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Sample records for active crustal deformation

  1. Crustal deformation and volcanism at active plate boundaries

    NASA Astrophysics Data System (ADS)

    Geirsson, Halldor

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

  2. Crustal deformation and earthquakes

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.

    1984-01-01

    The manner in which the Earth's surface deforms during the cycle of stress accumulation and release along major faults is investigated. In an investigation of the crustal deformation associated with a thin channel asthenosphere displacements are reduced from those computed for a half space asthenosphere. A previous finding by other workers that displacements are enhanced when flow is confined to a thin channel is based on several invalid approximations. The major predictions of the finite element model are that the near field postseismic displacements and strain rates are less than those for a half space asthenosphere and that the postseismic strain rates at intermediate distances are greater (in magnitude). The finite width of the asthenosphere ceases to have a significant impact on the crustal deformation pattern when its magnitude exceeds about three lithosphere thicknesses.

  3. Evidence of ongoing crustal deformation related to magmatic activity near Socorro, New Mexico

    NASA Technical Reports Server (NTRS)

    Larsen, S.; Brown, L.; Reilinger, R.

    1986-01-01

    Leveling measurements conducted in 1980-1981 by the National Geodetic Survey in the Socorro area of the Rio Grande rift are analyzed. Crustal uplift related to magma inflation in the midcrustal magma body is detected; an uplift of 0.18 cm/yr is measured for the time between 1951-1980. The survey data of 1911 and 1959 are compared to the present data and good correlation is observed. The systematic leveling errors including height-dependence and refraction errors are studied. The 30-km-wide subsidence in the area is examined. The spatial correlation between seismic activity, the Socorro magma body, and crustal deformation in Socorro is investigated. The crustal movement from magma reservior activities is modeled using the formulations of Dieterich and Decker (1975). The modeling of the deformation reveals that the movement in the Socorro area is associated with the 19-km deep Socorro magma body.

  4. Crustal Deformation around Zhangjiakou-Bohai Seismically Active Belt

    NASA Astrophysics Data System (ADS)

    Jin, H.; Fu, G.; Kato, T.

    2011-12-01

    Zhangjiakou-Bohai belt is a seismically active belt located in Northern China around Beijing, the capital of China. Near such a belt many great earthquakes occurred in the past centuries (e.g. the 1976 Tanshan Ms7.8 earthquake, the 1998 Zhangbei Ms6.2 earthquake, etc). Chinese Government established dense permanent and regional Global Positioning System (GPS) stations in and near the area. We collected and analyzed all the GPS observation data between 1999 and 2009 around Zhangjiakou-Bohai seismic belt, and obtained velocities at 143 stations. At the same time we investigated Zhangjiakou-Bohai belt slip rate for three profiles from northwest to southeast, and constructed a regional strain field on the Zhangjiakou-Bohai seismic belt region by least-square collocation. Based on the study we found that: 1) Nowadays the Zhangjiakou-Bohai seismic belt is creeping with left-lateral slip rate of 2.0mm~2.4mm/a, with coupling depth of 35~50km; 2) In total, the slip and coupling depth of the northwestern seismic belt is less than the one of southeast side; 3) The maximum shear strain is about 3×10-8 at Beijing-Tianjin-Tangshan area.

  5. Earthquake relocations, crustal rheology, and active deformation in the central-eastern Alps (N Italy)

    NASA Astrophysics Data System (ADS)

    Viganò, Alfio; Scafidi, Davide; Ranalli, Giorgio; Martin, Silvana; Della Vedova, Bruno; Spallarossa, Daniele

    2015-10-01

    A revised seismic catalogue (1994-2007) for the central-eastern Alps (N Italy) is presented. 396 earthquake relocations, for local magnitudes in the 1.2-5.3 range, are performed using a 3D crustal velocity structure and probabilistic locations. The location procedure is validated by computing a set of 41 quarry shot solutions and all the results, both about shots and seismic events, are compared with those obtained using the routine location procedure. Results are shown for five contiguous seismotectonic domains, as supported by geological and geophysical evidence (e.g., fault systems, crustal tomography, focal mechanisms types). Earthquake hypocentres are mostly located in the upper crust (0-15 km of depth), in good agreement with thermo-rheological models about the brittle-ductile transitions (8-9 km of depth) and total crustal strengths (1.0-2.0 TN m- 1). Epicentres are clustered and/or aligned along present-day active geological structures. The proposed seismotectonic model shows dominant compression along the Giudicarie and Belluno-Bassano-Montello thrusts, with strain partitioning along the dominant right-lateral strike-slip faults of the Schio-Vicenza domain. The present-day deformation of the Southern Alps and the internal Alpine chain is compatible with Adria indentation and the related crustal stress distribution.

  6. Crustal-scale active deformation along the Ecuadorian Andes using Persistent Scatterers SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Champenois, J.; Baize, S.; Audin, L.; Pinel, V.; Alvarado, A.; Jomard, H.; Yepes, H. A.

    2013-12-01

    Located in the Northern Andes along the active subduction zone of the Nazca plate beneath the South American continent, Ecuador is highly exposed to seismic hazard. For the last ten years, numerous multidisciplinary studies focused on major seismicity related to the subduction, whereas few investigations concentrated on M>7 crustal seismicity in the upper plate (like 1797 Riobamba earthquake, ML 8.3, 12.000 deaths). The active faults producing these earthquakes are poorly known in term of slip rate and for some cases are even not identified yet. Additionnally, Ecuador is one of the most active volcanic areas of the northern Andean volcanic zone. Three among the nine active volcanoes are actually erupting (Reventador, Tungurahua, and Sangay). For the last 5 years, geodetic networks have been deployed in Ecuador to enhance crustal deformation monitoring, but these point-wise techniques cannot provide spatially dense maps of ground deformation and are quite expensive methods. To address this issue, we applied the Persistent Scatterers SAR Interferometry technique (StaMPS/MTI freeware developed by A. Hooper) to ENVISAT SAR data between 2003 and 2009. Using these cost-effective techniques, we are able to investigate both tectonic and volcanic surface deformations with an unprecedented spatial density of measurements. This study presents new PS-InSAR results along the Ecuadorian Andes, close to the area of Riobamba. We generated average velocity maps and consistent time-series of displacements measured along the radar line of sight. These results evidence large scale deformation localized on the Pallatanga fault system (locked fault) compatible with a model of locked strike slip fault. Moreover, these results show an important growth of the Tungurahua volcanic complex (maximum rate about 9 mm/yr) with a rapid uplift prior and post 2006 explosive eruption. We investigate the time-series of displacement for 22 images. Our results permitted to propose two crustal source

  7. The three-dimensional pattern of crustal deformation associated with active normal fault systems observed using continuous GPS geodesy

    NASA Astrophysics Data System (ADS)

    Bennett, R. A.; Hreinsdottir, S.

    2009-12-01

    Geological examples of shallow dipping normal faults with large displacements are exposed at numerous locations throughout the world and it is widely recognized that extensional deformation at brittle crustal levels is most efficiently accomplished by slip across such structures. It has previously been shown that lower dip angles reduce the regional stresses required to drive large horizontal displacements. Nevertheless, the traditional theory of fault mechanics—based on Anderson’s classification of stress regimes, the Coulomb failure criterion, and Byerlee’s friction law—precludes such faults from slipping at low angle. Observational support for this traditional theory includes the absence of large unequivocally low-angle normal fault earthquakes in the global catalog; all well-determined normal fault earthquakes appear to have occurred on moderate to steeply dipping planes. However, precise measurements of 3D crustal motions based on continuous GPS in central Italy and Utah reveal deformation patterns across active normal fault systems that are inconsistent with active slip across steeply dipping planes. Instead, the combination of observed horizontal and vertical surface motions are consistent with slip across low angle surfaces independently imaged in the subsurface by seismic reflection and other geophysical data. For the Alto Tiberina fault in central Italy, active aseismic creep occurs at shallow crustal levels, most likely within the brittle-frictional regime at which Andersonian-Byerlee fault mechanics should be applicable. The actively creeping portion of the fault inferred using GPS geodesy correlates well with the observed pattern of micro-seismicity, which concentrates along the inferred subsurface fault plane. GPS measurements across the greater Wasatch fault zone in the vicinity of Salt Lake City, Utah, reveal crustal motions consistent with aseismic displacement across a shallow dipping fault or sub-horizontal shear zone at mid-crustal

  8. Crustal deformation: Earth vs Venus

    NASA Technical Reports Server (NTRS)

    Turcotte, D. L.

    1989-01-01

    It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.

  9. Modeling crustal deformation near active faults and volcanic centers: a catalog of deformation models and modeling approaches

    USGS Publications Warehouse

    Battaglia, Maurizio; Cervelli; Peter, F.; Murray, Jessica R.

    2013-01-01

    This manual provides the physical and mathematical concepts for selected models used to interpret deformation measurements near active faults and volcanic centers. The emphasis is on analytical models of deformation that can be compared with data from the Global Positioning System (GPS) receivers, Interferometric synthetic aperture radar (InSAR), leveling surveys, tiltmeters and strainmeters. Source models include pressurized spherical, ellipsoidal, and horizontal penny-shaped geometries in an elastic, homogeneous, flat half-space. Vertical dikes and faults are described following the mathematical notation for rectangular dislocations in an elastic, homogeneous, flat half-space. All the analytical expressions were verified against numerical models developed by use of COMSOL Multyphics, a Finite Element Analysis software (http://www.comsol.com). In this way, typographical errors present were identified and corrected. Matlab scripts are also provided to facilitate the application of these models.

  10. Reports on crustal movements and deformations

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.; Peck, T.

    1981-01-01

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

  11. TerraSAR InSAR Investigation of Active Crustal Deformation

    NASA Astrophysics Data System (ADS)

    Lei, L.; Burgmann, R.

    2009-12-01

    We aim to utilize advanced analysis of TerraSAR-X data to investigate the dynamics and interactions of solid Earth deformation processes, such as earthquakes and fault creep, and Earth surface processes, such as land subsidence and groundwater movements, in a densely populated, urban region, the San Francisco Bay Area. Ongoing deformation imaging reveals a number of natural hazards including elastic strain accumulation about seismologic faults, active landsliding, land subsidence and rebound, and settling of unconsolidated sediments that are highly susceptible to liquefaction. Up to now, we have ordered and received 20 more TerraSAR-X Spotlight Single Look Complex (SLC) images and a few Stripmap SLC images delivered by DLR and got a few preliminary results. The TerraSAR-X images were acquired over the San Francisco Bay Area particularly around an area of active landsliding, coastal subsidence and shallow Hayward fault creep near the city of Berkeley. Berkeley is situated between latitude 37.45 and 38.00, longitude 237.30 and 238.00. The data acquisition interval is from November, 2008 to now. Four types of Spotlight images and one type of Stripmap images in time sequence were ordered and acquired: spot_012, spot_038, spot_049, spot_075 and strip_003, having different look angles and pass directions. Access to the SAR data is via ftp about 10 days after acquisition date. The data is supplied in TerraSAR-X standard SLC COSAR (COmplex SAR) format with orbital information in an Extensible Markup Language (XML) header. The file contains integer real-complex components with double sampling and calibration constants for values. I am using ROI_PAC to do the interferograms. But ROI_PAC was designed to process the raw data rather SLC images. So there are some problems in azimuth processing with TerraSAR SLC data especially the Spotlight data. We now have some preliminary results of Stripmap interferograms and Spotlight interferograms but still work on those problems and

  12. Recent plate motions and crustal deformation

    SciTech Connect

    Lisowski, M. )

    1991-01-01

    Reports by U.S. workers on geodetic measurements of recent plate motions or crustal deformation published in 1987-1990 are reviewed. The review begins with global plate motions, proceeds through plate boundaries in California, Alaska, and the Pacific Northwest, and finishes with volcanic phenomena, monument stability and longevity, and GPS relative position measurements. 184 refs.

  13. Reports on crustal movements and deformations

    SciTech Connect

    Cohen, S.C.; Peck, T.

    1983-05-01

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

  14. Reports on crustal movements and deformations. [bibliography

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.; Peck, T.

    1983-01-01

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

  15. Crustal deformation in Great California Earthquake cycles

    NASA Technical Reports Server (NTRS)

    Li, Victor C.; Rice, James R.

    1987-01-01

    A model in which coupling is described approximately through a generalized Elsasser model is proposed for computation of the periodic crustal deformation associated with repeated strike-slip earthquakes. The model is found to provide a more realistic physical description of tectonic loading than do simpler kinematic models. Parameters are chosen to model the 1857 and 1906 San Andreas ruptures, and predictions are found to be consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces. Results indicate that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps the crust-mantle transition zone.

  16. Crustal deformation along the San Andreas, California

    NASA Astrophysics Data System (ADS)

    Li, Victor C.

    1992-03-01

    The goal is to achieve a better understanding of the regional and local deformation and crustal straining processes in western North America, particularly the effects of the San Andreas and nearby faults on the spatial and temporal crustal deformation behavior. Construction of theoretical models based on the mechanics of coupled elastic plate, viscoelastic foundation and large scale crack mechanics provide a rational basis for the interpretation of seismic and aseismic anomalies and expedite efforts in forecasting the stability of plate boundary deformation. Special focus is placed on the three dimensional time dependent surface deformation due to localized slippage in a elastic layer coupled to a visco-elastic substrate. The numerical analysis is based on a 3-D boundary element technique. Extension to visco-elastic coupling demands the derivation of 3-D time dependent Green's function. This method was applied to analyze the viscoelastic surface displacements due to a dislocated embedded patch. Surface uplift as a function of time and position are obtained. Comparisons between surface uplift for long and short dislocated patches are made.

  17. Crustal deformation along the San Andreas, California

    NASA Technical Reports Server (NTRS)

    Li, Victor C.

    1992-01-01

    The goal is to achieve a better understanding of the regional and local deformation and crustal straining processes in western North America, particularly the effects of the San Andreas and nearby faults on the spatial and temporal crustal deformation behavior. Construction of theoretical models based on the mechanics of coupled elastic plate, viscoelastic foundation and large scale crack mechanics provide a rational basis for the interpretation of seismic and aseismic anomalies and expedite efforts in forecasting the stability of plate boundary deformation. Special focus is placed on the three dimensional time dependent surface deformation due to localized slippage in a elastic layer coupled to a visco-elastic substrate. The numerical analysis is based on a 3-D boundary element technique. Extension to visco-elastic coupling demands the derivation of 3-D time dependent Green's function. This method was applied to analyze the viscoelastic surface displacements due to a dislocated embedded patch. Surface uplift as a function of time and position are obtained. Comparisons between surface uplift for long and short dislocated patches are made.

  18. An algorithmic approach to crustal deformation analysis

    NASA Technical Reports Server (NTRS)

    Iz, Huseyin Baki

    1987-01-01

    In recent years the analysis of crustal deformation measurements has become important as a result of current improvements in geodetic methods and an increasing amount of theoretical and observational data provided by several earth sciences. A first-generation data analysis algorithm which combines a priori information with current geodetic measurements was proposed. Relevant methods which can be used in the algorithm were discussed. Prior information is the unifying feature of this algorithm. Some of the problems which may arise through the use of a priori information in the analysis were indicated and preventive measures were demonstrated. The first step in the algorithm is the optimal design of deformation networks. The second step in the algorithm identifies the descriptive model of the deformation field. The final step in the algorithm is the improved estimation of deformation parameters. Although deformation parameters are estimated in the process of model discrimination, they can further be improved by the use of a priori information about them. According to the proposed algorithm this information must first be tested against the estimates calculated using the sample data only. Null-hypothesis testing procedures were developed for this purpose. Six different estimators which employ a priori information were examined. Emphasis was put on the case when the prior information is wrong and analytical expressions for possible improvements under incompatible prior information were derived.

  19. Crustal deformation measurements in Guerrero, Mexico

    USGS Publications Warehouse

    Larson, K.M.; Lowry, A.R.; Kostoglodov, V.; Hutton, W.; Sanchez, O.; Hudnut, K.; Suarez, G.

    2004-01-01

    GPS measurements of crustal deformation in Guerrero, southern Mexico, include surveys collected between 1992 and 2001 as well as continuous GPS measurements at a few sites. These geodetic observations are used to calculate interseismic deformation rates and assess the presence and possible location of transient deformation during the period encompassing 1992.25 to 2001.75. The data are used to examine transient deformation in 1998 previously described from data at a single site by Lowry et al. [2001]. Survey measurements and continuous data from a site near Popocate??petl volcano confirm the 1998 transient, and survey data also suggest another transient occurred following the 14 September 1995 (Mw = 7.3) Copala earthquake. All of the available GPS position estimates have been inverted for a combined model of slip during each event plus the steady state slip on the plate interface. Modeling of the steady state deformation rates confirms that the Guerrero seismic gap is partially frictionally locked at depths shallower than about 25 km and accumulating strain that may eventually be released in a great earthquake. The data also suggest that there is frictional coupling to much greater (>40 km) depths, which releases more frequently in aseismic slip events. The locations and sizes of the transient events are only partially constrained by the available data. However, the transient models which best fit the GPS coordinate time series suggest that aseismic slip was centered downdip of the seismogenic portion of the plate-bounding thrust in both events, and the moment release had equivalent magnitudes Mw = 7.1 + 1.3/-1.0 in 1995-1996 and 7.1 + 0.4/-0.1 in 1998. Copyright 2004 by the American Geophysical Union.

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

    NASA Technical Reports Server (NTRS)

    Nur, Amos

    1990-01-01

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

  1. Crustal deformation in great California earthquake cycles

    NASA Technical Reports Server (NTRS)

    Li, Victor C.; Rice, James R.

    1986-01-01

    Periodic crustal deformation associated with repeated strike slip earthquakes is computed for the following model: A depth L (less than or similiar to H) extending downward from the Earth's surface at a transform boundary between uniform elastic lithospheric plates of thickness H is locked between earthquakes. It slips an amount consistent with remote plate velocity V sub pl after each lapse of earthquake cycle time T sub cy. Lower portions of the fault zone at the boundary slip continuously so as to maintain constant resistive shear stress. The plates are coupled at their base to a Maxwellian viscoelastic asthenosphere through which steady deep seated mantle motions, compatible with plate velocity, are transmitted to the surface plates. The coupling is described approximately through a generalized Elsasser model. It is argued that the model gives a more realistic physical description of tectonic loading, including the time dependence of deep slip and crustal stress build up throughout the earthquake cycle, than do simpler kinematic models in which loading is represented as imposed uniform dislocation slip on the fault below the locked zone.

  2. A fractal model for crustal deformation

    NASA Technical Reports Server (NTRS)

    Turcotte, D. L.

    1986-01-01

    It is hypothesized that crustal deformation occurs on a scale-invariant matrix of faults. For simplicity, a two-dimensional pattern of hexagons on which strike-slip faulting occurs is considered. The behavior of the system is controlled by a single parameter, the fractal dimension. Deformation occurs on all scales of faults. The fractal dimension determines the fraction of the total displacement that occurs on the first-order or primary faults. The value of the fractal dimension can be obtained from the frequency-magnitude relation for earthquakes. The results are applied to the San Andreas fault system in central California. Earthquake studies give D = 1.90. The main strand of the San Andreas fault is associated with the primary faults of the fractal system. It is predicted that the relative velocity across the main strand is 2.93 cm/yr. The remainder of the relative velocity of 5.5 cm/yr between the Pacific and North American plates occurs on higher-order faults. The predicted value is in reasonably good agreement with the value 3.39 + or - 0.29 cm/yr obtained from geological studies.

  3. On radon emanation as a possible indicator of crustal deformation

    USGS Publications Warehouse

    King, C.-Y.

    1979-01-01

    Radon emanation has been monitored in shallow capped holes by a Tracketch method along several active faults and in the vicinity of some volcanoes and underground nuclear explosions. The measured emanation shows large temporal variations that appear to be partly related to crustal strain changes. This paper proposes a model that may explain the observed tectonic variations in radon emanation, and explores the possibility of using radon emanation as an indicator of crustal deformation. In this model the emanation variation is assumed to be due to the perturbation of near-surface profile of radon concentration in the soil gas caused by a change in the vertical flow rate of the soil gas which, in turn, is caused by the crustal deformation. It is shown that, for a typical soil, a small change in the flow rate (3 ?? 10-4 cm sec-1) can effect a significant change (a factor of 2) in radon emanation detected at a fixed shallow depth (0.7 m). The radon concentration profile has been monitored at several depths at a selected site to test the model. The results appear to be in satisfactory agreement. ?? 1979.

  4. Plate tectonics and crustal deformation around the Japanese Islands

    NASA Technical Reports Server (NTRS)

    Hashimoto, Manabu; Jackson, David D.

    1993-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  6. A quantitative evaluation of models for Aegean crustal deformation

    NASA Astrophysics Data System (ADS)

    Nyst, M.; Thatcher, W.

    2003-04-01

    Modeling studies of eastern Mediterranean tectonics show that Aegean deformation is mainly determined by WSW directed expulsion of Anatolia and SW directed extension due to roll-back of African lithosphere along the Hellenic trench. How motion is transferred across the Aegean remains a subject of debate. The two most widely used hypotheses for Aegean tectonics assert fundamentally different mechanisms. The first model describes deformation as a result of opposing rotations of two rigid microplates separated by a zone of extension. In the second model most motion is accommodated by shear on a series of dextral faults and extension on graben systems. These models make different quantitative predictions for the crustal deformation field that can be tested by a new, spatially dense GPS velocity data set. To convert the GPS data into crustal deformation parameters we use different methods to model complementary aspects of crustal deformation. We parameterize the main fault and plate boundary structures of both models and produce representations for the crustal deformation field that range from purely rigid rotations of microplates, via interacting, elastically deforming blocks separated by crustal faults to a continuous velocity gradient field. Critical evaluation of these models indicates strengths and limitations of each and suggests new measurements for further refining understanding of present-day Aegean tectonics.

  7. Marginal deformation of crustal plates as key to crustal motion, crustal spirals, and the driving force

    SciTech Connect

    Wood, B.G.M.

    1986-07-01

    Present plate tectonic models concentrate on compressive- and extensive-type plate margins, often incorporating shear margins as a subtype of compressive margins. However, if a single moving plate is considered, it becomes apparent that the leading edge is a compressive margin, the trailing edge is an extensive margin, and the lateral edges are shear margins. Conversely, if a plate's margin can be recognized by identifying areas of subduction (compression), rifting (extension), and strike slip and buckle folding (shearing), then not only can a plate be identified but its motion can also be inferred. The Pacific plate provides an excellent example. It is bounded by subduction trenches along its west-northwest margin, extension rifts along its east-southeast margin, and shear and buckle-fold complexes along its south-southwest and north-northeast margins. A west-northwest motion is inferred. As other major plates are examined, two striking features are revealed. A west-northwest to northwest motion is consistently identified, and the plates line up end to end forming a northwest-spiraling segmented band encircling the globe. The lateral margins of this band form the well-known Tethyan shear system. The plates comprising this band are of varying sizes and composition, and the extent of deformation along a plate margin is directly related to plate size. The Pacific and Eurasian plates dominate in size and marginal deformation. The tail of this north-spiraling ribbon of crustal plates is deformed in the Southern Hemisphere, most notably in the area of the African, Indian, and Australian plates. Each southern plate has a strong north component of motion as well as a counterclockwise spiraling action. The plates appear to have rotated in response to drag along the southern margin of the Pacific and Eurasian plates.

  8. Mechanisms of crustal deformation in the western US

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald L.

    1986-01-01

    The deformation processes in the western United States were studied, considering both deterministic models and random or statistical models. The role of the intracrustal delamination and mechanisms of crustal thinning were also examined. The application of fractal techniques to understand how the crust is deforming was studied in complex regions. Work continued on the development of a fractal based model for deformation in the western United States. Fractal studies were also extended to the study of topography and the geoid.

  9. The Mw4.8 Norris Geyser Basin Earthquake of 30 March, 2014 and its Relationship to Crustal Deformation and Seismic Activity of the Yellowstone Volcanic System

    NASA Astrophysics Data System (ADS)

    Farrell, J.; Shelly, D. R.; Smith, R. B.; Puskas, C. M.; Chang, W. L.

    2014-12-01

    The largest earthquake to be recorded in Yellowstone in over 30 years, a magnitude 4.8 earthquake, occurred on March 30, 2014 near the Norris Geyser Basin on the NW side of the 0.64 Ma Yellowstone caldera. The earthquake was felt throughout Yellowstone and the surrounding region. We analyze this unusual event using data from the Yellowstone Seismic and Geodetic networks in the context of active volcanic-tectonic processes of the Yellowstone volcanic system and its relationship to regional swarm seismicity and crustal deformation. Moment tensor analysis of the March 30 earthquake revealed a strike-slip, double-couple source mechanism with no isotropic contribution. This earthquake was part of a larger sequence of earthquake swarm activity in the Norris Geyser Basin area that began in September 2013 and continued into June 2014. During that period, 50-60% of the total seismicity recorded in Yellowstone, including nearly all of the swarm seismicity (earthquakes clustered in time and space), occurred in the Norris Geyser Basin area. In addition, GPS derived deformation data revealed unusually high uplift rates at ~15 cm/yr in the Norris area prior to the MW4.8 event, while a dramatic reversal to subsidence at rates of ~20 cm/yr occurred after the event. Regionally, the much larger Yellowstone caldera had experienced subsidence since January 2010 at rates of ~1.5 cm/yr prior to the MW4.8 event. After March 30, 2014 the caldera reversed to regional uplift at rates of ~10 cm/yr, similar to accelerated uplift rates observed in mid-2004.

  10. Localized crustal deformation in the Godavari failed rift, India

    NASA Astrophysics Data System (ADS)

    Mahesh, P.; Gahalaut, V. K.; Catherine, J. K.; Ambikapathy, A.; Kundu, Bhaskar; Bansal, Amit; Chadha, R. K.; Narsaiah, M.

    2012-06-01

    Six years of GPS measurements of crustal deformation in the Godavari failed rift (GFR) of stable India plate suggest very localized deformation. Elsewhere, all along the GFR the deformation is very low (<1.5 mm/yr). Localized deformation (up to 3.3±0.5 mm/yr) at least at two sites, implying compression on steep faults located on the southern margin of the GFR, is coincident with the region characterized by high level low-magnitude seismicity of past six years and implies strain accumulation for future moderate to strong magnitude earthquake in the region. The localized deformation is consistent with the view about deformation in such regions where seismicity migrates and deformation rate changes with time.

  11. New buoy observation system for tsunami and crustal deformation

    NASA Astrophysics Data System (ADS)

    Takahashi, Narumi; Ishihara, Yasuhisa; Ochi, Hiroshi; Fukuda, Tatsuya; Tahara, Jun'ichiro; Maeda, Yosaku; Kido, Motoyuki; Ohta, Yusaku; Mutoh, Katsuhiko; Hashimoto, Gosei; Kogure, Satoshi; Kaneda, Yoshiyuki

    2014-09-01

    We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.

  12. Measuring Crustal Deformation in the American West.

    ERIC Educational Resources Information Center

    Jordan, Thomas H.; Minster, J. Bernard

    1988-01-01

    Suggests that there is a close relationship between deformation in the western United States and the large-scale motions of tectonic plates. Introduces very-long-baseline interferometry (VLBI) as one of the space-geodetic techniques, vector addition of the VLBI data and geological data, and a new geodetic network. (YP)

  13. Surface Deformation and Lower Crustal Flow in Eastern Tibet

    PubMed

    Royden; Burchfiel; King; Wang; Chen; Shen; Liu

    1997-05-01

    Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau. PMID:9115202

  14. Measuring crustal deformation in the American West

    SciTech Connect

    Jordan, T.H.; Minster, J.B.

    1988-08-01

    The crust of the western US is deforming as the Pacific and North American plates slide past each other along the San Andreas Fault, the Great Basin is spreading apart, and mountains are being thrust up along the California coast. Monitoring of these processes over the years has resulted in the San Andreas discrepancy, the mismatch between the rate and direction of horizontal slippage along the fault and the relative motion of the Pacific and North American plates.This process will soon be measured directly using the new developed technique of space geodesy, which uses radio waves from quasars or satellites to measure between fixed stations with an accuracy of a few centimeters.

  15. System for near real-time crustal deformation monitoring

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F. (Inventor)

    1979-01-01

    A system is described for use in detecting earth crustal deformation using an RF interferometer technique for such purposes as earthquake predictive research and eventual operational predictions. A lunar based RF transmission or transmissions from earth orbiting satellites are received at two locations on Earth, and a precise time dependent phase measurement is made of the RF signal as received at the two locations to determine two or three spatial parameters of the antenna relative positions. The received data are precisely time tagged and land-line routed to a central station for real-time phase comparison and analysis. By monitoring the antenna relative positions over an extended period of months or years, crustal deformation of the Earth can be detected.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    High-resolution Magellan images and altimetry of Venus reveal a wide range of styles and scales of surface deformation that cannot readily be explained within the classical terrestrial plate tectonic paradigm. The high correlation of long-wavelength topography and gravity and the large apparent depths of compensation suggest that Venus lacks an upper-mantle low-viscosity zone. A key difference between Earth and Venus may be the degree of coupling between the convecting mantle and the overlying lithosphere. Mantle flow should then have recognizable signatures in the relationships between surface topography, crustal deformation, and the observed gravity field.

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

    PubMed

    Lowry, Anthony R; Pérez-Gussinyé, Marta

    2011-03-17

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

  18. Implications of very long baseline interferometry measurements on North American intra-plate crustal deformation

    NASA Technical Reports Server (NTRS)

    Allenby, R. J.

    1979-01-01

    Very Long Baseline Interferometry experiments over the last 1-3/4 years between Owens Valley, CA and Haystack, MA Radio Observatories suggest an upper limit of east-west crustal deformation between the two sites of about 1 cm/yr. In view of the fact that the baseline between the two sites traverses most of the major geological provinces of the United States, this low rate of crustal deformation has direct relevance to intra-plate crustal tectonics. The most active region traversed by this baseline is the Basin and Range province, which was estimated by various researchers to be expanding in an east-west direction at rates of .3 to 1.5 cm/yr. The Colorado Plateau and Rocky Mountain system also appear to be expanding, but at a somewhat lower rate, while east of the Rocky Mountains, the predominant stress appears to be compressional, nearly horizontal, and east to northeast trending.

  19. Seismotectonics and crustal deformation in Africa

    NASA Astrophysics Data System (ADS)

    Ayadi, Abdelhakim

    2016-04-01

    We present the Seismotectonic Map of Africa based on a geological, geophysical and geodetic database including the instrumental seismicity and re-appraisal of large historical events, and harmonization and homogenization of earthquake parameters in catalogues. Although the seismotectonic framework of the African continent is a difficult task, several previous and ongoing projects provide a wealth of data and outstanding results. The database of large and moderate earthquakes in different geological domains includes the coseismic and Quaternary faulting that reveals the complex nature of the active tectonics in Africa. The map benefits from previous works on local and regional seismotectonic maps that needed to be integrated with the lithospheric and upper mantle structures, seismic anisotropy tomography and gravity anomaly, into a continental framework. The synthesis of earthquake and volcanic studies obtained from the analysis of late Quaternary faulting and geodetic data will serve as a basis for hazard calculations and the reduction of seismic risks. The map will be useful for the seismic hazard assessment and earthquake risk mitigation for significant infrastructures and their socio-economic implications in Africa. The constant population increase and infrastructure growth in the continent that exacerbate the earthquake risk justify the necessity for a continuous updating of this map. The database and related map are prepared in the framework of the IGC Project-601 "Seismotectonics and Seismic Hazards in Africa" of UNESCO-IUGS, funded by the Swedish International Development Agency and UNESCO-Nairobi for a period of 4 years (2011 - 2014, now extended to 2016).

  20. Crustal Deformation Analysis at CGPS Sites Spanning Mexico

    NASA Astrophysics Data System (ADS)

    Vazquez, G. E.; Bennett, R. A.; Spinler, J. C.; Grejner-Brzezinska, D. A.

    2014-12-01

    We conducted a study using data from continuous Global Positioning System (CGPS) stations throughout Mexico to understand a variety of factors that may have an impact on crustal deformation of Mexico—a research topic investigated for many years. This arises from the fact that Mexico is directly influenced by the interactions between the North American, Pacific, Cocos, Caribbean and Rivera tectonic plates. We analyzed CGPS data originating from several networks covering Mexico. These stations have been installed to serve diverse purposes and applications, and are administered by diverse organizations that include government agencies and public universities. We evaluated a total of 80 CGPS stations operating in Mexico; where dual-frequency geodetic-grade GPS receivers collected data continuously during periods between 1994 and 2014.5, in order to provide a synoptic view of the crustal velocity field of Mexico. The CGPS sites located in the Mexican territory were processed with respect to 133 sites outside of Mexico (i.e., Caribbean, Pacific, South and North American plates) in order to evaluate crustal deformation in Mexico in the context of the relative motions among these tectonic plates. Given the heterogeneous nature of the available GPS networks, we performed an analysis of time-series in terms of their duration and precision, finding generally high precision. From the estimated crustal velocities, we observe that these are very comparable (± 1 mm) with respect to previously derived values for stations located at the Baja Peninsula and the Oaxaca—Guerrero region. In general, the behavior of the northern CGPS spanning Mexico are very consistent with North American plate motion.

  1. Gravitational radiation from neutron stars deformed by crustal Hall drift

    NASA Astrophysics Data System (ADS)

    Suvorov, A. G.; Mastrano, A.; Geppert, U.

    2016-07-01

    A precondition for the radio emission of pulsars is the existence of strong, small-scale magnetic field structures (`magnetic spots') in the polar cap region. Their creation can proceed via crustal Hall drift out of two qualitatively and quantitatively different initial magnetic field configurations: a field confined completely to the crust and another which penetrates the whole star. The aim of this study is to explore whether these magnetic structures in the crust can deform the star sufficiently to make it an observable source of gravitational waves. We model the evolution of these field configurations, which can develop, within ˜104-105 yr, magnetic spots with local surface field strengths ˜1014 G maintained over ≳106 yr. Deformations caused by the magnetic forces are calculated. We show that, under favourable initial conditions, a star undergoing crustal Hall drift can have ellipticity ɛ ˜ 10-6, even with sub-magnetar polar field strengths, after ˜105 yr. A pulsar rotating at ˜102 Hz with such ɛ is a promising gravitational wave source candidate. Since such large deformations can be caused only by a particular magnetic field configuration that penetrates the whole star and whose maximum magnetic energy is concentrated in the outer core region, gravitational wave emission observed from radio pulsars can thus inform us about the internal field structures of young neutron stars.

  2. Detection, Measurement, Visualization, and Analysis of Seismic Crustal Deformation

    NASA Technical Reports Server (NTRS)

    Crippen, R.; Blom, R.

    1995-01-01

    Remote sensing plays a key role in the analysis of seismic crustal deformation. Recently radar interferometry has been used to measure one dimension of the strain fields of earthquakes at a resolution of centimeters. Optical imagery is useful in measuring the strain fields in both geographic dimensions of the strain field down to 1/20 of pixel size, and soon will be capable of high resolution. Visual observation of fault motion from space can also be used to detect fault motion from aerial photographs.

  3. Crust-mantle interactions and crustal deformations, some geological observations

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Crustal deformations at plate boundaries or intracontinental are governed by the relative movements of plates, and most published models consider the lithosphere as the main stress guide in extensional or compressional contexts. The possible contribution of the underlying asthenospheric flow to crustal deformation through viscous coupling is often neglected. Since the early days of plate tectonics, and even earlier, two schools of thought have been developed in parallel whether mantle convection is considered or not. This reflects nowadays in the difficulty of reconciling lithospheric-scale models and global-scale convection models to explain tectonic features observed at the surface. Still, recent studies reemphasized the role of mantle convection in shaping mountain belts or rifts and the consequences of different styles of convection on the geometry and kinematics of mountain belts. We present here a number of geological observations in convergent or divergent contexts that may suggest a strong coupling between asthenospheric flow and crustal deformation. Several of these examples, especially in extensional contexts, show a deformation distributed over wide zones, accommodated by shallow-dipping shear zones and with a constant asymmetry over large distances. This is the case of the Mediterranean back-arc basins, such as the Aegean Sea, the northern Tyrrhenian Sea or the Alboran domain, where extension is taken up by shallow-dipping extensional shear zones and normal faults with a constant asymmetry. A similar image is also observed across the Gulf of Lion passive margin that also belongs to the Mediterranean back-arc basins. Such is also the case of some of the Atlantic passive margins where shallow-dipping normal faults and extensional shear zones control the extraction of the lower crust and the mantle with a constant asymmetry across the entire margin. Finally, the distribution and geometry of normal faults across the Afar region also show a constant

  4. Geodynamics of crustal deformation and seismotectonic block movements in central Europe

    NASA Technical Reports Server (NTRS)

    Liu, H. S.

    1984-01-01

    Geological observations reveal the style of neotectonic near-surface stresses and deformations in central Europe. Seismic activity, focal depths and fault plane solutions of earthquakes indicate kinematic reactions within the crust. A crustal deformation model which may account for the Rhine graben systems and the associated seismotectonic block movements in Europe is presented. A computer aided tomography to gravity anomalies is used in determining the crustal stresses in central Europe. Tomographical interpretations of gravity data with respect to seismic stresses are discussed. Kinematics and dynamics are integrated to show that the measured regional stresses in central Europe are derivable from the convection generated traction on the boundary of the elastic spherical shell of the crust as inferred from satellite derived gravity data.

  5. An assessment of the crustal remelting hypothesis for volcanism in the Freyja Montes deformation zone

    NASA Technical Reports Server (NTRS)

    Namiki, Noriyuki; Solomon, Sean C.

    1991-01-01

    The linear mountain belts of Ishtar Terra on Venus are notable for their topographic relief and slope and for the intensity of surface deformation. The mountains surround the highland plain Lakshmi Planum, the site of two major paterae and numerous other volcanic features and deposits, and evidence is widespread for volcanism within the mountains and in terrain immediately outward of the mountain belt units. While two hypotheses for magmatism can be distinguished on the basis of the chemistry of the melts, chemical data are presently lacking for the Ishtar region. The competing hypotheses for magmatism in Western Ishtar Terra can also be tested with thermal models, given a kinematic or dynamic model for the evolution of the region. The crustal remelting hypothesis is assessed, using the kinematic scenario of Head for the evolution of Freyja Montes. In that scenario, Freyja Montes formed by a sequence of large scale underthrusts of the lithosphere of the North Polar Plains beneath Ishtar Terra, with successive blocks of underthrust crust sutured in imbricate fashion onto the thickened crust of Lakshmi Planum and the mantle portion of underthrusting lithosphere episodically detached. The numerical experiments thus show that volcanic activity associated with the formation of the Frejya Montes deformation zone can be explained by crustal melting, due either to direct contact of crustal material with the hot asthenosphere or to heat generation in a thickened crustal layer.

  6. Dislocation model for aseismic crustal deformation at Hollister, California

    NASA Technical Reports Server (NTRS)

    Matsuura, Mitsuhiro; Jackson, David D.; Cheng, Abe

    1986-01-01

    A model of crustal deformation during the interseismic phase is developed and applied (using the improved Bayesian inversion algorithm described by Jackson and Matsu'ura, 1985) to trilateration data for the USGS Hollister (CA) network. In the model, rigid blocks in motion relative to each other experience friction only in a brittle upper zone, while their ductile lower zones slide freely; the Hollister model comprises five blocks and nine rectangular fault patches. The data and results are presented in tables, graphs, and maps and characterized in detail. The model predicts steady block motion on time scales between 10 yr and 1 Myr, with net motion across the San Andreas/Calaveras fault system 38 + or - 3 mm/yr and brittle/ductile transition depths ranging from 0.4 to 11 km. Two San Andreas segments with higher probabilities of moderate-to-large earthquakes are identified.

  7. Monitoring of Seafloor Crustal Deformation Along the Suruga-Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Tadokoro, K.; Watanabe, T.; Nagai, S.; Okuda, T.; Ikuta, R.; Eto, S.; Yasuda, K.; Sakata, T.; Sayanagi, K.

    2011-12-01

    \\ \\ \\ The Suruga-Nankai Trough is one of the active plate boundaries in the world. The Philippine Sea plate subducts beneath the Amurian (Eurasian) plate along the Suruga-Nankai Trough, causing major subduction earthquakes. The subduction earthquakes, Nankai and Tonankai earthquakes, have repeatedly occurred with intervals of about 100-150 years. Headquarters for Earthquake Research Promotion, Japanese Government [2011] estimates the 30-years probabilities of the next major earthquakes at 60-70 %. It is necessary to monitor crustal deformation above the source regions of the major earthquakes. The source regions are located beneath the seafloor, and we developed a system for monitoring seafloor crustal deformation [Tadokoro et al., 2006, GRL; Ikuta et al., 2008, JGR]. The system is composed of the precise acoustic ranging with ultrasonic waves and kinematic GPS positioning techniques. \\ \\ \\ We monitor seafloor crustal deformation at five sites altogether along the Suruga-Nankai Trough, three in the Kumano region and two in the Suruga region, with the use of this system. We have repeatedly measured the coordinate of seafloor benchmark installed beforehand every about 2-3 months on the average. The monitoring results, the horizontal site velocities with relative to the Amurian Plate, as of 2010 are approximately 3-4 cm/yr in the direction of N70W at the three sites in the Kumano region, and approximately 2-4 cm/yr in the direction of N85-100W at the two sites in the Suruga region. The observed horizontal seafloor crustal deformations are consistent to the plate convergence along the Suruga-Nankai Trough, showing strain accumulation before the next major subduction earthquakes. Acknowledgments: We are grateful to the captain and crews of R/Vs "Hokuto," Tokai University and "Asama," Mie Prefecture Fisheries Research Institute, Japan. This study has been promoted by Ministry of Education, Culture, Sports, Science and Technology, Japanese Government.

  8. Geodetic and Seismic Investigation of Crustal Deformation in Northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Pasari, S.; Dikshit, O., Sr.; Kato, T.

    2014-12-01

    Underthrusting of Indian plate beneath the Eurasian plate results into a persistent compression and strain accumulation along a north-dipping detachment zone in the Himalayan orogen, producing a number of moderate and great interplate earthquakes. In this study, we present the ongoing crustal deformation from our GPS network comprising eight continuously operating permanent stations and three profiles of campaign stations which are lined up perpendicular to the Himalayan mega thrust faults. The campaign stations clearly reveal the ongoing deformation near the Himalayan Frontal Thrust (HFT) and the Main Boundary Thrust (MBT) zones. We further combine our geodetic results with the probalistic earthquake hazards of the northwestern Himalaya (280-320N, 740-800E) to provide a comprehensive report on the seismic hazard scenario of the thickly populated Himalayan cities. For this, the earthquake interevent times and conditional probabilities for events exceeding magnitude 6.0 are estimated from thirteen different probability models, namely exponential, gamma, lognormal, Weibull, Levy, Maxwell, Pareto, Rayleigh, inverse Gaussian (Brownian passage time), inverse Weibull (Frechet), exponentiated exponential, exponentiated Rayleigh (Burr type X), and exponentiated Weibull distributions.

  9. The behavior of a convergent plate boundary - Crustal deformation in the South Kanto district, Japan

    NASA Technical Reports Server (NTRS)

    Scholz, C. H.; Kato, T.

    1978-01-01

    The northwesternmost part of the Sagami trough, a part of the Philippine Sea-Eurasian plate boundary, was ruptured during the great South Kanto earthquake in 1923. Very extensive and frequent geodetic measurements of crustal deformation have been made in the South Kanto district since the 1890's, and these constitute the most complete data set on crustal movements in the world. These data were reanalyzed and interpreted and according to our interpretation indicate the following sequence of events. The coseismic movements were due to oblique thrust and right lateral slip of about 8 m on a fault outcropping at the base of the Sagami trough. This was followed by postseismic deformation resulting from reversed afterslip of 20-60 cm that occurred at an exponentially decaying rate in time. The interseismic deformation is produced by steady subduction at a rate of about 1.8 cm/yr. During subduction the top 10-15 km of the plate boundary is apparently locked, while deeper parts slip aseismically at an irregular rate. No significant precursory deformation was observed. The recurrence time for 1923 type earthquakes is 200-300 years. The Boso and Miura peninsulas are broken into a series of fault-bound blocks that move semi-independently of the surrounding region. The subduction zone itself, where it is exposed on land, is shown to be a wide zone encompassing several faults that are active at different times.

  10. Seismic Crustal and Mantle Deformation Indicators Along the Himalayan Arc

    NASA Astrophysics Data System (ADS)

    Schulte-Pelkum, V.; Levin, V. L.

    2015-12-01

    We compare two seismological indicators of lithospheric deformation along the Himalayan arc from the foothills to the Tibetan plateau, from the eastern to the western syntaxis. The first method is shear wave splitting of core phases such as SKS, which has poor depth resolution but is typically presumed to be primarily sensitive to mantle anisotropy. The data come from a network in western Tibet as well as a worldwide compilation database of results from temporary and permanent networks. The second method is an azimuthal harmonic analysis of receiver functions. Azimuthally varying arrivals in radial and transverse component receiver functions are generated by dipping isotropic contrasts as well as by contrasts in dipping foliation with anisotropy. Both show a two-lobed pattern with backazimuth that identifies the strike of the dipping isotropic contrast or of the foliation. If dipping isotropic contrasts and dipping foliation are formed in the same deformation regime, their strikes are expected to be parallel to one another. The method is different from splitting of P-to-S converted phases. We analyze receiver function data from temporary deployments and permanent stations extending from West Tibet to the eastern syntaxis. SKS results show considerable variation across the arc, including variation in splitting times as well as fast axes on a short spatial scale of ~ 50 km. The scatter is larger within the Himalaya and towards the syntaxes than in the plateau interior. The foliation and dip signal in receiver functions is dominated by crustal arrivals. The mapped strikes are parallel to along-arc faults and to known strike-slip systems and show high regional coherence. We show maps of statistical correlations between splitting fast axes and receiver function strikes and show models of expected orientations seen by the two methods in crust and mantle for different deformation models and compositions. We compare the results to different orogens such as Taiwan, where

  11. Different Phases of Earthquake Cycle Reflected in GPS Measured Crustal Deformations along the Andes

    NASA Astrophysics Data System (ADS)

    Khazaradze, G.; Klotz, J.

    2001-12-01

    The South American Geodynamic Activities (SAGA) project was initiated in 1993 by the GeoForschungsZentrum together with host organizations in Argentina and Chile with the main objective of studying the kinematics and dynamics of present-day deformation processes along the central and southern Andes. Currently the SAGA network consists of 230 geodetic markers spanning more than 2000 km long distance from Peru/Chile border in the north to Cape Horn in the south. The majority of the observed crustal deformation field is relatively homogenous: roughly parallel to the plate convergence direction and decreasing in magnitude away from the deformation front. This pattern is characteristic for the \\textit{inter-seismic} phase of earthquake deformation cycle and can be explained by the elastic strain accumulation due to locking of the thrust interface between the subducting Nazca and the overriding South America plates. However, in addition to the dominant inter-seismic signal, close examination of the observed velocity field also reveals significant spatial and temporal variations, contrary to the commonly used assumption of constant deformation rates. This variation is especially pronounced for the measurements in the vicinity of the 1995 Mw8.0 Antofagasta earthquake (22{° }S-26{° }S). Here, after capturing up to 1 meters of \\textit{co-seismic} displacements associated with this event, the analysis of data obtained during the three following field campaigns (1996-1999), reveals highly time dependent deformation pattern. This can be explained by the decreasing importance of \\textit{post-seismic} effects of the Antofagasta event relative to the increasing dominance of the inter-seismic phase of subduction. Perhaps, even more interesting time dependent observations have been detected in the southern part the SAGA network (38{° }S-43{° }S).Here, after 35 years of the occurrence of the 1960 Mw9.5 Chile earthquake, we still see the continuing post-seismic effects of this

  12. JERS-1 Synthetic Aperture Radar Interferometry Applications: Mapping of Rain Forest Environments and Crustal Deformation Studies

    NASA Technical Reports Server (NTRS)

    Rosen, P.; Hensley, S.; Peltzer, G.; Rignot, E.; Werner, C.

    1999-01-01

    This research using JERS-1 SAR data has been very fruitful, resulting in a strong collaboration with geodesists and geophysicists in Japan, and several important papers characterizing crustal deformation, and the capabilities and limitations of JERS data for these studies.

  13. Crustal Seismic Anisotropy Produced by Rock Fabric Terranes in the Taiwan Central Range Deformational Orogen: Integrative Study Combining Rock Physics, Structural Geology, and Passive/Active-Source Seismology

    NASA Astrophysics Data System (ADS)

    Okaya, D. A.; Ross, Z.; Christensen, N. I.; Wu, F. T.; Byrne, T. B.

    2014-12-01

    The island of Taiwan is currently under construction due to the collision of the northwestern corner of the Philippine Sea plate and the embedded Luzon island arc with the larger continental Eurasian plate. This collision is responsible for the current growth of the Central Range that dominates the eastern half of the island. An international collaboration involving several USA and Taiwan universities and academic institutions was formed to study how the orogen evolves through time and to understand the role of a colliding island arc in mountain building. The project, Taiwan Integrated Geodynamics Research (TAIGER), was funded by NSF-Continental Dynamics and Taiwan National Science Council. The Central Range grows at one of the most rapid rates of uplift in the world, exposing metamorphic rocks that were once at least 10 km deep. The range offers unique opportunities for studies of crustal seismic anisotropy for two major reasons: (1) its geological makeup is conducive for producing crustal seismic anisotropy; that is, the rocks are highly foliated; and (2) a seismological data volume of significant breadth offers extensive coverage of sources and recording stations throughout the region. We carried out a crustal shear wave splitting study by data mining 3300 local earthquakes collected in the TAIGER 2009 sea-land experiment. We used an automated P and S wave arrival time picking method (Ross and Ben-Zion, 2014) applied to over 100,000 event-station pairs. These data were analyzed for shear-wave splitting using the MFAST automated package (Savage et al., 2010), producing 3300 quality shear wave split measurements. The splitting results were then station-averaged. The results show NNE to NE orientation trends that are consistent with regional cleavage strikes. Average crustal shear wave split time is 0.244 sec. These measurements are consistent with rock physics measurements of Central Range slate and metamorphic acoustic velocities. The splits exhibit orientations

  14. Do crustal deformations observed by GPS in Tierra del Fuego (Argentina) reflect glacial-isostatic adjustment?

    NASA Astrophysics Data System (ADS)

    Mendoza, L.; Richter, A.; Hormaechea, J. L.; Perdomo, R.; Del Cogliano, D.; Dietrich, R.; Fritsche, M.

    2010-09-01

    Vertical site velocities determined by geodetic GPS observations in the Lago Fagnano area, Tierra del Fuego main island, are interpreted with respect to their potential relation with the glacial-isostatic crustal response to ice mass changes. The spatial pattern of the uplift rates, in combination with the horizontal crustal deformation pattern, point towards a fault-tectonic rather than glacial-isostatic origin of the determined vertical crustal deformations. This implies rather small GIA effects pointing towards relatively small Holocene ice-mass changes in Tierra del Fuego. However, these findings are considered to be preliminary. They should be confirmed by additional observations covering an extended area with GPS sites.

  15. New GPS Constrains on Crustal Deformation within the Puerto Rico-Virgin Islands Microplate

    NASA Astrophysics Data System (ADS)

    Solares, M. M.; Lopez, A. M.; Jansma, P. E.; Mattioli, G. S.

    2015-12-01

    Over twenty years of Global Positioning System (GPS) observations along the northeastern region of the Caribbean plate boundary zone have been used to evaluate crustal deformation in the Puerto Rico and Virgin Islands (PRVI) microplate, which generally translates westward relative to the Caribbean plate. New data from continuous GPS stations (cGPS) and re-occupied campaign GPS stations (eGPS) obtained between 2014 and 2015 allowed us to update the velocity field of the PRVI GPS Network and redefine the existing plate kinematics model of the PRVI microplate from previous measurements (Jansma et al., 2000; Jansma & Mattioli, 2005). Geodetic datasets for this epoch were processed with GIPSY/OASIS II (v.6.2) using an absolute point positioning strategy with final, precise orbits and clocks from JPL (IGS08). Results of sites velocity in the PRVI block are presented with respect to North America and Caribbean reference frames in ITRF08. The horizontal velocity components were used to calculate baseline lengths changes between selected GPS stations that span on-land faults and microplate boundaries, thus allowing quantification of internal deformation within the PRVI block. This enables us to locate zones of active deformation and faulting in order to understand how the relative motion between geological structures is accommodated. Our updated velocity field constrains intraplate deformation to 1-3 mm/yr across the PRVI microplate and active extension of 1-2 mm/yr in the Anegada passage eastern boundary. In addition, counterclockwise rotation has been observed and may be related to the deformation in southwestern Puerto Rico continuing offshore to the Muertos Trough along PRVI's southern boundary. Despite the PRVI microplate slow motion and small deformation, increasing velocities from east to west coincides with the most active microseismic zone and ongoing deformation in southwestern Puerto Rico suggesting independent motion along this segment of the PRVI block.

  16. Monitoring regional crustal deformation with horizontal geodetic data

    NASA Technical Reports Server (NTRS)

    Snay, R. A.; Gergen, J. G.

    1978-01-01

    The National Ocean Survey is developing an automated system to derive parameters of horizontal crustal motion from existing geodetic data by the process of least squares estimation. The estimated parameter will describe crustal motion as a function of geographic position. The system will first be tested in the Imperial Valley region of southern California, using data from 8 individual field projects spanning four decades of time.

  17. Determining the cause of crustal deformation from observations of crustal tilt and extensions

    NASA Astrophysics Data System (ADS)

    Ozawa, I.

    1983-09-01

    Observations of tilt, horizontal extensions and vertical extension of the crust have been performed in the Osakayama tunnel. The study seeks to identify the cause of crustal movements and to estimate the equivalent magnitude of associated earthquakes.

  18. Decadal correlation between crustal deformation and variation in length of day of the Earth

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Liang; Chen, Yun-Tai; Cui, Du-Xin; Wang, Wen-Ping; Liang, Wei-Feng

    2000-11-01

    Recently, in comparing with Earth rotation data, we found some exciting correlation phenomena between length-of-day (LOD) and crustal deformations as well as stress observations in China, the correlation appears most typically on decade time scales and seems to be direction-dependent. As LOD variation induced stress and deformation is far less than the observed ones, we infer that decade variations in crustal deformation and stress are very possibly attributed to the core-mantle coupling process, just like LOD decade variations are attributed to core-mantle coupling. More detailed and extended investigations are going on, and we believe that the similar correlation phenomena should also exist in other part of the world. The LOD-correlated crustal deformations are expected to provide a better constraint on verifying the real core-mantle coupling mechanism, topographic, electromagnetic or gravitational coupling.

  19. Detection of crustal deformation from the Landers earthquake sequence using continuous geodetic measurements

    USGS Publications Warehouse

    Bock, Y.; Agnew, D.C.; Fang, P.; Genrich, J.F.; Hager, B.H.; Herring, T.A.; Hudnut, K.W.; King, R.W.; Larsen, S.; Minster, J.-B.; Stark, K.; Wdowinski, S.; Wyatt, F.K.

    1993-01-01

    The measurement of crustal motions in technically active regions is being performed increasingly by the satellite-based Global Positioning System (GPS)1,2, which offers considerable advantages over conventional geodetic techniques3,4. Continuously operating GPS arrays with ground-based receivers spaced tens of kilometres apart have been established in central Japan5,6 and southern California to monitor the spatial and temporal details of crustal deformation. Here we report the first measurements for a major earthquake by a continuously operating GPS network, the Permanent GPS Geodetic Array (PGGA)7,9 in southern California. The Landers (magnitude Mw of 7.3) and Big Bear (Mw 6.2) earthquakes of 28 June 1992 were monitored by daily observations. Ten weeks of measurements, centred on the earthquake events, indicate significant coseismic motion at all PGGA sites, significant post-seismic motion at one site for two weeks after the earthquakes, and no significant preseismic motion. These measurements demonstrate the potential of GPS monitoring for precise detection of precursory and aftershock seismic deformation in the near and far field.

  20. Seismic evidence for widespread western-US deep-crustal deformation caused by extension.

    PubMed

    Moschetti, M P; Ritzwoller, M H; Lin, F; Yang, Y

    2010-04-01

    Laboratory experiments have established that many of the materials comprising the Earth are strongly anisotropic in terms of seismic-wave speeds. Observations of azimuthal and radial anisotropy in the upper mantle are attributed to the lattice-preferred orientation of olivine caused by the shear strains associated with deformation, and provide some of the most direct evidence for deformation and flow within the Earth's interior. Although observations of crustal radial anisotropy would improve our understanding of crustal deformation and flow patterns resulting from tectonic processes, large-scale observations have been limited to regions of particularly thick crust. Here we show that observations from ambient noise tomography in the western United States reveal strong deep (middle to lower)-crustal radial anisotropy that is confined mainly to the geological provinces that have undergone significant extension during the Cenozoic Era (since approximately 65 Myr ago). The coincidence of crustal radial anisotropy with the extensional provinces of the western United States suggests that the radial anisotropy results from the lattice-preferred orientation of anisotropic crustal minerals caused by extensional deformation. These observations also provide support for the hypothesis that the deep crust within these regions has undergone widespread and relatively uniform strain in response to crustal thinning and extension. PMID:20376148

  1. Crustal wedge deformation in an internally-driven, numerical subduction model

    NASA Astrophysics Data System (ADS)

    van Dinther, Ylona; Morra, Gabriele; Funiciello, Francesca; Rossetti, Federico; Faccenna, Claudio

    2010-05-01

    The Earth's active convergent margins are characterized by dynamic feedback mechanisms that interact to form an intricate system in which a crustal wedge is shaped and metamorphosed at the will of two large, converging plates. This framework is accompanied by complicated processes, such as seismogenesis and the exhumation of high pressure rocks. To honor the dynamic interaction between different entities and advance on these persisting issues, we model the interaction between the subducting and overriding lithospheres, the mantle and the crustal wedge explicitly, and observe how a crustal wedge evolves in detail within a set of rigid, internally-driven boundary conditions. We model crustal wedge evolution in an intra-oceanic subduction setting by using a plane-strain implicit solid-mechanical Finite Element Model, in which the mechanical conservation equations are solved using the software package ABAQUS. The crustal wedge is modeled as a thick-skinned accretionary wedge of inter-mediate thickness with a linear visco-elastic bulk rheology. The dynamic interaction between the subducting plate, the overriding plate, and crustal wedge is implemented using a Coulomb frictional algorithm. The interaction with the mantle is incorporated using a computationally favorable mantle drag formulation that simulates induced three-dimensional mantle flow. This results in a quasi-static framework with a freely moving slab, trench, and fault, where a weaker wedge deforms in response to self-regulating, rigid boundary conditions formed by single, frictional bounding faults. The self-regulating evolution of crustal wedge architecture follows three phases; 1) initial vertical growth, 2) coeval compression and extension leading to internal corner flow, and 3) a steady-state taper with continuous corner flow. Particle trajectories show that, as shortening continues throughout the second phase, wedge material is constantly forced upward against the backstop, while extension and ocean

  2. Detection of crustal deformation prior to the 2014 Mt. Ontake eruption by the stacking method

    NASA Astrophysics Data System (ADS)

    Miyaoka, Kazuki; Takagi, Akimichi

    2016-04-01

    The phreatic eruption of Mt. Ontake in central Japan occurred in September 27, 2014. No obvious crustal deformation was observed prior to the eruption, and the magnitudes of other precursor phenomena were very small. In this study, we used the stacking method to detect crustal deformation prior to the eruption. The stacking method is a technique to improve the signal-to-noise ratio by stacking multiple records of crustal deformation. We succeeded in detecting a slight crustal deformation caused by a volume change in the shallow region beneath the volcano's summit from 1 month prior to the eruption. We also detected a slight crustal deformation that may have been caused by a volume increase in the deep region from one and a half months before the eruption. The magnitude of the volume change in the shallow region did not differ significantly in the 2014 eruption compared to the volume change during the small Mt. Ontake eruption in 2007, and the volume change in the deep region was rather smaller in 2014 than in 2007.

  3. Active mantle flow and crustal dynamics in southern California

    NASA Astrophysics Data System (ADS)

    Fay, N.; Bennett, R.; Spinler, J.

    2007-12-01

    We present numerical modeling analysis of active upper mantle flow and its role in driving crustal deformation in southern California. The forces driving lithospheric deformation at tectonic plate boundaries can be thought of as the sum from two sources: (1) forces transmitted from the far-field by rigid tectonic plates, and (2) forces created locally at the plate boundary by heterogeneous density distribution. Here we quantify the latter by estimating the stresses acting on the base of the crust caused by density-driven flow of the upper mantle. Anomalous density structure is derived from shear wave velocity models (Yang & Forsyth, 2006) and is used to drive instantaneous incompressible viscous upper mantle flow relative to a fixed crust; this allows isolation of stresses acting on the crust. Comparison of results with the finite element codes Abaqus (commercial) and GALE (community- developed) is good. We find that horizontal tractions range from 0 to ~3 MPa and vertical tractions range between approximately -15 to 15 MPa (negative indicating downward, positive upward); Absolute magnitudes depend on the assumed velocity-density scaling relationship but the overall patterns of flow are more robust. Anomalous density beneath the Transverse Ranges, in particular beneath the San Bernardino Mountains and offshore beneath the Channel Islands, drives convergent horizontal tractions and negative vertical tractions on the base of the crust there. Anomalous buoyancy beneath the southern Walker Lane Belt and anomalous density beneath the southern Great Valley create a small convective cell (the Sierra Nevada "drip"), which promotes extension on the eastern edge of the Sierra Nevada block and subsidence of the Great Valley. Favorable comparison with contemporary crustal thickness, heat flow, and surface strain rate indicates that upper mantle flow plays a very important role in active crustal deformation in southern California and much of the non-ideal behavior of this

  4. Active Crustal Deformation in the Area of San Carlos, Baja California Sur, Mexico as Shown by Data of Local Earthquake Sequences

    NASA Astrophysics Data System (ADS)

    Munguía, Luis; González-Escobar, Mario; Navarro, Miguel; Valdez, Tito; Mayer, Sergio; Aguirre, Alfredo; Wong, Victor; Luna, Manuel

    2015-12-01

    earthquakes can occur along the coastline of Baja California, at 60 km east of the Tosco-Abreojos fault system. We conclude that transtensional deformation is taking place across a wide zone of the Pacific margin of Baja California. Finally, we point out that although the studied earthquakes were of small magnitude, they might serve as a reminder of the danger that future larger events pose to San Carlos.

  5. Kinematic model of crustal deformation of Fenwei basin, China based on GPS observations

    NASA Astrophysics Data System (ADS)

    Qu, Wei; Lu, Zhong; Zhang, Qin; Li, Zhenhong; Peng, Jianbin; Wang, Qingliang; Drummond, Jane; Zhang, Ming

    2014-04-01

    Using high precision GPS data for the period of 1999-2007 from the China Crustal Movement Observation Network, we have constructed a plate kinematic model of crustal deformation of Fenwei basin, China. We have examined different kinematic models that can fit the horizontal crustal deformation of the Fenwei basin using three steps of testing. The first step is to carry out unbiasedness and efficiency tests of various models. The second step is to conduct significance tests of strain parameters of the models. The third step is to examine whether strain parameters can fully represent the deformation characteristics of the 11 tectonic blocks over the Fenwei basin. Our results show that the degree of rigidity at the Ordos, Hetao, Yinshan and South China blocks is significant at the 95% confidence level, indicating the crustal deformation of these blocks can be represented by a rigid block model without the need to consider differential deformation within blocks. We have demonstrated that homogeneous strain condition is suitable for the Yinchuan basin but not for other 6 blocks. Therefore, inhomogeneous strains within blocks should be considered when establishing the crustal deformation model for these blocks. We have also tested that not all of the quadratic terms of strain parameters are needed for the Yuncheng-Linfen block. Therefore, four kinds of elastic kinematic models that can best represent the detailed deformation characteristics of the 11 blocks of Fenwei basin are finally obtained. Based on the established model, we have shown that the current tectonic strain feature of the Fenwei basin is mainly characterized by tensile strain in the NW-SE direction, and the boundaries betweem the Ganqing and Ordos blocks and the Shanxi graben possess the maximum shear strain. A comparison between our results and past geological and geophysical investigations further confirms that the model established in this paper is reasonable.

  6. Crustal deformation in southern California using SAR interferometry

    USGS Publications Warehouse

    Peltzer, G.; Rosen, P.; Rogez, F.; Hudnut, K.

    1997-01-01

    By combining pairs of ERS-1/2 SAR images of Southern California spanning long time intervals (1-4 years), we were able to measure the rate of slow deformation processes along faults activated during the Landers 1992 earthquake. Interferograms revealed several centimeters of post-seismic rebound in step-overs of the 1992 break, with a characteristic decay rate of -280 days. We interpreted this process as due to pore fluid flow as pore pressure gradients caused by coseismic stress changes dissipate. The data also revealed evidence of after-slip on different sections of the fault. The southern branches of the 1992 break experienced surface creep producing sharp phase cuts hi the interferometric maps. The same approach was used in the Los Angeles basin, which is currently undergoing NS shortening at a rate of ???8 mm/yr. The tectonic signal in imerferograms of the Los Angeles basin is intermingled with signals due to other sources such as ground subsidence caused by oil and water withdrawal.

  7. Aseismic crustal deformation in the Transverse Ranges of southern California

    NASA Technical Reports Server (NTRS)

    Cheng, Abe; Jackson, David J.; Matsu'ura, Mitsuhiro

    1987-01-01

    Using geodetic data at a plate boundary, the subsurface displacements that accompany plate motion were modeled as the sum of rigid block motion and the elastic effects of frictional drag between blocks in a model consisting of 12 blocks and 27 rectangular fault patches. The block motion inferred from the geodetic data has the same order of magnitude as the geologic estimates, and for many faults the agreement was excellent. The model implies about 20 mm/y of crustal shortening normal to the trend of the San Andreas fault.

  8. Subduction Related Crustal and Mantle Deformations and Their Implications for Plate Dynamics

    NASA Astrophysics Data System (ADS)

    Okeler, Ahmet

    Ocean-continent convergence and subsequent continental collision are responsible for continental growth, mountain building, and severe tectonic events including volcanic eruptions and earthquake activity. They are also key driving forces behind the extensive thermal and compositional heterogeneities at crustal and mantle depths. Active subduction along the Calabrian Arc in southern Italy and the Hellenic Arc are examples of such collisional tectonics. The first part of this thesis examines the subduction related deformations within the crust beneath the southern Apennines. By modeling regional surface wave recordings of the largest temporary deployment in the southern Apennines, a lower-crustal/upper-mantle low-velocity volume extending down to 50 km beneath the mountain chain is identified. The magnitude (˜ 0.4 km/s slower) and anisotropic nature (˜ 10%) of the anomaly suggest the presence of hot and partially molten emplacement that may extend into the upper-crust towards Mt. Vulture, a once active volcano. Since the Apulian basement units are deformed during the compressional and consequent extensional events, our observations favor the "thick-skin" tectonic growth model for the region. In the deeper mantle, active processes are thermodynamically imprinted on the depth and strength of the phase transitions. This thesis examines more than 15000 SS precursors and provides the present-day reflectivity structure and topography associated with these phase transitions. Through case studies I present ample evidence for both slab penetration into the lower mantle (beneath the Hellenic Arc, Kurile Island and South America) and slab stagnation at the bottom of the Mantle Transition Zone (beneath the Tyrrhenian Sea and eastern China). Key findings include (1) thermal anomalies (˜ 200 K) at the base of the MTZ, which represent the deep source for Cenozoic European Rift Zone, Mount Etna and Mount Cameroon volcanism, (2) significant depressions (by 20-40 km) at the bottom

  9. Crustal Deformation in the Southwestern Gulf of Mexico: Underthrusting of the Gulf of Mexico beneath Tehuantepec

    NASA Astrophysics Data System (ADS)

    Suarez, Gerardo; Aguilar, Sergio

    2016-04-01

    An array of 45 broad band sensors were installed along the Isthmus of Tehuantepec in southeastern. This experiment, called VEOX, was implemented on August 2007 to March 2009. Data were registered continuously during the whole period. In order to search in the seismic records of the data obtained for crustal events in the Isthmus of Tehuantepec, To this purpose, an STA/LTA algorithm was designed to detect earthquakes with S-P times indicating they occurred close the seismic stations, at crustal or upper mantle depths. During the 18 months that the experiment lasted, about 40 crustal earthquakes were recorded in more than three stations, allowing us to determine a hypo central location. All earthquakes occurring at depths greater than 120 km, within the subjected slab, were discarded. The majority of this crustal or upper mantle activity occurred in the northern part of the Isthmus, along the coast of the Gulf of Mexico or just inland from it. No velocity model exists in the area. Therefore, we tested three different velocity models, including one obtained in an adjacent region and based on seismic refraction data. One of these three models rendered the more stable solutions and smaller errors in the hypocentral locations and was used as the local seismic velocity model. In order to improve the quality of the locations, we experimented using a double difference hypocentral algorithm (HYPODD). There was no noticeable improvement in the quality of the hypocenters using this technique. The best located events suggest a southwestern-dipping zone of seismic seismicity, deepening from the Gulf of Mexico towards the interior of the Isthmus of Tehuantepec. The focal mechanisms of the earthquakes indicate the maximum axis of compresion (P axis) is oriented nearly horizontally and in a southwest-northeast direction. These mechanisms are similar to those observed for earthquakes previously studied in the region on the basis of teleseismic data, such as the Mw 6.9, 29 August

  10. Geodetic investigation of crustal deformation along the Dead Sea Transform and the Carmel Fault System

    NASA Astrophysics Data System (ADS)

    Sadeh, Maytal; Hamiel, Yariv; Ziv, Alon; Bock, Yehuda; Fang, Peng; Wdowinski, Shimon

    2013-04-01

    We use GPS measurements and elastic modeling to study the crustal deformation in the Levant. In this region, large-scale crustal deformation is mainly related to the Dead Sea Transform (DST) and the Carmel Fault System (CFS). The former is an active left lateral transform, bounding the Arabian plate and the Sinai sub-plate, and the latter branches out of the former and separates the Sinai sub-plate into two tectonic domains. In this study we obtain the velocities of 33 permanent GPS stations and 145 survey stations that were surveyed in three campaigns between 1996 and 2008. We use a simple elastic dislocation model to infer the slip rate and locking depth along various segments of the DST. We infer a 3.1-4.5 mm/yr slip rate and a 7.8-16.4 km locking depth along the DST north of the CFS, and a slip rate of 4.6-5.9 mm/yr and locking depth of 11.8-24 km along the Jericho Valley, south of the CFS. Further south, along the Arava Valley we obtain a slip rate of 4.6-5.4 mm/yr and a locking depth of 12.1-22.5 km. We identify an oblique motion along the Carmel fault with about 0.7 mm/yr left-lateral and about 0.6 mm/yr extension rates, resulting in N-S extension across the Carmel fault. This result, together with the decrease in DST slip velocity from the Jericho fault to the Jordan fault confirms previous suggestions, according to which part of the slip between Arabia and Sinai is being transferred from the DST to the CFS.

  11. Crustal Deformation and Seismicity in Southern Bavaria revealed by GNSS observations

    NASA Astrophysics Data System (ADS)

    Völksen, C.; Hackl, M.

