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Sample records for active seismic faults

  1. Searching for Seismically Active Faults in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Custodio, S.; Antunes, V.; Arroucau, P.

    2015-12-01

    The repeated occurrence of large magnitude earthquakes in southwest Iberia in historical and instrumental times suggests the presence of active fault segments in the region. However, due to an apparently diffuse seismicity pattern defining a broad region of distributed deformation west of Gibraltar Strait, the question of the location, dimension and geometry of such structures is still open to debate. We recently developed a new algorithm for earthquake location in 3D complex media with laterally varying interface depths, which allowed us to relocate 2363 events having occurred from 2007 to 2013, using P- and S-wave catalog arrival times obtained from the Portuguese Meteorological Institute (IPMA, Instituto Portugues do Mar e da Atmosfera), for a study area lying between 8.5˚W and 5˚W in longitude and 36˚ and 37.5˚ in latitude. The most remarkable change in the seismicity pattern after relocation is an apparent concentration of events, in the North of the Gulf of Cadiz, along a low angle northward-dipping plane rooted at the base of the crust, which could indicate the presence of a major fault. If confirmed, this would be the first structure clearly illuminated by seismicity in a region that has unleashed large magnitude earthquakes. Here, we present results from the joint analysis of focal mechanism solutions and waveform similarity between neighboring events from waveform cross-correlation in order to assess whether those earthquakes occur on the same fault plane.

  2. Fault mirrors of seismically active faults: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, L.; Song, S.; Suppe, J.

    2013-12-01

    Many faults are decorated with naturally polished and glossy surfaces named fault mirrors (FMs) formed during slips. The characterization of FMs is of paramount importance to investigate physico-chemical processes controlling dynamic fault mechanics during earthquakes. Here we present detailed microstructural and mineralogical observations of the FMs from borehole cores of seismically active faults. The borehole cores were recovered from 600 to 800 m depth located in the hanging wall of the Hsiaotungshi fault in Taiwan which ruptured during 1935 Mw7.1 Hsinchu-Taichung earthquake. Scanning electron microscope (SEM) images of FMs show that two distinct textural domains, fault gouge and coated materials (nanograins, melt patchs, and graphite), were cut by a well-defined boundary. Melt patches and graphite, determined by X-ray diffraction (XRD), Transmission electron microscope (TEM), and SEM-EDS analysis, were found to be distributed heterogeneously on the slip surfaces. On the basis of the current kinematic cross section of the Hsiaotungshi fault, all the FMs were exhumed less than 5 km, where ambient temperatures are less than 150°C. It seems that the amorphous materials on the FMs were generated by seismic slips. The sintering nanograins coating the slip surfaces was also suggested to be produced at high slip rates from both natural observation and recent rock deformation experiments. In addition, graphite could be produced by seismic slips and lubricate the fault based on the rock deformation experiments. Our observation suggests that the FMs were composed of several indicators of coseismic events (melt patches, sintering nanograins, and graphite) corresponding to small thermal perturbation generated by seismic slips. Although the contribution of these coseismic indicators on frictional behavior remains largely unknown, it suggests that multiple dynamic weakening mechanisms such as flash heating, powder lubrication and graphitization may be involved during

  3. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    NASA Astrophysics Data System (ADS)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  4. Active Faults, Modern Seismicity And Block Structure Of Eurasia

    NASA Astrophysics Data System (ADS)

    Gatinsky, Y.; Rundquist, D.

    2004-12-01

    The analysis of on active faults and seismicity shows that the only a northern part of Eurasia should be regarded as an indivisible lithosphere unit. We defined it as the North Eurasian plate (Gatinsky, Rundquist, 2004) unlike the Eurasian plate s.l., which can be used only for paleotectonic reconstructions. The North Eurasian plate is bordered by zones of seismic activity traced along the Gakkel ridge, the Chersky and Stanovoi ranges, the Baikal rift, Altai--Sayany region, northern Tien Shan, Pamir, Hindu Kush and Kopet Dagh, Great Caucasus, northern Anatolia, Rhodopes, Carpathians, eastern and central Alps. Relationships between this plate and Europe west of the Rhine grabens remain ambiguous. The satellite measurements for them seem to be similar (Nocquet, Calais, 2003), but structural and seismic evidences allow suggesting their incipient division. Wide zones between this plate and neighboring ones can be distinguished outside north Eurasia. These zones consist of numerous blocks of various sizes. Block boundaries are mainly characterized by the high seismicity and development of active wrench faults, thrusts or modern rifts. Some of such zones were named earlier as "diffuse plate boundaries" (Stein et al., 2002; Bird et al, 2003). We suggest to name them as "transit zones" because they are situated between large lithosphere plates and as if transfer the stress field of one of them to other. Blocks within the transit zones reveal local divergences in GPS vectors of their displacements in the ITRF system and especially with respect to fixed Eurasia. At the same time data of satellite measurements emphasize the unity of the North Eurasian plate, which moves eastward in absolute coordinates with some clockwise rotation. The stress distribution in inner parts of the continent is being affected by the interaction with different plates and blocks. It can be more effectively illustrated by a «triangle» of the maximal seismic activity of Eurasia in the central Asia

  5. Delineation of Active Basement Faults in the Eastern Tennessee and Charlevoix Intraplate Seismic Zones

    NASA Astrophysics Data System (ADS)

    Powell, C. A.; Langston, C. A.; Cooley, M.

    2013-12-01

    Recognition of distinct, seismogenic basement faults within the eastern Tennessee seismic zone (ETSZ) and the Charlevoix seismic zone (CSZ) is now possible using local earthquake tomography and datasets containing a sufficiently large number of earthquakes. Unlike the New Madrid seismic zone where seismicity clearly defines active fault segments, earthquake activity in the ETSZ and CSZ appears diffuse. New arrival time inversions for hypocenter relocations and 3-D velocity variations using datasets in excess of 1000 earthquakes suggest the presence of distinct basement faults in both seismic zones. In the ETSZ, relocated hypocenters align in near-vertical segments trending NE-SW, parallel to the long dimension of the seismic zone. Earthquakes in the most seismogenic portion of the ETSZ delineate another set of near-vertical faults trending roughly E-ESE. These apparent trends and steep dips are compatible with ETSZ focal mechanism solutions. The solutions are remarkably consistent and indicate strike-slip motion along the entire length of the seismic zone. Relocated hypocenter clusters in the CSZ define planes that trend and dip in directions that are compatible with known Iapitan rift faults. Seismicity defining the planes becomes disrupted where the rift faults encounter a major zone of deformation produced by a Devonian meteor impact. We will perform a joint statistical analysis of hypocenter alignments and focal mechanism nodal plane orientations in the ETSZ and the CSZ to determine the spatial orientations of dominant seismogenic basement faults. Quantifying the locations and dimensions of active basement faults will be important for seismic hazard assessment and for models addressing the driving mechanisms for these intraplate zones.

  6. Newly identified active faults in the Pollino seismic gap, southern Italy, and their seismotectonic significance

    NASA Astrophysics Data System (ADS)

    Brozzetti, Francesco; Cirillo, Daniele; de Nardis, Rita; Cardinali, Mauro; Lavecchia, Giusy; Orecchio, Barbara; Presti, Debora; Totaro, Cristina

    2017-01-01

    The following is a geological study of a Quaternary and active normal fault-system, which crops out in the Pollino area, a seismogenic sector of the Southern Apennines, Italy. From 2010 to 2014, this area was affected by long lasting seismic activity characterized by three major events which occurred in May 2012 (Mw 4.3), in October 2012 (Mw 5.2) and in June 2014 (Mw 4.0). The integration of structural-geological data with morpho-structural and remote sensing analyses, led to define the geometry, the kinematics, the cross-cutting relationships and the slip rates of the inferred active fault segments within and near the epicentral area. We reconstructed an asymmetric extensional pattern characterized by low-angle, E and NNE-dipping faults, and by antithetic, high-angle, SW- to WSW-dipping faults. The geometry of the faults at depth was constrained using high-resolution hypocenter distributions. The overall system fits well with the deformation field obtained from focal mechanisms and geodetic data. Comparing the fault pattern with the time-space evolution of the Pollino seismic activity, we identified the seismogenic sources in two, near-parallel, WSW-dipping faults, whose seismogenic potential were assessed. The peculiar perpendicular-to-fault-strike evolution of the seismic activity, is discussed in the frame of the reconstructed seismotectonic model.

  7. Recent high-resolution seismic reflection studies of active faults in the Puget Lowland

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2005-12-01

    In the past four years, new high-resolution seismic surveys have filled in key gaps in our understanding of active structures beneath the Puget Lowland, western Washington State. Although extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area, these marine profiles lack coverage on land and in shallow or restricted waterways. The recent high-resolution seismic surveys have targeted key structures beneath water bodies that large ships cannot navigate, and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. The surveys can therefore bridge the gap between paleoseismic and marine geophysical studies, and test key elements of models proposed by regional-scale geophysical studies. Results from these surveys have: 1) documented several meters of vertical displacement on at least two separate faults in the Olympia area; 2) clarified the relationship between the Catfish Lake scarp and the underlying kink band in the Tacoma fault zone; 3) provided a first look at the structures beneath the north portion of the western Tacoma fault zone, north of previous marine profiles; 4) documented that deformation along the Seattle fault extends well east of Lake Sammamish; 5) imaged the Seattle fault beneath the Vasa Park trench; and 6) documented multiple fault strands in and south of the Seattle fault zone south of Bellevue. The results better constrain interpretations of paleoseismic investigations of past earthquakes on these faults, and provide targets for future paleoseismic studies.

  8. The offshore Yangsan fault activity in the Quaternary, SE Korea: Analysis of high-resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Kim, Han-Joon; Moon, Seonghoon; Jou, Hyeong-Tae; Lee, Gwang Hoon; Yoo, Dong Geun; Lee, Sang Hoon; Kim, Kwang Hee

    2016-12-01

    The NNE-trending dextral Yangsan fault is a > 190-km-long structure in the Korean Peninsula traced to the southeastern coast. The scarcity of Quaternary deposits onland precludes any detailed investigation of the Quaternary activity and structure of the Yangsan fault using seismic reflection profiling. We acquired offshore high-resolution seismic profiles to investigate the extension of the Yangsan fault and constrain its Quaternary activity using stratigraphic markers. The seismic profiles reveal a NNE-trending fault system consisting of a main fault and an array of subsidiary faults that displaced Quaternary sequences. Stratigraphic analysis of seismic profiles indicates that the offshore faults were activated repeatedly in the Quaternary. The up-to-the-east sense of throw on the main fault and plan-view pattern of the fault system are explained by dextral strike-slip faulting. The main fault, when projected toward the Korean Peninsula along its strike, aligns well with the Yangsan fault. We suggest that the offshore fault system is a continuation of the Yangsan fault and has spatial correlation with weak but ongoing seismicity.

  9. Active faulting in low- to moderate-seismicity regions: the SAFE project

    NASA Astrophysics Data System (ADS)

    Sebrier, M.; Safe Consortium

    2003-04-01

    SAFE (Slow Active Faults in Europe) is an EC-FP5 funded multidisciplinary effort which proposes an integrated European approach in identifying and characterizing active faults as input for evaluating seismic hazard in low- to moderate-seismicity regions. Seismically active western European regions are generally characterized by low hazard but high risk, due to the concentration of human and material properties with high vulnerability. Detecting, and then analysing, tectonic deformations that may lead to destructive earthquakes in such areas has to take into account three major limitations: - the typical climate of western Europe (heavy vegetation cover and/or erosion) ; - the subdued geomorphic signature of slowly deforming faults ; - the heavy modification of landscape by human activity. The main objective of SAFE, i.e., improving the assessment of seismic hazard through understanding of the mechanics and recurrence of active faults in slowly deforming regions, is achieved through four major steps : (1) extending geologic and geomorphic investigations of fault activity beyond the Holocene to take into account various time-windows; (2) developing an expert system that combines diverse lines of geologic, seismologic, geomorphic, and geophysical evidence to diagnose the existence and seismogenic potential of slow active faults; (3) delineating and characterising high seismic risk areas of western Europe, either from historical or geological/geomorphic evidence; (4) demonstrating and discussing the impact of the project results on risk assessment through a seismic scenario in the Basel-Mulhouse pilot area. To take properly into account known differences in source behavior, these goals are pursued both in extensional (Lower and Upper Rhine Graben, Catalan Coast) and compressional tectonic settings (southern Upper Rhine Graben, Po Plain, and Provence). Two arid compressional regions (SE Spain and Moroccan High Atlas) have also been selected to address the limitations

  10. Probabilistic seismic hazard study based on active fault and finite element geodynamic models

    NASA Astrophysics Data System (ADS)

    Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

    2016-04-01

    We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and

  11. Assessing low-activity faults for the seismic safety of dams

    SciTech Connect

    Page, W.D.; Savage, W.U.; McLaren, M.K.

    1995-12-31

    Dams have been a familiar construct in the northern Sierra Nevada range in California (north of the San Joaquin River) since the forty-niners and farmers diverted water to their gold mines and farms in the mid 19th century. Today, more than 370 dams dot the region from the Central Valley to the eastern escarpment. Fifty-five more dam streams on the eastern slope. The dams are of all types: 240 earth fill; 56 concrete gravity; 45 rock and earth fills; 35 rock fill; 14 concrete arch; 9 hydraulic fill; and 29 various other types. We use the northern Sierra Nevada to illustrate the assessment of low-activity faults for the seismic safety of dams. The approach, techniques, and methods of evaluation are applicable to other regions characterized by low seismicity and low-activity faults having long recurrence intervals. Even though several moderate earthquakes had shaken the Sierra Nevada since 1849 (for example, the 1875 magnitude 5.8 Honey Lake and the 1909 magnitudes 5 and 5.5 Downieville earthquakes), seismic analyses for dams in the area generally were not performed prior to the middle of this century. Following the 1971 magnitude 6.7 San Fernando earthquake, when the hydraulic-fill Lower Van Norman Dam in southern California narrowly escaped catastrophic failure, the California Division of Safety of Dams and the Federal Energy Regulatory Commission required seismic safety to be addressed with increasing rigor. In 1975, the magnitude 5.7 Oroville earthquake on the Cleveland Hill fault near Oroville Dam in the Sierra Nevada foothills, showed convincingly that earthquakes and surface faulting could occur within the range. Following this event, faults along the ancient Foothills fault system have been extensively investigated at dam sites.

  12. Increased radon-222 in soil gas because of cumulative seismicity at active faults

    NASA Astrophysics Data System (ADS)

    Koike, Katsuaki; Yoshinaga, Tohru; Ueyama, Takayoshi; Asaue, Hisafumi

    2014-12-01

    This study demonstrates how the radon-222 (222Rn) concentration of soil gas at an active fault is sensitive to cumulative recent seismicity by examining seven active faults in western Japan. The 222Rn concentration was found to correlate well with the total earthquake energy within a 100-km radius of each fault. This phenomenon can probably be ascribed to the increase of pore pressure around the source depth of 222Rn in shallow soil caused by frequently induced strain. This increase in pore pressure can enhance the ascent velocity of 222Rn carrier gas as governed by Darcy's law. Anomalous 222Rn concentrations are likely to originate from high gas velocities, rather than increased accumulations of parent nuclides. The high velocities also can yield unusual young gas under the radioactive nonequilibrium condition of short elapsed time since 222Rn generation. The results suggest that ongoing seismicity in the vicinity of an active fault can cause accumulation of strain in shallow fault soils. Therefore, the 222Rn concentration is a possible gauge for the degree of strain accumulation.

  13. Dense seismic networks as a tool to characterize active faulting in regions of slow deformation

    NASA Astrophysics Data System (ADS)

    Custódio, Susana; Arroucau, Pierre; Carrilho, Fernando; Cesca, Simone; Dias, Nuno; Matos, Catarina; Vales, Dina

    2016-04-01

    The theory of plate tectonics states that the relative motion between lithospheric plates is accommodated at plate boundaries, where earthquakes occur on long faults. However, earthquakes with a wide range of magnitudes also occur both off plate boundaries, in intra-plate settings, and along discontinuous, diffuse plate boundaries. These settings are characterized by low rates of lithospheric deformation. A fundamental limitation in the study of slowly deforming regions is the lack of high-quality observations. In these regions, earthquake catalogs have traditionally displayed diffuse seismicity patterns. The location, geometry and activity rate of faults - all basic parameters for understanding fault dynamics - are usually poorly known. The dense seismic networks deployed in the last years around the world have opened new windows in observational seismology. Although high-magnitude earthquakes are rare in regions of slow deformation, low-magnitude earthquakes are well observable on the time-scale of these deployments. In this presentation, we will show how data from dense seismic deployments can be used to characterize faulting in regions of slow deformation. In particular, we will present the case study of western Iberia, a region undergoing low-rate deformation and which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). The methods that we employ include automated earthquake detection methods to lower the completeness magnitude of catalogs, earthquake relocations, focal mechanisms patterns, waveform similarity and clustering analysis.

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

    NASA Astrophysics Data System (ADS)

    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

  15. Active faults and induced seismicity in the Val d'Agri area (Southern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Valoroso, L.; Improta, L.; Chiaraluce, L.; Di Stefano, R.; Ferranti, L.; Govoni, A.; Chiarabba, C.

    2009-07-01

    The NW-SE trending Val d'Agri extensional basin is one of the regions in Italy with the highest seismogenic potential. Field data do not univocally define which of the fault systems bordering the basin on the two opposite sides is accommodating the active deformation. In this study, we detect and locate, by using an automatic picking procedure, almost 2000 low-magnitude earthquakes (-0.2 < ML < 2.7) recorded by a dense network during a 13-months-long seismic experiment. Events are mostly located along the southwestern flank of the basin. To the south, intense swarm-type microseismicity defines a major cluster ~5km wide from 1 to 5km depth. To the west, a clear alignment of events, characterized by normal faulting kinematics, defines a NE-dipping normal fault between 1 and 6km depth. The upward continuation of this structure, ~5km long, matches a mapped active normal fault recognized by field and palaeoseismological surveys. A temporal correlation found between the intense swarm-type microseismicity and the water level changes in the nearby artificial Pertusillo lake suggests that this seismicity is reservoir-induced.

  16. Fault activation after vigorous eruption: the December 8, 2015 seismic swarm at Mt. Etna

    NASA Astrophysics Data System (ADS)

    Alparone, Salvatore; Bonforte, Alessandro; Guglielmino, Francesco; Maiolino, Vincenza; Puglisi, Giuseppe; Ursino, Andrea

    2016-04-01

    From December 2, 2015, volcanic activity suddenly occurred on Mt. Etna with very violent fire fountaining at central crater, known also as "Voragine". This activity continued with other intense episodes at the same crater during the three following days and involving also, in turn, all the other three summit craters. This sudden eruption produced a rapid deflation of the volcano and was followed, from December 8, by a seismic swarm, with almost eighty earthquakes during this day, located on the uppermost segment of the Pernicana-Provenzana fault system (PFS). This seismicity was characterized by shallow foci (from few hundred meters until 1.5 km below the sea level) and mainshock with 3.6 magnitude. In order to investigate and measure the dynamics controlling and accompanying the PFS activation, a dataset composed of C-Band Sentinel-1A data has been used for SAR Interferometry (InSAR) analysis. Some interferograms have been generated from ascending and descending orbits in order to analyze both short- and long-term deformation. The availability of GPS data allowed comparing and integrating them with InSAR for ground truth and modeling aims. The surface kinematics and modeling obtained by DInSAR and GPS data and integration have been compared to the distribution of the seismicity and related focal mechanisms in order to define the fault geometry and motion. Moreover, essential constraints have been achieved about the PFS dynamic and its relationship with the intense volcanic activity occurred.

  17. Active faults in the deformation zone off Noto Peninsula, Japan, revealed by high- resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Okamura, Y.; Murakami, F.; Kimura, H.; Ikehara, K.

    2008-12-01

    Recently, a lot of earthquakes occur in Japan. The deformation zone which many faults and folds have concentrated exists on the Japan Sea side of Japan. The 2007 Noto Hanto Earthquake (MJMA 6.9) and 2007 Chuetsu-oki Earthquake (MJMA 6.8) were caused by activity of parts of faults in this deformation zone. The Noto Hanto Earthquake occurred on 25 March, 2007 under the northwestern coast of Noto Peninsula, Ishikawa Prefecture, Japan. This earthquake is located in Quaternary deformation zone that is continued from northern margin of Noto Peninsula to southeast direction (Okamura, 2007a). National Institute of Advanced Industrial Science and Technology (AIST) carried out high-resolution seismic survey using Boomer and 12 channels short streamer cable in the northern part off Noto Peninsula, in order to clarify distribution and activities of active faults in the deformation zone. A twelve channels short streamer cable with 2.5 meter channel spacing developed by AIST and private corporation is designed to get high resolution seismic profiles in shallow sea area. The multi-channel system is possible to equip on a small fishing boat, because the data acquisition system is based on PC and the length of the cable is short and easy to handle. Moreover, because the channel spacing is short, this cable is very effective for a high- resolution seismic profiling survey in the shallow sea, and seismic data obtained by multi-channel cable can be improved by velocity analysis and CDP stack. In the northern part off Noto Peninsula, seismic profiles depicting geologic structure up to 100 meters deep under sea floor were obtained. The most remarkable reflection surface recognized in the seismic profiles is erosion surface at the Last Glacial Maximum (LGM). In the western part, sediments about 30 meters (40 msec) thick cover the erosional surface that is distributed under the shelf shallower than 100m in depth and the sediments thin toward offshore and east. Flexures like deformation in

  18. Investigating active faulting in the south-central Chilean forearc by local seismicity and moment tensor inversions

    NASA Astrophysics Data System (ADS)

    Rietbrock, A.; Bohm, M.; Echtler, H.; Melnick, D.; Bruhn, C.; Bataille, K.

    2004-12-01

    The seismological ISSA experiment is giving a detailed insight into the seismicity distribution of southern Chile, where major earthquakes (M>8) have repeatedly ruptured the surface, involving vertical offsets of several meters. During a nearly 5-month observation period in 1999 and 2000 a temporary seismic network recorded approximately 350 local earthquakes. Two localized areas, North and South of the Arauco peninsula, showed a very high seismic activity in and above the interplate seismic zone of the Nazca-South America convergent margin. We used a double-difference relocation technique to obtain detailed images of the seismicity distribution in these areas. We also determined fault plane solutions to interpret the observed alignment of earthquakes hypocenters. Due to the low signal to noise ratio reliable first motion reading were difficult to achieve, which only very few clear readings. To overcome this problem we used moment tensor inversions to estimate reliable source mechanisms. However, for small magnitude earthquakes (<5) the biggest obstacle is the alignment of synthetic and observed waveforms. Inverting only for the amplitude spectrum, and therefore dropping the information in the phase spectrum can mostly circumvent the alignment problem. The two clusters investigated show high waveform correlation coefficients for most of the earthquakes indicating that possibly changes in fluid pressure can be responsible for triggering the events. After relocation most of the hypocenters in each of the two clusters align on a eastward dipping fault. Source mechanisms obtained indicate thrust faulting, where one of the possible fault planes aligns with the steep eastward dipping fault based on the seismicity distribution. These faults are reaching down to the top of the seismogenic zone and may serve as pathways for ascending fluids released in the subduction process. Active crustal-scale faulting below and active uplift of the coast account for active tectonic

  19. Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

    SciTech Connect

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; Moridis, George J.

    2015-03-01

    We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismic moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.

  20. The 2013 earthquake swarm in Helike, Greece: seismic activity at the root of old normal faults

    NASA Astrophysics Data System (ADS)

    Kapetanidis, V.; Deschamps, A.; Papadimitriou, P.; Matrullo, E.; Karakonstantis, A.; Bozionelos, G.; Kaviris, G.; Serpetsidaki, A.; Lyon-Caen, H.; Voulgaris, N.; Bernard, P.; Sokos, E.; Makropoulos, K.

    2015-09-01

    The Corinth Rift in Central Greece has been studied extensively during the past decades, as it is one of the most seismically active regions in Europe. It is characterized by normal faulting and extension rates between 6 and 15 mm yr-1 in an approximately N10E° direction. On 2013 May 21, an earthquake swarm was initiated with a series of small events 4 km southeast of Aigion city. In the next days, the seismic activity became more intense, with outbursts of several stronger events of magnitude between 3.3 and 3.7. The seismicity migrated towards the east during June, followed by a sudden activation of the western part of the swarm on July 15th. More than 1500 events have been detected and manually analysed during the period between 2013 May 21 and August 31, using over 15 local stations in epicentral distances up to 30 km and a local velocity model determined by an error minimization method. Waveform similarity-based analysis was performed, revealing several distinct multiplets within the earthquake swarm. High-resolution relocation was applied using the double-difference algorithm HypoDD, incorporating both catalogue and cross-correlation differential traveltime data, which managed to separate the initial seismic cloud into several smaller, densely concentrated spatial clusters of strongly correlated events. Focal mechanism solutions for over 170 events were determined using P-wave first motion polarities, while regional waveform modelling was applied for the calculation of moment tensors for the 18 largest events of the sequence. Selected events belonging to common spatial groups were considered for the calculation of composite mechanisms to characterize different parts of the swarm. The solutions are mainly in agreement with the regional NNE-SSW extension, representing typical normal faulting on 30-50° north-dipping planes, while a few exhibit slip in an NNE-SSW direction, on a roughly subhorizontal plane. Moment magnitudes were calculated by spectral analysis

  1. Active Fault Geometry and Crustal Deformation Along the San Andreas Fault System Through San Gorgonio Pass, California: The View in 3D From Seismicity

    NASA Astrophysics Data System (ADS)

    Nicholson, C.; Hauksson, E.; Plesch, A.

    2012-12-01

    Understanding the 3D geometry and deformation style of the San Andreas fault (SAF) is critical to accurate dynamic rupture and ground motion prediction models. We use 3D alignments of hypocenter and focal mechanism nodal planes within a relocated earthquake catalog (1981-2011) [Hauksson et al., 2012] to develop improved 3D fault models for active strands of the SAF and adjacent secondary structures. Through San Gorgonio Pass (SGP), earthquakes define a mechanically layered crust with predominantly high-angle strike-slip faults in the upper ~10 km, while at greater depth, intersecting sets of strike-slip, oblique slip and low-angle thrust faults define a wedge-shaped volume deformation of the lower crust. In some places, this interface between upper and lower crustal deformation may be an active detachment fault, and may have controlled the down-dip extent of recent fault rupture. Alignments of hypocenters and nodal planes define multiple principal slip surfaces through SGP, including a through-going steeply-dipping predominantly strike-slip Banning fault strand at depth that upward truncates a more moderately dipping (40°-50°) blind, oblique North Palm Springs fault. The North Palm Springs fault may be the active down-dip extension of the San Gorgonio Pass thrust offset at depth by the principal, through-going Banning strand. In the northern Coachella Valley, seismicity indicates that the Garnet Hill and Banning fault strands are most likely sub-parallel and steeply dipping (~70°NE) to depths of 8-10 km, where they intersect and merge with a stack of moderately dipping to low-angle oblique thrust faults. Gravity and water well data confirm that these faults are sub-parallel and near vertical in the upper 2-3 km. Although the dense wedge of deep seismicity below SGP and largely south of the SAF contains multiple secondary fault sets of different orientations, the predominant fault set appears to be a series of en echelon NW-striking oblique strike-slip faults

  2. Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

    DOE PAGES

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; ...

    2015-03-01

    We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismicmore » moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.« less

  3. High-resolution 3D seismic reflection imaging across active faults and its impact on seismic hazard estimation in the Tokyo metropolitan area

    NASA Astrophysics Data System (ADS)

    Ishiyama, Tatsuya; Sato, Hiroshi; Abe, Susumu; Kawasaki, Shinji; Kato, Naoko

    2016-10-01

    We collected and interpreted high-resolution 3D seismic reflection data across a hypothesized fault scarp, along the largest active fault that could generate hazardous earthquakes in the Tokyo metropolitan area. The processed and interpreted 3D seismic cube, linked with nearby borehole stratigraphy, suggests that a monocline that deforms lower Pleistocene units is unconformably overlain by middle Pleistocene conglomerates. Judging from structural patterns and vertical separation on the lower-middle Pleistocene units and the ground surface, the hypothesized scarp was interpreted as a terrace riser rather than as a manifestation of late Pleistocene structural growth resulting from repeated fault activity. Devastating earthquake scenarios had been predicted along the fault in question based on its proximity to the metropolitan area, however our new results lead to a significant decrease in estimated fault length and consequently in the estimated magnitude of future earthquakes associated with reactivation. This suggests a greatly reduced seismic hazard in the Tokyo metropolitan area from earthquakes generated by active intraplate crustal faults.

  4. High-resolution shallow reflection seismic image and surface evidence of the Upper Tiber Basin active faults (Northern Apennines, Italy)

    USGS Publications Warehouse

    Donne, D.D.; Plccardi, L.; Odum, J.K.; Stephenson, W.J.; Williams, R.A.

    2007-01-01

    Shallow seismic reflection prospecting has been carried out in order to investigate the faults that bound to the southwest and northeast the Quaternary Upper Tiber Basin (Northern Apennines, Italy). On the northeastern margin of the basin a ??? 1 km long reflection seismic profile images a fault segment and the associated up to 100 meters thick sediment wedge. Across the southwestern margin a 0.5 km-long seismic profile images a 50-55??-dipping extensional fault, that projects to the scarp at the base of the range-front, and against which a 100 m thick syn-tectonic sediment wedge has formed. The integration of surface and sub-surface data allows to estimate at least 190 meters of vertical displacement along the fault and a slip rate around 0.25 m/kyr. Southwestern fault might also be interpreted as the main splay structure of regional Alto Tiberina extensional fault. At last, the 1917 Monterchi earthquake (Imax=X, Boschi et alii, 2000) is correlable with an activation of the southwestern fault, and thus suggesting the seismogenic character of this latter.

  5. Physical modeling of the formation and evolution of seismically active fault zones

    USGS Publications Warehouse

    Ponomarev, A.V.; Zavyalov, A.D.; Smirnov, V.B.; Lockner, D.A.

    1997-01-01

    Acoustic emission (AE) in rocks is studied as a model of natural seismicity. A special technique for rock loading has been used to help study the processes that control the development of AE during brittle deformation. This technique allows us to extend to hours fault growth which would normally occur very rapidly. In this way, the period of most intense interaction of acoustic events can be studied in detail. Characteristics of the acoustic regime (AR) include the Gutenberg-Richter b-value, spatial distribution of hypocenters with characteristic fractal (correlation) dimension d, Hurst exponent H, and crack concentration parameter Pc. The fractal structure of AR changes with the onset of the drop in differential stress during sample deformation. The change results from the active interaction of microcracks. This transition of the spatial distribution of AE hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b-value. The characteristic structure that develops in the low-energy background AE is similar to the sequence of the strongest microfracture events. When the AR fractal structure develops, the variations of d and b are synchronous and d = 3b. This relation which occurs once the fractal structure is formed only holds for average values of d and b. Time variations of d and b are anticorrelated. The degree of temporal correlation of AR has time variations that are similar to d and b variations. The observed variations in laboratory AE experiments are compared with natural seismicity parameters. The close correspondence between laboratory-scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature. ?? 1997 Elsevier Science B.V. All rights reserved.

  6. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    NASA Astrophysics Data System (ADS)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  7. Characterising Active Fault Earthquake Sources Beneath the Coastal Environments of Christchurch and Wellington Cities, New Zealand, Using Seismic Reflection Profiles and Fault Displacement Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Barnes, P.; Nodder, S.; Gorman, A. R.; Woelz, S.; Orpin, A. R.

    2014-12-01

    The coastal cities of Christchurch and Wellington, New Zealand, lie in different tectonic settings within the obliquely convergent Pacific-Australian plate boundary zone. Both cities have experienced damaging earthquakes in the last three years, which highlight the importance of locating and characterising hidden active faults close to urban areas. The devastating and geologically complex Canterbury earthquake sequence of 2010-2012 developed on the periphery of the plate boundary, and reactivated several previously unidentified strike-slip and reverse faults. Major aftershocks initially beneath land, generally migrated eastward over time, and finally advanced offshore into Pegasus Bay. A study of active submarine faulting beneath the bay highlights the role of inherited crustal structure and inversion tectonics. Marine seismic reflection data reveals that faults have very low slip rate and negligible post-glacial (<15 ka) deformation, which is consistent with inferred long recurrence intervals between large magnitude (Mw>6) earthquakes. Wellington City is surrounded by numerous high-slip rate strike-slip faults overlying the Hikurangi subduction zone. A dense network of secondary basement structures previously recognised throughout the region, mainly from tectonic geomorphology, have, until recently, been considered mostly inactive and excluded from seismic hazard models. We used high-resolution geophysical, bathymetric and sediment-core data to determine the structure, earthquake history and earthquake potential of a newly discovered active reverse fault beneath the inner reaches of Wellington Harbour. The fault has a slip rate of ~0.6 ± 0.3 mm/y, and a vertical displacement history indicating at least two large magnitude (Mw 6.3-7.1), surface-rupturing earthquakes in the last 10 ka. We infer that the fault extends southwards onshore beneath the city and potentially into Cook Strait, and represents a significant previously unrecognised seismic hazard.

  8. Active fault mapping in Karonga-Malawi after the December 19, 2009 Ms 6.2 seismic event

    NASA Astrophysics Data System (ADS)

    Macheyeki, A. S.; Mdala, H.; Chapola, L. S.; Manhiça, V. J.; Chisambi, J.; Feitio, P.; Ayele, A.; Barongo, J.; Ferdinand, R. W.; Ogubazghi, G.; Goitom, B.; Hlatywayo, J. D.; Kianji, G. K.; Marobhe, I.; Mulowezi, A.; Mutamina, D.; Mwano, J. M.; Shumba, B.; Tumwikirize, I.

    2015-02-01

    The East African Rift System (EARS) has natural hazards - earthquakes, volcanic eruptions, and landslides along the faulted margins, and in response to ground shaking. Strong damaging earthquakes have been occurring in the region along the EARS throughout historical time, example being the 7.4 (Ms) of December 1910. The most recent damaging earthquake is the Karonga earthquake in Malawi, which occurred on 19th December, 2009 with a magnitude of 6.2 (Ms). The earthquake claimed four lives and destroyed over 5000 houses. In its effort to improve seismic hazard assessment in the region, Eastern and Southern Africa Seismological Working Group (ESARSWG) under the sponsorship of the International Program on Physical Sciences (IPPS) carried out a study on active fault mapping in the region. The fieldwork employed geological and geophysical techniques. The geophysical techniques employed are ground magnetic, seismic refraction and resistivity surveys but are reported elsewhere. This article gives findings from geological techniques. The geological techniques aimed primarily at mapping of active faults in the area in order to delineate presence or absence of fault segments. Results show that the Karonga fault (the Karonga fault here referred to as the fault that ruptured to the surface following the 6th-19th December 2009 earthquake events in the Karonga area) is about 9 km long and dominated by dip slip faulting with dextral and insignificant sinistral components and it is made up of 3-4 segments of length 2-3 km. The segments are characterized by both left and right steps. Although field mapping show only 9 km of surface rupture, maximum vertical offset of about 43 cm imply that the surface rupture was in little excess of 14 km that corresponds with Mw = 6.4. We recommend the use or integration of multidisciplinary techniques in order to better understand the fault history, mechanism and other behavior of the fault/s for better urban planning in the area.

  9. Sag-ponding and its Significance in determining Paleo-seismic events along the active strike- slip fault

    NASA Astrophysics Data System (ADS)

    Li, C.; Zhang, P.; Yuan, D.

    2007-12-01

    During the development of one active fault, we really want to know how it behaves and what it will do next. This mostly depends on the record and preservation of the information showing the action of the fault. Sparse young sediments or sediments with coarse grain along most of big strike-slip faults make it hard record and preserve the vestige of the paleo-seismic events. This extremely restricts the development of the Paleo-seismic research. Sag-ponding as well as the deposits in ponds, which are formed by the movement of the fault, can help settling the difficulty. Periodic sag-ponding is a feature to which should be paid more attention along the strike-slip fault, it can develop a pond to capture plenty fine sediments which well record the action of the faults. Sag-ponding can easily be found on the main active strike-slip faults in northern and eastern Tibet. By disclosing the sag-ponding depositions with 3-D excavations, sediment distribution and characters of relevant sag-ponds, and the relation between the sag-ponding and faulting were discussed. 1. Mechanism of the formation of the sag-pond When the valleys and ridges intersecting with the fault are displaced, the fault scarps will block the flow of the streams cut by the fault, or make the gullies develop ancon-like bend. This would form a space for water-storage, and thus a sag-pond comes into being. If the fault behaves like this many times, multi-sag-ponding will occur. 2. Rhythmic sag-ponding deposition features and stratigraphic sequence (1) Vertical characteristics. Observed from the stratigraphic profiles disclosed by the excavation, stratigraphic sequence shows good rhythms. There are several rhythms in each pond, and one rhythm is composed of the lower coarse layers and the upper fine layers. That is, the grains are coarser below and finer upward. (2) Transverse variation. In the direction parallel to the fault, the deposition center of each sag-pond appears regular movement, or migration

  10. Active normal fault network of the Apulian Ridge (Eastern Mediterranean Sea) imaged by multibeam bathymetry and seismic data

    NASA Astrophysics Data System (ADS)

    Pellegrini, Claudio; Marchese, Fabio; Savini, Alessandra; Bistacchi, Andrea

    2016-04-01

    The Apulian ridge (North-eastern Ionian margin - Mediterranean Sea) is formed by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a NNW-SSE penetrative normal fault system and is part of the present foreland system of both the Apennine to the west and the Hellenic arc to the east. The geometry, age, architecture and kinematics of the fault network were investigated integrating data of heterogeneous sources, provided by previous studies: regional scale 2D seismics and three wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, very high resolution seismic (VHRS - Sparker and Chirp-sonar data), multi-beam echosounder bathymetry and results from sedimentological and geo-chronological analysis of sediment samples collected on the seabed. Multibeam bathymetric data allowed in particular assessing the 3D continuity of structures imaged in 2D seismics, thanks to the occurrence of continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides), revealing the vertical extent and finite displacement associated to fault scarps. A penetrative network of relatively small faults, always showing a high dip angle, composes the NNW-SSE normal fault system, resulting in frequent relay zones, which are particularly well imaged by seafloor geomorphology. In addition, numerous fault scarps appear to be roughly coeval with quaternary submarine mass-wasting deposits colonised by Cold-Water Corals (CWC). Coral colonies, yielding ages between 11 and 14 kA, develop immediately on top of late Pleistocene mass-wasting deposits. Mutual cross-cutting relationships have been recognized between fault scarps and landslides, indicating that, at least in places, these features may be coeval. We suppose that fault activity lasted at least as far as the Holocene-Pleistocene boundary and that the NNW-SSW normal fault network in the Apulian Plateau can be

  11. Present activity and seismogenic potential of a low-angle normal fault system (Città di Castello, Italy): Constraints from surface geology, seismic reflection data and seismicity

    NASA Astrophysics Data System (ADS)

    Brozzetti, Francesco; Boncio, Paolo; Lavecchia, Giusy; Pace, Bruno

    2009-01-01

    We present new constraints on an active low-angle normal fault system in the Città di Castello-Sansepolcro basin (CSB) of the northern Apennines of Italy. New field data from the geological survey of the Carta Geologica d' Italia (CARG project) define the surface geometry of the normal fault system and lead to an interpretation of the CROP 03 deep-crust seismic reflection profile (Castiglion Fiorentino-Urbania segment), with particular attention paid to the geometry of the Plio-Quaternary extensional structures. Surface and sub-surface geological data are integrated with instrumental and historical seismicity in order to define the seismotectonics of the area. Low-angle east-dipping reflectors are the seismic expression of the well-known Altotiberina Fault (AF), a regional extensional detachment on which both east- and west-dipping high-angle faults, bounding the CSB, sole out. The AF breakaway zone is located ˜ 10 km west of the CSB. Within the extensional allochthon, synthetic east-dipping planes prevail. Displacement along the AF is ˜ 4.5 km, which agrees with the cumulative offset due to its synthetic splays. The evolution of the CSB has mainly been controlled by the east-dipping fault system, at least since Early Pleistocene time; this system is still active and responsible for the seismicity of the area. A low level of seismic activity was recorded instrumentally within the CSB, but several damaging earthquakes have occurred in historical times. The instrumental seismicity and the intensity data points of the largest historical earthquakes (5 events with maximum MCS intensity of IX to IX-X) allow us to propose two main seismogenic structures: the Monte Santa Maria Tiberina (Mmax = 5.9) and Città di Castello (Mmax up to 6.5) normal faults. Both are synthetic splays of the AF detachment, dipping to the NE at moderate (45-50°) to low (25-30°) angles and cutting the upper crust up to the surface. This study suggests that low-angle normal faults (at least

  12. Active Faults and Seismic Sources of the Middle East Region: Earthquake Model of the Middle East (EMME) Project

    NASA Astrophysics Data System (ADS)

    Gulen, L.; EMME WP2 Team*

    2011-12-01

    The Earthquake Model of the Middle East (EMME) Project is a regional project of the GEM (Global Earthquake Model) project (http://www.emme-gem.org/). The EMME project covers Turkey, Georgia, Armenia, Azerbaijan, Syria, Lebanon, Jordan, Iran, Pakistan, and Afghanistan. Both EMME and SHARE projects overlap and Turkey becomes a bridge connecting the two projects. The Middle East region is tectonically and seismically very active part of the Alpine-Himalayan orogenic belt. Many major earthquakes have occurred in this region over the years causing casualties in the millions. The EMME project consists of three main modules: hazard, risk, and socio-economic modules. The EMME project uses PSHA approach for earthquake hazard and the existing source models have been revised or modified by the incorporation of newly acquired data. The most distinguishing aspect of the EMME project from the previous ones is its dynamic character. This very important characteristic is accomplished by the design of a flexible and scalable database that permits continuous update, refinement, and analysis. An up-to-date earthquake catalog of the Middle East region has been prepared and declustered by the WP1 team. EMME WP2 team has prepared a digital active fault map of the Middle East region in ArcGIS format. We have constructed a database of fault parameters for active faults that are capable of generating earthquakes above a threshold magnitude of Mw≥5.5. The EMME project database includes information on the geometry and rates of movement of faults in a "Fault Section Database", which contains 36 entries for each fault section. The "Fault Section" concept has a physical significance, in that if one or more fault parameters change, a new fault section is defined along a fault zone. So far 6,991 Fault Sections have been defined and 83,402 km of faults are fully parameterized in the Middle East region. A separate "Paleo-Sites Database" includes information on the timing and amounts of fault

  13. Martian seismicity through time from surface faulting

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Tanaka, Kenneth L.; Banerdt, W. B.; Tralli, D.

    1991-01-01

    An objective of future Mars missions involves emplacing a seismic network on Mars to determine the internal structure of the planet. An argument based on the relative geologic histories of the terrestrial planets suggests that Mars should be seismically more active than the Moon, but less active than the Earth. The seismicity is estimated which is expected on Mars through time from slip on faults visible on the planets surface. These estimates of martian seismicity must be considered a lower limit as only structures produced by shear faulting visible at the surface today are included (i.e., no provision is made for buried structures or non-shear structures); in addition, the estimate does not include seismic events that do not produce surface displacement (e.g., activity associated with hidden faults, deep lithospheric processes or volcanism) or events produced by tidal triggering or meteorite impacts. Calibration of these estimates suggests that Mars may be many times more seismically active than the Moon.

  14. Probabilistic seismic hazard at Mt. Etna (Italy): The contribution of local fault activity in mid-term assessment

    NASA Astrophysics Data System (ADS)

    Azzaro, R.; D'Amico, S.; Peruzza, L.; Tuvè, T.

    2013-02-01

    In this work, we tackle the problem of seismic hazard at Etna deriving from the recurrent seismogenic activity of local faults, by adopting two independent methods based on probabilistic approaches. We assess the hazard in terms of macroseismic intensity and represent the occurrence probability calculated for different exposure times both on maps and at fault scale. Seismic hazard maps obtained by applying the "site approach" through the SASHA code and a new probabilistic attenuation model, indicate the eastern flank of the volcano as the most hazardous, with expected intensity (Iexp) in 50 years (i.e. the standard exposure time adopted in the seismic regulations) ranging from degrees IX to X EMS. In shorter exposure periods (20, 10, 5 years), values of Iexp up to IX are also reached in the same area, but they are clearly determined by the earthquakes generated by the Timpe fault system. In order to quantify the contribution of local seismogenic sources to the hazard of the region, we reconstruct the seismic history of each fault and calculate with SASHA the probability that earthquakes of a given intensity may be generated in different exposure times. Results confirm the high level of hazard due to the S. Tecla, Moscarello and Fiandaca faults especially for earthquakes of moderate intensity, i.e. VI ≤ I0 ≤ VII, with probabilities respectively exceeding 50% and 20% in 10 years, and 30% and 10% in 5 years. Occurrence probability of major events (I0 ≥ VIII) at the fault scale has also been investigated by statistics on intertimes. Under stationary assumptions we obtain a probability of 6.8% in 5 years for each structure; by introducing the time-dependency (time elapsed since the last event occurred on each fault) through a BPT model, we identify the Moscarello and S. Tecla faults as the most probable sources to be activated in the next 5 years (2013-2017). This result may represent a useful indication to establish priority criteria for actions aimed at reducing

  15. Locating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data

    SciTech Connect

    SGP-TR-150-16

    1995-01-26

    Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is {approx} 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/s, which is sandwiched between two half spaces with relatively higher velocities (P wave velocity 5.60 km/s, and S wave velocity 3.20 km/s). zones having vertical or nearly vertical dipping fault planes.

  16. Using core properties and seismic reflectivity to estimate pore pressure in an active decollement fault

    SciTech Connect

    Tobin, H.J.; Moore, J.C.

    1996-12-31

    In the decollement zone of the Barbados accretionary prism, a 3-D seismic image exhibits patchy high-amplitude negative polarity reflections, which have been attributed to large overpressures confined to the fault zone. We collected laboratory P-wave velocity and porosity vs. pore pressure data, using core samples from and adjacent to the decollement zone at ODP Site 948. Logs constrain density and velocity through the decollement zone at Site 948. We use these data to calibrate the reflectivity of the fault zone to pore pressure through waveform and amplitude models of the fault plane reflections. Modeling of the positive polarity Site 948 reflection indicates that it can be explained by a lithologic boundary coincident with the decollement, without anomalous fault properties. By contrast, the dominantly-negative polarity waveform of the reflection {approx}2 km arcward (beneath Site 947) is best modeled by inserting a 16-19 m thick zone of extremely low impedance into the Site 948 impedance structure, with a gradational return to {open_quotes}normal{close_quotes} impedance just above the positive boundary. Relative amplitudes in this reflection indicate a larger impedance contrast than can be accounted for at sub-lithostatic fluid pressure, based on the core properties data. We conclude that lithostatic pore pressure with attendant hydraulic dilation of the fault zone is required to generate the negative-polarity reflections. Mapping of these reflections thus delineates zones of elevated fluid content and zero effective stress in the fault zone.

  17. Using core properties and seismic reflectivity to estimate pore pressure in an active decollement fault

    SciTech Connect

    Tobin, H.J. ); Moore, J.C. )

    1996-01-01

    In the decollement zone of the Barbados accretionary prism, a 3-D seismic image exhibits patchy high-amplitude negative polarity reflections, which have been attributed to large overpressures confined to the fault zone. We collected laboratory P-wave velocity and porosity vs. pore pressure data, using core samples from and adjacent to the decollement zone at ODP Site 948. Logs constrain density and velocity through the decollement zone at Site 948. We use these data to calibrate the reflectivity of the fault zone to pore pressure through waveform and amplitude models of the fault plane reflections. Modeling of the positive polarity Site 948 reflection indicates that it can be explained by a lithologic boundary coincident with the decollement, without anomalous fault properties. By contrast, the dominantly-negative polarity waveform of the reflection [approx]2 km arcward (beneath Site 947) is best modeled by inserting a 16-19 m thick zone of extremely low impedance into the Site 948 impedance structure, with a gradational return to [open quotes]normal[close quotes] impedance just above the positive boundary. Relative amplitudes in this reflection indicate a larger impedance contrast than can be accounted for at sub-lithostatic fluid pressure, based on the core properties data. We conclude that lithostatic pore pressure with attendant hydraulic dilation of the fault zone is required to generate the negative-polarity reflections. Mapping of these reflections thus delineates zones of elevated fluid content and zero effective stress in the fault zone.

  18. Active faulting in the Inner California Borderlands: new constraints from high-resolution multichannel seismic and multibeam bathymetric data.

    NASA Astrophysics Data System (ADS)

    Bormann, J. M.; Holmes, J. J.; Sahakian, V. J.; Klotsko, S.; Kent, G.; Driscoll, N. W.; Harding, A. J.; Wesnousky, S. G.

    2014-12-01

    Geodetic data indicate that faults offshore of Southern California accommodate 6-8 mm/yr of dextral Pacific-North American relative plate motion. In the Inner California Borderlands (ICB), modern strike-slip deformation is overprinted on topography formed during plate boundary reorganization 30-15 Ma. Despite its proximity to urban Southern California, the hazard posed by active faults in the ICB remains poorly understood. We acquired a 4000-line-km regional grid of high-resolution, 2D multichannel seismic (MCS) reflection data and multibeam bathymetry to examine the fault architecture and tectonic evolution of the ICB. We interpret the MCS data using a sequence stratigraphic approach to establish a chronostratigraphy and identify discrete episodes of deformation. We present our results in a regional fault model that distinguishes active deformation from older structures. Significant differences exist between our model of ICB deformation and existing models. Mounting evidence suggests a westward temporal migration of slip between faults in the ICB. In the eastern ICB, slip on the Newport-Inglewood/Rose Canyon fault and the neighboring Coronado Bank fault (CBF) diminishes to the north and appears to decrease over time. Undeformed Late Pliocene sediments overlie the northern extent of the CBF and the breakaway zone of the purported Oceanside Blind Thrust. Therefore, CBF slip rate estimates based on linkage with the Palos Verdes fault to the north are unwarranted. Deformation along the San Mateo, San Onofre, and Carlsbad trends is best explained as localized deformation resulting from geometrical complexities in a dextral strike-slip fault system. In the western ICB, the San Diego Trough fault (SDTF) offsets young sediments between the US/Mexico border and the eastern margin of Avalon Knoll, where the fault is spatially coincident with the San Pedro Basin fault (SPBF). Farther west, the San Clemente fault (SCF) has a strong linear bathymetric expression. The length

  19. Active normal faulting during the 1997 seismic sequence in Colfiorito, Umbria: Did slip propagate to the surface?

    NASA Astrophysics Data System (ADS)

    Mildon, Zoë K.; Roberts, Gerald P.; Faure Walker, Joanna P.; Wedmore, Luke N. J.; McCaffrey, Ken J. W.

    2016-10-01

    In order to determine whether slip during an earthquake on the 26th September 1997 propagated to the surface, structural data have been collected along a bedrock fault scarp in Umbria, Italy. These collected data are used to investigate the relationship between the throw associated with a debated surface rupture (observed as a pale unweathered stripe at the base of the bedrock fault scarp) and the strike, dip and slip-vector. Previous studies have suggested that the surface rupture was produced either by primary surface slip or secondary compaction of hangingwall sediments. Some authors favour the latter because sparse surface fault dip measurements do not match nodal plane dips at depth. It is demonstrated herein that the strike, dip and height of the surface rupture, represented by a pale unweathered stripe at the base of the bedrock scarp, shows a systematic relationship with respect to the geometry and kinematics of faulting in the bedrock. The strike and dip co-vary and the throw is greatest where the strike is oblique to the slip-vector azimuth where the highest dip values are recorded. This implies that the throw values vary to accommodate spatial variation in the strike and dip of the fault across fault plane corrugations, a feature that is predicted by theory describing conservation of strain along faults, but not by compaction. Furthermore, published earthquake locations and reported fault dips are consistent with the analysed surface scarps when natural variation for surface dips and uncertainty for nodal plane dips at depth are taken into account. This implies that the fresh stripe is indeed a primary coseismic surface rupture whose slip is connected to the seismogenic fault at depth. We discuss how this knowledge of the locations and geometry of the active faults can be used as an input for seismic hazard assessment.

  20. Deep reaching versus vertically restricted Quaternary normal faults: Implications on seismic potential assessment in tectonically active regions: Lessons from the middle Aterno valley fault system, central Italy

    NASA Astrophysics Data System (ADS)

    Falcucci, E.; Gori, S.; Moro, M.; Fubelli, G.; Saroli, M.; Chiarabba, C.; Galadini, F.

    2015-05-01

    We investigate the Middle Aterno Valley fault system (MAVF), a poorly investigated seismic gap in the central Apennines, adjacent to the 2009 L'Aquila earthquake epicentral area. Geological and paleoseismological analyses revealed that the MAVF evolved through hanging wall splay nucleation, its main segment moving at 0.23-0.34 mm/year since the Middle Pleistocene; the penultimate activation event occurred between 5388-5310 B.C. and 1934-1744 B.C., the last event after 2036-1768 B.C. and just before 1st-2nd century AD. These data define hard linkage (sensu Walsh and Watterson, 1991; Peacock et al., 2000; Walsh et al., 2003, and references therein) with the contiguous Subequana Valley fault segment, able to rupture in large magnitude earthquakes (up to 6.8), that did not rupture since about two millennia. By the joint analysis of geological observations and seismological data acquired during to the 2009 seismic sequence, we derive a picture of the complex structural framework of the area comprised between the MAVF, the Paganica fault (the 2009 earthquake causative fault) and the Gran Sasso Range. This sector is affected by a dense array of few-km long, closely and regularly spaced Quaternary normal fault strands, that are considered as branches of the MAVF northern segment. Our analysis reveals that these structures are downdip confined by a decollement represented by to the presently inactive thrust sheet above the Gran Sasso front limiting their seismogenic potential. Our study highlights the advantage of combining Quaternary geological field analysis with high resolution seismological data to fully unravel the structural setting of regions where subsequent tectonic phases took place and where structural interference plays a key role in influencing the seismotectonic context; this has also inevitably implications for accurately assessing seismic hazard of such structurally complex regions.

  1. The character and reactivation history of the southern extension of the seismically active Clarendon Linden Fault System, western New York State

    NASA Astrophysics Data System (ADS)

    Jacobi, Robert D.; Fountain, John

    2002-08-01

    Integration of 11 types of data sets enabled us to determine the location, character and fault history of the southern extension of the Clarendon-Linden Fault System (CLF) in southwestern New York State. The data sets utilized include detailed stratigraphic and fracture measurements at more than 1000 sites, soil gas anomalies, seismic reflection profiles, well logs and lineaments on air photos, topographic maps, Landsat and SLAR images. The seismically active CLF consists of as many as 10 parallel, segmented faults across the fault system. The fault segments are truncated by NW-striking cross-strike discontinuities (CSDs). The faults of the CLF and intersecting CSDs form fault blocks that have semi-independent subsidence and uplift histories. East-dipping reflectors in the Precambrian basement indicate the southward continuation of thrusts of the intra-Grenvillian Elzevir-Frontenac Boundary Zone. These thrusts were reactivated during Iapetan rifting as normal (listric) growth faults. In Ordovician Black River to Trenton time, the southern CLF segments experienced a second phase of growth fault activity, with faults displaying a cumulative stratigraphic throw of as much as ˜170 m. Thrusting on the same east-dipping Precambrian reflectors typified the CLF in Taconic (post-Trenton) times. Detailed comparisons among the fault segments show that the fault activity in Silurian and Devonian times generally alternated between the western and central main faults. In Late Devonian time, the fault motion reversed from down-on-the-east to down-on-the-west about the time the Appalachian Basin axis passed across the CLF in its westward migration. The deep Precambrian faults of the CLF were thus reactivated as the Appalachian Basin developed in Acadian times. Finally, the CLF thrust fault imaged on seismic line CLF-1 offsets all bedrock (Devonian) units; thus, significant motion occurred along this fault during Late Acadian, or more likely, Alleghanian time.

  2. Synthetic earthquake catalogs simulating seismic activity in the Corynth Gulf, Greece, fault system

    NASA Astrophysics Data System (ADS)

    Console, R.; Carluccio, R.; Papadimitriou, E. E.; Karakostas, V. G.

    2014-12-01

    The characteristic earthquake hypothesis is the basis of time-dependent modeling of earthquake recurrence on major faults, using the renewal process methodology. However, the characteristic earthquake hypothesis is not strongly supported by observational data. Few fault segments have long historical or paleoseismic records of individually dated ruptures, and when data and parameter uncertainties are allowed for, the form of the recurrence-distribution is difficult to establish. This is the case, for instance, of the Corinth gulf fault system, for which documents about strong earthquakes exist for at least two thousand years, but they can be considered complete for magnitudes > 6.0 only for the latest 300 years, during which only few characteristic earthquakes are reported for single fault segments. The use of a physics-based earthquake simulator has allowed the production of catalogs lasting 100,000 years and containing more than 500,000 events of magnitudes > 4.0. The main features of our simulation algorithm are (1) the imposition of an average slip rate released by earthquakes to every single segment recognized in the investigated fault system, (2) the interaction between earthquake sources, (3) a self-organized earthquake magnitude distribution, and (4) the effect of minor earthquakes in redistributing stress. The application of our simulation algorithm to the Corinth gulf fault system has shown realistic features in time, space and magnitude behavior of the seismicity. These features include long-term periodicity of strong earthquakes, short-term clustering of both strong and smaller events, and a realistic earthquake magnitude distribution departing from the Gutenberg-Richter distribution in the higher magnitude range.

  3. A prediction of mars seismicity from surface faulting

    USGS Publications Warehouse

    Golombek, M.P.; Banerdt, W.B.; Tanaka, K.L.; Tralli, D.M.

    1992-01-01

    The shallow seismicity of Mars has been estimated by measurement of the total slip on faults visible on the surface of the planet throughout geologic time. Seismicity was calibrated with estimates based on surface structures on the moon and measured lunar seismicity that includes the entire seismogenic lithosphere. Results indicate that Mars is seismically active today, with a sufficient number of detectable marsquakes to allow seismic investigations of its interior.

  4. The organization of seismicity on fault networks.

    PubMed Central

    Knopoff, L

    1996-01-01

    Although models of homogeneous faults develop seismicity that has a Gutenberg-Richter distribution, this is only a transient state that is followed by events that are strongly influenced by the nature of the boundaries. Models with geometrical inhomogeneities of fracture thresholds can limit the sizes of earthquakes but now favor the characteristic earthquake model for large earthquakes. The character of the seismicity is extremely sensitive to distributions of inhomogeneities, suggesting that statistical rules for large earthquakes in one region may not be applicable to large earthquakes in another region. Model simulations on simple networks of faults with inhomogeneities of threshold develop episodes of lacunarity on all members of the network. There is no validity to the popular assumption that the average rate of slip on individual faults is a constant. Intermediate term precursory activity such as local quiescence and increases in intermediate-magnitude activity at long range are simulated well by the assumption that strong weakening of faults by injection of fluids and weakening of asperities on inhomogeneous models of fault networks is the dominant process; the heat flow paradox, the orientation of the stress field, and the low average stress drop in some earthquakes are understood in terms of the asperity model of inhomogeneous faulting. PMID:11607672

  5. Frictional evolution, acoustic emissions activity, and off-fault damage in simulated faults sheared at seismic slip rates

    NASA Astrophysics Data System (ADS)

    Passelègue, François. X.; Spagnuolo, Elena; Violay, Marie; Nielsen, Stefan; Di Toro, Giulio; Schubnel, Alexandre

    2016-10-01

    We present a series of high-velocity friction tests conducted on Westerly granite, using the Slow to HIgh Velocity Apparatus (SHIVA) installed at Istituto Nazionale di Geofisica e Vulcanologia Roma with acoustic emissions (AEs) monitored at high frequency (4 MHz). Both atmospheric humidity and pore fluid (water) pressure conditions were tested, under effective normal stress σneff in the range 5-20 MPa and at target sliding velocities Vs in the range 0.003-3 m/s. Under atmospheric humidity two consecutive friction drops were observed. The first one is related to flash weakening, and the second one to the formation and growth of a continuous layer of melt in the slip zone. In the presence of fluid, a single drop in friction was observed. Average values of fracture energy are independent of effective normal stress and sliding velocity. However, measurements of elastic wave velocities on the sheared samples suggested that larger damage was induced for 0.1 < Vs<0.3 m/s. This observation is supported by AEs recorded during the test, most of which were detected after the initiation of the second friction drop, once the fault surface temperature was high. Some AEs were detected up to a few seconds after the end of the experiments, indicating thermal rather than mechanical cracking. In addition, the presence of pore water delayed the onset of AEs by cooling effects and by reducing of the heat produced, supporting the link between AEs and the production and diffusion of heat during sliding. Using a thermoelastic crack model developed by Fredrich and Wong (1986), we confirm that damage may be induced by heat diffusion. Indeed, our theoretical results predict accurately the amount of shortening and shortening rate, supporting the idea that gouge production and gouge comminution are in fact largely controlled by thermal cracking. Finally, we discuss the contribution of thermal cracking in the seismic energy balance. In fact, while a dichotomy exists in the literature regarding

  6. Managing the Risk of Triggered Seismicity: Can We Identify (and Avoid) Potentially Active Faults? - A Practical Case Study in Oklahoma

    NASA Astrophysics Data System (ADS)

    Zoback, M. D.; Alt, R. C., II; Walsh, F. R.; Walters, R. J.

    2014-12-01

    It is well known that throughout the central and eastern U.S. there has been a marked increase in seismicity since 2009, at least some of which appears to increased wastewater injection. No area has seen a greater increase in seismicity than Oklahoma. In this paper, we utilize newly available information on in situ stress orientation and relative magnitudes, the distribution of high volume injection wells and knowledge of the intervals used for waste water disposal to identify the factors potentially contributing to the occurrence of triggered seismicity. While there are a number of sites where in situ stress data has been successfully used to identify potentially active faults, we are investigating whether this methodology can be implemented throughout a state utilizing the types of information frequently available in areas of oil and gas development. As an initial test of this concept, we have been compiling stress orientation data from wells throughout Oklahoma provided by private industry. Over fifty new high quality data points, principally drilling-induced tensile fractures observed in image logs, result in a greatly improved understanding of the stress field in much of the state. A relatively uniform ENE direction of maximum compressive stress is observed, although stress orientations (and possibly relative stress magnitudes) differ in the southern and southwestern parts of the state. The proposed methodology can be tested in the area of the NE-trending fault that produced the M 5+ earthquakes in the Prague, OK sequence in 2011, and the Meers fault in southwestern OK, that produced a M~7 reverse faulting earthquake about 1100 years ago. This methodology can also be used to essentially rule out slip on other major faults in the area, such as the ~N-S trending Nemaha fault system. Additional factors leading to the occurrence of relatively large triggered earthquakes in Oklahoma are 1) the overall increase in injection volumes throughout the state in recent

  7. Multiscale seismic imaging of active fault zones for hazard assessment: A case study of the Santa Monica fault zone, Los Angeles, California

    USGS Publications Warehouse

    Pratt, T.L.; Dolan, J.F.; Odum, J.K.; Stephenson, W.J.; Williams, R.A.; Templeton, M.E.

    1998-01-01

    High-resolution seismic reflection profiles at two different scales were acquired across the transpressional Santa Monica Fault of north Los Angeles as part of an integrated hazard assessment of the fault. The seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies. The trench shows a series of near-vertical strike-slip faults beneath a topographic scarp inferred to be caused by thrusting on the Santa Monica fault. Analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike-slip faults within the past 50 000 years, with the latest being 1000 to 3000 years ago. A 3.8-km-long, high-resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the Santa Monica Fault (upper 300 m) to dip northward between 30?? and 55??, most likely 30?? to 35??, in contrast to the 60?? to 70?? dip interpreted for the deeper portion of the fault. Prominent, nearly continuous reflectors on the profile are interpreted to be the erosional unconformity between the 1.2 Ma and older Pico Formation and the base of alluvial fan deposits. The unconformity lies at depths of 30-60 m north of the fault and 110-130 m south of the fault, with about 100 m of vertical displacement (180 m of dip-slip motion on a 30??-35?? dipping fault) across the fault since deposition of the upper Pico Formation. The continuity of the unconformity on the seismic profile constrains the fault to lie in a relatively narrow (50 m) zone, and to project to the surface beneath Ohio Avenue immediately south of the trench. A very high-resolution seismic profile adjacent to the trench images reflectors in the 15 to 60 m depth range that are arched slightly by folding just north of the fault. A disrupted zone on the profile beneath the south end of the trench is interpreted as being caused by the deeper portions of the trenched strike

  8. Locadiff with ambient seismic noise : theoretical background and application to monitoring volcanoes and active faults.

    NASA Astrophysics Data System (ADS)

    Larose, Eric; Obermann, Anne; Planes, Thomas; Rossetto, Vincent; Margerin, Ludovic; Sens-Schoenfelder, Christoph; Campillo, Michel

    2015-04-01

    This contribution will cover recent theoretical, numerical, and field data processing developments aiming at modeling how coda waves are perturbed (in phase and amplitude) by mechanical changes in the crust. Using continuous ambient seismic noise, we cross-correlate data every day and compare the coda of the correlograms. We can relative velocity changes and waveform decorrelation along the year, that are related to mechanical changes in the shallow crust, associated to the seismic or volcanic activity, but also to environmental effects such as hydrology. Bibliography : Anne Obermann, Thomas Planes, Eric Larose and Michel Campillo, Imaging pre- and co-eruptive structural changes of a volcano with ambient seismic noise, J. Geophys. Res. 118 6285-6294 (2013). A. Obermann, B. Froment, M. Campillo, E. Larose, T. Planès, B. Valette, J. H. Chen, and Q. Y. Liu, Seismic noise correlations to image structural and mechanical changes associated with the Mw7.9 2008-Wenchuan earthquake, J. Geophys. Res. Solid Earth, 119, 1-14,(2014). Thomas Planès, Eric Larose, Ludovic Margerin, Vincent Rossetto, Christoph Sens-Schoenfelder, Decorrelation and phase-shift of coda waves induced by local changes : Multiple scattering approach and numerical validation, Waves in Random and Complex Media 24, 99-125, (2014)

  9. Creeping Faults and Seismicity: Lessons From The Hayward Fault, California

    NASA Astrophysics Data System (ADS)

    Malservisi, R.; Furlong, K. P.; Gans, C.

    While faults remain mostly locked between large strain releasing events, they can dissipate some of the accumulating elastic strain through creep. One such fault that releases a significant fraction of accumulating strain by creep is the Hayward fault in the San Francisco Bay region of California. The seismic risk associated with creeping faults such as the Hayward fault will depend in part on the net rate of moment accu- mulation (slip deficit) on the fault. Using a visco-elastic finite-element model driven by far field plate motions, we have investigated how the specific geometry of locked and free portions of the fault, and the interactions between the fault zone and the sur- rounding lithosphere influence creep on the fault plane and thus the seismic risk. In contrast to previous studies of the effects of the geometry of locked patches on the surface creep rate that specified rates on those patches, we specify only "creepable" regions and allow the system to adjust the creep rate. With our approach, we can infer fault zone geometries and physical properties that can produce the observed surface creep on the Hayward fault letting the rheology, geometry, and mechanics of sys- tem determine patterns of creep on the fault plane. Our results show that the creep rate decreases smoothly moving toward the locked patches. This leads to "creepable" (low friction) areas that accumulate a high slip deficit as compared to other low fric- tion segments of the fault. A comparison of the creep pattern from our results with Hayward fault micro-seismicity indicates that events cluster in the "creepable" re- gions with a creeping-velocity gradient that leads to a significant strain accumulation rate in the elastic material surrounding the creeping fault. This correlation provides an additional tool to map deformation patterns and strain accumulation on the fault. Micro-seismicity, surface deformation, and geodynamic modeling combine to allow us to refine our estimation of net

  10. Active crustal deformation of the El Salvador Fault Zone (ESFZ) using GPS data: Implications in seismic hazard assessment

    NASA Astrophysics Data System (ADS)

    Staller, Alejandra; Benito, Belen; Jesús Martínez-Díaz, José; Hernández, Douglas; Hernández-Rey, Román; Alonso-Henar, Jorge

    2014-05-01

    El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90º-100ºE direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

  11. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (∼33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-01-01

    The crustal-scale west-vergent San Ramón thrust fault system at the foot of the main Andean Cordillera in central Chile is a geologically active structure with Quaternary manifestations of complex surface rupture along fault segments in the eastern border of Santiago city. From the comparison of geophysical and geological observations, we assessed the subsurface structure pattern affecting sedimentary cover and rock-substratum topography across fault scarps, which is critic for evaluating structural modeling and associated seismic hazard along this kind of faults. We performed seismic profiles with an average length of 250 m, using an array of twenty-four geophones (GEODE), and 25 shots per profile, supporting high-resolution seismic tomography for interpreting impedance changes associated to deformed sedimentary cover. The recorded traveltime refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both velocities and reflections interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps supported subsurface resistivity tomographic profiles, which revealed systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, clearly limited by well-defined east-dipping resistivity boundaries. The latter can be interpreted in terms of structurally driven fluid content-change between the hanging wall and the footwall of a permeability boundary associated with the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ∼55° E at subsurface levels in piedmont sediments, with local complexities being probably associated to fault surface rupture propagation, fault-splay and

  12. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (~33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-08-01

    The crustal-scale west-vergent San Ramón thrust fault system, which lies at the foot of the main Andean Cordillera in central Chile, is a geologically active structure with manifestations of late Quaternary complex surface rupture on fault segments along the eastern border of the city of Santiago. From the comparison of geophysical and geological observations, we assessed the subsurface structural pattern that affects the sedimentary cover and rock-substratum topography across fault scarps, which is critical for evaluating structural models and associated seismic hazard along the related faults. We performed seismic profiles with an average length of 250 m, using an array of 24 geophones (Geode), with 25 shots per profile, to produce high-resolution seismic tomography to aid in interpreting impedance changes associated with the deformed sedimentary cover. The recorded travel-time refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both the velocities and the reflections that are interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps were used to construct subsurface resistivity tomographic profiles, which reveal systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, and clearly show well-defined east-dipping resistivity boundaries. These boundaries can be interpreted in terms of structurally driven fluid content change between the hanging wall and the footwall of the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ~55° E in the subsurface beneath the piedmont sediments, with local complexities likely associated with variations in fault

  13. Central Asia Active Fault Database

    NASA Astrophysics Data System (ADS)

    Mohadjer, Solmaz; Ehlers, Todd A.; Kakar, Najibullah

    2014-05-01

    The ongoing collision of the Indian subcontinent with Asia controls active tectonics and seismicity in Central Asia. This motion is accommodated by faults that have historically caused devastating earthquakes and continue to pose serious threats to the population at risk. Despite international and regional efforts to assess seismic hazards in Central Asia, little attention has been given to development of a comprehensive database for active faults in the region. To address this issue and to better understand the distribution and level of seismic hazard in Central Asia, we are developing a publically available database for active faults of Central Asia (including but not limited to Afghanistan, Tajikistan, Kyrgyzstan, northern Pakistan and western China) using ArcGIS. The database is designed to allow users to store, map and query important fault parameters such as fault location, displacement history, rate of movement, and other data relevant to seismic hazard studies including fault trench locations, geochronology constraints, and seismic studies. Data sources integrated into the database include previously published maps and scientific investigations as well as strain rate measurements and historic and recent seismicity. In addition, high resolution Quickbird, Spot, and Aster imagery are used for selected features to locate and measure offset of landforms associated with Quaternary faulting. These features are individually digitized and linked to attribute tables that provide a description for each feature. Preliminary observations include inconsistent and sometimes inaccurate information for faults documented in different studies. For example, the Darvaz-Karakul fault which roughly defines the western margin of the Pamir, has been mapped with differences in location of up to 12 kilometers. The sense of motion for this fault ranges from unknown to thrust and strike-slip in three different studies despite documented left-lateral displacements of Holocene and late

  14. Seismic Activity Related to the 2002-2003 Mt. Etna Volcano Eruption (Italy): Fault Plane Solutions and Stress Tensor Computation

    NASA Astrophysics Data System (ADS)

    Barberi, G.; Cammarata, L.; Cocina, O.; Maiolino, V.; Musumeci, C.; Privitera, E.

    2003-04-01

    Late on the night of October 26, 2002, a bi-lateral eruption started on both the eastern and the southeastern flanks of Mt. Etna. The opening of the eruptive fracture system on the NE sector and the reactivation of the 2001 fracture system, on the S sector, were accompanied by a strong seismic swarm recorded between October 26 and 28 and by sharp increase of volcanic tremor amplitude. After this initial phase, on October 29 another seismogenetic zone became active in the SE sector of the volcano. At present (January 2003) the eruption is still in evolution. During the whole period a total of 862 earthquakes (Md≫1) was recorded by the local permanent seismic network run by INGV - Sezione di Catania. The maximum magnitude observed was Md=4.4. We focus our attention on 55 earthquakes with magnitude Md≫ 3.0. The dataset consists of accurate digital pickings of P- and S-phases including first-motion polarities. Firstly earthquakes were located using a 1D velocity model (Hirn et alii, 1991), then events were relocated by using two different 3D velocity models (Aloisi et alii, 2002; Patane et alii, 2002). Results indicate that most of earthquakes are located to the east of the Summit Craters and to northeast of them. Fault plane solutions (FPS) obtained show prevalent strike-slip rupture mechanisms. The suitable FPSs were considered for the application of Gephart and Forsyth`s algorithm in order to evaluate seismic stress field characteristics. Taking into account the preliminary results we propose a kinematic model of the eastern flank eastward movement in response of the intrusion processes in the central part of the volcano. References Aloisi M., Cocina O., Neri G., Orecchio B., Privitera E. (2002). Seismic tomography of the crust underneath the Etna volcano, Sicily. Physics of the Earth and Planetary Interiors 4154, pp. 1-17 Hirn A., Nercessian A., Sapin M., Ferrucci F., Wittlinger G. (1991). Seismic heterogeneity of Mt. Etna: structure and activity. Geophys. J

  15. Marine and land active-source seismic imaging of mid-Miocene to Holocene-aged faulting near geothermal prospects at Pyramid Lake, Nevada

    SciTech Connect

    Eisses, A.; Kell, A.; Kent, G.; Driscoll, N.; Karlin, R.; Baskin, R.; Louie, J.; Pullammanappallil, S.

    2016-08-01

    Amy Eisses, Annie Kell, Graham Kent, Neal Driscoll, Robert Karlin, Rob Baskin, John Louie, and Satish Pullammanappallil, 2011, Marine and land active-source seismic imaging of mid-Miocene to Holocene-aged faulting near geothermal prospects at Pyramid Lake, Nevada: presented at Geothermal Resources Council Annual Meeting, San Diego, Oct. 23-26.

  16. A Comparison of Structural Data and Seismic Images For Low-Angle Normal Faults in the Northern Apennines (Central Italy): Constraints on Geometry and Activity

    NASA Astrophysics Data System (ADS)

    Collettini, C.; Barchi, M. R.

    2001-12-01

    During the last 20 Myr extensional tectonics in the Northern Apennines have moved from the Tyrrhenian sea toward east. Much of the extension is due to low-angle east-dipping normal faults now exhumed in the Tyrrhenian islands and Tuscany, while still accommodating deformation in the Apenninic chain (Umbria region 200 km eastward). This tectonic framework provide an example where exhumed structures can be compared with active extensional structures and processes affecting the Umbria region. It is here proposed the case study of two of these low angle normal faults, the Zuccale fault (Zf), cropping out in the Elba island and the Altotiberina fault (ATF) mainly detected by seismic profiles crossing the Umbria region. The Zf in the eastern part of the Elba island juxtaposes along a gently ( ~ 10° ) eastward dipping contact, the Upper Cretaceous Helminthoid flysch in its hangingwall over the Permian-Triassic (?) phyllitic basement in its footwall. Structural analysis of the brittle structures that characterise the fault zone has been used to constraint the state of stress under which the fault slipped. From the N-S trending vertical vein system perpendicular to the slickenlines of the fault plane and from the Andersonian normal faults present within the fault gouge, some of them rotated according to a top to the east movement, we infer that (1) the maximum principal stress was sub vertical during the fault activity (2) the fault accommodate slip under low values of differential stress and at dips similar to its present flat geometry (3) local fluid overpressures were attained during the fault activity favoured by a thick fault gouge. The geological scenario described in the Elba island shows similarities with the active deformation of the Umbria region. Seismic profiles crossing this area matched with surface geology highlight the presence of an east-dipping low-angle ( ~ 20° ) normal fault, the Altotiberina fault (ATF), and antithetic seismogenic structures bounding

  17. Marine and land active-source seismic imaging of mid-Miocene to Holocene-aged faulting near geothermal prospects at Pyramid Lake, Nevada

    SciTech Connect

    Eisses, A.; Kell, A.; Kent, G.; Driscoll, N.; Karlin, R.; Baskin, R.; Louie, J.; Pullammanappallil, S.

    2016-08-01

    Amy Eisses, Annie Kell, Graham Kent, Neal Driscoll, Robert Karlin, Rob Baskin, John Louie, and Satish Pullammanappallil, 2011, Marine and land active-source seismic imaging of mid-Miocene to Holocene-aged faulting near geothermal prospects at Pyramid Lake, Nevada: Geothermal Resources Council Transactions, 35, 7 pp. Preprint at http://crack.seismo.unr.edu/geothermal/Eisses-GRCpaper-sm.pdf The Pyramid Lake fault zone lies within a vitally important area of the northern Walker Lane where not only can transtension can be studied through a complex arrangement of strike-slip and normal faults but also geothermal activity can be examined in the extensional regime for productivity. This study used advanced and economical seismic methods in attempt to develop the Paiute Tribe’s geothermal reservoir and to expand upon the tectonics and earthquake hazard knowledge of the area. 500 line-kilometers of marine CHIRP data were collected on Pyramid Lake combined with 27 kilometers of vibrator seismic on-land data from the northwest side of the basin were collected in 2010 that highlighted two distinct phases of faulting. Preliminary results suggest that the geothermal fluids in the area are controlled by the late Pleistoceneto Holocene-aged faults and not through the mid-Miocene-aged conduits as originally hypothesized.

