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Sample records for system seismic boundary

  1. Regional variations in seismic boundaries

    NASA Astrophysics Data System (ADS)

    Shumlyanska, Ludmila

    2010-05-01

    Dividing of the Earth into zones in the frame one-dimensional velocity model was proposed Jeffreys and Gutenberg is the first half of XX century. They recovered the following zones: A - the crust; B - zone in the depth interval 33-413 km, C - zone 413-984 km, D - zone 984-2898 km, E - 2898-4982 km, F - 4982-5121 km, G - 5121-6371 km (centre of the Earth). These zones differ in their seismic properties. Later, zone D was divided to the areas D' (984-2700 km) and D" (2700-2900 km). At present, this scheme is significantly modified and only the layer D" is in wide use. The more seismological studies are carried out, the more seismic boundaries appear. Boundaries at 410, 520, 670, and 2900 km, at which increase in the velocity of the seismic waves is particularly noticeable are considered as having global significance. Moreover, there are indications of the existence of geophysical boundaries at 800, 1200-1300, 1700, 1900-2000 km. Using 3D P-velocity model of the mantle based on Taylor approximation method for solving of the inverse kinematics multi-dimensional seismic task we have obtained seismic boundaries for the area covering 20-55° E × 40-55° N. Data on the time of first arrivals of P waves from earthquakes and nuclear explosions recorded at ISC stations during 1964-2002 were used as input to construct a 3-D model. The model has two a priori limits: 1) the velocity is a continuous function of spatial coordinates, 2) the function v(r)/r where r is a radius in the spherical coordinate system r, φ, λ decreases with depth. The first limitation is forced since velocity leaps can not be sustainably restored from the times of first arrival; the second one follows from the nature of the observed data. Results presented as horizontal sections of the actual velocity every 25 km in the depth interval 850-2850 km, and as the longitudinal and latitudinal sections of the discrepancy on the 1-D reference model, obtained as a result of solving of the inversion task at 1

  2. Seismic link at plate boundary

    NASA Astrophysics Data System (ADS)

    Ramdani, Faical; Kettani, Omar; Tadili, Benaissa

    2015-06-01

    Seismic triggering at plate boundaries has a very complex nature that includes seismic events at varying distances. The spatial orientation of triggering cannot be reduced to sequences from the main shocks. Seismic waves propagate at all times in all directions, particularly in highly active zones. No direct evidence can be obtained regarding which earthquakes trigger the shocks. The first approach is to determine the potential linked zones where triggering may occur. The second step is to determine the causality between the events and their triggered shocks. The spatial orientation of the links between events is established from pre-ordered networks and the adapted dependence of the spatio-temporal occurrence of earthquakes. Based on a coefficient of synchronous seismic activity to grid couples, we derive a network link by each threshold. The links of high thresholds are tested using the coherence of time series to determine the causality and related orientation. The resulting link orientations at the plate boundary conditions indicate that causal triggering seems to be localized along a major fault, as a stress transfer between two major faults, and parallel to the geothermal area extension.

  3. Imaging a Fault Boundary System Using Controlled-Source Data Recorded on a Large-N Seismic Array

    NASA Astrophysics Data System (ADS)

    Paschall, O. C.; Chen, T.; Snelson, C. M.; Ralston, M. D.; Rowe, C. A.

    2016-12-01

    The Source Physics Experiment (SPE) is a series of chemical explosions conducted in southern Nevada with an objective of improving nuclear explosion monitoring. Five chemical explosions have occurred thus far in granite, the most recent being SPE-5 on April 26, 2016. The SPE series will improve our understanding of seismic wave propagation (primarily S-waves) due to explosions, and allow better discrimination of background seismicity such as earthquakes and explosions. The Large-N portion of the project consists of 996 receiver stations. Half of the stations were vertical component and the other half were three-component geophones. All receivers were deployed for 30 days and recorded the SPE-5 shot, earthquakes, noise, and an additional controlled-source: a large weight-drop, which is a 13,000 kg modified industrial pile driver. In this study, we undertake reflection processing of waveforms from the weight-drop, as recorded by a line of sensors extracted from the Large-N array. The profile is 1.2 km in length with 25 m station spacing and 100 m shot point spacing. This profile crosses the Boundary Fault that separates granite body and an alluvium basin, a strong acoustic impedance boundary that scatters seismic energy into S-waves and coda. The data were processed with traditional seismic reflection processing methods that include filtering, deconvolution, and stacking. The stack will be used to extract the location of the splays of the Boundary Fault and provide geologic constraints to the modeling and simulation teams within the SPE project.

  4. Seismic Velocity and Elastic Properties of Plate Boundary Faults

    NASA Astrophysics Data System (ADS)

    Jeppson, Tamara N.