    2012-04-01

    A geodetic network consisting of approximately 30 GNSS stations in Southern Bavaria, bordered by the Alps and the river Danube within Bavaria, has been analysed over the past 5 years. The network itself consists of several GNSS stations that have been installed for crustal deformation studies in the Bavarian Alps, some sites of the EUREF Permanent Network (EPN) and mainly stations of the GNSS network of the Bavarian Office for Surveying and Geographic Information. The later stations mainly serve for real-time positioning at the 1 cm level for engineering surveys, land register, aerial imagery and other surveying applications. For these sites it is crucial that the data are permanently available, reliable, integrity monitored and well maintained. Since the focus of these sites is not crustal deformation monitoring they are continuously modernized and the equipment is regularly exchanged to fulfil the most recent real-time standards, which in turn provokes frequent coordinate jumps due to the systematic biases caused by the different GNSS antennas or receivers. It is therefore necessary to analyse the time series of the coordinate changes very carefully in order to estimate a reliable mean velocity along with the uncertainty for each site with frequent position shifts within the entire observation period. The derived geodetic velocity models can be used to identify rotations of the continental crust or even active geological features. In addition 2-D strain rate tensors have been derived based on the geodetic velocity model. The analysis of the tensors provide strain characteristics like dilatation and shear strain rates, which in turn support the seismic hazard assessment. Based on the analysed data, two areas of high strain rates have been identified that agree very well with the observed seismicity in Bavaria.

  12. A dynamical basis for crustal deformation and seismotectonic block movements in central Europe

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1983-01-01

    The stress field in the earth's crust as inferred from satellite gravity data causes crustal deformation and seismotectonic block movements in central Europe. The satellite-determined stresses in the crust of central Europe are consistent with earthquake focal mechanisms, joint-orientation and in situ stress measurements.

  13. Crustal structure and deformation under the Longmenshan and its surroundings revealed by receiver function data

    NASA Astrophysics Data System (ADS)

    Sun, Ya; Liu, Jianxin; Zhou, Keping; Chen, Bo; Guo, Rongwen

    2015-07-01

    The convergence of India and Eurasia and the obstruction from the rigid Sichuan Basin cause the Longmenshan (LMS) to have the steepest topographic gradient at the eastern margin of the Tibetan Plateau. However, the mechanisms of surface uplift are still controversial. In this paper, we estimate the crustal structure and deformation under the LMS and its surroundings by analyzing a large amount of receiver function data recorded by regional seismic networks of the China Earthquake Administration. We apply a comprehensive splitting measurement technique on Ps conversion phase at the Moho (Moho Ps splitting) to calculate crustal anisotropy from azimuthal variations of receiver functions. Our results show that most of the seismic stations beneath the LMS area exhibit significant seismic anisotropy with the splitting time of 0.22-0.94 s and a fast polarization direction of NW-SE, while less or even no crustal anisotropy has been observed under the Sichuan Basin. Comparing the fast polarization directions of Moho Ps splitting with the indicators of lithospheric deformation (such as shear wave splitting, absolute plate motion, and global positioning system) imply a consistent tendency of deformation between the lower crust and upper mantle, but decoupling deformation in the crust beneath the LMS area. We further compare Moho Ps splitting time to that estimated from previous SKS splitting, indicating that crustal anisotropy is an important source of the SKS splitting time in this study area. In addition, a thick crust (>50 km) with high Vp/Vs values (1.74-1.86) is also observed using the H-κ stacking method. These seismic observations are consistent with the scenario that the LMS area has been built by the lower crustal flow. Combined with the seismic reflection/refraction profile and geology studies, we further suggest that the lower crustal flow may extrude upward into the upper crust along the steeply dipping strike faults under the LMS area, resulting in the surface

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  15. Groundwater pressure changes and crustal deformation before and after the 2007 and 2014 eruptions of Mt. Ontake

    NASA Astrophysics Data System (ADS)

    Koizumi, Naoji; Sato, Tsutomu; Kitagawa, Yuichi; Ochi, Tadafumi

    2016-03-01

    Volcanic activity generally causes crustal deformation, which sometimes induces groundwater changes, and both of these phenomena are sometimes detected before volcanic eruptions. Therefore, investigations of crustal deformation and groundwater changes can be useful for predicting volcanic eruptions. The Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, has been observing groundwater pressure at Ohtaki observatory (GOT) since 1998. GOT is about 10 km southeast of the summit of Mt. Ontake. During this observation period, Mt. Ontake has erupted twice, in 2007 and in 2014. Before the 2007 eruption, the groundwater pressure at GOT clearly dropped, but it did not change before or after the 2014 eruption. These observations are consistent with the crustal deformation observed by Global Navigation Satellite System stations of the Geospatial Information Authority of Japan. The difference between the 2007 and 2014 eruptions can be explained if a relatively large magma intrusion occurred before the 2007 eruption but no or a small magma intrusion before the 2014 eruption.

  16. Models for rupture mechanics of plate boundaries and crustal deformation

    NASA Astrophysics Data System (ADS)

    Nur, A.

    1983-02-01

    The role of pull aparts and pushups in transcurrent systems, the rotation of faults and blocks within transcurrent fault systems, the role of accretion tectonics in plate boundary deformation, and power law creep behavior and the yielding at plate boundaries were investigated.

  17. Present-day crustal movements and the mechanics of cyclic deformation

    SciTech Connect

    Thatcher, W.

    1990-01-01

    Contemporary crustal movements in California are concentrated within a plate-boundary deformation zone that is typically 50 to 200 km wide, centered approximately on the San Andreas fault. Observations of coseismic, postseismic, and interseismic movements define the earthquake deformation cycle and constrain models of strain accumulation and release for strike-slip plate boundaries. This chapter describes shear strain on the San Andreas fault system; aseismic slip, integrated displacement rates, and Pacific-North American plate motion; detailed displacement-rate patterns; and thick- and thin-lithosphere models and stress-slip-constitutive-law fault models of deformation.

  18. Crustal Deformation of the Yellowstone Hotspot: Unifying GPS and Geologic Data and Intraplate Modeling

    NASA Astrophysics Data System (ADS)

    Puskas, C. M.; Smith, R. B.; Meertens, C. M.

    2001-12-01

    The 800-km long Yellowstone-Snake River Plain (YSRP) volcanic system reflects the trace of the North American Plate across a mantle hotspot. The system is comprised of the Yellowstone Plateau, the current center of volcanic activity, and the SRP, a region of minimal earthquake activity and low topography surrounded by a parabola of active faults, high seismicity, and mountain ranges. The objectives of this project are to assess regional deformation and to integrate the GPS data with that of fault slip rates, topography, and regional geology to better understand the interaction of the overriding plate with the hotspot source. Campaign (1987-2000) and continuous GPS measurements were made for the YSRP and the surrounding tectonic parabola as part of a collaborative experiment on the geodynamics of the Yellowstone hotspot. The data of the University of Utah's 140-station network across the YSRP were augmented with GPS measurements of 80 stations in the SRP and Idaho in 1990 and 1999. GPS results, calculated with respect to a fixed North America reference frame, show NE-SW extension of 1.9 mm/yr of the Snake River Plain, which is notably slower than the 4-5 mm/yr of NE-SW deformation rate across the Yellowstone Plateau. This difference in extension rates requires a zone of intraplate compression SW of Yellowstone. The extension of the SRP itself is comparable to the sum of the horizontal slip rates of the large normal faults bounding the SRP, so that there is no discrepancy between extension of the seismically active normal faults and the SRP. This requires a mechanism by which the aseismic SRP matches fault-related extension of the surrounding Basin and Range. One potential mechanism is dike intrusion. Another possibility is that the SRP deforms elastically but does not have faults because of lithospheric strengthening from volcanic intrusion of a high-strength, high-density mid-crustal layer. Finite element models of the velocity fields for each of the scenarios are

  19. Crustal anisotropy and deformation of the southeastern margin of the Tibetan Plateau revealed by Pms splitting

    NASA Astrophysics Data System (ADS)

    Cai, Yan; Wu, Jianping; Fang, Lihua; Wang, Weilai; Yi, Shuang

    2016-05-01

    The crustal seismic anisotropy in the southeastern margin of the Tibetan Plateau was obtained by analyzing receiver functions of a newly deployed dense seismic array. The measured splitting time of the Pms phase varies from 0.02 to 0.88 s, with an average value of approximately 0.28 s, which is much larger than the splitting time in the upper crust (top 15 km), implying that the crustal anisotropy is mainly generated within the middle and lower crust (below 15 km). The fast polarization directions of Pms are in good agreement with the directions of principle compression stress in the sub-blocks and are parallel with the strikes of the faults near the Xiaojiang fault, the Red River fault, and the Lancangjiang fault. The splitting time shows a conspicuous contrast with a small value in the east of the Xiaojiang fault zone and a large value in the west. We assume that the differential movement in the ductile middle-to-lower crust caused the alignment of materials along the movement directions and developed the crustal anisotropy in the sub-blocks. Near the major faults, the low-velocity zone, high Poisson's ratio and high heat flow in the crust provide evidence for the existence of partial melt, which may be related to the strong crustal anisotropy in this area. The crustal deformation near these faults is mainly caused by the strike-slip motion, resulting in the alignment of minerals and partial melts along the strikes of these faults. Analyzing the anisotropy pattern from SKS and Pms splitting, we speculate that the crustal deformation is mechanically decoupled from the upper mantle in our study region.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  1. Crustal accretion and deformation processes above the Galápagos hotspot

    NASA Astrophysics Data System (ADS)

    Ebinger, C. J.; Davidge, L.; Ruiz, M. C.; Bagnardi, M.; Amelung, F.; Tepp, G.; Cote, D. M.

    2012-12-01

    Ocean island volcanoes initiate and grow as plates move over mantle upwellings, producing chains of volcanoes with long-lived magmatic plumbing systems that store mantle melts. Pressure changes that accompany the arrival of new batches of melt into the magma chamber, or the release of magma to surface eruptions and/or dikes, cause surface deformation, and changes in state-of-stress in the overlying rocks. Nowhere are these surface variations more pronounced than along the chain of 7 active volcanoes in the western Galápagos, each of which has a large, deep summit caldera. Our aim is to evaluate the relative importance of magma intrusion, circumferential and intra-caldera faulting, radial dike intrusions, and sill emplacement to volcano deformation during inter-eruption periods. The SIGNET 2009-11 seismic array on Isabela Island, Galápagos recorded nearly 2000 local earthquakes that provide constraints on magma storage and fault systems accommodating the rapid volcano inflation. Seismicity largely is restricted to the uppermost 2 km of Sierra Negra, excepting the pipe-like zone beneath the eastern side of the caldera; depths of earthquakes on Alcedo and the shallow platform outside the array are poorly constrained. Seismicity is localized around the caldera ring fault system and the sinuous ridge within the caldera. The orientation of reverse fault mechanisms suggest that the intra-caldera ridge formed through compression of the > 2 km-thick lid above the magma chamber, consistent with slip along inward-dipping ring faults. Swarms of seismicity coincide with aligned chains of cinder cones and vents between Sierra Negra and Cerro Azul, between Sierra Negra and Alcedo, between Sierra Negra and Santa Cruz volcanoes, and along the southern flank of Isabela Island, suggesting ongoing dike intrusion and/or degassing. Migrating swarms of seismicity initiating in the caldera may mark small volume radial dike intrusions. Deformation is not restricted to the ring fault

  2. Measuring Crustal Deformation Caused by the Nepal (Gorkha) Earthquake Using ALOS-2 SAR Interferometry

    NASA Astrophysics Data System (ADS)

    Morishita, Y.; Kobayashi, T.; Yarai, H.

    2015-12-01

    A huge earthquake (Mw 7.8, USGS) occurred on 25 April, 2015 in Nepal, followed by the largest aftershock (Mw 7.3, USGS) on 12 May. We applied an InSAR technique to detect crustal deformation caused by the earthquakes using L-band SAR data acquired by ALOS-2. One of the advantages of ALOS-2 over ALOS is ScanSAR interferometry. Beam synchronization, which is a critical factor for ScanSAR interferometry, is always tuned among ALOS-2 observations. While a width of 350 km is covered by a ScanSAR acquisition, the provided data is divided into five swaths with each width of 70 km. Adjacent swaths have an overlapping area with a width of several kilometers, where interferometric phases for two swaths are basically comparable. We processed each swath independently. Preliminary interferograms are contaminated by noises with long wavelength, which makes it difficult to measure the amount of the crustal deformation accurately. We reduce the noises by following steps. First, pseudo reference points with no displacement are put at intervals of 40-100 km outside of the possible deforming area. The differential phase at the points are assumed to be due to the noises. The curved surface of the noises is estimated by smoothly interpolating the differential phase at the points. Note that the pseudo reference points should be located in a high coherence area where the phases can be unwrapped. Furthermore the points in the overlapping area between adjacent swaths allow to preserve consistency of the phases between adjacent swaths. The interferograms show the clear and detailed crustal deformation (published on http://www.gsi.go.jp/cais/topic150429-index-e.html). The maximum of a quasi up-down component of the deformation estimated from the interferograms with different beam directions reaches over 1.4 m uplift at 20 km northeast from Kathmandu and 0.6 m subsidence at a northern part of the deforming area.

  3. Recent Observational Results of Seafloor Crustal Deformation Along the Suruga-Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    The Suruga-Nankai Trough is one of the active plate boundaries in the world. The Philippine Sea plate is subducting beneath the Amurian (Eurasian) plate along the tough, and major subduction earthquakes, Nankai and Tonankai earthquakes, have repeatedly occurred with intervals of about 100-150 years. The 1944 Tonankai and 1946 Nankai earthquakes are the most recent significant earthquakes along the trough. Therefore, the 50-years probabilities of the next major earthquakes are estimated at 80-90% by Headquarters for Earthquake Research Promotion, Japanese Government. It is, therefore, necessary to start monitoring crustal deformation above the source regions of the major earthquakes where in the ocean area. We developed a new system composed of the precise acoustic ranging and kinematic GPS positioning techniques for monitoring of seafloor crustal deformation [Tadokoro et al., 2006, GRL; Ikuta et al., 2008, JGR]. We had installed seven seafloor benchmarks for acoustic ranging at the Suruga-Nankai Trough region between 2002 and 2004. The water depths at the benchmarks are about 800 to 2000 m. We installed a new seafloor benchmark at the eastern margin of the Kumano Basin on June 23, 2008. Three seafloor benchmarks had been aligned perpendicular to the trough axis. In contrast, the new benchmark was installed eastward relative to the pre-installed benchmarks, and we can monitor lateral variations in crustal deformation at the region. We started the repeated measurements at four benchmarkes (two at the Kumano Basin named KMN and KMS, and the other two at the Suruga Bay named SNW and SNE) in 2005. The number of times we have measured are seven, eleven, three and nine times at KMN, KMS, SNW and SNE, respectively. Recent results of the repeated measurements show the following horizontal velocities with relative to the Amurian Plate: 6.4 cm/yr, N86W at KMN; 5.3 cm/yr, N71W at KMS; 3.3 cm/yr, N57W at SNE. The errors of the horizontal velocities are 1-3 cm/yr. Unfortunately

  4. Preliminary crustal deformation model deduced from GPS and earthquakes’ data at Abu-Dabbab area, Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Mohamed, Abdel-Monem S.; Hosny, A.; Abou-Aly, N.; Saleh, M.; Rayan, A.

    2013-06-01

    A local geodetic network consisting of eleven benchmarks has been established to study the recent crustal deformation in the Abu-Dabbab area. Seven campaigns of GPS measurements have been collected started from October 2008 and ended in March 2012. The collected data were processed using Bernese version 5.0, and the result values were adjusted to get the more accurate positions of the GPS stations. The magnitudes of horizontal displacements are variable from one epoch to another and in the range of 1-3 (±0.2) mm/yr. Due to the differences in rates of the horizontal displacement; the area is divided into two main blocks. The first one, moves to the east direction of about 3 mm/yr, while the second block, moves to the SW direction of about 6 mm/yr. According to the strain fields that were calculated for the different epochs of measurement, the main force is compression force and is taken the NW-SE to NWW-SEE direction. This force could be because of local and regional tectonic processes affecting on the study area. The maximum values of compression stress are found in the southern central and western part of study area. Estimated accumulation of this strain energy may be considered as an indicator of the possibility of earthquake occurrence. From the seismic tomography study, the 3D Vp and Vp/Vs crustal models indicate high Vp/Vs values forms an elongated anomaly, in the central part of the study area, that extends from a depth of 12 km to about 1-2 km of depth is obtained. By using this crustal model in relocations all seismicity informed that most of the seismicity strongly tend to occur in a cluster manner exactly above the southern part of the study area. Based on the conducted source mechanism study, it is noticed that shallow earthquakes are associated by a high CLVD ratio (up to 40%). Furthermore, initiation of a high level seismic activity, without a large seismic main shock is observed in the Abu-Dabbab area. The distribution of micro-earthquakes tends to

  5. Bulk crustal properties in NE Tibet and its implication for deformation model

    NASA Astrophysics Data System (ADS)

    Tian, Xiaobo

    2014-05-01

    The crust beneath the northeastern (NE) Tibetan Plateau records far field effects of collision and convergence occurring between the Indian and Eurasian plates. A better structural understanding of the crust beneath NE Tibet can improve our understanding of Cenozoic deformation resulting from the India-Eurasia collision. Taking advantage of the relatively dense coverage in most areas in NE Tibet except for the Qaidam basin by regional seismic networks of Gansu and Qinghai Provinces, we isolate receiver functions from the teleseismic P wave data recorded from 2007 to 2009 and resolve the spatial distribution of crustal thickness and Vp/Vs ratio beneath NE Tibet from H-K scanning. Our results can be summarized as: (1) NE Tibet is characterized by ~ 60-km-thick crust beneath the Nan Shan, Qilian Shan thrust belts and the Anyemaqen Shan, and 45-50 km-thick crust beneath the Tarim basin, the Alashan depression and the Ordos basin; the crust thins gradually from west to east in addition to the previously observed pronounced thinning from south to north; (2) the crust of NE Tibet exhibits a relatively lower Vp/Vs ratio of 1.72 than the north China block and a decrease in average crustal Vp/Vs ratio with increasing crustal thickness; and (3) the crustal thicknesses are less than the values predicted by the simple isostatic model of throughout Tibetan plateau in where the elevation is larger than 3.0 km. Our observations can be explained by the hypothesis that deformation occurring in NE Tibet is predominated by upper-crustal thickening or lower-crust extrusion.

  6. Block rotations, fault domains and crustal deformation in the western US

    NASA Technical Reports Server (NTRS)

    Nur, Amos

    1990-01-01

    The aim of the project was to develop a 3D model of crustal deformation by distributed fault sets and to test the model results in the field. In the first part of the project, Nur's 2D model (1986) was generalized to 3D. In Nur's model the frictional strength of rocks and faults of a domain provides a tight constraint on the amount of rotation that a fault set can undergo during block rotation. Domains of fault sets are commonly found in regions where the deformation is distributed across a region. The interaction of each fault set causes the fault bounded blocks to rotate. The work that has been done towards quantifying the rotation of fault sets in a 3D stress field is briefly summarized. In the second part of the project, field studies were carried out in Israel, Nevada and China. These studies combined both paleomagnetic and structural information necessary to test the block rotation model results. In accordance with the model, field studies demonstrate that faults and attending fault bounded blocks slip and rotate away from the direction of maximum compression when deformation is distributed across fault sets. Slip and rotation of fault sets may continue as long as the earth's crustal strength is not exceeded. More optimally oriented faults must form, for subsequent deformation to occur. Eventually the block rotation mechanism may create a complex pattern of intersecting generations of faults.

  7. Interseismic Crustal Deformation in and around the Atotsugawa Fault System, Central Japan, Detected by InSAR and GNSS

    NASA Astrophysics Data System (ADS)

    Takada, Y.; Sagiya, T.; Nishimura, T.

    2015-12-01

    Interseismic crustal deformation of active faults provides crucial information to understand the stress accumulation process on the fault planes. Recently, the interseismic surface movements are detected with very high spatial resolution using combination of InSAR and GNSS survey. Most of the successful reports, however, addressed the fault creep in less vegetated area which enables C-band SAR interferometry. In this study, we report the interseismic crustal deformation in and around the Atotsugawa fault system, a strike-slip active fault in central Japan. This area is covered with dense vegetation in summer and with heavy snow in winter. We created a series of InSAR images acquired by ALOS/PALSAR and applied SBAS based time-series analysis (Berardino et al., 2002) to extract small deformation. Next, we corrected the long wave-length phase trend by GNSS network maintained by Japanese University Group (e.g, Ohzono et al., 2011) and GSI, Japan. The mean velocity field thus obtained shows a strain concentration zone along the Ushikubi fault, a major strand of the Atotsugawa fault system. The Ushikubi fault is seismically less active than the Atotsugawa fault, but it shows good correlation with a zone of large spatial gradient of Bouguer gravity anomaly. We further discuss on the deformation style at the junction between the Atotsugawa fault and the Hida mountain range (Tateyama volcano). Acknowledgement: The PALSAR level 1.0 data were provided by JAXA via the PALSAR Interferometry Consortium to Study our Evolving Land surface (PIXEL) based on a cooperative research contract between JAXA and the ERI, the University of Tokyo. The PALSAR product is owned by JAXA and METI.

  8. The 10 April 2014 Earthquake in Central Nicaragua: Evidence of Complex Crustal Deformation in Central America

    NASA Astrophysics Data System (ADS)

    Suarez, G.; Muñoz, A.; Talavera, E.; Tenorio, V.; Farraz, I.; Novelo-Casanova, D. A.; Sánchez, A.

    2014-12-01

    On 10 April 2014 a magnitude Mw 6.1 struck central Nicaragua. The main event and the aftershocks were clearly recorded by the Nicaraguan seismic network. These crustal earthquakes were strongly felt but caused relatively little damage to the city of Managua and to the surrounding cities and towns. This is in sharp contrast to the destructive effects of the 1972 earthquake in the capital city of Managua. The differences in damage stem from the fact that in 1972, the earthquake occurred on a fault beneath the city; in contrast, the 2014 event lies offshore, under Lake Managua. The distribution of aftershocks shows two clusters of seismic activity. In the northwestern part of Lake Managua, an alignment of aftershocks suggests a southeast trending fault. The reported source mechanism suggests right-lateral strike slip motion on a plane with the same azimuth as the aftershock sequence. A second cluster of seismic activity occurred simultaneously, but spatially separated, beneath Apoyeque volcano. There is no clear alignment of the epicenters in this cluster. Seismic scaling relations between magnitude and the fault length predict a length of approximately 10 km for an earthquake of this magnitude. This is in agreement with the extent of the fault defined by the aftershock sequence. The northeast - southwest trending Tiscapa and Ciudad Jardín faults that broke during the 1972 and 1931 Managua earthquakes are orthogonal to the fault where the 10 April earthquake occurred. This set of conjugate faults confirms that Central Nicaragua is being deformed in a complex tectonic style of deformation. The forearc sliver between the trench and the volcanic arc moves to the northwest relative to the Caribbean plate. This deformation, however, does not take place on a single set of faults. The motion is apparently accommodated by a system of conjugate faults: right lateral, strike-slip faults oriented parallel to the volcanic arc and another set of faults trending northeast

  9. Changes in crustal seismic deformation rates associated with the 1964 Great Alaska earthquake

    USGS Publications Warehouse

    Doser, D.I.; Ratchkovski, N.A.; Haeussler, P.J.; Saltus, R.

    2004-01-01

    We calculated seismic moment rates from crustal earthquake information for the upper Cook Inlet region, including Anchorage, Alaska, for the 30 yr prior to and 36 yr following the 1964 Great Alaska earthquake. Our results suggest over a factor of 1000 decrease in seismic moment rate (in units of dyne centimeters per year) following the 1964 mainshock. We used geologic information on structures within the Cook Inlet basin to estimate a regional geologic moment rate, assuming the structures extend to 30 km depth and have near-vertical dips. The geologic moment rates could underestimate the true rates by up to 70% since it is difficult determine the amount of horizontal offset that has occurred along many structures within the basin. Nevertheless, the geologic moment rate is only 3-7 times lower than the pre-1964 seismic moment rate, suggesting the 1964 mainshock has significantly slowed regional crustal deformation. If we compare the geologic moment rate to the post-1964 seismic moment rate, the moment rate deficit over the past 36 yr is equivalent to a moment magnitude 6.6-7.0 earthquake. These observed differences in moment rates highlight the difficulty in using seismicity in the decades following a large megathrust earthquake to adequately characterize long-term crustal deformation.

  10. Analysis of crustal deformation and strain characteristics in the Tianshan Mountains with least-squares collocation

    NASA Astrophysics Data System (ADS)

    Li, S. P.; Chen, G.; Li, J. W.

    2015-11-01

    By fitting the observed velocity field of the Tianshan Mountains from 1992 to 2006 with least-squares collocation, we established a velocity field model in this region. The velocity field model reflects the crustal deformation characteristics of the Tianshan reasonably well. From the Tarim Basin to the Junggar Basin and Kazakh platform, the crustal deformation decreases gradually. Divided at 82° E, the convergence rates in the west are obviously higher than those in the east. We also calculated the parameter values for crustal strain in the Tianshan Mountains. The results for maximum shear strain exhibited a concentration of significantly high values at Wuqia and its western regions, and the values reached a maxima of 4.4×10-8 a-1. According to isogram distributions for the surface expansion rate, we found evidence that the Tianshan Mountains have been suffering from strong lateral extrusion by the basin on both sides. Combining this analysis with existing results for focal mechanism solutions from 1976 to 2014, we conclude that it should be easy for a concentration of earthquake events to occur in regions where maximum shear strains accumulate or mutate. For the Tianshan Mountains, the possibility of strong earthquakes in Wuqia-Jiashi and Lake Issyk-Kul will persist over the long term.

  11. Resistant river basins as recorder of distributed crustal deformation: examples from New Zealand and Lebanon

    NASA Astrophysics Data System (ADS)

    Castelltort, S.; Goren, L.; Willett, S.; Champagnac, J.; Herman, F.

    2011-12-01

    Rivers are useful markers of crustal deformation because they deform together with the rocks over which they flow. For instance, at the scale of individual faults, offset rivers and alluvial fans have been used to reconstruct past slip rates(1), while the basins of major rivers have been utilized to estimate pervasive crustal strain at the continental scale(2). However, river basins have also been claimed to reorganize into similar equilibrium forms(3) independently of the tectonic regime. According to this latter view, river basins cannot serve as reliable markers of deformation since their boundaries adjust dynamically during deformation by processes of capture and divide migration. Here we show that both views are correct under different conditions, as different basins in the same tectonic field may or may not be persistent and record the history of deformation, depending on the relation between their geomorphic position and the nature and directionality of the strain field. To demonstrate this new understanding we study the planform of drainage basins along two major transpressive plate boundaries that partly show patterns that are spatially consistent with the assumed tectonic regime: the Alpine Fault in the South Island of New Zealand which marks the boundary between the Pacific and the Australian plates, and the Dead Sea Fault in Lebanon which strands the Africa-Arabia plate boundary. First we use a combination specific river basin modeling and planview morphometric analysis to unravel deformation from reorganization and identify the basins that may serve as reliable deformation markers. Then we use these reliable markers to constrain the slip rate over these two plate boundaries. Our analysis results show that, both in New Zealand and in Lebanon, a significant proportion of up to 55% of the plate motion over geological time scales is absorbed by distributed deformation away from the plate boundary. (1)--Allen, C. R. Transcurrent Faults in Continental Areas

  12. Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanisms

    NASA Astrophysics Data System (ADS)

    Galgana, Gerald; Hamburger, Michael; McCaffrey, Robert; Corpuz, Ernesto; Chen, Qizhi

    2007-03-01

    We utilize regional GPS velocities from Luzon, Philippines, with focal mechanism data from the Harvard Centroid Moment Tensor (CMT) Catalog, to constrain tectonic deformation in the complex plate boundary zone between the Philippine Sea Plate and Eurasia (the Sundaland block). Processed satellite imagery and digital elevation models are used with existing gravity anomaly, seismicity, and geologic maps to define a suite of six elastic blocks. Geodetic and focal mechanism data are inverted simultaneously to estimate plate rotations and fault-locking parameters for each of the tectonic blocks and faults comprising Luzon. Major tectonic structures that were found to absorb the plate convergence include the Manila Trench (20-100 mm yr - 1 ) and East Luzon Trough (˜ 9-15 mm yr - 1 )/Philippine Trench (˜ 29-34 mm yr - 1 ), which accommodate eastward and westward subduction beneath Luzon, respectively; the left-lateral strike-slip Philippine Fault (˜ 20-40 mm yr - 1 ), and its northward extensions, the Northern Cordillera Fault (˜ 17-37 mm yr - 1 transtension), and the Digdig Fault (˜ 17-27 mm yr - 1 transpression). The Macolod Corridor, a zone of active volcanism, crustal thinning, extension, and extensive normal and strike-slip faulting in southwestern Luzon, is associated with left-lateral, transtensional slip of ˜ 5-10 mm yr - 1 . The Marikina Fault, which separates the Central Luzon block from the Southwestern Luzon block, reveals ˜ 10-12 mm yr - 1 of left-lateral transpression. Our analysis suggests that much of the Philippine Fault and associated splays are locked to partly coupled, while the Manila and Philippine trenches appear to be poorly coupled. Luzon is best characterized as a tectonically active plate boundary zone, comprising six mobile elastic tectonic blocks between two active subduction zones. The Philippine Fault and associated intra-arc faults accommodate much of the trench-parallel component of relative plate motion.

  13. Evidence of Crustal Faulting and Deformation in the Muckleshoot Basin, Washington

    NASA Astrophysics Data System (ADS)

    Cox, J.; Wolf, L. W.

    2015-12-01

    The Muckleshoot basin of western Washington, sandwiched between the Seattle Uplift on the west and the Cascade Range on the east, is deforming under north-south shortening and clockwise rotation of the north Cascadia forearc. Accommodating the regional strain are crustal faults in the Puget Lowland that cluster around three azimuths: east-west, northwest-southeast, and north-northwest-south-southeast. Evidence for all three groups appears on the periphery of the Muckleshoot basin. In this study, we add gravity measurements to an existing database to better define the geometry of the Muckleshoot basin and its relation to previously mapped faults appearing on the basin margins. A northwest-trending gravity high bisects the basin into two sub-basins, a larger one to the south and a smaller one to the north. We suggest that the gravity high is associated with a deep basement structure and its orientation is consistent with northward-directed crustal shortening. Regional-residual separation methods and derivative maps show pronounced magnetic lineations that extend faults expressed along the basin margins to east-west trending faults that cross the Puget Sound. Three intersecting cross-sectional models produced for this study are consistent with the following hypotheses: (1) the northwest-trending White River and Green River faults mapped on the eastern basin margin appear as south-verging, steeply dipping reverse faults in the central basin; (2) the north-northwest trending Franklin fault, mapped previously as a strike-slip fault, projects into the basin and shows little vertical offset in the single profile it crosses, and (3) the northwest trajectory of both the White River and Green River faults appears to curve southward as the faults traverse the Muckleshoot basin, following east-west oriented gravity and magnetic anomalies that cross the Puget Sound. Results from the study suggest that the faults and folds in Muckleshoot basin are actively interacting with other

  14. Post-Seismic Crustal Deformation Following The 1999 Izmit Earthquake, Western Part Of North Anatolian Fault Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Gurkan, O.; Ozener, H.

    2004-12-01

    The North Anatolian Fault is an about 1500 km long, extending from the Karliova to the North Aegean. Turkey is a natural laboratory with high tectonic activity caused by the relative motion of the Eurasian, Arabian and Anatolian plates. Western part of Turkey and its vicinity is a seismically active 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 fault zone, seismically low active part, (2) Sapanca Network, installed on the Izmit-Sapanca fault zone, seismically active part, (3) Akyazi Network, installed on their intersection area, the Mudurnu fault 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

  15. Fault locking, block rotation and crustal deformation in the Pacific Northwest

    USGS Publications Warehouse

    McCaffrey, R.; Qamar, A.I.; King, R.W.; Wells, R.; Khazaradze, G.; Williams, C.A.; Stevens, C.W.; Vollick, J.J.; Zwick, P.C.

    2007-01-01

    We interpret Global Positioning System (GPS) measurements in the northwestern United States and adjacent parts of western Canada to describe relative motions of crustal blocks, locking on faults and permanent deformation associated with convergence between the Juan de Fuca and North American plates. To estimate angular velocities of the oceanic Juan de Fuca and Explorer plates and several continental crustal blocks, we invert the GPS velocities together with seafloor spreading rates, earthquake slip vector azimuths and fault slip azimuths and rates. We also determine the degree to which faults are either creeping aseismically or, alternatively, locked on the block-bounding faults. The Cascadia subduction thrust is locked mainly offshore, except in central Oregon, where locking extends inland. Most of Oregon and southwest Washington rotate clockwise relative to North America at rates of 0.4-1.0?? Myr-1. No shear or extension along the Cascades volcanic arc has occurred at the mm/yr level during the past decade, suggesting that the shear deformation extending northward from the Walker Lane and eastern California shear zone south of Oregon is largely accommodated by block rotation in Oregon. The general agreement of vertical axis rotation rates derived from GPS velocities with those estimated from palaeomagnetic declination anomalies suggests that the rotations have been relatively steady for 10-15 Ma. Additional permanent dextral shear is indicated within the Oregon Coast Range near the coast. Block rotations in the Pacific Northwest do not result in net westward flux of crustal material - the crust is simply spinning and not escaping. On Vancouver Island, where the convergence obliquity is less than in Oregon and Washington, the contractional strain at the coast is more aligned with Juan de Fuca-North America motion. GPS velocities are fit significantly better when Vancouver Island and the southern Coast Mountains move relative to North America in a block

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

    PubMed

    Pan, Yuanjin; Shen, Wen-Bin; Hwang, Cheinway; Liao, Chaoming; Zhang, Tengxu; Zhang, Guoqing

    2016-01-01

    Surface vertical deformation includes the Earth's elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs), in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE) mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA) contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet. PMID:27490550

  17. Crustal deformation along the Longmen-Shan fault zone and its implications for seismogenesis

    NASA Astrophysics Data System (ADS)

    Wang, Zhi; Huang, Runqiu; Pei, Shunping

    2014-01-01

    The Longmen-Shan fault zone, at the eastern margin of the Tibetan Plateau, is one of the most extensively studied areas in the world, yet the deformation model and earthquake-generating mechanism remain subjects of vigorous debate. This paper presents a new three-dimensional (3-D) velocity model determined using a large volume of seismic data and two-dimensional (2-D) magnetotelluric (MT) profiles from previous studies, to investigate the mechanisms of crustal deformation and earthquake generation along the reverse-thrust and strike-slip fault zone. It has been observed that low-velocity, and low-resistivity anomalies related to the Sichuan foreland basin, is in sharp contrast to high-velocity and high-resistivity anomalies in the Songpan-Ganze block in the upper crust. The tomographic model presented here reveals two crustal bodies with low-velocity and high-conductivity anomalies underneath the Longmen-Shan fault zone, separated into three contrasting segments by the two crustal bodies. The two low-velocity and low-resistivity bodies have been interpreted as being associated with extrusion of either fluids or products of partial melting from the lower crust and/or the upper mantle. This suggests strong variations in the rheological strength of the rock along the fault zone. This finding implies that coupling between these presumably fluid-bearing bodies and earthquake generation could be extremely complex and that there is dramatic variation from the southwestern area to the northeastern segment along the fault belt. It is suggested here that this complex and variable deformation system along the fault zone played a principal role in controlling seismic generation and rupturing during the 2008 Wenchuan earthquake (Ms 8.0) and that it will do so again during possible future earthquakes in the region.

  18. Crustal stacking and expulsion tectonics during continental subduction: P-T deformation constraints from Oman

    NASA Astrophysics Data System (ADS)

    Agard, Philippe; Searle, Michael P.; Alsop, G. Ian; Dubacq, B.

    2010-10-01

    The northeastern continental margin of Oman in the Saih Hatat region is characterized by high-pressure (HP) chloritoid- or carpholite-bearing metasediments and highly deformed mafic eclogites and blueschists in a series of tectonic units bounded by high-strain ductile shear zones. New data on the upper cover units of this HP nappe stack indicate that all of them underwent similar P conditions to the underlying Hulw structural unit (with a cooler exhumation pressure-temperature path). Early SSW directed crustal thickening during ophiolite emplacement created recumbent folds and strong schistose fabrics in these Permian-Mesozoic shelf carbonates and was followed by later NNE dipping normal sense shear zones and normal faults. The Mayh unit shows high strain in a 15-25 km long sheath fold that likely formed at carpholite grade pressures of 8-10 kbar. We show that there are no significant P differences across the Hulw shear zone (upper plate-lower plate discontinuity) or between the overlying Mayh, Yenkit-Yiti, and Ruwi units. Postpeak metamorphic exhumation of the HP rocks was therefore accomplished by bottom-to-SSW (rather than top-to-NNE) active footwall extrusion beneath a fixed, static, passive hanging wall. Footwall uplift beneath these passive roof faults resulted in progressive expulsion of the HP rocks from depths of ˜80-90 km (eclogites) and mainly 30-35 km (blueschists and chloritoid-/carpholite-bearing units) during the Campanian-Early Maastrichtian. Oman thus provides a detailed record of how continental material (thick platform shelf carbonates) progressively jammed a subduction zone and emphasizes the contrasting behavior between cover units and their underlying basement.

  19. Late Cenozoic crustal deformation of the north-central Basin and Range

    SciTech Connect

    Eyal, Y. . Dept. of Geology); Ron, H. )

    1993-04-01

    Late Cenozoic deformation of Basin and Range in north-central Nevada is examined by small fault analysis. Consistency between fault types, fault trends and sense of displacement was found for this area in which normal faults strike N-S, and right-lateral and left-lateral faults strike NNW and NNE respectively. The existence of strike-slip faulting, mainly right-lateral, is consistent with horizontal counter clockwise rotation suggested by paleomagnetic declination data. The results of this analysis indicate that crustal deformation of this area did not occur by only simple E-W uniaxial extension but also by N-S compression and shortening, and that the contribution of strike slip faulting to the extension of this area is substantial almost similar to that of normal faulting.

  20. Crustal deformation measurements in central Japan determined by a Global Positioning System fixed-point network

    NASA Technical Reports Server (NTRS)

    Shimada, Seiichi; Bock, Yehuda

    1992-01-01

    Results are presented from temporally dense measurements of crustal deformation associated with the convergence of the Eurasian (EUR), Pacific, North American, and Philippine Sea (PHS) plates, carried out in April 1988 by a 10-station GPS fixed-point network established in central Japan. Using regional orbit relaxation methods, the analysis of the first 17-month data revealed significant horizontal deformation across the Suruga trough. Namely, it was found that a site in the northern tip of PHS plate moved nearly westward with a velocity of 28 +/-5 mm per year, and a site at the southeastern tip of EUR plate moved south-southwestward with a velocity of 18 +/-5 mm per year. A significant vertical uplift with a velocity of 20 mm/yr was detected at a site inland of the Tokai district located in the Akaishi uplift zone and at a site on the Hatsushima Island in Sagami Bay.

  1. Relationship of the crustal structure and its deformation from arc to back-arc basin in the eastern Japan Sea deduced from the seismic survey

    NASA Astrophysics Data System (ADS)

    Sato, Takeshi; No, Tetsuo; Miura, Seiichi; Kodaira, Shuichi; Sato, Hiroshi

    2015-04-01

    The Japan Sea is a back-arc basin in the northwestern Pacific. Based on geophysical, geological, and petrological results, it is suggested that the opening of the Japan Sea was initiated by crustal rifting and the separation of Japan Island arcs from the Asian continent in the Early Oligocene, followed by the ocean floor spreading in the Late Oligocene (e.g., Tamaki et al., 1992). After 3.5 Ma, the crustal shortening by a strong compression occurred in the eastern margin (e.g., Sato, 1994). In the eastern margin, because of the extension associated with the opening of the Japan Sea and this shortening, the deformation such as active faults and folds formed have developed and large earthquakes with magnitudes-7 class repeatedly occurred (e.g., Okamura et al., 2007). The Japan Sea has a unique setting in terms of the connection between the back-arc basin opening and the crustal deformation. However, we have little information concerning with a crustal structure formed by the back-arc opening in the margin and the deformation. To obtain the information, we have been carrying out active-source seismic surveys using ocean bottom seismographs (OBSs) and multi-channel streamer system (MCS) to cover the eastern margin of the Japan Sea. The obtained results show a difference in crustal structures between the northern and the southern parts of the eastern Japan Sea. In the northern part from the arc to the back-arc basin, the crust is divided into three types; the rifted island arc crust, the thicker oceanic crust and the oceanic crust, based on the comparison of the P-wave velocity distribution and the crustal thickness of a typical oceanic crust (White et al., 1992) and of the northeastern Japan Island arc crust (Iwasaki et al., 2001). On the other hand, the southern part from the arc to the back-arc basin has two crustal types, which are the rifted island arc crust and the thicker oceanic crust. In the northern part, the deformation is distributed in a structural boundary

  2. Involving Undergraduates and K-14 Teachers in Research: Measuring and Modeling Crustal Deformation in Southern California

    NASA Astrophysics Data System (ADS)

    Fryxell, J. E.; Hams, J.; Barley, M.; Hobart, K.; Ramirez, J.; McGill, S.; Lyzenga, G.

    2003-12-01

    With funding from the NSF OEDG, we initiated a project to: (1) involve undergraduate students and K-14 teachers to research in geology, and (2) use GPS to monitor deformation across the plate boundary zone in southern California, and to model partitioning on specific faults that account for that deformation in the upper crust. Starting in July 2002, we collected campaign-style GPS data twice a year from 13 sites along a line across the San Andreas and San Jacinto faults near CSUSB. Our field crews have included 43 students and teachers in our three campaigns to date. These include 30 undergraduate and 3 graduate students, 1 middle school and 8 high school teachers, and 1 community college professor. We are also modeling site velocities from the SCEC Crustal Deformation Velocity Map. Our preliminary results are presented in session ED14 at this meeting. Our most recent campaign (June 2003) was expanded to include workshops. As before, the field crews got one day of hands-on training in setup and operation of the geodetic-quality receivers and antennae. In addition, we held a one-day workshop before the campaign on the active tectonics of southern California, elastic rebound theory, and the scientific goals of the project. After the campaign another one-day workshop was held to plot GPS position results from previous campaigns for a station crew members had occupied during the campaign, and to estimate a velocity for that station. Participants also tried modeling SCEC site velocity data from a transect across the San Andreas, San Jacinto and Elsinore faults. Four of the co-authors on this abstract were campaign participants, and have continued to work with faculty on processing our data and on modeling SCEC data. Students (geology and other majors) felt that participation in the campaign stimulated their interest in geology, and that their participation was a worthwhile experience. Most students are interested in participating in upcoming campaigns, and would

  3. Crustal deformation at the Nankai Trough estimated from seafloor geodetic observations

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Tadokoro, K.; Ikuta, R.; Okuda, T.; Nagai, S.; Kuno, M.

    2012-12-01

    The Philippine Sea plate subducts beneath the southwest Japan along the Nankai Trough with a rate of about 4-6 cm/yr, where megathrust earthquakes have repeatedly occurred every 100-150 years. Because the region expected to be the hypocentral area of next Nankai and Tonankai earthquakes is almost located in offshore area, it is important to know the spatio-temporal variation of crustal deformation accompanied with plate interaction in high precision. For this issue, we have conducted seafloor geodetic observation at the Nankai Trough using a GPS/Acoustic technique since 2004. In this system, we estimate the position of a surveying vessel by Kinematic GPS analysis and measure the distance between the vessel and the benchmark on the seafloor by Acoustic measurements. Next we determine the location of the benchmark. For the repeatability of this observation, the location of benchmark is determined within a precision of 2-3 cm at horizontal components. Several seafloor benchmarks are located at the Nankai Trough, which are individually operated by Japan Coast Guard, Tohoku University, and Nagoya University. In the Kumano Basin, we have three seafloor benchmarks located about 60-80 km away from the deformation front of the Nankai Trough. The observations from 2005 to 2011 have illustrated that those benchmarks are moving at rates of about 4 cm/yr toward west-northwest with velocity uncertainties of about 2 cm/yr relative to the Amurian plate. In this study, to explain the crustal deformation derived from seafloor geodetic observations especially at the shallower part of the Nankai Trough, we conduct numerical simulations using finite element method and then discuss the interplate coupling at the Nankai Trough.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  6. Extraction of Crustal Deformation from Seafloor Hydraulic Pressure Gauges: A trial collaboration study

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    , we propose a new interpretation of seismic plate coupling around the Tonankai region along the Nankai Trough, and discuss how to detect it by using the DONET data effectively. In the future, we have to extract the crustal deformation component by separating other components such as instrumental drift and oceanic changes as an integral study collaborated by seismology, geodesy, physical oceanography, and mechanical engineering.

  7. A method for mapping crustal deformation and anisotropy with receiver functions and first results from USArray

    NASA Astrophysics Data System (ADS)

    Schulte-Pelkum, Vera; Mahan, Kevin H.

    2014-09-01

    orientation of dipping and anisotropic features without waveform modeling. Combining radial and tangential components with a shift in backazimuth fills holes that may otherwise exist in azimuthal event coverage. We validate the method against active source results from the Wind River Thrust fault in Wyoming and against a waveform modeling study targeting deep crustal anisotropy in southern California. We then present initial results across the continental U.S. using Transportable Array data. First-order features are high amplitudes along the West Coast plate boundary and elevated amplitudes in parts of the intermountain West, a transition to low amplitudes in the central U.S. at the Rocky Mountain/Laramide front, and high amplitudes along the Appalachian-Ouachita belt. Foliation strike roughly aligns with the strike of mountains, but high signal amplitudes and matching strikes outline geological features with little current expression in surface topography, such as the Southern Oklahoma aulacogen, high-grade rocks in the Appalachian Piedmont, and the Midcontinent Rift. We conclude that lithospheric deformation can be targeted with receiver functions without extensive waveform modeling, allowing first cuts through large data sets such as that from USArray.

  8. Is it Possible to Detect Crustal Deformation of the Seafloor Using Interferometric Sonar?

    NASA Astrophysics Data System (ADS)

    Thomsen, D. R.; Sandwell, D. T.

    2002-12-01

    The advent of interferometric synthetic aperture radar (InSAR) has enabled the examination of crustal deformation due to both long and short timescale processes at incredibly high resolutions. While GPS geodesy can measure centimeter-scale crustal movement at discrete locations InSAR provides much better spatial coverage. Spectacular examples include interferograms of the Hector Mine and Landers earthquakes in central California. Similar high-resolution techniques are not available to monitor volcanic and tectonic deformation on the seafloor. To achieve interferometric synthetic aperture sonar (InSAS) requires two developments: 1) formation of a synthetic aperture image (SAS) and 2) differencing the phase of reference and repeat images. First, we examine the feasibility of adapting synthetic aperture radar theory to a multibeam sonar system, specifically the Simrad EM120 system on the R/V Roger Revelle. The range resolution of the EM120 system is 16m - a value comparable to that using SAR spacecraft. Although the standard azimuth resolution is 150 m, it is theoretically possible to achieve 3.5 m resolution using synthetic aperture techniques. The requirements are the ship speed must be less than 2.5 knots, the ship position must be known to a fraction of the sonar wavelength (12 cm), and the phase distortion due to sound velocity variations must be corrected. Recent DARPA-funded research at Dynamics Technology in Torrance, CA has achieved the theoretical limits of the SAS by correcting secondary phase errors with a point reflector. A more challenging second possibility is to create a sonar interferogram between repeated ship surveys spanning a period of crustal deformation. The main theoretical requirement of InSAS is that the spacing between the ship tracks of the reference and repeat acquisitions must be less than the critical baseline of 10 m. In reasonable sea state, this is possible with real-time GPS navigation. We hope to collect raw hydrophone data on R

  9. InSAR Observations and Finite Element Modeling of Crustal Deformation Around a Surging Glacier, Iceland

    NASA Astrophysics Data System (ADS)

    Spaans, K.; Auriac, A.; Sigmundsson, F.; Hooper, A. J.; Bjornsson, H.; Pálsson, F.; Pinel, V.; Feigl, K. L.

    2014-12-01

    Icelandic ice caps, covering ~11% of the country, are known to be surging glaciers. Such process implies an important local crustal subsidence due to the large ice mass being transported to the ice edge during the surge in a few months only. In 1993-1995, a glacial surge occurred at four neighboring outlet glaciers in the southwestern part of Vatnajökull ice cap, the largest ice cap in Iceland. We estimated that ~16±1 km3 of ice have been moved during this event while the fronts of some of the outlet glaciers advanced by ~1 km.Surface deformation associated with this surge has been surveyed using Interferometric Synthetic Aperture Radar (InSAR) acquisitions from 1992-2002, providing high resolution ground observations of the study area. The data show about 75 mm subsidence at the ice edge of the outlet glaciers following the transport of the large volume of ice during the surge (Fig. 1). The long time span covered by the InSAR images enabled us to remove ~12 mm/yr of uplift occurring in this area due to glacial isostatic adjustment from the retreat of Vatnajökull ice cap since the end of the Little Ice Age in Iceland. We then used finite element modeling to investigate the elastic Earth response to the surge, as well as confirm that no significant viscoelastic deformation occurred as a consequence of the surge. A statistical approach based on Bayes' rule was used to compare the models to the observations and obtain an estimate of the Young's modulus (E) and Poisson's ratio (v) in Iceland. The best-fitting models are those using a one-kilometer thick top layer with v=0.17 and E between 12.9-15.3 GPa underlain by a layer with v=0.25 and E from 67.3 to 81.9 GPa. Results demonstrate that InSAR data and finite element models can be used successfully to reproduce crustal deformation induced by ice mass variations at Icelandic ice caps.Fig. 1: Interferograms spanning 1993 July 31 to 1995 June 19, showing the surge at Tungnaárjökull (Tu.), Skaftárjökull (Sk.) and S

  10. The InSAR Italy portal for open access to crustal deformation data

    NASA Astrophysics Data System (ADS)

    Salvi, Stefano; Tolomei, Cristiano; Pezzo, Giuseppe; Lanari, Riccardo; Pepe, Antonio; Marchetti, Pier Giorgio; Della Vecchia, Andrea; Mantovani, Simone

    2014-05-01

    InSAR Italy is a web portal devised to provide open access services to crustal deformation data measured using multitemporal SAR Interferometry techniques over the Italian territory. It is an evolution of the VELISAR initiative, promoted in 2006 by the Istituto Nazionale di Geofisica e Vulcanologia, and originally participated by IREA-CNR and TRE srl. InSAR Italy was developed tailoring the Multi-sensor Evolution Analysis (MEA) environment, an Earth Observation and geospatial data analysis tool empowered with OGC standard interfaces. The web interface allows an easy browsing of the ground deformation maps obtained for each satellite image dataset, leading to a clear picture and improved analysis of the displacement time series over single pixels or large areas. Web Coverage Service (WCS) and Web Coverage Processing Service (WCPS) are used to access and process the maps, respectively. The crustal deformation data are provided by INGV and IREA-CNR as products of publicly-funded research projects, and are disseminated in compliance with the national legislation on the Open Data Access; metadata associated to the products are published according to the INSPIRE specifications. The information provided through InSAR Italy is mainly based on InSAR data maintained in the ESA archives, in particular from the ERS satellites for the 1992-2000 period, and ENVISAT for the period 2003-2010, however, ground velocity maps obtained from COSMO-SkyMed data will also be released in the near future. The InSAR Italy deformation maps consist of time series of ground displacement at resolution varying between 5 and 80 m, and the relative mean velocity values. The data sets can be queried and mean velocities can be recalculated over user-defined time periods, to account for possible non-linear displacement trends. The MEA spatiotemporal data analysis capability allows to investigate deformation phenomena occurring at very different spatial scales, from single buildings to entire regions

  11. Crustal deformation, the earthquake cycle, and models of viscoelastic flow in the asthenosphere

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.; Kramer, M. J.

    1983-01-01

    The crustal deformation patterns associated with the earthquake cycle can depend strongly on the rheological properties of subcrustal material. Substantial deviations from the simple patterns for a uniformly elastic earth are expected when viscoelastic flow of subcrustal material is considered. The detailed description of the deformation pattern and in particular the surface displacements, displacement rates, strains, and strain rates depend on the structure and geometry of the material near the seismogenic zone. The origin of some of these differences are resolved by analyzing several different linear viscoelastic models with a common finite element computational technique. The models involve strike-slip faulting and include a thin channel asthenosphere model, a model with a varying thickness lithosphere, and a model with a viscoelastic inclusion below the brittle slip plane. The calculations reveal that the surface deformation pattern is most sensitive to the rheology of the material that lies below the slip plane in a volume whose extent is a few times the fault depth. If this material is viscoelastic, the surface deformation pattern resembles that of an elastic layer lying over a viscoelastic half-space. When the thickness or breath of the viscoelastic material is less than a few times the fault depth, then the surface deformation pattern is altered and geodetic measurements are potentially useful for studying the details of subsurface geometry and structure. Distinguishing among the various models is best accomplished by making geodetic measurements not only near the fault but out to distances equal to several times the fault depth. This is where the model differences are greatest; these differences will be most readily detected shortly after an earthquake when viscoelastic effects are most pronounced.

  12. GPS-based crustal deformations in Azerbaijan and their influence on seismicity and mud volcanism

    NASA Astrophysics Data System (ADS)

    Kadirov, F. A.; Guliyev, I. S.; Feyzullayev, A. A.; Safarov, R. T.; Mammadov, S. K.; Babayev, G. R.; Rashidov, T. M.

    2014-11-01

    Using Shen's method (Shen et al., 1996), deformations of the Earth's crust in Azerbaijan were studied based on GPS measurements. For estimating the rate of deformation, we used the field of velocity vectors for Azerbaijan, Iran, Georgia, and Armenia that were derived from GPS measurements during 1998-2012. It is established that compression is observable along the Greater Caucasus, in Gobustan, the Kura depression, Nakhchyvan Autonomous Republic, and adjacent areas of Iran. The axes of compression/contraction of the crust in the Greater Caucasus region are oriented in the S-NE direction. The maximum strain rate (approximately 200 × 10-9 per annum) is documented in the zone of mud volcanism at the SHIK site (Shykhlar), which is marked by a sharp change in the direction of the compression axes (SW-NE). It is revealed that the deformation field also includes the zones where strain rates are very low approximating 5 × 10-9 per annum. These zones include the Caspian-Guba and northern Gobustan areas, characterized by extensive development of mud volcanism. The extension zones are confined to the Lesser Caucasus and are revealed in the Gedabek (GEDA) and Shusha (SHOU) areas, as well as in the zone located between the DAMO and PIRM sites (Iran), where the deformation rate amounts to 100 × 10-9 per annum. It is concluded that the predominant factor responsible for the eruption of mud volcanoes is the intensity of gas-generation processes in the earth's interior, while deformation processes play the role of a trigger. The zone of the epicenters of strong earthquakes is correlated to the gradient zone in the crustal strain rates.

  13. Crustal deformation, the earthquake cycle, and models of viscoelastic flow in the asthenosphere

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.; Kramer, M. J.

    1984-01-01

    The crustal deformation patterns associated with the earthquake cycle can depend strongly on the rheological properties of subcrustal material. Substantial deviations from the simple patterns for a uniformly elastic earth are expected when viscoelastic flow of subcrustal material is considered. The detailed description of the deformation pattern and in particular the surface displacements, displacement rates, strains, and strain rates depend on the structure and geometry of the material near the seismogenic zone. The origin of some of these differences are resolved by analyzing several different linear viscoelastic models with a common finite element computational technique. The models involve strike-slip faulting and include a thin channel asthenosphere model, a model with a varying thickness lithosphere, and a model with a viscoelastic inclusion below the brittle slip plane. The calculations reveal that the surface deformation pattern is most sensitive to the rheology of the material that lies below the slip plane in a volume whose extent is a few times the fault depth. If this material is viscoelastic, the surface deformation pattern resembles that of an elastic layer lying over a viscoelastic half-space. When the thickness or breath of the viscoelastic material is less than a few times the fault depth, then the surface deformation pattern is altered and geodetic measurements are potentially useful for studying the details of subsurface geometry and structure. Distinguishing among the various models is best accomplished by making geodetic measurements not only near the fault but out to distances equal to several times the fault depth. This is where the model differences are greatest; these differences will be most readily detected shortly after an earthquake when viscoelastic effects are most pronounced.

  14. Earthquake cycle deformation in the Tibetan plateau with a weak mid-crustal layer

    NASA Astrophysics Data System (ADS)

    Robinson, P. M.; Meade, B. J.

    2012-12-01

    Geodetic observations of interseismic deformation across the Tibetan plateau contain information about both tectonic and earthquake cycle processes. Time-variations in surface velocities between large earthquakes are sensitive to the rheologic structure of the sub-seismogenic crust, and, in particular, the viscosity of the middle and lower crust. Here we derive a semi-analytic solution for time-dependent surface velocities resulting from viscoelastic stress relaxation in a mid-crustal layer in response to forcing by periodic earthquakes. Earthquake cycle models with a mid-crustal layer exhibit substantially more pre-earthquake strain localization than do classic 2-layer models at short Maxwell times. We apply both this 3-layer channel-like model and the classic 2-layer model to geodetic observations before and after the 2001 MW=7.8 Kokoxili and 1997 MW=7.6 Manyi strike-slip earthquakes in Tibet in order to estimate the viscosity of the crust below a 20 km thick seismogenic layer. For these events, interseismic stress relaxation in a weak (viscosity ≤1018.5 Pa s) and thin (height ≤20 km) mid-crustal layer explains observations of both near-fault strain localization late in the earthquake cycle and rapid (>50 mm/yr) postseismic velocities in the years following the coseismic ruptures. We suggest that the classic 2-layer model requires a rheology with multiple relaxation time scales to simultaneously explain both pre- and post-seismic observations while the channel-like model can explain the same behavior with a single Maxwell viscosity.

  15. The analysis of GPS crustal deformation, seismicity, and strain rate in October 2013 Ruisui, Taiwan Earthquake

    NASA Astrophysics Data System (ADS)

    Min-Chien, Tsai; Shui-Beih, Yu; Tzay-Chyn, Shin

    2016-04-01

    Continuous GPS network, a groundwater station specially designed for observation of seismic precursor signals. Most of all, the shock is located in the area with very active seismicity and fast crustal deformation. Furthermore, the quality of Central Weather Bureau Seismic Network (CWBSN) seismic data has been significantly improved and reached micro-earthquake level. Therefore, we have plenty data to do the case research for this earthquake event. To try to understand the possible seismogenic mechanism and tectonic structure. We also try to search for any pre-seismic signal and assess the capability of very short-term prediction in the area during the earthquake.

  16. Rapid assessment of Cascadia tsunamis from real-time PANGA GPS crustal deformation measurements

    NASA Astrophysics Data System (ADS)

    Melbourne, T. I.; Santillan, M.; Miner, A.; Webb, F.

    2008-12-01

    Cascadia's natural hazards include earthquakes, tsunamis, volcanic eruptions, landslides, and tectonic subsidence along its coasts and inland waterways exacerbated by sea-level rise. The Pacific Northwest Geodetic Array, now comprised of nearly 200 continuous GPS receivers, has been deployed over the last two decades to focus exclusively on mitigating these hazards. In addition, over 150 receivers of the EarthScope Plate Boundary Observatory have also been installed in Cascadia, thus comprising a combined network of over 350 instruments. Of the 200 PANGA stations, nearly 140 are high-rate, real-time telemetered receivers mounted on CWU-built, tectonics-grade monuments. These stations straddle active crustal faults, volcanoes and landslides, they span the megathrust forearc and tsunamigenic regions along the Pacific coast, and they monitor ageing man-made structures such as dams, levees and elevated freeways. All data from this array, currently at over 140 stations, is streamed in real-time into CWU where it is archived and processed with JPL's GIPSY software. In 2005 PANGA received support from NASA, NSF and the USGS to implement real-time processing in support of mitigating Cascadia's natural hazards. We have implemented Trimble Navigation's proprietary RTK software and network monitoring software on all 140 stations, and specific parameter estimation routines on a subset of these stations. Pending available funding, we are also working to implement processing of this data with the RTGipsy software, which produces position time series within a global, not local, reference frame. We are currently writing applications that will facilitate rapid recovery during and after a large seismic event, tsunami, or volcanic eruption. These applications are focused on: - Inverting GPS deformation measurements for earthquake fault location, size, and slip distribution; - Using slip distributions to predict tsunami magnitude and run-up estimates; - Real-time monitoring of

  17. Crustal motion and deformation in Greece from a decade of GPS measurements, 1993 2003

    NASA Astrophysics Data System (ADS)

    Hollenstein, Ch.; Müller, M. D.; Geiger, A.; Kahle, H.-G.

    2008-03-01

    The Hellenic plate boundary region, located in the collision zone between the Nubian/Arabian and Eurasian lithospheric plates, is one of the seismo-tectonically most active areas of Europe. During the last 15 years, GPS measurements have been used to determine the crustal motion in the area of Greece with the aim to better understand the geodynamical processes of this region. An extended reoccupation network covering whole Greece has been measured periodically in numerous GPS campaigns since the late eighties, and a continuous GPS network has been operated in the region of the Ionian Sea since 1995. In this paper, we present a new detailed high-quality solution of continuous and campaign-type measurements acquired between 1993 and 2003. During the GPS processing, a special effort was made to obtain consistent results with highest possible accuracies and reliabilities. Data of 54 mainly European IGS and EUREF sites were included in the GPS processing in order to obtain results which are internally consistent with the European kinematic field and order to allow for a regional interpretation. After an overview of the results of the IGS/EUREF sites, the results from more than 80 stations in Greece are presented in terms of velocities, time series, trajectories and strain rates. Previous geodetic, geological and seismological findings are generally confirmed and substantially refined. New important results include the observation of deformation zones to the north and to the south of the North Aegean Trough and in the West Hellenic arc region, arc-parallel extension of about 19 mm/yr along the Hellenic arc, and compression between the Ionian islands and the Greek mainland. Due to continuous long-term observations of 4-8 years, it was possible to extract height changes from the GPS time series. In Greece, we observe a differential subsidence of the order of 2 mm/yr between the northern and central Ionian islands across the Kefalonia fault zone. The differential subsidence

  18. Crustal deformation in the Western Solomon Islands revealed by GPS observation during 2009 - 2012

    NASA Astrophysics Data System (ADS)

    Kuo, Y.; Lin, K.; Ku, C.; Taylor, F. W.; Chen, Y.; Huang, B.

    2012-12-01

    The plate boundary along the southern margin of the Solomon Islands, southwestern Pacific, is characterized by convergent tectonic processes between the Indo-Australian Plate and Pacific Plate. The horizontal convergence rate between two plates is 135 mm/yr in the direction of N45°E. In terms of the structure, this subduction zone is relatively complicated because large seamounts are involved in subduction of extremely young lithosphere generated by the Woodlark spreading system. Hence, the crustal deformation is essential to reconstructing the structural model that constitutes and operates the entire subduction system. For the purpose of monitoring crustal motion, we began to deploy continuous mode GPS stations in September 2009. All of them have been working for 1-3 yr. The total horizontal rates are 95±1, 52±3, 78±7, 120±14, 114±7, and 114±7 mm/yr for Sibo, Nusu, Lale, Husu, Tepa, and Sege respectively. However, the moving directions are N23°E, N63°W, N10°W, N65°W, N63°W, and N69°W. During 2009, the uplift rates are -31±8 and 50±17 mm/yr for Sibo and Nusu, but during 2010, the rate are 2±2 and 13±9 mm/yr. The larger slips may cause of the postseismic deformation of 2007 Mw8.1 Solomon Earthquake. It also shows the large uplift rates on Husu (98±36 mm/yr), Tepa (60±11 mm/yr) and Sege (33±10 mm/yr) after the 2010 Mw7.1 Solomon Earthquake; however, it still needs longer measuring time to confirm the tectonic behavior.

  19. Crustal deformation at the Nankai subduction zone inferred from onshore GPS velocities and seafloor geodetic observations

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Tadokoro, K.; Ikuta, R.; Okuda, T.; Nagai, S.; Kuno, M.

    2011-12-01

    The Philippine Sea plate (PH) subducts beneath the southwest Japan along the Nankai Trough with a rate of about 4-6 cm/yr, where megathrust earthquakes have repeatedly occurred every 100-150 years. The probability of earthquake occurrence within 30 years from January 1st, 2011 are estimated to be 87 %, 70 %, and 60 % for the next Tokai, Tonankai, and Nankai earthquakes, respectively. We are concerned about the expansion of earthquake damage because these earthquakes have possibilities of interlocking with adjacent segments according to the historical record. Thus, it is important to know the spatio-temporal variation of crustal deformation accompanied with plate interaction. For this issue, we have conducted seafloor geodetic observation at the Nankai Trough using a GPS/Acoustic technique since 2004. In this system, we estimate the position of a surveying vessel by Kinematic GPS analysis and measure the distance between the vessel and the benchmark on the seafloor by Acoustic measurements. Next we determine the location of the benchmark. For the repeatability of this observation, the location of benchmark is determined within a precision of 2-3 cm at horizontal components. Recently, a number of research institutes have conducted seafloor geodetic observation using this technique before and after earthquakes occurred in offshore area, and then they have provided significant achievement to understand inter-, co-, and post-seismic crustal deformation. Several seafloor benchmarks are located at the Nankai subduction zone, which are individually operated by Japan Coast Guard, Tohoku University, and Nagoya University. In the Kumano Basin, we have three seafloor benchmarks located about 60-80 km away from the deformation front of the Nankai Trough. The observations from 2005 to 2010 have illustrated that those benchmarks are moving at rates of about 3-4 cm/yr toward west-northwest with velocity uncertainties of about 2 cm/yr relative to the Amurian plate (AM). In this

  20. A numerical simulation of magma motion, crustal deformation, and seismic radiation associated with volcanic eruptions

    USGS Publications Warehouse

    Nishimura, T.; Chouet, B.

    2003-01-01

    The finite difference method is used to calculate the magma dynamics, seismic radiation, and crustal deformation associated with a volcanic eruption. The model geometry consists of a cylindrical reservoir and narrow cylindrical conduit embedded in a homogeneous crust. We consider two models of eruption. In the first model, a lid caps the vent and the magma is overpressurized prior to the eruption. The eruption is triggered by the instantaneous removal of the lid, at which point the exit pressure becomes equal to the atmospheric pressure. In the second model, a plug at the reservoir outlet allows pressurization of only the magmatic fluid in the reservoir before the eruption. Magma transfer between the reservoir and conduit is triggered by the instantaneous removal of the plug, and the eruption occurs when the pressure at the conduit orifice exceeds the material strength of the lid capping the vent. In both models, magma dynamics are expressed by the equations of mass and momentum conservation in a compressible fluid, in which fluid expansion associated with depressurization is accounted for by a constitutive law relating pressure and density. Crustal motions are calculated from the equations of elastodynamics. The fluid and solid are dynamically coupled by applying the continuity of wall velocities and normal stresses across the conduit and reservoir boundaries. Free slip is allowed at the fluid-solid boundary. Both models predict the gradual depletion of the magma reservoir, which causes crustal deformation observed as a long-duration dilatational signal. Superimposed on this very-long-period (VLP) signal generated by mass transport are long-period (LP) oscillations of the magma reservoir and conduit excited by the acoustic resonance of the reservoir-conduit system during the eruption. The volume of the reservoir, vent size, and magma properties control the duration of VLP waves and dominant periods of LP oscillations. The second model predicts that when the

  1. Central and eastern Anatolian crustal deformation rate and velocity fields derived from GPS and earthquake data

    NASA Astrophysics Data System (ADS)

    Simão, N. M.; Nalbant, S. S.; Sunbul, F.; Komec Mutlu, A.

    2016-01-01

    We present a new strain-rate and associated kinematic model for the eastern and central parts of Turkey. In the east, a quasi N-S compressional tectonic regime dominates the deformation field and is partitioned through the two major structural elements of the region, which are the conjugate dextral strike-slip North Anatolian Fault Zone (NAFZ) and the sinistral strike slip East Anatolian Fault Zone (EAFZ). The observed surface deformation is similar to that inferred by anisotropy studies which sampled the region of the mantle closer to the crust (i.e. the lithospheric mantle and the Moho), and is dependent on the presence or absence of a lithospheric mantle, and of the level of coupling between it and the overlaying crust. The areas of the central and eastern parts of Turkey which are deforming at elevated rates are situated above areas with strong gradients in crustal thickness. This seems to indicate that these transition zones, situated between thinner and thicker crusts, promote more deformation at the surface. The regions that reveal elevated strain-rate values are 1) the Elaziğ-Bingol segment of the EAFZ, 2) the region around the Karlıova triple-junction including the Yedisu segment and the Varto fault, 3) the section of the NAFZ that extends from the Erzincan province up to the NAFZ-Ezinepazarı fault junction, and 4) sections of the Tuz Gölü Fault Zone. Other regions like the Adana basin, a significant part of the Central Anatolian Fault Zone (CAFZ), the Aksaray and the Ankara provinces, are deforming at smaller but still considerable rates and therefore should be considered as areas well capable of producing damaging earthquakes (between M6 and 7). This study also reveals that the central part of Turkey is moving at a faster rate towards the west than the eastern part Turkey, and that the wedge region between the NAFZ and the EAFZ accounts for the majority of the counter clockwise rotation between the eastern and the central parts of Turkey. This

  2. Crustal structure and active tectonics in the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Brückl, E.; Behm, M.; Decker, K.; Grad, M.; Guterch, A.; Keller, G. R.; Thybo, H.

    2010-04-01

    During the last decade, a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the Eastern Alps and their adjacent tectonic provinces. A fragmentation of the lithosphere into three blocks, Europe (EU), Adria (AD), and the new Pannonian fragment (PA), was interpreted and a triple junction was inferred. The goal of this study has been to relate these deep crustal structures to active tectonics. We used elastic plate modeling to reconsider the Moho fragmentation. We interpret subduction of EU below AD and PA from north to south and underthusting of AD mantle below PA from southwest to northeast. The Moho fragmentation correlates well with major upper crustal structures and is supported by gravity, seismic, and geodetic data. An analysis of crustal thickening suggests that active convergence is associated with continued thrusting and lateral extrusion in the central Eastern Alps and thickening of the Adriatic indenter under the Southern Alps. According to the velocity relations at the triple junction, PA moves relative to EU and AD along ENE and SE striking faults, mainly by strike slip. An eastward directed extensional component is compensated by the lateral extrusion of the central Eastern Alps. The Periadriatic (Insubric) line east of the triple junction and the mid-Hungarian fault zone have relatively recently lost their role as first-order active structures. We favor the idea that the Pannonian fragment and the TISZA block merged to a "soft" microplate surrounded by the Eastern and Southern Alpine, Carpathian, and Dinaric orogens.

  3. Monitoring and understanding crustal deformation by means of GPS and InSAR data

    NASA Astrophysics Data System (ADS)

    Zerbini, Susanna; Prati, Claudio; Bruni, Sara; Errico, Maddalena; Musicò, Elvira; Novali, Fabrizio; Santi, Efisio

    2014-05-01

    Monitoring deformation of the Earth's crust by using data acquired by both the GNSS and SAR techniques allows describing crustal movements with high spatial and temporal resolution. This is a key contribution for achieving a deeper and better insight of geodynamic processes. Combination of the two techniques provides a very powerful means, however, before combing the different data sets it is important to properly understand their respective contribution. For this purpose, strictly simultaneous and long time series would be necessary. This is not, in general, a common case due to the relatively long SAR satellites revisit time. A positive exception is represented by the data set of COSMO SKYMed (CSK) images made available for this study by the Italian Space Agency (ASI). The flyover area encompass the city of Bologna and the smaller nearby town of Medicina where permanent GPS stations are operational. At the times of the CSK flyovers, we compared the GPS and SAR Up and East coordinates of a few stations as well as differential tropospheric delays derived by both techniques. The GPS time series were carefully screened and corrected for the presence of discontinuities by adopting a dedicated statistical procedure. The comparisons of both the estimated deformation and the tropospheric delays are encouraging and highlight the need for having available a more evenly sampled SAR data set.