  18. 3D modelling of the active normal fault network in the Apulian Ridge (Eastern Mediterranean Sea): Integration of seismic and bathymetric data with implicit surface methods

    NASA Astrophysics Data System (ADS)

    Bistacchi, Andrea; Pellegrini, Caludio; Savini, Alessandra; Marchese, Fabio

    2016-04-01

    The Apulian ridge (North-eastern Ionian Sea, Mediterranean), interposed between the facing Apennines and Hellenides subduction zones (to the west and east respectively), is characterized by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a penetrative network of NNW-SSE normal faults. These are exposed onshore in Puglia, and are well represented offshore in a dataset composed of 2D seismics and wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, recent very high resolution seismics (VHRS - Sparker and Chirp-sonar data), multibeam echosounder bathymetry, and sedimentological and geo-chronological analyses of sediment samples collected on the seabed. Faults are evident in 2D seismics at all scales, and their along-strike geometry and continuity can be characterized with multibeam bathymetric data, which show continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides). Fault scarps also reveal the finite displacement accumulated in the Holocene-Pleistocene. We reconstructed a 3D model of the fault network and suitable geological boundaries (mainly unconformities due to the discontinuous distribution of quaternary and tertiary sediments) with implicit surface methods implemented in SKUA/GOCAD. This approach can be considered very effective and allowed reconstructing in details complex structures, like the frequent relay zones that are particularly well imaged by seafloor geomorphology. Mutual cross-cutting relationships have been recognized between fault scarps and submarine mass-wasting deposits (Holocene-Pleistocene), indicating that, at least in places, these features are coeval, hence the fault network should be considered active. At the regional scale, the 3D model allowed measuring the horizontal WSW-ENE stretching, which can be associated to the bending moment applied to the Apulian Plate by the combined effect

  19. Imaging fault zones using 3D seismic image processing techniques

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Butler, Rob; Purves, Steve

    2013-04-01

    and collecting these into "disturbance geobodies". These seismic image processing methods represents a first efficient step toward a construction of a robust technique to investigate sub-seismic strain, mapping noisy deformed zones and displacement within subsurface geology (Dutzer et al.,2011; Iacopini et al.,2012). In all these cases, accurate fault interpretation is critical in applied geology to building a robust and reliable reservoir model, and is essential for further study of fault seal behavior, and reservoir compartmentalization. They are also fundamental for understanding how deformation localizes within sedimentary basins, including the processes associated with active seismogenetic faults and mega-thrust systems in subduction zones. Dutzer, JF, Basford., H., Purves., S. 2009, Investigating fault sealing potential through fault relative seismic volume analysis. Petroleum Geology Conference series 2010, 7:509-515; doi:10.1144/0070509 Marfurt, K.J., Chopra, S., 2007, Seismic attributes for prospect identification and reservoir characterization. SEG Geophysical development Iacopini, D., Butler, RWH. & Purves, S. (2012). 'Seismic imaging of thrust faults and structural damage: a visualization workflow for deepwater thrust belts'. First Break, vol 5, no. 30, pp. 39-46.

  20. Evidence for Holocene palaeoseismicity along the Basel-Reinach active normal fault (Switzerland): a seismic source for the 1356 earthquake in the Upper Rhine graben

    NASA Astrophysics Data System (ADS)

    Ferry, Matthieu; Meghraoui, Mustapha; Delouis, Bertrand; Giardini, Domenico

    2005-02-01

    We conducted a palaeoseismic study with geomorphologic mapping, geophysical prospecting and trenching along an 8-km-long NNE-SSW trending fault scarp south of Basel. The city as well as 40 castles within a 20-km radius were destroyed or heavily damaged by the earthquake of 1356 October 18 (Io = IX-X), the largest historical seismic event in central Europe. Active river incisions as well as late Quaternary alluvial terraces are uplifted along the linear Basel-Reinach (BR) fault scarp. The active normal fault is comprised of at least two main branches reaching the surface as evident by resistivity profiles, reflection seismic data and direct observations in six trenches. In trenches, the normal fault rupture affects three colluvial wedge deposits up to the base of the modern soil. Radiocarbon as well as thermoluminescence (TL) age determinations from other trenches helped to reconstruct the Holocene event chronology. We identified three seismic events with an average coseismic movement of 0.5-0.8 m and a total vertical displacement of 1.8 m in the last 7800 yr and five events in the last 13 200 yr. The most recent event occurred in the interval AD 500-1450 (2σ) and may correspond to the 1356 earthquake. Furthermore, the morphology suggests both a southern and northern fault extensions that may reach 20 km across the Jura mountains and across the Rhine valley. Taking this fault length and a 10-km-thick seismogenic layer suggests a Mw 6.5 or greater event as a possible scenario for the seismic hazard assessment of the Basel region.

  1. Evidence for Holocene paleoseismicity along the Basel-Reinach Active Normal Fault (Switzerland): A Seismic Source for the 1356 Earthquake in the Upper Rhine Graben

    NASA Astrophysics Data System (ADS)

    Ferry, M.; Meghraoui, M.; Delouis, B.; Giardini, D.

    2003-04-01

    We conducted a paleoseismic study with geomorphologic mapping, geophysical prospecting and trenching along an 8-km-long NNE-SSW trending fault scarp south of Basel. The city as well as 40 castles within a 20-km radius were destroyed or heavily damaged by the earthquake of 18th October 1356 (Io = IX-X MKS), the largest historical seismic event in central Europe. Active river incisions as well as late Quaternary alluvial terraces are uplifted along the linear Basel-Reinach fault scarp. The active normal fault shows at least two main branches reaching the surface as attested by resistivity profiles, reflection seismic data, and direct observations in six trenches. In trenches, the normal fault rupture affects three colluvial wedge deposits up to the base of the present day soil. Radiocarbon as well as thermoluminescence age determinations from other trenches helped reconstruct the Holocene events chronology. We identified three seismic events with an average coseismic movement of 0.5 - 0.8 m and a total vertical displacement of 1.8 m in the last 7800 years and five events in the last 13200 years. The most recent event occurred in the interval 610 - 1475 A.D. (2sigma) and may likely correspond to the 1356 earthquake. Furthermore, the morphology suggests both a southern and northern fault extensions that may reach 20 km across the Jura Mountains and across the Rhine Valley. Taking this fault length and a 10 km-thick seismogenic layer suggests a M 6.5 or greater event as a possible scenario for the seismic hazard assessment of the Basel region.

  2. Seismicity of the Quebrada, Discovery, and Gofar Transform Faults

    NASA Astrophysics Data System (ADS)

    McGuire, J. J.; Collins, J. A.; Roland, E. C.; Behn, M. D.

    2009-12-01

    The Quebrada, Discovery, and Gofar transform faults exhibit many of the primary features of oceanic transform seismicity including abundant earthquake swarms and a significant contrast in seismic coupling between Gofar and Discovery (90% seismic) and Quebrada (>90% aseismic). Additionally, the Gofar and Discovery faults have a relatively regular seismic cycle with their largest earthquakes repeating roughly every five years. Using a network of 38 ocean bottom seismometers, we monitored the seismicity on these three faults for calendar year 2008. We detected over 100,000 earthquakes between the three faults ranging from magnitude 0.5 to 6.0. The earthquakes were located using P and S-wave arrival time picks and a 1-d velocity model appropriate for oceanic crust. Our array covered the 90 km long, westernmost segment of the Gofar fault. The large earthquakes corresponding to the end of this faults' most recent seismic cycle propagated from east to west along strike and our dataset captured the final ruptures in this cycle including a Mw 6.0 event on September 18, 2008 that was recorded on scale by strong-motion accelerometers. The western Gofar segment is a highly localized plate boundary with perhaps only a single active fault, but it is divided along-strike into 4 distinct seismicity zones. The easternmost region last ruptured in August 2007 and we found it to have a relatively low level of microseismicity in 2008. To the west of this area is a ~10km long region that has likely been a barrier to rupture propagation in the last 4 seismic cycles. This barrier region had by far the highest rates of microseismicity during the first nine months of 2008 and had a large swarm in early September. The seismicity-rate in the barrier region was greatly reduced immediately after the September 18th Mw 6.0 event. The ~20 km long segment west of the barrier ruptured in the September 18th 2008 earthquake and shows a clear Omori-like aftershock sequence. The westernmost ~20 km of

  3. "High resolution seismic imaging of an active fault in the eastern Guadalquivir Basin (Betic Cordillera, Southern Spain)"

    NASA Astrophysics Data System (ADS)

    Serrano, Inmaculada; Torcal, Federico; Martín, José Benito

    2015-10-01

    We calculated the high resolution seismic velocity, Poisson's ratio, crack density and saturation ratio structures in and around the source areas of the Torreperogil seismic series (October 2012-April 2013). This seismic series, characterized by a large number of low magnitude (below Mw 3.7 or Md 3.9) and very shallow microearthquakes, took place in the Guadalquivir Basin, a large flexural foreland basin with a linear ENE-WSW trending bounded to the north by the Iberian Massif and to the south by the Betic Cordillera and filled from a middle Miocene to Plio-Quaternary sedimentary sequence. In the upper layers of the crust, strong low-velocity anomalies are extensively distributed under the central zone, which together with high Poisson's ratio and crack density values may correspond to rocks which are less likely to fracture, perhaps due to the accumulation of tectonic and seismic stress. 93% of the earthquakes occurred at depths of up to 8 km, which could indicate that the base of the seismogenic zone lies at this depth. The seismic series was concentrated in layers of strong structural heterogeneities (in the boundary area between low and high anomalies), which were likely to generate earthquakes due to differential strain accumulation beneath the region. The high velocity areas are also considered to be strong yet brittle parts of the fault zone, which may generate earthquakes (at depths of between 5 km and 9 km). By contrast, low velocity areas are less prone to fracture, allowing seismic slippage to take place (from 2 to 4 km depth). The best estimate of the depth of the main shock (mbLg 3.9) is 7.6 km, which could tend to nucleate at the base of the seismogenic zone, at the "fault end" on the boundary between a low velocity zone to the east and a high velocity zone to the west, indicating the fault plane which separates both areas laterally. Assuming that this seismic contrast is one of the main Torreperogil faults it could imply that stress has accumulated

  4. Fault gouge evolution during rupture and healing: Continual active-seismic observations across laboratory-scale fault zones

    NASA Astrophysics Data System (ADS)

    Krysta, M.; Kusmierczyk-Michulec, J.; Nikkinen, M.; Carter, J. A.

    2011-12-01

    In order to support its mission of monitoring compliance with the treaty banning nuclear explosions, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) operates four global networks of, respectively, seismic, infrasound, hydroacoustic sensors and air samplers accompanied with radionuclide detectors. The role of the International Data Centre (IDC) of CTBTO is to associate the signals detected in the monitoring networks with the physical phenomena which emitted these signals, by forming events. One of the aspects of associating detections with emitters is the problem of inferring the sources of radionuclides from the detections made at CTBTO radionuclide network stations. This task is particularly challenging because the average transport distance between a release point and detectors is large. Complex processes of turbulent diffusion are responsible for efficient mixing and consequently for decreasing the information content of detections with an increasing distance from the source. The problem is generally addressed in a two-step process. In the first step, an atmospheric transport model establishes a link between the detections and the regions of possible source location. In the second step this link is inverted to infer source information from the detections. In this presentation, we will discuss enhancements of the presently used regression-based inversion algorithm to reconstruct a source of radionuclides. To this aim, modern inversion algorithms accounting for prior information and appropriately regularizing an under-determined reconstruction problem will be briefly introduced. Emphasis will be on the CTBTO context and the choice of inversion methods. An illustration of the first tests will be provided using a framework of twin experiments, i.e. fictitious detections in the CTBTO radionuclide network generated with an atmospheric transport model.

  5. Parameters of induced and natural seismicity recorded in the vicinity of an active low angle normal fault in the Northern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Braun, T.; Cesca, S.; Martirosian, A.; Dahm, T.

    2012-12-01

    The Upper Tiber Valley is situated in the northern part of the Central Apennines and is setting of a number of geological phenomena, like CO2 degassing, moderate earthquakes (M < 6) and a strong microseismicity. The major part of the recorded seismicity can be associated to a Low Angle Normal Fault (LANF) - the so called Alto Tiberina Fault - but some of the recorded seismograms show signals similar to those recorded on active volcanoes. In the vicinity of the ATF human activity provides a number of candidates, capable to influence the local stress regime and the seismic release in the area: (i) a huge barrier lake is directly situated on the ATF and is characterized by significant seasonal water level oscillations, (ii) a cement plant and decommissioned mines present in the area are in the direct vicinity of epicentres of tornillo-like seismograms and episodes of non-volcanic tremor, (iii) since July 2011, a private company extracts CO2 by a 4 km deep borehole (PSS1). Since 2003 different seismic network and array configurations have been deployed to monitor the local seismicity. Human related influences, as realized by the industrial activities of cement plants, quarries or superficial mines may produce seismic signals, but will not directly have an impact on the mechanical behaviour of an active fault system at crustal depth. However, water level changes in the huge barrier lake or long term CO2-extraction from the upper crust have the capability to directly influence the stress field at depth. Since summer 2011 the reservoir user produces about 4 tons per hour of reservoir gases for commercial usage and trading. This production lead to a pore pressure change and slow depletion of the reservoir formation, similar to many other gas fields under production. Since production volumes and pore pressure changes are relatively well known, we consider the local depletion-induced stress changes on the ATF and in the surrounding rock as driving forces to the system. The

  6. The Servita Fault, Colombian Eastern Cordillera: Origin, Geotectonics, and Seismicity

    NASA Astrophysics Data System (ADS)

    Chicangana, G.; Kammer, A.; Vargas Jiménez, C. A.; Caneva, A.; Pedraza, P.; Salcedo, E.; Gomez, A.; Muñoz, F.

    2014-12-01

    The Servita fault is a thrust located in the center of Colombia and whose main scarp is at 5 km west of Villavicencio (500.000 inhabitants). According to geophysics data as gravity, magnetic, and seismic, this fault was confirmed how a large cortical structure in the Colombian Eastern Cordillera. The Servita fault possibly was originated like a suture that derived of a continental collision in Late Mesoproterozoic times when Rodinia was conform totally. The Servita Fault as normal fault in Mesozoic times contributed to the Colombian Cretaceous basin development. In Late Cretaceous because to collision of the Caribbean plate with the northwestern corner of South America a strong compressive stress was occur and kinematics changes were presented in the normal faults restrained to the basin like among others the Servita Fault, where these were converted in inverse faults. From early Pliocene until Present times the Servita Fault controlled the growth of the Cordillera and the Llanos foothills in this sector of Central Colombia. Result of this is the seismicity activity registered for this region from historical times (less of 500 years for Colombian case). Two earthquakes have transcended in this region in last three centuries: the first one occurred on October 18th, 1743 with a current probabilistic magnitude greater than 6.5 and the second one struck on May 24th, 2008 with a M = 5.9. In this work we show how this fault has develop from its origin, and how this can would produce a M > 6.5 earthquake very close to metropolitan area of Bogota D.C., and Villavicencio. This earthquake would destroy both urban areas resulting in high losses in lives and economic terms. The seismicity activity of the Servita Fault and its associated structures is registered by the National Seismological Network of Colombia and the Sabana de Bogotá Seismological Network.

  7. Detection of precursory slips on a fault by the quiescence and activation of seismicity relative to the ETAS model and by the anomalous trend of the geodetic time series of distances between GPS stations around the fault

    NASA Astrophysics Data System (ADS)

    Ogata, Y.

    2006-12-01

    This paper is concerned with the detection of precursory slip on a rupturing fault, supported by both seismic and geodetic records. Basically, the detection relies on the principle that, assuming precursory slip on the rupturing fault, the seismic activity around the fault should be enhanced or reduced in the zones where increment of the Coulomb failure stress (CFS) is positive or negative, respectively. However, any occurring event also affects the stress changes in neighboring regions, which can trigger further aftershock clusters. Whereas such stress transfers are too difficult to be computed precisely, due to the unknown complex fault system, the ordinary short-term occurrence rate of earthquakes in a region is easily predicted using the ETAS model of triggering seismicity; and any anomalous seismic activity, such as quiescence and activation, can be quantified by identifying a significant deviation from the predicted rate. Such anomalies are revealed to have occurred during several years leading up to the 2004 Chuetsu Earthquake of M6.8, central Honshu, and also the 2005 Western Fukuoka-Ken-Oki Earthquake of M7.0, Kyushu, Japan. Quiescence and activation in the regions coincided with negative and positive increments of the CFS, respectively, and were probably transferred from possible aseismic slips on the focal fault plane. Such slips are further supported by transient crustal movement around the source preceding the rupture. Time series records of the baseline distances between the permanent GPS stations deviated from the predicted trends, with the deviations consistent with the coseismic horizontal displacements of the stations due to these earthquakes. References Ogata, Y. (2006) Report of the Coordinating Committee for Earthquake Prediction, 76 (to appear, in Japanese).

  8. Seismicity and faulting attributable to fluid extraction

    USGS Publications Warehouse

    Yerkes, R.F.; Castle, R.O.

    1976-01-01

    The association between fluid injection and seismicity has been well documented and widely publicized. Less well known, but probably equally widespread are faulting and shallow seismicity attributable solely to fluid extraction, particularly in association with petroleum production. Two unequivocable examples of seismicity and faulting associated with fluid extraction in the United States are: The Goose Creek, Texas oil field event of 1925 (involving surface rupture); and the Wilmington, California oil field events (involving subsurface rupture) of 1947, 1949, 1951 (2), 1955, and 1961. Six additional cases of intensity I-VII earthquakes (M < 4.6) without reported faulting may be attributable to shallow production from other large oil and gas fields. In addition to these examples are thirteen cases of apparently aseismic surface rupture associated with production from California and Texas oil fields. Small earthquakes in the Eloy-Picacho area of Arizona may be attributable to withdrawal of groundwater, but their relation to widespread fissuring is enigmatic. The clearest example of extraction-induced seismicity outside of North America is the 1951 series of earthquakes associated with gas production from the Po River delta near Caviga, Italy. Faulting and seismicity associated with fluid extraction are attributed to differential compaction at depth caused by reduction of reservoir fluid pressure and attendant increase in effective stress. Surface and subsurface measurements and theoretical and model studies show that differential compaction leads not only to differential subsidence and centripetally-directed horizontal displacements, but to changes in both vertical- and horizontal-strain regimes. Study of well-documented examples indicates that the occurrence and nature of faulting and seismicity associated with compaction are functions chiefly of: (1) the pre-exploitation strain regime, and (2) the magnitude of contractional horizontal strain centered over the

  9. Fault-zone attenuation of high-frequency seismic waves

    NASA Astrophysics Data System (ADS)

    Blakeslee, Sam; Malin, Peter; Alvarez, Marcos

    1989-11-01

    We have developed a technique to measure seismic attenuation within an active fault-zone at seismogenic depths. Utilizing a pair of stations and pairs of earthquakes, spectral ratios are performed to isolate attenuation produced by wave-propagation within the fault-zone. This empirical approach eliminates common source, propagation, instrument and near-surface site effects. The technique was applied to a cluster of 19 earthquakes recorded by a pair of downhole instruments located within the San Andreas fault-zone, at Parkfield California. Over the 1-40 Hz bandwidth used in this analysis, amplitudes are found to decrease exponentially with frequency. Furthermore, the fault-zone propagation distance correlates with the severity of attenuation. Assuming a constant Q attenuation operator, the S-wave quality factor within the fault-zone at a depth of 5-6 kilometers is 31 (+7,-5). If fault-zones are low-Q environments, then near-source attenuation of high-frequency seismic waves may help to explain phenomenon such as fmax. Fault-zone Q may prove to be a valuable indicator of the mechanical behavior and rheology of fault-zones. Specific asperities can be monitored for precursory changes associated with the evolving stress-field within the fault-zone. The spatial and temporal resolution of the technique is fundamentally limited by the uncertainty in earthquake location and the interval time between earthquakes.

  10. Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

    NASA Astrophysics Data System (ADS)

    Audin, Laurence; Lacan, Pierre; Tavera, Hernando; Bondoux, Francis

    2008-11-01

    The South America plate boundary is one of the most active subduction zone. The recent Mw = 8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, at a longer time scale, a recurrent Quaternary transtensive tectonic activity of the CFS is expressed by offset river gullies and alluvial fans. The presence of such extensional fault systems trending orthogonal to the trench along the Coastal Cordillera in southern Peru is interpreted to reflect a strong coupling between the two plates. In this particular case, stress transfer to the upper plate, at least along the coastal fringe, appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake. The seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones. However, after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern Peru, we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern Peru continental margin.

  11. Seismicity and Faulting in an Urbanized area: Flagstaff, Arizona

    NASA Astrophysics Data System (ADS)

    Brumbaugh, D. S.

    2013-12-01

    Flagstaff, Arizona is a community of more than 60,000 and lies in an area of active tectonism. Well documented evidence exists of geologically recent volcanism and fault related seismicity. The urban area is located within a volcanic field that is considered active and the area is also the locus of numerous fault systems, some of whose members are considered to be potentially active. This suggestion of active faulting and seismicity for the area is supported by the recent 1993 Mw 5.3 Cataract Creek earthquake. Chief concern for Flagstaff is focused upon the Anderson Mesa fault which has a mapped surface length of 40 kilometers with the north end extending into the city limits of Flagstaff. A worse case scenario for rupture along the entire length of the fault would be the occurrence of an Mw 6.9 earthquake. The slip rate for this fault is low, however it is not well determined due to a lack of Neogene or Quaternary deposits. The historic record of seismicity adjacent to the surface expression of the Anderson Mesa fault includes two well recorded earthquake swarms (1979,2011) as well as other individual events over this time period all of which are of M< 4.0. The epicentral locations of these events are of interest with respect to the fault geometry which shows four prominent segments: North, Central, South, Ashurst. All of the historic events are located within the central segment. This distribution can be compared to evidence available for the orientation of regional stresses. The focal mechanism for the 1993 Mw 5.3 Cataract Creek earthquake shows a northwest striking preferred slip surface with a trend (300) parallel to that of the Central segment of the Anderson Mesa fault (300-305). The other three fault segments of the Anderson Mesa fault have north-south trends. The seismicity of the Central segment of the fault suggests that slip on this segment may occur in the future. Given the length of this segment a MCE event could be as large as Mw 6.3.

  12. Borehole and High-Resolution Seismic Reflection Evidence for Holocene Activity on the Compton Blind-Thrust Fault, Los Angeles Basin, California

    NASA Astrophysics Data System (ADS)

    Leon, L. A.; Dolan, J. F.; Shaw, J. H.; Pratt, T. L.

    2006-12-01

    Newly collected borehole and high-resolution seismic reflection data from a site ~6 km south of downtown Los Angeles demonstrate that the Compton blind-thrust fault has generated multiple large-magnitude earthquakes during the Holocene. This large blind thrust fault, which was originally identified by Shaw and Suppe (1996) using industry seismic reflection profiles and well data, extends northwest-southeast for 40 km beneath the western edge of the Los Angeles basin. The industry seismic reflection data define a growth fault-bend fold associated with the thrust ramp, which, combined with well data, reveal compelling evidence for Pliocene and Pleistocene activity. The industry data, however, do not image deformation in the uppermost few hundred meters. In order to bridge this gap, we acquired high-resolution seismic reflection profiles at two scales across the back limb active axial surface of the fault-bend fold above the Compton thrust ramp, using a truck-mounted weight drop and sledgehammer sources. These profiles delineate the axial surfaces of the fold from <20 m depth downward to overlap with the upper part of the industry reflection data within the upper 500 m. The seismic reflection data reveal an upward-narrowing zone of folding that extends to <100 m of the surface. These data, in turn, allowed us to accurately and efficiently site a fault-perpendicular transect of eight continuously cored boreholes across the axial surface of the fold observed in both industry and high-resolution seismic reflection data. The borehole data reveal folding within a discrete kink band that is <~150 m wide in the shallow subsurface. Preliminary analysis of the deformed, shallow growth strata reveals evidence for a number of discrete uplift events, which we interpret as having occurred during several large-magnitude (M >7) earthquakes on the Compton fault. Although we do not as yet have age control for this transect, numerous organic-rich clay and silt layers, as well as

  13. Laboratory micro-seismic signature of shear faulting and fault slip in shale

    NASA Astrophysics Data System (ADS)

    Sarout, J.; Le Gonidec, Y.; Ougier-Simonin, A.; Schubnel, A.; Guéguen, Y.; Dewhurst, D. N.

    2017-03-01

    This article reports the results of a triaxial deformation experiment conducted on a transversely isotropic shale specimen. This specimen was instrumented with ultrasonic transducers to monitor the evolution of the micro-seismic activity induced by shear faulting (triaxial failure) and subsequent fault slip at two different rates. The strain data demonstrate the anisotropy of the mechanical (quasi-static) compliance of the shale; the P-wave velocity data demonstrate the anisotropy of the elastic (dynamic) compliance of the shale. The spatio-temporal evolution of the micro-seismic activity suggests the development of two distinct but overlapping shear faults, a feature similar to relay ramps observed in large-scale structural geology. The shear faulting of the shale specimen appears quasi-aseismic, at least in the 0.5 MHz range of sensitivity of the ultrasonic transducers used in the experiment. Concomitantly, the rate of micro-seismic activity is strongly correlated with the imposed slip rate and the evolution of the axial stress. The moment tensor inversion of the focal mechanism of the high quality micro-seismic events recorded suggests a transition from a non-shear dominated to a shear dominated micro-seismic activity when the rock evolves from initial failure to larger and faster slip along the fault. The frictional behaviour of the shear faults highlights the possible interactions between small asperities and slow slip of a velocity-strengthening fault, which could be considered as a realistic experimental analogue of natural observations of non-volcanic tremors and (very) low-frequency earthquakes triggered by slow slip events.

  14. Finite-element models on spatiotemporal variations in intraplate seismicity caused by postglacial unloading and rebound: Implications for active normal faults in the Basin and Range Province

    NASA Astrophysics Data System (ADS)

    Karow, T.; Hampel, A.

    2007-12-01

    The actively extending Basin and Range Province was covered by numerous pluvial lakes and glaciers on several of the higher ranges during the Last Glacial Maximum (Osburn and Bevis, QSR, 2001). The largest lakes were Lake Bonneville and Lake Lahontan, located in the eastern and western parts of the Basin and Range Province, respectively. Regression of these lakes at the end of last glacial period caused significant isostatic rebound of the lithosphere (Bills et al., JGR, 1994; Bills et al., JGR, 2007). The rebound associated with the regression of Lake Bonneville has been shown, using two-dimensional numerical models, to affect the stress field of the lithosphere and to cause a slip rate increase on the Wasatch normal fault (Hetzel and Hampel, Nature 2005). Here we use three-dimensional finite-element models of normal fault arrays to investigate spatiotemporal variations in the regional stress field and in the rate of normal faulting caused by glacial-interglacial variations of the surface load. Our models indicate that regression of Lake Lahontan but also of smaller lakes and glaciers alter the regional stress field and hence may ultimately affect the intraplate seismicity. Paleoseismological data from faults in the east-central and northern Basin and Range Province seem to support the idea of an increase in seismicity after the Last Glacial Maximum (Friedrich el al., JGR, 2003; Stickney and Bartholomew, BSSA, 1987; Wesnousky et al., JGR, 2005).

  15. High Resolution Seismic Imaging of the Brawley Seismic Fault Zone

    NASA Astrophysics Data System (ADS)

    Goldman, M.; Catchings, R. D.; Rymer, M. J.; Lohman, R. B.; McGuire, J. J.; Sickler, R. R.; Criley, C.; Rosa, C.

    2011-12-01

    In March 2010, we acquired a series of high-resolution P-wave seismic reflection and refraction data sets across faults in the Brawley seismic zone (BSZ) within the Salton Sea Geothermal Field (SSGF). Our objectives were to determine the dip, possible structural complexities, and seismic velocities within the BSZ. One dataset was 3.4 km long trending east-west, and consisted of 334 shots recorded by a 2.4 km spread of 40 hz geophones placed every 10 meters. The spread was initially laid out from the first station at the eastern end of the profile to roughly 2/3 into the profile. After about half the shots, the spread was shifted from roughly 1/3 into the profile to the last station at the western end of the profile. P-waves were generated by Betsy-Seisgun 'shots' spaced every 10 meters. Initial analysis of first breaks indicate near-surface velocities of ~500-600 meters/sec, and deeper velocities of around 2000 meters/sec. Preliminary investigation of shot gathers indicate a prominent fault that extends to the ground surface. This fault is on a projection of the Kalin fault from about 40 m to the south, and broke the surface down to the west with an approximately north-south strike during a local swarm of earthquakes in 2005 and also slipped at the surface in association with the 2010 El Mayor-Cucapah earthquake in Baja California. The dataset is part of the combined Obsidian Creep data set, and provides the most detailed, publicly available subsurface images of fault structures in the BSZ and SSGF.

  16. Seismic site characterization for the Deep-Fault-Drilling-Project Alpine Fault

    NASA Astrophysics Data System (ADS)

    Glomb, Vera; Buske, Stefan; Kovacs, Adrienn; Gorman, Andrew

    2013-04-01

    The Alpine Fault in New Zealand (South Island) is one of the largest active plate-bounding continental fault zones on earth with earthquakes of magnitude 7.9 occuring every 200-400 years. Due to the surface exposure and the shallow depth of mechanical and chemical transitions it is a globally significant natural laboratory. Within the ICDP Deep-Fault-Drilling-Project Alpine Fault (DFDP-AF; https://wiki.gns.cri.nz/DFDP) a drill hole shall give insight into the geological structure of the fault zone and its evolution to understand the related deformation and earthquake processes. With the help of advanced seismic imaging techniques the shallow structure of the Alpine Fault is imaged to find the most suitable drill site location. A new seismic reflection profile has been acquired in 2011 by the WhataDUSIE project team consisting of partners from the University of Otago (New Zealand), TU Bergakademie Freiberg (Germany) and the University of Alberta (Canada). The reflection profile, located in the Whataroa river valley, has a total length of about 5 km. Up to 643 geophones with spacings between 4-8 m recorded the approximately 100 shot points along the profile line. Single shot gathers as well as preliminary imaging results will be presented. The high-quality data show various indicators of the Alpine Fault such as strong reflections and distorted first-arrival wavefields which are clearly visible already in single shot gathers. With the help of high resolution seismic images we can study the shallow structures of the subsurface thus gaining information about the location and dip of reflectors. Further detailed processing and intensive interpretative work will enable a seismic site characterization providing important information for the selection of the borehole location. Additionally the high resolution seismic images themselves allow a better understanding of the tectonic and geodynamic settings.

  17. Abundant off-fault seismicity and orthogonal structures in the San Jacinto fault zone

    PubMed Central

    Ross, Zachary E.; Hauksson, Egill; Ben-Zion, Yehuda

    2017-01-01

    The trifurcation area of the San Jacinto fault zone has produced more than 10% of all earthquakes in southern California since 2000, including the June 2016 Mw (moment magnitude) 5.2 Borrego Springs earthquake. In this area, the fault splits into three subparallel strands and is associated with broad VP/VS anomalies. We synthesize spatiotemporal properties of historical background seismicity and aftershocks of the June 2016 event. A template matching technique is used to detect and locate more than 23,000 aftershocks, which illuminate highly complex active fault structures in conjunction with a high-resolution regional catalog. The hypocenters form dipping seismicity lineations both along strike and nearly orthogonal to the main fault, and are composed of interlaced strike-slip and normal faults. The primary faults change dip with depth and become listric by transitioning to a dip of ~70° near a depth of 10 km. The Mw 5.2 Borrego Springs earthquake and past events with M > 4.0 occurred on the main faults, whereas most of the low-magnitude events are located in a damage zone (several kilometers wide) at seismogenic depths. The lack of significant low-magnitude seismicity on the main fault traces suggests that they do not creep. The very high rate of aftershocks likely reflects the large geometrical fault complexity and perhaps a relatively high stress due to a significant length of time elapsed since the last major event. The results provide important insights into the physics of faulting near the brittle-ductile transition. PMID:28345036

  18. Abundant off-fault seismicity and orthogonal structures in the San Jacinto fault zone.

    PubMed

    Ross, Zachary E; Hauksson, Egill; Ben-Zion, Yehuda

    2017-03-01

    The trifurcation area of the San Jacinto fault zone has produced more than 10% of all earthquakes in southern California since 2000, including the June 2016 Mw (moment magnitude) 5.2 Borrego Springs earthquake. In this area, the fault splits into three subparallel strands and is associated with broad VP /VS anomalies. We synthesize spatiotemporal properties of historical background seismicity and aftershocks of the June 2016 event. A template matching technique is used to detect and locate more than 23,000 aftershocks, which illuminate highly complex active fault structures in conjunction with a high-resolution regional catalog. The hypocenters form dipping seismicity lineations both along strike and nearly orthogonal to the main fault, and are composed of interlaced strike-slip and normal faults. The primary faults change dip with depth and become listric by transitioning to a dip of ~70° near a depth of 10 km. The Mw 5.2 Borrego Springs earthquake and past events with M > 4.0 occurred on the main faults, whereas most of the low-magnitude events are located in a damage zone (several kilometers wide) at seismogenic depths. The lack of significant low-magnitude seismicity on the main fault traces suggests that they do not creep. The very high rate of aftershocks likely reflects the large geometrical fault complexity and perhaps a relatively high stress due to a significant length of time elapsed since the last major event. The results provide important insights into the physics of faulting near the brittle-ductile transition.

  19. The activation of a single fault as a reduced self-affine image of the whole regional seismicity and a magnified self-affine image of the laboratory seismicity in terms of kHz electromagnetic precursors

    NASA Astrophysics Data System (ADS)

    Papadimitriou, C.; Kalimeri, M.; Kopanas, J.; Antonopoulos, G.; Peratzakis, A.; Eftaxias, K.

    2009-04-01

    Huang and Turcotte [1] have pointed out that the statistics of regional seismicity could be merely a macroscopic reflection of the physical processes in earthquake (EQ) source. Herein, we check this hypothesis in terms of precursory kHz electromagnetic (EM) emissions possibly associated with the fracture of high strength and large asperities that are distributed along the activated single fault sustaining the system [2]. The study has been attempted by means of: (i) A regional fault dynamics in terms of the slipping of two rough and rigid Brownian profiles one over the other [3]; (ii) Gutenberg-Richter law; (iii) A comparison between "roughness" of topography of fracture surfaces on one hand and "roughness" of pre-seismic kHz EM emissions on the other hand; (iv) A model for EQ dynamics consisting of two rough profiles interacting via fragments filling the gap has been recently introduced by Solotongo-Costa and Posadas [4]. The irregularities of the fault planes can interact with the fragments between them to develop a mechanism for triggering EQs. The fragments size distribution function comes from a nonextensive Tsallis formulation, starting from first principles. An energy distribution function, which gives a Gutenberg-Richter type law as a particular case, is analytically deduced: ( ) [ ( ) ( )] log(N (> m)) = logN + 2--q- × log 1- 1--q- 102m-- 1- q 2- q α2/3 (1) where N is the total number of EQs, N(> m) the number of EQs with magnitude larger than m, and m ≈ log(ɛ). α is the constant of proportionality between the EQ energy, ɛ, and the size of fragment, r. The above mentioned equation provides an excellent fit to seismicities generated in large geographic areas usually identified as "seismic regions", each of them covering many geological faults. The main result of the present distribution is that the statistics of regional seismicity can really be a macroscopic reflection of the physical processes in EQ source and a magnified self-affine image of the

  20. Naval weapons center active fault map series

    NASA Astrophysics Data System (ADS)

    Roquemore, G. R.; Zellmer, J. T.

    1987-08-01

    The NWC Active Fault Map Series shows the locations of active faults and features indicative of active faulting within much of Indian Wells Valley and portions of the Randsburg Wash/Mojave B test range areas of the Naval Weapons Center. Map annotations are used extensively to identify criteria employed in identifying the fault offsets, and to present other valuable data. All of the mapped faults show evidence of having moved during about the last 12,500 years or represent geologically young faults that occur within seismic gaps. Only faults that offset the surface or show other evidence of surface deformation were mapped. A portion of the City of Ridgecrest is recommended as being a Seismic Hazard Special Studies Zone in which detailed earthquake hazard studies should be required.

  1. A Comparison of Seismicity Characteristics and Fault Structure Between Stick-Slip Experiments and Nature

    NASA Astrophysics Data System (ADS)

    Goebel, T. H. W.; Sammis, C. G.; Becker, T. W.; Dresen, G.; Schorlemmer, D.

    2015-08-01

    Fault zones contain structural complexity on all scales. This complexity influences fault mechanics including the dynamics of large earthquakes as well as the spatial and temporal distribution of small seismic events. Incomplete earthquake records, unknown stresses, and unresolved fault structures within the crust complicate a quantitative assessment of the parameters that control factors affecting seismicity. To better understand the relationship between fault structure and seismicity, we examined dynamic faulting under controlled conditions in the laboratory by creating saw-cut-guided natural fractures in cylindrical granite samples. The resulting rough surfaces were triaxially loaded to produce a sequence of stick-slip events. During these experiments, we monitored stress, strain, and seismic activity. After the experiments, fault structures were imaged in thin sections and using computer tomography. The laboratory fault zones showed many structural characteristics observed in upper crustal faults, including zones of localized slip embedded in a layer of fault gouge. Laboratory faults also exhibited a several millimeter wide damage zone with decreasing micro-crack density at larger distances from the fault axis. In addition to the structural similarities, we also observed many similarities between our observed distribution of acoustic emissions (AEs) and natural seismicity. The AEs followed the Gutenberg-Richter and Omori-Utsu relationships commonly used to describe natural seismicity. Moreover, we observed a connection between along-strike fault heterogeneity and variations of the Gutenberg-Richter b value. As suggested by natural seismicity studies, areas of low b value marked the nucleation points of large slip events and were located at large asperities within the fault zone that were revealed by post-experimental tomography scans. Our results emphasize the importance of stick-slip experiments for the study of fault mechanics. The direct correlation of

  2. Seismic velocity changes associated with aseismic deformations of a fault stimulated by fluid injection

    NASA Astrophysics Data System (ADS)

    Rivet, Diane; De Barros, Louis; Guglielmi, Yves; Cappa, Frédéric; Castilla, Raymi; Henry, Pierre

    2016-09-01

    Fluid pressure plays an important role in the stability of tectonic faults. However, the in situ mechanical response of faults to fluid pressure variations is still poorly known. To address this question, we performed a fluid injection experiment in a fault zone in shales while monitoring fault movements at the injection source and seismic velocity variations from a near-distance (<10 m) monitoring network. We measured and located the P and S wave velocity perturbations in and around the fault using repetitive active sources. We observed that seismic velocity perturbations dramatically increase above 1.5 MPa of injection pressure. This is consistent with an increase of fluid flow associated with an aseismic dilatant shearing of the fault as shown by numerical modeling. We find that seismic velocity changes are sensitive to both fault opening by fluid invasion and effective stress variations and can be an efficient measurement for monitoring fluid-driven aseismic deformations of faults.

  3. Seismicity and recent faulting in eastern California and western and central Nevada: A preliminary report

    NASA Technical Reports Server (NTRS)

    Abdel-Gawad, M. (Principal Investigator); Silverstein, J.; Tubbesing, L.

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery covering the eastern California-Nevada seismic belt were utilized to study the fault pattern in relation to the distribution of earthquake epicenters and Quaternary volcanic rocks. Many suspected faults not previously mapped were identified. These include several suspected shear zones in Nevada, faults showing evidence of recent breakage, and major lineaments. Highly seismic areas are generally characterized by Holocene faulting and Quaternary volcanic activity. However, several major fault segments showing evidence of recent breakage are associated with little or no seismicity. The tectonic pattern strongly suggests that the eastern California-Nevada seismic belt coincides with a major crustal rift associated with zones of lateral shear. New data on potentially active fault zones have direct practical applications in national and local earthquake hazard reduction programs. Positive contacts have been made with Kern and Ventura Counties to make results of this investigation available for application to their earthquake hazards definition projects.

  4. Seismic Structure of the Endeavour Segment, Juan de Fuca Ridge: Correlations of Crustal Magma Chamber Properties With Seismicity, Faulting, and Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    van Ark, E. M.; Detrick, R. S.; Canales, J. P.; Carbotte, S. M.; Diebold, J. B.; Harding, A.; Kent, G.; Nedimovic, M. R.; Wilcock, W. S.

    2003-12-01

    -related cracking above the magma chamber, although the cross-axis line at the Salty Dawg vent field shows seismicity localized along a steeply dipping fault-like plane that terminates just above the magma chamber. A faint reflector at ~1.5 km below the seafloor (~700 m below the layer 2a reflector) is present near the top of this axial zone of seismicity and may represent a cracking-related boundary in the porosity structure of the shallow crust.

  5. Detecting hazardous New Zealand faults at depth using seismic velocity gradients

    NASA Astrophysics Data System (ADS)

    Ellis, S.; Van Dissen, R.; Eberhart-Phillips, D.; Reyners, M.; Dolan, J. F.; Nicol, A.

    2017-04-01

    Many large damaging earthquakes occur along previously unmapped faults, because it is difficult to locate active faults that have slow average slip rates, long recurrence intervals, and weak surface expression. We use recently collected seismic wave velocity data from New Zealand to test whether there is a strong correlation between seismic velocity gradients deep in the earth's crust, known active faults, and large shallow historical earthquakes. The correlation with active faults is significant at the 99% confidence level, suggesting that seismic velocity gradients at depth can pinpoint active - and in some cases unmapped - faults that may reactivate and rupture in infrequent earthquakes. In addition, all eight of the post-1840 Mw > 7 upper crustal earthquakes in New Zealand within the region of good tomographic coverage are spatially correlated with mid-crustal seismic velocity gradients and ruptured faults that intersect them. Many of the seismic velocity gradients coincide with the faulted edges of strong blocks within basement rocks, consistent with these marking preferred sites for fault reactivation owing to inherited strength contrasts. We propose that seismic velocity gradients provide a means to map potentially hazardous undiscovered faults at mid-crustal depths, in advance of their activation in future damaging earthquakes.

  6. Identifying active interplate and intraplate fault zones in the western Caribbean plate from seismic reflection data and the significance of the Pedro Bank fault zone in the tectonic history of the Nicaraguan Rise

    NASA Astrophysics Data System (ADS)

    Ott, B.; Mann, P.

    2015-12-01

    The offshore Nicaraguan Rise in the western Caribbean Sea is an approximately 500,000 km2 area of Precambrian to Late Cretaceous tectonic terranes that have been assembled during the Late Cretaceous formation of the Caribbean plate and include: 1) the Chortis block, a continental fragment; 2) the Great Arc of the Caribbean, a deformed Cretaceous arc, and 3) the Caribbean large igneous province formed in late Cretaceous time. Middle Eocene to Recent eastward motion of the Caribbean plate has been largely controlled by strike-slip faulting along the northern Caribbean plate boundary zone that bounds the northern margin of the Nicaraguan Rise. These faults reactivate older rift structures near the island of Jamaica and form the transtensional basins of the Honduran Borderlands near Honduras. Recent GPS studies suggest that small amount of intraplate motion within the current margin of error of GPS measurements (1-3 mm/yr) may occur within the center of the western Caribbean plate at the Pedro Bank fault zone and Hess Escarpment. This study uses a database of over 54,000 km of modern and vintage 2D seismic data, combined with earthquake data and results from previous GPS studies to define the active areas of inter- and intraplate fault zones in the western Caribbean. Intraplate deformation occurs along the 700-km-long Pedro Bank fault zone that traverses the center of the Nicaraguan Rise and reactivates the paleo suture zone between the Great Arc of the Caribbean and the Caribbean large igneous province. The Pedro Bank fault zone also drives active extension at the 200-km-long San Andres rift along the southwest margin of the Nicaraguan Rise. Influence of the Cocos Ridge indentor may be contributing to reactivation of faulting along the southwesternmost, active segment of the Hess Escarpment.

  7. High Resolution Seismic Reflection Survey for Coal Mine: fault detection

    NASA Astrophysics Data System (ADS)

    Khukhuudei, M.; Khukhuudei, U.

    2014-12-01

    High Resolution Seismic Reflection (HRSR) methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration. Modern coal mining requires certainly about geological faults and structural features. This paper focuses on 2D Seismic section mapping results from an "Zeegt" lignite coal mine in the "Mongol Altai" coal basin, which required the establishment of major structure for faults and basement. HRSR method was able to detect subsurface faults associated with the major fault system. We have used numerical modeling in an ideal, noise free environment with homogenous layering to detect of faults. In a coal mining setting where the seismic velocity of the high ranges from 3000m/s to 3600m/s and the dominant seismic frequency is 100Hz, available to locate faults with a throw of 4-5m. Faults with displacements as seam thickness detected down to several hundred meter beneath the surface.

  8. Self-induced seismicity due to fluid circulation along faults

    NASA Astrophysics Data System (ADS)

    Aochi, Hideo; Poisson, Blanche; Toussaint, Renaud; Rachez, Xavier; Schmittbuhl, Jean

    2014-03-01

    In this paper, we develop a system of equations describing fluid migration, fault rheology, fault thickness evolution and shear rupture during a seismic cycle, triggered either by tectonic loading or by fluid injection. Assuming that the phenomena predominantly take place on a single fault described as a finite permeable zone of variable width, we are able to project the equations within the volumetric fault core onto the 2-D fault interface. From the basis of this `fault lubrication approximation', we simulate the evolution of seismicity when fluid is injected at one point along the fault to model-induced seismicity during an injection test in a borehole that intercepts the fault. We perform several parametric studies to understand the basic behaviour of the system. Fluid transmissivity and fault rheology are key elements. The simulated seismicity generally tends to rapidly evolve after triggering, independently of the injection history and end when the stationary path of fluid flow is established at the outer boundary of the model. This self-induced seismicity takes place in the case where shear rupturing on a planar fault becomes dominant over the fluid migration process. On the contrary, if healing processes take place, so that the fluid mass is trapped along the fault, rupturing occurs continuously during the injection period. Seismicity and fluid migration are strongly influenced by the injection rate and the heterogeneity.

  9. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  10. Active, capable, and potentially active faults - a paleoseismic perspective

    USGS Publications Warehouse

    Machette, M.N.

    2000-01-01

    Maps of faults (geologically defined source zones) may portray seismic hazards in a wide range of completeness depending on which types of faults are shown. Three fault terms - active, capable, and potential - are used in a variety of ways for different reasons or applications. Nevertheless, to be useful for seismic-hazards analysis, fault maps should encompass a time interval that includes several earthquake cycles. For example, if the common recurrence in an area is 20,000-50,000 years, then maps should include faults that are 50,000-100,000 years old (two to five typical earthquake cycles), thus allowing for temporal variability in slip rate and recurrence intervals. Conversely, in more active areas such as plate boundaries, maps showing faults that are <10,000 years old should include those with at least 2 to as many as 20 paleoearthquakes. For the International Lithosphere Programs' Task Group II-2 Project on Major Active Faults of the World our maps and database will show five age categories and four slip rate categories that allow one to select differing time spans and activity rates for seismic-hazard analysis depending on tectonic regime. The maps are accompanied by a database that describes evidence for Quaternary faulting, geomorphic expression, and paleoseismic parameters (slip rate, recurrence interval and time of most recent surface faulting). These maps and databases provide an inventory of faults that would be defined as active, capable, and potentially active for seismic-hazard assessments.

  11. The Olmsted fault zone, southernmost Illinois: A key to understanding seismic hazard in the northern new Madrid seismic zone

    USGS Publications Warehouse

    Bexfield, C.E.; McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.

    2005-01-01

    Geological deformation in the northern New Madrid seismic zone, near Olmsted, Illinois (USA), is analyzed using integrated compressional-wave (P) and horizontally polarized-wave (SH) seismic reflection and regional and dedicated borehole information. Seismic hazards are of special concern because of strategic facilities (e.g., lock and dam sites and chemical plants on the Ohio River near its confluence with the Mississippi River) and because of alluvial soils subject to high amplification of earthquake shock. We use an integrated approach starting with lower resolution, but deeper penetration, P-wave reflection profiles to identify displacement of Paleozoic bedrock. Higher resolution, but shallower penetration, SH-wave images show deformation that has propagated upward from bedrock faults into Pleistocene loess. We have mapped an intricate zone more than 8 km wide of high-angle faults in Mississippi embayment sediments localized over Paleozoic bedrock faults that trend north to northeast, parallel to the Ohio River. These faults align with the pattern of epicenters in the New Madrid seismic zone. Normal and reverse offsets along with positive flower structures imply a component of strike-slip; the current stress regime favors right-lateral slip on northeast-trending faults. The largest fault, the Olmsted fault, underwent principal displacement near the end of the Cretaceous Period 65 to 70 million years ago. Strata of this age (dated via fossil pollen) thicken greatly on the downthrown side of the Olmsted fault into a locally subsiding basin. Small offsets of Tertiary and Quaternary strata are evident on high-resolution SH-wave seismic profiles. Our results imply recent reactivation and possible future seismic activity in a critical area of the New Madrid seismic zone. This integrated approach provides a strategy for evaluating shallow seismic hazard-related targets for engineering concerns. ?? 2005 Elsevier B.V. All rights reserved.

  12. [X-ray diffraction and infrared spectrum analysis of fault gouge in Wenchuan seismic belt].

    PubMed

    Wang, Zheng-Yang; Cao, Jian-Jin; Luo, Song-Ying; Liao, Yi-Peng

    2014-05-01

    Wenchuan earthquake produced a series of co-seismic surface ruptures in Leigu and Zhaojiagou, and we collected samples of co-seismic fault gouge in the surface ruptures as well as the old gouge in the fault of Nanba. Testing The new and old fault gouge was tested with X-ray diffraction and infrared absorption spectra, and its characteristics such as mineral compositions, clay mineral contents and combinations were comprehensively analyzed. The results display obvious differences between the new and old fault gouge, showing that the old fault gouge is mainly composed of wall rock debris or milled powders, while the main components of new fault gouge are clay minerals. The assemblage of clay minerals composition shows that the environment of the fault activity was mainly warm and humid, and the clay minerals were mainly transformed by low temperature and low pressure dynamic metamorphism. And this also partly indicates that the latest way of the fault activity in this area may be a creeping. However the previous researches on the fault gouge of Wenchuan earthquake fault zone are mainly focused on its mechanical properties as well as its texture and structure, the research in this paper is to determine the physical and chemical environment of fault activity through the mineral compositions and clay mineral contents in the fault gouge characteristics, and this research has important scientific significance to the researches on the evolution of the fault environment and the activity mechanism of the earthquake.

  13. 3-D seismic response of buried pipelines laid through fault

    SciTech Connect

    Liang, J.W.

    1995-12-31

    An ideal model for the non-causative fault is put forward in which the fault is assumed to be composed by three horizontally adjacent soil media. Dynamic behaviors of pipelines laid through the fault is analyzed. Although simple, this model may qualitatively illustrate the accumulation of seismic waves in the fault, so illustrate the dynamic behaviors of the pipelines. The results show that, the fault is materially different from a two soil site even if the fault width is very narrow, and the dynamic behaviors of the pipelines laid through the fault are determined by the fault width, the stiffness ratio of the three soil media, and the type of the seismic waves.

  14. Fault interaction and implications for seismic hazard in the southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Luo, G.; Liu, M.

    2013-12-01

    Longmenshan fault at ~50-100 Pa/yr. On the other hand, active seismicity on the Longmenshan fault transfers more stresses to the southern Xianshuihe fault, but interseismic locking on the Longmenshan fault increases stress accumulation on the Anninghe fault.

  15. Seismic Velocity Structure Across the Quebrada and Gofar Oceanic Transform Faults from 2D Refraction Tomography - A Comparison of Faults with High and Low Seismic Slip Deficits

    NASA Astrophysics Data System (ADS)

    Roland, E. C.; McGuire, J. J.; Collins, J. A.; Lizarralde, D.

    2009-12-01

    We perform two 2-D tomographic inversions using data collected as a part of the Quebrada-Discovery-Gofar (QDG) Transform Fault Active/Passive Experiment. The QDG transform faults are located in the southern Pacific Ocean and offset the East Pacific Rise (EPR) at approximately 4° south. In the spring of 2008, two ~100 km refraction profiles were collected, each using 8 short period Ocean Bottom Seismometers (OBS) from OBSIP and over 900 shots from the RV Marcus Langseth, across the easternmost segments of the Quebrada and Gofar transform faults. The two refraction profiles are modeled using a 2-D tomographic code that allows joint inversion of the Pg, PmP, and Pn arrivals (Korenaga et al., 2000). Variations in crustal velocity and thickness, as well as the width and depth extent of a significant low velocity zone within and below the transform valley provide some insight into the material properties of each of the fault-zones. Reduced seismic velocities that are 0.5 to over 1.0 km/s slower than velocities associated with the oceanic crust outside the fault zone may indicate the highly fractured fault zone lithology. The low velocity zone associated with the Quebrada fault also extends to the south of the active fault zone, beneath a fossil fault trace. Because Gofar is offset by an intratransform spreading center, we are able to compare ‘normal’ oceanic crust produced at the EPR to the south of the fault with crust associated with the ~15 km intratransform spreading center to the north. These two high slip rate (14 cm/yr) faults look similar morphologically and demonstrate comparable microseismicity characteristics, however their abilities to generate large earthquakes differ significantly. Gofar generates large earthquakes (Mw ~6) regularly every few years, but in the past 24 years only one large (Mw 5.6) event has been reliably located on Quebrada. The contrasting seismic behavior of these faults represents the range of behavior observed in the global

  16. Modeling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale-gas reservoirs

    EPA Pesticide Factsheets

    LBNL, in consultation with the EPA, expanded upon a previous study by injecting directly into a 3D representation of a hypothetical fault zone located in the geologic units between the shale-gas reservoir and the drinking water aquifer.

  17. Field measurements of fault slow slip and associated seismicity

    NASA Astrophysics Data System (ADS)

    Guglielmi, Y.; Cappa, F.; Avouac, J. P.; Henry, P.; Elsworth, D.

    2015-12-01

    We show results of slow slip (1-to-10 micrometers/seconds) activations along faults in carbonates and in shales using a hydromechanical in situ testing method. A controlled step-rate injection of a given water volume is conducted between two inflatable packers in an uncased borehole, to produce elastic and inelastic deformations of the surrounding fractured rock mass, with synchronously monitoring of borehole fluid pressure and wall deformation with a specially designed probe. The transition between elastic/inelastic slip occurs at the fault extension pressure (FEP) at the onset of injection flowrate increase. In a typical test, the FEP transition associated with the characterization of the activated slip (strike and dip) on the faults may be used for calibration in a slip sensitivity study related to the ambient stress field. The potential use of the post FEP's response to estimate the variation of the friction coefficient as a function of slip, slip rate and other static controls is discussed taking different in situ test examples. We show that permeability increase may be a predominant control on fault stability and induced seismicity.

  18. Shallow seismic imaging of folds above the Puente Hills blind-thrust fault, Los Angeles, California

    NASA Astrophysics Data System (ADS)

    Pratt, Thomas L.; Shaw, John H.; Dolan, James F.; Christofferson, Shari A.; Williams, Robert A.; Odum, Jack K.; Plesch, Andreas

    2002-05-01

    High-resolution seismic reflection profiles image discrete folds in the shallow subsurface (<600 m) above two segments of the Puente Hills blind-thrust fault system, Los Angeles basin, California. The profiles demonstrate late Quaternary activity at the fault tip, precisely locate the axial surfaces of folds within the upper 100 m, and constrain the geometry and kinematics of recent folding. The Santa Fe Springs segment of the Puente Hills fault zone shows an upward-narrowing kink band with an active anticlinal axial surface, consistent with fault-bend folding above an active thrust ramp. The Coyote Hills segment shows an active synclinal axial surface that coincides with the base of a 9-m-high scarp, consistent with tip-line folding or the presence of a backthrust. The seismic profiles pinpoint targets for future geologic work to constrain slip rates and ages of past events on this important fault system.

  19. Shallow seismic imaging of folds above the Puente Hills blind-thrust fault, Los Angeles, California

    USGS Publications Warehouse

    Pratt, T.L.; Shaw, J.H.; Dolan, J.F.; Christofferson, S.A.; Williams, R.A.; Odum, J.K.; Plesch, A.

    2002-01-01

    High-resolution seismic reflection profiles image discrete folds in the shallow subsurface (<600 m) above two segments of the Puente Hills blind-thrust fault system, Los Angeles basin, California. The profiles demonstrate late Quaternary activity at the fault tip, precisely locate the axial surfaces of folds within the upper 100 m, and constrain the geometry and kinematics of recent folding. The Santa Fe Springs segment of the Puente Hills fault zone shows an upward-narrowing kink band with an active anticlinal axial surface, consistent with fault-bend folding above an active thrust ramp. The Coyote Hills segment shows an active synclinal axial surface that coincides with the base of a 9-m-high scarp, consistent with tip-line folding or the presence of a backthrust. The seismic profiles pinpoint targets for future geologic work to constrain slip rates and ages of past events on this important fault system.

  20. Injection-induced seismicity on basement faults including poroelastic stressing

    NASA Astrophysics Data System (ADS)

    Chang, K. W.; Segall, P.

    2016-04-01

    Most significant induced earthquakes occur on faults within the basement beneath sedimentary cover. In this two-dimensional plane strain numerical study, we examine the full poroelastic response of basement faults to fluid injection into overlying strata, considering both (1) the permeability of the fault zone and (2) the hydraulic connectivity of the faults to the target horizon. Given hydraulic and mechanical properties, we compute the spatiotemporal change in Coulomb stress, which we separate into (1) the change in poroelastic stresses Δτs+fΔσn, where Δτs and Δσn are changes in shear and normal stress (Δτs>0 and Δσn>0 both favor slip), and (2) the change in pore pressure fΔp. Pore pressure diffusion into hydraulically connected, permeable faults dominates their mechanical stability. For hydraulically isolated or low-permeability faults, however, poroelastic stresses transmitted to deeper basement levels can trigger slip, even without elevated pore pressure. The seismicity rate on basement fault zones is predicted using the model of Dieterich (1994). High seismicity rates can occur on permeable, hydraulically connected faults due to direct pore pressure diffusion. Lower rates are predicted on isolated steeply dipping normal faults, caused solely by poroelastic stressing. In contrast, seismicity on similarly oriented reverse faults is inhibited.

  1. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, D.; Butler, R. W. H.; Purves, S.; McArdle, N.; De Freslon, N.

    2016-08-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic (10 s m) to seismic scale (100 s m). They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies from the Taranaki basin and deep-water Niger delta are presented. These resolve SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  2. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Butler, Rob; Purves, Steve

    2016-04-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic to seismic scale. They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data scale. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies, from the Taranaki basin and deep-water Niger delta are presented. These resolve structure within SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  3. a case of casing deformation and fault slip for the active fault drilling

    NASA Astrophysics Data System (ADS)

    Ge, H.; Song, L.; Yuan, S.; Yang, W.

    2010-12-01

    Active fault is normally defined as a fault with displacement or seismic activity during the geologically recent period (in the last 10,000 years, USGS). Here, we refer the active fault to the fault that is under the post-seismic stress modification or recovery. Micro-seismic, fault slip would happen during the recovery of the active faults. It is possible that the drilling through this active fault, such as the Wenchuan Fault Scientific Drilling(WFSD), will be accompanied with some possible wellbore instability and casing deformation, which is noteworthy for the fault scientific drilling. This presentation gives a field case of the Wenchuan earthquake. The great Wenchuan earthquake happened on May 12, 2008. An oilfield is 400km apart from the epicenter and 260km from the main fault. Many wells were drilled or are under drilling. Some are drilled through the active fault and a few tectonic active phenomenons were observed. For instance, a drill pipe was cut off in the well which was just drilled through the fault. We concluded that this is due to the fault slip,if not, so thick wall pipe cannot be cut off. At the same time, a mass of well casings of the oilfield deformed during the great Wenchuan Earthquake. The analysis of the casing deformation characteristic, formation structure, seismicity, tectonic stress variation suggest that the casing deformation is closely related to the Wenchuan Earthquake. It is the tectonic stress variation that induces seismic activities, fault slip, salt/gypsum creep speedup, and deformation inconsistent between stratums. Additional earthquake dynamic loads were exerted on the casing and caused its deformation. Active fault scientific drilling has become an important tool to understand earthquake mechanism and physics. The casing deformation and wellbore instability is not only a consequence of the earthquake but also an indicator of stress modification and fault activity. It is noteworthy that tectonic stress variation and fault

  4. Slip deficit and location of seismic gaps along the Dead Sea Fault

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha; Toussaint, Renaud; Ferry, Matthieu; Nguema-Edzang, Parfait

    2015-04-01

    The Dead Sea Fault (DSF), a ~ 1000-km-long North-South trending transform fault presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short-term slip rates along the Dead Sea fault. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these long-term estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. Indeed, recent GPS results showing 3 +-0.5 mm/yr velocity rate of the northern DSF appear to be in contradiction with the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern with the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this contribution, we present the calculated seismic slip deficit along the fault segments and discuss the identification of seismic gaps and the implication for the seismic hazard assessment.

  5. The Relationship Between Seismicity and Fault Structure on the Discovery Transform Fault, East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Wolfson-Schwehr, M.; Boettcher, M. S.; McGuire, J. J.; Collins, J. A.

    2013-12-01

    , 2001, and 2012, suggesting that this fault segment may be fully locked between large events. By contrast, the centroid location for the second largest rupture patch (4 Mw 5.5 - 5.8 earthquakes in 1996, 2001, 2007, and 2012) on the western segment coincides with the area of highest microseismicity rate. This 5-km wide zone contains approximately 25% of the relocated microseismicity on Discovery. The smallest rupture patch on Discovery (3 Mw 5.4 - 5.5 earthquakes in 1998, 2003, and 2007) is located just west of the intra-transform spreading center and coincides with a zone of low seismic productivity, suggesting increased seismic coupling. The two rupture patches on the eastern segment of Discovery were outside the OBS array, and thus the microseismic activity in those regions is not well constrained. The results of this study suggest that physical fault structure influences the location and size of large repeating rupture patches, and provides a secondary control on the location of microseismicity. Fault structure, however, cannot account for all aspects of seismic activity on Discovery, and thus we suspect that varying mechanical properties along the fault, and specifically within the large rupture patches, are the primary controls on the location and rate of microseismicity.

  6. High Resolution Seismic Imaging of Fault Zones: Methods and Examples From The San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Catchings, R. D.; Rymer, M. J.; Goldman, M.; Prentice, C. S.; Sickler, R. R.; Criley, C.

    2011-12-01

    Seismic imaging of fault zones at shallow depths is challenging. Conventional seismic reflection methods do not work well in fault zones that consist of non-planar strata or that have large variations in velocity structure, two properties that occur in most fault zones. Understanding the structure and geometry of fault zones is important to elucidate the earthquake hazard associated with fault zones and the barrier effect that faults impose on subsurface fluid flow. In collaboration with the San Francisco Public Utilities Commission (SFPUC) at San Andreas Lake on the San Francisco peninsula, we acquired combined seismic P-wave and S-wave reflection, refraction, and guided-wave data to image the principal strand of the San Andreas Fault (SAF) that ruptured the surface during the 1906 San Francisco earthquake and additional fault strands east of the rupture. The locations and geometries of these fault strands are important because the SFPUC is seismically retrofitting the Hetch Hetchy water delivery system, which provides much of the water for the San Francisco Bay area, and the delivery system is close to the SAF at San Andreas Lake. Seismic reflection images did not image the SAF zone well due to the brecciated bedrock, a lack of layered stratigraphy, and widely varying velocities. Tomographic P-wave velocity images clearly delineate the fault zone as a low-velocity zone at about 10 m depth in more competent rock, but due to soil saturation above the rock, the P-waves do not clearly image the fault strands at shallower depths. S-wave velocity images, however, clearly show a diagnostic low-velocity zone at the mapped 1906 surface break. To image the fault zone at greater depths, we utilized guided waves, which exhibit high amplitude seismic energy within fault zones. The guided waves appear to image the fault zone at varying depths depending on the frequency of the seismic waves. At higher frequencies (~30 to 40 Hz), the guided waves show strong amplification at the

  7. An induced seismicity experiment across a creeping segment of the Philippine Fault

    NASA Astrophysics Data System (ADS)

    Prioul, R.; Cornet, F. H.; Dorbath, C.; Dorbath, L.; Ogena, M.; Ramos, E.

    2000-06-01

    The location of seismicity induced by forced fluid flow provides information about domains of pore pressure variation, while changes in fluid content are identified through changes in seismic velocity. These effects have been investigated in the geothermal field of Tongonan, which lies on a creeping portion of the Philippine Fault on Ley te Island. Locally, the left-lateral strike-slip Philippine Fault branches out into three subparallel segments (Eastern, Central and Western Fault Lines). In June-July 1997, a water stimulation was undertaken in a well that intersects the Central Fault Line 1980 m below ground surface; 36,000 m3 were injected between the casing shoe at 1308 m and the well bottom at 2177 m. The seismicity was monitored with a surface station network of 18 stations. More than 400 events, induced by the injection experiment as well as by routine injections associated with the geothermal field exploitation, were recorded in the vicinity of the well. They have been located through a simultaneous three-dimensional (3-D) velocity-hypocenter inversion procedure. None of the microearthquakes are located along the Central Fault Line, they all occurred below the casing shoe to the east of the fault line, i.e., within the geothermal reservoir and mostly below the bottom of the well. Results from the injection experiment and the 18 months of seismic monitoring along the Central and West Fault Lines suggest an aseismic behavior of this major continental fault at this location. The 3-D velocity model, determined from the travel time inversion for seismic events observed during injections, is compared to that obtained from seismic monitoring conducted prior to any injection activities. An increase of P wave velocity is observed during the water injection. This velocity increase is localized within the seismicity cloud and is interpreted as an increase in liquid content within the initial liquid-vapor multiphase part of the reservoir.

  8. Heating and Weakening of Major Faults During Seismic Rupture

    NASA Astrophysics Data System (ADS)

    Rice, J. R.

    2007-12-01

    The absence of significant heat flow from major fault zones, and scarcity of evidence for their seismic melting, means that during earthquake slip such zones could not retain shear strength comparable to the typically high static friction strength of rocks. One line of explanation is that they are actually statically weak, which could be because materials of exceptionally low friction (smectites, talc) accumulate along fault zones, or perhaps because pore pressure within the fault core is far closer to lithostatic than hydrostatic. Without dismissing either, the focus here is on how thermal processes during the rapid slips of seismic rupture can weaken a fault which is indeed statically strong. (The discussion also leaves aside another kind of non- thermal dynamic weakening, possible when there is dissimilarity in seismic properties across the fault, and/or in poroelastic properties and permeability within fringes of damaged material immediately adjoining the slip surface. Spatially nonuniform mode II slip like near a propagating rupture front may then induce a substantial reduction in the effective normal stress \\barσ.) The heating and weakening processes to be discussed divide roughly into two camps: (1) Those which are expected to be active from the start of seismic slip, and hence will be present in all earthquakes; and (2) Those that kick-in after threshold conditions of rise of temperature T or accumulation of slip are reached, and hence become a feature of larger, or at least deeper slipping, earthquakes. It has been argued that the two major players of (1) are as follows: (1.1) Flash heating and weakening of frictional contact asperities in rapid slip [Rice, 1999, 2006; Tullis and Goldsby, 2003; Goldsby and Hirth, 2006; Beeler et al., 2007; Yuan and Prakash, 2007]. That gives a strong velocity-weakening character to the friction coefficient, which is consistent with inducing self-healing rupture modes [Noda et al., 2006; Lu et al., 2007]. It is a process

  9. Steep-dip seismic imaging of the shallow San Andreas Fault near Parkfield

    USGS Publications Warehouse

    Hole, J.A.; Catchings, R.D.; St. Clair, K.C.; Rymer, M.J.; Okaya, D.A.; Carney, B.J.

    2001-01-01

    Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70° to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed locations of earthquakes and the surface fault trace. The seismic velocity cross section shows strong lateral variations. Relatively low velocity (10 to 30%), high electrical conductivity, and low density indicate a 1-kilometer-wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace.

  10. Nonlinear dynamic failure process of tunnel-fault system in response to strong seismic event

    NASA Astrophysics Data System (ADS)

    Yang, Zhihua; Lan, Hengxing; Zhang, Yongshuang; Gao, Xing; Li, Langping

    2013-03-01

    Strong earthquakes and faults have significant effect on the stability capability of underground tunnel structures. This study used a 3-Dimensional Discrete Element model and the real records of ground motion in the Wenchuan earthquake to investigate the dynamic response of tunnel-fault system. The typical tunnel-fault system was composed of one planned railway tunnel and one seismically active fault. The discrete numerical model was prudentially calibrated by means of the comparison between the field survey and numerical results of ground motion. It was then used to examine the detailed quantitative information on the dynamic response characteristics of tunnel-fault system, including stress distribution, strain, vibration velocity and tunnel failure process. The intensive tunnel-fault interaction during seismic loading induces the dramatic stress redistribution and stress concentration in the intersection of tunnel and fault. The tunnel-fault system behavior is characterized by the complicated nonlinear dynamic failure process in response to a real strong seismic event. It can be qualitatively divided into 5 main stages in terms of its stress, strain and rupturing behaviors: (1) strain localization, (2) rupture initiation, (3) rupture acceleration, (4) spontaneous rupture growth and (5) stabilization. This study provides the insight into the further stability estimation of underground tunnel structures under the combined effect of strong earthquakes and faults.

  11. Interaction between Cenozoic fault activity and sediment influx in the Arctic region: new thermochronologic data and seismic study

    NASA Astrophysics Data System (ADS)

    Bigot-Buschendorf, Maelianna; Mouthereau, Frédéric; Fillon, Charlotte; Loget, Nicolas; Labrousse, Loïc; Werner, Philippe; Bernet, Matthias; Ehlers, Todd

    2015-04-01

    The Alaskan Brooks Range and its canadian counterpart, the British Mountains result from the Meso-Cenozoic collision of the Arctic continental margin with accreted volcanic arcs and adjacent continental terranes. Because of its location and known potential for oil industries, more attention has been brought to this area for the last few years. While the timing of collisional events, duration, and rates of exhumation associated with mountain building is now better understood, the causes of these exhumation events are still largely unknown. Published constraints and our present data are consistent with progressive cooling from 105 to 25 Ma, with rates of exhumation constant across the range until 35-25 Ma. From 35 Ma onwards, exhumation likely slowed in concomitance with underplating/duplexing in the inner part of the belt (Doonerak window) and activation of the northernmost thrust. The earliest cooling stage (from 100 Ma) marking the onset of the Brookian orogeny is recorded by a low order coarsening upward sequence in the foreland. On the contrary, the latest stage of cooling (at 35 Ma) is not linked to the construction of the range but more likely due to a reorganization of the wedge possibly related to changes in the regional climatic or geodynamic boundary conditions. First, we aim at reconstructing the time-temperature evolution of the British Mountains by combining new (U-Th)/He and fission-tracks ages on zircon and apatite ; our first thermochronological data in the British Mountains show ages ranging from 110 to 25 Ma from range to basin. These data will permit to reconstruct the thermal history of the British Mountains and its basin, and to estimate the exhumation rates associated to the main unities. Then, we also examine the role of climate during the Tertiary period. Some markers indicate a climate change at this period which could be registered in the sedimentation. Therefore we determine the part of climate by analyzing seismic lines in the Beaufort

  12. Seismic images and fault relations of the Santa Monica thrust fault, West Los Angeles, California

    USGS Publications Warehouse

    Catchings, R.D.; Gandhok, G.; Goldman, M.R.; Okaya, D.

    2001-01-01

    In May 1997, the US Geological Survey (USGS) and the University of Southern California (USC) acquired high-resolution seismic reflection and refraction images on the grounds of the Wadsworth Veterans Administration Hospital (WVAH) in the city of Los Angeles (Fig. 1a,b). The objective of the seismic survey was to better understand the near-surface geometry and faulting characteristics of the Santa Monica fault zone. In this report, we present seismic images, an interpretation of those images, and a comparison of our results with results from studies by Dolan and Pratt (1997), Pratt et al. (1998) and Gibbs et al. (2000). The Santa Monica fault is one of the several northeast-southwest-trending, north-dipping, reverse faults that extend through the Los Angeles metropolitan area (Fig. 1a). Through much of area, the Santa Monica fault trends subparallel to the Hollywood fault, but the two faults apparently join into a single fault zone to the southwest and to the northeast (Dolan et al., 1995). The Santa Monica and Hollywood faults may be part of a larger fault system that extends from the Pacific Ocean to the Transverse Ranges. Crook et al. (1983) refer to this fault system as the Malibu Coast-Santa Monica-Raymond-Cucamonga fault system. They suggest that these faults have not formed a contiguous zone since the Pleistocene and conclude that each of the faults should be treated as a separate fault with respect to seismic hazards. However, Dolan et al. (1995) suggest that the Hollywood and Santa Monica faults are capable of generating Mw 6.8 and Mw 7.0 earthquakes, respectively. Thus, regardless of whether the overall fault system is connected and capable of rupturing in one event, individually, each of the faults present a sizable earthquake hazard to the Los Angeles metropolitan area. If, however, these faults are connected, and they were to rupture along a continuous fault rupture, the resulting hazard would be even greater. Although the Santa Monica fault represents

  13. Patterns of seismic activity preceding large earthquakes

    NASA Technical Reports Server (NTRS)

    Shaw, Bruce E.; Carlson, J. M.; Langer, J. S.

    1992-01-01

    A mechanical model of seismic faults is employed to investigate the seismic activities that occur prior to major events. The block-and-spring model dynamically generates a statistical distribution of smaller slipping events that precede large events, and the results satisfy the Gutenberg-Richter law. The scaling behavior during a loading cycle suggests small but systematic variations in space and time with maximum activity acceleration near the future epicenter. Activity patterns inferred from data on seismicity in California demonstrate a regional aspect; increased activity in certain areas are found to precede major earthquake events. One example is given regarding the Loma Prieta earthquake of 1989 which is located near a fault section associated with increased activity levels.

  14. Seismicity distribution and locking depth along the Main Marmara Fault, Turkey

    NASA Astrophysics Data System (ADS)

    Schmittbuhl, J.; Karabulut, H.; Lengliné, O.; Bouchon, M.

    2016-03-01

    The seismicity along the Main Marmara Fault (MMF) below the Marmara Sea is analyzed during the 2007-2012 period to provide insights on the recent evolution of this important regional seismic gap. High precision locations show that seismicity is strongly varying along strike and depth providing fine details of the fault behavior that are inaccessible from geodetic observations. The activity strongly clusters at the regions of transition between basins. The Central basin shows significant seismicity located below the shallow locking depth inferred from GPS measurements. Its b-value is low and the average seismic slip is high. All observations are consistent with a deep creep of this segment. On the contrary, the Kumburgaz basin at the center of the fault shows sparse seismicity with the hallmarks of a locked segment. In the eastern Marmara Sea, the seismicity distribution along the Princes Island segment in the Cinarcik basin, is consistent with the geodetic locking depth of 10 km and a low contribution to the regional seismic energy release. The assessment of the locked segment areas provide an estimate of the magnitude of the main forthcoming event to be about 7.3 assuming that the rupture will not enter significantly within creeping domains.

  15. Prediction of sub-seismic faults and fractures to ensure carbon traps - joint project PROTECT

    NASA Astrophysics Data System (ADS)

    Ziesch, Jennifer; Tanner, David C.; Beilecke, Thies; Krawczyk, Charlotte M.

    2015-04-01

    Deformation in the form of fractures and faults affects many reservoirs and their overburden. In a 3-D seismic data set we can identify faults on the large scale, while in well data we observe small-scale fractures. A large number of faults at the intermediate scale (sub-seismic space) also plays a very important role, but these are not detectable with conventional geophysical methods. Therefore, we use the retro-deformation approach within the context of long-term CO2 storage integrity to determine the characteristics of potential fluid migration pathways between reservoir and surface. This allows to produce strain maps, in order to analyse fault behaviour in the sub-seismic space. As part of the PROTECT (prediction of deformation to ensure carbon traps) project we focus on the sub-seismic faults of the CO2CRC Otway Project site in Australia. We interpreted a geological 3-D model of 8 km x 7 km x 4.5 km that comprises 8 stratigraphic horizons and 24 large-scale faults. This confirmed the site to contain a complex system of south-dipping normal faults and north-dipping antithetic normal faults. The most important aspect is that two different types of fault kinematics were simultaneously active: Dip-slip and a combination of dip-slip with dextral strike slip movement. After the retro-deformation of the 3-D model we calculated strain tensor maps to locate highly deformed or fractured zones and their orientation within the stratigraphic volume. The e1-strain magnitude shows heterogeneous distribution. The south of the study area is at least twice as much fractured on a sub-seismic scale. Four major faults act as "controlling faults" with smaller faults in between. The overburden is tilted northwards after retro-deformation. Thus, we believe that the area was affected by an even larger normal fault outside of the study area. In summary, this study reveals that good knowledge of the kinematics of the large-scale faults is essential to predict sub-seismic structures

  16. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    SciTech Connect

    Rutqvist, Jonny; Rinaldi, Antonio P.; Cappa, Frédéric; Moridis, George J.

    2013-07-01

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned towards conditions usually encountered in the Marcellus shale play in the Northeastern US at an approximate depth of 1500 m (~;;4,500 feet). Our modeling simulations indicate that when faults are present, micro-seismic events are possible, the magnitude of which is somewhat larger than the one associated with micro-seismic events originating from regular hydraulic fracturing because of the larger surface area that is available for rupture. The results of our simulations indicated fault rupture lengths of about 10 to 20 m, which, in rare cases can extend to over 100 m, depending on the fault permeability, the in situ stress field, and the fault strength properties. In addition to a single event rupture length of 10 to 20 m, repeated events and aseismic slip amounted to a total rupture length of 50 m, along with a shear offset displacement of less than 0.01 m. This indicates that the possibility of hydraulically induced fractures at great depth (thousands of meters) causing activation of faults and creation of a new flow path that can reach shallow groundwater resources (or even the surface) is remote. The expected low permeability of faults in producible shale is clearly a limiting factor for the possible rupture length and seismic magnitude. In fact, for a fault that is initially nearly-impermeable, the only possibility of larger fault slip event would be opening by hydraulic fracturing; this would allow pressure to penetrate the matrix along the fault and to reduce the frictional strength over a sufficiently large fault surface patch. However, our simulation results show that if the fault is initially impermeable, hydraulic fracturing along the fault results in numerous small micro-seismic events along with the propagation, effectively

  17. Seismicity along the Main Marmara Fault, Turkey: from space-time distribution to repeating events

    NASA Astrophysics Data System (ADS)

    Schmittbuhl, Jean; Karabulut, Hayrullah; Lengliné, Olivier; Bouchon, Michel

    2016-04-01

    The North Anatolian Fault (NAF) poses a significant hazard for the large cities surrounding the Marmara Sea region particularly the megalopolis of Istanbul. Indeed, the NAF is presently hosting a long unruptured segment below the Sea of Marmara. This seismic gap is approximately 150 km long and corresponds to the Main Marmara Fault (MMF). The seismicity along the Main Marmara Fault (MMF) below the Marmara Sea is analyzed here during the 2007-2012 period to provide insights on the recent evolution of this important regional seismic gap. High precision locations show that seismicity is strongly varying along strike and depth providing fine details of the fault behavior that are inaccessible from geodetic inversions. The activity strongly clusters at the regions of transition between basins. The Central basin shows significant seismicity located below the shallow locking depth inferred from GPS measurements. Its b-value is low and the average seismic slip is high. Interestingly we found also several long term repeating earthquakes in this domain. Using a template matching technique, we evidenced two new families of repeaters: a first family that typically belongs to aftershock sequences and a second family of long lasting repeaters with a multi-month recurrence period. All observations are consistent with a deep creep of this segment. On the contrary, the Kumburgaz basin at the center of the fault shows sparse seismicity with the hallmarks of a locked segment. In the eastern Marmara Sea, the seismicity distribution along the Princes Island segment in the Cinarcik basin, is consistent with the geodetic locking depth of 10km and a low contribution to the regional seismic energy release. The assessment of the locked segment areas provide an estimate of the magnitude of the main forthcoming event to be about 7.3 assuming that the rupture will not enter significantly within creeping domains.