    The elastic properties of fault zone rock at depth play a key role in rupture nucleation, propagation, and the magnitude of fault slip. Materials that lie within major plate boundary fault zones often have very different material properties than standard crustal rock values. In order to understand the mechanics of faulting at plate boundaries, we need to both measure these properties and understand how they govern the behavior of different types of faults. Mature fault zones tend to be identified in large-scale geophysical field studies as zones with low seismic velocity and/or electrical resistivity. These anomalous properties are related to two important mechanisms: (1) mechanical or diagenetic alteration of the rock materials and/or (2) pore fluid pressure and stress effects. However, in remotely-sensed and large-length-scale data it is difficult to determine which of these mechanisms are affecting the measured properties. The objective of this dissertation research is to characterize the seismic velocity and elastic properties of fault zone rocks at a range of scales, with a focus on understanding why the fault zone properties are different from those of the surrounding rock and the potential effects on earthquake rupture and fault slip. To do this I performed ultrasonic velocity experiments under elevated pressure conditions on drill core and outcrops samples from three plate boundary fault zones: the San Andreas Fault, California, USA; the Alpine Fault, South Island, New Zealand; and the Japan Trench megathrust, Japan. Additionally, I compared laboratory measurements to sonic log and large-scale seismic data to examine the scale-dependence of the measured properties. The results of this study provide the most comprehensive characterization of the seismic velocities and elastic properties of fault zone rocks currently available. My work shows that fault zone rocks at mature plate boundary faults tend to be significantly more compliant than surrounding crustal

  5. Seismicity and Seismic Hazard along the Western part of the Eurasia-Nubia plate boundary

    NASA Astrophysics Data System (ADS)

    Bezzeghoud, Mourad; Fontiela, João; Ferrão, Celia; Borges, José Fernando; Caldeira, Bento; Dib, Assia; Ousadou, Farida

    2016-04-01

    The seismic phenomenon is the most damaging natural hazard known in the Mediterranean area. The western part of the Eurasia-Nubia plate boundary extends from the Azores to the Mediterranean region. The oceanic part of the plate boundary is well delimited from the Azores Islands, along the Azores-Gibraltar fault to approximately 12°W (west of the Strait of Gibraltar). From 12°W to 3.5°E, including the Iberia-Nubia region and extending to the western part of Algeria, the boundary is more diffuse and forms a wider area of deformation. The boundary between the Iberia and Nubia plates is the most complex part of the margin. This region corresponds to the transition from an oceanic boundary to a continental boundary, where Iberia and Nubia collide. Although most earthquakes along this plate boundary are shallow and generally have magnitudes less than 5.5, there have been several high-magnitude events. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss and considerable economic damage to the region. From 1920 to present, three earthquakes with magnitudes of about 8.0 (Mw 8.2, 25 November 1941; Ms 8.0, 25 February 1969; and Mw 7.9, 26 May 1975) occurred in the oceanic region, and four earthquakes with magnitudes of about 7.0 (Mw 7.1, 8 May 1939, Santa Maria Island and Mw 7.1, January 1980, Terceira and Graciosa Islands, both in the Azores; Ms 7.1, 20 May 1931, Azores-Gibraltar fracture zone; and Mw 7.3, 10 October 1980, El Asnam, Algeria) occurred along the western part of the Eurasia-Nubia plate boundary. In general, large earthquakes (M ≥7) occur within the oceanic region, with the exception of the El Asnam (Algeria) earthquakes. Some of these events caused extensive damage. The 1755 Lisbon earthquake (˜Mw 9) on the Portugal Atlantic margin, about 200 km W-SW of Cape St. Vincent, was followed by a tsunami and fires that caused the near-total destruction of Lisbon and adjacent areas. Estimates of the death toll in Lisbon alone (~70

  6. Sensitivities Kernels of Seismic Traveltimes and Amplitudes for Quality Factor and Boundary Topography

    NASA Astrophysics Data System (ADS)

    Hsieh, M.; Zhao, L.; Ma, K.

    2010-12-01

    Finite-frequency approach enables seismic tomography to fully utilize the spatial and temporal distributions of the seismic wavefield to improve resolution. In achieving this goal, one of the most important tasks is to compute efficiently and accurately the (Fréchet) sensitivity kernels of finite-frequency seismic observables such as traveltime and amplitude to the perturbations of model parameters. In scattering-integral approach, the Fréchet kernels are expressed in terms of the strain Green tensors (SGTs), and a pre-established SGT database is necessary to achieve practical efficiency for a three-dimensional reference model in which the SGTs must be calculated numerically. Methods for computing Fréchet kernels for seismic velocities have long been established. In this study, we develop algorithms based on the finite-difference method for calculating Fréchet kernels for the quality factor Qμ and seismic boundary topography. Kernels for the quality factor can be obtained in a way similar to those for seismic velocities with the help of the Hilbert transform. The effects of seismic velocities and quality factor on either traveltime or amplitude are coupled. Kernels for boundary topography involve spatial gradient of the SGTs and they also exhibit interesting finite-frequency characteristics. Examples of quality factor and boundary topography kernels will be shown for a realistic model for the Taiwan region with three-dimensional velocity variation as well as surface and Moho discontinuity topography.