  4. Present-day crustal deformation along the El Salvador Fault Zone from ZFESNet GPS network

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    This paper presents the results and conclusions obtained from new GPS data compiled along the El Salvador Fault Zone (ESFZ). We calculated a GPS-derived horizontal velocity field representing the present-day crustal deformation rates in the ESFZ based on the analysis of 30 GPS campaign stations of the ZFESNet network, measured over a 4.5 year period from 2007 to 2012. The velocity field and subsequent strain rate analysis clearly indicate dextral strike-slip tectonics with extensional component throughout the ESFZ. Our results suggest that the boundary between the Salvadoran forearc and Caribbean blocks is a deformation zone which varies along the fault zone. We estimate that the movement between the two blocks is at least ~ 12 mm yr- 1. From west to east, this movement is variably distributed between faults or segments of the ESFZ. We propose a kinematic model with three main blocks; the Western, Central and Eastern blocks delimited by major faults. For the first time, we were able to provide a quantitative measure of the present-day horizontal geodetic slip rate of the main segments of ESFZ, ranging from ~ 2 mm yr- 1 in the east segment to ~ 8 mm yr- 1, in the west and central segments. This study contributes new kinematic and slip rate data that should be used to update and improve the seismic hazard assessments in northern Central America.

  5. Monitoring crustal deformation in The Geysers-Clear Lake geothermal area, California

    USGS Publications Warehouse

    Lofgren, Ben Elder

    1978-01-01

    Geodetic surveys since 1972-73 reveal significant crustal deformation in The Geysers-Clear Lake region. Resurveys of precise control networks are measuring both vertical and horizontal ground movement, with most of the change continuing in the area of geothermal fluid withdrawal. Preliminary evidence suggests right-lateral horizontal movement on northwest-trending fault systems and vertical and horizontal compression of the deep geothermal reservoir system. A direct correlation is suggested between ground-surface deformation and subsurface pressure changes in the reservoir system. Although surface changes appear too small to be of environmental concern in The Geysers-Clear Lake region, they indicate hydrodynamic changes in the reservoir of significant import. Two types of vertical changes in The Geysers production area are indicated in the 1973-77 data--(a) a regional subsidence between the Collayomi and Mercuryville fault zones and (b) local subsidence directly related to the area of principal steam production. Maximum subsidence of 13 centimeters in 4? years occurred in the area of most concentrated steam withdrawals and where fluid-pressure declines were near maximum. Subsidence rates throughout the production area from 1973 to 1975 were about half the 1975-77 rates in apparent correlation with pressure changes measured in the reservoir system. Horizontal ground movement as great as 2.0 centimeters per year, generally inward toward the center of production, was measured around the perimeter of the steam production area.

  6. Indian National GNSS Programme: Crustal deformation measurements in the Indian Sub-continent

    NASA Astrophysics Data System (ADS)

    Verma, Mithila; Bansal, Brijesh K.

    2012-05-01

    The Indian National GNSS Programme was launched about one and half decades ago with a view to provide a boost to crustal deformation measurements for constraining the movement of Indian plate, identifying the regions of strain accumulation, and to estimate the convergence rates across some identified faults/boundaries. Under this programme, a network of 50 permanent GPS receivers has been established, which is fully functional for the last about 8 yrs. The network has generated very important data sets, which in turn have helped in the estimation of Indian plate motion, regions and rate of strain accumulation, rate of convergence across some identified faults, etc. The measurements have also been utilized in monitoring co-seismic and postseismic deformation related to recent earthquakes that occurred in India and adjoining regions, such as the 2001 Bhuj, 2004 Sumatra-Andaman and 2005 Kashmir earthquake. This article presents some salient results obtained for specific corridors in the Himalaya, Indo-Burmese arc region, Andaman-Nicobar Island region and Indian plate interior region.

  7. A mid-crustal strain-transfer model for continental deformation: A new perspective from high-resolution deep seismic-reflection profiling across NE Tibet

    NASA Astrophysics Data System (ADS)

    Wang, Chengshan; Gao, Rui; Yin, An; Wang, Haiyan; Zhang, Yuxiu; Guo, Tonglou; Li, Qusheng; Li, Yalin

    2011-06-01

    Understanding why continental deformation departs from the theory of plate tectonics requires a detailed knowledge of three-dimensional structures at a lithospheric scale. In Tibet, the end-member models of continental deformation make distinctively different predictions on strain distribution and contrasting structural geometry as a function of depth. Specifically, the thin-viscous-sheet model predicts vertically coherent deformation while channel-flow and continental-subduction models predict the presence of sub-horizontal detachment zones within or at the base of the Tibetan crust during the Cenozoic deformation. To differentiate the above models, we conducted a high-resolution seismic-reflection survey across the active left-slip Kunlun fault and its nearby contractional structures. The results of this work show that the actively deforming middle Tibetan crust is dominated by discrete sub-horizontal simple-shear zones that terminate the sub-vertical, left-slip Kunlun fault above and mantle-cutting thrusts below. The flat shear zones appear to act as roof and floor thrusts of large duplex structures that transfer shortening strain from locally deformed and coupled lower crust and mantle lithosphere below to the high-strain domains of the upper crust above. The middle-crustal strain-transfer model proposed here implies that the weak Tibetan middle crust may not be active everywhere during the Indo-Asian collision. It also predicts that the kinematics of the activated portions of the middle crust, whether being deformed by simple shear or channel-flow deformation, may vary from place to place, depending strongly on the lateral variation of mechanical strength at different depths of the lithosphere. Our approach of establishing the kinematics of middle-crust deformation departs significantly from the early work that emphasizes exclusively the role of vertically varying rheology in controlling the mode of continental deformation.

  8. Geodetic observation of sea-level change and crustal deformation in the Baltic Sea region

    NASA Astrophysics Data System (ADS)

    Richter, A.; Groh, A.; Dietrich, R.

    Based on tide gauge observations spanning almost 200 years, homogeneous time series of the mean relative sea level were derived for nine sites at the southern coast of the Baltic Sea. Our regionally concentrated data were complemented by long-term relative sea-level records retrieved from the data base of the Permanent Service for Mean Sea Level (PSMSL). From these records relative sea-level change rates were derived at 51 tide gauge stations for the period between 1908 and 2007. A minimum observation time of 60 years is required for the determination of reliable sea-level rates. At present, no anthropogenic acceleration in sea-level rise is detected in the tide gauge observations in the southern Baltic. The spatial variation of the relative sea-level rates reflects the fingerprint of GIA-induced crustal uplift. Time series of extreme sea levels were also inferred from the tide gauge records. They were complemented by water level information from historic storm surge marks preserved along the German Baltic coast. Based on this combined dataset the incidence and spatial variation of extreme sea levels induced by storm surges were analysed yielding important information for hazard assessments. Permanent GPS observations were used to determine recent crustal deformation rates for 44 stations in the Baltic Sea region. The GPS derived height change rates were applied to reduce the relative sea-level changes observed by tide gauges yielding an estimate for the eustatic sea-level change. For 13 tide gauge-GPS colocation sites a mean eustatic sea-level trend of 1.3 mm/a was derived for the last 100 years.

  9. InSAR and GPS time series analysis: Crustal deformation in the Yucca Mountain, Nevada region

    NASA Astrophysics Data System (ADS)

    Li, Z.; Hammond, W. C.; Blewitt, G.; Kreemer, C. W.; Plag, H.

    2010-12-01

    Several previous studies have successfully demonstrated that long time series (e.g. >5 years) of GPS measurements can be employed to detect tectonic signals with a vertical rate greater than 0.3 mm/yr (e.g. Hill and Blewitt, 2006; Bennett et al. 2009). However, GPS stations are often sparse, with spacing from a few kilometres to a few hundred kilometres. Interferometric SAR (InSAR) can complement GPS by providing high horizontal spatial resolution (e.g. meters to tens-of metres) over large regions (e.g. 100 km × 100 km). A major source of error for repeat-pass InSAR is the phase delay in radio signal propagation through the atmosphere. The portion of this attributable to tropospheric water vapour causes errors as large as 10-20 cm in deformation retrievals. InSAR Time Series analysis with Atmospheric Estimation Models (InSAR TS + AEM), developed at the University of Glasgow, is a robust time series analysis approach, which mainly uses interferograms with small geometric baselines to minimise the effects of decorrelation and inaccuracies in topographic data. In addition, InSAR TS + AEM can be used to separate deformation signals from atmospheric water vapour effects in order to map surface deformation as it evolves in time. The principal purposes of this study are to assess: (1) how consistent InSAR-derived deformation time series are with GPS; and (2) how precise InSAR-derived atmospheric path delays can be. The Yucca Mountain, Nevada region is chosen as the study site because of its excellent GPS network and extensive radar archives (>10 years of dense and high-quality GPS stations, and >17 years of ERS and ENVISAT radar acquisitions), and because of its arid environment. The latter results in coherence that is generally high, even for long periods that span the existing C-band radar archives of ERS and ENVISAT. Preliminary results show that our InSAR LOS deformation map agrees with GPS measurements to within 0.35 mm/yr RMS misfit at the stations which is the

  10. Crustal Deformation in Southcentral Alaska: The 1964 Prince William Sound Earthquake Subduction Zone

    NASA Technical Reports Server (NTRS)

    Cohen, Steven C.; Freymueller, Jeffrey T.

    2003-01-01

    This article, for Advances in Geophysics, is a summary of crustal deformation studies in southcentral Alaska. In 1964, southcentral Alaska was struck by the largest earthquake (moment magnitude 9.2) occurring in historical times in North America and the second largest earthquake occurring in the world during the past century. Conventional and space-based geodetic measurements have revealed a complex temporal-spatial pattern of crustal movement. Numerical models suggest that ongoing convergence between the North America and Pacific Plates, viscoelastic rebound, aseismic creep along the tectonic plate interface, and variable plate coupling all play important roles in controlling both the surface and subsurface movements. The geodetic data sets include tide-gauge observations that in some cases provide records back to the decades preceding the earthquake, leveling data that span a few decades around the earthquake, VLBI data from the late 1980s, and GPS data since the mid-1990s. Geologic data provide additional estimates of vertical movements and a chronology of large seismic events. Some of the important features that are revealed by the ensemble of studies that are reviewed in this paper include: (1) Crustal uplift in the region that subsided by up 2 m at the time of the earthquake is as much as 1 m since the earthquake. In the Turnagain Arm and Kenai Peninsula regions of southcentral Alaska, uplift rates in the immediate aftermath of the earthquake reached 150 mm/yr , but this rapid uplift decayed rapidly after the first few years following the earthquake. (2) At some other locales, notably those away the middle of the coseismic rupture zone, postseismic uplift rates were initially slower but the rates decay over a longer time interval. At Kodiak Island, for example, the uplift rates have been decreasing at a rate of about 7mm/yr per decade. At yet other locations, the uplift rates have shown little time dependence so far, but are thought not to be sustainable

  11. CRUSDE: A plug-in based simulation framework for composable CRUstal DEformation studies using Green's functions

    NASA Astrophysics Data System (ADS)

    Grapenthin, R.

    2014-01-01

    CRUSDE is a plug-in based simulation framework written in C/C++ for Linux platforms (installation information, download and test cases: http://www.grapenthin.org/crusde). It utilizes Green's functions for simulations of the Earth's response to changes in surface loads. Such changes could involve, for example, melting glaciers, oscillating snow loads, or lava flow emplacement. The focus in the simulation could be the response of the Earth's crust in terms of stress changes, changes in strain rates, or simply uplift or subsidence and the respective horizontal displacements of the crust (over time). Rather than implementing a variety of specific models, CRUSDE approaches crustal deformation problems from a general formulation in which model elements (Green's function, load function, relaxation function, load history), operators, pre- and postprocessors, as well as input and output routines are independent, exchangeable, and reusable on the basis of a plug-in approach (shared libraries loaded at runtime). We derive the general formulation CRUSDE is based on, describe its architecture and use, and demonstrate its capabilities in a test case. With CRUSDE users can: (1) dynamically select software components to participate in a simulation (through XML experiment definitions), (2) extend the framework independently with new software components and reuse existing ones, and (3) exchange software components and experiment definitions with other users. CRUSDE's plug-in mechanism aims for straightforward extendability allowing modelers to add new Earth models/response functions. Current Green's function implementations include surface displacements due to the elastic response, final relaxed response, and pure thick plate response for a flat Earth. These can be combined to express exponential decay from elastic to final relaxed response, displacement rates due to one or multiple disks, irregular loads, or a combination of these. Each load can have its own load history and

  12. Monitoring of seafloor crustal deformation using GPS/Acoustic technique along the Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Yasuda, K.; Tadokoro, K.; Ikuta, R.; Watanabe, T.; Fujii, C.; Matsuhiro, K.; Sayanagi, K.

    2014-12-01

    Seafloor crustal deformation is crucial for estimating the interplate locking at the shallow subduction zone and has been carried out at subduction margins in Japan, e.g., Japan Trench and Nankai Trough [Sato et al., 2011; Tadokoro et al., 2012]. Iinuma et al. [2012] derived slip distributions during the 2011 Tohoku-Oki earthquake using GPS/Acoustic data and on-land GPS data. The result showed that maximum slip is more than 85 m near the trench axis. The focal area along the Nankai trough extended to the trough axis affected this earthquake by cabinet office, government of Japan.  We monitored seafloor crustal deformation along the Nankai trough, Japan. Observation regions are at the eastern end of Nankai trough (named Suruga trough) and at the central Nankai trough. We established and monitored by two sites across the trough at each region. In the Suruga trough region, we repeatedly observed from 2005 to 2013. We observed 13 and 14 times at a foot wall side (SNE) and at a hanging wall side (SNW), respectively. We estimated the displacement velocities with relative to the Amurian plate from the result of repeated observation. The estimated displacement velocity vectors at SNE and SNW are 42±8 mm/y to N94±3˚W direction and 39±11 mm/y to N84±9˚W direction, respectively. The directions are the same as those measured at the on-land GPS stations. The magnitudes of velocity vector indicate significant shortening by approximately 4 mm/y between SNW and on-land GPS stations at hanging wall side of the Suruga Trough. This result shows that the plate interface at the northernmost Suruga trough is strongly locked. In the central Nankai trough region, we established new two stations across the central Nankai trough (Both stations are about 15km distance from trough) and observed only three times, August 2013, January 2014, and June 2014. We report the results of monitoring performed in this year.

  13. Crustal Velocity Field from InSAR and GPS reveals Internal Deformation of Western Tibet

    NASA Astrophysics Data System (ADS)

    Wang, H.; Wright, T. J.

    2010-12-01

    Two contrasting views continue to dominate the debate about continental tectonics - do the continents behave like the oceans, with a few large plates (blocks) separated by major faults (e.g. Tapponnier et al., 1982, 2001; Thatcher, 2007; Meade, 2007), or is a smooth continuum a more appropriate and compact description (e.g. England and Molnar, 1997, 2005). The Tibetan plateau has long been the testing ground for this debate and despite decades of research it has yet to be put to bed. Existing observations of crustal deformation in Tibet are largely derived from the Global Positioning System (GPS). Because large gaps in the GPS coverage exist, particularly in central and Western Tibet, the data have been used to support both the models (e.g. England and Molnar, 2005; Thatcher, 2007; Meade, 2007). On the other hand, Interferometric Synthetic Aperture Radar (InSAR) offers an independent means of measuring present-day crustal deformation with a spatial resolution of a few tens of meters and an accuracy comparable to with GPS (e.g., Wright et al., 2001, 2004; Wang et al 2009). We have used InSAR data from multiple tracks in conjunction with available GPS to constrain a 2D velocity field model for the Tibetan plateau. About 300 ERS/Envisat interferograms are produced spanning 6 tracks (five descending and one ascending), covering ~200,000 km2 of Western Tibet. Each track is analysed using a network approach which yields line-of-sight deformation rates and realistic uncertainties (Biggs et al., 2007; Elliott et al., 2008; Wang et al., 2009). These are combined with the GPS, using full covariances, by adapting the velocity field method of England and Molnar (1997) to incorporate InSAR observations. Initially, we set up a triangular mesh spanning the target area; we then solve for the horizontal velocities on each node, as well as additional orbital and atmospheric terms for the InSAR data. The solution is regularised using Laplacian smoothing, whose weight is determined as

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  15. InSAR and the Hector Mine Earthquake: Crustal Deformation v Atmospheric Anomaly

    NASA Astrophysics Data System (ADS)

    Calzia, J.

    2005-12-01

    A series of SAR interferograms of the southwestern Mojave Desert record the apparent development and collapse of a topographic anomaly near the epicenter of the 16 Oct 1999 Mw7.1 Hector Mine Earthquake. Interferograms generated from Feb 1999 to June 2000 ERS data, using GAMMA software, record the development of an elliptical uplift, centered about 20 km north-northeast of the epicenter. The uplift covers approximately 2700 km2 and a regional amplitude of 2.8 cm; peak amplitude is nearly 7 cm. Although NOAA records indicate no rain fall in the area of the anomaly for October 1999, the close correlation between topography and interference fringes suggests atmospheric stratification between the highest peak and valley floor. Reprocessing the SAR data, using DIAPASON software, resulted in inversion of the anomaly from uplift to depression. This inversion suggests that the topographic anomaly is not caused by crustal deformation, but is a near-surface atmospheric anomaly caused by local transient conditions such as dust or smoke. Although InSAR offers a powerful new tool for earthquake prediction, this study confirms the impact that minor atmosphere contaminants can have on the interpretation of SAR data.

  16. Jurassic crustal deformation in west-central part of Colorado Plateau

    SciTech Connect

    Peterson, F.

    1985-05-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle Jurassic time, the region had been tilted westward and structural troughs formed in the area of the present-day Circle Cliffs uplift and in the vicinity of the Circle Cliffs and Black Mesa regions were uplifted and the nearby Henry and Kaiparowits regions began to be downwarped as troughs or basins. It cannot be determined if or how the present-day monoclines flexed during the Jurassic. However, the direction of structural tilt across these areas changed from west side down to east side down during the late Middle and early Late Jurassic. The Monument region, the largest and most persistent structural element in the region, changed from a structural bench to a positive structure in the early Late Jurassic. In most cases the positive structures subsided more slowly than adjacent downwarps. Two exceptions during the Late Jurassic are the Black Mesa and Emery uplifts. These are the only uplifts that actually rose above the level of sediment accumulation. Jurassic rocks are not known to contain significant hydrocarbon resources in this region, but their tectonic history may offer clues to the structural history of underlying Paleozoic strata, which are the primary hydrocarbon exploration targets.

  17. Crustal vertical deformation response to different spatial scales of GRACE and GCMs surface loading

    NASA Astrophysics Data System (ADS)

    Yan, Haoming; Chen, Wu; Yuan, Linguo

    2016-01-01

    Crustal vertical deformation (CVD) observed by continuous GPS height time-series can be explained largely by surface loading effects recovered from both Gravity Recover and Climate Experiment (GRACE) and General Circulation Models (GCMs) data. We first show that lower degree CVD spatial spectrum due to the Earth's elastic response to a uniform surface loading plays more important roles than that of high-degree case. We then demonstrate that GRACE data with 300-400 km spatial resolution have the ability to detect 99 per cent power of global and regional CVD in spatial spectrum domain using a global frequency-wavenumber spectrum method. We can just use either GRACE or GCMs 36 degree/order (d/o) spherical harmonic coefficients (SHCs) which correspond to 500 km spatial resolution to acquire more than 90 per cent variance of total CVD modeled by up to 180 d/o SHCs at 98 per cent global gridpoints. Globally, CVD modeled by GRACE loading can explain 72 per cent annual amplitude and 69 per cent variance of GPS observed height time-series, which is better than the GCMs results of 64 per cent for annual amplitude and 41 per cent for variance. Using a three cornered hat method, we also show that the noise level of monthly averaged CVD is about 3 mm for both GPS height time-series and GRACE loading result, while that of GCMs result is only 1.3 mm.

  18. Pointwise functions for flexible implementation of crustal deformation physics in PyLith

    NASA Astrophysics Data System (ADS)

    Aagaard, B.; Knepley, M.; Williams, C. A.

    2015-12-01

    The next stage of development for PyLith, a flexible, open-source finite-element code (http://geodynamics.org/cig/software/pylith/) for modeling quasi-static and dynamic crustal deformation with an emphasis earthquake faulting, focuses on refactoring the code to provide greater flexibility in support of a broader range of physics, discretizations, and optimizations for a variety of computer hardware. We separate the finite-element integration into a discretization-specific portion and discretization-independent pointwise functions associated with the governing equations. The discretization-specific portion is designed to accommodate arbitrary order finite elements and multiple implementations for optimization targeting specific hardware (e.g., CPU and GPU). The pointwise functions encapsulate the physics, including the governing equations and rheologies. Users can easily extend the code by adding new pointwise functions to implement different rheologies and/or governing equations. PyLith currently includes pointwise functions for quasi-static and dynamic elasticity for several elastic, viscoelastic, and elastoplastic rheologies. We plan to add pointwise functions for coupling of elasticity with fluid flow and incompressible elasticity. Tight integration with the Portable, Extensible Toolkit for Scientific Computation (PETSc) provides support for a wide range of linear and nonlinear solvers and time-stepping algorithms.

  19. The development of space geodetic observations of crustal kinematics and deformation.

    NASA Astrophysics Data System (ADS)

    Smith, D. E.

    2012-12-01

    Space geodesy for crustal dynamics studies reached maturity around the time of the Apollo landings. The techniques of laser ranging to earth satellites (SLR) and the Moon (LLR), and very long baseline interferometry (VLBY) all started to approach a viable quality. This enabled each technique to start the process of demonstrating on a regular and consistent basis that they could make observations that would enable earth scientists to better understand the movements along active fault lines, the rotation of the Earth, and improve the model of the Earth's gravity field. Much of the early years were consumed with understanding the strengths of each technique for various approaches and it was not until a decade later that the space agencies felt comfortable in establishing funded long-term programs. In the US it was the Crustal Dynamics Project and about the same time the WEGENER program in Europe under the auspices if the IAG were established. Together these programs eventually established SLR, LLR, and VLBI sites on almost all the major tectonic blocks and the real kinematics of the present-day geological blocks became known. While this was happening the Global Positioning System (GPS) emerged as the technique of choice for many local observations, complementing the other techniques, and together bringing the world this remarkable capability to understand dynamics of planet earth.

  20. Crustal structure and deformation beneath the NE margin of the Tibetan plateau constrained by teleseismic receiver function data

    NASA Astrophysics Data System (ADS)

    Wang, Qiong; Niu, Fenglin; Gao, Yuan; Chen, Yuntai

    2016-01-01

    We analysed a large amount of teleseismic receiver function data recorded by 172 broadband stations in the NE Tibetan plateau and its surrounding areas to investigate the crustal velocity and anisotropy structure beneath the margin. We first applied the modified H-κ stacking technique to measure the crustal thickness and average Vp/Vs ratio, and then employed a joint inversion scheme to measure azimuthal anisotropy of the crust beneath each station. The observed crustal thickness and Vp/Vs ratio exhibit large variations across the study area, varying from 32 to 75.6 km and from 1.601 to 1.864, respectively. We also found significant azimuthal anisotropy within the crust beneath 12 stations, with a splitting time between 0.36 and 1.06s. The fast polarization directions align well with surface structures, and follow the directions of the maximum horizontal tensile stress. The low Vp/Vs ratio and the strong azimuthal anisotropy observed beneath the margin suggest that whole crustal shortening might be the dominant mechanism for producing the thick crust in NE Tibet. We compared the measured seismic anisotropy with those measured from XKS (SKS, PKS and SKKS), and found that crustal anisotropy appears to play an important role in explaining the amount of XKS splitting times. More importantly, the Moho Ps and the XKS share similar fast polarization directions, suggesting a vertically coherent deformation within the lithosphere beneath the margin.

  1. Metamorphic reactions, grain size reduction and deformation of mafic lower crustal rocks

    NASA Astrophysics Data System (ADS)

    Degli Alessandrini, Giulia; Menegon, Luca; Beltrando, Marco; Dijkstra, Arjan; Anderson, Mark

    2016-04-01

    and their relative abundance in the layers are believed to influence the deformation of the layers themselves. In symplectite-rich layers (domains 1, 4) deformation is localised, grain-size is below 30μm and phases are well mixed. On the other hand, in pyroxene or plagioclase-rich layers, deformation is less localised, the phases are less mixed and the grain size is larger (domain 2, 3). These preliminary results suggest that syn-kinematic metamorphic reactions forming symplectites played an essential role in grain size reduction, phase mixing and strain localization. We speculate that the compositional domains with symplectites localized deformation more efficiently, by activation of grain size sensitive creep, most likely because those domains were originally more hydrated than the others. On the contrary, domains without symplectites accommodated deformation less efficiently, either through fracturing (clinopyroxene, garnet) or dislocation creep + recrystallization (orthopyroxene, plagioclase).

  2. Crustal deformation associated with an M8.1 earthquake in the Solomon Islands, detected by ALOS/PALSAR

    NASA Astrophysics Data System (ADS)

    Miyagi, Yousuke; Ozawa, Taku; Shimada, Masanobu

    2009-10-01

    On April 1, 2007 (UTC), a large Mw 8.1 interplate earthquake struck the Solomon Islands subduction zone where complicated tectonics result from the subduction of four plates. Extensive ground movements and a large tsunami occurred in the epicentral area causing severe damage over a wide area. Using ALOS/PALSAR data and the DInSAR technique, we detected crustal deformation exceeding 2 m in islands close to the epicenter. A slip distribution of the inferred seismic fault was estimated using geodetic information derived from DInSAR processing and field investigations. The result indicates large slip areas around the hypocenter and the centroid. It is possible that the largest slip area is related to subduction of the plate boundary between the Woodlark and Australian plates. A small slip area between those large slip areas may indicate weak coupling due to thermal activity related to volcanic activity on Simbo Island. The 2007 earthquake struck an area where large earthquake has not occurred since 1970. Most of this seismic gap was filled by the 2007 events, however a small seismic gap still remains in the southeastern region of the 2007 earthquake.

  3. Seismic Mapping of Crustal and Mantle Deformation beneath the SE Tibetan Plateau with Receiver Function and SKS Splitting Data

    NASA Astrophysics Data System (ADS)

    Zuo, J.; Niu, F.

    2014-12-01

    The SE margin of the Tibetan plateau is characterized by complex Cenozoic structures created during the India-Asia collision since ~50 Ma. Details on the uplift and deformation, especially those inside the lower crust and upper mantle are still debated. Seismic anisotropy measured from SKS splitting data has been combined with surface GPS data to determine whether the crust and upper mantle beneath the margin have coherent deformation. Due to the poor depth resolution of the SKS data, it is still difficult to constrain the distribution of crustal and upper mantle anisotropy separately with the combined dataset. In this study we used the receiver function to measure crustal anisotropy and combined it with SKS splitting data to determine the anisotropy within the upper mantle. We applied this technique to 80 permanent broadband stations in the area operated by the China Earthquake Administration (CEA). The receiver function data indicate that the crust beneath the plateau possesses a strong azimuthal anisotropic component, with measured delay time varying from 0.50 to 0.90 s. To constrain mantle anisotropy with SKS data, we first correct the waveform distortion induced by crustal anisotropy, and then use them to estimate the splitting parameters. The splitting time measured from the corrected SKS data varies from 0.45 to 0.95 s with rather complicated lateral distribution. These results will be further compared with numerical data to better constrain the deformation mechanism of the area.

  4. Crustal dynamics project: The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1990-01-01

    The focus of the research was in two broad areas: (1) the nature and dynamics of time-dependent deformation and stress along major seismic zones, and (2) the nature of long-wavelength oceanic geoid anomalies in terms of lateral variations in upper mantle temperature and composition. The principal findings are described in the appendices.

  5. I. Studies in crustal deformation using GPS and tiltmeters. II. New statistical techniques in static stress triggering

    NASA Astrophysics Data System (ADS)

    Anderson, Gregory J.

    1999-10-01

    The topics covered by this dissertation are seemingly quite disparate: continuous Global Positioning System (GPS) geodetic measurements made on land, long-baseline tiltmeter measurements made on the seafloor, and studies of stress interactions following a large earthquake in southern California. However, all these subjects are variations on the theme of studying crustal deformation over a variety of spatial and temporal scales and in a range of tectonic environments. Chapter 1 briefly lays out the general theory behind the use of GPS in studying crustal deformation and then applies it to a seven-year record of continuous GPS measurements in southern California. The chapter gives detailed histories for the sites used, and then focuses on describing the effects on the data set of various alterations in processing technique, as well as the temporal and spectral characteristics of the particular data set used. Chapter 2 describes the theory of operation and the development of a long-baseline fluid-tube tiltmeter for use in the seafloor environment. The chapter's primary focus is the data returned from an operational deployment of four such tiltmeters on Axial Seamount on the Juan de Fuca Ridge. The work in the chapter shows that, while further development is needed to lower the noise level in the instrument, this tiltmeter design is currently capable of resolving deflation events associated with volcanism on active seamounts and segments of the Mid-Ocean Ridge system. Chapter 3 discusses static stress interactions and their impact on regional seismicity following a large earthquake. The main focus is on development of a new statistical method for confirming the existence of such triggering. This method begins by computing the Coulomb stress changes experienced by a set of earthquakes spanning the occurrence of a mainshock. It then uses the Kolmogorov-Smirnov test to compare the distribution of stress changes for earthquakes after the mainshock to that for shocks

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  7. Tracing the evolution of crustal-scale, transient permeability in a tectonically active, mid-crustal, low-permeability environment by means of quartz veins

    NASA Astrophysics Data System (ADS)

    Sintubin, M.

    2013-12-01

    In mid-crustal, low-permeability environments pervasive fluid flow is primarily driven by the production of internally-derived metamorphic fluids, causing a near permanent state of near-lithostatic fluid-pressure conditions. In a tectonically active crust, these overpressured fluids will generate intermittently an enhanced permeability that will facilitate fluid flow through the crust. The High-Ardenne slate belt (Belgium, France, Germany) can be considered as a fossil (late Palaeozoic) analogue of such mid-crustal, low-permeability environment at the brittle-plastic transition (depth range from 7 to 15 km). Low-grade metamorphic (250°C-350°C), predominantly fine-grained, siliciclastic metasediments were affected by a contraction-dominated deformation, materialized by a pervasive slaty cleavage. Quartz veins, abundantly present in the slate belt, are used as a proxy for the enhanced permeability. Detailed structural, petrographical, mineralogical and geochemical studies of different quartz-vein occurrences has enabled to reconstruct the evolution of the crustal-scale permeability , as well as to constrain the coupled fluid-pressure and stress-state evolution throughout the orogenic history. Extensive veining on a regional scale seems confined to periods of tectonic stress inversion, both at the onset (compressional stress inversion) and in the final stages (extensional stress inversion) of orogeny. Firstly, compressional stress inversion is expressed by pre-orogenic bedding-normal extension veins, consistently arranged in parallel arrays, followed by early orogenic bedding-parallel hybrid veins. Fluid-inclusion studies demonstrate near-lithostatic to supralithostatic fluid pressures, respectively. Secondly, discordant veins, transecting the pre-existing cleavage fabric, are interpreted to be initiated shortly after the extensional stress inversion, reflecting the late-orogenic extensional destabilisation of the slate belt. Veining again occurred at high fluid

  8. Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations

    SciTech Connect

    Rutqvist, J.

    2010-06-01

    This paper presents recent advancement in and applications of TOUGH-FLAC, a simulator for multiphase fluid flow and geomechanics. The TOUGH-FLAC simulator links the TOUGH family multiphase fluid and heat transport codes with the commercial FLAC{sup 3D} geomechanical simulator. The most significant new TOUGH-FLAC development in the past few years is a revised architecture, enabling a more rigorous and tight coupling procedure with improved computational efficiency. The applications presented in this paper are related to modeling of crustal deformations caused by deep underground fluid movements and pressure changes as a result of both industrial activities (the In Salah CO{sub 2} Storage Project and the Geysers Geothermal Field) and natural events (the 1960s Matsushiro Earthquake Swarm). Finally, the paper provides some perspectives on the future of TOUGH-FLAC in light of its applicability to practical problems and the need for high-performance computing capabilities for field-scale problems, such as industrial-scale CO{sub 2} storage and enhanced geothermal systems. It is concluded that despite some limitations to fully adapting a commercial code such as FLAC{sup 3D} for some specialized research and computational needs, TOUGH-FLAC is likely to remain a pragmatic simulation approach, with an increasing number of users in both academia and industry.

  9. Finite element modelling of stress field perturbations and interseismic crustal deformation in the Val d'Agri region, southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Candela, Stefania; Mazzoli, Stefano; Megna, Antonella; Santini, Stefano

    2015-08-01

    The Val d'Agri area provides the opportunity to analyse active structures in a seismic region for which a large amount of subsurface data is available. This area, which was struck in 1857 by one of the most destructive earthquakes in Italy (MW = 7.03), represents a unique natural laboratory to gain new insights into geometry, modes and rates of faulting controlling crustal deformation in an actively extending orogen. In this study, a crustal geological section through the southern Apennines is discretized into a finite element model (FEM). We present a 2D elastoplastic FEM that reproduces stress perturbations and strain field around the Val d'Agri active fault system. The influence of fault strand activity on interseismic crustal deformation is tested by a series of computer models, whose predictions are compared with the horizontal velocity components of continuous GPS sites in the region and with stress directions and geological data. The best fit with available geological and geophysical constraints is obtained with a 300 km long, 29 km deep model formed by a multilayer including three components having different rheological characteristics and including several shallow, locked fault segments, which branch into a freely slipping major basement fault at depth. Finite element modelling provides new insights into the controversial and widely debated active tectonic setting of the study area, pointing out the fundamental role played by a structural reactivation process involving inherited, long-lived, mature fault systems at depth. Our FEM, reconciling apparently contrasting geological and geophysical constraints from the study area, points to maximum stress build up and strain accumulation at a depth of 15 ± 5 km. Such a depth range is suggested as the most likely one for the nucleation of large events such as the 1857 Val d'Agri earthquake.

  10. Impact of acoustic velocity structure to measurement of ocean bottom crustal deformation

    NASA Astrophysics Data System (ADS)

    Ikuta, R.; Tadokoro, K.; Okuda, T.; Sugimoto, S.; Watanabe, T.; Eto, S.; Ando, M.

    2010-12-01

    We are developing a geodetic method of monitoring crustal deformation under the ocean using kinematic GPS and acoustic ranging. The goal of our research is to achieve sub-centimeter accuracy in measuring oceanic crustal deformation by a very short-time measurement like 10 hours. In this study, we focused on lateral variation of acoustic velocity structure in seawater and introduced an inclined acoustic velocity structure model to improve accuracy of the measurement. We have a few measurement sites along Nankai trough, Japan. In each sites, we deployed a trio of transponders on ocean floor (seafloor benchmark units) within distance comparable with the depth. An ultrasonic signal is generated from a surface vessel drifting over the benchmark unit, which is received and replied by the benchmark unit. In this system, both acoustic velocity structure and the benchmark unit positions were determined simultaneously for the each measurement using a tomographic technique. This tomographic technique was adopted on an assumption that the acoustic velocity structure is horizontally layered and changes only in time, not in space. Ikuta et al., (AGU fall meeting 2009) reported an approach to improve accuracy of benchmark positioning using a new additional assumption. The additional assumption was that the configuration of the transponders trio constituting one benchmark unit does not change. They determined the time evolution of weight center for the fixed transponder triangle between different measurements using all repetitively obtained data sets at once. This is contrasting to the previous method in which each data set for different measurement was solved independently. This assumption worked well in reducing number of unknown parameters. As a result, repeatability of benchmark positioning improved from 5 cm to 3 cm. We conducted numerical experiments synthesizing acoustic travel-time data to evaluate the robustness of this new approach. When acoustic travel-time data is

  11. Deformation of Granulite at 1-2 GPa: Implications for Deep Crustal Earthquakes

    NASA Astrophysics Data System (ADS)

    Green, H. W.; Zhang, J.

    2006-12-01

    The eclogitic pseudotachylytes from western Norway demonstrate unambiguously that faulting took place in deep-seated lower crustal rock °C dry granulite, perhaps at pressures approaching 3 GPa. However, the corresponding faulting mechanism remains unclear. It is questionable whether earthquakes can occur by unassisted brittle shear fracture or frictional sliding at such depths, a fluid source is prerequisite for dehydration embrittlement and the transformation-induced faulting mechanism can only operate during polymorphic phase changes with a significant ΔV. Runaway shear heating is also problematic due to lack of evidence of large strains or rapid strain rates in the granulite. Therefore, all these potential high- pressure faulting mechanisms are unlikely to operate alone in the dry Norwegian granulites. We have conducted preliminary deformation experiments on synthetic granulite (+/- added serpentinite for fault trigger) prepared from Norway granulite kindly provided by T. M. Boundy. Rheological experiments on granulite alone show plastic flow with very high strength within and outside its stability field; no evidence was found for a faulting instability. The eclogitization process is extremely sluggish within the dry experimental samples. Most permanent strain is partitioned into feldspar; pyroxene and garnet remain almost rigid. In contrast, experiments with a short specimen of serpentinite on top of a short specimen of granulite showed that faults generated in serpentinite by dehydration propagated into granulite. The fault zones consist of fine- grained (< 1 μm) angular fragments likely to be eclogitic phase transformation products together with water. Based upon such observations, we hypothesize that pseudotachylyte formation occurs during deceleration of fault propagation rather than during acceleration as is generally assumed. Such hypothesis also has potentially important implications for fault propagation into otherwise stable materials at great

  12. Deformation of quaternary strata and its relationship to crustal folds and faults, south-central Puget Lowland, Washington State

    USGS Publications Warehouse

    Booth, D.B.; Troost, K.G.; Hagstrum, J.T.

    2004-01-01

    Folded Quaternary deposits across the south-central Puget Lowland, an area just south of the Seattle fault that extends across the Seattle uplift and its boundary with the adjacent Tacoma basin, provide increased resolution of the character and rate of crustal deformation. They also constrain alternative, and partly incompatible, views of crustal structure previously suggested by geophysical investigations. Tectonic deformation has been progressive for at least the past few hundred thousand years: older sediments display greater deformation than the youngest exposed deposits in the study area. Strain rates across the Seattle uplift have probably been between 0.25 and 1.0 mm/yr during this period, accounting for ???10% of the total strain shortening of the western Washington crust. The Seattle uplift displays Quaternary deformation across its full north-south extent and has structural discontinuities at both its northern and southern boundaries. Previous workers have already established the faulted nature of its northern boundary; exposed Quaternary strata across its southern boundary display intense folding, the location of which generally corresponds to the projection of a "Tacoma fault" suggested by prior geophysical studies. ?? 2004 Geological Society of America.

  13. Syncollisional extension along the India-Asia suture zone, south-central Tibet: Implications for crustal deformation of Tibet

    NASA Astrophysics Data System (ADS)

    Murphy, M. A.; Sanchez, V.; Taylor, M. H.

    2010-02-01

    Crustal deformation models of the Tibetan plateau are assessed by investigating the nature of Neogene deformation along the India-Asia suture zone through geologic mapping in south-central Tibet (84°30'E). Our mapping shows that the suture zone is dominated by a system of 3 to 4 ENE-striking, south-dipping thrust faults, rather than strike-slip faults as predicted by models calling upon eastward extrusion of the Tibetan plateau. Faults along the suture zone are not active, as they are cut by a system of NNW-striking oblique slip normal faults, referred to herein as the Lopukangri fault system. Fault-slip data from the Lopukangri fault system shows that the mean slip direction of its hanging wall is N36W. We estimate the net slip on the Lopukangri fault by restoring components of the thrust system. We estimate that the fault has accommodated ˜ 7 km of right-slip and ˜ 8 km of normal dip-slip, yielding a net slip of ˜ 10.5 km, and 6 km of horizontal east-west extension. The Lopukangri fault system is active and geomorphic offsets indicate right separations and westside-down dip-separation. The mapview curviplanar geometry and geomorphic expression of the Lopukangri fault system is similar to faults and rift basins to its east and west. These extensional faults are en echelon in map view and encompass a region that is 200 km long (east-west) and 95 km wide (north-south). Assuming our results for the Lopukangri fault are applicable to the entire system, we estimate a maximum of 18% extension across the zone. All active faults in the system terminate southward adjacent to the India-Asia suture zone. Because the individual rift geometries are similar and suggest a common kinematic relationship, we propose that the extensional system formed as a trailing extensional imbricate fan at the southern termination of the central Tibet conjugate fault zone. Alternatively, the extensional system may terminate to the north and represent a group of isolated crustal tears. Both

  14. The 10 April 2014 Nicaraguan Crustal Earthquake: Evidence of Complex Deformation of the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Suárez, Gerardo; Muñoz, Angélica; Farraz, Isaac A.; Talavera, Emilio; Tenorio, Virginia; Novelo-Casanova, David A.; Sánchez, Antonio

    2015-11-01

    On 10 April 2014, an M w 6.1 earthquake struck central Nicaragua. The main event and the aftershocks were clearly recorded by the Nicaraguan national seismic network and other regional seismic stations. These crustal earthquakes were strongly felt in central Nicaragua but caused relatively little damage. This is in sharp contrast to the destructive effects of the 1972 earthquake in the capital city of Managua. The differences in damage stem from the fact that the 1972 earthquake occurred on a fault beneath the city; in contrast, the 2014 event lies offshore, under Lake Managua. The distribution of aftershocks of the 2014 event shows two clusters of seismic activity. In the northwestern part of Lake Managua, an alignment of aftershocks suggests a northwest to southeast striking fault, parallel to the volcanic arc. The source mechanism agrees with this right-lateral, strike-slip motion on a plane with the same orientation as the aftershock sequence. For an earthquake of this magnitude, seismic scaling relations between fault length and magnitude predict a sub-surface fault length of approximately 16 km. This length is in good agreement with the extent of the fault defined by the aftershock sequence. A second cluster of aftershocks beneath Apoyeque volcano occurred simultaneously, but spatially separated from the first. There is no clear alignment of the epicenters in this cluster. Nevertheless, the decay of the number of earthquakes beneath Apoyeque as a function of time shows the typical behavior of an aftershock sequence and not of a volcanic swarm. The northeast-southwest striking Tiscapa/Ciudad Jardín and Estadio faults that broke during the 1972 and 1931 Managua earthquakes are orthogonal to the fault where the 10 April earthquake occurred. These orthogonal faults in close geographic proximity show that Central Nicaragua is being deformed in a complex tectonic setting. The Nicaraguan forearc sliver, between the trench and the volcanic arc, moves to the

  15. Crustal Deformation at the Arabian Plate-Boundary observed by InSAR

    NASA Astrophysics Data System (ADS)

    Jonsson, S.; Cavalié, O.; Akoglu, A. M.; Wang, T.; Xu, W.; Feng, G.; Dutta, R.; Abdullin, A. K.

    2013-12-01

    The Arabian plate is bounded by a variety of active plate boundaries, with extension in the Red Sea and Gulf of Aden to the south, compression in Turkey and Iran to the north, and transform faults to the west and to the east. Internally, however, the Arabian plate has been shown to be tectonically rather stable, despite evidence of recent volcanism and earthquake faulting. We use InSAR observations to study recent tectonic and volcanic activity at several locations at the Arabian plate boundary as well within the plate itself. The region near the triple junction between the Arabian, Eurasian, and Anatolian plates has often been the focus of studies on continental deformation behavior and interseismic deformation. Here we use large-scale InSAR data processing to map the deformation near the triple junction and find the deformation to be focused on major faults with little intra-plate deformation. The eastern part of the East Anatolian Fault appears to have a very shallow locking depth with limited fault-normal deformation. Several major earthquakes that have occurred in recent years on the Arabian plate boundary, including the 2011 magnitude 7.1 Van earthquake in eastern Turkey. It occurred as a result of convergence of the Arabian plate towards Eurasia and caused significant surface deformation that we have analyzed with multiple coseismic InSAR, GPS, and coastal uplift observations. We use high-resolution Cosmo-Skymed and TerraSAR-X data to derive 3D coseismic displacements from offsets alone, as some of the interferograms are almost completely incoherent. By identifying point-like targets within the images, we were able to derive accurate pixel offsets between SAR sub-images containing such targets, which we used to estimate the 3D coseismic displacements. The derived 3D displacement field helped in constraining the causative northward dipping thrust-fault. The Qadimah fault is a recently discovered fault located on the Red Sea coast north of Jeddah and under the

  16. Intrusion Triggering of Explosive Eruptions: Lessons Learned from EYJAFJALLAJÖKULL 2010 Eruptions and Crustal Deformation Studies

    NASA Astrophysics Data System (ADS)

    Sigmundsson, F.; Hreinsdottir, S.; Hooper, A. J.; Arnadottir, T.; Pedersen, R.; Roberts, M. J.; Oskarsson, N.; Auriac, A.; Decriem, J.; Einarsson, P.; Geirsson, H.; Hensch, M.; Ofeigsson, B. G.; Sturkell, E. C.; Sveinbjornsson, H.; Feigl, K.

    2010-12-01

    Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajökull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic. This eruption was preceded by an effusive flank eruption of olivine basalt from 20 March - 12 April 2010. Geodetic and seismic observations revealed the growth of an intrusive complex in the roots of the volcano during three months prior to eruptions. After initial horizontal growth, modelling indicates both horizontal and sub-vertical growth in three weeks prior the first eruption. The behaviour is attributed to subsurface variations in crustal stress and strength originating from complicated volcano foundations. A low-density layer may capture magma allowing pressure to build before an intrusion can ascend towards higher levels. The intrusive complex was formed by olivine basalt as erupted on the volcano flank 20 March - 12 April; the intrusive growth halted at the onset of this eruption. Deformation associated with the eruption onset was minor as the dike had reached close to the surface in the days before. Isolated eruptive vents opening on long-dormant volcanoes may represent magma leaking upwards from extensive pre-eruptive intrusions formed at depth. A deflation source activated during the summit eruption of trachyandesite is distinct from, and adjacent to, all documented sources of inflation in the volcano roots. Olivine basalt magma which recharged the volcano appears to have triggered the summit eruption, although the exact mode of triggering is uncertain. Scenarios include stress triggering or propagation of olivine basalt into more evolved magma. The trachyandesite includes crystals that can be remnants of minor recent intrusion of olivine basalt

  17. Southeast Papuan crustal tectonics: Imaging extension and buoyancy of an active rift

    NASA Astrophysics Data System (ADS)

    Abers, G. A.; Eilon, Z.; Gaherty, J. B.; Jin, G.; Kim, YH.; Obrebski, M.; Dieck, C.

    2016-02-01

    Southeast Papua hosts the world's youngest ultra-high-pressure (UHP) metamorphic rocks. These rocks are found in an extensional setting in metamorphic core complexes. Competing theories of extensional shear zones or diapiric upwelling have been suggested as driving their exhumation. To test these theories, we analyze the CDPAPUA temporary array of 31 land and 8 seafloor broadband seismographs. Seismicity shows that deformation is being actively accommodated on the core complex bounding faults, offset by transfer structures in a manner consistent with overall north-south extension rather than radial deformation. Rayleigh wave dispersion curves are jointly inverted with receiver functions for crustal velocity structure. They show crustal thinning beneath the core complexes of 30-50% and very low shear velocities at all depths beneath the core complexes. On the rift flanks velocities resemble those of normal continents and increase steadily with depth. There is no evidence for velocity inversions that would indicate that a major density inversion exists to drive crustal diapirs. Also, low-density melt seems minor within the crust. Together with the extension patterns apparent in seismicity, these data favor an extensional origin for the core complexes and limit the role of diapirism as a secondary exhumation mechanism, although deeper mantle diapirs may be undetected. A small number of intermediate-depth earthquakes, up to 120 km deep, are identified for the first time just northeast of the D'Entrecasteaux Islands. They occur at depths similar to those recorded by UHP rocks and similar temperatures, indicating that the modern seismicity occurs at the setting that generates UHP metamorphism.

  18. CrusDe: A plug-in based simulation framework for composable CRUStal DEformation simulations

    NASA Astrophysics Data System (ADS)

    Grapenthin, R.

    2008-12-01

    Within geoscience, Green's method is an established mathematical tool to analyze the dynamics of the Earth's crust in response to the application of a mass force, e.g. a surface load. Different abstractions from the Earth's interior as well as the particular effects caused by such a force are expressed by means of a Green's function, G, which is a particular solution to an inhomogeneous differential equation with boundary conditions. Surface loads, L, are defined by real data or as analytical expressions. The response of the crust to a surface load is gained by a 2D-convolution (**) of the Green's function with this load. The crustal response can be thought of as an instantaneous displacement which is followed by a gradual transition towards the final relaxed state of displacement. A relaxation function, R, describing such a transition depends on the rheological model for the ductile layer of the crust. The 1D-convolution (*) of the relaxation function with a load history, H, allows to include the temporal evolution of the surface load into a model. The product of the two convolution results expresses the displacement (rate) of the crust, U, at a certain time t: Ut = (R * H)t · (G ** L) Rather than implementing a variety of specific models, approaching crustal deformation problems from the general formulation in equation~1 opens the opportunity to consider reuse of model building blocks within a more flexible simulation framework. Model elements (Green's function, load function, etc.), operators, pre- and postprocessing, and even input and output routines could be part of a framework that enables a user to freely compose software components to resemble equation~1. The simulation framework CrusDe implements equation~1 in the proposed way. CrusDe's architecture defines interfaces for generic communication between the simulation core and the model elements. Thus, exchangeability of the particular model element implementations is possible. In the presented plug

  19. Early Himalayan Erosion: Constraints to Models of Crustal Deformation, Changes in Ocean Geochemistry and Global Climate

    NASA Astrophysics Data System (ADS)

    Najman, Y.; Bickle, M.; Boudagher-Fadel, M.; Carter, A.; Garzanti, E.; Paul, M.; Wijbrans, J.; Willett, E.; Oliver, G.; Parrish, R.; Akhter, S.; Allen, R.; Ando, S.; Chisty, E.; Reisberg, L.; Vezzoli, G.

    2007-12-01

    Dating the onset of Himalayan erosion is critical to understanding crustal deformation, and the proposed link with global climate and ocean geochemistry. The most commonly quoted age of India-Asia collision is ~50 Ma, yet the record of Paleogene Himalayan erosion is scant, either absent or of low age resolution. We identify sediments shed from the rapidly exhuming southern flanks of the eastern-central Himalaya at 38 Ma, in the >1 km thick deltaic Barail Formation of the Bengal Basin, Bangladesh. This formation was previously of disputed provenance and poorly dated. New provenance data from the Barail Formation, (seismic, petrographic, geochemical, and Ar-Ar, U-Pb, ZFT, Sm-Nd and Re-Os isotopic ratios) is consistent with Himalayan, and inconsistent with Indian cratonic or Burman sources. The biostratigraphic and isotopic mineral ages date the Barail Formation as spanning Late Eocene to Early Miocene. Lag time data show that exhumation of the orogen was rapid by 38 Ma. These data 1) reduce the delay between collision, and oldest known record of substantial and rapid erosion of the Indian crust of the central-eastern Himalaya's southern flanks, from >20 Myrs to 12 Myrs, and 2) indicate that thrusting and crustal thickening had generated sufficient relief by 38 Ma to generate efficient erosion. They also explain a previously puzzling discrepancy between the timing of early hinterland metamorphism and exhumation inferred from bedrock and the lack of corresponding evidence in the erosional record. Older sediments derived from the orogen's southern flanks may be found in the future. However, we consider the Barail Formation to represent the onset of significant accelerated erosion from the southern flanks of the central-eastern Himalaya at a regionally applicable scale because 1) earlier input of significant clastic material to the Bengal Basin is inconsistent with the pre-Barail carbonate shelf depositional environment, 2) the Bengal Basin is the only obvious exit point

  20. Using Receiver Functions to Analyze Rapid Transitions in Crustal Structure and Deformation in Northern California

    NASA Astrophysics Data System (ADS)

    Hayes, G. P.; Furlong, K. P.; Schwartz, S. Y.

    2004-12-01

    The Coast Ranges of Northern California have formed in association with the passage of the Mendocino triple junction through the region over the past 10-15 million years. Present day crustal structure reflects the way triple junction processes have driven crustal evolution in this area. Receiver function analyses at a suite of broadband stations in the Coast Ranges allow us to map a rapid change in crustal thickness over a relatively short distance: a decrease from 35+km to <25km thick over a distance of only 50km. This rapid transition coincides with a sharp variation in topography, and is also near an area of proposed lower crustal melts (Levander et. al, Geology, 1998). One of our broadband stations (FREY) is located in the vicinity of this sharp transition. Station FREY has been in operation since October 1999, and has produced receiver functions for approximately 20 events with good azimuthal coverage from the NW, W, SW, S and SE and reasonable ray parameter variation. Although there may be complications from dipping layers in this area, a careful analysis can help constrain this rapid change in crustal structure. Initial results at FREY suggest a distinct difference in crustal thickness imaged from the southeast ( ˜22km) compared to that from the northwest to southwest ( ˜25km) associated with this transition, and potentially constraining where the crustal thinning takes place. Crustal structure characteristics (such as Poisson's Ratio) for these directions also differs, a phenomenon that may be associated with the presence (or lack of) melt in the lower crust.

  1. Dissolution and Replacement Creep:A Significant Deformation Mechanism in Mid-crustal Rocks

    NASA Astrophysics Data System (ADS)

    Wintsch, R. P.

    2001-12-01

    Zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss from the Bronson Hill terrane, New England indicate that strain and S-C fabrics in these rocks were produced by dissolution, precipitation, and replacement processes, even at epidote-amphibolite facies metamorphic conditions. The metamorphic fabric is defined by alternating layers and folia dominated by quartz, feldspars, and biotite + epidote. Zoning patterns in most metamorphic plagioclase, orthoclase, epidote, and sphene are truncated at boundaries normal to the shortening direction, suggesting dissolution. Interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite, epidote and myrmekitic intergrowths of plagioclase and quartz. Metamorphic plagioclase grains are also replaced by epidote. We interpret these microstructures to reflect strain-enhanced dissolution. The cores of many grains show asymmetric overgrowths with at least two generations of beards, all oriented on the ends of grains that face the extension direction. We interpret these textures to reflect precipitation of components dissolved by deformation enhanced dissolution. While biotite and quartz probably deformed by dislocation creep, the overall deformation was accommodated by dissolution perpendicular to the shortening direction, and precipitation parallel to it. These chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks. Thus wet crust is likely to be weaker than calculated from these experimental studies. Where such processes dominate, stress may not be high enough to reach brittle failure.

  2. Dissolution and replacement creep: a significant deformation mechanism in mid-crustal rocks

    NASA Astrophysics Data System (ADS)

    Wintsch, R. P.; Yi, Keewook

    2002-07-01

    Zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss indicate that strain and S- C fabrics in these rocks were produced by dissolution, precipitation, and replacement processes, even at epidote-amphibolite facies metamorphic conditions. The metamorphic fabric is defined by alternating layers and folia dominated by quartz, feldspars, and biotite+epidote. Zoning patterns in most metamorphic plagioclase, orthoclase, epidote, and sphene are truncated at boundaries normal to the shortening direction, suggesting dissolution. Interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite, epidote, and myrmekitic intergrowths of plagioclase and quartz. Metamorphic plagioclase grains are also replaced by epidote. We interpret these microstructures to reflect strain-enhanced dissolution. The cores of many grains show asymmetric overgrowths with at least two generations of beards, all oriented on the ends of grains that face the extension direction. We interpret these textures to reflect precipitation of components dissolved by deformation-enhanced dissolution. While biotite and quartz probably deformed by dislocation creep, the overall deformation was accommodated by dissolution perpendicular to the shortening direction, and precipitation parallel to it. These chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks. Thus wet crust is likely to be weaker than calculated from these experimental studies.

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

    NASA Astrophysics Data System (ADS)

    Spinler, Joshua C.

    determining the slip-rates on each of the major crustal faults prior to the earthquake, we are able to model the pre-earthquake velocity field for comparison with velocities measured using sites constructed post-earthquake. We then determine how individual site velocities have changed in the 3 years following the earthquake, with implications for the rate at which the lower crust and upper mantle viscously relax through time. We find that the viscosity of the lower crust is at least an order of magnitude higher than that of the uppermost mantle, and hypothesize that this is due to mafic material emplaced at the base of the crust as the spreading center developed beneath the Salton Trough since about 6 Ma. The final study investigates crustal deformation and fault slip rates for faults in the northern Mojave and southern Walker Lane regions of the ECSZ. Previous geodetic studies estimated slip-rates roughly double those inferred via geological dating methods in this region for NW striking strike-slip faults, but significantly smaller than geologic estimates for the Garlock fault. Through construction of a detailed elastic block model, which selects only active fault structures, and applying a new, dense GPS velocity field in this region, we are able to estimate slip-rates for the strike-slip faults in the ECSZ that are much closer to those reported from geology.

  4. Crustal development and deformation of Laurentia during the Trans-Hudson and Alleghenian orogenies

    NASA Astrophysics Data System (ADS)

    Growdon, Martha Lynne

    The Kisseynew domain in Manitoba and the Orange-Milford complex in Connecticut are exhumed orogenic terranes that record the development of Laurentia along rigid basement margins during continent-continent collision and terrane accretion. The Kisseynew domain lies within the Paleoproterozoic Trans-Hudson Orogen and the Orange-Milford complex is a tectonic domain within the Paleozoic New England Appalachians. The response of continental crust to continent collisions ˜1.8 Ga contrasts with that during terrane accretions ˜300 Ma because the metamorphic evolution of each terrane is strongly controlled by the configuration of the converging tectonic blocks. The Paleoproterozoic Kisseynew domain is situated between three Archean cratons: the Hearne-Rae, Superior and Sask. The development of folds with axes oriented primarily NE-SW shows evidence for east-west compression of the rocks between the Superior and Hearne cratons. However, arching along a roughly east-west axis suggests a contribution of late north-south shortening between the Sask and Hearne cratons. Metamorphic temperatures exceeded 850°C and rocks now exposed at the surface were buried to at least 40 km due to the convergence of these three continental blocks. In contrast to these very high-grade rocks, the Orange-Milford complex is situated on the edge of the New York Promontory, a crustal buttress that localized strain from oblique terrane accretion into transpression, and contains an Acadian Barrovian-style metamorphic gradient. New 40Ar/39Ar thermochronology indicates a late phase of muscovite+chlorite growth occurred ˜300Ma during retrograde Alleghenian greenschist-facies deformation. The associated chlorite-muscovite fabrics are pervasive and cross-cut all older fabrics. These structures, that develop in association with the New York Promontory, are elongated parallel to the margin and contain evidence of significant along-strike stretching and thinning. In this setting rocks escape along the

  5. Crustal deformation and gas emission from the Krýsuvík high temperature geothermal system, Iceland

    NASA Astrophysics Data System (ADS)

    Rakel Gudjonsdottir, Sylvia; Ilyinskaya, Evgenia; Hreinsdottir, Sigrun; Michakczewska, Karolina; Bergsson, Baldur; Auippa, Alessandro; Agla Oladottir, Audur; Rut Hjartardottir, Asta

    2016-04-01

    The Krýsuvík volcanic system is located at the oblique spreading Reykjanes Peninsula, Iceland. Since early 2009 the region has been undergoing episodes of localized ground uplift and subsidence. From March 2011 to the end of 2012 the region inflated by over 7 cm, triggering upper crustal earthquakes at the plate boundary. From 2012 to present the region has been subsiding at a relatively steady rate, reaching the pre inflation state by the end of 2015. GPS measurements indicate that the deflation source is located at 3 km depth coinciding with a previously mapped low resistivity zone from MT measurements suggesting the presence of water, magma or conductive minerals. In April 2013, near-real time monitoring of gas emissions started in Krýsuvík using a MultiGAS sensor system to collect data gas composition. Gas emissions are correlated with crustal deformation and seismicity within the Krýsuvík geothermal system. The dataset comprises near-continuous gas composition time series (MultiGAS); quantification of diffuse CO2 gas flux; direct samples of dry gas; seismic records; and GPS dataset. The gas emissions from the Krýsuvík system are H2O dominated with CO2 as the most abundant dry gas species, followed by lesser amounts of H2S. The subsurface equilibrium temperature is calculated as 278°C. This is consistent with previous observations made through sporadical sampling campaigns (e.g. Arnórsson, 1987). In addition, the semi-continuous MultiGAS dataset reveals higher variations of gas composition than previously reported by spot sampling. The diffuse CO2 soil flux is found to be variable between the three degassing areas in Krýsuvík ranging from 10.9-70.9 T/day with the highest flux in Hveradalir where the MultiGAS station is located. The total flux was calculated as 101.4 T/day. Correlation of the MultiGAS data with the geophysical data shows that peaks of H2O-rich emissions follow events of crustal movements. Coinciding with the H2O-rich peaks, SO2 is

  6. Crustal Deformation and the Seismic Cycle across the Kodiak Islands, Alaska

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne; Carver, G.; Cohen, Steven C.; King, Robert

    2004-01-01

    The Kodiak Islands are located approximately 130 to 250 km from the Alaska-Aleutian Trench where the Pacific plate is underthrusting the North American plate at a rate of about 57 mm/yr. The southern extent of the 1964 Prince William Sound (${M-w}$ = 9.2) earthquake rupture occurred offshore and beneath the eastern portion of the Kodiak Islands. Here we report GPS results (1993-2001) from northern Kodiak Island that span the transition between the 1964 uplift region along the eastern coast and the region of coseismic subsidence further inland. The horizontal velocity vectors range from 22.9 $\\pm$ 2.2 mm/yr at N26.3$\\deg$W $\\pm$ 2.5$\\deg$, about 150 km from the trench, to 5.9 $\\pm$ 1.3 mm/yr at N65.9$\\deg$W $\\pm$ 6.6$\\deg$, about 190 km from the trench. Near the northeastern coast of Kodiak the velocity vector above the shallow, locked main thrust zone is between the orientation of PCFC-NOAM plate motion (N22$/deg$W) and the trench-normal (N3O$\\deg$W). Further west, our geodetic results suggest the accumulation of shear strain that will be released eventually as left-lateral motion on upper plate faults such as the Kodiak Island fault. These results are consistent with the hypothesis that the difference between the Pacific-North American plate motion and the orientation of the down going slab would lead to 4-8 mm/yr of left-lateral slip. Short-term geodetic uplift rates range from 2 - 14 mm/yr, with the maximum uplift located near the axis of maximum subsidence during the 1964 earthquake. We evaluated alternate interseismic models for Kodiak to test the importance of various mechanisms responsible for crustal deformation rates. These models are based on the plate interface slip history inferred from earlier modeling of coseismic and post-seismic geodetic results. The horizontal (trench perpendicular) and vertical deformation rates across Kodiak are consistent with a model that includes the viscoelastic response to : (1) a downgoing Pacific plate interface

  7. Application of an ultra-high-resolution FBG strain sensor for crustal deformation measurements at the Aburatsubo Bay, Japan

    NASA Astrophysics Data System (ADS)

    Tokunaga, T.; Liu, Q.; He, Z.; Mogi, K.; Matsui, H.; Wang, H. F.; Kato, T.

    2011-12-01

    For crustal deformation measurements, high-resolution strain sensors on the order of tens of nano-strains are desirable. Current sensors for this purpose include quartz-tube extensometers, free-space laser interferometers, and borehole strainmeters. The former two sensors show quite high strain resolution, however, these are large in size, from tens to hundreds of meter long, and hence, are difficult to measure spatial strain distribution. The optical fiber strain sensors have advantages of multiplexing capability and relatively low cost, and are widely adopted in the applications for structural health monitoring of civil structures such as bridges and buildings. Thus, as long as the strain resolution can be high enough to meet the requirement of crustal deformation measurements, fiber strain sensors can be an attractive tool. We have been developing an ultra-high strain-resolution fiber Bragg grating (FBG) sensor for static strain measurement, interrogated by a narrow line-width tunable laser. The sensor consists of a pair of FBGs, one for strain sensing and the other for temperature compensation. The Bragg wavelength difference between the two FBGs is evaluated using a cross-correlation algorithm. We already demonstrated that an ultra-high resolution corresponding to 2.6 nano-strain was obtained in the case where no strain was applied to the sensor, which was considered to be the ultimate performance of our measurement system. By directly applying variable strains to the developed sensor with a piezo-stage, a resolution of 17.6 nano-strain was demonstrated. This time, the sensor was installed into the vault at Aburatsubo, Japan, to measure crustal deformation caused by ocean tide, and the measured data were compared with the results obtained by a quartz-tube extensometer at the site, which has been measured by the University of Tokyo's Earthquake Research Institute. The deformation induced by oceanic tide was measured by the FBG sensor with the resolution about

  8. NASA plan for international crustal dynamics studies

    NASA Technical Reports Server (NTRS)

    1979-01-01

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

  9. Crustal deformation along the Dead Sea Transform and the Carmel Fault inferred from 12 years of GPS measurements

    NASA Astrophysics Data System (ADS)

    Sadeh, M.; Hamiel, Y.; Ziv, A.; Bock, Y.; Fang, P.; Wdowinski, S.

    2012-08-01

    Large-scale crustal deformation in the Levant is mainly related to the DST and the CFS. The former is an active left lateral transform, bounding the Arabian plate and the Sinai sub-plate, and the latter branches out of the former and separates the Sinai sub-plate into two tectonic domains. In this study we obtain the velocities of 33 permanent GPS stations and 145 survey stations that were surveyed in three campaigns between 1996 and 2008. We use a simple 1-D elastic dislocation model to infer the slip rate and locking depth along various segments of the DST. We infer a 3.1-4.5 mm/yr slip rate and a 7.8-16.5 km locking depth along the DST north of the CFS, and a slip rate of 4.6-5.9 mm/yr and locking depth of 11.8-24 km along the Jericho Valley, south of the CFS. Further south, along the Arava Valley we obtain a slip rate of 4.7-5.4 mm/yr and a locking depth of 12.1-23 km. We identify an oblique motion along the Carmel Fault with ˜0.7 mm/yr left-lateral and ˜0.6 mm/yr extension rates, resulting in N-S extension across the Carmel Fault. This result, together with the decrease in DST slip velocity from the Jericho Valley to the segment north of the CFS, confirms previous suggestions, according to which part of the slip between Arabia and Sinai is being transferred from the DST to the CFS.

  10. Crustal Deformation along the Dead Sea Transform and Carmel Fault Inferred from 12 years of GPS Measurements in Israel

    NASA Astrophysics Data System (ADS)

    Sadeh, M.; Hamiel, Y.; Ziv, A.; Bock, Y.; Fang, P.

    2011-12-01

    We quantify the interseismic slip rates and locking depths along the Dead-Sea Transform (DST) in Israel using GPS observations and elastic modeling. Large-scale crustal deformation and earthquakes in Israel are mainly related to the Dead Sea Transform (DST) and the Carmel-Gilboa-Faria Fault System (CFS). The former is an active left lateral transform, bounding the Arabian plate and the Sinai sub-plate, and the latter branches out of the former and separates the Sinai sub-plate into two tectonic domains. GPS observations from 18 permanent GPS stations and 147 densely spaced stations that were surveyed in three campaigns between 1996 and 2008 are used in this study. The GPS data is processed using the GAMIT/GLOBK software package, providing station coordinates and velocities relative to a fixed Sinai reference frame. Using a simple 2-D elastic model, we infer a slip rate of 3-4.2 mm/yr and a locking depth of 6.7-15.4 km along the DST north of the CFS, and a slip rate of 4.4-5.1 mm/yr and a locking depth of 12.3-23 km south of the CFS. Additionally, we infer a left lateral slip rate of 0.5-1.3 along the CFS, and a rate of about 0.5 mm/yr of extension perpendicular to it. Near fault observations rule out the possibility of shallow creep along the Northern segment of the DST, but suggest that creep may occur along the Dead Sea West Boundary Fault.

  11. Co-Seismic and Post-Seismic Crustal Deformation of Sumitra-Andaman Islands Earthquake from GPS Measurements

    NASA Astrophysics Data System (ADS)

    Reddy, C.; Prajapati, S.

    2005-05-01

    In view of the devastating Sumitra-Andaman Islands earthquake and tsunami on December, 26th 2004, understating the Indian lithosphere beneath the Andaman Islands has gained great importance. This region is a transition zone between India & Burmese plates possessing high strain rate distribution. To estimate the co-seismic and post-seismic deformation, GPS data from IGS sites IISC, HYDE, LHAS, KUNM, PIMO, NTUS, DGAR, BAKO, COCO, MALE and a network of nine GPS sites in Andaman and Nicobar Islands have been analyzed using GAMIT/GLOBK software. Time series of the baselines and position coordinates indicate significant crustal deformation. The GPS results are discussed in conjunction with the litho-tectonics of the Andaman region.

  12. Temporal evolution of continental lithospheric strength in actively deforming regions

    USGS Publications Warehouse

    Thatcher, W.; Pollitz, F.F.

    2008-01-01

    It has been agreed for nearly a century that a strong, load-bearing outer layer of earth is required to support mountain ranges, transmit stresses to deform active regions and store elastic strain to generate earthquakes. However the dept and extent of this strong layer remain controversial. Here we use a variety of observations to infer the distribution of lithospheric strength in the active western United States from seismic to steady-state time scales. We use evidence from post-seismic transient and earthquake cycle deformation reservoir loading glacio-isostatic adjustment, and lithosphere isostatic adjustment to large surface and subsurface loads. The nearly perfectly elastic behavior of Earth's crust and mantle at the time scale of seismic wave propagation evolves to that of a strong, elastic crust and weak, ductile upper mantle lithosphere at both earthquake cycle (EC, ???10?? to 103 yr) and glacio-isostatic adjustment (GIA, ???103 to 104 yr) time scales. Topography and gravity field correlations indicate that lithosphere isostatic adjustment (LIA) on ???106-107 yr time scales occurs with most lithospheric stress supported by an upper crust overlying a much weaker ductile subtrate. These comparisons suggest that the upper mantle lithosphere is weaker than the crust at all time scales longer than seismic. In contrast, the lower crust has a chameleon-like behavior, strong at EC and GIA time scales and weak for LIA and steady-state deformation processes. The lower crust might even take on a third identity in regions of rapid crustal extension or continental collision, where anomalously high temperatures may lead to large-scale ductile flow in a lower crustal layer that is locally weaker than the upper mantle. Modeling of lithospheric processes in active regions thus cannot use a one-size-fits-all prescription of rheological layering (relation between applied stress and deformation as a function of depth) but must be tailored to the time scale and tectonic

  13. Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

    NASA Astrophysics Data System (ADS)

    Xu, Xiao; Gao, Rui; Guo, Xiaoyu

    2016-04-01

    The eastern Tibetan plateau has been getting more and more attention because it combines active faults, uplifting, and large earthquakes together in a high-population region. Based on the previous researches, the most of Cenozoic tectonic activities were related to the regional structure of the local blocks within the crustal scale. Thus, a better understanding of the crustal structure of the regional tectonic blocks is an important topic for further study. In this paper, we combined the simple Bouguer gravity anomaly with the Moho depths from previous studies to investigate the crustal structure in this area. To highlight the crustal structures, the gravity anomaly caused by the Moho relief has been reduced by forward modeling calculations. A total horizontal derivative (THD) had been applied on the gravity residuals. The results indicated that the crustal gravity residual is compatible with the topography and the geological settings of the regional blocks, including the Sichuan basin, the Chuxiong basin, the Xiaojiang fault, and the Jinhe fault, as well as the Longmenshan fault zone. The THD emphasized the west margin of Yangtze block, i.e., the Longriba fault zone and the Xiaojiang fault cut through the Yangtze block. The checkboard pattern of the gravity residual in the Songpan-Garze fold belt and Chuandian fragment shows that the crust is undergoing a southward and SE-directed extrusion, which is coincident with the flowing direction indicated from the GPS measurements. By integrating the interpretations, the stepwise extensional mechanism of the eastern Tibetan plateau is supported by the southeastward crustal deformation, and the extrusion of Chuandian fragment is achieved by Xianshuihe fault.

