ability to associate fault attributes from the spreadsheet to locations of individual fault trace segments. In particular, there was no direct link between attributes of the active faults in the spreadsheet and the active fault locations in the GIS database. In addition, the hypocenter location resolution in the pre-1983 data was less accurate than for later data. These pre-1983 hypocenters were eliminated from further analysis.

Evidence for chaotic fault interactions in the seismicity of the San Andreas fault and Nankai trough

Science.gov (United States)

Huang, Jie; Turcotte, D. L.

1990-01-01

The dynamical behavior introduced by fault interactions is examined here using a simple spring-loaded, slider-block model with velocity-weakening friction. The model consists of two slider blocks coupled to each other and to a constant-velocity driver by elastic springs. For an asymmetric system in which the frictional forces on the two blocks are not equal, the solutions exhibit chaotic behavior. The system's behavior over a range of parameter values seems to be generally analogous to that of weakly coupled segments of an active fault. Similarities between the model simulations and observed patterns of seismicity on the south central San Andreas fault in California and in the Nankai trough along the coast of southwestern Japan.

Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonites

Science.gov (United States)

Adam, L.; Frehner, M.; Sauer, K. M.; Toy, V.; Guerin-Marthe, S.; Boulton, C. J.

2017-12-01

Reconciling experimental and static-dynamic numerical estimations of seismic anisotropy in Alpine Fault mylonitesLudmila Adam1, Marcel Frehner2, Katrina Sauer3, Virginia Toy3, Simon Guerin-Marthe4, Carolyn Boulton5(1) University of Auckland, New Zealand, (2) ETH Zurich, Switzerland, (3) University of Otago, New Zealand (4) Durham University, Earth Sciences, United Kingdom (5) Victoria University of Wellington, New Zealand Quartzo-feldspathic mylonites and schists are the main contributors to seismic wave anisotropy in the vicinity of the Alpine Fault (New Zealand). We must determine how the physical properties of rocks like these influence elastic wave anisotropy if we want to unravel both the reasons for heterogeneous seismic wave propagation, and interpret deformation processes in fault zones. To study such controls on velocity anisotropy we can: 1) experimentally measure elastic wave anisotropy on cores at in-situ conditions or 2) estimate wave velocities by static (effective medium averaging) or dynamic (finite element) modelling based on EBSD data or photomicrographs. Here we compare all three approaches in study of schist and mylonite samples from the Alpine Fault. Volumetric proportions of intrinsically anisotropic micas in cleavage domains and comparatively isotropic quartz+feldspar in microlithons commonly vary significantly within one sample. Our analysis examines the effects of these phases and their arrangement, and further addresses how heterogeneity influences elastic wave anisotropy. We compare P-wave seismic anisotropy estimates based on millimetres-scale ultrasonic waves under in situ conditions, with simulations that account for micrometre-scale variations in elastic properties of constitutent minerals with the MTEX toolbox and finite-element wave propagation on EBSD images. We observe that the sorts of variations in the distribution of micas and quartz+feldspar within any one of our real core samples can change the elastic wave anisotropy by 10

Sparsity guided empirical wavelet transform for fault diagnosis of rolling element bearings

Science.gov (United States)

Wang, Dong; Zhao, Yang; Yi, Cai; Tsui, Kwok-Leung; Lin, Jianhui

2018-02-01

Rolling element bearings are widely used in various industrial machines, such as electric motors, generators, pumps, gearboxes, railway axles, turbines, and helicopter transmissions. Fault diagnosis of rolling element bearings is beneficial to preventing any unexpected accident and reducing economic loss. In the past years, many bearing fault detection methods have been developed. Recently, a new adaptive signal processing method called empirical wavelet transform attracts much attention from readers and engineers and its applications to bearing fault diagnosis have been reported. The main problem of empirical wavelet transform is that Fourier segments required in empirical wavelet transform are strongly dependent on the local maxima of the amplitudes of the Fourier spectrum of a signal, which connotes that Fourier segments are not always reliable and effective if the Fourier spectrum of the signal is complicated and overwhelmed by heavy noises and other strong vibration components. In this paper, sparsity guided empirical wavelet transform is proposed to automatically establish Fourier segments required in empirical wavelet transform for fault diagnosis of rolling element bearings. Industrial bearing fault signals caused by single and multiple railway axle bearing defects are used to verify the effectiveness of the proposed sparsity guided empirical wavelet transform. Results show that the proposed method can automatically discover Fourier segments required in empirical wavelet transform and reveal single and multiple railway axle bearing defects. Besides, some comparisons with three popular signal processing methods including ensemble empirical mode decomposition, the fast kurtogram and the fast spectral correlation are conducted to highlight the superiority of the proposed method.

Fault Recoverability Analysis via Cross-Gramian

DEFF Research Database (Denmark)

Shaker, Hamid Reza

2016-01-01

Engineering systems are vulnerable to different kinds of faults. Faults may compromise safety, cause sub-optimal operation and decline in performance if not preventing the whole system from functioning. Fault tolerant control (FTC) methods ensure that the system performance maintains within...... with feedback control. Fault recoverability provides important and useful information which could be used in analysis and design. However, computing fault recoverability is numerically expensive. In this paper, a new approach for computation of fault recoverability for bilinear systems is proposed...... approach for computation of fault recoverability is proposed which reduces the computational burden significantly. The proposed results are used for an electro-hydraulic drive to reveal the redundant actuating capabilities in the system....

Radon emanation on San Andreas Fault

International Nuclear Information System (INIS)

King, C.-Y.

1978-01-01

It is stated that subsurface radon emanation monitored in shallow dry holes along an active segment of the San Andreas fault in central California shows spatially coherent large temporal variations that seem to be correlated with local seismicity. (author)

New Geologic Data on the Seismic Risks of the Most Dangerous Fault on Shore in Central Japan, the Itoigawa-Shizuoka Tectonic Line Active Fault System

Science.gov (United States)

Okumura, K.; Kondo, H.; Toda, S.; Takada, K.; Kinoshita, H.

2006-12-01

Ten years have past since the first official assessment of the long-term seismic risks of the Itoigawa-Shizuoka tectonic line active fault system (ISTL) in 1996. The disaster caused by the1995 Kobe (Hyogo-ken-Nanbu) earthquake urged the Japanese government to initiated a national project to assess the long-term seismic risks of on-shore active faults using geologic information. ISTL was the first target of the 98 significant faults and the probability of a M7 to M8 event turned out to be the highest among them. After the 10 years of continued efforts to understand the ISTL, now it is getting ready to revise the assessment. Fault mapping and segmentation: The most active segment of the Gofukuji fault (~1 cm/yr left-lateral strike slip, R=500~800 yrs.) had been maped only for less than 10 km. Adjacent segments were much less active. This large slip on such a short segment was contradictory. However, detailed topographic study including Lidar survey revealed the length of the Gofukuji fault to be 25 km or more. High slip rate with frequent earthquakes may be restricted to the Gofukuji fault while the 1996 assessment modeled frequent >100 km rupture scenario. The geometry of the fault is controversial especially on the left-lateral strike-slip section of the ISTL. There are two models of high-angle Middel ISTL and low-angle Middle ISTL with slip partitioning. However, all geomorphic and shallow geologic data supports high-angle almost pure strike slip on the faults in the Middle ISTL. CRIEPI's 3- dimensional trenching in several sites as well as the previous results clearly demonstrated repeated pure strike-slip offset during past a few events. In Middle ISTL, there is no evidence of recent activity of pre-existing low-angle thrust faults that are inferred to be active from shallow seismic survey. Separation of high (~3000 m) mountain ranges and low (lack of reliable time constraints on past earthquakes. In order to solve this problem, we have carried out intensive

Dynamic rupture simulation of the 2017 Mw 7.8 Kaikoura (New Zealand) earthquake: Is spontaneous multi-fault rupture expected?

Science.gov (United States)

Ando, R.; Kaneko, Y.

2017-12-01

The coseismic rupture of the 2016 Kaikoura earthquake propagated over the distance of 150 km along the NE-SW striking fault system in the northern South Island of New Zealand. The analysis of In-SAR, GPS and field observations (Hamling et al., 2017) revealed that the most of the rupture occurred along the previously mapped active faults, involving more than seven major fault segments. These fault segments, mostly dipping to northwest, are distributed in a quite complex manner, manifested by fault branching and step-over structures. Back-projection rupture imaging shows that the rupture appears to jump between three sub-parallel fault segments in sequence from the south to north (Kaiser et al., 2017). The rupture seems to be terminated on the Needles fault in Cook Strait. One of the main questions is whether this multi-fault rupture can be naturally explained with the physical basis. In order to understand the conditions responsible for the complex rupture process, we conduct fully dynamic rupture simulations that account for 3-D non-planar fault geometry embedded in an elastic half-space. The fault geometry is constrained by previous In-SAR observations and geological inferences. The regional stress field is constrained by the result of stress tensor inversion based on focal mechanisms (Balfour et al., 2005). The fault is governed by a relatively simple, slip-weakening friction law. For simplicity, the frictional parameters are uniformly distributed as there is no direct estimate of them except for a shallow portion of the Kekerengu fault (Kaneko et al., 2017). Our simulations show that the rupture can indeed propagate through the complex fault system once it is nucleated at the southernmost segment. The simulated slip distribution is quite heterogeneous, reflecting the nature of non-planar fault geometry, fault branching and step-over structures. We find that optimally oriented faults exhibit larger slip, which is consistent with the slip model of Hamling et al

Stress state and movement potential of the Kar-e-Bas fault zone, Fars, Iran

Science.gov (United States)

Sarkarinejad, Khalil; Zafarmand, Bahareh

2017-08-01

The Kar-e-Bas or Mengharak basement-inverted fault is comprised of six segments in the Zagros foreland folded belt of Iran. In the Fars region, this fault zone associated with the Kazerun, Sabz-Pushan and Sarvestan faults serves as a lateral transfer zone that accommodates the change in shortening direction from the western central to the eastern Zagros. This study evaluates the recent tectonic stress regime of the Kar-e-Bas fault zone based on inversion of earthquake focal mechanism data, and quantifies the fault movement potential of this zone based on the relationship between fault geometric characteristics and recent tectonic stress regimes. The trend and plunge of σ 1 and σ 3 are S25°W/04°-N31°E/05° and S65°E/04°-N60°W/10°, respectively, with a stress ratio of Φ = 0.83. These results are consistent with the collision direction of the Afro-Arabian continent and the Iranian microcontinent. The near horizontal plunge of maximum and minimum principle stresses and the value of stress ratio Φ indicate that the state of stress is nearly strike-slip dominated with little relative difference between the value of two principal stresses, σ 1 and σ 2. The obliquity of the maximum compressional stress into the fault trend reveals a typical stress partitioning of thrust and strike-slip motion in the Kar-e-Bas fault zone. Analysis of the movement potential of this fault zone shows that its northern segment has a higher potential of fault activity (0.99). The negligible difference between the fault-plane dips of the segments indicates that their strike is a controlling factor in the changes in movement potential.

Structure of the San Andreas Fault Zone in the Salton Trough Region of Southern California: A Comparison with San Andreas Fault Structure in the Loma Prieta Area of Central California

Science.gov (United States)

Fuis, G. S.; Catchings, R.; Scheirer, D. S.; Goldman, M.; Zhang, E.; Bauer, K.

2016-12-01

The San Andreas fault (SAF) in the northern Salton Trough, or Coachella Valley, in southern California, appears non-vertical and non-planar. In cross section, it consists of a steeply dipping segment (75 deg dip NE) from the surface to 6- to 9-km depth, and a moderately dipping segment below 6- to 9-km depth (50-55 deg dip NE). It also appears to branch upward into a flower-like structure beginning below about 10-km depth. Images of the SAF zone in the Coachella Valley have been obtained from analysis of steep reflections, earthquakes, modeling of potential-field data, and P-wave tomography. Review of seismological and geodetic research on the 1989 M 6.9 Loma Prieta earthquake, in central California (e.g., U.S. Geological Survey Professional Paper 1550), shows several features of SAF zone structure similar to those seen in the northern Salton Trough. Aftershocks in the Loma Prieta epicentral area form two chief clusters, a tabular zone extending from 18- to 9-km depth and a complex cluster above 5-km depth. The deeper cluster has been interpreted to surround the chief rupture plane, which dips 65-70 deg SW. When double-difference earthquake locations are plotted, the shallower cluster contains tabular subclusters that appear to connect the main rupture with the surface traces of the Sargent and Berrocal faults. In addition, a diffuse cluster may surround a steep to vertical fault connecting the main rupture to the surface trace of the SAF. These interpreted fault connections from the main rupture to surface fault traces appear to define a flower-like structure, not unlike that seen above the moderately dipping segment of the SAF in the Coachella Valley. But importantly, the SAF, interpreted here to include the main rupture plane, appears segmented, as in the Coachella Valley, with a moderately dipping segment below 9-km depth and a steep to vertical segment above that depth. We hope to clarify fault-zone structure in the Loma Prieta area by reanalyzing active

A Systematic Methodology for Gearbox Health Assessment and Fault Classification

Directory of Open Access Journals (Sweden)

Jay Lee

2011-01-01

Full Text Available A systematic methodology for gearbox health assessment and fault classification is developed and evaluated for 560 data sets of gearbox vibration data provided by the Prognostics and Health Management Society for the 2009 data challenge competition. A comprehensive set of signal processing and feature extraction methods are used to extract over 200 features, including features extracted from the raw time signal, time synchronous signal, wavelet decomposition signal, frequency domain spectrum, envelope spectrum, among others. A regime segmentation approach using the tachometer signal, a spectrum similarity metric, and gear mesh frequency peak information are used to segment the data by gear type, input shaft speed, and braking torque load. A health assessment method that finds the minimum feature vector sum in each regime is used to classify and find the 80 baseline healthy data sets. A fault diagnosis method based on a distance calculation from normal along with specific features correlated to different fault signatures is used to diagnosis specific faults. The fault diagnosis method is evaluated for the diagnosis of a gear tooth breakage, input shaft imbalance, bent shaft, bearing inner race defect, and bad key, and the method could be further extended for other faults as long as a set of features can be correlated with a known fault signature. Future work looks to further refine the distance calculation algorithm for fault diagnosis, as well as further evaluate other signal processing method such as the empirical mode decomposition to see if an improved set of features can be used to improve the fault diagnosis accuracy.

Solving fault diagnosis problems linear synthesis techniques

CERN Document Server

Varga, Andreas

2017-01-01

This book addresses fault detection and isolation topics from a computational perspective. Unlike most existing literature, it bridges the gap between the existing well-developed theoretical results and the realm of reliable computational synthesis procedures. The model-based approach to fault detection and diagnosis has been the subject of ongoing research for the past few decades. While the theoretical aspects of fault diagnosis on the basis of linear models are well understood, most of the computational methods proposed for the synthesis of fault detection and isolation filters are not satisfactory from a numerical standpoint. Several features make this book unique in the fault detection literature: Solution of standard synthesis problems in the most general setting, for both continuous- and discrete-time systems, regardless of whether they are proper or not; consequently, the proposed synthesis procedures can solve a specific problem whenever a solution exists Emphasis on the best numerical algorithms to ...

Coulomb stress transfer and tectonic loading preceding the 2002 Denali fault earthquake

Science.gov (United States)

Bufe, Charles G.

2006-01-01

Pre-2002 tectonic loading and Coulomb stress transfer are modeled along the rupture zone of the M 7.9 Denali fault earthquake (DFE) and on adjacent segments of the right-lateral Denali–Totschunda fault system in central Alaska, using a three-dimensional boundary-element program. The segments modeled closely follow, for about 95°, the arc of a circle of radius 375 km centered on an inferred asperity near the northeastern end of the intersection of the Patton Bay fault with the Alaskan megathrust under Prince William Sound. The loading model includes slip of 6 mm/yr below 12 km along the fault system, consistent with rotation of the Wrangell block about the asperity at a rate of about 1°/m.y. as well as slip of the Pacific plate at 5 cm/yr at depth along the Fairweather–Queen Charlotte transform fault system and on the Alaska megathrust. The model is consistent with most available pre-2002 Global Positioning System (GPS) displacement rate data. Coulomb stresses induced on the Denali–Totschunda fault system (locked above 12 km) by slip at depth and by transfer from the M 9.2 Prince William Sound earthquake of 1964 dominated the changing Coulomb stress distribution along the fault. The combination of loading (∼70–85%) and coseismic stress transfer from the great 1964 earthquake (∼15–30%) were the principal post-1900 stress factors building toward strike-slip failure of the northern Denali and Totschunda segments in the M 7.9 earthquake of November 2002. Postseismic stresses transferred from the 1964 earthquake may also have been a significant factor. The M 7.2–7.4 Delta River earthquake of 1912 (Carver et al., 2004) may have delayed or advanced the timing of the DFE, depending on the details and location of its rupture. The initial subevent of the 2002 DFE earthquake was on the 40-km Susitna Glacier thrust fault at the western end of the Denali fault rupture. The Coulomb stress transferred from the 1964 earthquake moved the Susitna Glacier thrust

Integrating angle-frequency domain synchronous averaging technique with feature extraction for gear fault diagnosis

Science.gov (United States)

Zhang, Shengli; Tang, J.

2018-01-01

Gear fault diagnosis relies heavily on the scrutiny of vibration responses measured. In reality, gear vibration signals are noisy and dominated by meshing frequencies as well as their harmonics, which oftentimes overlay the fault related components. Moreover, many gear transmission systems, e.g., those in wind turbines, constantly operate under non-stationary conditions. To reduce the influences of non-synchronous components and noise, a fault signature enhancement method that is built upon angle-frequency domain synchronous averaging is developed in this paper. Instead of being averaged in the time domain, the signals are processed in the angle-frequency domain to solve the issue of phase shifts between signal segments due to uncertainties caused by clearances, input disturbances, and sampling errors, etc. The enhanced results are then analyzed through feature extraction algorithms to identify the most distinct features for fault classification and identification. Specifically, Kernel Principal Component Analysis (KPCA) targeting at nonlinearity, Multilinear Principal Component Analysis (MPCA) targeting at high dimensionality, and Locally Linear Embedding (LLE) targeting at local similarity among the enhanced data are employed and compared to yield insights. Numerical and experimental investigations are performed, and the results reveal the effectiveness of angle-frequency domain synchronous averaging in enabling feature extraction and classification.

Fault geometry and earthquake mechanics

Directory of Open Access Journals (Sweden)

D. J. Andrews

1994-06-01

Full Text Available Earthquake mechanics may be determined by the geometry of a fault system. Slip on a fractal branching fault surface can explain: 1 regeneration of stress irregularities in an earthquake; 2 the concentration of stress drop in an earthquake into asperities; 3 starting and stopping of earthquake slip at fault junctions, and 4 self-similar scaling of earthquakes. Slip at fault junctions provides a natural realization of barrier and asperity models without appealing to variations of fault strength. Fault systems are observed to have a branching fractal structure, and slip may occur at many fault junctions in an earthquake. Consider the mechanics of slip at one fault junction. In order to avoid a stress singularity of order 1/r, an intersection of faults must be a triple junction and the Burgers vectors on the three fault segments at the junction must sum to zero. In other words, to lowest order the deformation consists of rigid block displacement, which ensures that the local stress due to the dislocations is zero. The elastic dislocation solution, however, ignores the fact that the configuration of the blocks changes at the scale of the displacement. A volume change occurs at the junction; either a void opens or intense local deformation is required to avoid material overlap. The volume change is proportional to the product of the slip increment and the total slip since the formation of the junction. Energy absorbed at the junction, equal to confining pressure times the volume change, is not large enongh to prevent slip at a new junction. The ratio of energy absorbed at a new junction to elastic energy released in an earthquake is no larger than P/µ where P is confining pressure and µ is the shear modulus. At a depth of 10 km this dimensionless ratio has th value P/µ= 0.01. As slip accumulates at a fault junction in a number of earthquakes, the fault segments are displaced such that they no longer meet at a single point. For this reason the

Late Quaternary faulting in the Vallo di Diano basin (southern Apennines, Italy)

Science.gov (United States)

Villani, F.; Pierdominici, S.; Cinti, F. R.

2009-12-01

The Vallo di Diano is the largest Quaternary extensional basin in the southern Apennines thrust-belt axis (Italy). This portion of the chain is highly seismic and is currently subject to NE-extension, which triggers large (M> 6) normal-faulting earthquakes along NW-trending faults. The eastern edge of the Vallo di Diano basin is bounded by an extensional fault system featuring three main NW-trending, SW-dipping, right-stepping, ~15-17 km long segments (from north to south: Polla, Atena Lucana-Sala Consilina and Padula faults). Holocene activity has been documented so far only for the Polla segment. We have therefore focused our geomorphological and paleoseismological study on the southern portion of the system, particularly along the ~ 4 km long Atena Lucana-Sala Consilina and Padula faults overlap zone. The latter is characterized by a complex system of coalescent alluvial fans, Middle Pleistocene to Holocene in age. Here we recognized a > 4 km long and 0.5-1.4 km wide set of scarps (ranging in height between 1 m and 2.5 m) affecting Late Pleistocene - Holocene alluvial fans. In the same area, two Late Pleistocene volcanoclastic layers at the top of an alluvial fan exposed in a quarry are affected by ~ 1 m normal displacements. Moreover, a trench excavated across a 2 m high scarp affecting a Holocene fan revealed warping of Late Holocene debris flow deposits, with a total vertical throw of about 0.3 m. We therefore infer the overlap zone of the Atena Lucana-Sala Consilina and Padula faults is a breached relay ramp, generated by hard-linkage of the two fault segments since Late Pleistocene. This ~ 32 km long fault system is active and is capable of generating Mw ≥6.5 earthquakes.

Along strike variation of active fault arrays and their effect on landscape morphology of the northwestern Himalaya

Science.gov (United States)

Nennewitz, Markus; Thiede, Rasmus; Bookhagen, Bodo

2017-04-01

The location and magnitude of the active deformation of the Himalaya has been debated for decades, but several aspects remain unknown. For instance, the spatial distribution of the deformation and the shortening that ultimately sustains Himalayan topography and the activity of major fault zones are not well constrained neither for the present day and nor for Holocene and Quarternary timescales. Because of these weakly constrained factors, many previous studies have assumed that the structural setting and the fault geometry of the Himalaya is continuous along strike and similar to fault geometries of central Nepal. Thus, the sub-surface structural information from central Nepal have been projected along strike, but have not been verified at other locations. In this study we use digital topographic analysis of the NW Himalaya. We obtained catchment-averaged, normalized steepness indexes of longitudinal river profiles with drainage basins ranging between 5 and 250km2 and analyzed the relative change in their spatial distribution both along and across strike. More specific, we analyzed the relative changes of basins located in the footwall and in the hanging wall of major fault zones. Under the assumption that along strike changes in the normalized steepness index are primarily controlled by the activity of thrust segments, we revealed new insights in the tectonic deformation and uplift pattern. Our results show three different segments along the northwest Himalaya, which are located, from east to west, in Garwhal, Chamba and Kashmir Himalaya. These have formed independent orogenic segments characterized by significant changes in their structural architecture and fault geometry. Moreover, their topographic changes indicate strong variations on fault displacement rates across first-order fault zones. With the help of along- and across-strike profiles, we were able to identify fault segments of pronounced fault activity across MFT, MBT, and the PT2 and identify the

Identifying Fault Connections of the Southern Pacific-North American Plate Boundary Using Triggered Slip and Crustal Velocities

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Donnellan, A.; Grant Ludwig, L.; Rundle, J. B.; Parker, J. W.; Granat, R.; Heflin, M. B.; Pierce, M. E.; Wang, J.; Gunson, M.; Lyzenga, G. A.

2017-12-01

The 2010 M7.2 El Mayor - Cucapah earthquake caused extensive triggering of slip on faults proximal to the Salton Trough in southern California. Triggered slip and postseismic motions that have continued for over five years following the earthquake highlight connections between the El Mayor - Cucapah rupture and the network of faults that branch out along the southern Pacific - North American Plate Boundary. Coseismic triggering follows a network of conjugate faults from the northern end of the rupture to the Coachella segment of the southernmost San Andreas fault. Larger aftershocks and postseismic motions favor connections to the San Jacinto and Elsinore faults further west. The 2012 Brawley Swarm can be considered part of the branching on the Imperial Valley or east side of the plate boundary. Cluster analysis of long-term GPS velocities using Lloyds Algorithm, identifies bifurcation of the Pacific - North American plate boundary; The San Jacinto fault joins with the southern San Andreas fault, and the Salton Trough and Coachella segment of the San Andreas fault join with the Eastern California Shear Zone. The clustering analysis does not identify throughgoing deformation connecting the Coachella segment of the San Andreas fault with the rest of the San Andreas fault system through the San Gorgonio Pass. This observation is consistent with triggered slip from both the 1992 Landers and 2010 El Mayor - Cucapah earthquakes that follows the plate boundary bifurcation and with paleoseismic evidence of smaller earthquakes in the San Gorgonio Pass.

Structural characteristics and implication on tectonic evolution of the Daerbute strike-slip fault in West Junggar area, NW China

Science.gov (United States)

Wu, Kongyou; Pei, Yangwen; Li, Tianran; Wang, Xulong; Liu, Yin; Liu, Bo; Ma, Chao; Hong, Mei

2018-03-01

The Daerbute fault zone, located in the northwestern margin of the Junggar basin, in the Central Asian Orogenic Belt, is a regional strike-slip fault with a length of 400 km. The NE-SW trending Daerbute fault zone presents a distinct linear trend in plain view, cutting through both the Zair Mountain and the Hala'alate Mountain. Because of the intense contraction and shearing, the rocks within the fault zone experienced high degree of cataclasis, schistosity, and mylonization, resulting in rocks that are easily eroded to form a valley with a width of 300-500 m and a depth of 50-100 m after weathering and erosion. The well-exposed outcrops along the Daerbute fault zone present sub-horizontal striations and sub-vertical fault steps, indicating sub-horizontal shearing along the observed fault planes. Flower structures and horizontal drag folds are also observed in both the well-exposed outcrops and high-resolution satellite images. The distribution of accommodating strike-slip splay faults, e.g., the 973-pluton fault and the Great Jurassic Trough fault, are in accordance with the Riedel model of simple shear. The seismic and time-frequency electromagnetic (TFEM) sections also demonstrate the typical strike-slip characteristics of the Daerbute fault zone. Based on detailed field observations of well-exposed outcrops and seismic sections, the Daerbute fault can be subdivided into two segments: the western segment presents multiple fault cores and damage zones, whereas the eastern segment only presents a single fault core, in which the rocks experienced a higher degree of rock cataclasis, schistosity, and mylonization. In the central overlapping portion between the two segments, the sediments within the fault zone are primarily reddish sandstones, conglomerates, and some mudstones, of which the palynological tests suggest middle Permian as the timing of deposition. The deformation timing of the Daerbute fault was estimated by integrating the depocenters' basinward

Geodetic exploration of strain along the El Pilar Fault in northeastern Venezuela

Science.gov (United States)

Reinoza, C.; Jouanne, F.; Audemard, F. A.; Schmitz, M.; Beck, C.

2015-03-01

We use Global Navigation Satellite Systems observations in northeastern Venezuela to constrain the El Pilar Fault (EPF) kinematics and to explore the effects of the variable elastic properties of the surrounding medium and of the fault geometry on inferred slip rates and locking depth. The velocity field exhibits an asymmetric velocity gradient on either side of the EPF. We use five different approaches to explore possible models to explain this asymmetry. First, we infer a 1.6 km locking depth using a classic elastic half-space dislocation model. Second, we infer a 1.5 km locking depth and a 0.33 asymmetry coefficient using a heterogeneous asymmetric model, including contrasting material properties on either side of a vertical fault, suggesting that the igneous-metamorphic terranes on the northern side are ~2 times more rigid than the sedimentary southern side. Third, we use a three-dimensional elastostatic model to evaluate the presence of a compliant zone, suggesting a 30% reduction of rigidity in the upper 3 km at the depth of a 1 to 5 km wide fault zone. Fourth, we evaluate the distribution of fault slip, revealing a widespread partial creep pattern in the eastern upper segment, while the upper western segment exhibits a partially locked area, which coincides with the rupture surface of the 1797 and 1929 earthquakes. To supplement these models, we upgrade the previously published displacement simulation method using nonvertical dislocations with data acquired between 2003 and 2013. The localized aseismic displacement pattern associated with creeping or partially creeping fault segments could explain the low level of historic seismicity.

Index for simultaneous rupture assessment of active faults. Part 3. Subsurface structure deduced from geophysical research

International Nuclear Information System (INIS)

Aoyagi, Yasuhira

2012-01-01

Tomographic inversion was carried out in the northern source region of the 1891 Nobi earthquake, the largest inland earthquake (M8.0) in Japan to detect subsurface structure to control simultaneous rupture of active fault system. In the step-over between the two ruptured fault segments in 1891, a remarkable low velocity zone is found between the Nukumi and Ibigawa faults at the depth shallower than 3-5 km. The low velocity zone forms a prism-like body narrowing down in the deeper. Hypocenters below the low velocity zone connecting the two ruptured segments indicate the possibility of their convergence in the seismogenic zone. Northern tip of the Neodani fault locates in the low velocity zone. The results show that fault rupture is easy to propagate in the low velocity zone between two parallel faults. In contrast an E-W cross-structure is found in the seismogenic depth between the Nobi earthquake and the 1948 Fukui earthquake (M7.1) source regions. It runs parallel to the Hida gaien belt, a major geologic structure in the district. P-wave velocity is lower and the hypocenter depths are obviously shallower in north of the cross-structure. Since a few faults lie in E-W direction just above it, a cross-structure zone including the Hida gaien belt might terminate the fault rupture. The results indicate fault rupture is difficult to propagate beyond major cross-structure. The length ratio of cross-structure to fault segment (PL/FL) is proposed to use for simultaneous rupture assessment. Some examples show that fault ruptures perhaps (PL/FL>3-4), maybe (∼1), and probably (<1) cut through such cross-structures. (author)

Vertical slip rates of active faults of southern Albania inferred from river terraces

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Oswaldo Guzmán

2014-02-01

Full Text Available Fluvial terraces of Shkumbin, Devoll, Osum and Vjosa rivers (southern Albania and northwestern Greece are studied in order to quantify the vertical slip rates of the large active faults of the Dinaric-Albanic-Hellenic Alpine fold belt. The spatial and temporal variations of the incision rates along these rivers were estimated from the geomorphological mapping of the Quaternary sediments, the geometry and the dating of the terraces. Eleven terraces levels were identified in Albania from 68 geochronological ages already published or acquired for this work. The five lower terraces of the four studied rivers are well dated (10 new and 23 already published ages. These terraces are younger than 30 ka and their remnants are numerous. Their restoration allows estimating the regional trend of incision rate and the identification of local shifts. We argue that these shifts are linked to the active tectonics when they coincide with the faults already mapped by previous authors. Vertical slip rates for eight active faults in southern Albania are thus estimated for the last 19 ka and vary from ~0.1 to ~2 mm/a. The Lushnje Tepelene Thrust, that extends more than 120 kilometers, has a throw rate that varies from 0.2 to 0.8 mm/a, whereas the active faults of the extensional domain are segmented but are very active, with throw rates reaching locally 2 mm/a.

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

Science.gov (United States)

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

2013-04-01

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

Late Pleistocene-Holocene Activity of the Strike-slip Xianshuihe Fault Zone, Tibetan Plateau, Inferred from Tectonic Landforms

Science.gov (United States)

Lin, A.; Yan, B.