  7. Reconciling deep seismic refraction and reflection data from the grenvillian-appalachian boundary in western New England

    USGS Publications Warehouse

    Hughes, S.; Luetgert, J.H.; Christensen, N.I.

    1993-01-01

    The Grenvillian-Appalachian boundary is characterized by pervasive mylonitic deformation and retrograde alteration of a suite of imbricated allochthonous and parautochthonous gneisses that were thrust upon the Grenvillian continental margin during the lower Paleozoic. Seismic reflection profiling across this structural boundary zone reveals prominent dipping reflectors interpreted as overthrust basement slices (parautochthons) of the Green Mountain Anticlinorium. In contrast, a seismic refraction study of the Grenvillian-Appalachian boundary reveals a sub-horizontally layered seismic velocity model that is difficult to reconcile with the pronounced sub-vertical structures observed in the Green mountains. A suite of rock samples was collected from the Green Mountain Anticlinorium and measured at high pressures in the laboratory to determine the seismic properties of these allochthonous and parautochthonous gneisses. The laboratory-measured seismic velocities agree favorably with the modelled velocity structure across the Grenvillian-Appalachian boundary suggesting that the rock samples are reliable indicators of the rock mass as whole. Samples of the parautochthonous Grenvillian basement exposed in the Green Mountains have lower velocities, by about 0.5 km/s, than lithologically equivalent units exposed in the eastern Adirondack Highlands. Velocity reduction in the Green Mountain parautochthons can be accounted for by retrograde metamorphic alteration (hydration) of the paragneisses. Seismic anisotropies, ranging from 2 to 12%, in the mylonitized Green Mountain paragneisses may also contribute to the observation of lower seismic velocities, where the direction of ray propagation is normal to the foliation. The velocity properties of the Green Mountain paragneisses are thus insufficiently different from the mantling Appalachian allochthons to permit their resolution by the Ontario-New York-New England seismic refraction profile. ?? 1993.

  8. Interferometric Seismic Sources on the Core Mantle Boundary Revealed by Seismic Coda Crosscorrelation

    NASA Astrophysics Data System (ADS)

    Pham, T. S.; Tkalcic, H.; Sambridge, M.

    2017-12-01

    The crosscorrelation of earthquake coda can be used to extract seismic body waves which are sensitive to deep Earth interior. The retrieved peaks in crosscorrelation of two seismic records are commonly interpreted as seismic phases that originate at a point source collocated with the first recorder (Huygens-Fresnel principle), reflected upward from prominent underground reflectors and reaching the second recorder. From the time shift of these peaks measured at different interstation distances, new travel time curves can be constructed. This study focuses on a previously unexplained interferometric phase (named temporarily a ghost or "G phase") observed in crosscorrelogram stack sections utilizing seismic coda. In particular, we deploy waveforms recorded by two regional seismic networks, one in Australia and another in Alaska. We show that the G phase cannot be explained by as a reflection. Moreover, we demonstrate that the G phase is explained through the principle of energy partitioning, and specifically, conversions from compressional to shear motions at the core-mantle boundary (CMB). This can be thought of in terms of a continuous distribution of Huygens sources across the CMB that are "activated" in long-range wavefield coda following significant earthquakes. The newly explained phase is renamed to cPS, to indicate a CMB origin and the P to S conversion. This mechanism explains a range of newly observed global interferometric phases that can be used in combination with existing phases to constrain Earth structure.

  9. Seismic images of a Grenvillian terrane boundary

    USGS Publications Warehouse

    Milkereit, B.; Forsyth, D. A.; Green, A.G.; Davidson, A.; Hanmer, S.; Hutchinson, Deborah R.; Hinze, W. J.; Mereu, R.F.

    1992-01-01

    A series of gently dipping reflection zones extending to mid-crustal depths is recorded by seismic data from Lakes Ontario and Erie. These prominent reflection zones define a broad complex of southeast-dipping ductile thrust faults in the interior of the Grenville orogen. One major reflection zone provides the first image of a proposed Grenvillian suture—the listric boundary zone between allochthonous terranes of the Central Gneiss and Central Metasedimentary belts. Curvilinear bands of reflections that may represent "ramp folds" and "ramp anticlines" that originally formed in a deep crustal-scale duplex abut several faults. Vertical stacking of some curvilinear features suggests coeval or later out-of-sequence faulting of imbricated and folded thrust sheets. Grenvillian structure reflections are overlain by a thin, wedge-shaped package of shallow-dipping reflections that probably originates from sediments deposited in a local half graben developed during a period of post-Grenville extension. This is the first seismic evidence for such extension in this region, which could have occurred during terminal collapse of the Grenville orogen, or could have marked the beginning of pre-Appalachian continental rifting.