  14. High-Frequency CTD Measurements for Accurate GPS/acoustic Sea-floor Crustal Deformation Measurement System

    NASA Astrophysics Data System (ADS)

    Tadokoro, K.; Yasuda, K.; Taniguchi, S.; Uemura, Y.; Matsuhiro, K.

    2015-12-01

    The GPS/acoustic sea-floor crustal deformation measurement system has developed as a useful tool to observe tectonic deformation especially at subduction zones. One of the factors preventing accurate GPS/acoustic sea-floor crustal deformation measurement is horizontal heterogeneity of sound speed in the ocean. It is therefore necessary to measure the gradient directly from sound speed structure. We report results of high-frequency CTD measurements using Underway CTD (UCTD) in the Kuroshio region. We perform the UCTD measurements on May 2nd, 2015 at two stations (TCA and TOA) above the sea-floor benchmarks installed across the Nankai Trough, off the south-east of Kii Peninsula, middle Japan. The number of measurement points is six at each station along circles with a diameter of 1.8 nautical miles around the sea-floor benchmark. The stations TCA and TOA are located on the edge and the interior of the Kuroshio current, respectively, judging from difference in sea water density measured at the two stations, as well as a satellite image of sea-surface temperature distribution. We detect a sound speed gradient of high speeds in the southern part and low speeds in the northern part at the two stations. At the TCA station, the gradient is noticeable down to 300 m in depth; the maximum difference in sound speed is +/- 5 m/s. The sound speed difference is as small as +/- 1.3 m/s at depths below 300 m, which causes seafloor benchmark positioning error as large as 1 m. At the TOA station, the gradient is extremely small down to 100 m in depth. The maximum difference in sound speed is less than +/- 0.3 m/s that is negligible small for seafloor benchmark positioning error. Clear gradient of high speed is observed to the depths; the maximum difference in sound speed is +/- 0.8-0.9 m/s, causing seafloor benchmark positioning error of several tens centimeters. The UCTD measurement is effective tool to detect sound speed gradient. We establish a method for accurate sea

  15. Kinematics of SW Anatolia implications on crustal deformation above slab tear

    NASA Astrophysics Data System (ADS)

    Özkaptan, Murat; Koç, Ayten; Lefebvre, Côme; Gülyüz, Erhan; Uzel, Bora; Kaymakci, Nuretdin; Langereis, Cornelis G.; Özacar, Arda A.; Sözbilir, Hasan

    2014-05-01

    measurements are also consistent with earthquake focal mechanisms suggesting active extension in the region. Thus, the FBFZ is characterized at the surface mainly by extension unlike previously proposed transcurrent deformation. We think, the FBFZ may represent a deep structure that formed at the ancient northern track of the STEP fault that reflected to the surface as a wide extensional zone displaying counter-clockwise rigid body rotation since late Miocene possibly due to fast Aegean slab retreat towards south. This research is supported byTubitak-Turkish National Science Foundation Grant Number 111Y239.

  16. Numerical modeling of forceful pluton emplacement and associated deformation at different crustal levels - instantaneous, continuous or episodic intrusion?

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Nabelek, P. I.

    2015-12-01

    The Papoose Flat pluton in the White-Inyo Range, California, is one of the best examples of forceful magma emplacement at mid-crustal levels that is revealed by a highly strained aureole. A thermo-rheological 2-D model of the pluton and its aureole is proposed. We explored how the frequency of magma input, from instantaneous to continuous to the bottom of the laccolith, affects the ductile width of the aureole and the crystallinity of the pluton, which has implications for eruption of magma. We modeled these aspects at mid- and upper-crustal levels. The pluton was assumed to be 5 km thick in the middle and 13 km wide. Except for instantaneous growth, pluton was assumed to grow over 5 m.y. The aureole was assumed to have power-law rheology of quartz with dependence on H2O fugacity, which was calculated using the CORK equation (Holland & Powell, 1991) Our result shows that the bottom of the Papoose Flat pluton was emplaced at the brittle-ductile transition zone of the crust. The crustal rheology profile assisted the softening of rocks around the pluton. The simulated temperature and strength profiles confirm that ductile deformation was related to thermal weakening (Saint-Blanquat et al., 2001). Results of incremental growth calculations show that the pluton remains hot and only partially crystalline for millions of years when it grows by frequent input of small batches of liquid. At the mid-crustal level, the ductile region around the pluton is much wider and exists longer than at the shallow crustal level. Brittle rheology is dominant during the late stage growth at the shallow depth. When the pluton grows instantly or by only few episodes of large batches of input, the mobile part of the pluton is thin and the ductile aureole is narrower. High-frequency incremental growth by smaller magma batches produces a large volume of mobile magma that has the potential to induce internal magmatic layering that may be reflected in aligned acquired magnetic susceptibility (AMS

  17. Earthquake activity and crustal stresses in stable plate interiors

    NASA Astrophysics Data System (ADS)

    Camelbeeck, Thierry; Calais, Eric; Mazzotti, Stéphane; Stein, Seth

    2016-04-01

    Unlike plate-boundary earthquakes that are explained by plate motions and their recurrence interval inferred from the rate at which these motions are released seismically, we have a limited understanding on the triggering causes of earthquakes in stable plate interiors as well as on the mechanisms explaining their apparent episodic, clustered, and migrating nature. An alternative model explaining those characteristics of the seismic activity in those regions where no discernable strain is building up today is that earthquakes result from the release of strain from a long-term pre-stressed lithosphere, triggered by processes weakening fault zones, like fluid circulation, or modifying applied normal stress on well oriented faults, like regional or more local erosion, water or ice loadings. In this talk, we present examples of three complementary approaches that should permit better understanding the mechanisms of this intraplate earthquake activity. They rely on studying their possible triggering factors and regional stresses controlling their mechanism, and also on modelling the possible strain rates of geological domains in relationship to their geological history and their fabrics. Among other things, we question whether the spatial variations of the short wavelengths gravitational potential energy associated to lateral variations of surface topography and crustal density can induce local stress perturbations explaining the complexity of the present-day tectonics in Western Europe and its possible relationship to earthquake activity.

  18. Crustal Deformation Caused by an M8.1 Earthquake in the Solomon Islands, Detected by ALOS/PALSAR

    NASA Astrophysics Data System (ADS)

    Miyagi, Y.; Ozawa, T.; Shimada, M.

    2009-12-01

    On April 1, 2007 (UTC), a large Mw 8.1 interplate earthquake occurred in the Solomon Islands subduction zone where Pacific, Australian, Solomon Sea, and Woodlark Plates produce complicated tectonics. This earthquake was accompanied by a large tsunami and caused considerable damage in the epicentral area. The Japan Aerospace Exploration Agency (JAXA) performed emergency observations using the Advanced Land Observing Satellite (ALOS). A remote-sensing technique has the advantage of being able to observe and monitor a disaster in a remote location like the Solomon Islands that is difficult to access and receives few geophysical observations. Especially the Phased Array type L-band Synthetic Aperture Rader (PALSAR) can observe the target and get high coherence even under cloudy conditions in heavily-vegetated tropical region. We applied Differential Interferometric SAR (DInSAR) technique using data from the PALSAR installed on ALOS, and detected significant crustal deformation over wide area associated with the earthquake. Then we inverted the geodetic information from DInSAR result jointly with the field investigation data (Tomita et al., 2008), and estimated a slip distribution on the inferred seismic fault (Miyagi et al., 2009). The modeling result shows large slip areas around the hypocenter and the centroid, and the estimated slip pattern was corresponding to those deduced from teleseismic data (e.g. Yagi, 2007). It can be interpreted that the large slip area around the centroid is consistent with a strong coupling area due to a subduction of the plate boundary between the Woodlark and Australian plates, and that the small slip area is consistent with the weak coupling area under the Simbo Island caused by thermal activities related to volcanic activity of Simbo Island. The 2007 earthquake occurred in the area where has occurred no M7- or larger-sized earthquake since 1970. Although a part of the seismic gap was filled in the 2007 events, small seismic gap

  19. Li and Sr isotope systematics of spring water around Ontake volcano in Japan: origin of fluid causes crustal deformation

    NASA Astrophysics Data System (ADS)

    Nishio, Y.; Okamura, K.; Sano, Y.

    2008-12-01

    Since 1978, earthquake swarms have been observed continuously on the east flank of Ontake volcano in central Japan. Earthquakes bigger than M4 have been occurred one or two a year. In September 1984, the M6.8 Western Nagano Prefecture earthquake occurred, and the Otaki village was devastating by collapse of volcanic edifice. In this earthquake swarm region, uplift of 3-6mm has been detected in 2002-2004 (Kimata et al., 2004). Also, a low-resistivity region at a depth 2km beneath the uplift area has been inferred from specific electric conductivity measurements (Kasaya et al., 2002). The resistivity index is lower than 100 ohm/m, suggesting the presence of hydrothermal chamber rather than magma. Our research group has carried out continuous geochemical survey for gas in hot and mineral springs around Ontake volcano since 1981. The results show that an anomalous increase in δ13C of CO2 and 3He/4He ratios was observed at the Shirakawa spring that is near the region of uplift (Takahata et al., 2003). Based on these features, it has been inferred that the observed uplift is related to changes in a shallow seismogenic layer due to increased hydrothermal input from the earthquake swarp area (Kimata et al., 2004). However, it has been unknown that the origin of the hydrothermal fluid that causes crustal deformation. The non-traditional lithium (Li) isotopic tracer has a great potential to provide us new knowledge for fluid that causes crustal deformation. Accordingly, we have analyzed 7Li/6Li ratios together with 87Sr/86Sr ratios and chemical compositions of filtrated spring water around Ontake volcano. Analyzed hot and mineral spring water has been sampled biennially since 2000. The results show that the delta 7Li values of spring water from the earthquake swarm region that is located in east flank of Ontake volcano are significantly lower than those of island arc volcanic rocks (δ7Li = ca. +3 ~ +5 per mil). From this, it is inferred that the fluid that causes crustal

  20. Detecting deep crustal magma movement: Exploring linkages between increased gas emission, deep seismicity, and deformation (Invited)

    NASA Astrophysics Data System (ADS)

    Werner, C. A.; Poland, M. P.; Power, J. A.; Sutton, A. J.; Elias, T.; Grapenthin, R.; Thelen, W. A.

    2013-12-01

    Typically in the weeks to days before a volcanic eruption there are indisputable signals of unrest that can be identified in geophysical and geochemical data. Detection of signals of volcanic unrest months to years prior to an eruption, however, relies on our ability to recognize and link more subtle changes. Deep long-period earthquakes, typically 10-45 km beneath volcanoes, are thought to represent magma movement and may indicate near future unrest. Carbon dioxide (CO2 ) exsolves from most magmas at similar depths and increases in CO2 discharge may also provide a months-to-years precursor as it emits at the surface in advance of the magma from which it exsolved. Without the use of sensitive monitoring equipment and routine measurements, changes in CO2 can easily go undetected. Finally, inflation of the surface, through use of InSAR or GPS stations (especially at sites tens of km from the volcano) can also indicate accumulation of magma in the deep crust. Here we present three recent examples, from Redoubt, Kilauea, and Mammoth Mountain volcanoes, where increases in CO2 emission, deep long-period earthquakes, and surface deformation data indicate either the intrusion of magma into the deep crust in the months to years preceding volcanic eruptions or a change in ongoing volcanic unrest. At Redoubt volcano, Alaska, elevated CO2 emission (~ 1200 t/d, or roughly 20 times the background emission) was measured in October, 2008, over 5 months prior to the first magmatic eruption in March, 2009. In addition to CO2 release, deep long-period earthquakes were first recorded in December, 2008, and a deep deformation signal was detected starting in May 2008, albeit retrospectively. At Kilauea, Hawaii, increases in CO2 emissions from the summit (up to nearly 25 kt/d, over three times the background emission) were measured mid-2004, roughly coincident with a change in deformation behavior from deflation to inflation. Nearly 3 years later, a change in eruptive activity occurred

  1. An elastic/viscoelastic finite element analysis method for crustal deformation using a 3-D island-scale high-fidelity model

    NASA Astrophysics Data System (ADS)

    Ichimura, Tsuyoshi; Agata, Ryoichiro; Hori, Takane; Hirahara, Kazuro; Hashimoto, Chihiro; Hori, Muneo; Fukahata, Yukitoshi

    2016-07-01

    As a result of the accumulation of high-resolution observation data, 3-D high-fidelity crustal structure data for large domains are becoming available. However, it has been difficult to use such data to perform elastic/viscoelastic crustal deformation analyses in large domains with quality assurance of the numerical simulation that guarantees convergence of the numerical solution with respect to the discretization size because the costs of analysis are significantly high. This paper proposes a method of constructing a high-fidelity crustal structure finite element (FE) model using high-fidelity crustal structure data and fast FE analysis to reduce the costs of analysis (based on automatic FE model generation for parallel computation, OpenMP/MPI hybrid parallel computation on distributed memory computers, a geometric multigrid, variable preconditioning and multiple precision arithmetic). Using the proposed methods, we construct 10 billion degree-of-freedom high-fidelity crustal structure FE models for the entire Japan, and conduct elastic/viscoelastic crustal deformation analysis using this model with enough high accuracy of the numerical simulation.

  2. An Elastic/Viscoelastic Finite Element Analysis Method for Crustal Deformation using a 3D Island-scale High-fidelity Model

    NASA Astrophysics Data System (ADS)

    Ichimura, Tsuyoshi; Agata, Ryoichiro; Hori, Takane; Hirahara, Kazuro; Hashimoto, Chihiro; Hori, Muneo; Fukahata, Yukitoshi

    2016-04-01

    As a result of the accumulation of high-resolution observation data, three-dimensional high-fidelity crustal structure data for large domains are becoming available. However, it has been difficult to use such data to perform elastic/viscoelastic crustal deformation analyses in large domains with quality assurance of the numerical simulation that guarantees convergence of the numerical solution with respect to the discretisation size, because the costs of analysis are significantly high. This paper proposes a method of constructing a high-fidelity crustal structure finite element (FE) model using high-fidelity crustal structure data and fast FE analysis to reduce the costs of analysis (based on automatic FE model generation for parallel computation, OpenMP/MPI hybrid parallel computation on distributed memory computers, a geometric multigrid, variable preconditioning, and multiple precision arithmetic). Using the proposed methods, we construct 10 billion degree-of-freedom high-fidelity crustal structure FE models for the entire Japan, and conduct elastic/viscoelastic crustal deformation analysis using this model with enough high accuracy of the numerical simulation.

  3. Block modeling of crustal deformation in Tierra del Fuego from GNSS velocities

    NASA Astrophysics Data System (ADS)

    Mendoza, L.; Richter, A.; Fritsche, M.; Hormaechea, J. L.; Perdomo, R.; Dietrich, R.

    2015-05-01

    The Tierra del Fuego (TDF) main island is divided by a major transform boundary between the South America and Scotia tectonic plates. Using a block model, we infer slip rates, locking depths and inclinations of active faults in TDF from inversion of site velocities derived from Global Navigation Satellite System observations. We use interseismic velocities from 48 sites, obtained from field measurements spanning 20 years. Euler vectors consistent with a simple seismic cycle are estimated for each block. In addition, we introduce far-field information into the modeling by applying constraints on Euler vectors of major tectonic plates. The difference between model and observed surface deformation near the Magallanes Fagnano Fault System (MFS) is reduced by considering finite dip in the forward model. For this tectonic boundary global plate circuits models predict relative movements between 7 and 9 mm yr- 1, while our regional model indicates that a strike-slip rate of 5.9 ± 0.2 mm yr- 1 is accommodated across the MFS. Our results indicate faults dipping 66- 4+ 6° southward, locked to a depth of 11- 5+ 5 km, which are consistent with geological models for the MFS. However, normal slip also dominates the fault perpendicular motion throughout the eastern MFS, with a maximum rate along the Fagnano Lake.

  4. Crustal deformation and interplate coupling from GPS observation in the West-Java Indonesia

    NASA Astrophysics Data System (ADS)

    Meilano, Irwan; Abidin, Hasanuddin A.; Subarya, Cecep; Andreas, Heri; Kato, Teruyuki; Harjono, Hery; Anggreni, Dina; Kimata, Fumiaki

    2010-05-01

    The Sunda trench plate boundaries along Sumatra have the potential to generate large thrust-type earthquakes. While less frequent and smaller events occur along Java where subduction of older seafloor takes place relatively aseismically. This latest need further investigation since 3 deadly earthquakes occurred for the last 4 years. The first once is the Yogyakarta May 2006 Earthquake then the Pangandaran July 2006 tsunami earthquake and the last one West Java 2009 earthquake. Java trench might have a unique earthquake potential. Therefore, more research is needed related to the 2009 earthquake in West Java to obtain a deep understanding of the mechanisms of subduction beneath the Java Island and its surrounding areas. We have conducted four times GPS campaign observation in West Java, 2006 (December), 2007 (August), 2008 (August) and 2009 (June and August). The activity of local fault; sinistral motion of Cimandiri fault and Lembang fault control the deformation pattern in West Java. Using simple elastic half-space model we estimate geodetic slip-rate of Cimandiri fault is 5mm/yr and 3mm/yr for Lembang fault. By assuming BAKO station as a fixed station, almost all GPS stations move to the north with velocity less than 1 cm/yr. This suggests that the interplate coupling is very weak or if any it only extend at very shallow portion.

  5. Crustal Deformation Along the Northern San Andreas Fault System From Geodetic and Geologic Data

    NASA Astrophysics Data System (ADS)

    Murray, M. H.

    2004-12-01

    The San Andreas fault system north of the San Francisco Bay area is composed of three sub-parallel right-lateral faults: the San Andreas, Rodgers Creek-Ma'acama, and Green Valley-Bartlett Springs. The San Andreas has been essentially aseismic since it last ruptured in 1906, and no major historical earthquakes have occurred on the more seismically active Ma'acama and Bartlett Springs faults, although the slip deficit on the Ma'acama fault may now be large enough to generate a magnitude 7 earthquake. Since 2002, we have been collecting GPS measurements at about 80 monuments that form roughly 10-station profiles across the northern San Andreas fault system from Pt. Reyes to Cape Mendocino. Most of the monuments were last observed in 1993 or 1995, so the new observations significantly improve estimates of their relative motion and models of average interseismic strain accumulation, including possible spatial variations along the fault system. We use angular velocity-backslip block modeling to determine a self-consistent northern California deformation field and rates of strain accumulation along the northern San Andreas fault system. Preliminary results from our modeling, which includes 2 blocks within the San Andreas fault system, as well as a Sierran-Great Valley block, and the Pacific and North America plates, show agreement between observed and predicted velocities at less than 2 mm/yr. Fault-parallel deformation across the entire San Andreas fault system is 38 mm/yr, but deep slip rates on the sub-parallel faults are poorly constrained due to significant correlations between the deep slip rates and locking depths, which we fully characterize using Monte Carlo techniques. We use Bayesian techniques to combine the GPS observations with constraints derived from other seismic, geodetic, and paleoseismic observations, such as locking depths, surface creep rates, and inferred geologic slip rates. These additional constraints significantly improve the estimates of the

  6. Long-Span Continuous Self-Potential Measurements Around Earthquake Swarms for Monitoring Crustal Activity

    NASA Astrophysics Data System (ADS)

    Yoshimura, R.; Oshiman, N.; Yamazaki, K.; Uyeshima, M.; Ogawa, T.

    2008-12-01

    Earthquake swarm activity has been continuously observed around the southeastern flank of Ontake stratovolcano since 1976. A large earthquake with the depth about 2 km and a magnitude of 6.8 occurred in 1984 in the southeastern flank of the volcano. Recently, Kimata et al. (2004) revealed uplift ground deformation above the earthquake swarm area by using repeated leveling. Furthermore, MagnetoTelluric (MT) soundings estimated a low resistivity region with the depth about 2km beneath the uplift area (Kasaya et al., 2002). In order to investigate a relationship between tectonic movements and subsurface low resistivity zone, Yoshimura et al. (2007) carried out self-potential (SP) measurements from 2003 to 2005 around the earthquake swarm areas. As the result of SP measurements, a torus-shape positive SP anomaly has been detected at the eastern part of the survey profile. This anomaly is located between recent active clusters of earthquakes and near the ground uplift detected by Kimata et al. (2004). Given that the obtained anomaly delineates the subsurface fluid"fs motion due to thermal or crustal activities, it could be expected that the anomaly varies in association with fluctuation of crustal activities. In February 2007, we established a continuous SP observation network with the aim of monitoring the crustal/hydrothermal activity by reference to the obtained SP distribution. This network consists of 8 Pb- PbCl2 electrodes and uses metallic telephone lines as insulated cables for measuring SP. Voltage differences between electrodes are measured at an interval of 1 sec. This observation technique, called "Network-MT", has been developed to determine large-scale electrical conductivity structure and the spatial distribution of the telluric potentials (Uyeshima, 2007). As a preliminary result of longitudinal data analysis, night time daily median values showed remarkable stepwise SP time variations with relaxation time about 15 days in August 2007. Additionally

  7. Secular crustal deformation and interplate coupling of the Japanese Islands as deduced from continuous GPS array, 1996 2001

    NASA Astrophysics Data System (ADS)

    El-Fiky, Gamal; Kato, Teruyuki

    2006-08-01

    Data from the nation-wide GPS continuous tracking network that has been operated by the Geographical Survey Institute of Japan since April 1996 were used to study crustal deformation in the Japanese Islands. We first extracted site coordinate from daily SINEX files for the period from April 1, 1996 to February 24, 2001. Since raw time series of station coordinates include coseismic and postseismic displacements as well as seasonal variation, we model each time series as a combination of linear and trigonometric functions and jumps for episodic events. Estimated velocities were converted into a kinematic reference frame [Heki, K., 1996. Horizontal and vertical crustal movements from three-dimensional very long baseline interferometry kinematic reference frame: implication for reversal timescale revision. J. Geophys. Res., 101: 3187-3198.] to discuss the crustal deformation relative to the stable interior of the Eurasian plate. A Least-Squares Prediction technique has been used to segregate the signal and noise in horizontal as well as vertical velocities. Estimated horizontal signals (horizontal displacement rates) were then differentiated in space to calculate principal components of strain. Dilatations, maximum shear strains, and principal axes of strain clearly portray tectonic environments of the Japanese Islands. On the other hand, the interseismic vertical deformation field of the Japanese islands is derived for the same GPS data interval. The GPS vertical velocities are combined with 31 year tide gage records to estimate absolute vertical velocity. The results of vertical deformation show that (1) the existence of clear uplift of about 6 mm/yr in Shikoku and Kii Peninsula, whereas pattern of subsidence is observed in the coast of Kyushu district. This might reflect strong coupling between the Philippine Sea plate and overriding plate at the Nankai Trough and weak coupling off Kyushu, (2) no clear vertical deformation pattern exists along the Pacific coast of

  8. Distance corrections for single- and dual-color lasers by ray tracing. [for earth crustal deformation and strain measurement

    NASA Technical Reports Server (NTRS)

    Berg, E.; Carter, J. A.

    1980-01-01

    The physical arc length difference between the red and blue beam of a dual-color laser generates an error term in determining Delta-n as well as n (the refractive index) and D (the line length). Numerical ray trace examples and theoretical approximations show that the resulting relative error Delta-D/D increases as D-squared. Error reduction by a factor of nearly 10 is possible by using the pressure, temperature, and humidity of both endpoints to calculate n. The present study results from a desire to improve the precision of monitoring the local and regional position of the Lunar Laser Ranging Observatory atop Haleakala, Maui, Hawaii; the monitoring of the earth's crustal deformation and strain is a primary concern of the study.

  9. Topographic growth around the Orange River valley, southern Africa: A Cenozoic record of crustal deformation and climatic change

    NASA Astrophysics Data System (ADS)

    Dauteuil, Olivier; Bessin, Paul; Guillocheau, François

    2015-03-01

    We reconstruct the history of topographic growth in southern Africa on both sides of the Orange River valley from an integrated analysis of erosion surfaces, crustal deformation and climate change. First, we propose an inventory of erosion surfaces observed in the study area and classify them according to their most likely formative process, i.e. chemical weathering or mechanical erosion. Among the various land units observed we define a new class of landform: the pedivalley, which corresponds to a wide valley with a flat erosional floor. In the Orange River valley, we mapped three low-relief erosion surfaces, each bevelling a variety of lithologies. The oldest and most elevated is (1) a stripped etchplain evolving laterally into (2) a stepped pediplain bearing residual inselbergs; (3) a younger pediplain later formed in response to a more recent event of crustal deformation. These are all Cenozoic landforms: the etchplain is associated with a late Palaeocene to middle Eocene weathering event, and the two pediplains are older than the middle Miocene alluvial terraces of the Orange River. Landscape evolution was first driven by slow uplift (10 m/Ma), followed by a second interval of uplift involving a cumulative magnitude of at least 200 m. This event shaped the transition between the two pediplains and modified the drainage pattern. A final phase of uplift (magnitude: 60 m) occurred after the Middle Miocene and drove the incision of the lower terraces of the Orange River. Climate exerted a major control over the denudation process, and involved very humid conditions responsible for lateritic weathering, followed by more arid conditions, which promoted the formation of pedivalleys. Collectively, these produce pediplains.

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1991-01-01

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

  11. InSAR time series analysis of crustal deformation in southern California from 1992-2010

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Lundgren, P.

    2010-12-01

    Since early the 1990’s, Interferometric Satellite Aperture Radar (InSAR) data has had some success imaging surface deformation of plate boundary deformation zones. The ~18 years of extensive data collection over southern California now make it possible to generate a long time interval InSAR-based line-of-sight (LOS) velocity map to examine the resolution of both steady-state and transient deformation processes. We perform InSAR time series analysis on an extensive catalog of ERS-1/2 and Envisat data from 1992 up to the present in southern California by applying a variant of the Small Baseline Subset (SBAS) time series analysis approach. Despite the limitation imposed by atmospheric phase delay, the large number of data acquisitions and long duration of data sampling allow us to effectively suppress the atmospheric noise through spatiotemporal smoothing in the time series analysis. We integrate an updated version of a California GPS velocity solution with InSAR to constrain the long wavelength deformation signals while estimating and removing the effect of orbital error. A large number of interferograms (> 800) over 5 tracks in southern California have been processed and analyzed. We examine the time dependency of resulting deformation patterns. Preliminary results from the ~18 year time series already reveal some interesting features. For example, the InSAR LOS displacements show significant transient variations in greater spatial resolution following the 1999 Mw7.1 Hector Mine earthquake. The 7-year post-seismic rate map demonstrates a broad transient deformation pattern and much localized deformation near the fault surface trace, reflecting a combined effect from afterslip, poroelastic, and viscoelastic relaxation at different spatiotemporal scales. We observe a variation of deformation rate across the Blackwater-Little lake fault system in the Eastern California Shear Zone, suggesting a possible transient variation over this part of the plate boundary. The In

  12. Review of crustal seismicity in the Aleutian Arc and implications for arc deformation

    NASA Astrophysics Data System (ADS)

    Ruppert, Natalia A.; Kozyreva, Natalia P.; Hansen, Roger A.

    2012-02-01

    Central and eastern Aleutian Arc is characterized by oblique convergence between the subducting Pacific and overriding Bering Plates. This results in westward arc translation and formation of rotating crustal blocks in the forearc. In 2006-2010 several moderate, shallow crustal earthquakes (up to magnitude 6.7) occurred in the region. These events are located about 150 km away from the trench, on the volcanic axis, and have either strike-slip (west of 174°W) or normal (east of 174°W) faulting mechanisms. We improve aftershock locations by applying precise relocation methods to aid in identifying preferred fault planes. We also review similar earthquakes that occurred prior to 2006. For the central Aleutian Arc we conclude that, while some of these events occurred along the boundaries of the rotating blocks, the majority are left-lateral strike-slip events on NW- to N-oriented fault planes in the unrotated Bering massif. These manifest Riedel shearing in response slip partitioning due to the oblique convergence. Normal faulting events in eastern Aleutian Arc reflect along-arc extension.

  13. Spatiotemporal model for crustal deformation around the focal area of the 2008 Iwate-Miyagi Inland Earthquake, northeastern Japan, estimated by GPS and InSAR

    NASA Astrophysics Data System (ADS)

    Ohzono, M.; McCaffrey, R.; Ohta, Y.; Miura, S.; Iinuma, T.; Tachibana, K.; Sato, T.

    2009-12-01

    Applying the program tDEFNODE [McCaffrey, GRL09] to model elastic lithospheric block rotations and strains, and locking or coseismic slip on block-bounding faults, we model GPS and InSAR data of crustal deformation before and after the 2008 M7.2 Iwate-Miyagi Inland Earthquake (IMEQ). The epicenter of the IMEQ is located in a high strain rate zone along the Ou Backbone Range (OBR) in northeastern Japan, where volcanic front runs subparallel to the Japan Trench. Along eastern and western margin of the OBR, major inland active faults have been growing. In order to clarify detailed strain field around these active faults, Japan Nuclear Energy Safety Organization (JNES) installed 7 new continuous GPS sites with ~5 km spacing across the Dedana Fault (DF), which is a part of the eastern marginal active faults, in October 2007. Because the DF is located at only ~20 km northeast from the hypocenter of the IMEQ, the detailed coseismic and postseismic crustal deformation was obtained at these GPS sites [Ohta et al., EPS08; Iinuma et al., GRL09]. Takada et al. [EPS09] also estimated coseismic faults from InSAR with pixel-offset method. These studies, however, handled each data independently. We unify both GPS and InSAR data to model crustal deformation over inter-, co-, and post-seismic period using tDEFNODE. This code interprets geodetic timeseries data by assuming elastic block rotation, transient phenomena such as slow slip, and coseismic slip, on the block boundary faults. We use timeseries data obtained by continuous GPS networks conducted by JNES, Tohoku University, Geographical Survey Institute (GSI), National Astronomical Observatory (NAO), and IGS from 2006 to June 2009, together with a temporal network for postseismic deformation installed by Japanese University Consortium for GPS Research (JUNCO). InSAR data is obtained by analyzing images of ALOS/PALSAR mission. We presumed three blocks in the study area divided by two boundary faults. We expressed the time

  14. Modeling crustal deformation and rupture processes related to upwelling of deep CO2-rich fluids during the 1965-1967 Matsushiro Earthquake Swarm in Japan

    SciTech Connect

    Cappa, F.; Rutqvist, J.; Yamamoto, K.

    2009-05-15

    In Matsushiro, central Japan, a series of more than 700,000 earthquakes occurred over a 2-year period (1965-1967) associated with a strike-slip faulting sequence. This swarm of earthquakes resulted in ground surface deformations, cracking of the topsoil, and enhanced spring-outflows with changes in chemical compositions as well as carbon dioxide (CO{sub 2}) degassing. Previous investigations of the Matsushiro earthquake swarm have suggested that migration of underground water and/or magma may have had a strong influence on the swarm activity. In this study, employing coupled multiphase flow and geomechanical modelling, we show that observed crustal deformations and seismicity can have been driven by upwelling of deep CO{sub 2}-rich fluids around the intersection of two fault zones - the regional East Nagano earthquake fault and the conjugate Matsushiro fault. We show that the observed spatial evolution of seismicity along the two faults and magnitudes surface uplift, are convincingly explained by a few MPa of pressurization from the upwelling fluid within the critically stressed crust - a crust under a strike-slip stress regime near the frictional strength limit. Our analysis indicates that the most important cause for triggering of seismicity during the Matsushiro swarm was the fluid pressurization with the associated reduction in effective stress and strength in fault segments that were initially near critically stressed for shear failure. Moreover, our analysis indicates that a two order of magnitude permeability enhancement in ruptured fault segments may be necessary to match the observed time evolution of surface uplift. We conclude that our hydromechanical modelling study of the Matsushiro earthquake swarm shows a clear connection between earthquake rupture, deformation, stress, and permeability changes, as well as large-scale fluid flow related to degassing of CO{sub 2} in the shallow seismogenic crust. Thus, our study provides further evidence of the

  15. Kinematic interpretation of present-day crustal deformation in central Greece from continuous GPS measurements

    NASA Astrophysics Data System (ADS)

    Chousianitis, Konstantinos; Ganas, Athanassios; Gianniou, Michail

    2013-11-01

    We processed 30-s GPS data from continuous GPS stations in central Greece using the Kalman filtering approach and accounting for time-correlated noise content obtaining a velocity field in the ITRF2008 and the Eurasian-fixed reference frame. The station distribution allowed us to compute 1D strain through rates of baseline length changes as well as to construct the image of the 2D strain and rotation rate fields. The obtained baselines range in length from 11 to 132 km and show rates from -1.95 mm/yr up to 14.14 mm/yr (estimated uncertainties from 0.3 to 0.8 mm/yr), while the calculated 1D strain rate ranges from -27 ns/yr up to 226 ns/yr (average uncertainty ˜15 ns/yr). Largest extension (192-226 ns/yr) is observed in the western and central part of the Corinth rift while similar extension rates (80-120 ns/yr) are obtained for the eastern part of the Corinth rift and its continuation in the south Viotia-south of Evia region and across the Sperchios-Kammena Vourla rift. The coherent picture of the velocity pattern for Attica and north-eastern Peloponnese (Corinth) stations indicates that these areas belong to the same crustal block, separating by the Viotia region by a nearly E-W crustal discontinuity along the Kaparelli-Asopos valley faults. However, some internal strain is present within Attica's crust as well as across the Saronic Gulf resulting in extension rates of the order of 25 ns/yr. We also find extension (54-71 ns/yr) across "rigid" Peloponnese taken by normal faults in the greater Kalavryta region.

  16. Tectonic Deformation Associated with the 1964 Alaska Earthquake: The earthquake of 27 March 1964 resulted in observable crustal deformation of unprecedented areal extent.

    PubMed

    Plafker, G

    1965-06-25

    Alaska's Good Friday earthquake of 27 March 1964 was accompanied by vertical tectonic deformation over an area of 170,000 to 200,000 square kilometers in south-central Alaska. The deformation included two major northeast-trending zones of uplift and subsidence situated between the Aleutian Trench and the Aleutian Volcanic Arc; together they are 700 to 800 kilometers long and from 150 to 250 kilometers wide. The seaward zone is one in which uplift of as much as 10 meters on land and 15 meters on the sea floor has occurred as a result of both crustal warping and local faulting. Submarine uplift within this zone generated a train of seismic sea waves with half-wave amplitudes of more than 7 meters along the coast near the source. The adjacent zone to the northwest is one of subsidence that averages about 1 meter and attains a measured maximum of 2.3 meters. A second zone of slight uplift may exist along all or part of the Aleutian and Alaska ranges northwest of the zone of subsidence. PMID:17819412

  17. Inversion for sources of crustal deformation and gravity change at the Yellowstone caldera

    SciTech Connect

    Vasco, D.W.; Taylor, C.L. ); Smith, R.B. )

    1990-11-10

    The Yellowstone caldera was formed in the latest of three explosive eruptions of rhyolites and ash flow tuffs totaling 3,700 km{sup 3} at 2, 1.2, and 0.6 m.y. before present. Its youthful volcanic history, widespread hydrothermal activity, intense seismicity, and extremely high heat flow, in excess of 30 times the continental average, marks the Yellowstone volcanic system as a giant caldera at unrest. Orthometric height increases of the caldera of up to 76 cm, measured from precise leveling surveys from 1923 to 1975-1977, were inverted to determine volume expansion source models for the caldera-wide deformation. For the 1923 to 1977 uplift episode, two regions of expansion were found: (1) in the northern part of the caldera near the Sour Creek resurgent dome of {approximately}0.37 km{sub 3}, and (2) in the southern part of the caldera, near the Mallard Lake resurgent dome of {approximately}0.41 km{sub 3}. Both bodies occur in the upper crust from near-surface depths to 6.0 km, but the largest volume expansions were found in the 3.0-6.0 km depth range. The southern caldera source volume, near the Mallard Lake dome, may extend down to 9.0 km. From 1976 to 1987, nearly simultaneous measurements of elevation and gravity changes were made on a profile across the northern caldera during a period of net uplift. Models of the temporal gravity variation infer that the volume increase for the northern caldera source must lie above 9.0 km and involved a density perturbation greater than +0.002 g/cm{sup 3}. The modeled volumetric sources are in the same general locations as bodies of low P wave velocities, high seismic attenuation, and large negative Bouguer gravity anomalies. It is likely that the modeled volumetric increases were caused by migration of magmas and/or the introduction of large volumes of hydrothermal fluids into the upper crust.

  18. The observation of crustal deformation derived from Taiwan Continuous GPS Array (2007-2013)

    NASA Astrophysics Data System (ADS)

    Min-Chien, Tsai; Shui-Beih, Yu; Tzay-Chyn, Shin

    2015-04-01

    Data collected by 281 sites of Taiwan Continuous GPS Array from 2007 to 2013 are processed with GAMIT/GLOBK software. The acquired GPS position time series are described by model parameters such as linear rate, annual and semi-annual periodic motions, coseismic offsets, postseismic rate change, and exponential decay after earthquakes. Stacking of power spectral densities from 281 continuous GPS data in Taiwan, we found the slopes of spectra (spectral index) are -0.72, -0.77, and -0.57 for the E, N, U components, respectively. It indicates the errors of continuous GPS data can be described as a combination of white noise and flicker noise. The common-mode errors are removed by stacking data from 50 continuous GPS sites with data period more than 5 years. By removing common-mode errors, the precision of GPS data is further improved to 2.3 mm, 1.9 mm, and 6.9 mm in the E, N, U components, respectively. After strictly data quality control, time series analysis and noise analysis, we derive a new ITRF2008 velocity field and velocity field relative to Penghu using GPS data from 2007 to 2013 in the Taiwan area. The general pattern of the newly derived 2007-2013 velocity field is quite similar with that from previous studies, but the station density is much larger and spatial coverage is better, too. About 80 mm/yr plate convergence rate is observed, approximately half of plate convergence rate is accommodated on the fold and thrust belt of western Taiwan and another half is taken up in the Longitudinal Valley and the Coastal Range in eastern Taiwan. The velocities in western Taiwan generally show a fan-shaped pattern, consistent with the direction of maximum compression tectonic stress. In northern Taiwan, the velocity vectors reveal clockwise rotation, indicating the on-going extensional deformation related to the back-arc extension of the Okinawa Trough. In southern Taiwan, the horizontal velocity increases from about 40 mm/yr at Chiayi-Tainan to 55 mm/yr in the

  19. Crustal composition in southern Norway from active and passive source seismology

    NASA Astrophysics Data System (ADS)

    Stratford, W. R.; Frassetto, A. M.; Thybo, H.

    2010-12-01

    Crustal composition and structure beneath the Fennoscandian shield are highly variable due to the method of crustal accretion and the long history of extensional and compressional tectonics. In southern Norway, the Moho and crust are inferred to be the youngest of the shield, however, it is likely that a large discrepancy between crustal age and Moho age exists beneath the high southern Scandes where the Caledonian orogeny was in effect and beneath the Oslo Graben where 60 million years of rifting and magmatism has altered the crust. Crustal structure in southern Norway was targeted with a multi-disciplinary seismic study (Magnus-Rex - Mantle investigations of Norwegian uplift Structure). Three ~400 km long active source seismic profiles across the southern Norway and a region wide array of broadband seismometers were deployed. P and S-wave arrivals were recorded in the Magnus-Rex project, from which Poisson ratios for the crust in southern Norway are calculated from both active source profiling and receiver functions. Unusually strong S-wave arrivals allow rare insight into crustal Poisson’s ratio structure, within crustal layers, that is not normally available from active source data and are usually determined by earthquake tomography studies where only bulk crustal values are available. An average Poisson’s ratio of 0.25 is calculated for the crust in southern Norway, suggesting it is predominantly of felsic-intermediate composition and lacks any significant mafic lower crust. This differs significantly from the adjacent crust in the Svecofennian domain of the Fennoscandian shield where Moho depths reach ~50 km and an up to 20 km thick mafic lower crust is present. The vast difference in Moho depths in the Fennoscandian shield are, therefore, mostly due to the variation in thickness of the high Vp lower crust. Estimates of crustal composition and the effect of Magma intrusion within the Oslo Graben, and possible delamination of the lowermost crust beneath

  20. Alaska Crustal Deformation: Finite Element Modeling Constrained by Geologic and Very Long Baseline Interferometry Data

    NASA Technical Reports Server (NTRS)

    Lundgren, Paul; Saucier, Fraancois; Palmer, Randy; Langon, Marc

    1995-01-01

    We compute crustal motions in Alaska by calculating the finite element solution for an elastic spherical shell problem. The method we use allows the finite element mesh to include faults and very long baseline interferometry (VLBI) baseline rates of change. Boundary conditions include Pacific-North American (PA-NA) plate motions. The solution is constrained by the oblique orientation of the Fairweather-Queen Charlotte strike-slip faults relative to the PA-NA relative motion direction and the oblique orientation from normal convergence of the eastern Aleutian trench fault systems, as well as strike-shp motion along the Denali and Totschunda fault systems. We explore the effects that a range of fault slip constraints and weighting of VLBI rates of change has on the solution. This allows us to test the motion on faults, such as the Denali fault, where there are conflicting reports on its present-day slip rate. We find a pattern of displacements which produce fault motions generally consistent with geologic observations. The motion of the continuum has the general pattern of radial movement of crust to the NE away from the Fairweather-Queen Charlotte fault systems in SE Alaska and Canada. This pattern of crustal motion is absorbed across the Mackenzie Mountains in NW Canada, with strike-slip motion constrained along the Denali and Tintina fault systems. In south central Alaska and the Alaska forearc oblique convergence at the eastern Aleutian trench and the strike-shp motion of the Denali fault system produce a counterclockwise pattern of motion which is partially absorbed along the Contact and related fault systems in southern Alaska and is partially extruded into the Bering Sea and into the forearc parallel the Aleutian trench from the Alaska Peninsula westward. Rates of motion and fault slip are small in western and northern Alaska, but the motions we compute are consistent with the senses of strike-slip motion inferred geologically along the Kaltag, Kobuk Trench

  1. Crustal deformation due to fluid extraction and re-injection in the Hengill geothermal area in Southwest Iceland

    NASA Astrophysics Data System (ADS)

    Juncu, D.; Arnadottir, T.; Budzińska, K.; Hooper, A. J.

    2014-12-01

    doing so, we hope to learn more about parameters that we don't have a priori knowledge about, e.g. hydraulic conductivity and elastic properties of the crust. Furthermore, we hope to gain a better understanding of what are the key mechanisms that drive crustal deformation in areas of geothermal energy production.

  2. The Effect of Horizontal Advection of Topography and Time Dependent Crustal Deformation on Tsunami Generation

    NASA Astrophysics Data System (ADS)

    Barak, S.; Beroza, G. C.

    2013-12-01

    Initial conditions used in tsunami modeling are commonly simplified due to lack of observations, poor understanding of the mechanics of tsunami generation, and limitations on computational power and processing time. First, since the time-varying deformation of the seafloor has a negligible effect far from the source, often, only the static, or the residual deformation is used to excite the tsunami model. However, when the earthquake occurs close to the coast, the dynamic displacement of the seafloor might have a significant effect on coastal wave height and arrival time. Second, it is common to use only the vertical component of the seafloor displacement, while neglecting the horizontal co-seismic displacements in the absence of landslides. While this assumption is valid for a flat or shallowly-dipping seafloor, it has been shown that in certain conditions, such as the combination of a shallow-dipping thrust fault with relatively steep topography, the contribution of the horizontal displacement is significant and might help explain discrepancies in wave height predictions. In this study we are using the abundant observations recorded during the 2011 Tohoku-Oki earthquake and tsunami to study the effects of time-varying deformation and the contribution of horizontal seafloor displacement on tsunami generation. We use SPECFEM3D, a spectral element numerical code, to solve the elasto-dynamic problem including wave propagation and the residual static deformation, to determine the time-dependent seafloor deformation. To simulate the earthquake we use a kinematic rupture model, in which the fault slip (magnitude and direction) is determined at each point in space and time for the assumed fault geometry. In order to test the contribution of topography we run the simulation with and without the surface topography and compare the results. In addition, we compare our results to real observations, where they are available, to validate of our model. Finally, our next step will

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  4. Delineating Crustal Deformation by Onshore/Offshore Seismic Experiments in the Backstop Region of the Mediterranean Ridge

    NASA Astrophysics Data System (ADS)

    Papoulia, J. E.; Makris, J.

    2009-12-01

    Preapulian zone was observed under all five seismic lines and seems to dominate at least at the western part of the Backstop. Since the metamorphic limestone of the Ionian zone was not observed west of the three major thrusts, we have concluded that all the northern part of the backstop region is part of Preapulia. Tectonically, the main elements are thrusts that are still active and are marked by high seismicity and dextral strike slip faults. The main one, called the “Andravida fault” was followed deep into the Ionian Sea, building a large transtensional basin in the Kyparissiakos gulf. The Andravida fault system is of the same orientation as the Cephalonia fault, accommodating the expansion of the Aegean Microplate to the west. It is also marked by significant seismicity. Several normal faults were also mapped, usually associated with the thrust systems. Since most of the faults can be followed to the sea bottom, deforming also the most recent sediments, and are associated with high seismicity, we concluded that the recent tectonisation is very active and prone to seismic hazard.

  5. The BIFROST project: 21 years of search for the true crustal deformation in Fennoscandia

    NASA Astrophysics Data System (ADS)

    Johansson, Jan; Kierulf, Halfdan; Kristiansen, Oddgeir; Lidberg, Martin; Steffen, Holger

    2015-04-01

    in activities like BIFROST are issues regarding reference frames, which are especially important while searching for true vertical velocities, as well as long-term stability in the observation system including new generation of satellites and changes in the ground seg-ment. These issues will also be discussed in the presentation. References Johansson, J.M., Davis, J.L., Scherneck, H.-G., Milne, G.A., Vermeer, M., Mitrovica, J.X., Bennett, R.A., Jonsson, B., Elgered, G., Elósegui, P., Koivula, H., Poutanen, M., Rönnäng, B.O., Shapiro, I.I., 2002. Continuous GPS measurements of postglacial adjustment in Fen-noscandia 1. Geodetic results. J. Geophys. Res. 107 (B8), doi:10.1029/2001B000400. Lidberg, M., J.M. Johansson, H.-G. Scherneck, and G.A. Milne. 2010. Recent results based on continuous GPS observations of the GIA process in Fennoscandia from BIFROST. J. Geodyn. 50: 8-18. Milne, G.A., Mitrovica, J.X., Scherneck, H.-G., Davis, J.L., Johansson, J.M., Koivula, H., Vermeer, M., 2004. Continuous GPS measurements of postglacial adjustment in Fennoscandia. 2. Model-ing results. J. Geophys. Res. 109, B02412, doi:10.1029/2003JB002619. Scherneck, H.-G., Johansson, J.M., Elgered, G., Davis, J.L., Jonsson, B., Hedling, G., Koivula, H., Ollikainen, M., Poutanen, M., Vermeer, M.,Mitrovica, J.X., Milne, G.A., 2002. BIFROST: observ-ing the three-dimensional deformation of Fennoscandia. In: Ice Sheets, Sea Level and the Dy-namic Earth; Geodynamic Series 29. American Geophysical Union.

  6. Impact of lithosphere rheology and pre-existing tectonic stress field on surface topography, crustal and mantle deformation during plume-lithosphere interactions in continents: insights from 3D numerical experiments

    NASA Astrophysics Data System (ADS)

    Koptev, Alexander; Burov, Evgueni; Gerya, Taras

    2014-05-01

    We implement high-resolution 3D thermo-mechanical numerical models to elucidate the impact of realistically implemented rheological structure of continental lithosphere and of far-field tectonic stress/strain field on the localization and style of deformation during the emplacement of a mantle plume at the bottom of continental lithosphere. Numerical models demonstrate strong dependence of crustal strain distributions and surface topography on the rheological composition of the lower crust and the initial thermal structure of the lithosphere. In contrast to the usual inferences from passive rifting models, distributed wide rifting takes place in case of cold (500° C at Moho depth) initial isotherm and mafic composition of the lower crust, whereas hotter geotherms and weaker (wet quartzite) lower crustal rheology lead to strong localization of rifting. Moreover, it appears that the prerequisite of strongly anisotropic strain localization (linear rift structures) refers to simultaneous presence of an active mantle plume and of some, even very weak, slow (< 3 mm/y) passive horizontal extension produced by far-field tectonic forces. Higher (than 1.5-3 mm/y) velocities of supplementary far-field extension expectedly lead to enlargement of the active fault zone for the same lapse of time. Yet, simultaneous rise of the lithospheric geotherm associated with active rifting has an opposite effect leading to the narrowing of the rift zone. Consequently, interplays between active and passive rifting result in highly varying rifts styles hence breaking common rift-style classifications. The importance of the rheological properties of the continental crust for deformation regime is demonstrated not only by considerable difference in surface morphology and crustal strain patterns between the models with different lower crustal rheology, but also by a noticeable distinction in deep distribution of the plume head material, with consequent effect for magmatic processes and mantle

  7. Upper plate deformation, magmatism and mineralization illuminating crustal and mantle dynamics in the eastern Mediterranean region: kinematic reconstructions and numerical models

    NASA Astrophysics Data System (ADS)

    Menant, Armel; Jolivet, Laurent; Sternai, Pietro; Guillou-Frottier, Laurent; Gerya, Taras

    2015-04-01

    , besides the general southward migration of this magmatic-hydrothermal activity since the late Cretaceous, a secondary westward migration is observed during the Miocene from the Menderes massif to the Cyclades. This feature is a possible consequence of a slab tearing event and related asthenospheric flow, as suggested notably by tomographic models below western Anatolia. Using 3D high-resolution thermo-mechanical numerical models, we test the effects of slab retreat and tearing on asthenospheric flow and its consequences on crustal deformation and magmatic activity. Results suggest that this asthenospheric flow partly controls both the crustal deformation in hot regions (such as in the back-arc domain) and the lateral migration of partially molten materials stored at the base of the stretched crust.

  8. Detection of crustal deformation from the Landers earthquake sequence using continuous geodetic measurements

    NASA Technical Reports Server (NTRS)

    Bock, Yehuda; Agnew, Duncan C.; Fang, Peng; Genrich, Joachim F.; Hager, Bradford H.; Herring, Thomas A.; Hudnut, Kenneth W.; King, Robert W.; Larsen, Shawn; Minster, J.-B.

    1993-01-01

    The first measurements are reported for a major earthquake by a continuously operating GPS network, the permanent GPS Genetic ARRY (PGGA) in southern California. The Landers and Big Bear earthquakes of June 28, 1992 were monitored by daily observations. Ten weeks of measurements indicate significant coseismic motion at all PGGA sites, significant postseismic motion at one site for two weeks after the earthquakes, and no significant preseismic motion. These measurements demonstrate the potential of GPS monitoring for precise detection of precursory and aftershock seismic deformation in the near and far field.

  9. Utilization of temperature and pressure simulator for ocean-bottom and bore-hole observatories for quantitative crustal deformation

    NASA Astrophysics Data System (ADS)

    Machida, Y.; Matsumoto, H.; Araki, E.; Kimura, T.; Nishida, S.; Kawaguchi, K.

    2015-12-01

    JAMSTEC has developed temperature and pressure simulator for ocean-bottom and bore-hole observatories in 2010, which is mainly composed of temperature chamber and hydraulic pressure standard. We call this equipment "environment simulator". Temperature chamber is capable to control its target temperature from -10 to 180 ℃, hence it is supposed for ocean-bottom to bore-hole environment. Pressure standard in which the dead weight is mounded on the piston-cylinder module produces the reference pressure up to 100 MPa (ca. 10,000 meters deep), which makes it possible to apply the constant pressure to the pressure sensors via the hydraulic pressure tube. Thus, our environment simulator can demonstrate ocean-bottom or bore-hole environment in the laboratory. The main purpose of the pressure simulator is to evaluate long-term pressure sensor's stability, i.e., sensor's drift by applying the constant pressure under the constant temperature. Here, we introduce two applications of our environment simulator. The first application is to evaluate the initial behavior of pressure sensors to be used in the Dense Ocean-floor Network system for Earthquakes and Tsunamis (DONET) in the Nankai Trough, Japan. DONET pressure sensors have been deployed in order for detection of not only tsunami but also crustal deformation. We applied 20 MPa pressure under 2 ℃ temperature to the pressure sensors for one month before deploying into the deep-sea. As a result, the initial sensor drift of 5 hPa per month in maximum was measured. The second application is to provide the reference pressure to the mobile pressure sensor which is designed for the in-situ calibration for the pressure sensors being in operation. We have developed the in-situ pressure calibration tool equipped with the high precision pressure sensor. The concept is that we carry the reference pressure to the on-site to calibrate the pressure sensor. Before carrying it to the deep-sea, the reference pressure is given to the mobile

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  11. Deep crustal deformation by sheath folding in the Adirondack Mountains, USA

    NASA Astrophysics Data System (ADS)

    McLelland, J. M.

    As described by McLelland and Isachsen, the southern half of the Adirondacks are underlain by major isoclinal (F sub 1) and open-upright (F sub 2) folds whose axes are parallel, trend approximately E-W, and plunge gently about the horizontal. These large structures are themselves folded by open upright folds trending NNE (F sub 3). It is pointed out that elongation lineations in these rocks are parallel to X of the finite strain ellipsoid developed during progressive rotational strain. The parallelism between F sub 1 and F sub 2 fold axes and elongation lineations led to the hypothesis that progressive rotational strain, with a west-directed tectonic transport, rotated earlier F sub 1-folds into parallelism with the evolving elongation lineation. Rotation is accomplished by ductile, passive flow of F sub 1-axes into extremely arcuate, E-W hinges. In order to test these hypotheses a number of large folds were mapped in the eastern Adirondacks. Other evidence supporting the existence of sheath folds in the Adirondacks is the presence, on a map scale, of synforms whose limbs pass through the vertical and into antiforms. This type of outcrop pattern is best explained by intersecting a horizontal plane with the double curvature of sheath folds. It is proposed that sheath folding is a common response of hot, ductile rocks to rotational strain at deep crustal levels. The recognition of sheath folds in the Adirondacks reconciles the E-W orientation of fold axes with an E-W elongation lineation.

  12. Deep crustal deformation by sheath folding in the Adirondack Mountains, USA

    NASA Technical Reports Server (NTRS)

    Mclelland, J. M.

    1988-01-01

    As described by McLelland and Isachsen, the southern half of the Adirondacks are underlain by major isoclinal (F sub 1) and open-upright (F sub 2) folds whose axes are parallel, trend approximately E-W, and plunge gently about the horizontal. These large structures are themselves folded by open upright folds trending NNE (F sub 3). It is pointed out that elongation lineations in these rocks are parallel to X of the finite strain ellipsoid developed during progressive rotational strain. The parallelism between F sub 1 and F sub 2 fold axes and elongation lineations led to the hypothesis that progressive rotational strain, with a west-directed tectonic transport, rotated earlier F sub 1-folds into parallelism with the evolving elongation lineation. Rotation is accomplished by ductile, passive flow of F sub 1-axes into extremely arcuate, E-W hinges. In order to test these hypotheses a number of large folds were mapped in the eastern Adirondacks. Other evidence supporting the existence of sheath folds in the Adirondacks is the presence, on a map scale, of synforms whose limbs pass through the vertical and into antiforms. This type of outcrop pattern is best explained by intersecting a horizontal plane with the double curvature of sheath folds. It is proposed that sheath folding is a common response of hot, ductile rocks to rotational strain at deep crustal levels. The recognition of sheath folds in the Adirondacks reconciles the E-W orientation of fold axes with an E-W elongation lineation.

  13. Crustal deformation in the New Madrid seismic zone and the role of postseismic processes

    USGS Publications Warehouse

    Boyd, Oliver; Robert Smalley, Jr; Zeng, Yuehua

    2015-01-01

    Global Navigation Satellite System data across the New Madrid seismic zone (NMSZ) in the central United States over the period from 2000 through 2014 are analyzed and modeled with several deformation mechanisms including the following: (1) creep on subsurface dislocations, (2) postseismic frictional afterslip and viscoelastic relaxation from the 1811–1812 and 1450 earthquakes in the NMSZ, and (3) regional strain. In agreement with previous studies, a dislocation creeping at about 4 mm/yr between 12 and 20 km depth along the downdip extension of the Reelfoot fault reproduces the observations well. We find that a dynamic model of postseismic frictional afterslip from the 1450 and February 1812 Reelfoot fault events can explain this creep. Kinematic and dynamic models involving the Cottonwood Grove fault provide minimal predictive power. This is likely due to the smaller size of the December 1811 event on the Cottonwood Grove fault and a distribution of stations better suited to constrain localized strain across the Reelfoot fault. Regional compressive strain across the NMSZ is found to be less than 3 × 10−9/yr. If much of the present-day surface deformation results from afterslip, it is likely that many of the earthquakes we see today in the NMSZ are aftershocks from the 1811–1812 New Madrid earthquakes. Despite this conclusion, our results are consistent with observations and models of intraplate earthquake clustering. Given this and the recent paleoseismic history of the region, we suggest that seismic hazard is likely to remain significant.

  14. Deformation history of a subducted continental crust (Gran Paradiso, Western Alps): continuing crustal shortening during exhumation

    NASA Astrophysics Data System (ADS)

    Le Bayon, Benjamin; Ballèvre, Michel

    2006-05-01

    Eclogite-facies continental basement in the Western Alps outcrops as tectonic windows below the oceanic units. In the Gran Paradiso massif, eclogite-facies assemblages in mafic rocks display a N-S stretching lineation (D A1). The main-phase foliation formed under epidote amphibolite-facies conditions (D A2) and defines a regional dome structure for the whole Gran Paradiso massif. Structural data, including new detailed mapping, microstructural analyses and metamorphic studies in the northern part of the Gran Paradiso (Cogne valley) reveal the occurrence of major thrusts in this continental basement associated with the D A2 deformation. E-W-trending stretching lineations and fold axes are associated with this second and main deformation. Nappe stacking of the different units was achieved by top-to-the-west shearing during exhumation of the eclogite-facies basement. The antiformal doming of the Gran Paradiso basement is thus produced by the nappe stacking during exhumation, under epidote amphibolite facies.

  15. Crustal deformation at long Valley Caldera, eastern California, 1992-1996 inferred from satellite radar interferometry

    USGS Publications Warehouse

    Thatcher, W.; Massonnet, D.

    1997-01-01

    Satellite radar interferometric images of Long Valley caldera show a pattern of surface deformation that resembles that expected from analysis of an extensive suite of ground-based geodetic data. Images from 2 and 4 year intervals respectively, are consistent with uniform movement rates determined from leveling surveys. Synthetic interferograms generated from ellipsoidal-inclusion source models based on inversion of the ground-based data show generally good agreement with the observed images. Two interferograms show evidence for a magmatic source southwest of the caldera in a region not covered by ground measurements. Poorer image quality in the 4 year interferogram indicates that temporal decorrelation of surface radar reflectors is progressively degrading the fringe pattern in the Long Valley region. Copyright 1997 by the American Geophysical Union.

  16. Deep seismic structure and tectonics of northern Alaska: Crustal-scale duplexing with deformation extending into the upper mantle

    USGS Publications Warehouse

    Fuis, G.S.; Murphy, J.M.; Lutter, W.J.; Moore, T.E.; Bird, K.J.; Christensen, N.I.

    1997-01-01

    Seismic reflection and refraction and laboratory velocity data collected along a transect of northern Alaska (including the east edge of the Koyukuk basin, the Brooks Range, and the North Slope) yield a composite picture of the crustal and upper mantle structure of this Mesozoic and Cenozoic compressional orogen. The following observations are made: (1) Northern Alaska is underlain by nested tectonic wedges, most with northward vergence (i.e., with their tips pointed north). (2) High reflectivity throughout the crust above a basal decollement, which deepens southward from about 10 km depth beneath the northern front of the Brooks Range to about 30 km depth beneath the southern Brooks Range, is interpreted as structural complexity due to the presence of these tectonic wedges, or duplexes. (3) Low reflectivity throughout the crust below the decollement is interpreted as minimal deformation, which appears to involve chiefly bending of a relatively rigid plate consisting of the parautochthonous North Slope crust and a 10- to 15-km-thick section of mantle material. (4) This plate is interpreted as a southward verging tectonic wedge, with its tip in the lower crust or at the Moho beneath the southern Brooks Range. In this interpretation the middle and upper crust, or all of the crust, is detached in the southern Brooks Range by the tectonic wedge, or indentor: as a result, crust is uplifted and deformed above the wedge, and mantle is depressed and underthrust beneath this wedge. (5) Underthrusting has juxtaposed mantle of two different origins (and seismic velocities), giving rise to a prominent sub-Moho reflector. Copyright 1997 by the American Geophysical Union.

  17. Southern California Permanent GPS Geodetic Array: Continuous measurements of regional crustal deformation between the 1992 Landers and 1994 Northridge earthquakes

    USGS Publications Warehouse

    Bock, Y.; Wdowinski, S.; Fang, P.; Zhang, Jiahua; Williams, S.; Johnson, H.; Behr, J.; Genrich, J.; Dean, J.; Van Domselaar, M.; Agnew, D.; Wyatt, F.; Stark, K.; Oral, B.; Hudnut, K.; King, R.; Herring, T.; Dinardo, S.; Young, W.; Jackson, D.; Gurtner, W.

    1997-01-01

    The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific-North America plate boundary to continuously monitor crustal deformation. We describe the development of the array and the time series of daily positions estimated for its first 10 sites in the 19-month period between the June 28, 1992 (Mw=7.3), Landers and January 17, 1994 (Mw=6.7), Northridge earthquakes. We compare displacement rates at four site locations with those reported by Feigl et al. [1993], which were derived from an independent set of Global Positioning System (GPS) and very long baseline interferometry (VLBI) measurements collected over nearly a decade prior to the Landers earthquake. The velocity differences for three sites 65-100 km from the earthquake's epicenter are of order of 3-5 mm/yr and are systematically coupled with the corresponding directions of coseismic displacement. The fourth site, 300 km from the epicenter, shows no significant velocity difference. These observations suggest large-scale postseismic deformation with a relaxation time of at least 800 days. The statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets; two possible noise models fit the PGGA data equally well as described in the companion paper by Zhang et al. [this issue]; the pre-Landers data are too sparse and heterogeneous to derive a reliable noise model. Under a fractal white noise model for the PGGA data we find that the velocity differences for all three sites are statistically different at the 99% significance level. A white noise plus flicker noise model results in significance levels of only 94%, 43%, and 88%. Additional investigations of the pre-Landers data, and analysis of longer spans of PGGA data, could have an important effect on the significance of these results and will be addressed in future work. Copyright 1997 by the American Geophysical Union.

  18. Crustal deformation in the Western Solomon Islands revealed by GPS observation and D_InSAR during 2009 - 2013

    NASA Astrophysics Data System (ADS)

    Kuo, Y. T.; Ku, C. S.; Wang, Y.; Lin, Y. N. N. N.; Chen, Y. G.; Lin, K. C.; Huang, B. S.; Hsu, Y. J.; Taylor, F. W.

    2014-12-01

    The Solomon Islands are located in the southwestern Pacific, where the Australian Plate underthrusts the Solomon Plate towards ~N70 E at a rate of ~100 mm/yr. The Coleman seamount on the Australian plate is impinging on the forearc at Rendova Island and may cause both the seismicity and tectonic behavior to be more complicated than usual. Hence, an understanding o f the ongoing crustal deformation is essential to reconstructing the structural framework that controls the entire subduction system, particularly earthquake generation on the megathrust fault and possible subsidiary faults. Based on the results from GPS and D_InSAR, the horizontal velocity profiles across the trench for areas of the forearc to the west and to the east of the impinging Coleman seamount show different characteristics. The eastern profile shows convergence rates of ~100 mm/yr only 10 km from the trench at the western end of the Tetepare Island, and the western profile reaches 70 mm/yr at 30 km from the trench. This difference might be caused by the shallow locked depth consistent with co-seismic slip located extremely close to the trench during the Mw 7.1 Solomon Earthquake on 3rd January, 2010. We have a hypothesis to argue that the behavior of the fault geometry should be very different on the two sides of the seamount. However, the coupling ratio could be realized by further detailed analysis.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  20. Differential GPS measurements as a tool to quantify Late Cenozoic crustal deformation (Oman, Arabian Peninsula)

    NASA Astrophysics Data System (ADS)

    Rupprechter, M.; Roepert, A.; Hoffmann, G.

    2012-04-01

    The Sultanate of Oman is situated in the north-eastern part of the Arabian Plate. It therefore represents the leading edge as the plate is drifting north relative to the Eurasian Plate. The movement results in continent-continent collision in the northwest (Zagros fold and thrust belt) and ocean-continent collision in the northeast (Makran subduction zone). We follow the hypothesis that this plate tectonic setting results in an internal deformation of the Arabian Plate. The study presented here is part of a larger project that aims at quantifying the forcing factors of coastal evolution (Hoffmann et al. 2012). The sea level development, climate - and associated rates of weathering and sediment supply - and differential land movement (neotectonics) are identified as key factors during the Late Cenozoic. Recent vertical land movement is obvious and expressed in differences of the coastal morphology. Parts of the coastline are subsiding: these areas show drowned wadi mouths. Other parts are characterised by a straightened coastline and raised wave-cut terraces are evident well above present mean sea-level. Despite these erosional terraces, depositional terraces on alluvial fans are also encountered in close vicinity to the mountain chain. Detailed topographic profile measurements are carried out using a LEICA Viva GNSS-GS15 differential GPS. The instrument yields data with an accuracy of 1-2 cm relatively to the base station. The profile measurements are orientated perpendicular to the coastline and therefore perpendicular to the raised wave-cut terraces. Up to 6 terraces are encountered in elevations up to 400 m above present sea level with the older ones being the highest. The data allow calculating the scarp height, tread length and tread angle of the terraces. The results indicate that the terraces show an increased seaward tilting with age. This observation is interpreted as reflecting ongoing uplift. A coast-parallel deformation pattern becomes obvious when

  1. Observing crustal deformation and atmospheric signals from COSMO-SKYMED and GPS data

    NASA Astrophysics Data System (ADS)

    Zerbini, S.; Prati, C.; Cappello, G.; Errico, M.; Novali, F.

    2012-04-01

    The combined use of InSAR and GPS allows for the full exploitation of the complementary aspects of the two techniques by overcoming the limitations inherent in the use of each technique alone. Additionally, GPS-based estimates of tropospheric delays may contribute in obtaining better corrections of the wet tropospheric path delay in InSAR signals. This will enhance the coherence and will allow the application of InSAR in a wider range of applications. We have compared the InSAR and GPS data at Bologna (urbanized area) and Medicina (agricultural area), in northeastern Italy, where two permanent GPS stations of the University of Bologna are operational since mid 1999 and 1996 respectively. The InSAR data used are the COSMO-SkyMed (CSK) images made available by the Italian Space Agency (ASI) in the framework of the research contract AO-1140. The Permanent Scatterers (PS) technique was applied to a number of repeated CSK strip map SAR images acquired over a 40x40 square km area encompassing the two towns mentioned above. The results of this work demonstrate on the one hand the CSK capabilities to operate in a repeated interferometric survey mode for measuring ground deformation with millimeter accuracy in different environments. On the other, the comparison of the differential height between the two stations derived with the GPS and the InSAR data, using both acquisition geometries, is satisfactory. Elevation, ground deformation and atmospheric artifacts were estimated in correspondence of the identified PS and compared with the GPS measurements carried out at the same acquisition time by the permanent stations at Bologna and Medicina. The comparison of the differential height between the two stations shows the sensitivity of the GPS height solution to the length of the observation interval. The vertical dispersion achieved by GPS is higher than that achieved by PS InSAR, as expected; however, a similar linear trend appears in the results of both techniques. The

  2. Microbial life in cold, hydrologically active oceanic crustal fluids

    NASA Astrophysics Data System (ADS)

    Meyer, J. L.; Jaekel, U.; Girguis, P. R.; Glazer, B. T.; Huber, J. A.

    2012-12-01

    It is estimated that at least half of Earth's microbial biomass is found in the deep subsurface, yet very little is known about the diversity and functional roles of these microbial communities due to the limited accessibility of subseafloor samples. Ocean crustal fluids, which may have a profound impact on global nutrient cycles given the large volumes of water moving through the crustal aquifer, are particularly difficult to sample. Access to uncontaminated ocean crustal fluids is possible with CORK (Circulation Obviation Retrofit Kit) observatories, installed through the Integrated Ocean Drilling Program (IODP). Here we present the first microbiological characterization of the formation fluids from cold, oxygenated igneous crust at North Pond on the western flank of the Mid Atlantic Ridge. Fluids were collected from two CORKs installed at IODP boreholes 1382A and 1383C and include fluids from three different depth horizons within oceanic crust. Collection of borehole fluids was monitored in situ using an oxygen optode and solid-state voltammetric electrodes. In addition, discrete samples were analyzed on deck using a comparable lab-based system as well as a membrane-inlet mass spectrometer to quantify all dissolved volatiles up to 200 daltons. The instruments were operated in parallel and both in situ and shipboard geochemical measurements point to a highly oxidized fluid, revealing an apparent slight depletion of oxygen in subsurface fluids (~215μM) relative to bottom seawater (~245μM). We were unable to detect reduced hydrocarbons, e.g. methane. Cell counts indicated the presence of roughly 2 x 10^4 cells per ml in all fluid samples, and DNA was extracted and amplified for the identification of both bacterial and archaeal community members. The utilization of ammonia, nitrate, dissolved inorganic carbon, and acetate was measured using stable isotopes, and oxygen consumption was monitored to provide an estimate of the rate of respiration per cell per day

  3. Earthquake cycle deformation in the Tibetan plateau with a weak mid-crustal layer

    NASA Astrophysics Data System (ADS)

    Devries, Phoebe M. R.; Meade, Brendan J.

    2013-06-01

    observations of interseismic deformation across the Tibetan plateau contain information about both tectonic and earthquake cycle processes. Time-variations in surface velocities between large earthquakes are sensitive to the rheological structure of the subseismogenic crust, and, in particular, the viscosity of the middle and lower crust. Here we develop a semianalytic solution for time-dependent interseismic velocities resulting from viscoelastic stress relaxation in a localized midcrustal layer in response to forcing by a sequence of periodic earthquakes. Earthquake cycle models with a weak midcrustal layer exhibit substantially more near-fault preseismic strain localization than do classic two-layer models at short (<100 yr) Maxwell times. We apply both this three-layer model and the classic two-layer model to geodetic observations before and after the 1997 MW = 7.6 Manyi and 2001 MW = 7.8 Kokoxili strike-slip earthquakes in Tibet to estimate the viscosity of the crust below a 20 km thick seismogenic layer. For these events, interseismic stress relaxation in a weak (viscosity ≤1018.5 Paṡs) and thin (height ≤20 km) midcrustal layer explains observations of both preseismic near-fault strain localization and rapid (>50 mm/yr) postseismic velocities in the years following the coseismic ruptures. We suggest that earthquake cycle models with a localized midcrustal layer can simultaneously explain both preseismic and postseismic geodetic observations with a single Maxwell viscosity, while the classic two-layer model requires a rheology with multiple relaxation time scales.