2017-12-01

Knowledges on the activity of the strike-slip fault zones on the Tibetan Plateau have been promoted greatly by the interpretation of remote sensing images (Molnar and Tapponnier, 1975; Tapponnier and Molnar, 1977). The active strike-slip Xianshuihe-Xiaojiang Fault System (XXFS), with the geometry of an arc projecting northeastwards, plays an important role in the crustal deformation of the Tibetan Plateau caused by the continental collision between the Indian and Eurasian plates. The Xianshuihe Fault Zone (XFZ) is located in the central segment of the XXFS and extends for 370 km, with a maximum sinistral offset of 60 km since 13‒5 Ma. In this study, we investigated the tectonic landforms and slip rate along the central segment of the left-lateral strike-slip XFZ. Field investigations and analysis of ttectonic landforms show that horizontal offset has been accumulated on the topographical markers of different scales that developed since the Last Glacial Maximum (LGM). The central segment of the XFZ is composed of three major faults: Yalahe, Selaha, and Zheduotang faults showing a right-stepping echelon pattern, that is characterized by systematical offset of drainages, alluvial fans and terrace risers with typical scissoring structures, indicating a structural feature of left-lateral strike-slip fault. Based on the offset glacial morphology and radiocarbon dating ages, we estimate the Late Pleistocene-Holocene slip rate to be 10 mm/yr for the central segment of the XFZ, which is consistent with that estimated from the GPS observations and geological evidence as reported previously. Across the central segment of the XFZ, the major Selaha and Zheduotang faults participate a slip rate of 5.8 mm/yr and 3.4 mm/yr, respectively. Detailed investigations of tectonic landforms are essential for the understanding the activity of active faults. Our findings suggest that the left-lateral slipping of the XFZ partitions the deformation of eastward extrusion and northeastward

Dynamic Behavior of Fault Slip Induced by Stress Waves

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Guang-an Zhu

2016-01-01

Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.

Influence of pre-existing basement faults on the structural evolution of the Zagros Simply Folded belt: 3D numerical modelling

Science.gov (United States)

Ruh, Jonas B.; Gerya, Taras

2015-04-01

The Simply Folded Belt of the Zagros orogen is characterized by elongated fold trains symptomatically defining the geomorphology along this mountain range. The Zagros orogen results from the collision of the Arabian and the Eurasian plates. The Simply Folded Belt is located southwest of the Zagros suture zone. An up to 2 km thick salt horizon below the sedimentary sequence enables mechanical and structural detachment from the underlying Arabian basement. Nevertheless, deformation within the basement influences the structural evolution of the Simply Folded Belt. It has been shown that thrusts in form of reactivated normal faults can trigger out-of-sequence deformation within the sedimentary stratigraphy. Furthermore, deeply rooted strike-slip faults, such as the Kazerun faults between the Fars zone in the southeast and the Dezful embayment and the Izeh zone, are largely dispersing into the overlying stratigraphy, strongly influencing the tectonic evolution and mechanical behaviour. The aim of this study is to reveal the influence of basement thrusts and strike-slip faults on the structural evolution of the Simply Folded Belt depending on the occurrence of intercrustal weak horizons (Hormuz salt) and the rheology and thermal structure of the basement. Therefore, we present high-resolution 3D thermo-mechnical models with pre-existing, inversively reactivated normal faults or strike-slip faults within the basement. Numerical models are based on finite difference, marker-in-cell technique with (power-law) visco-plastic rheology accounting for brittle deformation. Preliminary results show that deep tectonic structures present in the basement may have crucial effects on the morphology and evolution of a fold-and-thrust belt above a major detachment horizon.

Interpretive geophysical fault map across the central block of Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Ponce, D.A.

1996-01-01

Geophysical data collected along 29 traverses across the central block of Yucca Mountain in southwest Nevada reveal anomalies associated with known fault sand indicate a number of possible concealed faults beneath the eastern flank of Yucca Mountain. Geophysical interpretations indicate that Midway Valley is characterized by several known and previously unknown faults, that the existence of the Yucca Wash fault is equivocal, and that the central part of the eastern flank of Yucca Mountain is characterized by numerous low-amplitude anomalies that probably reflect numerous small-scale faults. Gravity and magnetic data also reveal several large-amplitude anomalies that reflect larger-scale faulting along the margins of the central block

Engine gearbox fault diagnosis using empirical mode ...

Indian Academy of Sciences (India)

Kiran Vernekar

Department of Mechanical Engineering, National Institute of Technology Karnataka,. Surathkal ... proposed approach is an effective method for engine fault diagnosis. Keywords. Engine fault ... (DAQ) card and analysed using LabVIEW software from. Figure 1. .... and reduce numerical difficulties during the calculation. T.

Towards three-dimensional continuum models of self-consistent along-strike megathrust segmentation

Science.gov (United States)

Pranger, Casper; van Dinther, Ylona; May, Dave; Le Pourhiet, Laetitia; Gerya, Taras

2016-04-01

At subduction megathrusts, propagation of large ruptures may be confined between the up-dip and down-dip limits of the seismogenic zone. This opens a primary role for lateral rupture dimensions to control the magnitude and severity of megathrust earthquakes. The goal of this study is to improve our understanding of the ways in which the inherent variability of the subduction interface may influence the degree of interseismic locking, and the propensity of a rupture to propagate over regions of variable slip potential. The global absence of a historic record sufficiently long to base risk assessment on, makes us rely on numerical modelling as a way to extend our understanding of the spatio-temporal occurrence of earthquakes. However, the complex interaction of the subduction stress environment, the variability of the subduction interface, and the structure and deformation of the crustal wedge has made it very difficult to construct comprehensive numerical models of megathrust segmentation. We develop and exploit the power of a plastic 3D continuum representation of the subduction megathrust, as well as off-megathrust faulting to model the long-term tectonic build-up of stresses, and their sudden seismic release. The sheer size of the 3D problem, and the time scales covering those of tectonics as well as seismology, force us to explore efficient and accurate physical and numerical techniques. We thus focused our efforts on developing a staggered grid finite difference code that makes use of the PETSc library for massively parallel computing. The code incorporates a newly developed automatic discretization algorithm, which enables it to handle a wide variety of equations with relative ease. The different physical and numerical ingredients - like attenuating visco-elasto-plastic materials, frictional weakening and inertially driven seismic release, and adaptive time marching schemes - most of which have been implemented and benchmarked individually - are now combined

Slip in the 1857 and earlier large earthquakes along the Carrizo Plain, San Andreas Fault.

Science.gov (United States)

Zielke, Olaf; Arrowsmith, J Ramón; Grant Ludwig, Lisa; Akçiz, Sinan O

2010-02-26

The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a approximately 350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the approximately 60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes. New high-resolution topographic data show that the average slip along the Carrizo segment during the 1857 event was 5.3 +/- 1.4 meters, eliminating the core assumption for a linkage between Carrizo segment rupture and recurrence of major earthquakes along the south-central San Andreas Fault. Earthquake slip along the Carrizo segment may recur in earthquake clusters with cumulative slip of approximately 5 meters.

Late Cenozoic faulting and the stress state in the south-eastern segment of the Siberian platform

Directory of Open Access Journals (Sweden)

V. A. Sankov

2017-01-01

Full Text Available We have studied the structural geology and geomorphology of the fault zones in the junction area of the Angara-Lena uplift and the Predbaikalsky trough. We have analyzed faults and folds and reconstructed paleostresses for this junction area named the Irkutsk amphitheatre. Our study shows that syn-fold (Middle Paleozoic faults include thrusts, reverse faults and strike-slip faults with reverse components, that occurred due to compression from the neighbouring folded region. Recently, contrary to compression, faulting took place under the conditions of extension of the sedimentary cover: most of these recent faults have been classified as normal faults. In the Late Cenozoic, the platform cover was subjected to brittle and partly plicative deformation due to the NW–SE-trending extension that is most clearly observed in the adjacent Baikal rift. Thus, the divergent boundary between the Siberian block of the North Eurasian plate and the Transbaikalia block of the Amur plate is a zone of dynamic influence, which occupies the area considerably exceeding the mountainous region on the Siberian platform. Important factors of faulting are differentiated vertical movements of the blocks comprising the platform. Such vertical movements might have been related to displacements of brine volumes. In the Late Cenozoic basins, movements along separate faults took place in the Late Pleistocene – Holocene.

Stress Transfer Processes during Great Plate Boundary Thrusting Events: A Study from the Andaman and Nicobar Segments

Science.gov (United States)

Andrade, V.; Rajendran, K.

2010-12-01

The response of subduction zones to large earthquakes varies along their strike, both during the interseismic and post-seismic periods. The December 26, 2004 earthquake nucleated at 3° N latitude and its rupture propagated northward, along the Andaman-Sumatra subduction zone, terminating at 15°N. Rupture speed was estimated at about 2.0 km per second in the northern part under the Andaman region and 2.5 - 2.7 km per second under southern Nicobar and North Sumatra. We have examined the pre and post-2004 seismicity to understand the stress transfer processes within the subducting plate, in the Andaman (10° - 15° N ) and Nicobar (5° - 10° N) segments. The seismicity pattern in these segments shows distinctive characteristics associated with the outer rise, accretionary prism and the spreading ridge, all of which are relatively better developed in the Andaman segment. The Ninety East ridge and the Sumatra Fault System are significant tectonic features in the Nicobar segment. The pre-2004 seismicity in both these segments conform to the steady-state conditions wherein large earthquakes are fewer and compressive stresses dominate along the plate interface. Among the pre-2004 great earthquakes are the 1881 Nicobar and 1941 Andaman events. The former is considered to be a shallow thrust event that generated a small tsunami. Studies in other subduction zones suggest that large outer-rise tensional events follow great plate boundary breaking earthquakes due to the the up-dip transfer of stresses within the subducting plate. The seismicity of the Andaman segment (1977-2004) concurs with the steady-state stress conditions where earthquakes occur dominantly by thrust faulting. The post-2004 seismicity shows up-dip migration along the plate interface, with dominance of shallow normal faulting, including a few outer rise events and some deeper (> 100 km) strike-slip faulting events within the subducting plate. The September 13, 2002, Mw 6.5 thrust faulting earthquake at

An effort allocation model considering different budgetary constraint on fault detection process and fault correction process

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Vijay Kumar

2016-01-01

Full Text Available Fault detection process (FDP and Fault correction process (FCP are important phases of software development life cycle (SDLC. It is essential for software to undergo a testing phase, during which faults are detected and corrected. The main goal of this article is to allocate the testing resources in an optimal manner to minimize the cost during testing phase using FDP and FCP under dynamic environment. In this paper, we first assume there is a time lag between fault detection and fault correction. Thus, removal of a fault is performed after a fault is detected. In addition, detection process and correction process are taken to be independent simultaneous activities with different budgetary constraints. A structured optimal policy based on optimal control theory is proposed for software managers to optimize the allocation of the limited resources with the reliability criteria. Furthermore, release policy for the proposed model is also discussed. Numerical example is given in support of the theoretical results.

Active faults, paleoseismology, and historical fault rupture in northern Wairarapa, North Island, New Zealand

International Nuclear Information System (INIS)

Schermer, E.R.; Van Dissen, R.; Berryman, K.R.; Kelsey, H.M.; Cashman, S.M.

2004-01-01

highly segmented, disconnected, and probably structurally immature, which implies that apparent geometric discontinuities at the surface may not be significant barriers to rupture propagation at depth and that the surface rupture record significantly under-represents the seismic slip on faults in the region. (author). 76 refs., 10 figs., 4 tabs

Fault Severity Evaluation and Improvement Design for Mechanical Systems Using the Fault Injection Technique and Gini Concordance Measure

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Jianing Wu

2014-01-01

Full Text Available A new fault injection and Gini concordance based method has been developed for fault severity analysis for multibody mechanical systems concerning their dynamic properties. The fault tree analysis (FTA is employed to roughly identify the faults needed to be considered. According to constitution of the mechanical system, the dynamic properties can be achieved by solving the equations that include many types of faults which are injected by using the fault injection technique. Then, the Gini concordance is used to measure the correspondence between the performance with faults and under normal operation thereby providing useful hints of severity ranking in subsystems for reliability design. One numerical example and a series of experiments are provided to illustrate the application of the new method. The results indicate that the proposed method can accurately model the faults and receive the correct information of fault severity. Some strategies are also proposed for reliability improvement of the spacecraft solar array.

Fault activity characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake

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Dongzhuo Xu

2016-07-01

Full Text Available Fault deformation characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake are investigated through time-series and structural geological analysis based on cross-fault observation data from the Qilian Mountain–Haiyuan Fault belt and the West Qinling Fault belt. The results indicate: 1 Group short-term abnormal variations appeared in the Qilian Mountain–Haiyuan Fault belt and the West Qinling Fault belt before the Menyuan Ms6.4 earthquake. 2 More medium and short-term anomalies appear in the middle-eastern segment of the Qilian Mountain Fault belt and the West Qinling Fault belt, suggesting that the faults' activities are strong in these areas. The faults' activities in the middle-eastern segment of the Qilian Fault belt result from extensional stress, as before the earthquake, whereas those in the West Qinling Fault belt are mainly compressional. 3 In recent years, moderate-strong earthquakes occurred in both the Kunlun Mountain and the Qilian Mountain Fault belts, and some energy was released. It is possible that the seismicity moved eastward under this regime. Therefore, we should pay attention to the West Qinling Mountain area where an Ms6–7 earthquake could occur in future.

Stress Interactions Between the 1976 Magnitude 7.8 Tangshan Earthquake and Adjacent Fault Systems in Northern China

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Zhang, Z.; Lin, J.; Chen, Y. J.

2004-12-01

The 28 July 1976 ML = 7.8 Tangshan earthquake struck a highly populated metropolitan center in northern China and was one of the most devastating earthquakes in modern history. Its occurrence has significantly changed the Coulomb stresses on a complex network of strike-slip, normal, and thrust faults in the region, potentially heightened the odds of future earthquakes on some of these fault segments. We have conducted a detailed analysis of the 3D stress effects of the Tangshan earthquake on its neighboring faults, the relationship between stress transfer and aftershock locations, and the implications for future seismic hazard in the region. Available seismic and geodetic data, although limited, indicate that the Tangshan main shock sequence is composed of complex rupture on 2-3 fault segments. The dominant rupture mode is right-lateral strike-slip on two adjoining sub-segments that strike N5¡aE and N35¡aE, respectively. We calculated that the Tangshan main shock sequence has increased the Coulomb failure stress by more than 1 bar in the vicinity of the Lunanxian district to the east, where the largest aftershock (ML = 7.1) occurred 15 hours after the Tangshan main event. The second largest aftershock (ML = 6.8) occurred on the Ninghe fault to the southwest of the main rupture, in a transitional region between the calculated Coulomb stress increase and decrease. The majority of the ML > 5.0 aftershocks also occurred in areas of calculated Coulomb stress increase. Our analyses further indicate that the Coulomb stress on portions of other fault segments, including the Leting and Lulong fault to the east and Yejito fault to the north, may also have been increased. Thus it is critical to obtain estimates of earthquake repeat times on these and other tectonic faults and to acquire continuous GPS and space geodetic measurements. Investigation of stress interaction and earthquake triggering in northern China is not only highly societal relevant but also important for

Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

Science.gov (United States)

Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

2018-04-01

Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

Numerical investigation on the implications of spring temperature and discharge rate with respect to the geothermal background in a fault zone

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Jiang, Zhenjiao; Xu, Tianfu; Mariethoz, Gregoire

2018-04-01

Geothermal springs are some of the most obvious indicators of the existence of high-temperature geothermal resources in the subsurface. However, geothermal springs can also occur in areas of low average subsurface temperatures, which makes it difficult to assess exploitable zones. To address this problem, this study quantitatively analyzes the conditions associated with the formation of geothermal springs in fault zones, and numerically investigates the implications that outflow temperature and discharge rate from geothermal springs have on the geothermal background in the subsurface. It is concluded that the temperature of geothermal springs in fault zones is mainly controlled by the recharge rate from the country rock and the hydraulic conductivity in the fault damage zone. Importantly, the topography of the fault trace on the land surface plays an important role in determining the thermal temperature. In fault zones with a permeability higher than 1 mD and a lateral recharge rate from the country rock higher than 1 m3/day, convection plays a dominant role in the heat transport rather than thermal conduction. The geothermal springs do not necessarily occur in the place having an abnormal geothermal background (with the temperature at certain depth exceeding the temperature inferred by the global average continental geothermal gradient of 30 °C/km). Assuming a constant temperature (90 °C here, to represent a normal geothermal background in the subsurface at a depth of 3,000 m), the conditions required for the occurrence of geothermal springs were quantitatively determined.

Neuroadaptive Fault-Tolerant Control of Nonlinear Systems Under Output Constraints and Actuation Faults.

Science.gov (United States)

Zhao, Kai; Song, Yongduan; Shen, Zhixi

2018-02-01

In this paper, a neuroadaptive fault-tolerant tracking control method is proposed for a class of time-delay pure-feedback systems in the presence of external disturbances and actuation faults. The proposed controller can achieve prescribed transient and steady-state performance, despite uncertain time delays and output constraints as well as actuation faults. By combining a tangent barrier Lyapunov-Krasovskii function with the dynamic surface control technique, the neural network unit in the developed control scheme is able to take its action from the very beginning and play its learning/approximating role safely during the entire system operational envelope, leading to enhanced control performance without the danger of violating compact set precondition. Furthermore, prescribed transient performance and output constraints are strictly ensured in the presence of nonaffine uncertainties, external disturbances, and undetectable actuation faults. The control strategy is also validated by numerical simulation.

The 2009 MW MW 6.1 L'Aquila fault system imaged by 64k earthquake locations

International Nuclear Information System (INIS)

Valoroso, Luisa

2016-01-01

On April 6 2009, a MW 6.1 normal-faulting earthquake struck the axial area of the Abruzzo region in central Italy. We investigate the complex architecture and mechanics of the activated fault system by using 64k high-resolution foreshock and aftershock locations. The fault system is composed by two major SW dipping segments forming an en-echelon NW trending system about 50 km long: the high-angle L’Aquila fault and the listric Campotosto fault, located in the first 10 km depth. From the beginning of 2009, fore shocks activated the deepest portion of the main shock fault. A week before the MW 6.1 event, the largest (MW 4.0) foreshock triggered seismicity migration along a minor off-fault segment. Seismicity jumped back to the main plane a few hours before the main shock. High-precision locations allowed to peer into the fault zone showing complex geological structures from the metre to the kilometre scale, analogous to those observed by field studies and seismic profiles. Also, we were able to investigate important aspects of earthquakes nucleation and propagation through the upper crust in carbonate-bearing rocks such as: the role of fluids in normal-faulting earthquakes; how crustal faults terminate at depths; the key role of fault zone structure in the earthquake rupture evolution processes.

Deformation associated with continental normal faults

Science.gov (United States)

Resor, Phillip G.

Deformation associated with normal fault earthquakes and geologic structures provide insights into the seismic cycle as it unfolds over time scales from seconds to millions of years. Improved understanding of normal faulting will lead to more accurate seismic hazard assessments and prediction of associated structures. High-precision aftershock locations for the 1995 Kozani-Grevena earthquake (Mw 6.5), Greece image a segmented master fault and antithetic faults. This three-dimensional fault geometry is typical of normal fault systems mapped from outcrop or interpreted from reflection seismic data and illustrates the importance of incorporating three-dimensional fault geometry in mechanical models. Subsurface fault slip associated with the Kozani-Grevena and 1999 Hector Mine (Mw 7.1) earthquakes is modeled using a new method for slip inversion on three-dimensional fault surfaces. Incorporation of three-dimensional fault geometry improves the fit to the geodetic data while honoring aftershock distributions and surface ruptures. GPS Surveying of deformed bedding surfaces associated with normal faulting in the western Grand Canyon reveals patterns of deformation that are similar to those observed by interferometric satellite radar interferometry (InSAR) for the Kozani Grevena earthquake with a prominent down-warp in the hanging wall and a lesser up-warp in the footwall. However, deformation associated with the Kozani-Grevena earthquake extends ˜20 km from the fault surface trace, while the folds in the western Grand Canyon only extend 500 m into the footwall and 1500 m into the hanging wall. A comparison of mechanical and kinematic models illustrates advantages of mechanical models in exploring normal faulting processes including incorporation of both deformation and causative forces, and the opportunity to incorporate more complex fault geometry and constitutive properties. Elastic models with antithetic or synthetic faults or joints in association with a master

Pulse-Like Rupture Induced by Three-Dimensional Fault Zone Flower Structures

KAUST Repository

Pelties, Christian; Huang, Yihe; Ampuero, Jean-Paul

2014-01-01

interface. This effect is robust against a wide range of fault zone widths, absence of frictional healing, variation of initial stress conditions, attenuation, and off-fault plasticity. These numerical studies covered two-dimensional problems with fault

How fault evolution changes strain partitioning and fault slip rates in Southern California: Results from geodynamic modeling

Science.gov (United States)

Ye, Jiyang; Liu, Mian

2017-08-01

In Southern California, the Pacific-North America relative plate motion is accommodated by the complex southern San Andreas Fault system that includes many young faults (faults and their impact on strain partitioning and fault slip rates are important for understanding the evolution of this plate boundary zone and assessing earthquake hazard in Southern California. Using a three-dimensional viscoelastoplastic finite element model, we have investigated how this plate boundary fault system has evolved to accommodate the relative plate motion in Southern California. Our results show that when the plate boundary faults are not optimally configured to accommodate the relative plate motion, strain is localized in places where new faults would initiate to improve the mechanical efficiency of the fault system. In particular, the Eastern California Shear Zone, the San Jacinto Fault, the Elsinore Fault, and the offshore dextral faults all developed in places of highly localized strain. These younger faults compensate for the reduced fault slip on the San Andreas Fault proper because of the Big Bend, a major restraining bend. The evolution of the fault system changes the apportionment of fault slip rates over time, which may explain some of the slip rate discrepancy between geological and geodetic measurements in Southern California. For the present fault configuration, our model predicts localized strain in western Transverse Ranges and along the dextral faults across the Mojave Desert, where numerous damaging earthquakes occurred in recent years.

Frequency of fault occurrence at shallow depths during Plio-Pleistocene and estimation of the incident of new faults

International Nuclear Information System (INIS)

Shiratsuchi, H.; Yoshida, S.

2009-01-01

It is required that buried high-level radioactive wastes should not be broken directly by faulting in the future. Although a disposal site will be selected in an area where no active faults are present, the possibility of new fault occurrence in the site has to be evaluated. The probability of new fault occurrence is estimated from the frequency of faults which exist in Pliocene and Pleistocene strata distributed beneath 3 large plains in Japan, where a large number of seismic profiles and borehole data are obtained. Estimation of the frequency of faults having occurred and/or reached at shallow depth during Plio-Pleistocene time. The frequency of fault occurrence was estimated by counting the number of faults that exist in Plio-Pleistocene strata that are widely distributed in large plains in Japan. Three plains, Kanto, Nobi and Osaka Plains are selected for this purpose because highly precise geological profiles, which were prepared from numerous geological drillings and geophysical investigations, are available in them. (authors)

GO2OGS 1.0: a versatile workflow to integrate complex geological information with fault data into numerical simulation models

Science.gov (United States)

Fischer, T.; Naumov, D.; Sattler, S.; Kolditz, O.; Walther, M.

2015-11-01

We offer a versatile workflow to convert geological models built with the ParadigmTM GOCAD© (Geological Object Computer Aided Design) software into the open-source VTU (Visualization Toolkit unstructured grid) format for usage in numerical simulation models. Tackling relevant scientific questions or engineering tasks often involves multidisciplinary approaches. Conversion workflows are needed as a way of communication between the diverse tools of the various disciplines. Our approach offers an open-source, platform-independent, robust, and comprehensible method that is potentially useful for a multitude of environmental studies. With two application examples in the Thuringian Syncline, we show how a heterogeneous geological GOCAD model including multiple layers and faults can be used for numerical groundwater flow modeling, in our case employing the OpenGeoSys open-source numerical toolbox for groundwater flow simulations. The presented workflow offers the chance to incorporate increasingly detailed data, utilizing the growing availability of computational power to simulate numerical models.

Kinematics of the 2015 San Ramon, California earthquake swarm: Implications for fault zone structure and driving mechanisms

Science.gov (United States)

Xue, Lian; Bürgmann, Roland; Shelly, David R.; Johnson, Christopher W.; Taira, Taka'aki

2018-05-01

Earthquake swarms represent a sudden increase in seismicity that may indicate a heterogeneous fault-zone, the involvement of crustal fluids and/or slow fault slip. Swarms sometimes precede major earthquake ruptures. An earthquake swarm occurred in October 2015 near San Ramon, California in an extensional right step-over region between the northern Calaveras Fault and the Concord-Mt. Diablo fault zone, which has hosted ten major swarms since 1970. The 2015 San Ramon swarm is examined here from 11 October through 18 November using template matching analysis. The relocated seismicity catalog contains ∼4000 events with magnitudes between - 0.2 fault segments of km-scale dimension and thickness of up to 200 m. The segments contain coexisting populations of different focal-mechanisms, suggesting a complex fault zone structure with several sets of en échelon fault orientations. The migration of events along the three planar structures indicates a complex fluid and faulting interaction processes. We searched for correlations between seismic activity and tidal stresses and found some suggestive features, but nothing that we can be confident is statistically significant.

Sliding window denoising K-Singular Value Decomposition and its application on rolling bearing impact fault diagnosis

Science.gov (United States)

Yang, Honggang; Lin, Huibin; Ding, Kang

2018-05-01

The performance of sparse features extraction by commonly used K-Singular Value Decomposition (K-SVD) method depends largely on the signal segment selected in rolling bearing diagnosis, furthermore, the calculating speed is relatively slow and the dictionary becomes so redundant when the fault signal is relatively long. A new sliding window denoising K-SVD (SWD-KSVD) method is proposed, which uses only one small segment of time domain signal containing impacts to perform sliding window dictionary learning and select an optimal pattern with oscillating information of the rolling bearing fault according to a maximum variance principle. An inner product operation between the optimal pattern and the whole fault signal is performed to enhance the characteristic of the impacts' occurrence moments. Lastly, the signal is reconstructed at peak points of the inner product to realize the extraction of the rolling bearing fault features. Both simulation and experiments verify that the method could extract the fault features effectively.

The Relationships of Subparallel Synthetic Faults and Pre-existing Structures in the Central Malawi Rift

Science.gov (United States)

Johnson, S.; Mendez, K.; Beresh, S. C. M.; Mynatt, W. G.; Elifritz, E. A.; Laó-Dávila, D. A.; Atekwana, E. A.; Abdelsalam, M. G.; Chindandali, P. R. N.; Chisenga, C.; Gondwe, S.; Mkumbura, M.; Kalaguluka, D.; Kalindekafe, L.; Salima, J.

2017-12-01

The objective of our research is to explore the evolution of synthetic fault systems in continental rifts. It has been suggested that during the rifting process border faults may become locked and strain is then accommodated within the hanging wall. The Malawi Rift provides an opportunity to study the evolution of these faults within a young (8 Ma), active and magma-poor continental rift. Two faults in central Malawi may show the transference of strain into the hanging wall. These faults are the older Chirobwe-Ntcheu with a length of 115 km and a scarp height of 300-1000 m and the younger Bilila-Mtakataka with a length of 130 km and a scarp height of 4-320 m. We used high-resolution aeromagnetic data and 30m resolution Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM) to provide a 3D spatial characterization of the fault system. Additionally 10cm resolution DEMs were created using unmanned aerial system (UAS) derived aerial photography and Structure from Motion to document the regional Precambrian foliation and joint patterns. Moreover, displacement profiles where extracted from the SRTM-DEM data to compare the segmentation and linkage of the outer and inner faults. Our preliminary results show that the strike of each fault is approximately NW-SE which follows the strike of the Precambrian fabric. The magnetic fabric has a strike of NW-SE in the south changing to NE-SW in the north suggesting that the faults are controlled in part by an inherited Precambrian fabric. The displacement profile of the inner Bilila-Mtakataka fault is asymmetric and displays five fault segments supporting the interpretation that this is a relatively young fault. The expected results of this study are information about segmentation and displacement of each fault and their relationship to one another. The results from the aeromagnetic data utilizing Source Parameter Imaging to produce an approximate depth to basement which will support the displacement profiles derived

Identification of active fault using analysis of derivatives with vertical second based on gravity anomaly data (Case study: Seulimeum fault in Sumatera fault system)

Science.gov (United States)

Hududillah, Teuku Hafid; Simanjuntak, Andrean V. H.; Husni, Muhammad

2017-07-01

Gravity is a non-destructive geophysical technique that has numerous application in engineering and environmental field like locating a fault zone. The purpose of this study is to spot the Seulimeum fault system in Iejue, Aceh Besar (Indonesia) by using a gravity technique and correlate the result with geologic map and conjointly to grasp a trend pattern of fault system. An estimation of subsurface geological structure of Seulimeum fault has been done by using gravity field anomaly data. Gravity anomaly data which used in this study is from Topex that is processed up to Free Air Correction. The step in the Next data processing is applying Bouger correction and Terrin Correction to obtain complete Bouger anomaly that is topographically dependent. Subsurface modeling is done using the Gav2DC for windows software. The result showed a low residual gravity value at a north half compared to south a part of study space that indicated a pattern of fault zone. Gravity residual was successfully correlate with the geologic map that show the existence of the Seulimeum fault in this study space. The study of earthquake records can be used for differentiating the active and non active fault elements, this gives an indication that the delineated fault elements are active.

Using marine magnetic survey data to identify a gold ore-controlling fault: a case study in Sanshandao fault, eastern China

Science.gov (United States)

Yan, Jiayong; Wang, Zhihui; Wang, Jinhui; Song, Jianhua

2018-06-01

The Jiaodong Peninsula has the greatest concentration of gold ore in China and is characterized by altered tectonite-type gold ore deposits. This type of gold deposit is mainly formed in fracture zones and is strictly controlled by faults. Three major ore-controlling faults occur in the Jiaodong Peninsula—the Jiaojia, Zhaoping and Sanshandao faults; the former two are located on land and the latter is located near Sanshandao and its adjacent offshore area. The discovery of the world’s largest marine gold deposit in northeastern Sanshandao indicates that the shallow offshore area has great potential for gold prospecting. However, as two ends of the Sanshandao fault extend to the Bohai Sea, conventional geological survey methods cannot determine the distribution of the fault and this is constraining the discovery of new gold deposits. To explore the southwestward extension of the Sanshandao fault, we performed a 1:25 000 scale marine magnetic survey in this region and obtained high-quality magnetic survey data covering 170 km2. Multi-scale edge detection and three-dimensional inversion of magnetic anomalies identify the characteristics of the southwestward extension of the Sanshandao fault and the three-dimensional distribution of the main lithologies, providing significant evidence for the deployment of marine gold deposit prospecting in the southern segment of the Sanshandao fault. Moreover, three other faults were identified in the study area and faults F2 and F4 are inferred as ore-controlling faults: there may exist other altered tectonite-type gold ore deposits along these two faults.

Dynamic rupture simulations of the 2016 Mw7.8 Kaikōura earthquake: a cascading multi-fault event

Science.gov (United States)

Ulrich, T.; Gabriel, A. A.; Ampuero, J. P.; Xu, W.; Feng, G.