  10. Seismic waveform sensitivity to global boundary topography

    NASA Astrophysics Data System (ADS)

    Colombi, Andrea; Nissen-Meyer, Tarje; Boschi, Lapo; Giardini, Domenico

    2012-09-01

    We investigate the implications of lateral variations in the topography of global seismic discontinuities, in the framework of high-resolution forward modelling and seismic imaging. We run 3-D wave-propagation simulations accurate at periods of 10 s and longer, with Earth models including core-mantle boundary topography anomalies of ˜1000 km spatial wavelength and up to 10 km height. We obtain very different waveform signatures for PcP (reflected) and Pdiff (diffracted) phases, supporting the theoretical expectation that the latter are sensitive primarily to large-scale structure, whereas the former only to small scale, where large and small are relative to the frequency. PcP at 10 s seems to be well suited to map such a small-scale perturbation, whereas Pdiff at the same frequency carries faint signatures that do not allow any tomographic reconstruction. Only at higher frequency, the signature becomes stronger. We present a new algorithm to compute sensitivity kernels relating seismic traveltimes (measured by cross-correlation of observed and theoretical seismograms) to the topography of seismic discontinuities at any depth in the Earth using full 3-D wave propagation. Calculation of accurate finite-frequency sensitivity kernels is notoriously expensive, but we reduce computational costs drastically by limiting ourselves to spherically symmetric reference models, and exploiting the axial symmetry of the resulting propagating wavefield that collapses to a 2-D numerical domain. We compute and analyse a suite of kernels for upper and lower mantle discontinuities that can be used for finite-frequency waveform inversion. The PcP and Pdiff sensitivity footprints are in good agreement with the result obtained cross-correlating perturbed and unperturbed seismogram, validating our approach against full 3-D modelling to invert for such structures.

  11. The nature of crustal boundaries: combined interpretation of wide-angle and normal-incidence seismic data

    NASA Astrophysics Data System (ADS)

    Long, Roger E.; Matthews, Patricia A.; Graham, Daniel P.

    1994-04-01

    After a few seconds two-way traveltime, normal-incidence seismic reflection sections are composed mainly of assemblages of short reflections. Very rarely are seen continuous reflections that might correspond to the Moho or a mid-crustal discontinuity. The inferred continuity of these boundaries has traditionally come from refraction seismology. There is now a body of high quality, coincident wide-angle and normal-incidence seismic data that have been recorded with 50-100 m shot spacing and with high frequency sources (e.g. MOBIL, BABEL). The complexity and characteristics of the wide-angle arrivals seen on these data suggest that they do not originate from continuous boundaries. It is suggested that these arrivals are reflections from the same assemblage of short length reflectors that are responsible for normal-incidence reflections. Seismic velocities below the middle crust may (1) change corresponding to normal-incidence reflectivity, or (2) generally increase with depth with localised sills or lens structures of different velocity accounting for the observed reflections. Wide-angle arrivals that have traditionally been identified as reflections from crustal boundaries (e.g. the mid-crust and Moho) and which were considered indicative of a sharp velocity discontinuity from continuous boundaries, may instead result from a concentration of lamellae.

  12. Unsuccessful initial search for a midmantle chemical boundary with seismic arrays

    USGS Publications Warehouse

    Vidale, J.E.; Schubert, G.; Earle, P.S.

    2001-01-01

    Compositional layering of the midmantle has been proposed to account for seismic and geochemical patterns [van der Hilst and Karason, 1999], and inferred radiogenic heat source concentrations [Kellogg et al., 1999]. Compositional layering would require thermal boundary layers both above and below an interface. We construct a minimal 1-D model of a mid-mantle boundary consistent with the observed nearly adiabatic compressional velocity structure [Dziewonksi and Anderson, 1981] and the proposed high heat flow from the lower mantle [Albarede and van der Hilst, 1999; Kellogg et al., 1999]. Ray tracing and reflectivity synthetic seismograms show that a distinct triplication is predicted for short-period P waves. Although topography on a boundary would cause uncertainty in the strength and the range of the triplication, many clear observations would be expected. We examine data from the US West Coast regional networks in the most likely distance range of 60?? to 70?? for a 1770-km-depth boundary, and find no evidence for P wave triplications.

  13. Seismic intrusion detector system

    DOEpatents

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  14. Estimation of coefficients and boundary parameters in hyperbolic systems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Murphy, K. A.

    1984-01-01

    Semi-discrete Galerkin approximation schemes are considered in connection with inverse problems for the estimation of spatially varying coefficients and boundary condition parameters in second order hyperbolic systems typical of those arising in 1-D surface seismic problems. Spline based algorithms are proposed for which theoretical convergence results along with a representative sample of numerical findings are given.