  4. A fault-based model for crustal deformation, fault slip-rates and off-fault strain rate in California

    USGS Publications Warehouse

    Zeng, Yuehua; Shen, Zheng-Kang

    2016-01-01

    We invert Global Positioning System (GPS) velocity data to estimate fault slip rates in California using a fault‐based crustal deformation model with geologic constraints. The model assumes buried elastic dislocations across the region using Uniform California Earthquake Rupture Forecast Version 3 (UCERF3) fault geometries. New GPS velocity and geologic slip‐rate data were compiled by the UCERF3 deformation working group. The result of least‐squares inversion shows that the San Andreas fault slips at 19–22  mm/yr along Santa Cruz to the North Coast, 25–28  mm/yr along the central California creeping segment to the Carrizo Plain, 20–22  mm/yr along the Mojave, and 20–24  mm/yr along the Coachella to the Imperial Valley. Modeled slip rates are 7–16  mm/yr lower than the preferred geologic rates from the central California creeping section to the San Bernardino North section. For the Bartlett Springs section, fault slip rates of 7–9  mm/yr fall within the geologic bounds but are twice the preferred geologic rates. For the central and eastern Garlock, inverted slip rates of 7.5 and 4.9  mm/yr, respectively, match closely with the geologic rates. For the western Garlock, however, our result suggests a low slip rate of 1.7  mm/yr. Along the eastern California shear zone and southern Walker Lane, our model shows a cumulative slip rate of 6.2–6.9  mm/yr across its east–west transects, which is ∼1  mm/yr increase of the geologic estimates. For the off‐coast faults of central California, from Hosgri to San Gregorio, fault slips are modeled at 1–5  mm/yr, similar to the lower geologic bounds. For the off‐fault deformation, the total moment rate amounts to 0.88×1019  N·m/yr, with fast straining regions found around the Mendocino triple junction, Transverse Ranges and Garlock fault zones, Landers and Brawley seismic zones, and farther south. The overall California moment rate is 2.76×1019

  5. Crustal Deformation in the Isthmus of Tehuantepec, Mexico Observed from Microseismic Data recorded by the VEOX Experiment

    NASA Astrophysics Data System (ADS)

    Suarez, G.; Aguilar, S.

    2015-12-01

    An array of 45 broad band sensors was installed across the 300-km-long Isthmus of Techuantepec, in the narrowest part of Mexico. This array was deployed from August of 2007 to March of 2009. Data was recorded in a continous manner in all seismographs throughout the whole deployment period. We used an LTA/STA algorithm to automatically detect earthquakes recorded by the norhernmost stations near the coast of the Gulf of Mexico. Earthquakes recorded by one station were searched in adjaecent sites. This allowed a thorough and systematic search of the seismic traces in order to identify seismic events recorded by the northern segment of the array. The earthquakes culled from the algorithm were filtered in order to include only those with crustal or upper mantle depths that reflect deformation of the overriding plate. Intermediate depth earthquakes occurring within the subducted slab were filtered out. In total, during the 18 month duration of the experiment, 34 earthquakes were clearly identified and located within the crust and the upper mantle. Tests on the location accuracy were conducted using different velocity models proposed for this region. A selection criteria of the best located earthquakes was applied observing the stability of the hypocentral locations to changes in the velocity model. The resulting subset of the best-located earthquakes indicate that the deformation of the upper North American plate is concentrated in the northern part of the Isthmus of Tehuantepec, along the coast of the Gulf of Mexico. Only a few events occurred farther inland, to the south of the coast of the Gulf of Mexico. The location of these microseismic events coincides with the location of moderate events recorded in the past. In particular, the largest cluster of microearthquakes occurs near where the 29 August 1959 earthquake. The location and depth of the microearthquakes located further demonstrates that the overriding North American plate is being deformed, probably by the

  6. Late Quaternary tectonic activity and crustal shortening rate of the Bogda mountain area, eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Wu, Chuanyong; Wu, Guodong; Shen, Jun; Dai, Xunye; Chen, Jianbo; Song, Heping

    2016-04-01

    The Bogda mountain range is the highest range among the northern Tian Shan mountains. Based on geologic and geomorphologic field surveys, trench excavation and optically stimulated luminescence (OSL) dating, we targeted the active Fukang fault along the Bogda mountain range and identified the late Quaternary deformation characteristics of this area. We found that the Fukang fault dislocated different geomorphic surfaces of the northern Bogda piedmont. The vertical fault displacement corresponds to the topographic relief of the Bogda over long time scales. Since the late Quaternary, the crustal shortening rate was estimated to be 0.90 ± 0.20 mm/yr, which is less than that of the western segment of the northern Tian Shan. We interpret the Bogda fold and thrust belt to be a thick-skinned structure, since a high angle thrust fault bounds the Bogda mountain range and the foreland basin. The deformation characteristics of this region have been dominated by vertical uplift, and the component of propagation toward the basin has been very limited. This tectonic deformation is evidenced as vertical growth. Although the deformation rate is small, the uplift amplitude is very significant in this region.

  7. Present-day crustal deformation along the Magallanes-Fagnano Fault System in Tierra del Fuego from repeated GPS observations

    NASA Astrophysics Data System (ADS)

    Mendoza, L.; Perdomo, R.; Hormaechea, J. L.; Del Cogliano, D.; Fritsche, M.; Richter, A.; Dietrich, R.

    2011-03-01

    The present-day deformation of the earth crust in the Argentine part of Tierra del Fuego main island (southernmost South America) is here investigated based on repeated geodetic GPS observations. The island is traversed by the active transform boundary between the South American and Scotia tectonic plates, represented by the Magallanes-Fagnano fault system. Since 1993 a regional network comprising to date 29 GPS sites has been observed almost every year. The complete set of accumulated observations was processed using the Bernese GPS software and state-of-the-art processing strategies and models. The utilization of homogeneous GPS products resulting from a reprocessing of the global IGS network warrants a stable realization of a global reference frame. For each GPS site 3-D positions and linear velocities with error estimates were obtained. A strain analysis of the horizontal velocity components revealed the zones of major deformation activity. A 30-km-wide deformation belt centred on the main trace of the fault system was identified. This belt is bordered to the north (South America) and south (Scotia) by geodynamically stable zones, which move horizontally with a relative average velocity of 4.4 ± 0.6 (east) and -0.3 ± 0.4 (north) mm a-1. Within the deformation belt a maximum strain rate in the order of 0.25 μstrain per year has been detected. A pronounced change in the deformation style from transtension (east) to transpression (west) is observed. The area of predominating shortening of the crust coincides with a local rotation minimum and relative uplift. Throughout the period covered by the GPS observations the displacements and deformations occurred to be linear with time.

  8. The SCEC 3D Community Fault Model (CFM-v5): An updated and expanded fault set of oblique crustal deformation and complex fault interaction for southern California

    NASA Astrophysics Data System (ADS)

    Nicholson, C.; Plesch, A.; Sorlien, C. C.; Shaw, J. H.; Hauksson, E.

    2014-12-01

    Southern California represents an ideal natural laboratory to investigate oblique deformation in 3D owing to its comprehensive datasets, complex tectonic history, evolving components of oblique slip, and continued crustal rotations about horizontal and vertical axes. As the SCEC Community Fault Model (CFM) aims to accurately reflect this 3D deformation, we present the results of an extensive update to the model by using primarily detailed fault trace, seismic reflection, relocated hypocenter and focal mechanism nodal plane data to generate improved, more realistic digital 3D fault surfaces. The results document a wide variety of oblique strain accommodation, including various aspects of strain partitioning and fault-related folding, sets of both high-angle and low-angle faults that mutually interact, significant non-planar, multi-stranded faults with variable dip along strike and with depth, and active mid-crustal detachments. In places, closely-spaced fault strands or fault systems can remain surprisingly subparallel to seismogenic depths, while in other areas, major strike-slip to oblique-slip faults can merge, such as the S-dipping Arroyo Parida-Mission Ridge and Santa Ynez faults with the N-dipping North Channel-Pitas Point-Red Mountain fault system, or diverge with depth. Examples of the latter include the steep-to-west-dipping Laguna Salada-Indiviso faults with the steep-to-east-dipping Sierra Cucapah faults, and the steep southern San Andreas fault with the adjacent NE-dipping Mecca Hills-Hidden Springs fault system. In addition, overprinting by steep predominantly strike-slip faulting can segment which parts of intersecting inherited low-angle faults are reactivated, or result in mutual cross-cutting relationships. The updated CFM 3D fault surfaces thus help characterize a more complex pattern of fault interactions at depth between various fault sets and linked fault systems, and a more complex fault geometry than typically inferred or expected from

  9. Crustal deformation associated with glacial fluctuations in the eastern Chugach Mountains, Alaska

    USGS Publications Warehouse

    Sauber, Jeanne; Plafker, George; Molnia, Bruce F.; Bryant, Mark A.

    2000-01-01

    The changes of the solid Earth in south central Alaska in response to two major glacial fluctuations on different temporal and spatial scales have been estimated and we evaluated their influence on the stress state and ongoing tectonic deformation of the region. During the recent (1993–1995) Bering Glacier surge, a large transfer of ice from the Bagley Ice Field to the Bering Glacier terminus region occurred. We estimated the elastic displacement of the solid Earth due to ice mass redistribution from Global Positioning System (GPS) measurements at sites near the surging glacier. We can account for these displacements by transfer of an ice volume of about 14 km3 from the surge reservoir area to the terminus region. We examined the background seismicity (ML ≥ 2.5) before, during, and after the surge. We found that the occurrence of small earthquakes (ML ≤ 4.0) in the surge reservoir region increased during the surge time interval possibly in response to a decrease in ice mass. This suggests that a small decrease in the vertical stress, σ3, could be enough to modulate the occurrence of small, shallow earthquakes in this dominantly thrust fault setting. During this century the southern Alaska coastal glaciers have been undergoing an overall decrease in volume. Based on our compilation of changes in the extent and thickness of the coastal glaciers between the Malaspina and Bering, we calculated surface displacements due to the Earth's viscoelastic response to annual thinning and to the cumulative retreat over the last 100 years. The uplift of the region due to an average annual thinning rate of 1–6 m/yr in the ablation region is 1–12 mm/yr. For our reference model with a viscosity of 5×1019 Pa s for depths between ≈ 40 and 200 km the total viscoelastic response due to the retreat over the last century may be as much as a couple of meters within the coastal ablation zone near Icy Bay. The maximum decrease in σv between 0 and 10 km was ≈ 1.0 MPa, which is

  10. Crustal Deformation Associated with Glacial Fluctuations in the Eastern Chugach Mountains, Alaska

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne; Plafker, George; Molnia, Bruce F.; Bryant, Mark A.

    2000-01-01

    The changes of the solid Earth in south central Alaska in response to two major glacial fluctuations on different temporal and spatial scales have been estimated and we evaluated their influence on the stress state and ongoing tectonic deformation of the region. During the recent (1993-1995) Bering Glacier surge, a large transfer of ice from the Bagley Ice Field to the Bering Glacier terminus region occurred. We estimated the elastic displacement of the solid Earth due to ice mass redistribution from Global Positioning System (GPS) measurements at sites near the surging glacier. We can account for these displacements by transfer of an ice volume of about 14 cubic km from the surge reservoir area to the terminus region. We examined the background seismicity (M(sub L) > 2.5) before, during, and after the surge. We found that the occurrence of small earthquakes (M(sub L) < 4.0) in the surge reservoir region increased during the surge time interval possibly in response to a decrease in ice mass. This suggests that a small decrease in the vertical stress, o,3, could be enough to modulate the occurrence of small, shallow earthquakes in this dominantly thrust fault setting. During this century the southern Alaska coastal glaciers have been undergoing an overall decrease in volume. Based on our compilation of changes in the extent and thickness of the coastal glaciers between the Malaspina and Bering, we calculated surface displacements due to the Earth's viscoelastic response to annual thinning and to the cumulative retreat over the last 100 years. The uplift of the region due to an average annual thinning rate of 1-6 m/yr in the ablation region is 1-12 mm/yr. For our reference model with a viscosity of 5 x 10(exp 19) Pa s for depths between approximately equal 40 and 200 km the total viscoelastic response due to the retreat over the last century may be as much as a couple of meters within the coastal ablation zone near Icy Bay. The maximum decrease in sigma(sub V

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1989-01-01

    A particularly detailed set of observations in the vicinity of an intraplate, thrust earthquake (M 7.4) in Argentina, indicate a cyclic pattern of deformation very similar to that reported previously for interplate earthquakes. This deformation cycle, which may be characteristic of many seismically active areas, consists of: (1) steady strain accumulation, possibly punctuated by strain reversals; (2) coseismic strain release; (3) a period of continued strain release due to afterslip (persisting for perhaps a year or so); and (4) rapid postseismic strain accumulation which decreases exponentially and grades into steady strain accumulation. Deformation associated with three earthquakes in the U.S. (1940, M7.1 Imperial Valley California; 1964, M8.4 Alaska; 1959, M7.5 Hebgen Lake, Montana) are interpreted in light of this general earthquake cycle and are used to investigate the mechanics of strain release for these events. These examples indicate that large postseismic movements can occur for strike-slip, thrust, and normal fault events, and both viscoelastic relaxation and postseismic after-slip must be incorporated in models of earthquake related deformation. The mechanics of the strain release process revealed by these examples has implications for estimating earthquake repeat times from geodetic observations near active faults.

  12. Proterozoic Diabase Dyke Swarms of Northern Ontario: Paleomagnetic Indicators of Broad-Scale Crustal Deformation of the Archean Superior Province

    NASA Astrophysics Data System (ADS)

    Halls, H. C.

    2004-05-01

    KZ (Halls and Davis, 2004). Lateral variations in clouding intensity and hydrous alteration levels in dyke feldspars reveal that the shield has been gently tilted towards the south, and that superimposed on this tilting is a series of fault-bounded, mostly uplifted, crustal blocks that constitute the KZ. In summary, results from more than 400 paleomagnetic sites in Ontario dykes show that the Superior province, despite being generally regarded as the epitome of a stable craton, has been regionally deformed, perhaps in several stages centred around 2.0 ± 0.2 Ga. If rotation across the KZ accompanied rifting beneath Hudson Bay, it may explain the overall butterfly - shaped outline of the Superior Province. References: Bates, M. and Halls, H. 1991, CJES 28: 1780; Ernst, R. and Halls, H. 1984, CJES 21:1499; Halls, H. and Palmer, H. 1990, CJES 27: 87; Halls, H., Palmer, H.,Bates, M. and Phinney, W. 1994, CJES 31:1182; Halls, H. and Zhang, B. 2003, Tectonophysics 362:123; Halls, H. and Stott, G. 2003, OGS Open File Rept. No. 6120, 7p; Halls, H. and Davis, D. CJES 41,(in press); Percival, J. and West, G. 1994, CJES 31:1256.

  13. Interpretation of Crustal Deformation following the 2011 Tohoku-oki Megathrust Earthquake by the Combined Effect of Afterslip and Viscoelastic Stress Relaxation

    NASA Astrophysics Data System (ADS)

    Noda, A.; Takahama, T.; Ohba, M.; Ito, T.; Matsu'ura, M.

    2015-12-01

    Crustal deformation following the 2011 Tohoku-oki megathrust earthquake, occurred at the North American-Pacific plate interface, has been revealed by GPS measurement on land (Geospatial Information Authority of Japan) and GPS/Acoustic measurement on seafloor (Japan Coast Guard). The essential causes of the postseismic crustal deformation are considered to be slow afterslip at the downdip extension of the main rupture zone and viscoelastic relaxation of stress changes induced in the asthenosphere. Crustal responses to the afterslip and the viscoelastic relaxation are different in both space and time. So, given proper plate interface geometry and proper crust-mantle rheological structure, we can estimate unbiased spatiotemporal distribution of afterslip through the inversion analysis of observed geodetic data. In the present analysis, we used a 3-D realistic model developed by Hashimoto et al. (2004) for plate interface geometry and a standard elastic-viscoelastic layered model, consisting of a 60 km-thick elastic surface layer and a Maxwell-type viscoelastic substratum with the viscosity of 1019 Pa s, for crust-mantle rheological structure. First, following Noda et al. (2013), we transformed the GPS displacement data on land into the average strains of triangular elements composed of adjacent three GPS stations. Then, by applying a sequential method of stepwise (every two months) inversion to the strain data, we estimated the spatiotemporal distribution of afterslip together with coseismic slip distribution. The estimated results show that significant afterslip has proceeded for the first one and a half years at the downdip extension of the main rupture zone off Iwate and Miyagi with decaying its rate. Finally, based on the estimated results, we computed postseismic offshore crustal movements by using the same elastic-viscoelastic structure model and compared them with seafloor geodetic observations (Watanabe et al., 2014). The good agreement between the computed

  14. Reciprocating motion of active deformable particles

    NASA Astrophysics Data System (ADS)

    Tarama, M.; Ohta, T.

    2016-05-01

    Reciprocating motion of an active deformable particle in a homogeneous medium is studied theoretically. For generality, we employ a simple model derived from symmetry considerations for the center-of-mass velocity and elliptical and triangular deformations in two dimensions. We carry out, for the first time, a systematic investigation of the reciprocating motion of a self-propelled particle. It is clarified that spontaneous breaking of the front-rear asymmetry is essential for the reciprocating motion. Moreover, two routes are found for the formation of the reciprocating motion. One is a bifurcation from a motionless stationary state. The other is destabilisation of an oscillatory rectilinear motion.

  15. Development of a GPS buoy system for monitoring tsunami, sea waves, ocean bottom crustal deformation and atmospheric water vapor

    NASA Astrophysics Data System (ADS)

    Kato, Teruyuki; Terada, Yukihiro; Nagai, Toshihiko; Koshimura, Shun'ichi

    2010-05-01

    We have developed a GPS buoy system for monitoring tsunami for over 12 years. The idea was that a buoy equipped with a GPS antenna and placed offshore may be an effective way of monitoring tsunami before its arrival to the coast and to give warning to the coastal residents. The key technology for the system is real-time kinematic (RTK) GPS technology. We have successfully developed the system; we have detected tsunamis of about 10cm in height for three large earthquakes, namely, the 23 June 2001 Peru earthquake (Mw8.4), the 26 September 2003 Tokachi earthquake (Mw8.3) and the 5 September 2004 earthquake (Mw7.4). The developed GPS buoy system is also capable of monitoring sea waves that are mainly caused by winds. Only the difference between tsunami and sea waves is their frequency range and can be segregated each other by a simple filtering technique. Given the success of GPS buoy experiments, the system has been adopted as a part of the Nationwide Ocean Wave information system for Port and HArborS (NOWPHAS) by the Ministry of Land, Infrastructure, Transport and Tourism of Japan. They have established more than eight GPS buoys along the Japanese coasts and the system has been operated by the Port and Airport Research Institute. As a future scope, we are now planning to implement some other additional facilities for the GPS buoy system. The first application is a so-called GPS/Acoustic system for monitoring ocean bottom crustal deformation. The system requires acoustic waves to detect ocean bottom reference position, which is the geometrical center of an array of transponders, by measuring distances between a position at the sea surface (vessel) and ocean bottom equipments to return the received sonic wave. The position of the vessel is measured using GPS. The system was first proposed by a research group at the Scripps Institution of Oceanography in early 1980's. The system was extensively developed by Japanese researchers and is now capable of detecting ocean

  16. Lower crustal deformation beneath the central Transverse Ranges, southern California: Results from the Los Angeles Region Seismic Experiment

    USGS Publications Warehouse

    Godfrey, N.J.; Fuis, G.S.; Langenheim, V.; Okaya, D.A.

    2002-01-01

    We present a P wave velocity model derived from active source seismic data collected during the 1994 Los Angeles Region Seismic Experiment. Our model extends previously published upper crustal velocity models to mantle depths. Our model was developed by both ray tracing through a layered model and calculating travel times through a gridded model. It includes an 8-km-thick crustal root centered beneath the surface trace of the San Andreas fault, north of the highest topography in the San Gabriel Mountains. A simple mass balance calculation suggests that ???36 km of north-south shortening across the San Andreas fault in the central Transverse Ranges could have formed this root. If north-south compression began when the "Big Bend" in the San Andreas fault formed at ???5 Ma, 36 km of shortening implies a north-south contraction rate of ???7.1 mm/yr across the central Transverse Ranges. If, instead, north-south compression began when the Transverse Ranges formed at 3.4-3.9 Ma, 36 km of shortening implies a contraction rate of 9.2-10.6 mm/yr. North of the San Andreas fault, the Mojave Desert crust has a low-velocity (6.3 km/s) mid and lower crust and a 28-km-deep Moho. South of the San Andreas fault, beneath the Los Angeles and San Gabriel Valley basins, there is a fast (6.6-6.8 km/s), thick (10-12 km) lower crust with a 27-km-deep Moho. Farther south still, the lower crust of the Continental Borderland is fast (6.6-6.8 km/s) and thin (5 km) with a shallow (22 km deep) Moho.

  17. Crustal deformation of Miyakejima volcano, Japan since the eruption of 2000 using dense GPS campaign observation

    NASA Astrophysics Data System (ADS)

    Fukui, M.; Matsushima, T.; Oikawa, J.; Watanabe, A.; Okuda, T.; Ozawa, T.; Kohno, Y.; Miyagi, Y.

    2013-12-01

    Miyakejima is an active volcanic Island located about 175 km south of Tokyo, Japan. Miyakejima volcano erupted approximately every 20 years in the past 100 years. The latest eruptive activities since 2000 was different from those of the last 100 years, in that the activities included a caldera formation for the first time in 2500 years and gigantic volcanic gas emission that forced islander to evacuate over four and half years. In 2000, a dense GPS observation campaign had detected the magma intrusion in detail (e.g., Irwan et al., 2003; Murase et al., 2006). However, this campaign observation ceased from 2002 to 2010 because a large amount of volcanic gas prevented from entering to the island. Since 2011, we restarted the campaign observation by the dense GPS network, and examined the ongoing magma accumulation process beneath Miyakejima volcano to get insights about the future activity. In this analysis, we combined the data of our campaign observations, the data of the University Union in 2000, and the GEONET data. The observation data were analyzed by RTK-LIB (Takasu et al., 2007) using GPS precise ephemeris from IGS. We estimated the locations and volumes of the pressure sources beneth Miyakejima using an elevation-modified Mogi model (Fukui et al., 2003) and open crack model (Okada, 1992) during the two periods (2000 ~ 2012 and 2011 ~ 2012). We used the software of Magnetic and Geodetic data Computer Analysis Program for Volcano (MaGCAP-V) (Fukui et al., 2010), and estimated the source parameters by trial and error. During 2000 and 2012, a contracting spherical source and contracting dyke were estimated beneath the caldera and at the southwestern part of the island, respectively. In contrast, during 2011 and 2012, an spherical inflation source was estimated a few km beneath the caldera. This result suggest that Miyakejima is now storing new magma for the next eruption. Geospatial Information Authority of Japan (GSI) (2011) suggested that the inflation started

  18. Incipient Crustal Stretching across AN Active Collision Belt: the Case of the Siculo-Calabrian Rift Zone (central Mediterranean)

    NASA Astrophysics Data System (ADS)

    Catalano, S.; Tortorici, G.; Romagnoli, G.; Pavano, F.

    2012-12-01

    increase in the elevation of the marine terraces of the last 600 ka. In the two analysed crustal blocks, the crustal doming with the related basin collapses and the concurrent tectonic motion without any back-stop can be respectively related to the thermal anomalies and to the drag forces exerted by a hot Mantle flow, triggered by the opening of a vertical slab windows at the southern edge of the Calabrian arc. This process has favored the migration of hot Mantle material towards the sectors of larger rollback of the subduction hinge, producing the spectacular tectonic uplift and active magmatism of the region. The increase of the volume of the Mantle wedged in the subduction zone of the Calabrian arc has been also effective to accommodate the differential roll-back between the adjacent segments of Nubia Plate, thus replacing the motion along the pre-existing transform faults dissecting the orogenic belt. In this frame, the deformation of the Hyblean-Etnean and the Peloritani-Aeolian blocks heralded the development of the two Sicily branches of the SCRZ. The delayed crustal stretching responsible for the propagation of the rift zone across the orogenic belt can be framed in the dynamic of a still active convergent margin if interpreted as the result of the sliding of the crust along the Ionian flank of the Mantle flow.

  19. An Investigation on the Crustal Deformations in Istanbul after Eastern Marmara Earthquakes in 1999

    NASA Astrophysics Data System (ADS)

    Ozludemir, M.; Ozyasar, M.

    2008-12-01

    Since the introduction of the GPS technique in mid 1970's there has been great advances in positioning activities. Today such Global Navigational Satellite Systems (GNSS) based positioning techniques are widely used in daily geodetic applications. High order geodetic network measurements are one of such geodetic applications. Such networks are established to provide reliable infrastructures for all kind of geodetic work from the production of cadastral plans to the surveying processes during the construction of engineering structures. In fact such positional information obtained in such engineering surveys could be useful for other studies as well. One of such fields is geodynamic studies where such positional information could be valuable to understand the characteristics of tectonic movements. In Turkey being located in a tectonically active zones and having major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. In this paper an example of such engineering surveys is discussed. This example is the Istanbul GPS (Global Positioning System) Network, first established in 1997 and remeasured in 2005. Between these two measurement processes two major earthquakes took place, on August 17 and November 12, 1999 with magnitudes of 7.4 and 7.2, respectively. In the first measurement campaign in 1997, a network of about 700 points was measured, while in the second campaign in 2005 more than 1800 points were positioned. In these two campaigns are existing common points. The network covers the whole Istanbul area of about 6000 km2. All network points are located on the Eurasian plate to the north of the North Anatolian Fault Zone. In this study, the horizontal and vertical movements are presented and compared with the results obtained in geodynamic studies.

  20. UAVSAR and GPS Observations of Crustal Deformation in Southern California and Implications for Earthquake Risk

    NASA Astrophysics Data System (ADS)

    Donnellan, A.; Parker, J. W.; Lyzenga, G. A.; Rundle, J. B.; Grant Ludwig, L.; Granat, R. A.; Glasscoe, M. T.; Heflin, M. B.

    2010-12-01

    The 2010 El-Mayor Cucapah earthquake was the first earthquake to be observed with UAVSAR. UAVSAR observations, GPS time series analysis, and simulations suggest that the fault that ruptured in the earthquake is coupled to the Elsinore, San Jacinto, and San Andreas faults to the north. GPS and UAVSAR observations indicate a zone of shear that extends southward from the Big Bend of the San Andreas fault near Gorman through the San Fernando Valley towards the Newport-Inglewood fault. The zone steps over to the region of the Elsinore or San Jacinto faults, though the partitioning of strain between the two faults is not as clear. State changes in GPS time series data fall in line with the shear zone through the San Fernando Valley and extend northward from the El Mayor-Cucapah earthquake rupture. Seismicity hotspots also indicate elevated earthquake hazard near the San Fernando Valley and in the Inland Empire near the Elsinore and San Jacinto faults. Inversions of GPS velocity vectors favor a fault underlying the shear zone extending from the Big Bend to the Newport-Inglewood fault over substantial slip on the San Andreas fault under north of Los Angeles. Virtual California simulations of southern California are being analyzed for fault activity associated with the identified shear zone and for subsequent earthquakes that may be related to El Mayor-Cucapah type earthquakes in Baja.

  1. Exploratory results from a new rotary shear designed to reproduce the extreme deformation conditions of crustal earthquakes

    NASA Astrophysics Data System (ADS)

    Di Toro, G.; Nielsen, S. B.; Spagnuolo, E.; Smith, S.; Violay, M. E.; Niemeijer, A. R.; Di Felice, F.; Di Stefano, G.; Romeo, G.; Scarlato, P.

    2011-12-01

    A challenging goal in experimental rock deformation is to reproduce the extreme deformation conditions typical of coseismic slip in crustal earthquakes: large slip (up to 50 m), slip rates (0.1-10 m/s), accelerations (> 10 m/s2) and normal stress (> 50 MPa). Moreover, fault zones usually contain non-cohesive rocks (gouges) and fluids. The integration of all these deformation conditions is such a technical challenge that there is currently no apparatus in the world that can reproduce seismic slip. Yet, the determination of rock friction at seismic slip rates remains one of the main unknowns in earthquake physics, as it cannot be determined (or very approximately) by seismic wave inversion analysis. In the last thirty years, rotary shear apparatus were designed that combine large normal stresses and slip but low slip rates (high-pressure rotary shears first designed by Tullis) or low normal stresses but large slip rates and slip (rotary shears first designed by Shimamoto). Here we present the results of experiments using a newly-constructed Slow to HIgh Velocity Apparatus (SHIVA), installed at INGV in Rome, which extends the combination of normal stress, slip and slip rate achieved by previous apparatus and reproduces the conditions likely to occur during an earthquake in the shallow crust. SHIVA uses two brushless engines (max power 300 kW, max torque 930 Nm) and an air actuator (thrust 5 tons) in a rotary shear configuration (nominally infinite displacement) to slide hollow rock cylinders (30/50 mm int./ext. diameter) at slip rates ranging from 10 micron/s up to 6.5 m/s, accelerations up to 80 m/s2 and normal stresses up to 50 MPa. SHIVA can also perform experiments in which the torque on the sample (rather than the slip rate) is progressively increased until spontaneous failure occurs: this experimental capability should better reproduce natural conditions. The apparatus is equipped with a sample chamber to carry out experiments in the presence of fluids (up to 15

  2. Locating Active Plate Boundaries by Earthquake Data. Crustal Evaluation Education Project. Teacher's Guide [and] Student Investigation.

    ERIC Educational Resources Information Center

    Stoever, Edward C., Jr.

    Crustal Evolution Education Project (CEEP) modules were designed to: (1) provide students with the methods and results of continuing investigations into the composition, history, and processes of the earth's crust and the application of this knowledge to man's activities and (2) to be used by teachers with little or no previous background in the…

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  4. Temporal Variations of Gamma-Ray for Detecting Crustal Activity Changes in the Longitudinal Valley, Eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Fu, C. C.; Wang, P. G.; Lee, L. C.; Lin, C. H.; Giuliani, G.; Ouzounov, D.

    2014-12-01

    A gamma-ray station was established along the Longitudinal Valley Fault, which is an extremely active high-angle thrust with NNE-striking on the boundary between Eurasia plate and Philippine Sea plate. Stresses arise in the crust in accordance with crustal deformations due to plate motions and geodynamic processes. Gamma-ray emission associated with the radioactive decay of radon is continuously recorded in the station, considered to be discharged into surface from deep source area. Fluctuations of gamma-ray data are found to show a clear inverse correction with atmospheric temperature. Based on the linear regression method, possible temperature effects can be removed and the corrected data can be obtained. Variations exceeding the normal trend can be used to identify events associated with geodynamic processes such as earthquake. These anomalies usually appeare as procursors a few days before the local earthquakes, which occur in eastern Taiwan. It is noted that there are two significant increases in the gamma-ray counting rate during the period of 20th to 25th March and the period of 22nd April to 1st May. These increases are observed one week before the earthquake swarm. Furthermore, a progressive anomalies were recorded two weeks before the Fanglin earthquake (ML = 5.9, May 21, 2014) located in the Longitudinal Valley area. A continuous monitoring on the multiple parameters can improve our understanding of the relationship between the observed gamma-ray variations and the regional crustal stress/strain in the area.

  5. Deformation Monitoring of AN Active Fault

    NASA Astrophysics Data System (ADS)

    Ostapchuk, A.

    2015-12-01

    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 fault zones. Conditions for generating different slip modes are still unclear. The most vital question is whether a certain slip mode is intrinsic for a fault 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 Fault. Main Sayanskiy Fault is right-lateral strike-slip fault. Observations were performed in the tunnel of Talaya seismic 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 fault 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 active fault 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 fault 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).

  6. Deep crustal deformation of the Longmen Shan, eastern margin of the Tibetan Plateau, from seismic reflection and Finite Element modeling

    NASA Astrophysics Data System (ADS)

    Feng, Shao-ying; Zhang, Pei-zhen; Liu, Bao-jin; Wang, Ming; Zhu, Shou-biao; Ran, Yong-kan; Wang, Wei-tao; Zhang, Zhu-qi; Zheng, Wen-jun; Zheng, De-wen; Zhang, Hui-ping; Tian, Xiao-feng

    2016-02-01

    Rivaling the Himalaya in relief, the Longmen Shan is probably one of the most enigmatic mountain ranges in the world: high mountains reach more than 4000 m relief but without adjacent foreland subsidence and with only slow active convergence. What are geological and geodynamic processes that built the Longmen Shan? Coseismic deformation associated with the 2008 Wenchuan earthquake could hold clues to answer these questions. The primary features associated with the 2008 Wenchuan earthquake rupture have been narrowly distributed coseismic deformation and predominantly vertical displacements that could be interpreted as the result of slips on high-angle listric seismogenic faults. Deep sounding seismic reflection profiling across the seismogenic faults indeed reveals high-angle listric reverse faulting in the brittle upper crust and east-dipping reflectors that we interpret as ductile shearing, in the viscous lower crust. In conjunction with a visco-elastic finite element modeling of coseismic displacements associated with the Wenchuan earthquake, we show that the high-angle listric nature of earthquake faults produces insignificant horizontal shortening across the fault and facilitates upward slips along the fault that both explain the localized coseismic deformation and vertical displacement, as well as the presence of high mountains without adjacent foreland flexure. We suggest that the formation of the Longmen Shan may be better understood in terms of partitioned lithospheric pure-shear thickening in which upward high-angle listric faulting of brittle upper crust is linked to thickening of the more viscous lithospheric mantle through downward ductile shearing of rheologically deformable lower crust.

  7. Crustal versus asthenospheric relaxation and post-seismic deformation for shallow normal faulting earthquakes:the Umbria-Marche (central Italy) case

    NASA Astrophysics Data System (ADS)

    Riva, R.; Aoudia, A.; Vermeersen, L. L. A.; Sabadini, R.; Panza, G. F.

    2000-06-01

    Following a normal mode approach for a stratified viscoelastic earth, we investigate the effects induced by shallow normal faulting earthquakes, on surface post-seismic vertical displacement and velocity at the surface, when stress relaxation occurs in the crust or in the asthenosphere. The modelled earthquake is a moderate one characteristic of some slowly deforming plate boundaries in the central Mediterranean region. We focus on the Umbria-Marche (central Italy) region where deep seismic reflection studies (CROP03) and the 1997 earthquake sequence clearly show a seismogenic layer decoupled from the lower crust by a sizeable transition zone. Accordingly, the crust is subdivided into three layers: an elastic upper crust, a transition zone and a low-viscosity lower crust. The fault is embedded in the upper crust. The layered viscoelastic structure of the crust and mantle imposes a pattern and scale on the modelled coseismic and post-seismic deformation with a major contribution from the transition crustal zone and low-viscosity lower crust, stress relaxation in the mantle being negligible. We show that significant vertical deformation rates of the order of 1mmyr-1 could be expected for a shallow and moderate event such as the recent Umbria-Marche earthquake for viscosity values of 1019 and 1018Pas in the crustal transition zone and lower crust, respectively.

  8. Global Positioning System constraints on crustal deformation before and during the 21 February 2008 Wells, Nevada M6.0 earthquake

    USGS Publications Warehouse

    Hammond, William C.; Blewitt, Geoffrey; Kreemer, Corné; Murray-Moraleda, Jessica R.; Svarc, Jerry L.

    2011-01-01

    Using Global Positioning System (GPS) data from permanent sites and U.S. Geological Survey (USGS) campaign data we have estimated co-seismic displacements and secular background crustal deformation patterns associated with the 21 February 2008 Wells Nevada earthquake. Estimated displacements at nearby permanent GPS sites ELKO (84 km distant) and GOSH (81 km distant) are 1.0±0.2 mm and 1.1±0.3 mm, respectively. The magnitude and direction are in agreement with those predicted from a rupture model based on InSAR measurements of the near-field co-seismic surface displacement. Analysis of long GPS time series (>10 years) from the permanent sites within 250 km of the epicenter indicate the eastern Nevada Basin and Range undergoes steady tectonic transtension with rates on the order of 1 mm/year over approximately 250 km. The azimuth of maximum horizontal crustal extension is consistent with the azimuth of the Wells earthquake co-seismic slip vector. The orientation of crustal shear is consistent with deformation associated with Pacific/North America plate boundary relative motion seen elsewhere in the Basin and Range. In response to the event, we deployed a new GPS site with the capability to telemeter high rate, low latency data that will in the future allow for rapid estimation of surface displacement should aftershocks or postseismic deformations occur. We estimated co-seismic displacements using campaign GPS data collected before and after the event, however in most cases their uncertainties were larger than the offsets. Better precision in co-seismic displacement could have been achieved for the campaign sites if they had been surveyed more times or over a longer interval to better estimate their pre-event velocity.

  9. Insights from low-temperature thermochronometry into transpressional deformation and crustal exhumation along the San Andreas fault in the western Transverse Ranges, California

    NASA Astrophysics Data System (ADS)

    Niemi, Nathan A.; Buscher, Jamie T.; Spotila, James A.; House, Martha A.; Kelley, Shari A.

    2013-12-01

    San Emigdio Mountains are an example of an archetypical, transpressional structural system, bounded to the south by the San Andreas strike-slip fault, and to the north by the active Wheeler Ridge thrust. Apatite (U-Th)/He and apatite and zircon fission track ages were obtained along transects across the range and from wells in and to the north of the range. Apatite (U-Th)/He ages are 4-6 Ma adjacent to the San Andreas fault, and both (U-Th)/He and fission track ages grow older with distance to the north from the San Andreas. The young ages north of the San Andreas fault contrast with early Miocene (U-Th)/He ages from Mount Pinos on the south side of the fault. Restoration of sample paleodepths in the San Emigdio Mountains using a regional unconformity at the base of the Eocene Tejon Formation indicates that the San Emigdio Mountains represent a crustal fragment that has been exhumed more than 5 km along the San Andreas fault since late Miocene time. Marked differences in the timing and rate of exhumation between the northern and southern sides of the San Andreas fault are difficult to reconcile with existing structural models of the western Transverse Ranges as a thin-skinned thrust system. Instead, these results suggest that rheologic heterogeneities may play a role in localizing deformation along the Big Bend of the San Andreas fault as the San Emigdio Mountains are compressed between the crystalline basement of Mount Pinos and oceanic crust that underlies the southern San Joaquin Valley.

  10. The use of baseline measurements and geophysical models for the estimation of crustal deformations and the terrestrial reference system. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bock, Y.

    1982-01-01

    Four possible estimators are investigated for the monitoring of crustal deformations from a combination of repeated baseline length measurements and adopted geophysical models, particularly an absolute motion plate model. The first estimator is an extension of the familiar free adjustment. The next two are Bayesian type estimators, one weak and one strong. Finally, a weighted constraint estimator is presented. The properties of these four estimators are outlined and their physical interpretations discussed. A series of simulations are performed to test the four estimators and to determine whether or not to incorporate a plate model for the monitoring of deformations. The application of these estimations to the maintenance of a new conventional terrestrial reference system is discussed.

  11. A domain decomposition approach to implementing fault slip in finite-element models of quasi-static and dynamic crustal deformation

    USGS Publications Warehouse

    Aagaard, B.T.; Knepley, M.G.; Williams, C.A.

    2013-01-01

    We employ a domain decomposition approach with Lagrange multipliers to implement fault slip in a finite-element code, PyLith, for use in both quasi-static and dynamic crustal deformation applications. This integrated approach to solving both quasi-static and dynamic simulations leverages common finite-element data structures and implementations of various boundary conditions, discretization schemes, and bulk and fault rheologies. We have developed a custom preconditioner for the Lagrange multiplier portion of the system of equations that provides excellent scalability with problem size compared to conventional additive Schwarz methods. We demonstrate application of this approach using benchmarks for both quasi-static viscoelastic deformation and dynamic spontaneous rupture propagation that verify the numerical implementation in PyLith.

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

    NASA Astrophysics Data System (ADS)

    Hori, T.; Ichimura, T.

    2015-12-01

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

  13. Active Beam Shaping System and Method Using Sequential Deformable Mirrors

    NASA Technical Reports Server (NTRS)

    Norman, Colin A. (Inventor); Pueyo, Laurent A. (Inventor)

    2015-01-01

    An active optical beam shaping system includes a first deformable mirror arranged to at least partially intercept an entrance beam of light and to provide a first reflected beam of light, a second deformable mirror arranged to at least partially intercept the first reflected beam of light from the first deformable mirror and to provide a second reflected beam of light, and a signal processing and control system configured to communicate with the first and second deformable mirrors. The first deformable mirror, the second deformable mirror and the signal processing and control system together provide a large amplitude light modulation range to provide an actively shaped optical beam.

  14. Quantifying crustal response to deep active intrusions with geodesy-based finite element modeling

    NASA Astrophysics Data System (ADS)

    Henderson, S. T.; Pritchard, M. E.; Elliott, J.

    2013-12-01

    The Altiplano-Puna Volcanic Complex (APVC, 21-24 S, 66-69 W) is a first order feature of the Central Andes Volcanic Arc. The APVC consists of over 10,000 km^3 of dacitic ignimbrites deposited in the late Miocene, making it one of the largest concentrations of silicic volcanism in the world. The persistent and intense magmatic flux in this region has likely contributed to the thickened crust (50-70 km), elevated geotherm (>50 C/km) and extensive partial melt (<20 %) inferred under the APVC in modern times. Furthermore, satellite geodetic measurements show surface deformation centered on Uturuncu Volcano (22.27 S, 67.22 W) that is consistent with an ongoing magmatic intrusion in the middle to lower crust. The unique geologic setting and availability of multiple geophysical datasets provide an exceptional opportunity to locate fluid accumulation depths and model the resulting crustal mechanical response. InSAR data between 05/1992 and 01/2011 show that the deformation anomaly is characterized by axis-symmetric constant vertical uplift of 1-10 mm/yr over a radius of 35 km, which is surrounded by 1-4 mm/yr subsidence out to 75 km. One possible explanation for such a signal is diapiric rise of melt from the middle crust. We seek to determine if observed deformation can be alternatively explained by vertical ascent of magma from the lower (~70 km) to middle crust (~20 km). Such a model would be consistent with the short duration of deformation from geomorphic studies (less than 2200 years) and the potential abrupt cessation of uplift seen in a single continuous GPS station starting in 04/2010 near the center of deformation. We therefore test multiple finite element models that match spatial and temporal surface deformation, achieve mass balance between source and sink reservoirs, and require physically realistic rheological parameters of the crust. Modeling is performed with Pylith finite element software on a cylindrical three dimensional domain with a radius of 300 km

  15. Heat flux and crustal radio-activity near the Sudbury neutrino observatory, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Mareschal, J.; Perry, C.; Jaupart, C.

    2009-05-01

    During its next phase, the Sudbury neutrino observatory (SNO) will detect geoneutrinos, antineutrinos produced by the decay of U and Th in the Earth. These observations will provide direct constraints on the contribution of radiogenic heat production in the crust and mantle to the energy budget of the Earth. The geoneutrino flux at SNO depends on the local level of crustal radio-activity. Surface heat flux data record average crustal radio-activity unaffected by small scale heterogeneities. We review all available heat flux data measurements in the Sudbury structure as well as measurements of U, Th, and K concentrations in the main geological units of the area. With all available data, the average heat flux in the Sudbury basin is ~53mW m-2, higher than the mean value of 42mW m-2 for the entire Canadian Shield. The elevated heat flux is due to high heat production in the shallow crust. We estimate that the average heat production of the upper crust near Sudbury is >1.5μ W m-3 compared to an average of 0.95μ W m-3 for the Superior Province. The high crustal radio-activity near Sudbury results in an about 50% increase of the local crustal component of the geoneutrino flux. Crustal radio-activity is highest in the southern part of the structure, near the Creighton mine where SNO is located. High heat flux and heat production values are also found in the Southern Province, on the margin of the Superior Province. An azimuthal variation in the geoneutrino flux with a higher flux from the south than from the north is expected on the basis on the present information. However, we shall need better estimates of the contribution of the rocks in the Superior Province to the North to assess the extent of azimuthal effects. The many available exploration drill holes and core samples provide an opportunity to determine the spatial variations in crustal radioactivity near SNO and improve the interpretation of future measurements of the geoneutrino flux.

  16. Active fault kinematics and crustal stresses along the Ionian margin of southeastern Sicily

    NASA Astrophysics Data System (ADS)

    Adam, J.; Reuther, C.-D.; Grasso, M.; Torelli, L.

    2000-11-01

    Since the late Cretaceous onset of plate convergence between Africa and Europe, the Malta Escarpment has been converted from a Mesozoic passive margin into a mega-hinge fault system with an additional sinistral strike-slip component. The modern tectonic stress regime with NW-SE-directed maximum horizontal stresses has been established since Late Messinian times. Since the Pleistocene, sinistral strike-slip deformation and contemporaneous normal faulting along the Malta Escarpment have induced the opening of oblique trending onshore grabens at the eastern margin of the Hyblean Plateau. In this study, we focus on the kinematics, the controlling state of stress, and the temporal variation of the neotectonic to active strike-slip and normal fault structures. The stress-tensor calculations reveals that the widespread map-scaled to meso-scaled normal fault structures are governed by the long-term extensional state of stress during the Quaternary. This long-term stress tensor is predominantly controlled by gravitational induced stresses due to vertical load ( σ1= SV) and lateral extension due to the topographic gradient of the Malta Escarpment ( σ3= Sh=NE-SW). In this case, the average tectonic stresses ( σ2= SH=NW-SE) transmitted by the regional to plate-tectonic stress field are significantly smaller than the gravitational induced stresses. In contrast, the clear localization of conjugate sets of meso-scaled strike-slip fault structures and shear zones without accompanying normal fault structures give strong indications for episodic seismotectonic strike-slip faulting under critical stress conditions. In this state, tectonically induced maximum horizontal stresses are successively increased by ongoing plate convergence from low-level stress magnitudes ( σ1= SV, σ2= SH=NW-SE) up to critical stress magnitudes ( σ1= SH=NW-SE, σ2= SV), which are significantly larger than gravitational stresses. At the critical state, seismotectonic stress release occurs by active

  17. Versatile Membrane Deformation Potential of Activated Pacsin

    PubMed Central

    Byrnes, Laura J.; Sondermann, Holger

    2012-01-01

    Endocytosis is a fundamental process in signaling and membrane trafficking. The formation of vesicles at the plasma membrane is mediated by the G protein dynamin that catalyzes the final fission step, the actin cytoskeleton, and proteins that sense or induce membrane curvature. One such protein, the F-BAR domain-containing protein pacsin, contributes to this process and has been shown to induce a spectrum of membrane morphologies, including tubules and tube constrictions in vitro. Full-length pacsin isoform 1 (pacsin-1) has reduced activity compared to its isolated F-BAR domain, implicating an inhibitory role for its C-terminal Src homology 3 (SH3) domain. Here we show that the autoinhibitory, intramolecular interactions in pacsin-1 can be released upon binding to the entire proline-rich domain (PRD) of dynamin-1, resulting in potent membrane deformation activity that is distinct from the isolated F-BAR domain. Most strikingly, we observe the generation of small, homogenous vesicles with the activated protein complex under certain experimental conditions. In addition, liposomes prepared with different methods yield distinct membrane deformation morphologies of BAR domain proteins and apparent activation barriers to pacsin-1's activity. Theoretical free energy calculations suggest bimodality of the protein-membrane system as a possible source for the different outcomes, which could account for the coexistence of energetically equivalent membrane structures induced by BAR domain-containing proteins in vitro. Taken together, our results suggest a versatile role for pacsin-1 in sculpting cellular membranes that is likely dependent both on protein structure and membrane properties. PMID:23236520

  18. Central Compact Objects in Kes 79 and RCW 103 as `Hidden' Magnetars with Crustal Activity

    NASA Astrophysics Data System (ADS)

    Popov, S. B.; Kaurov, A. A.; Kaminker, A. D.

    2015-05-01

    We propose that observations of `hidden' magnetars in central compact objects can be used to probe crustal activity of neutron stars with large internal magnetic fields. Estimates based on calculations by Perna & Pons, Pons & Rea and Kaminker et al. suggest that central compact objects, which are proposed to be `hidden' magnetars, must demonstrate flux variations on the time scale of months-years. However, the most prominent candidate for the `hidden' magnetars - CXO J1852.6+0040 in Kes 79 - shows constant (within error bars) flux. This can be interpreted by lower variable crustal activity than in typical magnetars. Alternatively, CXO J1852.6+0040 can be in a high state of variable activity during the whole period of observations. Then we consider the source 1E161348 - 5055 in RCW103 as another candidate. Employing a simple 2D-modelling we argue that properties of the source can be explained by the crustal activity of the magnetar type. Thus, this object may be supplemented for the three known candidates for the `hidden' magnetars among central compact objects discussed in literature.

  19. Precursory slow crustal deformation before short-term slow slip event in January 2006, recorded at Shingu borehole station southern Kii Peninsula

    NASA Astrophysics Data System (ADS)

    Fukuda, M.; Sagiya, T.

    2007-12-01

    In January 2006, a deep low frequency tremor activity and an associated short-term slow slip event occurred in the eastern Kii Peninsula and this coupled activity migrated to the northeast at a rate of 10km/day. We are monitoring crustal deformation at Shingu borehole station in the southeastern Kii peninsula. The Shingu borehole site is located about 100km landward from the Nankai Trough axis, and close to the epicenter of the 1944 Tonankai Earthquake. The borehole is 500 m deep and is equipped with an integrated multi-component borehole monitoring system developed by Ishii et al. (2002), consisting of 6 strain sensors (4 in horizontal, 2 in vertical), 2 pendulum tilt sensors, a magnetic direction finder, and a quartz thermometer. Each signal is originally recorded with a sampling frequency of 50 Hz. We decimated the original data into hourly data, which we decomposed into tidal response, barometric response, smoothed trend and random noise component by applying BAYTAP-G software [Tamura et al., 1991]. In the trend component from November 2005 to March 2006, we did not found deformation signal at the time of the Jan. 2006 tremor event. However, we found three significant slow strain changes from the processed records. Two of them coincide with the occurrence of the tremor activities in the southern Kii Peninsula, and are characterized by N-S contraction (0.019-0.031 ppm) and E-W extension (0.025-0.038 ppm). These are the first evidence of the short-term slow slip event in this area. The third change is characterized by NW-SE extension (0.026 ppm), N-S contraction (0.012 ppm), E-W extension (0.022 ppm), and southwestward tilting (0.23 micro rad). It occurred from December 29, 2005 to January 2, 2006, just before the tremor and slip event in January 2006, but was not accompanied by any tremor activity. We conducted a series of inversion analysis to infer the source of this possible slow slip event. We assumed that the slow slip event was caused by a reverse fault

  20. Crustal movements at a divergent plate boundary: interplay between volcano deformation, geothermal processes, and plate spreading in the Northern Volcanic Zone, Iceland since 2008.

    NASA Astrophysics Data System (ADS)

    Drouin, Vincent; Sigmundsson, Freysteinn; Hreinsdóttir, Sigrún; Ofeigsson, Benedikt G.; Sturkell, Erik; Islam, Tariqul

    2014-05-01

    Iceland is a subaerial part of the Mid-Atlantic Ridge, where the divergent plate boundary between the North-American and Eurasian Plates can be studied. The Northern Volcanic Zone (NVZ) of Iceland, comprised of several volcanic systems, is particularly well suited to study interplay between volcanoes, geothermal areas and plate spreading, as the zone is relatively simple and accommodates the full spreading of the plates (18.6 mm/yr in a direction of 105 degrees according to NUVEL-1A predictions). The most recent volcanic activity in the area was the Krafla rifting episode (1975-1984). In 2007-2008 two intrusive events were detected: one in Upptypingar and the other in Þeistareykir. Extensive crustal deformation studies have been carried out in the NVZ; we report the results of recent GPS and Interferometric Synthetic Aperture Radar (InSAR) studies focusing on Krafla, Þeistareykir and Askja volcanic systems in the NVZ. An extensive GPS survey was undertaken in 2013, with over 135 stations occupied. This data was evaluated in conjunction with data acquired since 2008, to generate a velocity field spanning this entire time period. In addition to an existing continuous GPS (cGPS) station, three cGPS stations were installed in the area in 2011-2012. The 2008-2013 GPS velocities were compared to earlier GPS results, and complementary analysis of InSAR images was undertaken. Earlier studies have shown that the Krafla caldera underwent uplift during 1984-1989, followed by subsidence. Since 1995, the maximum subsidence in Krafla has shifted from directly above the shallow magma chamber towards an array of boreholes (geothermal exploitation) in Leirbotnar. Similar subsidence has been observed around another array of boreholes in Bjarnaflag, 7 km further south. The most significant signal on the velocities calculated from campaign GPS data over the 5 year period, is plate spreading with an E-W velocity of about 12 mm/yr over a 30 km wide area. However it also shows an

  1. Quaternary deformation

    SciTech Connect

    Brown, R.D. Jr.

    1990-01-01

    Displaced or deformed rock units and landforms record the past 2 m.y. of faulting, folding, uplift, and subsidence in California. Properly interpreted, such evidence provides a quantitative basis for predicting future earthquake activity and for relating many diverse structures and landforms to the 5 cm/yr of horizontal motion at the boundary between the North American and Pacific plates. Modern techniques of geologic dating and expanded research on earthquake hazards have greatly improved our knowledge of the San Andreas fault system. Much of this new knowledge has been gained since 1965, and that part which concerns crustal deformation during the past 2 m.y. is briefly summarized here.

  2. Crustal deformation and seismic measurements in the region of McDonald Observatory, West Texas. [Texas and Northern Chihuahua, Mexico

    NASA Technical Reports Server (NTRS)

    Dorman, H. J.

    1981-01-01

    The arrival times of regional and local earthquakes and located earthquakes in the Basin and Range province of Texas and in the adjacent areas of Chihuahua, Mexico from January 1976 to August 1980 at the UT'NASA seismic array are summarized. The August 1931 Texas earthquake is reevaluated and the seismicity and crustal structure of West Texas is examined. A table of seismic stations is included.

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

    NASA Astrophysics Data System (ADS)

    Azzouzi, R.

    2009-04-01

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

  4. Late Cenozoic regional uplift and localised crustal deformation within the northern Arabian Platform in southeast Turkey: Investigation of the Euphrates terrace staircase using multidisciplinary techniques

    NASA Astrophysics Data System (ADS)

    Demir, Tuncer; Seyrek, Ali; Westaway, Rob; Guillou, Hervé; Scaillet, Stéphane; Beck, Ant; Bridgland, David R.

    2012-09-01

    We present the results of detailed field investigations of the fluvial succession exposed along the Euphrates valley adjoining the Atatürk Dam in the northern part of the Arabian Platform within SE Turkey. This work, which has used Differential GPS surveying to obtain accurate heights of deposits and Shuttle Radar Topographic Mission imagery for location purposes, has included documentation of many fresh sections exposed by quarrying. The work has been supplemented by unspiked Ksbnd Ar dating of late Middle Miocene to Late Miocene basalt flows, which are widespread in the region, providing a chronology for the early stages of development of this river system following regional emergence above sea-level in the early Middle Miocene. For example, beside the Atatürk Dam Lake at Siverek İskelesi, basalt dated to 10.24 ± 0.22 Ma (± 2σ) caps a polymict Euphrates gravel some 80 m above the modern river; this is the oldest Euphrates terrace currently recognised. However, amounts and rates of fluvial incision are shown to vary across the northern Arabian Platform in a complex manner, due to the interaction between regional uplift and localised vertical crustal motions caused by slip on active reverse faults beneath anticlines. The study reach downstream of the Atatürk Dam includes the footwall of one such fault, beneath the Bozova Anticline; we estimate that the resulting rate of localised subsidence, superimposed onto the regional uplift that has also been occurring, has been ~ 0.01 mm a- 1 during the present phase of crustal deformation, which began at ~ 3.7-3.6 Ma, but was higher, maybe ~ 0.03 mm a- 1, during the previous phase, which began at ~ 6 Ma, when the pattern of plate motions in the surrounding region was different. A large palaeo-lake centred north of the present study region around the city of Adıyaman is inferred to have existed during this ~ 6 Ma to ~ 3.7-3.6 Ma phase of plate motion, apparently because the relatively rapid localised hanging

  5. Active and long-lived permanent forearc deformation driven by the subduction seismic cycle

    NASA Astrophysics Data System (ADS)

    Aron Melo, Felipe Alejandro

    I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the permanent deformation style experienced by the forearc following great subduction ruptures, such as the 2010 M w8.8 Maule, Chile and 2011 Mw9.0 Tohoku, Japan earthquakes. These events triggered large, shallow seismicity on upper plate normal faults above the rupture reaching Mw7.0. First I present new structural data from the Chilean Coastal Cordillera over the rupture zone of the Maule earthquake. The study area contains the Pichilemu normal fault, which produced the large crustal aftershocks of the megathrust event. Normal faults are the major neotectonic structural elements but reverse faults also exist. Crustal seismicity and GPS surface displacements show that the forearc experiences pulses of rapid coseismic extension, parallel to the heave of the megathrust, and slow interseismic, convergence-parallel shortening. These cycles, over geologic time, build the forearc structural grain, reactivating structures properly-oriented respect to the deformation field of each stage of the interplate cycle. Great subduction events may play a fundamental role in constructing the crustal architecture of extensional forearc regions. Static mechanical models of coseismic and interseismic upper plate deformation are used to explore for distinct features that could result from brittle fracturing over the two stages of the interplate cycle. I show that the semi-elliptical outline of the first-order normal faults along the Coastal Cordillera may define the location of a characteristic, long-lived megathrust segment. Finally, using data from the Global CMT catalog I analyzed the seismic behavior through time of forearc regions that have experienced great subduction ruptures >Mw7.7 worldwide. Between 61% and 83% of the cases where upper plate earthquakes exhibited periods of increased seismicity

  6. Active deformation and seismicity in the Southern Alps (Italy): The Montello hill as a case study

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Pondrelli, Silvia; Salimbeni, Simone; Cavaliere, Adriano; Serpelloni, Enrico; Danecek, Peter; Lovati, Sara; Massa, Marco

    2015-06-01

    The Montello anticline is a morphotectonic feature of the east pede-mountain of the South Alpine Chain in northern Italy, which lies ca. 40 km northwest of Venice, Italy. The purpose of this study is to characterize the present-day crustal deformation and seismotectonics of the Montello area through multi-parametric geophysical observations. We used new data obtained from the installation of a temporary network of 12 seismic stations and 6 GPS sites. The GPS observations indicate that there is ~ 1 mm/yr shortening across the Montello thrust. Sites located north of the Montello thrust front deviate from the ~ NNW-ward Adria-Eurasia convergence direction, as they are constrained by a relative rotation pole in northwestern Italy that has a NNE-ward motion trend. Over 18 months, seismographic recordings allowed us to locate 142 local seismic events with Ml 0.5-3.5 with good reliability (rms < 0.5). After cross-correlation analysis, we classified 42 of these events into six clusters, with cross-correlation thresholds > 0.80. The source focal solutions indicate that: (i) there is thrusting seismic activity on the basal, sub-horizontal, portion of the Montello structure; and (ii) strike-slip source kinematics prevail on the western edge of the Montello hill. Our observations on the source mechanisms and the measured crustal deformation confirm that the Montello thrust is tectonically active.

  7. Dependency of continental crustal rupture, decompression melt initiation and OCT architecture on lithosphere deformation modes during continental breakup: Numerical experiments

    NASA Astrophysics Data System (ADS)

    Jeanniot, L.; Kusznir, N. J.; Manatschal, G.

    2012-12-01

    During the continental breakup process, the initiation of sea-floor spreading requires both the rupture of the continental crust and the initiation of decompression melting. Using numerical experiments, we investigate how the deformation mode of continental lithosphere thinning and stretching controls the rupture of continental crust and lithospheric mantle, the onset of decompression melting and their relative timing. We use a two dimensional finite element viscous flow model to describe lithosphere and asthenosphere deformation. This flow field is used to advect lithosphere and asthenosphere material and temperature. Decompression melting is predicted using the parameterization scheme of Katz et al. (2003). Consistent with the observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996), we assume that the topmost continental and oceanic lithosphere, corresponding to the cooler brittle seismogenic layer, deforms by extensional faulting (which we approximate to pure-shear deformation) and magmatic intrusion. Beneath this topmost lithosphere layer approximately 15-20 km thick, we assume that deformation occurs in response to passive upwelling and thermal and melt buoyancy driven small-scale convection. The relative contribution of these deformation components is parameterised by the ratio Vz/Vx, where Vx is the half spreading rate applied to the topmost lithosphere deformation and Vz is the upwelling velocity associated with the small scale convection. We use a series of numerical experiments to investigate the dependency of continental crust and lithosphere rupture, decompression melt initiation, rifted margin ocean-continent transition architecture and subsidence history on the half-spreading rate Vx, buoyancy driven upwelling rate Vz, the ratio Vz/Vx and upper lithosphere pure-shear width W. Based on the numerical experiment results we explore a polyphase evolution of deformation modes leading to continental breakup, sea

  8. Rapid, Repeat-sample Monitoring of Crustal Deformations and Environmental Phenomena with the Uninhabited Aerial Vehicle Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Smith, Robert C.

    2006-01-01

    The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) is a precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR) mission being developed by the Jet Propulsion Laboratory and the Dryden Flight Research Center in support of NASA s Science Mission Directorate. UAVSAR's unique ability to fly a repeatable flight path, along with an electronically steerable array, allows interferometric data to be obtained with accuracies measured in millimeters. Deploying the radar on an airborne platform will also allow for radar images to be collected and compared with images from the same area taken hours or even years later - providing for long-term trending and near real-time notification of changes and deformations. UAVSAR s data processing algorithms will provide for near-real time data reduction providing disaster planning and response teams with highly accurate data to aid in the prediction of, and response to, natural phenomena. UAVSAR data can be applied to increasing our understanding of the processes behind solid earth, cryosphere, carbon cycle and other areas of interest in earth science. Technologies developed for UAVSAR may also be applicable to a future earth-orbiting InSAR mission and possibly for missions to the Moon or Mars. The UAVSAR is expected to fly on a Gulfstream III aircraft this winter, followed by a flight test program lasting until the second half of 2007. Following radar calibration and data reduction activities, the platform will be ready for science users in the summer of 2008.

  9. GPS measurements of crustal deformation within the Pacific-Australia plate boundary zone in Irian Jaya, Indonesia

    NASA Astrophysics Data System (ADS)

    Puntodewo, S. S. O.; McCaffrey, R.; Calais, E.; Bock, Y.; Rais, J.; Subarya, C.; Poewariardi, R.; Stevens, C.; Genrich, J.; Fauzi; Zwick, P.; Wdowinski, S.

    1994-10-01

    Global Positioning System (GPS) measurements made in 1991, 1992 and 1993 provide preliminary estimates of slip distribution between the Australian and Pacific plates in Irian Jaya, Indonesia. We interpret the GPS results with constraints from earthquake mechanisms and slip vectors, recent marine surveys, and geology. Three GPS sites in southeastern Irian Jaya show motions that are within 10 mm/yr of the expected motion of Australia. A coast-to-coast N-S baseline along 140.5°E crosses all known onland regions of active deformation but reveals no more than 15 mm/yr of shortening and 20 mm/yr of left-lateral shear in the 27-month period. The remaining 40 mm/yr of expected convergence between the Pacific and Australian plates probably occurs at the New Guinea trough. GPS sites on the island of Biak, at 136°E, and at Sorong, near the western tip of Bird's Head (at 131°E), both move 90-100 mm/yr in a WSW direction relative to Irian Jaya, but less than 15 mm/yr relative to each other. These sites are on either side of the Sorong fault and demonstrate that it is not presently the major boundary between the Australian and Pacific plates. Instead the plate boundary is now south of the Sorong and Biak sites. Earthquakes suggest possible structures that accomodate motion between Bird's Head and Australia but the relative importance of them remains uncertain.

  10. A densely spaced array of sea level monitors for the detection of vertical crustal deformation in the Shumagin seismic gap, Alaska

    NASA Technical Reports Server (NTRS)

    Beavan, John; Hurst, Ken; Bilham, Roger; Shengold, Laurence

    1986-01-01

    A network of sea level gauges has been installed with about 40 km spacing in the Shumagin Islands in order to detect relative vertical motion, in particular, possible crustal motion precursory to an expected major earthquake. This required the development and deployment of a pressure sensor sea level gauge suitable for installation on remote and harsh coastlines. Data are collected in near-real-time via satellite, both in order to exploit fully any precursors that may be observed and to provide continuous information on the status of the instruments. Using Wiener filtering techniques, it has been determined conservatively that no relative vertical crustal motion greater than 0.1 m between stations has occurred during 1981-1985. This is consistent with independent geodetic leveling and trilateration data, though evidence exists for more rapid deformation during 1978-1980. The sea level data collected so far have an rms noise level of about 0.04 m after processing; this is limited in part by the pressure sensor and associated electronics. Improved prressure gauges with better long-term stability have recently been installed. A short-baseline tiltmeter operating in a tunnel has demonstrated that suitably designed and located land-based tiltmeters have a lower noise level, and hence better precursor detection characteristics than the sea level gauges, at monthly and shorter periods.

  11. Crustal deformation at very long baseline interferometry sites due to seasonal air-mass and ground water variations

    NASA Technical Reports Server (NTRS)

    Stolz, A.; Larden, D. R.

    1980-01-01

    The seasonal deformation normal to the Earth's surface was calculated at stations involved or interested in very long baseline interferometry (VLBI) geodesy and at hypothetical sites in Australia and Brazil using global atmospheric pressure data, values for groundwater storage, and load Love numbers deduced from current Earth models. It was found that the annual range of deformation approached the centimeter level measuring potential of the VLBI technqiue at Greenbank, Haystack, and the Brazil site.

  12. Monitoring crustal deformations in the Northern Caucasus using a high precision long base laser strainmeter and the GPS/GLONASS network

    NASA Astrophysics Data System (ADS)

    Milyukov, Vadim; Kopaev, Alexander; Zharov, Vladimir; Mironov, Alexey; Myasnikov, Andrey; Kaufman, Mark; Duev, Dmitry

    2010-04-01

    The results of long-term monitoring of crustal deformations in the Northern Caucasus using a high precision long base laser strainmeter and the GPS/GLONASS network are presented. The Baksan laser interferometer-strainmeter with a measuring arm length of 75 m and resolution of 2.3×10-13 is mounted inside an underground gallery in a mountainous area near to the dormant volcano Elbrus. An analysis of crustal strains recorded by the Baksan laser interferometer revealed the shallow magmatic chamber in the structure of Elbrus Volcano. The analysis is based on estimation of parameters of the resonant modes of magmatic structures excited by powerful teleseismic signals. We estimated the depth and dimensions of the magma chamber, as well as the properties of the magma fluid which are corroborated by available geological and geophysical evidence. The harmonic analysis of tidal strains, performed with the help of the ETERNA software package, is defined that amplitude factors of the main diurnal and semidiurnal waves appear to have been underestimated. The observed anomaly of the M2 wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus Volcano. The GPS observations in the Nortern Caucasus area began in 1993 as a part of the SELF project. Currently, four stationary GPS/GLONASS stations located in this area form the base of the regional Northern Caucasus Deformation Array (NCDA). Based on the results of first observations we find constraints on the velocity field and uplift of the Nortern Caucasus. The modern motion of the Northern Caucasus is characterised by the velocity value of 28 mm/year and is mainly defined by the general tectonic movement of the Eurasian plate in the northeast direction in the ITRF.

  13. Upper crustal emplacement and deformation of granitoids inside the Uppermost Unit of the Cretan nappe stack: constraints from U-Pb zircon dating, microfabrics and paleostress analyses

    NASA Astrophysics Data System (ADS)

    Kneuker, Tilo; Dörr, Wolfgang; Petschick, Rainer; Zulauf, Gernold

    2015-03-01

    The present study is dealing with the emplacement and deformation of diorite and quartz diorite exposed along new road cuts between Agios Nikolaos and Sitia (Uppermost Unit, eastern Crete). Mingling of both melt types is indicated by enclaves of diorite inside quartz diorite and vice versa. The diorite and quartz diorite intruded into coarse-grained white marble, which is in lateral contact to, but also forms the roof of, the intrusive body. Evidence for contact metamorphism is indicated by increasing grain size of calcite in the marble with decreasing distance from the diorite. U-Pb (TIMS) dating of zircons, separated from quartz diorite, yielded a concordant age at 74.0 ± 0.25 Ma, which is interpreted as emplacement age. As this age is close to published K-Ar cooling ages of hornblende and biotite, the melt should have intruded and cooled down rapidly at upper structural levels, which is not common for granitoids of the Uppermost Unit of Crete. Upper crustal melt emplacement is also documented by stoped blocks and by the lack of any ductile (viscous) deformation. The diorite and quartz diorite, however, are affected by strong post-Oligocene brittle faulting. Paleostress analysis, based on these faults, revealed a change in stress field from N-S and NNW-SSE shortening by thrusting (convergence between African and European plates) to NNE-SSW and NE-SW shortening accommodated by strike-slip (SW-ward extrusion of the Anatolian microplate). Calcite-twin density indicates high differential stress (260 ± 20 MPa) related to these phases of crustal shortening.

  14. Crustal structure of the northwestern Vizcaino block and Gorda Escarpment, offshore northern California, and implications for postsubduction deformation of a paleoaccretionary margin

    NASA Astrophysics Data System (ADS)

    Leitner, Beate; TréHu, Anne M.; Godfrey, Nicola J.

    1998-10-01

    The Vizcaino block is an anomalously shallow region of the western U.S. continental margin located southwest of the Mendocino triple junction. It originated as part of the accretionary prism of the North America plate and was transferred to the Pacific plate in the Miocene as the Pacific-North America plate boundary migrated ˜130 km eastward, forming the Gorda Escarpment at its northern boundary. We present hybrid crustal models for the northwestern part of the Vizcaino block derived from marine seismic and gravity data. The velocity and density structure of the northwestern Vizcaino block are compatible with paleoaccretionary complex material similar to San Simeon/Patton terrane overlying oceanic crust or a mafic layer. The most significant result of our modeling is an abrupt increase in Moho dip from ˜5° to ˜20-30° beneath the western edge of the Oconostota ridge along the northwestern margin of the Vizcaino block. This Moho dip is steeper than observed anywhere along the Cascadia subduction zone, indicating postsubduction deformation. We suggest that the paleotrench was deformed by compression, which reactivated preexisting thrust faults in the upper crust and thickened the crust within this apparent weak zone. At least part of the deformation predates late Pliocene Pacific-North America plate convergence and may result mainly from north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault. North-south compression continues today and may dynamically support the uplifted northern margin of the Vizcaino block, although the primary locus of deformation shifted to the relatively weak Gorda plate sometime prior to 3 Ma.

  15. GPS observations of seasonal crustal deformation and long-term land subsidence in response to water storage changes in California

    NASA Astrophysics Data System (ADS)

    Anderson, K. J.; De Linage, C.; Famiglietti, J. S.

    2011-12-01

    Observations of vertical land surface height from Scripps Orbit and Permanent Array Center (SOPAC) GPS stations throughout California and the Western United States reveal significant seasonal and long-term land surface responses to water storage changes. Long-term land surface subsidence in the Central Valley is due to aquifer compaction resulting from ongoing groundwater depletion. Seasonal motion of the land surface due to elastic crustal loading provides insight about seasonal surface water loads such as snow water equivalent, soil moisture, and reservoir storage. This research explores the relationship between water storage changes observed by GRACE and Snotel and the land surface responses observed by GPS, and the potential for new applications of GPS for monitoring various components of water storage.

  16. Vertical crustal motion of active plate convergence in Taiwan derived from tide gauge, altimetry, and GPS data

    NASA Astrophysics Data System (ADS)

    Chang, Emmy T. Y.; Chao, Benjamin F.; Chiang, Chieh-Chung; Hwang, Cheinway

    2012-11-01

    Located at the converging junction between the Eurasian and Philippine Sea plates, the island of Taiwan is subject to an active lithospheric deformation as well as seismicity. Taking the difference between the satellite altimetry data (ALT) that give the absolute sea level variation and the tide gauge data (TG) that record the relative sea level variation, we obtain the absolute vertical crustal motion of the tide gauge sites. We use 20 TG stations along the west and east coasts of Taiwan along with the ALT measurements from the TOPEX/Poseidon-Jason satellites in the nearby waters. The ALT-TG results are compared with vertical GPS measurements in discussing vertical motion. We find a general subsidence of the entire Taiwan coast during the past two decades. The west coast sees no prominent vertical motion but with a severe local subsidence due to the over-withdrawal of groundwater. On the east coast, the ALT-TG results in the northern section demonstrate a northward dipping motion. The elastic thickness of the neighboring oceanic lithosphere modeled as an elastic plate with the flexure of the subducting plate shows that the adjacent Philippine Sea plate should be an old, thick oceanic plate, which could drag the slab into the mantle as manifested in a gentle northward subsidence in the northeast Taiwan. In the southern section of the east coast, the ALT-TG results reveal a segmented or undulating pattern in the vertical-motion rates. Judging from the different behaviors between the co-seismic and interseismic vertical motions marked by the major earthquakes during the studied period, we postulate a temporal saw-tooth scenario for the deformation in phases. It demonstrates the opposite motions under different mechanisms in the frontal sections of the subduction zone, which can be understood with lateral collision and slab dragging subject to varied temporal and spatial dependences.