  18. Seismic Imaging at Whataroa Valley (New Zealand) for the Deep-Fault-Drilling-Project Alpine Fault

    NASA Astrophysics Data System (ADS)

    Lay, V.; Buske, S.; Kovacs, A.; Gorman, A. R.

    2013-12-01

    The Alpine Fault in New Zealand (South Island) is one of the largest active plate-bounding continental fault zones on Earth with earthquakes of magnitude 7.9 occuring every 200-400 years. Due to the surface exposure and the shallow depth of mechanical and chemical transitions it is a globally significant natural laboratory. Within the ICDP Deep-Fault-Drilling-Project Alpine Fault (DFDP-AF; https://wiki.gns.cri.nz/DFDP) a drill hole shall give insight into the geological structure of the fault zone and its evolution to understand the related deformation and earthquake processes. With the help of advanced seismic imaging techniques the shallow structure of the Alpine Fault is imaged to find the most suitable drill site location. A new seismic reflection profile has been acquired in 2011 by the WhataDUSIE project team consisting of partners from the University of Otago (New Zealand), TU Bergakademie Freiberg (Germany) and the University of Alberta (Canada). The reflection profile, located in the Whataroa river valley, has a total length of about 5 km. Up to 643 geophones with spacings between 4-8 m recorded the approximately 100 shots along the profile line. Single shot gathers as well as imaging results will be presented. The obtained data quality was in general very good. Nevertheless, extensive preprocessing of the data had to be performed to obtain shot gathers usable for imaging. Due to the field conditions the profile was divided into 5 parts with different features concerning geophone spacing and eigenfrequency of the geophones. To combine the single stations to one shot gather, we used overlapping geophones to derive the relative time corrections by crosscorrelating these particular traces. Additionally three Reftek 130 stations were recording continuously. By correlating the absolute Reftek time and the adjacent geophone trace we extracted the absolute shot time and applied the resulting time-shift to the corresponding traces. Finally the merged single shot

  19. Initial Seismic Characterization of a Fault Controlled Hydrothermal Area

    NASA Astrophysics Data System (ADS)

    Bradford, J.; Lyle, M.; Clement, B.; Liberty, L.; Myers, R.; Paul, C.

    2002-12-01

    As part of an interdisciplinary project that aims to study the link between the physical characteristics of hydrothermal systems and the biota that occupy those systems, we have begun a detailed geophysical characterization of the Borax Lake hydrothermal area located near the center of Alvord Valley in the basin and range province of southeast Oregon. Basement rock is comprised of Miocene volcanic deposits overlain by up to 700 m of unconsolidated alluvium. Previous workers, based on gravity data and surface mapping, suggest that the Borax Lake hydrothermal area lies directly over a north/south trending fault. We are conducting seismic investigations on both a basin scale, to place the hydrothermal system in a larger geologic context, and a local high resolution scale for detailed imaging of fault architecture and hydrothermal flow paths. In this initial investigation, our primary objectives are to verify that a fault zone is present beneath the Borax Lake hot springs and to conduct tests to constrain acquisition parameters for detailed 3D seismic investigation. Initial seismic source tests indicate that the area is well suited to high resolution seismic investigation with clear reflections as deep as 300 ms and frequency content up to 500 Hz. Walk-away gathers show that the fluid distribution near the hot springs is complex with sharp gradients in the piezometric surface. To test the fault zone interpretation, and begin to build a large scale image of basin geometry, we acquired a 3.5 km seismic reflection profile perpendicular to the suspected fault zone. The profile consists of 30-fold CMP data acquired using a trailer mounted, 400 lb accelerated weight drop. Reflections are evident to depths of at least 500 m. Additionally, we acquired parallel magnetic profiles to constrain interpretation of the seismic data. Evidence for faulting is clear with the seismic image showing a complex normal fault zone bounded to the west by a structural high. Refraction analysis

  20. Characteristic scale of heterogeneity of seismically active fault and its manifestation in scaling of earthquake source spectra

    NASA Astrophysics Data System (ADS)

    Gusev, A. A.

    2016-10-01

    Previously, similarity of source spectra of Kamchatka earthquakes with respect to the common corner frequency f c1 and the expressed deviations from similarity for the second f c2 and the third f c3 corner frequencies were revealed. The value of f c3 reflects the characteristic size L is of fault surface; correspondingly, L is ≈ v r T is , where v r is the rupture speed and T is ≈ 1/ f c3 is characteristic time. The estimates of f c3 are used for normalizing f c1 and f c2. In this way one obtains dimensionless rupture temporal parametres τ1 and τ2 and can further study the dependence τ2 (τ1). The growth of a rupture is considered as a process of aggregation of elementary fault spots of the size L is . The dimensionless width of the random front of aggregation is on the order of τ2. The relationship τ2 (τ1) approximately follows power law with exponent β. The estimates of β derived from earthquake populations of Kamchatka, USA and Central Asia (β = 0.35-0.6) agree with values expected from the known Eden's theory of random aggregation growth and from its generalizations.

  1. Seismic slip history of the Aterno-Sulmona fault system in central Apennines (Italy) using in situ produced 36Cl cosmic ray exposure dating.

    NASA Astrophysics Data System (ADS)

    Jim, T.; Benedetti, L. C.; Bruno, P.; Visini, F.; Aumaitre, G.; Bourles, D. L.

    2014-12-01

    Acquiring long records of past earthquakes on a large population of faults is a key step to understand how strain release along those fault systems varies spatially and temporally.In central Italy, NE-SW extension (~4 mm/yr) is accommodated on a wide normal fault system (50 x 100km). Benedetti et al. (2013) found that 7 of these faults, belonging to the Fucino fault system, have their seismic activity synchronized during short (less than 1 ka) paroxysmal phases of activity. 36Cl measurements and rare earth elements (REE) concentrations were used to reconstruct the seismic slip history of four major faults belonging to an adjacent 30-km-long fault system, the Aterno-Sulmona fault system, at the southeastward tip of the Paganica fault that ruptured during the 2009 L'Aquila earthquake.The preliminary results suggest that 3-7 seismic events have occurred on each fault over the last 11 ka (from NE to SW the Roccapreturo, the Castel di Ieri, the Roccacasale and the Pizzalto faults), with 50 cm to 2 m of associated slip per event. These events appear clustered within intense period of seismic activity lasting less than 1ka (2 to 4 seismic events) separated by 2 to 3 ka periods with no seismic events. The most recent recorded paroxysmal activity occurred about 2.5 ka ago with all four studied faults rupturing in more than 15 earthquakes over a period lasting less than 1ka. These results thus suggest that, as already observed on the Fucino fault system, the seismic activity of the Aterno-Sulmona fault system is also synchronized during short periods of paroxysmal seismic activity.When clustering periods are compared, the seismic activity of the Fucino and the Aterno-Sulmona fault system, are, however, apparently unsynchronized since the most recent clustering period for the Aterno-Sulmona system corresponds to a quiescent period for the Fucino fault system.

  2. Episodic activity of a dormant fault in tectonically stable Europe: The Rauw fault (NE Belgium)

    NASA Astrophysics Data System (ADS)

    Verbeeck, Koen; Wouters, Laurent; Vanneste, Kris; Camelbeeck, Thierry; Vandenberghe, Dimitri; Beerten, Koen; Rogiers, Bart; Schiltz, Marco; Burow, Christoph; Mees, Florias; De Grave, Johan; Vandenberghe, Noël

    2017-03-01

    Our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology. Here, we evaluate the co-seismic character and movement history of the Rauw fault in Belgium, which lacks geomorphological expression and historical/present seismicity. This 55-km-long normal fault, with known Neogene and possibly Early Pleistocene activity, is the largest offset fault west of the active Roer Valley Graben. Its trace was identified in the shallow subsurface based on high resolution geophysics. All the layers within the Late Pliocene Mol Formation (3.6 to 2.59 Ma) are displaced 7 m vertically, without growth faulting, but deeper deposits show increasing offset. A paleoseismic trench study revealed cryoturbated, but unfaulted, late glacial coversands overlying faulted layers of Mol Formation. In-between those deposits, the fault tip was eroded, along with evidence for individual displacement events. Fragmented clay gouge observed in a micromorphology sample of the main fault evidences co-seismic faulting, as opposed to fault creep. Based on optical and electron spin resonance dating and trench stratigraphy, the 7 m combined displacement is bracketed to have occurred between 2.59 Ma and 45 ka. The regional presence of the Sterksel Formation alluvial terrace deposits, limited to the hanging wall of the Rauw fault, indicates a deflection of the Meuse/Rhine confluence (1.0 to 0.5 Ma) by the fault's activity, suggesting that most of the offset occurred prior to/at this time interval. In the trench, Sterksel Formation is eroded but reworked gravel testifies for its former presence. Hence, the Rauw fault appears as typical of plate interior context, with an episodic seismic activity concentrated between 1.0 and 0.5 Ma or at least between 2.59 Ma to 45 ka, possibly related to activity variations in the adjacent, continuously active Roer Valley

  3. Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada

    SciTech Connect

    Frary, Roxanna

    2012-05-05

    The Truckee Meadows basin is situated adjacent to the Sierra Nevada microplate, on the western boundary of the Walker Lane. Being in the transition zone between a range-front normal fault on the west and northwest-striking right-lateral strike slip faults to the east, there is no absence of faulting in this basin. The Reno- Sparks metropolitan area is located in this basin, and with a signi cant population living here, it is important to know where these faults are. High-resolution seismic reflection surveys are used for the imaging of these faults along the Truckee River, across which only one fault was previously mapped, and in southern Reno near and along Manzanita Lane, where a swarm of short faults has been mapped. The reflection profiles constrain the geometries of these faults, and suggest additional faults not seen before. Used in conjunction with depth to bedrock calculations and gravity measurements, the seismic reflection surveys provide de nitive locations of faults, as well as their orientations. O sets on these faults indicate how active they are, and this in turn has implications for seismic hazard in the area. In addition to seismic hazard, the faults imaged here tell us something about the conduits for geothermal fluid resources in Reno.

  4. High Resolution Seismic Imaging of the Trench Canyon Fault Zone, Mono Lake, Northeastern California

    NASA Astrophysics Data System (ADS)

    Novick, M. W.; Jayko, A. S.; Roeske, S.; McClain, J. S.; Hart, P. E.; Boyle, M.

    2009-12-01

    High resolution seismic imaging of Mono Lake, located in northeastern California, has revealed an approximately northwest striking fault in the area to the west of aerially exposed Negit Volcano. This fault, henceforth referred to as the Trench Canyon Fault (TCF), has also been mapped onshore along a correlating strike as far north as Cedar Hill Volcano, located to the northeast of the lake on the California/Nevada border. Onshore, the TCF was mapped for approximately 10 kilometers using air photos, DEM images, and standard geologic pace and compass mapping techniques. The TCF post- dates the last glacial maximum, evidenced by the cutting of wave cut benches along Cedar Hill Volcano. Relict, non-historic shorelines, left by the steady evaporation of Mono Lake beginning approximately 13k, are also repeatedly cut by the fault. Additional evidence of fault presence includes sag ponds, pressure ridges, tectonically fractured rocks, and normal fault scarps found along strike. Offshore, DEM images show a northeast striking structure to the northwest of Negit Volcano, which is co-linear with the onshore TCF. High resolution seismic imaging of the structure, using an applied acoustic/SIG mini-sparker system, reveals steeply dipping Holocene sediments, as well as volcanic deposits from active vents which have erupted in the last 1000 years, offset by the fault. Detailed structural analysis of the previously unstudied Trench Canyon Fault (TFC) and faults in the Cedar Hill region of northern California, along with seismic studies of sediments beneath Mono Lake not only allow for a better comprehension of this minor fault system, but provide greater understanding of the larger and more complex Walker Lane Shear Zone. Fault analyses, combined and correlated with those from CHV, give a better understanding of how slip is transferred into the complicated Mina defection to the east, from the dextral and normal faults along the Sierra Nevada Range front.

  5. Seismic imaging of a megathrust splay fault in the North Chilean subduction zone (Central Andes)

    NASA Astrophysics Data System (ADS)

    Storch, Ina; Buske, Stefan; Schmelzbach, Cedric; Wigger, Peter

    2016-10-01

    Prominent trench-parallel fault systems in the arc and fore-arc of the Chilean subduction zone can be traced for several thousand kilometers in north-south direction. These fault systems possibly crosscut the entire crust above the subduction megathrust and are expected to have a close relationship to transient processes of the subduction earthquake cycles. With the motivation to image and characterize the structural inventory and the processes that occur in the vicinity of these large-scale fault zones, we re-processed the ANCORP'96 controlled-source seismic data set to provide images of the faults at depth and to allow linking geological information at the surface to subsurface structures. The correlation of the imaging results with observed hypocenter locations around these fault systems reveals the origin and the nature of the seismicity bound to these fault systems. Active and passive seismic data together yield a picture of a megathrust splay fault beneath the Longitudinal Valley at mid-crustal level, which can be observed from the top of the subduction plate interface and which seems to be connected to the Precordilleran Fault System (PFS) known at the surface. This result supports a previously proposed tectonic model where a megathrust splay fault defines the Western Altiplano as a crustal-scale fault-bend-fold. Furthermore, we clearly imaged two branches of the Uyuni-Kenayani Fault (UKF) in a depth range between 0 and 20 km. In summary, imaging of these faults is important for a profound understanding of the tectonic evaluation and characterization of the subduction zone environment, for which the results of this study provide a reliable basis.

  6. Distributed Seismic Moment Fault Model, Spectral Characteristics and Radiation Patterns

    NASA Astrophysics Data System (ADS)

    Shani-Kadmiel, Shahar; Tsesarsky, Michael; Gvirtzman, Zohar

    2014-05-01

    We implement a Distributed Seismic Moment (DSM) fault model, a physics-based representation of an earthquake source based on a skewed-Gaussian slip distribution over an elliptical rupture patch, for the purpose of forward modeling of seismic-wave propagation in 3-D heterogeneous medium. The elliptical rupture patch is described by 13 parameters: location (3), dimensions of the patch (2), patch orientation (1), focal mechanism (3), nucleation point (2), peak slip (1), rupture velocity (1). A node based second order finite difference approach is used to solve the seismic-wave equations in displacement formulation (WPP, Nilsson et al., 2007). Results of our DSM fault model are compared with three commonly used fault models: Point Source Model (PSM), Haskell's fault Model (HM), and HM with Radial (HMR) rupture propagation. Spectral features of the waveforms and radiation patterns from these four models are investigated. The DSM fault model best incorporates the simplicity and symmetry of the PSM with the directivity effects of the HMR while satisfying the physical requirements, i.e., smooth transition from peak slip at the nucleation point to zero at the rupture patch border. The implementation of the DSM in seismic-wave propagation forward models comes at negligible computational cost. Reference: Nilsson, S., Petersson, N. A., Sjogreen, B., and Kreiss, H.-O. (2007). Stable Difference Approximations for the Elastic Wave Equation in Second Order Formulation. SIAM Journal on Numerical Analysis, 45(5), 1902-1936.

  7. Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

    USGS Publications Warehouse

    McGuire, Jeffrey J.; Lohman, Rowena B.; Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.

    2015-01-01

    The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from

  8. Surficial geology indicates early Holocene faulting and seismicity, central Sweden

    NASA Astrophysics Data System (ADS)

    Smith, Colby A.; Sundh, Martin; Mikko, Henrik

    2014-09-01

    In Sweden, knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long-term nuclear disposal facility. To improve understanding and modeling of the complex ice-induced and tectonic stresses associated with glacially induced faulting, field studies detailing the location and timing of movement of such structures are required. Although the fault has not been confirmed in the bedrock, multi-proxy surficial geologic evidence indicates that the recently discovered scarp in Bollnäs is such a structure. Machine-excavated trenches across the scarp reveal landsliding down the scarp and, in one location, faulted and vertically offset fine-grained glacial sediments. The presence of water-escape structures in trenches excavated on a topographic high strongly suggests a co-seismic origin derived from earthquake magnitudes >5.5. Numerous landslides in till exist in the region as well. Four slopes with landslides were examined in detail, and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger. Basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co-seismic landslides. The oldest date indicates sliding prior to 10,180 calendar years before the present. The proposed Bollnäs Fault is 400 km south of the so called Lapland Fault Province. To date, it is the southernmost confirmed glacially induced fault in Sweden. The results of this study are consistent with existing modeling results that indicate fault instability in this region of central Sweden following deglaciation.

  9. Quaternary deformation and fault structure in the Northern Mississippi Embayment as imaged by near-surface seismic reflection data

    NASA Astrophysics Data System (ADS)

    Guo, Lei; Magnani, Maria Beatrice; McIntosh, Kirk; Waldron, Brian

    2014-05-01

    Seismicity in the New Madrid seismic zone (NMSZ) in the central United States constrains the location of present deformation at depth along four main distinct arms, while the surface expression of the ongoing deformation is still unclear. To better constrain the surface deformation in the NMSZ, we integrate existing seismic reflection data with a new ~300 km-long high-resolution seismic reflection profile acquired along the Mississippi River from Cape Girardeau, MO, to Caruthersville, MO. Based on the data, we interpret the Reelfoot Thrust and the New Markham Fault as upward splays of a blind master fault defined by the seismicity and extending at depth farther north. To the south, two faults, the Axial Fault and the Cottonwood Grove Fault, are imaged above the southern arm of the NMSZ. Both fault display deformation of the Paleozoic through the Tertiary sediments, and a relief of ~20-25 m at the base of the Quaternary alluvium, which we interpret as the result of strike-slip motion along a complex fault plane geometry. We propose two alternative interpretations for the relationship between the shallow faults and the seismicity in this area: (1) the faults merge at depth and are presently both active and (2) the faults are distinct at depth and were active during the Quaternary and only the Axial Fault is presently deforming. Geological structures mapped at the surface as part of this study show that Quaternary deformation is accommodated along a fault network that is more complex than the simple four-arm system illuminated by the seismicity, a behavior predicted by analog and computer models.

  10. Assessing the seismic coupling of shallow continental faults and its impact on seismic hazard estimates: a case-study from Italy

    NASA Astrophysics Data System (ADS)