  15. A seismic gap along an accreting plate boundary : Example of the Djibouti Ridge, Afar, East Africa

    NASA Astrophysics Data System (ADS)

    Ruegg, Jean-Claude; Lépine, Jean-Claude

    1983-05-01

    A segment of the Gulf of Tadjoura (Djibouti, East-Africa) accreting plate boundary, shows a period of quiescence in the seismic activity since 1974. This segment corresponds to the extension area of the aftershock activity that has occured after a cluster of magnitude 5.5 earthquakes in April 1973. From this example we propose that the seismic gap concept can be extended to moderate earthquakes occuring at extensional plate boundaries. The magnitude of the largest earthquakes at the spreading axis is limited by the size of the rupture length and by the strength of the brittle lithosphere. In the case of the Djibouti ridge recurrence time of 10-20 years are found for earthquakes of about M =6.

  16. On the likelihood of post-perovskite near the core-mantle boundary: A statistical interpretation of seismic observations

    NASA Astrophysics Data System (ADS)

    Cobden, Laura; Mosca, Ilaria; Trampert, Jeannot; Ritsema, Jeroen

    2012-11-01

    Recent experimental studies indicate that perovskite, the dominant lower mantle mineral, undergoes a phase change to post-perovskite at high pressures. However, it has been unclear whether this transition occurs within the Earth's mantle, due to uncertainties in both the thermochemical state of the lowermost mantle and the pressure-temperature conditions of the phase boundary. In this study we compare the relative fit to global seismic data of mantle models which do and do not contain post-perovskite, following a statistical approach. Our data comprise more than 10,000 Pdiff and Sdiff travel-times, global in coverage, from which we extract the global distributions of dln VS and dln VP near the core-mantle boundary (CMB). These distributions are sensitive to the underlying lateral variations in mineralogy and temperature even after seismic uncertainties are taken into account, and are ideally suited for investigating the likelihood of the presence of post-perovskite. A post-perovskite-bearing CMB region provides a significantly closer fit to the seismic data than a post-perovskite-free CMB region on both a global and regional scale. These results complement previous local seismic reflection studies, which have shown a consistency between seismic observations and the physical properties of post-perovskite inside the deep Earth.

  17. Eastern boundary of the Siletz terrane in the Puget Lowland from gravity and magnetic modeling with implications for seismic hazard analysis

    NASA Astrophysics Data System (ADS)

    Anderson, M. L.; Blakely, R. J.; Wells, R. E.; Dragovich, J.

    2011-12-01

    The forearc of the Cascadia subduction zone in coastal Oregon and Washington is largely composed of a 15-30 km-thick stack of basalt flows comprising the Crescent Formation (WA) and Siletz River Volcanics (OR), and collectively termed the Siletz terrane. We are developing 3-D structural maps of the Puget Lowland to distinguish older and currently active structures for seismic hazard analysis. The boundaries of the Siletz terrane in particular may strongly influence crustal rheology and neotectonic structures of the region. Careful analysis of the areal extent of this terrane will also facilitate more accurate interpretation of seismic data and gravity anomalies, which will help define the extent and shape of overlying basins. Absence of extensive outcrop in the Lowland and a widespread veneer of Quaternary deposits require extensive subsurface geophysical studies to establish Lowland-wide crustal structure. Previous studies have used active seismic surveys and interpretation of existing industry seismic data, with several studies using gravity and magnetic data or passive-source tomography support. However, steeply dipping boundaries in the mid-crust are difficult targets for seismic study. We need to independently discriminate between potential models established by seismic data using gravity and magnetic datasets. In the Puget Lowland the Siletz is a region of high seismic wave speed, density, and magnetic susceptibility, and therefore its mid-crustal boundaries are good targets for definition by gravity and magnetic data. We present interpretations of gravity and magnetic anomalies for the Puget Lowland region that together establish the most likely position and structure of the Crescent Formation boundary in the mid-upper crust. Well-constrained physical properties of Crescent basalts inform our aeromagnetic map interpretation and give us baseline values for constructing three two-dimensional models by simultaneous forward modeling of aeromagnetic and isostatic

  18. Tectonics of the Scotia-Antarctica plate boundary constrained from seismic and seismological data

    NASA Astrophysics Data System (ADS)

    Civile, D.; Lodolo, E.; Vuan, A.; Loreto, M. F.

    2012-07-01

    The plate boundary between the Scotia and Antarctic plates runs along the broadly E-W trending South Scotia Ridge. It is a mainly transcurrent margin that juxtaposes thinned continental and transitional crust elements with restricted oceanic basins and deep troughs. Seismic profiles and regional-scale seismological constraints are used to define the peculiarities of the crustal structures in and around the southern Scotia Sea, and focal solutions from recent earthquakes help to understand the present-day geodynamic setting. The northern edge of the western South Scotia Ridge is marked by a sub-vertical, left-lateral master fault. Locally, a narrow wedge of accreted sediments is present at the base of the slope. This segment represents the boundary between the Scotia plate and the independent South Shetland continental block. Along the northern margin of the South Orkney microcontinent, the largest fragment of the South Scotia Ridge, an accretionary prism is present at the base of the slope, which was possibly created by the eastward drift of the South Orkney microcontinent and the consequent subduction of the transitional crust present to the north. East of the South Orkney microcontinent, the physiography and structure of the plate boundary are less constrained. Here the tectonic regime exhibits mainly strike-slip behavior with some grade of extensional component, and the plate boundary is segmented by a series of NNW-SSE trending release zones which favored the fragmentation and dispersion of the crustal blocks. Seismic data have also identified, along the north-western edge of the South Scotia Ridge, an elevated region - the Ona Platform - which can be considered, along with the Terror Rise, as the conjugate margin of the Tierra del Fuego, before the Drake Passage opening. We propose here an evolutionary sketch for the plate boundary (from the Late Oligocene to the present) encompassing the segment from the Elephant Island platform to the Herdman Bank.