2017-12-01

The Mw7.8 Kaikōura earthquake struck the Northern part of New Zealand's South Island roughly one year ago. It ruptured multiple segments of the contractional North Canterbury fault zone and of the Marlborough fault system. Field observations combined with satellite data suggest a rupture path involving partly unmapped faults separated by large stepover distances larger than 5 km, the maximum distance usually considered by the latest seismic hazard assessment methods. This might imply distant rupture transfer mechanisms generally not considered in seismic hazard assessment. We present high-resolution 3D dynamic rupture simulations of the Kaikōura earthquake under physically self-consistent initial stress and strength conditions. Our simulations are based on recent finite-fault slip inversions that constrain fault system geometry and final slip distribution from remote sensing, surface rupture and geodetic data (Xu et al., 2017). We assume a uniform background stress field, without lateral fault stress or strength heterogeneity. We use the open-source software SeisSol (www.seissol.org) which is based on an arbitrary high-order accurate DERivative Discontinuous Galerkin method (ADER-DG). Our method can account for complex fault geometries, high resolution topography and bathymetry, 3D subsurface structure, off-fault plasticity and modern friction laws. It enables the simulation of seismic wave propagation with high-order accuracy in space and time in complex media. We show that a cascading rupture driven by dynamic triggering can break all fault segments that were involved in this earthquake without mechanically requiring an underlying thrust fault. Our prefered fault geometry connects most fault segments: it does not features stepover larger than 2 km. The best scenario matches the main macroscopic characteristics of the earthquake, including its apparently slow rupture propagation caused by zigzag cascading, the moment magnitude and the overall inferred slip

Fault Diagnosis for Actuators in a Class of Nonlinear Systems Based on an Adaptive Fault Detection Observer

Directory of Open Access Journals (Sweden)

Runxia Guo

2016-01-01

Full Text Available The problem of actuators’ fault diagnosis is pursued for a class of nonlinear control systems that are affected by bounded measurement noise and external disturbances. A novel fault diagnosis algorithm has been proposed by combining the idea of adaptive control theory and the approach of fault detection observer. The asymptotical stability of the fault detection observer is guaranteed by setting the adaptive adjusting law of the unknown fault vector. A theoretically rigorous proof of asymptotical stability has been given. Under the condition that random measurement noise generated by the sensors of control systems and external disturbances exist simultaneously, the designed fault diagnosis algorithm is able to successfully give specific estimated values of state variables and failures rather than just giving a simple fault warning. Moreover, the proposed algorithm is very simple and concise and is easy to be applied to practical engineering. Numerical experiments are carried out to evaluate the performance of the fault diagnosis algorithm. Experimental results show that the proposed diagnostic strategy has a satisfactory estimation effect.

Postglacial seismic activity along the Isovaara-Riikonkumpu fault complex

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Ojala, Antti E. K.; Mattila, Jussi; Ruskeeniemi, Timo; Palmu, Jukka-Pekka; Lindberg, Antero; Hänninen, Pekka; Sutinen, Raimo

2017-10-01

Analysis of airborne LiDAR-based digital elevation models (DEMs), trenching of Quaternary deposits, and diamond drilling through faulted bedrock was conducted to characterize the geological structure and full slip profiles of the Isovaara-Riikonkumpu postglacial fault (PGF) complex in northern Finland. The PGF systems are recognized from LiDAR DEMs as a complex of surface ruptures striking SW-NE, cutting through late-Weichselian till, and associated with several postglacial landslides within 10 km. Evidence from the terrain rupture characteristics, the deformed and folded structure of late-Weichselian till, and the 14C age of 11,300 cal BP from buried organic matter underneath the Sotka landslide indicates a postglacial origin of the Riikonkumpu fault (PGF). The fracture frequency and lithology of drill cores and fault geometry in the trench log indicate that the Riikonkumpu PGF dips to WNW with a dip angle of 40-45° at the Riikonkumpu site and close to 60° at the Riikonvaara site. A fault length of 19 km and the mean and maximum cumulative vertical displacement of 1.3 m and 4.1 m, respectively, of the Riikonkumpu PGF system indicate that the fault potentially hosted an earthquake with a moment magnitude MW ≈ 6.7-7.3 assuming that slip was accumulated in one seismic event. Our interpretation further suggests that the Riikonkumpu PGF system is linked to the Isovaara PGF system and that, together, they form a larger Isovaara-Riikonkumpu fault complex. Relationships between the 38-km-long rupture of the Isovaara-Riikonkumpu complex and the fault offset parameters, with cumulative displacement of 1.5 and 8.3 m, respectively, indicate that the earthquake(s) contributing to the PGF complex potentially had a moment magnitude of MW ≈ 6.9-7.5. In order to adequately sample the uncertainty space, the moment magnitude was also estimated for each major segment within the Isovaara-Riikonkumpu PGF complex. These estimates vary roughly between MW ≈ 5-8 for the individual

Late Cenozoic tephrochronology, stratigraphy, geomorphology, and neotectonics of the Western Black Mountains Piedmont, Death Valley, California: Implications for the spatial and temporal evolution of the Death Valley fault zone

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Knott, Jeffrey Rayburn

This study presents the first detailed tephrochronologic study of the central Death Valley area by correlation of a Nomlaki-like tuff (>3.35 Ma), tuffs of the Mesquite Spring family (3.1 -- 3.35 Ma), a tuff of the lower Glass Mountain family (1.86 -- 2.06 Ma), and tephra layers from the upper Glass Mountain family (0.8 -- 1.2 Ma), the Bishop ash bed (0.76 Ma), the Lava Creek B ash bed (~0.66 Ma), and the Dibekulewe ash bed (~0.51 Ma). Correlation of these tuffs and tephra layers provides the first reliable numeric-age stratigraphy for late Cenozoic alluvial fan and lacustrine deposits for Death Valley and resulted in the naming of the informal early to middle Pleistocene Mormon Ploint formation. Using the numeric-age stratigraphy, the Death Valley fault zone (DVFZ) is interpreted to have progressively stepped basinward since the late Pliocene at Mormon Point and Copper Canyon. The Mormon Point turtleback or low-angle normal fault is shown to have unequivocal late Quaternary slip at its present low angle dip. Tectonic geomorphic analysis indicates that the (DVFZ) is composed of five geomorphic segments with the most persistent segment boundaries being the en-echelon step at Mormon Point and the bedrock salient at Artists Drive. Subsequent geomorphic studies resulting from the numeric-age stratigraphy and structural relations include application of Gilberts field criteria to the benches at Mormon Point indicating that the upper bench is a lacustrine strandline and the remaining topographically-lower benches are fault scarps across the 160--185 ka lake abrasion platform. In addition, the first known application of cosmogenic 10Be and 26Al exposure dating to a rock avalanche complex south of Badwater yielded an age of 29.5 +/- 1.9 ka for the younger avalanche. The 28 meter offset of the older avalanche may be interpreted as post-160--185 ka yielding a 0.1 mm/year slip rate, or post-29.5 +/- 1.9 ka yielding a maximum slip rate of 0.9 nun/year for the DVFZ. A consequence

Fault tectonics and earthquake hazards in parts of southern California. [penninsular ranges, Garlock fault, Salton Trough area, and western Mojave Desert

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Merifield, P. M. (Principal Investigator); Lamar, D. L.; Gazley, C., Jr.; Lamar, J. V.; Stratton, R. H.

1976-01-01

The author has identified the following significant results. Four previously unknown faults were discovered in basement terrane of the Peninsular Ranges. These have been named the San Ysidro Creek fault, Thing Valley fault, Canyon City fault, and Warren Canyon fault. In addition fault gouge and breccia were recognized along the San Diego River fault. Study of features on Skylab imagery and review of geologic and seismic data suggest that the risk of a damaging earthquake is greater along the northwestern portion of the Elsinore fault than along the southeastern portion. Physiographic indicators of active faulting along the Garlock fault identifiable in Skylab imagery include scarps, linear ridges, shutter ridges, faceted ridges, linear valleys, undrained depressions and offset drainage. The following previously unrecognized fault segments are postulated for the Salton Trough Area: (1) An extension of a previously known fault in the San Andreas fault set located southeast of the Salton Sea; (2) An extension of the active San Jacinto fault zone along a tonal change in cultivated fields across Mexicali Valley ( the tonal change may represent different soil conditions along opposite sides of a fault). For the Skylab and LANDSAT images studied, pseudocolor transformations offer no advantages over the original images in the recognition of faults in Skylab and LANDSAT images. Alluvial deposits of different ages, a marble unit and iron oxide gossans of the Mojave Mining District are more readily differentiated on images prepared from ratios of individual bands of the S-192 multispectral scanner data. The San Andreas fault was also made more distinct in the 8/2 and 9/2 band ratios by enhancement of vegetation differences on opposite sides of the fault. Preliminary analysis indicates a significant earth resources potential for the discrimination of soil and rock types, including mineral alteration zones. This application should be actively pursued.

Fault structures in the focal area of the 2016 Kumamoto earthquake revealed by derivatives and structure parameters of a gravity gradient tensor

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Hiramatsu, Y.; Matsumoto, N.; Sawada, A.

2016-12-01

We analyze gravity anomalies in the focal area of the 2016 Kumamoto earthquake, evaluate the continuity, segmentation and faulting type of the active fault zones, and discuss relationships between those features and the aftershock distribution. We compile the gravity data published by the Gravity Research Group in Southwest Japan (2001), the Geographical Survey Institute (2006), Yamamoto et al. (2011), Honda et al. (2012), and the Geological Survey of Japan, AIST (2013). We apply terrain corrections with 10 m DEM and a low-pass filter, then remove a linear trend to obtain Bouguer anomalies. We calculate the first horizontal derivative (HD), the first vertical derivative (VD), the normalized total horizontal derivative (TDX) (Cooper and Cowan, 2006), the dimensionality index (Di) (Beki and Pedersen, 2010), and dip angle (β) (Beki, 2013) from a gravity gradient tensor. The HD, VD and TDX show the existence of the continuous fault structure along the Futagawa fault zone, extending from the Uto peninsula to the Beppu Bay except Mt. Aso area. Aftershocks are distributed along this structural boundary from the confluence of the Futagawa and the Hinagu fault zones to the east end of the Aso volcano. The distribution of dip angle β along the Futagawa fault zone implies a normal faulting, which corresponds to the coseismic faulting estimated geologically and geomorphologically. We observe the S-shaped distribution of the Bouguer anomalies around the southern part of the Hinagu segment, indicating a right lateral faulting. The VD and TDX support the existence of the fault structure along the segment but it is not so clear. We can recognize no clear structural boundaries along the Takano-Shirahata segment. TDX implies the existence of a structural boundary with a NW-SE trend around the boundary between the Hinagu and Takano-Shirahata segments. The Di shows that this boundary has a 3D-like structure rather than a 2D-like one, suggesting the discontinuity of 2D-like fault

Influence of mineralogy and microstructures on strain localization and fault zone architecture of the Alpine Fault, New Zealand

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Ichiba, T.; Kaneki, S.; Hirono, T.; Oohashi, K.; Schuck, B.; Janssen, C.; Schleicher, A.; Toy, V.; Dresen, G.

2017-12-01

The Alpine Fault on New Zealand's South Island is an oblique, dextral strike-slip fault that accommodated the majority of displacement between the Pacific and the Australian Plates and presents the biggest seismic hazard in the region. Along its central segment, the hanging wall comprises greenschist and amphibolite facies Alpine Schists. Exhumation from 35 km depth, along a SE-dipping detachment, lead to mylonitization which was subsequently overprinted by brittle deformation and finally resulted in the fault's 1 km wide damage zone. The geomechanical behavior of a fault is affected by the internal structure of its fault zone. Consequently, studying processes controlling fault zone architecture allows assessing the seismic hazard of a fault. Here we present the results of a combined microstructural (SEM and TEM), mineralogical (XRD) and geochemical (XRF) investigation of outcrop samples originating from several locations along the Alpine Fault, the aim of which is to evaluate the influence of mineralogical composition, alteration and pre-existing fabric on strain localization and to identify the controls on the fault zone architecture, particularly the locus of brittle deformation in P, T and t space. Field observations reveal that the fault's principal slip zone (PSZ) is either a thin (< 1 cm to < 7 cm) layered structure or a relatively thick (10s cm) package lacking a detectable macroscopic fabric. Lithological and related rheological contrasts are widely assumed to govern strain localization. However, our preliminary results suggest that qualitative mineralogical composition has only minor impact on fault zone architecture. Quantities of individual mineral phases differ markedly between fault damage zone and fault core at specific sites, but the quantitative composition of identical structural units such as the fault core, is similar in all samples. This indicates that the degree of strain localization at the Alpine Fault might be controlled by small initial

Strong paleoearthquakes along the Talas-Fergana Fault, Kyrgyzstan

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A.M. Korzhenkov

2014-02-01

Full Text Available The Talas-Fergana Fault, the largest strike-slip structure in Centred. Asia, forms an obliquely oriented boundary between the northeastern and southwestern parts of the Tianshan mountain belt. The fault underwent active right-lateral strike-slip during the Paleozoic, with right-lateral movements being rejuvenated in the Late Cenozoic. Tectonic movements along the intracontinental strike-slip faults contribute to absorb part of the regional crustal shortening linked to the India-Eurasia collision; knowledge of strike-slip motions along the Talas-Fergana Fault are necessary for a complete assessment of the active deformation of the Tianshan orogen. To improve our understanding of the intracontinental deformation of the Tianshan mountain belt and the occurrence of strong earthquakes along the whole length of the Talas-Fergana Fault, we identify features of relief arising during strong paleoearthquakes along the Talas-Fergana Fault, fault segmentation, the length of seismogenic ruptures, and the energy and age of ancient catastrophes. We show that during neotectonic time the fault developed as a dextral strike-slip fault, with possible dextral displacements spreading to secondary fault planes north of the main fault trace. We determine rates of Holocene and Late Pleistocene dextral movements, and our radiocarbon dating indicates tens of strong earthquakes occurring along the fault zone during arid interval of 15800 years. The reoccurrence of strong earthquakes along the Talas-Fergana Fault zone during the second half of the Holocene is about 300 years. The next strong earthquake along the fault will most probably occur along its southeastern chain during the next several decades. Seismotectonic deformation parameters indicate that M > 7 earthquakes with oscillation intensity I > IX have occurred.

Dynamical instability produces transform faults at mid-ocean ridges.

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Gerya, Taras

2010-08-27

Transform faults at mid-ocean ridges--one of the most striking, yet enigmatic features of terrestrial plate tectonics--are considered to be the inherited product of preexisting fault structures. Ridge offsets along these faults therefore should remain constant with time. Here, numerical models suggest that transform faults are actively developing and result from dynamical instability of constructive plate boundaries, irrespective of previous structure. Boundary instability from asymmetric plate growth can spontaneously start in alternate directions along successive ridge sections; the resultant curved ridges become transform faults within a few million years. Fracture-related rheological weakening stabilizes ridge-parallel detachment faults. Offsets along the transform faults change continuously with time by asymmetric plate growth and discontinuously by ridge jumps.

Variations in strength and slip rate along the san andreas fault system.

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Jones, C H; Wesnousky, S G

1992-04-03

Convergence across the San Andreas fault (SAF) system is partitioned between strike-slip motion on the vertical SAF and oblique-slip motion on parallel dip-slip faults, as illustrated by the recent magnitude M(s) = 6.0 Palm Springs, M(s) = 6.7 Coalinga, and M(s) = 7.1 Loma Prieta earthquakes. If the partitioning of slip minimizes the work done against friction, the direction of slip during these recent earthquakes depends primarily on fault dip and indicates that the normal stress coefficient and frictional coefficient (micro) vary among the faults. Additionally, accounting for the active dip-slip faults reduces estimates of fault slip rates along the vertical trace of the SAF by about 50 percent in the Loma Prieta and 100 percent in the North Palm Springs segments.

The postglacial Stuoragurra Fault, North Norway - A textural and mineralogical study.

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Roaldset, E.

2012-04-01

The postglacial Stuoragurra Fault, North Norway - A textural and mineralogical study Elen Roaldset(1), Mari Åm (2), and Oddleiv Olesen(3) 1) Natural History Museum, University of Oslo, P.O.Box 1172 Blindern, 0318 Oslo, Norway 2) Statoil R &D, P. O. Box 2470, 7005 Trondheim, Norway 3) Norwegian Geological Survey, P.O.Box 6315 Sluppen, 7491 Trondheim, Norway The Stuoragurra Fault is part of the Lapland province of postglacial faults and was identified in 1983 during a colloborative project between the Geological Surveys of Finland Norway and Sweden. The Stuoragurra Fault is an 80 km long fault zone which contains three main segments of eastward dipping faults (30-55 deg.) with up to 10 m of reverse displacement and a 7 m high escarpment. It cross-cuts glaciofluvial deposits and consequently being younger than 10.000 years. The postglacial fault segments follow to a large extent older fault zones represented by lithified breccias and diabases of Proterozoic age. In this paper we will present textural and mineralogical study of a 135 m continous core drilled across the fault zone. The investigation methods include quality assessments by rock quality designation methods (RQD and Q- methods), textural and petrological descriptions visually and by thin section microscopy, and mineralogical analysis by X-ray diffraction. Special attention is drawn to neoformed and/or degraded minerals like clay minerals and iron oxides/hydroxides. The quality assessments of the cored material reflect the degree of rock deformation and fragmentation and show the quality of the bedrock generally to be of very poor (about 60%) to poor quality" (25%) The main minerals in the fresh rock are quarts, feldspar, mica and iron oxides (magnetite and ilmenite). Throughout the cored borehole products of weathering have formed on fissures, fractures and in strongly deformed, gravelly, zones. The neoformed minerals include kaolinite, smectite, and vermiculite, as well as goethite. The mineralogical

Electromagnetic Imaging of Fluids in the San Andreas Fault; FINAL

International Nuclear Information System (INIS)

Martyn Unsworth

2002-01-01

OAK 270 - Magnetotelluric data were collected on six profiles across the san Andreas Fault at Cholame,Parkfield, and Hollister in Central California. On each profile, high electrical resistivities were imaged west of the fault, and are due to granitic rocks of the Salinian block. East of the fault, lower electrical resistivities are associated with rocks of the Fanciscan formation. On the seismically active Parkfield and Hollister segments, a region of low resistivity was found in the fault zone that extends to a depth of several kilometers. This is due to a zone of fracturing (the damaged zone) that has been infiltrated by saline ground water. The shallowest micro-earthquakers occur at a depth that is coincident with the base of the low resistivity wedge. This strongly suggests that above this depth, the fault rocks are too weak to accumulate sufficient stress for earthquake rupture to occur and fault motion is accommodated through aseismic creep

Undulator Hall Air Temperature Fault Scenarios

International Nuclear Information System (INIS)

Sevilla, J.

2010-01-01

Recent experience indicates that the LCLS undulator segments must not, at any time following tuning, be allowed to change temperature by more than about ±2.5 C or the magnetic center will irreversibly shift outside of acceptable tolerances. This vulnerability raises a concern that under fault conditions the ambient temperature in the Undulator Hall might go outside of the safe range and potentially could require removal and retuning of all the segments. In this note we estimate changes that can be expected in the Undulator Hall air temperature for three fault scenarios: (1) System-wide power failure; (2) Heating Ventilation and Air Conditioning (HVAC) system shutdown; and (3) HVAC system temperature regulation fault. We find that for either a system-wide power failure or an HVAC system shutdown (with the technical equipment left on), the short-term temperature changes of the air would be modest due to the ability of the walls and floor to act as a heat ballast. No action would be needed to protect the undulator system in the event of a system-wide power failure. Some action to adjust the heat balance, in the case of the HVAC power failure with the equipment left on, might be desirable but is not required. On the other hand, a temperature regulation failure of the HVAC system can quickly cause large excursions in air temperature and prompt action would be required to avoid damage to the undulator system.

Assessing the Progress of Trapped-Ion Processors Towards Fault-Tolerant Quantum Computation

Science.gov (United States)

Bermudez, A.; Xu, X.; Nigmatullin, R.; O'Gorman, J.; Negnevitsky, V.; Schindler, P.; Monz, T.; Poschinger, U. G.; Hempel, C.; Home, J.; Schmidt-Kaler, F.; Biercuk, M.; Blatt, R.; Benjamin, S.; Müller, M.

2017-10-01

A quantitative assessment of the progress of small prototype quantum processors towards fault-tolerant quantum computation is a problem of current interest in experimental and theoretical quantum information science. We introduce a necessary and fair criterion for quantum error correction (QEC), which must be achieved in the development of these quantum processors before their sizes are sufficiently big to consider the well-known QEC threshold. We apply this criterion to benchmark the ongoing effort in implementing QEC with topological color codes using trapped-ion quantum processors and, more importantly, to guide the future hardware developments that will be required in order to demonstrate beneficial QEC with small topological quantum codes. In doing so, we present a thorough description of a realistic trapped-ion toolbox for QEC and a physically motivated error model that goes beyond standard simplifications in the QEC literature. We focus on laser-based quantum gates realized in two-species trapped-ion crystals in high-optical aperture segmented traps. Our large-scale numerical analysis shows that, with the foreseen technological improvements described here, this platform is a very promising candidate for fault-tolerant quantum computation.

Tearing, segmentation, and backstepping of subduction in the Aegean: New insights from seismicity

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Bocchini, G. M.; Brüstle, A.; Becker, D.; Meier, T.; van Keken, P. E.; Ruscic, M.; Papadopoulos, G. A.; Rische, M.; Friederich, W.

2018-06-01

This study revisits subduction processes at the Hellenic Subduction Zone (HSZ) including tearing, segmentation, and backstepping, by refining the geometry of the Nubian slab down to 150-180 km depth using well-located hypocentres from global and local seismicity catalogues. At the western termination of the HSZ, the Kefalonia Transform Fault marks the transition between oceanic and continental lithosphere subducting to the south and to the north of it, respectively. A discontinuity is suggested to exist between the two slabs at shallow depths. The Kefalonia Transform Fault is interpreted as an active Subduction-Transform-Edge-Propagator-fault formed as consequence of faster trench retreat induced by the subduction of oceanic lithosphere to the south of it. A model reconstructing the evolution of the subduction system in the area of Peloponnese since 34 Ma, involving the backstepping of the subduction to the back-side of Adria, provides seismological evidence that supports the single-slab model for the HSZ and suggests the correlation between the downdip limit of the seismicity to the amount of subducted oceanic lithosphere. In the area of Rhodes, earthquake hypocentres indicate the presence of a NW dipping subducting slab that rules out the presence of a NE-SW striking Subduction-Transform-Edge-Propagator-fault in the Pliny-Strabo trenches region. Earthquake hypocentres also allow refining the slab tear beneath southwestern Anatolia down to 150-180 km depth. Furthermore, the distribution of microseismicity shows a first-order slab segmentation in the region between Crete and Karpathos, with a less steep and laterally wider slab segment to the west and a steeper and narrower slab segment to the east. Thermal models indicate the presence of a colder slab beneath the southeastern Aegean that leads to deepening of the intermediate-depth seismicity. Slab segmentation affects the upper plate deformation that is stronger above the eastern slab segment and the seismicity

Undersea acoustic telemetry across the North Anatolian Fault, Marmara Sea: results from the first 6 months of monitoring of the fault displacement

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Royer, J. Y.; Deschamps, A.; Piete, H.; Sakic, P.; Ballu, V.; Apprioual, R.; Kopp, H.; Lange, D.; Ruffine, L.; Géli, L.

2015-12-01

Located in the Marmara Sea, the Istanbul-Silivri segment of the North Anatolian Fault (NAF) is known to be a seismic gap since 1766, although, in the last century, the NAF has caused major devastating earthquakes over most of its extent. This fault segment, void of seismicity, may be either creeping aseismically or blocked and accumulating enough strain to produce an earthquake of magnitude 7 or greater. This section of the NAF may thus represent a major seismic and tsunamigenic hazard for the Istanbul megalopolis, located only 40 km away. The objective of the MARSITE project, funded by the European Union and coordinated by the Observatory of the University of Kandilli (KOERI), is to determine the blocking state of the Istanbul-Silivri fault segment. In this context, an array of 10 acoustic transponders has been deployed on either sides of the fault, in the eastern part of the Kumburgaz Basin, to measure the displacements of the fault over a period of 3 to 5 years. The telemetric beacons (4 from the University of Brest and 6 from the GEOMAR Institute in Kiel) form two arrays fitted in one another. The principle of the experiment is to repeatedly measure the distance (ie two-way-travel time of acoustic pings) between pairs of beacons and thus to monitor the deformation of an array of 9 baselines, 500m to 3000m long, of which 5 cross obliquely the assumed fault trace. The French and German arrays are independent but ensure a redundancy of rangings along common baselines. Each acoustic transponder also monitors the temperature, pressure, sound-velocity and attitude (tiltmeters), every one or two hours. Data are stored in each beacon and can be downloaded from the surface using an acoustic modem. We present here the first 6 months of recording by the French array, from November 1st, 2014 to April 25, 2015. All acoustic transponders worked nominally for 6 months and appear to have remained stable on the seafloor. Recorded sea-bottom temperatures provide evidence for

Variable slip-rate and slip-per-event on a plate boundary fault: The Dead Sea fault in northern Israel

Science.gov (United States)

Wechsler, Neta; Rockwell, Thomas K.; Klinger, Yann

2018-01-01

We resolved displacement on buried stream channels that record the past 3400 years of slip history for the Jordan Gorge (JGF) section of the Dead Sea fault in Israel. Based on three-dimensional (3D) trenching, slip in the past millennium amounts to only 2.7 m, similar to that determined in previous studies, whereas the previous millennium experienced two to three times this amount of displacement with nearly 8 m of cumulative slip, indicating substantial short term variations in slip rate. The slip rate averaged over the past 3400 years, as determined from 3D trenching, is 4.1 mm/yr, which agrees well with geodetic estimates of strain accumulation, as well as with longer-term geologic slip rate estimates. Our results indicate that: 1) the past 1200 years appear to significantly lack slip, which may portend a significant increase in future seismic activity; 2) short-term slip rates for the past two millennia have varied by more than a factor of two and suggest that past behavior is best characterized by clustering of earthquakes. From these observations, the earthquake behavior of the Jordan Gorge fault best fits is a "weak segment model" where the relatively short fault section (20 km), bounded by releasing steps, fails on its own in moderate earthquakes, or ruptures with adjacent segments.

4D stress evolution models of the San Andreas Fault System: Investigating time- and depth-dependent stress thresholds over multiple earthquake cycles

Science.gov (United States)

Burkhard, L. M.; Smith-Konter, B. R.

2017-12-01

4D simulations of stress evolution provide a rare insight into earthquake cycle crustal stress variations at seismogenic depths where earthquake ruptures nucleate. Paleoseismic estimates of earthquake offset and chronology, spanning multiple earthquakes cycles, are available for many well-studied segments of the San Andreas Fault System (SAFS). Here we construct new 4D earthquake cycle time-series simulations to further study the temporally and spatially varying stress threshold conditions of the SAFS throughout the paleoseismic record. Interseismic strain accumulation, co-seismic stress drop, and postseismic viscoelastic relaxation processes are evaluated as a function of variable slip and locking depths along 42 major fault segments. Paleoseismic earthquake rupture histories provide a slip chronology dating back over 1000 years. Using GAGE Facility GPS and new Sentinel-1A InSAR data, we tune model locking depths and slip rates to compute the 4D stress accumulation within the seismogenic crust. Revised estimates of stress accumulation rate are most significant along the Imperial (2.8 MPa/100yr) and Coachella (1.2 MPa/100yr) faults, with a maximum change in stress rate along some segments of 11-17% in comparison with our previous estimates. Revised estimates of earthquake cycle stress accumulation are most significant along the Imperial (2.25 MPa), Coachella (2.9 MPa), and Carrizo (3.2 MPa) segments, with a 15-29% decrease in stress due to locking depth and slip rate updates, and also postseismic relaxation from the El Mayor-Cucapah earthquake. Because stress drops of major strike-slip earthquakes rarely exceed 10 MPa, these models may provide a lower bound on estimates of stress evolution throughout the historical era, and perhaps an upper bound on the expected recurrence interval of a particular fault segment. Furthermore, time-series stress models reveal temporally varying stress concentrations at 5-10 km depths, due to the interaction of neighboring fault

Numerical Control Machine Tool Fault Diagnosis Using Hybrid Stationary Subspace Analysis and Least Squares Support Vector Machine with a Single Sensor

Directory of Open Access Journals (Sweden)

Chen Gao

2017-03-01

Full Text Available Tool fault diagnosis in numerical control (NC machines plays a significant role in ensuring manufacturing quality. However, current methods of tool fault diagnosis lack accuracy. Therefore, in the present paper, a fault diagnosis method was proposed based on stationary subspace analysis (SSA and least squares support vector machine (LS-SVM using only a single sensor. First, SSA was used to extract stationary and non-stationary sources from multi-dimensional signals without the need for independency and without prior information of the source signals, after the dimensionality of the vibration signal observed by a single sensor was expanded by phase space reconstruction technique. Subsequently, 10 dimensionless parameters in the time-frequency domain for non-stationary sources were calculated to generate samples to train the LS-SVM. Finally, the measured vibration signals from tools of an unknown state and their non-stationary sources were separated by SSA to serve as test samples for the trained SVM. The experimental validation demonstrated that the proposed method has better diagnosis accuracy than three previous methods based on LS-SVM alone, Principal component analysis and LS-SVM or on SSA and Linear discriminant analysis.

Paleoseismic evidence of characteristic slip on the Western segment of the North Anatolian fault, Turkey

Science.gov (United States)

Klinger, Yann; Sieh, K.; Altunel, E.; Akoglu, A.; Barka, A.; Dawson, Tim; Gonzalez, Tania; Meltzner, A.; Rockwell, Thomas

2003-01-01

We have conducted a paleoseismic investigation of serial fault rupture at one site along the 110-km rupture of the North Anatolian fault that produced the Mw 7.4 earthquake of 17 August 1999. The benefit of using a recent rupture to compare serial ruptures lies in the fact that the location, magnitude, and slip vector of the most recent event are all very well documented. We wished to determine whether or not the previous few ruptures of the fault were similar to the recent one. We chose a site at a step-over between two major strike-slip traces, where the principal fault is a normal fault. Our two excavations across the 1999 rupture reveal fluvial sands and gravels with two colluvial wedges related to previous earthquakes. Each wedge is about 0.8 m thick. Considering the processes of collapse and subsequent diffusion that are responsible for the formation of a colluvial wedge, we suggest that the two paleoscarps were similar in height to the 1999 scarp. This similarity supports the concept of characteristic slip, at least for this location along the fault. Accelerator mass spectrometry (AMS) radiocarbon dates of 16 charcoal samples are consistent with the interpretation that these two paleoscarps formed during large historical events in 1509 and 1719. If this is correct, the most recent three ruptures at the site have occurred at 210- and 280-year intervals.

Automatic fault extraction using a modified ant-colony algorithm

International Nuclear Information System (INIS)

Zhao, Junsheng; Sun, Sam Zandong

2013-01-01

The basis of automatic fault extraction is seismic attributes, such as the coherence cube which is always used to identify a fault by the minimum value. The biggest challenge in automatic fault extraction is noise, including that of seismic data. However, a fault has a better spatial continuity in certain direction, which makes it quite different from noise. Considering this characteristic, a modified ant-colony algorithm is introduced into automatic fault identification and tracking, where the gradient direction and direction consistency are used as constraints. Numerical model test results show that this method is feasible and effective in automatic fault extraction and noise suppression. The application of field data further illustrates its validity and superiority. (paper)

A bottom-driven mechanism for distributed faulting in the Gulf of California rift

Science.gov (United States)

Persaud, Patricia; Tan, Eh; Contreras, Juan; Lavier, Luc

2017-11-01

Observations of active faulting in the continent-ocean transition of the Northern Gulf of California show multiple oblique-slip faults distributed in a 200 × 70 km2 area developed some time after a westward relocation of the plate boundary at 2 Ma. In contrast, north and south of this broad pull-apart structure, major transform faults accommodate Pacific-North America plate motion. Here we propose that the mechanism for distributed brittle deformation results from the boundary conditions present in the Northern Gulf, where basal shear is distributed between the Cerro Prieto strike-slip fault (southernmost fault of the San Andreas fault system) and the Ballenas Transform Fault. We hypothesize that in oblique-extensional settings whether deformation is partitioned in a few dip-slip and strike-slip faults, or in numerous oblique-slip faults may depend on (1) bottom-driven, distributed extension and shear deformation of the lower crust or upper mantle, and (2) the rift obliquity. To test this idea, we explore the effects of bottom-driven shear on the deformation of a brittle elastic-plastic layer with the help of pseudo-three dimensional numerical models that include side forces. Strain localization results when the basal shear abruptly increases in a step-function manner while oblique-slip on numerous faults dominates when basal shear is distributed. We further explore how the style of faulting varies with obliquity and demonstrate that the style of delocalized faulting observed in the Northern Gulf of California is reproduced in models with an obliquity of 0.7 and distributed basal shear boundary conditions, consistent with the interpreted obliquity and boundary conditions of the study area.