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

    The nature and dynamics of time-dependent deformation along major seismic zones including the influence of irregularities in fault geometry on the earthquake cycle, and the processes contributing to the state of stress and rates of strain in plate interior regions were studied. The principle findings of the research are discussed.

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

    NASA Technical Reports Server (NTRS)

    Soloman, Sean C.

    1991-01-01

    The focus was in two broad areas during the most recent 6-month period: (1) the nature and dynamics of time dependent deformation and stress along major seismic zones; and (2) the nature of long-wavelength oceanic geoid anomalies in terms of lateral variations in upper mantle temperature and composition. The principle findings are described in the accompanying appendices.

  19. Mapping of surface ruptures and crustal deformations by field investigations and PALSAR/InSAR for the 2008 Wenchuan Earthquake, China

    NASA Astrophysics Data System (ADS)

    Hao, K.; Si, H.; Fujiwara, H.; Ozawa, T.

    2009-12-01

    The 2008 Wenchuan earthquake (Mw 7.9) ruptured partial faults along the 500 km-length Longmen Shan (LMS) thrust faults, resulted in major damage to the areas more than 100,000 km2, the death toll over 87,400, and the homeless of five million. Three weeks later we investigated the fields of heavily damage-belts along the LMS faults. The challenges of fieldworks included road blocked by landslides, inaccessible high-mountain areas, and unexpectedly political restrictions. On the three-sets of field investigations we found over 10 sites of coseismic surface ruptures along Guanxian-Anxian(GX-AX), and Yingxiu-Beichuan fault (YX-BC). Of them the maximum reached ~5m horizontal and ~6m vertical displacements at Housheng along YX-BC fault, and ~2m vertical at Bailu along GX-AX fault. Moreover, the left-slip fault at Xiaoyudong between of the two LMS faults, ruptured ~2.8m horizontal, and 1.5m vertical displacements as well. However, the irregularly distributed surface fault-ruptures and the huge areas inaccessible still left unknown even if many distinguished faults reported. Using interferometric synthetic aperture radar (InSAR) technology and Phased Array L-band SAR sensor (PALSAR) equipped on Advanced Land Observing Satellite (ALOS), we captured the whole pictures of faults movements and crustal deformations from the two-sets of data before and after the event. The larger deformation zones where the data was out of correlation range, occurred over 300km length of LMS faults, with a width of ~30 km in southwestern section, ~10km in northeastern section. Therefore, we created a novel bi-fault-slip model based on the field and satellite information along the LMS faults. The Inversion analysis of the elastic half-space dislocation theory using InSAR interferogram resulted in the fault-slips distributions on the bi-fault-slip model. The surface fault-slips analyzed are similarly with the field results. Furthermore, simulation of the fault-slips reconstructed the

  20. Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

    USGS Publications Warehouse

    Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

    2015-01-01

    Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

  1. Three-dimensional crustal structure in the Southern Alps region of New Zealand from inversion of local earthquake and active source data

    NASA Astrophysics Data System (ADS)

    Eberhart-Phillips, Donna; Bannister, Stephen

    2002-10-01

    P and S-P arrival time data from 311 earthquakes and several thousand offshore and onshore shots have been used in simultaneous inversion for hypocenters, three-dimensional (3-D) Vp and Vp/Vs models in the Southern Alps region, New Zealand. The combined data result in a highly nonuniform ray path distribution, and linked nodes are used in sparsely sampled areas. Gravity data are used to improve the model below 20-km depth, where it is poorly sampled by local earthquakes. The crustal Vp from 5 to 25 km depth is fairly uniform, generally ranging from 5.5 to 6.5 km/s, typical of graywacke and schist. Active fault zones tend to be correlated with low-velocity zones. Where the Alpine fault is primarily strike slip, it is characterized by a vertical low-velocity zone, to at least 15-km depth. Where the fault is dipping and has a large dip-slip component, it is characterized by a large region of low velocity above and southeast of the fault, to at least 14-km depth, consistent with fluids and fracture density from active deformation. A large high-velocity, high-resistivity feature in the eastern Southern Alps may represent Mesozoic schist of higher metamorphic grade than its surroundings, which is relatively rigid and serves to both reduce deformation in the overlying basin and concentrate deformation in the adjoining low-velocity region. The imaged crustal root is deepest 80-km south of Mt. Cook and is asymmetric with a sharper gradient on the northwestern side. The approximate Moho shows regional variation, with 5-10 km thicker crust in Otago than Canterbury.

  2. Constraints on crustal rheology and age of deformation from models of gravitational spreading in Ishtar Terra, Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, Suzanne E.; Soloman, Sean C.

    1992-01-01

    Gravitational spreading is expected to lead to rapid relaxation of high relief due to the high surface temperature and associated weak crust on Venus. In this study, we use new Magellan radar and altimetry data to determine the extent of gravitational relaxation in Ishtar Terra, which contains the highest relief on Venus as well as areas of extremely high topographic slope. Within Ishtar Terra the only mountain belts found on Venus, Akna, Danu, Freyja, and Maxwell Montes, nearly encircle the smooth, high (3-4 km) plateau of Lakshmi Planum. Finite-element models of this process give expected timescales for relaxation of relief and failure at the surface. From these modeling results we attempt to constrain the strength of the crust and timescales of deformation in Ishtar Terra. Below we discuss observational evidence for gravitational spreading in Ishtar Terra, results from the finite-element modeling, independent age constraints, and implications for the rheology and timing of deformation.

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

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1987-01-01

    The focus of the research was in two broad areas during the most recent 6 month period: the nature and dynamics of time-dependent deformation along major seismic zones, including the influence of irregularities in fault geometry on the earthquake cycles, and the processes contributing to the state of stress and rates of strain in plate interior regions. The principal findings of the research to date are described.

  4. Progressive deformation and superposed fabrics related to Cretaceous crustal underthrusting in western Arizona, U.S.A.

    USGS Publications Warehouse

    Laubach, S.E.; Reynolds, S.J.; Spencer, J.E.; Marshak, S.

    1989-01-01

    In the Maria fold and thrust belt, a newly recognized E-trending Cretaceous orogenic belt in the southwestern United States, ductile thrusts, large folds and superposed cleavages record discordant emplacement of crystalline thrust sheets across previously tilted sections of crust. Style of deformation and direction of thrusting are in sharp contrast to those of the foreland fold-thrust belt in adjacent segments of the Cordillera. The net effect of polyphase deformation in the Maria belt was underthrusting of Paleozoic and Mesozoic metasedimentary rocks under the Proterozoic crystalline basement of North America. The structure of the Maria belt is illustrated by the Granite Wash Mountains in west-central Arizona, where at least four non-coaxial deformation events (D1-D4) occurred during the Cretaceous. SSE-facing D1 folds are associated with S-directed thrusts and a low-grade slaty cleavage. D1 structures are truncated by the gently-dipping Hercules thrust zone (D2), a regional SW-vergent shear zone that placed Proterozoic and Jurassic crystalline rocks over upturned Paleozoic and Mesozoic supracrustal rocks. Exposures across the footwall margin of the Hercules thrust zone show the progressive development of folds, cleavage and metamorphism related to thrusting. D3 and D4 structures include open folds and spaced cleavages that refold or transect D1 and D2 folds. The D2 Hercules thrust zone and a D3 shear zone are discordantly crosscut by late Cretaceous plutons. ?? 1989.

  5. GPS-derived estimates of crustal deformation in the central and north Ionian Sea, Greece: 3-yr results from NOANET continuous network data

    NASA Astrophysics Data System (ADS)

    Ganas, A.; Marinou, A.; Anastasiou, D.; Paradissis, D.; Papazissi, K.; Tzavaras, P.; Drakatos, G.

    2013-07-01

    Ionian Sea (western Greece) is a plate-boundary region of high seismicity and complex tectonics, dominated by frequent earthquake activity along the right-lateral Cephalonia transform fault. We present an analysis of 30-s GPS data from five (5) continuous stations of NOANET (NOA permanent GPS network) spanning the period 2007-2010. Our results show N-S crustal shortening onshore Lefkada island of the order of 2-3 mm/yr which is probably related to increased locking on the offshore Lefkada fault. We also calculated a large difference (1:3) in the principal strain rate amplitude between extension and shortening for the central Ionian Sea.

  6. GPS Constraints on Eastern Nevada Basin and Range Crustal Deformation Before and During the February 21, 2008 M6.0 Wells, NV Earthquake

    NASA Astrophysics Data System (ADS)

    Hammond, W. C.; Blewitt, G.; Kreemer, C.

    2008-12-01

    oriented N59°W and contraction rates of 2.8±1.1 nanostrains/per year oriented N31°E (uncertainties scaled so that the normalized residual scatter in the velocities after removing the strain rate model is unity). This suggests that eastern Nevada experiences secular crustal deformation that is 1) significantly greater than zero, 2) has an orientation similar to the prevailing azimuth of shear in the Pacific/North America plate boundary zone, and 3) has direction of extension similar to the direction of coseismic extension during the earthquake.

  7. Mid-crustal emplacement and deformation of plutons in an Andean-style continental arc along the northern margin of the North China Block and tectonic implications

    NASA Astrophysics Data System (ADS)

    Zhang, Shuan-Hong; Zhao, Yue

    2013-11-01

    Outcrop mapping and thermobarometrical, thermochronological and microstructural analyses in five Late Carboniferous-Early Permian arc plutons in the northern North China Block (NCB) indicate a transition of tectonic regime from arc-perpendicular contraction to transpression and successive uplift and exhumation of the crustal rocks during magma emplacement and construction of the continental arc system. The early emplaced Daguangding and Boluonuo plutons (324-302 Ma) display well-developed, penetrative, moderately to steeply dipping magmatic foliations and high-temperature sub-solidus foliations that are parallel to host rock foliation near the contact. Widespread high-temperature sub-solidus foliations in these plutons indicate that they are syn-tectonic with N-S, arc-perpendicular shortening and record arc construction at a convergent continental margin. However, the late emplaced Tianqiao and Xianghuangqi-Wudaoyingzi plutons (288-274 Ma) display relatively weak magmatic fabrics at their margins and lack sub-solidus foliations and pluton-related ductile deformation of the contact host rocks. These structural differences likely reflect a kinematic transition from early arc-perpendicular contraction to late sinistral transpression during continental arc formation. Aluminum-in-hornblende barometry shows that their estimated emplacement depths decrease gradually from the Late Carboniferous (18.7 ± 0.8 km) to Early Permian (13.8 ± 0.9 km), indicating successive exhumation of the crustal rocks at an average rate of ca. 123 mm/ka over 40 million years of arc formation. 40Ar/39Ar thermochronological results show that cooling of the continental crust was very slow (4.9 °C/Ma) during arc construction in the Late Carboniferous-Late Permian but increased significantly during the Late Permian-Middle Triassic after arc termination. The mid-crust of the northern NCB remained very hot (> 530 °C) during arc construction and emplacement of the arc batholiths. Combined with

  8. Exploring Subduction, Slab Breakoff, and Upper-Plate Deformation in the Georgian Greater Caucasus: Shortening Estimates from Area- and Line-Balanced Crustal Scale Cross Sections

    NASA Astrophysics Data System (ADS)

    Trexler, C. C.; Cowgill, E.; Niemi, N. A.; Godoladze, T.

    2015-12-01

    Between the Black and Caspian Seas, the Greater Caucasus Mountains (GC) delineate the northern margin of the Arabia-Eurasia collision zone. The role of subduction in formation of the GC is not widely recognized, despite patterns of subcrustal seismicity attesting to its importance at the E end of the range. The GC currently absorbs most orogen-perpendicular plate convergence (11 mm/yr, 70% of total), but its tectonic evolution relation to subduction remain unclear. Proposed models include 1) subduction of an ~400 km wide backarc ocean basin followed by slab breakoff under the W end of the range; 2) loss of a lithospheric root followed by buoyancy-driven uplift; and 3) closure of a small (~100 km?) basin with no/minimal subduction. Patterns of modern seismicity, exhumation, and shortening are most consistent with the subduction/slab breakoff model, suggesting the western GC may capture the surface expression of processes associated with recent slab breakoff. Each model of the GC makes specific predictions for the amount of shortening within the orogen, with the subduction/breakoff model predicting large magnitudes of convergence. Here we estimate orogenic shortening by balancing mass along several, orogen-perpendicular, crustal-scale cross sections across the GC. First we estimate the original length of undeformed crust by comparing the modern deformed volume (determined from modern topography and moho depth and assuming no net erosional loss) with hypothesized end-member original crustal thicknesses (based on seismic data in the Eastern Black Sea and Scythian platform). These end-member assumptions allow shortening magnitudes as great as ~700 km (12 km-thick oceanic crust), and as small as ~100 km (39 km-thick Scythian margin). Second, we use line-length balanced crustal-scale geologic cross sections to estimate shortening in the western and central GC. We generated these sections using previously published 1:200k geologic maps and our own focused field

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

    NASA Technical Reports Server (NTRS)

    Soloman, Sean C.

    1991-01-01

    The focus of the research was in two broad areas: (1) the nature and dynamics of time dependent deformation and stress along major seismic zones; and (2) the nature of long wavelength oceanic geoid anomalies in terms of lateral variations in upper mantle temperature and composition. The principle findings of the research are described in the accompanying appendices. The first two and the fourth appendices are reprints of papers recently submitted for publication, and the third is the abstract of a recently completed thesis supported by this project.

  10. Application of the Global Positioning System to crustal deformation measurements. 3: Result from the southern California borderlands

    SciTech Connect

    Larson, K.M.

    1993-12-01

    Five years of measurements from the Global Positioning System (GPS) satellites collected between 1986 and 1991 are used to investigate deformation in the offshore regions of southern California. GPS provides the first practical technique to make precise geodetic measurements in the region. The geodetic network is situated along the California coastline from Vandenberg (120.6 deg W, 34.6 deg N) to San Diego, with additional sites on Santa Cruz, San Nicolas, Santa Catalina, Santa Rosa, and San Clemente Islands. The precision of horizontal interstation vectors is subcentimeter, and the interstation vector rate between Owens Valley Radio Observatory (OVRO) and Vandenberg agrees with the very long baseline interferometry derived rate to within one standard deviation. No significant motion is observed in th e western Santa Barbara Channel between Vandenberg and Santa Rosa Island, 0.5 +/- 1.6 mm/yr, where the quoted uncertainties are one standard deviation. Motions in the eastern Santa Barbara Channel are consistent with compressional deformation of 6 +/- 1 mm/yr at N16 +/- 3 deg E. This motion is in agreement with seismicity and an independent geodetic analysis for the period 1971-1987 (Larsen, 1991). San Clemente Island is moving relative to San Diego at the rate of 5.9 +/- 1.8/yr at a direction of N38 +/- 20 deg W. The motion between San Nicolas Island and San Clemente Island, 0.8 +/- 1.5 mm/yr, is insignificant.

  11. Compositional dependence of lower crustal viscosity

    NASA Astrophysics Data System (ADS)

    Shinevar, William J.; Behn, Mark D.; Hirth, Greg

    2015-10-01

    We calculate the viscosity structure of the lower continental crust as a function of its bulk composition using multiphase mixing theory. We use the Gibbs free-energy minimization routine Perple_X to calculate mineral assemblages for different crustal compositions under pressure and temperature conditions appropriate for the lower continental crust. The effective aggregate viscosities are then calculated using a rheologic mixing model and flow laws for the major crust-forming minerals. We investigate the viscosity of two lower crustal compositions: (i) basaltic (53 wt % SiO2) and (ii) andesitic (64 wt % SiO2). The andesitic model predicts aggregate viscosities similar to feldspar and approximately 1 order of magnitude greater than that of wet quartz. The viscosity range calculated for the andesitic crustal composition (particularly when hydrous phases are stable) is most similar to independent estimates of lower crust viscosity in actively deforming regions based on postglacial isostatic rebound, postseismic relaxation, and paleolake shoreline deflection.

  12. Effect of length-scale on localization of shear zones along precursor fractures and layers during deformation of middle to lower crustal rocks

    NASA Astrophysics Data System (ADS)

    Mancktelow, Neil; Pennacchioni, Giorgio; Hawemann, Friedrich; Wex, Sebastian; Camacho, Alfredo

    2016-04-01

    Deformation of high grade rocks at middle to lower crustal levels involves both distributed and more highly localized ductile strain, with localized shear zones developing on elongate near-planar rheological precursors. These planar heterogeneities may be compositional layers (e.g. dykes) or pre-existing or newly developed fractures, with or without pseudotachylyte. Usual rheological models for viscous rock deformation are scale independent. The geometry of developing localized shear zones should therefore be scalable and depend only on the pre-existing geometry and imposed boundary conditions, as shown in numerical and analogue models. However, this is not what is observed in natural examples. Shear zones preferentially or exclusively develop on long fractures and dykes, typically on the scales of many (tens of) metres to (tens of) kilometres, whereas smaller-scale healed fractures, basic enclaves and short layers or inclusions are less prone to reactivation and locally may be largely ignored. Preferential localization of strain on these longer structures means that the intervening rock volumes remain low-strain domains, so that the smaller-scale planar heterogeneities are effectively shielded during progressive deformation. Any localized deformation of these intervening low-strain domains requires the formation of new elongate fractures acting as a necessary precursor for subsequent localization. These field observations suggest that ductile shear zone localization is more effective with increasing length of the approximately planar precursor. Localized shear zones do not develop by propagation away from an initial small heterogeneity. Instead, their length is largely predetermined by the length of the controlling precursor structure and in-plane propagation of the tips appears to be very limited. Preferential shear reactivation of longer precursors introduces a length-scale dependence from the very initiation of localized "viscous" or "ductile" shear zones

  13. Crustal deformation and magmatic processes at Laguna del Maule volcanic field (Chile): Geodetic measurements and numerical models

    NASA Astrophysics Data System (ADS)

    Le Mevel, Helene

    The Laguna del Maule (LdM) volcanic field in Chile is an exceptional example of postglacial rhyolitic volcanism in the Southern Volcanic Zone of the Andes. Since 2007, LdM has experienced an unrest episode characterized by high rates of deformation measured by interferometric analysis of synthetic aperture radar (SAR) images acquired between 2007 and 2016, and data from the Global Positioning System (GPS) recorded since 2012 at five stations. The inflating region includes most of the 16--km-by--14--km ring of rhyolitic domes and coulees. The fastest-moving GPS station (MAU2) has a velocity vector of [[special character omited]72 +/- 4, 19 +/- 1, 194 +/- 3] mm/yr between 2012 and 2016 for the eastward, northward, and upward components, respectively. First, we model the InSAR observations assuming a rectangular dislocation in a half space with uniform elastic properties. The best time function for modeling the InSAR data set is a double exponential model with rates increasing from 2007 through 2010 and decreasing slowly since 2011. Modeling of historical uplift at Yellowstone, Long Valley, and Three Sisters volcanic fields suggests a common temporal evolution of vertical displacement rates. We hypothesize that magma intruding into an existing silicic magma reservoir is driving the surface deformation and present a new dynamic model to describe this process. A Newtonian fluid characterized by its viscosity, density, and pressure flows through a vertical conduit, intruding into a reservoir embedded in an elastic domain and leading to time-dependent surface deformation. Using a grid-search optimization, we minimize the misfit to the InSAR displacement data by varying the three parameters governing the analytical solution: the characteristic timescale tauP for magma propagation, the injection pressure, and the inflection time when the acceleration switches from positive to negative. For a spheroid with semi-major axis a = 6200 m, semi-minor axis c = 100 m, located at a

  14. Analytical modeling of gravity changes and crustal deformation at volcanoes: The Long Valley caldera, California, case study

    USGS Publications Warehouse

    Battaglia, Maurizio; Hill, D.P.

    2009-01-01

    Joint measurements of ground deformation and micro-gravity changes are an indispensable component for any volcano monitoring strategy. A number of analytical mathematical models are available in the literature that can be used to fit geodetic data and infer source location, depth and density. Bootstrap statistical methods allow estimations of the range of the inferred parameters. Although analytical models often assume that the crust is elastic, homogenous and isotropic, they can take into account different source geometries, the influence of topography, and gravity background noise. The careful use of analytical models, together with high quality data sets, can produce valuable insights into the nature of the deformation/gravity source. Here we present a review of various modeling methods, and use the historical unrest at Long Valley caldera (California) from 1982 to 1999 to illustrate the practical application of analytical modeling and bootstrap to constrain the source of unrest. A key question is whether the unrest at Long Valley since the late 1970s can be explained without calling upon an intrusion of magma. The answer, apparently, is no. Our modeling indicates that the inflation source is a slightly tilted prolate ellipsoid (dip angle between 91?? and 105??) at a depth of 6.5 to 7.9??km beneath the caldera resurgent dome with an aspect ratio between 0.44 and 0.60, a volume change from 0.161 to 0.173??km3 and a density of 1241 to 2093??kg/m3. The larger uncertainty of the density estimate reflects the higher noise of gravity measurements. These results are consistent with the intrusion of silicic magma with a significant amount of volatiles beneath the caldera resurgent dome. ?? 2008 Elsevier B.V.

  15. RNGCHN: a program to calculate displacement components from dislocations in an elastic half-space with applications for modeling geodetic measurements of crustal deformation

    NASA Astrophysics Data System (ADS)

    Feigl, Kurt L.; Dupré, Emmeline

    1999-07-01

    The RNGCHN program calculates a single component of the displacement field due to a finite or point-source dislocation buried in an elastic half space. This formulation approximates the surface movements produced by earthquake faulting or volcanic intrusion. As such, it is appropriate for modeling crustal deformation measured by geodetic surveying techniques, such as spirit leveling, trilateration, Very Long Baseline Interferometry (VLBI), Global Positioning System (GPS), or especially interferometric analysis of synthetic aperture radar (SAR) images. Examples suggest that this model can fit simple coseismic earthquake signatures to within their measurement uncertainties. The program's input parameters include fault position, depth, length, width, strike, dip, and three components of slip. The output consists of displacement components in the form of an ASCII list or a rectangular array of binary integers. The same program also provides partial derivatives of the displacement component with respect to all 10 input parameters. The FORTRAN source code for the program is in the public domain and available as the compressed tar file rngchn.tar.Z in the directory/pub/GRGS via the Internet by anonymous ftp to spike.cst. cnes.fr. This distribution includes worked examples and a MATLAB interface.

  16. Investigation of the deep crustal structure and magmatic activity at the NW Hellenic Volcanic Arc with 3-D aeromagnetic inversion and seimotectonic analysis.

    NASA Astrophysics Data System (ADS)

    Efstathiou, Angeliki; Tzanis, Andreas; Chailas, Stylianos; Stamatakis, Michael

    2013-04-01

    We report the results of a joint analysis of geophysical (aeromagnetic) and seismotectonic data, applied to the investigation of the deep structure, magmatic activity and geothermal potential of the north-western stretches of the Hellenic Volcanic Arc (HVA). The HVA is usually considered to be a single arcuate entity stretching from Sousaki (near Corinth) at the NW, to Nisyros Island at the SE. However, different types of and their ages indicate the presence of two different volcanic groups. Our study focuses on the northern part of the west (older) volcanic group and includes the Crommyonian (Sousaki) volcanic field at the west end of Megaris peninsula (east margin on the contemporary Corinth Rift), the Aegina and Methana volcanic complex at the Saronic Gulf, where typical Quaternary calc-alkaline volcanics predominate, and the Argolid peninsula to the south and south-west. In addition to the rocks associated with Quaternary volcanism, the study area includes a series of Mesozoic ultramafic (ophiolitic) outcrops at the Megaris peninsula, to the north and north-east of the Crommyonian volcanic field, as well as throughout the Argolid. A major deep structural and tectonic feature of the study area, and one with profound influence on crustal deformation and the evolution of rapidly deforming extensional structures like the Corinth Rift and the Saronic Gulf, is the local geometry and dynamics of the African oceanic crust subducting beneath the Aegean plate. Locally, the subducting slab has a NNW strike and ENE plunge, with the dip angle changing rapidly (steepening) approx. beneath the Argolid. The aeromagnetic data was extracted from the recently (re)compiled aeromagnetic map of Greece (Chailas et al, 2010) and was inverted with the UBC-GIF magnetic inversion suite (Li and Oldenburg, 1996). The inversion included rigorous geological constraints introduced by means of numerous in-situ magnetic susceptibility measurements. The inversion has imaged several isolated

  17. Crustal root beneath the Rif Cordillera as imaged from both active seismic data and teleseismic receiver functions.

    NASA Astrophysics Data System (ADS)

    Diaz, Jordi; Gil, Alba; Gallart, Josep; Carbonell, Ramon; Harnafi, Mimoun; Levander, Alan

    2015-04-01

    The Rif cordillera forms, together with the Betic ranges, one of the tightest orogenic arcs on Earth. This continental boundary zone is dominated now by the slow convergence between Nubia and Eurasia, but with clear evidences of extensional tectonics. One of the missing elements to constrain the complex geodynamics of the Gibraltar Arc System is the knowledge of the crustal architecture beneath northern Morocco. In the last decade a major effort has been done in this sense, from active and passive seismics. We compile here the recent results available from the Rif domains. Two 330 km long wide angle DSS profiles were recorded end of 2011 across the Rif in NS and EW transects within the Rifsis project, complemented by onshore recordings of the Gassis-WestMed marine profiles. At the same period, BB seismic arrays were deployed in the area within Topo-Iberia and Picasso projects, allowing receiver function analyses of crustal depths. The ray-tracing modeling of the Rifsis profiles reveal a large Moho step and an area of crustal thickening both in EW and NS directions, grossly coincident with the Bouguer gravity anomalies. The deployment logistics allowed that all the stations recorded all the shots, thus providing useful offline data. We will use here all available in-line and offline data to provide a map of the crustal thickness in northern Morocco. We combined two approaches: i) a hyperbolic time reduction applied to the seismic data, resulting in low-fold stacks in which the reflections from the Moho should appear as subhorizontal lines; ii) the arrival times of the observed PmP phases allow, assuming a mean crustal velocity, to assign a midpoint crustal thickness to each lecture. Although some uncertainties may be inherent to those approaches, a large crustal root, reaching more than 50 km, is well documented in the central part of the Rif Cordillera, close to the zone where the Alboran slab may still be attached to the lithosphere. We also compared these results

  18. Measurement of short-base deformations in one of the regions of active fracturing in the Hanoi depression (the Socialist Republic of Vietnam)

    NASA Astrophysics Data System (ADS)

    Karmaleeva, R. M.; Yem, Nguyen Trong; Tu, Nguyen Dinh; Quoc, Le Minh; Chan Quoc, Hung

    1992-02-01

    Observations of deformation processes were carried out in one of the regions of active fracturing in the territory of the Hanoi depression, with the purpose of determining the rates of recent crustal movements during time intervals of about 1 yr to several years. The measurements were conducted with deformometers and hydrostatic levellers installed in a 5 m deep trench. The observation data for the 1985-1988 period indicate a high tectonic activity in the region studied. The horizontal deformation rates are (1-10) 10 -5/yr, and the vertical rates are 10 -4-10 -3/yr. Spectral characteristics of recorded processes have been obtained as well as meteorological effects.

  19. New design deforming controlling system of the active stressed lap

    NASA Astrophysics Data System (ADS)

    Ying, Li; Wang, Daxing

    2008-07-01

    A 450mm diameter active stressed lap has been developed in NIAOT by 2003. We design a new lap in 2007. This paper puts on emphases on introducing the new deforming control system of the lap. Aiming at the control characteristic of the lap, a new kind of digital deforming controller is designed. The controller consists of 3 parts: computer signal disposing, motor driving and force sensor signal disposing. Intelligent numeral PID method is applied in the controller instead of traditional PID. In the end, the result of new deformation are given.

  20. Transient crustal deformation in the South Iceland Seismic Zone observed by GPS and InSAR during 2000-2008

    NASA Astrophysics Data System (ADS)

    Decriem, J.; Árnadóttir, T.

    2012-12-01

    Repeated geodetic (GPS and InSAR) observations in the South Iceland Seismic Zone (SISZ) show transient surface deformation signals following two M6.5 earthquakes in June 2000. Previous studies concluded that the postseismic signal observed during the 2000-2005 time period was primarily due to viscoelastic relaxation in the lower crust and upper mantle, rather than afterslip. Here, we add continuous and campaign GPS observations from 2005 to 2008. Our analysis indicates that the postseismic signal is very small after 2005. We test viscoelastic models using Maxwell and standard linear solid (SLS) rheologies to explain the transient signal observed during 2000-2008. In order to explain the rapid decay in the surface velocities we observe in the longer GPS time series, our preferred viscoelastic model consists of a thick (~ 15 km) elastic crust overlying an upper mantle with SLS rheology (a viscosity of 1-3 • 1018 Pa s and relaxation strength between 0.1 and 0.25). Our preferred model differs from previous models for the postseismic relaxation in the SISZ in that we find an elastic lower crust and a more rapidly relaxing upper mantle rather than a lower crust with a Maxwell rheology and a viscosity of 1 • 1019 Pa s. The June 2000 earthquakes were followed eight years later by an earthquake doublet of composite magnitude 6.3 in the western part of the SISZ. We find that the Coulomb failure stress change due to viscoelastic relaxation increased the loading of the faults that ruptured on 29 May 2008 by about 0.05 MPa. This stress increase is, however, an order of magnitude smaller than the static stress changes estimated for the June 2000 main shocks. The viscoelastic relaxation thus loaded the faults that failed in May 2008, but additional loading processes may need to be considered to fully explain the time delay between the June 2000 and the May 2008 earthquakes.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  2. Active compressive intraoceanic deformation: early stages of ophiolites emplacement?

    NASA Astrophysics Data System (ADS)

    Chamot-Rooke, Nicolas; Delescluse, Matthias; Montési, Laurent

    2010-05-01

    Oceanic lithosphere is strong and continental lithosphere is weak. As a result, there is relatively little deformation in the oceanic domain away from plate boundaries. However, the interior of oceanic lithosphere does deform when highly stressed. We review here places where intraoceanic compression is at work. In the more than 30 years since the first observations of active compressive intraplate deformation in the Central Indian Ocean through seismic profiling (Eittreim et al., 1972), compressive deformation has been identified in a variety of other oceanic tectonic settings: as a result of small differential motion between large plates (between North America and South America in the Central Atlantic; between Eurasia and Nubia offshore Gibraltar; between Macquarie and Australia plates in the Southern Ocean), within back-arcs (northwest Celebes Sea, Okushiri Ridge in the Japan Sea, on the eastern border of the Caroline plate), and ahead of subduction (Zenisu Ridge off Nankai Trough). Deformation appears to be more diffuse when larger plates are involved, and more localized for younger plates, perhaps in relation with the increasing rigidity of oceanic plates with age. The best example of diffuse deformation studied so far remains the Central Indian Ocean. Numerous marine data have been collected in this area, including shallow and deep seismic, heat flow measurements, multibeam bathymetry. The present-day deformation field has been modeled using GPS and earthquakes as far field and near field constraints respectively. Reactivation of the oceanic fabric (including for portions of the Indo-Australian plate which are now in subduction as evidenced by the September 2009 Padang earthquake), selective fault abandonment (Delescluse et al., 2008) and serpentinization (Delescluse and Chamot-Rooke, 2008) are some of the important processes that shape the present-day pattern of deformation. These rare intraplate deformation areas constitute excellent natural laboratories to

  3. Active deformation in Western Turkey: new GPS observations and models

    NASA Astrophysics Data System (ADS)

    Nocquet, J.; Aktug, B.; Parsons, B.; Cingoz, A.; England, P.; Erkan, Y.; Soyer, N.; Akdeniz, H.; Kilicoglu, A.

    2007-12-01

    How the continents deform remains a matter of debate. One view postulates that continental deforming zones are comprised of a limited numbers of rigid (elastic) microplates. If true, the surface motion can then be described by the relative rotation of blocks, and strain should be localized along the major faults separating the blocks. An alternative view is that the deformation at depth is distributed over wide areas, can be modelled by a viscous flow responding to boundary conditions applied on it and gravitational potential energy gradients related to variations in topography, and the surface strain simply reflects this deformation. Western Turkey is a region of crustal extension, part of the Nubia/Eurasia plate boundary. Its kinematics is often modelled by the relative motion of a small number of rigid blocks (Nyst & Thatcher, 2005, Reilinger et al., 2006). However, until now, the limited number of GPS velocity vectors available has prevented a detailed examination of which is the more appropriate description. We present a new geodetic velocity field including ~100 sites from the longitude the Central Anatolian plateau to the Aegean coast, derived from a combination of campaigns carried out between 1997 and 2006, and continuous GPS operating since 2003, which we use to test the different models. While the kinematics of the area can be correctly modelled by a block model, a good fit to the velocity field requires blocks with sizes smaller than 100 km and still fails to adequately predict the strain rate observed within blocks . Alternatively, we test an approach where the lithosphere is modelled as a thin viscous sheet, responding to the gravitational potentiel energy contrast between the high plateau of eastern Turkey to the east and the subduction along the Hellenic trench in the southwest. The simplistic model has only one free parameter (the force applied by the subducting oceanic lithosphere on the Aegean ), but provides a good agreement with the observed

  4. Active deformation in the inner western Alps inferred from comparison between 1972-classical and 1996-GPS geodetic surveys

    NASA Astrophysics Data System (ADS)

    Sue, Christian; Martinod, Joseph; Tricart, Pierre; Thouvenot, François; Gamond, Jean-François; Fréchet, Julien; Marinier, Delphine; Glot, Jean-Paul; Grasso, Jean-Robert

    2000-04-01

    Eighteen geodetic points surveyed in 1972 by the French National Geographic Institute (IGN) were remeasured by GPS in 1996 in the Briançonnais and Piémont Zones, east of the Pelvoux massif (French Western Alps). A displacement vector set was determined for the two surveys' common points. Calculations of the strain-rate tensors associated with 15 triangular cells of the network have been performed. Only four of them show a strain rate significant at a 95% level of confidence. These data suggest an E-W extension of about 2-4 mm/yr between the western and eastern part of the network (Pelvoux external crystalline massif and Queyras blueschists, respectively) associated with N-S shortening. This active deformation agrees with neotectonic and seismotectonic data. The measured tectonic motion seems to be distributed throughout the central part of the Briançonnais zone, where the seismic activity is concentrated. The local seismicity has been precisely surveyed since 1989. It is moderate ( Ml<4.7) and no larger earthquake occured in the 1972-1989 period. The seismic deformation of the 1972-1996 period, extrapolated from the 1989-1996 local seismicity, accounts for less than 10% of the geodetic deformation. Thus, aseismic processes accommodated more than 90% of the observed deformation during this period. This could correspond to accumulation of elastic strain on locked faults, creep on faults or plastic deformation in a large crustal volume.

  5. Monocytic Cells Become Less Compressible but More Deformable upon Activation

    PubMed Central

    Ravetto, Agnese; Wyss, Hans M.; Anderson, Patrick D.; den Toonder, Jaap M. J.; Bouten, Carlijn V. C.

    2014-01-01

    Aims Monocytes play a significant role in the development of atherosclerosis. During the process of inflammation, circulating monocytes become activated in the blood stream. The consequent interactions of the activated monocytes with the blood flow and endothelial cells result in reorganization of cytoskeletal proteins, in particular of the microfilament structure, and concomitant changes in cell shape and mechanical behavior. Here we investigate the full elastic behavior of activated monocytes in relation to their cytoskeletal structure to obtain a better understanding of cell behavior during the progression of inflammatory diseases such as atherosclerosis. Methods and Results The recently developed Capillary Micromechanics technique, based on exposing a cell to a pressure difference in a tapered glass microcapillary, was used to measure the deformation of activated and non-activated monocytic cells. Monitoring the elastic response of individual cells up to large deformations allowed us to obtain both the compressive and the shear modulus of a cell from a single experiment. Activation by inflammatory chemokines affected the cytoskeletal organization and increased the elastic compressive modulus of monocytes with 73–340%, while their resistance to shape deformation decreased, as indicated by a 25–88% drop in the cell’s shear modulus. This decrease in deformability is particularly pronounced at high strains, such as those that occur during diapedesis through the vascular wall. Conclusion Overall, monocytic cells become less compressible but more deformable upon activation. This change in mechanical response under different modes of deformation could be important in understanding the interplay between the mechanics and function of these cells. In addition, our data are of direct relevance for computational modeling and analysis of the distinct monocytic behavior in the circulation and the extravascular space. Lastly, an understanding of the changes of monocyte

  6. Effects of the troposphere on GPS and InSAR point target analysis for measurement of crustal deformation and vertical motion near Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Hammond, W. C.; Blewitt, G.; Plag, H.; Kreemer, C. W.; Li, Z.

    2009-12-01

    Precise measurement of vertical motions of the solid Earth with space based geodetic techniques such as GPS and Interferometric Synthetic Aperture Radar (InSAR) is complicated by the presence of the atmosphere. A fundamental question is to what degree do GPS and InSAR provide similar information about the delays in signal propagation associated with the troposphere. Knowledge of this relationship can improve methods for using GPS to correct for the effects of atmosphere in InSAR, or vice versa. To isolate residual signals associated with the atmosphere in GPS using the GIPSY-OASIS II software, we apply a height-dependent dry delay, and solve for wet zenith delay and its two horizontal gradients every five minutes as a random walk process. We estimate the residual phase from InSAR as the difference between phase and the expected phase based on interferometric point target analysis performed with the Gamma IPTA software module. We will investigate correlations between 1) the GPS troposphere zenith delay estimates at the time of radar scene acquisition, 2) the GPS height estimate residual to the linear rate in height, and 3) the GAMMA IPTA derived atmospheric delays (including orbit errors). As a test case we will use the long running and stable GPS sites of the Basin and Range Geodetic Network (BARGEN) in the vicinity of Yucca Mountain, Nevada. These sites have been shown to exhibit extremely clean time series, likely attributable to the very high quality monumentation, stability of GPS equipment, dry atmosphere over the Great Basin, and low rates of crustal deformation. This, in addition to the high density of stations (16 sites within a 50 km radius), makes the Yucca mountain regional network one of the best possible localities for the analysis of the relative contributions to noise in GPS vertical rates and atmospheric contributions to InSAR measurements.

  7. Crustal deformation along the Northern Hyblean Plateau margin (Sicily, Italy) from GPS measurements and comparison with stress data

    NASA Astrophysics Data System (ADS)

    Mattia, M.; Bruno, V.; Cannavò, F.; Palano, M.

    2009-04-01

    In this work we analyze data from permanent and non-permanent GPS stations collected between 1998 and 2006 on a dense geodetic network covering a large area of the Hyblean Plateau (southern Italy). This is a seismogenetic area, where strong earthquakes destroyed many cities and killed thousands of people in the past. The analysis of geodetic velocities referring to an Eurasian and an African reference frames, reveals the occurrence of active shortening in the northern sector of the plateau along the boundary defined by the Gela-Catania Foredeep, coupled with an active lengthening in the central sector of the plateau itself. Starting from the estimated velocity at each station, the horizontal strain-rate field of the Hyblean Plateau was calculated. The strain rate pattern clearly defines an area of a prevailing N-S compression along the northern rim of the Hyblean Plateau. Furthermore the central sector of the plateau is affected by a NNW-SSE and NE-SW extensional strain rate pattern. A comparison with seismological and structural data, available for the studied area, allows improving the knowledge of the tectonic processes in the Hyblean Plateau and their implications for seismic hazard.

  8. Seismic activity, inferred crustal stresses and seismotectonics in the Rana region, Northern Norway

    NASA Astrophysics Data System (ADS)

    Hicks, Erik C.; Bungum, Hilmar; Lindholm, Conrad D.

    2000-10-01

    The seismotectonic significance of the Rana region is known both from the fact that this was the location of the largest known earthquake in Fennoscandia in recent times, the MS 5.8-6.2 earthquake of August 31, 1819, and from its relatively high, constant seismic activity also in the 20th century. In order to study this region in more detail, a local seismic network has been in operation there since July 1997, as part of the NEONOR (Neotectonics in Norway) project. The network was primarily designed to detect possible activity on the Båsmoen fault which runs ˜50 km subparallel to the Rana fjord, and which shows signs of likely post glacial activity. The results have revealed a quite complex spatio-temporal distribution of seismic activity, and has also shown no activity on the Båsmoen fault itself. During the first 18 months of operation (July 1997-January 1999), the network has detected 373 locatable seismic events, of which 267 were local earthquakes. Most of these earthquakes occurred in five groups in the western parts of the network. All five groups had similar NNW-ESW trends in epicenter locations, and all have shallow foci (2-12 km), similar to what has also been found earlier for other concentrated earthquake zones in Northern Norway, and the magnitude range is between ML 0.1 and 2.8. Earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline (implying an unusual coast-parallel orientation of the principal horizontal compressive stress). The earthquakes occur in a region of maximum post-glacial uplift gradients, which supports deglaciation flexure as a viable explanation for these earthquakes. A certain influence from more local factors, however, tied in general to crustal in homogeneities, cannot be ruled out.

  9. Crustal Structure Across the Okavango Rift Zone, Botswana: Initial Results From the PRIDE-SEISORZ Active-Source Seismic Profile

    NASA Astrophysics Data System (ADS)

    Canales, J. P.; Moffat, L.; Lizarralde, D.; Laletsang, K.; Harder, S. H.; Kaip, G.; Modisi, M.

    2015-12-01

    The PRIDE project aims to understand the processes of continental rift initiation and evolution by analyzing along-axis trends in the southern portion of the East Africa Rift System, from Botswana through Zambia and Malawi. The SEISORZ active-source seismic component of PRIDE focused on the Okavango Rift Zone (ORZ) in northwestern Botswana, with the main goal of imaging the crustal structure across the ORZ. This will allow us to estimate total crustal extension, determine the pattern and amount of thinning, assess the possible presence of melt within the rift zone, and assess the contrasts in crustal blocks across the rift, which closely follows the trend of a fold belt. In November 2014 we conducted a crustal-scale, 450-km-long seismic refraction/wide-angle reflection profile consisting of 19 sources (shots in 30-m-deep boreholes) spaced ~25 km apart from each other, and 900 receivers (IRIS/PASSCAL "Texan" dataloggers and 4.5Hz geophones) with ~500 m spacing. From NW to SE, the profile crosses several tectonic domains: the Congo craton, the Damara metamorphic belt and the Ghanzi-Chobe fold belt where the axis of the ORZ is located, and continues into the Kalahari craton. The record sections display clear crustal refraction (Pg) and wide-angle Moho reflection (PmP) phases for all 17 of the good-quality shots, and a mantle refraction arrival (Pn), with the Pg-PmP-Pn triplication appearing at 175 km offset. There are distinct changes in the traveltime and amplitude of these phases along the transect, and on either side of the axis, that seem to correlate with sharp transitions across tectonic terrains. Initial modeling suggests: (1) the presence of a sedimentary half-graben structure at the rift axis beneath the Okavango delta, bounded to the SE by the Kunyere-Thamalakane fault system; (2) faster crustal Vp in the domains to the NW of the ORZ; and (3) thicker crust (45-50 km) at both ends of the profile within the Congo and Kalahari craton domains than at the ORZ and

  10. A reduced crustal magnetization zone near the first observed active hydrothermal vent field on the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Lin, Jian; Chen, Yongshun J.; Tao, Chunhui; German, Christopher R.; Yoerger, Dana R.; Tivey, Maurice A.

    2010-09-01

    Inversion of near-bottom magnetic data reveals a well-defined low crustal magnetization zone (LMZ) near a local topographic high (37°47‧S, 49°39‧E) on the ultraslow-spreading Southwest Indian Ridge (SWIR). The magnetic data were collected by the autonomous underwater vehicle ABE on board R/V DaYangYiHao in February-March 2007. The first active hydrothermal vent field observed on the SWIR is located in Area A within and adjacent to the LMZ at the local topographic high, implying that this LMZ may be the result of hydrothermal alteration of magnetic minerals. The maximum reduction in crustal magnetization is 3 A/M. The spatial extent of the LMZ is estimated to be at least 6.7 × 104 m2, which is larger than that of the LMZs at the TAG vent field on the Mid-Atlantic Ridge (MAR), as well as the Relict Field, Bastille, Dante-Grotto, and New Field vent-sites on the Juan de Fuca Ridge (JdF). The calculated magnetic moment, i.e., the product of the spatial extent and amplitude of crustal magnetization reduction is at least -3 × 107 Am2 for the LMZ on the SWIR, while that for the TAG field on the MAR is -8 × 107 Am2 and that for the four individual vent fields on the JdF range from -5 × 107 to -3 × 107 Am2. Together these results indicate that crustal demagnetization is a common feature of basalt-hosted hydrothermal vent fields at mid-ocean ridges of all spreading rates. Furthermore, the crustal demagnetization of the Area A on the ultraslow-spreading SWIR is comparable in strength to that of the TAG area on the slow-spreading MAR.

  11. Nanocalorimetric Characterization of Microbial Activity in Deep Subsurface Oceanic Crustal Fluids

    PubMed Central

    Robador, Alberto; LaRowe, Douglas E.; Jungbluth, Sean P.; Lin, Huei-Ting; Rappé, Michael S.; Nealson, Kenneth H.; Amend, Jan P.

    2016-01-01

    Although fluids within the upper oceanic basaltic crust harbor a substantial fraction of the total prokaryotic cells on Earth, the energy needs of this microbial population are unknown. In this study, a nanocalorimeter (sensitivity down to 1.2 nW ml-1) was used to measure the enthalpy of microbially catalyzed reactions as a function of temperature in samples from two distinct crustal fluid aquifers. Microorganisms in unamended, warm (63°C) and geochemically altered anoxic fluids taken from 292 meters sub-basement (msb) near the Juan de Fuca Ridge produced 267.3 mJ of heat over the course of 97 h during a step-wise isothermal scan from 35.5 to 85.0°C. Most of this heat signal likely stems from the germination of thermophilic endospores (6.66 × 104 cells ml-1FLUID) and their subsequent metabolic activity at temperatures greater than 50°C. The average cellular energy consumption (5.68 pW cell-1) reveals the high metabolic potential of a dormant community transported by fluids circulating through the ocean crust. By contrast, samples taken from 293 msb from cooler (3.8°C), relatively unaltered oxic fluids, produced 12.8 mJ of heat over the course of 14 h as temperature ramped from 34.8 to 43.0°C. Corresponding cell-specific energy turnover rates (0.18 pW cell-1) were converted to oxygen uptake rates of 24.5 nmol O2 ml-1FLUID d-1, validating previous model predictions of microbial activity in this environment. Given that the investigated fluids are characteristic of expansive areas of the upper oceanic crust, the measured metabolic heat rates can be used to constrain boundaries of habitability and microbial activity in the oceanic crust. PMID:27092118

  12. Nanocalorimetric Characterization of Microbial Activity in Deep Subsurface Oceanic Crustal Fluids.

    PubMed

    Robador, Alberto; LaRowe, Douglas E; Jungbluth, Sean P; Lin, Huei-Ting; Rappé, Michael S; Nealson, Kenneth H; Amend, Jan P

    2016-01-01

    Although fluids within the upper oceanic basaltic crust harbor a substantial fraction of the total prokaryotic cells on Earth, the energy needs of this microbial population are unknown. In this study, a nanocalorimeter (sensitivity down to 1.2 nW ml(-1)) was used to measure the enthalpy of microbially catalyzed reactions as a function of temperature in samples from two distinct crustal fluid aquifers. Microorganisms in unamended, warm (63°C) and geochemically altered anoxic fluids taken from 292 meters sub-basement (msb) near the Juan de Fuca Ridge produced 267.3 mJ of heat over the course of 97 h during a step-wise isothermal scan from 35.5 to 85.0°C. Most of this heat signal likely stems from the germination of thermophilic endospores (6.66 × 10(4) cells ml(-1) FLUID) and their subsequent metabolic activity at temperatures greater than 50°C. The average cellular energy consumption (5.68 pW cell(-1)) reveals the high metabolic potential of a dormant community transported by fluids circulating through the ocean crust. By contrast, samples taken from 293 msb from cooler (3.8°C), relatively unaltered oxic fluids, produced 12.8 mJ of heat over the course of 14 h as temperature ramped from 34.8 to 43.0°C. Corresponding cell-specific energy turnover rates (0.18 pW cell(-1)) were converted to oxygen uptake rates of 24.5 nmol O2 ml(-1) FLUID d(-1), validating previous model predictions of microbial activity in this environment. Given that the investigated fluids are characteristic of expansive areas of the upper oceanic crust, the measured metabolic heat rates can be used to constrain boundaries of habitability and microbial activity in the oceanic crust. PMID:27092118

  13. Detailed crustal deformation and fault rupture of the 2015 Gorkha earthquake, Nepal, revealed from ScanSAR-based interferograms of ALOS-2

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tomokazu; Morishita, Yu; Yarai, Hiroshi

    2015-12-01

    We have successfully detected widely distributed ground displacements for the 2015 Gorkha earthquake by applying a ScanSAR-based interferometry analysis of Advanced Land Observing Satellite 2 (ALOS-2) L-band data. A major displacement area extends with a length of about 160 km in the east-west direction, and the most concentrated crustal deformation with ground displacement exceeding 1 m is located 20-30 km east from Kathmandu. A quasi-vertical displacement estimated by combining the ascending and the descending data indicates upheaval of about 1.4 m at maximum. We inverted the synthetic aperture radar interferometry (InSAR) data including both of the main shock (moment magnitude (Mw) 7.8) and the largest aftershock (Mw 7.3) to construct a slip distribution model. Our model shows a nearly pure reverse fault motion with a slip amount of approximately 6 m at maximum, and the spatial extent is zonally distributed within a distance of 50 to 100 km from the surface along downdip direction. The downdip end of the slip is quite consistent with that of the interseismic coupling area geodetically inferred in previous studies. On the other hand, there is no significant slip at shallow depth in spite of the fact that the plate interface is thought to be fully locked there, may be suggesting that there still remains a potential of fault slip. The slip distribution unnaturally bifurcates in the east, and we can identify a clear-cut slip deficit area with a radius of ~10 km just west side of the Mw 7.3 event, where the slip amount reaches only 20 cm at most. This area is presumably subjected to a strong shear stress which should promote a reverse fault slip. There is a possibility to produce a fault slip equivalent to Mw ~7.0 in the future although we do not know if the slip heterogeneity would be smoothed out by a seismic event or an aseismic event.

  14. Spectral damping scaling factors for shallow crustal earthquakes in active tectonic regions

    USGS Publications Warehouse

    Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Campbell, Kenneth; Abrahamson, Norman; Silva, Walter

    2012-01-01

    Ground motion prediction equations (GMPEs) for elastic response spectra, including the Next Generation Attenuation (NGA) models, are typically developed at a 5% viscous damping ratio. In reality, however, structural and non-structural systems can have damping ratios other than 5%, depending on various factors such as structural types, construction materials, level of ground motion excitations, among others. This report provides the findings of a comprehensive study to develop a new model for a Damping Scaling Factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE to spectral ordinates with damping ratios between 0.5 to 30%. Using the updated, 2011 version of the NGA database of ground motions recorded in worldwide shallow crustal earthquakes in active tectonic regions (i.e., the NGA-West2 database), dependencies of the DSF on variables including damping ratio, spectral period, moment magnitude, source-to-site distance, duration, and local site conditions are examined. The strong influence of duration is captured by inclusion of both magnitude and distance in the DSF model. Site conditions are found to have less significant influence on DSF and are not included in the model. The proposed model for DSF provides functional forms for the median value and the logarithmic standard deviation of DSF. This model is heteroscedastic, where the variance is a function of the damping ratio. Damping Scaling Factor models are developed for the “average” horizontal ground motion components, i.e., RotD50 and GMRotI50, as well as the vertical component of ground motion.

  15. Relation of Volcanism to Crustal Deformation in Klamath Falls, Oregon: Transition from Calc-alkaline Basaltic Andesite to High Alumina Olivine Tholeiite

    NASA Astrophysics Data System (ADS)

    Priest, G. R.; Hladky, F. R.; Murray, R. B.

    2009-12-01

    This paper is based on geologic mapping by Priest et al. (2008) at Klamath Falls, Oregon on the southernmost end of the Klamath Graben. Northeast-southwest extension across this area caused northeast tilting of fault blocks on the east side and southwest tilting of blocks on the west side of the Graben. Dominant strike of these Basin and Range fault blocks is N. 30-40° W. At Klamath Falls the two opposing groups of tilted blocks are separated not by a keystone graben but by a complex of bounding faults striking ~N. 65° W. The bounding faults appear to have components of right-lateral or reverse motion, cut rocks dated at ~4 Ma, and terminate to the northwest against northeast-striking faults at the southern boundary of the Graben. Normal faults within the study area cut basalt dated at 1.8 Ma on the west side of the Graben. Holocene talus is cut on the east side of the Graben immediately north of the study area. The 1993 magnitude 5.9 and 6.0 earthquakes on the west margin of the Klamath Graben are evidence that extensional deformation is continuing there. The youngest proven deformation in the map area south of the Graben boundary is offset Pleistocene alluvial fans at the base of Hogback Mountain. These fans are now preserved as discontinuous hills but once filled the local Altamont basin by up to 150 m higher than its present surface. Much of this sand and gravel has been eroded, possibly coincident with breaching of the basin at ~1 Ma by headward erosion of the Klamath River. Magmatic composition changed as crustal extension in the area progressed and the width of the Cascade volcanic arc decreased. Between ~6 and 4 Ma, calc-alkaline basaltic andesite and andesite from local volcanic centers of the volcanic arc flowed unimpeded across the area, thus the current Basin and Range topography had not developed. Angular unconformities within sequences of volcanic and volcaniclastic rocks dated at 4-2.7 Ma indicate contemporaneous tilting of fault blocks, but much

  16. Crustal Structure in the Imperial Valley Region of California From Active-Source Seismic Investigations

    NASA Astrophysics Data System (ADS)

    Fuis, G. S.; Mooney, W. D.

    2008-12-01

    shallow as 12 km beneath the Imperial Valley. Modeling of gravity data requires that this layer deepen and/or pinch out beneath the bordering mesas and mountain ranges. This pinch-out is imaged in the 1992 data beneath the Chocolate Mountains. Based on its high velocity and the presence of intrusive basaltic rocks in the sedimentary section in the Imperial Valley, the subbasement is thought to be a mafic intrusive complex similar to oceanic middle crust. (4) Crustal thickness and upper-mantle velocity are 21-22 km and 7.6-7.7 km/s, respectively, beneath the Imperial Valley but increase to 27 km and 8.0 km/s, respectively, beneath the Chocolate Mountains. Our results from the Salton Trough may be contrasted with active-source seismic results from the northern Gulf of California (Guaymas basin; Lizarralde et al., 2007). These results show the crust to thin to 10-14 km within the Gulf. Below 3-4 km of sediment, the crust has a velocity of 6.8 km/s, interpreted to be new igneous (gabbroic) crust. Thus, the rifting process appears to have produced negligible metasedimentary basement and a crustal thickness as little as half that beneath the Salton Trough.

  17. A province-scale block model of Walker Lane and western Basin and Range crustal deformation constrained by GPS observations (Invited)

    NASA Astrophysics Data System (ADS)

    Hammond, W. C.; Bormann, J.; Blewitt, G.; Kreemer, C.

    2013-12-01

    The Walker Lane in the western Great Basin of the western United States is an 800 km long and 100 km wide zone of active intracontinental transtension that absorbs ~10 mm/yr, about 20% of the Pacific/North America plate boundary relative motion. Lying west of the Sierra Nevada/Great Valley microplate (SNGV) and adjoining the Basin and Range Province to the east, deformation is predominantly shear strain overprinted with a minor component of extension. The Walker Lane responds with faulting, block rotations, structural step-overs, and has distinct and varying partitioned domains of shear and extension. Resolving these complex deformation patterns requires a long term observation strategy with a dense network of GPS stations (spacing ~20 km). The University of Nevada, Reno operates the 373 station Mobile Array of GPS for Nevada transtension (MAGNET) semi-continuous network that supplements coverage by other networks such as EarthScope's Plate Boundary Observatory, which alone has insufficient density to resolve the deformation patterns. Uniform processing of data from these GPS mega-networks provides a synoptic view and new insights into the kinematics and mechanics of Walker Lane tectonics. We present velocities for thousands of stations with time series between 3 to 17 years in duration aligned to our new GPS-based North America fixed reference frame NA12. The velocity field shows a rate budget across the southern Walker Lane of ~10 mm/yr, decreasing northward to ~7 mm/yr at the latitude of the Mohawk Valley and Pyramid Lake. We model the data with a new block model that estimates rotations and slip rates of known active faults between the Mojave Desert and northern Nevada and northeast California. The density of active faults in the region requires including a relatively large number of blocks in the model to accurately estimate deformation patterns. With 49 blocks, our the model captures structural detail not represented in previous province-scale models, and

  18. Strains and tilts on crustal blocks

    NASA Technical Reports Server (NTRS)

    Bilham, R. G.; Beavan, R. J.

    1979-01-01

    Geodetic work done over the past century is examined to investigate block motion in areas of intense tectonic deformation, with special attention to geodetic releveling data obtained for Japan. Problems in interpreting strainmeter and tiltmeter to study the behavior of crustal blocks and block boundaries are discussed. Block dimensions of 5 to 50 km seem to occur frequently in regions of intense tectonic activity. Block boundaries are often considerably weaker than contiguous crustal blocks, resulting in a concentration of strains at boundaries and decrease of strains within blocks. Block to block variations in tilt phase and magnitude are observed. There is some evidence that block boundaries may exhibit strain-dependent elastic properties or respond viscoelastically, possibly accounting for the slow transmission of tectonic deformation reported in Japan. If nonlinear behavior is characteristic of regions fragmented by crustal blocks, it will generally not be possible to apply a site correction factor based on the observed distortion of tidal or seismic strains in interpreting secular strains.

  19. 3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)

    NASA Astrophysics Data System (ADS)

    Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.

    2013-04-01

    The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian-Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent margins. To investigate the effects of active margin evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod™. The crustal structure inherited from Mesozoic Gondwana margin breakup and processes related to modern Hikurangi convergent margin initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.

  20. The role of the Montello hill in the seismicity and active deformation of Southern Alps

    NASA Astrophysics Data System (ADS)

    Pondrelli, S.; Serpelloni, E.; Danesi, S.; Lovati, S.; Massa, M.; Mastrolembo Ventura, B.; Danecek, P.; Cavaliere, A.; Salimbeni, S.

    2013-12-01

    The most remarkable geomorphological feature of the eastern Southern Alps (northern Italy) is the Montello anticline, a ~15km long SSW-NNE elongated hill, sited ~40km north of Venice, and offset of ~15 km to the south from the main pede-Alpine thrust front. It has been generated by the uplift and the deformation produced by a S-verging blind thrust, constrained by morphotectonic analyses of uplifted river terraces and sub-surface data. Despite it is presently considered as one of the main S-verging seismogenic segments of the tectonically active Southern Alps thrust front, its real seismogenic potential is still matter of debate. Although the area has been hit in 1695 by a Mw 6.5 earthquake, the Montello is currently characterized by slower seismicity activity than its confining segments and geodetic deformation rates are at the mm/yr level. In order to study the present day crustal deformation at the fault-scale and to improve the detection of background seismicity associated to the 'seismically silent' Montello thrust and to understand its interseismic behavior, we have installed a temporary multi-parametric geophysical network, which integrates space geodetic (GPS) and seismological observations during the 2010-2011 time-interval, running semi-continuous GPS experiments from 2009 to 2013. We recorded 142 local events (compared to the 43 events located by the Italian Seismic Network), located with good reliability (rms < 0.5) with Ml between 1.5 and 3.5. The available continuous and semi-continuous GPS data show that ~2 mm/yr of N-S convergence are accommodated across this sector of the Southern Alps, but the deformation signal appears more complex than what expected by a single thrust fault. GPS, although preliminary and not sampling optimally possible lateral variations of the strain-rate field, show a remarkable change of the kinematics across the external Montello thrust front. The GPS and seismological data collected during the experiment suggest that the

  1. Evolution of Deformation Studies on Active Hawaiian Volcanoes

    USGS Publications Warehouse

    Decker, Robert; Okamura, Arnold; Miklius, Asta; Poland, Michael

    2008-01-01

    Everything responds to pressure, even rocks. Deformation studies involve measuring and interpreting the changes in elevations and horizontal positions of the land surface or sea floor. These studies are variously referred to as geodetic changes or ground-surface deformations and are sometimes indexed under the general heading of geodesy. Deformation studies have been particularly useful on active volcanoes and in active tectonic areas. A great amount of time and energy has been spent on measuring geodetic changes on Kilauea and Mauna Loa Volcanoes in Hawai`i. These changes include the build-up of the surface by the piling up and ponding of lava flows, the changes in the surface caused by erosion, and the uplift, subsidence, and horizontal displacements of the surface caused by internal processes acting beneath the surface. It is these latter changes that are the principal concern of this review. A complete and objective review of deformation studies on active Hawaiian volcanoes would take many volumes. Instead, we attempt to follow the evolution of the most significant observations and interpretations in a roughly chronological way. It is correct to say that this is a subjective review. We have spent years measuring and recording deformation changes on these great volcanoes and more years trying to understand what makes these changes occur. We attempt to make this a balanced as well as a subjective review; the references are also selective rather than exhaustive. Geodetic changes caused by internal geologic processes vary in magnitude from the nearly infinitesimal - one micron or less, to the very large - hundreds of meters. Their apparent causes also are varied and include changes in material properties and composition, atmospheric pressure, tidal stress, thermal stress, subsurface-fluid pressure (including magma pressure, magma intrusion, or magma removal), gravity, and tectonic stress. Deformation is measured in units of strain or displacement. For example, tilt

  2. Plate boundary deformation of the Pacific plate. Two case studies. (1) Crustal structure of the northwestern Vizcaino block and Gorda escarpment, offshore northern California, and implications for postsubduction deformation of a paleoaccretionary margin. (2) A focused look at the Alpine fault, New Zealand: Seismicity, focal mechanisms and stress observations

    NASA Astrophysics Data System (ADS)

    Leitner, Beate

    Two examples of Pacific rim plate boundary deformation are presented. In the first part of the thesis crustal models are derived for the northwestern part of the Vizcaino block in California using marine seismic and gravity data collected by the Mendocino Triple Junction Seismic Experiment. A northwest-southeast trending kink in the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10--12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this

  3. Permo-Triassic changes in bulk crustal shortening direction during deformation and metamorphism of the Taebaeksan Basin, South Korea using foliation intersection/inflection axes: Implications for tectonic movement at the eastern margin of Eurasia during the Songrim (Indosinian) orogeny

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong Soo; Ree, Jin-Han

    2013-03-01

    The Permo-Triassic Songrim (Indosinian) orogeny in South Korea was a major tectonic event involving complicated continental collisions at the eastern margin of Eurasia. Previous studies have examined the structural and metamorphic features of the Songrim orogeny in each of the Paleozoic terranes of the orogenic belt (i.e., the Taebaeksan Basin, the Okcheon Basin, and the Imjingang Belt), but correlations of these features among the terranes remain uncertain. The aim of this paper is to reveal deformation history including bulk crustal shortening directions in the Taebaeksan Basin, and to correlate the tectono-metamorphic evolution of the Taebaeksan Basin with other Phanerozoic mobile belts in eastern Asia based on a combined analysis of foliation intersection/inflection axes (FIA) trends and metamorphic P-T and T-t (time) paths. The orientations and relative timing of FIA preserved as inclusion trails within porphyroblasts of andalusite, chloritoid, garnet, and staurolite reveal two age groups of inclusion trails in the Pyeongan Supergroup at the northeastern margin of the Taebaeksan Basin. These microstructures indicate the development of early NNW-NNE-trending structures and fabrics, followed by later E-W-trending ones. These observations suggest a change in the orientation of bulk crustal shortening from E-W to N-S during the Songrim orogeny. Based on the similar microstructures and temperature-time paths of the three Paleozoic terranes, we interpret that the E-W bulk crustal shortening influenced the eastern part of the Korean Peninsula during the early stages of the Songrim orogeny, presumably related to amalgamation between the proto-Japan terrane and the eastern margin of Eurasia, whereas the N-S bulk crustal shortening was stronger in the western part of the peninsula during the later stages of the orogeny, related to collision between the South and North China blocks.

  4. Crustal Dynamics Project: Catalogue of site information

    NASA Technical Reports Server (NTRS)

    1985-01-01

    This document represents a catalogue of site information for the Crustal Dynamics Project. It contains information and descriptions of those sites used by the Project as observing stations for making the precise geodetic measurements useful for studies of the Earth's crustal movements and deformation.

  5. Crustal Dynamics Project: Catalogue of site information

    NASA Technical Reports Server (NTRS)

    Noll, Carey E. (Editor)

    1988-01-01

    This document represents a catalog of site information for the Crustal Dynamics Project. It contains information on and descriptions of those sites used by the Project as observing stations for making the precise geodetic measurements necessary for studies of the Earth's crustal movements and deformation.

  6. Recent crustal deformation of İzmir, Western Anatolia and surrounding regions as deduced from repeated GPS measurements and strain field

    NASA Astrophysics Data System (ADS)

    Aktuğ, Bahadır; Kılıçoğlu, Ali

    2006-07-01

    To investigate contemporary neotectonic deformation in İzmir, Western Anatolia and in its neighborhood, a relatively dense Global Positioning System (GPS) monitoring network was established in 2001. Combination of three spatially dense GPS campaigns in 2001, 2003 and 2004 with temporally dense campaigns between 1992 and 2004 resulted in a combined velocity field representing active deformation rate in the region. We computed horizontal and vertical velocity fields with respect to Earth-centered, Earth-fixed ITRF2000, to Eurasia and to Anatolia as well. The rates of principal and shear strains along with rigid-body rotation rates were derived from velocity field. Results show east-west shortening between Karaburun Peninsula and northern part of İzmir Bay together with the extension of İzmir Bay in accordance with general extension regime of Western Anatolia and Eastern Agea. East-west shortening and north-south extension of Karaburun Peninsula are closely related to right-lateral faulting and a clockwise rotation. There exists a block in the middle of the peninsula with a differential motion at a rate of 3-5 ± 1 mm/year and 5-6 ± 1 mm/year to the east and south, respectively. As is in Western Anatolia, north-south extension is dominant in almost all parts of the region despite the fact that they exhibit significantly higher rates in the middle of the peninsula. Extensional rates along Tuzla Fault lying nearly perpendicular to İzmir Bay and in its west are maximum in the region with an extension rate of 300-500 ± 80-100 nanostrain/year and confirm its active state. Extensional rates in other parts of the region are at level of 50-150 nanostrain/year as expected in the other parts of Western Anatolia.

  7. InSAR analysis of the crustal deformation affecting the megacity of Istanbul: the results of the FP7 Marsite Project as a GEO Supersite Initiative

    NASA Astrophysics Data System (ADS)

    Solaro, Giuseppe; Bonano, Manuela; Manzo, Mariarosaria

    2016-04-01

    The North Anatolian Fault (NAF) is one of the most active faults worldwide, extending approximately 1,200 km from Eastern Turkey to the Northern Aegean Sea. During the 20th century series of damaging earthquakes occurred along the NAF, generally propagated westward towards Istanbul; the last one occurred in 1999 at Izmit, a city 80 km away from Istanbul. Within this scenario, the FP7 MARsite project (New Directions in Seismic Hazard assessment through Focused Earth Observation in Marmara Supersite), supported by EU, intends to collect, share and integrate multidisciplinary data (seismologic, geochemical, surveying, satellite, etc.) in order to carry out assessment, mitigation and management of seismic risk in the region of the Sea of Marmara. In the framework of the MARsite project, we performed the analysis and monitoring of the surface deformation affecting the Istanbul mega city by exploiting the large archives of X-band satellite SAR data, made available through the Supersites Initiatives, and by processing them via the advanced multi-temporal and multi-scale InSAR technique, known as the Small BAseline Subset (SBAS) approach. In particular, we applied the SBAS technique to a dataset of 101 SAR images acquired by the TerraSAR-X constellation of the German Space Agency (DLR) over descending orbits and spanning the November 2010 - August 2014 time interval. From,these images, we generated 312 differential interferograms with a maximum spatial separation (perpendicular baseline) between the acquisition orbits of about 500 m., that were used to generate, via the SBAS approach, mean deformation velocity map and corresponding ground time series of the investigated area. The performed InSAR analysis reveals a generalized stability over the Istanbul area, except for some localized displacements, related to subsidence and slope instability phenomena. In particular, we identified: (i) a displacement pattern related to the Istanbul airport, showing a mostly linear

  8. Strain Partitioning During Continental Extension: Role Of Crustal Decoupling And Lower Crustal Flow

    NASA Astrophysics Data System (ADS)

    Huismans, Ritske S.; Beaumont, Christopher

    Lithosphere extension is accommodated by localized deformation of brittle and vis- cous shear zones. Distributed lower crustal flow may also occur in response to the changing crustal and mantle lithosphere geometry during extension and the associated buoyancy forces. We investigate the relationship between the localised deformation and distributed flow in a series of model experiments. Successive experiments increase the decoupling of the upper crust from the upper mantle lithosphere by increasing the contribution of thermally activated creep in the lower crust. We use visco-plastic fully thermally coupled numerical experiments to simulate the thermo-mechanical evolu- tion of the extending lithosphere. In our first set of numerical models, crust and man- tle lithosphere have normal thickness and thermal conditions. In the reference model, strong coupling between crust and mantle is achieved by scaling up the crustal viscos- ity by a factor of 100. Subsequently, decoupling is achieved by allowing for thermally activated creep in the lower crust. The models suggest that strong coupling between crust and mantle lithosphere may result in relatively narrow rift basins bounded by nested conjugate fault systems. In contrast, the decoupled models show outward prop- agation of synthetic fault systems and the formation of multiple crustal necks, where the frictional shears sole out in the lower crustal decollement. In our second set of nu- merical models we investigate the effect of introducing a zone of thick and hot crust in the centre of the model. Under these circumstances, channel flow directed toward the rift in the middle and lower crust becomes increasingly important at the expense of the frictional plastic behaviour of the upper crust and upper mantle lithosphere. We test the sensitivity of the model results to the initial position in either crust or mantle where localisation first occurs. The thick crust models show a natural progression from core complex style of

  9. Crustal structures under the active volcanic areas of central and eastern Mediterranean (M-44)

    NASA Technical Reports Server (NTRS)

    Gasparini, P. (Principal Investigator); Mantovani, M. S. M.; Monaco, F.; Pierattini, D.; Fedi, M.

    1981-01-01

    Programs are being adapted to the UNIVAC 1000 computer and others are being developed for immediate utilization in processing MAGSAT data. stability intermediate for lower continental crust and to upper manele conditions. Attempts to residuate crustal anomalies from one selected profile passing through western mediterranean using procedures commonly used at NASA yielded dubious results because of uncertainties in the adoption of coefficients in the expression accounting for the effect of equatorial ring currents and the empirical approach used for other corrections. Instead, filtering techniques are to be applied to each profile once investigator B tapes relative to the whole planet are received.