  19. An effective absorbing layer for the boundary condition in acoustic seismic wave simulation

    NASA Astrophysics Data System (ADS)

    Yao, Gang; da Silva, Nuno V.; Wu, Di

    2018-04-01

    Efficient numerical simulation of seismic wavefields generally involves truncating the Earth model in order to keep computing time and memory requirements down. Absorbing boundary conditions, therefore, are applied to remove the boundary reflections caused by this truncation, thereby allowing for accurate modeling of wavefields. In this paper, we derive an effective absorbing boundary condition for both acoustic and elastic wave simulation, through the simplification of the damping term of the split perfectly matched layer (SPML) boundary condition. This new boundary condition is accurate, cost-effective, and easily implemented, especially for high-performance computing. Stability analysis shows that this boundary condition is effectively as stable as normal (non-absorbing) wave equations for explicit time-stepping finite differences. We found that for full-waveform inversion (FWI), the strengths of the effective absorbing layer—a reduction of the computational and memory cost coupled with a simplistic implementation—significantly outweighs the limitation of incomplete absorption of outgoing waves relative to the SPML. More importantly, we demonstrate that this limitation can easily be overcome through the use of two strategies in FWI, namely variable cell size and model extension thereby fully compensating for the imperfectness of the proposed absorbing boundary condition.

  20. Imaging the crustal structure of Haiti's transpressional fault system using seismicity and tomography

    NASA Astrophysics Data System (ADS)

    Possee, D.; Keir, D.; Harmon, N.; Rychert, C.; Rolandone, F.; Leroy, S. D.; Stuart, G. W.; Calais, E.; Boisson, D.; Ulysse, S. M. J.; Guerrier, K.; Momplaisir, R.; Prepetit, C.

    2017-12-01

    Oblique convergence of the Caribbean and North American plates has partitioned strain across an extensive transpressional fault system that bisects Haiti. Most recently the 2010, MW7.0 earthquake ruptured multiple thrust faults in southern Haiti. However, while the rupture mechanism has been well studied, how these faults are segmented and link to deformation across the plate boundary is still debated. Understanding the link between strain accumulation and faulting in Haiti is also key to future modelling of seismic hazards. To assess seismic activity and fault structures we used data from 31 broadband seismic stations deployed on Haiti for 16-months. Local earthquakes were recorded and hypocentre locations determined using a 1D velocity model. A high-quality subset of the data was then inverted using travel-time tomography for relocated hypocentres and 2D images of Vp and Vp/Vs crustal structure. Earthquake locations reveal two clusters of seismic activity, the first delineates faults associated with the 2010 earthquake and the second shows activity 100km further east along a thrust fault north of Lake Enriquillo (Dominican Republic). The velocity models show large variations in seismic properties across the plate boundary; shallow low-velocity zones with a 5-8% decrease in Vp and high Vp/Vs ratios of 1.85-1.95 correspond to sedimentary basins that form the low-lying terrain on Haiti. We also image a region with a 4-5% decrease in Vp and an increased Vp/Vs ratio of 1.80-1.85 dipping south to a depth of 20km beneath southern Haiti. This feature matches the location of a major thrust fault and suggests a substantial damage zone around this fault. Beneath northern Haiti a transition to lower Vp/Vs values of 1.70-1.75 reflects a compositional change from mafic facies such as the Caribbean large igneous province in the south, to arc magmatic facies associated with the Greater Antilles arc in the north. Our seismic images are consistent with the fault system across

  1. Oceanic broad multifault transform plate boundaries

    NASA Astrophysics Data System (ADS)

    Ligi, Marco; Bonatti, Enrico; Gasperini, Luca; Poliakov, Alexei N. B.

    2002-01-01

    Oceanic transform plate boundaries consist of a single, narrow (a few kilometers wide) strike-slip seismic zone offsetting two mid-ocean ridge segments. However, we define here a new class of oceanic transform boundaries, with broad complex multifault zones of deformation, similar to some continental strike-slip systems. Examples are the 750-km- long, 120-km-wide Andrew Bain transform on the Southwest Indian Ridge, and the Romanche transform, where the Mid-Atlantic Ridge is offset by a lens-shaped, ˜900-km- long, ˜100-km-wide sliver of deformed lithosphere bound by two major transform valleys. One of the valleys is seismically highly active and constitutes the present-day principal transform boundary. However, strike-slip seismic events also occur in the second valley and elsewhere in the deformed zone. Some of these events may be triggered by earthquakes from the principal boundary. Numerical modeling predicts the development of wide multiple transform boundaries when the age offset is above a threshold value of ˜30 m.y., i.e., in extra-long (>500 km) slow-slip transforms. Multiple boundaries develop so that strike-slip ruptures avoid very thick and strong lithosphere.