    Carafa, Michele M. C.; Valensise, Gianluca; Bird, Peter

    2017-01-01

    SUMMARYWe propose an objective and reproducible algorithmic path to forecast <span class="hlt">seismicity</span> in Italy from long-term deformation models. These models are appropriate for Italy and its neighboring countries and seas thanks to the availability of rich, reliable and regularly updated historical earthquake and seismogenic <span class="hlt">fault</span> databases, and to the density of permanent GPS stations. However, so far little has been done to assess the <span class="hlt">seismic</span> coupling of Italian <span class="hlt">active</span> <span class="hlt">faults</span>, i.e. to quantify their ability to release earthquakes. This must be determined in order to use geodetic and <span class="hlt">active</span> <span class="hlt">faulting</span> observations in alternative <span class="hlt">seismicity</span> models, to overcome possible limitations of the earthquake record for the assessment of <span class="hlt">seismic</span> hazard. We use a probabilistic method to assign upper crustal earthquakes from the historical catalogue to their presumed causative <span class="hlt">faults</span>, then collect all the events into three subcatalogues corresponding to the compressional, extensional and strike-slip <span class="hlt">faulting</span> classes. We then determine the parameters of their Gutenberg-Richter frequency/magnitude relations using maximum-likelihood methods and integrate these distributions to estimate the long-term <span class="hlt">seismic</span> moment rate for each class. Finally, we compare these <span class="hlt">seismicity</span> rates to the long-term tectonic deformation based on GPS data, thus determining the coupled thickness (and estimating <span class="hlt">seismic</span> coupling) for each <span class="hlt">fault</span> class. We find that in our study region the <span class="hlt">seismic</span> coupling and the related coupled thickness is on average two times larger for extensional than for compressional <span class="hlt">faults</span>. As for the spatial distribution of earthquake rates, a larger number of events is predicted for the extensional settings of the Apennines chain, in agreement with the inferred <span class="hlt">seismic</span> coupling but also with the long-term strain rates. We also find that the frequency/magnitude distributions indicate that the largest earthquakes occur in extensional settings, whereas compressional <span class="hlt">faults</span> are expected to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S11C..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S11C..01M"><span>Discriminating Between Induced vs. Tectonic <span class="hlt">Seismicity</span> From Long-Term History of <span class="hlt">Fault</span> Behavior in Intraplate Regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Magnani, M. B.; Hornbach, M. J.; DeShon, H. R.; Hayward, C.; Blanpied, M. L.</p> <p>2015-12-01</p> <p>Since 2009 there has been an increase in rate of <span class="hlt">seismicity</span> in the Central US (CUS), a major fraction of which has been associated with shale gas production and related wastewater injection. Within this context it is important to discriminate between <span class="hlt">seismic</span> <span class="hlt">activity</span> that is anthropogenically induced from that arising from natural tectonic deformation. This discrimination is particularly challenging because tectonic strain rates and natural <span class="hlt">seismicity</span> rates are low in this intraplate region, such that tectonically <span class="hlt">active</span> <span class="hlt">faults</span> may display periods of quiescence that are long (100's to 1000's of years) relative to the short (10's of years) instrumental record. In addition, causative <span class="hlt">faults</span> are unknown with a poor surface expression, both types of <span class="hlt">seismicity</span> occur on or reactivate ancient <span class="hlt">faults</span> in the Precambrian basement, and the instrumental <span class="hlt">seismic</span> record is sparse. While <span class="hlt">seismicity</span> provides information about the short-term history of deformation on the involved <span class="hlt">faults</span>, the long-term is missing. <span class="hlt">Seismic</span> reflection data offer a means by which to interrogate the long-term history of these <span class="hlt">faults</span>, which can be discriminatory. In this paper we present examples from two regions of the CUS. The first region shows examples of tectonically <span class="hlt">active</span> <span class="hlt">faults</span> within the northern Mississippi Embayment south of the New Madrid <span class="hlt">Seismic</span> Zone, which were imaged by a high-resolution <span class="hlt">seismic</span> reflection survey along the Mississippi River. The <span class="hlt">faults</span> deform Quaternary alluvium and underlying sediments dating from Tertiary through Paleozoic, with increasing amount of deformation with formation age, suggesting a long history of <span class="hlt">activity</span>. The second region shows examples from the North Texas basin, a region of ongoing shale gas exploitation. Here, industry <span class="hlt">seismic</span> reflection data image basement <span class="hlt">faults</span> showing deformation of the Precambrian and Paleozoic sequences, and little to no deformation of younger formations. Specifically, vertical offsets, if any, in the post</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSeis...8..331V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSeis...8..331V"><span><span class="hlt">Seismic</span> hazard impact of the Lower Tagus Valley <span class="hlt">Fault</span> Zone (SW Iberia)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vilanova, Susana P.; Fonseca, Joao F. B. D.</p> <p></p> <p>The <span class="hlt">seismic</span> hazard of SW Iberia is composed of two contributions: offshore, large to very large events on the plate boundary between Africa and Eurasia such as the Lisbon earthquake of 1755 or the Gorringe Bank earthquake of 1969; and onshore, moderate to strong intraplate earthquakes on inherited crustal fractures. One of these zones of crustal weakness is the Lower Tagus Valley (LTV) <span class="hlt">fault</span> zone, which displays the highest level of <span class="hlt">seismic</span> hazard in Western Iberia. In this paper we review the <span class="hlt">active</span> tectonics and <span class="hlt">seismicity</span> of the LTV, integrating previous geophysical data with recent results of paleoseismological investigations, and discuss its impact on the <span class="hlt">seismic</span> hazard of SW Iberia. We conclude that the <span class="hlt">seismic</span> zonation for hazard assessment currently in force in the building code is biased towards the scenario of distant offshore rupture, and does not take adequately into account the LTV <span class="hlt">seismic</span> source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T23E2627W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T23E2627W"><span>An Ambient <span class="hlt">Seismic</span> Noise Tomography Focused on the New Madrid <span class="hlt">Fault</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walsh, R.; Lawrence, J. F.</p> <p>2013-12-01</p> <p>The ambient <span class="hlt">seismic</span> field has emerged as a viable tool for imaging Earth structure through the estimation of surface-wave Green's functions. The seismotectonic context of the New Madrid <span class="hlt">Fault</span> Zone is puzzling, and we aim to better understand the structure using surface waves. The signature of an <span class="hlt">active</span> <span class="hlt">fault</span> zone should translate into relatively high attenuation and clear velocity variations. We use the Spatial AutoCorrelation Method to extract phase velocity and attenuation measurements from USArray mobile <span class="hlt">seismic</span> network data in the central and eastern United States. We produce images of spatial variation in phase velocity and attenuation, sampling the crust and upper mantle at various depths. We investigate the lithospheric context within which the New Madrid <span class="hlt">fault</span> zone resides, to help shed light on its likelihood for future <span class="hlt">seismic</span> hazard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023654','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023654"><span><span class="hlt">Seismic</span> reflection images of shallow <span class="hlt">faulting</span>, northernmost Mississippi embayment, north of the New Madrid <span class="hlt">seismic</span> zone</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McBride, J.H.; Nelson, W.J.</p> <p>2001-01-01</p> <p>High-resolution <span class="hlt">seismic</span> reflection surveys document tectonic <span class="hlt">faults</span> that displace Pleistocene and older strata just beyond the northeast termination of the New Madrid <span class="hlt">seismic</span> zone, at the northernmost extent of the Mississippi embayment. These <span class="hlt">faults</span>, which are part of the Fluorspar Area <span class="hlt">fault</span> complex in southeastern Illinois, are directly in line with the northeast-trending <span class="hlt">seismic</span> zone. The reflection data were acquired using an elastic weight-drop source recorded to 500 msec by a 48-geophone array (24-fold) with a 10-ft (??3.0m) station interval. Recognizable reflections were recorded to about 200 msec (100-150 m). The effects of multiple reflections, numerous diffractions, low apparent velocity (i.e., steeply dipping) noise, and the relatively low-frequency content of the recorded signal provided challenges for data processing and interpreting subtle <span class="hlt">fault</span> offsets. Data processing steps that were critical to the detection of <span class="hlt">faults</span> included residual statics, post-stack migration, deconvolution, and noise-reduction filtering. <span class="hlt">Seismic</span> migration was crucial for detecting and mitigating complex <span class="hlt">fault</span>-related diffraction patterns, which produced an apparent 'folding' of reflectors on unmigrated sections. Detected individual offsets of shallow reflectors range from 5 to 10 m for the top of Paleozoic bedrock and younger strata. The migrated sections generally indicate vertical to steeply dipping normal and reverse <span class="hlt">faults</span>, which in places outline small horsts and/or grabens. Tilting or folding of stratal reflectors associated with <span class="hlt">faulting</span> is also locally observed. At one site, the observed <span class="hlt">faulting</span> is superimposed over a prominent antiformal structure, which may itself be a product of the Quaternary deformation that produced the steep normal and reverse <span class="hlt">faults</span>. Our results suggest that <span class="hlt">faulting</span> of the Paleozoic bedrock and younger sediments of the northern Mississippi embayment is more pervasive and less localized than previously thought.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.S53A1468Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.S53A1468Z"><span>Three-dimensional <span class="hlt">seismic</span> structure of a Mid-Atlantic Ridge segment characterized by <span class="hlt">active</span> detachment <span class="hlt">faulting</span> (TAG, 25°55’N-26°20’N)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, M.; Canales, J.</p> <p>2009-12-01</p> <p>The Trans-Atlantic Geotraverse (TAG) segment of the Mid-Atlantic Ridge (MAR) (25°55'N-26°20'N) is characterized by massive <span class="hlt">active</span> and relict high-temperature hydrothermal deposits. Previous geological and geophysical studies indicate that the <span class="hlt">active</span> TAG hydrothermal mound sits on the hanging wall of an <span class="hlt">active</span> detachment <span class="hlt">fault</span>. The STAG microseismicity study revealed that <span class="hlt">seismicity</span> associated to detachment <span class="hlt">faulting</span> extends deep into the crust/uppermost mantle (>6 km), forming an arcuate band (in plan view) extending along ~25 km of the rift valley floor (deMartin et al., Geology, 35, 711-714, 2007). Two-dimensional analysis of the STAG <span class="hlt">seismic</span> refraction data acquired with ocean bottom seismometers (OBSs) showed that the eastern rift valley wall is associated with high P-wave velocities (>7 km/s) at shallow levels (>1 km depth), indicating uplift of lower crustal and/or upper mantle rocks along the detachment <span class="hlt">fault</span> (Canales et al., Geochem., Geophys., Geosyst., 8, Q08004, doi:08010.01029/02007GC001629, 2008). Here we present a three-dimensional (3D) <span class="hlt">seismic</span> tomography analysis of the complete STAG <span class="hlt">seismic</span> refraction OBS dataset to illuminate the 3D crustal architecture of the TAG segment. Our new results provide, for the first time, a detailed picture of the complex, dome-shaped geometry and structure of a nascent oceanic core complex being exhumed by a detachment <span class="hlt">fault</span>. Our results show a relatively low-velocity anomaly embedded within the high-velocity body forming the footwall of the detachment <span class="hlt">fault</span>. The low velocity sits 2-3 km immediately beneath the <span class="hlt">active</span> TAG hydrothermal mound. Although velocities within the low-velocity zone are too high (6 km/s) to represent partial melt, we speculate that this low velocity zone is intimately linked to hydrothermal processes taking place at TAG. We consider three possible scenarios for its origin: (1) a highly fissured zone produced by extensional stresses during footwall exhumation that may help localize fluid flow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NHESD...1..323C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NHESD...1..323C"><span><span class="hlt">Seismicity</span> in northeast edge of the Mexican Volcanic Belt (MVB), <span class="hlt">activation</span> of an undocumented <span class="hlt">fault</span>: the Peñamiller earthquake sequence of 2011, Queretaro, Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clemente-Chavez, A.; Figueroa-Soto, A.; Zúñiga, F. R.; Arroyo, M.; Montiel, M.; Chavez, O.</p> <p>2013-02-01</p> <p>The Peñamiller town, in the Queretaro state, Mexico is located at the northeast border of the seismogenic zone known as the Mexican Volcanic Belt (MVB), which covers a central fringe of Mexico with east-west orientation. In this town, a sequence of small earthquakes occurred during the end of 2010 and beginning of 2011. <span class="hlt">Seismicity</span> frequent in of the continental regimen of central Mexico are not common, however, it is known that there are precedents of large earthquakes (Mw magnitude greater than 6.0) occurring in this zone. In order to enrich <span class="hlt">seismic</span> information, which has not been analyzed nor documented until this moment, is presented this work. This will contribute to gain more insight into the tectonic situation of the central Mexico region. Twenty-four shallow earthquakes records of the Peñamiller, Queretaro <span class="hlt">seismic</span> sequence of 2011 were recorded by a provisional accelerograph network from the Universidad Autonoma de Queretaro (UAQ). The data were analysed in order to determine the source locations and for the estimation of the source parameters. The study was carried out through an inversion process and by spectral analysis. The results show that the largest earthquake, occurred on 8 February 2011 at 19:53:48.6 UTC, had a moment magnitude Mw = 3.5, and was located at latitude 21.039° and longitude -99.752°, at a depth of 5.6 km. This zone is located less than 7 km away in south-east direction from downtown Peñamiller. The focal mechanisms are mostly normal <span class="hlt">faults</span> with a small lateral component. This feature is consistent with the extensional regimen of the southern extension of the Basin and Range (BR) province. The source area of the largest event was estimated to have a radius of 0.5 km, which corresponds to a normal <span class="hlt">fault</span> with azimuth of 174° and an almost pure dip slip; this caused Peak Ground Acceleration (PGA) of up to 100 cm s-2 in the horizontal direction. It is evident that the shallow earthquakes induced by crustal <span class="hlt">faulting</span> can present a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.4155L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.4155L"><span><span class="hlt">Fault</span> Pattern and <span class="hlt">Seismicity</span> of The Western Part of The Tunka Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lunina, O.; Gladkov, A.</p> <p></p> <p>The Tunka basin is a part of the Baikal rift zone and is characterized by complex geodynamical setting. Its western termination is the most interesting site to study the relationship between <span class="hlt">faults</span> and <span class="hlt">seismicity</span>. The <span class="hlt">active</span> Tunka and South Tunka <span class="hlt">faults</span>, which limit the boards of the Tunka basin, converge there, and the density of earthquake epicenters is highest. We compared the <span class="hlt">fault</span> pattern and epicenters of earthquakes within this part from the Nilovsky interbasin link to the Mondinsky local basin. We drawn a scheme of <span class="hlt">faults</span> in scale of 1:200000 from the data on detailed field investigations in structural geology and tectonophysics, analysis of lineaments on topographical maps, geophysical data, and materials of the State geological sur- vey. High-angle <span class="hlt">faults</span> of sublatitudinal strike, with the traces of <span class="hlt">active</span> movements (displacements and deformations in the Quaternary and Neogene sediments), are of the first importance in the structure of <span class="hlt">fault</span> pattern of the investigated area. Besides, the NE <span class="hlt">faults</span>, characterized by the same features of <span class="hlt">activity</span> as the latitudinal <span class="hlt">faults</span>, are obviously traced within the western part of the Tunka basin. The large NW <span class="hlt">faults</span> are primarily concentrated in the ridges that frame the Tunka basin, and within the Nilovsky link. The submeridional <span class="hlt">faults</span> emerge in the parts of interbasin links and within the Mondinsky local basin. The features of <span class="hlt">active</span> displacements along the NW and submeridional <span class="hlt">faults</span> are of less evidence in respect of structural geology. The comparison between the <span class="hlt">fault</span> pattern of the western part of the Tunka rift basin and M>3.3 earthquakes showed that the most of them lay on the mapped <span class="hlt">faults</span> or in the vicinity of the latter. Much smaller amount is in blocks. Large earthquakes are mainly related to the <span class="hlt">faults</span> of sublatitudinal and north-eastern strike and do not make big con- centrations in the place of convergence of the Tunka and South Tunka <span class="hlt">faults</span>, where the rocks are the most dislocated. Perhaps, a high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817828G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817828G"><span>A comparative study of <span class="hlt">seismicity</span> statistics in laboratory stick-slip experiments and nature: Implications for <span class="hlt">fault</span> mechanics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goebel, Thomas; Kwiatek, Grzegorz; Becker, Thorsten; Sammis, Charles; Dresen, Georg</p> <p>2016-04-01</p> <p><span class="hlt">Fault</span> properties can rarely be monitored under in-situ conditions at seismogenic depth. At these depths <span class="hlt">seismicity</span> records are possibly the only high-resolution data that can provide insight into state of stress and mechanics of <span class="hlt">faulting</span>. We analyze series of laboratory experiments on <span class="hlt">faults</span> that developed during stick-slip on saw-cut and fractured surfaces under upper crustal stress conditions. Stick-slip experiments were performed on surfaces with varying roughness and fracture surfaces that evolved into <span class="hlt">fault</span> zones with pronounced damage zones. We monitor and analyze acoustic emission events that exhibit many striking similarities to natural <span class="hlt">seismicity</span> across all examined scales. These similarities include pronounced Gutenberg-Richter-type magnitude distributions, Omori-type aftershock decay, and off-<span class="hlt">fault</span> <span class="hlt">seismicity</span> distributions that decay as a power law with distance. In the laboratory, <span class="hlt">fault</span> roughness and heterogeneity are critical in concentrating stresses that lead to local AE clustering, and differences in off-<span class="hlt">fault</span> <span class="hlt">activities</span> and lower b-values. Similar observations of earthquake clustering and b-value variations were made for natural <span class="hlt">faults</span> such as the Parkfield segment of the San Andreas <span class="hlt">fault</span>. In addition to <span class="hlt">seismicity</span> statistics, we conducted a detailed analysis of moment tensors, focusing on relative contributions from isotropic and deviatoric components to laboratory <span class="hlt">seismicity</span>. In contrast to natural <span class="hlt">seismicity</span>, our results revealed a larger contribution from isotropic components. These contributions are a result of ongoing fracture processes within the evolving <span class="hlt">fault</span> which are most pronounced after stick-slip events. Our study shows, that <span class="hlt">seismicity</span> analyses in laboratory experiments can significantly advance our understanding of <span class="hlt">fault</span> mechanics from the scale of single asperities to large <span class="hlt">fault</span> zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026288','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026288"><span>Triggered deformation and <span class="hlt">seismic</span> <span class="hlt">activity</span> under Mammoth Mountain in long Valley caldera by the 3 November 2002 Mw 7.9 Denali <span class="hlt">fault</span> earthquake</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Johnston, M.J.S.; Prejean, S.G.; Hill, D.P.</p> <p>2004-01-01</p> <p>The 3 November 2002 Mw 7.9 Denali <span class="hlt">fault</span> earthquake triggered deformational offsets and microseismicity under Mammoth Mountain (MM) on the rim of Long Valley caldera, California, some 3460 km from the earthquake. Such strain offsets and microseismicity were not recorded at other borehole strain sites along the San Andreas <span class="hlt">fault</span> system in California. The Long Valley offsets were recorded on borehole strainmeters at three sites around the western part of the caldera that includes Mammoth Mountain - a young volcano on the southwestern rim of the caldera. The largest recorded strain offsets were -0.1 microstrain at PO on the west side of MM, 0.05 microstrain at MX to the southeast of MM, and -0.025 microstrain at BS to the northeast of MM with negative strain extensional. High sample rate strain data show initial triggering of the offsets began at 22:30 UTC during the arrival of the first Rayleigh waves from the Alaskan earthquake with peak-to-peak dynamic strain amplitudes of about 2 microstrain corresponding to a stress amplitude of about 0.06 MPa. The strain offsets grew to their final values in the next 10 min. The associated triggered <span class="hlt">seismicity</span> occurred beneath the south flank of MM and also began at 22:30 UTC and died away over the next 15 min. This relatively weak <span class="hlt">seismicity</span> burst included some 60 small events with magnitude all less than M = 1. While poorly constrained, these strain observations are consistent with triggered slip and intrusive opening on a north-striking normal <span class="hlt">fault</span> centered at a depth of 8 km with a moment of l016 N m, or the equivalent of a M 4.3 earthquake. The cumulative <span class="hlt">seismic</span> moment for the associated <span class="hlt">seismicity</span> burst was more than three orders of magnitude smaller. These observations and this model resemble those for the triggered deformation and slip that occurred beneath the north side of MM following the 16 October 1999 M 7.1 Hector Mine, California, earthquake. However, in this case, we see little post-event slip decay reflected in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T33B2224A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T33B2224A"><span>A summary of the <span class="hlt">active</span> <span class="hlt">fault</span> investigation in the extension sea area of Kikugawa <span class="hlt">fault</span> and the Nishiyama <span class="hlt">fault</span> , N-S direction <span class="hlt">fault</span> in south west Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abe, S.</p> <p>2010-12-01</p> <p>In this study, we carried out two sets of <span class="hlt">active</span> <span class="hlt">fault</span> investigation by the request from Ministry of Education, Culture, Sports, Science and Technology in the sea area of the extension of Kikugawa <span class="hlt">fault</span> and the Nishiyama <span class="hlt">fault</span>. We want to clarify the five following matters about both <span class="hlt">active</span> <span class="hlt">faults</span> based on those results. (1)<span class="hlt">Fault</span> continuity of the land and the sea. (2) The length of the <span class="hlt">active</span> <span class="hlt">fault</span>. (3) The division of the segment. (4) <span class="hlt">Activity</span> characteristics. In this investigation, we carried out a digital single channel <span class="hlt">seismic</span> reflection survey in the whole area of both <span class="hlt">active</span> <span class="hlt">faults</span>. In addition, a high-resolution multichannel <span class="hlt">seismic</span> 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 <span class="hlt">active</span> <span class="hlt">faults</span> was extremely clear. The characteristics of the lateral <span class="hlt">fault</span> such as flower structure, the dispersion of the <span class="hlt">active</span> <span class="hlt">fault</span> 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 <span class="hlt">fault</span> extended to the offing than the existing results of research by a result of this investigation. In addition, the width of the <span class="hlt">active</span> <span class="hlt">fault</span> seems to become wide toward the offing while dispersing. At present, we think that we can divide Kikugawa <span class="hlt">fault</span> into some segments based on the distribution form of the segment. About the Nishiyama <span class="hlt">fault</span>, reflection profiles to show the existence of the <span class="hlt">active</span> <span class="hlt">fault</span> 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 <span class="hlt">fault</span> and the Ooshima offing <span class="hlt">active</span> <span class="hlt">fault</span> are a series of structure. As for Ooshima offing <span class="hlt">active</span> <span class="hlt">fault</span>, the upheaval side changes, and a direction changes too. Therefore, we</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10550047','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10550047"><span><span class="hlt">Fault</span> slip rates in the modern new madrid <span class="hlt">seismic</span> zone</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mueller; Champion; Guccione; Kelson</p> <p>1999-11-05</p> <p>Structural and geomorphic analysis of late Holocene sediments in the Lake County region of the New Madrid <span class="hlt">seismic</span> zone indicates that they are deformed by <span class="hlt">fault</span>-related folding above the blind Reelfoot thrust <span class="hlt">fault</span>. The widths of narrow kink bands exposed in trenches were used to model the Reelfoot scarp as a forelimb on a <span class="hlt">fault</span>-bend fold; this, coupled with the age of folded sediment, yields a slip rate on the blind thrust of 6.1 +/- 0.7 mm/year for the past 2300 +/- 100 years. An alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4.8 +/- 0.2 mm/year. Geometric relations suggest that the right lateral slip rate on the New Madrid <span class="hlt">seismic</span> zone is 1.8 to 2.0 mm/year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2930P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2930P"><span>FiSH: put <span class="hlt">fault</span> data in a <span class="hlt">seismic</span> hazard basket</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pace, Bruno; Visini, Francesco; Peruzza, Laura</p> <p>2016-04-01</p> <p>The practice of using <span class="hlt">fault</span> sources in <span class="hlt">seismic</span> hazard studies is growing in popularity, including in regions with moderate <span class="hlt">seismic</span> <span class="hlt">activity</span>, such as the European countries. In these areas, <span class="hlt">fault</span> identification may be affected by similarly large uncertainties in the historical and instrumental <span class="hlt">seismic</span> histories of more <span class="hlt">active</span> areas that have not been inhabited for long periods of time. Certain studies have effectively applied a time-dependent perspective to combine historical and instrumental <span class="hlt">seismic</span> data with geological and paleoseismological information, partially compensating for a lack of information. We present a package of Matlab® tools (called FiSH), in publication on Seismological Research Letters, designed to help <span class="hlt">seismic</span> hazard modellers analyse <span class="hlt">fault</span> data. These tools enable the derivation of expected earthquake rates given common <span class="hlt">fault</span> data, and allow you to test the consistency between the magnitude frequency distributions assigned to a <span class="hlt">fault</span> and some available observations. The basic assumption of FiSH is that the geometric and kinematic features of a <span class="hlt">fault</span> are the expression of its seismogenic potential. Three tools have been designed to integrate the variable levels of information available: (a) the first tool allows users to convert <span class="hlt">fault</span> geometry and slip rates into a global budget of the <span class="hlt">seismic</span> moment released in a given time frame, taking uncertainties into account; (b) the second tool computes the recurrence parameters and associated uncertainties from historical and/or paleoseismological data; 
(c) the third tool outputs time-independent or time-dependent earthquake rates for different magnitude frequency distribution models. We present moreover a test case to illustrate the capabilities of FiSH, on the Paganica normal <span class="hlt">fault</span> in Central Italy that ruptured during the L'Aquila 2009 earthquake sequence (mainshock Mw 6.3). FiSH is available at http://fish-code.com, and the source codes are open. We encourage users to handle the scripts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.693..489B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.693..489B"><span>Along-<span class="hlt">fault</span> migration of the Mount McKinley restraining bend of the Denali <span class="hlt">fault</span> defined by late Quaternary <span class="hlt">fault</span> patterns and <span class="hlt">seismicity</span>, Denali National Park & Preserve, Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burkett, Corey A.; Bemis, Sean P.; Benowitz, Jeff A.</p> <p>2016-12-01</p> <p>The tallest mountain in North America, Denali (formerly Mount McKinley, 6,190 m), is situated inside an abrupt bend in the right-lateral strike-slip Denali <span class="hlt">fault</span>. This anomalous topography is clearly associated with the complex geometry of the Denali <span class="hlt">fault</span>, but how this restraining bend has evolved in conjunction with the regional topography is unknown. To constrain how this bend in the Denali <span class="hlt">fault</span> is deforming, we document the Quaternary <span class="hlt">fault</span>-related deformation north of the Denali <span class="hlt">fault</span> through combined geologic mapping, <span class="hlt">active</span> <span class="hlt">fault</span> characterization, and analysis of background <span class="hlt">seismicity</span>. Our mapping illustrates an east-west change in <span class="hlt">faulting</span> style where normal <span class="hlt">faults</span> occur east of the <span class="hlt">fault</span> bend and thrust <span class="hlt">faults</span> predominate to the west. The complex and elevated regional <span class="hlt">seismicity</span> corroborates the style of <span class="hlt">faulting</span> adjacent to the <span class="hlt">fault</span> bend and provides additional insight into the change in local stress field in the crust adjacent to the bend. The style of <span class="hlt">active</span> <span class="hlt">faulting</span> and <span class="hlt">seismicity</span> patterns define a deforming zone that accommodates the southwestward migration of this restraining bend. <span class="hlt">Fault</span> slip rates for the <span class="hlt">active</span> <span class="hlt">faults</span> north of the Denali <span class="hlt">fault</span>, derived from offset glacial outwash surfaces, indicate that the Mount McKinley restraining bend is migrating along the Denali <span class="hlt">fault</span> at a late Pleistocene/Holocene rate of 2-6 mm/yr. Ongoing thermochronologic and structural studies of the Mount McKinley restraining bend will extend these constraints on the migration and evolution of the restraining bend deeper in time and to the south of the Denali <span class="hlt">fault</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T22D..07G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T22D..07G"><span>Transition Zone of the Cascadia Subduction <span class="hlt">Fault</span>: Insights from <span class="hlt">Seismic</span> Imaging of Slow Earthquakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, A.</p> <p>2012-12-01</p> <p>Transition zone lies between the updip locked and downdip freely slipping zone, and presumably marks the downdip extent of rupture during large megathrust earthquakes. Tectonic behavior of the transition zone and its possible implications on the occurrence of destructive megathurst earthquakes, however, remain poorly understood mainly due to lack of <span class="hlt">seismic</span> events in this zone. Slow earthquakes, marked by <span class="hlt">seismically</span> observed tremor and geodetically observed slow slip, occur in the transition zone offering a unique window to this zone, and allow us to study the dynamics of this enigmatic part of the <span class="hlt">fault</span>. I developed a novel multi beam-backprojection (MBBP) algorithm to image slow earthquakes with high resolution using small-aperture <span class="hlt">seismic</span> arrays. Application of MBBP technique on slow earthquakes in Cascadia indicates that the majority of the tremor is located near the plate interface [Ghosh et al., JGR, 2012]. Spatiotemporal distribution of tremor is fairly complex, and strikingly different over different time scales. Transition zone appears to be characterized by several patches with dimension of tens of kilometers. The patches behave like asperities, and possibly represent more <span class="hlt">seismic</span> part of the <span class="hlt">fault</span> embedded within a relatively aseismic background. Tremor asperities are spatially stable and marked by prolific tremor <span class="hlt">activity</span>. These tremor asperities seem to control evolution of slow earthquakes and likely represent rheological and/or frictional heterogeneity on the <span class="hlt">fault</span> plane. In addition, structural features on the <span class="hlt">fault</span> plane of the transition zone seem to play an important role in shaping the characteristics of the <span class="hlt">seismic</span> energy radiated from here. Dynamically evolving state-of-stress during slow earthquakes and its interaction with the <span class="hlt">fault</span> structures possibly govern near-continuous rapid streaking of tremor [Ghosh et al., G-cubed, 2010] and diverse nature of tremor propagations observed over different time scales. Overall, slow quakes are giving</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7952S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7952S"><span>Frictional behavior of experimental <span class="hlt">faults</span> during a simulated <span class="hlt">seismic</span> cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spagnuolo, Elena; Nielsen, Stefan; Violay, Marie; Di Felice, Fabio; Di Toro, Giulio</p> <p>2016-04-01</p> <p>Laboratory friction studies of earthquake mechanics aim at understanding complex phenomena either driving or characterizing the <span class="hlt">seismic</span> cycle. Previous experiments were mainly conducted on bi-axial machines imposing velocity steps conditions, where slip and slip-rate are usually less than 10 mm and 1 mm/s, respectively. However, earthquake nucleation on natural <span class="hlt">faults</span> results from the combination of the frictional response of <span class="hlt">fault</span> materials and wall rock stiffness with complex loading conditions. We propose an alternative experimental approach which consists in imposing a step-wise increase in the shear stress on an experimental <span class="hlt">fault</span> under constant normal stress. This experimental configuration allows us to investigate the relevance of spontaneous <span class="hlt">fault</span> surface reworking in (1) driving frictional instabilities, (2) promoting the diversity of slip events including the eventual runaway, and (3) ruling weakening and re-strengthening processes during the <span class="hlt">seismic</span> cycle. Using a rotary shear apparatus (SHIVA, INGV, Rome) with an on-purpose designed control system, the shear stress acting on a simulated <span class="hlt">fault</span> can be increased step-wise while both slip and slip-rate are allowed to evolve spontaneously (the slip is namely infinite) to accommodate the new state of stress. This unconventional procedure, which we term "shear stress-step loading", simulates how <span class="hlt">faults</span> react to either a remote tectonic loading or a sudden <span class="hlt">seismic</span> or strain event taking place in the vicinity of a <span class="hlt">fault</span> patch. Our experiments show that the spontaneous slip evolution results in velocity pulses whose shape and occurrence rate are controlled by the lithology and the state of stress. With increasing shear stress and cumulative slip, the experimental <span class="hlt">fault</span> exhibits three frictional behaviors: (1) stable behavior or individual slip pulses up to few cm/s for few mm of slip in concomitance to the step-wise increase in shear stress; (2) unstable oscillatory slip or continuous slip but with abrupt changes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T12C..06F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T12C..06F"><span><span class="hlt">Seismicity</span> within the Irpinia <span class="hlt">Fault</span> System As Monitored By Isnet (Irpinia <span class="hlt">Seismic</span> Network) and Its Possible Relation with Fluid Storage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Festa, G.; Zollo, A.; Amoroso, O.; Ascione, A.; Colombelli, S.; Elia, L.; Emolo, A.; Martino, C.; Mazzoli, S.; Orefice, A.; Russo, G.</p> <p>2014-12-01</p> <p>ISNet (http://isnet.fisica.unina.it) is deployed in Southern Apennines along the <span class="hlt">active</span> <span class="hlt">fault</span> system responsible for the 1980, M 6.9 Irpinia earthquake. ISNet consists of 32 <span class="hlt">seismic</span> stations equipped with both strong motion and velocimetric instruments (either broadband or short-period), with the aim of capture a broad set of <span class="hlt">seismic</span> signals, from ambient noise to strong motion. Real time and near real time procedures run at ISNet with the goal of monitoring the <span class="hlt">seismicity</span>, check possible space-time anomalies, detect <span class="hlt">seismic</span> sequences and launch an earthquake early warning in the case of potential significant ground shaking in the area. To understand the role of fluids on the <span class="hlt">seismicity</span> of the area, we investigated velocity and attenuation models. The former is built from accurate cross-correlation picking and S wave detection based onto polarization analysis. Joint inversion of both P and S arrival times is then based on a linearized multi-scale tomographic approach. Attenuation is instead obtained from inversion of displacement spectra, deconvolving for the source effect. High VP/VS and QS/QP >1 were found within a ~15 km wide rock volume where intense microseismicity is located. This indicates that concentration of <span class="hlt">seismicity</span> is possibly controlled by high pore fluid pressure. This earthquake reservoir may come from a positive feedback between the <span class="hlt">seismic</span> pumping that controls the fluid transmission through the fractured damage zone and the low permeability of cross <span class="hlt">fault</span> barrier, increasing the fluid pore pressure within the <span class="hlt">fault</span> bounded block. In this picture, sequences mostly occur at the base of this fluid rich layer. They show an anomalous pattern in the earthquake occurrence per magnitude classes; main events evolve with a complex source kinematics, as obtained from backprojection of apparent source time functions, indicating possible directivity effects. In this area sequences might be the key for understanding the transition between the deep</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JSG....26..709A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JSG....26..709A"><span>Co-<span class="hlt">seismic</span> strike-slip <span class="hlt">fault</span> displacement determined from push-up structures: the Selsund <span class="hlt">Fault</span> case, South Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angelier, Jacques; Bergerat, Françoise; Bellou, Magalie; Homberg, Catherine</p> <p>2004-04-01</p> <p>We analysed push-up structures along the Selsund <span class="hlt">Fault</span>, a N-S right-lateral strike-slip <span class="hlt">fault</span> <span class="hlt">activated</span> during the 1912 earthquake in the South Iceland <span class="hlt">Seismic</span> Zone. Volume changes and syn-tectonic collapse affected push-ups during the earthquake, followed by post-<span class="hlt">seismic</span> gravitational sagging. To determine the push-up shortening, and hence the strike-slip <span class="hlt">fault</span> motion, we define a virtual push-up structure, without volume change and collapse, and we compare it with the present-day configuration. Whereas length comparisons are subject to errors, volumetric analysis allows determination of shortening through evaluation of the thickness of the deformed layer affected by the push-ups. We determine a co-<span class="hlt">seismic</span> peak displacement of 2.4 m along the rupture trace. This value is consistent with the magnitude 7 of the earthquake, based on empirical relationships. Neglecting volume changes and collapse effects gives underestimated displacement. The new method for analysing push-up structures thus allows better determination of magnitudes of ancient earthquakes along strike-slip <span class="hlt">faults</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816701D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816701D"><span><span class="hlt">Active</span> <span class="hlt">Fault</span> Characterization in the Urban Area of Vienna</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Decker, Kurt; Grupe, Sabine; Hintersberger, Esther</p> <p>2016-04-01</p> <p>The identification of <span class="hlt">active</span> <span class="hlt">faults</span> that lie beneath a city is of key importance for <span class="hlt">seismic</span> hazard assessment. <span class="hlt">Fault</span> mapping and characterization in built-up areas with strong anthropogenic overprint is, however, a challenging task. Our study of Quaternary <span class="hlt">faults</span> in the city of Vienna starts from the re-assessment of a borehole database of the municipality containing several tens of thousands of shallow boreholes. Data provide tight constraints on the geometry of Quaternary deposits and highlight several locations with <span class="hlt">fault</span>-delimited Middle to Late Pleistocene terrace sediments of the Danube River. Additional information is obtained from geological descriptions of historical outcrops which partly date back to about 1900. The latter were found to be particularly valuable by providing unprejudiced descriptions of Quaternary <span class="hlt">faults</span>, sometimes with stunning detail. The along-strike continuations of some of the identified <span class="hlt">faults</span> are further imaged by industrial 2D/3D <span class="hlt">seismic</span> acquired outside the city limits. The interpretation and the assessment of <span class="hlt">faults</span> identified within the city benefit from a very well constrained tectonic model of the <span class="hlt">active</span> Vienna Basin <span class="hlt">fault</span> system which derived from data obtained outside the city limits. This data suggests that the urban <span class="hlt">faults</span> are part of a system of normal <span class="hlt">faults</span> compensating <span class="hlt">fault</span>-normal extension at a releasing bend of the sinistral Vienna Basin Transfer <span class="hlt">Fault</span>. Slip rates estimated for the <span class="hlt">faults</span> in the city are in the range of several hundredths of millimetres per year and match the slip rates of normal <span class="hlt">faults</span> that were trenched outside the city. The lengths/areas of individual <span class="hlt">faults</span> estimated from maps and <span class="hlt">seismic</span> reach up to almost 700 km² suggesting that all of the identified <span class="hlt">faults</span> are capable of producing earthquakes with magnitudes M>6, some with magnitudes up to M~6.7.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T22D..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T22D..06T"><span><span class="hlt">Seismicity</span> and Crustal Anisotropy Beneath the Western Segment of the North Anatolian <span class="hlt">Fault</span>: Results from a Dense <span class="hlt">Seismic</span> Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turkelli, N.; Teoman, U.; Altuncu Poyraz, S.; Cambaz, D.; Mutlu, A. K.; Kahraman, M.; Houseman, G. A.; Rost, S.; Thompson, D. A.; Cornwell, D. G.; Utkucu, M.; Gülen, L.</p> <p>2013-12-01</p> <p>The North Anatolian <span class="hlt">Fault</span> (NAF) is one of the major strike slip <span class="hlt">fault</span> systems on Earth comparable to San Andreas <span class="hlt">Fault</span> in some ways. Devastating earthquakes have occurred along this system causing major damage and casualties. In order to comprehensively investigate the shallow and deep crustal structure beneath the western segment of NAF, a temporary dense <span class="hlt">seismic</span> network for North Anatolia (DANA) consisting of 73 broadband sensors was deployed in early May 2012 surrounding a rectangular grid of by 70 km and a nominal station spacing of 7 km with the aim of further enhancing the detection capability of this dense <span class="hlt">seismic</span> array. This joint project involves researchers from University of Leeds, UK, Bogazici University Kandilli Observatory and Earthquake Research Institute (KOERI), and University of Sakarya and primarily focuses on upper crustal studies such as earthquake locations (especially micro-<span class="hlt">seismic</span> <span class="hlt">activity</span>), receiver functions, moment tensor inversions, shear wave splitting, and ambient noise correlations. To begin with, we obtained the hypocenter locations of local earthquakes that occured within the DANA network. The dense 2-D grid geometry considerably enhanced the earthquake detection capability which allowed us to precisely locate events with local magnitudes (Ml) less than 1.0. Accurate earthquake locations will eventually lead to high resolution images of the upper crustal structure beneath the northern and southern branches of NAF in Sakarya region. In order to put additional constraints on the <span class="hlt">active</span> tectonics of the western part of NAF, we also determined <span class="hlt">fault</span> plane solutions using Regional Moment Tensor Inversion (RMT) and P wave first motion methods. For the analysis of high quality <span class="hlt">fault</span> plane solutions, data from KOERI and the DANA project were merged. Furthermore, with the aim of providing insights on crustal anisotropy, shear wave splitting parameters such as lag time and fast polarization direction were obtained for local events recorded</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H33D1163K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H33D1163K"><span>Micro-<span class="hlt">seismicity</span>, <span class="hlt">fault</span> structure, and hydrologic compartmentalization within the Coso Geothermal Field, California, from 1996 until present</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaven, J. O.; Hickman, S.; Davatzes, N. C.</p> <p>2010-12-01</p> <p>Geothermal reservoirs derive their capacity for fluid and heat transport in large part from <span class="hlt">faults</span> and fractures. In conventional reservoirs, preexisting <span class="hlt">faults</span> and fractures are the main conduits for fluid flow, while in enhanced geothermal systems (EGS), fractures and <span class="hlt">faults</span> that are generated or enlarged (i.e., through increases in surface area and aperture) by hydraulic stimulation provide the main pathways for fluids and heat. In both types of geothermal systems, <span class="hlt">seismicity</span> can be used to locate <span class="hlt">active</span> <span class="hlt">faults</span>, which can act either as conduits for along-<span class="hlt">fault</span> fluid flow and/or barriers to cross-<span class="hlt">fault</span> flow. We relocate 14 years of <span class="hlt">seismicity</span> in the Coso Geothermal Field (CGF) using differential travel time relocations to improve our knowledge of the subsurface geologic and hydrologic structure. The <span class="hlt">seismicity</span> at Coso has been recorded on a local network operated by the Navy Geothermal Program, which provides exceptional coverage and quality of data. Using the relocated catalog, we employ a newly developed algorithm for <span class="hlt">fault</span> identification using the spatial <span class="hlt">seismicity</span> distribution and a priori constraints on <span class="hlt">fault</span> zone width derived from local geologic mapping. We avoid having to assume a particular <span class="hlt">fault</span>-normal <span class="hlt">seismicity</span> distribution by finding regions of maximum spatial <span class="hlt">seismicity</span> density. Assuming a maximum spatial density is physically plausible since <span class="hlt">faults</span>, or more accurately <span class="hlt">fault</span> zones, generate most of the associated <span class="hlt">seismicity</span> within a central <span class="hlt">fault</span> core or damage zone. These techniques are developed for naturally occurring, <span class="hlt">active</span> <span class="hlt">faults</span> within the CGF on which <span class="hlt">seismicity</span> is induced, in part, by changes in production and injection. They can also be applied to EGS if <span class="hlt">seismicity</span> is induced within newly created fracture systems of comparable width or if this <span class="hlt">seismicity</span> is generated by stimulating pre-existing, partially sealed <span class="hlt">faults</span>. The results of the relocations reveal that clouds of <span class="hlt">seismicity</span> shrink into distinct oblate volumes of <span class="hlt">seismicity</span> in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018219','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018219"><span>Scaling of the critical slip distance for <span class="hlt">seismic</span> <span class="hlt">faulting</span> with shear strain in <span class="hlt">fault</span> zones</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Marone, C.; Kilgore, B.</p> <p>1993-01-01</p> <p>THEORETICAL and experimentally based laws for <span class="hlt">seismic</span> <span class="hlt">faulting</span> contain a critical slip distance1-5, Dc, which is the slip over which strength breaks down during earthquake nucleation. On an earthquake-generating <span class="hlt">fault</span>, this distance plays a key role in determining the rupture nucleation dimension6, the amount of premonitory and post-<span class="hlt">seismic</span> slip7-10, and the maximum <span class="hlt">seismic</span> ground acceleration1,11. In laboratory friction experiments, Dc has been related to the size of surface contact junctions2,5,12; thus, the discrepancy between laboratory measurements of Dc (??? 10-5 m) and values obtained from modelling earthquakes (??? 10-2 m) has been attributed to differences in roughness between laboratory surfaces and natural <span class="hlt">faults</span>5. This interpretation predicts a dependence of Dc on the particle size of <span class="hlt">fault</span> gouge 2 (breccia and wear material) but not on shear strain. Here we present experimental results showing that Dc scales with shear strain in simulated <span class="hlt">fault</span> gouge. Our data suggest a new physical interpretation for the critical slip distance, in which Dc is controlled by the thickness of the zone of localized shear strain. As gouge zones of mature <span class="hlt">faults</span> are commonly 102-103 m thick13-17, whereas laboratory gouge layers are 1-10 mm thick, our data offer an alternative interpretation of the discrepancy between laboratory and field-based estimates of Dc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Sci...352.1293J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Sci...352.1293J"><span>Deeper penetration of large earthquakes on <span class="hlt">seismically</span> quiescent <span class="hlt">faults</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Junle; Lapusta, Nadia</p> <p>2016-06-01</p> <p>Why many major strike-slip <span class="hlt">faults</span> 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 <span class="hlt">fault</span> behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas <span class="hlt">Fault</span> 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 <span class="hlt">fault</span> segments, potentially increasing the associated <span class="hlt">seismic</span> hazard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27284188','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27284188"><span>Deeper penetration of large earthquakes on <span class="hlt">seismically</span> quiescent <span class="hlt">faults</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jiang, Junle; Lapusta, Nadia</p> <p>2016-06-10</p> <p>Why many major strike-slip <span class="hlt">faults</span> 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 <span class="hlt">fault</span> behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas <span class="hlt">Fault</span> 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 <span class="hlt">fault</span> segments, potentially increasing the associated <span class="hlt">seismic</span> hazard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S43F2539Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S43F2539Y"><span>Monitoring <span class="hlt">seismic</span> wave speed by an <span class="hlt">active</span> <span class="hlt">seismic</span> source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yokoyama, K.; Kawakata, H.; Doi, I.; Okubo, M.; Saiga, A.</p> <p>2012-12-01</p> <p>Decreases in elastic wave speed around cracked zones prior to <span class="hlt">faulting</span> in rock fracture experiments have been reported (e.g., Yukutake, 1989; Yoshimitsu et al., 2009). These decreases in wave speed have been considered to be associated with crack and <span class="hlt">fault</span> growth based on non-destructive observation using X-ray CT scan (Kawakata et al., 1999). Meanwhile, there were some reports on the decreases in <span class="hlt">seismic</span> wave speed along paths that cross the hypocentral area in periods including some large earthquakes. Uchida et al. (2002) analyzed <span class="hlt">seismic</span> waveform with explosive sources before and after the 1998 northern Iwate prefecture earthquake, and they showed that the decrease in <span class="hlt">seismic</span> wave speed approximately 0.1-0.9 % by the earthquake occurrence. Justin et al. (2007) reported the reduction in <span class="hlt">seismic</span> wave speed accompanied with the 2003 Tokachi oki earthquake around the rupture area by using the four repeating earthquakes that occurred before and after the 2003 Tokachi oki earthquake. However, seismograms of explosive sources or repeating earthquakes are hard to be frequently recorded, which makes the time intervals of estimated <span class="hlt">seismic</span> wave speed be too long to distinguish preseismic changes from coseismic and post <span class="hlt">seismic</span> changes. In order to monitor crustal structures and detecting the variation of rock properties in the crust, a kind of <span class="hlt">active</span> <span class="hlt">seismic</span> source systems ACROSS (Accurately Controlled Routinely Operated Signal System) has been developed(e.g., Kunitomo and Kumazawa, 2004). We used the controlled <span class="hlt">seismic</span> source ACROSS, which installed at the Tono mine, Gifu prefecture, central Japan and has been routinely operated by Tono Geoscience center of JAEA (Japan Atomic Energy Agency), automatically. Frequency modulated <span class="hlt">seismic</span> waves are continuously radiated from approximately 10-20 Hz by eccentric rotation of the source. In order to investigate the stability of ACROSS signals, we used seismograms recorded at the 110m depth of Shobasama observing site, which is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814222V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814222V"><span>Dealing with completeness, structural hierarchy, and <span class="hlt">seismic</span> coupling issues: three major challenges for #<span class="hlt">Fault</span>2SHA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valensise, Gianluca; Barba, Salvatore; Basili, Roberto; Bonini, Lorenzo; Burrato, Pierfrancesco; Carafa, Michele; Kastelic, Vanja; Fracassi, Umberto; Maesano, Francesco Emanuele; Tarabusi, Gabriele; Tiberti, Mara Monica; Vannoli, Paola</p> <p>2016-04-01</p> <p>The vast majority of <span class="hlt">active</span> <span class="hlt">faulting</span> studies are performed at the scale of individual, presumably seismogenic <span class="hlt">faults</span> or <span class="hlt">fault</span> strands. Most SHA approaches and models, however, require homogeneus information on potential earthquake sources over the entire tectonic domain encompassing the site(s) of interest. Although it is out of question that accurate SHA must rely on robust investigations of individual potential earthquake sources, it is only by gathering this information in regionally extensive databases that one can address some of the most outstanding issues in the use of #<span class="hlt">Fault</span>2SHA. We will briefly recall three issues that are particularly relevant in the investigation of seismogenic <span class="hlt">faulting</span> in southern Europe. A fundamental challenge is the completeness of the geologic record of <span class="hlt">active</span> <span class="hlt">faulting</span>. In most tectonic environments many potential seismogenic <span class="hlt">faults</span> are blind or hidden, or deform the lower crust without leaving a discernible signal at the surface, or occur offshore, or slip so slowly that nontectonic erosional-depositional processes easily outpace their surface effects. Investigating only well-expressed <span class="hlt">faults</span> is scientifically rewarding but also potentially misleading as it draws attention on the least insidious <span class="hlt">faults</span>, leading to a potential underestimation of the regional earthquake potential. A further issue concerns the hierarchy of <span class="hlt">fault</span> systems. Most <span class="hlt">active</span> <span class="hlt">faults</span> do not comprise seismogenic sources per se but are part of larger systems, and slip only in conjunction with the master <span class="hlt">fault</span> of each system. In the most insidious cases, only secondary <span class="hlt">faults</span> are expressed at the surface while the master <span class="hlt">fault</span> lies hidden beneath them. This may result in an overestimation of the true number of seismogenic sources that occur in each region and in a biased identification of the characteristics of the main player in each system. Recent investigations of geologic and geodetic vs earthquake release budgets have shown that the "<span class="hlt">seismic</span> coupling", which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T31A2848C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T31A2848C"><span>Historical <span class="hlt">Seismicity</span> of the Algeciras <span class="hlt">Fault</span> System, Southwestern Colombia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chicangana, G.; Gomez-Capera, A.; Salcedo-Hurtado, E.</p> <p>2015-12-01</p> <p>The Algeciras <span class="hlt">Fault</span> System (AFS) is located in the Eastern Cordillera south western Colombia. This <span class="hlt">fault</span> system has been allocated at least four big earthquakes in the last 230 years. In this work we describe the macroseismic intensities of these earthquakes not only to its epicentral zone but also in others places as Bogotá metropolitan area far from AFS more of 200 km. The AFS is shaped by three thrust <span class="hlt">faults</span>. From north to south these are Guayuriba <span class="hlt">Fault</span> with with 160 km of lengh, the Algeciras <span class="hlt">Fault</span> with 149 km of lengh, and the Garzon - Pitalito <span class="hlt">Fault</span> with 128 km of lengh. The big earthquakes, whose macroseismic data are analyzed here, its that of the 1785 (M=6.8) event, for which the Guayuriba <span class="hlt">Fault</span> was related; it caused heavy damage in Bogotá and Neiva. This <span class="hlt">fault</span> also produced the 1917 (6.9Ms) earthquake which significantly affected to Bogotá and Villavicencio. The 1967 earthquake (7.2Mw) is related to the Algeciras <span class="hlt">Fault</span>; this event was very destructive in rural villages of Huila Department and caused significant damage in Bogotá and Neiva. With the latter earthquake high vulnerability was evident in the Bogota metropolitan area front to a large event ocurred by this <span class="hlt">fault</span> system. The 16 November 1827 (M=7.3) earthquake ocurred on the Garzon - Pitalito <span class="hlt">Fault</span> and was felt throughout the whole Andean region of Colombia. This event produced high intensities both in Bogota like in Popayan, Neiva, Pasto and where today are located the cities of Armenia, Manizales and Pereira toward west of Colombia. These lattest cities were founded in the second half of nineteen century after happened this earthquake. From historical <span class="hlt">seismicity</span> review, we can determine the scope of <span class="hlt">seismic</span> hazard for this <span class="hlt">fault</span> system which not only affects its area of influence but also the center and west of the country, a región inhabited by more than 65% of the population of Colombia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814160G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814160G"><span>How new <span class="hlt">fault</span> data and models affect <span class="hlt">seismic</span> hazard results? Examples from southeast Spain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaspar-Escribano, Jorge M.; Belén Benito, M.; Staller, Alejandra; Ruiz Barajas, Sandra; Quirós, Ligia E.</p> <p>2016-04-01</p> <p>In this work, we study the impact of different approaches to incorporate <span class="hlt">faults</span> in a <span class="hlt">seismic</span> hazard assessment analysis. Firstly, we consider two different methods to distribute the <span class="hlt">seismicity</span> of the study area into <span class="hlt">faults</span> and area-sources, based on magnitude partitioning and on moment rate distribution. We use two recurrence models to characterize <span class="hlt">fault</span> <span class="hlt">activity</span>: the characteristic earthquake model and the modified Gutenberg-Richter exponential frequency-magnitude distribution. An application of the work is developed in the region of Murcia (southeastern Spain), due to the availability of <span class="hlt">fault</span> data and because is one of the areas in Spain with higher <span class="hlt">seismic</span> hazard. The parameters used to model <span class="hlt">fault</span> sources are derived from paleoseismological and field studies obtained from the literature and online repositories. Additionally, for some significant <span class="hlt">faults</span> only, geodetically-derived slip rates are used to compute recurrence periods. The results of all the <span class="hlt">seismic</span> hazard computations carried out using different models and data are represented in maps of expected peak ground accelerations for a return period of 475 years. Maps of coefficients of variation are presented to constraint the variability of the end-results to different input models and values. Additionally, the different hazard maps obtained in this study are compared with the <span class="hlt">seismic</span> hazard maps obtained in previous work for the entire Spanish territory and more specifically for the region of Murcia. This work is developed in the context of the MERISUR project (ref. CGL2013-40492-R), with funding from the Spanish Ministry of Economy and Competitiveness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S21B2505S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S21B2505S"><span><span class="hlt">Seismic</span> tomography of the Canterbury Plains and the geometry and evolution of <span class="hlt">seismicity</span> of the Greendale <span class="hlt">fault</span> system, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Syracuse, E. M.; Thurber, C. H.; Savage, M. K.</p> <p>2012-12-01</p> <p>The previously unknown Greendale <span class="hlt">fault</span> produced the September 4, 2010 M 7.1 Darfield earthquake and later triggered the destructive February 22, 2011 M 6.3 Christchurch earthquake, as well as later M>5 aftershocks east of Christchurch. Surface rupture from the Darfield earthquake indicates up to 5 m of strike-slip motion along the main portion of the Greendale <span class="hlt">fault</span>, while various geodetic and <span class="hlt">seismic</span> models also indicate reverse <span class="hlt">faulting</span> on surrounding smaller <span class="hlt">faults</span>. We combine <span class="hlt">seismic</span> data from a variety of sources (permanent network seismometers and strong motion instruments, temporary intermediate to broadband seismometers) to understand the geometry of these various sections of <span class="hlt">faults</span> and the evolution of <span class="hlt">seismicity</span> along them for the first four months of aftershocks from the Darfield earthquake. We identify 4 to 5 <span class="hlt">fault</span> segments that were likely <span class="hlt">active</span> in the Darfield earthquake and an additional 5 to 6 segments that were <span class="hlt">active</span> during the study period, prior to the Christchurch earthquake. While relocating hypocenters, we also jointly invert for 3D Vp, Vs, and Vp/Vs in the Canterbury region using an extended version of the double-difference tomography code tomoDD (Zhang et al., 2009). In the area of the Greendale and associated <span class="hlt">faults</span>, Vp, Vs, and Vp/Vs are generally reduced from the top 8 km of the average velocity model for the Canterbury region of New Zealand. from the surface to ~8 km depth, below which the resolution begins to decline. Beneath Christchurch and areas immediately to the south and west, Vp and Vs are elevated and Vp/Vs is reduced from the surface to ~8 km depth, corresponding to the location of a negative Bouguer gravity anomaly and an increase in depth to basement (Hicks, 1989). In the northwest portion of the model, Vp and Vs increase when approaching the foothills of the Southern Alps. There are no clearly defined features in the velocity model that cross or are offset by the Greendale <span class="hlt">fault</span> and no apparent contrast in velocities</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T21B2332K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T21B2332K"><span><span class="hlt">Seismic</span> slip propagation along a <span class="hlt">fault</span> in the Shimanto accretionary prism detected by vitrinite reflectance studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kitamura, M.; Mukoyoshi, H.; Hirose, T.</p> <p>2011-12-01</p> <p>Quantitative assessment of heat generation along <span class="hlt">faults</span> during <span class="hlt">fault</span> movement is of primary importance in understanding the dynamics of earthquakes. Last several years localized heat anomaly in a <span class="hlt">fault</span> zone due to rapid <span class="hlt">seismic</span> sliding has been detected by various analyses of <span class="hlt">fault</span> zone materials, such as ferromagnetic resonance signal (Fukuchi et al., 2005), trace elements and isotopes (e.g., Ishikawa et al., 2008) and mineralogical change of clay (e.g., Hirono et al., 2008) and vitrinite reflectance (O'Hara, 2004). Here we report a heat anomaly found in a <span class="hlt">fault</span> zone in the Shimanto accretionary complex by vitrinite reflectance measurements. Mature <span class="hlt">faults</span> in nature mostly experience multiple <span class="hlt">seismic</span> events, resulting in integrated heat anomaly. Thus, in addition to vitrinite reflectance measurements across natural <span class="hlt">faults</span>, we performed high-velocity friction experiments on a mixture of quartz and vitrinite grains to evaluate how multiple rapid-slip events affect vitrinite reflectance in a <span class="hlt">fault</span> zone. A localized heat anomaly is found in one of <span class="hlt">fault</span> zones which are developed within a mélange unit in the Cretaceous Shimanto belt, SW Japan. A principle slip zone with thickness of ~5 mm forms within cataclastic damage zone with thickness of ~3 m. The slip zone is mainly composed of well-foliated clay minerals. Host rocks are characterized by a block-in-matrix texture: aligned sandstone and chert blocks embedded in mudstone matrix. We measured vitrinite reflectance across the <span class="hlt">fault</span> zone by the same method as reported in Sakaguchi et al., (2011). The measurement reveals that the principle slip zone underwent localized temperature of more than 220°C, while background temperature of both damage zone and host rocks is ~170°C. Since <span class="hlt">fault</span> motion along most <span class="hlt">active</span> <span class="hlt">faults</span> occurs seismological, that inevitably generates frictional heat, the localized heat anomaly is possibly caused by the rapid <span class="hlt">seismic</span> slip. In order to evaluate the change in vitrinite reflectance by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17784489','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17784489"><span><span class="hlt">Seismic</span>-wave attenuation associated with crustal <span class="hlt">faults</span> in the new madrid <span class="hlt">seismic</span> zone.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hamilton, R M; Mooney, W D</p> <p>1990-04-20</p> <p>The attenuation of upper crustal <span class="hlt">seismic</span> waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid <span class="hlt">seismic</span> zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the <span class="hlt">seismic</span> trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/or <span class="hlt">seismic</span> scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong <span class="hlt">seismic</span>-wave attenuation may be a useful criterion for identifying seismogenic <span class="hlt">fault</span> zones.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010CEJG....2..455K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010CEJG....2..455K"><span>Earthquake source parameters at the sumatran <span class="hlt">fault</span> zone: Identification of the <span class="hlt">activated</span> <span class="hlt">fault</span> plane</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kasmolan, Madlazim; Santosa, Bagus Jaya; Lees, Jonathan M.; Utama, Widya</p> <p>2010-12-01</p> <p>Fifteen earthquakes (Mw 4.1-6.4) occurring at ten major segments of the Sumatran <span class="hlt">Fault</span> Zone (SFZ) were analyzed to identify their respective <span class="hlt">fault</span> planes. The events were relocated in order to assess hypocenter uncertainty. Earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and GEOFON broadband lA networks. Epicentral distances of all stations were less than 10°. Moment tensor solutions of the events were calculated, along with simultaneous determination of centroid position. Joint analysis of hypocenter position, centroid position, and nodal planes produced clear outlines of the Sumatran <span class="hlt">fault</span> planes. The preferable seismotectonic interpretation is that the events <span class="hlt">activated</span> the SFZ at a depth of approximately 14-210 km, corresponding to the interplate Sumatran <span class="hlt">fault</span> boundary. The identification of this <span class="hlt">seismic</span> <span class="hlt">fault</span> zone is significant to the investigation of <span class="hlt">seismic</span> hazards in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMNS43B..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMNS43B..02W"><span>Including <span class="hlt">Faults</span> Detected By Near-Surface <span class="hlt">Seismic</span> Methods in the USGS National <span class="hlt">Seismic</span> Hazard Maps - Some Restrictions Apply</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, R. A.; Haller, K. M.</p> <p>2014-12-01</p> <p>Every 6 years, the USGS updates the National <span class="hlt">Seismic</span> Hazard Maps (new version released July 2014) that are intended to help society reduce risk from earthquakes. These maps affect hundreds of billions of dollars in construction costs each year as they are used to develop <span class="hlt">seismic</span>-design criteria of buildings, bridges, highways, railroads, and provide data for risk assessment that help determine insurance rates. <span class="hlt">Seismic</span> source characterization, an essential component of hazard model development, ranges from detailed trench excavations across <span class="hlt">faults</span> at the ground surface to less detailed analysis of broad regions defined mainly on the basis of historical <span class="hlt">seismicity</span>. Though it is a priority for the USGS to discover new Quaternary <span class="hlt">fault</span> sources, the discovered <span class="hlt">faults</span> only become a part of the hazard model if there are corresponding constraints on their geometry (length and depth extent) and slip-rate (or recurrence interval). When combined with <span class="hlt">fault</span> geometry and slip-rate constraints, near-surface <span class="hlt">seismic</span> studies that detect young (Quaternary) <span class="hlt">faults</span> have become important parts of the hazard source model. Examples of <span class="hlt">seismic</span> imaging studies with significant hazard impact include the Southern Whidbey Island <span class="hlt">fault</span>, Washington; Santa Monica <span class="hlt">fault</span>, San Andreas <span class="hlt">fault</span>, and Palos Verdes <span class="hlt">fault</span> zone, California; and Commerce <span class="hlt">fault</span>, Missouri. There are many more <span class="hlt">faults</span> in the hazard model in the western U.S. than in the expansive region east of the Rocky Mountains due to the higher rate of tectonic deformation, frequent surface-rupturing earthquakes and, in some cases, lower erosion rates. However, the recent increase in earthquakes in the central U.S. has revealed previously unknown <span class="hlt">faults</span> for which we need additional constraints before we can include them in the <span class="hlt">seismic</span> hazard maps. Some of these new <span class="hlt">faults</span> may be opportunities for <span class="hlt">seismic</span> imaging studies to provide basic data on location, dip, style of <span class="hlt">faulting</span>, and recurrence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70003857','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70003857"><span>Recent <span class="hlt">faulting</span> in western Nevada revealed by multi-scale <span class="hlt">seismic</span> reflection</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Frary, Roxanna N.; Louie, John N.; Stephenson, William J.; Odum, Jackson K.; Kell, Annie; Eisses, Amy; Kent, Graham M.; Driscoll, Neal W.; Karlin, Robert; Baskin, Robert L.; Pullammanappallil, Satish; Liberty, Lee M.</p> <p>2011-01-01</p> <p>The main goal of this study is to compare different reflection methods used to image subsurface structure within different physical environments in western Nevada. With all the methods employed, the primary goal is <span class="hlt">fault</span> imaging for structural information toward geothermal exploration and <span class="hlt">seismic</span> hazard estimation. We use <span class="hlt">seismic</span> CHIRP (a swept-frequency marine acquisition system), weight drop (an accelerated hammer source), and two different vibroseis systems to characterize <span class="hlt">fault</span> structure. We focused our efforts in the Reno metropolitan area and the area within and surrounding Pyramid Lake in northern Nevada. These different methods have provided valuable constraints on the <span class="hlt">fault</span> geometry and <span class="hlt">activity</span>, as well as associated fluid movement. These are critical in evaluating the potential for large earthquakes in these areas, and geothermal exploration possibilities near these structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033959','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033959"><span>Recent <span class="hlt">faulting</span> in western Nevada revealed by multi-scale <span class="hlt">seismic</span> reflection</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Frary, R.N.; Louie, J.N.; Stephenson, W.J.; Odum, J.K.; Kell, A.; Eisses, A.; Kent, G.M.; Driscoll, N.W.; Karlin, R.; Baskin, R.L.; Pullammanappallil, S.; Liberty, L.M.</p> <p>2011-01-01</p> <p>The main goal of this study is to compare different reflection methods used to image subsurface structure within different physical environments in western Nevada. With all the methods employed, the primary goal is <span class="hlt">fault</span> imaging for structural information toward geothermal exploration and <span class="hlt">seismic</span> hazard estimation. We use <span class="hlt">seismic</span> CHIRP a swept-frequency marine acquisition system, weight drop an accelerated hammer source, and two different vibroseis systems to characterize <span class="hlt">fault</span> structure. We focused our efforts in the Reno metropolitan area and the area within and surrounding Pyramid Lake in northern Nevada. These different methods have provided valuable constraints on the <span class="hlt">fault</span> geometry and <span class="hlt">activity</span>, as well as associated fluid movement. These are critical in evaluating the potential for large earthquakes in these areas, and geothermal exploration possibilities near these structures. ?? 2011 Society of Exploration Geophysicists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S51A1912B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S51A1912B"><span>Effect of <span class="hlt">Fault</span> Segmentations on Simulation of Long-Period Earthquake Ground Motions and <span class="hlt">Seismic</span> Load</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bykovtsev, A.; Research Team Of Geotechnical; Structural Engineers</p> <p>2010-12-01</p> <p>Effect of <span class="hlt">fault</span> segmentation on simulation of long-period earthquake ground motions(LPEQM) and <span class="hlt">seismic</span> load(SP) will be presented for sites located within 6 miles of an <span class="hlt">active</span> <span class="hlt">fault</span>. According to AASHTO guide(2009) <span class="hlt">seismic</span> design for sites located within 6 miles of an <span class="hlt">active</span> <span class="hlt">fault</span> studies shall be considered to quantify near-<span class="hlt">fault</span> effects on ground motions to determine if these could significantly influence the bridge response. It will be demonstrated that in near-field (D<6 miles) LPEQM may contain pulses with multiple oscillations which can cause severe nonlinear structural response, predictable only through nonlinear time-history analyses. The main question for discussion will be “IS IT APPROPRIATE TO USE SIMPLE BRUNE’S MODEL FOR OBSERVED TIME HISTORY WITH MULTIPLE OSCILLATIONS?” The widespread Brune’s Model proposed a simple interpretation method for the spectrum of a small earthquake. It was OK to characterize the observed spectrum by three parameters: low-frequency level proportional to the <span class="hlt">seismic</span> moment; corner frequency; and power of high-frequency asymptotic decay. The secondary parameters are usually interpreted by an earthquake source model in which a FLAT CIRCULAR RUPTURE PLANE (FCRP) is formed spreading at a constant speed from the center with a uniform stress drop. I see an OUTSTANDING PROBLEM with this approach. 1. As a rule the OBSERVED RECORDS in time domain are DIFFERENT from those predicted for the FCRP MODEL, although the shapes of observed and theoretical amplitude spectra in frequency domain are roughly similar to each other. 2. The simulated time history for displacement for the FCRP is a single spike of a triangle-like shape. However, the OBSERVED TIME HISTORIES are composed of MANY OSCILLATIONS. Two reasons exist for explanations of these oscillations. 1. Traditional approach: Apparently, the <span class="hlt">seismic</span> signal arrives along multiple paths due to inhomogeneous structure and spreads over a time length which increases with travel</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70000290','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70000290"><span>Structure of the eastern Seattle <span class="hlt">fault</span> zone, Washington state: New insights from <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Liberty, L.M.; Pratt, T.L.</p> <p>2008-01-01</p> <p>We identify and characterize the <span class="hlt">active</span> Seattle <span class="hlt">fault</span> zone (SFZ) east of Lake Washington with newly acquired <span class="hlt">seismic</span> reflection data. Our results focus on structures observed in the upper 1 km below the cities of Bellevue, Sammamish, Newcastle, and Fall City, Washington. The SFZ appears as a broad zone of <span class="hlt">faulting</span> and folding at the southern boundary of the Seattle basin and north edge of the Seattle uplift. We interpret the Seattle <span class="hlt">fault</span> as a thrust <span class="hlt">fault</span> that accommodates north-south shortening by forming a <span class="hlt">fault</span>-propagation fold with a forelimb breakthrough. The blind tip of the main <span class="hlt">fault</span> forms a synclinal growth fold (deformation front) that extends at least 8 km east of Vasa Park (west side of Lake Sammamish) and defines the south edge of the Seattle basin. South of the deformation front is the forelimb break-through <span class="hlt">fault</span>, which was exposed in a trench at Vasa Park. The Newcastle Hills anticline, a broad anticline forming the north part of the Seattle uplift east of Lake Washington, is interpreted to lie between the main blind strand of the Seattle <span class="hlt">fault</span> and a backthrust. Our profiles, on the northern limb of this anticline, consistently image north-dipping strata. A structural model for the SFZ east of Lake Washington is consistent with about 8 km of slip on the upper part of the Seattle <span class="hlt">fault</span>, but the amount of motion is only loosely constrained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4707V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4707V"><span>Modeling <span class="hlt">seismic</span> hazard in the Lower Rhine Graben using a <span class="hlt">fault</span>-based source model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vanneste, Kris; Vleminckx, Bart; Verbeeck, Koen; Camelbeeck, Thierry</p> <p>2013-04-01</p> <p>The Lower Rhine Graben (LRG) is an <span class="hlt">active</span> tectonic structure in intraplate NW Europe. It is characterized by NW-SE oriented normal <span class="hlt">faults</span>, and moderate but rather continuous <span class="hlt">seismic</span> <span class="hlt">activity</span>. Probabilistic <span class="hlt">seismic</span> hazard assessments (PHSA) in this region have hitherto been based on area source models, in which the LRG is modeled as a single or a small number of seismotectonic zones, where the occurrence of earthquakes is assumed to be uniform. Hazard engines usually model earthquakes in area sources as point sources or finite ruptures in a horizontal plane at a fixed depth. The past few years, efforts have increasingly been directed to using <span class="hlt">fault</span> sources in PSHA, in order to obtain more realistic patterns of ground motion. This requires an inventory of all <span class="hlt">fault</span> sources, and definition of their physical properties (at least length, width, strike, dip, rake, slip rate, and maximum magnitude). The LRG is one of the few regions in intraplate NW Europe where <span class="hlt">seismic</span> <span class="hlt">activity</span> can be linked to <span class="hlt">active</span> <span class="hlt">faults</span>. In the frame of the EC project SHARE ("<span class="hlt">Seismic</span> Hazard Harmonization in Europe", http://www.share-eu.org/), we have compiled the first parameterized <span class="hlt">fault</span> model for the LRG that can be used in PSHA studies. We construct the magnitude-frequency distribution (MFD) of each <span class="hlt">fault</span> from two contributions: 1) up to the largest observed magnitude (M=5.7), we use the MFD determined from the historical and instrumental earthquake catalog, weighted in proportion to the total moment rate, and 2) the frequency of the maximum earthquake predicted by the <span class="hlt">fault</span> model. We consider the ground-motion prediction equations (GMPE) that were selected in the SHARE project for <span class="hlt">active</span> shallow crust. This selection includes GMPE's with different distance metrics, the main difference being whether depth of rupture is taken into account or not. <span class="hlt">Seismic</span> hazard is computed with OpenQuake (http://openquake.org/), an open-source hazard and risk engine that is developed in the frame of the Global</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70073701','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70073701"><span>Enriquillo–Plantain Garden <span class="hlt">fault</span> zone in Jamaica: paleoseismology and <span class="hlt">seismic</span> hazard</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Koehler, R.D.; Mann, P.; Prentice, Carol S.; Brown, L.; Benford, B.; Grandison-Wiggins, M.</p> <p>2013-01-01</p> <p>The countries of Jamaica, Haiti, and the Dominican Republic all straddle the Enriquillo–Plantain Garden <span class="hlt">fault</span> zone ( EPGFZ), a major left-lateral, strike-slip <span class="hlt">fault</span> system bounding the Caribbean and North American plates. Past large earthquakes that destroyed the capital cities of Kingston, Jamaica (1692, 1907), and Port-au-Prince, Haiti (1751, 1770), as well as the 2010 Haiti earthquake that killed more than 50,000 people, have heightened awareness of <span class="hlt">seismic</span> hazards in the northern Caribbean. We present here new geomorphic and paleoseismic information bearing on the location and relative <span class="hlt">activity</span> of the EPGFZ, which marks the plate boundary in Jamaica. Documentation of a river bank exposure and several trenches indicate that this <span class="hlt">fault</span> is <span class="hlt">active</span> and has the potential to cause major destructive earthquakes in Jamaica. The results suggest that the <span class="hlt">fault</span> has not ruptured the surface in at least 500 yr and possibly as long as 28 ka. The long period of quiescence and subdued geomorphic expression of the EPGFZ indicates that it may only accommodate part of the ∼7–9 mm=yr plate deformation rate measured geodetically and that slip may be partitioned on other undocumented <span class="hlt">faults</span>. Large uncertainties related to the neotectonic framework of Jamaica remain and more detailed <span class="hlt">fault</span> characterization studies are necessary to accurately assess <span class="hlt">seismic</span> hazards.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EaFut...2..440T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EaFut...2..440T"><span><span class="hlt">Fault</span> zone regulation, <span class="hlt">seismic</span> hazard, and social vulnerability in Los Angeles, California: Hazard or urban amenity?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toké, Nathan A.; Boone, Christopher G.; Arrowsmith, J. Ramón</p> <p>2014-09-01</p> <p>Public perception and regulation of environmental hazards are important factors in the development and configuration of cities. Throughout California, probabilistic <span class="hlt">seismic</span> hazard mapping and geologic investigations of <span class="hlt">active</span> <span class="hlt">faults</span> have spatially quantified earthquake hazard. In Los Angeles, these analyses have informed earthquake engineering, public awareness, the insurance industry, and the government regulation of developments near <span class="hlt">faults</span>. Understanding the impact of natural hazards regulation on the social and built geography of cities is vital for informing future science and policy directions. We constructed a relative social vulnerability index classification for Los Angeles to examine the social condition within regions of significant <span class="hlt">seismic</span> hazard, including areas regulated as Alquist-Priolo (AP) Act earthquake <span class="hlt">fault</span> zones. Despite hazard disclosures, social vulnerability is lowest within AP regulatory zones and vulnerability increases with distance from them. Because the AP Act requires building setbacks from <span class="hlt">active</span> <span class="hlt">faults</span>, newer developments in these zones are bisected by parks. Parcel-level analysis demonstrates that homes adjacent to these <span class="hlt">fault</span> zone parks are the most valuable in their neighborhoods. At a broad scale, a Landsat-based normalized difference vegetation index shows that greenness near AP zones is greater than the rest of the metropolitan area. In the parks-poor city of Los Angeles, <span class="hlt">fault</span> zone regulation has contributed to the construction of park space within areas of earthquake hazard, thus transforming zones of natural hazard into amenities, attracting populations of relatively high social status, and demonstrating that the distribution of social vulnerability is sometimes more strongly tied to amenities than hazards.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tecto..32.1571P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tecto..32.1571P"><span><span class="hlt">Seismic</span> transpressive basement <span class="hlt">faults</span> and monocline development in a foreland basin (Eastern Guadalquivir, SE Spain)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedrera, A.; Ruiz-Constán, A.; Marín-Lechado, C.; Galindo-Zaldívar, J.; González, A.; Peláez, J. A.</p> <p>2013-12-01</p> <p>We examine the late Tortonian to present-day deformation of an <span class="hlt">active</span> <span class="hlt">seismic</span> sector of the eastern Iberian foreland basement of the Betic Cordillera, in southern Spain. Transpressive <span class="hlt">faults</span> affecting Paleozoic basement offset up to Triassic rocks. Late Triassic clays and evaporites constitute a décollement level decoupling the basement rocks and a ~100 m thick cover of Jurassic carbonates. Monoclines trending NE-SW to ENE-WSW deform the Jurassic cover driven by the propagation of high-angle transpressive right-lateral basement <span class="hlt">faults</span>. They favor the migration of clays and evaporites toward the propagated <span class="hlt">fault</span> tip, i.e., the core of the anticline, resulting in fluid overpressure, fluid flow, and precipitation of fibrous gypsum parallel to a vertical σ3. The overall geometry of the studied monoclines, as well as the intense deformation within the clays and evaporites, reproduces three-layer discrete element models entailing a weak middle unit sandwiched between strong layers. Late Tortonian syn-folding sediments recorded the initial stages of the <span class="hlt">fault</span>-propagation folding. Equivalent unexposed transpressive structures and associated monoclines reactivated under the present-day NW-SE convergence are recognized and analyzed in the Sabiote-Torreperogil region, using <span class="hlt">seismic</span> reflection, gravity, and borehole data. A <span class="hlt">seismic</span> series of more than 2100 low-magnitude earthquakes was recorded within a very limited area of the basement of this sector from October 2012 to May 2013. <span class="hlt">Seismic</span> <span class="hlt">activity</span> within a major NE-SW trending transpressive basement <span class="hlt">fault</span> plane stimulated rupture along a subsidiary E-W (~N95°E) strike-slip relay <span class="hlt">fault</span>. The biggest event (mbLg 3.9, MW 3.7) occurred at the junction between them in a transpressive relay sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.G13B..05V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.G13B..05V"><span>20 years of GPS interseismic measurements across strike slip <span class="hlt">faults</span> (comparison with geologic estimates, implications on <span class="hlt">faults</span> mechanics, lithosphere rheology and <span class="hlt">seismic</span> hazard)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vernant, P.</p> <p>2011-12-01</p> <p>Measurements of interseismic strain across <span class="hlt">active</span> <span class="hlt">faults</span> are an important key to better assess <span class="hlt">faults</span> dynamics and <span class="hlt">seismic</span> hazard. Based on geodetic observations across the San Andreas <span class="hlt">fault</span> Savage and Burford in 1973 have proposed a dislocation in an elastic half space model to fit the observations. Since then, the advent of the Global Positioning System (GPS) and InSAR have allowed to monitor several other <span class="hlt">faults</span> and one can wonder if this rheologically unrealistic model is still a good one to extrapolate the <span class="hlt">fault</span> slip rate using the interseimic GPS velocity solution. We have now enough data to start to look at common features for strike slip <span class="hlt">faults</span>. I will present new velocity solutions across strike slip <span class="hlt">faults</span> that I will use with results from other studies to discuss what can we learn from geodetic measurement of interseismic strain across strike slip <span class="hlt">fault</span>. Data from 10 strike slip <span class="hlt">faults</span> will be used to estimate locking depth and strike slip rate. When available geologic slip rate will be compared to geodetic slip rate. Consistent estimates between geodesy and geology and between several <span class="hlt">faults</span> suggest a constant behavior through the interseismic time period. This implies that GPS is important for the <span class="hlt">seismic</span> hazard assessment, but is probably not the key data in the <span class="hlt">seismic</span> hazard assessment models. Common characteristics between slow and fast slip rate <span class="hlt">faults</span>, almost pre-<span class="hlt">seismic</span> and early interseismic period measurements bring new information to discuss the validity of existing interseismic models and to further develop new interseismic models. Indeed, the elastic and viscoelastic two layers model of the crust or the lithosphere although more accurate than the elastic dislocation does not withstand this comparative study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70173983','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70173983"><span>High-resolution <span class="hlt">seismic</span> reflection imaging of growth folding and shallow <span class="hlt">faults</span> beneath the Southern Puget Lowland, Washington State</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Odum, Jackson K.; Stephenson, William J.; Pratt, Thomas L.; Blakely, Richard J.</p> <p>2016-01-01</p> <p>Marine <span class="hlt">seismic</span> reflection data from southern Puget Sound, Washington, were collected to investigate the nature of shallow structures associated with the Tacoma <span class="hlt">fault</span> zone and the Olympia structure. Growth folding and probable Holocene surface deformation were imaged within the Tacoma <span class="hlt">fault</span> zone beneath Case and Carr Inlets. Shallow <span class="hlt">faults</span> near potential field anomalies associated with the Olympia structure were imaged beneath Budd and Eld Inlets. Beneath Case Inlet, the Tacoma <span class="hlt">fault</span> zone includes an ∼350-m wide section of south-dipping strata forming the upper part of a fold (kink band) coincident with the southern edge of an uplifted shoreline terrace. An ∼2 m change in the depth of the water bottom, onlapping postglacial sediments, and increasing stratal dips with increasing depth are consistent with late Pleistocene to Holocene postglacial growth folding above a blind <span class="hlt">fault</span>. Geologic data across a topographic lineament on nearby land indicate recent uplift of late Holocene age. Profiles acquired in Carr Inlet 10 km to the east of Case Inlet showed late Pleistocene or Holocene <span class="hlt">faulting</span> at one location with ∼3 to 4 m of vertical displacement, south side up. North of this <span class="hlt">fault</span> the data show several other disruptions and reflector terminations that could mark <span class="hlt">faults</span> within the broad Tacoma <span class="hlt">fault</span> zone. <span class="hlt">Seismic</span> reflection profiles across part of the Olympia structure beneath southern Puget Sound show two apparent <span class="hlt">faults</span> about 160 m apart having 1 to 2 m of displacement of subhorizontal bedding. Directly beneath one of these <span class="hlt">faults</span>, a dipping reflector that may mark the base of a glacial channel shows the opposite sense of throw, suggesting strike-slip motion. Deeper <span class="hlt">seismic</span> reflection profiles show disrupted strata beneath these <span class="hlt">faults</span> but little apparent vertical offset, consistent with strike-slip <span class="hlt">faulting</span>. These <span class="hlt">faults</span> and folds indicate that the Tacoma <span class="hlt">fault</span> and Olympia structure include <span class="hlt">active</span> structures with probable postglacial motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.5805P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.5805P"><span>Stress changes induced at neighbouring <span class="hlt">faults</span> by the June 2000 earthquakes, South Iceland <span class="hlt">Seismic</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plateaux, Romain; Angelier, Jacques; Bergerat, Françoise; Cappa, Frédéric; Stefansson, Ragnar</p> <p>2010-05-01</p> <p>The Icelandic rift system belongs to the Mid-Atlantic Ridge and is connected to the offshore Reykjanes and Kolbeinsey ridges by two <span class="hlt">active</span> transform zones. Plate separation occurs at a rate of nearly 2 cm/yr along the N105°E direction. With respect to the Icelandic Hotspot, westward plate velocities in Iceland are 1.8-2.2 cm/yr for North America and 0-0.4 cm/yr for Eurasia, resulting in a westward displacement of the Icelandic Rift relative to the hotspot. Rift jumps occur when the plate boundary has migrated to a critical point to the west, and a new rift develops above the hotspot apex while the old rift is dying out. The two <span class="hlt">active</span> transform zones, the Tjörnes Fracture Zone (TFZ) and the South Iceland <span class="hlt">Seismic</span> Zone (SISZ), resulted from such eastward rift jumps. Our study focuses on the SISZ which is an onland, E-W trending transform zone where N-S trending right-lateral strike-slip <span class="hlt">faults</span> accommodate left-lateral transform motion as revealed by historical <span class="hlt">seismicity</span>. During the most recent <span class="hlt">seismic</span> crisis, in June 2000, two major earthquakes of magnitude (Mw) 6.4 occurred along N-S right-lateral <span class="hlt">faults</span> in the central segment of the SISZ. The high sensitivity SIL (South Iceland Lowlands) <span class="hlt">seismic</span> network run by the Icelandic Meteorological Office (IMO) provided a complete record of earthquakes down to magnitude Mw = -1. Here, we present an analysis of this earthquakes sequence in term of stress regimes in order to examine the response of two <span class="hlt">faults</span> that did not experience significant motion during the earthquakes, and hence to determine how far such <span class="hlt">fault</span> zones provide information about stress changes in space and time when large earthquakes occur at distance of some tens of kilometres. The <span class="hlt">faults</span> considered are the Skard and Leirubakki <span class="hlt">faults</span>, along which large earthquakes and significant displacement occurred in the past Using seismological data recorded from 1991 to 2007, we carried out stress inversion of focal mechanisms of 1,340 earthquakes that affected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.105.2221P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.105.2221P"><span>Geophysical characterization of buried <span class="hlt">active</span> <span class="hlt">faults</span>: the Concud <span class="hlt">Fault</span> (Iberian Chain, NE Spain)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pueyo Anchuela, Óscar; Lafuente, Paloma; Arlegui, Luis; Liesa, Carlos L.; Simón, José L.</p> <p>2016-11-01</p> <p>The Concud <span class="hlt">Fault</span> is a 14-km-long <span class="hlt">active</span> <span class="hlt">fault</span> that extends close to Teruel, a city with about 35,000 inhabitants in the Iberian Range (NE Spain). It shows evidence of recurrent <span class="hlt">activity</span> during Late Pleistocene time, posing a significant <span class="hlt">seismic</span> hazard in an area of moderate-to-low tectonic rates. A geophysical survey was carried out along the mapped trace of the southern branch of the Concud <span class="hlt">Fault</span> to evaluate the geophysical signature from the <span class="hlt">fault</span> and the location of paleoseismic trenches. The survey identified a lineation of inverse magnetic dipoles at residual and vertical magnetic gradient, a local increase in apparent conductivity, and interruptions of the underground sediment structure along GPR profiles. The origin of these anomalies is due to lateral contrast between both <span class="hlt">fault</span> blocks and the geophysical signature of Quaternary materials located above and directly south of the <span class="hlt">fault</span>. The spatial distribution of anomalies was successfully used to locate suitable trench sites and to map non-exposed segments of the <span class="hlt">fault</span>. The geophysical anomalies are related to the sedimentological characteristics and permeability differences of the deposits and to deformation related to <span class="hlt">fault</span> <span class="hlt">activity</span>. The results illustrate the usefulness of geophysics to detect and map non-exposed <span class="hlt">faults</span> in areas of moderate-to-low tectonic <span class="hlt">activity</span> where <span class="hlt">faults</span> are often covered by recent pediments that obscure geological evidence of the most recent earthquakes. The results also highlight the importance of applying multiple geophysical techniques in defining the location of buried <span class="hlt">faults</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T12C..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T12C..08L"><span>Detecting Aseismic <span class="hlt">Fault</span> Slip and Magmatic Intrusion From <span class="hlt">Seismicity</span> Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Llenos, A. L.; McGuire, J. J.</p> <p>2007-12-01</p> <p><span class="hlt">Seismicity</span> triggered by aseismic deformation, such as magmatic intrusions or afterslip, can be used to detect the occurrence of these otherwise difficult to observe processes. Recent studies suggest that aseismic deformation can trigger large amounts of <span class="hlt">seismicity</span> in a variety of plate tectonic settings. We have developed a new technique that takes advantage of this triggered <span class="hlt">seismicity</span> to estimate the time-history of aseismic stressing rate on a <span class="hlt">fault</span>- zone by combining the rate and state dependent friction and the Epidemic Type Aftershock Sequence (ETAS) models of <span class="hlt">seismicity</span>-rate [ Dieterich, 1994; Ogata, 1988]. In the rate-state model, the integration of an observed <span class="hlt">seismicity</span> rate results in an estimate of the stress rate acting in a given space-time window. However, the <span class="hlt">seismicity</span> rate observed in any catalog comes from 3 primary sources: coseismically-triggered <span class="hlt">seismicity</span> (aftershocks), tectonically-triggered <span class="hlt">seismicity</span> (i.e., from long-term tectonic loading), and aseismically-triggered <span class="hlt">seismicity</span> (e.g., from dike intrusion, aseismic slip transients, or fluid migration). In catalogs dominated by directly triggered aftershocks (i.e., ETAS branching ratios >~0.7), the coseismically-triggered <span class="hlt">seismicity</span> rate will be much larger than the aseismically-triggered rate and will dominate the estimate of stressing-rate, obscuring the aseismic transient of interest if the rate-state method is applied directly. The challenge therefore lies in isolating the aseismically-triggered <span class="hlt">seismicity</span> rate from the coseismically-triggered <span class="hlt">seismicity</span> rate. The ETAS model [ Ogata, 1988] provides a natural way to separate the aseismic and coseismic <span class="hlt">seismicity</span> rates, as the ETAS parameter μ essentially reflects the aseismically-triggered rate (as well as the background tectonically-triggered rate). To develop a method that can resolve the magnitude and time history of aseismic stress transients even in high branching ratio regions, we combine the rate-state and ETAS models into a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.S11A0537S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.S11A0537S"><span>High-Resolution <span class="hlt">Seismic</span> Imaging of Quaternary <span class="hlt">Faults</span> and Deformation in the Los Angeles Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stephenson, W. J.; Odum, J. K.; Williams, R. A.; Pratt, T. L.; Dolan, J.; Shaw, J. H.</p> <p>2001-12-01</p> <p>We present results from several P-wave high-resolution <span class="hlt">seismic</span> imaging studies in the Los Angeles region that characterize Quaternary <span class="hlt">fault</span> <span class="hlt">activity</span> and associated deformation. From high-resolution <span class="hlt">seismic</span> reflection data, we seek crucial information on shallow basin geometry as well as near-surface <span class="hlt">fault</span> geometry, displacement, slip rates, and timing of Quaternary deformation. Data acquired along a profile in Sherman Oaks reveal a geologic structure in the upper 600 m that contributed to the increased earthquake ground shaking in the high-damage areas south of and along the Los Angeles River resulting from the 1994 Northridge earthquake. A shallow sub-basin imaged on the Sherman Oaks line correlates with an area that experienced greater earthquake damage from possible geometric focussing effects. Finite-difference modeling of the imaged structural geometry along the profile suggests that a peak horizontal-velocity amplification factor of two-and-greater, as well as spatial variability, can be explained in the high-damage area by the sub-basin. High-resolution <span class="hlt">seismic</span> reflection data acquired across the Santa Monica <span class="hlt">fault</span> confirm the location of the <span class="hlt">fault</span> and link related shallow strike-slip <span class="hlt">faults</span> seen in a nearby trench to deeper structures previously observed in regional studies. The high-resolution <span class="hlt">seismic</span> data image deformation as shallow as 15 m depth and show the Santa Monica <span class="hlt">fault</span> dips about 30 degrees north in the upper 300 m. These data, combined with soil age estimates from the trench, yield a reverse-slip rate for the <span class="hlt">fault</span> of about 0.5 mm/yr. The Puente Hills thrust <span class="hlt">fault</span> is one of the major <span class="hlt">faults</span> underlying the urban Los Angeles Basin. Industry-scale and high-resolution <span class="hlt">seismic</span> reflection images define the location and geometry of <span class="hlt">active</span> folds above the Puente Hills thrust <span class="hlt">fault</span>. Four <span class="hlt">seismic</span> profiles acquired at two locations delineate fold geometry above the thrust. At one of these sites we image an <span class="hlt">active</span> synclinal axial surface with strata</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T51B2588H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T51B2588H"><span>Lidar-Based Mapping of Late Quaternary <span class="hlt">Faulting</span> Along the Grizzly Valley <span class="hlt">Fault</span>, Walker Lane <span class="hlt">Seismic</span> Belt, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hitchcock, C. S.; Hoirup, D. F.; Barry, G.; Pearce, J.; Glick, F.