  10. Active Printed Materials for Complex Self-Evolving Deformations

    PubMed Central

    Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

    2014-01-01

    We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus. PMID:25522053

  11. Active printed materials for complex self-evolving deformations.

    PubMed

    Raviv, Dan; Zhao, Wei; McKnelly, Carrie; Papadopoulou, Athina; Kadambi, Achuta; Shi, Boxin; Hirsch, Shai; Dikovsky, Daniel; Zyracki, Michael; Olguin, Carlos; Raskar, Ramesh; Tibbits, Skylar

    2014-01-01

    We propose a new design of complex self-evolving structures that vary over time due to environmental interaction. In conventional 3D printing systems, materials are meant to be stable rather than active and fabricated models are designed and printed as static objects. Here, we introduce a novel approach for simulating and fabricating self-evolving structures that transform into a predetermined shape, changing property and function after fabrication. The new locally coordinated bending primitives combine into a single system, allowing for a global deformation which can stretch, fold and bend given environmental stimulus. PMID:25522053

  12. Discontinuous fluidization transition in dense suspensions of actively deforming particles

    NASA Astrophysics Data System (ADS)

    Tjhung, Elsen; Berthier, Ludovic

    Collective dynamics of self-propelled particles at high density have been shown to display a glass-like transition with a critical slowing down of 2 to 4 orders of magnitude. In this talk, we propose a new mechanism of injecting energy or activity via volume fluctuations. We show that the behaviour of actively deforming particles is strikingly different from that of self-propelled particles. In particular, we find a discontinuous non-equilibrium phase transition from a flowing state to an arrested state. Our minimal model might also explain the collective dynamics in epithelial tissues. In particular, without needing self-propulsion or cell-cell adhesion, volume fluctuations of individual cells alone might be sufficient to give rise to an active fluidization and collective dynamics in densely packed tissues.

  13. Crustal dynamics project observing plan for highly mobile systems 1981 - 1986

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1980-01-01

    Measurement of crustal motion in the western United States and other tectonically active regions makes use of fixed, movable and highly mobile satellite laser ranging and very long baseline interferometry systems. Measurement of the rotational dynamics of the Earth as well as regional deformation and plate motion are discussed.

  14. Active deformation of the northern front of the Eastern Great Caucasus

    NASA Astrophysics Data System (ADS)

    Niviere, Bertrand; Gagala, Lukasz; Callot, Jean-Paul; Regard, Vincent; Ringenbach, Jean-Claude

    2016-04-01

    The Arabia-Eurasia collision involved a mosaic of island arcs and microcontinents. Their accretion to the complex paleogeographic margin of Neotethys was marked by numerous collisional events. The Greater Caucasus constitute the northernmost tectonic element of this tectonic collage, developed as a back arc extensional zone now inverted, which relationships to the onset of Arabia-Eurasia continental collision and/or to the reorganization of the Arabia-Eurasia plate boundary at ˜5 Ma remain controversial. Structurally, the Greater Caucasus are a former continental back arc rift, now the locus of ongoing continental shortening. Modern geodetic observations suggest that in the west, the strain north of the Armenian Plateau is accommodated almost exclusively along the margins of the Greater Caucasus. This differs from regions further east where strain accommodation is distributed across both the Lesser and Greater Caucasus, and within the Greater Caucasus range, with a unique southward vergence. We question here the amount and mechanisms by which the Eastern Greater Caucasus accommodate part of the Arabia-Eurasia convergence. Morphostructural analysis of the folded late Pleistocene marine terrace along the northern slope of the Eastern Greater Caucasus evidences an on going tectonic activity in the area where GPS measurements record no motion. Most of the recent foreland deformation is accommodated by south-vergent folds and thrust, i. e. opposite to the vergence of the Caucasus frontal northern thrust. A progressive unconformity in the folded beds shows that it was already active during the late Pliocene. Cosmogenic dating of the terrace and kinematic restoration of the remnant terrace, linked to the subsurface geology allows for the estimation of a shortening rate ranging from a few mm/yr to 1 cm/yr over the last 5 Myr along the greater Caucasus northern front. Thus more than one third of the shortening between the Kura block / Lesser Caucasus domain and the Stable

  15. Correcting Thermal Deformations in an Active Composite Reflector

    NASA Technical Reports Server (NTRS)

    Bradford, Samuel C.; Agnes, Gregory S.; Wilkie, William K.

    2011-01-01

    Large, high-precision composite reflectors for future space missions are costly to manufacture, and heavy. An active composite reflector capable of adjusting shape in situ to maintain required tolerances can be lighter and cheaper to manufacture. An active composite reflector testbed was developed that uses an array of piezoelectric composite actuators embedded in the back face sheet of a 0.8-m reflector panel. Each individually addressable actuator can be commanded from 500 to +1,500 V, and the flatness of the panel can be controlled to tolerances of 100 nm. Measuring the surface flatness at this resolution required the use of a speckle holography interferometer system in the Precision Environmental Test Enclosure (PETE) at JPL. The existing testbed combines the PETE for test environment stability, the speckle holography system for measuring out-of-plane deformations, the active panel including an array of individually addressable actuators, a FLIR thermal camera to measure thermal profiles across the reflector, and a heat source. Use of an array of flat piezoelectric actuators to correct thermal deformations is a promising new application for these actuators, as is the use of this actuator technology for surface flatness and wavefront control. An isogrid of these actuators is moving one step closer to a fully active face sheet, with the significant advantage of ease in manufacturing. No extensive rib structure or other actuation backing structure is required, as these actuators can be applied directly to an easy-to-manufacture flat surface. Any mission with a surface flatness requirement for a panel or reflector structure could adopt this actuator array concept to create lighter structures and enable improved performance on orbit. The thermal environment on orbit tends to include variations in temperature during shadowing or changes in angle. Because of this, a purely passive system is not an effective way to maintain flatness at the scale of microns over several

  16. Cenozoic to active deformation in Western Yunnan (Myanmar China border)

    NASA Astrophysics Data System (ADS)

    Socquet, A.; Pubellier, M.

    2003-04-01

    The northward movement of India induces a right-lateral shear band from the Sunda trench to the easternmost Himalaya, where wrenching between India and Sunda plates, interfere with a clockwise flow of material around the Eastern Himalayan Syntaxis. We describe brittle and ductile deformation styles in Western Yunnan and Northern Myanmar, using field data and Landsat 7 imagery for Cenozoic structures as well as GPS and seismicity for active structures to unravel the Neogene to Present evolution. Western Yunnan is crossed by three continental-size ductile shear zones characterized by high mountain belts mainly composed of high-grade metamorphics and mylonitic rocks, and affected by active faulting. The easternmost metamorphic range, the Gaoligong Shan composed of verticalized foliated granites and mylonites is flattened westward and joins the Mogok metamorphic belt in Myanmar. East of the Gaoligong Shan, lie the Chong Shan and the Ailao / Diangcan Shan metamorphic ranges, which presents a vertical shistosity and a left-lateral motion. These three shear zones are separated by sedimentary fold-and-thrust-belts in the East, and , West of the Gaoligong, by Quaternary basins and volcanics. Preliminary results indicate that the Shan Scarp constituted the major strike-slip boundary between Indochina and India during Eocene to Miocene time, and accommodated deformation in right-lateral wrench. At the same time, the Ailao / Diangcan Shan and the Chong Shan zones were sheared left-laterally allowing the displacement toward the SE of Indochina block relative to south China. In the Miocene, ductile deformation migrated north along the Shan Scarp to the Mogok / Ruili metamorphic belt and the Gaoligong belt, dragging the Chong Shan right-laterally and superimposing a late right-lateral ductile deformation on its metamorphic rocks. The present-day relative motion between India and Sundaland, inferred from GPS processing, reaches 35 mm / yr in the Myanmar area. It is classically

  17. The Diffuse Plate boundary of Nubia and Iberia in the Western Mediterranean: Crustal deformation evidence for viscous coupling and fragmented lithosphere

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    A spatially dense GNSS-based crustal velocity field for the Iberian Peninsula and Northern Africa allows us to provide new insights into two main tectonic processes currently occurring in this area. In particular, we provide, for the first time, clear evidence for a large-scale clockwise rotation of the Iberian Peninsula with respect to stable Eurasia (Euler pole component: N42.612°, W1.833°, clockwise rotation rate of 0.07 deg/Myr). We favor the interpretation that this pattern reflects the quasi-continuous straining of the ductile lithosphere in some sectors of South and Western Iberia in response to viscous coupling of the NW Nubia and Iberian plate boundary in the Gulf of Cádiz. We furnish evidence for a fragmentation of the western Mediterranean basin into independent crustal tectonic blocks, which are delimited by inherited lithospheric shear structures. Among these blocks, an (oceanic-like western) Algerian one is currently transferring a significant fraction of the Nubia-Eurasia convergence rate into the Eastern Betics (SE Iberia) and likely causing the eastward motion of the Baleares Promontory. These processes can be mainly explained by spatially variable lithospheric plate forces imposed along the Nubia-Eurasia convergence boundary.

  18. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation.

    PubMed

    Norman, J Farley; Phillips, Flip; Cheeseman, Jacob R; Thomason, Kelsey E; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B; Lamirande, Davora

    2016-01-01

    It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped "glaven") for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object's shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions-e.g., the participants' performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531

  19. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation

    PubMed Central

    Cheeseman, Jacob R.; Thomason, Kelsey E.; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B.; Lamirande, Davora

    2016-01-01

    It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped “glaven”) for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object’s shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions–e.g., the participants’ performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531

  20. Bulk arc strain, crustal thickening, magma emplacement, and mass balances in the Mesozoic Sierra Nevada arc

    NASA Astrophysics Data System (ADS)

    Cao, Wenrong; Paterson, Scott; Saleeby, Jason; Zalunardo, Sean

    2016-03-01

    Quantifying crustal deformation is important for evaluating mass balance, material transfer, and the interplay between tectonism and magmatism in continental arcs. We present a dataset of >650 finite strain analyses compiled from published works and our own studies with associated structural, geochronologic, and geobarometric information in central and southern Sierra Nevada, California, to quantify the arc crust deformation. Our results show that Mesozoic tectonism results in 65% arc-perpendicular bulk crust shortening under a more or less plane strain condition. Mesozoic arc magmatism replaced ∼80% of this actively deforming arc crust with plutons requiring significantly greater crustal thickening. We suggest that by ∼85 Ma, the arc crust thickness was ∼80 km with a 30-km-thick arc root, resulting in a ∼5 km elevation. Most tectonic shortening and magma emplacement must be accommodated by downward displacements of crustal materials into growing crustal roots at the estimated downward transfer rate of 2-13 km/Myr. The downward transfer of crustal materials must occur in active magma channels, or in "escape channels" in between solidified plutons that decrease in size with time and depth resulting in an increase in the intensity of constrictional strain with depth. We argue that both tectonism and magmatism control the thickness of the crust and surface elevation with slight modification by surface erosion. The downward transported crustal materials initially fertilize the MASH zone thus enhancing to the generation of additional magmas. As the crustal root grows it may potentially pinch out and cool the mantle wedge and thus cause reduction of arc magmatism.

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

    NASA Technical Reports Server (NTRS)

    Toksoz, M. Nafi

    1988-01-01

    The long-term objective of this project is to interpret NASA's Crustal Dynamics measurements (SLR) in the Eastern Mediterranean region in terms of relative plate movements and intraplate deformation. The approach is to combine realistic modeling studies with analysis of available geophysical and geological observations to provide a framework for interpreting NASA's measurements. This semi-annual report concentrates on recent results regarding the tectonics of Anatolia and surrounding regions from ground based observations. Also reported on briefly is progress in the use of the Global Positioning System to densify SLR observations in the Eastern Mediterranean. Reference is made to the previous annual report for a discussion of modeling results.

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

    NASA Technical Reports Server (NTRS)

    Toksoz, M. Nafi

    1987-01-01

    The long term objective of this project is to interpret NASA's Crustal Dynamics measurements (SLR) in the Eastern Mediterranean region in terms of relative plate motions and intraplate deformation. The approach is to combine realistic modeling studies with an analysis of available geophysical and geological observations to provide a framework for interpreting NASA's measurements. This semi-annual report concentrates on recent results regarding the tectonics of Anatolia and surrounding regions from ground based observations. Also briefly reported on is progress made in using GPS measurements to densify SLR observations in the Eastern Mediterranean.

  3. Viscoelastic deformation of lunar impact basins: Implications for heterogeneity in the deep crustal paleo-thermal state and radioactive element concentration

    NASA Astrophysics Data System (ADS)

    Kamata, Shunichi; Sugita, Seiji; Abe, Yutaka; Ishihara, Yoshiaki; Harada, Yuji; Morota, Tomokatsu; Namiki, Noriyuki; Iwata, Takahiro; Hanada, Hideo; Araki, Hiroshi; Matsumoto, Koji; Tajika, Eiichi

    2013-03-01

    Diverse geological characteristics found for the three major lunar provinces (i.e., the Feldspathic Highlands Terrane (FHT), the South Pole-Aitken Terrane (SPAT), and the Procerallum KREEP Terrane (PKT)) strongly suggest their distinctly different thermal histories. Quantitative differences among these provinces in their early thermal histories and crustal radioactive element concentrations, however, are highly unknown. One of the few observables that retain a record of the ancient lunar thermal structure is the viscoelastic state of impact basins. This study investigates the long-term evolution of basin structures using global lunar gravity field data obtained by Kaguya tracking and derives constraints for (1) the paleo-thermal state of impact basins and for (2) crustal column-averaged radioactive element concentrations for each province. Our calculation results indicate that impact basins in the central anorthositic region of the FHT (i.e., the FHT-An) require a very cold interior ( dT / dr ≤ 20 K km - 1 on the surface). This result strongly suggests that the deep portion of the thick farside highlands crust is highly depleted in radioactive elements (Th ≤ 0.5 ppm), indicating that the Th-rich SPA basin floor crust is clearly different from the lower crust underneath the FHT-An and cannot be accounted for by simple exposure of the lower crust. Our analysis also indicates that the observed basin structure allows as high as ˜ 6 ppm of column-averaged Th concentration in the crust inside the PKT. These results indicate that radioactive element concentrations deep in the crust probably vary greatly region by region, similarly to those observed on the surface.

  4. Microseismicity and active deformation of Messinia, SW Greece

    NASA Astrophysics Data System (ADS)

    Papoulia, J.; Makris, J.

    By deploying a 30 3-component digital seismic array in the Messiniakos gulf and the surrounding region, we recorded for a period of 45 days the microseismic activity. With a minimum of six records per event, we located 1121 earthquakes corresponding to an average of 20 events per day. For the hypocenter location we used a local velocity model adopted to two controlled source seismic experiments. Within the array, traveltime residuals were within ± 0.2 s and the epicentral accuracy in the order of ± 2 km, while the hypocentral one is twice this value. Correlation of the seismicity with the tectonic elements indicated that most of the NW-SE oriented faults are active with strike-slip movement along this orientation and extension perpendicular to it. The neogene basins of Messini, Meligalas and Megalopolis are seismically very active and their eastern flanks are delineated by higher seismic activity than their western ones. This indicates that the basins are asymmetric with master faults defining their eastern-northeastern flanks. This hypothesis is supported by the asymmetric structure mapped at the offshore Messiniakos basin as densely spaced high resolution reflection seismic profiles have revealed. The western margins of the basins are less deformed and the seismic activity is dispersed over several minor NW-SE faults. Since the NW-SE striking faults onshore are truncated by major NE-SW oriented ones, their overall length is shortened, reducing their seismic potential and capacity to store large stresses that could produce events above Ms6.1. Offshore western Messinia, in the Ionian Sea, the size and activity of the faults is significantly larger and prone to develop events of larger magnitudes. Subcrustal seismicity indicates a deepening of the foci to the east-northeast.

  5. Activities and source mechanisms of volcanic deep low-frequency earthquakes and its implication for deep crustal process in magmatic arc (Invited)

    NASA Astrophysics Data System (ADS)

    Nakamichi, H.

    2013-12-01

    Rocks under upper mantle and lower crustal temperatures and pressures typically deform in a ductile manner, therefore it is difficult to accumulate enough deviatoric stress in rocks to generate brittle failure under this condition. However earthquakes occur at upper mantle and lower crust beneath active volcanoes, and are recognized as volcanic deep low-frequency earthquakes (VDLFs). VDLFs are characterized by mostly low-frequency energy (<5 Hz), emergent arrivals and long-duration codas. VDLF activity observed at depths of 10-50 km in Japan, the Philippines, Alaska and the Western US (Power et al., 2004; Ukawa, 2005; Nichols et al. 20011), has generally been attributed to magma transport in the mid-to-lower crustal and uppermost mantle regions. However because VDLF seismicity is infrequent, with relatively weak and emergent signals, the relationship between deep magma transport and seismic radiation remains poorly understood. Borehole dense seismic observation systems, such as the high-sensitivity seismograph network 'Hi-net' in Japan (Obara et al. 2005), are effective for detecting not only non-VDLFs (Obara, 2002) but also VDLFs. Since 1997 the Japan Meteorological Agency has routinely detected and located DLFs using the Hi-net dataset, and have identified DLFs in and around most quaternary volcanoes in Japan (Takahashi and Miyamura, 2009). Several studies have attempted to estimate source mechanisms of VDLFs in Japan. The first attempt by Ukawa and Ohtake (1987), obtained a single force as the source mechanism of a VDLF beneath Izu-Ohshima by using particle motions of S-waves. Following that work strike-slip type and non-double-couple source mechanisms were obtained using waveform inversions for VDLFs in Northeast Japan (Nishidomi and Takeo 1996; Okada and Hasegawa, 2000). Nakamichi et al. (2003; 2004) estimated the source mechanisms of Mts. Iwate and Fuji through the moment tensor inversion of spectral ratios of body waves from using data from a dense seismic

  6. Deep Continental Crustal Earthquakes and Lithospheric Structure: A Global Synthesis

    NASA Astrophysics Data System (ADS)

    Devlin, S.; Isacks, B. L.

    2007-12-01

    measurements indicate that lower crustal earthquakes exist within continental regions experiencing youthful (generally Neogene to present) tectonism typically with < 15 % strain. We propose a model that describes relative continental deformation and corresponding seismogenic thickness. In stable seismogenic regions, earthquakes are limited to depths where near-surface derived fluids can induce activity and therefore TS < 25 km. As continental lithosphere passes into an intermediate state of deformation, fluids from the near surface and melts formed in situ or derived from the mantle can act to seismically activate the entire continental crust. As deformation continues, percent strains can reach 100 % or more, mantle lithosphere is typically thinned or absent, and the lower crust via heating and/or sufficient weakening becomes aseismic.

  7. Application of space technology to crustal dynamics and earthquake research

    NASA Technical Reports Server (NTRS)

    1979-01-01

    In cooperation with other Federal government agencies, and the governments of other countries, NASA is undertaking a program of research in geodynamics. The present program activities and plans for extension of these activities in the time period 1979-1985 are described. The program includes operation of observatories for laser ranging to the Moon and to artificial satellites, and radio observatories for very long baseline microwave interferometry (VLBI). These observatories are used to measure polar motion, earth rotation, and tectonic plate movement, and serve as base stations for mobile facilities. The mobile laser ranging and VLBI facilities are used to measure crustal deformation in tectonically active areas.

  8. Investigation of the deep crustal structure and magmatic activity at the NW Hellenic Volcanic Arc with 3-D aeromagnetic inversion and seimotectonic analysis.

    NASA Astrophysics Data System (ADS)

    Efstathiou, Angeliki; Tzanis, Andreas; Chailas, Stylianos; Stamatakis, Michael

    2013-04-01

    We report the results of a joint analysis of geophysical (aeromagnetic) and seismotectonic data, applied to the investigation of the deep structure, magmatic activity and geothermal potential of the north-western stretches of the Hellenic Volcanic Arc (HVA). The HVA is usually considered to be a single arcuate entity stretching from Sousaki (near Corinth) at the NW, to Nisyros Island at the SE. However, different types of and their ages indicate the presence of two different volcanic groups. Our study focuses on the northern part of the west (older) volcanic group and includes the Crommyonian (Sousaki) volcanic field at the west end of Megaris peninsula (east margin on the contemporary Corinth Rift), the Aegina and Methana volcanic complex at the Saronic Gulf, where typical Quaternary calc-alkaline volcanics predominate, and the Argolid peninsula to the south and south-west. In addition to the rocks associated with Quaternary volcanism, the study area includes a series of Mesozoic ultramafic (ophiolitic) outcrops at the Megaris peninsula, to the north and north-east of the Crommyonian volcanic field, as well as throughout the Argolid. A major deep structural and tectonic feature of the study area, and one with profound influence on crustal deformation and the evolution of rapidly deforming extensional structures like the Corinth Rift and the Saronic Gulf, is the local geometry and dynamics of the African oceanic crust subducting beneath the Aegean plate. Locally, the subducting slab has a NNW strike and ENE plunge, with the dip angle changing rapidly (steepening) approx. beneath the Argolid. The aeromagnetic data was extracted from the recently (re)compiled aeromagnetic map of Greece (Chailas et al, 2010) and was inverted with the UBC-GIF magnetic inversion suite (Li and Oldenburg, 1996). The inversion included rigorous geological constraints introduced by means of numerous in-situ magnetic susceptibility measurements. The inversion has imaged several isolated

  9. Water flow based geometric active deformable model for road network

    NASA Astrophysics Data System (ADS)

    Leninisha, Shanmugam; Vani, Kaliaperumal

    2015-04-01

    A width and color based geometric active deformable model is proposed for road network extraction from remote sensing images with minimal human interception. Orientation and width of road are computed from a single manual seed point, from which the propagation starts both right and left hand directions of the starting point, which extracts the interconnected road network from the aerial or high spatial resolution satellite image automatically. Here the propagation (like water flow in canal with defined boundary) is restricted with color and width of the road. Road extraction is done for linear, curvilinear (U shape and S shape) roads first, irrespective of width and color. Then, this algorithm is improved to extract road with junctions in a shape of L, T and X along with center line. Roads with small break or disconnected roads are also extracts by a modified version of this same algorithm. This methodology is tested and evaluated with various remote sensing images. The experimental results show that the proposed method is efficient and extracting roads accurately with less computation time. However, in complex urban areas, the identification accuracy declines due to the various sizes of obstacles, over bridges, multilane etc.

  10. The Internal Structure of Fault Zones in Carbonates Deformed at Shallow Crustal Level - Evidence From Scaled Physical Models Using Cohesive Powder.

    NASA Astrophysics Data System (ADS)

    van Gent, H. W.; Holland, M.; Urai, J. L.; Loosveld, R.

    2006-12-01

    In cohesive carbonates deformed at shallow depth the ratio of the rock's compressive stress and the in-situ mean effective stress is usually large and faults are highly dilatant. This makes it difficult to do detailed studies outcrop or core, because the structures are fragile and easily damaged. We present scaled physical models of these structures made from fine-grained, cohesive Hemihydrate powder. Extensive deformation experiments characterize the material's properties to allow scaling with respect to the natural prototypes. Uniaxial consolidation test shows void ratio linearly dependent on pressure and a coefficient of compressibility (change of void ratio over change of normal load) of 0.0001/Pa. Compression and shear tests show that tensile strength of the powder is between 5 and 50 Pa, and cohesion varies between 50 and 250 Pa. Cohesion and tensile strength are inversely proportional to void ratio whereas the friction angle remains virtually constant. The powder's properties can be described by a Cam-Clay type constitutive relation, where the cohesion and tensile strength of the powder changes with depth in the model. We studied the evolution of normal faults in a graben above a rigid basement containing a fault with a dip of 60 DEG, in homogeneous or layered models with sand or graphite-gypsum mixtures to represent the weaker layers. The structural evolution and displacement field was analyzed by time-lapse digital photography and Particle Imaging Velocimetry (PIV). The initial displacement field is continuous: we interpret this as elastic strain prior to brittle failure. Localization of deformation produces both mode I and mode II fractures depending on the depth in the model. Characteristic structures are dilational jogs, fragmentation and fault gouge formation by gravity-driven mass transport along the open sections. The model show good correspondence with what is known from the structures in naturally occurring dilatant fault systems in carbonates.

  11. Crustal deformation across the Sierra Nevada, northern Walker Lane, Basin and Range transition, western United States measured with GPS, 2000-2004

    NASA Astrophysics Data System (ADS)

    Hammond, William C.; Thatcher, Wayne

    2007-05-01

    Global Positioning System (GPS) data collected in campaigns in 2000 and 2004 were processed and interpreted with other GPS data in the western Basin and Range province to provide new constraints on the rate, style, and pattern of deformation of the central and northern Walker Lane (WL), which lies near the western boundary of the Basin and Range. Across the central WL, near 38°N latitude, the velocities with respect to North America increase westward by ˜10 mm/yr inducing dextral shear. Farther north between 40° and 41°N latitude, a western zone of ˜7 mm/yr relative motion undergoes dextral shear, and an eastern zone of ≤3 mm/yr relative motion undergoes extension and shear. These data show that the northern WL is essentially a dextral shear zone experiencing minor net dilatation (ɛΔ = 2.6 ± 0.8 nstrain/yr). Near most Holocene normal faults, dilatation inferred from the velocity field is not greater than the uncertainties. However, near the central Nevada seismic belt we detect significant dilatation expressed as extension in a direction approximately normal to the range fronts (ɛΔ = 23.0 ± 3.9 nstrain/yr), some of which is attributable to transient postseismic deformation following large historic earthquakes. A block model constrained by velocities corrected for transient effects shows that the sum of dextral slip rates across the Honey Lake, Warm Springs, east Pyramid fault system, and Mohawk Valley faults is ˜7 mm/yr. The WL is a zone whose width and dilatation rate increase northwestward, consistent with counterclockwise rotation of the Sierra Nevada microplate and transfer of deformation into the Pacific Northwest.

  12. Crustal deformation of the Yellowstone-Snake River Plain volcano-tectonic system-Campaign and continuous GPS observations, 1987-2004

    USGS Publications Warehouse

    Puskas, C.M.; Smith, R.B.; Meertens, Charles M.; Chang, W. L.

    2007-01-01

    The Yellowstone-Snake River Plain tectonomagmatic province resulted from Late Tertiary volcanism in western North America, producing three large, caldera-forming eruptions at the Yellowstone Plateau in the last 2 Myr. To understand the kinematics and geodynamics of this volcanic system, the University of Utah conducted seven GPS campaigns at 140 sites between 1987 and 2003 and installed a network of 15 permanent stations. GPS deployments focused on the Yellowstone caldera, the Hebgen Lake and Teton faults, and the eastern Snake River Plain. The GPS data revealed periods of uplift and subsidence of the Yellowstone caldera at rates up to 15 mm/yr. From 1987 to 1995, the caldera subsided and contracted, implying volume loss. From 1995 to 2000, deformation shifted to inflation and extension northwest of the caldera. From 2000 to 2003, uplift continued to the northwest while caldera subsidence was renewed. The GPS observations also revealed extension across the Hebgen Lake fault and fault-normal contraction across the Teton fault. Deformation rates of the Yellowstone caldera and Hebgen Lake fault were converted to equivalent total moment rates, which exceeded historic seismic moment release and late Quaternary fault slip-derived moment release by an order of magnitude. The Yellowstone caldera deformation trends were superimposed on regional southwest extension of the Yellowstone Plateau at up to 4.3 ± 0.2 mm/yr, while the eastern Snake River Plain moved southwest as a slower rate at 2.1 ± 0.2 mm/yr. This southwest extension of the Yellowstone-Snake River Plain system merged into east-west extension of the Basin-Range province. Copyright 2007 by the American Geophysical Union.

  13. Crustal velocity model along the southern Cuban margin: implications for the tectonic regime at an active plate boundary

    NASA Astrophysics Data System (ADS)

    Moreno, Bladimir; Grandison, Margaret; Atakan, Kuvvet

    2002-11-01

    A new 1-D velocity model along the southern Cuban margin has been determined using local earthquake data, which are the result of the merged Cuban and Jamaican catalogues. Simultaneous inversion using joint-hypocentre determination was applied to solve the coupled hypocentre-velocity model problem. We obtained a seven-layer model with an average Moho interface at 20 km. The average velocity was found to be 7.6 km s-1 on the top of the crust-mantle transition zone and 6.9 km s-1 in the basaltic layer of the crust. The improvement in the earthquake locations allowed us for the first time to use local seismicity to characterize the activity on local faults and the stress regime in the area. For this purpose, 34 earthquake focal mechanisms were determined along the eastern segments of the Oriente Fault. These solutions are consistent with the known left-lateral strike-slip motion along this major structure as well as with the stress regime of two local structures: (1) the Cabo Cruz Basin and (2) the Santiago deformed belt. The first structure is dominated by normal faults with minor strike-slip components and the second by reverse faults. The shallow seismicity in the Cabo Cruz Basin is associated with fault planes trending N55°-58°E and dipping 38°-45° to the north. The Santiago deformed belt, on the other hand, exhibits diverse fault plane orientations. These local structures account for most of the earthquake activity along the southern Cuban margin. Deep seismicity observed in the Santiago deformed belt, supported by focal mechanisms, suggests underthrusting of the Gonave Microplate beneath the Cuban Block in this area. The principal stress orientations obtained from stress inversion of earthquake focal mechanisms suggest a thrust faulting regime along the Southern Cuban margin. We obtained a nearly horizontal σ1 and nearly vertical σ3, which indicates active compressional deformation along the major Oriente transcurrent fault in agreement with the dominant

  14. Crustal structure during active rifting in the central Salton Trough, California, constrained by the Salton Seismic Imaging Project (SSIP)

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Stock, J. M.; Fuis, G. S.; Driscoll, N. W.; Kell, A. M.; Kent, G.; Harding, A. J.; Gonzalez-Fernandez, A.; Lazaro-Mancilla, O.

    2013-12-01

    Seismic refraction and reflection travel times from the Salton Seismic Imaging Project (SSIP) were used to constrain crustal structure during active continental rifting in the central Salton Trough, California. SSIP, funded by NSF and USGS, acquired seismic data in and across the Salton Trough in 2011 to investigate rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. Seven lines of refraction and low-fold reflection data were acquired onshore, two lines and a grid of airgun and OBS data were acquired in the Salton Sea, and onshore-offshore data were recorded. North American lithosphere in the central Salton Trough appears to have been rifted apart and replaced by new crust added by magmatism from below and sedimentation from above. Ongoing active rifting of this new crust is manifested by shallow (<10km depth) seismicity in the oblique Brawley Seismic Zone (connecting the Imperial and San Andreas transform faults), the small Salton Buttes volcanoes, and very high heat flow that enables geothermal energy production. Analyses of the onshore-offshore seismic line that extends along the axis of the Salton Trough, parallel to the direction of plate motion, constrains rifted crustal structure. Crystalline basement (~5 km/s) generally occurs at ~4 km depth, but is at 2-3 km depth in a localized region beneath the Salton Buttes and Salton Sea geothermal field. This crystalline rock is interpreted to be late Pliocene to Quaternary Colorado River sediment that has been metamorphosed by high heat flow to a depth of at least 10km. The shallower basement under the volcanic and geothermal field is due to more intense metamorphism and hydrothermal alteration in this region of extreme heat flow. Faster velocity (6.2-6.4 km/s) observed at 10-13 km depth might be the remains of ruptured pre-existing crust or might be produced by deeper magmatism. Seismic travel times indicate

  15. Temporal variation of crustal deformation during the days preceding a thrust-type great earthquake — The 1944 Tonankai earthquake of magnitude 8.1, Japan

    NASA Astrophysics Data System (ADS)

    Mogi, Kiyoo

    1984-11-01

    The temporal variation in precursory ground tilt prior to the 1944 Tonankai (Japan) earthquake, which is a great thrust-type earthquake along the Nankai Trough, is discussed using the analysis of data from repeated surveys along short-distance leveling routes. Sato (1970) pointed out that an anomalous tilt occurred one day before the earthquake at Kakegawa near the northern end of the focal region of the earthquake. From the analysis of additional leveling data, Sato's result is re-examined and the temporal change in the ground tilt is deduced for the period of about ten days beginning six days before the earthquake. A remarkable precursory tilt started two or three days before the earthquake. The direction of the precursory tilt was up towards the south (uplift on the southern Nankai Trough side), but the coseismic tilt was up towards the southeast, perpendicular to the strike of the main thrust fault of the Tonankai earthquake. The postseismic tilt was probably opposite of the coseismic tilt. The preseismic tilt is attributed to precursory slip on part of the main fault. If similar precursory deformation occurs before a future earthquake expected to occur in the adjacent Tokai region, the deformation may help predict the time of the Tokai earthquake.

  16. Numerical modelling of crustal deformation due to fluid extraction and re-injection in the Hengill geothermal area in South Iceland

    NASA Astrophysics Data System (ADS)

    Juncu, Daniel; Árnadóttir, Thóra; Ali, Tabrez; Hooper, Andrew

    2015-04-01

    Several high temperature geothermal energy production fields are currently harnessed in Iceland. One of these is located at the Hengill triple junction, where the oblique plate motion along the Reykjanes peninsula is partitioned between the E-W oriented transform along the South Iceland Seismic Zone (SISZ) and spreading across the Western Volcanic Zone in SW Iceland. The Hengill volcano is a high temperature geothermal area that is utilized by the Hellisheiði and Nesjavellir power plants. The regions around the power plants are subject to surface deformation due to several processes. These include the motion of the Earth's crust due to plate spreading, co- and post seismic deformation due to earthquakes in the South Iceland Seismic Zone and deformation due to water and steam extraction and wastewater re-injection near geothermal power plants. We measure surface displacement in the Hengill area using both GPS and InSAR data. The former are obtained from four continuous and more than 15 campaign GPS stations in the area, with time-series starting after two M6 earthquakes on 29 May 2008 in Ölfus - the westernmost part of the SISZ. The InSAR data consist of 10 images taken by the TerraSar-X mission, starting October 2009. The InSAR time-series has a temporal resolution of 1 to 3 images per year, taken at an incidence angle of approximately 30° from the vertical. In the InSAR data we can see a clear subsidence signal in the proximity of the power plants with a maximum of ~24 mm/yr in Line-of-Sight direction (LOS) at Hellisheiði, after correcting for plate motion. The subsidence is elongated in NNE-SSW direction and possibly related to the orientation of the Hengill fissure swarm. In addition to subsidence, we observe an uplift signal of ca. 10 mm/yr in LOS west of the Hellisheiði site, potentially due to wastewater re-injection in the area. The area of maximum uplift is located close to the epicenters of two M4 earthquakes that occurred in October 2011. We run

  17. Crustal structure beneath Southwestern Mexico

    NASA Astrophysics Data System (ADS)

    Suhardja, S.; Grand, S.; Wilson, D.; Guzman Speziale, M.; Gomez Gonzalez, J.; Ni, J.; Dominguez Reyes, T.

    2007-12-01

    The MARS ( Mapping the Rivera Subduction zone ) project started in January 2006 deploying 50 broadband seismometers across southwestern Mexico for one and a half year duration. The stations were deployed in Jalisco, Michoacan and Colima states. The goal of the project is to understand the geometry of the Rivera and Cocos subducting plates and the effect of the subduction on the overriding plate. In this study, we employ the teleseismic receiver function technique to map out the lateral variation in Moho depth as well as the Vp/Vs ratio of the crust in this tectonically and magmatically active area. The ambiguity between the delay time of Ps and crustal Vp/Vs ratio is reduced by stacking later phases, the PpPs and PpSs + PsPs, for different values of Moho depth and Vp/Vs ratio (Zhu et al. ). An average crustal depth and crustal Vp/Vs ratio is obtained by finding the highest combination of parameters that give the largest amplitude stack. We find that the average Moho depth is 39 km but varies significantly from 25 to 45 km thick. The average crustal Vp/Vs ratio is 1.82 but is also variable ranging from 1.7 to 1.9. We will discuss correlations of crustal thickness and Vp/Vs ratio with crustal composition and magmatic activity.

  18. Strain accumulation and fluid-rock interaction in a naturally deformed diamictite, Willard thrust system, Utah (USA): Implications for crustal rheology and strain softening

    NASA Astrophysics Data System (ADS)

    Yonkee, W. Adolph; Czeck, Dyanna M.; Nachbor, Amelia C.; Barszewski, Christine; Pantone, Spenser; Balgord, Elizabeth A.; Johnson, Kimberly R.

    2013-05-01

    Structural and geochemical patterns of heterogeneously deformed diamictite in northern Utah (USA) record interrelations between strain accumulation, fluid-rock interaction, and softening processes across a major fault (Willard thrust). Different clast types in the diamictite have varying shape fabrics related to competence contrasts with estimated effective viscosity ratios relative to micaceous matrix of: ˜6 and 8 for large quartzite clasts respectively in the Willard hanging wall and footwall; ˜5 and 2 for less altered and more altered granitic clasts respectively in the hanging wall and footwall; and ˜1 for micaceous clasts that approximate matrix strain. Within the footwall, matrix X-Z strain ratios increase from ˜2 to 8 westward along a distinct deformation gradient. Microstructures record widespread mass transfer, alteration of feldspar to mica, and dislocation creep of quartz within matrix and clasts. Fluid influx along microcracks and mesoscopic vein networks increased westward and led to reaction softening and hydrolytic weakening, in conjunction with textural softening from alignment of muscovite aggregates. Consistent Si, Al, and Ti concentrations between matrix, granitic clasts, and protoliths indicate limited volume change. Mg gain and Na loss reflect alteration of feldspar to phengitic muscovite. Within the hanging wall, strain is overall lower with matrix X-Z strain ratios of ˜2 to 4. Microstructures record mass transfer and dislocation creep concentrated in the matrix. Greater Al and Ti concentrations and lower Si concentrations in matrix indicate volume loss by quartz dissolution. Na gain in granitic clasts reflects albitization. Large granitic clasts have less mica alteration and greater competence compared to smaller clasts. Differences in strain and alteration patterns across the Willard thrust fault suggest overall downward (up-temperature) fluid flow in the hanging wall and upward (down-temperature) fluid flow in the footwall.

  19. Crustal differentiation due to partial melting of granitic rocks in an active continental margin, the Ryoke Belt, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Akasaki, Eri; Owada, Masaaki; Kamei, Atsushi

    2015-08-01

    The continental margin of Pacific Asia is dominated by the voluminous Cretaceous to Paleogene granitic rocks. The Ryoke granitoids that occur in the Ryoke Belt in the Southwest Japan Arc are divided into the older and younger granites. The high-K Kibe Granite represents the younger granitic intrusion and is exposed in the Yanai area in the western part of Ryoke Belt. The Kibe Granite is associated with the coeval Himurodake Quartz Diorite and their intrusive age is 91 Ma. However, the Gamano-Obatake Granodiorite, the older granite, intruded the host Ryoke gneisses at 95 Ma. The Gamano-Obatake Granodiorite is characterized by the localized development of migmatitic structure attributed to the intrusion of the Himurodake Quartz Diorite into the granodiorite. Leucocratic pools and patches occur in the granodiorite in the vicinity of the quartz diorite. The Sr and Nd isotopic compositions of the Gamano-Obatake Granodiorite corrected to 91 Ma are plotted within those of the Kibe Granite. Geochemical modeling suggests that partial melting took place in the Gamano-Obatake Granodiorite and resulted in the formation of the Kibe Granite magma. The Himurodake Quartz Diorite is believed to be a heat source for this event. This can be considered as an essential process for the formation of the evolved younger Ryoke granite and for the crustal differentiation in the active continental margin.

  20. Damping scaling factors for elastic response spectra for shallow crustal earthquakes in active tectonic regions: "average" horizontal component

    USGS Publications Warehouse

    Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Abrahamson, Norman; Campbell, Kenneth; Silva, Walter

    2014-01-01

    Ground motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and nonstructural systems can have other damping ratios. This paper develops a new model for a damping scaling factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5% to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables, such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions, are examined. The strong influence of duration is captured by the inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

  1. Mechanics of dielectric elastomer-activated deformable transmission grating

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Zhou, Jinxiong; Sun, Wenjie; Wu, Xiaohong; Zhang, Ling

    2014-09-01

    Laminating a thin layer of elastomeric grating on the surface of a prestretched dielectric elastomer (DE) membrane forms a basic design of electrically tunable transmission grating. We analyze the inhomogeneous deformation of a circular multiple-region configuration. Variation of the geometric and material parameters, as well as of the critical condition determined by loss of tension instability, is probed to aid the design of a DE-based deformable grating. The predicted changes in the grating period agree substantially with the experimental results reported by Aschwanden et al (Aschwanden et al 2007 IEEE Photon. Technol. Lett. 19 1090).

  2. Crustal deformation across the Imperial Fault: Results from kinematic GPS surveys and trilateration of a densely spaced, small-aperture network

    NASA Astrophysics Data System (ADS)

    Genrich, Joachim F.; Bock, Yehuda; Mason, Ronald G.

    1997-03-01

    Kinematic Global Positioning System (GPS) surveys in 1991 and 1993 of a 66-station, small-aperture network across a 12-km-long segment of the Imperial Fault near El Centro, California, reveal a fairly uniform secular displacement field consistent with right-lateral slip along a single, vertical dislocation surface. Total relative motion across the array equals 20±3 mm/yr at N49±7°W for sites 5-6 km away from the fault trace on opposite sides. These rates agree with simple dislocation models that assume 10 mm/yr of creep along the fault trace from the surface to a locking depth of 9 km and a plate boundary rate of 45 mm/yr oriented N40°W at depth. Model fit does not significantly improve if creep rates are permitted to vary along strike by several millimeters per year. A comparison of 1991/1993 GPS with 1987 high-precision electronic distance measurements validates the dislocation models but suggests a smoother deformation field than that defined by the 1991/1993 velocities. The difference can be attributed to the poorer 1991 kinematic positioning accuracy rather than to temporal variations in strain. There is evidence for 20 mm of sympathetic coseismic slip from the 1987 Superstition Hills earthquake, although aseismic slip along both faults appears to be completely decoupled.

  3. Active Deformation in the Greater Himalayan Zone in Western Nepal from Inversion of New (U-Th)/He Cooling Ages

    NASA Astrophysics Data System (ADS)

    Harvey, J. E.; Burbank, D.

    2015-12-01

    Much of the central Himalaya features an abrupt rise in mean elevation from ~1.5 km in the Lesser Himalaya to ~4-5 km Greater Himalaya and Tibetan Plateau. This physiographic transition is known as PT2, and is often interpreted as the surface expression of transport over a ramp in the Main Himalayan Thrust (MHT). In western Nepal, however, the same rise in elevation occurs over two distinct topographic steps (PT2-N and PT2-S). In previous work, Harvey et al. (2015) argue that this anomalous topography is the result of recent southward-migration of mid-crustal deformation along the MHT. Due to the seismogenic potential of the MHT it is important to constrain its geometry in the western Nepal seismic gap, which has not had a large earthquake in over 600 years. To test the above hypothesis, we perform [U-Th]/He dating on 39 apatite and 47 zircon samples collected along seven relief transects throughout western Nepal. We constrain exhumation histories by inverting these new cooling ages with the 3-D thermo-kinematic model Pecube. Five transects collected from the Greater Himalaya north of PT2-N are best fit by relatively rapid exhumation rates (~1-2 km/Myr) since ~4 Ma. The other two, collected from farther south near PT2-S, require rapid (~1-2 km/Myr) exhumation until around 8-11 Ma, followed by much slower (~0.1-0.2 km/Myr) exhumation until at least the late Pliocene. Assuming that exhumation rates reflect uplift rates, the rapid Plio-Pleistocene exhumation in the Greater Himalaya north of PT2-N suggest that this physiographic transition is similar to that at the foot of the Greater Himalaya in central Nepal. It follows that active deformation is occurring along a NW-trend as much as 100 km farther north than would be expected if simply projecting PT2 across western Nepal. This finding is consistent with transport over a more northerly MHT ramp or perhaps oblique slip along the recently identified, surface-breaking WNFZ. Although the geomorphology and microseismicity

  4. Deformation-induced diagenesis and microbial activity in the Nankai accretionary prism

    NASA Astrophysics Data System (ADS)

    Famin, V.; Andreani, M.; Boullier, A. M.; Raimbourg, H.; Magnin, V.

    2014-12-01

    We performed a microscopic and chemical study of diagenetic reactions in deformation microstructures within deep mud sediments from the Nankai accretionary prism (SW Japan) collected during IODP Expedition 315. Our study reveals that deformation microstructures localize the crystallization of pyrite, a diagenetic reaction also found in large megasplay faults of the prism. Textural observation shows that pyrite crystallization is synchronous of the sediment deformation. The framboidal shape of pyrite crystals, the barium depletion and the strong arsenic enrichment observed in deformation microstructures compared with the sediment matrix, suggest that pyrite crystallization is mediated by the proliferation of anoxic archae. During scientific drilling expeditions IODP 315, 316 and 319, microbial life has been evidenced at depths of up to 800 m below the sea floor by the presence of biogenic methane and sulfate reducers in sediments. We suggest that deformation structures localize microbial proliferation because the fracturing of silicate minerals produces hydrogen, a necessary compound for bacteria under anoxic conditions. Bacteria proliferate as long as active deformation supplies hydrogen, and vanish when the deformation stops. The development of bacteria in deformation structures impacts our mechanical understanding of fault zones in accretionary prisms: Firstly, bacterial activity converts carbon from organic matter and hydrogen into methane and/or water, which may alter the fluid budget of fault zones and the recurrence of dynamic ruptures in megathrusts. Secondly, the abundance of bacteria could be used to recognize active fault zones from inactive ones in drilling cores.

  5. Active Dehydration, Delamination and Deformation of Transitional Continental Crust in an Arc-Continent Collision, Taiwan

    NASA Astrophysics Data System (ADS)

    Byrne, T. B.; Rau, R. J.; Chen, K. H.; Huang, H. H.; Wang, Y. J.; Ouimet, W. B.

    2014-12-01

    A new study of the 3-D velocity structure of Taiwan, using a new tomographic model (Vp and Vs; Huang et al., 2014), suggests that subducted continental crust is delaminated from the subducting mantle of the Eurasia plate and progressively deformed by the subducting Philippine Sea plate. In southern Taiwan, vertical sections show an east-dipping, asymmetric lobe of low velocity that projects down dip to a band of seismicity interpreted as the Wadati-Benioff zone of the subducting Eurasian plate. Seismic tremors in the mid-crust also suggest dehydration (Chuang et al., 2014), consistent with prograde metamorphism of crustal materials. In central Taiwan, however, the seismicity of the W-B zone progressively disappears and the low velocity lobe shallows and broadens. The velocity structure of the lower and middle crust (represented by the 7.5 and 6.5 km/sec isovelocity surfaces, respectively) also appear distinctly out-of-phase, with the lower crust forming a broad, smooth synformal structure that contrasts with the higher amplitude undulations of the middle crust. These mid-crust structures appear as smaller irregular lobes separated by patches of higher velocity. In northern Taiwan, the velocity structure of the lower and middle crust again appear "in phase" and form a symmetrical crustal root centered beneath the Central Range. Seismicity patterns and 3-D analysis of the velocity structure also show the western edge of the PSP subducting beneath the eastern Central Range. We interpret these south-to-north changes to reflect the partial subduction (southern Taiwan), delamination (central Taiwan) and deformation (northern Taiwan) of continental-like crust. Support for these interpretation comes from: 1) unusually high rates of surface uplift (up to 15 mm/yr; Ching et al., 2011); 2) Vp and Vs attenuation studies that suggest anomalously high temperatures; 3) evidence for NE-SW extension; and 4) anomalous areas of low topographic relief.

  6. Estimation of active faulting in a slow deformation area: Culoz fault as a case study (Jura-Western Alps junction).

    NASA Astrophysics Data System (ADS)

    de La Taille, Camille; Jouanne, Francois; Crouzet, Christian; Jomard, Hervé; Beck, Christian; de Rycker, Koen; van Daele, Maarten; Lebourg, Thomas

    2014-05-01

    The north-western Alps foreland is considered as still experiencing distal effects of Alpine collision, resulting in both horizontal and vertical relative displacements. Based on seismological and geodetic surveys, detailed patterns of active faulting (including subsurface décollements, blind ramps and deeper crustal thrusts have been proposed (Thouvenot et al., 1998), underlining the importance of NW-SE left-lateral strike-slip offsets as along the Vuache and Culoz faults (cf. the 1996 Epagny event: M=5.4; Thouvenot et al., 1998 and the 1822 Culoz event I=VII-VIII; Vogt, 1979). In parallel to this tectonic evolution, the last glaciation-deglaciation cycles contributed to develop large and over-deepened lacustrine basins, such as Lake Le Bourget (Perrier, 1980). The fine grain, post LGM (ie post 18 ky), sedimentary infill gives a good opportunity to evidence late quaternary tectonic deformations. This study focuses on the Culoz fault, extending from the Jura to the West, to the Chautagne swamp and through the Lake Le Bourget to the East. Historical earthquakes are known nearby this fault as ie the 1822 Culoz event. The precise location and geometry of the main fault is illustrated but its Eastern termination still needs to be determined. High resolution seismic sections and side-scan sonar images performed in the 90's (Chapron et al., 1996) showed that the Col du Chat and Culoz faults have locally deformed the quaternary sedimentary infill of the lake. These studies, mainly devoted to paleo-climate analysis were not able to determine neither the geometry of the fault, or to quantify the observed deformations. A new campaign devoted to highlight the fault geometry and associated deformation, has been performed in October 2013. Very tight profiles were performed during this high resolution seismic survey using seistec boomer and sparker sources. In several places the rupture reaches the most recent seismic reflectors underlying that these faults were active during

  7. Active Fibers: Matching Deformable Tract Templates to Diffusion Tensor Images

    PubMed Central

    Eckstein, Ilya; Shattuck, David W.; Stein, Jason L.; McMahon, Katie L.; de Zubicaray, Greig; Wright, Margaret J.; Thompson, Paul M.; Toga, Arthur W.

    2009-01-01

    Reliable quantitative analysis of white matter connectivity in the brain is an open problem in neuroimaging, with common solutions requiring tools for fiber tracking, tractography segmentation and estimation of intersubject correspondence. This paper proposes a novel, template matching approach to the problem. In the proposed method, a deformable fiber-bundle model is aligned directly with the subject tensor field, skipping the fiber tracking step. Furthermore, the use of a common template eliminates the need for tractography segmentation and defines intersubject shape correspondence. The method is validated using phantom DTI data and applications are presented, including automatic fiber-bundle reconstruction and tract-based morphometry. PMID:19457360

  8. Surface Deformation Analysis of the Active Faults revealed by InSAR Observations and Geodetic Data in Southern Part of the Taitung Longitudinal Valley, Eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Tung, H.; Chen, H. Y.; Hu, J. C.

    2009-04-01

    The NNE-striking Longitudinal Valley Fault (LVF) in eastern Taiwan is an extremely active inverse fault, which is considered as a collision boundary between the Eurasian and the Philippine Sea plates. The fault segments of the LVF demonstrate different slip behaviors, especially in the southern segment of the LVF. The deformation is partitioned by the strike-slip (Lichi fault segment) and the reverse faulting (Luyeh segment). Thus we investigate crustal deformation pattern along the southern LVF by using SAR interferometry and precise leveling data. The SAR data of the Longitudinal Valley area were collected by ERS-1, ERS-2 and Envisat satellite of the European Space Agency in both descending (track: 232; frame: 3141) and ascending (track: 311; frame: 459) orbits. However, this area is so heavily vegetated that high coherence area is limited in the Taitung City and good interfergrams with better coherence are limited to short time span and small perpendicular baseline pairs. Therefore we made three stacking image from the higher coherence interferograms representing deformation interval from 1995-1996, 1996-1998 and 2006-2008 separately. These three results show a same relative subsidence between Luyeh fault and Lichi fault, which is consistent with leveling data measured that time. Besides, we also used the PSInSAR technique to trace the discrete points that were minimally affected by the decorrelation of radar signals through time. Finally we constrain the deformation map based on PSInSAR with leveling data for better understanding the deformation patterns in the southern Longitudinal Valley area.

  9. Deformation of partially pumped active mirrors for high average-power diode-pumped solid-state lasers.

    PubMed

    Albach, Daniel; LeTouzé, Geoffroy; Chanteloup, Jean-Christophe

    2011-04-25

    We discuss the deformation of a partially pumped active mirror amplifier as a free standing disk, as implemented in several laser systems. We rely on the Lucia laser project to experimentally evaluate the analytical and numerical deformation models. PMID:21643092

  10. Creep cavitation bands control porosity and fluid flow in lower crustal shear zones

    SciTech Connect

    Menegon, Luca; Fusseis, Florian; Stunitz, Holger; Xiao, Xianghui

    2015-03-01

    Shear zones channelize fluid flow in Earth’s crust. However, little is known about deep crustal fluid migration and how fluids are channelized and distributed in a deforming lower crustal shear zone. This study investigates the deformation mechanisms, fluid-rock interaction, and development of porosity in a monzonite ultramylonite from Lofoten, northern Norway. The rock was deformed and transformed into an ultramylonite under lower crustal conditions (temperature = 700–730 °C, pressure = 0.65–0.8 GPa). The ultramylonite consists of feldspathic layers and domains of amphibole + quartz + calcite, which result from hydration reactions of magmatic clinopyroxene. The average grain size in both domains is <25 mm. Microstructural observations and electron backscatter diffraction analysis are consistent with diffusion creep as the dominant deformation mechanism in both domains. Festoons of isolated quartz grains define C'-type bands in feldspathic layers. These quartz grains do not show a crystallographic preferred orientation. The alignment of quartz grains is parallel to the preferred elongation of pores in the ultramylonites, as evidenced from synchrotron X-ray microtomography. Such C'-type bands are interpreted as creep cavitation bands resulting from diffusion creep deformation associated with grain boundary sliding. Mass-balance calculation indicates a 2% volume increase during the protolith-ultramylonite transformation, which is consistent with synkinematic formation of creep cavities producing dilatancy. Thus, this study presents evidence that creep cavitation bands may control deep crustal porosity and fluid flow. Nucleation of new phases in creep cavitation bands inhibits grain growth and enhances the activity of grain size–sensitive creep, thereby stabilizing strain localization in the polymineralic ultramylonites.

  11. Collaborative Research: Analysis and Interpretation of Multi-Scale Phenomena in Crustal Deformation Processes Using Numerical Simulations of Complex Nonlinear Earth Systems

    SciTech Connect

    Rundle, John B.

    2004-12-31

    In both our past work and the work in progress we focused on understanding the physics and statistical patterns in earthquake faults and fault systems. Our approach had three key aspects. The first was to look for patterns of seismic activity in earthquake fault systems. The second was to understand the physics of a sequence of models for faults and fault systems that are increasingly more realistic. The third key element was to connect the two previous approaches by investigating specific properties found in models to see if they are indeed properties of real faults. A specific example of how this approach works can be seen in the following: In the papers discussed below, we demonstrated that the cellular automation (CA) versions of the slider block models with long range stress transfer are ergodic and could be described by a Boltzmann-Gibbs distribution in the meanfield limit. The ergodicity follows from the fact that the long range stress transfer makes the model meanfield. The meanfield nature of the CA models, generated by long range stress transfer, also allows a description of the CA models by a Langevin equation. The Langevin equation indicates that evolution of seismicity in the model over relatively short times is linear in time. This appears to be consistent with the success of a forecasting algorithm we have developed that is based on a linear evolution of seismicity patterns. This algorithm has had considerable success in that the regions of the Southern California fault system which have been predicted to have a higher probability of an event greater than magnitude 5 have consistently been the sites where such events occur. These two results have led to the question as to whether the Southern California fault system is ergodic and can be described by a Langevin equation like the model. To answer this question we ran a series of tests for ergodicity very much like the ones run on the models. Our results, which have been accepted for publication in

  12. Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington

    USGS Publications Warehouse

    Barnett, Elizabeth A.; Haugerud, Ralph A.; Sherrod, Brian L.; Weaver, Craig S.; Pratt, Thomas L.; Blakely, Richard J.

    2010-01-01

    This atlas presents an up-to-date map compilation of the geological and geophysical observations that underpin interpretations of active, surface-deforming faults in the Puget Lowland, Washington. Shallow lowland faults are mapped where observations of deformation from paleoseismic, seismic-reflection, and potential-field investigations converge. Together, results from these studies strengthen the identification and characterization of regional faults and show that as many as a dozen shallow faults have been active during the Holocene. The suite of maps presented in our atlas identifies sites that have evidence of deformation attributed to these shallow faults. For example, the paleoseismic-investigations map shows where coseismic surface rupture and deformation produced geomorphic scarps and deformed shorelines. Other maps compile results of seismic-reflection and potential-field studies that demonstrate evidence of deformation along suspected fault structures in the subsurface. Summary maps show the fault traces derived from, and draped over, the datasets presented in the preceding maps. Overall, the atlas provides map users with a visual overview of the observations and interpretations that support the existence of active, shallow faults beneath the densely populated Puget Lowland.

  13. Active upper crust deformation pattern along the southern edge of the Tyrrhenian subduction zone (NE Sicily): Insights from a multidisciplinary approach

    NASA Astrophysics Data System (ADS)

    Palano, Mimmo; Schiavone, Domenico; Loddo, Mariano; Neri, Marco; Presti, Debora; Quarto, Ruggiero; Totaro, Cristina; Neri, Giancarlo

    2015-08-01

    Using a multidisciplinary dataset based on gravimetric, seismic, geodetic and geological observations, we provide an improved picture of the shallow structure and dynamics of the southern edge of the Tyrrhenian subduction zone. With a local earthquake tomography we clearly identify two main crustal domains in the upper 15 km characterized by different P-wave velocity values: a high-velocity domain comprising southeasternmost Tyrrhenian Sea, NE Sicily and Messina Straits, and a low-velocity domain comprising Mt. Etna and eastern Sicily. The transition between the two domains shows a good spatial correspondence with a wider set of faults including the Taormina Fault System (TFS) and the Aeolian-Tindari-Letojanni Fault System (ATLFS), two nearly SE-striking fault systems crossing northeastern Sicily and ending on the Ionian shoreline of Sicily according to many investigators. Within this set of faults, most of the deformation/seismicity occurs along the northern and central segments of ATLFS, compared to low activity along TFS. A lack of seismicity (both recent and historical) is observed in the southern sector of ATLFS where, however, geodetic data reveal significant deformation. Our multidisciplinary dataset including offshore observations suggests the southeastward continuation of the ATLFS into the Ionian Sea until joining with the faults cutting the Ionian accretionary wedge described in the recent literature. Our findings imply the existence of a highly segmented crustal shear zone extending from the Aeolian Islands to the Ionian Abyssal plain, that we believe plays the role of accommodating differential motion between the Southern Tyrrhenian unit and the western compressional domain of Sicily. The ATLFS, which is a main part of the inferred shear zone, behaves similarly to what often observed at the edges of retreating subduction slabs, where the overriding plate drifts with a highly non-uniform transform motion along the lateral borders.

  14. Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: Observations in groundwaters along the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Deeds, Daniel A.; Kulongoski, Justin T.; Mühle, Jens; Weiss, Ray F.

    2015-02-01

    Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (Cre; ∼30 fmol kg-1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1-9 times Cre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10-980 times Cre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20-100 km) suggests that the SAFS potentially emits (0.3- 1) ×10-1 kg CF4 yr-1 to the Earth's surface. For comparison, the chemical weathering of ∼ 7.5 ×104km2 of granitic rock in California is estimated to release (0.019- 3.2) ×10-1 kg CF4 yr-1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial-interglacial transitions.

  15. The role of mechanical heterogeneities in evaporite sequence during deformation initiated by basement fault activity

    NASA Astrophysics Data System (ADS)

    Adamuszek, Marta; Dabrowski, Marcin; Burliga, Stanisław

    2016-04-01

    Kłodawa Salt Structure (KSS) situated in the centre of the Polish Zechstein Basin started to rise above a basement fault in the Early Triassic. Geological studies of the KSS revealed significant differences in the deformation patterns between the PZ1-PZ2 (intensely deformed) and PZ3-PZ4 (less deformed) cycle evaporites. These two older and two younger cycle evaporite complexes are separated by the thick Main Anhydrite (A3) bed. We use numerical simulations to assess the impact of a thick anhydrite bed on intrasalt deformation. In our models, the overburden consists of clastic sediments. A normal fault located in the rigid basement beneath the salt is activated due to model extension. At the same time, the sedimentation process takes place. The evaporites consist of a salt bed intercalated with a thick anhydrite layer of varying position and geometry. To understand the role of anhydrite layer, we run comparative simulations, in which no anhydrite layer is present. In the study, we use our own numerical codes implemented in MATLAB combined with the MILAMIN and MUTILS numerical packages. Our investigations revealed a significant influence of the anhydrite on deformation style in the evaporate series. The supra-anhydrite domain is characterized by weaker deformation and lower rates of salt flow in comparison to the sub-anhydrite domain. The highest contrast in the rate of salt flow between the two domains is observed in the case of the anhydrite layer situated close to the bottom of the salt complex. The thick anhydrite layer additionally diminishes the deformation rate in the supra-anhydrite domain and can lead to detachment of the basement deformation from its overlay. Our numerical simulations showed that the presence of the A3 Main Anhydrite bed could be the dominant factor responsible for the decoupling of deformation in the KSS salt complex.

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

    NASA Technical Reports Server (NTRS)

    Toksoz, M. Nafi

    1987-01-01

    The primary effort in this study during the past year has been directed along two separate lines: (1) expanding finite element models to include the entire Anatolian plate, the Aegean Sea and the Northeastern Mediterranean Sea, and (2) investigating the relationship between fault geometry and earthquake activity for the North Anatolian and similar strike-slip faults (e.g., San Andreas Fault). Both efforts are designed to provide an improved basis for interpreting the Crustal Dynamics measurements NASA has planned for this region. The initial phases of both investigations have been completed and the results are being prepared for publication. These investigations are described briefly.

  17. 2012 ROCK DEFORMATION: FEEDBACK PROCESSES IN ROCK DEFORMATION GORDON RESEARCH CONFERENCE, AUGUST 19-24, 2012

    SciTech Connect

    Kelemen, Peter

    2012-08-24

    Topics covered include: Failure At High Confining Pressure; Fluid-assisted Slip, Earthquakes & Fracture; Reaction-driven Cracking; Fluid Transport, Deformation And Reaction; Localized Fluid Transport And Deformation; Earthquake Mechanisms; Subduction Zone Dynamics And Crustal Growth.

  18. Block rotations, fault domains and crustal deformation

    NASA Technical Reports Server (NTRS)

    Nur, A.; Ron, H.

    1987-01-01

    Much of the earth's crust is broken by sets of parallel strike-slip faults which are organized in domains. A simple kinematic model suggests that when subject to tectonic strain, the faults, and the blocks bound by them, rotate. The rotation can be estimated from the structurally-determined fault slip and fault spacing, and independently from local deviations of paleomagnetic declinations from global values. A rigorous test of this model was carried out in northern Israel, where good agreement was found between the two rotations.

  19. Preferred orientation in experimentally deformed stishovite: implications for deformation mechanisms

    NASA Astrophysics Data System (ADS)

    Kaercher, P. M.; Zepeda-Alarcon, E.; Prakapenka, V.; Kanitpanyacharoen, W.; Smith, J.; Sinogeikin, S. V.; Wenk, H. R.

    2014-12-01

    The crystal structure of the high pressure SiO2 polymorph stishovite has been studied in detail, yet little is known about its deformation mechanisms. Information about how stishovite deforms under stress is important for understanding subduction of quartz-bearing crustal rocks into the mantle. Particularly, stishovite is elastically anisotropic and thus development of crystallographic preferred orientation (CPO) during deformation may contribute to seismic anomalies in the mantle. We converted a natural sample of flint to stishovite in a laser heated diamond anvil cell and compressed the stishovite aggregate up to 38 GPa. Diffraction patterns were collected in situ in radial geometry at the Advanced Light Source (ALS) and the Advanced Photon Source (APS) to examine development of CPO during deformation. We find that (001) poles preferentially align with the compression direction and infer deformation mechanisms leading to the observed CPO with visco-plastic self consistent (VPSC) polycrystal plasticity models. Our results show pyramidal and basal slip are most likely active at high pressure and ambient temperature, in agreement with transmission electron microscopy (TEM) studies of rutile (TiO2) and paratellurite (TeO2), which are isostructural to stishovite. Conversely other TEM studies of stishovite done at higher temperature suggest dominant prismatic slip. This indicates that a variety of slip systems may be active in stishovite, depending on conditions. As a result, stishovite's contribution to the seismic signature in the mantle may vary as a function of pressure and temperature and thus depth.

  20. Crustal Movement Observation Network of China and Its Application

    NASA Astrophysics Data System (ADS)

    Li, J.; Zhang, R.

    2013-12-01

    China is a country with serious earthquake hazards and active faults, how to use GPS and other new technologies to monitor the crustal deformation and predict earthquakes is an important issue in China. So, we established the Crustal Movement Observation Network of China (CMONOC). The network was a comprehensive, open and unified network of continuous observation for various applications with data shared by many institutions, it based on GNSS observations, and supplemented by the space technology of VLBI and SLR, and it also include precise gravity and leveling. The network includes 260 continuous GNSS stations, and more than 2000 campaign GNSS stations. The continuous stations have been observed since 2010, and the campaign stations were observed irregularly. Some of them are observed annually, and most of them were observed every two years. Use these data, we can study the changes of tectonic environment of China, explore its impact on resource, environment and natural disasters, deepen the understanding of the earth and environmental science and other related disciplines, promote the generation of significant scientific and innovative achievements. It also provides important basic data for solving scientific problems related with present-day crustal movement, earthquake prediction, geodynamics, geodesy, atmospheric science and space science.

  1. Receiver function analysis of crustal structure beneath northeast Tibet

    NASA Astrophysics Data System (ADS)

    Li, X.; Shen, Y.; Li, H.; Shi, D.; Sandvol, E. A.; Li, A.

    2013-12-01

    The Tibetan Plateau has been the prime site to understand the processes of continental collision, mountain building, and the interaction between tectonics. More detailed studies of crustal structure in northeast Tibet can be of great benefit to the understanding of crustal deformation and plateau growth mechanisms. We investigat crustal structure beneath 64 seismic stations in the northeast Tibet using the receiver function method to estimate the crustal thickness by analyzing the collected three-component teleseismic data recorded by 29 stations between June, 2008 and July, 2010 deployed by China University of Geosciences and 35 Ascent stations deployed between May, 2007 and August, 2008. The distributions of the crustal thickness have a good correlation with the known geological tectonic features. The images of Moho depth suggests the lateral variations of the crustal thickness decreasing from the northeastern margin of the Tibet (~70 km) to the Ordos Block (~40 km). The observations disagree with the crustal composition beneath the northeastern margin of the Tibetan plateau. Our results of crustal structure in this study area not only reveal the lateral inhomogeneity of the crustal structure but also provide some constraints on understanding the mechanism of uplift and crustal thickening of the Tibet and insights into the geodynamic process between the Tibet and its adjacent blocks.

  2. Crustal shear velocity structure in the Southern Lau Basin constrained by seafloor compliance

    NASA Astrophysics Data System (ADS)

    Zha, Yang; Webb, Spahr C.

    2016-05-01

    Seafloor morphology and crustal structure vary significantly in the Lau back-arc basin, which contains regions of island arc formation, rifting, and seafloor spreading. We analyze seafloor compliance: deformation under long period ocean wave forcing, at 30 ocean bottom seismometers to constrain crustal shear wave velocity structure along and across the Eastern Lau Spreading Center (ELSC). Velocity models obtained through Monte Carlo inversion of compliance data show systematic variation of crustal structure in the basin. Sediment thicknesses range from zero thickness at the ridge axis to 1400 m near the volcanic arc. Sediment thickness increases faster to the east than to the west of the ELSC, suggesting a more abundant source of sediment near the active arc volcanoes. Along the ELSC, upper crustal velocities increase from the south to the north where the ridge has migrated farther away from the volcanic arc front. Along the axial ELSC, compliance analysis did not detect a crustal low-velocity body, indicating less melt in the ELSC crustal accretion zone compared to the fast spreading East Pacific Rise. Average upper crust shear velocities for the older ELSC crust produced when the ridge was near the volcanic arc are 0.5-0.8 km/s slower than crust produced at the present-day northern ELSC, consistent with a more porous extrusive layer. Crust in the western Lau Basin, which although thought to have been produced through extension and rifting of old arc crust, is found to have upper crustal velocities similar to older oceanic crust produced at the ELSC.

  3. Two-layer Crustal Structure of the Contiguous United States from Joint Inversion of USArray Receiver Functions and Gravity

    NASA Astrophysics Data System (ADS)

    Ma, X.; Lowry, A. R.

    2015-12-01

    The composition and thickness of crustal layering is fundamental to understanding the evolution and dynamics of continental lithosphere. Lowry and Pérez-Gussinyé (2011) found that the western Cordillera of the United States, characterized by active deformation and high heat flow, is strongly correlated with low bulk crustal seismic velocity ratio. They interpreted this observation as evidence that quartz controls continental tectonism and deformation. We will present new imaging of two-layer crustal composition and structure from cross-correlation of observed receiver functions and model synthetics. The cross-correlation coefficient of the two-layer model increases significantly relative to an assumed one-layer model, and the lower crustal thickness map from raw two-layer modeling (prior to Bayesian filtering with gravity models and Optimal Interpolation) clearly shows Colorado plateau and Appalachian boundaries, which are not apparent in upper crustal models, and also the high vP/vS fill the most of middle continental region while low vP/vS are on the west and east continental edge. In the presentation, we will show results of a new algorithm for joint Bayesian inversion of thickness and vP/vS of two-layer continental crustal structure. Recent thermodynamical modeling of geophysical models based on lab experiment data (Guerri et al., 2015) found that a large impedance contrast can be expected in the midcrust due to a phase transition that decreases plagioclase and increases clinopyroxene, without invoking any change in crustal chemistry. The depth of the transition depends on pressure, temperature and hydration, and in this presentation we will compare predictions of layer thicknesses and vP/vS predicted by mineral thermodynamics to those we observe in the USArray footprint.

  4. Evolution of Deformation Studies on Active Hawaiian Volcanoes

    NASA Astrophysics Data System (ADS)

    Decker, R.; Okamura, A.

    2004-12-01

    Summarizing 1600 years of observations and interpretations into a brief presentation forces some difficult choices on highlighting the following techniques that are presented chronologically: Visual Observations, 400 AD to present: Missionary William Ellis' Hawaiian Guides told him that Kilauea "had been burning from time immemorial, or, to use their own words, `mai ka po mai', from chaos till now...that in earlier ages it used to boil up, overflow its banks, and inundate the adjacent country...and on occasions they supposed Pele went by a road under ground from her house in the crater to the shore". Observations of the nearly-continuous lava lake in Kilauea Caldera from 1823 until 1924 established that its surface level fluctuated from about 700 to 1100 m above sea level in 10 up-and-down episodes. Tilt Measurements, 1914 to present: Horizontal-seismometer drift and water-tube tiltmeters show that the range of long-term, ground-surface tilt radial to Halemaumau Crater exceeds 500 microradians. Triangulation and Leveling, 1920: R. M. Wilson measured deformation changes related to major Kilauea summit subsidence in 1924. The caldera area around Halemaumau subsided concentrically as much as 4 m relative to the Volcano House benchmark, and triangulation points moved toward Halemaumau by as much as 1.6 m in the caldera area. K. Mogi in 1958 modeled Kilauea leveling data and inferred 3-4 km-deep magma reservoirs. Gravity Measurements, 1959 to present: Changes were first measured during Kilauea summit subsidence related to the lower-east-rift Kapoho eruption. Surveys made before and after the 1975 M7.2 Kalapana Earthquake show that gravity changes are not a simple proxy for elevation changes. Electronic Distance Measurements (EDM), 1964 to present: D. A. Swanson, W. A. Duffield, and R. S. Fiske use EDM for trilateration proving movement of the south flank of Kilauea toward the sea. EDM show displacements as large as 8.7 m of Kilauea's south flank toward the sea related

  5. Deformation Microstructure of a Reduced-Activation Ferritic/Martensitic Steel Irradiated in HFIR

    SciTech Connect

    Hashimoto, N.; Klueh, R.L.; Ando, M.; Tanigawa, H.; Sawai, T.; Shiba, K.