Numerical Modeling on Co-seismic Influence of Wenchuan 8.0 Earthquake in Sichuan-Yunnan Area, China

Science.gov (United States)

Chen, L.; Li, H.; Lu, Y.; Li, Y.; Ye, J.

2009-12-01

In this paper, a three dimensional finite element model for active faults which are handled by contact friction elements in Sichuan-Yunnan area is built. Applying the boundary conditions determined through GPS data, a numerical simulations on spatial patterns of stress-strain changes induced by Wenchuan Ms8.0 earthquake are performed. Some primary results are: a) the co-seismic displacements in Longmen shan fault zone by the initial cracking event benefit not only the NE-direction expanding of subsequent fracture process but also the focal mechanism conversions from thrust to right lateral strike for the most of following sub-cracking events. b) tectonic movements induced by the Wenchuan earthquake are stronger in the upper wall of Longmen shan fault belt than in the lower wall and are influenced remarkably by the northeast boundary faults of the rhombic block. c) the extrema of stress changes induced by the main shock are 106Pa and its spatial size is about 400km long and 100km wide. The total stress level is reduced in the most regions in Longmen shan fault zone, whereas stress change is rather weak in its southwest segment and possibly result in fewer aftershocks in there. d) effects induced by the Wenchuan earthquake to the major active faults are obviously different from each other. e) triggering effect of the Wenchuan earthquake to the following Huili 6.1 earthquake is very weak.

Late Quaternary eruption of the Ranau Caldera and new geological slip rates of the Sumatran Fault Zone in Southern Sumatra, Indonesia

Science.gov (United States)

Natawidjaja, Danny Hilman; Bradley, Kyle; Daryono, Mudrik R.; Aribowo, Sonny; Herrin, Jason

2017-12-01

Over the last decade, studies of natural hazards in Sumatra have focused primarily on great earthquakes and associated tsunamis produced by rupture of the Sunda megathrust. However, the Sumatran Fault and the active volcanic arc present proximal hazards to populations on mainland Sumatra. At present, there is little reliable information on the maximum magnitudes and recurrence intervals of Sumatran Fault earthquakes, or the frequency of paroxysmal caldera-forming (VEI 7-8) eruptions. Here, we present new radiocarbon dates of paleosols buried under the voluminous Ranau Tuff that constrain the large caldera-forming eruption to around 33,830-33,450 calender year BP (95% probability). We use the lateral displacement of river channels incised into the Ranau Tuff to constrain the long-term slip rate of two segments of the Sumatran Fault. South of Ranau Lake, the Kumering segment preserves isochronous right-lateral channel offsets of approximately 350 ± 50 m, yielding a minimum slip rate of 10.4 ± 1.5 mm/year for the primary active fault trace. South of Suoh pull-apart depression, the West Semangko segment offsets the Semangko River by 230 ± 60 m, yielding an inferred slip rate of 6.8 ± 1.8 mm/year. Compared with previous studies, these results indicate more recent high-volume volcanism in South Sumatra and increased seismic potency of the southernmost segments of the Sumatran Fault Zone.

Spatio-temporal evolution of fault networks: implications for deep radioactive waste disposal sites

International Nuclear Information System (INIS)

Hardacre, K.; Scotti, O.

2001-01-01

The objective of this work is to provide estimates of both vertical and lateral propagation rates, on time scales of 100 000 years, for the faults systems known to be present today in the region of Bure, the site of an underground rock laboratory. The project is divided into three parts: 1) literature review (fault growth processes and data), 2) benchmarking against data a numerical code that allows for spontaneous development and growth of faults and 3) application to the Bure site. A brief overview of fault growth processes and observed fault propagation rates shows that non-negligible values (20-50 mm/yrs or roughly 5 km in 100 000 years) can be reached. Preliminary results obtained from two numerical simulations 1) fault growth of a pre-existing weaknesses and 2) fault growth of a spontaneously generated fault system, provide encouraging results with values that are comparable with those observed in nature for the growth of normal fault systems. The application to strike-slip system that characterizes the Bure site is still underway. (authors)

Late Holocene paleoseismicity of the Pahiatua section of the Wellington Fault, New Zealand

International Nuclear Information System (INIS)

Langridge, R.M.; Berryman, K.R.; Van Dissen, R.J.

2007-01-01

considered together, they suggest that: (1) the last four large earthquakes along the Pahiatua section have involved rupture of the entire section; (2) these events broadly correlate with other dated paleoearthquake events along the Wellington-Hutt Valley segment and Tararua section of the fault, and the southern end of the Mohaka Fault; (3) the most recent faulting event along the Pahiatua section is somewhat younger than for the Wellington-Hutt Valley segment or Tararua section; and (4) either single or dual segment/section rupture scenarios existed along these four fault sections. (author). 26 refs., 14 figs., 4 tabs

Multiple-step fault estimation for interval type-II T-S fuzzy system of hypersonic vehicle with time-varying elevator faults

Directory of Open Access Journals (Sweden)

Jin Wang

2017-03-01

Full Text Available This article proposes a multiple-step fault estimation algorithm for hypersonic flight vehicles that uses an interval type-II Takagi–Sugeno fuzzy model. An interval type-II Takagi–Sugeno fuzzy model is developed to approximate the nonlinear dynamic system and handle the parameter uncertainties of hypersonic firstly. Then, a multiple-step time-varying additive fault estimation algorithm is designed to estimate time-varying additive elevator fault of hypersonic flight vehicles. Finally, the simulation is conducted in both aspects of modeling and fault estimation; the validity and availability of such method are verified by a series of the comparison of numerical simulation results.

Geophysical Characterization of the Hilton Creek Fault System

Science.gov (United States)

Lacy, A. K.; Macy, K. P.; De Cristofaro, J. L.; Polet, J.

2016-12-01

The Long Valley Caldera straddles the eastern edge of the Sierra Nevada Batholith and the western edge of the Basin and Range Province, and represents one of the largest caldera complexes on Earth. The caldera is intersected by numerous fault systems, including the Hartley Springs Fault System, the Round Valley Fault System, the Long Valley Ring Fault System, and the Hilton Creek Fault System, which is our main region of interest. The Hilton Creek Fault System appears as a single NW-striking fault, dipping to the NE, from Davis Lake in the south to the southern rim of the Long Valley Caldera. Inside the caldera, it splays into numerous parallel faults that extend toward the resurgent dome. Seismicity in the area increased significantly in May 1980, following a series of large earthquakes in the vicinity of the caldera and a subsequent large earthquake swarm which has been suggested to be the result of magma migration. A large portion of the earthquake swarms in the Long Valley Caldera occurs on or around the Hilton Creek Fault splays. We are conducting an interdisciplinary geophysical study of the Hilton Creek Fault System from just south of the onset of splay faulting, to its extension into the dome of the caldera. Our investigation includes ground-based magnetic field measurements, high-resolution total station elevation profiles, Structure-From-Motion derived topography and an analysis of earthquake focal mechanisms and statistics. Preliminary analysis of topographic profiles, of approximately 1 km in length, reveals the presence of at least three distinct fault splays within the caldera with vertical offsets of 0.5 to 1.0 meters. More detailed topographic mapping is expected to highlight smaller structures. We are also generating maps of the variation in b-value along different portions of the Hilton Creek system to determine whether we can detect any transition to more swarm-like behavior towards the North. We will show maps of magnetic anomalies, topography

HOT Faults", Fault Organization, and the Occurrence of the Largest Earthquakes

Science.gov (United States)

Carlson, J. M.; Hillers, G.; Archuleta, R. J.

2006-12-01

We apply the concept of "Highly Optimized Tolerance" (HOT) for the investigation of spatio-temporal seismicity evolution, in particular mechanisms associated with largest earthquakes. HOT provides a framework for investigating both qualitative and quantitative features of complex feedback systems that are far from equilibrium and punctuated by rare, catastrophic events. In HOT, robustness trade-offs lead to complexity and power laws in systems that are coupled to evolving environments. HOT was originally inspired by biology and engineering, where systems are internally very highly structured, through biological evolution or deliberate design, and perform in an optimum manner despite fluctuations in their surroundings. Though faults and fault systems are not designed in ways comparable to biological and engineered structures, feedback processes are responsible in a conceptually comparable way for the development, evolution and maintenance of younger fault structures and primary slip surfaces of mature faults, respectively. Hence, in geophysical applications the "optimization" approach is perhaps more aptly replaced by "organization", reflecting the distinction between HOT and random, disorganized configurations, and highlighting the importance of structured interdependencies that evolve via feedback among and between different spatial and temporal scales. Expressed in the terminology of the HOT concept, mature faults represent a configuration optimally organized for the release of strain energy; whereas immature, more heterogeneous fault networks represent intermittent, suboptimal systems that are regularized towards structural simplicity and the ability to generate large earthquakes more easily. We discuss fault structure and associated seismic response pattern within the HOT concept, and outline fundamental differences between this novel interpretation to more orthodox viewpoints like the criticality concept. The discussion is flanked by numerical simulations of a

Oblique transfer of extensional strain between basins of the middle Rio Grande rift, New Mexico: Fault kinematic and paleostress constraints

Science.gov (United States)

Minor, Scott A.; Hudson, Mark R.; Caine, Jonathan S.; Thompson, Ren A.

2013-01-01

The structural geometry of transfer and accommodation zones that relay strain between extensional domains in rifted crust has been addressed in many studies over the past 30 years. However, details of the kinematics of deformation and related stress changes within these zones have received relatively little attention. In this study we conduct the first-ever systematic, multi-basin fault-slip measurement campaign within the late Cenozoic Rio Grande rift of northern New Mexico to address the mechanisms and causes of extensional strain transfer associated with a broad accommodation zone. Numerous (562) kinematic measurements were collected at fault exposures within and adjacent to the NE-trending Santo Domingo Basin accommodation zone, or relay, which structurally links the N-trending, right-stepping en echelon Albuquerque and Española rift basins. The following observations are made based on these fault measurements and paleostresses computed from them. (1) Compared to the typical northerly striking normal to normal-oblique faults in the rift basins to the north and south, normal-oblique faults are broadly distributed within two merging, NE-trending zones on the northwest and southeast sides of the Santo Domingo Basin. (2) Faults in these zones have greater dispersion of rake values and fault strikes, greater dextral strike-slip components over a wide northerly strike range, and small to moderate clockwise deflections of their tips. (3) Relative-age relations among fault surfaces and slickenlines used to compute reduced stress tensors suggest that far-field, ~E-W–trending σ3 stress trajectories were perturbed 45° to 90° clockwise into NW to N trends within the Santo Domingo zones. (4) Fault-stratigraphic age relations constrain the stress perturbations to the later stages of rifting, possibly as late as 2.7–1.1 Ma. Our fault observations and previous paleomagnetic evidence of post–2.7 Ma counterclockwise vertical-axis rotations are consistent with increased

The relationship of near-surface active faulting to megathrust splay fault geometry in Prince William Sound, Alaska

Science.gov (United States)

Finn, S.; Liberty, L. M.; Haeussler, P. J.; Northrup, C.; Pratt, T. L.

2010-12-01

We interpret regionally extensive, active faults beneath Prince William Sound (PWS), Alaska, to be structurally linked to deeper megathrust splay faults, such as the one that ruptured in the 1964 M9.2 earthquake. Western PWS in particular is unique; the locations of active faulting offer insights into the transition at the southern terminus of the previously subducted Yakutat slab to Pacific plate subduction. Newly acquired high-resolution, marine seismic data show three seismic facies related to Holocene and older Quaternary to Tertiary strata. These sediments are cut by numerous high angle normal faults in the hanging wall of megathrust splay. Crustal-scale seismic reflection profiles show splay faults emerging from 20 km depth between the Yakutat block and North American crust and surfacing as the Hanning Bay and Patton Bay faults. A distinct boundary coinciding beneath the Hinchinbrook Entrance causes a systematic fault trend change from N30E in southwestern PWS to N70E in northeastern PWS. The fault trend change underneath Hinchinbrook Entrance may occur gradually or abruptly and there is evidence for similar deformation near the Montague Strait Entrance. Landward of surface expressions of the splay fault, we observe subsidence, faulting, and landslides that record deformation associated with the 1964 and older megathrust earthquakes. Surface exposures of Tertiary rocks throughout PWS along with new apatite-helium dates suggest long-term and regional uplift with localized, fault-controlled subsidence.

Blind Source Separation and Dynamic Fuzzy Neural Network for Fault Diagnosis in Machines

International Nuclear Information System (INIS)

Huang, Haifeng; Ouyang, Huajiang; Gao, Hongli

2015-01-01

Many assessment and detection methods are used to diagnose faults in machines. High accuracy in fault detection and diagnosis can be achieved by using numerical methods with noise-resistant properties. However, to some extent, noise always exists in measured data on real machines, which affects the identification results, especially in the diagnosis of early- stage faults. In view of this situation, a damage assessment method based on blind source separation and dynamic fuzzy neural network (DFNN) is presented to diagnose the early-stage machinery faults in this paper. In the processing of measurement signals, blind source separation is adopted to reduce noise. Then sensitive features of these faults are obtained by extracting low dimensional manifold characteristics from the signals. The model for fault diagnosis is established based on DFNN. Furthermore, on-line computation is accelerated by means of compressed sensing. Numerical vibration signals of ball screw fault modes are processed on the model for mechanical fault diagnosis and the results are in good agreement with the actual condition even at the early stage of fault development. This detection method is very useful in practice and feasible for early-stage fault diagnosis. (paper)

Slip-accumulation patterns and earthquake recurrences along the Talas-Fergana Fault - Contributions of high-resolution geomorphic offsets.

Science.gov (United States)

Rizza, M.; Dubois, C.; Fleury, J.; Abdrakhmatov, K.; Pousse, L.; Baikulov, S.; Vezinet, A.

2017-12-01

In the western Tien-Shan Range, the largest intracontinental strike-slip fault is the Karatau-Talas Fergana Fault system. This dextral fault system is subdivided into two main segments: the Karatau fault to the north and the Talas-Fergana fault (TFF) to the south. Kinematics and rates of deformation for the TFF during the Quaternary period are still debated and are poorly constrained. Only a few paleoseismological investigations are availabe along the TFF (Burtman et al., 1996; Korjenkov et al., 2010) and no systematic quantifications of the dextral displacements along the TFF has been undertaken. As such, the appraisal of the TFF behavior demands new tectonic information. In this study, we present the first detailed analysis of the morphology and the segmentation of the TFF and an offset inventory of morphological markers along the TFF. To discuss temporal and spatial recurrence patterns of slip accumulated over multiple seismic events, our study focused on a 60 km-long section of the TFF (Chatkal segment). Using tri-stereo Pleiades satellite images, high-resolution DEMs (1*1 m pixel size) have been generated in order to (i) analyze the fine-scale fault geometry and (ii) thoroughly measure geomorphic offsets. Photogrammetry data obtained from our drone survey on high interest sites, provide higher-resolution DEMs of 0.5 * 0.5 m pixel size.Our remote sensing mapping allows an unprecedented subdivision - into five distinct segments - of the study area. About 215 geomorphic markers have been measured and offsets range from 4.5m to 180 m. More than 80% of these offsets are smaller than 60 m, suggesting landscape reset during glacial maximum. Calculations of Cumulative Offset Probability Density (COPD) for the whole 60 km-long section as well as for each segments support distinct behavior from a segment to another and thus variability in slip-accumulation patterns. Our data argue for uniform slip model behavior along this section of the TFF. Moreover, we excavated a

Fault zone structure and kinematics from lidar, radar, and imagery: revealing new details along the creeping San Andreas Fault

Science.gov (United States)

DeLong, S.; Donnellan, A.; Pickering, A.

2017-12-01

Aseismic fault creep, coseismic fault displacement, distributed deformation, and the relative contribution of each have important bearing on infrastructure resilience, risk reduction, and the study of earthquake physics. Furthermore, the impact of interseismic fault creep in rupture propagation scenarios, and its impact and consequently on fault segmentation and maximum earthquake magnitudes, is poorly resolved in current rupture forecast models. The creeping section of the San Andreas Fault (SAF) in Central California is an outstanding area for establishing methodology for future scientific response to damaging earthquakes and for characterizing the fine details of crustal deformation. Here, we describe how data from airborne and terrestrial laser scanning, airborne interferometric radar (UAVSAR), and optical data from satellites and UAVs can be used to characterize rates and map patterns of deformation within fault zones of varying complexity and geomorphic expression. We are evaluating laser point cloud processing, photogrammetric structure from motion, radar interferometry, sub-pixel correlation, and other techniques to characterize the relative ability of each to measure crustal deformation in two and three dimensions through time. We are collecting new and synthesizing existing data from the zone of highest interseismic creep rates along the SAF where a transition from a single main fault trace to a 1-km wide extensional stepover occurs. In the stepover region, creep measurements from alignment arrays 100 meters long across the main fault trace reveal lower rates than those in adjacent, geomorphically simpler parts of the fault. This indicates that deformation is distributed across the en echelon subsidiary faults, by creep and/or stick-slip behavior. Our objectives are to better understand how deformation is partitioned across a fault damage zone, how it is accommodated in the shallow subsurface, and to better characterize the relative amounts of fault creep

Inelastic deformations of fault and shear zones in granitic rock

International Nuclear Information System (INIS)

Wilder, D.G.

1986-02-01

Deformations during heating and cooling of three drifts in granitic rock were influenced by the presence of faults and shear zones. Thermal deformations were significantly larger in sheared and faulted zones than where the rock was jointed, but neither sheared nor faulted. Furthermore, thermal deformations in faulted or sheared rock were not significantly recovered during subsequent cooling, thus a permanent deformation remained. This inelastic response is in contrast with elastic behavior identified in unfaulted and unsheared rock segments. A companion paper indicates that deformations in unsheared or unfaulted rock were effectively modeled as an elastic response. We conclude that permanent deformations occurred in fractures with crushed minerals and fracture filling or gouge materials. Potential mechanisms for this permanent deformation are asperity readjustments during thermal deformations, micro-shearing, asperity crushing and crushing of the secondary fracture filling minerals. Additionally, modulus differences in sheared or faulted rock as compared to more intact rock would result in greater deformations in response to the same thermal loads

3D numerical simulations of multiphase continental rifting

Science.gov (United States)

Naliboff, J.; Glerum, A.; Brune, S.

2017-12-01

Observations of rifted margin architecture suggest continental breakup occurs through multiple phases of extension with distinct styles of deformation. The initial rifting stages are often characterized by slow extension rates and distributed normal faulting in the upper crust decoupled from deformation in the lower crust and mantle lithosphere. Further rifting marks a transition to higher extension rates and coupling between the crust and mantle lithosphere, with deformation typically focused along large-scale detachment faults. Significantly, recent detailed reconstructions and high-resolution 2D numerical simulations suggest that rather than remaining focused on a single long-lived detachment fault, deformation in this phase may progress toward lithospheric breakup through a complex process of fault interaction and development. The numerical simulations also suggest that an initial phase of distributed normal faulting can play a key role in the development of these complex fault networks and the resulting finite deformation patterns. Motivated by these findings, we will present 3D numerical simulations of continental rifting that examine the role of temporal increases in extension velocity on rifted margin structure. The numerical simulations are developed with the massively parallel finite-element code ASPECT. While originally designed to model mantle convection using advanced solvers and adaptive mesh refinement techniques, ASPECT has been extended to model visco-plastic deformation that combines a Drucker Prager yield criterion with non-linear dislocation and diffusion creep. To promote deformation localization, the internal friction angle and cohesion weaken as a function of accumulated plastic strain. Rather than prescribing a single zone of weakness to initiate deformation, an initial random perturbation of the plastic strain field combined with rapid strain weakening produces distributed normal faulting at relatively slow rates of extension in both 2D and

Evidence of Quaternary and recent activity along the Kyaukkyan Fault, Myanmar

Science.gov (United States)

Crosetto, Silvia; Watkinson, Ian M.; Soe Min; Gori, Stefano; Falcucci, Emanuela; Nwai Le Ngal

2018-05-01

Cenozoic right-lateral shear between the eastern Indian margin and Eurasia is expressed by numerous N-S trending fault systems inboard of the Sunda trench, including the Sagaing Fault. The most easterly of these fault systems is the prominent ∼500 km long Kyaukkyan Fault, on the Shan Plateau. Myanmar's largest recorded earthquake, Mw 7.7 on 23rd May 1912, focused near Maymyo, has been attributed to the Kyaukkyan Fault, but the area has experienced little significant seismicity since then. Despite its demonstrated seismic potential and remarkable topographic expression, questions remain about the Kyaukkyan Fault's neotectonic history.

Aeromagnetic anomalies over faulted strata

Science.gov (United States)

Grauch, V.J.S.; Hudson, Mark R.

2011-01-01

High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift in New Mexico and Colorado. High-resolution aeromagnetic data from these areas reveal numerous, curvilinear, low-amplitude (2–15 nT at 100-m terrain clearance) anomalies that consistently correspond to intrasedimentary normal faults (Figure 1). Detailed geophysical and rock-property studies provide evidence for the magnetic sources at several exposures of these faults in the central Rio Grande rift (summarized in Grauch and Hudson, 2007, and Hudson et al., 2008). A key result is that the aeromagnetic anomalies arise from the juxtaposition of magnetically differing strata at the faults as opposed to chemical processes acting at the fault zone. The studies also provide (1) guidelines for understanding and estimating the geophysical parameters controlling aeromagnetic anomalies at faulted strata (Grauch and Hudson), and (2) observations on key geologic factors that are favorable for developing similar sedimentary sources of aeromagnetic anomalies elsewhere (Hudson et al.).

Mechanical evolution of transpression zones affected by fault interactions: Insights from 3D elasto-plastic finite element models

Science.gov (United States)

Nabavi, Seyed Tohid; Alavi, Seyed Ahmad; Mohammadi, Soheil; Ghassemi, Mohammad Reza

2018-01-01

The mechanical evolution of transpression zones affected by fault interactions is investigated by a 3D elasto-plastic mechanical model solved with the finite-element method. Ductile transpression between non-rigid walls implies an upward and lateral extrusion. The model results demonstrate that a, transpression zone evolves in a 3D strain field along non-coaxial strain paths. Distributed plastic strain, slip transfer, and maximum plastic strain occur within the transpression zone. Outside the transpression zone, fault slip is reduced because deformation is accommodated by distributed plastic shear. With progressive deformation, the σ3 axis (the minimum compressive stress) rotates within the transpression zone to form an oblique angle to the regional transport direction (∼9°-10°). The magnitude of displacement increases faster within the transpression zone than outside it. Rotation of the displacement vectors of oblique convergence with time suggests that transpression zone evolves toward an overall non-plane strain deformation. The slip decreases along fault segments and with increasing depth. This can be attributed to the accommodation of bulk shortening over adjacent fault segments. The model result shows an almost symmetrical domal uplift due to off-fault deformation, generating a doubly plunging fold and a 'positive flower' structure. Outside the overlap zone, expanding asymmetric basins subside to 'negative flower' structures on both sides of the transpression zone and are called 'transpressional basins'. Deflection at fault segments causes the fault dip fall to less than 90° (∼86-89°) near the surface (∼1.5 km). This results in a pure-shear-dominated, triclinic, and discontinuous heterogeneous flow of the transpression zone.

Fault-patch stress-transfer efficiency in presence of sub-patch geometric complexity

KAUST Repository

Zielke, Olaf

2015-04-01

It is well known that faults are not planar surfaces. Instead they exhibit self-similar or self-affine properties that span a wide range of spatial (sub-micrometer to tens-of-kilometer). This geometric fault roughness has a distinct impact on amount and distribution of stresses/strains induced in the medium and on other portions of the fault. However, when numerically simulated (for example in multi-cycle EQ rupture simulations or Coulomb failure stress calculations) this roughness is largely ignored: individual fault patches --the incremental elements that build the fault surface in the respective computer models-- are planar and fault roughness at this and lower spatial scales is not considered. As a result, the fault-patch stress-transfer efficiency may be systematically too large in those numerical simulations with respect to the "actual" efficiency level. Here, we investigate the effect of sub-patch geometric complexity on fault-patch stress-transfer efficiency. For that, we sub-divide a fault patch (e.g., 1x1km) into a large number of sub-patches (e.g., 20x20m) and determine amount of induced stresses at selected positions around that patch for different levels and realizations of fault roughness. For each fault roughness level, we compute mean and standard deviation of the induced stresses, enabling us to compute the coefficient of variation. We normalize those values with stresses from the corresponding single (planar) fault patch, providing scaling factors and their variability for stress transfer efficiency. Given a certain fault roughness that is assumed for a fault, this work provides the means to implement the sub-patch fault roughness into investigations based on fault-patch interaction schemes.

Microseismicity at the North Anatolian Fault in the Sea of Marmara offshore Istanbul, NW Turkey

Science.gov (United States)

Bulut, Fatih; Bohnhoff, Marco; Ellsworth, William L.; Aktar, Mustafa; Dresen, Georg

2009-01-01

The North Anatolian Fault Zone (NAFZ) below the Sea of Marmara forms a “seismic gap” where a major earthquake is expected to occur in the near future. This segment of the fault lies between the 1912 Ganos and 1999 İzmit ruptures and is the only NAFZ segment that has not ruptured since 1766. To monitor the microseismic activity at the main fault branch offshore of Istanbul below the Çınarcık Basin, a permanent seismic array (PIRES) was installed on the two outermost Prince Islands, Yassiada and Sivriada, at a few kilometers distance to the fault. In addition, a temporary network of ocean bottom seismometers was deployed throughout the Çınarcık Basin. Slowness vectors are determined combining waveform cross correlation and P wave polarization. We jointly invert azimuth and traveltime observations for hypocenter determination and apply a bootstrap resampling technique to quantify the location precision. We observe seismicity rates of 20 events per month for M etermine composite focal mechanisms implementing recordings of surrounding permanent land stations. Fault plane solutions have a predominant right-lateral strike-slip mechanism, indicating that normal faulting along this part of the NAFZ plays a minor role. Toward the west we observe increasing components of thrust faulting. This supports the model of NW trending, dextral strike-slip motion along the northern and main branch of the NAFZ below the eastern Sea of Marmara.

A multiple kernel classification approach based on a Quadratic Successive Geometric Segmentation methodology with a fault diagnosis case.

Science.gov (United States)

Honório, Leonardo M; Barbosa, Daniele A; Oliveira, Edimar J; Garcia, Paulo A Nepomuceno; Santos, Murillo F

2018-03-01

This work presents a new approach for solving classification and learning problems. The Successive Geometric Segmentation technique is applied to encapsulate large datasets by using a series of Oriented Bounding Hyper Box (OBHBs). Each OBHB is obtained through linear separation analysis and each one represents a specific region in a pattern's solution space. Also, each OBHB can be seen as a data abstraction layer and be considered as an individual Kernel. Thus, it is possible by applying a quadratic discriminant function, to assemble a set of nonlinear surfaces separating each desirable pattern. This approach allows working with large datasets using high speed linear analysis tools and yet providing a very accurate non-linear classifier as final result. The methodology was tested using the UCI Machine Learning repository and a Power Transformer Fault Diagnosis real scenario problem. The results were compared with different approaches provided by literature and, finally, the potential and further applications of the methodology were also discussed. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Structural features of the San Andreas fault at Tejon Pass, California

Science.gov (United States)

Dewers, T. A.; Reches, Z.; Brune, J. N.

2002-12-01

We mapped a 2 km belt along the San Andreas fault (SAF) in the Tejon Pass area where road cuts provide fresh exposures of the fault zone and surrounding rocks. Our 1:2,000 structural mapping is focused on analysis of faulting processes and is complementary to regional mapping at 1:12,000 scale by Ramirez (M.Sc., UC Santa Barbara, 1984). The dominant rock units are the Hungry Valley Formation of Pliocene age (clastic sediments) exposed south of the SAF, and the Tejon Lookout granite (Cretaceous) and Neenach Volcanic Formation exposed north of it. Ramirez (1983) deduced ~220 km of post-Miocene lateral slip. The local trend of the SAF is about N60W and it includes at least three main, subparallel segments that form a 200 m wide zone. The traces of the segments are quasi-linear, discontinuous, and they are stepped with respect to each other, forming at least five small pull-aparts and sag ponds in the mapping area. The three segments were not active semi-contemporaneously and the southern segment is apparently the oldest. The largest pull-apart, 60-70 m wide, displays young (Quaternary?) silt and shale layers. We found two rock bodies that are suspected as fault-rocks. One is a 1-2 m thick sheet-like body that separates the Tejon Lookout granite from young (Recent?) clastic rocks. In the field, it appears as a gouge zone composed of poorly cemented, dark clay size grains; however, the microstructure of this rock does not reveal clear shear features. The second body is the 80-120 m wide zone of Tejon Lookout granite that extends for less than 1 km along the SAF in the mapped area. It is characterized by three structural features: (1) pulverization into friable, granular material by multitude of grain-crossing fractures; (2) abundance of dip-slip small faults that are gently dipping toward and away from the SAF; and (3) striking lack of evidence for shear parallel to the SAF. The relationships between these features and the large right-lateral shear along the SAF are

Fault on-off versus strain rate and earthquakes energy

Directory of Open Access Journals (Sweden)

C. Doglioni

2015-03-01

Full Text Available We propose that the brittle-ductile transition (BDT controls the seismic cycle. In particular, the movements detected by space geodesy record the steady state deformation in the ductile lower crust, whereas the stick-slip behavior of the brittle upper crust is constrained by its larger friction. GPS data allow analyzing the strain rate along active plate boundaries. In all tectonic settings, we propose that earthquakes primarily occur along active fault segments characterized by relative minima of strain rate, segments which are locked or slowly creeping. We discuss regional examples where large earthquakes happened in areas of relative low strain rate. Regardless the tectonic style, the interseismic stress and strain pattern inverts during the coseismic stage. Where a dilated band formed during the interseismic stage, this will be shortened at the coseismic stage, and vice-versa what was previously shortened, it will be dilated. The interseismic energy accumulation and the coseismic expenditure rather depend on the tectonic setting (extensional, contractional, or strike-slip. The gravitational potential energy dominates along normal faults, whereas the elastic energy prevails for thrust earthquakes and performs work against the gravity force. The energy budget in strike-slip tectonic setting is also primarily due elastic energy. Therefore, precursors may be different as a function of the tectonic setting. In this model, with a given displacement, the magnitude of an earthquake results from the coseismic slip of the deformed volume above the BDT rather than only on the fault length, and it also depends on the fault kinematics.

Joint Inversion of 1-D Magnetotelluric and Surface-Wave Dispersion Data with an Improved Multi-Objective Genetic Algorithm and Application to the Data of the Longmenshan Fault Zone

Science.gov (United States)

Wu, Pingping; Tan, Handong; Peng, Miao; Ma, Huan; Wang, Mao

2018-05-01

Magnetotellurics and seismic surface waves are two prominent geophysical methods for deep underground exploration. Joint inversion of these two datasets can help enhance the accuracy of inversion. In this paper, we describe a method for developing an improved multi-objective genetic algorithm (NSGA-SBX) and applying it to two numerical tests to verify the advantages of the algorithm. Our findings show that joint inversion with the NSGA-SBX method can improve the inversion results by strengthening structural coupling when the discontinuities of the electrical and velocity models are consistent, and in case of inconsistent discontinuities between these models, joint inversion can retain the advantages of individual inversions. By applying the algorithm to four detection points along the Longmenshan fault zone, we observe several features. The Sichuan Basin demonstrates low S-wave velocity and high conductivity in the shallow crust probably due to thick sedimentary layers. The eastern margin of the Tibetan Plateau shows high velocity and high resistivity in the shallow crust, while two low velocity layers and a high conductivity layer are observed in the middle lower crust, probably indicating the mid-crustal channel flow. Along the Longmenshan fault zone, a high conductivity layer from 8 to 20 km is observed beneath the northern segment and decreases with depth beneath the middle segment, which might be caused by the elevated fluid content of the fault zone.

Comparative Laboratory and Numerical Simulations of Shearing Granular Fault Gouge: Micromechanical Processes

Science.gov (United States)

Morgan, J. K.; Marone, C. J.; Guo, Y.; Anthony, J. L.; Knuth, M. W.