</p> <p>2012-12-01</p> <p>The Grizzly Valley <span class="hlt">fault</span> (GVF) is located within the northern Walker Lane, a zone of right-lateral shear between the Sierra Nevada and the Basin and Range in Plumas County. The GVF extends southeasterly from near Mt. Ingalls along the eastern side of Lake Davis. It may partially connect with the Hot Creek <span class="hlt">fault</span> within Sierra Valley and extend south to Loyalton with an overall approximate length of 50 km. Comparison of high-resolution topography developed from LiDAR data with published bedrock geologic mapping documents the presence of geomorphic features that provide information on <span class="hlt">fault</span> <span class="hlt">activity</span> of the GVF. Field mapping verified tectonically deformed and offset late Quaternary surfaces identified on bare-earth LiDAR imagery across the GVF within glacial deposits on the eastern margin of Lake Davis, and alluvial deposits in Sierra Valley. Along the GVF, conspicuous geomorphic and hydrologic features include scarps in alluvial surfaces, elongated depressions aligned with adjacent linear escarpments, truncated bedrock spurs, closed depressions, linear swales, right-lateral deflections of creeks and river courses, and shutter ridges, as well as springs and linear seeps consistent with right-lateral strike-slip <span class="hlt">faulting</span>. The discontinuous nature of observed <span class="hlt">fault</span> traces combined with the apparent down-to-the-west offset of alluvial surfaces at the southern and northern ends of the eastern margin of Lake Davis are consistent with a broad bend or step over in the <span class="hlt">fault</span>. Scarp profiles of apparently <span class="hlt">faulted</span> surfaces extracted from LiDAR data document vertical offsets of up to 14 m. Our study suggest that the GVF is an oblique, right-lateral <span class="hlt">fault</span> that has been <span class="hlt">active</span> in the late Quaternary. This study complements on-going investigations by DWR to assess the impact of <span class="hlt">seismic</span> hazards on State Water Project infrastructure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70041795','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70041795"><span>Significant earthquakes on the Enriquillo <span class="hlt">fault</span> system, Hispaniola, 1500-2010: Implications for <span class="hlt">seismic</span> hazard</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bakun, William H.; Flores, Claudia H.; ten Brink, Uri S.</p> <p>2012-01-01</p> <p>Historical records indicate frequent <span class="hlt">seismic</span> <span class="hlt">activity</span> along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo <span class="hlt">fault</span> system in the eighteenth century. An intensity magnitude MI 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and the accounts of the shaking in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the 18 October 1751 MI 7.4–7.5 earthquake, probably located near the eastern end of the <span class="hlt">fault</span> in the Dominican Republic, followed by the 21 November 1751 MI 6.6 earthquake near Port-au-Prince, Haiti, and the 3 June 1770 MI 7.5 earthquake west of the 2010 earthquake rupture. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo <span class="hlt">fault</span> system after 240 years of <span class="hlt">seismic</span> quiescence. The entire Enriquillo <span class="hlt">fault</span> system appears to be <span class="hlt">seismically</span> <span class="hlt">active</span>; Haiti and the Dominican Republic should prepare for future devastating earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhDT.......123K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhDT.......123K"><span>Enhanced <span class="hlt">seismic</span> depth imaging of complex <span class="hlt">fault</span>-fold structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirtland Grech, Maria Graziella</p> <p></p> <p>Synthetic <span class="hlt">seismic</span> data were acquired over numerical and physical models, representing <span class="hlt">fault</span>-fold structures encountered in the Canadian Rocky Mountain Foothills, to investigate which migration algorithm produces the best image in such complex environments. Results showed that pre-stack depth migration from topography with the known velocity model yielded the optimum migrated image. Errors in the positioning of a target underneath a dipping antisotropic overburden were also studied using multicomponent data. The largest error was observed on P-wave data where anisotropy was highest at 18%. For an overburden thickness of 1500 m, the target was imaged 300 m updip from the true location. Field data from a two-dimensional surface <span class="hlt">seismic</span> line and a multioffset vertical <span class="hlt">seismic</span> profile (VSP) from the Foothills of southern Alberta, Canada, were processed using a flow designed to yield an optimum depth image. Traveltime inversion of the first arrivals from all the shots from the multioffset VSP revealed that the Mesozoic shale strata in the area exhibit <span class="hlt">seismic</span> velocity anisotropy. The anisotropy parameters, ε and delta, were calculated to be 0.1 and 0.05 respectively. Anisotropic pre-stack depth migration code for VSP and surface <span class="hlt">seismic</span> data, which uses a modified version of a raytracer developed in this thesis for the computation of traveltime tables, was also developed. The algorithm was then used in a new method for integrated VSP and surface <span class="hlt">seismic</span> depth imaging. Results from the migration of synthetic and field data show that the resulting integrated image is superior to that obtained from the migration of either data set alone or to that obtained from the conventional "splicing" approach. The combination of borehole and surface <span class="hlt">seismic</span> data for anisotropy analysis, velocity model building, and depth migration, yielded a robust image even when the geology was complex, thus permitting a more accurate interpretation of the exploration target.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMMR33C2605O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMMR33C2605O"><span>Deformation Monitoring of AN <span class="hlt">Active</span> <span class="hlt">Fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ostapchuk, A.</p> <p>2015-12-01</p> <p>The discovery of low frequency earthquakes, slow slip events and other deformation phenomena, new for geophysics, change our understanding of how the energy accumulated in the Earth's crust do release. The new geophysical data make one revise the underlying mechanism of geomechanical processes taking place in <span class="hlt">fault</span> zones. Conditions for generating different slip modes are still unclear. The most vital question is whether a certain slip mode is intrinsic for a <span class="hlt">fault</span> or may be controlled by external factors. This work presents the results of two and a half year deformation monitoring of a discontinuity in the zone of the Main Sayanskiy <span class="hlt">Fault</span>. Main Sayanskiy <span class="hlt">Fault</span> is right-lateral strike-slip <span class="hlt">fault</span>. Observations were performed in the tunnel of Talaya <span class="hlt">seismic</span> station (TLY), Irkutsk region, Russia. Measurements were carried out 70 m away from the entrance of the tunnel, the thickness of overlying rock was about 30 m. Inductive sensors of displacement were mounted at the both sides of a discontinuity, which recorded three components of relative <span class="hlt">fault</span> side displacement with the accuracy of 0.2 mcm. Temperature variation inside the tunnel didn't exceed 0.5oC during the all period of observations. Important information about deformation properties of an <span class="hlt">active</span> <span class="hlt">fault</span> was obtained. A pronounced seasonality of deformation characteristics of discontinuity is observed in the investigated segment of rock. A great number of slow slip events with durations from several hours to several weeks were registered. Besides that alterations of <span class="hlt">fault</span> deformation characteristics before the megathrust earthquake M9.0 Tohoku Oki 11 March 2011 and reaction to the event itself were detected. The work was supported by the Russian Science Foundation (grant no. 14-17-00719).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.9934G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.9934G"><span>Seismotectonic properties with implications on <span class="hlt">faulting</span> identification revealed from recent <span class="hlt">seismicity</span> in Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkarlaouni, Ch. G.; Karakostas, V. G.; Papadimitriou, E. E.; Kilias, A. A.</p> <p>2012-04-01</p> <p>The essence of studying microseismicity variations in time and space lies upon the observation that the occurrence of small events in a seismogenic region often delineates areas which hide the potential of an upcoming strong earthquake. Revealing a strong societal impact, studying the spatio-temporal properties of small earthquakes is inevitable. The spatial distribution of the epicentres and the accurately determined hypocenters illuminate <span class="hlt">fault</span> geometry, often difficult to distinguish in any other way. This approach reveals additional information on the development of the seismogenic structures that exist within an <span class="hlt">active</span> seismotectonic environment such as the <span class="hlt">seismically</span> <span class="hlt">active</span> grabens that are met in Greece. Recordings for different sub regions within the prevailing extensional stress field, which are provided by the national seismological network, are analysed in detail and they are relocated. Therefore, complete <span class="hlt">seismicity</span> data sets have been constrained for the purpose of the present study. The relocation of the available events incorporates the operation of a dense established network surrounding the study areas and the application of an appropriate <span class="hlt">seismic</span> velocity model that approximates in the best way the brittle structure of the earth's crust. For this reason, the Wadati method was applied, in order to constrain a crustal model that <span class="hlt">seismically</span> describes best the study area. For this reason, arrival times of well recorded events that occurred were taken into account and the focal parameters of all earthquakes were re-estimated. Accurate determination of hypocenters is provided, giving a measure for a better characterization of the seismogenic zone and its depth, where <span class="hlt">fault</span> populations are initiated and developed. Earthquake <span class="hlt">activity</span> is characterised by spatial properties that often defines clusters in space in association with the underlying presence of the <span class="hlt">active</span> seismogenic sources. Cross sections normal to the long axis of each cluster illustrate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S43D..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S43D..07W"><span>High-resolution 3D <span class="hlt">seismic</span> imaging of the Longmenshan <span class="hlt">fault</span> zone structure using double-difference <span class="hlt">seismic</span> tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, X.; Yu, X.; Zhang, W.</p> <p>2011-12-01</p> <p>The Longmenshan <span class="hlt">fault</span> zone where the 2008 M8.0 Wenchuan, China, earthquake occurred is located in the boundary area between the Songpan-Garze block to the west and the Sichuan basin to the east. This area is characterized by complex structures and <span class="hlt">active</span> seismotectonics. We collected both direct P wave absolute arrival times and differential arrival times from 2551 events in the period of 1992 to 1999 recorded by China National <span class="hlt">Seismic</span> Network. The double-difference <span class="hlt">seismic</span> tomography (tomoDD) method is used to determine event relocations and the P wave crustal and upper mantle velocity structure. Our results show that obvious velocity variations exist in the crust and upper mantle beneath the Longmenshan <span class="hlt">fault</span> zone. The inferred velocity structure of the upper crust correlates well with the surface geological and topographic features in this area: the east of Tibet plateau is imaged as a prominent high-velocity zone, while the Longmenshan <span class="hlt">fault</span> and Sichuan basin are imaged as a low-velocity feature. Compared with upper crust, the Longmenshan <span class="hlt">fault</span> zone lies in the transition zone between high velocity anomalies to the west and low velocity anomalies to the east in the middle crust, where most earthquakes occurred. While in the lower crust, the <span class="hlt">fault</span> zone lies in the transition zone between low velocity anomalies to the west and high velocity anomalies to the east. In upper mantle, a prominent low velocity anomaly exists under the Wenchuan main shock region. This suggests that lower crustal flow has affect on the occurrence of the Wenchuan earthquake. There is also a obvious velocity structure difference between the south and north segment of the Longmenshan <span class="hlt">fault</span> zone in the whole crust and upper mantle, low velocity anomalies in the south segment and prominent lateral heterogeneous in the north segment, respectively. The velocity difference maybe resulted in the northeastwards of the Wenchuan aftershocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3353283','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3353283"><span>Anatomy of a microearthquake sequence on an <span class="hlt">active</span> normal <span class="hlt">fault</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stabile, T. A.; Satriano, C.; Orefice, A.; Festa, G.; Zollo, A.</p> <p>2012-01-01</p> <p>The analysis of similar earthquakes, such as events in a <span class="hlt">seismic</span> sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of <span class="hlt">active</span> <span class="hlt">fault</span> systems. We are observing <span class="hlt">seismicity</span> that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake <span class="hlt">fault</span> zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the <span class="hlt">fault</span> system. In this study, we focused on a sequence that occurred along the main <span class="hlt">fault</span> segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the <span class="hlt">fault</span> system. PMID:22606366</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714622K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714622K"><span>Quaternary layer anomalies around the Carlsberg <span class="hlt">Fault</span> zone mapped with high-resolution shear-wave <span class="hlt">seismics</span> south of Copenhagen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kammann, Janina; Hübscher, Christian; Nielsen, Lars; Boldreel, Lars Ole</p> <p>2015-04-01</p> <p>The Carlsberg <span class="hlt">Fault</span> zone is located in the N-S striking Höllviken Graben and traverses the city of Copenhagen. The <span class="hlt">fault</span> zone is a NNW-SSE striking structure in direct vicinity to the transition zone of the Danish Basin and the Baltic Shield. Recent small earthquakes indicate <span class="hlt">activity</span> in the area, although none of the mapped earthquakes appear to have occurred on the Carlsberg <span class="hlt">Fault</span>. We examined the <span class="hlt">fault</span> evolution by a combination of very high resolution onshore shear-wave <span class="hlt">seismic</span> data, one conventional onshore <span class="hlt">seismic</span> profile and marine reflection <span class="hlt">seismic</span> profiles. The chalk stratigraphy and the localization of the <span class="hlt">fault</span> zone at depth was inferred from previous studies by other authors. We extrapolated the Jurassic and Triassic stratigraphy from the Pomeranian Bay to the area of investigation. The <span class="hlt">fault</span> zone shows a flower structure in the Triassic as well as in Cretaceous sediments. The <span class="hlt">faulting</span> geometry indicates strong influence of Triassic processes when subsidence and rifting prevailed in the Central European Basin System. Growth strata within the surrounding Höllviken Graben reveal syntectonic sedimentation in the lower Triassic, indicating the opening to be a result of Triassic rifting. In the Upper Cretaceous growth <span class="hlt">faulting</span> documents continued rifting. This finding contrasts the Late Cretaceous to Paleogene inversion tectonics in neighbouring structures, as the Tornquist Zone. The high-resolution shear-wave <span class="hlt">seismic</span> method was used to image structures in Quaternary layers in the Carlsberg <span class="hlt">Fault</span> zone. The portable compact vibrator source ElViS III S8 was used to acquire a 1150 m long <span class="hlt">seismic</span> section on the island Amager, south of Copenhagen. The shallow subsurface in the investigation area is dominated by Quaternary glacial till deposits in the upper 5-11 m and Danian limestone below. In the shear-wave profile, we imaged the 30 m of the upward continuation of the Carlsberg <span class="hlt">Fault</span> zone. In our area of investigation, the <span class="hlt">fault</span> zone appears to comprise</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.U12A..04V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.U12A..04V"><span>The 2009 L'Aquila <span class="hlt">seismic</span> sequence (Central Italy): <span class="hlt">fault</span> system geometry and kinematics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valoroso, L.; Amato, A.; Cattaneo, M.; Cecere, G.; Chiarabba, C.; Chiaraluce, L.; de Gori, P.; Delladio, A.; de Luca, G.; di Bona, M.; di Stefano, R.; Govoni, A.; Lucente, F. P.; Margheriti, L.; Mazza, S.; Monachesi, G.; Moretti, M.; Olivieri, M.; Piana Agostinetti, N.; Selvaggi, G.; Improta, L.; Piccinini, D.; Mariscal, A.; Pequegnat, C.; Schlagenhauf, A.; Salaun, G.; Traversa, P.; Voisin, C.; Zuccarello, L.; Azzaro, R.</p> <p>2009-12-01</p> <p>On April 6 (01:32 UTC) 2009 a destructive MW 6.3 earthquake struck the Abruzzi region in Central Italy, causing nearly 300 deaths, 40.000 homeless, and strong damage to the cultural heritage of the L'Aquila city and its province. Two strong earthquakes hit the area in historical times (e.g. the 1461 and 1703 events), but the main <span class="hlt">fault</span> that drives the extension in this portion of the Apennines was unknown. The ground surveys carried out after the earthquake find ambiguous evidence of surface <span class="hlt">faulting</span>. We use aftershocks distribution to investigate the geometry of the <span class="hlt">activated</span> <span class="hlt">fault</span> system and to report on spatio-temporal <span class="hlt">seismicity</span> pattern and kinematics of the whole <span class="hlt">seismic</span> sequence. <span class="hlt">Seismic</span> data were recorded at both permanent stations of the Centralized Italian National <span class="hlt">Seismic</span> Network managed by the INGV and 45 temporary stations installed in the epicentral area. To manage such a large amount of earthquakes, we implemented a semi-automatic procedure able to identify local earthquakes and to provide consistently weighted P- and S-wave arrival times. We show that this procedure yields consistent earthquake detection and high-quality arrival times data for hundreds of events per day. The accurate location for thousands of aftershocks defines a complex, 40 km long, NW-trending normal <span class="hlt">fault</span> system, with <span class="hlt">seismicity</span> nucleating within the upper 12 km of the crust. We show the geometry of two major SW-dipping normal <span class="hlt">faults</span> that form a right lateral en-echelon system. The main <span class="hlt">fault</span> <span class="hlt">activated</span> by the 6th of April earthquake is 20 km-long, NW-trending and about 50° SW-dipping and is located below the city of L'Aquila. To the north, we find a second <span class="hlt">fault</span>, <span class="hlt">activated</span> on the 9th of April by a MW 5.4 earthquake, that is about 12-km-long and shows a dip angle of about 40° with hypocenters mainly located in the 6 to 10 km depth range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611097L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611097L"><span>Offshore <span class="hlt">fault</span> system in the Al Hoceima region from new high-resolution bathymetric and <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lafosse, Manfred; d'Acremont, Elia; Rabaute, Alain; Mercier de l'Epinay, Bernard; Gorini, Christian; André Gutscher, Marc; Poort, Jeffrey; Ammar, Abdellah; Tahayt, Abdelilah; Leroy, Pascal; Smit, Jeroen; Do Couto, Damien; Cancouët, Romain; Prunier, Christophe; Ercilla, Gemma</p> <p>2014-05-01</p> <p>The Al-Hoceima Region (Morocco) is the one of the most <span class="hlt">active</span> <span class="hlt">seismic</span> area of the western Mediterranean Sea. Detailed surveys in a shallow water environment are required to identify the connecting onshore-offshore <span class="hlt">active</span> structures and to propose a tectonic framework. We use combined high-resolution <span class="hlt">seismic</span> reflection and swath-bathymetry data from the Marlboro-2 cruise, which took place in 2012 off the coast of Al Hoceima, to detail the <span class="hlt">fault</span> system through the Nekor basin, between the Trougout <span class="hlt">Fault</span> and the Boussekour Agdal <span class="hlt">fault</span>. The Boussekour-Agdal <span class="hlt">fault</span> is a N026 oriented <span class="hlt">fault</span>, dipping east and affecting the plio-quaternary sequence offshore and the internal units of the oriental Rif onshore. The <span class="hlt">fault</span> trace shows a vertical offset of 6.5 m on the high-resolution swath bathymetry close to the shoreline, while the northern prolongation of the <span class="hlt">fault</span> is buried. The Bokkoya <span class="hlt">fault</span> (Calvert et al. 1997) is a N029 oriented <span class="hlt">fault</span> dipping east. The vertical offset at the seafloor is 13m. This <span class="hlt">fault</span> affects sedimentary structures above a paleo-terrace at -105mbsl, probably related to the last sea-level fall. The onshore-offshore N-S oriented Trougout <span class="hlt">fault</span> corresponds to the eastern boundary between the plio-quaternary Nekor basin and the volcano-clastic deposits of Ras Tarf. This <span class="hlt">fault</span> produces a vertical offset of 2.3m at the sea-floor. These three major <span class="hlt">fault</span> zones limit two basins: the Nekor basin between the Bokkoya and the Trougout <span class="hlt">faults</span>, and a depression between the Boussekour-Agdal and the Bokkoya <span class="hlt">Faults</span>. The quaternary deposits are syn-tectonic. In the Nekor basin secondary normal <span class="hlt">faults</span> are oriented N150, shift the sea-floor and affect the Messinian unconformity. Successive positions of a paleo-canyon (seen in the <span class="hlt">seismic</span> lines) show a migration of the subsidence from east to west inside the Nekor basin. <span class="hlt">Faults</span> affecting the Messinian unconformity control this subsidence. Between the Boussekour-Agdal and the Bokkoya <span class="hlt">faults</span>, the thickness and the geometry of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.T11D1294Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.T11D1294Y"><span><span class="hlt">Seismic</span> reflection profiling around the hypocentral area of the 2003 Miyagi-ken Hokubu earthquake (Mj6.4): Reactivated thrust <span class="hlt">faulting</span> of a Miocene normal <span class="hlt">fault</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yokokura, T.; Yamaguchi, K.; Kano, N.; Yokota, T.; Tanaka, A.; Ohtaki, T.</p> <p>2004-12-01</p> <p>The 2003 Miyagi-ken Hokubu (northern Miyagi) earthquake occurred on July 26, which was preceded by the largest foreshock of Mj5.6 and was followed by the largest aftershock of Mj5.5. Although these earthquakes were not so large in magnitude, they caused large damages. The earthquakes occurred just beneath the Asahiyama hills, where exist the <span class="hlt">active</span> Asahiyama flexure. Aftershock observations delineate a clear <span class="hlt">fault</span> plane that extends toward the Sue hills in the east, not toward the Asahiyama hills. However neither surface ruptures nor <span class="hlt">active</span> <span class="hlt">fault</span> assocciated with the earthquakes were observed in this region. To clarify both the surface extension of the <span class="hlt">fault</span> and geologic structure of this region, we conducted 17km-long <span class="hlt">seismic</span> reflection profiling, using a 17.5-ton vibrator. Geologically, this region was subjected rapid EW extension in middle Miocene and thus produced rift basin was filled by the Matsushima-wan Group (syn-rift sediments) which was bounded by a normal <span class="hlt">fault</span>, the Ishinomaki-wan <span class="hlt">fault</span>, in the eastern side of the basin. The Matsushima-wan Group was unconformably overlain by the Shida Group (Miocene post-rift sediments). The Shida Group was unconformably overlain by the Pliocene and post-Pliocene sediments. Deformed Pliocene strata show thrust <span class="hlt">faulting</span>, indicating EW compression after early Pliocene. Detailed data processing reveals that the <span class="hlt">seismic</span> profile is essentially concordant with the structure inferred from surface geology. A west-dipping <span class="hlt">fault</span> with about 50 degrees is found beneath the southeastern extension of the Sue hills where the Ishinomaki-wan <span class="hlt">fault</span> was supposed to extend. The deeper part of the <span class="hlt">fault</span> extends toward the earthquake <span class="hlt">fault</span> plane determined by aftershocks and the shallower part shows a thrust-like structure, which indicate basin inversion using this <span class="hlt">fault</span>. Thus the 2003 Miyagi-ken Hokubu earthquake occurred as reactivated thrust <span class="hlt">faulting</span> of the Miocene normal <span class="hlt">fault</span> bounding the eastern side of the rift basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JSeis..17.1139M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JSeis..17.1139M"><span><span class="hlt">Seismic</span> <span class="hlt">activation</span> of tectonic stresses by mining</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marcak, Henryk; Mutke, Grzegorz</p> <p>2013-10-01</p> <p>Hard coal mining in the area of the Bytom Syncline (Upper Silesia Coal Basin, Poland) has been associated with the occurrence of high-energy <span class="hlt">seismic</span> events (up to 109 J; local magnitude up to 4.0), which have been recorded by the local mining seismological network and regional seismological network. It has been noticed that the strongest <span class="hlt">seismic</span> events occur when the mine longwall alignments coincide with the syncline axis. Data recorded by the improved local <span class="hlt">seismic</span> network in the Bobrek Mine allow the estimation of the depths of the events’ hypocentres during excavation of longwall panel 3 as it approached the syncline axis. The recorded data were also used to estimate the location of the rupture surface and stress distribution in the <span class="hlt">seismic</span> focus region. It was concluded that tectonic stresses, particularly horizontal stress components, are essential in the distribution of <span class="hlt">seismic</span> tremors resulting from reverse <span class="hlt">faulting</span>. The stresses induced by mining <span class="hlt">activity</span> are only triggering tectonic deformations. The hypocentres of the strongest <span class="hlt">seismic</span> events during mining of longwall panel 3/503 were located 300-800 m deeper than the level of coal seam 503.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712654R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712654R"><span>The Pollino <span class="hlt">Seismic</span> Sequence: <span class="hlt">Activated</span> Graben Structures in a <span class="hlt">Seismic</span> Gap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rößler, Dirk; Passarelli, Luigi; Govoni, Aladino; Bindi, Dino; Cesca, Simone; Hainzl, Sebatian; Maccaferri, Francesco; Rivalta, Eleonora; Woith, Heiko; Dahm, Torsten</p> <p>2015-04-01</p> <p>The Mercure Basin (MB) and the Castrovillari <span class="hlt">Fault</span> (CF) in the Pollino range (Southern Apennines, Italy) represent one of the most prominent <span class="hlt">seismic</span> gaps in the Italian <span class="hlt">seismic</span> catalogue, with no M>5.5 earthquakes during the last centuries. In historical times several swarm-like <span class="hlt">seismic</span> sequences occurred in the area including two intense swarms within the past two decades. The most energetic one started in 2010 and has been still <span class="hlt">active</span> in 2014. The <span class="hlt">seismicity</span> culminated in autumn 2012 with a M=5 event on 25 October. The range hosts a number of opposing normal <span class="hlt">faults</span> forming a graben-like structure. Their rheology and their interactions are unclear. Current debates include the potential of the MB and the CF to host large earthquakes and the style of deformation. Understanding the <span class="hlt">seismicity</span> and the behaviour of the <span class="hlt">faults</span> is necessary to assess the tectonics and the <span class="hlt">seismic</span> hazard. The GFZ German Research Centre for Geosciences and INGV, Italy, have jointly monitored the ongoing <span class="hlt">seismicity</span> using a small-aperture <span class="hlt">seismic</span> array, integrated in a temporary <span class="hlt">seismic</span> network. Based on this installation, we located more than 16,000 local earthquakes that occurred between November 2012 and September 2014. Here we investigate quantitatively all the phases of the <span class="hlt">seismic</span> sequence starting from January 2010. Event locations along with moment tensor inversion constrain spatially the structures <span class="hlt">activated</span> by the swarm and the migration pattern of the <span class="hlt">seismicity</span>. The <span class="hlt">seismicity</span> forms clusters concentrated within the southern part of the MB and along the Pollino <span class="hlt">Fault</span> linking MB and CF. Most earthquakes are confined to the upper 10 km of the crust in an area of ~15x15 km2. However, sparse <span class="hlt">seismicity</span> at depths between 15 and 20 km and moderate <span class="hlt">seismicity</span> further north with deepening hypocenters also exist. In contrast, the CF appears aseismic; only the northern part has experienced micro-<span class="hlt">seismicity</span>. The spatial distribution is however more complex than the major tectonic structures</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6311980','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6311980"><span><span class="hlt">Seismic</span> analysis and design of buried pipelines for <span class="hlt">fault</span> movement</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, L.R.L.; Yeh, Y.H.</p> <p>1984-06-01</p> <p>Lifelines, such as gas and oil transmission lines and water and sewer pipelines have been damaged heavily in recent earthquakes. The damages of these lifelines have caused major, catastrophic disruption of essential service to human needs. Large abrupt differential ground movements resulted at an <span class="hlt">active</span> <span class="hlt">fault</span> present one of the most severe earthquake effects on a buried pipeline system. Although simplified analysis procedures for buried pipelines across strike-slip <span class="hlt">fault</span> zones causing tensive failure of the pipeline (called tensile strike-slip <span class="hlt">fault</span>) have been proposed, the results are not accurate enough because of several assumptions involved. Furthermore, several other important failure mechanisms and parameters have not been investigated. This paper is to present the analysis procedures and results for buried pipeline subjected to tensile strike-slip <span class="hlt">fault</span> after modifying some of the assumptions used previously. Based on the analysis results, this paper also discusses the design criteria for buried pipelines subjected to various <span class="hlt">fault</span> movements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Tectp.699..227A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Tectp.699..227A"><span>Systematic assessment of <span class="hlt">fault</span> stability in the Northern Niger Delta Basin, Nigeria: Implication for hydrocarbon prospects and increased <span class="hlt">seismicities</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adewole, E. O.; Healy, D.</p> <p>2017-03-01</p> <p>Accurate information on <span class="hlt">fault</span> networks, the full stress tensor, and pore fluid pressures are required for quantifying the stability of structure-bound hydrocarbon prospects, carbon dioxide sequestration, and drilling prolific and safe wells, particularly fluid injections wells. Such information also provides essential data for a proper understanding of superinduced <span class="hlt">seismicities</span> associated with areas of intensive hydrocarbon exploration and solid minerals mining <span class="hlt">activities</span>. Pressure and stress data constrained from wells and <span class="hlt">seismic</span> data in the Northern Niger Delta Basin (NNDB), Nigeria, have been analysed in the framework of <span class="hlt">fault</span> stability indices by varying the maximum horizontal stress direction from 0° to 90°, evaluated at depths of 2 km, 3.5 km and 4 km. We have used <span class="hlt">fault</span> dips and azimuths interpreted from high resolution 3D <span class="hlt">seismic</span> data to calculate the predisposition of <span class="hlt">faults</span> to failures in three <span class="hlt">faulting</span> regimes (normal, pseudo-strike-slip and pseudo-thrust). The weighty decrease in the <span class="hlt">fault</span> stability at 3.5 km depth from 1.2 MPa to 0.55 MPa demonstrates a reduction of the <span class="hlt">fault</span> strength by high magnitude overpressures. Pore fluid pressures > 50 MPa have tendencies to increase the risk of <span class="hlt">faults</span> to failure in the study area. Statistical analysis of stability indices (SI) indicates <span class="hlt">faults</span> dipping 50°-60°, 80°-90°, and azimuths ranging 100°-110° are most favourably oriented for failure to take place, and thus likely to favour migrations of fluids given appropriate pressure and stress conditions in the dominant normal <span class="hlt">faulting</span> regime of the NNDB. A few of the locally assessed stability of <span class="hlt">faults</span> show varying results across <span class="hlt">faulting</span> regimes. However, the near similarities of some model-based results in the <span class="hlt">faulting</span> regimes explain the stability of subsurface structures are greatly influenced by the maximum horizontal stress (SHmax) direction and magnitude of pore fluid pressures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T23E..01B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T23E..01B"><span>High Resolution Imaging of <span class="hlt">Fault</span> Zone Structures With <span class="hlt">Seismic</span> <span class="hlt">Fault</span> Zone Waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ben-Zion, Y.; Zhigang, P.; Lewis, M. A.; McGuire, J.</p> <p>2006-12-01</p> <p>Large <span class="hlt">fault</span> zone (FZ) structures with damaged rocks and material discontinuity interfaces can generate several indicative wave propagation signals. High crack density may produce prominent scattering and non-linear effects. A preferred crack orientation can lead to shear wave splitting. A lithology contrast can produce FZ head waves that propagate along the material interface with the velocity and motion polarity of the faster medium. A coherent low velocity layer may generate FZ trapped waves. These signals can be used to obtain high resolution imaging of the subsurface structure of <span class="hlt">fault</span> zones, and to track possible temporal evolution of FZ material properties. Several results have emerged from recent systematic analyses of such signals. The trapped waves are generated typically by ~100 m wide layers that extend only to ~3-4 km depth and are characterized by 30-50% velocity reduction and strong attenuation. The trapping structures are surrounded by broader anisotropic and scattering zones limited primarily also to the shallow crust. Results associated with anisotropy and scattering around the North Anatolian <span class="hlt">fault</span> using repeating earthquake clusters do not show precursory temporal evolution. The anisotropy results show small co-<span class="hlt">seismic</span> changes, while the scattering results show larger co-<span class="hlt">seismic</span> changes and post-<span class="hlt">seismic</span> logarithmic recovery. The temporal changes probably reflect damage evolution in the top few hundred m of the crust. Systematic analyses of head waves along several sections of the San Andreas <span class="hlt">fault</span> reveal material interfaces that extend to the bottom of the seismogenic zone. Joint arrival time inversions of direct and FZ head waves imply velocity contrasts of 20% or more in the top 3 km and lower contrasts of 5-15% in the deeper section. In several places, analyses of trapped and head waves indicate that the shallow damaged layers are asymmetric across the <span class="hlt">fault</span>. The observed damage asymmetry may reflect preferred propagation direction of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T21F..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T21F..05C"><span><span class="hlt">Fault</span> zone structure and inferences on past <span class="hlt">activities</span> of the <span class="hlt">active</span> Shanchiao <span class="hlt">Fault</span> in the Taipei metropolis, northern Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, C.; Lee, J.; Chan, Y.; Lu, C.</p> <p>2010-12-01</p> <p>The Taipei Metropolis, home to around 10 million people, is subject to <span class="hlt">seismic</span> hazard originated from not only distant <span class="hlt">faults</span> or sources scattered throughout the Taiwan region, but also <span class="hlt">active</span> <span class="hlt">fault</span> lain directly underneath. Northern Taiwan including the Taipei region is currently affected by post-orogenic (Penglai arc-continent collision) processes related to backarc extension of the Ryukyu subduction system. The Shanchiao <span class="hlt">Fault</span>, an <span class="hlt">active</span> normal <span class="hlt">fault</span> outcropping along the western boundary of the Taipei Basin and dipping to the east, is investigated here for its subsurface structure and <span class="hlt">activities</span>. Boreholes records in the central portion of the <span class="hlt">fault</span> were analyzed to document the stacking of post- Last Glacial Maximum growth sediments, and a tulip flower structure is illuminated with averaged vertical slip rate of about 3 mm/yr. Similar <span class="hlt">fault</span> zone architecture and post-LGM tectonic subsidence rate is also found in the northern portion of the <span class="hlt">fault</span>. A correlation between geomorphology and structural geology in the Shanchiao <span class="hlt">Fault</span> zone demonstrates an array of subtle geomorphic scarps corresponds to the branch <span class="hlt">fault</span> while the surface trace of the main <span class="hlt">fault</span> seems to be completely erased by erosion and sedimentation. Such constraints and knowledge are crucial in earthquake hazard evaluation and mitigation in the Taipei Metropolis, and in understanding the kinematics of transtensional tectonics in northern Taiwan. Schematic 3D diagram of the <span class="hlt">fault</span> zone in the central portion of the Shanchiao <span class="hlt">Fault</span>, displaying regional subsurface geology and its relation to topographic features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.8700D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.8700D"><span><span class="hlt">Fault</span> Specific <span class="hlt">Seismic</span> Hazard Maps as Input to Loss Reserves Calculation for Attica Buildings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deligiannakis, Georgios; Papanikolaou, Ioannis; Zimbidis, Alexandros; Roberts, Gerald</p> <p>2014-05-01</p> <p>Greece is prone to various natural disasters, such as wildfires, floods, landslides and earthquakes, due to the special environmental and geological conditions dominating in tectonic plate boundaries. <span class="hlt">Seismic</span> is the predominant risk, in terms of damages and casualties in the Greek territory. The historical record of earthquakes in Greece has been published from various researchers, providing useful data in <span class="hlt">seismic</span> hazard assessment of Greece. However, the completeness of the historical record in Greece, despite being one of the longest worldwide, reaches only 500 years for M ≥ 7.3 and less than 200 years for M ≥ 6.5. Considering that <span class="hlt">active</span> <span class="hlt">faults</span> in the area have recurrence intervals of a few hundred to several thousands of years, it is clear that many <span class="hlt">active</span> <span class="hlt">faults</span> have not been <span class="hlt">activated</span> during the completeness period covered by the historical records. New <span class="hlt">Seismic</span> Hazard Assessment methodologies tend to follow <span class="hlt">fault</span> specific approaches where <span class="hlt">seismic</span> sources are geologically constrained <span class="hlt">active</span> <span class="hlt">faults</span>, in order to address problems related to the historical records incompleteness, obtain higher spatial resolution and calculate realistic source locality distances, since <span class="hlt">seismic</span> sources are very accurately located. <span class="hlt">Fault</span> specific approaches provide quantitative assessments as they measure <span class="hlt">fault</span> slip rates from geological data, providing a more reliable estimate of <span class="hlt">seismic</span> hazard. We used a <span class="hlt">fault</span> specific <span class="hlt">seismic</span> hazard assessment approach for the region of Attica. The method of <span class="hlt">seismic</span> hazard mapping from geological <span class="hlt">fault</span> throw-rate data combined three major factors: Empirical data which combine <span class="hlt">fault</span> rupture lengths, earthquake magnitudes and coseismic slip relationships. The radiuses of VI, VII, VIII and IX isoseismals on the Modified Mercalli (MM) intensity scale. Attenuation - amplification functions for <span class="hlt">seismic</span> shaking on bedrock compared to basin filling sediments. We explicitly modeled 22 <span class="hlt">active</span> <span class="hlt">faults</span> that could affect the region of Attica, including</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026309','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026309"><span>Apparent stress, <span class="hlt">fault</span> maturity and <span class="hlt">seismic</span> hazard for normal-<span class="hlt">fault</span> earthquakes at subduction zones</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Choy, G.L.; Kirby, S.H.</p> <p>2004-01-01</p> <p>The behavior of apparent stress for normal-<span class="hlt">fault</span> earthquakes at subduction zones is derived by examining the apparent stress (?? a = ??Es/Mo, where E s is radiated energy and Mo is <span class="hlt">seismic</span> moment) of all globally distributed shallow (depth, ?? 1 MPa) are also generally intraslab, but occur where the lithosphere has just begun subduction beneath the overriding plate. They usually occur in cold slabs near trenches where the direction of plate motion across the trench is oblique to the trench axis, or where there are local contortions or geometrical complexities of the plate boundary. Lower ??a (< 1 MPa) is associated with events occurring at the outer rise (OR) complex (between the OR and the trench axis), as well as with intracrustal events occurring just landward of the trench. The average apparent stress of intraslab-normal-<span class="hlt">fault</span> earthquakes is considerably higher than the average apparent stress of interplate-thrust-<span class="hlt">fault</span> earthquakes. In turn, the average ?? a of strike-slip earthquakes in intraoceanic environments is considerably higher than that of intraslab-normal-<span class="hlt">fault</span> earthquakes. The variation of average ??a with focal mechanism and tectonic regime suggests that the level of ?? a is related to <span class="hlt">fault</span> maturity. Lower stress drops are needed to rupture mature <span class="hlt">faults</span> such as those found at plate interfaces that have been smoothed by large cumulative displacements (from hundreds to thousands of kilometres). In contrast, immature <span class="hlt">faults</span>, such as those on which intraslab-normal-<span class="hlt">fault</span> earthquakes generally occur, are found in cold and intact lithosphere in which total <span class="hlt">fault</span> displacement has been much less (from hundreds of metres to a few kilometres). Also, <span class="hlt">faults</span> on which high ??a oceanic strike-slip earthquakes occur are predominantly intraplate or at evolving ends of transforms. At subduction zones, earthquakes occurring on immature <span class="hlt">faults</span> are likely to be more hazardous as they tend to generate higher amounts of radiated energy per unit of moment than</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27856850','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27856850"><span><span class="hlt">Fault</span> <span class="hlt">activation</span> by hydraulic fracturing in western Canada.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bao, Xuewei; Eaton, David W</p> <p>2016-12-16</p> <p>Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a <span class="hlt">seismically</span> <span class="hlt">active</span> Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a <span class="hlt">fault</span> that appears to extend from the injection zone into crystalline basement. Patterns of <span class="hlt">seismicity</span> indicate that stress changes during operations can <span class="hlt">activate</span> <span class="hlt">fault</span> slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a <span class="hlt">fault</span> yields episodic <span class="hlt">seismicity</span> that can persist for months.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Sci...354.1406B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Sci...354.1406B"><span><span class="hlt">Fault</span> <span class="hlt">activation</span> by hydraulic fracturing in western Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bao, Xuewei; Eaton, David W.</p> <p>2016-12-01</p> <p>Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a <span class="hlt">seismically</span> <span class="hlt">active</span> Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a <span class="hlt">fault</span> that appears to extend from the injection zone into crystalline basement. Patterns of <span class="hlt">seismicity</span> indicate that stress changes during operations can <span class="hlt">activate</span> <span class="hlt">fault</span> slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a <span class="hlt">fault</span> yields episodic <span class="hlt">seismicity</span> that can persist for months.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023303','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023303"><span><span class="hlt">Fault</span> zone amplified waves as a possible <span class="hlt">seismic</span> hazard along the Calaveras <span class="hlt">fault</span> in central California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Spudich, P.; Olsen, K.B.</p> <p>2001-01-01</p> <p>The Calaveras <span class="hlt">fault</span> lies within a low velocity zone (LVZ) 1-2 km wide near Gilroy, California. Accelerographs G06, located in the LVZ 1.2 km from the Calaveras <span class="hlt">fault</span>, and G07, 4 km from G06, recorded both the M 6.2 1984 Morgan Hill and the M 6.9 1989 Loma Prieta earthquakes. Comparison of the ground motions shows that a large 0.6-1.0 Hz velocity pulse observed at G06 during the Morgan Hill event may be amplified by focussing caused by the LVZ. Such amplified waves might be a mappable <span class="hlt">seismic</span> hazard, and the zone of increased hazard can extend as much as 1.2 km from the surface trace of the <span class="hlt">fault</span>. Finite-difference simulations of ground motions in a simplified LVZ model show a zone of amplified motion similar to the observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021300','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021300"><span>Stress sensitivity of <span class="hlt">fault</span> <span class="hlt">seismicity</span>: A comparison between limited-offset oblique and major strike-slip <span class="hlt">faults</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Parsons, T.; Stein, R.S.; Simpson, R.W.; Reasenberg, P.A.</p> <p>1999-01-01</p> <p>We present a new three-dimensional inventory of the southern San Francisco Bay area <span class="hlt">faults</span> and use it to calculate stress applied principally by the 1989 M = 7.1 Loma Prieta earthquake and to compare <span class="hlt">fault</span> <span class="hlt">seismicity</span> rates before and after 1989. The major high-angle right-lateral <span class="hlt">faults</span> exhibit a different response to the stress change than do minor oblique (right-lateral/thrust) <span class="hlt">faults</span>. <span class="hlt">Seismicity</span> on oblique-slip <span class="hlt">faults</span> in the southern Santa Clara Valley thrust belt increased where the <span class="hlt">faults</span> were unclamped. The strong dependence of <span class="hlt">seismicity</span> change on normal stress change implies a high coefficient of static friction. In contrast, we observe that <span class="hlt">faults</span> with significant offset (>50-100 km) behave differently; microseismicity on the Hayward <span class="hlt">fault</span> diminished where right-lateral shear stress was reduced and where it was unclamped by the Loma Prieta earthquake. We observe a similar response on the San Andreas <span class="hlt">fault</span> zone in southern California after the Landers earthquake sequence. Additionally, the offshore San Gregorio <span class="hlt">fault</span> shows a <span class="hlt">seismicity</span> rate increase where right-lateral/oblique shear stress was increased by the Loma Prieta earthquake despite also being clamped by it. These responses are consistent with either a low coefficient of static friction or high pore fluid pressures within the <span class="hlt">fault</span> zones. We can explain the different behavior of the two styles of <span class="hlt">faults</span> if those with large cumulative offset become impermeable through gouge buildup; coseismically pressurized pore fluids could be trapped and negate imposed normal stress changes, whereas in more limited offset <span class="hlt">faults</span>, fluids could rapidly escape. The difference in behavior between minor and major <span class="hlt">faults</span> may explain why frictional failure criteria that apply intermediate coefficients of static friction can be effective in describing the broad distributions of aftershocks that follow large earthquakes, since many of these events occur both inside and outside major <span class="hlt">fault</span> zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030550','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030550"><span>Structure of the San Andreas <span class="hlt">fault</span> zone at SAFOD from a <span class="hlt">seismic</span> refraction survey</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hole, J.A.; Ryberg, T.; Fuis, G.S.; Bleibinhaus, F.; Sharma, A.K.</p> <p>2006-01-01</p> <p>Refraction traveltimes from a 46-km long <span class="hlt">seismic</span> survey across the San Andreas <span class="hlt">Fault</span> were inverted to obtain two-dimensional velocity structure of the upper crust near the SAFOD drilling project. The model contains strong vertical and lateral velocity variations from <2 km/s to ???6 km/s. The Salinian terrane west of the San Andreas <span class="hlt">Fault</span> has much higher velocity than the Franciscan terrane east of the <span class="hlt">fault</span>. Salinian basement deepens from 0.8 km subsurface at SAFOD to ???2.5 km subsurface 20 km to the southwest. A strong reflection and subtle velocity contrast suggest a steeply dipping <span class="hlt">fault</span> separating the Franciscan terrane from the Great Valley Sequence. A low-velocity wedge of Cenozoic sedimentary rocks lies immediately southwest of the San Andreas <span class="hlt">Fault</span>. This body is bounded by a steep <span class="hlt">fault</span> just northeast of SAFOD and approaches the depth of the shallowest earthquakes. Multiple <span class="hlt">active</span> and inactive <span class="hlt">fault</span> strands complicate structure near SAFOD. Copyright 2006 by the American Geophysical Union.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036182','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036182"><span><span class="hlt">Seismic</span> hazard of the Enriquillog-Plantain Garden <span class="hlt">fault</span> in Haiti inferred from palaeoseismology</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Prentice, C.S.; Mann, P.; Crone, A.J.; Gold, R.D.; Hudnut, K.W.; Briggs, R.W.; Koehler, R.D.; Jean, P.</p> <p>2010-01-01</p> <p>The Enriquillog-Plantain Garden <span class="hlt">fault</span> zone is recognized as one of the primary plate-bounding <span class="hlt">fault</span> systems in Haiti. The strike-slip <span class="hlt">fault</span> runs adjacent to the city of Port-au-Prince and was initially thought to be the source of the 12 January 2010, M w 7.0 earthquake. Haiti experienced significant earthquakes in 1751 and 1770 (refsA, 3, 4, 5), but the role of the Enriquillog-Plantain Garden <span class="hlt">fault</span> zone in these earthquakes is poorly known. We use satellite imagery, aerial photography, light detection and ranging (LIDAR) and field investigations to document Quaternary <span class="hlt">activity</span> on the Enriquillog-Plantain Garden <span class="hlt">fault</span>. We report late Quaternary, left-lateral offsets of up to 160m, and a set of small offsets ranging from 1.3 to 3.3m that we associate with one of the eighteenth century earthquakes. The size of the small offsets implies that the historical earthquake was larger than M w 7.0, but probably smaller than M w 7.6. We found no significant surface rupture associated with the 2010 earthquake. The lack of surface rupture, coupled with other seismologic, geologic and geodetic observations, suggests that little, if any, accumulated strain was released on the Enriquillog-Plantain Garden <span class="hlt">fault</span> in the 2010 earthquake. These results confirm that the Enriquillog-Plantain Garden <span class="hlt">fault</span> remains a significant <span class="hlt">seismic</span> hazard. ?? 2010 Macmillan Publishers Limited. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NHESS..16.2511E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NHESS..16.2511E"><span><span class="hlt">Seismic</span> hazard in low slip rate crustal <span class="hlt">faults</span>, estimating the characteristic event and the most hazardous zone: study case San Ramón <span class="hlt">Fault</span>, in southern Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Estay, Nicolás P.; Yáñez, Gonzalo; Carretier, Sebastien; Lira, Elias; Maringue, José</p> <p>2016-11-01</p> <p>Crustal <span class="hlt">faults</span> located close to cities may induce catastrophic damages. When recurrence times are in the range of 1000-10 000 or higher, actions to mitigate the effects of the associated earthquake are hampered by the lack of a full <span class="hlt">seismic</span> record, and in many cases, also of geological evidences. In order to characterize the <span class="hlt">fault</span> behavior and its effects, we propose three different already-developed time-integration methodologies to define the most likely scenarios of rupture, and then to quantify the hazard with an empirical equation of peak ground acceleration (PGA). We consider the following methodologies: (1) stream gradient and (2) sinuosity indexes to estimate <span class="hlt">fault</span>-related topographic effects, and (3) gravity profiles across the <span class="hlt">fault</span> to identify the <span class="hlt">fault</span> scarp in the basement. We chose the San Ramón <span class="hlt">Fault</span> on which to apply these methodologies. It is a ˜ 30 km N-S trending <span class="hlt">fault</span> with a low slip rate (0.1-0.5 mm yr-1) and an approximated recurrence of 9000 years. It is located in the foothills of the Andes near the large city of Santiago, the capital of Chile (> 6 000 000 inhabitants). Along the <span class="hlt">fault</span> trace we define four segments, with a mean length of ˜ 10 km, which probably become <span class="hlt">active</span> independently. We tested the present-day <span class="hlt">seismic</span> <span class="hlt">activity</span> by deploying a local seismological network for 1 year, finding five events that are spatially related to the <span class="hlt">fault</span>. In addition, <span class="hlt">fault</span> geometry along the most evident scarp was imaged in terms of its electrical resistivity response by a high resolution TEM (transient electromagnetic) profile. <span class="hlt">Seismic</span> event distribution and TEM imaging allowed the constraint of the <span class="hlt">fault</span> dip angle (˜ 65°) and its capacity to break into the surface. Using the empirical equation of Chiou and Youngs (2014) for crustal <span class="hlt">faults</span> and considering the characteristic <span class="hlt">seismic</span> event (thrust high-angle <span class="hlt">fault</span>, ˜ 10 km, Mw = 6.2-6.7), we estimate the acceleration distribution in Santiago and the hazardous zones. City domains that are under</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1975/of75-41/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1975/of75-41/"><span>A review of recently <span class="hlt">active</span> <span class="hlt">faults</span> in Taiwan</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bonilla, Manuel G.</p> <p>1975-01-01</p> <p>Six <span class="hlt">faults</span> associated with five large earthquakes produced surface displacements ranging from 1 to 3 m in the period 1906 through 1951. Four of the ruptures occurred in the western coastal plain and foothills, and two occurred in the Longitudinal Valley of eastern Taiwan. Maps are included showing the locations and dimensions of the displacements. The published geological literature probably would not lead one to infer the existence of a <span class="hlt">fault</span> along most of the 1906 rupture, except for descriptions of the rupture itself. Over most of its length the 1935 rupture on the Chihhu <span class="hlt">fault</span> is parallel to but more than 0.5 km from nearby <span class="hlt">faults</span> shown on geologic maps published in 1969 and 1971; only about 1.5 km of its 15 km length coincides with a mapped <span class="hlt">fault</span>. The coastal plain part of the Tuntzuchio <span class="hlt">fault</span> which ruptured in 1935 is apparently not revealed by landforms, and only suggested by other data. Part of the 1946 Hsinhua <span class="hlt">faulting</span> coincides with a <span class="hlt">fault</span> identified in the subsurface by <span class="hlt">seismic</span> work but surface indications of the <span class="hlt">fault</span> are obscure. The 1951 Meilun <span class="hlt">faulting</span> occurred along a conspicuous pre-1951 scarp and the 1951 Yuli <span class="hlt">faulting</span> occurred near or in line with pre-1951 scarps. More than 40 <span class="hlt">faults</span> which, according to the published literature, have had Pleistocene or later movement are shown on a small-scale map. Most of these <span class="hlt">faults</span> are in the densely-populated western part of Taiwan. The map and text calls attention to <span class="hlt">faults</span> that may be <span class="hlt">active</span> and therefore may be significant in planning important structures. Equivocal evidence suggestive of <span class="hlt">fault</span> creep was found on the Yuli <span class="hlt">fault</span> and the Hsinhua <span class="hlt">fault</span>. <span class="hlt">Fault</span> creep was not found at several places examined along the 1906 <span class="hlt">fault</span> trace. Tectonic uplift has occurred in Taiwan in the last 10,000 years and application of eustatic sea level curves to published radiocarbon dates shows that the minimum rate of uplift is considerably different in different parts of the island. Incomplete data indicate that the rate is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA188425','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA188425"><span>Naval Weapons Center <span class="hlt">Active</span> <span class="hlt">Fault</span> Map Series.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1987-08-31</p> <p>SECURITY CLASSIFICATION OF ’MiS PACE NWC TP 6828 CONTENTS Introduction . . . . . . . . . . . . . . . . . ........... 2 <span class="hlt">Active</span> <span class="hlt">Fault</span> Definition ...established along the trace of the Little Take <span class="hlt">fault</span> zone, within the City of Ridgecrest. <span class="hlt">ACTIVE</span> <span class="hlt">FAULT</span> DEFINITION Although it is a commonly used term...34<span class="hlt">active</span> <span class="hlt">fault</span>" lacks a pre- cise and universally accepted definition . Most workers, however, accept the following: "<span class="hlt">Active</span> <span class="hlt">fault</span> - a <span class="hlt">fault</span> along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810134A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810134A"><span>Structure of Suasselkä Postglacial <span class="hlt">Fault</span> in northern Finland obtained by analysis of ambient <span class="hlt">seismic</span> noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Afonin, Nikita; Kozlovskaya, Elena</p> <p>2016-04-01</p> <p>Understanding inner structure of seismogenic <span class="hlt">faults</span> and their ability to reactivate is particularly important in investigating the continental intraplate <span class="hlt">seismicity</span> regime. In our study we address this problem using analysis of ambient <span class="hlt">seismic</span> noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive <span class="hlt">seismic</span> array experiment was to characterize the present-day <span class="hlt">seismicity</span> of the Suasselkä post-glacial <span class="hlt">fault</span> (SPGF) that was proposed as one potential target for the DAFNE (Drilling <span class="hlt">Active</span> <span class="hlt">Faults</span> in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous <span class="hlt">seismic</span> stations installed in the close vicinity of the <span class="hlt">fault</span> area. The array recorded continuous <span class="hlt">seismic</span> data during September, 2011-May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the <span class="hlt">fault</span> area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural <span class="hlt">seismic</span> events originating from the <span class="hlt">fault</span> area, which proves that the <span class="hlt">fault</span> is still <span class="hlt">seismically</span> <span class="hlt">active</span>. In order to study the inner structure of the SPGF we use cross-correlation of ambient <span class="hlt">seismic</span> noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1-1 Hz and to calculate correspondent surface wave dispersion curves. After that S-wave velocity models were obtained as a result of dispersion curves inversion using Geopsy software. The results suggest that the area of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017707','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017707"><span><span class="hlt">Seismic</span> tomography and deformation modeling of the junction of the San Andreas and Calaveras <span class="hlt">faults</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dorbath, C.; Oppenheimer, D.; Amelung, F.; King, G.</p> <p>1996-01-01</p> <p>Local earthquake P traveltime data is inverted to obtain a three-dimensional tomographic image of the region centered on the junction of the San Andreas and Calaveras <span class="hlt">faults</span>. The resulting velocity model is then used to relocate more than 17,000 earthquakes and to produce a model of <span class="hlt">fault</span> structure in the region. These <span class="hlt">faults</span> serve as the basis for modeling the topography using elastic dislocation methods. The region is of interest because <span class="hlt">active</span> <span class="hlt">faults</span> join, it marks the transition zone from creeping to locked <span class="hlt">fault</span> behavior on the San Andreas <span class="hlt">fault</span>, it exhibits young topography, and it has a good spatial distribution of <span class="hlt">seismicity</span>. The tomographic data set is extensive, consisting of 1445 events, 96 stations, and nearly 95,000 travel time readings. Tomographic images are resolvable to depths of 12 km and show significant velocity contrasts across the San Andreas and Calaveras <span class="hlt">faults</span>, a low-velocity zone associated with the creeping section of the San Andreas <span class="hlt">fault</span>, and shallow low-velocity sediments in the southern Santa Clara valley and northern Salinas valley. Relocated earthquakes only occur where vp>5 km/s and indicate that portions of the San Andreas and Calaveras <span class="hlt">faults</span> are non vertical, although we cannot completely exclude the possibility that all or part of this results from ray tracing problems. The new dips are more consistent with geological observations that dipping <span class="hlt">faults</span> intersect the surface where surface traces have been mapped. The topographic modeling predicts extensive subsidence in regions characterized by shallow low-velocity material, presumably the result of recent sedimentation. Some details of the topography at the junction of the San Andreas and Calaveras <span class="hlt">faults</span> are not consistent with the modeling results, suggesting that the current position of this "triple junction" has changed with time. The model also predicts those parts of the <span class="hlt">fault</span> subject to contraction or extension perpendicular to the <span class="hlt">fault</span> strike and hence the sense of any</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019264','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019264"><span>Two-dimensional <span class="hlt">seismic</span> image of the San Andreas <span class="hlt">Fault</span> in the Northern Gabilan Range, central California: Evidence for fluids in the <span class="hlt">fault</span> zone</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Thurber, C.; Roecker, S.; Ellsworth, W.; Chen, Y.; Lutter, W.; Sessions, R.</p> <p>1997-01-01</p> <p>A joint inversion for two-dimensional P-wave velocity (Vp), P-to-S velocity ratio (Vp/Vs), and earthquake locations along the San Andreas <span class="hlt">fault</span> (SAF) in central California reveals a complex relationship among <span class="hlt">seismicity</span>, <span class="hlt">fault</span> zone structure, and the surface <span class="hlt">fault</span> trace. A zone of low Vp and high Vp/Vs lies beneath the SAF surface trace (SAFST), extending to a depth of about 6 km. Most of the <span class="hlt">seismic</span> <span class="hlt">activity</span> along the SAF occurs at depths of 3 to 7 km in a southwest-dipping zone that roughly intersects the SAFST, and lies near the southwest edge of the low Vp and high Vp/Vs zones. Tests indicate that models in which this <span class="hlt">seismic</span> zone is significantly closer to vertical can be confidently rejected. A second high Vp/Vs zone extends to the northeast, apparently dipping beneath the Diablo Range. Another zone of <span class="hlt">seismicity</span> underlies the northeast portion of this Vp/Vs high. The high Vp/Vs zones cut across areas of very different Vp values, indicating that the high Vp/Vs values are due to the presence of fluids, not just lithology. The close association between the zones of high Vp/Vs and <span class="hlt">seismicity</span> suggests a direct involvement of fluids in the <span class="hlt">faulting</span> process. Copyright 1997 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019665','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019665"><span><span class="hlt">Active</span> <span class="hlt">faults</span> of the Baikal depression</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Levi, K.G.; Miroshnichenko, A.I.; San'kov, V. A.; Babushkin, S.M.; Larkin, G.V.; Badardinov, A.A.; Wong, H.K.; Colman, S.; Delvaux, D.</p> <p>1997-01-01</p> <p>The Baikal depression occupies a central position in the system of the basins of the Baikal Rift Zone and corresponds to the nucleus from which the continental lithosphere began to open. For different reasons, the internal structure of the Lake Baikal basin remained unknown for a long time. In this article, we present for the first time a synthesis of the data concerning the structure of the sedimentary section beneath Lake Baikal, which were obtained by complex <span class="hlt">seismic</span> and structural investigations, conducted mainly from 1989 to 1992. We make a brief description of the most interesting <span class="hlt">seismic</span> profiles which provide a rough idea of a sedimentary unit structure, present a detailed structural interpretation and show the relationship between <span class="hlt">active</span> <span class="hlt">faults</span> in the lake, heat flow anomalies and recent hydrothermalism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815756L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815756L"><span><span class="hlt">Seismic</span> imaging of deformation zones associated with normal <span class="hlt">fault</span>-related folding</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lapadat, Alexandru; Imber, Jonathan; Iacopini, David; Hobbs, Richard</p> <p>2016-04-01</p> <p>Folds associated with normal <span class="hlt">faulting</span>, which are mainly the result of <span class="hlt">fault</span> propagation and linkage of normal <span class="hlt">fault</span> segments, can exhibit complex deformation patterns, with multiple synthetic splay <span class="hlt">faults</span>, reverse <span class="hlt">faults</span> and small antithetic Riedel structures accommodating flexure of the beds. Their identification is critical in evaluating connectivity of potential hydrocarbon reservoirs and sealing capacity of <span class="hlt">faults</span>. Previous research showed that <span class="hlt">seismic</span> attributes can be successfully used to image complex structures and deformation distribution in submarine thrust folds. We use <span class="hlt">seismic</span> trace and coherency attributes, a combination of instantaneous phase, tensor discontinuity and semblance attributes to identify deformation structures at the limit of <span class="hlt">seismic</span> resolution, which accommodate <span class="hlt">seismic</span> scale folding associated with normal <span class="hlt">faulting</span> from Inner Moray Firth Basin, offshore Scotland. We identify synthetic splay <span class="hlt">faults</span> and reverse <span class="hlt">faults</span> adjacent to the master normal <span class="hlt">faults</span>, which are localized in areas with highest fold amplitudes. This zone of small scale <span class="hlt">faulting</span> is the widest in areas with highest <span class="hlt">fault</span> throw / fold amplitude, or where a bend is present in the main <span class="hlt">fault</span> surface. We also explore the possibility that changes in elastic properties of the rocks due to deformation can contribute to amplitude reductions in the <span class="hlt">fault</span> damage zones. We analyse a pre-stack time-migrated 3D <span class="hlt">seismic</span> data-set, where <span class="hlt">seismic</span> reflections corresponding to a regionally-continuous and homogeneous carbonate layer display a positive correlation between strain distribution and amplitude variations adjacent to the <span class="hlt">faults</span>. <span class="hlt">Seismic</span> amplitude values are homogeneously distributed within the undeformed area of the footwall, with a minimum deviation from a mean amplitude value calculated for each <span class="hlt">seismic</span> line. Meanwhile, the amplitude dimming zone is more pronounced (negative deviation increases) and widens within the relay zone, where sub-<span class="hlt">seismic</span> scale <span class="hlt">faults</span>, which accommodate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.8232G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.8232G"><span>Implication of <span class="hlt">fault</span> interaction to <span class="hlt">seismic</span> hazard assessment in Sichuan-Yunnan provinces of Southeastern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkarlaouni, C.; Papadimitriou, E. E.; Karakostas, V. G.; Wen, Xue–Ze; Jin, Xue–Shen; Kilias, A.; Pan, Hua</p> <p>2009-04-01</p> <p>Strong <span class="hlt">seismicity</span> in China and adjacent regions is distributed over specific zones that configure rigid lithospheric subplates often bounded by <span class="hlt">active</span> <span class="hlt">faults</span>. Sichuan and Yunnan provinces correspond to a so-called rhombic shaped subplate that experiences the strongest intraplate <span class="hlt">seismicity</span> in the territory of China. The region exhibits a complicated tectonic regime that consists of various rupture zones and different <span class="hlt">faulting</span> types with strike slip prevailing, consistent with the regional stress field and geological background. During the 20th century, 35 devastating earthquakes with magnitude Ms≥6.5 occurred nearby densely populated areas causing a majority of casualties and deaths. The fact that Sichuan and Yunnan provinces are densely populated and industrially developed urges the necessity for investigating the occurrence pattern of the region's stronger events through the stress evolutionary model and also identifying the structures that are apt to produce a potential strong <span class="hlt">seismic</span> event in the future. The tectonic complexity reveals a real challenge for our investigation, since the interaction is sought among different <span class="hlt">faulting</span> types. Stress transfer seems not to be restricted in a single however segmented <span class="hlt">fault</span> but also expands over the adjacent <span class="hlt">faults</span> or conjugate zones often bringing them toward rupture. The characteristic of the tectonic setting is that various long strike slip, normal and some thrust <span class="hlt">faults</span> exist within the same area, interacting with each other. Such interaction of strong earthquakes has been proved by previous investigation concerning the Xianshuihe <span class="hlt">fault</span> zone (Papadimitriou et al., 2004) and the stress evolution for the northeast Tibetan Plateau from 1920 till present for a viscoelastic model (Wan et al., 2007). A feature characterizing long <span class="hlt">fault</span> zones is that they are found segmented and distinct parts of <span class="hlt">faults</span> rupture each time until they complete a <span class="hlt">seismic</span> cycle. Although <span class="hlt">fault</span> surfaces are irregular and ruptures are more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011NHESS..11.1433B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011NHESS..11.1433B"><span><span class="hlt">Active</span> <span class="hlt">faults</span> crossing trunk pipeline routes: some important steps to avoid disaster</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Besstrashnov, V. M.; Strom, A. L.</p> <p>2011-05-01</p> <p>Assessment of <span class="hlt">seismic</span> strong motion hazard produced by earthquakes originating within causative <span class="hlt">fault</span> zones allows rather low accuracy of localisation of these structures that can be provided by indirect evidence of <span class="hlt">fault</span> <span class="hlt">activity</span>. In contrast, the relevant accuracy of localisation and characterisation of <span class="hlt">active</span> <span class="hlt">faults</span>, capable of surface rupturing, can be achieved solely by the use of direct evidence of <span class="hlt">fault</span> <span class="hlt">activity</span>. This differentiation requires strict definition of what can be classified as "<span class="hlt">active</span> <span class="hlt">fault</span>" and the normalisation of methods used for identification and localisation of <span class="hlt">active</span> <span class="hlt">faults</span> crossing oil and natural gas trunk pipelines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V14A..03Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V14A..03Z"><span>Hydroacoustic <span class="hlt">seismicity</span> along oceanic transform <span class="hlt">faults</span>: Contrasts between the East Pacific Rise and Mid-Atlantic Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, T.; Lin, J.; Zhong, Q.</p> <p>2015-12-01</p> <p>We investigate the characteristics of <span class="hlt">seismicity</span> of oceanic transform <span class="hlt">faults</span> through analyzing hydroacoustic data recorded along the fast-spreading East Pacific Rise (EPR) and slow-spreading Mid-Atlantic Ridge (MAR), respectively. The investigated region on the EPR is within 15°S-15°N from the Garrett to Clipperton Transform <span class="hlt">Fault</span> during time period of June 1996 to September 2002. Meanwhile, the investigated region on the MAR is within 15°-37°N from the Fifteen-Twenty to Oceanographer Transform <span class="hlt">Fault</span> during time period of February 1999 to August 2003. Using space-time correlation analysis, we matched hydroacoustic events with earthquakes from the Global Centroid Moment Tensor (GCMT) solutions for event magnitude greater than 4.8. Our analyses revealed systematic differences in the <span class="hlt">seismicity</span> characteristics between the EPR and MAR: (1) Along the EPR, more than ninety percent of <span class="hlt">seismicity</span> occurred within several kilometers from transform <span class="hlt">faults</span>, a few percent occurred near over-lapping spreading centers, while the rest occurred along the ridge axis. Along the MAR, hydroacoustic <span class="hlt">seismicity</span> is much more scattered near the ridge axis, transform <span class="hlt">faults</span>, and non-transform offsets. (2) Near the EPR transform <span class="hlt">faults</span>, the standard deviation of the separation distance of the hydroacoustic events from the morphologically-determined transform <span class="hlt">fault</span> axis is s = 5.7 km. In contrast, the separation distance of hydroacoustic events to the transform <span class="hlt">faults</span> is greater (s = 11.9 km), reflecting possibly more complex acoustic scattering due to complex MAR topography as well as more complex tectonic <span class="hlt">activity</span>. (3) The mean hydroacoustic magnitude of the investigated EPR events is 3.3 (s = 0.6), while the mean hydroacoustic magnitude of the studied MAR events is 3.0 (s = 0.7). The mean hydroacoustic <span class="hlt">seismicity</span> rate is 2.1 events per year per km of the EPR transform <span class="hlt">fault</span> length, comparing to the mean <span class="hlt">seismicity</span> rate of 0.5 events per year per km of the MAR transform <span class="hlt">fault</span> length. (4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNH43B1879B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNH43B1879B"><span><span class="hlt">Seismic</span> characterization of the Wasatch <span class="hlt">fault</span> system beneath Salt Lake City using a land streamer system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brophy, B.; Liberty, L. M.; Gribler, G.</p> <p>2015-12-01</p> <p>We characterize the <span class="hlt">active</span> Wasatch <span class="hlt">fault</span> system beneath downtown Salt Lake City by measuring p- and s-wave velocities and <span class="hlt">seismic</span> reflection profiling. Our focus was on the segment boundary between the Warm Springs and East Bench <span class="hlt">faults</span>. We collected 14.5 km along 9 west-east profiles in 3 field days using a 60 m aperture <span class="hlt">seismic</span> land streamer and 200 kg weight drop system. From a p-wave refraction analysis, we measure velocities from 230-3900 m/s for the upper 20-25 meters. Shear wave velocities for the upper 30 m, derived from a multi-channel analysis of surface waves (MASW) approach, show velocities that range from 100-1800 m/s. P-wave reflection images from the upper 100 m depth indicate offset and truncated (mostly) west-dipping strata (Bonneville Lake deposits?) that suggest <span class="hlt">active</span> <span class="hlt">faults</span> extend beneath the downtown urban corridor. We identify saturated sediments on the lower elevation (western) portions of the profiles and shallow high velocity (dry) strata to the east of the mapped <span class="hlt">faults</span>. We observe slow p-wave velocities near identified <span class="hlt">faults</span> that may represent the <span class="hlt">fault</span>'s colluvial wedge. These velocity results are best highlighted with Vp/Vs ratios. Analyzing shear wave velocities by NEHRP class, we estimate soft soil (NEHRP D) limited less than 1 m depth along most profiles, and stiff soil (NEHRP C) to up to 25 m depth in some locations. However near steep topographic slopes (footwall deposits), we identify NEHRP Class D stiff soil velocities to less than 2 m depth before transition to NEHRP Class C soft rock. Depth to hard rock (velocities >760 m/s) are as shallow as 20 m below the land surface on some steep slopes beneath north Salt Lake City and greater than our imaging depths along the western portions of our profiles. Our findings suggest large variations in <span class="hlt">seismic</span> velocities beneath the Salt Lake City corridor and that multiple <span class="hlt">fault</span> strands related to the Warm Springs <span class="hlt">fault</span> segment extend beneath downtown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026174','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026174"><span><span class="hlt">Seismic</span> velocity models for the Denali <span class="hlt">fault</span> zone along the Richardson Highway, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brocher, T.M.; Fuis, G.S.; Lutter, W.J.; Christensen, N.I.; Ratchkovski, N.A.</p> <p>2004-01-01</p> <p>Crustal-scale <span class="hlt">seismic</span>-velocity models across the Denali <span class="hlt">fault</span> zone along the Richardson Highway show a 50-km-thick crust, a near vertical <span class="hlt">fault</span> trace, and a 5-km-wide damage zone associated with the <span class="hlt">fault</span> near Trans-Alaska Pipeline Pump Station 10, which provided the closest strong ground motion recordings of the 2002 Denali <span class="hlt">fault</span> earthquake. We compare models, derived from <span class="hlt">seismic</span> reflection and refraction surveys acquired in 1986 and 1987, to laboratory measurements of <span class="hlt">seismic</span> velocities for typical metamorphic rocks exposed along the profiles. Our model for the 1986 <span class="hlt">seismic</span> reflection profile indicates a 5-km-wide low-velocity zone in the upper 1 km of the Denali <span class="hlt">fault</span> zone, which we interpret as <span class="hlt">fault</span> gouge. Deeper refractions from our 1987 line image a 40-km wide, 5-km-deep low-velocity zone along the Denali <span class="hlt">fault</span> and nearby associated <span class="hlt">fault</span> strands, which we attribute to a composite damage zone along several strands of the Denali <span class="hlt">fault</span> zone and to the obliquity of the <span class="hlt">seismic</span> line to the <span class="hlt">fault</span> zone. Our velocity model and other geophysical data indicate a nearly vertical Denali <span class="hlt">fault</span> zone to a depth of 30 km. After-shocks of the 2002 Denali <span class="hlt">fault</span> earthquake and our velocity model provide evidence for a flower structure along the <span class="hlt">fault</span> zone consisting of <span class="hlt">faults</span> dipping toward and truncated by the Denali <span class="hlt">fault</span>. Wide-angle reflections indicate that the crustal thickness beneath the Denali <span class="hlt">fault</span> is transitional between the 60-km-thick crust beneath the Alaska Range to the south, and the extended, 30-km-thick crust of the Yukon-Tanana terrane to the north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811563O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811563O"><span>Thrust <span class="hlt">fault</span> segmentation and downward <span class="hlt">fault</span> propagation in accretionary wedges: New Insights from 3D <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orme, Haydn; Bell, Rebecca; Jackson, Christopher</p> <p>2016-04-01</p> <p>The shallow parts of subduction megathrust <span class="hlt">faults</span> are typically thought to be aseismic and incapable of propagating <span class="hlt">seismic</span> rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow <span class="hlt">seismic</span> rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D <span class="hlt">seismic</span> reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D <span class="hlt">seismic</span> reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic <span class="hlt">Seismic</span> Portal, Marine Geoscience Data System) to examine how imbricate thrust <span class="hlt">fault</span> networks evolve during accretionary wedge growth. We unravel the evolution of <span class="hlt">faults</span> within the protothrust and imbricate thrust zones by interpreting multiple horizons across <span class="hlt">faults</span> and measuring <span class="hlt">fault</span> displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of <span class="hlt">faults</span>, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated <span class="hlt">fault</span> segments. Although we often assume imbricate <span class="hlt">faults</span> are likely to have propagated upwards from the décollement we show strong evidence for <span class="hlt">fault</span> nucleation at shallow depths and downward propagation to intersect the décollement. The complex <span class="hlt">fault</span> interactions documented here have implications for hydraulic compartmentalisation and pore</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1132114','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1132114"><span><span class="hlt">Faulting</span> processes in <span class="hlt">active</span> <span class="hlt">faults</span> - Evidences from TCDP and SAFOD drill core samples</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Janssen, C.; Wirth, R.; Wenk, H. -R.; Morales, L.; Naumann, R.; Kienast, M.; Song, S. -R.; Dresen, G.</p> <p>2014-08-20</p> <p>The microstructures, mineralogy and chemistry of representative samples collected from the cores of the San Andreas <span class="hlt">Fault</span> drill hole (SAFOD) and the Taiwan Chelungpu-<span class="hlt">Fault</span> Drilling project (TCDP) have been studied using optical microscopy, TEM, SEM, XRD and XRF analyses. SAFOD samples provide a transect across undeformed host rock, the <span class="hlt">fault</span> damage zone and currently <span class="hlt">active</span> deforming zones of the San Andreas <span class="hlt">Fault</span>. TCDP samples are retrieved from the principal slip zone (PSZ) and from the surrounding damage zone of the Chelungpu <span class="hlt">Fault</span>. Substantial differences exist in the clay mineralogy of SAFOD and TCDP <span class="hlt">fault</span> gouge samples. Amorphous material has been observed in SAFOD as well as TCDP samples. In line with previous publications, we propose that melt, observed in TCDP black gouge samples, was produced by <span class="hlt">seismic</span> slip (melt origin) whereas amorphous material in SAFOD samples was formed by comminution of grains (crush origin) rather than by melting. Dauphiné twins in quartz grains of SAFOD and TCDP samples may indicate high <span class="hlt">seismic</span> stress. The differences in the crystallographic preferred orientation of calcite between SAFOD and TCDP samples are significant. Microstructures resulting from dissolution–precipitation processes were observed in both <span class="hlt">faults</span> but are more frequently found in SAFOD samples than in TCDP <span class="hlt">fault</span> rocks. As already described for many other <span class="hlt">fault</span> zones clay-gouge fabrics are quite weak in SAFOD and TCDP samples. Clay-clast aggregates (CCAs), proposed to indicate frictional heating and thermal pressurization, occur in material taken from the PSZ of the Chelungpu <span class="hlt">Fault</span>, as well as within and outside of the SAFOD deforming zones, indicating that these microstructures were formed over a wide range of slip rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.450..292S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.450..292S"><span>Origin and role of fluids involved in the <span class="hlt">seismic</span> cycle of extensional <span class="hlt">faults</span> in carbonate rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smeraglia, Luca; Berra, Fabrizio; Billi, Andrea; Boschi, Chiara; Carminati, Eugenio; Doglioni, Carlo</p> <p>2016-09-01</p> <p>We examine the potentially-<span class="hlt">seismic</span> right-lateral transtensional-extensional Tre Monti <span class="hlt">Fault</span> (central Apennines, Italy) with structural and geochemical methods and develop a conceptual evolutionary model of extensional <span class="hlt">faulting</span> with fluid involvement in shallow (≤3 km depth) <span class="hlt">faults</span> in carbonate rocks. In the analysed <span class="hlt">fault</span> zone, multiscale <span class="hlt">fault</span> rock structures include injection veins, fluidized ultracataclasite layers, and crackle breccias, suggesting that the <span class="hlt">fault</span> slipped <span class="hlt">seismically</span>. We reconstructed the relative chronology of these structures through cross-cutting relationship and cathodoluminescence analyses. We then used C- and O-isotope data from different generations of <span class="hlt">fault</span>-related mineralizations to show a shift from connate (marine-derived) to meteoric fluid circulation during exhumation from 3 to ≤1 km depths and concurrent fluid cooling from ∼68 to <30 °C. Between ∼3 km and ∼1 km depths, impermeable barriers within the sedimentary sequence created a semi-closed hydrological system, where prevalently connate fluids circulated within the <span class="hlt">fault</span> zone at temperatures between 60° and 75 °C. During <span class="hlt">fault</span> zone exhumation, at depths ≤1 km and temperatures <30 °C, the hydrological circulation became open and meteoric-derived fluids progressively infiltrated and circulated within the <span class="hlt">fault</span> zone. The role of these fluids during syn-exhumation <span class="hlt">seismic</span> cycles of the Tre Monti <span class="hlt">Fault</span> has been substantially passive along the whole <span class="hlt">fault</span> zone, the fluids being passively redistributed at hydrostatic pressure following co-<span class="hlt">seismic</span> dilatancy. Only the principal <span class="hlt">fault</span> has been characterized, locally and transiently, by fluid overpressures. The presence of low-permeability clayey layers in the sedimentary sequence contributed to control the type of fluids infiltrating into the <span class="hlt">fault</span> zone and possibly their transient overpressures. These results can foster the comprehension of <span class="hlt">seismic</span> <span class="hlt">faulting</span> at shallow depths in carbonate rocks of other fold-thrust belts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JVGR..301..159M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JVGR..301..159M"><span><span class="hlt">Faults</span> strengthening and <span class="hlt">seismicity</span> induced by geothermal exploitation on a spreading volcano, Mt. Amiata, Italia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazzoldi, Alberto; Borgia, Andrea; Ripepe, Maurizio; Marchetti, Emanuele; Ulivieri, Giacomo; Schiava, Massimo della; Allocca, Carmine</p> <p>2015-08-01</p> <p>Seismogenic structures such as <span class="hlt">faults</span> play a primary role in geothermal system generation, recharge and output. They are also the most susceptible to release <span class="hlt">seismic</span> energy over fluid injection/extraction operations during anthropic exploitation. We describe the microseismic <span class="hlt">activity</span> recorded in 2000-2001 in the Piancastagnaio geothermal field, on the SE flank of Mt. Amiata volcano, southern Tuscany, Italy. From our field observations we find that a relatively high percentage (i.e. about 5%) of the recorded events are of hydro-fracturing origin and have a distinct waveform <span class="hlt">seismic</span> signature when compared to the recorded events of tectonic shear-fracturing origin. While hydrofracturing events are mostly concentrated around the geothermal fields, the spatial distribution of hypocenters shows a deepening and a density increase of the micro-<span class="hlt">seismic</span> <span class="hlt">activity</span> from the volcanic axis toward the exploited geothermal reservoir, suggesting that volcanic spreading at Amiata is still <span class="hlt">active</span>. The study of different data-sets from different time periods together with the knowledge from Terzaghi's law that production of large quantity of pore-fluid with the associated fluid pressure reduction could augment the stress normal to <span class="hlt">faults</span>' surfaces (and thus their resistance to slip), make us argue that the process of volcanic spreading affecting the edifice of Amiata may allow augmented accumulation of stresses on <span class="hlt">faults</span>, eventually leading to the release of higher stress drops, once ruptures occur. The Gutenberg-Richter magnitude-frequency distribution shows that the strongest events on record have a local magnitude in the 5-5.5 ML range, for 100-year recurrence time. In conclusions, we infer that geothermal exploitation at Mt. Amiata should be closely monitored in order to understand how fluid injection/production is responsible for the hydrofracturing <span class="hlt">seismic</span> <span class="hlt">activity</span> and affects stress accumulation on and rupture of <span class="hlt">faults</span> within and in the neighborhood of the geothermal fields</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S13B2841R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S13B2841R"><span>Monitoring in situ deformation induced by a fluid injection in a <span class="hlt">fault</span> zone in shale using <span class="hlt">seismic</span> velocity changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rivet, D.; De Barros, L.; Guglielmi, Y.; Castilla, R.</p> <p>2015-12-01</p> <p>We monitor <span class="hlt">seismic</span> velocity changes during an experiment at decametric scale aimed at artificially reactivate a <span class="hlt">fault</span> zone by a high-pressure hydraulic injection in a shale formation of the underground site of Tournemire, South of France. A dense and a multidisciplinary instrumentation, with measures of pressure, fluid flow, strain, <span class="hlt">seismicity</span>, <span class="hlt">seismic</span> properties and resistivity allow for the monitoring of this experiment. We couple hydromechanical and <span class="hlt">seismic</span> observations of the <span class="hlt">fault</span> and its adjacent areas to better understand the deformation process preceding ruptures, and the role played by fluids. 9 accelerometers recorded repeated hammers shots on the tunnel walls. For each hammer shot we measured small travel time delays on direct P and S waves. We then located the <span class="hlt">seismic</span> velocity perturbations using a tomography method. At low injection pressure, i.e. P< 15 Bars, we observe an increase of P-waves velocity around the injection, while we measure no change in S waves velocity. When the pressure overcomes 15 Bars, velocity perturbations dramatically increase with both P and S waves affected. A decrease of velocity is observed close to the injection point and is surrounded by regions of increasing velocity. Our observations are consistent with hydromechanical measures. Below 15 Bars, we interpret the P-wave velocity increase to be related to the compression of the <span class="hlt">fault</span> zone around the injection chamber. Above 15 Bars, we measure a shear and dilatant <span class="hlt">fault</span> movement, and a rapid increase in the injected fluid flow. At this step, our measures are coherent with a poroelastic opening of the <span class="hlt">fault</span> with velocities decrease at the injection source and velocities increase related to stress transfer in the far field. Velocity changes prove to be efficient to monitor stress/strain variation in an <span class="hlt">activated</span> <span class="hlt">fault</span>, even if these observations might produce complex signals due to the highly contrasted hydromechanical responses in a heterogeneous media such as a <span class="hlt">fault</span> zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70003765','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70003765"><span>Characterization of intrabasin <span class="hlt">faulting</span> and deformation for earthquake hazards in southern Utah Valley, Utah, from high-resolution <span class="hlt">seismic</span> imaging</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stephenson, William J.; Odum, Jack K.; Williams, Robert A.; McBride, John H.; Tomlinson, Iris</p> <p>2012-01-01</p> <p>We conducted <span class="hlt">active</span> and passive <span class="hlt">seismic</span> imaging investigations along a 5.6-km-long, east–west transect ending at the mapped trace of the Wasatch <span class="hlt">fault</span> in southern Utah Valley. Using two-dimensional (2D) P-wave <span class="hlt">seismic</span> reflection data, we imaged basin deformation and <span class="hlt">faulting</span> to a depth of 1.4 km and developed a detailed interval velocity model for prestack depth migration and 2D ground-motion simulations. Passive-source microtremor data acquired at two sites along the <span class="hlt">seismic</span> reflection transect resolve S-wave velocities of approximately 200 m/s at the surface to about 900 m/s at 160 m depth and confirm a substantial thickening of low-velocity material westward into the valley. From the P-wave reflection profile, we interpret shallow (100–600 m) bedrock deformation extending from the surface trace of the Wasatch <span class="hlt">fault</span> to roughly 1.5 km west into the valley. The bedrock deformation is caused by multiple interpreted <span class="hlt">fault</span> splays displacing <span class="hlt">fault</span> blocks downward to the west of the range front. Further west in the valley, the P-wave data reveal subhorizontal horizons from approximately 90 to 900 m depth that vary in thickness and whose dip increases with depth eastward toward the Wasatch <span class="hlt">fault</span>. Another inferred <span class="hlt">fault</span> about 4 km west of the mapped Wasatch <span class="hlt">fault</span> displaces horizons within the valley to as shallow as 100 m depth. The overall deformational pattern imaged in our data is consistent with the Wasatch <span class="hlt">fault</span> migrating eastward through time and with the abandonment of earlier synextensional <span class="hlt">faults</span>, as part of the evolution of an inferred 20-km-wide half-graben structure within Utah Valley. Finite-difference 2D modeling suggests the imaged subsurface basin geometry can cause fourfold variation in peak ground velocity over distances of 300 m.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H13L..08R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H13L..08R"><span>Geomechanical Modeling of <span class="hlt">Fault</span> Responses and the Potential for Notable <span class="hlt">Seismic</span> Events during Underground CO2 Injection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rutqvist, J.; Cappa, F.; Mazzoldi, A.; Rinaldi, A.</p> <p>2012-12-01</p> <p>The importance of geomechanics associated with large-scale geologic carbon storage (GCS) operations is now widely recognized. There are concerns related to the potential for triggering notable (felt) <span class="hlt">seismic</span> events and how such events could impact the long-term integrity of a CO2 repository (as well as how it could impact the public perception of GCS). In this context, we review a number of modeling studies and field observations related to the potential for injection-induced <span class="hlt">fault</span> reactivations and <span class="hlt">seismic</span> events. We present recent model simulations of CO2 injection and <span class="hlt">fault</span> reactivation, including both aseismic and <span class="hlt">seismic</span> <span class="hlt">fault</span> responses. The model simulations were conducted using a slip weakening <span class="hlt">fault</span> model enabling sudden (<span class="hlt">seismic</span>) <span class="hlt">fault</span> rupture, and some of the numerical analyses were extended to fully dynamic modeling of <span class="hlt">seismic</span> source, wave propagation, and ground motion. The model simulations illustrated what it will take to create a magnitude 3 or 4 earthquake that would not result in any significant damage at the groundsurface, but could raise concerns in the local community and could also affect the deep containment of the stored CO2. The analyses show that the local in situ stress field, <span class="hlt">fault</span> orientation, <span class="hlt">fault</span> strength, and injection induced overpressure are critical factors in determining the likelihood and magnitude of such an event. We like to clarify though that in our modeling we had to apply very high injection pressure to be able to intentionally induce any <span class="hlt">fault</span> reactivation. Consequently, our model simulations represent extreme cases, which in a real GCS operation could be avoided by estimating maximum sustainable injection pressure and carefully controlling the injection pressure. In fact, no notable <span class="hlt">seismic</span> event has been reported from any of the current CO2 storage projects, although some unfelt microseismic <span class="hlt">activities</span> have been detected by geophones. On the other hand, potential future commercial GCS operations from large power plants</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.198.1159H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.198.1159H"><span>A smoothed stochastic earthquake rate model considering <span class="hlt">seismicity</span> and <span class="hlt">fault</span> moment release for Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiemer, S.; Woessner, J.; Basili, R.; Danciu, L.; Giardini, D.; Wiemer, S.</p> <p>2014-08-01</p> <p>We present a time-independent gridded earthquake rate forecast for the European region including Turkey. The spatial component of our model is based on kernel density estimation techniques, which we applied to both past earthquake locations and <span class="hlt">fault</span> moment release on mapped crustal <span class="hlt">faults</span> and subduction zone interfaces with assigned slip rates. Our forecast relies on the assumption that the locations of past <span class="hlt">seismicity</span> is a good guide to future <span class="hlt">seismicity</span>, and that future large-magnitude events occur more likely in the vicinity of known <span class="hlt">faults</span>. We show that the optimal weighted sum of the corresponding two spatial densities depends on the magnitude range considered. The kernel bandwidths and density weighting function are optimized using retrospective likelihood-based forecast experiments. We computed earthquake <span class="hlt">activity</span> rates (a- and b-value) of the truncated Gutenberg-Richter distribution separately for crustal and subduction <span class="hlt">seismicity</span> based on a maximum likelihood approach that considers the spatial and temporal completeness history of the catalogue. The final annual rate of our forecast is purely driven by the maximum likelihood fit of <span class="hlt">activity</span> rates to the catalogue data, whereas its spatial component incorporates contributions from both earthquake and <span class="hlt">fault</span> moment-rate densities. Our model constitutes one branch of the earthquake source model logic tree of the 2013 European <span class="hlt">seismic</span> hazard model released by the EU-FP7 project `<span class="hlt">Seismic</span> HAzard haRmonization in Europe' (SHARE) and contributes to the assessment of epistemic uncertainties in earthquake <span class="hlt">activity</span> rates. We performed retrospective and pseudo-prospective likelihood consistency tests to underline the reliability of our model and SHARE's area source model (ASM) using the testing algorithms applied in the collaboratory for the study of earthquake predictability (CSEP). We comparatively tested our model's forecasting skill against the ASM and find a statistically significant better performance for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.S23C..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.S23C..07W"><span>Insurance Applications of <span class="hlt">Active</span> <span class="hlt">Fault</span> Maps Showing Epistemic Uncertainty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woo, G.