    2003-09-15

    In order to determine the contributions of different microstructural features to strength and to deformation mode, microstructure of deformed flat tensile specimens of irradiated reduced activation F82H (IEA heat) base metal (BM) and its tungsten inert-gas (TIG) weldments (weld metal and weld joint) were investigated by transmission electron microscopy (TEM), following fracture surface examination by scanning electron microscopy (SEM). After irradiation, the fracture surfaces of F82H BM and TIG weldment showed a martensitic mixed quasi-cleavage and ductile-dimple fracture. The microstructure of the deformed region of irradiated F82H BM contained dislocation channels. This suggests that dislocation channeling could be the dominant deformation mechanism in this steel, resulting in the loss of strain-hardening capacity. While, the necked region of the irradiated F82H TIG, where showed less hardening than F82H BM, showed deformation bands only. From these results, it is suggested that the pre-irradiation microstructure, especially the dislocation density, could affect the post-irradiation deformation mode.

  6. Patterns of brittle deformation under extension on Venus

    NASA Technical Reports Server (NTRS)

    Neumann, G. A.; Zuber, M. T.

    1994-01-01

    The development of fractures at regular length scales is a widespread feature of Venusian tectonics. Models of lithospheric deformation under extension based on non-Newtonian viscous flow and brittle-plastic flow develop localized failure at preferred wavelengths that depend on lithospheric thickness and stratification. The characteristic wavelengths seen in rift zones and tessera can therefore provide constraints on crustal and thermal structure. Analytic solutions were obtained for growth rates in infinitesimal perturbations imposed on a one-dimensional, layered rheology. Brittle layers were approximated by perfectly-plastic, uniform strength, overlying ductile layers exhibiting thermally-activated power-law creep. This study investigates the formation of faults under finite amounts of extension, employing a finite-element approach. Our model incorporates non-linear viscous rheology and a Coulomb failure envelope. An initial perturbation in crustal thickness gives rise to necking instabilities. A small amount of velocity weakening serves to localize deformation into planar regions of high strain rate. Such planes are analogous to normal faults seen in terrestrial rift zones. These 'faults' evolve to low angle under finite extension. Fault spacing, orientation and location, and the depth to the brittle-ductile transition, depend in a complex way on lateral variations in crustal thickness. In general, we find that multiple wavelengths of deformation can arise from the interaction of crustal and mantle lithosphere.

  7. Active optics experiments. II - Measurement of mirror deformation by holographic method

    NASA Astrophysics Data System (ADS)

    Itoh, Noboru; Mikami, Izumi; Miyawaki, Keizou; Sasaki, Aki; Tabata, Masao

    An active optics experiment was performed to study the feasibility of using an active correction system for the Japanese National Large Telescope (Wilson, 1986). A thin mirror was deformed with an active support mechanism and the mirror surface was measured by a holographic method. The experiment is performed for several cases of excess force distributions assigned at the supporting points. The results show good agreement with predictions from FEM analysis.

  8. Detection of crustal strains in Egypt using GPS networks

    NASA Astrophysics Data System (ADS)

    Mahmoud, S. M.

    2003-04-01

    DETECTION OF CRUSTAL STRAINS IN EGYPT USING GPS NETWORKS S.M. Mahmoud National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt. Fax: 202 554 80 20 Email: salahm55@yahoo.com Abstract. Studies of crustal deformation in Egypt started as early as 1983 following the occurrence of Aswan earthquake in 1981. Several publications were published and presented in local and international meetings. On November 14, 1981 an earthquake with magnitude 5.6 occurred at kalabsha fault, 70-Km southwest of Aswan City. This earthquake is considered as an important event as it is located not far from the Aswan High Dam. Therefore, the first program for monitoring crustal deformation has been started in Kalabsha area during the winter of 1983 with the cooperation between the National Research Institute of Astronomy and Geophysics (NRIAG) and the Aswan &High Dam Authority. A local network of 18 terrestrial geodetic points was established at kalabsha area in 1983 in order to monitor the horizontal and vertical crustal movements along Kalabsha fault. The initial measurements were carried out in December 1984. These measurements were repeated twice a year till December 1994.An other terrestrial network were established at seiyal fault, 15 km to the north of kalabsha fault. The initial measurements of seiyal network were carried out in March 1989 and repeated twice a year till August 1992. Analysis of the terrestrial horizontal measurements from both networks for the epoch from December 1984 till December 1994 indicated significant deformations varying from 3x10-6 to 7x10-6. Since the year of 1994 till now, the geodetic observations by means of Space Techniques which known as Global Positioning System (GPS) were applied instead of the Terrestrial ones to cover some other regions of the country. Data adjustment and analysis of the reapted GPS campaigns from the different networks prevailed significant movements which helps in more understanding the geodynamics of

  9. Modern Tectonic Deformation in the Active Basin-And Province Northwest of Beijing, China

    NASA Astrophysics Data System (ADS)

    Mi, S.; Wen, X.

    2012-12-01

    Our study region is the northwest of Beijing, northern north China. The most typical extensional active tectonic area of the China continent, called the active basin-and-range province northwest of Beijing, exist there. This active tectonic province is made up of several NE-trending Quaternary graben basins and horst ranges between basins. An about 1500-year-long written historical record has suggested that there have been no major earthquakes with magnitude 7 or greater occurred in most of the study region since AD 512. So, the characteristic of modern tectonic deformation of the study region and its implication for the future seismic potential of major earthquakes are important scientific issues. In this study, based on data of regional GPS station velocities and active tectonics, combining relocated earthquake distribution, we make a preliminary analysis on the characteristic of the modern tectonic deformation of the study region. We design three zones across deferent segments of the active basin-and-range province to analyze both the present tectonic deformation from the GPS velocity profiles and the major fault's downward-extents from the relocated hypocenters. Our analyses reveal that: (1) Significant NNW-ward and SSE-ward horizontal extension exists on different segments of the active basin-and-range province northwest of Beijing at rates of 2 to 3mm /yr, accompanied with right-lateral shear deformation at 1 to 2mm/yr. (2) On the present tectonic deformation, the southeastern margin of the Datong-Yangyuan basin, the biggest graben basin of the active tectonic province, shows as a turning belt of the extensional rates, suggesting that relatively high tensile strain accumulation could exist there. (3)On the northeastern segment of the studied active basin-and-range province, both the Zhangjiakou-Yanhui graben basin and the Beijing graben basin have also been being in significant extensional and shear deformation. (4) The relocated hypocenter distribution have

  10. A deformable lung tumor tracking method in fluoroscopic video using active shape models: a feasibility study

    NASA Astrophysics Data System (ADS)

    Xu, Qianyi; Hamilton, Russell J.; Schowengerdt, Robert A.; Jiang, Steve B.

    2007-09-01

    A dynamic multi-leaf collimator (DMLC) can be used to track a moving target during radiotherapy. One of the major benefits for DMLC tumor tracking is that, in addition to the compensation for tumor translational motion, DMLC can also change the aperture shape to conform to a deforming tumor projection in the beam's eye view. This paper presents a method that can track a deforming lung tumor in fluoroscopic video using active shape models (ASM) (Cootes et al 1995 Comput. Vis. Image Underst. 61 38-59). The method was evaluated by comparing tracking results against tumor projection contours manually edited by an expert observer. The evaluation shows the feasibility of using this method for precise tracking of lung tumors with deformation, which is important for DMLC-based real-time tumor tracking.

  11. New GPS constraints on active deformation along the Africa-Iberia plate boundary

    NASA Astrophysics Data System (ADS)

    Koulali, A.; Ouazar, D.; Tahayt, A.; King, R. W.; Vernant, P.; Reilinger, R. E.; McClusky, S.; Mourabit, T.; Davila, J. M.; Amraoui, N.

    2011-08-01

    We use velocities from 65 continuous stations and 31 survey-mode GPS sites as well as kinematic modeling to investigate present day deformation along the Africa-Iberia plate boundary zone in the western Mediterranean region. The GPS velocity field shows southwestward motion of the central part of the Rif Mountains in northern Morocco with respect to Africa varying between 3.5 and 4.0 mm/yr, consistent with prior published results. Stations in the southwestern part of the Betic Mountains of southern Spain move west-southwest with respect to Eurasia (˜ 2-3 mm/yr). The western component of Betics motion is consistent with partial transfer of Nubia-Eurasia plate motion into the southern Betics. The southward component of Betics motion with respect to Iberia is kinematically consistent with south to southwest motion of the Rif Mountains with respect to Africa. We use block modeling, constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures. Our preferred plate boundary geometry includes one block between Iberia and Africa including the SW Betics, Alboran Sea, and central Rif. This geometry provides a good fit to the observed motions, suggesting a wide transpressive boundary in the westernmost Mediterranean, with deformation mainly accommodated by the Gloria-Azores fault system to the West and the Rif-Tell lineament to the East. Block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles: (i) extension along the NE-SW trending Trans-Alboran shear zone, (ii) dextral strike-slip in the Betics corresponding to a well defined E-W seismic lineament, and (iii) right lateral strike-slip motion extending West to the Azores and right-lateral motion with compression extending East along the Algerian Tell. We interpret differential motion in the Rif-Alboran-Betic system to be driven both by surface processes related the Africa-Eurasia oblique convergence and

  12. Coherence between geodetic and seismic deformation in a context of slow tectonic activity (SW Alps, France)

    NASA Astrophysics Data System (ADS)

    Walpersdorf, A.; Sue, C.; Baize, S.; Cotte, N.; Bascou, P.; Beauval, C.; Collard, P.; Daniel, G.; Dyer, H.; Grasso, J.-R.; Hautecoeur, O.; Helmstetter, A.; Hok, S.; Langlais, M.; Menard, G.; Mousavi, Z.; Ponton, F.; Rizza, M.; Rolland, L.; Souami, D.; Thirard, L.; Vaudey, P.; Voisin, C.; Martinod, J.

    2015-04-01

    A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north-south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E-W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.

  13. Use of polyurethane foam deformation sensor to record respiratory activity

    NASA Astrophysics Data System (ADS)

    Bredov, V. I.; Baranov, V. S.

    1980-05-01

    The sensor developed has some substantial advantages over other known types. It is highly sensitive over a wide range of strain loads. The level of the output signal is linearly related to the force exerted on it, and it is sufficient for direct recording without using amplifiers of electric signals. The sensor is based on elastic, spongy material, polyurethane foam (porolon) with current-conducting material on the pore surface, current-conducting carbon black or electrode paste. The elastic properties of the sensor are built in the actual base of the strain-sensitive element, which simplifies the construction substantially and increases the reliability of the unit. In order to test the possibility of using this sensor to examine respiratory function, human pneumograms were recorded with the subject in a calm state along with the respiratory activity of experimental animals (dogs). Samples of the respiratory curve are shown. The simplicity of design of the sensor makes it possible to use it in various physiological experiments.

  14. The Mendocino crustal conveyor: Making and breaking the California crust

    USGS Publications Warehouse

    Furlong, K.P.; Lock, J.; Guzofski, C.; Whitlock, J.; Benz, H.

    2003-01-01

    The northward migration of the Mendocino triple junction has resulted in a fundamental modification of the crust of coastal California. As a consequence of viscous coupling between the southern edge of the Gorda slab and the base of the North American crust beneath the Coast Ranges of central and northern California, the crust of coastal California was first thickened and then thinned. This viscous coupling and ephemeral crustal thickening has produced a distinctive pattern of uplift that allows us to map the three-dimensional extent of crustal modification. This pattern of crustal deformation has combined with the strain field of the developing San Andreas fault system to produce the observed pattern of near-surface deformation. The rapid rise in heat flow south of the triple junction observed in the northern Coast Ranges is a direct consequence of development and removal of the crustal welt that migrated with the triple junction.

  15. Deformation of the Calabrian Arc subduction complex and its relation to STEP activity at depth.

    NASA Astrophysics Data System (ADS)

    Polonia, Alina; Wortel, Rinus; Nijholt, Nicolai; Govers, Rob; Torelli, Luigi

    2015-04-01

    Propagating tear faults at the edge of subducted slabs ("Subduction transform edge propagator", STEP) are an intrinsic part of lithospheric plate dynamics. The surface expression of a STEP is generally not known yet, and is expected to vary significantly from one region to the other. We choose the Sicily -Calabria-Ionian Sea region, of which the lithosphere-upper mantle structure has the characteristics of a STEP zone, as a study area. The area has a very prominent accretionary wedge, the formation and subsequent deformation of which presumably were affected by the STEP activity at depth. In this contribution, we use seismic data on the near surface structure and deformation in combination with numerical model results to investigate the relation between deep STEP activity and near surface expression. Prominent features in the surface tectonics are the Malta escarpment (with predominantly normal faulting), the newly identified Ionian Fault and Alfeo-Etna fault system, and a distinct longitudinal division of the wedge into a western and an eastern lobe (Polonia et al., Tectonics, 2011). The two lobes are characterized by different structural style, deformation rates and basal detachment depths. Numerical model results indicate that the regional lithospheric structure, such as the orientation of the eastern passive (albeit subsequently activated) margin of Sicily relative to the Calabrian subduction zone, has a profound effect on possible fault activity along the Malta escarpment. Fault activity along the above primary fault structures may have varied in time, implying the possibility of intermittent activity. Interpreting seismicity in the context of a possible STEP, and the accompanying deformation zone at or near the surface, is not (yet) straightforward. Although direct evidence for recognizing all aspects of STEP activity is - as usual - lacking, a comparison with two well-known STEP regions, the northern part of the Tonga subduction zone and southern part of the

  16. The Tyrrhenian Basin: fault activity migration, focusing of deformation, break up, magmatism and fast mantle exhumation

    NASA Astrophysics Data System (ADS)

    Ranero, Cesar R.; Sallarés, Valenti; Vendrell, Montserrat G.; Prada, Manuel; Grevemeyer, Ingo; Zitellini, Nevio

    2015-04-01

    We present a new interpretation of the creation of the geological domains and the processes forming the Tyrrhenian basin by rifting of Cratonic Variscan lithosphere. The basin is not presently extending, but its crustal structure preserves information of the temporal evolution of rifting processes. Our work is based on the tectonic structure and stratigraphy of over 3000 km of calibrated multichannel seismic data and full coverage multibeam bathymetry of the basin. From these data circa 2000 km are new and about 1000 are vintage data. The seismic data are used to understand the formation of the domains (continental, backarc magmatism, exhumed mantle) defined with our recently published, under review, or submitted 5 across-the-basin wide-angle reflection and refraction transects. The 5 transects provide the Vp distribution of the crust and upper mantle. This information has allowed defining the petrological nature and distribution of the geological domains, and to infer the importance of magmatism in the rifting process, to constrain the location of break up and the expanse of the region of mantle exhumation. The seismic reflection images have been interpreted to map in time and space the evolution of the deformation across the basin. We analyzed the tectonic structure and mapped the calibrated stratigraphy across the basin to understand the temporal evolution and styles of faulting processes. The stratigraphy provides also constraints on the rates at which the different processes of extension, magmatism, break up and mantle exhumation have occurred. The basin has opened with different extension factors from north to south. The northern region stopped opening after a relatively low extension factors. Towards the south extension increased up to full crustal separation. Here extension in some areas was coeval with abundant magmatism. Changing in the locus of faulting and rates of extension led to break up and to a surprisingly fast mantle exhumation. Subsequent

  17. Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: observations in groundwaters along the San Andreas Fault

    USGS Publications Warehouse

    Deeds, Daniel A.; Kulongoski, Justin T.; Muhle, Jens; Weiss, Ray F.

    2015-01-01

    Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (CreCre; ∼30 fmol kg−1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1–9 times CreCre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10–980 times CreCre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20–100 km) suggests that the SAFS potentially emits (0.3–1)×10−1 kg(0.3–1)×10−1 kg CF4 yr−1 to the Earth's surface. For comparison, the chemical weathering of ∼7.5×104 km2∼7.5×104 km2 of granitic rock in California is estimated to release (0.019–3.2)×10−1 kg(0.019–3.2)×10−1 kg CF4 yr−1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial–interglacial transitions.

  18. Chemopreventive activity of sesquiterpene lactones (SLs) from yacon against TPA-induced Raji cells deformation.

    PubMed

    Siriwan, D; Miyawaki, C; Miyamoto, T; Naruse, T; Okazaki, K; Tamura, H

    2011-05-15

    Yacon is a medicinal plant used as a traditional medicine by the natives in South America. In Japan, it becomes popular as a health food. Sesquiterpene Lactones (SLs) from yacon leaves were investigated and the active SLs such as enhydrin, uvedalin and sonchifolin, bearing alpha-methylene-gamma-lactone and epoxides as the active functional groups, were identified by 1H-6000 MHz-NMR. Chemopreventive and cytotoxic activities were determined using different primary screening methods. In this study, all tested SLs strongly inhibited TPA-induced deformed of Raji cells. The IC50 values of yacon SLs from anti-deforming assay were 0.04-0.4 microM. Interestingly, yacon SLs showed more potential of chemo preventive activity than both curcumin and parthenolide. However, the cytotoxicity on Raji cells was observed at high concentration of yacon SLs. The degree of anti-deformation was ranked in order: enhydrin >uvedalin >sonchifolin >parthenolide >curcumin. As according to structure-activity relationship, the high activities of enhydrin, uvedalin and sonchifolin may be due to the 2-methyl-2-butenoate and its epoxide moiety. PMID:22097098

  19. Space active optics: performance of a deformable mirror for in-situ wave-front correction in space telescopes

    NASA Astrophysics Data System (ADS)

    Laslandes, Marie; Hourtoule, Claire; Hugot, Emmanuel; Ferrari, Marc; Lopez, Céline; Devilliers, Christophe; Liotard, Arnaud; Chazallet, Frederic

    2012-09-01

    MADRAS (Mirror Active, Deformable and Regulated for Applications in Space) project aims at demonstrating the interest of Active Optics for space applications. We present the prototype of a 24 actuators, 100 mm diameter deformable mirror to be included in a space telescope's pupil relay to compensate for large lightweight primary mirror deformation. The mirror design has been optimized with Finite Element Analysis and its experimental performance characterized in representative conditions. The developed deformable mirror provides an efficient wave-front correction with a limited number of actuators and a design fitting space requirements.

  20. Lower crustal mush generation and evolution

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Recent seismic, field, and petrologic studies on several active and fossil volcanic settings provide important constraints on the time, volume, and melt fraction of their lower crustal magma bodies. However, these studies provide an incomplete picture of the time and length scales involved during their thermal and compositional evolution. What has been lacking is a thermal model that explains the temporal evolution and state of the lower crustal magma bodies during their growth. Here we use a two-dimensional thermal model and quantify the time and length scales involved in the long-term thermal and compositional evolution of the lower crustal mush regions underlying the Salton Sea Geothermal Field (USA), Mt St Helens (USA), and the Ivrea-Verbano Zone (North Italy). Although a number of seismic, tectonic, petrologic, and field studies explained the tectonic and magmatic evolution of these regions, controversy remains on their lower crustal heat sources, melt fraction, and origin of erupted magmas. Our thermal modeling results suggest that given a geologically reasonable range of basalt fluxes (~10^-3 to 10^-4 km3/yr), a long-lived (>105 yr) crystalline mush is formed in the lower crust. The state of the lower crustal mush is strongly influenced by the magma flux, crustal thickness, and water content of intruded basalt, giving an average melt fraction of <0.2 in thin crust with dry injections (Salton Sea Geothermal Field) and up to 0.4-0.5 in thicker crust with wet injections (Mt St Helens and Ivrea Zone). The melt in the lower crustal mush is mainly evolving through fractional crystallization of basalt with minor crustal assimilation in all regions, in agreement with isotopic studies. Quantification of the lower crustal mush regions is key to understanding the mass and heat balance in the crust, evolution of magma plumbing systems, and geothermal energy exploration.

  1. Crustal structure of northern California

    NASA Astrophysics Data System (ADS)

    Godfrey, Nicola Jane

    This thesis presents work from two regions in northern California, using seismic data collected during the Mendocino Triple Junction Experiment (1993 and 1994), and USGS data collected in 1977. Much of California geology records subduction processes active during much of the Mesozoic. About 29 Ma ago, the East Pacific Rise began interacting with the California subduction margin, and two triple junctions formed. One moved north and one moved south, with the San Andreas transform system between them. The northern triple junction, the Mendocino triple junction, is currently situated close to Cape Mendocino, northern California. Northern California geology now has the added complication of processes associated with the northward moving triple junction and lengthening San Andreas fault system. Chapters 1 and 2 focus on the Great Valley, a forearc basin associated with Mesozoic subduction. The three major parts of the subduction system are the magmatic arc (Sierra Nevada batholith), forearc basin (Great Valley basin) and accretionary prism (Franciscan complex). Chapter 1 presents evidence from seismic data, for a complete ophiolitic sequence, including an unserpentinized mantle section (velocities of 8.1 km.ssp{-1} at 5-18 km depth) beneath the northernmost Great Valley. A combination velocity/density model shows the ophiolite is underlain by low-density material associated with the Sierra Nevada. Chapter 2 presents geophysical models, (seismic reflection, refraction, gravity and magnetic models) published by different authors over the last 14 years from the entire Great Valley, to explore the nature of the Great Valley ophiolite along the length of the forearc basin. Chapter 3 focuses offshore, west of the San Andreas fault, on an anomalous piece of crust, the Vizcaino block, situated immediately southwest of the Mendocino triple junction. This chapter discusses the crustal thickness of the Vizcaino block, the nature of its accretionary prism basement, and deformation

  2. Continental crustal composition and lower crustal models

    NASA Technical Reports Server (NTRS)

    Taylor, S. R.

    1983-01-01

    The composition of the upper crust is well established as being close to that of granodiorite. The upper crustal composition is reflected in the uniform REE abundances in shales which represent an homogenization of the various REE patterns. This composition can only persist to depths of 10-15 km, for heat flow and geochemical balance reasons. The composition of the total crust is model dependent. One constraint is that it should be capable of generating the upper granodioritic (S.L.) crust by partial melting within the crust. This composition is based on the andesite model, which assumes that the total crust has grown by accretion of island arc material. A representation of the growth rate of the continental crust is shown. The composition of the lower crust, which comprises 60-80% of the continental crust, remains a major unknown factor for models of terrestrial crustal evolution. Two approaches are used to model the lower crust.

  3. Modern Tectonic Deformation in the Active Basin-and-Range Province Northwest of Beijing, China

    NASA Astrophysics Data System (ADS)

    Mi, Suting; Wen, Xueze

    2013-04-01

    Our study region is the northwest of Beijing, northern north China. The most typical extensional active tectonic area of the China continent, called the active basin-and-range province northwest of Beijing, exist there. This active tectonic province is made up of several NE-trending Quaternary graben basins and horst ranges between basins. An about 1500-year-long written historical record has suggested that there have been no major earthquakes with magnitude 7 or greater occurred in most of the study region since AD 512. So, the characteristic of modern tectonic deformation of the study region and its implication for the future seismic potential of major earthquakes are important scientific issues. In this study, based on data of regional GPS station velocities and active tectonics, combining relocated earthquake distribution, we make a preliminary analysis on the characteristic of the modern tectonic deformation of the study region. We design three zones across deferent segments of the active basin-and-range province to analyze both the present tectonic deformation from the GPS velocity profiles and the major fault's downward-extents from the relocated hypocenters. Our analyses reveal that: (1) Significant NNW-ward and SSE-ward horizontal extension exists on different segments of the active basin-and-range province northwest of Beijing at rates of 2 to 3mm /yr, accompanied with right-lateral shear deformation at 1 to 2mm/yr. (2) On the western and middle segments of the active basin and range province, most of the total horizontal extension and shear deformation happen in the width from the Huangqihai basin to the Datong-Yanggao basin , suggesting that some major faults in this width could have had relatively-high strain build-up. (3) It is possible that one or more basement detachment belts exist under the active basins, and it or they possibly dip(s) southeastern-ward. (4) The modern tectonic extensional rate is up to 2 to 3mm /yr in the study region. However

  4. Characterization of micro-scale creep deformation of an electro-active paper actuator

    NASA Astrophysics Data System (ADS)

    Lee, Sangwoo; Kim, Joo-Hyung; Kang, Kwangseon; Kim, Jaehwan; Kim, Heung Soo; Yang, Chulho

    2009-09-01

    The creep deformation process of an electro-active paper (EAPap) actuator was investigated by adapting stepwise dead-weight loading. To understand the deformation mechanism of the EAPap film, including morphological and structural changes, various loading conditions below yield strength were applied to cellophane EAPap. From the structural observation, micro-dimples and micro-cracks were detected at applied load lower than 10% of yield strength, while they were not found in higher load conditions. It is hypothesized that only short and random fibers in the amorphous region may respond to the applied stress at the low loading condition, not the fibers in the crystalline area. As a result, deformation energy at the localized spot accumulated and created micro-defects at the surface. Meanwhile, fibers in the crystalline region may sustain most of the loads as creep load increases to a high level. Molecular chains in the fiber may rotate and elongate with high load. Elongated fibers were observed only at a high level of load. From the structural change as a function of applied load, a peak shift of crystal orientation was observed only in high load conditions by wide angle x-ray measurement. This may confirm that creep deformation could give rise to structure changes in EAPap.

  5. Root Hair Deformation Activity of Nodulation Factors and Their Fate on Vicia sativa.

    PubMed Central

    Heidstra, R.; Geurts, R.; Franssen, H.; Spaink, H. P.; Van Kammen, A.; Bisseling, T.

    1994-01-01

    We used a semiquantitative root hair deformation assay for Vicia sativa (vetch) to study the activity of Rhizobium leguminosarum bv viciae nodulation (Nod) factors. Five to 10 min of Nod factor-root interaction appears to be sufficient to induce root hair deformation. The first deformation is visible within 1 h, and after 3 h about 80% of the root hairs in a small susceptible zone of the root are deformed. This zone encompasses root hairs that have almost reached their maximal size. The Nod factor accumulates preferentially to epidermal cells of the young part of the root, but is not restricted to the susceptible zone. In the interaction with roots, the glucosamine backbone of Nod factors is shortened, presumably by chitinases. NodRlv-IV(C18:4,Ac) is more stable than NodRlv-V(C18:4,Ac). No correlation was found between Nod factor degradation and susceptibility. Degradation occurs both in the susceptible zone and in the mature zone. Moreover, degradation is not affected by NH4NO3 and is similar in vetch and in the nonhost alfalfa (Medicago sativa). PMID:12232242

  6. Correction of an active space telescope mirror using a gradient approach and an additional deformable mirror

    NASA Astrophysics Data System (ADS)

    Allen, Matthew R.; Kim, Jae Jun; Agrawal, Brij N.

    2015-09-01

    High development cost is a challenge for space telescopes and imaging satellites. One of the primary reasons for this high cost is the development of the primary mirror, which must meet diffraction limit surface figure requirements. Recent efforts to develop lower cost, lightweight, replicable primary mirrors include development of silicon carbide actuated hybrid mirrors and carbon fiber mirrors. The silicon carbide actuated hybrid mirrors at the Naval Postgraduate School do not meet the surface quality required for an optical telescope due to high spatial frequency residual surface errors. A technique under investigation at the Naval Postgraduate School is to correct the residual surface figure error using a deformable mirror in the optical path. We present a closed loop feedback gradient controller to actively control a SMT active segment and an additional deformable mirror to reduce residual wavefront error. The simulations and experimental results show that the gradient controller reduces the residual wavefront error more than an integral controller.

  7. The Interpretation of Crustal Dynamics Data in Terms of Plate Interactions and Active Tectonics of the Anatolian Plate and Surrounding Regions in the Middle East

    NASA Technical Reports Server (NTRS)

    Toksoz, M. Nafi; Reilinger, Robert E.

    1990-01-01

    During the past 6 months, efforts were concentrated on the following areas: (1) Continued development of realistic, finite element modeling of plate interactions and associated deformation in the Eastern Mediterranean; (2) Neotectonic field investigations of seismic faulting along the active fault systems in Turkey with emphasis on identifying seismic gaps along the North Anatolian fault; and (3) Establishment of a GPS regional monitoring network in the zone of ongoing continental collision in eastern Turkey (supported in part by NSF).

  8. Bedrock temperature as a potential method for monitoring change in crustal stress: Theory, in situ measurement, and a case history

    NASA Astrophysics Data System (ADS)

    Chen, Shunyun; Liu, Peixun; Liu, Liqiang; Ma, Jin

    2016-06-01

    Experimental studies have confirmed that temperature is notably affected by rock deformation; therefore, change in crustal stress should be indicated by measurable changes in bedrock temperature. In this work, we investigated the possibility that the bedrock temperature might be used to explore the state of crustal stress. In situ measurement of bedrock temperature at three stations from 2011 to 2013 was used as the basis for the theoretical analysis of this approach. We began with theoretical analyses of temperature response to change in crustal stress, and of the effect of heat conduction. This allowed distinction between temperature changes produced by crustal stress (stress temperature) from temperature changes caused by conduction from the land surface (conduction temperature). Stress temperature has two properties (synchronous response and a high-frequency feature) that allow it to be distinguished from conduction temperature. The in situ measurements confirmed that apparently synchronous changes in the stress temperature of the bedrock occur and that there exist obvious short-term components of the in situ bedrock temperature, which agrees with theory. On 20 April 2013, an earthquake occurred 95 km away from the stations, fortuitously providing a case study by which to verify our method for obtaining the state of crustal stress using temperature. The results indicated that the level of local or regional seismic activity, representing the level of stress adjustment, largely accords with the stress temperature. This means that the bedrock temperature is a tool that might be applied to understand the state of stress during seismogenic tectonics. Therefore, it is possible to record changes in the state of crustal stress in a typical tectonic position by long-term observation of bedrock temperature. Hereby, the measurement of bedrock temperature has become a new tool for gaining insight into changes in the status of shallow crustal stress.

  9. Lithospheric Structure, Crustal Kinematics, and Earthquakes in North China: An Integrated Study

    NASA Astrophysics Data System (ADS)

    Liu, M.; Yang, Y.; Sandvol, E.; Chen, Y.; Wang, L.; Zhou, S.; Shen, Z.; Wang, Q.

    2007-12-01

    The North China block (NCB) is geologically part of the Archaean Sino-Korean craton. But unusual for a craton, it was thermally rejuvenated since late Mesozoic, and experienced widespread extension and volcanism through much of the Cenozoic. Today, the NCB is characterized by strong internal deformation and seismicity, including the 1976 Tangshan earthquake that killed ~250,000 people. We have started a multidisciplinary study to image the lithospheric and upper mantle structure using seismological methods, to delineate crustal kinematics and deformation via studies of neotectonics and space geodesy, and to investigate the driving forces, the stress states and evolution, and seismicity using geodynamic modeling. Both seismic imaging and GPS results indicate that the Ordos plateau, which is the western part of the NCB and a relic of the Sino-Korean craton, has been encroached around its southern margins by mantle flow and thus is experiencing active cratonic destruction. Some of the mantle flow may be driven by the Indo-Asian collision, although the cause of the broad mantle upwelling responsible for the Mesozoic thinning of the NCB lithosphere remains uncertain. At present, crustal deformation in the NCB is largely driven by gravitational spreading of the expanding Tibetan Plateau. Internal deformation within the NCB is further facilitated by the particular tectonic boundary conditions around the NCB, and the large lateral contrasts of lithospheric strength and rheology. Based on the crustal kinematics and lithospheric structure, we have developed a preliminary geodynamic model for stress states and strain energy in the crust of the NCB. The predicted long-term strain energy distribution is comparable with the spatial pattern of seismic energy release in the past 2000 years. We are exploring the cause of the spatiotemporal occurrence of large earthquakes in the NCB, especially the apparent migration of seismicity from the Weihe-Shanxi grabens around the Ordos to

  10. Projection Moire Interferometry for Rotorcraft Applications: Deformation Measurements of Active Twist Rotor Blades

    NASA Technical Reports Server (NTRS)

    Fleming, Gary A.; Soto, Hector L.; South, Bruce W.

    2002-01-01

    Projection Moire Interferometry (PMI) has been used during wind tunnel tests to obtain azimuthally dependent blade bending and twist measurements for a 4-bladed Active Twist Rotor (ATR) system in simulated forward flight. The ATR concept offers a means to reduce rotor vibratory loads and noise by using piezoelectric active fiber composite actuators embedded in the blade structure to twist each blade as they rotate throughout the rotor azimuth. The twist imparted on the blades for blade control causes significant changes in blade loading, resulting in complex blade deformation consisting of coupled bending and twist. Measurement of this blade deformation is critical in understanding the overall behavior of the ATR system and the physical mechanisms causing the reduction in rotor loads and noise. PMI is a non-contacting, video-based optical measurement technique capable of obtaining spatially continuous structural deformation measurements over the entire object surface within the PMI system field-of-view. When applied to rotorcraft testing, PMI can be used to measure the azimuth-dependent blade bending and twist along the full span of the rotor blade. This paper presents the PMI technique as applied to rotorcraft testing, and provides results obtained during the ATR tests demonstrating the PMI system performance. PMI measurements acquired at select blade actuation conditions generating minimum and maximum rotor loads are provided to explore the interrelationship between rotor loads, blade bending, and twist.

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  13. The surface geometry of inherited joint and fracture trace patterns resulting from active and passive deformation

    NASA Technical Reports Server (NTRS)

    Podwysocki, M. H.; Gold, D. P.

    1974-01-01

    Hypothetical models are considered for detecting subsurface structure from the fracture or joint pattern, which may be influenced by the structure and propagated to the surface. Various patterns of an initially orthogonal fracture grid are modeled according to active and passive deformation mechanisms. In the active periclinal structure with a vertical axis, fracture frequency increased both over the dome and basin, and remained constant with decreasing depth to the structure. For passive periclinal features such as a reef or sand body, fracture frequency is determined by the arc of curvature and showed a reduction over the reefmound and increased over the basin.

  14. A three-dimensional Vp, Vs, and Vp/Vs crustal structure in Fujian, Southeast China, from active- and passive-source experiments

    NASA Astrophysics Data System (ADS)

    Cai, Hui-Teng; Kuo-Chen, Hao; Jin, Xin; Wang, Chien-Ying; Huang, Bor-Shouh; Yen, Horng-Yuan

    2015-11-01

    Fujian, Southeastern China, has experienced multistage tectonic activities since the Neoproterozoic Era and is currently influenced by collision between the Eurasian and Philippine Sea plates. Topography, fault zones, and patterns of seismicity are the imprints of tectonic evolution. Historically, there have been several catastrophic earthquakes in the southeastern part of Fujian. To understand the crustal structure related to the fault zones, we performed Vp, Vs, and Vp/Vs travel-time tomography using joint inversion of active and passive sources. A total of 75,827 and 31,044 arrivals of P and S waves, respectively, from 33 explosions and 2543 earthquakes are used in our study. As a result, seismicity has indicated that two NE strike seismogenic zones, the Zhenghe-Dapu and Changle-Zhaoan fault zones, are currently active. Low Vp/Vs ratios in inland Fujian imply that the crust is mainly composed of felsic rocks as part of the Eurasian continental crust, which is consistent with geological observations at the surface. Based on Vp tomography, the thickness of the crust along the coastline is shallower than that on land, which is related to higher heat flow and the Bouguer anomaly. This shallow crust phenomenon near the coastline could be related to the regional extensional stress: the remaining structure of the back-arc extension that stretched the continental crust during the Mesozoic Era or/and the Cenozoic extension due to South China sea opening in Taiwan Strait.

  15. Removal of daytime thermal deformations in the GBT active surface via out-of-focus holography

    NASA Astrophysics Data System (ADS)

    Hunter, T. R.; Mello, M.; Nikolic, B.; Mason, B. S.; Schwab, F. R.; Ghigo, F. D.; Dicker, S. R.

    2009-01-01

    The 100-m diameter Green Bank Telescope (GBT) was built with an active surface of 2209 actuators in order to achieve and maintain an accurate paraboloidal shape. While much of the large-scale gravitational deformation of the surface can be described by a finite element model, a significant uncompensated gravitational deformation exists. In recent years, the elevation-dependence of this residual deformation has been successfully measured during benign nighttime conditions using the out-of-focus (OOF) holography technique (Nikolic et al, 2007, A&A 465, 685). Parametrized by a set of Zernike polynomials, the OOF model correction was implemented into the active surface and has been applied during all high frequency observations since Fall 2006, yielding a consistent gain curve that is constant with elevation. However, large-scale thermal deformation of the surface has remained a problem for daytime high-frequency observations. OOF holography maps taken throughout a clear winter day indicate that surface deformations become significant whenever the Sun is above 10 degrees elevation, but that they change slowly while tracking a single source. In this paper, we describe a further improvement to the GBT active surface that allows an observer to measure and compensate for the thermal surface deformation using the OOF technique. In order to support high-frequency observers, "AutoOOF" is a new GBT Astrid procedure that acquires a quick set of in-focus and out-of-focus on-the-fly continuum maps on a quasar using the currently active receiver. Upon completion of the maps, the data analysis software is launched automatically which produces and displays the surface map along with a set of Zernike coefficients. These coefficients are then sent to the active surface manager which combines them with the existing gravitational Zernike terms and FEM in order to compute the total active surface correction. The end-to-end functionality has been tested on the sky at Q-Band and Ka

  16. Crustal controls on the dynamics of collisional orogenesis

    NASA Astrophysics Data System (ADS)

    Greene, P.; Pysklywec, R. N.

    2013-12-01

    The role of extensional inheritance and crustal thickness in determining modes of colli- sional orogenesis is not well resolved. However, the wide variety of non-volcanic continental margin widths and continental moho depths observed implies that crustal geometry may play a first-order roll in the evolution of orogenesis. To elucidate the effect these parameters have on continental collision, a series of freely evolving 2D upper mantle numerical exper- iments were performed with systematically varied continental margin widths and crustal thicknesses. Results show that the 2D vertical geometry of subducting continental crust controls both crustal and lithosphere scale deformation. On both scales, deformational end-members can be identified, namely: breakoff vs. delamination of continental mantle lithosphere, and double vergence vs. single vergence crustal thrust fronts. We find that the subduction of upper crust to depths >100km promotes lithospheric delamination and is most easily achieved when a hyper-extended margin is present or continental crust is thin. Similarly, modelled orogens are singly vergent in cases of thinned or hyper-extended crustal subduction. An intermediate between lithospheric end-members is also observed with a ˜2Ma period of 'eduction' after breakoff followed by delamination. This interme- diate mode of subduction may present an analog of the Miocene-present evolution of the Northern Apennines and Dinarides. Corollaries can also be drawn between these model results and Phanerozoic orogens such as the Zargos, and Pyrenees.

  17. Crustal Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Ravat, D.; Frawley, James J.

    1999-01-01

    Cosmos 49, Polar Orbit Geophysical Observatory (POGO) (Orbiting Geophysical Observatory (OGO-2, 4 and 6)) and Magsat have been the only low-earth orbiting satellites to measure the crustal magnetic field on a global scale. These missions revealed the presence of long- wavelength (> 500 km) crustal anomalies predominantly located over continents. Ground based methods were, for the most part, unable to record these very large-scale features; no doubt due to the problems of assembling continental scale maps from numerous smaller surveys acquired over many years. Questions arose as to the source and nature of these long-wave length anomalies. As a result there was a great stimulant given to the study of the magnetic properties of the lower crust and upper mantle. Some indication as to the nature of these deep sources has been provided by the recent results from the deep crustal drilling programs. In addition, the mechanism of magnetization, induced or remanent, was largely unknown. For computational ease these anomalies were considered to result solely from induced magnetization. However, recent results from Mars Orbiter Laser Altimeter (MOLA), a magnetometer-bearing mission to Mars, have revealed crustal anomalies with dimensions similar to the largest anomalies on Earth. These Martian features could only have been produced by remanent magnetization, since Mars lacks an inducing field. The origin of long-wavelength crustal anomalies, however, has not been completely determined. Several large crustal magnetic anomalies (e.g., Bangui, Kursk, Kiruna and Central Europe) will be discussed and the role of future satellite magnetometer missions (Orsted, SUNSAT and Champ) in their interpretation evaluated.

  18. Constraining fault activity by investigating tectonically-deformed Quaternary palaeoshorelines using a synchronous correlation method: the Capo D'Orlando Fault as a case study (NE Sicily, Italy)

    NASA Astrophysics Data System (ADS)

    Meschis, Marco; Roberts, Gerald P.; Robertson, Jennifer

    2016-04-01

    Long-term curstal extension rates, accommodated by active normal faults, can be constrained by investigating Late Quaternary vertical movements. Sequences of marine terraces tectonically deformed by active faults mark the interaction between tectonic activity, sea-level changes and active faulting throughout the Quaternary (e.g. Armijo et al., 1996, Giunta et al, 2011, Roberts et al., 2013). Crustal deformation can be calculated over multiple seismic cycles by mapping Quaternary tectonically-deformed palaeoshorelines, both in the hangingwall and footwall of active normal faults (Roberts et al., 2013). Here we use a synchronous correlation method between palaeoshorelines elevations and the ages of sea-level highstands (see Roberts et al., 2013 for further details) which takes advantage of the facts that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower paleoshoreline does not necessarily correlate with the next older or younger sea-level highstand. We investigated a flight of Late Quaternary marine terraces deformed by normal faulting as a result of the Capo D'Orlando Fault in NE Sicily (e.g. Giunta et al., 2011). This fault lies within the Calabrian Arc which has experienced damaging seismic events such as the 1908 Messina Straits earthquake ~ Mw 7. Our mapping and previous mapping (Giunta et al. (2011) demonstrate that the elevations of marine terraces inner edges change along the strike the NE - SW oriented normal fault. This confirms active deformation on the Capo D'Orlando Fault, strongly suggesting that it should be added into the Database of Individual Seismogenic Sources (DISS, Basili et al., 2008). Giunta et al. (2011) suggested that uplift rates and hence faults lip-rates vary through time for this examples. We update the ages assigned to

  19. Failure and deformation mechanisms at macro- and nano-scales of alkali activated clay

    NASA Astrophysics Data System (ADS)

    Sekhar Das, Pradip; Bhattacharya, Manjima; Chanda, Dipak Kr; Dalui, Srikanta; Acharya, Saikat; Ghosh, Swapankumar; Mukhopadhyay, Anoop Kumar

    2016-06-01

    Here we report two qualitative models on failure and deformation mechanisms at macro- and nano-scales of alkali activated clay (AACL), a material of extraordinary importance as a low cost building material. The models were based on experimental data of compressive failure and nanoindentation response of the AACL materials. A 420% improvement in compressive strength (σ c) of the AACL was achieved after 28 days (d) of curing at room temperature and it correlated well with the decrements in the residual alkali and pH concentrations with the increase in curing time. Based on extensive post-mortem FE-SEM examinations, a schematic model for the compressive failure mechanism of AACL was proposed. In addition, the nanoindentation results of AACL provided the first ever experimental evidence of the presence of nano-scale plasticity and a nano-scale contact deformation resistance that increased with the applied load. These results meant the development of a unique strain tolerant microstructure in the AACL of Indian origin. The implications of these new observations were discussed in terms of a qualitative model based on the deformation of layered clay structure.

  20. Space active optics: in situ compensation of lightweight primary mirrors' deformations

    NASA Astrophysics Data System (ADS)

    Laslandes, M.; Ferrari, M.; Hugot, E.; Lemaitre, G.

    2010-12-01

    The need for both high quality images and light structures is a constant concern in the conception of space telescopes. The goal here is to determine how an active optics system could be embarked on a satellite in order to correct the wave front deformations of the optical train. The optical aberrations appearing in a space environment are due to mirrors' deformations, with three main origins: the thermal variations, the weightlessness conditions and the use of large weightlighted primary mirrors. We are developing a model of deformable mirror as minimalist as possible, especially in term of number of actuators, which is able to correct the first Zernike polynomials in a specified range of amplitude and precision. Flight constraints as weight, volume and power consumption are considered. Firstly, such a system is designed according to the equations from the elasticity theory: we determine the geometrical and mechanical characteristics of the mirror, the location of the forces to be applied and the way to apply them. Then the concept is validated with a Finite Element Analysis, allowing to optimize the system by taking into account parameters absent from the theory. At the end, the mirror will be realized and characterized in a representative optical configuration.

  1. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  2. Mirror actively deformed and regulated for applications in space: design and performance

    NASA Astrophysics Data System (ADS)

    Laslandes, Marie; Hugot, Emmanuel; Ferrari, Marc; Hourtoule, Claire; Singer, Christian; Devilliers, Christophe; Lopez, Céline; Chazallet, Frédéric

    2013-09-01

    The need for both high quality images and lightweight structures is one of the main drivers in space telescope design. An efficient wavefront control system will become mandatory in future large observatories, retaining performance while relaxing specifications in the global system's stability. We present the mirror actively deformed and regulated for applications in space project, which aims to demonstrate the applicability of active optics for future space instrumentation. It has led to the development of a 24-actuator, 90-mm-diameter active mirror, able to compensate for large lightweight primary mirror deformations in the telescope's exit pupil. The correcting system has been designed for expected wavefront errors from 3-m-class lightweight primary mirrors, while also taking into account constraints for space use. Finite element analysis allowed an optimization of the system in order to achieve a precision of correction better than 10 nm rms. A dedicated testbed has been designed to fully characterize the integrated system performance in representative operating conditions. It is composed of: a telescope simulator, an active correction loop, a point spread function imager, and a Fizeau interferometer. All conducted tests demonstrated the correcting mirror performance and has improved this technology maturity to a TRL4.

  3. Crustal signatures of the tectonic development of the North American midcontinent

    NASA Astrophysics Data System (ADS)

    McGlannan, Austin J.; Gilbert, Hersh

    2016-01-01

    The stable eastern portion of the North American continent offers an excellent environment to study the tectonic development of intra-continental structures. The midcontinent of North America formed by the accretion of Proterozoic terranes, and has since experienced episodes of deformation during the subsidence of the Illinois Basin and uplift of the Ozark Plateau. Rifting also initiated in eastern North America, but extension did not continue and arms of failed rifts extend across the region. The New Madrid Seismic Zone, situated within a portion of the failed Reelfoot Rift, represents an active zone of intraplate seismicity. Analyzing the structure of the crust and upper mantle within the midcontinent will therefore provide insight into the factors that lead to intraplate deformation. Using data from over 180 Transportable Array seismic stations, we calculate receiver functions to investigate the crust and upper mantle of the midcontinent. At close to 40 km thick, the crust of the New Madrid Seismic Zone is thinner than in the surrounding areas outside of the Reelfoot Rift and Rough Creek Graben. The Illinois Basin cannot be characterized by a single crustal structure, as crust near 50 km thick in the central portion of the basin thins to between 40 and 45 km thick towards the northern and southern portions of the basin. Discontinuities within the crust and upper mantle are prominent in and around the New Madrid Seismic Zone and mark locations of crustal modification and underplating. Comparing changes in crustal structure to the distribution of Bouguer gravity anomalies, the presence of positive gravity anomalies suggests that higher density crust plays a role in maintaining low surface elevations within the Reelfoot Rift. Conversely, a negative gravity anomaly in an area of thinner crust within the Ozark Plateau supports the need for low-density crustal material to influence the uplift of the plateau.

  4. Active deformation in the northern Sierra de Valle Fértil, Sierras Pampeanas, Argentina

    NASA Astrophysics Data System (ADS)

    Ortiz, Gustavo; Alvarado, Patricia; Fosdick, Julie C.; Perucca, Laura; Saez, Mauro; Venerdini, Agostina

    2015-12-01

    The Western Sierras Pampeanas region in the San Juan Province is characterized by thick-skinned deformation with approximately N-S trending ranges of average heights of 2500 m and a high frequency occurrence of seismic activity. Its location to the east of the mainly thin-skinned tectonics of the Argentine Precordillera fold-and-thrust belt suggests that at 30°S, deformation is concentrated in a narrow zone involving these two morphostructural units. In this paper, we present new apatite (U-Th)/He results (AHe) across the northern part of the Sierra de Valle Fértil (around 30°S) and analyze them in a framework of thermochronologic available datasets. We found Pliocene AHe results for Carboniferous and Triassic strata in the northern Sierra de Valle Fértil consistent with the hypothesis of recent cooling and inferred erosional denudation concentrated along the northern end of this mountain range. Our analysis shows that this northern region may have evolved under different conditions than the central part of the Sierra de Valle Fértil. Previous studies have observed AHe ages consistent with Permian through Cretaceous cooling, indicating the middle part of the Sierra de Valle Fértil remained near surface before the Pampean slab subduction flattening process. Those studies also obtained ˜5 My cooling ages in the southern part of the Sierra de Valle Fértil, which are similar to our results in the northern end of the range. Taken together, these results suggest a pattern of young deformation in the northern and southern low elevation ends of the Sierra de Valle Fértil consistent with regions of high seismic activity, and Quaternary active faulting along the western-bounding thrust fault of the Sierra de Valle Fértil.

  5. Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD

    NASA Astrophysics Data System (ADS)

    Morrow, C.; Lockner, D. A.; Hickman, S.

    2015-12-01

    The San Andreas Fault Observatory at Depth (SAFOD) scientific drill hole near Parkfield, California, crosses the San Andreas Fault at a depth of 2.7 km. Downhole measurements and analysis of core retrieved from Phase 3 drilling reveal two narrow, actively deforming zones of smectite-clay gouge within a roughly 200 m wide fault damage zone of sandstones, siltstones, and mudstones. Here we report electrical resistivity and permeability measurements on core samples from all of these structural units at effective confining pressures up to 120 MPa. Electrical resistivity (~10 Ω-m) and permeability (10-21 to 10-22 m2) in the actively deforming zones were 1 to 2 orders of magnitude lower than the surrounding damage zone material, consistent with broader-scale observations from the downhole resistivity and seismic velocity logs. The higher porosity of the clay gouge, 2 to 8 times greater than that in the damage zone rocks, along with surface conduction were the principal factors contributing to the observed low resistivities. The high percentage of fine-grained clay in the deforming zones also greatly reduced permeability to values low enough to create a barrier to fluid flow across the fault. Together, resistivity and permeability data can be used to assess the hydrogeologic characteristics of the fault, key to understanding fault structure and strength. The low resistivities and strength measurements of the SAFOD core are consistent with observations of low resistivity clays that are often found in the principal slip zones of other active faults making resistivity logs a valuable tool for identifying these zones.

  6. Crustal Evolution Introduced.

    ERIC Educational Resources Information Center

    Stoever, Edward C., Jr.; Korporaal, Arie R.

    1979-01-01

    Detailed are the origins, development, and implementation of the Crustal Evolution Education Project (CEEP). This group has produced, for use in earth science and other classes in grades 8-10, a series of instructional modules based on current scientific research in the composition, history, and processes of the earth's crust. (BT)

  7. Long-term crustal rheology in the Apennines of Italy: implications for the base of the seismogenic zone

    NASA Astrophysics Data System (ADS)

    Balestra, F.; Boncio, P.; Barba, S.

    2008-12-01

    The seismicity of the Apennines of Italy is now rather well known, thanks to seismologic-seismotectonic studies of earthquake sequences and locally-recorded background seismicity. Less has been done about the systematic analysis of the rheology of the crust at the scale of the entire Apennines and the possible implications in terms of seismogenic layer(s); this has implications also on the 3D geometry and seismogenic potential of active faults and therefore on seismic hazard assessments. The improved knowledge about the crustal structure (CROP project, DSS, seismic tomography) and seismotectonic regime (state of stress, strain rates) of Italy makes worth such an analysis. In this work we apply a homogeneous methodology to calculate the crustal rheology along a number of deep crustal sections (CROP and DSS sections) crossing the actively deforming Apennines. The analysis includes: i) definition of crustal stratigraphy, ii) computation of geotherms, iii) association to crustal layers of known rheological parameters on the basis of seismic velocities and, iv) computation of rheological profiles by comparing frictional strength, brittle fracture strength and power-law creep strength of the likely crustal rocks (e.g., Sibson 1974 Nature 249; Ranalli and Murphy 1987 Tectonoph. 132; Zang et al. 2007 Tectonoph. 429). Where possible, the results are compared with the distribution at depth of well-located background seismicity and aftershocks. Locally (e.g., Southern Apennines), possible complicating factors, such as high pore-fluid pressure and variations in strain rate due to seismogenic faulting are considered. Although the simple rheological profiles used here cannot constrain the conditions for velocity-weakening unstable (seismogenic) or velocity-strengthening stable-sliding (aseismic) faulting, the results obtained in this work suggest that this kind of rheological analysis might still provide useful information on the likely seismogenic behaviour of the crust, as

  8. Crustal motion in the Antarctic interior from a decade of Global Positioning System measurements

    NASA Astrophysics Data System (ADS)

    Willis, Michael J.

    A decade of Global Positioning System (GPS) data have been collected at bedrock sites in southern Victoria Land, Antarctica. Measured motions of the crust have been examined to determine if ongoing tectonic deformation occurs within the study area, across the structural boundary between East and West Antarctica. Crustal motions are used to test for activity over the offshore Terror Rift, where young faulting is documented, and to assess locally whether the active Erebus volcano deforms the crust. Bedrock motions caused by large scale ice-mass changes that have occurred in the area since the Last Glacial Maximum are also a major focus of the study. The horizontal GPS motions record Antarctic plate motion of ˜15 mm/yr to the southeast. No deformation is observed over the Transantarctic Mountains Front Zone. Very small amounts of deformation are observed along the Terror Rift, however the recorded direction of motions may be the result of Glacial Isostatic Adjustment (GIA), rather than active tectonics. Recorded motions observed to the south of Ross Island suggest that the Terror Rift continues beneath the Ross Ice Shelf. No volcanic loading signal is observed. Vertical crustal motions exhibit a down-to-the-east tilt over the study area. A suite of earth models, including more than three hundred different mantle viscosity profiles, three different lithospheric thicknesses and three different ice histories, were used to model uplift due to Glacial Isostatic Adjustment driven by ice mass change. None replicate the observed tilt. Two Relative Sea Level curves for the region also could not be replicated by GIA models examined. Comparison of GPS vertical velocities and our GIA models produce well-constrained earth models for the study area, but suggest that current ice history models for the region must be revised to replicate measured crustal motions. We compare the output of our GPS-constrained models with published crustal uplift rates used in modern ice mass balance

  9. Attenuation Properties of Fontainebleau Sandstone During True-Triaxial Deformation using Active and Passive Ultrasonics

    NASA Astrophysics Data System (ADS)

    Goodfellow, S. D.; Tisato, N.; Ghofranitabari, M.; Nasseri, M. H. B.; Young, R. P.

    2015-11-01

    Active and passive ultrasonic methods were used to study the evolution of attenuation properties in a sample of Fontainebleau sandstone during true-triaxial deformation. A cubic sample of Fontainebleau sandstone (80 mm × 80 mm × 80 mm) was deformed under true-triaxial stresses until failure. From the stress state: σ _3 = 5 MPa and σ _1 = σ _2 = 35 MPa, σ _1 was increased at a constant displacement rate until the specimen failed. Acoustic emission (AE) activity was monitored by 18 piezoelectric sensors and bandpass filtered between 100 kHz and 1 MHz. A source location analysis was performed on discrete AE data harvested from the continuous record where 48,502 events were locatable inside the sample volume. AE sensors were sequentially pulsed during periodic P-wave surveys among 135 raypaths. Analytical solutions for Biot, squirt flow, viscous shear, and scattering attenuation were used to discuss to observed attenuation at various stages of the experiment. We concluded that initial attenuation anisotropy was stress induced and resulted from friction and squirt flow. Later attenuation of the high-frequency spectrum was attributed to scattering as a result of the formation of large macroscopic vertical fractures. Passive (AE) ultrasonic data produced similar information to that from active data but with enhanced temporal and spacial resolution.

  10. PS-InSAR measurements at the most active volcanoes in Iceland: role of the GEO supersite initiative in deformation monitoring at Bárðarbunga, Askja, Hekla, Katla and Eyjafjallajökull volcanoes

    NASA Astrophysics Data System (ADS)

    Parks, Michelle; Dumont, Stéphanie; Drouin, Vincent; Sigmundsson, Freysteinn; Spaans, Karsten; Hooper, Andrew; Ófeigsson, Benedikt; Árnadóttir, Þóra; Hreinsdóttir, Sigrún; Michalczewska, Karolina; Hjaltadóttir, Sigurlaug; María Friðriksdóttir, Hildur; Rut Hjartardóttir, Ásta; Magnússon, Eyjólfur; Vogfjörd, Kristín; Jónsdóttir, Kristín; Hensch, Martin; Guðmundsson, Gunnar; Geirsson, Halldór; Sturkell, Erik

    2015-04-01

    deformation studies utilising data spanning this eruption, have provided insight into the shallow plumbing system, which may explain the large reduction in eruption repose interval following the 1970 eruption. InSAR and GPS observations at Katla volcano prior to 2010 suggest no magma induced deformation. However, deformation associated with a small flood at Mýrdalsjökull in July 2011, followed by an increase in micro-seismic earthquakes, could be interpreted in relation to magma movements. Post-eruption deformation observations reveal inflation at Eyjafjallajökull possibly related to the influx of new melt or readjustment of crustal stresses following the 2010 eruption. Continued deflation at Askja caldera since 1983 may have led to crustal weakening and the triggering of a mega rockslide and subsequent tsunami occurring on the 21 July 2014. Interferograms spanning the recent unrest and eruption within the Bárðarbunga volcanic system display both pre-eruptive and co-eruptive deformation associated with the initial dyke emplacement and ongoing magma withdrawal from beneath the Bárðarbunga central volcano. Continued high-resolution geodetic observations at these volcanoes are essential for assessing changes in their behaviour and the associated hazards. Rapid analysis of interferograms combined with GPS and earthquake seismicity measurements assists in tracking the evolution of magmatic activity during volcanic unrest/eruption, and may facilitate the assessment of associated hazards.

  11. Distribution of deformation on an active normal fault network, NW Corinth Rift

    NASA Astrophysics Data System (ADS)

    Ford, Mary; Meyer, Nicolas; Boiselet, Aurélien; Lambotte, Sophie; Scotti, Oona; Lyon-Caen, Hélène; Briole, Pierre; Caumon, Guillaume; Bernard, Pascal

    2013-04-01

    Over the last 20-25 years, geodetic measurements across the Gulf of Corinth have recorded high extension rates varying from 1.1 cm/a in the east to a maximum of 1.6 cm/a in the west. Geodetic studies also show that current deformation is confined between two relatively rigid blocks defined as Central Greece (to the north) and the Peloponnesus to the south. Active north dipping faults (<1 Ma) define the south coast of the subsiding Gulf, while high seismicity (major earthquakes and micro-seismicity) is concentrated at depth below and to the north of the westernmost Gulf. How is this intense deformation distributed in the upper crust? Our objectives here are (1) to propose two models for the distribution of deformation in the upper crust in the westernmost rift since 1 Ma, and (2) to place the tectonic behaviour of the western Gulf in the context of longer term rift evolution. Over 20 major active normal faults have been identified in the CRL area based specific characteristics (capable of generating earthquakes M> 5.5, active in the last 1 M yrs, slip rate >0.5 mm/a). Because of the uncertainty related to fault geometry at depth two models for 3D fault network geometry in the western rift down to 10 km were constructed using all available geophysical and geological data. The first model assumes planar fault geometries while the second uses listric geometries for major faults. A model for the distribution of geodetically-defined extension on faults is constructed along five NNE-SSW cross sections using a variety of data and timescales. We assume that the role of smaller faults in accommodating deformation is negligible so that extension is fully accommodated on the identified major faults. Uncertainties and implications are discussed. These models provide estimates of slip rate for each fault that can be used in seismic hazard models. A compilation of onshore and offshore data shows that the western Gulf is the youngest part of the Corinth rift having initiated

  12. Exhumed analogues of seismically active carbonate-bearing thrusts: fault architecture and deformation mechanisms

    NASA Astrophysics Data System (ADS)

    Tesei, T.; Collettini, C.; Viti, C.; Barchi, M. R.

    2012-12-01

    In May 2012 a M = 5.9 earthquake followed by a long aftershock sequence struck the Northern Italy. The sequence occurred at 4-10 km depth within the active front of Northern Apennines Prism and the major events nucleate within, or propagate through, a thick sequence of carbonates. In an inner sector of the Northern Apennines, ancient carbonate-bearing thrusts exposed at the surface, represent exhumed analogues of structures generating seismicity in the active front. Here we document fault architecture and deformation mechanisms of three regional carbonate bearing thrusts with displacement of several kilometers and exhumation in the range of 1-4 km. Fault zone structure and deformation mechanisms are controlled by the lithology of the faulted rocks. In layered limestones and marly-limestones the fault zone is up to 200 m thick and is characterized by intense pressure solution. In massive limestones the deformation generally occurs along thin and sharp slip planes that are in contact with fault portions affected by either cataclasis or pressure solution. SEM and TEM observations show that pressure solution surfaces, made of smectite lamellae, with time tend to form an interconnected network affected by frictional sliding. Sharp slipping planes along massive limestones show localization along Y shear planes that separate an extremely comminuted cataclasites from an almost undeformed protolith. The comparison of the three shear zones depicts a fault zone structure extremely heterogeneous as the result of protolith lithology, geometrical complexities and the presence of inherited structures. We observe the competition between brittle (cataclasis, distributed frictional sliding along phyllosilicates and extremely localized slip within carbonates) and pressure solution processes, that suggest a multi-mode of slip behaviour. Extreme localization along carbonate-bearing Y shear planes is our favorite fault zone feature representing past seismic ruptures along the studied

  13. Rates and kinematics of active shortening along the eastern Qilian Shan, China, inferred from deformed fluvial terraces

    NASA Astrophysics Data System (ADS)

    Hu, Xiaofei; Pan, Baotian; Kirby, Eric; Gao, Hongshan; Hu, Zhenbo; Cao, Bo; Geng, Haopeng; Li, Qingyang; Zhang, Guoliang

    2015-12-01

    In the eastern Qilian Shan, a flight of fluvial terraces developed along the Jinta River valley are deformed across the Nanying anticline. Four individual fluvial terraces are preserved at different elevations above the river, and higher terrace treads are draped by systematically thicker aeolian loess. Optically stimulated luminescence dating of deposits at the base of the loess provides constraints on the timing of surface abandonment; terraces were abandoned at 69 ± 4 ka B.P. (T4), 57 ± 4 ka B.P. (T3), and between 34 ± 3 ka B.P. (T2), respectively. Differential GPS measurement of the terrace profile across the anticline allows reconstruction of subsurface fault geometry; we model terrace deformation above a listric thrust fault with a tip line at 2.2 ± 0.1 km depth and whose dip shallows systematically to 23 ± 3° at depth of 5.8 ± 1.1 km. Combining terrace ages with this model of fault geometry, we estimate a shortening rate of 0.8 ± 0.2 mm/a across the Nanying fold and a shortening rate of ~0.1 mm/a across the mountain front fault since ~70 ka B.P. This rate suggests that the frontal fault system along the eastern Qilian Shan accomplishes crustal shortening at rates of approximately 0.9 ± 0.3 mm/a during late Pleistocene time.

  14. 10Be surface exposure dating reveals strong active deformation in the central Andean backarc interior

    NASA Astrophysics Data System (ADS)

    García Morabito, Ezequiel; Terrizzano, Carla; Zech, Roland; Willett, Sean; Yamin, Marcela; Haghipour, Negar; Wuethrich, Lorenz; Christl, Marcus; María Cortes, José; Ramos, Victor

    2016-04-01

    Understanding the deformation associated with active thrust wedges is essential to evaluate seismic hazard. How is active faulting distributed throughout the wedge, and how much deformation is taken up by individual structures? We address these questions for our study region, the central Andean backarc of Argentina. We combined a structural and geomorphological approach with surface exposure dating (10Be) of alluvial fans and strath terraces in two key localities at ~32° S: the Cerro Salinas, located in the active orogenic front of the Precordillera, and the Barreal block in the interior of the Andean mountain range. We analysed 22 surface samples and 6 depth profiles. At the thrust front, the oldest terrace (T1) yields an age of 100-130 ka, the intermediate terrace (T2) between 40-95 ka, and the youngest terrace (T3) an age of ~20 ka. In the Andean interior, T1´ dates to 117-146 ka, T2´ to ~70 ka, and T3´ to ~20 ka, all calculations assuming negligible erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Vertical slip rates of fault offsets are 0.3-0.5 mm/yr and of 0.6-1.2 mm/yr at the thrust front and in the Andean interior, respectively. Our results highlight: i) fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone. Internal structures have been active during the last 150 ka, ii) deformation rates in the Andean interior are comparable or even higher that those estimated and reported along the emerging thrust front, iii) distribution of active faulting seems to account for unsteady state conditions, and iv) seismic hazards may be more relevant in the internal parts of the Andean orogen than assumed so far. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary Science Letters 104: 424-439. Stone, J.O., 2000: Air pressure and cosmogenic isotope production. Journal of Geophysical

  15. Active salt deformation and rapid, transient incision along the Colorado River near Moab, Utah

    NASA Astrophysics Data System (ADS)

    Jochems, Andrew P.; Pederson, Joel L.

    2015-04-01

    In certain settings, erosion is driven by and balanced with tectonic uplift, but the evolution of many landscapes is dominated by other factors such as geologic substrate, drainage history, and transient incision. The Colorado Plateau is an example where these controls are debated and where salt deformation is hypothesized to be locally active and driven by differential unloading, although this is unconfirmed and unquantified in most places. We use luminescence-dated Colorado River terraces upstream of Moab, Utah, to quantify rates of salt-driven subsidence and uplift at the local scale. Active deformation in the study area is also supported by patterns of concavity along tributary drainages crossing salt structures. Subsidence in Professor Valley at a time-averaged rate of ~500 m/Myr (meters/million years) is superimposed upon rapid bedrock incision rates that increase from ~600 to ~900 m/Myr upstream through the study area. Such high rates are unexpected given the absence of sources of regional tectonic uplift here. Instead, the incision rate pattern across the greater area is consistent with a transient signal, perhaps still from ancient drainage integration through Grand Canyon far downstream, and then amplified by unloading at both the broad regional scale and at the local canyon scale.

  16. Active deformation along the Andaman-Nicobar subduction zone from seismic reflection studies

    NASA Astrophysics Data System (ADS)

    Moeremans, R. E.; Singh, S. C.

    2013-12-01

    The Andaman-Sumatra subduction zone is one of the most seismically active regions on Earth and is a prime example of oblique subduction. It is the result of the oblique convergence between the downgoing Indo-Australian and the overriding Eurasian plates, leading to slip partitioning into a trench-normal thrust component along the plate interface and a trench-subparallel strike-slip component along a sliver fault. The direction of convergence is 90° with respect to the trench near Java, reduces to 45° off of northern Sumatra, and becomes almost parallel to the trench along the Andaman-Nicobar portion of the subduction. Rates of subduction vary from 63 mm/yr off of Java, 50 mm/yr near Nias Island, 45 mm/yr northwest of Sumatra, and 39 mm/yr near the Andaman Islands. After the great December 2004 earthquake, the Sumatran section of the subduction zone was heavily investigated using marine geophysical studies, but the deformation processes in the Andaman-Nicobar region remain poorly understood due to the lack of data. Here, we present seismic reflection profiles from the Andaman-Nicobar region that cover the deformation front, the forearc high, and the forearc basin. We find that the presence of thick (> 3 s TWT) sediments lead to slip taking place predominantly along landward vergent frontal faults. The frontal fault vergence changes to seaward due to the thinning (< 2 s TWT) of the sediments in the region where the Ninetyeast ridge subducts. The presence of a thick (> 3 s TWT) 20 km-long unit of undeformed sediments, possibly resulting from the landward vergence of the frontal thrusts, suggests that ~40 km of the Ninetyeast ridge has subducted beneath the Andaman forearc. The forearc is widest between the Andaman and Nicobar Islands, likely due to the subduction of thick sediments. The forearc basin is bounded in the west by a series of backthrusts and is underlain by a continental crust, which was once a part of the Malay Peninsula. The forearc basin is crescent

  17. Active tectonics of the Binalud Mountains, a key puzzle segment to describe Quaternary deformations at the northeastern boundary of the Arabia-Eurasia collision

    NASA Astrophysics Data System (ADS)

    Shabanian, Esmaeil; Bellier, Olivier; Siame, Lionel L.; Abbassi, Mohammad R.; Leanni, Laetitia; Braucher, Régis; Farbod, Yassaman; Bourlès, Didier L.

    2010-05-01

    , the relative motion between central Iran and Eurasia is partly taken-up by dextral-reverse oblique-slip faulting along the Neyshabur and Mashhad fault systems. This faulting mechanism implies a long-term rate of ~4 mm/yr for the range-parallel strike-slip faulting, and an uplift rate of ~2.4 mm/yr due to the range-normal shortening during late Quaternary. Our data provide the first geological constraints on the rate of active faulting on both sides of the Binalud Mountains, and allow us to examine the geological reliability of preexisting tectonic models proposed to describe the kinematics of active deformation at the northeastern boundary of the Arabia-Eurasia collision. Our results favor the northward translation of central Iran with respect to Eurasia through strike-slip faulting localized along distinct crustal scale fault systems rather than systematic block rotations around vertical axes.

  18. Martian sub-crustal stress from gravity and topographic models

    NASA Astrophysics Data System (ADS)

    Tenzer, Robert; Eshagh, Mehdi; Jin, Shuanggen

    2015-09-01

    The latest Martian gravity and topographic models derived from the Mars Orbiter Laser Altimeter and the Mars Global Surveyor spacecraft tracking data are used to compute the sub-crustal stress field on Mars. For this purpose, we apply the method for a simultaneous determination of the horizontal sub-crustal stress component and the crustal thickness based on solving the Navier-Stokes problem and incorporating the Vening Meinesz-Moritz inverse problem of isostasy. Results reveal that most of the Martian sub-crustal stress is concentrated in the Tharsis region, with the most prominent signatures attributed to a formation of Tharsis major volcanoes followed by crustal loading. The stress distribution across the Valles Marineris rift valleys indicates extensional tectonism. This finding agrees with more recent theories of a tectonic origin of Valles Marineris caused, for instance, by a crustal loading of the Tharsis bulge that resulted in a regional trusting and folding. Aside from these features, the Martian stress field is relatively smooth with only a slightly enhanced pattern of major impact basins. The signatures of active global tectonics and polar ice load are absent. Whereas the signature of the hemispheric dichotomy is also missing, the long-wavelength spectrum of the stress field comprises the signature of additional dichotomy attributed to the isostatically uncompensated crustal load of Tharsis volcanic accumulations. These results suggest a different origin of the Earth's and Martian sub-crustal stress. Whereas the former is mainly related to active global tectonics, the latter is generated by a crustal loading and regional tectonism associated with a volcanic evolution on Mars. The additional sub-crustal stress around major impact basins is likely explained by a crustal extrusion after impact followed by a Moho uplift.

  19. Research on the Calculated Methods of Active Control Value for Antenna Panel Deformations under Gravity

    NASA Astrophysics Data System (ADS)

    Fu, L.; Zhong, W. Y.; Qiao, H. H.; Liu, G. X.; Qian, H. L.

    2015-07-01

    The methods of ideal reflector surface, two-parameter, five-parameter, and six-parameter best-fit paraboloid are presented in this paper. Based on these methods, the adjustment values of gravity deformations are calculated for the main reflector of large-scale Cassegrain antenna. Accordingly, the positions of subreflector are corrected, and the effects of offset-focus on electric performance are also analyzed. Taking Shanghai 65 m antenna as a research object, the adjustment values of actuator and hexapod, the accuracy of the main reflector surface, and the pointing error after offsetting the focus are contrasted. As a result, the method of six-parameter best-fit paraboloid is ideal to calculate active control value for antenna panels after the effects of feed defocus have been adjusted and modified. The results offer data for the active control of antenna.