  2. Correlation of offshore seismic profiles with onshore New Jersey Miocene sediments

    USGS Publications Warehouse

    Monteverde, D.H.; Miller, K.G.; Mountain, Gregory S.

    2000-01-01

    The New Jersey passive continental margin records the interaction of sequences and sea-level, although previous studies linking seismically defined sequences, borehole control, and global ??18O records were hindered by a seismic data gap on the inner-shelf. We describe new seismic data from the innermost New Jersey shelf that tie offshore seismic stratigraphy directly to onshore boreholes. These data link the onshore boreholes to existing seismic grids across the outer margin and to boreholes on the continental slope. Surfaces defined by age; facies, and log signature in the onshore boreholes at the base of sequences Kw2b, Kw2a, Kw1c, and Kw0 are now tied to seismic sequence boundaries m5s, m5.2s, m5.4s, and m6s, respectively, defined beneath the inner shelf. Sequence boundaries recognized in onshore boreholes and inner shelf seismic profiles apparently correlate with reflections m5, m5.2, m5.4, and m6, respectively, that were dated at slope boreholes during ODP Leg 150. We now recognize an additional sequence boundary beneath the shelf that we name m5.5s and correlate to the base of the onshore sequence Kw1b. The new seismic data image prograding Oligocene clinoforms beneath the inner shelf, consistent with the results from onshore boreholes. A land-based seismic profile crossing the Island Beach borehole reveals reflector geometries that we tie to Lower Miocene litho- and bio-facies in this borehole. These land-based seismic profiles image well-defined sequence boundaries, onlap and downlap truncations that correlate to Transgressive Systems Tracts (TST) and Highstand Systems Tracts (HST) identified in boreholes. Preliminary analysis of CH0698 data continues these system tract delineations across the inner shelf The CH0698 seismic profiles tie seismically defined sequence boundaries with sequences identified by lithiologic and paleontologic criteria. Both can now be related to global ??18O increases and attendant glacioeustatic lowerings. This integration of core

  3. SHAKING TABLE TEST AND EFFECTIVE STRESS ANALYSIS ON SEISMIC PERFORMANCE WITH SEISMIC ISOLATION RUBBER TO THE INTERMEDIATE PART OF PILE FOUNDATION IN LIQUEFACTION

    NASA Astrophysics Data System (ADS)

    Uno, Kunihiko; Otsuka, Hisanori; Mitou, Masaaki

    The pile foundation is heavily damaged at the boundary division of the ground types, liquefied ground and non-liquefied ground, during an earthquake and there is a possibility of the collapse of the piles. In this study, we conduct a shaking table test and effective stress analysis of the influence of soil liquefaction and the seismic inertial force exerted on the pile foundation. When the intermediate part of the pile, there is at the boundary division, is subjected to section force, this part increases in size as compared to the pile head in certain instances. Further, we develop a seismic resistance method for a pile foundation in liquefaction using seismic isolation rubber and it is shown the middle part seismic isolation system is very effective.

  4. Seismic evidence of the lithosphere-asthenosphere boundary beneath Izu-Bonin area

    NASA Astrophysics Data System (ADS)

    Cui, H.; Gao, Y.; Zhou, Y.

    2016-12-01

    The lithosphere-asthenosphere boundary (LAB), separating the rigid lithosphere and the ductile asthenosphere layers, is the seismic discontinuity with the negative velocity contrast of the Earth's interior [Fischer et al., 2010]. The LAB has been also termed the Gutenberg (G) discontinuity that defines the top of the low velocity zone in the upper mantle [Gutenberg, 1959; Revenaugh and Jordan, 1991]. The seismic velocity, viscosity, resistivity and other physical parameters change rapidly with the depths across the boundary [Eaton et al., 2009]. Seismic detections on the LAB in subduction zone regions are of great help to understand the interactions between the lithosphere and asthenosphere layers and the geodynamic processes related with the slab subductions. In this study, the vertical broadband waveforms are collected from three deep earthquake events occurring from 2000 to 2014 with the focal depths of 400 600 km beneath the Izu-Bonin area. The waveform data is processed with the linear slant stack method [Zang and Zhou, 2002] to obtain the vespagrams in the relative travel-time to slowness domain and the stacked waveforms. The sP precursors reflected on the LAB (sLABP), which have the negative polarities with the amplitude ratios of 0.17 0.21 relative to the sP phases, are successfully extracted. Based on the one-dimensional modified velocity model (IASP91-IB), we obtain the distributions for six reflected points of the sLABP phases near the source region. Our results reveal that the LAB depths range between 58 and 65 km beneath the Izu-Bonin Arc, with the average depth of 62 km and the small topography of 7 km. Compared with the results of the tectonic stable areas in Philippine Sea [Kawakatsu et al., 2009; Kumar and Kawakatsu, 2011], the oceanic lithosphere beneath the Izu-Bonin Arc shows the obvious thinning phenomena. We infer that the lithospheric thinning is closely related with the partial melting, which is caused by the volatiles continuously released