2004-12-01

Laboratory studies of granular shear zones have provided significant insight into fault zone processes and the mechanics of earthquakes. The micromechanisms of granular deformation are more difficult to ascertain, but have been hypothesized based on known variations in boundary conditions, particle properties and geometries, and mechanical behavior. Numerical simulations using particle dynamics methods (PDM) can offer unique views into deforming granular shear zones, revealing the precise details of granular microstructures, particle interactions, and packings, which can be correlated with macroscopic mechanical behavior. Here, we describe a collaborative program of comparative laboratory and numerical experiments of granular shear using idealized materials, i.e., glass beads, glass rods or pasta, and angular sand. Both sets of experiments are carried out under similar initial and boundary conditions in a non-fracturing stress regime. Phenomenologically, the results of the two sets of experiments are very similar. Peak friction values vary as a function of particle dimensionality (1-D vs. 2-D vs. 3-D), particle angularity, particle size and size distributions, boundary roughness, and shear zone thickness. Fluctuations in shear strength during an experiment, i.e., stick-slip events, can be correlated with distinct changes in the nature, geometries, and durability of grain bridges that support the shear zone walls. Inclined grain bridges are observed to form, and to support increasing loads, during gradual increases in assemblage strength. Collapse of an individual grain bridge leads to distinct localization of strain, generating a rapidly propagating shear surface that cuts across multiple grain bridges, accounting for the sudden drop in strength. The distribution of particle sizes within an assemblage, along with boundary roughness and its periodicity, influence the rate of formation and dissipation of grain bridges, thereby controlling friction variations during

The Hanford Site's Gable Mountain structure: A comparison of the recurrence of design earthquakes based on fault slip rates and a probabilistic exposure model

International Nuclear Information System (INIS)

Rohay, A.C.

1991-01-01

Gable Mountain is a segment of the Umtanum Ridge-Gable Mountain structural trend, an east-west trending series of anticlines, one of the major geologic structures on the Hanford Site. A probabilistic seismic exposure model indicates that Gable Mountain and two adjacent segments contribute significantly to the seismic hazard at the Hanford Site. Geologic measurements of the uplift of initially horizontal (11-12 Ma) basalt flows indicate that a broad, continuous, primary anticline grew at an average rate of 0.009-0.011 mm/a, and narrow, segmented, secondary anticlines grew at rates of 0.009 mm/a at Gable Butte and 0.018 mm/a at Gable Mountain. The buried Southeast Anticline appears to have a different geometry, consisting of a single, intermediate-width anticline with an estimated growth rate of 0.007 mm/a. The recurrence rate and maximum magnitude of earthquakes for the fault models were used to estimate the fault slip rate for each of the fault models and to determine the implied structural growth rate of the segments. The current model for Gable Mountain-Gable Butte predicts 0.004 mm/a of vertical uplift due to primary faulting and 0.008 mm/a due to secondary faulting. These rates are roughly half the structurally estimated rates for Gable Mountain, but the model does not account for the smaller secondary fold at Gable Butte. The model predicted an uplift rate for the Southeast Anticline of 0.006 mm/a, caused by the low open-quotes fault capabilityclose quotes weighting rather than a different fault geometry. The effects of previous modifications to the fault models are examined and potential future modifications are suggested. For example, the earthquake recurrence relationship used in the current exposure model has a b-value of 1.15, compared to a previous value of 0.85. This increases the implied deformation rates due to secondary fault models, and therefore supports the use of this regionally determined b-value to this fault/fold system

Static stress transfer during the 2002 Nenana Mountain-Denali Fault, Alaska, earthquake sequence

Science.gov (United States)

Anderson, G.; Ji, C.

2003-01-01

On 23 October 2002, the Mw 6.7 Nenana Mountain earthquake occurred in central Alaska. It was followed on 3 November 2002 by the Mw 7.9 Denali Fault mainshock, the largest strike-slip earthquake to occur in North America during the past 150 years. We have modeled static Coulomb stress transfer effects during this sequence. We find that the Nenana Mountain foreshock transferred 30-50 kPa of Coulomb stress to the hypocentral region of the Denali Fault mainshock, encouraging its occurrence. We also find that the two main earthquakes together transferred more than 400 kPa of Coulomb stress to the Cross Creek segment of the Totschunda fault system and to the Denali fault southeast of the mainshock rupture, and up to 80 kPa to the Denali fault west of the Nenana Mountain rupture. Other major faults in the region experienced much smaller static Coulomb stress changes.

Crustal Density Variation Along the San Andreas Fault Controls Its Secondary Faults Distribution and Dip Direction

Science.gov (United States)

Yang, H.; Moresi, L. N.

2017-12-01

The San Andreas fault forms a dominant component of the transform boundary between the Pacific and the North American plate. The density and strength of the complex accretionary margin is very heterogeneous. Based on the density structure of the lithosphere in the SW United States, we utilize the 3D finite element thermomechanical, viscoplastic model (Underworld2) to simulate deformation in the San Andreas Fault system. The purpose of the model is to examine the role of a big bend in the existing geometry. In particular, the big bend of the fault is an initial condition of in our model. We first test the strength of the fault by comparing the surface principle stresses from our numerical model with the in situ tectonic stress. The best fit model indicates the model with extremely weak fault (friction coefficient 200 kg/m3) than surrounding blocks. In contrast, the Mojave block is detected to find that it has lost its mafic lower crust by other geophysical surveys. Our model indicates strong strain localization at the jointer boundary between two blocks, which is an analogue for the Garlock fault. High density lower crust material of the Great Valley tends to under-thrust beneath the Transverse Range near the big bend. This motion is likely to rotate the fault plane from the initial vertical direction to dip to the southwest. For the straight section, north to the big bend, the fault is nearly vertical. The geometry of the fault plane is consistent with field observations.

The significance of strike-slip faulting in the basement of the Zagros fold and thrust belt

Energy Technology Data Exchange (ETDEWEB)

Hessami, K.; Koyi, H.A.; Talbot, C.J. [Uppsala University (Sweden). Institute of Earth Sciences

2000-01-01

Lateral offsets in the pattern of seismicity along the Zagros fold and thrust belt indicate that transverse faults segmenting the Arabian basement are active deep-seated strike-slip faults. The dominant NW-SE trending features of the belt have undergone repeated horizontal displacements along these transverse faults. These reactivated basement faults, which are inherited from the Pan-African construction phase, controlled both deposition of the Phanerozoic cover before Tertiary-Recent deformation of the Zagros and probably the entrapment of hydrocarbons on the NE margin of Arabia and in the Zagros area. We have used observations of faulting recognized on Landsat satellite images, in conjunction with the spatial distribution of earthquakes and their focal mechanism solutions, to infer a tectonic model for the Zagros basement. Deformation in the NW Zagros appears to be concentrated on basement thrusts and a few widely-spaced north-south trending strike-slip faults which separate major structural segments. In the SE Zagros, two main structural domains can be distinguished. A domain of NNW-trending right-lateral faults in the northern part of the SE Zagros implies that fault-bounded blocks are likely to have rotated anticlockwise about vertical axes relative to both Arabia and Central Iran. In contrast, the predominance of NNE-trending left-lateral faults in the southern part of the SE Zagros implies that fault-bounded blocks may have rotated clockwise about vertical axes. We propose a tectonic model in which crustal blocks bounded by strike-slip faults in a zone of simple shear rotate about vertical axes relative to both Arabia and Central Iran. The presence of domains of strike-slip and thrust faulting in the Zagros basement suggest that some of the convergence between Arabia and Central Iran is accommodated by rotation and possible lateral movement of crust along the belt by strike-slip faults, as well as by obvious crustal shortening and thickening along thrust

Inelastic response evaluation of steel frame structure subjected to near-fault ground motions

Energy Technology Data Exchange (ETDEWEB)

Choi, In Kil; Kim, Hyung Kyu; Choun, Young Sun; Seo, Jeong Moon

2004-04-01

A survey on some of the Quaternary fault segments near the Korean nuclear power plants is ongoing. It is likely that these faults would be identified as active ones. If the faults are confirmed as active ones, it will be necessary to reevaluate the seismic safety of nuclear power plants located near the fault. This study was performed to acquire overall knowledge of near-fault ground motions and evaluate inealstic response characteristics of near-fault ground motions. Although Korean peninsular is not located in the strong earthquake region, it is necessary to evaluate seismic safety of NPP for the earthquakes occurred in near-fault area with characteristics different from that of general far-fault earthquakes in order to improve seismic safety of existing NPP structures and equipment. As a result, for the seismic safety evaluation of NPP structures and equipment considering near-fault effects, this report will give many valuable information. In order to improve seismic safety of NPP structures and equipment against near-fault ground motions, it is necessary to consider inelastic response characteristics of near-fault ground motions in current design code. Also in Korea where these studies are immature yet, in the future more works of near-fault earthquakes must be accomplished.

The pulsed migration of hydrocarbons across inactive faults

Directory of Open Access Journals (Sweden)

S. D. Harris

1999-01-01

Full Text Available Geological fault zones are usually assumed to influence hydrocarbon migration either as high permeability zones which allow enhanced along- or across-fault flow or as barriers to the flow. An additional important migration process inducing along- or across-fault migration can be associated with dynamic pressure gradients. Such pressure gradients can be created by earthquake activity and are suggested here to allow migration along or across inactive faults which 'feel' the quake-related pressure changes; i.e. the migration barriers can be removed on inactive faults when activity takes place on an adjacent fault. In other words, a seal is viewed as a temporary retardation barrier which leaks when a fault related fluid pressure event enhances the buoyancy force and allows the entry pressure to be exceeded. This is in contrast to the usual model where a seal leaks because an increase in hydrocarbon column height raises the buoyancy force above the entry pressure of the fault rock. Under the new model hydrocarbons may migrate across the inactive fault zone for some time period during the earthquake cycle. Numerical models of this process are presented to demonstrate the impact of this mechanism and its role in filling traps bounded by sealed faults.

Structural Design of Systems with Safe Behavior under Single and Multiple Faults

DEFF Research Database (Denmark)

Blanke, Mogens; Staroswiecki, Marcel

2006-01-01

Handling of multiple simultaneous faults is a complex issue in fault-tolerant control. The design task is particularly made difficult by to the numerous different cases that need be analyzed. Aiming at safe fault-handling, this paper shows how structural analysis can be applied to find...... to structural analysis to disclose which faults could be isolated from a structural point of view using active fault isolation. Results from application on a marine control system illustrate the concepts....... the analytical redundancy relations for all relevant combinations of faults, and can cope with the complexity and size of a real system. Being essential for fault-tolerant control schemes that shall handle particular cases of faults/failures, fault isolation is addressed. The paper introduces an extension...

A New Perspective on Fault Geometry and Slip Distribution of the 2009 Dachaidan Mw 6.3 Earthquake from InSAR Observations.

Science.gov (United States)

Liu, Yang; Xu, Caijun; Wen, Yangmao; Fok, Hok Sum

2015-07-10

On 28 August 2009, the northern margin of the Qaidam basin in the Tibet Plateau was ruptured by an Mw 6.3 earthquake. This study utilizes the Envisat ASAR images from descending Track 319 and ascending Track 455 for capturing the coseismic deformation resulting from this event, indicating that the earthquake fault rupture does not reach to the earth's surface. We then propose a four-segmented fault model to investigate the coseismic deformation by determining the fault parameters, followed by inverting slip distribution. The preferred fault model shows that the rupture depths for all four fault planes mainly range from 2.0 km to 7.5 km, comparatively shallower than previous results up to ~13 km, and that the slip distribution on the fault plane is complex, exhibiting three slip peaks with a maximum of 2.44 m at a depth between 4.1 km and 4.9 km. The inverted geodetic moment is 3.85 × 10(18) Nm (Mw 6.36). The 2009 event may rupture from the northwest to the southeast unilaterally, reaching the maximum at the central segment.

Geological interpretation of volcanism and segmentation of the Mariana back-arc spreading center between 12.7°N and 18.3°N

Science.gov (United States)

Anderson, Melissa O.; Chadwick, William W.; Hannington, Mark D.; Merle, Susan G.; Resing, Joseph A.; Baker, Edward T.; Butterfield, David A.; Walker, Sharon L.; Augustin, Nico

2017-06-01

The relationships between tectonic processes, magmatism, and hydrothermal venting along ˜600 km of the slow-spreading Mariana back-arc between 12.7°N and 18.3°N reveal a number of similarities and differences compared to slow-spreading mid-ocean ridges. Analysis of the volcanic geomorphology and structure highlights the complexity of the back-arc spreading center. Here, ridge segmentation is controlled by large-scale basement structures that appear to predate back-arc rifting. These structures also control the orientation of the chains of cross-arc volcanoes that characterize this region. Segment-scale faulting is oriented perpendicular to the spreading direction, allowing precise spreading directions to be determined. Four morphologically distinct segment types are identified: dominantly magmatic segments (Type I); magmatic segments currently undergoing tectonic extension (Type II); dominantly tectonic segments (Type III); and tectonic segments currently undergoing magmatic extension (Type IV). Variations in axial morphology (including eruption styles, neovolcanic eruption volumes, and faulting) reflect magma supply, which is locally enhanced by cross-arc volcanism associated with N-S compression along the 16.5°N and 17.0°N segments. In contrast, cross-arc seismicity is associated with N-S extension and increased faulting along the 14.5°N segment, with structures that are interpreted to be oceanic core complexes—the first with high-resolution bathymetry described in an active back-arc basin. Hydrothermal venting associated with recent magmatism has been discovered along all segment types.

Transient behavior of high-interaction MHD generator following external loading faults

International Nuclear Information System (INIS)

Ishikawa, Motoo

1983-01-01

Transient behavior consequent to external loading faults is studied numerically on four configurations of high-interaction MHD generators-subsonic Faraday, supersonic Faraday, subsonic diagonal and supersonic diagonal, to provide a variable data base to serve in selecting the type of large-scale MHD generator. Time-dependent one-dimensional Navier-Stokes equations are solved with the 1969 MacCormack method, in combination with the Maxwell equations and the generalized Ohm's law. An artificial viscosity term is added to the Navier-Stokes equations to maintain numerical stability. It is shown that, with both supersonic and subsonic flows, the Faraday generator is liable to sustain more harmful effect from short than from open faults of the external loading circuit. For large-scale diagonal types, on the other hand, open faults are more dangerous. With subsonic flow, a shock wave propagating upstream is induced by short fault in the Faraday, and by open fault in the diagonal-type generator. In the case of supersonic flow, propagation upstream of the disturbance is completely obstructed. Larger electrical stress is foreseen for Faraday than for diagonal configuration. (author)

Earthquake rupture process recreated from a natural fault surface

Science.gov (United States)

Parsons, Thomas E.; Minasian, Diane L.

2015-01-01

What exactly happens on the rupture surface as an earthquake nucleates, spreads, and stops? We cannot observe this directly, and models depend on assumptions about physical conditions and geometry at depth. We thus measure a natural fault surface and use its 3D coordinates to construct a replica at 0.1 m resolution to obviate geometry uncertainty. We can recreate stick-slip behavior on the resulting finite element model that depends solely on observed fault geometry. We clamp the fault together and apply steady state tectonic stress until seismic slip initiates and terminates. Our recreated M~1 earthquake initiates at contact points where there are steep surface gradients because infinitesimal lateral displacements reduce clamping stress most efficiently there. Unclamping enables accelerating slip to spread across the surface, but the fault soon jams up because its uneven, anisotropic shape begins to juxtapose new high-relief sticking points. These contacts would ultimately need to be sheared off or strongly deformed before another similar earthquake could occur. Our model shows that an important role is played by fault-wall geometry, though we do not include effects of varying fluid pressure or exotic rheologies on the fault surfaces. We extrapolate our results to large fault systems using observed self-similarity properties, and suggest that larger ruptures might begin and end in a similar way, though the scale of geometrical variation in fault shape that can arrest a rupture necessarily scales with magnitude. In other words, fault segmentation may be a magnitude dependent phenomenon and could vary with each subsequent rupture.

An Efficient Algorithm for Server Thermal Fault Diagnosis Based on Infrared Image

Science.gov (United States)

Liu, Hang; Xie, Ting; Ran, Jian; Gao, Shan

2017-10-01

It is essential for a data center to maintain server security and stability. Long-time overload operation or high room temperature may cause service disruption even a server crash, which would result in great economic loss for business. Currently, the methods to avoid server outages are monitoring and forecasting. Thermal camera can provide fine texture information for monitoring and intelligent thermal management in large data center. This paper presents an efficient method for server thermal fault monitoring and diagnosis based on infrared image. Initially thermal distribution of server is standardized and the interest regions of the image are segmented manually. Then the texture feature, Hu moments feature as well as modified entropy feature are extracted from the segmented regions. These characteristics are applied to analyze and classify thermal faults, and then make efficient energy-saving thermal management decisions such as job migration. For the larger feature space, the principal component analysis is employed to reduce the feature dimensions, and guarantee high processing speed without losing the fault feature information. Finally, different feature vectors are taken as input for SVM training, and do the thermal fault diagnosis after getting the optimized SVM classifier. This method supports suggestions for optimizing data center management, it can improve air conditioning efficiency and reduce the energy consumption of the data center. The experimental results show that the maximum detection accuracy is 81.5%.

Methodology for Designing Fault-Protection Software

Science.gov (United States)

Barltrop, Kevin; Levison, Jeffrey; Kan, Edwin

2006-01-01

A document describes a methodology for designing fault-protection (FP) software for autonomous spacecraft. The methodology embodies and extends established engineering practices in the technical discipline of Fault Detection, Diagnosis, Mitigation, and Recovery; and has been successfully implemented in the Deep Impact Spacecraft, a NASA Discovery mission. Based on established concepts of Fault Monitors and Responses, this FP methodology extends the notion of Opinion, Symptom, Alarm (aka Fault), and Response with numerous new notions, sub-notions, software constructs, and logic and timing gates. For example, Monitor generates a RawOpinion, which graduates into Opinion, categorized into no-opinion, acceptable, or unacceptable opinion. RaiseSymptom, ForceSymptom, and ClearSymptom govern the establishment and then mapping to an Alarm (aka Fault). Local Response is distinguished from FP System Response. A 1-to-n and n-to- 1 mapping is established among Monitors, Symptoms, and Responses. Responses are categorized by device versus by function. Responses operate in tiers, where the early tiers attempt to resolve the Fault in a localized step-by-step fashion, relegating more system-level response to later tier(s). Recovery actions are gated by epoch recovery timing, enabling strategy, urgency, MaxRetry gate, hardware availability, hazardous versus ordinary fault, and many other priority gates. This methodology is systematic, logical, and uses multiple linked tables, parameter files, and recovery command sequences. The credibility of the FP design is proven via a fault-tree analysis "top-down" approach, and a functional fault-mode-effects-and-analysis via "bottoms-up" approach. Via this process, the mitigation and recovery strategy(s) per Fault Containment Region scope (width versus depth) the FP architecture.

Influence of fault asymmetric dislocation on the gravity changes

Directory of Open Access Journals (Sweden)

Duan Hurong

2014-08-01

Full Text Available A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth’s crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, energy release associated with rapid movement on active faults is the cause of most earthquakes. The relationship between unevenness dislocation and gravity changes was studied on the theoretical thought of differential fault. Simulated observation values were adopted to deduce the gravity changes with the model of asymmetric fault and the model of Okada, respectively. The characteristic of unevennes fault momentum distribution is from two end points to middle by 0 according to a certain continuous functional increase. However, the fault momentum distribution in the fault length range is a constant when the Okada model is adopted. Numerical simulation experiments for the activities of the strike-slip fault, dip-slip fault and extension fault were carried out, respectively, to find that both the gravity contours and the gravity variation values are consistent when either of the two models is adopted. The apparent difference lies in that the values at the end points are 17. 97% for the strike-slip fault, 25. 58% for the dip-slip fault, and 24. 73% for the extension fault.

A Lateral Tensile Fracturing Model for Listric Fault

Science.gov (United States)

Qiu, Z.

2007-12-01

The new discovery of a major seismic fault of the great 1976 Tangshan earthquake suggests a lateral tensile fracturing process at the seismic source. The fault is in listric shape but can not be explained with the prevailing model of listric fault. A double-couple of forces without moment is demonstrated to be applicable to simulate the source mechanism. Based on fracture mechanics, laboratory experiments as well as numerical simulations, the model is against the assumption of stick-slip on existing fault as the cause of the earthquake but not in conflict with seismological observations. Global statistics of CMT solutions of great earthquakes raises significant support to the idea that lateral tensile fracturing might account for not only the Tangshan earthquake but also others.

Event-Triggered Fault Detection of Nonlinear Networked Systems.

Science.gov (United States)

Li, Hongyi; Chen, Ziran; Wu, Ligang; Lam, Hak-Keung; Du, Haiping

2017-04-01

This paper investigates the problem of fault detection for nonlinear discrete-time networked systems under an event-triggered scheme. A polynomial fuzzy fault detection filter is designed to generate a residual signal and detect faults in the system. A novel polynomial event-triggered scheme is proposed to determine the transmission of the signal. A fault detection filter is designed to guarantee that the residual system is asymptotically stable and satisfies the desired performance. Polynomial approximated membership functions obtained by Taylor series are employed for filtering analysis. Furthermore, sufficient conditions are represented in terms of sum of squares (SOSs) and can be solved by SOS tools in MATLAB environment. A numerical example is provided to demonstrate the effectiveness of the proposed results.

Discovery of amorphous carbon veins in the 2008 Wenchuan earthquake fault zone: implications for the fault weakening mechanism

Science.gov (United States)

Liu, J.; Zhang, J.; Zhang, B.; Li, H.

2013-12-01

The 2008 Wenchuan earthquake generated 270- and 80-km-long surface ruptures along Yingxiu-Beichuan fault and Guanxian-Anxian fault, respectively. At the outcrop near Hongkou village, southwest segment of Yingxiu-Beichuan rupture, network black amorphous carbon veins were discovered near fault planes in the 190-m-wide earthquake fault zone. These veins are mainly composed of ultrafine- and fine-grained amorphous carbon, usually narrower than 5mm and injected into faults and cracks as far as several meter. Flowage structures like asymmetrical structures around few stiff rock fragments indicate materials flew when the veins formed. Fluidization of cataclastic amorphous carbon and the powerful driving force in the veins imply high pore pressure built up during earthquakes. High pore pressure solution and graphite reported in the fault gouge (Togo et al., 2011) can lead very low dynamic friction during the Wenchuan earthquake. This deduction hypothesis is in accordance with the very low thermal abnormal measured on the principle fault zone following the Wenchuan earthquake (Mori et al., 2010). Furthermore, network amorphous carbon veins of different generations suggest similar weakening mechanism also worked on historical earthquakes in Longmenshan fault zone. Reference: Brodsky, E. E., Li, H., Mori, J. J., Kano, Y., and Xue, L., 2012, Frictional Stress Measured Through Temperature Profiles in the Wenchuan Scientific Fault Zone Drilling Project. American Geophysical Union, Fall Meeting. San Francisco, T44B-07 Li, H., Xu, Z., Si, J., Pei, J., Song, S., Sun, Z., and Chevalier, M., 2012, Wenchuan Earthquake Fault Scientific Drilling program (WFSD): Overview and Results. American Geophysical Union, Fall Meeting. San Francisco, T44B-01 Mori, J. J., Li, H., Wang, H., Kano, Y., Pei, J., Xu, Z., and Brodsky, E. E., 2010, Temperature measurements in the WFSD-1 borehole following the 2008 Wenchuan earthquake (MW7.9). American Geophysical Union, Fall Meeting. San Francisco, T53E

Spatial clustering and repeating of seismic events observed along the 1976 Tangshan fault, north China

Science.gov (United States)

Li, Le; Chen, Qi-Fu; Cheng, Xin; Niu, Fenglin

2007-12-01

Spatial and temporal features of the seismicity occurring along the Tangshan fault in 2001-2006 were investigated with data recorded by the Beijing metropolitan digital Seismic Network. The relocated seismicity with the double difference method clearly exhibits a dextral bend in the middle of the fault. More than 85% of the earthquakes were found in the two clusters forming the northern segment where relatively small coseismic slips were observed during the 1976 M7.8 earthquake. The b values calculated from the seismicity occurring in the northern and southern segment are 1.03 +/- 0.02 and 0.85 +/- 0.03, respectively. The distinct seismicity and b values are probably the collective effect of the fault geometry and the regional stress field that has an ENE-WSW oriented compression. Using cross-correlation and fine relocation analyses, we also identified a total of 21 doublets and 25 multiplets that make up >50% of the total seismicity. Most of the sequences are aperiodic with recurrence intervals varying from a few minutes to hundreds of days. Based on a quasi-periodic sequence, we obtained a fault slip rate of <=2.6 mm/yr at ~15 km, which is consistent with surface GPS measurements.

3D Constraints On Fault Architecture and Strain Distribution of the Newport-Inglewood Rose Canyon and San Onofre Trend Fault Systems

Science.gov (United States)

Holmes, J. J.; Driscoll, N. W.; Kent, G. M.

2017-12-01

The Inner California Borderlands (ICB) is situated off the coast of southern California and northern Baja. The structural and geomorphic characteristics of the area record a middle Oligocene transition from subduction to microplate capture along the California coast. Marine stratigraphic evidence shows large-scale extension and rotation overprinted by modern strike-slip deformation. Geodetic and geologic observations indicate that approximately 6-8 mm/yr of Pacific-North American relative plate motion is accommodated by offshore strike-slip faulting in the ICB. The farthest inshore fault system, the Newport-Inglewood Rose Canyon (NIRC) Fault is a dextral strike-slip system that is primarily offshore for approximately 120 km from San Diego to the San Joaquin Hills near Newport Beach, California. Based on trenching and well data, the NIRC Fault Holocene slip rate is 1.5-2.0 mm/yr to the south and 0.5-1.0 mm/yr along its northern extent. An earthquake rupturing the entire length of the system could produce an Mw 7.0 earthquake or larger. West of the main segments of the NIRC Fault is the San Onofre Trend (SOT) along the continental slope. Previous work concluded that this is part of a strike-slip system that eventually merges with the NIRC Fault. Others have interpreted this system as deformation associated with the Oceanside Blind Thrust Fault purported to underlie most of the region. In late 2013, we acquired the first high-resolution 3D Parallel Cable (P-Cable) seismic surveys of the NIRC and SOT faults as part of the Southern California Regional Fault Mapping project. Analysis of stratigraphy and 3D mapping of this new data has yielded a new kinematic fault model of the area that provides new insight on deformation caused by interactions in both compressional and extensional regimes. For the first time, we can reconstruct fault interaction and investigate how strain is distributed through time along a typical strike-slip margin using 3D constraints on fault

Numerical model for the thermal-hydraulic solution of shell-and-U-tubes heat exchanger with segmental baffles

International Nuclear Information System (INIS)

Baptista Filho, Benedito Dias

1979-01-01

A numerical model has been developed to calculate the flow, pressure and temperature distribution of steady-state |for the tube and shell-side fluids in a shell-and-U-tubes heat exchanger with segmental baffles. It was based on the Subchannel Analysis Method- The model, checked with experimental results from one heat exchanger, predicted with good accuracy outlet temperatures for both fluids. The method, implemented ' in a computer program of low cost and easy application, can be used in the design and performance evaluation of commercial units.(author)

Groundwater Flow and Radionuclide Transport in Fault Zones in Granitic Rock

International Nuclear Information System (INIS)

Geier, Joel Edward

2004-12-01

Fault zones are potential paths for release of radioactive nuclides from radioactive-waste repositories in granitic rock. This research considers detailed maps of en echelon fault zones at two sites in southern Sweden, as a basis for analyses of how their internal geometry can influence groundwater flow and transport of radioactive nuclides. Fracture intensity within these zones is anisotropic and correlated over scales of several meters along strike, corresponding to the length and spacing of the en echelon steps. Flow modeling indicates these properties lead to correlation of zone transmissivity over similar scales. Intensity of fractures in the damage zone adjoining en echelon segments decreases exponentially with distance. These fractures are linked to en echelon segments as a hierarchical pattern of branches. Echelon steps also show a hierarchical internal structure. These traits suggest a fractal increase in the amount of pore volume that solute can access by diffusive mass transfer, with increasing distance from en echelon segments. Consequences may include tailing of solute breakthrough curves, similar to that observed in underground tracer experiments at one of the mapping sites. The implications of echelon-zone architecture are evaluated by numerical simulation of flow and solute transport in 2-D network models, including deterministic models based directly on mapping data, and a statistical model. The simulations account for advection, diffusion-controlled mixing across streamlines within fractures and at intersections, and diffusion into both stagnant branch fractures and macroscopically unfractured matrix. The simulations show that secondary fractures contribute to retardation of solute, although their net effect is sensitive to assumptions regarding heterogeneity of transmissivity and transport aperture. Detailed results provide insight into the function of secondary fractures as an immobile domain affecting mass transfer on time scales relevant to

Detection of aseismic creep along the San Andreas fault near Parkfield, California with ERS-1 radar interferometry

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Werner, Charles L.; Rosen, Paul; Hensley, Scott; Fielding, Eric; Buckley, Sean

1997-01-01

The differential interferometric analysis of ERS data from Parkfield (CA) observations revealed the wide area distribution of creep along the moving fault segment of the San Andreas fault over a 15 month interval. The removal of the interferometric phase related to the surface topography was carried out. The fault was clearly visible in the differential interferogram. The magnitude of the tropospheric water vapor phase distortions is greater than the signal and hinders quantitative analysis beyond order of magnitude calculations.

Bayesian fault detection and isolation using Field Kalman Filter

Science.gov (United States)

Baranowski, Jerzy; Bania, Piotr; Prasad, Indrajeet; Cong, Tian

2017-12-01

Fault detection and isolation is crucial for the efficient operation and safety of any industrial process. There is a variety of methods from all areas of data analysis employed to solve this kind of task, such as Bayesian reasoning and Kalman filter. In this paper, the authors use a discrete Field Kalman Filter (FKF) to detect and recognize faulty conditions in a system. The proposed approach, devised for stochastic linear systems, allows for analysis of faults that can be expressed both as parameter and disturbance variations. This approach is formulated for the situations when the fault catalog is known, resulting in the algorithm allowing estimation of probability values. Additionally, a variant of algorithm with greater numerical robustness is presented, based on computation of logarithmic odds. Proposed algorithm operation is illustrated with numerical examples, and both its merits and limitations are critically discussed and compared with traditional EKF.

Multi-Fault Rupture Scenarios in the Brawley Seismic Zone

Science.gov (United States)

Kyriakopoulos, C.; Oglesby, D. D.; Rockwell, T. K.; Meltzner, A. J.; Barall, M.