</p> <p>2005-12-01</p> <p>Insurance loss modeling for earthquakes utilizes available maps of <span class="hlt">active</span> <span class="hlt">faulting</span> produced by geoscientists. All such maps are subject to uncertainty, arising from lack of knowledge of <span class="hlt">fault</span> geometry and rupture history. Field work to undertake geological <span class="hlt">fault</span> investigations drains human and monetary resources, and this inevitably limits the resolution of <span class="hlt">fault</span> parameters. Some areas are more accessible than others; some may be of greater social or economic importance than others; some areas may be investigated more rapidly or diligently than others; or funding restrictions may have curtailed the extent of the <span class="hlt">fault</span> mapping program. In contrast with the aleatory uncertainty associated with the inherent variability in the dynamics of earthquake <span class="hlt">fault</span> rupture, uncertainty associated with lack of knowledge of <span class="hlt">fault</span> geometry and rupture history is epistemic. The extent of this epistemic uncertainty may vary substantially from one regional or national <span class="hlt">fault</span> map to another. However aware the local cartographer may be, this uncertainty is generally not conveyed in detail to the international map user. For example, an area may be left blank for a variety of reasons, ranging from lack of sufficient investigation of a <span class="hlt">fault</span> to lack of convincing evidence of <span class="hlt">activity</span>. Epistemic uncertainty in <span class="hlt">fault</span> parameters is of concern in any probabilistic assessment of <span class="hlt">seismic</span> hazard, not least in insurance earthquake risk applications. A logic-tree framework is appropriate for incorporating epistemic uncertainty. Some insurance contracts cover specific high-value properties or transport infrastructure, and therefore are extremely sensitive to the geometry of <span class="hlt">active</span> <span class="hlt">faulting</span>. Alternative Risk Transfer (ART) to the capital markets may also be considered. In order for such insurance or ART contracts to be properly priced, uncertainty should be taken into account. Accordingly, an estimate is needed for the likelihood of surface rupture capable of causing severe damage. Especially where a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.7319L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.7319L"><span>Assessing <span class="hlt">active</span> <span class="hlt">faulting</span> by hydrogeological modeling and superconducting gravimetry: A case study for Hsinchu <span class="hlt">Fault</span>, Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lien, Tzuyi; Cheng, Ching-Chung; Hwang, Cheinway; Crossley, David</p> <p>2014-09-01</p> <p>We develop a new hydrology and gravimetry-based method to assess whether or not a local <span class="hlt">fault</span> may be <span class="hlt">active</span>. We take advantage of an existing superconducting gravimeter (SG) station and a comprehensive groundwater network in Hsinchu to apply the method to the Hsinchu <span class="hlt">Fault</span> (HF) across the Hsinchu Science Park, whose industrial output accounts for 10% of Taiwan's gross domestic product. The HF is suspected to pose <span class="hlt">seismic</span> hazards to the park, but its existence and structure are not clear. The a priori geometry of the HF is translated into boundary conditions imposed in the hydrodynamic model. By varying the <span class="hlt">fault</span>'s location, depth, and including a secondary wrench <span class="hlt">fault</span>, we construct five hydrodynamic models to estimate groundwater variations, which are evaluated by comparing groundwater levels and SG observations. The results reveal that the HF contains a low hydraulic conductivity core and significantly impacts groundwater flows in the aquifers. Imposing the <span class="hlt">fault</span> boundary conditions leads to about 63-77% reduction in the differences between modeled and observed values (both water level and gravity). The test with <span class="hlt">fault</span> depth shows that the HF's most recent slip occurred in the beginning of Holocene, supplying a necessary (but not sufficient) condition that the HF is currently <span class="hlt">active</span>. A portable SG can act as a virtual borehole well for model assessment at critical locations of a suspected <span class="hlt">active</span> <span class="hlt">fault</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2333K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2333K"><span>Relative tectonic <span class="hlt">activity</span> assessment along the East Anatolian strike-slip <span class="hlt">fault</span>, Eastern Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khalifa, Abdelrahman</p> <p>2016-04-01</p> <p>The East Anatolian transform <span class="hlt">fault</span> is a morphologically distinct and <span class="hlt">seismically</span> <span class="hlt">active</span> left-lateral strike-slip <span class="hlt">fault</span> that extends for ~ 500 km from Karlıova to the Maraş defining the boundary between the Anatolian Block and Syrian Foreland. Deformed landforms along the East Anatolian <span class="hlt">fault</span> provide important insights into the nature of landscape development within an intra-continental strike-slip <span class="hlt">fault</span> system. Geomorphic analysis of the East Anatolian <span class="hlt">fault</span> using geomorphic indices including mountain front sinuosity, stream length-gradient index, drainage density, hypsometric integral, and the valley-width to valley height ratio helped differentiate the <span class="hlt">faulting</span> into segments of differing degrees of the tectonic and geomorphic <span class="hlt">activity</span>. Watershed maps for the East Anatolian <span class="hlt">fault</span> showing the relative relief, incision, and maturity of basins along the <span class="hlt">fault</span> zone help define segments of the higher <span class="hlt">seismic</span> risk and help evaluate the regional <span class="hlt">seismic</span> hazard. The results of the geomorphic indices show a high degree of <span class="hlt">activity</span>, reveal each segment along the <span class="hlt">fault</span> is <span class="hlt">active</span> and represent a higher <span class="hlt">seismic</span> hazard along the entire <span class="hlt">fault</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005Tectp.402..111W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005Tectp.402..111W"><span>Crystal fractionation in the friction melts of <span class="hlt">seismic</span> <span class="hlt">faults</span> (Alpine <span class="hlt">Fault</span>, New Zealand)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Warr, Laurence N.; van der Pluijm, Ben A.</p> <p>2005-06-01</p> <p>Compositional variations are documented in friction melts along the Hari Hari section of the Alpine <span class="hlt">Fault</span>, New Zealand, with multiple stages of melt injection into quartzo-feldspathic schists. Intermediate to felsic melts were heterogeneous in composition, but all fractions show a common trend, with a tendency for the younger melt layers and glasses to be more alkali - (Na + K) and Si-enriched, while being depleted in mafic (Fe + Mg + Mn) components. These changes are attributed primarily to crystal fractionation of the melt during transport. Farther traveled molten layers were on the whole less viscous, mostly due to a higher melt-to-clast ratio; however, compositional change, together with a decrease in volatile content, produced a progressively more viscous liquid melt with time. The glass phase is interpreted as a remnant of this high viscosity felsic residual melt that was preserved during final quenching. Following initial failure, the formation of largely phyllosilicate-derived, volatile-rich, lower viscosity melt corresponds with a phase of <span class="hlt">fault</span> weakening. Subsequent rapid crystal fractionation during melt transport, the loss of volatiles and freezing of residual melt contributed to the strengthening of the <span class="hlt">fault</span> during <span class="hlt">seismic</span> slip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GGG....17.4128O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GGG....17.4128O"><span>Dependence of <span class="hlt">seismic</span> coupling on normal <span class="hlt">fault</span> style along the Northern Mid-Atlantic Ridge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olive, Jean-Arthur; Escartín, Javier</p> <p>2016-10-01</p> <p>While normal <span class="hlt">faults</span> are essential in shaping the seafloor formed at slow spreading mid-ocean ridges, information on their behavior on short (<span class="hlt">seismic</span> cycle) time scales is limited. Here we combine catalogs of hydro-acoustically and teleseismically recorded earthquakes to characterize the state of <span class="hlt">seismic</span> coupling along the Northern Mid-Atlantic Ridge (MAR) between 12°N and 35°N. Along this portion of the MAR axis, tectonic extension is either taken up by steep conjugate <span class="hlt">faults</span> that outline well-defined ridge-parallel abyssal hills, or dominantly by a large-offset detachment <span class="hlt">fault</span> on one side of the axis. We investigate variations in <span class="hlt">seismicity</span> and <span class="hlt">seismic</span> moment release rates across 30 ridge sections that can be clearly characterized either as abyssal hill or detachment bearing. We find that detachment-bearing sections are associated with significantly greater <span class="hlt">seismicity</span> and moment release rates than abyssal hill-bearing sections but show variability that may reflect the along-axis extent of individual detachment <span class="hlt">faults</span>. Overall, the measured <span class="hlt">seismic</span> moment release rates fail to account for the long-term <span class="hlt">fault</span> slip rates. This apparent <span class="hlt">seismic</span> deficit could indicate a mixed-mode of <span class="hlt">fault</span> slip where earthquakes only account for ˜10-30% of offset buildup at abyssal hill <span class="hlt">faults</span>, while the rest is accommodated by some form of transient aseismic creep. We find this <span class="hlt">seismic</span> coupling fraction to be significantly greater (˜40-60%) at individual detachment systems, which is somewhat at odds with the common inference that detachment <span class="hlt">faults</span> can sustain long-lived localized strain because they are weak. We therefore propose alternative interpretations for <span class="hlt">seismic</span> coupling based on dynamic friction theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoJI.tmp...62W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoJI.tmp...62W"><span><span class="hlt">Fault</span> Mechanics and Post-<span class="hlt">seismic</span> Deformation at Bam, SE Iran</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wimpenny, Sam; Copley, Alex; Ingleby, Tom</p> <p>2017-02-01</p> <p>The extent to which aseismic deformation relaxes co-<span class="hlt">seismic</span> stress changes on a <span class="hlt">fault</span> zone is fundamental to assessing the future <span class="hlt">seismic</span> hazard following any earthquake, and in understanding the mechanical behaviour of <span class="hlt">faults</span>. Here we use models of stress-driven afterslip and visco-elastic relaxation, in conjunction with post-<span class="hlt">seismic</span> InSAR measurements, to show that there has been minimal release of co-<span class="hlt">seismic</span> stress changes through post-<span class="hlt">seismic</span> deformation following the 2003 Mw 6.6 Bam earthquake. Our analysis indicates the <span class="hlt">faults</span> at Bam remain predominantly locked, suggesting that the co- plus inter-<span class="hlt">seismically</span> accumulated elastic strain stored down-dip of the 2003 rupture patch may be released in a future Mw 6 earthquake. Our observations and models also provide an opportunity to probe the growth of topography at Bam. We find that, for our modelled afterslip distribution to be consistent with forming the sharp step in the local topography over repeated earthquake cycles, and also to be consistent with the geodetic observations, requires either (1) far-field tectonic loading equivalent to a 2-10 MPa deviatoric stress acting across the <span class="hlt">fault</span> system, which suggests it supports stresses 60-100 times less than classical views of static <span class="hlt">fault</span> strength, or (2) that the <span class="hlt">fault</span> surface has some form of mechanical anisotropy, potentially related to corrugations on the <span class="hlt">fault</span> plane, that controls the sense of slip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021503','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021503"><span><span class="hlt">Active</span> tectonics of the Seattle <span class="hlt">fault</span> and central Puget sound, Washington - Implications for earthquake hazards</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Johnson, S.Y.; Dadisman, S.V.; Childs, J. R.; Stanley, W.D.</p> <p>1999-01-01</p> <p>We use an extensive network of marine high-resolution and conventional industry <span class="hlt">seismic</span>-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle <span class="hlt">fault</span> zone and crosscutting high-angle <span class="hlt">faults</span> in the Puget Lowland of western Washington. Analysis of <span class="hlt">seismic</span> profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates that the west-trending Seattle <span class="hlt">fault</span> comprises a broad (4-6 km) zone of three or more south-dipping reverse <span class="hlt">faults</span>. Quaternary sediment has been folded and <span class="hlt">faulted</span> along all <span class="hlt">faults</span> in the zone but is clearly most pronounced along <span class="hlt">fault</span> A, the northernmost <span class="hlt">fault</span>, which forms the boundary between the Seattle uplift and Seattle basin. Analysis of growth strata deposited across <span class="hlt">fault</span> 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 <span class="hlt">fault</span> is cut into two main segments by an <span class="hlt">active</span>, north-trending, high-angle, strike-slip <span class="hlt">fault</span> zone with cumulative dextral displacement of about 2.4 km. <span class="hlt">Faults</span> in this zone truncate and warp reflections in Tertiary and Quaternary strata and locally coincide with bathymetric lineaments. Cumulative slip rates on these <span class="hlt">faults</span> may exceed 0.2 mm/yr. Assuming no other crosscutting <span class="hlt">faults</span>, this north-trending <span class="hlt">fault</span> zone divides the Seattle <span class="hlt">fault</span> into 30-40-km-long western and eastern segments. Although this geometry could limit the area ruptured in some Seattle <span class="hlt">fault</span> earthquakes, a large event ca. A.D. 900 appears to have involved both segments. Regional <span class="hlt">seismic</span>-hazard assessments must (1) incorporate new information on <span class="hlt">fault</span> length, geometry, and displacement rates on the Seattle <span class="hlt">fault</span>, and (2) consider the hazard presented by the previously unrecognized, north-trending <span class="hlt">fault</span> zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T33A4638D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T33A4638D"><span>Inferring Earthquake Physics from Deep Drilling Projects of <span class="hlt">Active</span> <span class="hlt">Faults</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Toro, G.; Smith, S. A. F.; Kuo, L. W.; Mittempergher, S.; Remitti, F.; Spagnuolo, E.; Mitchell, T. M.; Gualtieri, A.; Hadizadeh, J.; Carpenter, B. M.</p> <p>2014-12-01</p> <p>Deep drilling projects of <span class="hlt">active</span> <span class="hlt">faults</span> offer the opportunity to correlate physical and chemical processes identified in core samples with experiments reproducing the <span class="hlt">seismic</span> cycle in the laboratory and with high-resolution seismological and geophysical data. Here we discuss the constraints about earthquakes source processes at depth gained by <span class="hlt">fault</span> cores retrieved from the deep drilling projects SAFOD (2.7 km depth, San Andreas <span class="hlt">Fault</span>), J-FAST (0.9 km depth, following the Mw 9.0 Tohoku 2011 earthquake), TCDP (1.1 km depth, following the Mw 7.6 Chi-Chi 1999 earthquake) and WFSD (1.2 km depth, following the Mw 7.9 Wenchuan 2008 earthquake). Recovered samples were tested at room temperature with the rotary shear apparatus SHIVA installed in Rome (INGV, Italy). All the tested samples were made by clay-rich gouges (usually including smectite/illite), though their bulk mineralogy and modal composition were different (e.g., SAFOD samples included saponite, WFSD carbonaceous materials). The gouges were investigated before and after the experiments with scanning and transmission electron microscopy, X-Ray diffraction, micro-Raman spectroscopy, etc. A common behavior of all the tested gouges was that their friction coefficient was low (often less than 0.1) under room-humidity and wet conditions when sheared at slip rates of ca. 1 m/s (<span class="hlt">seismic</span> deformation conditions). Moreover, when the natural <span class="hlt">fault</span> rocks next to the principal slipping zones were sheared from sub-<span class="hlt">seismic</span> (few micrometers/s) to <span class="hlt">seismic</span> slip rates, the experimental products had similar microstructures to those found in the principal slipping zones of the drilled <span class="hlt">faults</span>. This included the formation of mirror-like surfaces, graphite-rich materials, foliated gouges, nanograins, amorphous materials, etc. In most cases the mechanical data were consistent with several seismological (> 50 m of <span class="hlt">seismic</span> slip for the <span class="hlt">fault</span> zone drilled by J-FAST) and geophysical observations (absence of a thermal anomaly in the <span class="hlt">fault</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000094026&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dseismic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000094026&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dseismic"><span><span class="hlt">Seismic</span> Holography of Solar <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lindsey, Charles</p> <p>2000-01-01</p> <p>The basic goal of the project was to extend holographic <span class="hlt">seismic</span> imaging techniques developed under a previous NASA contract, and to incorporate phase diagnostics. Phase-sensitive imaging gives us a powerful probe of local thermal and Doppler perturbations in <span class="hlt">active</span> region subphotospheres, allowing us to map thermal structure and flows associated with "acoustic moats" and "acoustic glories". These remarkable features were discovered during our work, by applying simple acoustic power holography to <span class="hlt">active</span> regions. Included in the original project statement was an effort to obtain the first <span class="hlt">seismic</span> images of <span class="hlt">active</span> regions on the Sun's far surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811474S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811474S"><span><span class="hlt">Fault</span>2SHA- A European Working group to link <span class="hlt">faults</span> and Probabilistic <span class="hlt">Seismic</span> Hazard Assessment communities in Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scotti, Oona; Peruzza, Laura</p> <p>2016-04-01</p> <p>The key questions we ask are: What is the best strategy to fill in the gap in knowledge and know-how in Europe when considering <span class="hlt">faults</span> in <span class="hlt">seismic</span> hazard assessments? Are field geologists providing the relevant information for <span class="hlt">seismic</span> hazard assessment? Are <span class="hlt">seismic</span> hazard analysts interpreting field data appropriately? Is the full range of uncertainties associated with the characterization of <span class="hlt">faults</span> correctly understood and propagated in the computations? How can <span class="hlt">fault</span>-modellers contribute to a better representation of the long-term behaviour of <span class="hlt">fault</span>-networks in <span class="hlt">seismic</span> hazard studies? Providing answers to these questions is fundamental, in order to reduce the consequences of future earthquakes and improve the reliability of <span class="hlt">seismic</span> hazard assessments. An informal working group was thus created at a meeting in Paris in November 2014, partly financed by the Institute of Radioprotection and Nuclear Safety, with the aim to motivate exchanges between field geologists, <span class="hlt">fault</span> modellers and <span class="hlt">seismic</span> hazard practitioners. A variety of approaches were presented at the meeting and a clear gap emerged between some field geologists, that are not necessarily familiar with probabilistic <span class="hlt">seismic</span> hazard assessment methods and needs and practitioners that do not necessarily propagate the "full" uncertainty associated with the characterization of <span class="hlt">faults</span>. The group thus decided to meet again a year later in Chieti (Italy), to share concepts and ideas through a specific exercise on a test case study. Some solutions emerged but many problems of <span class="hlt">seismic</span> source characterizations with people working in the field as well as with people tackling models of interacting <span class="hlt">faults</span> remained. Now, in Wien, we want to open the group and launch a call for the European community at large to contribute to the discussion. The 2016 EGU session <span class="hlt">Fault</span>2SHA is motivated by such an urgency to increase the number of round tables on this topic and debate on the peculiarities of using <span class="hlt">faults</span> in <span class="hlt">seismic</span> hazard</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.173.2621C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.173.2621C"><span><span class="hlt">Seismicity</span> on Basement <span class="hlt">Faults</span> Induced by Simultaneous Fluid Injection-Extraction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, Kyung Won; Segall, Paul</p> <p>2016-08-01</p> <p>Large-scale carbon dioxide (CO2) injection into geological formations increases pore pressure, potentially inducing <span class="hlt">seismicity</span> on critically stressed <span class="hlt">faults</span> by reducing the effective normal stress. In addition, poroelastic expansion of the reservoir alters stresses, both within and around the formation, which may trigger earthquakes without direct pore-pressure diffusion. One possible solution to mitigate injection-induced earthquakes is to simultaneously extract pre-existing pore fluids from the target reservoir. To examine the feasibility of the injection-extraction strategy, we compute the spatiotemporal change in Coulomb stress on basement normal <span class="hlt">faults</span>, including: (1) the change in poroelastic stresses Δ τ _s+fΔ σ _n, where Δ τ _s and Δ σ _n are changes in shear and normal stress. respectively, and (2) the change in pore-pressure fΔ p. Using the model of (J. Geophys. Res. Solid Earth 99(B2):2601-2618, 1994), we estimate the <span class="hlt">seismicity</span> rate on basement <span class="hlt">fault</span> zones. Fluid extraction reduces direct pore-pressure diffusion into conductive <span class="hlt">faults</span>, generally reducing the risk of induced <span class="hlt">seismicity</span>. Limited diffusion into/from sealing <span class="hlt">faults</span> results in negligible pore pressure changes within them. However, fluid extraction can cause enhanced <span class="hlt">seismicity</span> rates on deep normal <span class="hlt">faults</span> near the injector as well as shallow normal <span class="hlt">faults</span> near the producer by poroelastic stressing. Changes in <span class="hlt">seismicity</span> rate driven by poroelastic response to fluid injection-extraction depends on <span class="hlt">fault</span> geometry, well operations, and the background stressing rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=256703&keyword=Hydraulic+AND+Modeling&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90583430&CFTOKEN=55621550','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=256703&keyword=Hydraulic+AND+Modeling&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90583430&CFTOKEN=55621550"><span>Modeling of <span class="hlt">fault</span> reactivation and induced <span class="hlt">seismicity</span> during hydraulic fracturing of shale-gas reservoirs</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>We have conducted numerical simulation studies to assess the potential for injection-induced <span class="hlt">fault</span> reactivation and notable <span class="hlt">seismic</span> events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.204..180G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.204..180G"><span>New constraints on extensional tectonics and <span class="hlt">seismic</span> hazard in northern Attica, Greece: the case of the Milesi <span class="hlt">Fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grützner, Christoph; Schneiderwind, Sascha; Papanikolaou, Ioannis; Deligiannakis, Georgios; Pallikarakis, Aggelos; Reicherter, Klaus</p> <p>2016-01-01</p> <p>Northern Attica in Greece is characterized by a set of north dipping, subparallel normal <span class="hlt">faults</span>. These <span class="hlt">faults</span> were considered to have low tectonic <span class="hlt">activity</span>, based on historical earthquake reports, instrumental <span class="hlt">seismicity</span> and slip rate estimates. This study presents new data for one of these <span class="hlt">faults</span>, the Milesi <span class="hlt">Fault</span>. We run GIS based geomorphological analyses on <span class="hlt">fault</span> offset distribution, field mapping of postglacial <span class="hlt">fault</span> scarps and ground penetrating radar profiling to image hangingwall deformation. The first palaeoseismological trenching in this part of Greece allowed obtaining direct data on slip rates and palaeoearthquakes. The trenching revealed downthrown and buried palaeosols, which were dated by radiocarbon. The results of our investigations show that the slip rates are higher than previously thought and that at least four palaeoearthquakes with magnitudes of around M6.2 occurred during the last 4000-6000 yr. We calculate an average recurrence interval of 1000-1500 yr and a maximum throw rate of ˜0.4-0.45 mm a-1. Based on the new geological earthquake data we developed a <span class="hlt">seismic</span> hazard scenario, which also incorporates geological site effects. Intensities up to IX must be expected for Northern Attica and the southeastern part of Evia. Earthquake environmental effects like liquefaction and mass movements are also likely to occur. This scenario is in contrast to the official Greek <span class="hlt">seismic</span> hazard zonation that is based on historical records and assigns different hazard zones for municipalities that will experience the same intensity by earthquakes on the Milesi <span class="hlt">Fault</span>. We show that the <span class="hlt">seismic</span> hazard is likely underestimated in our study area and emphasize the need to incorporate geological information in such assessments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992GeoRL..19..353W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992GeoRL..19..353W"><span><span class="hlt">Seismic</span> image of the Ivanhoe Lake <span class="hlt">Fault</span> Zone in the Kapuskasing Uplift of the Canadian Shield</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Jianjun; Mereu, Robert F.; Percival, John A.</p> <p>1992-02-01</p> <p>The Kapuskasing uplift, located in the central Canadian shield, represents an oblique exposure of the Archean middle to lower crust. The Ivanhoe Lake <span class="hlt">fault</span> zone, believed to be the basal thrust carrying the high-grade rocks of the Kapuskasing zone over the low-grade Abitibi greenstone belt, holds the key to understanding the nature and evolution of the Kapuskasing uplift. Despite numerous geological and geophysical studies, including LITHOPROBE deep <span class="hlt">seismic</span> reflection profiles, and because of very limited bedrock exposure in the area, the shallow structure of the Ivanhoe Lake <span class="hlt">fault</span> zone remains obscure. Here we present results obtained by reprocessing data from a LITHOPROBE <span class="hlt">seismic</span> reflection profile across the <span class="hlt">fault</span> zone. For the first time, the Ivanhoe Lake <span class="hlt">fault</span> zone is clearly imaged on the <span class="hlt">seismic</span> section as a series of west-dipping reflectors with an average dip of 20°, which can be traced to the surface. The results support the conclusion that <span class="hlt">fault</span> zones form good reflectors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.T41A1944L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.T41A1944L"><span>Wide-Angle <span class="hlt">Seismic</span> Experiment Across the Oeste <span class="hlt">Fault</span> Zone, Central Andes, Northern Chile.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lorenzo, J. M.; Yáñez, G. A.; Vera, E. E.; Sepúlveda, J.</p> <p>2008-12-01</p> <p>From December 6-21, 2007, we conducted a 3-component, radio-telemetric, <span class="hlt">seismic</span> survey along a ~ 15-km wide E-W transect in the Central Andes, at a latitude of ~ 22.41° S, centered north of the city of Calama (68.9° W), Chile. The study area is sandwiched between the Central Depression in the west and the Andean Western Cordillera of Chile. Recording stations, nominally spaced at intervals of either 125 or 250 m collected up to 3.5 s of refracted <span class="hlt">seismic</span> arrivals at maximum source-receiver offsets exceeding 15 km. Ten shothole sources, spaced 2-6 km apart focused energy on the shallow (0-3 km), crustal, Paleogene-age structures. Preliminary, tomographic inversions of refracted first arrivals show the top of a shallow (< 1km), high- velocity (VP, ~5 km/s) crust, deepening sharply eastward to at least 2 km. At the surface, this central basement step correlates to a regionally extensive (> 600 km), strike-slip <span class="hlt">fault</span> zone known as the Oeste <span class="hlt">fault</span>. Turning ray densities suggest the base of the overlying velocity gradient unit (VP, 2-4 km/s) dips inwardly from both east and west directions toward the Oeste <span class="hlt">fault</span> to depths of almost 1 km. Plate reorganization commencing at least by the latter half of the Oligocene led from oblique to more orthogonal convergence between the South American and the Nazca (Farallon) Plates. We interpret previously mapped, older, minor <span class="hlt">faults</span> as being generated within the right-lateral, orogen-parallel, Oeste strike-slip <span class="hlt">fault</span> zone, and postdated by Neogene, N-S striking thrust <span class="hlt">faults</span>. In this context we also interpret that the spatial distribution of velocity units requires an period of extensional <span class="hlt">activity</span> that may (1) postdate the transpressional strike slip <span class="hlt">fault</span> <span class="hlt">activity</span> of the Neogene, (2) be related to a later releasing bend through the translation and interaction of rigid blocks hidden at depth or even (3) be the consequence of inelastic failure from the result of flexural loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060037641&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseismic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060037641&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseismic"><span>New Perspectives on <span class="hlt">Active</span> Tectonics: Observing <span class="hlt">Fault</span> Motion, Mapping Earthquake Strain Fields, and Visualizing <span class="hlt">Seismic</span> Events in Multiple Dimensions Using Satellite Imagery and Geophysical Data Base</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Crippen, R.; Blom, R.</p> <p>1994-01-01</p> <p>By rapidly alternating displays of SPOT satellite images acquired on 27 July 1991 and 25 July 1992 we are able to see spatial details of terrain movements along <span class="hlt">fault</span> breaks associated with the 28 June 1992 Landers, California earthquake that are virtually undetectable by any other means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSG....86....1V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSG....86....1V"><span><span class="hlt">Seismic</span> slip recorded in tourmaline <span class="hlt">fault</span> mirrors from Elba Island (Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Viti, C.; Brogi, A.; Liotta, D.; Mugnaioli, E.; Spiess, R.; Dini, A.; Zucchi, M.; Vannuccini, G.</p> <p>2016-05-01</p> <p>This paper reports the first example of <span class="hlt">fault</span> mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms <span class="hlt">active</span> in the <span class="hlt">fault</span> zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at <span class="hlt">seismic</span> slip rate, as observed for other <span class="hlt">fault</span> mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with <span class="hlt">seismic</span> slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 μm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-<span class="hlt">activated</span> processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar interlobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.2798F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.2798F"><span>Geomechanical analysis of fluid injection and <span class="hlt">seismic</span> <span class="hlt">fault</span> slip for the Mw4.8 Timpson, Texas, earthquake sequence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Zhiqiang; Eichhubl, Peter; Gale, Julia F. W.</p> <p>2016-04-01</p> <p>An earthquake sequence that culminated in a Mw4.8 strike-slip event near Timpson, east Texas, the largest reported earthquake to date in that region, had previously been attributed to wastewater injection starting 17 months before the onset of recorded <span class="hlt">seismic</span> <span class="hlt">activity</span>. To test if this earthquake sequence can be attributed to wastewater injection, we conducted coupled poroelastic finite element simulations to assess the spatial and temporal evolution of pore pressure and stress field in the vicinity of the injection wells and to calculate the Coulomb failure stress on the seismogenic <span class="hlt">fault</span> as a function of the permeability of the injection layer, <span class="hlt">fault</span> orientation, <span class="hlt">fault</span> permeability, and orientation and magnitude of the in situ stress. We find that injection-induced <span class="hlt">fault</span> slip is plausible within the range of selected model input parameters, with slip favored by low reservoir permeability, low <span class="hlt">fault</span> permeability, and a favorable orientation of the <span class="hlt">fault</span> relative to the in situ stress state. Other combinations of equally plausible input parameters predict no slip within 96 months of simulated injection. Under most favorable boundary conditions for <span class="hlt">fault</span> slip, <span class="hlt">fault</span> slip occurs 7 months after the start of injection. Our results highlight the importance of detailed geomechanical site characterization for robust <span class="hlt">fault</span> stability assessment prior to wastewater injection.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR13A2265D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR13A2265D"><span>Deep pulverization along <span class="hlt">active</span> <span class="hlt">faults</span> ?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doan, M.</p> <p>2013-12-01</p> <p>Pulverization is a intensive damage observed along some <span class="hlt">active</span> <span class="hlt">faults</span>. Rarely found in the field, it has been associated with dynamic damage produced by large earthquakes. Pulverization has been so far only described at the ground surface, consistent with the high frequency tensile loading expected for earthquake occurring along bimaterial <span class="hlt">faults</span>. However, we discuss here a series of hints suggesting that pulverization is expected also several hundred of meters deep. In the deep well drilled within Nojima <span class="hlt">fault</span> after the 1995 Kobe earthquake, thin sections reveal non localized damage, with microfractured pervading a sample, but with little shear disturbing the initial microstructure. In the SAFOD borehole drilled near Parkfield, Wiersberg and Erzinger (2008) made gas monitoring while drilling found large amount of H2 gas in the sandstone west to the <span class="hlt">fault</span>. They attribute this high H2 concentration to mechanochemical origin, in accordance with some example of diffuse microfracturing found in thin sections from cores of SAFOD phase 3 and from geophysical data from logs. High strain rate experiments in both dry (Yuan et al, 2011) and wet samples (Forquin et al, 2010) show that even under confining pressures of several tens of megapascals, diffuse damage similar to pulverization is possible. This could explain the occurrence of pulverization at depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5455452','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5455452"><span>Evaluation of <span class="hlt">seismic</span> reflection data in the Davis and Lavender Canyons study area, Paradox Basin, Utah. [<span class="hlt">Faults</span>, folds, joints, and collapse structures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kitcho, C.A.; Wong, I.G.; Turcotte, F.T.</p> <p>1986-08-01</p> <p><span class="hlt">Seismic</span> reflection data purchased from petroleum industry brokers and acquired through group speculative surveys were interpreted for information on the regional subsurface geologic structure and stratigraphy within and surrounding the Davis and Lavender Canyons study area in the Paradox Basin of southeastern Utah. Structures of interest were <span class="hlt">faults</span>, folds, joints, and collapse structures related to salt dissolution. The <span class="hlt">seismic</span> reflection data were used to interpret stratigraphy by identifying continuous and discontinuous reflectors on the <span class="hlt">seismic</span> profiles. Thickening and thinning of strata and possible areas of salt flowage or dissolution could be identified from the <span class="hlt">seismic</span> data. Identifiable reflectors included the tops of the Precambrian and Mississippian, a distinctive interbed close to the middle of the Pennsylvanian Paradox salt formation (probably the interval between Salt Cycles 10 and 13), and near the top of the Paradox salt. Of the 56 <span class="hlt">faults</span> identified from the <span class="hlt">seismic</span> reflection interpretation, 33 trend northwest, west-northwest, or west, and most affect only the deeper part of the stratigraphic section. These <span class="hlt">faults</span> are part of the deep structural system found throughout the Paradox Basin, including the fold and <span class="hlt">fault</span> belt in the northeast part of the basin. The <span class="hlt">faults</span> bound basement Precambrian blocks that experienced minor <span class="hlt">activity</span> during Mississippian and early Pennsylvanian deposition, and showed major displacement during early Paradox salt deposition as the Paradox Basin subsided. Based on the <span class="hlt">seismic</span> data, most of these <span class="hlt">faults</span> appear to have an upward terminus between the top of the Mississippian and the salt interbed reflector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRB..122..308P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRB..122..308P"><span><span class="hlt">Seismic</span> swarms and diffuse fracturing within Triassic evaporites fed by deep degassing along the low-angle Alto Tiberina normal <span class="hlt">fault</span> (central Apennines, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piana Agostinetti, Nicola; Giacomuzzi, Genny; Chiarabba, Claudio</p> <p>2017-01-01</p> <p>We present high-resolution elastic models and relocated <span class="hlt">seismicity</span> of a very <span class="hlt">active</span> segment of the Apennines normal <span class="hlt">faulting</span> system, computed via transdimensional local earthquake tomography (trans-D LET). Trans-D LET, a fully nonlinear approach to <span class="hlt">seismic</span> tomography, robustly constrains high-velocity anomalies and inversions of P wave velocity, i.e., decreases of VP with depth, without introducing bias due to, e.g., a starting model, and giving the possibility to investigate the relation between <span class="hlt">fault</span> structure, <span class="hlt">seismicity</span>, and fluids. Changes in <span class="hlt">seismicity</span> rate and recurring <span class="hlt">seismic</span> swarms are frequent in the Apennines extensional belt. Deep fluids, upwelling from the delaminating continental lithosphere, are thought to be responsible for <span class="hlt">seismicity</span> clustering in the upper crust and lubrication of normal <span class="hlt">faults</span> during swarms and large earthquakes. We focus on the tectonic role played by the Alto Tiberina low-angle normal <span class="hlt">fault</span> (ATF), finding displacements across the <span class="hlt">fault</span> consistent with long-term accommodation of deformation. Our results show that recent <span class="hlt">seismic</span> swarms affecting the area occur within a 3 km thick, high VP/VS, densely cracked, and overpressurized evaporitic layer, composed of dolostones and anhydrites. A persistent low VP, low VP/VS volume, present on top of and along the ATF low-angle detachment, traces the location of mantle-derived CO2, the upward flux of which contributes to cracking within the evaporitic layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T33B2253B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T33B2253B"><span>The May 29 2008 earthquake aftershock sequence within the South Iceland <span class="hlt">Seismic</span> Zone: <span class="hlt">Fault</span> locations and source parameters of aftershocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandsdottir, B.; Parsons, M.; White, R. S.; Gudmundsson, O.; Drew, J.</p> <p>2010-12-01</p> <p>The mid-Atlantic plate boundary breaks up into a series of segments across Iceland. The South Iceland <span class="hlt">Seismic</span> Zone (SISZ) is a complex transform zone where left-lateral E-W shear between the Reykjanes Peninsula Rift Zone and the Eastern Volcanic Zone is accommodated by bookshelf <span class="hlt">faulting</span> along N-S lateral strike-slip <span class="hlt">faults</span>. The SISZ is also a transient feature, migrating sideways in response to the southward propagation of the Eastern Volcanic Zone. Sequences of large earthquakes (M > 6) lasting from days to years and affecting most of the <span class="hlt">seismic</span> zone have occurred repeatedly in historical time (last 1100 years), separated by intervals of relative quiescence lasting decades to more than a century. On May 29 2008, a Mw 6.1 earthquake struck the western part of the South Iceland <span class="hlt">Seismic</span> Zone, followed within seconds by a slightly smaller event on a second <span class="hlt">fault</span> ~5 km further west. Aftershocks, detected by a temporal array of 11 seismometers and three permanent Icelandic Meteorological Office stations were located using an automated Coalescence Microseismic Mapping technique. The epicenters delineate two major and several smaller N-S <span class="hlt">faults</span> as well as an E-W zone of <span class="hlt">activity</span> stretching further west into the Reykjanes Peninsula Rift Zone. <span class="hlt">Fault</span> plane solutions show both right lateral and oblique strike slip mechanisms along the two major N-S <span class="hlt">faults</span>. The aftershocks deepen from 3-5 km in the north to 8-9 km in the south, suggesting that the main <span class="hlt">faults</span> dip southwards. The <span class="hlt">faulting</span> is interpreted to be driven by the local stress due to transform motion between two parallel segments of the divergent plate boundary crossing Iceland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T41A2855M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T41A2855M"><span><span class="hlt">Seismic</span> and Aseismic Moment Budget and Implication for the <span class="hlt">Seismic</span> Potential of the Parkield Segment of the San Andreas <span class="hlt">Fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michel, S. G. R. M.</p> <p>2015-12-01</p> <p>This study explores methods to assess the <span class="hlt">seismic</span> potential of a <span class="hlt">fault</span> based on geodetic measurements, geological information of <span class="hlt">fault</span> slip rate and <span class="hlt">seismicity</span> data. The methods are applied to the Parkfield's section along the San Andreas <span class="hlt">Fault</span> at the transition zone between the SAF creeping segment in the North and the locked section to the south, where a Mw~6 earthquake has occurred every 24.5 years on average since the M7.7 Fort Tejon event in 1857. We compare the moment released by all the known earthquakes and associated postseismic deformation with the moment deficit accumulated during the interseismic period. We find that the recurrence of Mw6 earthquakes is insufficient to close the slip budget and that larger events are probably needed. We will discuss and evaluate various possible scenarios which might account for the residual moment deficit and implications of the possible magnitude and return period of Mw6 earthquakes on that <span class="hlt">fault</span> segment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRB..118.5956W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRB..118.5956W"><span>Automatic reconstruction of <span class="hlt">fault</span> networks from <span class="hlt">seismicity</span> catalogs including location uncertainty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y.; Ouillon, G.; Woessner, J.; Sornette, D.; Husen, S.</p> <p>2013-11-01</p> <p>introduce the anisotropic clustering of location uncertainty distributions (ACLUD) method to reconstruct <span class="hlt">active</span> <span class="hlt">fault</span> networks on the basis of both earthquake locations and their estimated individual uncertainties. After a massive search through the large solution space of possible reconstructed <span class="hlt">fault</span> networks, we apply six different validation procedures in order to select the corresponding best <span class="hlt">fault</span> network. Two of the validation steps (cross validation and Bayesian information criterion (BIC) process the fit residuals, while the four others look for solutions that provide the best agreement with independently observed focal mechanisms. Tests on synthetic catalogs allow us to qualify the performance of the fitting method and of the various validation procedures. The ACLUD method is able to provide solutions that are close to the expected ones, especially for the BIC and focal mechanism-based techniques. The clustering method complemented by the validation step based on focal mechanisms provides good solutions even in the presence of a significant spatial background <span class="hlt">seismicity</span> rate. Our new <span class="hlt">fault</span> reconstruction method is then applied to the Landers area in Southern California and compared with previous clustering methods. The results stress the importance of taking into account undersampled subfault structures as well as of the spatially inhomogeneous location uncertainties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5376508','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5376508"><span>1983 Borah Peak, Idaho earthquake: a review of <span class="hlt">seismicity</span>, surface <span class="hlt">faulting</span> and regional tectonics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Richins, W.D.</p> <p>1985-01-01</p> <p>The October 28, 1983 Borah Peak, Idaho earthquake (M/sub s/ = 7.3) occurred in an area of low historic <span class="hlt">seismicity</span> within east-central Idaho along a segment of the Lost River <span class="hlt">fault</span> <span class="hlt">active</span> during the Holocene. A dense network of portable short period seismographs (up to 45 stations, station spacings of 2 to 10 km) was installed beginning several hours after the main shock and operated for 22 days. In addition to records from the portable instrumentation, data from permanent seismograph stations operating in Idaho, Utah, Montana, Oregon, Washington, and Wyoming, provide a good regional data base. No foreshock <span class="hlt">activity</span> above magnitude 2.0 (M/sub L/) was detected for the two month period preceding the main shock. The distribution of 421 aftershocks of M/sub L/ > 2 defines an epicentral pattern, 75 km x 15 km, trending north-northwest parallel to the surface rupture but displaced laterally southwest by 5 to 10 km. The epicenter of the main shock is approximately 14 km south-southwest of the end of surface <span class="hlt">faulting</span>. This relationship suggests unilateral rupture propagating to the northwest. Aftershocks extend to depths of approximately 16 km and in the southeastern portion of the aftershock pattern define a zone, dipping approximately 45/sup 0/ SW, that intersects the surface near the <span class="hlt">fault</span> scarp. The entire aftershock zone as observed during the first 3.5 weeks was <span class="hlt">active</span> shortly after the main shock occurred. <span class="hlt">Fault</span> plane solutions indicate predominantly normal <span class="hlt">faulting</span> with varying components of strike slip. 17 refs., 8 figs. 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T51C2053G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T51C2053G"><span>Geometry and deformation history of the New Madrid <span class="hlt">seismic</span> zone <span class="hlt">fault</span> system, Central U.S. from high-resolution marine <span class="hlt">seismic</span> reflection data, and implications for intraplate deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, L.; Magnani, M.; McIntosh, K. D.; Waldron, B. A.; Saustrup, S.; Fave, X. J.</p> <p>2010-12-01</p> <p>The New Madrid <span class="hlt">Seismic</span> Zone (NMSZ) is the most <span class="hlt">seismically</span> <span class="hlt">active</span> area in the continental United States east of the Rocky Mountains, and by far the most studied intraplate <span class="hlt">seismic</span> zone in the world. The occurrence of large magnitude historical and prehistorical earthquakes, as well as the high level of instrumental <span class="hlt">seismicity</span> suggest that the North American plate is <span class="hlt">actively</span> deforming in this region. This observation appears to clash with geodetic evidence that shows minimal motion across the <span class="hlt">faults</span> illuminated by the present <span class="hlt">seismicity</span>, suggesting that either the present GPS vectors recorded at the surface are not typical of the long term deformation rate of the NMSZ <span class="hlt">faults</span>, or that the NMSZ <span class="hlt">fault</span> system is presently unloaded and not deforming. To better constrain the long-term deformation history of the NMSZ <span class="hlt">fault</span> system, in the summer of 2010 we acquired ~300 km of high-resolution <span class="hlt">seismic</span> marine reflection data along the Mississippi River from Cape Girardeau, MO to Caruthersville, MO. The profile crosses a large portion of the Mississippi Embayment, including three of the four main NMSZ <span class="hlt">active</span> <span class="hlt">faults</span>, and images the gently south-dipping unconsolidated sediments of the Mississippi Embayment from the Quaternary alluvium of the Mississippi River down to the top of Paleozoic sequences, at a depth of ~650 m. Among the most remarkable structures imaged by the profile is the Reelfoot <span class="hlt">fault</span>, interpreted as the NW-SE striking restraining bend connecting two NE-SW trending dextral strike-slip <span class="hlt">faults</span>. The Reelfoot thrust intersects the profile at three locations along the river meander known as the Kentucky Bend. The multiple crossings allow mapping of the along-strike variations of the <span class="hlt">fault</span> plane’s dip and structure. In particular the data show that a reverse offset of 42 m at the top of the Cretaceous is accommodated by a single <span class="hlt">fault</span> at the crossing north of town of Tiptonville, TN, west of the location where the Reelfoot thrust ruptured during the 7 February 1812 M7</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024067','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024067"><span><span class="hlt">Seismic</span> mapping of shallow <span class="hlt">fault</span> zones in the San Gabriel Mountains from the Los Angeles Region <span class="hlt">Seismic</span> Experiment, southern California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fuis, G.S.; Ryberg, T.; Lutter, W.J.; Ehlig, P.L.</p> <p>2001-01-01</p> <p>During the Los Angeles Region <span class="hlt">Seismic</span> Experiment (LARSE), a reflection/refraction survey was conducted along a profile (line 1) extending from Seal Beach, California, northeastward to the Mojave Desert and crossing the Los Angeles and San Gabriel Valley basins and San Gabriel Mountains. In most shot gathers from the southern and central San Gabriel Mountains, clear secondary arrivals are seen that merge, or appear to merge, with first arrivals at three locations, including the location of the Vincent thrust <span class="hlt">fault</span>, an exposed late Mesozoic/early Cenozoic megathrust. These secondary arrivals are interpretable as reflections in the shallow crust (<5 km depth) from a concave-upward interface that projects to the surface in the north near the Vincent thrust <span class="hlt">fault</span>, is offset in its central part at the San Gabriel <span class="hlt">fault</span> (an old branch of the San Andreas <span class="hlt">fault</span>), and terminates in the south at 1 to 2 km depth at the southern mountain front. The velocity structure above and below this interface strongly suggests it is the Vincent thrust <span class="hlt">fault</span>: intermediate velocities (6.2 km/s), consistent with mylonites overlying the Vincent thrust <span class="hlt">fault</span>, are observed above it; lower velocities (5.8 km/s), consistent with the Pelona Schist underlying the Vincent thrust <span class="hlt">fault</span>, are observed below it. Problems arise, however, in attempting to match this reflector to the exposed Vincent thrust <span class="hlt">fault</span>, which is seen in outcrops east of line 1. The Vincent thrust <span class="hlt">fault</span> is shallower than the reflector in most places. An unmapped structure (steep <span class="hlt">fault</span>, monocline, or thrust <span class="hlt">fault</span>) is required between line 1 and the outcrops that either drops the Vincent thrust <span class="hlt">fault</span> down to the depths of the reflector or repeats the Vincent thrust <span class="hlt">fault</span> beneath line 1 in the footwall of another thrust <span class="hlt">fault</span>. An alternative interpretation of the reflector is a deep greenstone horizon within the Pelona Schist, although this alternative is not favored by the velocity structure. Copyright 2001 by the American</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/7067100','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/7067100"><span>Pen Branch <span class="hlt">fault</span> program: Interim report on the High Resolution, Shallow <span class="hlt">Seismic</span> Reflection surveys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stieve, A.L. )</p> <p>1991-01-31</p> <p>The Pen Branch <span class="hlt">fault</span> was identified in the subsurface at the Savannah River Site in 1989 based upon the interpretation of earlier <span class="hlt">seismic</span> reflection surveys and other geologic investigations. A program was initiated at that time to further define the <span class="hlt">fault</span> in terms of its capability to release <span class="hlt">seismic</span> energy. The High-Resolution, Shallow <span class="hlt">Seismic</span> Reflection survey recently completed at SRS was initiated to determine the shallowest extent of the <span class="hlt">fault</span> and to demonstrate the presence of flat-lying sediments in the top 300 feet of sediments. Conclusions at this time are based upon this shallow <span class="hlt">seismic</span> survey and the Conoco deep <span class="hlt">seismic</span> survey (1988--1989). Deformation related to the Pen Branch <span class="hlt">fault</span> is at least 200 milliseconds beneath the surface in the Conoco data and at least 150 milliseconds in the shallow <span class="hlt">seismic</span> reflection data. This corresponds to approximately 300 feet below the surface. Sediments at that depth are lower Tertiary (Danian stage) or over 60 million years old. This indicates that the <span class="hlt">fault</span> is not capable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28386064','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28386064"><span>Ultra-thin clay layers facilitate <span class="hlt">seismic</span> slip in carbonate <span class="hlt">faults</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Smeraglia, Luca; Billi, Andrea; Carminati, Eugenio; Cavallo, Andrea; Di Toro, Giulio; Spagnuolo, Elena; Zorzi, Federico</p> <p>2017-04-06</p> <p>Many earthquakes propagate up to the Earth's surface producing surface ruptures. <span class="hlt">Seismic</span> slip propagation is facilitated by along-<span class="hlt">fault</span> low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. In particular, rotary shear experiments conducted at <span class="hlt">seismic</span> slip rates (1 ms(-1)) show that phyllosilicates can facilitate co-<span class="hlt">seismic</span> slip along <span class="hlt">faults</span> during earthquakes. This evidence is crucial for hazard assessment along oceanic subduction zones, where pelagic clays participate in <span class="hlt">seismic</span> slip propagation. Conversely, the reason why, in continental domains, co-<span class="hlt">seismic</span> slip along <span class="hlt">faults</span> can propagate up to the Earth's surface is still poorly understood. We document the occurrence of micrometer-thick phyllosilicate-bearing layers along a carbonate-hosted seismogenic extensional <span class="hlt">fault</span> in the central Apennines, Italy. Using friction experiments, we demonstrate that, at <span class="hlt">seismic</span> slip rates (1 ms(-1)), similar calcite gouges with pre-existing phyllosilicate-bearing (clay content ≤3 wt.%) micro-layers weaken faster than calcite gouges or mixed calcite-phyllosilicate gouges. We thus propose that, within calcite gouge, ultra-low clay content (≤3 wt.%) localized along micrometer-thick layers can facilitate <span class="hlt">seismic</span> slip propagation during earthquakes in continental domains, possibly enhancing surface displacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1818083R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1818083R"><span>Comparative modeling of <span class="hlt">fault</span> reactivation and <span class="hlt">seismicity</span> in geologic carbon storage and shale-gas reservoir stimulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rutqvist, Jonny; Rinaldi, Antonio; Cappa, Frederic</p> <p>2016-04-01</p> <p>The potential for <span class="hlt">fault</span> reactivation and induced <span class="hlt">seismicity</span> are issues of concern related to both geologic CO2 sequestration and stimulation of shale-gas reservoirs. It is well known that underground injection may cause induced <span class="hlt">seismicity</span> depending on site-specific conditions, such a stress and rock properties and injection parameters. To date no sizeable <span class="hlt">seismic</span> event that could be felt by the local population has been documented associated with CO2 sequestration <span class="hlt">activities</span>. In the case of shale-gas fracturing, only a few cases of felt <span class="hlt">seismicity</span> have been documented out of hundreds of thousands of hydraulic fracturing stimulation stages. In this paper we summarize and review numerical simulations of injection-induced <span class="hlt">fault</span> reactivation and induced <span class="hlt">seismicity</span> associated with both underground CO2 injection and hydraulic fracturing of shale-gas reservoirs. The simulations were conducted with TOUGH-FLAC, a simulator for coupled multiphase flow and geomechanical modeling. In this case we employed both 2D and 3D models with an explicit representation of a <span class="hlt">fault</span>. A strain softening Mohr-Coulomb model was used to model a slip-weakening <span class="hlt">fault</span> slip behavior, enabling modeling of sudden slip that was interpreted as a <span class="hlt">seismic</span> event, with a moment magnitude evaluated using formulas from seismology. In the case of CO2 sequestration, injection rates corresponding to expected industrial scale CO2 storage operations were used, raising the reservoir pressure until the <span class="hlt">fault</span> was reactivated. For the assumed model settings, it took a few months of continuous injection to increase the reservoir pressure sufficiently to cause the <span class="hlt">fault</span> to reactivate. In the case of shale-gas fracturing we considered that the injection fluid during one typical 3-hour fracturing stage was channelized into a <span class="hlt">fault</span> along with the hydraulic fracturing process. Overall, the analysis shows that while the CO2 geologic sequestration in deep sedimentary formations are capable of producing notable events (e</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028373','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028373"><span>Association of the 1886 Charleston, South Carolina, earthquake and <span class="hlt">seismicity</span> near Summervile with a 12º bend in the East Coast <span class="hlt">fault</span> system and triple-<span class="hlt">fault</span> junctions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Marple, R.; Miller, R.</p> <p>2006-01-01</p> <p><span class="hlt">Seismic</span>-reflection data were integrated with other geophysical, geologic, and <span class="hlt">seismicity</span> data to better determine the location and nature of buried <span class="hlt">faults</span> in the Charleston, South Carolina, region. Our results indicate that the 1886 Charleston, South Carolina, earthquake and <span class="hlt">seismicity</span> near Summerville are related to local stresses caused by a 12?? bend in the East Coast <span class="hlt">fault</span> system (ECFS) and two triple-<span class="hlt">fault</span> junctions. One triple junction is formed by the intersection of the northwest-trending Ashley River <span class="hlt">fault</span> with the two segments of the ECFS north and south of the bend. The other triple junction is formed by the intersection of the northeast-trending Summerville <span class="hlt">fault</span> and a newly discovered northwest-trending Berkeley <span class="hlt">fault</span> with the ECFS about 10 km north of the bend. The Summerville <span class="hlt">fault</span> is a northwest-dipping border <span class="hlt">fault</span> of the Triassic-age Jedburg basin that is undergoing reverse-style reactivation. This reverse-style reactivation is unusual because the Summerville <span class="hlt">fault</span> parallels the regional stress field axis, suggesting that the reactivation is from stresses applied by dextral motion on the ECFS. The southwest-dip and reverse-type motion of the Berkeley <span class="hlt">fault</span> are interpreted from <span class="hlt">seismicity</span> data and a <span class="hlt">seismic</span>-reflection profile in the western part of the study area. Our results also indicate that the East Coast <span class="hlt">fault</span> system is a Paleozoic basement <span class="hlt">fault</span> and that its reactivation since early Mesozoic time has fractured through the overlying allochthonous terranes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6063719','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6063719"><span><span class="hlt">Active</span> <span class="hlt">faulting</span> in the Southwestern Venezuelan Andes and Colombia borderland</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Singer, A.; Beltran, C.; Lugo, M. , Caracas )</p> <p>1993-02-01</p> <p>In the southern Andes, the Bocono <span class="hlt">fault</span> shows a progressive disactivation of its right lateral movement, resulting from its attenuation against the transversal system of Bramon and its kinematic connection to the [open quotes]Pamplona indenter,[close quotes] considered as a part of the plate boundary between the Caribbean and South America. Near the Colombian frontier, the velocity of Bocono <span class="hlt">fault</span> is probably less than 1 mm/yr. Such a decrease is explained because an increasing amount of the 1 cm/yr slip movement of the northern part of the <span class="hlt">fault</span> is absorbed through a complex branching of the <span class="hlt">active</span> trace, southwest Merida. Another significative amount of the rate movement of Bocono <span class="hlt">fault</span>, considered as plate boundary, results absorbed by subparallel <span class="hlt">active</span> <span class="hlt">faulting</span> systems located to the east (Uribante and Caparo Systems) and to the west sides (San Simon-Seboruco, and San Pedro-Aguas Calientes-La Don Juana systems). The last system, extending beyond the frontier, shows a particular seimotectonic importance, as a probable source of the 1875 Cucata earthquake. In this way, the weight of the southwestern end of Bocono <span class="hlt">fault</span> as a <span class="hlt">seismic</span> source loses importance respect to the northern segment located between la Grita and Merida where the 1610 and 1894 earthquakes occurred, and also as compared to the <span class="hlt">faults</span> that define the [open quotes]Pamplona indenter[close quotes] like probable source for several other destructive earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002Tectp.353..173F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002Tectp.353..173F"><span><span class="hlt">Seismic</span>-reflection profiles of the central part of the Clarendon Linden <span class="hlt">fault</span> system of western New York in relation to regional <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fakundiny, Robert H.; Pomeroy, Paul W.</p> <p>2002-08-01</p> <p>Geological and geophysical research in upstate New York, with few exceptions, has not definitively associated <span class="hlt">seismicity</span> with specific Proterozoic basement or Paleozoic bedrock structures. The central part of the Clarendon-Linden <span class="hlt">fault</span> system (CLFS) between Batavia and Dale, NY is one of those exceptions where <span class="hlt">seismicity</span> has been studied and has been spatially associated with structure. The CLFS is either a complex system of long <span class="hlt">faults</span> with associated shorter branches and parallel segments, or a region of many short <span class="hlt">faults</span> aligned north-south from the Lake Ontario shore southward to Allegany County, NY. Interpretation of 38 km of Vibroseis and approximately 56 km of conventional <span class="hlt">seismic</span>-reflection data along 13 lines suggests that the CLFS is a broad zone of small <span class="hlt">faults</span> with small displacements in the lower Paleozoic bedrock section that is at least 77 km long and 7-17 km wide and spatially coincident with a north-trending geophysical (combined aeromagnetic and gravity) lineament within the basement. The relative offset across the <span class="hlt">faults</span> of the system is more than 91 m near Attica, NY. The CLFS is the expression of tectonic crustal adjustments within the Paleozoic rock above the boundary of two basement megablocks of differing petrologic provinces and differing earthquake characteristics that forms the eastern side of the Elzevir-Frontenac boundary zone. Deep <span class="hlt">seismic</span>-reflection profiles display concave-eastward listric <span class="hlt">faults</span> that probably merge at depth near the mid-crustal boundary layer. An interpretive vertical section provides the setting for refined definitions of the CLFS, its extensions at depth and its relation to <span class="hlt">seismicity</span>. Most modern <span class="hlt">seismicity</span> in western New York and the Niagara Peninsula of Ontario occurs in apparent patterns of randomly dispersed <span class="hlt">activity</span>. The sole exception is a line of seven epicenters of small earthquakes that trend east from Attica, NY into the Rochester basement megablock. Earthquakes may be triggered at the intersections of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024330','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024330"><span><span class="hlt">Seismic</span>-reflection profiles of the central part of the Clarendon-Linden <span class="hlt">fault</span> system of western New York in relation to regional <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fakundiny, R.H.; Pomeroy, P.W.</p> <p>2002-01-01</p> <p>Geological and geophysical research in upstate New York, with few exceptions, has not definitively associated <span class="hlt">seismicity</span> with specific Proterozoic basement or Paleozoic bedrock structures. The central part of the Clarendon-Linden <span class="hlt">fault</span> system (CLFS) between Batavia and Dale, NY is one of those exceptions where <span class="hlt">seismicity</span> has been studied and has been spatially associated with structure. The CLFS is either a complex system of long <span class="hlt">faults</span> with associated shorter branches and parallel segments, or a region of many short <span class="hlt">faults</span> aligned north-south from the Lake Ontario shore southward to Allegany County, NY. Interpretation of 38 km of Vibroseis and approximately 56 km of conventional <span class="hlt">seismic</span>-reflection data along 13 lines suggests that the CLFS is a broad zone of small <span class="hlt">faults</span> with small displacements in the lower Paleozoic bedrock section that is at least 77 km long and 7-17 km wide and spatially coincident with a northtrending geophysical (combined aeromagnetic and gravity) lineament within the basement. The relative offset across the <span class="hlt">faults</span> of the system is more than 91 m near Attica, NY. The CLFS is the expression of tectonic crustal adjustments within the Paleozoic rock above the boundary of two basement megablocks of differing petrologic provinces and differing earthquake characteristics that forms the eastern side of the Elzevir-Frontenac boundary zone. Deep <span class="hlt">seismic</span>-reflection profiles display concave-eastward listric <span class="hlt">faults</span> that probably merge at depth near the mid-crustal boundary layer. An interpretive vertical section provides the setting for refined definitions of the CLFS, its extensions at depth and its relation to <span class="hlt">seismicity</span>. Most modern <span class="hlt">seismicity</span> in western New York and the Niagara Peninsula of Ontario occurs in apparent patterns of randomly dispersed <span class="hlt">activity</span>. The sole exception is a line of seven epicenters of small earthquakes that trend east from Attica, NY into the Rochester basement megablock. Earthquakes may be triggered at the intersections of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70037704','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70037704"><span>Shallow subsurface structure of the Wasatch <span class="hlt">fault</span>, Provo segment, Utah, from integrated compressional and shear-wave <span class="hlt">seismic</span> reflection profiles with implications for <span class="hlt">fault</span> structure and development</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McBride, J.H.; Stephenson, W.J.; Williams, R.A.; Odum, J.K.; Worley, D.M.; South, J.V.; Brinkerhoff, A.R.; Keach, R.W.; Okojie-Ayoro, A. O.</p> <p>2010-01-01</p> <p>Integrated vibroseis compressional and experimental hammer-source, shear-wave, <span class="hlt">seismic</span> reflection profiles across the Provo segment of the Wasatch <span class="hlt">fault</span> zone in Utah reveal near-surface and shallow bedrock structures caused by geologically recent deformation. Combining information from the <span class="hlt">seismic</span> surveys, geologic mapping, terrain analysis, and previous <span class="hlt">seismic</span> first-arrival modeling provides a well-constrained cross section of the upper ~500 m of the subsurface. <span class="hlt">Faults</span> are mapped from the surface, through shallow, poorly consolidated deltaic sediments, and cutting through a rigid bedrock surface. The new <span class="hlt">seismic</span> data are used to test hypotheses on changing <span class="hlt">fault</span> orientation with depth, the number of subsidiary <span class="hlt">faults</span> within the <span class="hlt">fault</span> zone and the width of the <span class="hlt">fault</span> zone, and the utility of integrating separate elastic methods to provide information on a complex structural zone. Although previous surface mapping has indicated only a few <span class="hlt">faults</span>, the <span class="hlt">seismic</span> section shows a wider and more complex deformation zone with both synthetic and antithetic normal <span class="hlt">faults</span>. Our study demonstrates the usefulness of a combined shallow and deeper penetrating geophysical survey, integrated with detailed geologic mapping to constrain subsurface <span class="hlt">fault</span> structure. Due to the complexity of the <span class="hlt">fault</span> zone, accurate <span class="hlt">seismic</span> velocity information is essential and was obtained from a first-break tomography model. The new constraints on <span class="hlt">fault</span> geometry can be used to refine estimates of vertical versus lateral tectonic movements and to improve <span class="hlt">seismic</span> hazard assessment along the Wasatch <span class="hlt">fault</span> through an urban area. We suggest that earthquake-hazard assessments made without <span class="hlt">seismic</span> reflection imaging may be biased by the previous mapping of too few <span class="hlt">faults</span>. ?? 2010 Geological Society of America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.6919K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.6919K"><span>Project DAFNE - Drilling <span class="hlt">Active</span> <span class="hlt">Faults</span> in Northern Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kukkonen, I. T.; Ask, M. S. V.; Olesen, O.</p> <p>2012-04-01</p> <p>We are currently developing a new ICDP project 'Drillling <span class="hlt">Active</span> <span class="hlt">Faults</span> in Northern Europe' (DAFNE) which aims at investigating, via scientific drilling, the tectonic and structural characteristics of postglacial (PG) <span class="hlt">faults</span> in northern Fennoscandia, including their hydrogeology and associated deep biosphere [1, 2]. During the last stages of the Weichselian glaciation (ca. 9,000 - 15,000 years B.P.), reduced ice load and glacially affected stress field resulted in <span class="hlt">active</span> <span class="hlt">faulting</span> in Fennoscandia with <span class="hlt">fault</span> scarps up to 160 km long and 30 m high. These postglacial (PG) <span class="hlt">faults</span> are usually SE dipping, SW-NE oriented thrusts, and represent reactivated, pre-existing crustal discontinuities. Postglacial <span class="hlt">faulting</span> indicates that the glacio-isostatic compensation is not only a gradual viscoelastic phenomenon, but includes also unexpected violent earthquakes, suggestively larger than other known earthquakes in stable continental regions. The research is anticipated to advance science in neotectonics, hydrogeology and deep biosphere studies, and provide important information for nuclear waste and CO2 disposal, petroleum exploration on the Norwegian continental shelf and studies of mineral resources in PG <span class="hlt">fault</span> areas. We expect that multidisciplinary research applying shallow and deep drilling of postglacial <span class="hlt">faults</span> would provide significant scientific results through generating new data and models, namely: (1) Understanding PG <span class="hlt">fault</span> genesis and controls of their locations; (2) Deep structure and depth extent of PG <span class="hlt">faults</span>; (3) Textural, mineralogical and physical alteration of rocks in the PG <span class="hlt">faults</span>; (4) State of stress and estimates of paleostress of PG <span class="hlt">faults</span>; (5) Hydrogeology, hydrochemistry and hydraulic properties of PG <span class="hlt">faults</span>; (6) Dating of tectonic reactivation(s) and temporal evolution of tectonic systems hosting PG <span class="hlt">faults</span>; (7) Existence/non-existence of deep biosphere in PG <span class="hlt">faults</span>; (8) Data useful for planning radioactive waste disposal in crystalline bedrock; (9) Data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6998M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6998M"><span>Determination of paleoseismic <span class="hlt">activity</span> over a large time-scale: <span class="hlt">Fault</span> scarp dating with 36Cl</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mozafari Amiri, Nasim; Tikhomirov, Dmitry; Sümer, Ökmen; Özkaymak, Çaǧlar; Uzel, Bora; Ivy-Ochs, Susan; Vockenhuber, Christof; Sözbilir, Hasan; Akçar, Naki</p> <p>2016-04-01</p> <p>Bedrock <span class="hlt">fault</span> scarps are the most direct evidence of past earthquakes to reconstruct <span class="hlt">seismic</span> <span class="hlt">activity</span> in a large time-scale using cosmogenic 36Cl dating if built in carbonates. For this method, a surface along the <span class="hlt">fault</span> scarp with a minimum amount of erosion is required to be chosen as an ideal target point. The section of the <span class="hlt">fault</span> selected for sampling should cover at least two meters of the <span class="hlt">fault</span> surface from the lower part of the scarp, where intersects with colluvium wedge. Ideally, sampling should be performed on a continuous strip along the direction of the <span class="hlt">fault</span> slip direction. First, samples of 10 cm high and 15 cm wide are marked on the <span class="hlt">fault</span> surface. Then, they are collected using cutters, hammer and chisel in a thickness of 3 cm. The main geometrical factors of scarp dip, scarp height, top surface dip and colluvium dip are also measured. Topographic shielding in the sampling spot is important to be estimated as well. Moreover, density of the <span class="hlt">fault</span> scarp and colluvium are calculated. The physical and chemical preparations are carried in laboratory for AMS and chemical analysis of the samples. A Matlab® code is used for modelling of <span class="hlt">seismically</span> <span class="hlt">active</span> periods based on increasing production rate of 36Cl following each rupture, when a buried section of a <span class="hlt">fault</span> is exposed. Therefore, by measuring the amount of cosmogenic 36Cl versus height, the timing of major ruptures and their offsets are determined. In our study, Manastır, Mugırtepe and Rahmiye <span class="hlt">faults</span> in Gediz graben, Priene-Sazlı, Kalafat and Yavansu <span class="hlt">faults</span> in Büyük Menderes graben and Ören <span class="hlt">fault</span> in Gökava half-graben have been examined in the <span class="hlt">seismically</span> <span class="hlt">active</span> region of Western Turkey. Our results reconstruct at least five periods of high <span class="hlt">seismic</span> <span class="hlt">activity</span> during the Holocene time, three of which reveal <span class="hlt">seismic</span> ruptures beyond the historical pre-existing data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994GeoRL..21.2637M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994GeoRL..21.2637M"><span>Scaling of intraplate earthquake recurrence interval with <span class="hlt">fault</span> length and implications for <span class="hlt">seismic</span> hazard assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marrett, Randall</p> <p>1994-12-01</p> <p>Consensus indicates that <span class="hlt">faults</span> follow power-law scaling, although significant uncertainty remains about the values of important parameters. Combining these scaling relationships with power-law scaling relationships for earthquakes suggests that intraplate earthquake recurrence interval scales with <span class="hlt">fault</span> length. Regional scaling data may be locally calibrated to yield a site-specific <span class="hlt">seismic</span> hazard assessment tool. Scaling data from small <span class="hlt">faults</span> (those that do not span the seismogenic layer) suggest that recurrence interval varies as a negative power of <span class="hlt">fault</span> length. Due to uncertainties regarding the recently recognized changes in scaling for large earthquakes, it is unclear whether recurrence interval varies as a negative or positive power of <span class="hlt">fault</span> length for large fauts (those that span the seismogenic layer). This question is of critical importance for <span class="hlt">seismic</span> hazard assessment.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T23C4680K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T23C4680K"><span>Microstructural study of the partition between <span class="hlt">seismic</span> and aseismic deformation along the North Anatolian <span class="hlt">Fault</span> zone, Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaduri, M.; Gratier, J. P.; Renard, F.; Cakir, Z.; Lasserre, C.</p> <p>2014-12-01</p> <p>Along the North Anatolian <span class="hlt">Fault</span> (Turkey), <span class="hlt">fault</span> sliding is accommodated both by earthquakes and by aseismic creep. The creep processes develop either as transient (post-<span class="hlt">seismic</span> or interseismic) sliding or as permanent sliding along zones localized on specific segments of the <span class="hlt">fault</span>. Creep processes relax the stress and contribute to stress redistribution within the seismogenic zone. They participate to the deformation budget during the <span class="hlt">seismic</span> cycle, sometimes delaying or on the contrary helping triggering the occurrence of large earthquakes. Identifying the mechanisms controlling creep and their evolution with time and space represents a major challenge for predicting the mechanical evolution of <span class="hlt">active</span> <span class="hlt">faults</span>. Our goal is to answer three main questions: How to identify at the outcrop scale permanent creep from transient creep? Is aseismic creep controlled by lithology? How does creep evolve before and after earthquakes? The challenge is to understand which key parameters control the shift from <span class="hlt">seismic</span> to aseismic deformation, such as the effect of fabric, rock lithology, <span class="hlt">fault</span> roughness, strain-rate, fluid pressure or stress.We collected samples from a dozen of fresh and well-preserved <span class="hlt">fault</span> outcrops along creeping and locked segments of the North Anatolian <span class="hlt">Fault</span>. We used various methods such as microscopic and geological observations, SEM, XRD analysis, strain measurements from image processing approaches in order to quantitatively characterize the amount of deformation and the mechanisms involved. Results show different relationships between lithology and mechanisms of deformation: (i) Along the locked segments of the North Anatolian <span class="hlt">Fault</span>, in massive limestone, we found evidence of large earthquakes followed by pre- or post-<span class="hlt">seismic</span> (i.e. afterslip) creep. (ii) Along some creeping segments, we observed gouges with weak clay (saponite) that could accommodate (or have accommodated in the past) large permanent creep. (iii) Along other creeping segments, we observed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51G3012W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51G3012W"><span><span class="hlt">Fault</span> Kinematics and <span class="hlt">Seismic</span> Anisotropy Patterns in the Natron-Magadi Basins, Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weinstein, A.</p> <p>2015-12-01</p> <p>Early-stage continental rift zones provide important insights into the deformation behavior of crust and mantle lithosphere, and its modification by the migration of magma and volatiles. In East Africa, lower crustal earthquakes provide opportunities to probe the deformation behavior of the entire crust. We use a catalogue of 3068 earthquakes of 1 < ML < 4.5 recorded on a 39-station <span class="hlt">seismic</span> array spanning three 3 rift segments ( Magadi-Natron-Manyara) of the Eastern rift, Africa to determine kinematics of large offset border <span class="hlt">faults</span>, their along-strike linkage, and their possible interactions with tomographically imaged magma conduits and reservoirs beneath <span class="hlt">active</span> and dormant volcanoes. Earthquake focal mechanisms are predominantly NS-striking normal <span class="hlt">faults</span> with steep dips from near surface to 25 km in the Natron and Magadi basins, whereas the strike of normal <span class="hlt">faults</span> locally rotates to N60E at the northern tip of the Manyara border <span class="hlt">fault</span>. This rift-oblique structure links the Manyara border <span class="hlt">fault</span> to Gelai shield volcano via Oldoinyo Lengai volcano, and may be a zone of magma transfer. Crustal anisotropy measurements from lower crustal earthquakes provide information on the orientation of fluid-filled cracks and any strain fabric. We compare our new crustal splitting observations with the rift parallel anisotropy determined by ambient noise tomography, and with mantle anisotropy patterns determined from SKS-splitting. Initial results of SKS-splitting (> 1 s) show both the NS and NE fast directions at different stations, suggesting that aligned melt-filled cracks contribute to the observed patterns, as in more evolved rift sectors, like the Ethiopian and Afar rifts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70023482','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70023482"><span>Imaging the Seattle <span class="hlt">Fault</span> Zone with high-resolution <span class="hlt">seismic</span> tomography</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Calvert, A.J.; Fisher, M.A.</p> <p>2001-01-01</p> <p>The Seattle <span class="hlt">fault</span>, which trends east-west through the greater Seattle metropolitan area, is a thrust <span class="hlt">fault</span> that, around 1100 years ago, produced a major earthquake believed to have had a magnitude greater than 7. We present the first high resolution image of the shallow P wave velocity variation across the <span class="hlt">fault</span> zone obtained by tomographic inversion of first arrivals recorded on a <span class="hlt">seismic</span> reflection profile shot through Puget Sound adjacent to Seattle. The velocity image shows that above 500 m depth the <span class="hlt">fault</span> zone extending beneath Seattle comprises three distinct <span class="hlt">fault</span> splays, the northernmost of which dips to the south at around 60??. The degree of uplift of Tertiary rocks within the <span class="hlt">fault</span> zone suggests that the slip-rate along the northernmost splay during the Quaternary is 0.5 mm a-1, which is twice the average slip-rate of the Seattle <span class="hlt">fault</span> over the last 40 Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10128177','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10128177"><span>Groundwater penetrating radar and high resolution <span class="hlt">seismic</span> for locating shallow <span class="hlt">faults</span> in unconsolidated sediments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wyatt, D.E. |; Waddell, M.G.; Sexton, B.G.</p> <p>1993-12-31</p> <p><span class="hlt">Faults</span> in shallow, unconsolidated sediments, particularly in coastal plain settings, are very difficult to discern during subsurface exploration yet have critical impact to groundwater flow, contaminant transport and geotechnical evaluations. This paper presents a case study using cross-over geophysical technologies in an area where shallow <span class="hlt">faulting</span> is probable and known contamination exists. A comparison is made between Wenner and dipole-dipole resistivity data, ground penetrating radar, and high resolution <span class="hlt">seismic</span> data. Data from these methods were verified with a cone penetrometer investigation for subsurface lithology and compared to existing monitoring well data. Interpretations from these techniques are compared with actual and theoretical shallow <span class="hlt">faulting</span> found in the literature. The results of this study suggests that (1) the CPT study, combined with the monitoring well data may suggest that discontinuities in correlatable zones may indicate that <span class="hlt">faulting</span> is present (2) the addition of the Wenner and dipole-dipole data may further suggest that offset zones exist in the shallow subsurface but not allow specific <span class="hlt">fault</span> planes or <span class="hlt">fault</span> stranding to be mapped (3) the high resolution <span class="hlt">seismic</span> data will image <span class="hlt">faults</span> to within a few feet of the surface but does not have the resolution to identify the <span class="hlt">faulting</span> on the scale of our models, however it will suggest locations for upward continuation of <span class="hlt">faulted</span> zones (4) offset 100 MHz and 200 MHz CMP GPR will image zones and features that may be <span class="hlt">fault</span> planes and strands similar to our models (5) 300 MHz GPR will image higher resolution features that may suggest the presence of deeper <span class="hlt">faults</span> and strands, and (6) the combination of all of the tools in this study, particularly the GPR and <span class="hlt">seismic</span> may allow for the mapping of small scale, shallow <span class="hlt">faulting</span> in unconsolidated sediments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4877B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4877B"><span>Late Pleistocene to Present - normal and strike slip - <span class="hlt">faulting</span> in the western Gulf of Corinth; data from high resolution <span class="hlt">seismic</span> reflection SISCOR surveys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beckers, Arnaud; Bodeux, Sarah; Beck, Christian; Hubert-Ferrari, Aurélia; Tripsanas, Efthymios; Sakellariou, Dimitris; De Batist, Marc; De Rycker, Koen; Bascou, Pascale; Versteeg, Willem</p> <p>2013-04-01</p> <p>The Gulf of Corinth is one of the fastest-spreading intracontinental rift on Earth, a 120km long E-W structure propagating westward toward the Aegean subduction zone. Present day kinematics (GPS data) indicates an opening direction oriented NNE-SSW and an opening rate increasing westward from 11 mm y-1 in the central part to 16 mm y-1 in the westernmost part. The high extension rate in the western part of the rift would imply a high <span class="hlt">seismic</span> hazard if <span class="hlt">faults</span> are not creeping. Our work concerns this western extremity of the Gulf of Corinth, for which we propose an accurate map of submarine <span class="hlt">faults</span>. The map is based on two high-resolution <span class="hlt">seismic</span> reflection surveys (single channel sparker) performed aboard HCMR's R/V ALKYON, within the frame of SISCOR ANR Project. About 600 km of <span class="hlt">seismic</span> lines were acquired, with a 200 mstwt maximum penetration, down to what we infer to represent the MIS 5 discontinuity. The highlighted <span class="hlt">faults</span> network can be described as follows. In the eastern part, where the water depth reaches 450m, the sedimentary infill is <span class="hlt">faulted</span> by the known North Eratini, South Eratini and West Channel <span class="hlt">faults</span>. At the longitude of the Trizonia Island, the seafloor in mainly horizontal and the only <span class="hlt">fault</span> is the south dipping Trizonia <span class="hlt">fault</span>. Between the Trizonia Island and the Mornos Delta, the shallower northern part of the gulf shows a diffuse pattern of deformation with <span class="hlt">faults</span> striking mainly E-W and ESE-WNW. It shows south and north dipping normal <span class="hlt">faults</span>, strike-slip <span class="hlt">faults</span>, as well as an inherited basement relief. To the south of this complex <span class="hlt">fault</span> network, numerous mass transport deposits coming from the Mornos Delta and from steep slopes at the western end of the Trizonia <span class="hlt">fault</span> make the identification of <span class="hlt">active</span> <span class="hlt">faults</span> difficult. In the southern part of the rift, no <span class="hlt">fault</span> has been observed between the Psatopyrgos <span class="hlt">fault</span> bounding the southern side of the Gulf and the Mornos Delta. To the West, between the Mornos Delta and the Rion Straits, three main south</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AnGp...59..102A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AnGp...59..102A"><span>Variation of the Earth tide-<span class="hlt">seismicity</span> compliance parameter during the recent <span class="hlt">seismic</span> <span class="hlt">activity</span> in Fthiotida, central Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arabelos, Dimitrios N.; Contadakis, Michael E.; Vergos, Georgios; Spatalas, Spyrous</p> <p>2016-01-01</p> <p>Based on the results of our previous studies concerning the tidal triggering effect on the <span class="hlt">seismicity</span> in Greece, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality, associated with earthquake occurrence. Then, we investigate whether the recent increase in the <span class="hlt">seismic</span> <span class="hlt">activity</span> at Fthiotida in Greek mainland indicates <span class="hlt">faulting</span> maturity and the possible production a stronger earthquake. In this paper we present the results of this investigation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NHESS..12.3255G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NHESS..12.3255G"><span>Acoustic and <span class="hlt">seismic</span> imaging of the Adra <span class="hlt">Fault</span> (NE Alboran Sea): in search of the source of the 1910 Adra earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gràcia, E.; Bartolome, R.; Lo Iacono, C.; Moreno, X.; Stich, D.; Martínez-Diaz, J. J.; Bozzano, G.; Martínez-Loriente, S.; Perea, H.; Diez, S.; Masana, E.; Dañobeitia, J. J.; Tello, O.; Sanz, J. L.; Carreño, E.; Event-Shelf Team</p> <p>2012-11-01</p> <p>Recently acquired swath-bathymetry data and high-resolution <span class="hlt">seismic</span> reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW-SE trending 20 km-long <span class="hlt">fault</span>, which we termed the Adra <span class="hlt">Fault</span>. <span class="hlt">Seismic</span> imaging across the structure depicts a sub-vertical <span class="hlt">fault</span> reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic <span class="hlt">activity</span>. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra <span class="hlt">Fault</span> agree with the <span class="hlt">fault</span> solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The <span class="hlt">fault</span> <span class="hlt">seismic</span> parameters indicate that the Adra <span class="hlt">Fault</span> is a potential source of large magnitude (Mw ≤ 6.5) earthquakes, which represents an unreported <span class="hlt">seismic</span> hazard for the neighbouring coastal areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019979','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019979"><span><span class="hlt">Seismic</span> interpretation of the deep structure of the Wabash Valley <span class="hlt">Fault</span> System</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bear, G.W.; Rupp, J.A.; Rudman, A.J.</p> <p>1997-01-01</p> <p>Interpretations of newly available <span class="hlt">seismic</span> reflection profiles near the center of the Illinois Basin indicate that the Wabash Valley <span class="hlt">Fault</span> System is rooted in a series of basement-penetrating <span class="hlt">faults</span>. The <span class="hlt">fault</span> system is composed predominantly of north-northeast-trending high-angle normal <span class="hlt">faults</span>. The largest <span class="hlt">faults</span> in the system bound the 22-km wide 40-km long Grayville Graben. Structure contour maps drawn on the base of the Mount Simon Sandstone (Cambrian System) and a deeper pre-Mount Simon horizon show dip-slip displacements totaling at least 600 meters across the New Harmony <span class="hlt">fault</span>. In contrast to previous interpretations, the N-S extent of significant <span class="hlt">fault</span> offsets is restricted to a region north of 38?? latitude and south of 38.35?? latitude. This suggests that the graben is not a NE extension of the structural complex composed of the Rough Creek <span class="hlt">Fault</span> System and the Reelfoot Rift as previously interpreted. Structural complexity on the graben floor also decreases to the south. Structural trends north of 38?? latitude are offset laterally across several large <span class="hlt">faults</span>, indicating strike-slip motions of 2 to 4 km. Some of the major <span class="hlt">faults</span> are interpreted to penetrate to depths of 7 km or more. Correlation of these <span class="hlt">faults</span> with steep potential field gradients suggests that the <span class="hlt">fault</span> positions are controlled by major lithologic contacts within the basement and that the <span class="hlt">faults</span> may extend into the depth range where earthquakes are generated, revealing a potential link between specific <span class="hlt">faults</span> and recently observed low-level <span class="hlt">seismicity</span> in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14657494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14657494"><span>A look inside the San Andreas <span class="hlt">Fault</span> at Parkfield through vertical <span class="hlt">seismic</span> profiling.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chavarria, J Andres; Malin, Peter; Catchings, Rufus D; Shalev, Eylon</p> <p>2003-12-05</p> <p>The San Andreas <span class="hlt">Fault</span> Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas <span class="hlt">fault</span>. This observatory includes a vertical <span class="hlt">seismic</span> profiling (VSP) array. VSP seismograms from nearby microearthquakes contain signals between the P and S waves. These signals may be P and S waves scattered by the local geologic structure. The collected scattering points form planar surfaces that we interpret as the San Andreas <span class="hlt">fault</span> and four other secondary <span class="hlt">faults</span>. The scattering process includes conversions between P and S waves, the strengths of which suggest large contrasts in material properties, possibly indicating the presence of cracks or fluids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025044','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025044"><span>A Look Inside the San Andreas <span class="hlt">fault</span> at Parkfield Through Vertical <span class="hlt">Seismic</span> Profiling</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chavarria, J.A.; Malin, P.; Catchings, R.D.; Shalev, E.</p> <p>2003-01-01</p> <p>The San Andreas <span class="hlt">Fault</span> Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas <span class="hlt">fault</span>. This observatory includes a vertical <span class="hlt">seismic</span> profiling (VSP) array. VSP seismograms from nearby micro-earthquakes contain signals between the P and S waves. These signals may be P and S waves scattered by the local geologic structure. The collected scattering points form planar surfaces that we interpret as the San Andreas <span class="hlt">fault</span> and four other secondary <span class="hlt">faults</span>. The scattering process includes conversions between P and S waves, the strengths of which suggest large contrasts in material properties, possibly indicating the presence of cracks or fluids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6240843','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6240843"><span><span class="hlt">Seismicity</span>, crustal structure, and tectonics near the northern termination of the San Andreas <span class="hlt">fault</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Knapp, J.S.</p> <p>1982-01-01</p> <p>Further evidence supporting the supposition that a triple junction has existed near Cape Mendocino in Late Cenezoic time was provided by the discovery of a layer of <span class="hlt">seismic</span> <span class="hlt">activity</span> dipping 12/sup 0/ beneath the continent north of the Mendocino fracture. A <span class="hlt">seismic</span> refraction profile shot along the continental slope and onshore velocity modeling confirms that this layer of earthquakes is confined within subducted oceanic layers 2 and 3. In this region, layer 2 appears to be slightly thickened and layer 3 anomalously thin. Travel time delays from offshore explosions and from teleseismically-recorded earthquakes indicate the presence of a large velocity discontinuity as great as 10% across the Mendocino escarpment represents the juxtaposition of two distinct lithospheric plates. The tectonic development of the region seems, however, to be shifting away from a stable triple junction configuration. Because the spreading direction at the Gorda ridge is no longer parallel to the Mendocino fracture, the Gorda plate is breaking up along a complex series of left-lateral, northeast-trending <span class="hlt">faults</span>, as suggested by the high level of intraplate <span class="hlt">seismicity</span> and by some aftershock distributions. By asymmetric spreading, the Gorda and Juan de Fuca ridges are undergoing clockwise rotation to bring them into alignment with the San Andreas-East Pacific rise system, eventually leading to the cessation of subduction beneath the northern California, Oregon, and Washington coasts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SMaS...24l5030Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SMaS...24l5030Y"><span>Sliding mode <span class="hlt">fault</span> detection and <span class="hlt">fault</span>-tolerant control of smart dampers in semi-<span class="hlt">active</span> control of building structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yeganeh Fallah, Arash; Taghikhany, Touraj</p> <p>2015-12-01</p> <p>Recent decades have witnessed much interest in the application of <span class="hlt">active</span> and semi-<span class="hlt">active</span> control strategies for <span class="hlt">seismic</span> protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its <span class="hlt">fault</span> detection observer and <span class="hlt">fault</span>-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ <span class="hlt">faults</span> which are used for calculating a <span class="hlt">fault</span> distribution matrix. Then the <span class="hlt">fault</span>-tolerant sliding mode controller reconfigures itself by the <span class="hlt">fault</span> distribution matrix and accommodates the <span class="hlt">fault</span> effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed <span class="hlt">fault</span>-tolerant control system. It was shown that the <span class="hlt">fault</span>-tolerant control system maintains the performance of the structure at an acceptable level in the post-<span class="hlt">fault</span> case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ExG....45..223Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ExG....45..223Z"><span><span class="hlt">Fault</span> and dyke detectability in high resolution <span class="hlt">seismic</span> surveys for coal: a view from numerical modelling*</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Binzhong </name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref><xref ref-type="aff" rid="aff3"><sup>3</sup></xref><contrib contrib-type="author"><name>Hatherly, Peter</p> <p>2014-10-01</p> <p>Modern underground coal mining requires certainty about geological <span class="hlt">faults</span>, dykes and other structural features. <span class="hlt">Faults</span> with throws of even just a few metres can create safety issues and lead to costly delays in mine production. In this paper, we use numerical modelling in an ideal, noise-free environment with homogeneous layering to investigate the detectability of small <span class="hlt">faults</span> by <span class="hlt">seismic</span> reflection surveying. If the layering is horizontal, <span class="hlt">faults</span> with throws of 1/8 of the wavelength should be detectable in a 2D survey. In a coal mining setting where the <span class="hlt">seismic</span> velocity of the overburden ranges from 3000 m/s to 4000 m/s and the dominant <span class="hlt">seismic</span> frequency is ~100 Hz, this corresponds to a <span class="hlt">fault</span> with a throw of 4-5 m. However, if the layers are dipping or folded, the <span class="hlt">faults</span> may be more difficult to detect, especially when their throws oppose the trend of the background structure. In the case of 3D <span class="hlt">seismic</span> surveying we suggest that <span class="hlt">faults</span> with throws as small as 1/16 of wavelength (2-2.5 m) can be detectable because of the benefits offered by computer-aided horizon identification and the improved spatial coherence in 3D <span class="hlt">seismic</span> surveys. With dykes, we find that Berkhout's definition of the Fresnel zone is more consistent with actual experience. At a depth of 500 m, which is typically encountered in coal mining, and a 100 Hz dominant <span class="hlt">seismic</span> frequency, dykes less than 8 m in width are undetectable, even after migration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.S51C1445S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.S51C1445S"><span>Coulomb Stress evolution and <span class="hlt">seismic</span> hazard along the Xianshuihe-Xiaojiang <span class="hlt">Fault</span> Zone of Western Sichuan, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shan, B.; Xiong, X.; Zheng, Y.</p> <p>2009-12-01</p> <p>The Xianshuihe-Xiaojiang <span class="hlt">fault</span> system (XXFS) in southwestern China is a curved left-lateral strike-slip structure extending at least 1400 km in the eastern margin of the Tibetan Plateau. Fieldworks confirm that the XXFS, whose slip motion releases strain that is related to the convergence between the Indian and Eurasian plates, is one of the largest and most <span class="hlt">seismically</span> <span class="hlt">active</span> <span class="hlt">faults</span> in China. The entire <span class="hlt">fault</span> has experienced at least 35 earthquakes of M>6 since 1700, and almost all segments of the system have been the locus of major earthquakes within the historic record. Since the XXFS region is heavily populated (over 50 million people), understanding the distribution of large earthquakes in space and time in this region is crucial for improving forecasting and reducing catastrophic life and monetary losses. We investigated a sequence of twenty-five earthquakes (M≥6.5) that occurred along the XXFS since 1713, and the interaction between the historical earthquakes and the Mw7.9 Wenchuan earthquake occurred on the Longmenshan <span class="hlt">Fault</span> last year. The layered model used in the study and relevant parameters were constrained by <span class="hlt">seismic</span> studies. <span class="hlt">Fault</span> rupture locations and geometries, as well as slip distributions of earthquakes were taken from field observations and <span class="hlt">seismic</span> studies. Numerical results showed a good correlation between stress transfer, accumulation and earthquakes. Fourteen of the twenty-four earthquakes occurred after the 1713 Xundian were encouraged by the preceding earthquakes with positive stress loading. Three events occurred in the stress shadow induced by preceding events. And others occurred in the probable area with Coulomb stress increment. The triggering process on the <span class="hlt">fault</span> zone may exist. According to our results, there are three visible earthquake gaps along the <span class="hlt">fault</span> zone, which are consistent with the results of historical earthquake study. The <span class="hlt">seismic</span> <span class="hlt">activity</span> and tectonic motion on XXFS reduced the shear stress on the epicenter of M8</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005BVol...67..370T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005BVol...67..370T"><span><span class="hlt">Fault</span> textures in volcanic conduits: evidence for <span class="hlt">seismic</span> trigger mechanisms during silicic eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tuffen, Hugh; Dingwell, Don</p> <p>2005-04-01</p> <p> of volcano <span class="hlt">seismic</span> <span class="hlt">activity</span>. Based on the textures observed, it is suggested that patterns of long-period and hybrid earthquakes at silicic lava domes reflect friction-controlled stick-slip movement and eventual healing of <span class="hlt">fault</span> zones in magma, which are an accelerated and smaller-scale analogue of tectonic <span class="hlt">faults</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27256901','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27256901"><span>Resolving Fine-Scale Heterogeneity of Co-<span class="hlt">seismic</span> Slip and the Relation to <span class="hlt">Fault</span> Structure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Milliner, C W D; Sammis, C; Allam, A A; Dolan, J F; Hollingsworth, J; Leprince, S; Ayoub, F</p> <p>2016-06-03</p> <p><span class="hlt">Fault</span> slip distributions provide important insight into the earthquake process. We analyze high-resolution along-strike co-<span class="hlt">seismic</span> slip profiles of the 1992 Mw = 7.3 Landers and 1999 Mw = 7.1 Hector Mine earthquakes, finding a spatial correlation between fluctuations of the slip distribution and geometrical <span class="hlt">fault</span> structure. Using a spectral analysis, we demonstrate that the observed variation of co-<span class="hlt">seismic</span> slip is neither random nor artificial, but self-affine fractal and rougher for Landers. We show that the wavelength and amplitude of slip variability correlates to the spatial distribution of <span class="hlt">fault</span> geometrical complexity, explaining why Hector Mine has a smoother slip distribution as it occurred on a geometrically simpler <span class="hlt">fault</span> system. We propose as a physical explanation that <span class="hlt">fault</span> complexity induces a heterogeneous stress state that in turn controls co-<span class="hlt">seismic</span> slip. Our observations detail the fundamental relationship between <span class="hlt">fault</span> structure and earthquake rupture behavior, allowing for modeling of realistic slip profiles for use in <span class="hlt">seismic</span> hazard assessment and paleoseismology studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4891690','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4891690"><span>Resolving Fine-Scale Heterogeneity of Co-<span class="hlt">seismic</span> Slip and the Relation to <span class="hlt">Fault</span> Structure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Milliner, C. W. D.; Sammis, C.; Allam, A. A.; Dolan, J. F.; Hollingsworth, J.; Leprince, S.; Ayoub, F.</p> <p>2016-01-01</p> <p><span class="hlt">Fault</span> slip distributions provide important insight into the earthquake process. We analyze high-resolution along-strike co-<span class="hlt">seismic</span> slip profiles of the 1992 Mw = 7.3 Landers and 1999 Mw = 7.1 Hector Mine earthquakes, finding a spatial correlation between fluctuations of the slip distribution and geometrical <span class="hlt">fault</span> structure. Using a spectral analysis, we demonstrate that the observed variation of co-<span class="hlt">seismic</span> slip is neither random nor artificial, but self-affine fractal and rougher for Landers. We show that the wavelength and amplitude of slip variability correlates to the spatial distribution of <span class="hlt">fault</span> geometrical complexity, explaining why Hector Mine has a smoother slip distribution as it occurred on a geometrically simpler <span class="hlt">fault</span> system. We propose as a physical explanation that <span class="hlt">fault</span> complexity induces a heterogeneous stress state that in turn controls co-<span class="hlt">seismic</span> slip. Our observations detail the fundamental relationship between <span class="hlt">fault</span> structure and earthquake rupture behavior, allowing for modeling of realistic slip profiles for use in <span class="hlt">seismic</span> hazard assessment and paleoseismology studies. PMID:27256901</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...627201M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...627201M"><span>Resolving Fine-Scale Heterogeneity of Co-<span class="hlt">seismic</span> Slip and the Relation to <span class="hlt">Fault</span> Structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Milliner, C. W. D.; Sammis, C.; Allam, A. A.; Dolan, J. F.; Hollingsworth, J.; Leprince, S.; Ayoub, F.