2017-12-01

Dynamic rupture complexity is strongly affected by both the geometric configuration of a network of faults and pre-stress conditions. Between those two, the geometric configuration is more likely to be anticipated prior to an event. An important factor in the unpredictability of the final rupture pattern of a group of faults is the time-dependent interaction between them. Dynamic rupture models provide a means to investigate this otherwise inscrutable processes. The Brawley Seismic Zone in Southern California is an area in which this approach might be important for inferring potential earthquake sizes and rupture patterns. Dynamic modeling can illuminate how the main faults in this area, the Southern San Andreas (SSAF) and Imperial faults, might interact with the intersecting cross faults, and how the cross faults may modulate rupture on the main faults. We perform 3D finite element modeling of potential earthquakes in this zone assuming an extended array of faults (Figure). Our results include a wide range of ruptures and fault behaviors depending on assumptions about nucleation location, geometric setup, pre-stress conditions, and locking depth. For example, in the majority of our models the cross faults do not strongly participate in the rupture process, giving the impression that they are not typically an aid or an obstacle to the rupture propagation. However, in some cases, particularly when rupture proceeds slowly on the main faults, the cross faults indeed can participate with significant slip, and can even cause rupture termination on one of the main faults. Furthermore, in a complex network of faults we should not preclude the possibility of a large event nucleating on a smaller fault (e.g. a cross fault) and eventually promoting rupture on the main structure. Recent examples include the 2010 Mw 7.1 Darfield (New Zealand) and Mw 7.2 El Mayor-Cucapah (Mexico) earthquakes, where rupture started on a smaller adjacent segment and later cascaded into a larger

A new digital ground-fault protection system for generator-transformer unit

Energy Technology Data Exchange (ETDEWEB)

Zielichowski, Mieczyslaw; Szlezak, Tomasz [Institute of Electrical Power Engineering, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50370 Wroclaw (Poland)

2007-08-15

Ground faults are one of most often reasons of damages in stator windings of large generators. Under certain conditions, as a result of ground-fault protection systems maloperation, ground faults convert into high-current faults, causing severe failures in power system. Numerous publications in renowned journals and magazines testify about ground-fault matter importance and problems reported by exploitators confirm opinions, that some issues concerning ground-fault protection of large generators have not been solved yet or have been solved insufficiently. In this paper a new conception of a digital ground-fault protection system for stator winding of large generator was proposed. The process of intermittent arc ground fault in stator winding has been briefly discussed and actual ground-fault voltage waveforms were presented. A new relaying algorithm, based on third harmonic voltage measurement was also drawn and the methods of its implementation and testing were described. (author)

Automated Fault Interpretation and Extraction using Improved Supplementary Seismic Datasets

Science.gov (United States)

Bollmann, T. A.; Shank, R.

2017-12-01

During the interpretation of seismic volumes, it is necessary to interpret faults along with horizons of interest. With the improvement of technology, the interpretation of faults can be expedited with the aid of different algorithms that create supplementary seismic attributes, such as semblance and coherency. These products highlight discontinuities, but still need a large amount of human interaction to interpret faults and are plagued by noise and stratigraphic discontinuities. Hale (2013) presents a method to improve on these datasets by creating what is referred to as a Fault Likelihood volume. In general, these volumes contain less noise and do not emphasize stratigraphic features. Instead, planar features within a specified strike and dip range are highlighted. Once a satisfactory Fault Likelihood Volume is created, extraction of fault surfaces is much easier. The extracted fault surfaces are then exported to interpretation software for QC. Numerous software packages have implemented this methodology with varying results. After investigating these platforms, we developed a preferred Automated Fault Interpretation workflow.

Multi-thresholds for fault isolation in the presence of uncertainties.

Science.gov (United States)

Touati, Youcef; Mellal, Mohamed Arezki; Benazzouz, Djamel

2016-05-01

Monitoring of the faults is an important task in mechatronics. It involves the detection and isolation of faults which are performed by using the residuals. These residuals represent numerical values that define certain intervals called thresholds. In fact, the fault is detected if the residuals exceed the thresholds. In addition, each considered fault must activate a unique set of residuals to be isolated. However, in the presence of uncertainties, false decisions can occur due to the low sensitivity of certain residuals towards faults. In this paper, an efficient approach to make decision on fault isolation in the presence of uncertainties is proposed. Based on the bond graph tool, the approach is developed in order to generate systematically the relations between residuals and faults. The generated relations allow the estimation of the minimum detectable and isolable fault values. The latter is used to calculate the thresholds of isolation for each residual. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Research on Fault Diagnosis for Pumping Station Based on T-S Fuzzy Fault Tree and Bayesian Network

Directory of Open Access Journals (Sweden)

Zhuqing Bi

2017-01-01

Full Text Available According to the characteristics of fault diagnosis for pumping station, such as the complex structure, multiple mappings, and numerous uncertainties, a new approach combining T-S fuzzy gate fault tree and Bayesian network (BN is proposed. On the one hand, traditional fault tree method needs the logical relationship between events and probability value of events and can only represent the events with two states. T-S fuzzy gate fault tree method can solve these disadvantages but still has weaknesses in complex reasoning and only one-way reasoning. On the other hand, the BN is suitable for fault diagnosis of pumping station because of its powerful ability to deal with uncertain information. However, it is difficult to determine the structure and conditional probability tables of the BN. Therefore, the proposed method integrates the advantages of the two methods. Finally, the feasibility of the method is verified through a fault diagnosis model of the rotor in the pumping unit, the accuracy of the method is verified by comparing with the methods based on traditional Bayesian network and BP neural network, respectively, when the historical data is sufficient, and the results are more superior to the above two when the historical data is insufficient.

Implications of Microstructural Studies of the SAFOD Gouge for the Strength and Deformation Mechanisms in the Creeping Segment of the San Andreas Fault

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Hadizadeh, J.; Gratier, J. L.; Mittempergher, S.; Renard, F.; Richard, J.; di Toro, G.; Babaie, H. A.

2010-12-01

The San Andreas Fault zone (SAF) in the vicinity of the San Andreas Fault Observatory at Depth (SAFOD)in central California is characterized by an average 21 mm/year aseismic creep and strain release through repeating Mmicroscopy, cathodoluminescence imaging, X-ray fluorescence mapping, and energy dispersive X-ray spectroscopy. The microstructural and analytical data suggest that deformation is by a coupling of cataclastic flow and pressure solution accompanied by widespread alteration of feldspar to clay minerals and other neomineralizations. The clay contents of the gouge and streaks of serpentinite are not uniformly distributed, but weakness of the creeping segment is likely to be due to intrinsically low frictional strength of the fault material. This conclusion, which is based on the overall ratio of clay/non-clay constituents and the presence of talc in the actively deforming zones, is consistent with the 0.3-0.45 coefficient of friction for the drill cuttings tested by others. We also considered weakening by diffusion-accommodated grain boundary sliding. There are two main trends in the microstructural data that provide a basis for explaining the creep rate and seismic activity: 1. Clay content of the gouge including serpentinite and talc increases toward the 1-3m wide borehole casing deformation zones, which are expected to be deforming at above the average creep rate 2. Evidence of pressure solution creep and fracture sealing is more abundant in the siltstone cataclasites than in the shale. Such rocks could act as rigid inclusions that are repeatedly loaded to seismic failure by creep of the surrounding clay gouge. Regular cycles of fracture and restrengthening by fracture sealing in and around the inclusions are thus expected. The inclusions may be viewed as asperity patches (or cluster of patches) that predominantly deform by pressure solution at below the average creep rate.

Periodic pulsing of characteristic microearthquakes on the San Andreas fault.

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Nadeau, Robert M; McEvilly, Thomas V

2004-01-09

Deep fault slip information from characteristically repeating microearthquakes reveals previously unrecognized patterns of extensive, large-amplitude, long-duration, quasiperiodic repetition of aseismic events along much of a 175-kilometer segment of the central San Andreas fault. Pulsing occurs both in conjunction with and independent of transient slip from larger earthquakes. It extends to depths of approximately 10 to 11 kilometers but may be deeper, and it may be related to similar phenomena occurring in subduction zones. Over much of the study area, pulse onset periods also show a higher probability of larger earthquakes, which may provide useful information for earthquake forecasting.

Can diligent and extensive mapping of faults provide reliable estimates of the expected maximum earthquakes at these faults? No. (Invited)

Science.gov (United States)

Bird, P.

2010-12-01

The hope expressed in the title question above can be contradicted in 5 ways, listed below. To summarize, an earthquake rupture can be larger than anticipated either because the fault system has not been fully mapped, or because the rupture is not limited to the pre-existing fault network. 1. Geologic mapping of faults is always incomplete due to four limitations: (a) Map-scale limitation: Faults below a certain (scale-dependent) apparent offset are omitted; (b) Field-time limitation: The most obvious fault(s) get(s) the most attention; (c) Outcrop limitation: You can't map what you can't see; and (d) Lithologic-contrast limitation: Intra-formation faults can be tough to map, so they are often assumed to be minor and omitted. If mapping is incomplete, fault traces may be longer and/or better-connected than we realize. 2. Fault trace “lengths” are unreliable guides to maximum magnitude. Fault networks have multiply-branching, quasi-fractal shapes, so fault “length” may be meaningless. Naming conventions for main strands are unclear, and rarely reviewed. Gaps due to Quaternary alluvial cover may not reflect deeper seismogenic structure. Mapped kinks and other “segment boundary asperities” may be only shallow structures. Also, some recent earthquakes have jumped and linked “separate” faults (Landers, California 1992; Denali, Alaska, 2002) [Wesnousky, 2006; Black, 2008]. 3. Distributed faulting (“eventually occurring everywhere”) is predicted by several simple theories: (a) Viscoelastic stress redistribution in plate/microplate interiors concentrates deviatoric stress upward until they fail by faulting; (b) Unstable triple-junctions (e.g., between 3 strike-slip faults) in 2-D plate theory require new faults to form; and (c) Faults which appear to end (on a geologic map) imply distributed permanent deformation. This means that all fault networks evolve and that even a perfect fault map would be incomplete for future ruptures. 4. A recent attempt

Earthquake behavior of the Enriquillo fault zone, Haiti revealed by interactive terrain visualization

Science.gov (United States)

Cowgill, E.; Bernardin, T. S.; Oskin, M. E.; Bowles, C. J.; Yikilmaz, M. B.; Kreylos, O.; Elliott, A. J.; Bishop, M. S.; Gold, R. D.; Morelan, A.; Bawden, G. W.; Hamann, B.; Kellogg, L. H.

2010-12-01

The Mw 7.0 January 12, 2010 Haiti earthquake ended 240 years of relative quiescence following earthquakes that destroyed Port-au-Prince in 1751 and 1770. We place the 2010 rupture in the context of past earthquakes and future hazards by using remote analysis of airborne LiDAR to observe the topographic expression of active faulting and develop a new conceptual model for the earthquake behavior of the eastern Enriquillo fault zone (EFZ). In this model, the 2010 event occupies a long-lived segment boundary at a stepover within the EFZ separating fault segments that likely ruptured in 1751 and 1770, explaining both past clustering and the lack of 2010 surface rupture. Immediately following the 2010 earthquake, an airborne LiDAR point cloud containing over 2.7 billion point measurements of surface features was collected by the Rochester Inst. of Technology. To analyze these data, we capitalize on the human capacity to visually identify meaningful patterns embedded in noisy data by conducting interactive visual analysis of the entire 66.8 GB Haiti terrain data in a 4-sided, 800 ft3 immersive virtual-reality environment at the UC Davis KeckCAVES using the software tools LiDAR Viewer (to analyze point cloud data) and Crusta (for 3D surficial geologic mapping on DEM data). We discovered and measured landforms displaced by past surface-rupturing earthquakes and remotely characterized the regional fault geometry. Our analysis of the ~50 km long reach of EFZ spanning the 2010 epicenter indicates that geomorphic evidence of active faulting is clearer east of the epicenter than to the west. West of the epicenter, and in the region of the 2010 rupture, the fault is poorly defined along an embayed, low-relief range front, with little evidence of recent surface rupture. In contrast, landform offsets of 6 to 50 m along the reach of the EFZ east of the epicenter and closest to Port-au-Prince attest to repeated recent surface-rupturing earthquakes here. Specifically, we found and

How does the architecture of a fault system controls magma upward migration through the crust?

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Iturrieta, P. C.; Cembrano, J. M.; Stanton-Yonge, A.; Hurtado, D.

2017-12-01

The orientation and relative disposition of adjacent faults locally disrupt the regional stress field, thus enhancing magma flow through previous or newly created favorable conduits. Moreover, the brittle-plastic transition (BPT), due to its stronger rheology, governs the average state of stress of shallower portions of the fault system. Furthermore, the BPT may coincide with the location of transient magma reservoirs, from which dikes can propagate upwards into the upper crust, shaping the inner structure of the volcanic arc. In this work, we examine the stress distribution in strike-slip duplexes with variable geometry, along with the critical fluid overpressure ratio (CFOP), which is the minimum value required for individual faults to fracture in tension. We also determine the stress state disruption of the fault system when a dike is emplaced, to answer open questions such as: what is the nature of favorable pathways for magma to migrate? what is the architecture influence on the feedback between fault system kinematics and magma injection? To this end, we present a 3D coupled hydro-mechanical finite element model of the continental lithosphere, where faults are represented as continuum volumes with an elastic-plastic rheology. Magma flow upon fracturing is modeled through non-linear Stoke's flow, coupling solid and fluid equilibrium. A non-linear sensitivity analysis is performed in function of tectonic, rheology and geometry inputs, to assess which are the first-order factors that governs the nature of dike emplacement. Results show that the CFOP is heterogeneously distributed in the fault system, and within individual fault segments. Minimum values are displayed near fault intersections, where local kinematics superimpose on regional tectonic loading. Furthermore, when magma is transported through a fault segment, the CFOP is now minimized in faults with non-favorable orientations. This suggests that these faults act as transient pathways for magma to

Earthquake rupture at focal depth, part II: mechanics of the 2004 M2.2 earthquake along the Pretorius Fault, TauTona Mine, South Africa

Science.gov (United States)

Heesakkers, V.; Murphy, S.; Lockner, D.A.; Reches, Z.

2011-01-01

We analyze here the rupture mechanics of the 2004, M2.2 earthquake based on our observations and measurements at focal depth (Part I). This event ruptured the Archean Pretorius fault that has been inactive for at least 2 Ga, and was reactivated due to mining operations down to a depth of 3.6 km depth. Thus, it was expected that the Pretorius fault zone will fail similarly to an intact rock body independently of its ancient healed structure. Our analysis reveals a few puzzling features of the M2.2 rupture-zone: (1) the earthquake ruptured four, non-parallel, cataclasite bearing segments of the ancient Pretorius fault-zone; (2) slip occurred almost exclusively along the cataclasite-host rock contacts of the slipping segments; (3) the local in-situ stress field is not favorable to slip along any of these four segments; and (4) the Archean cataclasite is pervasively sintered and cemented to become brittle and strong. To resolve these observations, we conducted rock mechanics experiments on the fault-rocks and host-rocks and found a strong mechanical contrast between the quartzitic cataclasite zones, with elastic-brittle rheology, and the host quartzites, with damage, elastic–plastic rheology. The finite-element modeling of a heterogeneous fault-zone with the measured mechanical contrast indicates that the slip is likely to reactivate the ancient cataclasite-bearing segments, as observed, due to the strong mechanical contrast between the cataclasite and the host quartzitic rock.

Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode.

Science.gov (United States)

Wright, Tim J; Ebinger, Cindy; Biggs, Juliet; Ayele, Atalay; Yirgu, Gezahegn; Keir, Derek; Stork, Anna

2006-07-20

Seafloor spreading centres show a regular along-axis segmentation thought to be produced by a segmented magma supply in the passively upwelling mantle. On the other hand, continental rifts are segmented by large offset normal faults, and many lack magmatism. It is unclear how, when and where the ubiquitous segmented melt zones are emplaced during the continental rupture process. Between 14 September and 4 October 2005, 163 earthquakes (magnitudes greater than 3.9) and a volcanic eruption occurred within the approximately 60-km-long Dabbahu magmatic segment of the Afar rift, a nascent seafloor spreading centre in stretched continental lithosphere. Here we present a three-dimensional deformation field for the Dabbahu rifting episode derived from satellite radar data, which shows that the entire segment ruptured, making it the largest to have occurred on land in the era of satellite geodesy. Simple elastic modelling shows that the magmatic segment opened by up to 8 m, yet seismic rupture can account for only 8 per cent of the observed deformation. Magma was injected along a dyke between depths of 2 and 9 km, corresponding to a total intrusion volume of approximately 2.5 km3. Much of the magma appears to have originated from shallow chambers beneath Dabbahu and Gabho volcanoes at the northern end of the segment, where an explosive fissural eruption occurred on 26 September 2005. Although comparable in magnitude to the ten year (1975-84) Krafla events in Iceland, seismic data suggest that most of the Dabbahu dyke intrusion occurred in less than a week. Thus, magma intrusion via dyking, rather than segmented normal faulting, maintains and probably initiated the along-axis segmentation along this sector of the Nubia-Arabia plate boundary.

Applications of magnetic resonance image segmentation in neurology

Science.gov (United States)

Heinonen, Tomi; Lahtinen, Antti J.; Dastidar, Prasun; Ryymin, Pertti; Laarne, Paeivi; Malmivuo, Jaakko; Laasonen, Erkki; Frey, Harry; Eskola, Hannu

1999-05-01

After the introduction of digital imagin devices in medicine computerized tissue recognition and classification have become important in research and clinical applications. Segmented data can be applied among numerous research fields including volumetric analysis of particular tissues and structures, construction of anatomical modes, 3D visualization, and multimodal visualization, hence making segmentation essential in modern image analysis. In this research project several PC based software were developed in order to segment medical images, to visualize raw and segmented images in 3D, and to produce EEG brain maps in which MR images and EEG signals were integrated. The software package was tested and validated in numerous clinical research projects in hospital environment.

Long Valley caldera and the UCERF depiction of Sierra Nevada range-front faults

Science.gov (United States)

Hill, David P.; Montgomery-Brown, Emily K.

2015-01-01

Long Valley caldera lies within a left-stepping offset in the north-northwest-striking Sierra Nevada range-front normal faults with the Hilton Creek fault to the south and Hartley Springs fault to the north. Both Uniform California Earthquake Rupture Forecast (UCERF) 2 and its update, UCERF3, depict slip on these major range-front normal faults as extending well into the caldera, with significant normal slip on overlapping, subparallel segments separated by ∼10  km. This depiction is countered by (1) geologic evidence that normal faulting within the caldera consists of a series of graben structures associated with postcaldera magmatism (intrusion and tumescence) and not systematic down-to-the-east displacements consistent with distributed range-front faulting and (2) the lack of kinematic evidence for an evolving, postcaldera relay ramp structure between overlapping strands of the two range-front normal faults. The modifications to the UCERF depiction described here reduce the predicted shaking intensity within the caldera, and they are in accord with the tectonic influence that underlapped offset range-front faults have on seismicity patterns within the caldera associated with ongoing volcanic unrest.

Modeling Fluid Flow in Faulted Basins

Directory of Open Access Journals (Sweden)

Faille I.

2014-07-01

Full Text Available This paper presents a basin simulator designed to better take faults into account, either as conduits or as barriers to fluid flow. It computes hydrocarbon generation, fluid flow and heat transfer on the 4D (space and time geometry obtained by 3D volume restoration. Contrary to classical basin simulators, this calculator does not require a structured mesh based on vertical pillars nor a multi-block structure associated to the fault network. The mesh follows the sediments during the evolution of the basin. It deforms continuously with respect to time to account for sedimentation, erosion, compaction and kinematic displacements. The simulation domain is structured in layers, in order to handle properly the corresponding heterogeneities and to follow the sedimentation processes (thickening of the layers. In each layer, the mesh is unstructured: it may include several types of cells such as tetrahedra, hexahedra, pyramid, prism, etc. However, a mesh composed mainly of hexahedra is preferred as they are well suited to the layered structure of the basin. Faults are handled as internal boundaries across which the mesh is non-matching. Different models are proposed for fault behavior such as impervious fault, flow across fault or conductive fault. The calculator is based on a cell centered Finite Volume discretisation, which ensures conservation of physical quantities (mass of fluid, heat at a discrete level and which accounts properly for heterogeneities. The numerical scheme handles the non matching meshes and guaranties appropriate connection of cells across faults. Results on a synthetic basin demonstrate the capabilities of this new simulator.

Irregular recurrence of large earthquakes along the san andreas fault: evidence from trees.

Science.gov (United States)

Jacoby, G C; Sheppard, P R; Sieh, K E

1988-07-08

Old trees growing along the San Andreas fault near Wrightwood, California, record in their annual ring-width patterns the effects of a major earthquake in the fall or winter of 1812 to 1813. Paleoseismic data and historical information indicate that this event was the "San Juan Capistrano" earthquake of 8 December 1812, with a magnitude of 7.5. The discovery that at least 12 kilometers of the Mojave segment of the San Andreas fault ruptured in 1812, only 44 years before the great January 1857 rupture, demonstrates that intervals between large earthquakes on this part of the fault are highly variable. This variability increases the uncertainty of forecasting destructive earthquakes on the basis of past behavior and accentuates the need for a more fundamental knowledge of San Andreas fault dynamics.

Low strength of deep San Andreas fault gouge from SAFOD core.

Science.gov (United States)

Lockner, David A; Morrow, Carolyn; Moore, Diane; Hickman, Stephen

2011-04-07

The San Andreas fault accommodates 28-34 mm yr(-1) of right lateral motion of the Pacific crustal plate northwestward past the North American plate. In California, the fault is composed of two distinct locked segments that have produced great earthquakes in historical times, separated by a 150-km-long creeping zone. The San Andreas Fault Observatory at Depth (SAFOD) is a scientific borehole located northwest of Parkfield, California, near the southern end of the creeping zone. Core was recovered from across the actively deforming San Andreas fault at a vertical depth of 2.7 km (ref. 1). Here we report laboratory strength measurements of these fault core materials at in situ conditions, demonstrating that at this locality and this depth the San Andreas fault is profoundly weak (coefficient of friction, 0.15) owing to the presence of the smectite clay mineral saponite, which is one of the weakest phyllosilicates known. This Mg-rich clay is the low-temperature product of metasomatic reactions between the quartzofeldspathic wall rocks and serpentinite blocks in the fault. These findings provide strong evidence that deformation of the mechanically unusual creeping portions of the San Andreas fault system is controlled by the presence of weak minerals rather than by high fluid pressure or other proposed mechanisms. The combination of these measurements of fault core strength with borehole observations yields a self-consistent picture of the stress state of the San Andreas fault at the SAFOD site, in which the fault is intrinsically weak in an otherwise strong crust. ©2011 Macmillan Publishers Limited. All rights reserved

Velocity Gradient Across the San Andreas Fault and Changes in Slip Behavior as Outlined by Full non Linear Tomography

Science.gov (United States)

Chiarabba, C.; Giacomuzzi, G.; Piana Agostinetti, N.

2017-12-01

The San Andreas Fault (SAF) near Parkfield is the best known fault section which exhibit a clear transition in slip behavior from stable to unstable. Intensive monitoring and decades of studies permit to identify details of these processes with a good definition of fault structure and subsurface models. Tomographic models computed so far revealed the existence of large velocity contrasts, yielding physical insight on fault rheology. In this study, we applied a recently developed full non-linear tomography method to compute Vp and Vs models which focus on the section of the fault that exhibit fault slip transition. The new tomographic code allows not to impose a vertical seismic discontinuity at the fault position, as routinely done in linearized codes. Any lateral velocity contrast found is directly dictated by the data themselves and not imposed by subjective choices. The use of the same dataset of previous tomographic studies allows a proper comparison of results. We use a total of 861 earthquakes, 72 blasts and 82 shots and the overall arrival time dataset consists of 43948 P- and 29158 S-wave arrival times, accurately selected to take care of seismic anisotropy. Computed Vp and Vp/Vs models, which by-pass the main problems related to linarized LET algorithms, excellently match independent available constraints and show crustal heterogeneities with a high resolution. The high resolution obtained in the fault surroundings permits to infer lateral changes of Vp and Vp/Vs across the fault (velocity gradient). We observe that stable and unstable sliding sections of the SAF have different velocity gradients, small and negligible in the stable slip segment, but larger than 15 % in the unstable slip segment. Our results suggest that Vp and Vp/Vs gradients across the fault control fault rheology and the attitude of fault slip behavior.

Active Fault Near-Source Zones Within and Bordering the State of California for the 1997 Uniform Building Code

Science.gov (United States)

Petersen, M.D.; Toppozada, Tousson R.; Cao, T.; Cramer, C.H.; Reichle, M.S.; Bryant, W.A.

2000-01-01

The fault sources in the Project 97 probabilistic seismic hazard maps for the state of California were used to construct maps for defining near-source seismic coefficients, Na and Nv, incorporated in the 1997 Uniform Building Code (ICBO 1997). The near-source factors are based on the distance from a known active fault that is classified as either Type A or Type B. To determine the near-source factor, four pieces of geologic information are required: (1) recognizing a fault and determining whether or not the fault has been active during the Holocene, (2) identifying the location of the fault at or beneath the ground surface, (3) estimating the slip rate of the fault, and (4) estimating the maximum earthquake magnitude for each fault segment. This paper describes the information used to produce the fault classifications and distances.

Use of spectral gamma ray as a lithology guide for fault rocks: A case study from the Wenchuan Earthquake Fault Scientific Drilling project Borehole 4 (WFSD-4).

Science.gov (United States)

Amara Konaté, Ahmed; Pan, Heping; Ma, Huolin; Qin, Zhen; Guo, Bo; Yevenyo Ziggah, Yao; Kounga, Claude Ernest Moussounda; Khan, Nasir; Tounkara, Fodé

2017-10-01

The main purpose of the Wenchuan Earthquake Fault Scientific drilling project (WFSD) was to produce an in-depth borehole into the Yingxiu-Beichuan (YBF) and Anxian-Guanxian faults in order to gain a much better understanding of the physical and chemical properties as well as the mechanical faulting involved. Five boreholes, namely WFSD-1, WFSD-2, WFSD-3P, WFSD-3 and WFSD-4, were drilled during the project entirety. This study, therefore, presents first-hand WFSD-4 data on the lithology (original rocks) and fault rocks that have been obtained from the WFSD project. In an attempt to determine the physical properties and the clay minerals of the lithology and fault rocks, this study analyzed the spectral gamma ray logs (Total gamma ray, Potassium, Thorium and Uranium) recorded in WFSD-4 borehole on the Northern segment of the YBF. The obtained results are presented as cross-plots and statistical multi log analysis. Both lithology and fault rocks show a variability of spectral gamma ray (SGR) logs responses and clay minerals. This study has shown the capabilities of the SGR logs for well-logging of earthquake faults and proves that SGR logs together with others logs in combination with drill hole core description is a useful method of lithology and fault rocks characterization. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fault geometry of 2015, Mw7.2 Murghab, Tajikistan earthquake controls rupture propagation: Insights from InSAR and seismological data

Science.gov (United States)

Sangha, Simran; Peltzer, Gilles; Zhang, Ailin; Meng, Lingsen; Liang, Cunren; Lundgren, Paul; Fielding, Eric

2017-03-01

Combining space-based geodetic and array seismology observations can provide detailed information about earthquake ruptures in remote regions. Here we use Landsat-8 imagery and ALOS-2 and Sentinel-1 radar interferometry data combined with data from the European seismology network to describe the source of the December 7, 2015, Mw7.2 Murghab (Tajikistan) earthquake. The earthquake reactivated a ∼79 km-long section of the Sarez-Karakul Fault, a NE oriented sinistral, trans-tensional fault in northern Pamir. Pixel offset data delineate the geometry of the surface break and line of sight ground shifts from two descending and three ascending interferograms constrain the fault dip and slip solution. Two right-stepping, NE-striking segments connected by a more easterly oriented segment, sub-vertical or steeply dipping to the west were involved. The solution shows two main patches of slip with up to 3.5 m of left lateral slip on the southern and central fault segments. The northern segment has a left-lateral and normal oblique slip of up to a meter. Back-projection of high-frequency seismic waves recorded by the European network, processed using the Multitaper-MUSIC approach, focuses sharply along the surface break. The time progression of the high-frequency radiators shows that, after a 10 second initiation phase at slow speed, the rupture progresses in 2 phases at super-shear velocity (∼4.3-5 km/s) separated by a 3 second interval of slower propagation corresponding to the passage through the restraining bend. The intensity of the high-frequency radiation reaches maxima during the initial and middle phases of slow propagation and is reduced by ∼50% during the super-shear phases of the propagation. These findings are consistent with studies of other strike-slip earthquakes in continental domain, showing the importance of fault geometric complexities in controlling the speed of fault propagation and related spatiotemporal pattern of the high-frequency radiation.

Seismic fragility analysis of a CANDU containment structure for near-fault ground motions

International Nuclear Information System (INIS)

Choi, In Kil; Choun, Young Sun; Seo, Jeong Moon; Ahn, Seong Moon

2005-01-01

The R. G. 1.60 spectrum used for the seismic design of Korean nuclear power plants provides a generally conservative design basis due to its broadband nature. A survey on some of the Quaternary fault segments near Korean nuclear power plants is ongoing. It is likely that these faults will be identified as active ones. If the faults are confirmed as active ones, it will be necessary to reevaluate the seismic safety of the nuclear power plants located near these faults. The probability based scenario earthquakes were identified as near-field earthquakes. In general, the near-fault ground motion records exhibit a distinctive long period pulse like time history with very high peak velocities. These features are induced by the slip of the earthquake fault. Near-fault ground motions, which have caused much of the damage in recent major earthquakes, can be characterized by a pulse-like motion that exposes the structure to a high input energy at the beginning of the motion. It is necessary to estimate the near-fault ground motion effects on the nuclear power plant structures and components located near the faults. In this study, the seismic fragility analysis of a CANDU containment structure was performed based on the results of nonlinear dynamic time-history analyses

Influence of crystallised igneous intrusions on fault nucleation and reactivation during continental extension

Science.gov (United States)

Magee, Craig; McDermott, Kenneth G.; Stevenson, Carl T. E.; Jackson, Christopher A.-L.

2014-05-01

Continental rifting is commonly accommodated by the nucleation of normal faults, slip on pre-existing fault surfaces and/or magmatic intrusion. Because crystallised igneous intrusions are pervasive in many rift basins and are commonly more competent (i.e. higher shear strengths and Young's moduli) than the host rock, it is theoretically plausible that they locally intersect and modify the mechanical properties of pre-existing normal faults. We illustrate the influence that crystallised igneous intrusions may have on fault reactivation using a conceptual model and observations from field and subsurface datasets. Our results show that igneous rocks may initially resist failure, and promote the preferential reactivation of favourably-oriented, pre-existing faults that are not spatially-associated with solidified intrusions. Fault segments situated along strike from laterally restricted fault-intrusion intersections may similarly be reactivated. This spatial and temporal control on strain distribution may generate: (1) supra-intrusion folds in the hanging wall; (2) new dip-slip faults adjacent to the igneous body; or (3) sub-vertical, oblique-slip faults oriented parallel to the extension direction. Importantly, stress accumulation within igneous intrusions may eventually initiate failure and further localise strain. The results of our study have important implications for the structural of sedimentary basins and the subsurface migration of hydrocarbons and mineral-bearing fluids.

Toward a physics-based rate and state friction law for earthquake nucleation processes in fault zones with granular gouge

Science.gov (United States)

Ferdowsi, B.; Rubin, A. M.

2017-12-01

Numerical simulations of earthquake nucleation rely on constitutive rate and state evolution laws to model earthquake initiation and propagation processes. The response of different state evolution laws to large velocity increases is an important feature of these constitutive relations that can significantly change the style of earthquake nucleation in numerical models. However, currently there is not a rigorous understanding of the physical origins of the response of bare rock or gouge-filled fault zones to large velocity increases. This in turn hinders our ability to design physics-based friction laws that can appropriately describe those responses. We here argue that most fault zones form a granular gouge after an initial shearing phase and that it is the behavior of the gouge layer that controls the fault friction. We perform numerical experiments of a confined sheared granular gouge under a range of confining stresses and driving velocities relevant to fault zones and apply 1-3 order of magnitude velocity steps to explore dynamical behavior of the system from grain- to macro-scales. We compare our numerical observations with experimental data from biaxial double-direct-shear fault gouge experiments under equivalent loading and driving conditions. Our intention is to first investigate the degree to which these numerical experiments, with Hertzian normal and Coulomb friction laws at the grain-grain contact scale and without any time-dependent plasticity, can reproduce experimental fault gouge behavior. We next compare the behavior observed in numerical experiments with predictions of the Dieterich (Aging) and Ruina (Slip) friction laws. Finally, the numerical observations at the grain and meso-scales will be used for designing a rate and state evolution law that takes into account recent advances in rheology of granular systems, including local and non-local effects, for a wide range of shear rates and slow and fast deformation regimes of the fault gouge.

A numerical study on the feasibility evaluation of a hybrid type superconducting fault current limiter applying thyristors

Energy Technology Data Exchange (ETDEWEB)

Nam, Seok Ho; Lee, Woo Seung; Lee, Ji Ho; Hwang, Young Jin; Ko, Tae Kuk [Yonsei University, Seoul (Korea, Republic of)

2013-12-15

Smart fault current controller (SFCC) proposed in our previous work consists of a power converter, a high temperature superconducting (HTS) DC reactor, thyristors, and a control unit [1]. SFCC can limit and control the current by adjusting firing angles of thyristors when a fault occurs. SFCC has complex structure because the HTS DC reactor generates the loss under AC. To use the DC reactor under AC, rectifier that consists of four thyristors is needed and it increases internal resistance of SFCC. For this reason, authors propose a hybrid type superconducting fault current limiter (SFCL). The hybrid type SFCL proposed in this paper consists of a non-inductive superconducting coil and two thyristors. To verify the feasibility of the proposed hybrid type SFCL, simulations about the interaction of the superconducting coil and thyristors are conducted when fault current flows in the superconducting coil. Authors expect that the hybrid type SFCL can control the magnitude of the fault current by adjusting the firing angles of thyristors after the superconducting coil limits the fault current at first peak.

A numerical study on the feasibility evaluation of a hybrid type superconducting fault current limiter applying thyristors

International Nuclear Information System (INIS)

Nam, Seok Ho; Lee, Woo Seung; Lee, Ji Ho; Hwang, Young Jin; Ko, Tae Kuk

2013-01-01

Smart fault current controller (SFCC) proposed in our previous work consists of a power converter, a high temperature superconducting (HTS) DC reactor, thyristors, and a control unit [1]. SFCC can limit and control the current by adjusting firing angles of thyristors when a fault occurs. SFCC has complex structure because the HTS DC reactor generates the loss under AC. To use the DC reactor under AC, rectifier that consists of four thyristors is needed and it increases internal resistance of SFCC. For this reason, authors propose a hybrid type superconducting fault current limiter (SFCL). The hybrid type SFCL proposed in this paper consists of a non-inductive superconducting coil and two thyristors. To verify the feasibility of the proposed hybrid type SFCL, simulations about the interaction of the superconducting coil and thyristors are conducted when fault current flows in the superconducting coil. Authors expect that the hybrid type SFCL can control the magnitude of the fault current by adjusting the firing angles of thyristors after the superconducting coil limits the fault current at first peak.

Segmentation along the Queen Charlotte Fault: The long-lived influence of plate-motion rotation and Explorer Ridge fracture zones

Science.gov (United States)

Miller, N. C.; Walton, M. A. L.; Brothers, D. S.; Haeussler, P. J.; Ten Brink, U. S.; Conrad, J. E.; Kluesner, J.; Andrews, B. D.

2017-12-01

The Queen Charlotte Fault (QCF) generally tracks the flow line for Pacific/North America (Pa/NA) relative motion since 20 Ma, indicating that the plate boundary localized along an optimally oriented small circle geometry. Rotation in Pa/NA motion at 10—12 Ma caused the QCF south of 53 N to be oblique to plate motion by 10—20. This oblique convergence appears to be accommodated in part by underthrusting of the Pacific Plate beneath Haida Gwaii and in part by slip on faults west of the QCF. On the west side of the QCF, a series of ridges and small basins oriented subparallel to either the QCF or relative plate motion form a 40-km-wide terrace. New high-resolution seismic reflection data image the seaward edge of the ridges as a vertical contact between horizontal or sometimes downwarped deep-sea sediments and west-vergent anticlinal structures within the ridges, supporting earlier interpretations that these ridges have accommodated some component of oblique motion. We argue that the ridges originated as step overs from fracture zones on Explorer Ridge, analogous to the current fault geometry at the southernmost end of the QCF. There, the Revere-Dellwood Fracture Zone (RDFZ) overlaps the QCF for 120 km and connects to the QCF via a more-optimally oriented extensional right step. 3.9—6.4 Mw strike-slip earthquakes along the RDFZ and a lack of contractional seafloor morphologies along the QCF south of the RDFZ-QCF right step suggest that the step over and reactivation along the RDFZ accommodates a majority of plate motion in this region. Kinematic reconstruction of ridges from 54—56 N indicates that they also originated in a similar location, potentially as right steps from either the RDFZ or Sovanco Fracture Zone. Similarly, the RDFZ flow path is coincident with a truncation of seafloor magnetic anomalies and the outer edge of the ridge-bounded terrace, which both parallel the QCF since at least the onset of Explorer Ridge spreading at 8 Ma. The RDFZ-QCF right

Numerical simulation and optimal design of Segmented Planar Imaging Detector for Electro-Optical Reconnaissance

Science.gov (United States)

Chu, Qiuhui; Shen, Yijie; Yuan, Meng; Gong, Mali

2017-12-01

Segmented Planar Imaging Detector for Electro-Optical Reconnaissance (SPIDER) is a cutting-edge electro-optical imaging technology to realize miniaturization and complanation of imaging systems. In this paper, the principle of SPIDER has been numerically demonstrated based on the partially coherent light theory, and a novel concept of adjustable baseline pairing SPIDER system has further been proposed. Based on the results of simulation, it is verified that the imaging quality could be effectively improved by adjusting the Nyquist sampling density, optimizing the baseline pairing method and increasing the spectral channel of demultiplexer. Therefore, an adjustable baseline pairing algorithm is established for further enhancing the image quality, and the optimal design procedure in SPIDER for arbitrary targets is also summarized. The SPIDER system with adjustable baseline pairing method can broaden its application and reduce cost under the same imaging quality.

Looking for Off-Fault Deformation and Measuring Strain Accumulation During the Past 70 years on a Portion of the Locked San Andreas Fault

Science.gov (United States)

Vadman, M.; Bemis, S. P.

2017-12-01

Even at high tectonic rates, detection of possible off-fault plastic/aseismic deformation and variability in far-field strain accumulation requires high spatial resolution data and likely decades of measurements. Due to the influence that variability in interseismic deformation could have on the timing, size, and location of future earthquakes and the calculation of modern geodetic estimates of strain, we attempt to use historical aerial photographs to constrain deformation through time across a locked fault. Modern photo-based 3D reconstruction techniques facilitate the creation of dense point clouds from historical aerial photograph collections. We use these tools to generate a time series of high-resolution point clouds that span 10-20 km across the Carrizo Plain segment of the San Andreas fault. We chose this location due to the high tectonic rates along the San Andreas fault and lack of vegetation, which may obscure tectonic signals. We use ground control points collected with differential GPS to establish scale and georeference the aerial photograph-derived point clouds. With a locked fault assumption, point clouds can be co-registered (to one another and/or the 1.7 km wide B4 airborne lidar dataset) along the fault trace to calculate relative displacements away from the fault. We use CloudCompare to compute 3D surface displacements, which reflect the interseismic strain accumulation that occurred in the time interval between photo collections. As expected, we do not observe clear surface displacements along the primary fault trace in our comparisons of the B4 lidar data against the aerial photograph-derived point clouds. However, there may be small scale variations within the lidar swath area that represent near-fault plastic deformation. With large-scale historical photographs available for the Carrizo Plain extending back to at least the 1940s, we can potentially sample nearly half the interseismic period since the last major earthquake on this portion of

Kinematics and Seismotectonics of the Montello Thrust Fault (Southeastern Alps, Italy) Revealed by Local GPS and Seismic Networks

Science.gov (United States)

Serpelloni, E.; Anderlini, L.; Cavaliere, A.; Danesi, S.; Pondrelli, S.; Salimbeni, S.; Danecek, P.; Massa, M.; Lovati, S.

2014-12-01

The southern Alps fold-and-thrust belt (FTB) in northern Italy is a tectonically active area accommodating large part of the ~N-S Adria-Eurasia plate convergence, that in the southeastern Alps ranges from 1.5 to 2.5 mm/yr, as constrained by a geodetically defined rotation pole. Because of the high seismic hazard of northeastern Italy, the area is well monitored at a regional scale by seismic and GPS networks. However, more localized seismotectonic and kinematic features, at the scale of the fault segments, are not yet resolved, limiting our knowledge about the seismic potential of the different fault segments belonging to the southeastern Alps FTB. Here we present the results obtained from the analysis of data collected during local seismic and geodetic experiments conducted installing denser geophysical networks across the Montello-Bassano-Belluno system, a segment of the FTB that is presently characterized by a lower sismicity rate with respect to the surrounding domains. The Montello anticline, which is the southernmost tectonic features of the southeastern Alps FTB (located ~15 km south of the mountain front), is a nice example of growing anticline associated with a blind thrust fault. However, how the Adria-Alps convergence is partitioned across the FTB and the seismic potential of the Montello thrust (the area has been struck by a Mw~6.5 in 1695 but the causative fault is still largely debated) remained still unresolved. The new, denser, GPS data show that this area is undergoing among the highest geodetic deformation rates of the entire south Alpine chain, with a steep velocity gradient across the Montello anticline. The earthquakes recorded during the experiment, precisely relocated with double difference methods, and the new earthquake focal mechanisms well correlate with available information about sub-surface geological structures and highlight the seismotectonic activity of the Montello thrust fault. We model the GPS velocities using elastic

Numerical experiments to investigate the accuracy of broad-band moment magnitude, Mwp

Science.gov (United States)

Hara, Tatsuhiko; Nishimura, Naoki

2011-12-01

We perform numerical experiments to investigate the accuracy of broad-band moment magnitude, Mwp. We conduct these experiments by measuring Mwp from synthetic seismograms and comparing the resulting values to the moment magnitudes used in the calculation of synthetic seismograms. In the numerical experiments using point sources, we have found that there is a significant dependence of Mwp on focal mechanisms, and that depths phases have a large impact on Mwp estimates, especially for large shallow earthquakes. Numerical experiments using line sources suggest that the effects of source finiteness and rupture propagation on Mwp estimates are on the order of 0.2 magnitude units for vertical fault planes with pure dip-slip mechanisms and 45° dipping fault planes with pure dip-slip (thrust) mechanisms, but that the dependence is small for strike-slip events on a vertical fault plane. Numerical experiments for huge thrust faulting earthquakes on a fault plane with a shallow dip angle suggest that the Mwp estimates do not saturate in the moment magnitude range between 8 and 9, although they are underestimates. Our results are consistent with previous studies that compared Mwp estimates to moment magnitudes calculated from seismic moment tensors obtained by analyses of observed data.

Back analysis of fault-slip in burst prone environment

Science.gov (United States)

Sainoki, Atsushi; Mitri, Hani S.

2016-11-01

In deep underground mines, stress re-distribution induced by mining activities could cause fault-slip. Seismic waves arising from fault-slip occasionally induce rock ejection when hitting the boundary of mine openings, and as a result, severe damage could be inflicted. In general, it is difficult to estimate fault-slip-induced ground motion in the vicinity of mine openings because of the complexity of the dynamic response of faults and the presence of geological structures. In this paper, a case study is conducted for a Canadian underground mine, herein called "Mine-A", which is known for its seismic activities. Using a microseismic database collected from the mine, a back analysis of fault-slip is carried out with mine-wide 3-dimensional numerical modeling. A back analysis is conducted to estimate the physical and mechanical properties of the causative fracture or shear zones. One large seismic event has been selected for the back analysis to detect a fault-slip related seismic event. In the back analysis, the shear zone properties are estimated with respect to moment magnitude of the seismic event and peak particle velocity (PPV) recorded by a strong ground motion sensor. The estimated properties are then validated through comparison with peak ground acceleration recorded by accelerometers. Lastly, ground motion in active mining areas is estimated by conducting dynamic analysis with the estimated values. The present study implies that it would be possible to estimate the magnitude of seismic events that might occur in the near future by applying the estimated properties to the numerical model. Although the case study is conducted for a specific mine, the developed methodology can be equally applied to other mines suffering from fault-slip related seismic events.

The Evergreen basin and the role of the Silver Creek fault in the San Andreas fault system, San Francisco Bay region, California

Science.gov (United States)

Jachens, Robert C.; Wentworth, Carl M.; Graymer, Russell W.; Williams, Robert; Ponce, David A.; Mankinen, Edward A.; Stephenson, William J.; Langenheim, Victoria

2017-01-01

The Evergreen basin is a 40-km-long, 8-km-wide Cenozoic sedimentary basin that lies mostly concealed beneath the northeastern margin of the Santa Clara Valley near the south end of San Francisco Bay (California, USA). The basin is bounded on the northeast by the strike-slip Hayward fault and an approximately parallel subsurface fault that is structurally overlain by a set of west-verging reverse-oblique faults which form the present-day southeastward extension of the Hayward fault. It is bounded on the southwest by the Silver Creek fault, a largely dormant or abandoned fault that splays from the active southern Calaveras fault. We propose that the Evergreen basin formed as a strike-slip pull-apart basin in the right step from the Silver Creek fault to the Hayward fault during a time when the Silver Creek fault served as a segment of the main route by which slip was transferred from the central California San Andreas fault to the Hayward and other East Bay faults. The dimensions and shape of the Evergreen basin, together with palinspastic reconstructions of geologic and geophysical features surrounding it, suggest that during its lifetime, the Silver Creek fault transferred a significant portion of the ∼100 km of total offset accommodated by the Hayward fault, and of the 175 km of total San Andreas system offset thought to have been accommodated by the entire East Bay fault system. As shown previously, at ca. 1.5–2.5 Ma the Hayward-Calaveras connection changed from a right-step, releasing regime to a left-step, restraining regime, with the consequent effective abandonment of the Silver Creek fault. This reorganization was, perhaps, preceded by development of the previously proposed basin-bisecting Mount Misery fault, a fault that directly linked the southern end of the Hayward fault with the southern Calaveras fault during extinction of pull-apart activity. Historic seismicity indicates that slip below a depth of 5 km is mostly transferred from the Calaveras

Using Earthquake Analysis to Expand the Oklahoma Fault Database

Science.gov (United States)

Chang, J. C.; Evans, S. C.; Walter, J. I.

2017-12-01

The Oklahoma Geological Survey (OGS) is compiling a comprehensive Oklahoma Fault Database (OFD), which includes faults mapped in OGS publications, university thesis maps, and industry-contributed shapefiles. The OFD includes nearly 20,000 fault segments, but the work is far from complete. The OGS plans on incorporating other sources of data into the OFD, such as new faults from earthquake sequence analyses, geologic field mapping, active-source seismic surveys, and potential fields modeling. A comparison of Oklahoma seismicity and the OFD reveals that earthquakes in the state appear to nucleate on mostly unmapped or unknown faults. Here, we present faults derived from earthquake sequence analyses. From 2015 to present, there has been a five-fold increase in realtime seismic stations in Oklahoma, which has greatly expanded and densified the state's seismic network. The current seismic network not only improves our threshold for locating weaker earthquakes, but also allows us to better constrain focal plane solutions (FPS) from first motion analyses. Using nodal planes from the FPS, HypoDD relocation, and historic seismic data, we can elucidate these previously unmapped seismogenic faults. As the OFD is a primary resource for various scientific investigations, the inclusion of seismogenic faults improves further derivative studies, particularly with respect to seismic hazards. Our primal focus is on four areas of interest, which have had M5+ earthquakes in recent Oklahoma history: Pawnee (M5.8), Prague (M5.7), Fairview (M5.1), and Cushing (M5.0). Subsequent areas of interest will include seismically active data-rich areas, such as the central and northcentral parts of the state.

The role of E-W basement faults in the Mesozoic geodynamic ...

Indian Academy of Sciences (India)

8

Zones 1 and 2. However, the Upper Cretaceous units are thicker westward. The thickness of. Cenozoic series decreases from west to east. This configuration highlights an Upper. Cretaceous tectonic activity of the segments of NW–SE fault that affects the series near the western periclinal termination of the Sehib anticline ...

Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali fault zone from double-difference tomography, receiver functions, and fault zone head waves

Science.gov (United States)

Allam, A. A.; Schulte-Pelkum, V.; Ben-Zion, Y.; Tape, C.; Ruppert, N.; Ross, Z. E.

2017-11-01

We examine the structure of the Denali fault system in the crust and upper mantle using double-difference tomography, P-wave receiver functions, and analysis (spatial distribution and moveout) of fault zone head waves. The three methods have complementary sensitivity; tomography is sensitive to 3D seismic velocity structure but smooths sharp boundaries, receiver functions are sensitive to (quasi) horizontal interfaces, and fault zone head waves are sensitive to (quasi) vertical interfaces. The results indicate that the Mohorovičić discontinuity is vertically offset by 10 to 15 km along the central 600 km of the Denali fault in the imaged region, with the northern side having shallower Moho depths around 30 km. An automated phase picker algorithm is used to identify 1400 events that generate fault zone head waves only at near-fault stations. At shorter hypocentral distances head waves are observed at stations on the northern side of the fault, while longer propagation distances and deeper events produce head waves on the southern side. These results suggest a reversal of the velocity contrast polarity with depth, which we confirm by computing average 1D velocity models separately north and south of the fault. Using teleseismic events with M ≥ 5.1, we obtain 31,400 P receiver functions and apply common-conversion-point stacking. The results are migrated to depth using the derived 3D tomography model. The imaged interfaces agree with the tomography model, showing a Moho offset along the central Denali fault and also the sub-parallel Hines Creek fault, a suture zone boundary 30 km to the north. To the east, this offset follows the Totschunda fault, which ruptured during the M7.9 2002 earthquake, rather than the Denali fault itself. The combined results suggest that the Denali fault zone separates two distinct crustal blocks, and that the Totschunda and Hines Creeks segments are important components of the fault and Cretaceous-aged suture zone structure.

Medical Image Segmentation for Mobile Electronic Patient Charts Using Numerical Modeling of IoT

Directory of Open Access Journals (Sweden)

Seung-Hoon Chae

2014-01-01

Full Text Available Internet of Things (IoT brings telemedicine a new chance. This enables the specialist to consult the patient’s condition despite the fact that they are in different places. Medical image segmentation is needed for analysis, storage, and protection of medical image in telemedicine. Therefore, a variety of methods have been researched for fast and accurate medical image segmentation. Performing segmentation in various organs, the accurate judgment of the region is needed in medical image. However, the removal of region occurs by the lack of information to determine the region in a small region. In this paper, we researched how to reconstruct segmentation region in a small region in order to improve the segmentation results. We generated predicted segmentation of slices using volume data with linear equation and proposed improvement method for small regions using the predicted segmentation. In order to verify the performance of the proposed method, lung region by chest CT images was segmented. As a result of experiments, volume data segmentation accuracy rose from 0.978 to 0.981 and from 0.281 to 0.187 with a standard deviation improvement confirmed.

Problem and solution of tally segment card in MCNP code

International Nuclear Information System (INIS)

Xie Jiachun; Zhao Shouzhi; Sun Zheng; Jia Baoshan

2010-01-01

Wrong results may be given when FS card (tally segment card) was used for tally with other tally cards in Monte Carlo code MCNP. According to the comparison of segment tally results which were obtained by FS card of three different models of the same geometry, the tally results of fuel regions were found to be wrong in fill pattern. The reason is that the fuel cells were described by Universe card and FILL card, and the filled cells were always considered at Universe card definition place. A proposed solution was that the segment tally for filled cells was done at Universe card definition place. Radial flux distribution of one example was calculated in this way. The results show that the fault of segment tally with FS card in fill pattern could be solved by this method. (authors)

Integrated core-log interpretation of Wenchuan earthquake Fault Scientific Drilling project borehole 4 (WFSD-4)

Science.gov (United States)

Konaté, Ahmed Amara; Pan, Heping; Ma, Huolin; Qin, Zhen; Traoré, Alhouseiny

2017-08-01

Understanding slip behavior of active fault is a fundamental problem in earthquake investigations. Well logs and cores data provide direct information of physical properties of the fault zones at depth. The geological exploration of the Wenchuan earthquake Scientific Fault drilling project (WFSD) targeted the Yingxiu-Beichuan fault and the Guanxian Anxian fault, respectively. Five boreholes (WFSD-1, WFSD-2, WFSD-3P WFSD-3 and WFSD-4) were drilled and logged with geophysical tools developed for the use in petroleum industry. WFSD-1, WFSD-2 and WFSD-3 in situ logging data have been reported and investigated by geoscientists. Here we present for the first time, the integrated core-log studies in the Northern segment of Yingxiu-Beichuan fault (WFSD-4) thereby characterizing the physical properties of the lithologies(original rocks), fault rocks and the presumed slip zone associated with the Wenchuan earthquake. We also present results from the comparison of WFSD-4 to those obtained from WFSD-1, WFSD-3 and other drilling hole in active faults. This study show that integrated core-log study would help in understanding the slip behavior of active fault.

Accounting for Fault Roughness in Pseudo-Dynamic Ground-Motion Simulations

KAUST Repository

Mai, Paul Martin

2017-04-03

Geological faults comprise large-scale segmentation and small-scale roughness. These multi-scale geometrical complexities determine the dynamics of the earthquake rupture process, and therefore affect the radiated seismic wavefield. In this study, we examine how different parameterizations of fault roughness lead to variability in the rupture evolution and the resulting near-fault ground motions. Rupture incoherence naturally induced by fault roughness generates high-frequency radiation that follows an ω−2 decay in displacement amplitude spectra. Because dynamic rupture simulations are computationally expensive, we test several kinematic source approximations designed to emulate the observed dynamic behavior. When simplifying the rough-fault geometry, we find that perturbations in local moment tensor orientation are important, while perturbations in local source location are not. Thus, a planar fault can be assumed if the local strike, dip, and rake are maintained. We observe that dynamic rake angle variations are anti-correlated with the local dip angles. Testing two parameterizations of dynamically consistent Yoffe-type source-time function, we show that the seismic wavefield of the approximated kinematic ruptures well reproduces the radiated seismic waves of the complete dynamic source process. This finding opens a new avenue for an improved pseudo-dynamic source characterization that captures the effects of fault roughness on earthquake rupture evolution. By including also the correlations between kinematic source parameters, we outline a new pseudo-dynamic rupture modeling approach for broadband ground-motion simulation.

Accounting for Fault Roughness in Pseudo-Dynamic Ground-Motion Simulations

Science.gov (United States)

Mai, P. Martin; Galis, Martin; Thingbaijam, Kiran K. S.; Vyas, Jagdish C.; Dunham, Eric M.

2017-09-01

Geological faults comprise large-scale segmentation and small-scale roughness. These multi-scale geometrical complexities determine the dynamics of the earthquake rupture process, and therefore affect the radiated seismic wavefield. In this study, we examine how different parameterizations of fault roughness lead to variability in the rupture evolution and the resulting near-fault ground motions. Rupture incoherence naturally induced by fault roughness generates high-frequency radiation that follows an ω-2 decay in displacement amplitude spectra. Because dynamic rupture simulations are computationally expensive, we test several kinematic source approximations designed to emulate the observed dynamic behavior. When simplifying the rough-fault geometry, we find that perturbations in local moment tensor orientation are important, while perturbations in local source location are not. Thus, a planar fault can be assumed if the local strike, dip, and rake are maintained. We observe that dynamic rake angle variations are anti-correlated with the local dip angles. Testing two parameterizations of dynamically consistent Yoffe-type source-time function, we show that the seismic wavefield of the approximated kinematic ruptures well reproduces the radiated seismic waves of the complete dynamic source process. This finding opens a new avenue for an improved pseudo-dynamic source characterization that captures the effects of fault roughness on earthquake rupture evolution. By including also the correlations between kinematic source parameters, we outline a new pseudo-dynamic rupture modeling approach for broadband ground-motion simulation.

Accounting for Fault Roughness in Pseudo-Dynamic Ground-Motion Simulations

KAUST Repository

Mai, Paul Martin; Galis, Martin; Thingbaijam, Kiran Kumar; Vyas, Jagdish Chandra; Dunham, Eric M.

2017-01-01

Geological faults comprise large-scale segmentation and small-scale roughness. These multi-scale geometrical complexities determine the dynamics of the earthquake rupture process, and therefore affect the radiated seismic wavefield. In this study, we examine how different parameterizations of fault roughness lead to variability in the rupture evolution and the resulting near-fault ground motions. Rupture incoherence naturally induced by fault roughness generates high-frequency radiation that follows an ω−2 decay in displacement amplitude spectra. Because dynamic rupture simulations are computationally expensive, we test several kinematic source approximations designed to emulate the observed dynamic behavior. When simplifying the rough-fault geometry, we find that perturbations in local moment tensor orientation are important, while perturbations in local source location are not. Thus, a planar fault can be assumed if the local strike, dip, and rake are maintained. We observe that dynamic rake angle variations are anti-correlated with the local dip angles. Testing two parameterizations of dynamically consistent Yoffe-type source-time function, we show that the seismic wavefield of the approximated kinematic ruptures well reproduces the radiated seismic waves of the complete dynamic source process. This finding opens a new avenue for an improved pseudo-dynamic source characterization that captures the effects of fault roughness on earthquake rupture evolution. By including also the correlations between kinematic source parameters, we outline a new pseudo-dynamic rupture modeling approach for broadband ground-motion simulation.

New Pleomagnetic Evidence for Counter Clockwise Rotation of the Dofan Magmatic Segment Linked to Variation in Fault Slip Directions Along the Different Fault Systems, Main Ethiopian Rift.

Science.gov (United States)

Birke, T. K.; Nugsse, K.

2017-12-01

Twenty-six paleomagnetic sites were sampled from basalt, trachyte and ignimbrite flows of the Dofan magmatic segment, Southern Afar Depression. The samples were then cut in to 200 standard and their Natural Remanent Magnetization (NRM) directions were measured using the JR6A Spinner Magnetometer, of Addis Ababa University. Twin specimens from same sample were subjected to stepwise alternative field (AF) and thermal (TH) demagnetizations respectively with the corresponding directional measurements done at each step. Directional analysis of individual specimens revealed either one or two components of NRM; the first is isolated below a temperature of 300°C or AF field below 20mT; the second is isolated above those steps and defined straight lines directed towards the origin, which were interpreted as the Characteristic Remanent Magnetization (ChRM) acquired during cooling. Rock magnetic experiments on representative specimens indicated that the dominant magnetic minerals are titanium poor titanomagnetite with few cases of titanohematites. The overall mean directions calculated for the 24 stable polarity sites of Dofan is Dec=351.8°, Inc=11.5° (N=24, K=21.4, α95=6.5°). When these values are compared with the 1.5 Ma mean expected geomagnetic dipole reference field directions Dec=1.0°, Inc=16.4° (N=32, K=105.6, α95=2.3°) obtained from African Apparent Polar Wander Path Curve (Besse & Courtillot, 1991, 2003); a difference in declination DD=-9.2°± 5.6° and inclination DI=4.9°±5.5° are determined. This declination difference is interpreted as counterclockwise rotation of the Dofan segment about vertical axis and it is consistent with previous paleomagnetic reports in Fentale area (Kidane et al., 2009) and also with the recent analogue models of RE-Orientation of extension directions and pure extensional faulting at the oblique rift margins of the Main Ethiopian Rift (MER) (Corti et al., 2013).

Fault Activity in the Terrebonne Trough, Southeastern Louisiana: A Continuation of Salt-Withdrawal Fault Activity from the Miocene into the late Quaternary and Implication for Subsidence Hot-Spots

Science.gov (United States)

Akintomide, A. O.; Dawers, N. H.

2017-12-01

The observed displacement along faults in southeastern Louisiana has raised questions about the kinematic history of faults during the Quaternary. The Terrebonne Trough, a Miocene salt withdrawal basin, is bounded by the Golden Meadow fault zone on its northern boundary; north dipping, so-called counter-regional faults, together with a subsurface salt ridge, define its southern boundary. To date, there are relatively few published studies on fault architecture and kinematics in the onshore area of southeastern Louisiana. The only publically accessible studies, based on 2d seismic reflection profiles, interpreted faults as mainly striking east-west. Our interpretation of a 3-D seismic reflection volume, located in the northwestern Terrebonne Trough, as well as industry well log correlations define a more complex and highly-segmented fault architecture. The northwest striking Lake Boudreaux fault bounds a marsh on the upthrown block from Lake Boudreaux on the downthrown block. To the east, east-west striking faults are located at the Montegut marsh break and north of Isle de Jean Charles. Portions of the Lake Boudreaux and Isle de Jean Charles faults serve as the northern boundary of the Madison Bay subsidence hot-spot. All three major faults extend to the top of the 3d seismic volume, which is inferred to image latest Pleistocene stratigraphy. Well log correlation using 11+ shallow markers across these faults and kinematic techniques such as stratigraphic expansion indices indicate that all three faults were active in the middle(?) and late Pleistocene. Based on expansion indices, both the Montegut and Isle de Jean Charles faults were active simultaneously at various times, but with different slip rates. There are also time intervals when the Lake Boudreaux fault was slipping at a faster rate compared to the east-west striking faults. Smaller faults near the margins of the 3d volume appear to relate to nearby salt stocks, Bully Camp and Lake Barre. Our work to date

The geometry of the active strike-slip El Tigre Fault, Precordillera of San Juan, Central-Western Argentina: integrating resistivity surveys with structural and geomorphological data

Science.gov (United States)

Fazzito, Sabrina Y.; Cortés, José M.; Rapalini, Augusto E.; Terrizzano, Carla M.

2013-07-01

The geometry and related geomorphological features of the right-lateral strike-slip El Tigre Fault, one of the main morphostructural discontinuities in the Central-Western Precordillera of Argentina, were investigated. Achievements of this survey include: recognition of structural and geometrical discontinuities along the fault trace, identification and classification of landforms associated with local transpressional and transtensional sectors, observation of significant changes in the fault strike and detection of right and left bends of different wavelength. In the Central Segment of the El Tigre Fault, 2D electrical resistivity tomography surveys were carried out across the fault zone. The resistivity imaging permitted to infer the orientation of the main fault surface, the presence of blind fault branches along the fault zone, tectonic tilting of the Quaternary sedimentary cover, subsurface structure of pressure ridges and depth to the water table. Based on this information, it is possible to characterize the El Tigre Fault also as an important hydro-geological barrier. Our survey shows that the main fault surface changes along different segments from a high-angle to a subvertical setting whilst the vertical-slip component is either reverse or normal, depending on the local transpressive or transtensive regime induced by major bends along the trace. These local variations are expressed as sections of a few kilometres in length with relatively homogeneous behaviour and frequently separated by oblique or transversal structures.

Quantitative evaluation of fault coverage for digitalized systems in NPPs using simulated fault injection method

International Nuclear Information System (INIS)

Kim, Suk Joon

2004-02-01

Even though digital systems have numerous advantages such as precise processing of data, enhanced calculation capability over the conventional analog systems, there is a strong restriction on the application of digital systems to the safety systems in nuclear power plants (NPPs). This is because we do not fully understand the reliability of digital systems, and therefore we cannot guarantee the safety of digital systems. But, as the need for introduction of digital systems to safety systems in NPPs increasing, the need for the quantitative analysis on the safety of digital systems is also increasing. NPPs, which are quite conservative in terms of safety, require proving the reliability of digital systems when applied them to the NPPs. Moreover, digital systems which are applied to the NPPs are required to increase the overall safety of NPPs. however, it is very difficult to evaluate the reliability of digital systems because they include the complex fault processing mechanisms at various levels of the systems. Software is another obstacle in reliability assessment of the systems that requires ultra-high reliability. In this work, the fault detection coverage for the digital system is evaluated using simulated fault injection method. The target system is the Local Coincidence Logic (LCL) processor in Digital Plant Protection System (DPPS). However, as the LCL processor is difficult to design equally for evaluating the fault detection coverage, the LCL system has to be simplified. The simulations for evaluating the fault detection coverage of components are performed by dividing into two cases and the failure rates of components are evaluated using MIL-HDBK-217F. Using these results, the fault detection coverage of simplified LCL system is evaluated. In the experiments, heartbeat signals were just emitted at regular interval after executing logic without self-checking algorithm. When faults are injected into the simplified system, fault occurrence can be detected by

Armenia-To Trans-Boundary Fault: AN Example of International Cooperation in the Caucasus

Science.gov (United States)

Karakhanyan, A.; Avagyan, A.; Avanesyan, M.; Elashvili, M.; Godoladze, T.; Javakishvili, Z.; Korzhenkov, A.; Philip, S.; Vergino, E. S.