</p> <p>2016-06-01</p> <p><span class="hlt">Fault</span> slip distributions provide important insight into the earthquake process. We analyze high-resolution along-strike co-<span class="hlt">seismic</span> slip profiles of the 1992 Mw = 7.3 Landers and 1999 Mw = 7.1 Hector Mine earthquakes, finding a spatial correlation between fluctuations of the slip distribution and geometrical <span class="hlt">fault</span> structure. Using a spectral analysis, we demonstrate that the observed variation of co-<span class="hlt">seismic</span> slip is neither random nor artificial, but self-affine fractal and rougher for Landers. We show that the wavelength and amplitude of slip variability correlates to the spatial distribution of <span class="hlt">fault</span> geometrical complexity, explaining why Hector Mine has a smoother slip distribution as it occurred on a geometrically simpler <span class="hlt">fault</span> system. We propose as a physical explanation that <span class="hlt">fault</span> complexity induces a heterogeneous stress state that in turn controls co-<span class="hlt">seismic</span> slip. Our observations detail the fundamental relationship between <span class="hlt">fault</span> structure and earthquake rupture behavior, allowing for modeling of realistic slip profiles for use in <span class="hlt">seismic</span> hazard assessment and paleoseismology studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10130228','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10130228"><span>Pen Branch <span class="hlt">fault</span> program: Consolidated report on the <span class="hlt">seismic</span> reflection surveys and the shallow drilling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stieve, A.L.; Stephenson, D.E.; Aadland, R.K.</p> <p>1991-03-23</p> <p>The Pen Branch <span class="hlt">fault</span> was identified in the subsurface at the Savannah River Site (SRS) in 1989 based upon interpretation of earlier <span class="hlt">seismic</span> reflection surveys and other geologic investigations (Seismorgraph Services Incorp., 1973; Chapman and DiStefano, 1989; Snipes, Fallaw and Price, 1989). A program was initiated at that time to determine the capability of the <span class="hlt">fault</span> to release <span class="hlt">seismic</span> energy (Price and others, 1989) as defined in the Nuclear Regulatory Commission regulatory guidelines, 10 CFR 100 Appendix A. This report presents the results of the Pen Branch <span class="hlt">fault</span> investigation based on data acquired from <span class="hlt">seismic</span> reflection surveys and shallow drilling across the <span class="hlt">fault</span> completed at this time. The Earth Science Advisory Committee (ESAC) has reviewed the results of these investigations and unanimously agrees with the conclusion of Westinghouse Savannah River Company (WSRC) that the Pen Branch <span class="hlt">fault</span> is a non-capable <span class="hlt">fault</span>. ESAC is a committee of 12 earth science professionals from academia and industry with the charter of providing outside peer review of SRS geotechnical, <span class="hlt">seismic</span>, and ground water modeling programs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.S51C1019P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.S51C1019P"><span>Anatomy of a Complex <span class="hlt">Fault</span> Zone: Land <span class="hlt">Seismic</span> Reflection Imaging of the Tacoma <span class="hlt">Fault</span> Zone, Washington State</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pape, K.; Liberty, L. M.; Pratt, T. L.</p> <p>2005-12-01</p> <p>Preliminary interpretations of new land-based <span class="hlt">seismic</span> reflection images across the Tacoma <span class="hlt">fault</span> zone in western Washington State document a complex pattern of <span class="hlt">faulting</span> and folding. The Tacoma <span class="hlt">fault</span> zone bounds gravity and aeromagnetic anomalies for 50 km across the central Puget Lowland west of the city of Tacoma, and tomography data suggest there is as much as 6 km of post-Eocene uplift of the hanging wall relative to Tacoma basin sediments to the south. We acquired four north-south <span class="hlt">seismic</span> reflection profiles to define the character and tectonic history of the Tacoma <span class="hlt">fault</span> zone. The 6-km long Powerline Road profile, located west of Case Inlet, perpendicularly crosses the 4-km-long Catfish Lake scarp discerned from Lidar data and trenching. The profile shows flat-lying strata on the south, but the north part of the profile is dominated by south-dipping Tertiary and older strata that appear to form the limb of an anticline. There appears to be at least one, and likely two <span class="hlt">faults</span> in the Tertiary and older strata, although it is not clear these <span class="hlt">faults</span> penetrate the shallowest Pleistocene strata. The 8.5-km long Carney Lake profile is located east of Case Inlet and spans two scarps imaged on Lidar data. This profile shows a similar geometry to the Powerline Road profile, folded and <span class="hlt">faulted</span> Tertiary and older strata adjacent to flat-lying marine sediments of the Tacoma Basin. The 9-km long Bethel-Burley profile across the east portion of the Tacoma <span class="hlt">fault</span> near Gig Harbor shows a significantly different reflector geometry than the profiles to the west. The Bethel-Burley profile is dominated by a strong, south-dipping reflection that becomes a prominent arch near the north end of the section. The strength of the reflector suggests that it marks the top of the Eocene basement rocks. South-dipping strata on this profile match those imaged on marine profiles from Carr Inlet. The new <span class="hlt">seismic</span> reflection data support an interpretation in which the north edge of the Tacoma basin</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S54A..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S54A..05W"><span>Correlation between Induced <span class="hlt">Seismic</span> Events and Hydraulic Fracturing <span class="hlt">activities</span> in California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walker, R.; Aminzadeh, F.; Tiwari, A.</p> <p>2014-12-01</p> <p>Induced <span class="hlt">seismicity</span> observed in Oklahoma and Ohio have raised environmental concern to an alarming level and thus any plausible correlation between subsurface injection and production <span class="hlt">activities</span> have become an significant area of study. As per US <span class="hlt">Seismic</span> Hazard map, California lies in highly sensitive zone, which makes understanding of stimulation induced <span class="hlt">seismic</span> events critically important. The copious number of <span class="hlt">seismic</span> events due to presence of numerous <span class="hlt">faults</span> in California benefits understanding <span class="hlt">seismicity</span> of the region but makes it difficult to distinguish induced <span class="hlt">seismic</span> events from naturally occurring <span class="hlt">seismic</span> events. Since regional models are considered more effective in understanding the <span class="hlt">seismicity</span> of the region, this study aims in understanding impact of hydraulic fracturing <span class="hlt">activities</span> in various oilfields in California. The focus of the study is to identify sensitive zones in California which might have observed <span class="hlt">seismic</span> <span class="hlt">activities</span> induced due to hydraulic fracturing. This has been done using the criteria of spatial and temporal co-relation between fracturing <span class="hlt">activities</span> and <span class="hlt">seismic</span> events for oilfields with significant number of fracturing <span class="hlt">activities</span>. The <span class="hlt">seismic</span> and well data used for this study is acquired from public sources and have been integrated in an efficient manner using the GIS tool and iterative querying. The two step methodology implemented for this work involves segregating the induced <span class="hlt">seismic</span> events from natural events based on the depth of the event and <span class="hlt">seismic</span> history of the region and then spatially and temporally studying it with regards to hydraulic fracturing in vicinity of the <span class="hlt">seismic</span> event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.4506D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.4506D"><span><span class="hlt">Fault</span> structure, stress, or pressure control of the <span class="hlt">seismicity</span> in shale? Insights from a controlled experiment of fluid-induced <span class="hlt">fault</span> reactivation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Barros, Louis; Daniel, Guillaume; Guglielmi, Yves; Rivet, Diane; Caron, Hervé; Payre, Xavier; Bergery, Guillaume; Henry, Pierre; Castilla, Raymi; Dick, Pierre; Barbieri, Ernesto; Gourlay, Maxime</p> <p>2016-06-01</p> <p>Clay formations are present in reservoirs and earthquake <span class="hlt">faults</span>, but questions remain on their mechanical behavior, as they can vary from ductile (aseismic) to brittle (<span class="hlt">seismic</span>). An experiment, at a scale of 10 m, aims to reactivate a natural <span class="hlt">fault</span> by fluid pressure in shale materials. The injection area was surrounded by a dense monitoring network comprising pressure, deformation, and <span class="hlt">seismicity</span> sensors, in a well-characterized geological setting. Thirty-two microseismic events were recorded during several injection phases in five different locations within the <span class="hlt">fault</span> zone. Their computed magnitude ranged between -4.3 and -3.7. Their spatiotemporal distribution, compared with the measured displacement at the injection points, shows that most of the deformation induced by the injection is aseismic. Whether the <span class="hlt">seismicity</span> is controlled by the <span class="hlt">fault</span> architecture, mineralogy of fracture filling, fluid, and/or stress state is then discussed. The <span class="hlt">fault</span> damage zone architecture and mineralogy are of crucial importance, as <span class="hlt">seismic</span> slip mainly localizes on the sealed-with-calcite fractures which predominate in the <span class="hlt">fault</span> damage zone. As no <span class="hlt">seismicity</span> is observed in the close vicinity of the injection areas, the presence of fluid seems to prevent <span class="hlt">seismic</span> slips. The <span class="hlt">fault</span> core acts as an impermeable hydraulic barrier that favors fluid confinement and pressurization. Therefore, the <span class="hlt">seismic</span> behavior seems to be strongly sensitive to the structural heterogeneity (including permeability) of the <span class="hlt">fault</span> zone, which leads to a heterogeneous stress response to the pressurized volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51A2841F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51A2841F"><span>Generation of Billow-like Wavy Folds by Thermal Pressurization in a <span class="hlt">Seismic</span> Slip Plane of Nojima <span class="hlt">Fault</span> Gouge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukuzawa, T.; Nakamura, N.</p> <p>2015-12-01</p> <p>Nojima <span class="hlt">fault</span> gouge has recorded physical processes during <span class="hlt">seismic</span> slip, and one can find billow-like wavy folds along slip planes in the gouge. The fold patterns are similar to the ones of Kelvin Helmholtz (KH)-instability which occurs in fluid. Therefore, the presence of such folds suggests the fluidization of gouge materials. This instability occurs at the interface between two fluids of different densities shearing at different velocities (Thorpe, 2005), and in low viscous fluid (Woods, 1969). If a temperature range for the generation of such billow-like folds could be determined, we can constrain the weakening mechanism of frictional strength of <span class="hlt">faults</span>. Here we show rock magnetic studies to prove the temperature rise in the generation of the billow-like folds, using a scanning magneto-impedance magnetic microscope. Its results showed the folds and the slip zones have been magnetized by the production of magnetite through thermal decomposition of siderite in the gouge. The thermal decomposition of siderite generally occurs at over about 350℃. This heating implies that thermal pressurization or melting were the driving mechanism of <span class="hlt">faulting</span>. In order to clarify which mechanism mainly drove in the <span class="hlt">fault</span> gouge, we constrained the temperature and viscosity condition of each melting model and thermal pressurization model from the perspective of the existence of the KH-instability. The melting model generates no such instability because of high viscosity (10 Pa·s), even if we postulate relatively high temperature melting (1300℃). On the other hands, we found that the thermal pressurization model can forced the <span class="hlt">fault</span> slip zone very low viscosity (1.0×10-3 Pa·s) enough to generate KH-instability, which requires a shear stress of at most 0.25 Pa during <span class="hlt">faulting</span>. It is supposed that the existence of the low viscosity fluid and the frictional heating decreased the frictional strength of the Nojima <span class="hlt">fault</span> at an ancient large <span class="hlt">seismic</span> <span class="hlt">activity</span>, accelerating the <span class="hlt">fault</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S31F..06A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S31F..06A"><span>Identifying induced <span class="hlt">seismicity</span> in <span class="hlt">active</span> tectonic regions: A case study of the San Joaquin Basin, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aminzadeh, F.; Göbel, T.</p> <p>2013-12-01</p> <p>Understanding the connection between petroleum-industry <span class="hlt">activities</span>, and <span class="hlt">seismic</span> event occurrences is essential to monitor, quantify, and mitigate <span class="hlt">seismic</span> risk. While many studies identified anthropogenically-induced <span class="hlt">seismicity</span> in intraplate regions where background <span class="hlt">seismicity</span> rates are generally low, little is known about how to distinguish naturally occurring from induced <span class="hlt">seismicity</span> in <span class="hlt">active</span> tectonic regions. Further, it is not clear how different oil and gas operational parameters impact the frequency and magnitude of the induced <span class="hlt">seismic</span> events. Here, we examine variations in frequency-size and spatial distributions of <span class="hlt">seismicity</span> within the Southern Joaquin basin, an area of both <span class="hlt">active</span> petroleum production and <span class="hlt">active</span> <span class="hlt">fault</span> systems. We analyze a newly available, high-quality, relocated earthquake catalog (Hauksson et al. 2012). This catalog includes many <span class="hlt">seismic</span> events with magnitudes up to M = 4.5 within the study area. We start by analyzing the overall quality and consistence of the <span class="hlt">seismic</span> catalog, focusing on temporal variations in <span class="hlt">seismicity</span> rates and catalog completeness which could indicate variations in network sensitivity. This catalog provides relatively homogeneous earthquake recordings after 1981, enabling us to compare <span class="hlt">seismicity</span> rates before and after the beginning of more pervasive petroleum-industry <span class="hlt">activities</span>, for example, hydraulic-fracturing and waste-water disposals. We conduct a limited study of waste-water disposal wells to establish a correlation between <span class="hlt">seismicity</span> statistics (i.e. rate changes, fractal dimension, b-value) within specific regions and anthropogenic influences. We then perform a regional study, to investigate spatial variations in <span class="hlt">seismicity</span> statistics which are then correlated to oil field locations and well densities. In order to distinguish, predominantly natural <span class="hlt">seismicity</span> from induced <span class="hlt">seismicity</span>, we perform a spatial mapping of b-values and fractal dimensions of earthquake hypocenters. <span class="hlt">Seismic</span> events in the proximity to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.4657K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.4657K"><span>Monitoring of low-energy <span class="hlt">seismic</span> <span class="hlt">activity</span> in Elbrus volcanic area with the use of underground <span class="hlt">seismic</span> array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kovalevsky, V.; Sobisevitch, A.</p> <p>2012-04-01</p> <p>Results of experiment with underground <span class="hlt">seismic</span> array for studying low-energy <span class="hlt">seismic</span> <span class="hlt">activity</span> in the Elbrus volcanic area are presented. Linear <span class="hlt">seismic</span> array of 2.5 km aperture is created in the tunnel of Baksan neutrino observatory. Horizontal tunnel of 4.3 km length is drilled in the mount Andyrchi at a distance of 20 km from Elbrus volcano. Array includes 6 three-component <span class="hlt">seismic</span> sensors with 24-byte recorders installed with 500 m interval one from another along the tunnel. Underground <span class="hlt">seismic</span> array is the new instrument of geophysical observatory organized for studies of geophysical processes in the Elbrus volcanic area. The observatory equipped with modern geophysical instruments including broadband tri-axial seismometers, quartz tilt-meters, magnetic variometers, geo-acoustic sensors, hi-precision distributed thermal sensors and gravimeters. The initial analysis of <span class="hlt">seismic</span> signals recorded by <span class="hlt">seismic</span> array allows us to detect low-energy <span class="hlt">seismic</span> <span class="hlt">activity</span> in the Elbrus volcanic area beginning from the distance of 3-5 km (the <span class="hlt">faults</span> in a vicinity of mount Andyrchi) up to 15-25 km (area of Elbrus volcano). The regional micro-earthquakes with magnitude 1-2 at the distances 50-100 km was also recorded. 2.5 km aperture of the underground linear <span class="hlt">seismic</span> array make it possible to determine with high accuracy hypocenters of local <span class="hlt">seismic</span> events associated with geodynamic of volcanic magmatic structures and to realize seismo-emission tomography of the <span class="hlt">active</span> zones of Elbrus volcano.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840007560','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840007560"><span>Combined use of remote sensing and <span class="hlt">seismic</span> observations to infer geologically recent crustal deformation, <span class="hlt">active</span> <span class="hlt">faulting</span>, and stress fields. [California and Pennsylvania</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alexander, S. S. (Principal Investigator)</p> <p>1982-01-01</p> <p>Characteristic traits for earthquakes associated with strike-slip motion in Central California and the Salton Sea area, as revealed in ground based studies and LANDSAT imagery, were compared. The mapped lineaments are found to be oriented in several dominant directions. One direction is the same as the trend of the San Andreas <span class="hlt">fault</span>. The other directions differ from area to area and may reflect the stresses of earlier geologic processes. The pattern of lineament orientations is significantly LANDSAT MSS data, SEASAT synthetic aperture radar data, and magnetic field data from the South Mountain area west of Gettysburg, Pennsylvania were registered to match each other in spatial position and merged. Pattern recognition techniques were applied to the composite data set to determine its utility in recognizing different rock types and structures in vegetated terrain around South Mountain. With the use of a texture algorithm to enhance geologic features, a classification of the entire area was made. A test of the correlation between SAR tone and texture, LANDSAT tone and texture, and magnetic field data revealed no tone or texture measures linking any two of the original data sets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.S72F1352M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.S72F1352M"><span>Remotely Triggered <span class="hlt">Seismicity</span> at Alaskan Volcanoes Following the Mw 7.9 Denali <span class="hlt">Fault</span> Earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moran, S. C.; Sanchez, J. J.; Power, J. A.; Stihler, S. D.; McNutt, S. R.</p> <p>2002-12-01</p> <p>The November 3, 2002, Mw 7.9 Denali <span class="hlt">Fault</span> earthquake provided the largest source yet to investigate triggered earthquakes at Alaskan volcanoes. The Alaska Volcano Observatory (AVO) operates short-period <span class="hlt">seismic</span> networks on 24 historically <span class="hlt">active</span> volcanoes in Alaska, 280 - 2100 km distant from the mainshock epicenter. The magnitude detection thresholds for these networks range from M 0.1 to M 1.5. Previous instances of triggered <span class="hlt">seismicity</span> in Alaska have been recorded in the Katmai Volcanic Cluster, where a number of triggered events occurred following two large earthquakes on December 6, 1999 (60 km distant, Mw 7.0), and January 10, 2001 (35 km distant, Mw 6.8). We searched for evidence of triggered <span class="hlt">seismicity</span> by examining the unfiltered waveforms for all stations in each volcano network for ~1 hour following the Mw 7.9 arrival. We looked for events within the mainshock coda with discrete P and S arrivals and/or arrivals on multiple stations. We also looked at filtered waveforms for time periods of several hours before and after the mainshock. We only found compelling evidence for triggering at the Katmai Volcanic Cluster (720-755 km SW of the mainshock), where two small earthquakes with distinct P and S arrivals appeared in the mainshock coda at one station. There was also a small increase in located earthquakes at Katmai over a period of several hours following the mainshock. Although it is certainly possible that triggered earthquakes occurred at other volcanoes while networks were clipped, our analysis indicates that any triggering was minimal. This is in striking contrast to triggered <span class="hlt">seismicity</span> recorded at Yellowstone, Mammoth Mountain, The Geysers, Coso and possibly Mount Rainier following the Denali earthquake. The comparative lack of triggering could be a result of differences in size and/or <span class="hlt">activity</span> of geothermal systems, directivity of the mainshock, the dominant frequency at each system, and/or local site conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2006/1158/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2006/1158/"><span><span class="hlt">Seismic</span> constraints and coulomb stress changes of a blind thrust <span class="hlt">fault</span> system, 2: Northridge, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Stein, Ross S.; Lin, Jian</p> <p>2006-01-01</p> <p>We review <span class="hlt">seismicity</span>, surface <span class="hlt">faulting</span>, and Coulomb stress changes associated with the 1994 Northridge, California, earthquake. All of the observed surface <span class="hlt">faulting</span> is shallow, extending meters to tens of meters below the surface. Relocated aftershocks reveal no <span class="hlt">seismicity</span> shallower than 2 km depth. Although many of the aftershocks lie along the thrust <span class="hlt">fault</span> and its up-dip extension, there are also a significant number of aftershocks in the core of the gentle anticline above the thrust, and elsewhere on the up-thrown block. These aftershocks may be associated with secondary ramp thrusts or flexural slip <span class="hlt">faults</span> at a depth of 2-4 km. The geological structures typically associated with a blind thrust <span class="hlt">fault</span>, such as anticlinal uplift and an associated syncline, are obscured and complicated by surface thrust <span class="hlt">faults</span> associated with the San Fernando <span class="hlt">fault</span> that overly the Northridge structures. Thus the relationship of the geological structure and topography to the underlying thrust <span class="hlt">fault</span> is much more complex for Northridge than it is for the 1983 Coalinga, California, earthquake. We show from a Coulomb stress analysis that secondary surface <span class="hlt">faulting</span>, diffuse aftershocks, and triggered sequences of moderate-sized mainshocks, are expected features of moderate-sized blind thrust earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7838C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7838C"><span>Impact of <span class="hlt">fault</span> models on probabilistic <span class="hlt">seismic</span> hazard assessment: the example of the West Corinth rift.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chartier, Thomas; Scotti, Oona; Boiselet, Aurelien; Lyon-Caen, Hélène</p> <p>2016-04-01</p> <p>Including <span class="hlt">faults</span> in probabilistic <span class="hlt">seismic</span> hazard assessment tends to increase the degree of uncertainty in the results due to the intrinsically uncertain nature of the <span class="hlt">fault</span> data. This is especially the case in the low to moderate <span class="hlt">seismicity</span> regions of Europe, where slow slipping <span class="hlt">faults</span> are difficult to characterize. In order to better understand the key parameters that control the uncertainty in the <span class="hlt">fault</span>-related hazard computations, we propose to build an analytic tool that provides a clear link between the different components of the <span class="hlt">fault</span>-related hazard computations and their impact on the results. This will allow identifying the important parameters that need to be better constrained in order to reduce the resulting uncertainty in hazard and also provide a more hazard-oriented strategy for collecting relevant <span class="hlt">fault</span> parameters in the field. The tool will be illustrated through the example of the West Corinth rifts <span class="hlt">fault</span>-models. Recent work performed in the gulf has shown the complexity of the normal <span class="hlt">faulting</span> system that is accommodating the extensional deformation of the rift. A logic-tree approach is proposed to account for this complexity and the multiplicity of scientifically defendable interpretations. At the nodes of the logic tree, different options that could be considered at each step of the <span class="hlt">fault</span>-related <span class="hlt">seismic</span> hazard will be considered. The first nodes represent the uncertainty in the geometries of the <span class="hlt">faults</span> and their slip rates, which can derive from different data and methodologies. The subsequent node explores, for a given geometry/slip rate of <span class="hlt">faults</span>, different earthquake rupture scenarios that may occur in the complex network of <span class="hlt">faults</span>. The idea is to allow the possibility of several <span class="hlt">faults</span> segments to break together in a single rupture scenario. To build these multiple-<span class="hlt">fault</span>-segment scenarios, two approaches are considered: one based on simple rules (i.e. minimum distance between <span class="hlt">faults</span>) and a second one that relies on physically</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T31B2862O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T31B2862O"><span>Thrust <span class="hlt">fault</span> growth within accretionary wedges: New Insights from 3D <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orme, H.; Bell, R. E.; Jackson, C. A. L.</p> <p>2015-12-01</p> <p>The shallow parts of subduction megathrust <span class="hlt">faults</span> are typically thought to be aseismic and incapable of propagating <span class="hlt">seismic</span> rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow <span class="hlt">seismic</span> rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D <span class="hlt">seismic</span> reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D <span class="hlt">seismic</span> reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic <span class="hlt">Seismic</span> Portal, Marine Geoscience Data System) to examine how imbricate thrust <span class="hlt">fault</span> networks evolve during accretionary wedge growth. Previous studies have reported en-echelon thrust <span class="hlt">fault</span> geometries from the NW part of the dataset, and have related this complex structure to seamount subduction. We unravel the evolution of <span class="hlt">faults</span> within the protothrust and imbricate thrust zones by interpreting multiple horizons across <span class="hlt">faults</span> and measuring <span class="hlt">fault</span> displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of <span class="hlt">faults</span>, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated <span class="hlt">fault</span> segments. We also demonstrate that the majority of <span class="hlt">faults</span> grew upward from the décollement, although there is some evidence for downward <span class="hlt">fault</span> propagation. Our observations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.689..115M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.689..115M"><span>Seismostratigraphy and tectonic architecture of the Carboneras <span class="hlt">Fault</span> offshore based on multiscale <span class="hlt">seismic</span> imaging: Implications for the Neogene evolution of the NE Alboran Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreno, Ximena; Gràcia, Eulàlia; Bartolomé, Rafael; Martínez-Loriente, Sara; Perea, Héctor; de la Peña, Laura Gómez; Iacono, Claudio Lo; Piñero, Elena; Pallàs, Raimon; Masana, Eulàlia; Dañobeitia, Juan José</p> <p>2016-10-01</p> <p>In the SE Iberian Margin, which hosts the convergent boundary between the European and African Plates, Quaternary <span class="hlt">faulting</span> <span class="hlt">activity</span> is dominated by a large left-lateral strike-slip system referred to as the Eastern Betic Shear Zone. This <span class="hlt">active</span> <span class="hlt">fault</span> system runs along more than 450 km and it is characterised by low to moderate magnitude shallow earthquakes, although large historical events have also occurred. The Carboneras <span class="hlt">Fault</span> is the longest structure of the Eastern Betic Shear Zone, and its southern termination extends further into the Alboran Sea. Previously acquired high-resolution data (i.e. swath-bathymetry, TOBI sidescan sonar and sub-bottom profiler) show that the offshore Carboneras <span class="hlt">Fault</span> is a NE-SW-trending upwarped zone of deformation with a length of 90 km long and a width of 0.5 to 2 km, which shows geomorphic features typically found in subaerial strike-slip <span class="hlt">faults</span>, such as deflected drainage, pressure ridges and "en echelon" folds. However, the neotectonic, depth architecture, and Neogene evolution of Carboneras <span class="hlt">Fault</span> offshore are still poorly known. In this work we present a multiscale <span class="hlt">seismic</span> imaging of the Carboneras <span class="hlt">Fault</span> (i.e. TOPAS, high-resolution multichannel-<span class="hlt">seismic</span> reflection, and deep penetration multichannel-<span class="hlt">seismic</span> reflection) carried out during three successive marine cruises, from 2006 to 2010. The new dataset allowed us to define a total of seven seismostratigraphic units (from Tortonian to Late Quaternary) above the basement, to characterise the tectonic architecture and structural segmentation of the Carboneras <span class="hlt">Fault</span>, and to estimate its maximum <span class="hlt">seismic</span> potential. We finally discuss the role of the basement in the present-day tectonic evolution of the Carboneras <span class="hlt">Fault</span>, and explore the northern and southern terminations of the <span class="hlt">fault</span> and how the strain is transferred to nearby structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024867','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024867"><span>Location, structure, and <span class="hlt">seismicity</span> of the Seattle <span class="hlt">fault</span> zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and <span class="hlt">seismic</span>-reflection data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Blakely, R.J.; Wells, R.E.; Weaver, C.S.; Johnson, S.Y.</p> <p>2002-01-01</p> <p>A high-resolution aeromagnetic survey of the Puget Lowland shows details of the Seattle <span class="hlt">fault</span> zone, an <span class="hlt">active</span> but largely concealed east-trending zone of reverse <span class="hlt">faulting</span> at the southern margin of the Seattle basin. Three elongate, east-trending magnetic anomalies are associated with north-dipping Tertiary strata exposed in the hanging wall; the magnetic anomalies indicate where these strata continue beneath glacial deposits. The northernmost anomaly, a narrow, elongate magnetic high, precisely correlates with magnetic Miocene volcanic conglomerate. The middle anomaly, a broad magnetic low, correlates with thick, nonmagnetic Eocene and Oligocene marine and fluvial strata. The southern anomaly, a broad, complex magnetic high, correlates with Eocene volcanic and sedimentary rocks. This tripartite package of anomalies is especially clear over Bainbridge Island west of Seattle and over the region east of Lake Washington. Although attenuated in the intervening region, the pattern can be correlated with the mapped strike of beds following a northwest-striking anticline beneath Seattle. The aeromagnetic and geologic data define three main strands of the Seattle <span class="hlt">fault</span> zone identified in marine <span class="hlt">seismic</span>-reflection profiles to be subparallel to mapped bedrock trends over a distance of >50 km. The locus of <span class="hlt">faulting</span> coincides with a diffuse zone of shallow crustal <span class="hlt">seismicity</span> and the region of uplift produced by the M 7 Seattle earthquake of A.D. 900-930.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5023614','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5023614"><span>Paleoseismicity of the Intermountain <span class="hlt">Seismic</span> Belt from Late Quaternary <span class="hlt">faulting</span> and parameter scaling of normal <span class="hlt">faulting</span> earthquakes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mason, D.B.; Smith, R.B. . Dept. of Geology and Geophysics)</p> <p>1993-04-01</p> <p>The eastern Basin-Range, 1,300 km-long Intermountain <span class="hlt">Seismic</span> Belt (ISB) is reflected by a [approximately]100 km-wide zone of scattered earthquakes that in general do not correlate with the mapped Quaternary <span class="hlt">faults</span>. Yet this region has experienced two of the largest historic earthquakes in the western US, the M[sub S] = 7.3, Borah Peak, Idaho, and the M[sub S] = 7.5, Hebgen Lake, Montana, events, which occurred in areas that had previously low historical <span class="hlt">seismicity</span>. These observations indicate the lack of spatial and temporal uniformity between the historical and Holocene <span class="hlt">seismic</span> record. The authors have studied this problem by first investigating <span class="hlt">fault</span>-magnitude scaling relationships using a global set of 16 large normal- to oblique-slip earthquakes, then applying the scaling laws to data from a compilation of well studied Late Quaternary <span class="hlt">faults</span> of the ISB. Several regression models were evaluated but the authors found that magnitudes predicted by displacement alone were consistently 20% larger than those determined from lengths. They suggest that the best estimator is given by: M[sub S] = 0.47 log (d[sub sM]L[sub s]) + 6.1. These results revealed at least 24 large multiple-segment, paleoearthquakes, 6.3 [le] M[sub s] [le] 7.3, that were associated with <span class="hlt">faults</span> within the dual-branched <span class="hlt">seismicity</span> belt which surrounds the aseismic Snake River Plain in the central ISB. They believe this unusual bow-wave pattern of <span class="hlt">seismicity</span> and <span class="hlt">faulting</span> is related to plume-plate interaction associated with the Yellowstone hotspot with an additional component of concomitant Basin-Range extension. In the southern ISB, the 370 km-long Wasatch <span class="hlt">fault</span>, Utah, experienced at least 7 multiple-segment paleoearthquakes, 7.1 [le] M[sub s] [le] 7.3, and contrasts with a historic record of <span class="hlt">seismic</span> quiescence. Intraplate crustal extension is though to be the primary mode of regional strain release for this region of the ISB.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032933','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032933"><span>Annual modulation of <span class="hlt">seismicity</span> along the San Andreas <span class="hlt">Fault</span> near Parkfield, CA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Christiansen, L.B.; Hurwitz, S.; Ingebritsen, S.E.</p> <p>2007-01-01</p> <p>We analyze <span class="hlt">seismic</span> data from the San Andreas <span class="hlt">Fault</span> (SAF) near Parkfield, California, to test for annual modulation in <span class="hlt">seismicity</span> rates. We use statistical analyses to show that <span class="hlt">seismicity</span> is modulated with an annual period in the creeping section of the <span class="hlt">fault</span> and a semiannual period in the locked section of the <span class="hlt">fault</span>. Although the exact mechanism for seasonal triggering is undetermined, it appears that stresses associated with the hydrologic cycle are sufficient to fracture critically stressed rocks either through pore-pressure diffusion or crustal loading/ unloading. These results shed additional light on the state of stress along the SAF, indicating that hydrologically induced stress perturbations of ???2 kPa may be sufficient to trigger earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT........46O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT........46O"><span>Hydrothermal <span class="hlt">fault</span> zone mapping using <span class="hlt">seismic</span> and electrical measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Onacha, Stephen Alumasa</p> <p></p> <p>This dissertation presents a new method of using earthquakes and resistivity data to characterize permeable hydrothermal reservoirs. The method is applied to field examples from Casa Diablo in the Long Valley Caldera, California; Mt. Longonot, Kenya; and Krafla, Iceland. The new method has significant practical value in the exploration and production of geothermal energy. The method uses P- and S-wave velocity, S-wave polarization and splitting magnitude, resistivity and magnetotelluric (MT) strike directions to determine fracture-porosity and orientation. The conceptual model used to characterize the buried, fluid-circulating <span class="hlt">fault</span> zones in hydrothermal systems is based on geological and fracture models. The method has been tested with field earthquake and resistivity data; core samples; temperature measurements; and, for the case of Krafla, with a drilled well. The use of resistivity and microearthquake measurements is based on theoretical formulation of shared porosity, anisotropy and polarization. The relation of resistivity and a double porosity-operator is solved using a basis function. The porosity-operator is used to generate a correlation function between P-wave velocity and resistivity. This correlation is then used to generate P-wave velocity from 2-D resistivity models. The resistivity models are generated from magnetotelluric (MT) by using the Non-Linear Conjugate Gradient (NLCG) inversion method. The <span class="hlt">seismic</span> and electrical measurements used come from portable, multi station microearthquake (MEQ) monitoring networks and multi-profile, MT and transient electromagnetic (TEM) observation campaigns. The main conclusions in this dissertation are listed below: (1) Strong evidence exists for correlation between MT strike direction and anisotropy and MEQ S-wave splitting at sites close to fluid-filled fracture zones. (2) A porosity operator generated from a double porosity model has been used to generate valid P-wave velocity models from resistivity data. This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1969/0015/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1969/0015/report.pdf"><span><span class="hlt">Seismic</span> <span class="hlt">activity</span> in the Sunnyside mining district, Utah, during 1967</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Barnes, Barton K.; Dunrud, C. Richard; Hernandez, Jerome</p> <p>1969-01-01</p> <p>A <span class="hlt">seismic</span> monitoring network near Sunnyside, Utah, consisting of a triangular array of seismometer stations that encompasses most of the mine workings in the district, recorded over 50,000 local earth tremors during 1967. About 540 of the tremors were of sufficient magnitude to be accurately located. Most of these were located within 2-3 miles of mine workings and were also near known or suspected <span class="hlt">faults</span>. The district-wide <span class="hlt">seismic</span> <span class="hlt">activity</span> generally consisted of two different patterns--a periodic increase in the daily number of tremors at weekly intervals, and also a less regular and longer term increase and decrease of <span class="hlt">seismic</span> <span class="hlt">activity</span> that occurred over a period of weeks or even months. The shorter and more regular pattern can be correlated with the mine work week and seems to result from mining. The longer term <span class="hlt">activity</span>, however, does not correlate with known mining causes sad therefore seems to be .caused by natural stresses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..144E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..144E"><span>Is there really an <span class="hlt">active</span> <span class="hlt">fault</span> (Cibyra <span class="hlt">Fault</span>?) cutting the Stadion of the ancient city of Cibyra? (Burdur-Fethiye <span class="hlt">Fault</span> Zone, Turkey)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Elitez, İrem; Yaltırak, Cenk</p> <p>2013-04-01</p> <p>The Cibyra segment of the Burdur-Fethiye <span class="hlt">Fault</span> Zone (BFFZ) is in a tectonically very <span class="hlt">active</span> region of southwestern Anatolia. The presence of the Cibyra <span class="hlt">Fault</span> was firstly suggested by Akyüz and Altunel (1997, 2001). Researchers identified traces of historical earthquakes in Cibyra by taking into account the collapsed seat rows on the east side of the stadion as reference. They claimed that the NNE-SSW left lateral <span class="hlt">fault</span> Cibyra <span class="hlt">Fault</span> (related to Burdur-Fethiye <span class="hlt">Fault</span> Zone) continues through Pliocene sediments on both eastern and western sides of the stadion of Cibyra. The questionable left-lateral <span class="hlt">fault</span> had been examined in detail by ourselves during our 60-days accommodation in the ancient city of Cibyra excavations for the Burdur-Fethiye <span class="hlt">Fault</span> Zone Project in 2008, 2009 and 2012. A left-lateral offset on the Stadion was firstly mentioned in a study whose aim is to find the traces of Burdur-Fethiye <span class="hlt">Fault</span> (Akyüz and Altunel, 2001) and many researchers accepted this <span class="hlt">fault</span> by reference (for example Alçiçek et al. 2002, 2004, 2005, 2006 and Karabacak, 2011). However as a result of the field observations it is understood that there is no <span class="hlt">fault</span> cutting the Stadion. By the reason of the fact that there are a lot of <span class="hlt">faults</span> in the region, however the <span class="hlt">fault</span> that devastated the ancient city is unknown. The deformation traces on the ruins of the ancient city display a <span class="hlt">seismic</span> movement occured in the region. It is strongly possible that this movement is related to the NE-SW left lateral oblique normal <span class="hlt">fault</span> named as Cibyra <span class="hlt">Fault</span> at the northwestern side of the city. Especially the ravages in the eastern part of the city indicate that the deformations are related to ground properties. If the rotation and overturn movement are considered and if both movements are the product of the same earthquake, the real Cibyra <span class="hlt">Fault</span> is compatible with normal <span class="hlt">fault</span> with left lateral compenent. After the 2011 excavations and 2012 field studies, the eastern wall of the Stadion showed that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EOSTr..90...55P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EOSTr..90...55P"><span>Illuminating Northern California's <span class="hlt">Active</span> <span class="hlt">Faults</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prentice, Carol S.; Crosby, Christopher J.; Whitehill, Caroline S.; Arrowsmith, J. Ramón; Furlong, Kevin P.; Phillips, David A.</p> <p>2009-02-01</p> <p>Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary <span class="hlt">faults</span> of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major <span class="hlt">active</span> <span class="hlt">fault</span> zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google Earth™ and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.680...67B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.680...67B"><span><span class="hlt">Seismic</span> sources and stress transfer interaction among axial normal <span class="hlt">faults</span> and external thrust fronts in the Northern Apennines (Italy): A working hypothesis based on the 1916-1920 time-space cluster of earthquakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonini, Marco; Corti, Giacomo; Donne, Dario Delle; Sani, Federico; Piccardi, Luigi; Vannucci, Gianfranco; Genco, Riccardo; Martelli, Luca; Ripepe, Maurizio</p> <p>2016-06-01</p> <p>In this study we analyse the main potential <span class="hlt">seismic</span> sources in some axial and frontal sectors of the Northern Apennines, in Italy. This region was hit by a peculiar series of earthquakes that started in 1916 on the external thrust fronts near Rimini. Later, in 1917-1921, <span class="hlt">seismicity</span> (up to Mw ≈ 6.5) shifted into the axial zone and clearly migrated north-westward, along the belt of <span class="hlt">active</span> normal <span class="hlt">faults</span>. The collection of <span class="hlt">fault</span>-slip data focused on the <span class="hlt">active</span> normal <span class="hlt">faults</span> potentially involved in this earthquake series. The acquired data allowed us to better characterize the geometry and kinematics of the <span class="hlt">faults</span>. In a few instances, the installation of local <span class="hlt">seismic</span> networks during recent <span class="hlt">seismic</span> sequences allowed the identification of the causative <span class="hlt">faults</span> that are hinted to be also responsible for past earthquakes, particularly in the Romagna region and north-eastern Mugello. The Coulomb stress changes produced by the historical earthquakes generally brought closer to failure all the <span class="hlt">faults</span> that supposedly caused the main <span class="hlt">seismic</span> events of 1916-1921. However, the stress change magnitude is generally small and thus the static stress interaction among the main <span class="hlt">seismic</span> sources is not supported by a significant <span class="hlt">seismic</span> correlation. Significant stress change loading may be instead inferred for the triggering of a number of <span class="hlt">seismic</span> events on neighbouring normal <span class="hlt">faults</span> by the Garfagnana 1920 earthquake. In addition, the computation of the <span class="hlt">seismic</span> stress changes suggests that <span class="hlt">seismic</span> events with magnitude ≥ 6 may transmit stresses from the axial normal <span class="hlt">faults</span> to specific external thrusts and vice versa. It is possible that a correlation may be made between loading applied by the major 1917-1920 extensional ruptures and the increased <span class="hlt">seismicity</span> on the distal external thrusts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T13D2567S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T13D2567S"><span>Structural Analysis of <span class="hlt">Active</span> North Bozgush <span class="hlt">Fault</span> Zone (NW Iran)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saber, R.; Isik, V.; Caglayan, A.</p> <p>2013-12-01</p> <p>NW Iran is one of the <span class="hlt">seismically</span> <span class="hlt">active</span> regions between Zagros Thrust Belt at the south and Caucasus at the north. Not only large magnitude historical earthquakes (Ms>7), but also 1987 Bozgush, 1997 Ardebil (Mw 6.1) and 2012 Ahar-Varzagan (Mw 6.4) earthquakes reveal that the region is <span class="hlt">seismically</span> <span class="hlt">active</span>. The North Bozgush <span class="hlt">Fault</span> Zone (NBFZ) in this region has tens of kilometers in length and hundreds of meters in width. The zone has produced some large and destructive earthquakes (1593 M:6.1 and 1883 M:6.2). The NBFZ affects the Cenozoic units and along this zone Eocene units thrusted over Miocene and/or Plio-Quaternary sedimentary units. Together with morphologic features (stream offsets and alluvial fan movements) affecting the young unites reveal that the zone is <span class="hlt">active</span>. The zone is mainly characterized by strike-slip <span class="hlt">faults</span> with reverse component and reverse <span class="hlt">faults</span>. Reverse <span class="hlt">faults</span> striking N55°-85°E and dip of 40°-50° to the SW while strike-slip <span class="hlt">faults</span> show right lateral slip with N60°-85°W and N60°-80°E directions. Our structural data analysis in NBFZ indicates that the axis direction of σ2 principal stress is vertical and the stress ratio (R) is 0.12. These results suggest that the tectonic regime along the North Bozgush <span class="hlt">Fault</span> Zone is transpressive. Obtained other principal stresses (σ1, σ3) results are compatible with stress directions and GPS velocity suggested for NW Iran.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E..40A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E..40A"><span><span class="hlt">Seismic</span> hazard assessment of Syria using <span class="hlt">seismicity</span>, DEM, slope, <span class="hlt">active</span> tectonic and GIS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmad, Raed; Adris, Ahmad; Singh, Ramesh</p> <p>2016-07-01</p> <p>In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of <span class="hlt">seismic</span> hazard areas in Syria. The present study is the first time effort to create <span class="hlt">seismic</span> hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and <span class="hlt">active</span> tectonic maps. Many important factors for evaluation of <span class="hlt">seismic</span> hazard were identified and corresponding thematic data layers (past earthquake epicenters, <span class="hlt">active</span> <span class="hlt">faults</span>, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of <span class="hlt">seismic</span> hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final <span class="hlt">seismic</span> hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of <span class="hlt">seismic</span> hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic <span class="hlt">seismic</span> hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of <span class="hlt">seismic</span> hazard map which is found to be very realistic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51B2870A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51B2870A"><span>Scandinavian postglacial <span class="hlt">faults</span> and their physical connection to present day <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arvidsson, R.</p> <p>2015-12-01</p> <p>In Scandinavia large earthquakes up to M~8.2 occurred 9500 yBP due to rapid deglaciation leaving <span class="hlt">fault</span> scarps with lengths up to 160km and vertical offsets of at least 10 m. Today a lion share of local earthquakes are located to the vicinity of the <span class="hlt">faults</span>. I show here from Coulomb failure stress modeling a physical connection between clustering of recent earthquakes and high Coulomb failure stresses around the <span class="hlt">faults</span>. This can be interpreted In such a fashion that the location of the current earthquakes resembles locations of aftershock sequences. The explanation is that when these <span class="hlt">faults</span> where formed it was due to state of stress in the crust at time of deglaciation, different from today's conditions. The crust was heavily depressed at deglaciation about 250 m in the region and due of the receding icesheet the crust was subjected to high stresses resulting in <span class="hlt">fault</span> motion. This <span class="hlt">fault</span> motion occurred in order to minimize state of stress at deglaciation. However, this state of stress has since changed with the regional postglacial uplift and thus today these <span class="hlt">faults</span> remain as perturbations in the crust with concentrations of high stresses. I elaborate on this mechanism. I also advocate that this correlation between high stressed <span class="hlt">fault</span> areas and locations of earthquakes indicates that <span class="hlt">seismicity</span> within stable continental regions like Scandinavia might be caused by previous crustal disturbances that show local perturbations of the stress field. Therefore if <span class="hlt">faults</span> are favorably oriented in the present stress field they can be released by brittle earthquake <span class="hlt">faulting</span> . Thus past transient tectonic events can explain part of the stable continental region's <span class="hlt">seismicity</span>. This may be of large importance to assessment of <span class="hlt">seismic</span> hazard within stable continental regions particularly for critical structures like e.g., nuclear waste deposits and hydroelectric dams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.570g2003S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.570g2003S"><span>Approximate <span class="hlt">active</span> <span class="hlt">fault</span> detection and control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Škach, Jan; Punčochář, Ivo; Šimandl, Miroslav</p> <p>2014-12-01</p> <p>This paper deals with approximate <span class="hlt">active</span> <span class="hlt">fault</span> detection and control for nonlinear discrete-time stochastic systems over an infinite time horizon. Multiple model framework is used to represent <span class="hlt">fault</span>-free and finitely many faulty models. An imperfect state information problem is reformulated using a hyper-state and dynamic programming is applied to solve the problem numerically. The proposed <span class="hlt">active</span> <span class="hlt">fault</span> detector and controller is illustrated in a numerical example of an air handling unit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70042757','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70042757"><span>Why the 2002 Denali <span class="hlt">fault</span> rupture propagated onto the Totschunda <span class="hlt">fault</span>: implications for <span class="hlt">fault</span> branching and <span class="hlt">seismic</span> hazards</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Schwartz, David P.; Haeussler, Peter J.; Seitz, Gordon G.; Dawson, Timothy E.</p> <p>2012-01-01</p> <p>The propagation of the rupture of the Mw7.9 Denali <span class="hlt">fault</span> earthquake from the central Denali <span class="hlt">fault</span> onto the Totschunda <span class="hlt">fault</span> has provided a basis for dynamic models of <span class="hlt">fault</span> branching in which the angle of the regional or local prestress relative to the orientation of the main <span class="hlt">fault</span> and branch plays a principal role in determining which <span class="hlt">fault</span> branch is taken. GeoEarthScope LiDAR and paleoseismic data allow us to map the structure of the Denali-Totschunda <span class="hlt">fault</span> intersection and evaluate controls of <span class="hlt">fault</span> branching from a geological perspective. LiDAR data reveal the Denali-Totschunda <span class="hlt">fault</span> intersection is structurally simple with the two <span class="hlt">faults</span> directly connected. At the branch point, 227.2 km east of the 2002 epicenter, the 2002 rupture diverges southeast to become the Totschunda <span class="hlt">fault</span>. We use paleoseismic data to propose that differences in the accumulated strain on each <span class="hlt">fault</span> 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, <span class="hlt">fault</span> geometry and structure, and connectivity, especially on high slip rate-short recurrence interval <span class="hlt">faults</span>, can be used to assess the likelihood of branching and its direction. Analysis of the Denali-Totschunda <span class="hlt">fault</span> intersection has implications for evaluating the potential for a rupture to propagate across other types of <span class="hlt">fault</span> intersections and for characterizing sources of future large earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70001345','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70001345"><span>Recurrence of <span class="hlt">seismic</span> migrations along the central California segment of the San Andreas <span class="hlt">fault</span> system</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wood, M.D.; Allen, S.S.</p> <p>1973-01-01</p> <p>VERIFICATIONS of tectonic concepts1 concerning seafloor spreading are emerging in a manner that has direct bearing on earthquake prediction. Although the gross pattern of worldwide <span class="hlt">seismicity</span> contributed to the formulation of the plate tectonic hypothesis, it is the space-time characteristics of this <span class="hlt">seismicity</span> that may contribute more toward understanding the kinematics and dynamics of the driving mechanism long speculated to originate in the mantle. If the lithosphere is composed of plates that move essentially as rigid bodies, then there should be <span class="hlt">seismic</span> edge effects associated with this movement. It is these interplate effects, especially <span class="hlt">seismic</span> migration patterns, that we discuss here. The unidirectional propagation at constant velocity (80 km yr-1 east to west) for earthquakes (M???7.2) on the Antblian <span class="hlt">fault</span> for the period 1939 to 1956 (ref. 2) is one of the earliest observations of such a phenomenon. Similar studies3,4 of the Alaska Aleutian <span class="hlt">seismic</span> zone and certain regions of the west coast of South America suggest unidirectional and recurring migrations of earthquakes (M???7.7) occur in these areas. Between these two regions along the great transform <span class="hlt">faults</span> of the west coast of North America, there is some evidence 5 for unidirectional, constant velocity and recurrent migration of great earthquakes. The small population of earthquakes (M>7.2) in Savage's investigation5 indicates a large spatial gap along the San Andreas system in central California from 1830 to 1970. Previous work on the <span class="hlt">seismicity</span> of this gap in central California indicates that the recurrence curves remain relatively constant, independent of large earthquakes, for periods up to a century6. Recurrence intervals for earthquakes along the San Andreas <span class="hlt">Fault</span> have been calculated empirically by Wallace7 on the basis of geological evidence, surface measurements and assumptions restricted to the surficial <span class="hlt">seismic</span> layer. Here we examine the evidence for recurrence of <span class="hlt">seismic</span> migrations along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T53C1605R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T53C1605R"><span>Co-<span class="hlt">seismic</span> thermal dissociation of carbonate <span class="hlt">fault</span> rocks: Naukluft Thrust, central Namibia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rowe, C. D.; Miller, J. A.; Sylvester, F.; Backeberg, N.; Faber, C.; Mapani, B.</p> <p>2009-12-01</p> <p>Frictional heating has been shown to dissociate carbonate minerals in <span class="hlt">fault</span> rocks and rock slides at high velocities, producing in-situ fluid pressure spikes and resulting in very low effective friction. We describe the textural and geochemical effects of repeated events of frictional-thermal dissociation and fluidization along a low-angle continental thrust <span class="hlt">fault</span>. The Naukluft Thrust in central Namibia is a regional décollement along which the Naukluft Nappe Complex was emplaced over the Nama Basin in the southern foreland of the ~ 550Ma Damara Orogen. <span class="hlt">Fault</span> rocks in the thrust show a coupled geochemical and structural evolution driven by dolomitization reactions during <span class="hlt">fault</span> <span class="hlt">activity</span> and facilitated by fluid flow along the <span class="hlt">fault</span> surface. The earliest developed <span class="hlt">fault</span> rocks are calcite-rich calcmylonites which were progressively dolomitized along foliation. Above a critical dolomite/calcite ratio, the rocks show only brittle deformation fabrics dominated by breccias, cataclasites, and locally, a thin (1-3cm) microcrystalline, smooth white ultracataclasite. The <span class="hlt">fault</span> is characterized by the prevalence of an unusual “gritty dolomite” yellow cataclasite containing very well rounded clasts in massive to flow-banded fine dolomitic matrix. This cataclasite, locally known as the “gritty dolomite”, may reach thicknesses of up to ~ 10m without evidence of internal cross-cutting relations with randomly distributed clasts (an “unsorted” texture). The gritty dolomite also forms clastic injections into the hanging wall of the <span class="hlt">fault</span>, frequently where the <span class="hlt">fault</span> surface changes orientation. Color-cathodoluminescence images show that individual carbonate grains within the “gritty dolomite” have multiple layers of thin (~10-100 micron) dolomite coatings and that the grains were smoothed and rounded between each episode of coating precipitation. Coated grains are in contact with one another but grain cores are never seen in contact. CL-bright red dolomite which forms</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010108005','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010108005"><span><span class="hlt">Seismic</span> Forecasting of Solar <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Braun, Douglas; Lindsey, Charles</p> <p>2001-01-01</p> <p>We have developed and improved helioseismic imaging techniques of the far-side of the Sun as part of a synoptic monitor of solar <span class="hlt">activity</span>. In collaboration with the MIDI team at Stanford University we are routinely applying our analysis to images within 24 hours of their acquisition by SOHO. For the first time, real-time <span class="hlt">seismic</span> maps of large <span class="hlt">active</span> regions on the Sun's far surface are publicly available. The synoptic images show examples of <span class="hlt">active</span> regions persisting for one or more solar rotations, as well as those initially detected forming on the solar far side. Until recently, imaging the far surface of the Sun has been essentially blind to <span class="hlt">active</span> regions more than about 50 degrees from the antipode of disk center. In a paper recently accepted for publication, we have demonstrated how acoustic travel-time perturbations may be mapped over the entire hemisphere of the Sun facing away from the Earth, including the polar regions. In addition to offering significant improvements to ongoing space weather forecasting efforts, the procedure offers the possibility of local <span class="hlt">seismic</span> monitoring of both the temporal and spatial variations in the acoustic properties of the Sun over the entire far surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JGeo...14...73K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JGeo...14...73K"><span><span class="hlt">Active</span> <span class="hlt">fault</span> and water loading are important factors in triggering earthquake <span class="hlt">activity</span> around Aswan Lake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kebeasy, R. M.; Gharib, A. A.</p> <p></p> <p>Aswan Lake started impounding in 1964 and reached the highest water level so far in 1978 with a capacity of 133.8 km 3, thus forming the second largest man-made lake in the world. An earthquake of magnitude 5.3 (Ms) took place on 14 November 1981 along the most <span class="hlt">active</span> part of the E-W Kalabsha <span class="hlt">fault</span> beneath the Kalabsha bay (the largest bay of the lake). This earthquake was followed by a tremendous number of smaller events that continue till now. A radio-telemetry network of 13 <span class="hlt">seismic</span> short period stations and a piezometer network of six wells were established around the northern part of the lake. Epicenters were found to cluster around <span class="hlt">active</span> <span class="hlt">faults</span> near the lake. The space-time distribution and the relation of the <span class="hlt">seismicity</span> with the lake water level fluctuations were studied. Six years after flooding the eastern segment of the Kalabsha <span class="hlt">fault</span>, strong <span class="hlt">seismicity</span> began following the main shock of 14 November 1981. It occurred four days after the reservoir had reached its seasonal max level. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most <span class="hlt">active</span> <span class="hlt">fault</span> segments uncovered, the <span class="hlt">activity</span> (Gebel Marawa area) decreased sharply. Also, the shallow <span class="hlt">activity</span> was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in <span class="hlt">seismicity</span>, offsets in the <span class="hlt">faults</span>, changes in <span class="hlt">fault</span> trends and focal mechanisms are closely related. No relation was found between earthquake <span class="hlt">activity</span> and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23878524','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23878524"><span>Estimation of recurrence interval of large earthquakes on the central Longmen Shan <span class="hlt">fault</span> zone based on <span class="hlt">seismic</span> moment accumulation/release model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ren, Junjie; Zhang, Shimin</p> <p>2013-01-01</p> <p>Recurrence interval of large earthquake on an <span class="hlt">active</span> <span class="hlt">fault</span> zone is an important parameter in assessing <span class="hlt">seismic</span> hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan <span class="hlt">fault</span> zone and ruptured the Yingxiu-Beichuan <span class="hlt">fault</span> (YBF) and the Guanxian-Jiangyou <span class="hlt">fault</span> (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-<span class="hlt">seismic</span> trenches showed that the central Longmen Shan <span class="hlt">fault</span> zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic <span class="hlt">seismic</span> moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan <span class="hlt">fault</span> zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 10¹⁷ N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for <span class="hlt">seismic</span> hazard analysis in the Longmen Shan region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3710655','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3710655"><span>Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan <span class="hlt">Fault</span> Zone Based on <span class="hlt">Seismic</span> Moment Accumulation/Release Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Shimin</p> <p>2013-01-01</p> <p>Recurrence interval of large earthquake on an <span class="hlt">active</span> <span class="hlt">fault</span> zone is an important parameter in assessing <span class="hlt">seismic</span> hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan <span class="hlt">fault</span> zone and ruptured the Yingxiu-Beichuan <span class="hlt">fault</span> (YBF) and the Guanxian-Jiangyou <span class="hlt">fault</span> (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-<span class="hlt">seismic</span> trenches showed that the central Longmen Shan <span class="hlt">fault</span> zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic <span class="hlt">seismic</span> moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan <span class="hlt">fault</span> zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 1017 N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for <span class="hlt">seismic</span> hazard analysis in the Longmen Shan region. PMID:23878524</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.T22A0897F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.T22A0897F"><span>ESR Detection of Frictional Heat in <span class="hlt">Seismic</span> <span class="hlt">Fault</span> Slip</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukuchi, T.; Mizoguchi, K.; Shimamoto, T.</p> <p>2001-12-01</p> <p>Electron spin resonance (ESR) is a spectroscopic method to detect paramagnetic defect centers or impurities in materials. Fukuchi (2001) measured ESR spectra of the Nojima pseudotachylyte found along the Nojima <span class="hlt">fault</span> that caused the 1995 Kobe Earthquake (M 7.2) in Japan. There has been controversy as to whether frictional melting or crushing is more essential for the origin of the Nojima pseudotachylyte. As a result of the ESR measurement, the Nojima pseudotachylyte gave a huge ESR signal of bulky trivalent iron (Fe3+) ions derived from ferrimagnetic iron oxides (γ -Fe2O3). It has turned out that the bulky Fe3+ ion signal is produced by heating the Nojima <span class="hlt">fault</span> gouge and that the <span class="hlt">fault</span> gouge changes from an ocherous paramagnetic material to a black ferrimagnetic one with heating. We carry out high-speed frictional experiments using a new rotary-shear high-speed frictional testing machine to confirm that frictional heat in <span class="hlt">faulting</span> can produce the black material like pseudotachylyte. By shearing under the condition that the axial stress is 0.61 MPa, the equivalent speed is 1.74 m/s and the average displacement is about 15m, the <span class="hlt">fault</span> gouge changes into the pseudotachylyte-like material with a strong bulky Fe3+ signal. From the <span class="hlt">fault</span> gouge after the shearing, the traces of dehydration are observed along the shear plane. This means that hot fluids dehydrated by frictional heating pass through the <span class="hlt">fault</span> gouge along the <span class="hlt">fault</span> plane in natural <span class="hlt">faulting</span>. Heat and mass transfer may occur with the hot fluid flow. Furthermore, we discuss how to estimate the temperature of frictional heat using the bulky Fe3+ signal. If we use the bulky Fe3+ signal detected from the Nojima pseudotachylyte, the maximum temperature in <span class="hlt">faulting</span> is estimated as about 600° C. This result supports that the Nojima pseudotachylyte is a crushing-originated one. >http://www.cc.yamaguchi-u.ac.jp/~fukuchi/index.html</a></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T23C2956K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T23C2956K"><span>3D insight into <span class="hlt">fault</span> geometries, deformation, and fluid-migration within the Hosgri <span class="hlt">Fault</span> Zone offshore central California: Results from high-resolution 3D <span class="hlt">seismic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kluesner, J.; Brothers, D. S.; Johnson, S. Y.; Watt, J. T.</p> <p>2015-12-01</p> <p>High-resolution 3D <span class="hlt">seismic</span> P-Cable data and advanced <span class="hlt">seismic</span> attribute analyses were used to detect and interpret complex strike-slip <span class="hlt">fault</span> geometries, deformation patterns, and fluid-pathways across a portion of the Hosgri <span class="hlt">Fault</span> Zone (HFZ) offshore central California. Combination of the <span class="hlt">fault</span> attribute results with structural analysis provides 3D insight into the geometry and internal structure of restraining and releasing bends, step-over zones, <span class="hlt">fault</span> convergence zones, and apparent paired <span class="hlt">fault</span> bends. The 3D <span class="hlt">seismic</span> volume covers a 13.7 km2 region along the HFZ offshore of Point Sal and was collected in 2012 as part of the PG&E Central California <span class="hlt">Seismic</span> Imaging Project (PG&E, 2014). Application of the <span class="hlt">fault</span> attribute workflow isolated and delineated <span class="hlt">fault</span> strands within the 3D volume. These results revealed that the northern and southern edges of the survey region are characterized by single <span class="hlt">fault</span> strands that exhibit an approximate 6° change in strike across the 3D volume. Between these single <span class="hlt">faults</span> strands is a complex network of <span class="hlt">fault</span> splays, bends, stepovers, and convergence zones. Structural analysis reveals that the southern portion of the HFZ in the region is characterized by transtensional deformation, whereas transpressional-related folding dominates the central and northern portions of the HFZ. In the central region, convergence of the Lions Head <span class="hlt">Fault</span> from the southeast results in an apparent impinging block, leading to development of a "paired <span class="hlt">fault</span> bend" to the west. Combination of the <span class="hlt">fault</span> and "chimney" attribute results indicates a strong connection between <span class="hlt">faults</span> and fluid-migration pathways. Fluid-pathways are concentrated along discrete <span class="hlt">faults</span> in the transtensional zones, but appear to be more broadly distributed amongst <span class="hlt">fault</span> bounded anticlines and structurally controlled traps in the transpressional zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAfES.119..160G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAfES.119..160G"><span>Integrated application of gravity and <span class="hlt">seismic</span> methods for determining the dip angle of a <span class="hlt">fault</span> plane: Case of Mahjouba <span class="hlt">fault</span> (Central Tunisian Atlas Province, North Africa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gabtni, H.; Hajji, O.; Jallouli, C.</p> <p>2016-07-01</p> <p>A procedure for a dip angle determination of a <span class="hlt">fault</span> plane from gravity field data is presented to constrain a <span class="hlt">seismic</span> profile interpretation. This procedure is applied on Mahjouba normal <span class="hlt">fault</span> at the western border of Kalaa Khesba graben (Central Tunisian Atlas Province, North Africa). <span class="hlt">Seismic</span> and detailed gravity data, in this region, were analyzed to provide more constraints on the geometry of the <span class="hlt">fault</span> dip angle. The Mahjouba <span class="hlt">fault</span> is mapped as three major parallel lineaments extended for 2 km with a NW-SE to N-S trend. The dip of the Mahjouba <span class="hlt">fault</span> is estimated from the gravity modeling data to be 45°E. This study reveals that integrating gravity and <span class="hlt">seismic</span> data provides accurate mapping of <span class="hlt">faults</span> geometry and such result provides useful information and constraints on the exploration of natural resources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019698','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019698"><span><span class="hlt">Seismic</span> evidence of Quaternary <span class="hlt">faulting</span> in the Benton Hills area, southeast Missouri</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Palmer, J.R.; Shoemaker, M.; Hoffman, D.; Anderson, N.L.; Vaughn, J.D.; Harrison, R.W.</p> <p>1997-01-01</p> <p>Two reflection <span class="hlt">seismic</span> profiles at English Hill, across the southern edge of the Benton Hills escarpment, southeast Missouri, establish that geologic structures at English Hill are of tectonic origin. The lowland area to the south of the escarpment is relatively undisturbed. The geology at English Hill is structurally complex, and reflection <span class="hlt">seismic</span> and geologic data indicate extensive and episodic <span class="hlt">faulting</span> of Paleozoic, Cretaceous, Tertiary, and Quaternary strata. The individual <span class="hlt">faults</span> have near-vertical <span class="hlt">fault</span> surfaces with maximum vertical separations on the order of 15 m. They appear to be clustered in north-northeast trending zones that essentially parallel one of the dominant Benton Hills structural trends. These observations suggest that previously mapped Quaternary <span class="hlt">faults</span> at English Hill are deep-seated and tectonic in origin. This paper documents recent <span class="hlt">faulting</span> at English Hill and is the first time late Quaternary, surface-rupture <span class="hlt">faulting</span> has been recognized in the middle Mississippi River Valley region outside of the New Madrid <span class="hlt">seismic</span> zone. This has important implications for earthquake assessment in the midcontinent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026246','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026246"><span>Remotely triggered <span class="hlt">seismicity</span> on the United States west coast following the Mw 7.9 Denali <span class="hlt">fault</span> earthquake</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Prejean, S.G.; Hill, D.P.; Brodsky, E.E.; Hough, S.E.; Johnston, M.J.S.; Malone, S.D.; Oppenheimer, D.H.; Pitt, A.M.; Richards-Dinger, K. B.</p> <p>2004-01-01</p> <p>The Mw 7.9 Denali <span class="hlt">fault</span> earthquake in central Alaska of 3 November 2002 triggered earthquakes across western North America at epicentral distances of up to at least 3660 km. We describe the spatial and temporal development of triggered <span class="hlt">activity</span> in California and the Pacific Northwest, focusing on Mount Rainier, the Geysers geothermal field, the Long Valley caldera, and the Coso geothermal field.The onset of triggered <span class="hlt">seismicity</span> at each of these areas began during the Love and Raleigh waves of the Mw 7.9 wave train, which had dominant periods of 15 to 40 sec, indicating that earthquakes were triggered locally by dynamic stress changes due to low-frequency surface wave arrivals. Swarms during the wave train continued for ∼4 min (Mount Rainier) to ∼40 min (the Geysers) after the surface wave arrivals and were characterized by spasmodic bursts of small (M ≤ 2.5) earthquakes. Dynamic stresses within the surface wave train at the time of the first triggered earthquakes ranged from 0.01 MPa (Coso) to 0.09 MPa (Mount Rainier). In addition to the swarms that began during the surface wave arrivals, Long Valley caldera and Mount Rainier experienced unusually large <span class="hlt">seismic</span> swarms hours to days after the Denali <span class="hlt">fault</span> earthquake. These swarms seem to represent a delayed response to the Denali <span class="hlt">fault</span> earthquake. The occurrence of spatially and temporally distinct swarms of triggered <span class="hlt">seismicity</span> at the same site suggests that earthquakes may be triggered by more than one physical process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tecto..34..232C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tecto..34..232C"><span>A new multilayered visco-elasto-plastic experimental model to study strike-slip <span class="hlt">fault</span> <span class="hlt">seismic</span> cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caniven, Y.; Dominguez, S.; Soliva, R.; Cattin, R.; Peyret, M.; Marchandon, M.; Romano, C.; Strak, V.</p> <p>2015-02-01</p> <p>Nowadays, technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with <span class="hlt">active</span> <span class="hlt">fault</span> <span class="hlt">seismic</span> cycle. However, the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years. To overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters, we have developed a new experimental approach allowing for the simulation of strike-slip <span class="hlt">fault</span> earthquakes and analyze in detail hundreds of successive <span class="hlt">seismic</span> cycle. Model rheology is made of multilayered visco-elasto-plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle/ductile coupling, postseismic deformation phase and far-field stress transfers. The kinematic evolution of the model surface is monitored using an optical system, based on subpixel spectral correlation of high-resolution digital images. First, results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the <span class="hlt">seismic</span> cycle indicating that model scaling is satisfactory. These results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth, along the <span class="hlt">fault</span> plane. Our analog modeling approach appears, then, as an efficient complementary approach to investigate earthquake dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036303','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036303"><span><span class="hlt">Seismic</span> and geodetic signatures of <span class="hlt">fault</span> slip at the Slumgullion Landslide Natural Laboratory</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.</p> <p>2011-01-01</p> <p>We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing <span class="hlt">fault</span> slip, specifically that slip along its basal surface and side-bounding strike-slip <span class="hlt">faults</span> occurs with comparable richness of aseismic and <span class="hlt">seismic</span> modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station <span class="hlt">seismic</span> network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of <span class="hlt">seismic</span> signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip <span class="hlt">faults</span>. The landslide basal surface beneath our <span class="hlt">seismic</span> network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip <span class="hlt">faults</span> controls the overall landslide motion, acting as <span class="hlt">seismically</span> radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale <span class="hlt">faults</span> suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control <span class="hlt">fault</span> slip at all scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Plate+AND+Tectonics&pg=7&id=EJ455032','ERIC'); return false;" href="http://eric.ed.gov/?q=Plate+AND+Tectonics&pg=7&id=EJ455032"><span>How <span class="hlt">Faults</span> Shape the Earth.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Bykerk-Kauffman, Ann</p> <p>1992-01-01</p> <p>Presents <span class="hlt">fault</span> <span class="hlt">activity</span> with an emphasis on earthquakes and changes in continent shapes. Identifies three types of <span class="hlt">fault</span> movement: normal, reverse, and strike <span class="hlt">faults</span>. Discusses the <span class="hlt">seismic</span> gap theory, plate tectonics, and the principle of superposition. Vignettes portray <span class="hlt">fault</span> movement, and the locations of the San Andreas <span class="hlt">fault</span> and epicenters of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817517G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817517G"><span>Geology and seismotectonics of the North-Anatolian <span class="hlt">Fault</span> in the Sea of Marmara: implications for <span class="hlt">seismic</span> hazards</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gasperini, Luca; Cedro, Vincenzo; Polonia, Alina; Cruise Party, Marmara</p> <p>2016-04-01</p> <p>Based on high-resolution multibeam and <span class="hlt">seismic</span> reflection data recently collected and analysed in the frame of Marsite (New Directions in <span class="hlt">Seismic</span> Hazard Assessment through Focused Earth Observation in the Marmara Supersite) EC FP7 Project, in conjunction with a large set of geophysical and geological data collected starting from 1999, we compiled a new morphotectonic map of the submerged part of the North-Anatolian <span class="hlt">Fault</span> system (NAF) in the Sea of Marmara. Data analysis allowed us to recognize <span class="hlt">active</span> <span class="hlt">fault</span> segments and their <span class="hlt">activity</span> at the scale of 10 ka, taking as stratigraphic reference the base of the latest marine ingression, which constitutes a clear marker in the sedimentary sequence of the Sea of Marmara. This is mainly due to the fact the Sea of Marmara was a fresh water lake during the Last Glacial Maximum, and switched to a marine environment when the global sea level reached to the -85 m relative to present day and crossed the Dardanelles sill during the transgression. The passage from lacustrine to marine environment is marked by a typical unconformity in high-resolution <span class="hlt">seismic</span> profiles, which can be correlated over the entire Marmara basin. According to the average recurrence time for major earthquake along the NAF, the time interval of 10 ka should include several earthquake cycle and is representative of the seismotectonic behavior of the <span class="hlt">fault</span> at geological time scales. Given the relatively high deformation rates relative to in relative to sediment supply, most <span class="hlt">active</span> tectonic structures have a morphological expression at the seafloor. This allowed us to correlate deformations from a <span class="hlt">seismic</span> section to the adjacent. <span class="hlt">Fault</span> strands not affecting the Holocene sequence were considered inactive. Three types of deformation patterns were observed and classified: almost purely E-W oriented strike-slip segments; NE-SW oriented trans-pressional structures; NW-SE trending trans-tensional features. Segmentation of the so-called Main Marmara <span class="hlt">Fault</span> in the Sea</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/177321','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/177321"><span>Characterization and application of microearthquake clusters to problems of scaling, <span class="hlt">fault</span> zone dynamics, and <span class="hlt">seismic</span> monitoring at Parkfield, California</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nadeau, Robert Michael</p> <p>1995-10-01</p> <p>This document contains information about the characterization and application of microearthquake clusters and <span class="hlt">fault</span> zone dynamics. Topics discussed include: Seismological studies; <span class="hlt">fault</span>-zone dynamics; periodic recurrence; scaling of microearthquakes to large earthquakes; implications of <span class="hlt">fault</span> mechanics and <span class="hlt">seismic</span> hazards; and wave propagation and temporal changes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310663J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310663J"><span>Reconciling <span class="hlt">seismicity</span> and geodetic locking depths on the Anza section of the San Jacinto <span class="hlt">fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Junle; Fialko, Yuri</p> <p>2016-10-01</p> <p>Observations from the Anza section of the San Jacinto <span class="hlt">Fault</span> in Southern California reveal that microseismicity extends to depths of 15-18 km, while the geodetically determined locking depth is less than 10 km. This contrasts with observations from other major <span class="hlt">faults</span> in the region and also with predictions of <span class="hlt">fault</span> models assuming a simple layered distribution of frictional properties with depth. We suggest that an anomalously shallow geodetic <span class="hlt">fault</span> locking may result from a transition zone at the bottom of seismogenic layer with spatially heterogeneous frictional properties. Numerical models of <span class="hlt">faults</span> that incorporate stochastic heterogeneity at transitional depths successfully reproduce the observed depth relation between <span class="hlt">seismicity</span> and geodetic locking, as well as complex spatiotemporal patterns of microseismicity with relatively scarce repeating earthquakes. Our models predict propagation of large earthquakes to the bottom of the transition zone, and ubiquitous aseismic transients below the locked zone, potentially observable using high-precision geodetic techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011IzPSE..47..600S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011IzPSE..47..600S"><span>Rigidity of the <span class="hlt">fault</span> zones in the Earth's crust estimated from <span class="hlt">seismic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spivak, A. A.</p> <p>2011-07-01</p> <p>Nonlinear effects in <span class="hlt">seismic</span> wave propagation are analyzed to determine the mechanical rigidity of different-order <span class="hlt">faults</span> that thread the tectonic structures in the central part of the East European platform (Moscow syneclise and Voronezh Crystalline Massif) and the <span class="hlt">fault</span> zones of the Balapan and Degelen mountain regions in Kazakhstan (the Degelen magmatic node in the Central Chingiz zone). The dependency of the rigidity of the <span class="hlt">fault</span> zone on the <span class="hlt">fault</span>'s length is obtained. The rigidity of the tectonic structures is found to experience well-expressed temporal variations with periods of 13-15 days, 27-32 days, and about one year. In the different-order <span class="hlt">fault</span> zones, the amplitudes of both normal k n and the shear k s rigidity for semimonthly, monthly, and annual variations can span a factor of 1.3, 1.5, and 2.5, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSeis.tmp...55T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSeis.tmp...55T"><span>The seismogenic <span class="hlt">fault</span> of the 2010 Efpalion moderate-size <span class="hlt">seismic</span> sequence (western Corinth gulf, Central Greece)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tranos, M. D.</p> <p>2016-08-01</p> <p>The 2010 Efpalion <span class="hlt">seismic</span> sequence with two main moderate earthquake events occurred in the northwestern part of the Corinth Gulf (Central Greece)—a region that has been intensely stretched due to an on-going N-S extensional stress regime. Previous studies assign these two events to <span class="hlt">activations</span> of (a) two <span class="hlt">faults</span> dipping to the north with low angles; (b) two <span class="hlt">faults</span> dipping at high angles, the first dipping to the south, and the second to the north; and (c) two <span class="hlt">faults</span> dipping at high angles, but the first dips to the north, and the second to the south. The recently proposed TR method for focal mechanisms that identifies the seismogenic <span class="hlt">fault</span> of an earthquake sequence is applied on the available focal mechanisms of the sequence, and its results are interrelated with the geology of the region, and previous contradictory interpretations. The focal mechanisms constructed with MT inversion define a steep north-dipping normal <span class="hlt">fault</span>, whereas those constructed with first motions of P-waves define the <span class="hlt">activation</span> of two adjoining <span class="hlt">faults</span> that dip with high angles to the SSE and south, respectively, and which are characterized by strain (slip) compatibility. The latter option fits well with the geology of the region that is dominated by a SE to S-dipping horse-tail splay <span class="hlt">fault</span> zone which exists at the eastern tip of the Nafpaktos Mountain Front. The application of the TR method reveals that the usage itself of different methods for the construction of the focal mechanisms complicates the problem of correctly identifying the seismogenic <span class="hlt">fault</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.680..122F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.680..122F"><span>Refining <span class="hlt">seismic</span> parameters in low <span class="hlt">seismicity</span> areas by 3D trenching: The Alhama de Murcia <span class="hlt">fault</span>, SE Iberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferrater, Marta; Ortuño, Maria; Masana, Eulàlia; Pallàs, Raimon; Perea, Hector; Baize, Stephane; García-Meléndez, Eduardo; Martínez-Díaz, José J.; Echeverria, Anna; Rockwell, Thomas K.; Sharp, Warren D.; Medialdea, Alicia; Rhodes, Edward J.</p> <p>2016-06-01</p> <p>Three-dimensional paleoseismology in strike-slip <span class="hlt">faults</span> with slip rates less than 1 mm per year involves a great methodological challenge. We adapted 3D trenching to track buried channels offset by the Alhama de Murcia seismogenic left-lateral strike-slip <span class="hlt">fault</span> (SE Iberia). A <span class="hlt">fault</span> net slip of 0.9 ± 0.1 mm/yr was determined using statistical analysis of piercing lines for one buried channel, whose age is constrained between 15.2 ± 1.1 ka and 21.9-22.3 cal BP. This value is larger and more accurate than the previously published slip rates for this <span class="hlt">fault</span>. The minimum number of five paleo-earthquakes identified since the deposition of dated layers suggests a maximum average recurrence interval of approximately 5 ka. The combination of both <span class="hlt">seismic</span> parameters yields a maximum slip per event between 5.3 and 6.3 m. We show that accurately planned trenching strategies and data processing may be key to obtaining robust paleoseismic parameters in low <span class="hlt">seismicity</span> areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760060003&hterms=Harris&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DHarris','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760060003&hterms=Harris&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DHarris"><span><span class="hlt">Active</span> <span class="hlt">faults</span> in southeastern Harris County, Texas</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clanton, U. S.; Amsbury, D. L.</p> <p>1975-01-01</p> <p>Aerial color infrared photography was used to investigate <span class="hlt">active</span> <span class="hlt">faults</span> in a complex graben in southeastern Harris County, Tex. The graben extends east-west across an oil field and an interstate highway through Ellington Air Force Base (EAFB), into the Clear Lake oil field and on to LaPorte, Tex. It was shown that the <span class="hlt">fault</span> pattern at EAFB indicates an appreciable horizontal component associated with the failure of buildings, streets, and runways. Another <span class="hlt">fault</span> system appears to control the shoreline configuration of Clear Lake, with some of the <span class="hlt">faults</span> associated with tectonic movements and the production of oil and gas, but many related to extensive ground water withdrawal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H51D1210M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H51D1210M"><span>Investigation of the stress state on the <span class="hlt">fault</span> planes and the magnitude of the <span class="hlt">seismic</span> events occurred from geothermal reservoirs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukuhira, Y.; Asanuma, H.; Häring, M. O.; Saeki, K.</p> <p>2013-12-01</p> <p>Occurrence of felt earthquakes is a critical environmental burden in geothermal development, and studies on control factors of the magnitude of the <span class="hlt">seismic</span> events have been <span class="hlt">activated</span> worldwide. We have identified <span class="hlt">fault</span> planes of the large events occurred from engineered geothermal systems (EGS) sites, at Cooper Basin, Australia, and Basel, Switzerland, and Yanaizu-Nishiyama, a Japanese hydrothermal field. Shear/normal stress working on these <span class="hlt">fault</span> planes was evaluated on the Mohr stress circles, comparing with the event magnitudes. It has been found that the large events at Basel and Yanaizu-Nishiyama occurred from <span class="hlt">fault</span> planes where relatively large shear stress is working, although smaller events also occurred from <span class="hlt">fault</span> planes with large shear stress. Identification of the <span class="hlt">fault</span> planes of the larger events at Basel showed that large events mainly occurred from two types of sub-vertical <span class="hlt">fault</span> planes with azimuth of WNW-ESE or N-S (see figure). FPSs of four felt earthquakes in Yanaizu-Nishiyama showed nearly common strike/dip. From these observations, it can be interpreted that the large events from Basel and Yanaizu-Nishiyama were likely to occur from particular <span class="hlt">fault</span> planes with large shear stress within complex facture system. Similar relationship between shear stress and the magnitude has been also found by several seismologists (e.g. Terakawa et al., 2012). The selectivity in occurrence of the large events among <span class="hlt">fault</span> planes under common shear stress suggests that there would be some additional factors to control scale of the failure. At Cooper Basin, where limited number of sub-horizontal fractures and vertical fractures connecting them compose the reservoir, the large events occurred from the sub-horizontal <span class="hlt">fault</span> planes on which many smaller events also occurred. In this case, the moderate shear stress was working on the sub-horizontal <span class="hlt">fault</span> planes, suggesting that the event magnitudes were mainly controlled by some unknown factors rather than the shear</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70019841','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70019841"><span>Boundary separating the <span class="hlt">seismically</span> <span class="hlt">active</span> reelfoot rift from the sparsely <span class="hlt">seismic</span> Rough Creek graben, Kentucky and Illinois</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wheeler, R.L.</p> <p>1997-01-01</p> <p>The Reelfoot rift is the most <span class="hlt">active</span> of six Iapetan rifts and grabens in central and eastern North America. In contrast, the Rough Creek graben is one of the least <span class="hlt">active</span>, being <span class="hlt">seismically</span> indistinguishable from the central craton of North America. Yet the rift and graben adjoin. Hazard assessment in the rift and graben would be aided by identification of a boundary between them. Changes in the strikes of single large <span class="hlt">faults</span>, the location of a Cambrian transfer zone, and the geographic extent of alkaline igneous rocks provide three independent estimates of the location of a structural boundary between the rift and the graben. The boundary trends north-northwest through the northeastern part of the Fluorspar Area <span class="hlt">Fault</span> Complex of Kentucky and Illinois, and has no obvious surface expression. The boundary involves the largest <span class="hlt">faults</span>, which are the most likely to penetrate to hypocentral depths, and the boundary coincides with the geographic change from abundant <span class="hlt">seismicity</span> in the rift to sparse <span class="hlt">seismicity</span> in the graben. Because the structural boundary was defined by geologic variables that are expected to be causally associated with <span class="hlt">seismicity</span>, it may continue to bound the Reelfoot rift <span class="hlt">seismicity</span> in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......181W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......181W"><span>The relationship between oceanic transform <span class="hlt">fault</span> segmentation, <span class="hlt">seismicity</span>, and thermal structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolfson-Schwehr, Monica</p> <p></p> <p>Mid-ocean ridge transform <span class="hlt">faults</span> (RTFs) are typically viewed as geometrically simple, with <span class="hlt">fault</span> lengths readily constrained by the ridge-transform intersections. This relative simplicity, combined with well-constrained slip rates, make them an ideal environment for studying strike-slip earthquake behavior. As the resolution of available bathymetric data over oceanic transform <span class="hlt">faults</span> continues to improve, however, it is being revealed that the geometry and structure of these <span class="hlt">faults</span> can be complex, including such features as intra-transform pull-apart basins, intra-transform spreading centers, and cross-transform ridges. To better determine the resolution of structural complexity on RTFs, as well as the prevalence of RTF segmentation, <span class="hlt">fault</span> structure is delineated on a global scale. Segmentation breaks the <span class="hlt">fault</span> system up into a series of subparallel <span class="hlt">fault</span> strands separated by an extensional basin, intra-transform spreading center, or <span class="hlt">fault</span> step. RTF segmentation occurs across the full range of spreading rates, from <span class="hlt">faults</span> on the ultraslow portion of the Southwest Indian Ridge to <span class="hlt">faults</span> on the ultrafast portion of the East Pacific Rise (EPR). It is most prevalent along the EPR, which hosts the fastest spreading rates in the world and has undergone multiple changes in relative plate motion over the last couple of million years. Earthquakes on RTFs are known to be small, to scale with the area above the 600°C isotherm, and to exhibit some of the most predictable behaviors in seismology. In order to determine whether segmentation affects the global RTF scaling relations, the scalings are recomputed using an updated <span class="hlt">seismic</span> catalog and <span class="hlt">fault</span> database in which RTF systems are broken up according to their degree of segmentation (as delineated from available bathymetric datasets). No statistically significant differences between the new computed scaling relations and the current scaling relations were found, though a few <span class="hlt">faults</span> were identified as outliers. Finite element</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815774H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815774H"><span>Spontaneous aseismic and <span class="hlt">seismic</span> slip on evolving <span class="hlt">faults</span> in a continuum-mechanics framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herrendörfer, Robert; van Dinther, Ylona; Gerya, Taras</p> <p>2016-04-01</p> <p>The convergent plate motion in subduction zones is accommodated both by <span class="hlt">seismic</span> events as well as by aseismic transients and steady slip. To better understand the long-term conditions in subduction zones that govern which portion of convergence is released through <span class="hlt">seismic</span> or aseismic slip, we need to simulate self-consistently these slip processes and the <span class="hlt">faults</span> along which they occur. For this purpose, we extended our continuum-based, visco-elasto-plastic numerical model in which cycles of earthquake-like ruptures were simulated through a purely slip rate-dependent friction, albeit at very low slip rates (van Dinther et al., JGR, 2013). To model a wider slip spectrum and to approach <span class="hlt">seismic</span> slip rates, we implemented an adaptive time-stepping scheme (Lapusta and Rice, JGR, 2001) and an innovative invariant reformulation of conventional rate-and state dependent friction (RSF). In a simplified subduction setup, we validate our new implementations by comparing our simulated stability transitions to those of conventional <span class="hlt">seismic</span> cycle models. We show a general agreement of the transitions between the occurrence of decaying oscillations towards stable sliding, periodic aseismic events, complex periodic behaviour and <span class="hlt">seismic</span> events. To demonstrate the advantages of this continuum approach, we simulate the spatiotemporal evolution of a complex <span class="hlt">fault</span> system beyond the megathrust within an otherwise visco-elastically deforming layered upper plate. Using the common assumption of zero cohesion in RSF applications, deformation localizes in <span class="hlt">fault</span>-like shear bands, while the degree of localization depends on the choice of RSF parameters. Deformation strongly localizes for rate-weakening friction within the usual laboratory-determined range (a-b~ -1e-2), whereas for rate-strengthening friction it only localizes clearly outside of this range (a-b~1e-4). Furthermore, the existence of these <span class="hlt">faults</span> is short-lived, because RSF describes only transient changes in <span class="hlt">fault</span> strength. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.9527S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.9527S"><span>Long-lasting <span class="hlt">seismic</span> repeaters in the Central Basin of the Main Marmara <span class="hlt">Fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmittbuhl, J.; Karabulut, H.; Lengliné, O.; Bouchon, M.</p> <p>2016-09-01</p> <p>The Main Marmara <span class="hlt">Fault</span> which crosses the whole Marmara Sea is a significant <span class="hlt">seismic</span> gap along the North Anatolian <span class="hlt">Fault</span>. Here we show that nine long-lasting strike-slip <span class="hlt">seismic</span> repeaters exist below the Central Basin within the seismogenic zone, in a 10 km region where deep creep was previously suggested from the analysis of the local <span class="hlt">seismicity</span>. The typical recurrence time was 8 months during the 2008-2015 period. The cumulative slip of the repeating sequence appears to be compatible with the regional geodetic slip rate if they are assumed to be part of a large single asperity (10 km). The repeaters also exhibit short-term crises and are possibly related to bursts of creep.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S43A2031R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S43A2031R"><span>The <span class="hlt">seismic</span> velocity structure of a foreshock zone on an oceanic transform <span class="hlt">fault</span>: Imaging a rupture barrier to the 2008 Mw 6.0 earthquake on the Gofar <span class="hlt">fault</span>, EPR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roland, E. C.; McGuire, J. J.; Lizarralde, D.; Collins, J. A.</p> <p>2010-12-01</p> <p>East Pacific Rise (EPR) oceanic transform <span class="hlt">faults</span> are known to exhibit a number of unique <span class="hlt">seismicity</span> characteristics, including abundant <span class="hlt">seismic</span> swarms, a prevalence of aseismic slip, and high rates of foreshock <span class="hlt">activity</span>. Until recently the details of how this behavior fits into the <span class="hlt">seismic</span> cycle of large events that occur periodically on transforms have remained poorly understood. In 2008 the most recent <span class="hlt">seismic</span> cycle of the western segment (G3) of the Gofar <span class="hlt">fault</span> (4 degrees South on the EPR) ended with a Mw 6.0 earthquake. <span class="hlt">Seismicity</span> associated with this event was recorded by a local array of ocean bottom seismometers, and earthquake locations reveal several distinct segments with unique slip behavior on the G3 <span class="hlt">fault</span>. Preceding the Mw 6.0 event, a significant foreshock sequence was recorded just to the east of the mainshock rupture zone that included more than 20,000 detected earthquakes. This foreshock zone formed the eastern barrier to the mainshock rupture, and following the mainshock, <span class="hlt">seismicity</span> rates within the foreshock zone remained unchanged. Based on aftershock locations of events following the 2007 Mw 6.0 event that completed the <span class="hlt">seismic</span> cycle on the eastern end of the G3 <span class="hlt">fault</span>, it appears that the same foreshock zone may have served as the western rupture barrier for that prior earthquake. Moreover, mainshock rupture associated with each of the last 8 large (~ Mw 6.0) events on the G3 <span class="hlt">fault</span> seems to terminate at the same foreshock zone. In order to elucidate some of the structural controls on <span class="hlt">fault</span> slip and earthquake rupture along transform <span class="hlt">faults</span>, we present a <span class="hlt">seismic</span> P-wave velocity profile crossing the center of the foreshock zone of the Gofar <span class="hlt">fault</span>, as well as a profile for comparison across the neighboring Quebrada <span class="hlt">fault</span>. Although tectonically similar, Quebrada does not sustain large earthquakes and is thought to accommodate slip primarily aseismically and with small magnitude earthquake swarms. Velocity profiles were obtained using data collected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JSG....31..989Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JSG....31..989Y"><span>Discrete element modeling of the <span class="hlt">faulting</span> in the sedimentary cover above an <span class="hlt">active</span> salt diapir</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yin, Hongwei; Zhang, Jie; Meng, Lingsen; Liu, Yuping; Xu, Shijing</p> <p>2009-09-01</p> <p>Geological mapping, <span class="hlt">seismic</span> analyses, and analogue experiments show that <span class="hlt">active</span> salt diapirism results in significant <span class="hlt">faulting</span> in the overburden strata. <span class="hlt">Faults</span> associated with <span class="hlt">active</span> diapirism generally develop over the crest of the dome and form a radial pattern. In this study, we have created a 3-D discrete element model and used this model to investigate the <span class="hlt">fault</span> system over <span class="hlt">active</span> diapirs. The model reproduces some common features observed in physical experiments and natural examples. The discrete element results show that most <span class="hlt">faults</span> initiate near the model surface and have displacement decreasing downward. In addition, model results indicate that the earliest <span class="hlt">fault</span>, working as the master <span class="hlt">fault</span>, has a strong influence on the subsequent <span class="hlt">fault</span> pattern. The footwall of the master <span class="hlt">fault</span> is mainly deformed by arc-parallel stretching and develops a subradial <span class="hlt">fault</span> pattern, whereas the hanging wall is deformed by both arc-parallel stretching and gliding along the master <span class="hlt">fault</span> and top of salt, and hence develops both parallel and oblique <span class="hlt">faults</span>. Model results replicate the <span class="hlt">fault</span> pattern and deformation mechanism of the Reitbrook dome, Germany.