2012-12-01

Studies of a trans-boundary active fault that cuts through the border of Armenia to Georgia in the area of the Javakheti volcanic highland have been conducted since 2007. The studies have been implemented based on the ISTC 1418 and NATO SfP 983284 Projects. The Javakheti Fault is oriented to the north-northwest and consists of individual segments displaying clear left-stepping trend. Fault mechanism is represented by right-lateral strike-slip with normal-fault component. The fault formed distinct scarps, deforming young volcanic and glacial sediments. The maximum-size displacements are recorded in the central part of the fault and range up to 150-200 m by normal fault and 700-900 m by right-lateral strike-slip fault. On both flanks, fault scarps have younger appearance, and displacement size there decreases to tens of meters. Fault length is 80 km, suggesting that maximum fault magnitude is estimated at 7.3 according to the Wells and Coppersmith (1994) relation. Many minor earthquakes and a few stronger events (1088, Mw=6.4, 1899 Mw=6.4, 1912, Mw=6.4 and 1925, Mw=5.6) are associated with the fault. In 2011/2012, we conducted paleoseismological and archeoseismological studies of the fault. By two paleoseismological trenches were excavated in the central part of the fault, and on its northern and southern flanks. The trenches enabled recording at least three strong ancient earthquakes. Presently, results of radiocarbon age estimations of those events are expected. The Javakheti Fault may pose considerable seismic hazard for trans-boundary areas of Armenia and Georgia as its northern flank is located at the distance of 15 km from the Baku-Ceyhan pipeline.

Radiation between segments of the seated human body

DEFF Research Database (Denmark)

Sørensen, Dan Nørtoft

2002-01-01

Detailed radiation properties for a thermal manikin were predicted numerically. The view factors between individual body-segments and between the body-segments and the outer surfaces were tabulated. On an integral basis, the findings compared well to other studies and the results showed...... that situations exist for which radiation between individual body segments is important....

Analysis of different power grid segmentation and transmission schemes for power system security improvement

International Nuclear Information System (INIS)

Shami, U.T.; Chaudhary, M.S.

2015-01-01

This paper explores the power grid segmentation concept for power system stability improvement in detail. First, the firewall property of grid segmentation is investigated for a two area network. Then two HVDC technologies, LCC and VSC, are compared for the same network. A two area VSC-AC segmented network is then compared with two area VSC segmented network. Suitable segmentation topology and suitable number of VSC segmented areas are then investigated. Simulation results show that grid segmentation offers network stability during fault conditions and VSC is the most suitable choice for segmentation over LCC. Results further show that having large number of DC segmented areas and using the radial segmentation topology improves the stability of the overall system. All the simulations were carried out in PSS at the rate E software provided by SIEMENS discussed. Section IV discusses the test systems under study in this research. Section V compares and analyzes the simulation results. Section VI contains the conclusion. (author)

Constraining slip rates and spacings for active normal faults

Science.gov (United States)

Cowie, Patience A.; Roberts, Gerald P.

2001-12-01

Numerous observations of extensional provinces indicate that neighbouring faults commonly slip at different rates and, moreover, may be active over different time intervals. These published observations include variations in slip rate measured along-strike of a fault array or fault zone, as well as significant across-strike differences in the timing and rates of movement on faults that have a similar orientation with respect to the regional stress field. Here we review published examples from the western USA, the North Sea, and central Greece, and present new data from the Italian Apennines that support the idea that such variations are systematic and thus to some extent predictable. The basis for the prediction is that: (1) the way in which a fault grows is fundamentally controlled by the ratio of maximum displacement to length, and (2) the regional strain rate must remain approximately constant through time. We show how data on fault lengths and displacements can be used to model the observed patterns of long-term slip rate where measured values are sparse. Specifically, we estimate the magnitude of spatial variation in slip rate along-strike and relate it to the across-strike spacing between active faults.

A compendium of computer codes in fault tree analysis

International Nuclear Information System (INIS)

Lydell, B.

1981-03-01

In the past ten years principles and methods for a unified system reliability and safety analysis have been developed. Fault tree techniques serve as a central feature of unified system analysis, and there exists a specific discipline within system reliability concerned with the theoretical aspects of fault tree evaluation. Ever since the fault tree concept was established, computer codes have been developed for qualitative and quantitative analyses. In particular the presentation of the kinetic tree theory and the PREP-KITT code package has influenced the present use of fault trees and the development of new computer codes. This report is a compilation of some of the better known fault tree codes in use in system reliability. Numerous codes are available and new codes are continuously being developed. The report is designed to address the specific characteristics of each code listed. A review of the theoretical aspects of fault tree evaluation is presented in an introductory chapter, the purpose of which is to give a framework for the validity of the different codes. (Auth.)

Ground Deformation Related to Caldera Collapse and Ring-Fault Activity

KAUST Repository

Liu, Yuan-Kai

2018-05-01

Volcanic subsidence, caused by partial emptying of magma in the subsurface reservoir has long been observed by spaceborne radar interferometry. Monitoring long-term crustal deformation at the most notable type of volcanic subsidence, caldera, gives us insights of the spatial and hazard-related information of subsurface reservoir. Several subsiding calderas, such as volcanoes on the Galapagos islands have shown a complex ground deformation pattern, which is often composed of a broad deflation signal affecting the entire edifice and a localized subsidence signal focused within the caldera floor. Although numerical or analytical models with multiple reservoirs are proposed as the interpretation, geologically and geophysically evidenced ring structures in the subsurface are often ignored. Therefore, it is still debatable how deep mechanisms relate to the observed deformation patterns near the surface. We aim to understand what kind of activities can lead to the complex deformation. Using two complementary approaches, we study the three-dimensional geometry and kinematics of deflation processes evolving from initial subsidence to later collapse of calderas. Firstly, the analog experiments analyzed by structure-from-motion photogrammetry (SfM) and particle image velocimetry (PIV) helps us to relate the surface deformation to the in-depth structures. Secondly, the numerical modeling using boundary element method (BEM) simulates the characteristic deformation patterns caused by a sill-like source and a ring-fault. Our results show that the volcano-wide broad deflation is primarily caused by the emptying of the deep magma reservoir, whereas the localized deformation on the caldera floor is related to ring-faulting at a shallower depth. The architecture of the ring-fault to a large extent determines the deformation localization on the surface. Since series evidence for ring-faulting at several volcanoes are provided, we highlight that it is vital to include ring-fault

Ground Deformation Related to Caldera Collapse and Ring-Fault Activity

KAUST Repository

Liu, Yuan-Kai

2018-01-01

Volcanic subsidence, caused by partial emptying of magma in the subsurface reservoir has long been observed by spaceborne radar interferometry. Monitoring long-term crustal deformation at the most notable type of volcanic subsidence, caldera, gives us insights of the spatial and hazard-related information of subsurface reservoir. Several subsiding calderas, such as volcanoes on the Galapagos islands have shown a complex ground deformation pattern, which is often composed of a broad deflation signal affecting the entire edifice and a localized subsidence signal focused within the caldera floor. Although numerical or analytical models with multiple reservoirs are proposed as the interpretation, geologically and geophysically evidenced ring structures in the subsurface are often ignored. Therefore, it is still debatable how deep mechanisms relate to the observed deformation patterns near the surface. We aim to understand what kind of activities can lead to the complex deformation. Using two complementary approaches, we study the three-dimensional geometry and kinematics of deflation processes evolving from initial subsidence to later collapse of calderas. Firstly, the analog experiments analyzed by structure-from-motion photogrammetry (SfM) and particle image velocimetry (PIV) helps us to relate the surface deformation to the in-depth structures. Secondly, the numerical modeling using boundary element method (BEM) simulates the characteristic deformation patterns caused by a sill-like source and a ring-fault. Our results show that the volcano-wide broad deflation is primarily caused by the emptying of the deep magma reservoir, whereas the localized deformation on the caldera floor is related to ring-faulting at a shallower depth. The architecture of the ring-fault to a large extent determines the deformation localization on the surface. Since series evidence for ring-faulting at several volcanoes are provided, we highlight that it is vital to include ring-fault

Effects of Fault Segmentation, Mechanical Interaction, and Structural Complexity on Earthquake-Generated Deformation

Science.gov (United States)

Haddad, David Elias

2014-01-01

Earth's topographic surface forms an interface across which the geodynamic and geomorphic engines interact. This interaction is best observed along crustal margins where topography is created by active faulting and sculpted by geomorphic processes. Crustal deformation manifests as earthquakes at centennial to millennial timescales. Given that…

Talc-bearing serpentinite and the creeping section of the San Andreas fault.

Science.gov (United States)

Moore, Diane E; Rymer, Michael J

2007-08-16

The section of the San Andreas fault located between Cholame Valley and San Juan Bautista in central California creeps at a rate as high as 28 mm yr(-1) (ref. 1), and it is also the segment that yields the best evidence for being a weak fault embedded in a strong crust. Serpentinized ultramafic rocks have been associated with creeping faults in central and northern California, and serpentinite is commonly invoked as the cause of the creep and the low strength of this section of the San Andreas fault. However, the frictional strengths of serpentine minerals are too high to satisfy the limitations on fault strength, and these minerals also have the potential for unstable slip under some conditions. Here we report the discovery of talc in cuttings of serpentinite collected from the probable active trace of the San Andreas fault that was intersected during drilling of the San Andreas Fault Observatory at Depth (SAFOD) main hole in 2005. We infer that the talc is forming as a result of the reaction of serpentine minerals with silica-saturated hydrothermal fluids that migrate up the fault zone, and the talc commonly occurs in sheared serpentinite. This discovery is significant, as the frictional strength of talc at elevated temperatures is sufficiently low to meet the constraints on the shear strength of the fault, and its inherently stable sliding behaviour is consistent with fault creep. Talc may therefore provide the connection between serpentinite and creep in the San Andreas fault, if shear at depth can become localized along a talc-rich principal-slip surface within serpentinite entrained in the fault zone.

How Long Is Long Enough? Estimation of Slip-Rate and Earthquake Recurrence Interval on a Simple Plate-Boundary Fault Using 3D Paleoseismic Trenching

Science.gov (United States)

Wechsler, N.; Rockwell, T. K.; Klinger, Y.; Agnon, A.; Marco, S.

2012-12-01

Models used to forecast future seismicity make fundamental assumptions about the behavior of faults and fault systems in the long term, but in many cases this long-term behavior is assumed using short-term and perhaps non-representative observations. The question arises - how long of a record is long enough to represent actual fault behavior, both in terms of recurrence of earthquakes and of moment release (aka slip-rate). We test earthquake recurrence and slip models via high-resolution three-dimensional trenching of the Beteiha (Bet-Zayda) site on the Dead Sea Transform (DST) in northern Israel. We extend the earthquake history of this simple plate boundary fault to establish slip rate for the past 3-4kyr, to determine the amount of slip per event and to study the fundamental behavior, thereby testing competing rupture models (characteristic, slip-patch, slip-loading, and Gutenberg Richter type distribution). To this end we opened more than 900m of trenches, mapped 8 buried channels and dated more than 80 radiocarbon samples. By mapping buried channels, offset by the DST on both sides of the fault, we obtained for each an estimate of displacement. Coupled with fault crossing trenches to determine event history, we construct earthquake and slip history for the fault for the past 2kyr. We observe evidence for a total of 9-10 surface-rupturing earthquakes with varying offset amounts. 6-7 events occurred in the 1st millennium, compared to just 2-3 in the 2nd millennium CE. From our observations it is clear that the fault is not behaving in a periodic fashion. A 4kyr old buried channel yields a slip rate of 3.5-4mm/yr, consistent with GPS rates for this segment. Yet in spite of the apparent agreement between GPS, Pleistocene to present slip rate, and the lifetime rate of the DST, the past 800-1000 year period appears deficit in strain release. Thus, in terms of moment release, most of the fault has remained locked and is accumulating elastic strain. In contrast, the

Fault Tolerant Control for Civil Structures Based on LMI Approach

Directory of Open Access Journals (Sweden)

Chunxu Qu

2013-01-01

Full Text Available The control system may lose the performance to suppress the structural vibration due to the faults in sensors or actuators. This paper designs the filter to perform the fault detection and isolation (FDI and then reforms the control strategy to achieve the fault tolerant control (FTC. The dynamic equation of the structure with active mass damper (AMD is first formulated. Then, an estimated system is built to transform the FDI filter design problem to the static gain optimization problem. The gain is designed to minimize the gap between the estimated system and the practical system, which can be calculated by linear matrix inequality (LMI approach. The FDI filter is finally used to isolate the sensor faults and reform the FTC strategy. The efficiency of FDI and FTC is validated by the numerical simulation of a three-story structure with AMD system with the consideration of sensor faults. The results show that the proposed FDI filter can detect the sensor faults and FTC controller can effectively tolerate the faults and suppress the structural vibration.

Modeling caprock fracture, CO2 migration and time dependent fault healing: A numerical study.

Science.gov (United States)

MacFarlane, J.; Mukerji, T.; Vanorio, T.

2017-12-01

The Campi Flegrei caldera, located near Naples, Italy, is one of the highest risk volcanoes on Earth due to its recent unrest and urban setting. A unique history of surface uplift within the caldera is characterized by long duration uplift and subsidence cycles which are periodically interrupted by rapid, short period uplift events. Several models have been proposed to explain this history; in this study we will present a hydro-mechanical model that takes into account the caprock that seismic studies show to exist at 1-2 km depth. Specifically, we develop a finite element model of the caldera and use a modified version of fault-valve theory to represent fracture within the caprock. The model accounts for fault healing using a simplified, time-dependent fault sealing model. Multiple fracture events are incorporated by using previous solutions to test prescribed conditions and determine changes in rock properties, such as porosity and permeability. Although fault-valve theory has been used to model single fractures and recharge, this model is unique in its ability to model multiple fracture events. By incorporating multiple fracture events we can assess changes in both long and short-term reservoir behavior at Campi Flegrei. By varying the model inputs, we model the poro-elastic response to CO2 injection at depth and the resulting surface deformation. The goal is to enable geophysicists to better interpret surface observations and predict outcomes from observed changes in reservoir conditions.

Linking fault permeability, fluid flow, and earthquake triggering in a hydrothermally active tectonic setting: Numerical Simulations of the hydrodynamics in the Tjörnes Fracture Zone, Iceland.

Science.gov (United States)

Lupi, M.; Geiger, S.; Graham, C.; Claesson, L.; Richter, B.

2007-12-01

A good insight into the transient fluid flow evolution within a hydrothermal system is of primary importance for the understanding of several geologic processes, for example the hydrodynamic triggering of earthquakes or the formation of mineral deposits. The strong permeability contrast between different crustal layers as well as the high geothermal gradient of these areas are elements that strongly affect the flow behaviour. In addition, the sudden and transient occurrence of joints, faults and magmatic intrusions are likely to change the hydrothermal flow paths in very short time. The Tjörnes Fracture Zone (TFZ) north of Iceland, is such a hydrothermal area where a high geothermal gradient, magmatic bodies, faults, and the strong contrast between sediments and fractured lava layers govern the large-scale fluid flow. The TFZ offsets the Kolbeinsey Ridge and the Northern Rift Zone. It is characterized by km-scale faults that link sub-seafloor sediments and lava layers with deeper crystalline rocks. These structures focus fluid flow and allow for the mixing between cold seawater and deep hydrothermal fluids. A strong seismic activity is present in the TFZ: earthquakes up to magnitude 7 have been recorded over the past years. Hydrogeochemical changes before, during and after a magnitude 5.8 earthquake suggest that the evolving stress state before the earthquake leads to (remote) permeability variations, which alter the fluid flow paths. This is in agreement with recent numerical fluid flow simulations which demonstrate that fluid flow in magmatic- hydrothermal systems is often convective and very sensitive to small variations in permeability. In order to understand the transient fluid flow behaviour in this complex geological environment, we have conducted numerical simulations of heat and mass transport in two geologically realistic cross-sectional models of the TFZ. The geologic models are discretised using finite element and finite volume methods. They hence have

Dynamic earthquake rupture simulations on nonplanar faults embedded in 3D geometrically complex, heterogeneous elastic solids

Energy Technology Data Exchange (ETDEWEB)

Duru, Kenneth, E-mail: kduru@stanford.edu [Department of Geophysics, Stanford University, Stanford, CA (United States); Dunham, Eric M. [Department of Geophysics, Stanford University, Stanford, CA (United States); Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA (United States)

2016-01-15

Dynamic propagation of shear ruptures on a frictional interface in an elastic solid is a useful idealization of natural earthquakes. The conditions relating discontinuities in particle velocities across fault zones and tractions acting on the fault are often expressed as nonlinear friction laws. The corresponding initial boundary value problems are both numerically and computationally challenging. In addition, seismic waves generated by earthquake ruptures must be propagated for many wavelengths away from the fault. Therefore, reliable and efficient numerical simulations require both provably stable and high order accurate numerical methods. We present a high order accurate finite difference method for: a) enforcing nonlinear friction laws, in a consistent and provably stable manner, suitable for efficient explicit time integration; b) dynamic propagation of earthquake ruptures along nonplanar faults; and c) accurate propagation of seismic waves in heterogeneous media with free surface topography. We solve the first order form of the 3D elastic wave equation on a boundary-conforming curvilinear mesh, in terms of particle velocities and stresses that are collocated in space and time, using summation-by-parts (SBP) finite difference operators in space. Boundary and interface conditions are imposed weakly using penalties. By deriving semi-discrete energy estimates analogous to the continuous energy estimates we prove numerical stability. The finite difference stencils used in this paper are sixth order accurate in the interior and third order accurate close to the boundaries. However, the method is applicable to any spatial operator with a diagonal norm satisfying the SBP property. Time stepping is performed with a 4th order accurate explicit low storage Runge–Kutta scheme, thus yielding a globally fourth order accurate method in both space and time. We show numerical simulations on band limited self-similar fractal faults revealing the complexity of rupture

3D Defect Localization on Exothermic Faults within Multi-Layered Structures Using Lock-In Thermography: An Experimental and Numerical Approach.

Science.gov (United States)

Bae, Ji Yong; Lee, Kye-Sung; Hur, Hwan; Nam, Ki-Hwan; Hong, Suk-Ju; Lee, Ah-Yeong; Chang, Ki Soo; Kim, Geon-Hee; Kim, Ghiseok

2017-10-13

Micro-electronic devices are increasingly incorporating miniature multi-layered integrated architectures. However, the localization of faults in three-dimensional structure remains challenging. This study involved the experimental and numerical estimation of the depth of a thermally active heating source buried in multi-layered silicon wafer architecture by using both phase information from an infrared microscopy and finite element simulation. Infrared images were acquired and real-time processed by a lock-in method. It is well known that the lock-in method can increasingly improve detection performance by enhancing the spatial and thermal resolution of measurements. Operational principle of the lock-in method is discussed, and it is represented that phase shift of the thermal emission from a silicon wafer stacked heat source chip (SSHSC) specimen can provide good metrics for the depth of the heat source buried in SSHSCs. Depth was also estimated by analyzing the transient thermal responses using the coupled electro-thermal simulations. Furthermore, the effects of the volumetric heat source configuration mimicking the 3D through silicon via integration package were investigated. Both the infrared microscopic imaging with the lock-in method and FE simulation were potentially useful for 3D isolation of exothermic faults and their depth estimation for multi-layered structures, especially in packaged semiconductors.

Double Fault Detection of Cone-Shaped Redundant IMUs Using Wavelet Transformation and EPSA

Directory of Open Access Journals (Sweden)

Wonhee Lee

2014-02-01

Full Text Available A model-free hybrid fault diagnosis technique is proposed to improve the performance of single and double fault detection and isolation. This is a model-free hybrid method which combines the extended parity space approach (EPSA with a multi-resolution signal decomposition by using a discrete wavelet transform (DWT. Conventional EPSA can detect and isolate single and double faults. The performance of fault detection and isolation is influenced by the relative size of noise and fault. In this paper; the DWT helps to cancel the high frequency sensor noise. The proposed technique can improve low fault detection and isolation probability by utilizing the EPSA with DWT. To verify the effectiveness of the proposed fault detection method Monte Carlo numerical simulations are performed for a redundant inertial measurement unit (RIMU.

Double Fault Detection of Cone-Shaped Redundant IMUs Using Wavelet Transformation and EPSA

Science.gov (United States)

Lee, Wonhee; Park, Chan Gook

2014-01-01

A model-free hybrid fault diagnosis technique is proposed to improve the performance of single and double fault detection and isolation. This is a model-free hybrid method which combines the extended parity space approach (EPSA) with a multi-resolution signal decomposition by using a discrete wavelet transform (DWT). Conventional EPSA can detect and isolate single and double faults. The performance of fault detection and isolation is influenced by the relative size of noise and fault. In this paper; the DWT helps to cancel the high frequency sensor noise. The proposed technique can improve low fault detection and isolation probability by utilizing the EPSA with DWT. To verify the effectiveness of the proposed fault detection method Monte Carlo numerical simulations are performed for a redundant inertial measurement unit (RIMU). PMID:24556675

Active fault and other geological studies for seismic assessment: present state and problems

International Nuclear Information System (INIS)

Kakimi, Toshihiro

1997-01-01

Evaluation system of earthquakes from an active fault is, in Japan, based on the characteristic earthquake model of a wide sense that postulates essentially the same (nearly the maximum) magnitude and recurrence interval during the recent geological times. Earthquake magnitude M is estimated by empirical relations among M, surface rupture length L, and surface fault displacement D per event of the earthquake faults on land in Japan. Recurrence interval R of faulting/earthquake is calculated from D and the long-term slip rate S of a fault as R=D/S. Grouping or segmentation of complicatedly distributed faults is an important, but difficult problem in order to distinguish a seismogenic fault unit corresponding to an individual characteristic earthquake. If the time t of the latest event is obtained, the 'cautiousness' of a fault can be judged from R-t or t/R. According to this idea, several faults whose t/R exceed 0.5 have been designated as the 'precaution faults' having higher probability of earthquake occurrence than the others. A part of above evaluation has been introduced at first into the seismic-safety examination system of NPPs in 1978. According to the progress of research on active faults, the weight of interest in respect to the seismic hazard assessment shifted gradually from the historic data to the fault data. Most of recent seismic hazard maps have been prepared in consideration with active faults on land in Japan. Since the occurrence of the 1995 Hyogoken-Nanbu earthquake, social attention has been concentrated upon the seismic hazard due to active faults, because this event was generated from a well-known active fault zone that had been warned as a 'precaution fault'. In this paper, a few recent topics on other geological and geotechnical researches aiming at improving the seismic safety of NPPs in Japan were also introduced. (J.P.N.)

Active fault and other geological studies for seismic assessment: present state and problems

Energy Technology Data Exchange (ETDEWEB)

Kakimi, Toshihiro [Nuclear Power Engineering Corp., Tokyo (Japan)

1997-03-01

Evaluation system of earthquakes from an active fault is, in Japan, based on the characteristic earthquake model of a wide sense that postulates essentially the same (nearly the maximum) magnitude and recurrence interval during the recent geological times. Earthquake magnitude M is estimated by empirical relations among M, surface rupture length L, and surface fault displacement D per event of the earthquake faults on land in Japan. Recurrence interval R of faulting/earthquake is calculated from D and the long-term slip rate S of a fault as R=D/S. Grouping or segmentation of complicatedly distributed faults is an important, but difficult problem in order to distinguish a seismogenic fault unit corresponding to an individual characteristic earthquake. If the time t of the latest event is obtained, the `cautiousness` of a fault can be judged from R-t or t/R. According to this idea, several faults whose t/R exceed 0.5 have been designated as the `precaution faults` having higher probability of earthquake occurrence than the others. A part of above evaluation has been introduced at first into the seismic-safety examination system of NPPs in 1978. According to the progress of research on active faults, the weight of interest in respect to the seismic hazard assessment shifted gradually from the historic data to the fault data. Most of recent seismic hazard maps have been prepared in consideration with active faults on land in Japan. Since the occurrence of the 1995 Hyogoken-Nanbu earthquake, social attention has been concentrated upon the seismic hazard due to active faults, because this event was generated from a well-known active fault zone that had been warned as a `precaution fault`. In this paper, a few recent topics on other geological and geotechnical researches aiming at improving the seismic safety of NPPs in Japan were also introduced. (J.P.N.)

Seismic trapped modes in the oroville and san andreas fault zones.

Science.gov (United States)

Li, Y G; Leary, P; Aki, K; Malin, P

1990-08-17

Three-component borehole seismic profiling of the recently active Oroville, California, normal fault and microearthquake event recording with a near-fault three-component borehole seismometer on the San Andreas fault at Parkfield, California, have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals. These wave trains are interpreted as fault zone-trapped seismic modes. Parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers, as shallow as 4 kilometers, and extend 12 kilometers along the fault on either side of the recording station. Selected Oroville and Parkfield wave forms are modeled as the fundamental and first higher trapped SH modes of a narrow low-velocity layer at the fault. Modeling results suggest that the Oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second, whereas at Parkfield, the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1.1 to 1.8 kilometers per second. These low-velocity layers are probably the rupture planes on which earthquakes occur.

Geomorphic evidence of active faults growth in the Norcia seismic area (central Apennines, Italy)

Science.gov (United States)

Materazzi, Marco; Aringoli, Domenico; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

2016-04-01

Fault-growth by segment linkage is one of the fundamental processes controlling the evolution, in both time and the space, of fault systems. In fact, step-like trajectories shown by length-displacement diagrams for individual fault arrays suggest that the development of evolved structures result by the linkage of single fault segments. The type of interaction between faults and the rate at which faults reactivate not only control the long term tectonic evolution of an area, but also influence the seismic hazard, as earthquake recurrence intervals tend to decrease as fault slip rate increase. The use of Geomorphological investigations represents an important tool to constrain the latest history of active faults. In this case, attention has to be given to recognize morphostructural, historical, environmental features at the surface, since they record the long-term seismic behavior due to the fault growth processes (Tondi and Cello, 2003). The aim of this work is to investigate the long term morphotectonic evolution of a well know seismic area in the central Apennines: the Norcia intramontane basin (Aringoli et al., 2005). The activity of the Norcia seismic area is characterized by moderate events and by strong earthquakes with maximum intensities of X-XI degrees MCS and equivalent magnitudes around 6.5±7.0 (CPTI, 2004). Based on the morphostructural features as well as on the historical seismicity of the area, we may divide the Norcia seismic area into three minor basins roughly NW-SE oriented: the Preci sub-basin in the north; the S. Scolastica and the Castel S. Maria sub-basins in the south. The wider basin (S. Scolastica) is separated from the other two by ridges transversally oriented with respect the basins themselves; they are the geomorphological response to the tectonic deformation which characterizes the whole area. Other geomorphological evidences of tectonic activity are represented by deformation of old summit erosional surfaces, hydrographic network

FRAMEWORK FOR COMPARING SEGMENTATION ALGORITHMS

Directory of Open Access Journals (Sweden)

G. Sithole

2015-05-01

Full Text Available The notion of a ‘Best’ segmentation does not exist. A segmentation algorithm is chosen based on the features it yields, the properties of the segments (point sets it generates, and the complexity of its algorithm. The segmentation is then assessed based on a variety of metrics such as homogeneity, heterogeneity, fragmentation, etc. Even after an algorithm is chosen its performance is still uncertain because the landscape/scenarios represented in a point cloud have a strong influence on the eventual segmentation. Thus selecting an appropriate segmentation algorithm is a process of trial and error. Automating the selection of segmentation algorithms and their parameters first requires methods to evaluate segmentations. Three common approaches for evaluating segmentation algorithms are ‘goodness methods’, ‘discrepancy methods’ and ‘benchmarks’. Benchmarks are considered the most comprehensive method of evaluation. This paper shortcomings in current benchmark methods are identified and a framework is proposed that permits both a visual and numerical evaluation of segmentations for different algorithms, algorithm parameters and evaluation metrics. The concept of the framework is demonstrated on a real point cloud. Current results are promising and suggest that it can be used to predict the performance of segmentation algorithms.

Non-Andersonian conjugate strike-slip faults: Observations, theory, and tectonic implications

International Nuclear Information System (INIS)

Yin, A; Taylor, M H

2008-01-01

Formation of conjugate strike-slip faults is commonly explained by the Anderson fault theory, which predicts a X-shaped conjugate fault pattern with an intersection angle of ∼30 degrees between the maximum compressive stress and the faults. However, major conjugate faults in Cenozoic collisional orogens, such as the eastern Alps, western Mongolia, eastern Turkey, northern Iran, northeastern Afghanistan, and central Tibet, contradict the theory in that the conjugate faults exhibit a V-shaped geometry with intersection angles of 60-75 degrees, which is 30-45 degrees greater than that predicted by the Anderson fault theory. In Tibet and Mongolia, geologic observations can rule out bookshelf faulting, distributed deformation, and temporal changes in stress state as explanations for the abnormal fault patterns. Instead, the GPS-determined velocity field across the conjugate fault zones indicate that the fault formation may have been related to Hagen-Poiseuille flow in map view involving the upper crust and possibly the whole lithosphere based on upper mantle seismicity in southern Tibet and basaltic volcanism in Mongolia. Such flow is associated with two coeval and parallel shear zones having opposite shear sense; each shear zone produce a set of Riedel shears, respectively, and together the Riedel shears exhibit the observed non-Andersonian conjugate strike-slip fault pattern. We speculate that the Hagen-Poiseuille flow across the lithosphere that hosts the conjugate strike-slip zones was produced by basal shear traction related to asthenospheric flow, which moves parallel and away from the indented segment of the collisional fronts. The inferred asthenospheric flow pattern below the conjugate strike-slip fault zones is consistent with the magnitude and orientations of seismic anisotropy observed across the Tibetan and Mongolian conjugate fault zones, suggesting a strong coupling between lithospheric deformation and asthenospheric flow. The laterally moving

Non-Andersonian conjugate strike-slip faults: Observations, theory, and tectonic implications

Energy Technology Data Exchange (ETDEWEB)

Yin, A [Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90025-1567 (United States); Taylor, M H [Department of Geology, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66044 (United States)], E-mail: yin@ess.ucla.edu

2008-07-01

Formation of conjugate strike-slip faults is commonly explained by the Anderson fault theory, which predicts a X-shaped conjugate fault pattern with an intersection angle of {approx}30 degrees between the maximum compressive stress and the faults. However, major conjugate faults in Cenozoic collisional orogens, such as the eastern Alps, western Mongolia, eastern Turkey, northern Iran, northeastern Afghanistan, and central Tibet, contradict the theory in that the conjugate faults exhibit a V-shaped geometry with intersection angles of 60-75 degrees, which is 30-45 degrees greater than that predicted by the Anderson fault theory. In Tibet and Mongolia, geologic observations can rule out bookshelf faulting, distributed deformation, and temporal changes in stress state as explanations for the abnormal fault patterns. Instead, the GPS-determined velocity field across the conjugate fault zones indicate that the fault formation may have been related to Hagen-Poiseuille flow in map view involving the upper crust and possibly the whole lithosphere based on upper mantle seismicity in southern Tibet and basaltic volcanism in Mongolia. Such flow is associated with two coeval and parallel shear zones having opposite shear sense; each shear zone produce a set of Riedel shears, respectively, and together the Riedel shears exhibit the observed non-Andersonian conjugate strike-slip fault pattern. We speculate that the Hagen-Poiseuille flow across the lithosphere that hosts the conjugate strike-slip zones was produced by basal shear traction related to asthenospheric flow, which moves parallel and away from the indented segment of the collisional fronts. The inferred asthenospheric flow pattern below the conjugate strike-slip fault zones is consistent with the magnitude and orientations of seismic anisotropy observed across the Tibetan and Mongolian conjugate fault zones, suggesting a strong coupling between lithospheric deformation and asthenospheric flow. The laterally moving

Semi-automatic mapping of fault rocks on a Digital Outcrop Model, Gole Larghe Fault Zone (Southern Alps, Italy)