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tecto..32..501H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tecto..32..501H"><span>Quaternary deformation along the Meeman-Shelby <span class="hlt">Fault</span> near Memphis, Tennessee, imaged by high-resolution marine and land <span class="hlt">seismic</span> reflection profiles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Yanjun; Magnani, Maria Beatrice; McIntosh, Kirk; Waldron, Brian; Guo, Lei</p> <p>2013-06-01</p> <p>series of high-resolution <span class="hlt">seismic</span> reflection surveys was carried out in 2008, 2010, and 2011, providing a total of five new <span class="hlt">seismic</span> profiles constraining the location and character of the Meeman-Shelby <span class="hlt">Fault</span> (MSF), about 9 km west of Memphis, Tennessee, in the Central U.S. The MSF is the best documented <span class="hlt">fault</span> closest to Memphis yet discovered and shows a recurrent <span class="hlt">fault</span> history. The <span class="hlt">fault</span>, as imaged by the reflection profiles, is ~45 km long, strikes N25°E, and dips west-northwest ~83°, exhibiting an up-to-the-west sense of motion with a possible right-lateral strike-slip component. The data show that on average, the MSF offsets the Paleozoic unit ~77 m and folds the top of the Cretaceous unit and the Paleocene-Eocene Wilcox Group ~44 and ~25 m, respectively. One <span class="hlt">seismic</span> profile acquired along the Mississippi River images the bottom of the Quaternary alluvium warped up ~28 m, indicating recent <span class="hlt">activity</span> of the MSF. Calculated vertical slip rates of the MSF during the deposition of the Upper Cretaceous, Paleocene, Eocene, and Quaternary sediments are 0.0022, 0.0010, 0.0004, and 0.2154 mm/yr, respectively, suggesting an increase in <span class="hlt">fault</span> <span class="hlt">activity</span> during the Quaternary. Consistent with the present stress field and the deformation of the New Madrid <span class="hlt">seismic</span> zone <span class="hlt">fault</span> system, we interpret the MSF as a P shear <span class="hlt">fault</span> in the context of a left-stepping, right-lateral constraining strike-slip <span class="hlt">fault</span> system under a nearly east-west oriented compressional stress field. Source scaling estimates indicate that the MSF is capable of generating a M6.9 earthquake if rupturing in one event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S21B2036A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S21B2036A"><span>Shallow <span class="hlt">seismicity</span> migration in a normal <span class="hlt">fault</span> test site in northern Apennines (Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amato, A.; Braun, T.; Cattaneo, M.; Chiaraluce, L.; Cocco, M.; D'Alema, E.; di Stefano, R.; Frapiccini, M.; Latorre, D.; Marzorati, S.; Monachesi, G.; Moretti, M.; Piana Agostinetti, N.; Piccinini, D.; Saccorotti, G.; Valoroso, L.; Selvaggi, G.</p> <p>2010-12-01</p> <p>In 2008-2010 a high-density, real-time <span class="hlt">seismic</span> network has been installed in the northern Apennines, integrating the INGV permanent national network. While the national network uses satellite links and leased telephone lines, the additional stations are connected with WiFi radio links and INGV-made GAIA digitizers. In march 2010, 10 additional remote stations were installed to further improve the monitoring. At present, a total of 30 stations are operational in the area. The scientific target of the network, funded by INGV and by the Italian Ministry of Research (project Airplane RBPR05B2ZJ) is to understand the deformation process in the area, characterized by: i) extension at 2-3 mm/yr; ii) a regional east-dipping, low-angle normal <span class="hlt">fault</span> (the Alto Tiberina <span class="hlt">Fault</span>, ATF) that limits the <span class="hlt">seismicity</span> downward in the upper 10-15 km of the crust; iii)historical earthquakes as large as M6.5; iv) a high rate of background <span class="hlt">seismicity</span>. The extensional area is underlayed by the west-dipping Adriatic continental slab with <span class="hlt">seismicity</span> down to 70-80 km below the belt. During the first year of operation, we located more than 3,000 local earthquakes with magnitude in the range -0.5 to 3.8. Part of the <span class="hlt">seismicity</span>, located with both absolute and relative techniques, clusters on shallow high-angle normal <span class="hlt">faults</span> above the ATF, and show a clear migration both along strike (at about 0.5 km/day) and in depth. This pattern has strong similarities with that observed in previous large normal <span class="hlt">faulting</span> events in the Apennines, and is likely related to fluid migration. Such a dense network allows us to detect seismogenic processes with an unprecedented detail. Data are accumulating fast and will illuminate other parts of this complex <span class="hlt">fault</span> system. Ongoing developments include a continuous GPS network and borehole seismometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990BROCS.........C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990BROCS.........C"><span>Current (1985-1988) <span class="hlt">seismic</span> <span class="hlt">activity</span> in Belgium: Comparison with historical and instrumental <span class="hlt">seismic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Camelbeeck, T.</p> <p>1990-12-01</p> <p>Reliable information concerning the historical and instrumental <span class="hlt">seismicity</span> in Belgium is discussed in comparison with the more recent data of microseismicity. The Brabant Massif and the north of France are characterized by an important historical <span class="hlt">seismicity</span>. Since the Middle Ages, four earthquakes caused considerable concern in that region. The actual <span class="hlt">seismic</span> <span class="hlt">activity</span> is not well known due to the lack of seismological stations. It is thus impossible to base the tectonic pattern on seismological data. The <span class="hlt">seismic</span> <span class="hlt">activity</span> in Hainaut was analyzed with the data of the <span class="hlt">seismic</span> sequence near Dour in 1987 and the reexamination of the bigger earthquakes having occurred since 1965. The seismogenic layer is limited to the 8 first km of the crust. The occurrence under the form of swarms or sequences is an evidence of strong fracturation. The <span class="hlt">fault</span>-plane solution of the Dour earthquake in 1987 indicates an almost north-south extension at this place of the Mons Basin. The focal mechanisms of 5 earthquakes in the center region shows a north-west south-east oriented maximal horizontal compressive stress. This information is in agreement with the dextral strike-slip of the 'shear zone of north-Artois' made conspicuous by geology. Important information about the seismotectonics in the eastern part of Belgium is given by the study of the actual microseismicity with a dense network of seismological stations. The <span class="hlt">fault</span>-plane solution of the Malmedy (12 May 1985, M (sub L) = 2.5) earthquake indicates a south-west north-east extension along a <span class="hlt">fault</span> of rhenish orientation. This is a favorable argument to the hypothesis of the prolongation across the Ardennes of the quaternary <span class="hlt">faults</span> of the lower Rhine embayment. The analysis of the Bilzen (16 Jul. 1985, M(sub L) = 3.0), Gulpen (17 Oct. 1988, M(sub L) = 3.5), and Sprimont (27 Dec. 1988, M(sub L) = 3.6) earthquakes supplies new information on the complex tectonics of the Liege region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.3164P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.3164P"><span>Induced <span class="hlt">seismicity</span> and CO2 leakage through <span class="hlt">fault</span> zones during large-scale underground injection in a multilayered sedimentary system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pio Rinaldi, Antonio; Rutqvist, Jonny; Jeanne, Pierre; Cappa, Frederic; Guglielmi, Yves</p> <p>2014-05-01</p> <p>Overpressure caused by the direct injection of CO2 into a deep sedimentary system may produce changes in the state of stress, as well as, have an impact on the sealing capabilities of the targeted system. The importance of geomechanics including the potential for reactivating <span class="hlt">faults</span> associated with large-scale geologic carbon sequestration operations has recently become more widely recognized. However, not withstanding the potential for triggering notable (felt) <span class="hlt">seismic</span> events, the potential for buoyancy-driven CO2 to reach potable groundwater and the ground surface is more important from safety and storage-efficiency perspectives. In this context, this work extends previous studies on the geomechanical modeling of <span class="hlt">fault</span> responses during underground carbon dioxide injection, focusing on both short- and long-term integrity of the sealing caprock, and hence of potential leakage of either brine or CO2 to shallow groundwater aquifers during <span class="hlt">active</span> injection. The first part of this work aims to study the <span class="hlt">fault</span> responses during underground carbon dioxide injection, focusing on the short-term (5 years) integrity of the CO2 repository, and hence on the potential leakage of CO2 to shallow groundwater aquifers. Increased pore pressure can alter the stress distribution on a <span class="hlt">fault</span>/fracture zone, which may produce changes in the permeability related to the elastic and/or plastic strain (or stress) during single (or multiple) shear ruptures. We account for stress/strain-dependent permeability and study the leakage through the <span class="hlt">fault</span> zone as its permeability changes along with strain and stress variations. We analyze several scenarios related to the injected amount of CO2 (and hence related to potential overpressure) involving both involving minor and major <span class="hlt">faults</span>, and analyze the profile risks of leakage for different stress/strain permeability coupling functions, as well as increasing the complexity of the system in terms of hydromechanical heterogeneities. We conclude that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T33E..05H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T33E..05H"><span>Geodetic Constraints on <span class="hlt">Fault</span> Slip Rates and <span class="hlt">Seismic</span> Hazard in the Greater Las Vegas Area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammond, W. C.; Kreemer, C.; Blewitt, G.; Broermann, J.; Bennett, R. A.</p> <p>2014-12-01</p> <p>We address fundamental questions about how contemporary tectonic deformation of the crust in the southern Great Basin occurs in the region around Las Vegas (LV) Nevada, western Arizona and eastern California. This area lies in the intersection of the eastern Walker Lane Belt, southern Great Basin and western Colorado Plateau (CP), sharing features of transtensional and extensional deformation associated with Pacific/North America relative motion. We use GPS data collected from 48 stations of the MAGNET semi-continuous network and 77 stations from continuous networks including BARGEN and EarthScope Plate Boundary Observatory. MAGNET stations have been observed for a minimum of 7 years, while most continuous stations have longer records. From these data we estimate the velocity of crustal motion for all stations with respect to the stable North America reference frame NA12. To correct for transients from recent large earthquakes including the 1999 Hector Mine and 2010 El Mayor-Cucapah events we use models of co- and post-<span class="hlt">seismic</span> deformation, subtracting the predicted motions from the time series before estimating interseismic stain rates. We find approximately 2 mm/yr of relative motion distributed over 200 km centered on Las Vegas, with a mean strain accumulation rate of 10 × 10-9 yr-1, with lower rates of predominantly extensional strain to the east and higher rates of predominantly shear deformation to the west. The mean strain rate is lower than that of the western Walker Lane but about twice that of eastern Nevada where e.g., the Wells, NV MW 6.0 earthquake occurred in 2008. From this new velocity field we generated a horizontal tensor strain rate map and a crustal block motion model to portray the transition of <span class="hlt">active</span> strain from the CP into the Walker Lane. For <span class="hlt">faults</span> in the Las Vegas Valley, including the Eglington <span class="hlt">Fault</span> and Frenchman Mountain <span class="hlt">Fault</span>, the observed velocity gradients and model results are consistent with normal slip rates of 0.2 mm/yr, which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.G13A0793G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.G13A0793G"><span>Post-<span class="hlt">Seismic</span> Crustal Deformation Following The 1999 Izmit Earthquake, Western Part Of North Anatolian <span class="hlt">Fault</span> Zone, Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gurkan, O.; Ozener, H.</p> <p>2004-12-01</p> <p>The North Anatolian <span class="hlt">Fault</span> is an about 1500 km long, extending from the Karliova to the North Aegean. Turkey is a natural laboratory with high tectonic <span class="hlt">activity</span> caused by the relative motion of the Eurasian, Arabian and Anatolian plates. Western part of Turkey and its vicinity is a <span class="hlt">seismically</span> <span class="hlt">active</span> area. Since 1972 crustal deformation has been observed by various kinds of geodetic measurements in the area. Three GPS networks were installed in this region by Geodesy Department of Kandilli Observatory and Earthquake Research Institute( KOERI ) of Bogazici University: (1) Iznik Network, installed on the Iznik-Mekece <span class="hlt">fault</span> zone, <span class="hlt">seismically</span> low <span class="hlt">active</span> part, (2) Sapanca Network, installed on the Izmit-Sapanca <span class="hlt">fault</span> zone, <span class="hlt">seismically</span> <span class="hlt">active</span> part, (3) Akyazi Network, installed on their intersection area, the Mudurnu <span class="hlt">fault</span> zone. First period observations were performed by using terrestrial methods in 1990 and these observations were repeated annually until 1993. Since 1994, GPS measurements have been carried out at the temporary and permanent points in the area and the crustal movements are being monitored. Horizontal deformations, which have not been detected by terrestrial methods, were determined from the results of GPS measurements. A M=7.4 earthquake hit Izmit, northern Turkey, on August 17, 1999. After this earthquake many investigations have been started in the region. An international project has been performed with the collaboration of Massachussets Institute of Technology, Turkish General Command of Mapping, Istanbul Technical University, TUBITAK-Marmara Research Center and Geodesy Department of KOERI. Postseismic movements have been observed by the region-wide network. A GPS network including 49 well spread points in Marmara region was observed twice a year between 1999 and 2003 years. During these surveys, another network with 6 points has been formed by using 2 points from each 3 microgeodetic networks on NAFZ with appropriate coverage and geometry. These</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70046030','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70046030"><span>The northwest trending north Boquerón Bay-Punta Montalva <span class="hlt">Fault</span> Zone; A through going <span class="hlt">active</span> <span class="hlt">fault</span> system in southwestern Puerto Rico</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Roig‐Silva, Coral Marie; Asencio, Eugenio; Joyce, James</p> <p>2013-01-01</p> <p>The North Boquerón Bay–Punta Montalva <span class="hlt">fault</span> zone has been mapped crossing the Lajas Valley in southwest Puerto Rico. Identification of the <span class="hlt">fault</span> was based upon detailed analysis of geophysical data, satellite images, and field mapping. The <span class="hlt">fault</span> zone consists of a series of Cretaceous bedrock <span class="hlt">faults</span> that reactivated and deformed Miocene limestone and Quaternary alluvial fan sediments. The <span class="hlt">fault</span> zone is <span class="hlt">seismically</span> <span class="hlt">active</span> (local magnitude greater than 5.0) with numerous locally felt earthquakes. Focal mechanism solutions suggest strain partitioning with predominantly east–west left-lateral displacements with small normal <span class="hlt">faults</span> striking mostly toward the northeast. Northeast-trending fractures and normal <span class="hlt">faults</span> can be found in intermittent streams that cut through the Quaternary alluvial fan deposits along the southern margin of the Lajas Valley, an east–west-trending 30-km-long <span class="hlt">fault</span>-controlled depression. Areas of preferred erosion within the alluvial fan trend toward the west-northwest parallel to the onland projection of the North Boquerón Bay <span class="hlt">fault</span>. The North Boquerón Bay <span class="hlt">fault</span> aligns with the Punta Montalva <span class="hlt">fault</span> southeast of the Lajas Valley. Both <span class="hlt">faults</span> show strong southward tilting of Miocene strata. On the western end, the Northern Boquerón Bay <span class="hlt">fault</span> is covered with flat-lying Holocene sediments, whereas at the southern end the Punta Montalva <span class="hlt">fault</span> shows left-lateral displacement of stream drainage on the order of a few hundred meters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NHESS..13.2521C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NHESS..13.2521C"><span><span class="hlt">Seismicity</span> at the northeast edge of the Mexican Volcanic Belt (MVB) and <span class="hlt">activation</span> of an undocumented <span class="hlt">fault</span>: the Peñamiller earthquake sequence of 2010-2011, Querétaro, Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clemente-Chavez, A.; Figueroa-Soto, A.; Zúñiga, F. R.; Arroyo, M.; Montiel, M.; Chavez, O.</p> <p>2013-10-01</p> <p>The town of Peñamiller in the state of Querétaro, Mexico, is located at the northeast border of the seismogenic zone known as the Mexican Volcanic Belt (MVB), which transects the central part of Mexico with an east-west orientation. In the vicinity of this town, a sequence of small earthquakes occurred during the end of 2010 and beginning of 2011. <span class="hlt">Seismicity</span> in the continental regimen of central Mexico is not too frequent; however, it is known that there are precedents of large earthquakes (Mw magnitude greater than 6.0) occurring in this zone. Three large earthquakes have occurred in the past 100 yr: the 19 November 1912 (MS = 7.0), the 3 January 1920 (MS = 6.4), and the 29 June 1935 (MS = 6.9) earthquakes. Prior to the instrumental period, the earthquake of 11 February 1875, which took place near the city of Guadalajara, caused widespread damage. The purpose of this article is to contribute to the available <span class="hlt">seismic</span> information of this region. This will help advance our understanding of the tectonic situation of the central Mexico MVB region. Twenty-four shallow earthquakes of the Peñamiller <span class="hlt">seismic</span> sequence of 2011 were recorded by a temporary accelerograph network installed by the Universidad Autónoma de Querétaro (UAQ). The data were analyzed in order to determine the source locations and to estimate the source parameters. The study was carried out through an inversion process and by spectral analysis. The results show that the largest earthquake occurred on 8 February 2011 at 19:53:48.6 UTC, had a moment magnitude Mw = 3.5, and was located at latitude 21.039° and longitude -99.752°, at a depth of 5.6 km. This location is less than 7 km away in a south-east direction from downtown Peñamiller. The focal mechanisms are mostly normal <span class="hlt">faults</span> with small lateral components. These focal mechanisms are consistent with the extensional regimen of the southern extension of the Basin and Range (BR) province. The source area of the largest event was estimated to</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6197R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6197R"><span>Complex patterns of <span class="hlt">faulting</span> revealed by 3D <span class="hlt">seismic</span> data at the West Galicia rifted margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reston, Timothy; Cresswell, Derren; Sawyer, Dale; Ranero, Cesar; Shillington, Donna; Morgan, Julia; Lymer, Gael</p> <p>2015-04-01</p> <p>The west Galicia margin is characterised by crust thinning to less than 3 km, well-defined <span class="hlt">fault</span> blocks, which overlie a bright reflection (the S reflector) generally interpreted as a tectonic Moho. The margin exhibits neither voluminous magmatism nor thick sediment piles to obscure the structures and the amount of extension. As such is represents an ideal location to study the process of continental breakup both through <span class="hlt">seismic</span> imaging and potentially through drilling. Prestack depth migration of existing 2D profiles has strongly supported the interpretation of the S reflector as both a detachment and as the crust-mantle boundary; wide-angle <span class="hlt">seismic</span> has also shown that the mantle beneath S is serpentinised. Despite the quality of the existing 2D <span class="hlt">seismic</span> images, a number of competing models have been advanced to explain the formation of this margin, including sequential <span class="hlt">faulting</span>, polyphase <span class="hlt">faulting</span>, multiple detachments and the gravitational collapse of the margin over exhumed mantle. As these models, all developed for the Galicia margin, have been subsequently applied to other margins, distinguishing between them has implications not only for the structure of the Galicia margin but for the process of rifting through to breakup more generally. To address these issues in summer of 2013 we collected a 3D combined <span class="hlt">seismic</span> reflection and wide-angle dataset over this margin. Here we present some of the results of ongoing processing of the 3D volume, focussing on the internal structure of some of the <span class="hlt">fault</span> blocks that overlies the S detachment. 2D processing of the data shows a relatively simple series of tilted <span class="hlt">fault</span> block, bound by west-dipping <span class="hlt">faults</span> that detach downwards onto the bright S reflector. However, inspection of the 3D volume produced by 3D pre-stack time migration reveals that the <span class="hlt">fault</span> blocks contain a complex set of sedimentary packages, with strata tilted to the east, west, north and south, each package bound by <span class="hlt">faults</span>. Furthermore, the top of crustal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSG....93...29S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSG....93...29S"><span>Phyllosilicate injection along extensional carbonate-hosted <span class="hlt">faults</span> and implications for co-<span class="hlt">seismic</span> slip propagation: Case studies from the central Apennines, Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smeraglia, Luca; Aldega, Luca; Billi, Andrea; Carminati, Eugenio; Doglioni, Carlo</p> <p>2016-12-01</p> <p>We document phyllosilicates occurrence along five shallow (exhumed from depths < 3 km) carbonate-hosted extensional <span class="hlt">faults</span> from the <span class="hlt">seismically-active</span> domain of the central Apennines, Italy. The shallow portion of this domain is characterized by a sedimentary succession consisting of ∼5-6 km thick massive carbonate deposits overlain by ∼2 km thick phyllosilicate-rich deposits (marls and siliciclastic sandstones). We show that the phyllosilicates observed within the studied carbonate-hosted <span class="hlt">faults</span> derived from the overlying phyllosilicate-rich sedimentary deposits and were involved in the <span class="hlt">faulting</span> processes. We infer that, during <span class="hlt">fault</span> zone evolution, the phyllosilicates downward injected into pull-aparts (i.e., dilational jogs) that were generated along staircase extensional <span class="hlt">faults</span>. With further displacement accumulation, the clayey material was smeared and concentrated into localized layers along the carbonate-hosted <span class="hlt">fault</span> surfaces. These layers are usually thin (a few centimeters to decimeters thick), but can reach also a few meters in thickness. We suggest that, even in tectonic settings dominated by high frictional strength rocks (e.g., carbonates), localized layers enriched in weak phyllosilicates can occur along shallow <span class="hlt">fault</span> surfaces thus reducing the expected <span class="hlt">fault</span> strength during earthquakes, possibly promoting co-<span class="hlt">seismic</span> slip propagation up to the Earth's surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMNH31C1637S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMNH31C1637S"><span>Geomorphic and Structural Analysis of the Verona-Williams-Pleasanton <span class="hlt">fault</span> zone and implications for <span class="hlt">seismic</span> hazard, eastern San Francisco Bay Area, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sawyer, T. L.; Unruh, J. R.; Hoirup, D. F.; Barry, G.; Pearce, J. T.</p> <p>2012-12-01</p> <p>Folds and thrust <span class="hlt">faults</span> adjacent to and beneath the Livermore Valley have accommodated Quaternary crustal shortening between major dextral <span class="hlt">faults</span> of the eastern San Andreas <span class="hlt">fault</span> system. The Verona and Williams <span class="hlt">faults</span> are NE-dipping thrust or reverse <span class="hlt">faults</span> that have uplifted the Pliocene-Pleistocene Livermore gravels along the western and southern margins of the valley. The Williams <span class="hlt">fault</span> extends ~13 km northwest from the Mt. Lewis <span class="hlt">seismic</span> trend to the sinistral Las Positas <span class="hlt">fault</span>, which forms the southern margin of the valley. A 3-km left step along the Las Positas <span class="hlt">fault</span> separates the surface traces of the Verona and Williams <span class="hlt">faults</span>. The Verona <span class="hlt">fault</span> extends ~8 km northwest from the stepover to southwestern Livermore Valley. It is possible that the Las Positas <span class="hlt">fault</span> extends to the base of the seismogenic crust and separates the Verona and Williams <span class="hlt">faults</span> into two kinematically independent structures. Alternatively, the Verona and Williams <span class="hlt">faults</span> may merge downdip into a common thrust <span class="hlt">fault</span> plane, with the Las Positas <span class="hlt">fault</span> confined to the hanging wall as a tear <span class="hlt">fault</span>. The Verona and Williams <span class="hlt">faults</span> exhibit geomorphic evidence for late Quaternary <span class="hlt">fault</span> rupture propagating to or very near the ground surface. The Williams <span class="hlt">fault</span> tightly folds and overturns the Livermore gravels, and appears to form scarps that impound late Quaternary alluvium and cross Holocene landslide deposits. Many Holocene(?) alluvial fans exhibit distinct convex longitudinal profiles across the <span class="hlt">fault</span> trace suggesting <span class="hlt">active</span> folding above the Verona <span class="hlt">fault</span>. The geomorphic position of a stream-terrace remnant suggests that >7 m of tectonic uplift is possible across the Verona <span class="hlt">fault</span> during the late Quaternary. Surficial geologic mapping and geomorphic analysis of the ancestral Arroyo Valle drainage system reveals numerous paleochannels that generally decrease in elevation (age) to the northwest, and provide useful isochronous markers delineating a subtle tectonic uplift in western Livermore Valley</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T33G2498H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T33G2498H"><span>The Salton <span class="hlt">Seismic</span> Imaging Project (SSIP): <span class="hlt">Active</span> Rift Processes in the Brawley <span class="hlt">Seismic</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, L.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Rymer, M. J.; Driscoll, N. W.; Kent, G.; Harding, A. J.; Gonzalez-Fernandez, A.; Lazaro-Mancilla, O.</p> <p>2011-12-01</p> <p>The Salton <span class="hlt">Seismic</span> Imaging Project (SSIP), funded by NSF and USGS, acquired <span class="hlt">seismic</span> data in and across the Salton Trough in southern California and northern Mexico in March 2011. The project addresses both rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas <span class="hlt">Fault</span> system. Seven lines of onshore refraction and low-fold reflection data were acquired in the Coachella, Imperial, and Mexicali Valleys, two lines and a grid of airgun and OBS data were acquired in the Salton Sea, and onshore-offshore data were recorded. Almost 2800 land seismometers and 50 OBS's were used in almost 5000 deployments at almost 4300 sites, in spacing as dense as 100 m. These instruments received <span class="hlt">seismic</span> signals from 126 explosive shots up to 1400 kg and over 2300 airgun shots. In the central Salton Trough, North American lithosphere appears to have been rifted completely apart. Based primarily on a 1979 <span class="hlt">seismic</span> refraction project, the 20-22 km thick crust is apparently composed entirely of new crust added by magmatism from below and sedimentation from above. <span class="hlt">Active</span> rifting of this new crust is manifested by shallow (<10km depth) <span class="hlt">seismicity</span> in the oblique Brawley <span class="hlt">Seismic</span> Zone (BSZ), small Salton Buttes volcanoes aligned perpendicular to the transform <span class="hlt">faults</span>, very high heat flow (~140 mW/m2), and geothermal energy production. This presentation is focused on an onshore-offshore line of densely sampled refraction and low-fold reflection data that crosses the Brawley <span class="hlt">Seismic</span> Zone and Salton Buttes in the direction of plate motion. At the time of abstract submission, data analysis was very preliminary, consisting of first-arrival tomography of the onshore half of the line for upper crustal <span class="hlt">seismic</span> velocity. Crystalline basement (>5 km/s), comprised of late-Pliocene to Quaternary sediment metamorphosed by the high heat flow, occurs at ~2 km depth beneath the Salton Buttes and geothermal field and ~4 km</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T11A4544W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T11A4544W"><span>Updated mapping and <span class="hlt">seismic</span> reflection data processing along the Queen Charlotte <span class="hlt">fault</span> system, southeast Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walton, M. A. L.; Gulick, S. P. S.; Haeussler, P. J.; Rohr, K.; Roland, E. C.; Trehu, A. M.</p> <p>2014-12-01</p> <p>The Queen Charlotte <span class="hlt">Fault</span> (QCF) is an obliquely convergent strike-slip system that accommodates offset between the Pacific and North America plates in southeast Alaska and western Canada. Two recent earthquakes, including a M7.8 thrust event near Haida Gwaii on 28 October 2012, have sparked renewed interest in the margin and led to further study of how convergent stress is accommodated along the <span class="hlt">fault</span>. Recent studies have looked in detail at offshore structure, concluding that a change in strike of the QCF at ~53.2 degrees north has led to significant differences in stress and the style of strain accommodation along-strike. We provide updated <span class="hlt">fault</span> mapping and <span class="hlt">seismic</span> images to supplement and support these results. One of the highest-quality <span class="hlt">seismic</span> reflection surveys along the Queen Charlotte system to date, EW9412, was shot aboard the R/V Maurice Ewing in 1994. The survey was last processed to post-stack time migration for a 1999 publication. Due to heightened interest in high-quality imaging along the <span class="hlt">fault</span>, we have completed updated processing of the EW9412 <span class="hlt">seismic</span> reflection data and provide prestack migrations with water-bottom multiple reduction. Our new imaging better resolves <span class="hlt">fault</span> and basement surfaces at depth, as well as the highly deformed sediments within the Queen Charlotte Terrace. In addition to re-processing the EW9412 <span class="hlt">seismic</span> reflection data, we have compiled and re-analyzed a series of publicly available USGS <span class="hlt">seismic</span> reflection data that obliquely cross the QCF. Using these data, we are able to provide updated maps of the Queen Charlotte <span class="hlt">fault</span> system, adding considerable detail along the northernmost QCF where it links up with the Chatham Strait and Transition <span class="hlt">fault</span> systems. Our results support conclusions that the changing geometry of the QCF leads to fundamentally different convergent stress accommodation north and south of ~53.2 degrees; namely, reactivated splay <span class="hlt">faults</span> to the north vs. thickening of sediments and the upper crust to the south</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.6372D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.6372D"><span><span class="hlt">Seismicity</span>, <span class="hlt">faulting</span>, and structure of the Koyna-Warna <span class="hlt">seismic</span> region, Western India from local earthquake tomography and hypocenter locations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dixit, Madan M.; Kumar, Sanjay; Catchings, R. D.; Suman, K.; Sarkar, Dipankar; Sen, M. K.</p> <p>2014-08-01</p> <p>Although <span class="hlt">seismicity</span> near Koyna Reservoir (India) has persisted for ~50 years and includes the largest induced earthquake (M 6.3) reported worldwide, the seismotectonic framework of the area is not well understood. We recorded ~1800 earthquakes from 6 January 2010 to 28 May 2010 and located a subset of 343 of the highest-quality earthquakes using the tomoDD code of Zhang and Thurber (2003) to better understand the framework. We also inverted first arrivals for 3-D Vp, Vs, and Vp/Vs and Poisson's ratio tomography models of the upper 12 km of the crust. Epicenters for the recorded earthquakes are located south of the Koyna River, including a high-density cluster that coincides with a shallow depth (<1.5 km) zone of relatively high Vp and low Vs (also high Vp/Vs and Poisson's ratios) near Warna Reservoir. This anomalous zone, which extends near vertically to at least 8 km depth and laterally northward at least 15 km, is likely a water-saturated zone of <span class="hlt">faults</span> under high pore pressures. Because many of the earthquakes occur on the periphery of the <span class="hlt">fault</span> zone, rather than near its center, the observed <span class="hlt">seismicity</span>-velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main <span class="hlt">fault</span> zone due to high pore pressure. We interpret our velocity images as showing a series of northwest trending <span class="hlt">faults</span> locally near the central part of Warna Reservoir and a major northward trending <span class="hlt">fault</span> zone north of Warna Reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70175906','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70175906"><span><span class="hlt">Seismicity</span>, <span class="hlt">faulting</span>, and structure of the Koyna-Warna <span class="hlt">seismic</span> region, Western India from local earthquake tomography and hypocenter locations</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dixit, Madan M.; Kumar, Sanjay; Catchings, Rufus D.; Suman, K.; Sarkar, Dipankar; Sen, M.K.</p> <p>2014-01-01</p> <p>Although <span class="hlt">seismicity</span> near Koyna Reservoir (India) has persisted for ~50 years and includes the largest induced earthquake (M 6.3) reported worldwide, the seismotectonic framework of the area is not well understood. We recorded ~1800 earthquakes from 6 January 2010 to 28 May 2010 and located a subset of 343 of the highest-quality earthquakes using the tomoDD code of Zhang and Thurber (2003) to better understand the framework. We also inverted first arrivals for 3-D Vp, Vs, and Vp/Vs and Poisson's ratio tomography models of the upper 12 km of the crust. Epicenters for the recorded earthquakes are located south of the Koyna River, including a high-density cluster that coincides with a shallow depth (<1.5 km) zone of relatively high Vp and low Vs (also high Vp/Vs and Poisson's ratios) near Warna Reservoir. This anomalous zone, which extends near vertically to at least 8 km depth and laterally northward at least 15 km, is likely a water-saturated zone of <span class="hlt">faults</span> under high pore pressures. Because many of the earthquakes occur on the periphery of the <span class="hlt">fault</span> zone, rather than near its center, the observed <span class="hlt">seismicity</span>-velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main <span class="hlt">fault</span> zone due to high pore pressure. We interpret our velocity images as showing a series of northwest trending <span class="hlt">faults</span> locally near the central part of Warna Reservoir and a major northward trending <span class="hlt">fault</span> zone north of Warna Reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70020147','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70020147"><span><span class="hlt">Seismic</span>-reflection evidence that the hayward <span class="hlt">fault</span> extends into the lower crust of the San Francisco Bay Area, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Parsons, T.</p> <p>1998-01-01</p> <p>This article presents deep <span class="hlt">seismic</span>-reflection data from an experiment across San Francisco Peninsula in 1995 using large (125 to 500 kg) explosive sources. Shot gathers show a mostly nonreflective upper crust in both the Franciscan and Salinian terranes (juxtaposed across the San Andreas <span class="hlt">fault</span>), an onset of weak lower-crustal reflectivity beginning at about 6-sec two-way travel time (TWTT) and bright southwest-dipping reflections between 11 and 13 sec TWTT. Previous studies have shown that the Moho in this area is no deeper than 25 km (~8 to 9 sec TWTT). Three-dimensional reflection travel-time modeling of the 11 to 13 sec events from the shot gathers indicates that the bright events may be explained by reflectors 15 to 20 km into the upper mantle, northeast of the San Andreas <span class="hlt">fault</span>. However, upper mantle reflections from these depths were not observed on marine-reflection profiles collected in San Francisco Bay, nor were they reported from a refraction profile on San Francisco Peninsula. The most consistent interpretation of these events from 2D raytracing and 3D travel-time modeling is that they are out-of-plane reflections from a high-angle (dipping ~70??to the southwest) impedance contrast in the lower crust that corresponds with the surface trace of the Hayward <span class="hlt">fault</span>. These results suggest that the Hayward <span class="hlt">fault</span> truncates the horizontal detachment <span class="hlt">fault</span> suggested to be <span class="hlt">active</span> beneath San Francisco Bay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRB..117.4306J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRB..117.4306J"><span><span class="hlt">Seismic</span> characterization of hydrates in <span class="hlt">faulted</span>, fine-grained sediments of Krishna-Godavari basin: Unified imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C. A.</p> <p>2012-04-01</p> <p>A combination of diffusion and advection in fine grained sediments can create a patchy Bottom Simulating Reflector (BSR) which has little to no apparent correlation with the overlying hydrate distribution. Using 2D <span class="hlt">seismic</span> data from <span class="hlt">faulted</span>, clay-rich sediments in the Krishna-Godavari (KG) basin, we show both the hydrate distribution and the BSR structure are <span class="hlt">fault</span> controlled. Our demonstration hinges upon a kinematically accurate P wave velocity (VP) model which is estimated using a composite traveltime-inversion, depth-migration method in an iterative manner. The flexibility of the method allows simultaneous usage of traveltimes from multiple, discontinuous reflectors. The application begins with a simple VP model from time processing which is reflective of a diffusive, continuous, hydrate- and free gas-bearing system. The application converges in three iterations yielding a final VPmodel which is suggestive of a patchy distribution of hydrates and free gas possibly developing through a combined diffusive-advective system. The depth image corresponding to the final VP model can be interpreted for <span class="hlt">faults</span> that suggest ongoing tectonism. The BSR appears to be truncated at <span class="hlt">active</span> <span class="hlt">faults</span> zones. Both the final VP model and the corresponding depth image can be reconciled with the hydrate distribution and BSR depth at logging/coring sites located ˜250 m away from the line by projecting the sites along the strike direction of the regional <span class="hlt">faults</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T41B4620L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T41B4620L"><span><span class="hlt">Seismicity</span> of the diffusive Iberian/African plate boundary at the eastern terminus of the Azores-Gibraltar Transform <span class="hlt">fault</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lange, D.; Grevemeyer, I.; Matias, L. M.</p> <p>2014-12-01</p> <p>The plate boundary at the eastern terminus of the Azores-Gibraltar transform <span class="hlt">fault</span> between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-<span class="hlt">active</span> deformation zone. The region, however, is also characterized by large earthquakes, such as the 1969 Mw=7.9 Horseshoe event and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work may suggest that the event occurred in the vicinity of the Horseshoe <span class="hlt">fault</span>, an oblique thrust <span class="hlt">fault</span>. However, estimates of tsunami arrival times suggested a source near the Gorringe Bank, a ~180 km-long and ~70 km-wide ridge that has a relieve of ~5000 m. Deep Sea Drilling (DSDP) and rock samples indicated that the bank is mainly composed of serpentinized peridotites with gabbroic intrusions, perhaps being created by overthrusting of the Horseshoe Abyssal Plain onto the Tagus Abyssal Plain in NW direction. Further, the Horseshoe Abyssal Plain is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip <span class="hlt">faults</span> that extend from the Gorringe Bank to the Gibraltar Arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM <span class="hlt">faults</span>. The <span class="hlt">fault</span> system may mark a developing Eurasia-Africa plate boundary. Two local <span class="hlt">seismic</span> networks were operated in the area. First, a network of 14 ocean-bottom seismometers (OBS) was operated between April and October 2012 in the vicinity of the Horseshoe <span class="hlt">fault</span> between 10°W to 11°W, and 35°50'N to 36°10'N. From October 2013 to March 2014 a second network of 15 OBS monitored <span class="hlt">seismicity</span> at the Gorringe Bank. Both networks benefitted from <span class="hlt">seismic</span> stations operated in Portugal. The first network provided in the order of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Tectp.632..160D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Tectp.632..160D"><span>High-resolution imagery of <span class="hlt">active</span> <span class="hlt">faulting</span> offshore Al Hoceima, Northern Morocco</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>d'Acremont, E.; Gutscher, M.-A.; Rabaute, A.; Mercier de Lépinay, B.; Lafosse, M.; Poort, J.; Ammar, A.; Tahayt, A.; Le Roy, P.; Smit, J.; Do Couto, D.; Cancouët, R.; Prunier, C.; Ercilla, G.; Gorini, C.</p> <p>2014-09-01</p> <p>Two recent destructive earthquakes in 1994 and 2004 near Al Hoceima highlight that the northern Moroccan margin is one of the most <span class="hlt">seismically</span> <span class="hlt">active</span> regions of the Western Mediterranean area. Despite onshore geodetic, seismological and tectonic field studies, the onshore-offshore location and extent of the main <span class="hlt">active</span> <span class="hlt">faults</span> remain poorly constrained. Offshore Al Hoceima, high-resolution <span class="hlt">seismic</span> reflection and swath-bathymetry have been recently acquired during the Marlboro-2 cruise. These data at shallow water depth, close to the coast, allow us to describe the location, continuity and geometry of three <span class="hlt">active</span> <span class="hlt">faults</span> bounding the offshore Nekor basin. The well-expressed normal-left-lateral onshore Trougout <span class="hlt">fault</span> can be followed offshore during several kilometers with a N171°E ± 3° trend. Westward, the Bousekkour-Aghbal normal-left-lateral onshore <span class="hlt">fault</span> is expressed offshore with a N020°E ± 4° trending <span class="hlt">fault</span>. The N030°E ± 2° Bokkoya <span class="hlt">fault</span> corresponds to the western boundary of the Plio-Quaternary offshore Nekor basin in the Al Hoceima bay and seems to define an en échelon tectonic pattern with the Bousekkour-Aghbal <span class="hlt">fault</span>. We propose that these three <span class="hlt">faults</span> are part of the complex transtensional system between the Nekor <span class="hlt">fault</span> and the Al-Idrissi <span class="hlt">fault</span> zone. Our characterization of the offshore expression of <span class="hlt">active</span> <span class="hlt">faulting</span> in the Al Hoceima region is consistent with the geometry and nature of the <span class="hlt">active</span> <span class="hlt">fault</span> planes deduced from onshore geomorphological and morphotectonic analyses, as well as seismological, geodetic and geodynamic data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18...78F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18...78F"><span>Growth of lithospheric-scale <span class="hlt">fault</span> system in NE Tibet: numerical modeling constrained by high-resolution <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fu, Zhen; Zhang, Haiming</p> <p>2016-04-01</p> <p>The growth of lithospheric-scale <span class="hlt">fault</span> system is strongly coupled with the deformation of continental lithosphere in Tibetan Plateau. Therefore, prediction of <span class="hlt">fault</span> growth is important to understand the tectonic history of continental deformation with <span class="hlt">fault</span> system. Recently, high-resolution <span class="hlt">seismic</span> reflection profiling across the Kunlun <span class="hlt">fault</span> in northeasten Tibet reveals several <span class="hlt">fault</span> systems at the scale of lithosphere. A 2D mid-crustal strain-transfer model, which emphasized on the lateral heterogeneity of crust, was proposed to explain the <span class="hlt">seismic</span> reflection profiling under the condition of compression. In order to understand the dynamic process of lithospheric deformation, an elastic-plastic constitutive relationship in finite element modeling is used to investigate the mechanism of the <span class="hlt">fault</span> growth in the section under the condition of compression by allowing permanent strains to develop in response to the applied loads. The vertical and lateral heterogeneity of material, effect of plastic parameters and geometry of models from nature structure are all discussed in this study. The results compared with high-resolution <span class="hlt">seismic</span> image show that well-designed geomechanical modeling can produce overall process of <span class="hlt">fault</span> growth for both continuum without preexisting <span class="hlt">fault</span> and discontinuous deformation with a peexisting <span class="hlt">fault</span>. But the model of the Kunlun <span class="hlt">fault</span> cutting down the Moho is not supported by the results compared with the <span class="hlt">seismic</span> data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PApGe.174..747D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PApGe.174..747D"><span>3D <span class="hlt">Seismic</span> Flexure Analysis for Subsurface <span class="hlt">Fault</span> Detection and Fracture Characterization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di, Haibin; Gao, Dengliang</p> <p>2017-03-01</p> <p><span class="hlt">Seismic</span> flexure is a new geometric attribute with the potential of delineating subtle <span class="hlt">faults</span> and fractures from three-dimensional (3D) <span class="hlt">seismic</span> surveys, especially those overlooked by the popular discontinuity and curvature attributes. Although the concept of flexure and its related algorithms have been published in the literature, the attribute has not been sufficiently applied to subsurface <span class="hlt">fault</span> detection and fracture characterization. This paper provides a comprehensive study of the flexure attribute, including its definition, computation, as well as geologic implications for evaluating the fundamental fracture properties that are essential to fracture characterization and network modeling in the subsurface, through applications to the fractured reservoir at Teapot Dome, Wyoming (USA). Specifically, flexure measures the third-order variation of the geometry of a <span class="hlt">seismic</span> reflector and is dependent on the measuring direction in 3D space; among all possible directions, flexure is considered most useful when extracted perpendicular to the orientation of dominant deformation; and flexure offers new insights into qualitative/quantitative fracture characterization, with its magnitude indicating the intensity of <span class="hlt">faulting</span> and fracturing, its azimuth defining the orientation of most-likely fracture trends, and its sign differentiating the sense of displacement of <span class="hlt">faults</span> and fractures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.tmp..184D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.tmp..184D"><span>3D <span class="hlt">Seismic</span> Flexure Analysis for Subsurface <span class="hlt">Fault</span> Detection and Fracture Characterization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di, Haibin; Gao, Dengliang</p> <p>2016-10-01</p> <p><span class="hlt">Seismic</span> flexure is a new geometric attribute with the potential of delineating subtle <span class="hlt">faults</span> and fractures from three-dimensional (3D) <span class="hlt">seismic</span> surveys, especially those overlooked by the popular discontinuity and curvature attributes. Although the concept of flexure and its related algorithms have been published in the literature, the attribute has not been sufficiently applied to subsurface <span class="hlt">fault</span> detection and fracture characterization. This paper provides a comprehensive study of the flexure attribute, including its definition, computation, as well as geologic implications for evaluating the fundamental fracture properties that are essential to fracture characterization and network modeling in the subsurface, through applications to the fractured reservoir at Teapot Dome, Wyoming (USA). Specifically, flexure measures the third-order variation of the geometry of a <span class="hlt">seismic</span> reflector and is dependent on the measuring direction in 3D space; among all possible directions, flexure is considered most useful when extracted perpendicular to the orientation of dominant deformation; and flexure offers new insights into qualitative/quantitative fracture characterization, with its magnitude indicating the intensity of <span class="hlt">faulting</span> and fracturing, its azimuth defining the orientation of most-likely fracture trends, and its sign differentiating the sense of displacement of <span class="hlt">faults</span> and fractures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5675640','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5675640"><span>High resolution <span class="hlt">seismic</span> survey, Pen Branch <span class="hlt">Fault</span>, Savannah River Site, South Carolina</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berkman, E. )</p> <p>1991-04-01</p> <p>An investigation of the Pen Branch <span class="hlt">Fault</span> at the Savannah River Site by a series of short, high resolution <span class="hlt">seismic</span> reflection lines was conducted. The purpose was to acquire, process, and interpret 19.9 miles of data, optimized for the upper 300 ft of geologic strata, in sufficient density such that processing performed in the conventional stepwise approach, followed by detailed interpretation, would define small scale spatial variability and structural features in the vicinity of the <span class="hlt">fault</span> leading to definition of the location of the <span class="hlt">fault</span>, the shallowest extent of the <span class="hlt">fault</span>, and the quantification of the sense and magnitude of motion. The depth of optimization for the last two lines was modified to the 300 ft of geologic strata immediately above basement. Three older <span class="hlt">seismic</span> surveys, other geophysical data, and associated borehole and geologic data were reviewed. The equipment and the acquisition, processing, and interpretation procedures are discussed in the report. The report includes a detailed line by line description and discussion of the interpretation. Figures include reference maps, contour displays of the stacking and interval velocities, diagrammatic references sketches of the interpreted layering and sedimentary features, index sketches, and specific color prints made on the workstation during the course of the interpretation. A volume of manuals on <span class="hlt">seismic</span> devices and related equipment is included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10131974','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10131974"><span>High resolution <span class="hlt">seismic</span> survey, Pen Branch <span class="hlt">Fault</span>, Savannah River Site, South Carolina. Final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berkman, E.</p> <p>1991-04-01</p> <p>An investigation of the Pen Branch <span class="hlt">Fault</span> at the Savannah River Site by a series of short, high resolution <span class="hlt">seismic</span> reflection lines was conducted. The purpose was to acquire, process, and interpret 19.9 miles of data, optimized for the upper 300 ft of geologic strata, in sufficient density such that processing performed in the conventional stepwise approach, followed by detailed interpretation, would define small scale spatial variability and structural features in the vicinity of the <span class="hlt">fault</span> leading to definition of the location of the <span class="hlt">fault</span>, the shallowest extent of the <span class="hlt">fault</span>, and the quantification of the sense and magnitude of motion. The depth of optimization for the last two lines was modified to the 300 ft of geologic strata immediately above basement. Three older <span class="hlt">seismic</span> surveys, other geophysical data, and associated borehole and geologic data were reviewed. The equipment and the acquisition, processing, and interpretation procedures are discussed in the report. The report includes a detailed line by line description and discussion of the interpretation. Figures include reference maps, contour displays of the stacking and interval velocities, diagrammatic references sketches of the interpreted layering and sedimentary features, index sketches, and specific color prints made on the workstation during the course of the interpretation. A volume of manuals on <span class="hlt">seismic</span> devices and related equipment is included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S11A2199C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S11A2199C"><span>Crustal Extensional <span class="hlt">Faulting</span> Triggered by the 2010 Chilean Earthquake: The Pichilemu <span class="hlt">Seismic</span> Sequence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Comte, D.; Farias, M.; Roecker, S. W.; Carrizo, D.</p> <p>2011-12-01</p> <p>The MW =8.8 south-central Chilean earthquake occurred on February 27th , 2010 is one of the largest event recorded by modern seismology. Its rupture area, located along the interplate contact between Nazca and South America was about 500 × 140 km2, striking parallel to the coast of South America and extending to about 45 km depth. Somewhat surprisingly, although there have been numerous aftershocks in the rupture zone, none of them has had a magnitude Mw greater than 6.5, except the one observed on January 2nd, 2011, almost one year after the mainshock, located in the southern edge of the rupture zone. The first largest aftershocks, (Mw=6.9 and Mw=7.0), occurred within 15 minutes of each other on 11 March 2010 within the overriding South American plate at the northern tip of the rupture zone near the city of Pichilemu. These events are part of a sequence of normal <span class="hlt">faulting</span> <span class="hlt">activated</span> by the Maule earthquake. The purpose of this study is to document the first well-recorded case of forearc <span class="hlt">faulting</span> due to a subduction megathrust earthquake in the Andean region. We combine evidence from local <span class="hlt">seismicity</span>, Global Centroid-Moment Tensor (gCMT) focal solutions, and geological-geomorphological observations to provide some context for the 11 March sequence in the framework of the 27 February megathrust. We hypothesize that the megathrust earthquake produced alterations on the stress field, enhancing fluid circulation in the forearc, which finally triggered intraplate <span class="hlt">faulting</span> in regions of pre-existing crustal weakness. In this study, we focus on the sequence of events associated with the March 11th aftershocks, which we name the Pichilemu <span class="hlt">seismic</span> sequence, in particular on a swarm of 350 events with M > 4 that occurred within the first 24 hours after the largest aftershocks, and the two largest subsequent events, a Mw=5.9 and a Mw=5.3 that occurred on May 2nd and May 21th, 2010 respectively. The hypocenters located in our final 3D model body-wave velocity model, define a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9895F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9895F"><span>Laboratory simulations of fluid-induced <span class="hlt">seismicity</span> in shallow volcanic <span class="hlt">faults</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fazio, Marco; Benson, Philip; Vinciguerra, Sergio; Meredith, Philip</p> <p>2015-04-01</p> <p><span class="hlt">Seismicity</span> is a key tool used for monitoring fracturing and <span class="hlt">faulting</span> in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic <span class="hlt">activity</span> driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced <span class="hlt">seismicity</span>. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF <span class="hlt">activity</span>. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF <span class="hlt">activity</span> akin to Long Period (LP) <span class="hlt">activity</span> on <span class="hlt">active</span> volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF <span class="hlt">seismic</span> signals. Data are used to forecast the final time of failure via the fracture forecast</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T22C..04F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T22C..04F"><span>Laboratory simulations of fluid-induced <span class="hlt">seismicity</span> in shallow volcanic <span class="hlt">faults</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fazio, M.; Benson, P. M.; Vinciguerra, S.</p> <p>2014-12-01</p> <p><span class="hlt">Seismicity</span> is a key tool used for monitoring fracturing and <span class="hlt">faulting</span> in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic <span class="hlt">activity</span> driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced <span class="hlt">seismicity</span>. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF <span class="hlt">activity</span>. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF <span class="hlt">activity</span> akin to Long Period (LP) <span class="hlt">activity</span> on <span class="hlt">active</span> volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF <span class="hlt">seismic</span> signals. Data are used to forecast the final time of failure via the fracture forecast</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70036794','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70036794"><span>Constructing constitutive relationships for <span class="hlt">seismic</span> and aseismic <span class="hlt">fault</span> slip</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Beeler, N.M.</p> <p>2009-01-01</p> <p>For the purpose of modeling natural <span class="hlt">fault</span> slip, a useful result from an experimental <span class="hlt">fault</span> mechanics study would be a physically-based constitutive relation that well characterizes all the relevant observations. This report describes an approach for constructing such equations. Where possible the construction intends to identify or, at least, attribute physical processes and contact scale physics to the observations such that the resulting relations can be extrapolated in conditions and scale between the laboratory and the Earth. The approach is developed as an alternative but is based on Ruina (1983) and is illustrated initially by constructing a couple of relations from that study. In addition, two example constitutive relationships are constructed; these describe laboratory observations not well-modeled by Ruina's equations: the unexpected shear-induced weakening of silica-rich rocks at high slip speed (Goldsby and Tullis, 2002) and <span class="hlt">fault</span> strength in the brittle ductile transition zone (Shimamoto, 1986). The examples, provided as illustration, may also be useful for quantitative modeling.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4773B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4773B"><span><span class="hlt">Fault</span> zone structure and <span class="hlt">seismic</span> reflection characteristics in zones of slow slip and tsunami earthquakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, Rebecca; Henrys, Stuart; Sutherland, Rupert; Barker, Daniel; Wallace, Laura; Holden, Caroline; Power, William; Wang, Xiaoming; Morgan, Joanna; Warner, Michael; Downes, Gaye</p> <p>2015-04-01</p> <p>Over the last couple of decades we have learned that a whole spectrum of different <span class="hlt">fault</span> slip behaviour takes place on subduction megathrust <span class="hlt">faults</span> from stick-slip earthquakes to slow slip and stable sliding. Geophysical data, including <span class="hlt">seismic</span> reflection data, can be used to characterise margins and <span class="hlt">fault</span> zones that undergo different modes of slip. In this presentation we will focus on the Hikurangi margin, New Zealand, which exhibits marked along-strike changes in <span class="hlt">seismic</span> behaviour and margin characteristics. Campaign and continuous GPS measurements reveal deep interseismic coupling and deep slow slip events (~30-60 km) at the southern Hikurangi margin. The northern margin, in contrast, experiences aseismic slip and shallow (<10-15 km) slow slip events (SSE) every 18-24 months with equivalent moment magnitudes of Mw 6.5-6.8. Updip of the SSE region two unusual megathrust earthquakes occurred in March and May 1947 with characteristics typical of tsunami earthquakes. The Hikurangi margin is therefore an excellent natural laboratory to study differential <span class="hlt">fault</span> slip behaviour. Using 2D <span class="hlt">seismic</span> reflection, magnetic anomaly and geodetic data we observe in the source areas of the 1947 tsunami earthquakes i) low amplitude interface reflectivity, ii) shallower interface relief, iii) bathymetric ridges, iv) magnetic anomaly highs and in the case of the March 1947 earthquake v) stronger geodetic coupling. We suggest that this is due to the subduction of seamounts, similar in dimensions to seamounts observed on the incoming Pacific plate, to depths of <10 km. We propose a source model for the 1947 tsunami earthquakes based on geophysical data and find that extremely low rupture velocities (c. 300 m/s) are required to model the observed large tsunami run-up heights (Bell et al. 2014, EPSL). Our study suggests that subducted topography can cause the nucleation of moderate earthquakes with complex, low velocity rupture scenarios that enhance tsunami waves, and the role of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G51B1103L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G51B1103L"><span><span class="hlt">Active</span> <span class="hlt">faults</span> in Lebanon : kinematics and interseismic behavior measured from radar interferometry (InSAR)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lasserre, C.; Pinel-Puysségur, B.; Vergnolle, M.; Klinger, Y.; Pathier, E.</p> <p>2012-12-01</p> <p>The Levant <span class="hlt">fault</span> system, more than 1000 km-long, marks the limit between the Arabian and Sinaï tectonic plates, extending from the Aqaba gulf in the Red Sea to Turkey. Mostly left-lateral, it forms a transpression zone in Lebanon, associating strike-slip <span class="hlt">faults</span> such as the Yammouneh <span class="hlt">fault</span> and thrust <span class="hlt">faults</span> such as the Mount Lebanon thrust. This <span class="hlt">fault</span> system in Lebanon is at the origin of large historical earthquakes during the past two thousand years (551 AD on the thrust offshore and 1837 along the Roum <span class="hlt">fault</span> inland, 1759 along the Rashaia and Sergaya <span class="hlt">faults</span>). We aim at characterizing the present-day behavior of <span class="hlt">active</span> <span class="hlt">faults</span> in Lebanon, in particular the Yammouneh <span class="hlt">fault</span> which did not break since 1202, to contribute to a better assessment of the <span class="hlt">seismic</span> hazard in this region. Space geodesy techniques (GPS, InSAR) allow to quantify the present-day displacements across <span class="hlt">faults</span> (a few mm/yr during the interseismic period), and to model stress loading and relaxation processes during the <span class="hlt">seismic</span> cycle, at the <span class="hlt">fault</span> scale and at the regional scale. GPS campaign measurements have been made along profiles perpendicular to the Yammouneh <span class="hlt">fault</span>. In addition, an important archive of radar images covering Lebanon (acquired by the ERS and Envisat satellites, along descending and ascending orbits) is also available. We process ERS and Envisat radar data to obtain the average interseismic velocity field across <span class="hlt">faults</span> over the past 15-20 years. Techniques of interferograms networks processing (MuLSAR), atmospheric phase delays correction from global atmospherical models, DEM correction and time series inversion (NSBAS) are used to overcome the main remaining limitations in the measurements accuracy (low coherence, strong atmospheric delays, long wavelength deformation signal). The final goal is to propose a modelling of the surface displacement field to quantify the present-day kinematics of <span class="hlt">active</span> fauts in Lebanon, taking into account GPS data as well as tectonic and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211122F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211122F"><span>Tectonic Morphology of the Hustai <span class="hlt">Fault</span> (Northern Mongolia) : A Source of <span class="hlt">Seismic</span> Hazard for the city of Ulaanbaatar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferry, Matthieu; Schlupp, Antoine; Ulzibat, Munkhuu; Munschy, Marc; Fleury, Simon; Baatarsuren, G.; Erdenezula, D.; Munkhsaikhan, A.; Ankhtsetseg, D.</p> <p>2010-05-01</p> <p>Beside the famous series of M 8 earthquakes that struck western Mongolia in the first half of the 20th c., the Hustai <span class="hlt">fault</span> in northern Mongolia presents a more directly concerning picture in terms of hazard and risk. With its northeastern tip located ~10 km from the city of Ulaanbaatar (1 M inhabitants), the 92-km-long <span class="hlt">fault</span> may produce consequential M 7+ earthquakes. No known historical earthquake occurred on the Hustai <span class="hlt">Fault</span> in the last 500 yrs while instrumental <span class="hlt">seismicity</span> shows continuous <span class="hlt">activity</span> with five M 4+ since 1974 and a M 5.4 event in that same year. Most events occur in the shallow crust above 10-20 km. We present preliminary results of a multi-disciplinary study of the Hustai <span class="hlt">Fault</span> in order to assess its seismogenic potential. By combining high-resolution satellite images, digital elevation models, magnetic mapping, geomorphology and trenching, we provide a detailed map of the <span class="hlt">fault</span>'s <span class="hlt">active</span> trace as well as insight on its recent episodes of surface <span class="hlt">faulting</span>. The Hustai <span class="hlt">Fault</span> is more than 92 km long and divided into three segments. The northern segment is 23 km long and oriented N 68; the central segment is 33 km long and oriented N 55; and the southern segment is at least 36 km long and oriented N23. Overall, the Hustai <span class="hlt">Fault</span> forms a wide W-shape open to the southeast. The <span class="hlt">active</span> trace runs along the foot of the main topography of the Hustai Range and is outlined by exhumed chert slabs, contrasts in water content and vegetation reflecting changing soil conditions, right-laterally offset streams and elongated sag basins. The latter are 600- to 800-m-wide and bounded at their SE edge by antithetic <span class="hlt">faults</span>. Stream bed topographic profiles show a systematic uplift of the NW block by 20-30 m and high-resolution satellite images document right-lateral offsets in the range of 20-30 m, thus suggesting an oblique regime. Antithetic <span class="hlt">faults</span> only exhibit dip-slip movement in the order of a few meters (< 10 m). An exploratory 106-m-long trench dug across the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAESc..91..218M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAESc..91..218M"><span>A paleo-seismological study of the Dauki <span class="hlt">fault</span> at Jaflong, Sylhet, Bangladesh: Historical <span class="hlt">seismic</span> events and an attempted rupture segmentation model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morino, Michio; Kamal, A. S. M. Maksud; Akhter, S. Humayun; Rahman, Md. Zillur; Ali, Reshad Md. Ekram; Talukder, Animesh; Khan, Md. Mahmood Hossain; Matsuo, Jun; Kaneko, Fumio</p> <p>2014-09-01</p> <p>A paleo-seismological study was conducted at Jaflong, Sylhet, Bangladesh, which is on the eastern part of the Dauki <span class="hlt">fault</span>. The geomorphology around Jaflong is divided into the Shillong Plateau, the foothills, the lower terraces, and the alluvial plain from north to south. Because the foothills and lower terraces are considered to be uplifted tectonically, an <span class="hlt">active</span> <span class="hlt">fault</span> is inferred to the south of the lower terraces. This <span class="hlt">fault</span>, which branches from the Dauki <span class="hlt">fault</span> as a foreland migration, is known as the Jaflong <span class="hlt">fault</span> in this paper. The trench investigation was conducted at the southern edge of the lower terrace. The angular unconformity accompanied by folding, which is thought to be the top of the growth strata, was identified in the trench. An asymmetric anticline with a steep southern limb and gentle northern limb is inferred from the back-tilted lower terrace and the folding of the gravel layer parallel to the lower terrace surface. The timing of the <span class="hlt">seismic</span> event which formed the folding and unconformity is dated to between AD 840 and 920. The trench investigation at Gabrakhari, on the western part of the Dauki <span class="hlt">fault</span>, revealed that the Dauki <span class="hlt">fault</span> ruptured in AD 1548 (Morino et al., 2011). Because the 1897 great Indian earthquake (M ⩾ 8.0; Yeats et al., 1997) was caused by the rupture of the Dauki <span class="hlt">fault</span> (Oldham, 1899), it is clear that the Dauki <span class="hlt">fault</span> has ruptured three times in the past one thousand years. The timing of these <span class="hlt">seismic</span> events coincides with that of the paleo-liquefactions confirmed on the Shillong Plateau. It is essential for the paleo-seismological study of the Dauki <span class="hlt">fault</span> to determine the surface ruptures of the 1897 earthquake. The Dauki <span class="hlt">fault</span> might be divided into four rupture segments, the western, central, eastern, and easternmost segments. The eastern and western segments ruptured in AD 840-920 and in 1548, respectively. The 1897 earthquake might have been caused by the rupture of the central segment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMED51B0752B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMED51B0752B"><span>Making Waves: <span class="hlt">Seismic</span> Waves <span class="hlt">Activities</span> and Demonstrations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braile, S. J.; Braile, L. W.</p> <p>2011-12-01</p> <p>The nature and propagation of <span class="hlt">seismic</span> waves are fundamental concepts necessary for understanding the exploration of Earth's interior structure and properties, plate tectonics, earthquakes, and <span class="hlt">seismic</span> hazards. Investigating <span class="hlt">seismic</span> waves is also an engaging approach to learning basic principles of the physics of waves and wave propagation. Several effective educational <span class="hlt">activities</span> and demonstrations are available for teaching about <span class="hlt">seismic</span> waves, including the stretching of a spring to demonstrate elasticity; slinky wave propagation <span class="hlt">activities</span> for compressional, shear, Rayleigh and Love waves; the human wave <span class="hlt">activity</span> to demonstrate P- and S- waves in solids and liquids; waves in water in a simple wave tank; <span class="hlt">seismic</span> wave computer animations; simple shake table demonstrations of model building responses to <span class="hlt">seismic</span> waves to illustrate earthquake damage to structures; processing and analysis of seismograms using free and easy to use software; and <span class="hlt">seismic</span> wave simulation software for viewing wave propagation in a spherical Earth. The use of multiple methods for teaching about <span class="hlt">seismic</span> waves is useful because it provides reinforcement of the fundamental concepts, is adaptable to variable classroom situations and diverse learning styles, and allows one or more methods to be used for authentic assessment. The methods described here have been used effectively with a broad range of audiences, including K-12 students and teachers, undergraduate students in introductory geosciences courses, and geosciences majors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003Tectp.368..211P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003Tectp.368..211P"><span>High resolution <span class="hlt">seismic</span> imaging of <span class="hlt">faults</span> beneath Limón Bay, northern Panama Canal, Republic of Panama</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pratt, Thomas L.; Holmes, Mark; Schweig, Eugene S.; Gomberg, Joan; Cowan, Hugh A.</p> <p>2003-06-01</p> <p>High-resolution <span class="hlt">seismic</span> reflection profiles from Limón Bay, Republic of Panama, were acquired as part of a <span class="hlt">seismic</span> hazard investigation of the northern Panama Canal region. The <span class="hlt">seismic</span> profiles image gently west and northwest dipping strata of upper Miocene Gatún Formation, unconformably overlain by a thin (<20 m) sequence of Holocene muds. Numerous <span class="hlt">faults</span>, which have northeast trends where they can be correlated between <span class="hlt">seismic</span> profiles, break the upper Miocene strata. Some of the <span class="hlt">faults</span> have normal displacement, but on many <span class="hlt">faults</span>, the amount and type of displacement cannot be determined. The age of displacement is constrained to be Late Miocene or younger, and regional geologic considerations suggest Pliocene movement. The <span class="hlt">faults</span> may be part of a more extensive set of north- to northeast-trending <span class="hlt">faults</span> and fractures in the canal region of central Panama. Low topography and the <span class="hlt">faults</span> in the canal area may be the result of the modern regional stress field, bending of the Isthmus of Panama, shearing in eastern Panama, or minor deformation of the Panama Block above the Caribbean subduction zone. For <span class="hlt">seismic</span> hazard analysis of the northern canal area, these <span class="hlt">faults</span> led us to include a source zone of shallow <span class="hlt">faults</span> proximal to northern canal facilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025499','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025499"><span>High resolution <span class="hlt">seismic</span> imaging of <span class="hlt">faults</span> beneath Limón Bay, northern Panama Canal, Republic of Panama</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pratt, Thomas L.; Holmes, Mark; Schweig, Eugene S.; Gomberg, Joan S.; Cowan, Hugh A.</p> <p>2003-01-01</p> <p>High-resolution <span class="hlt">seismic</span> reflection profiles from Limo??n Bay, Republic of Panama, were acquired as part of a <span class="hlt">seismic</span> hazard investigation of the northern Panama Canal region. The <span class="hlt">seismic</span> profiles image gently west and northwest dipping strata of upper Miocene Gatu??n Formation, unconformably overlain by a thin (<20 m) sequence of Holocene muds. Numerous <span class="hlt">faults</span>, which have northeast trends where they can be correlated between <span class="hlt">seismic</span> profiles, break the upper Miocene strata. Some of the <span class="hlt">faults</span> have normal displacement, but on many <span class="hlt">faults</span>, the amount and type of displacement cannot be determined. The age of displacement is constrained to be Late Miocene or younger, and regional geologic considerations suggest Pliocene movement. The <span class="hlt">faults</span> may be part of a more extensive set of north- to northeast-trending <span class="hlt">faults</span> and fractures in the canal region of central Panama. Low topography and the <span class="hlt">faults</span> in the canal area may be the result of the modern regional stress field, bending of the Isthmus of Panama, shearing in eastern Panama, or minor deformation of the Panama Block above the Caribbean subduction zone. For <span class="hlt">seismic</span> hazard analysis of the northern canal area, these <span class="hlt">faults</span> led us to include a source zone of shallow <span class="hlt">faults</span> proximal to northern canal facilities. ?? 2003 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGRB..115.2408B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGRB..115.2408B"><span>Clay clast aggregates in gouges: New textural evidence for <span class="hlt">seismic</span> <span class="hlt">faulting</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boutareaud, SéBastien; Boullier, Anne-Marie; AndréAni, Muriel; Calugaru, Dan-Gabriel; Beck, Pierre; Song, Sheng-Rong; Shimamoto, Toshihiko</p> <p>2010-02-01</p> <p>Spherical aggregates named clay-clast aggregates (CCAs) have been reported from recent investigations on retrieved clay-bearing <span class="hlt">fault</span> gouges from shallow depth seismogenic <span class="hlt">faults</span> and rotary shear experiments conducted on clay-bearing gouge at <span class="hlt">seismic</span> slip rates. The formation of CCAs appears to be related to the shearing of a smectite-rich granular material that expands and becomes fluidized. We have conducted additional high-velocity rotary shear experiments and low-velocity double-shear experiments. We demonstrate that a critical temperature depending on dynamic pressure-temperature conditions is needed for the formation of CCAs. This temperature corresponds to the phase transition of pore water from liquid to vapor or to critical, which induced gouge pore fluid expansion and therefore a thermal pressurization of the <span class="hlt">fault</span>. A detailed examination by energy dispersive X-ray spectrometry (EDX-SEM) element mapping, SEM, and transmission electron microscopy (TEM) shows strong similar characteristics of experimental and natural CCAs with a concentric well-organized fabric of the cortex and reveals that their development may result from the combination of electrostatic and capillary forces in a critical reactive medium during the dynamic slip weakening. Accordingly, the occurrence of CCAs in natural clay-rich <span class="hlt">fault</span> gouges constitutes new unequivocal textural evidence for shallow depth thermal pressurization and consequently for past <span class="hlt">seismic</span> <span class="hlt">faulting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1514000A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1514000A"><span><span class="hlt">Seismic</span> constraints on a large dyking event and initiation of a transform <span class="hlt">fault</span> zone in Western Gulf of Aden</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmed, AbdulHakim; Doubre, Cecile; Leroy, Sylvie; Perrot, Julie; Audin, Laurence; Rolandone, Frederique; Keir, Derek; Al-Ganad, Ismael; Sholan, Jamal; Khanbari, Khaled; Mohamed, Kassim; Vergne, Jerome; Jacques, Eric; Nercessian, Alex</p> <p>2013-04-01</p> <p> that the geodetic moment is one order of magnitude higher than the <span class="hlt">seismic</span> moment during such events, the <span class="hlt">seismic</span> <span class="hlt">activity</span> of this event of the Aden ridge represents a major rifting episode certainly associated with the opening of the segment by dyking estimated to be higher than 10 m. Several computed focal mechanisms are dextral strike-slip in the western part of the dyking area could be related to a nascent transform <span class="hlt">fault</span> zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005Tecto..24.3009W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005Tecto..24.3009W"><span><span class="hlt">Active</span> <span class="hlt">faulting</span> in the Walker Lane</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wesnousky, Steven G.</p> <p>2005-06-01</p> <p>Deformation across the San Andreas and Walker Lane <span class="hlt">fault</span> systems accounts for most relative Pacific-North American transform plate motion. The Walker Lane is composed of discontinuous sets of right-slip <span class="hlt">faults</span> that are located to the east and strike approximately parallel to the San Andreas <span class="hlt">fault</span> system. Mapping of <span class="hlt">active</span> <span class="hlt">faults</span> in the central Walker Lane shows that right-lateral shear is locally accommodated by rotation of crustal blocks bounded by steep-dipping east striking left-slip <span class="hlt">faults</span>. The left slip and clockwise rotation of crustal blocks bounded by the east striking <span class="hlt">faults</span> has produced major basins in the area, including Rattlesnake and Garfield flats; Teels, Columbus and Rhodes salt marshes; and Queen Valley. The Benton Springs and Petrified Springs <span class="hlt">faults</span> are the major northwest striking structures currently accommodating transform motion in the central Walker Lane. Right-lateral offsets of late Pleistocene surfaces along the two <span class="hlt">faults</span> point to slip rates of at least 1 mm/yr. The northern limit of northwest trending strike-slip <span class="hlt">faults</span> in the central Walker Lane is abrupt and reflects transfer of strike-slip to dip-slip deformation in the western Basin and Range and transformation of right slip into rotation of crustal blocks to the north. The transfer of strike slip in the central Walker Lane to dip slip in the western Basin and Range correlates to a northward broadening of the modern strain field suggested by geodesy and appears to be a long-lived feature of the deformation field. The complexity of <span class="hlt">faulting</span> and apparent rotation of crustal blocks within the Walker Lane is consistent with the concept of a partially detached and elastic-brittle crust that is being transported on a continuously deforming layer below. The regional pattern of <span class="hlt">faulting</span> within the Walker Lane is more complex than observed along the San Andreas <span class="hlt">fault</span> system to the west. The difference is attributed to the relatively less cumulative slip that has occurred across the Walker</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T33E2457C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T33E2457C"><span>Mineralogical Controls of <span class="hlt">Fault</span> Healing in Natural and Simulated Gouges with Implications for <span class="hlt">Fault</span> Zone Processes and the <span class="hlt">Seismic</span> Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carpenter, B. M.; Ikari, M.; Marone, C.</p> <p>2011-12-01</p> <p>The frictional strength and stability of tectonic <span class="hlt">faults</span> is determined by asperity contact processes, granular deformation, and <span class="hlt">fault</span> zone fabric development. The evolution of grain-scale contact area during the <span class="hlt">seismic</span> cycle likely exhibits significant control on overall <span class="hlt">fault</span> stability by influencing frictional restrengthening, or healing, during the interseismic period, and the rate-dependence of sliding friction, which controls earthquake nucleation and the mode of <span class="hlt">fault</span> slip. We report on laboratory experiments designed to explore the affect of mineralogy on <span class="hlt">fault</span> healing. We conducted frictional shear experiments in a double-direct shear configuration at room temperature, 100% relative humidity, and a normal stress of 20 MPa. We used samples from a wide range of natural <span class="hlt">faults</span>, including outcrop samples and core recovered during scientific drilling. <span class="hlt">Faults</span> include: Alpine (New Zealand), Zuccale (Italy), Rocchetta (Italy), San Gregorio (California), Calaveras (California), Kodiak (Alaska), Nankai (Japan), Middle America Trench (Costa Rica), and San Andreas (California). To isolate the role of mineralogy, we also tested simulated <span class="hlt">fault</span> gouges composed of talc, montmorillonite, biotite, illite, kaolinite, quartz, andesine, and granite. Frictional healing was measured at an accumulated shear strain of ~15 within the gouge layers. We conducted slide-hold-slide tests ranging from 3 to 3000 seconds. The main suite of experiments used a background shearing rate of 10 μm/s; these were augmented with sub-suites at 1 and 100 μm/s. We find that phyllosilicate-rich gouges (e.g. talc, montmorillonite, San Andreas <span class="hlt">Fault</span>) show little to no healing over all hold times. We find the highest healing rates (β ≈ 0.01, Δμ per decade in time, s) in gouges from the Alpine and Rocchetta <span class="hlt">faults</span>, with the rest of our samples falling into an intermediate range of healing rates. Nearly all gouges exhibit log-linear healing rates with the exceptions of San Andreas <span class="hlt">Fault</span> gouge and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26PSL.408..307T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26PSL.408..307T"><span>Heterogeneous strength and <span class="hlt">fault</span> zone complexity of carbonate-bearing thrusts with possible implications for <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tesei, Telemaco; Collettini, Cristiano; Barchi, Massimiliano R.; Carpenter, Brett M.; Di Stefano, Giuseppe</p> <p>2014-12-01</p> <p>The understanding of <span class="hlt">fault</span>-slip behaviour in carbonates has an important societal impact due to the widespread occurrence and propagation of earthquakes in these rocks. <span class="hlt">Fault</span> rock variations in carbonates are systematically controlled by the lithology of the <span class="hlt">faulted</span> protolith: cataclasis and hydraulic fracturing with evidence of past <span class="hlt">seismic</span> slip commonly affect <span class="hlt">fault</span> rocks in competent limestone formations whereas widespread pressure-solution and sliding along clay foliation are observed in marly rocks. We performed a series of friction experiments on carbonatic <span class="hlt">fault</span> rocks sampled from mature thrusts (>2 km displacement) in the Apennines of Italy. We sheared both intact wafers and powdered <span class="hlt">fault</span> materials at low (10 MPa) and in situ (53 MPa) normal stress under room-humidity and water-saturated conditions. We used velocity steps (1 to 300 μm/s) and slide-hold-slide (3-1000 s holds) to assess the frictional stability and healing behaviour of these rocks. We observe that cataclastic <span class="hlt">fault</span> rocks derived from competent limestones are characterized by high friction coefficients coupled with significant post-slip restrengthening and velocity-weakening behaviour. Conversely, intact foliated marly tectonites, sheared under the same conditions, show low friction, null post-slip healing and stable velocity-strengthening behaviour suggesting that these rocks deform aseismically. To extrapolate these opposite mechanical behaviours to the entire <span class="hlt">fault</span> surface we developed a <span class="hlt">fault</span> model integrating our mechanical data, field observations and balanced geological cross-sections. The mechanical heterogeneities highlighted in the model provide constraints for the distribution of <span class="hlt">fault</span> patches with higher seismogenic potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025485','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025485"><span>Imaging the complexity of an <span class="hlt">active</span> normal <span class="hlt">fault</span> system: The 1997 Colfiorito (central Italy) case study</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chiaraluce, L.; Ellsworth, W.L.; Chiarabba, C.; Cocco, M.</p> <p>2003-01-01</p> <p>Six moderate magnitude earthquakes (5 < Mw < 6) ruptured normal <span class="hlt">fault</span> segments of the southern sector of the North Apennine belt (central Italy) in the 1997 Colfiorito earthquake sequence. We study the progressive <span class="hlt">activation</span> of adjacent and nearby parallel <span class="hlt">faults</span> of this complex normal <span class="hlt">fault</span> system using ???1650 earthquake locations obtained by applying a double-difference location method, using travel time picks and waveform cross-correlation measurements. The lateral extent of the <span class="hlt">fault</span> segments range from 5 to 10 km and make up a broad, ???45 km long, NW trending <span class="hlt">fault</span> system. The geometry of each segment is quite simple and consists of planar <span class="hlt">faults</span> gently dipping toward SW with an average dip of 40??-45??. The <span class="hlt">fault</span> planes are not listric but maintain a constant dip through the entire seismogenic volume, down to 8 km depth. We observe the <span class="hlt">activation</span> of <span class="hlt">faults</span> on the hanging wall and the absence of <span class="hlt">seismicity</span> in the footwall of the structure. The observed <span class="hlt">fault</span> segmentation appears to be due to the lateral heterogeneity of the upper crust: preexisting thrusts inherited from Neogene's compressional tectonic intersect the <span class="hlt">active</span> normal <span class="hlt">faults</span> and control their maximum length. The stress tensor obtained by inverting the six main shock focal mechanisms of the sequence is in agreement with the tectonic stress <span class="hlt">active</span> in the inner chain of the Apennine, revealing a clear NE trending extension direction. Aftershock focal mechanisms show a consistent extensional kinematics, 70% of which are mechanically consistent with the main shock stress field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IzAOP..52..784A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IzAOP..52..784A"><span>Dynamics of radon <span class="hlt">activity</span> due to earthquakes (by the example of Altai <span class="hlt">seismically</span> <span class="hlt">active</span> region)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aptikaeva, O. I.; Shitov, A. V.</p> <p>2016-12-01</p> <p>The results of monitoring radon emanations in the territory of Gorno-Altaisk due to <span class="hlt">seismic</span> <span class="hlt">activity</span> and their influence on human health are considered. It is shown that the level of <span class="hlt">activity</span> of subsoil radon in the vicinity of the <span class="hlt">fault</span> zone in the territory of Gorno-Altaisk exceeds such a level recorded in Moscow by 3-4 times. There is ambiguity in the behavior of radon as a precursor of a <span class="hlt">seismic</span> event. Some radon anomalies are synchronous with moments of earthquakes and others correspond to quiet periods. The radon <span class="hlt">activity</span> is more closely associated with the earthquakes localized in the aftershock zone of the Chuya earthquake. This is assumed to be caused by the network of fluid-conducting channels within the <span class="hlt">active</span> <span class="hlt">fault</span> between this region and the observation station.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.S72F1353M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.S72F1353M"><span>Intermediate-Term Declines in <span class="hlt">Seismicity</span> at Two Volcanoes in Alaska Following the Mw7.9 Denali <span class="hlt">Fault</span> Earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McNutt, S. R.; Sanchez, J. J.; Moran, S. C.; Power, J. A.</p> <p>2002-12-01</p> <p>The Mw7.9 Denali <span class="hlt">Fault</span> earthquake provided an opportunity to look for intermediate-term (days to weeks) responses of Alaskan volcanoes to shaking from a large regional earthquake. The Alaska Volcano Observatory monitors 24 volcanoes with <span class="hlt">seismic</span> networks. We examined one station for each volcano, generally the closest (typically 5 km from the vent) unless noise, site response, or other factors made the data unusable. Data were digitally bandpass filtered between 0.8 and 5 Hz to reduce noise from microseisms and wind. Data for the period three days before to three days after the Mw7.9 earthquake were then plotted at a standard scale used for AVO routine monitoring. Shishaldin volcano, which has a background rate of several hundred <span class="hlt">seismic</span> events per day on station SSLS, showed no change from before to after the earthquake. Veniaminof volcano, which has had recent mild eruptions and a rate of several dozen <span class="hlt">seismic</span> events per day on station VNNF, suffered a drop in <span class="hlt">seismicity</span> at the time of the earthquake by a factor of 2.5; this lasted for 15 days. We tested this result using a different station, VNSS, and a different method of counting (non-filtered data on helicorder records) and found the same result. We infer that Veniaminof's <span class="hlt">activity</span> was modified by the Mw7.9 earthquake. Wrangell, the closest volcano, had a background rate of about 10 events per day. Data from station WANC could not be measured for 8 days after the Mw7.9 earthquake because the large number of aftershocks precluded identification of local <span class="hlt">seismicity</span>. For the following eight days, however, its <span class="hlt">seismicity</span> rate was 30 percent lower than before. While subtle, we infer that this may be related to the earthquake. It is known that Wrangell increased its heat output after the Mw9.2 Alaska earthquake of 1964 and again after the Ms7.1 St. Elias earthquake of 1979. The other 21 volcanoes showed no changes in <span class="hlt">seismicity</span> from 3 days before to 3 days after the Mw7.9 event. We conclude that intermediate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMOS11A1455D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMOS11A1455D"><span>CORK observations of hydrologic response to <span class="hlt">seismic</span> and aseismic <span class="hlt">fault</span> slip: Regional strain and local formation changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davis, E. E.; Becker, K.; Heesemann, M.; Villinger, H. W.; Kinoshita, M.</p> <p>2011-12-01</p> <p>Hydrologically <span class="hlt">active</span> areas in the deep ocean are also <span class="hlt">seismically</span> <span class="hlt">active</span>, and ever since early "CORK" (Circulation Obviation Retrofit Kit) hydrologic observatories were established in Ocean Drilling Program boreholes, transient signals related to earthquakes have been observed. In holes that are properly sealed, formation pressure anomalies appear to be the consequence of co-<span class="hlt">seismic</span> and post-<span class="hlt">seismic</span> strain, and of strain related to slow <span class="hlt">fault</span> slip. The sign of the anomalies is always consistent with that pedicted from the earthquake moment tensors. The magnitude of volumetric strain can be determined from pressure change using the calibration provided by the formation response to oceanographic loading at the seafloor. Examples at both subduction zone (Mariana forearc, Nankai Trough) and ridge and ridge flank settings (Juan de Fuca Ridge) show that co-<span class="hlt">seismic</span> strain inferred from pressure is typically one to two orders of magnitude greater than that predicted for the corresponding earthquakes. Transients observed in the Middle America Trench off Costa Rica follow slow slip and tremor events landward of the locked, or partially locked portion of the subduction plate interface. This relationship suggests that slow slip observed by way of GPS-constrained deformation and <span class="hlt">seismic</span> tremor on land can reach all the way to the trench with no <span class="hlt">seismic</span> energy generation. In holes that are not perfectly sealed, formation temperature transients concurrent with pressure transients have been observed, with temperature being sensitive to changes in the rate of flow within the boreholes. Examples from the Juan de Fuca Ridge flank suggest that formation physical properties may be affected near epicentres where ground motion intensity is large. In one recent example, pressure fell in response to dilatational strain, while the temperature, and hence rate of flow in an overpressured and leaking hole increased. This can only be explained by an increase in permeability. All examples</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PApGe.168.2365S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PApGe.168.2365S"><span>Principal Slip Zones in Limestone: Microstructural Characterization and Implications for the <span class="hlt">Seismic</span> Cycle (Tre Monti <span class="hlt">Fault</span>, Central Apennines, Italy)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, Steven A. F.; Billi, Andrea; Toro, Giulio Di; Spiess, Richard</p> <p>2011-12-01</p> <p>Earthquakes in central Italy, and in other areas worldwide, often nucleate within and rupture through carbonates in the upper crust. During individual earthquake ruptures, most <span class="hlt">fault</span> displacement is thought to be accommodated by thin principal slip zones. This study presents detailed microstructural observations of the slip zones of the <span class="hlt">seismically</span> <span class="hlt">active</span> Tre Monti normal <span class="hlt">fault</span> zone. All of the slip zones cut limestone, and geological constraints indicate exhumation from <2 km depth, where ambient temperatures are ≪100°C. Scanning electron microscope observations suggest that the slip zones are composed of 100% calcite. The slip zones of secondary <span class="hlt">faults</span> in the damage zone contain protocataclastic and cataclastic fabrics that are cross-cut by systematic fracture networks and stylolite dissolution surfaces. The slip zone of the principal <span class="hlt">fault</span> has much more microstructural complexity, and contains a 2-10 mm thick ultracataclasite that lies immediately beneath the principal slip surface. The ultracataclasite itself is internally zoned; 200-300 μm-thick ultracataclastic sub-layers record extreme localization of slip. Syn-tectonic calcite vein networks spatially associated with the sub-layers suggest fluid involvement in <span class="hlt">faulting</span>. The ultracataclastic sub-layers preserve compelling microstructural evidence of fluidization, and also contain peculiar rounded grains consisting of a central (often angular) clast wrapped by a laminated outer cortex of ultra-fine-grained calcite. These "clast-cortex grains" closely resemble those produced during layer fluidization in other settings, including the basal detachments of catastrophic landslides and saturated high-velocity friction experiments on clay-bearing gouges. An overprinting foliation is present in the slip zone of the principal <span class="hlt">fault</span>, and electron backscatter diffraction analyses indicate the presence of a weak calcite crystallographic preferred orientation (CPO) in the fine-grained matrix. The calcite c-axes are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111369P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111369P"><span>Earthquakes and <span class="hlt">faults</span> at Mt. Etna (Italy): time-dependent approach to the <span class="hlt">seismic</span> hazard of the eastern flank</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peruzza, L.; Azzaro, R.; D'Amico, S.; Tuve', T.</p> <p>2009-04-01</p> <p>A time dependent approach to <span class="hlt">seismic</span> hazard assessment, based on a renewal model using the Brownian Passage Time (BPT) distribution, has been applied to the best-known seismogenic <span class="hlt">faults</span> at Mt. Etna volcano. These structures have been characterised by frequent coseismic surface displacement, and a long list of historically well-documented earthquakes occurred in the last 200 years (CMTE catalogue, Azzaro et al., 2000, 2002, 2006). <span class="hlt">Seismic</span> hazard estimates, given in terms of earthquake rupture forecast, are conditioned to the time elapsed since the last event: impending events are expected on the S. Tecla <span class="hlt">Fault</span>, and secondly on the Moscatello <span class="hlt">Fault</span>, both involved in the highly <span class="hlt">active</span>, geodynamic processes affecting the eastern flank of Mt. Etna. Mean recurrence time of major events is calibrated by merging the inter-event times observed at each <span class="hlt">fault</span>; aperiodicity is tuned on b-values, following the approach proposed by Zoeller et al. (2008). Finally we compare these mean recurrence times with the values obtained by using only geometrical and kinematic information, as defined in Peruzza et al. (2008) for <span class="hlt">faults</span> in Italy. Time-dependent hazard assessment is compared with the stationary assumption of <span class="hlt">seismicity</span>, and validated in a retrospective forward model. Forecasted rates in a 5 years perspective (1st April 2009 to 1st April 2014), on magnitude bins compatible with macroseismic data are available for testing in the frame of the CSEP (Collaboratory for the study of Earthquake Predictability, www.cseptesting.org) project. Azzaro R., Barbano M.S., Antichi B., Rigano R.; 2000: Macroseismic catalogue of Mt. Etna earthquakes from 1832 to 1998. Acta Volcanol., con CD-ROM, 12 (1), 3-36. http://www.ct.ingv.it/Sismologia/macro/default.htm Azzaro R., D'Amico S., Mostaccio A., Scarfì L.; 2002: Terremoti con effetti macrosismici in Sicilia orientale - Calabria meridionale nel periodo Gennaio 1999 - Dicembre 2001. Quad. di Geof., 27, 1-59. Azzaro R., D'Amico S., Mostaccio A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T52B..02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T52B..02G"><span>Paper 58714 - Exploring <span class="hlt">activated</span> <span class="hlt">faults</span> hydromechanical processes from semi-controled field injection experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guglielmi, Y.; Cappa, F.; Nussbaum, C.</p> <p>2015-12-01</p> <p>The appreciation of the sensitivity of fractures and <span class="hlt">fault</span> zones to fluid-induced-deformations in the subsurface is a key question in predicting the reservoir/caprock system integrity around fluid manipulations with applications to reservoir leakage and induced <span class="hlt">seismicity</span>. It is also a question of interest in understanding earthquakes source, and recently the hydraulic behavior of clay <span class="hlt">faults</span> under a potential reactivation around nuclear underground depository sites. <span class="hlt">Fault</span> and fractures dynamics studies face two key problems (1) the up-scaling of laboratory determined properties and constitutive laws to the reservoir scale which is not straightforward when considering <span class="hlt">faults</span> and fractures heterogeneities, (2) the difficulties to control both the induced <span class="hlt">seismicity</span> and the stimulated zone geometry when a <span class="hlt">fault</span> is reactivated. Using instruments dedicated to measuring coupled pore pressures and deformations downhole, we conducted field academic experiments to characterize fractures and <span class="hlt">fault</span> zones hydromechanical properties as a function of their multi-scale architecture, and to monitor their dynamic behavior during the earthquake nucleation process. We show experiments on reservoir or cover rocks analogues in underground research laboratories where experimental conditions can be optimized. Key result of these experiments is to highlight how important the aseismic <span class="hlt">fault</span> <span class="hlt">activation</span> is compared to the induced <span class="hlt">seismicity</span>. We show that about 80% of the <span class="hlt">fault</span> kinematic moment is aseismic and discuss the complex associated <span class="hlt">fault</span> friction coefficient variations. We identify that the slip stability and the slip velocity are mainly controlled by the rate of the permeability/porosity increase, and discuss the conditions for slip nucleation leading to <span class="hlt">seismic</span> instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....7774C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....7774C"><span><span class="hlt">Fault</span> zone structure observations from the SAFOD Pilot Hole vertical <span class="hlt">seismic</span> array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chavarria, A.; Shalev, E.; Malin, P.</p> <p>2003-04-01</p> <p>In July 2003 we installed a 32 level array of 15 Hz, 3-component seismometers in the San Andreas <span class="hlt">Fault</span> Observatory at Depth Pilot Hole. The Pilot Hole sits on the southwestern side of the Parkfield segment of the San Andreas <span class="hlt">Fault</span> Zone. The array levels are spaced 40 m apart and cover the depth interval of 856 to 2096 m. Both surface explosion and earthquake data have been recorded with the array u