  5. Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

    NASA Astrophysics Data System (ADS)

    Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

    2017-12-01

    On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP

  6. Seismic experiment ross ice shelf 1990/91: Characteristics of the seismic reflection data

    USGS Publications Warehouse

    1993-01-01

    The Transantarctic Mountains, with a length of 3000-3500 km and elevations of up to 4500 m, are one of the major Cenozoic mountain ranges in the world and are by far the most striking example of rift-shoulder mountains. Over the 1990-1991 austral summer Seismic Experiment Ross Ice Shelf (SERIS) was carried out across the Transantarctic Mountain front, between latitudes 82 degrees to 83 degrees S, in order to investigate the transition zone between the rifted area of the Ross Embayment and the uplifted Transantarctic Mountains. This experiment involved a 140 km long seismic reflection profile together with a 96 km long coincident wide-angle reflection/refraction profile. Gravity and relative elevation (using barometric pressure) were also measured along the profile. The primary purpose was to examine the boundary between the rift system and the uplifted rift margin (represented by the Transantarctic Mountains) using modern multi-channel crustal reflection/refraction techniques. The results provide insight into crustal structure across the plate boundary. SERIS also represented one of the first large-scale and modern multi-channel seismic experiments in the remote interior of Antarctica. As such, the project was designed to test different seismic acquisition techniques which will be involved in future seismic exploration of the continent. This report describes the results from the analysis of the acquisition tests as well as detailing some of the characteristics of the reflection seismic data. (auths.)

  7. Simulating Seismic Wave Propagation in Viscoelastic Media with an Irregular Free Surface

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobo; Chen, Jingyi; Zhao, Zhencong; Lan, Haiqiang; Liu, Fuping

    2018-05-01

    In seismic numerical simulations of wave propagation, it is very important for us to consider surface topography and attenuation, which both have large effects (e.g., wave diffractions, conversion, amplitude/phase change) on seismic imaging and inversion. An irregular free surface provides significant information for interpreting the characteristics of seismic wave propagation in areas with rugged or rapidly varying topography, and viscoelastic media are a better representation of the earth's properties than acoustic/elastic media. In this study, we develop an approach for seismic wavefield simulation in 2D viscoelastic isotropic media with an irregular free surface. Based on the boundary-conforming grid method, the 2D time-domain second-order viscoelastic isotropic equations and irregular free surface boundary conditions are transferred from a Cartesian coordinate system to a curvilinear coordinate system. Finite difference operators with second-order accuracy are applied to discretize the viscoelastic wave equations and the irregular free surface in the curvilinear coordinate system. In addition, we select the convolutional perfectly matched layer boundary condition in order to effectively suppress artificial reflections from the edges of the model. The snapshot and seismogram results from numerical tests show that our algorithm successfully simulates seismic wavefields (e.g., P-wave, Rayleigh wave and converted waves) in viscoelastic isotropic media with an irregular free surface.

  8. Induced Seismicity Monitoring System

    NASA Astrophysics Data System (ADS)

    Taylor, S. R.; Jarpe, S.; Harben, P.

    2014-12-01

    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  9. The Caribbean-South American plate boundary at 65°W: Results from wide-angle seismic data

    NASA Astrophysics Data System (ADS)

    Bezada, M. J.; Magnani, M. B.; Zelt, C. A.; Schmitz, M.; Levander, A.

    2010-08-01

    We present the results of the analysis of new wide-angle seismic data across the Caribbean-South American plate boundary in eastern Venezuela at about 65°W. The ˜500 km long profile crosses the boundary in one of the few regions dominated by extensional structures, as most of the southeastern Caribbean margin is characterized by the presence of fold and thrust belts. A combination of first-arrival traveltime inversion and simultaneous inversion of PmP and Pn arrivals was used to develop a P wave velocity model of the crust and the uppermost mantle. At the main strike-slip fault system, we image the Cariaco Trough, a major pull-apart basin along the plate boundary. The crust under the Southern Caribbean Deformed Belt exhibits a thickness of ˜15 km, suggesting that the Caribbean Large Igneous Province extends to this part of the Caribbean plate. The velocity structures of basement highs and offshore sedimentary basins imaged by the profile are comparable to those of features found in other parts of the margin, suggesting similarities in their tectonic history. We do not image an abrupt change in Moho depth or velocity structure across the main strike-slip system, as has been observed elsewhere along the margin. It is possible that a terrane of Caribbean island arc origin was accreted to South America at this site and was subsequently bisected by the strike-slip fault system. The crust under the continental portion of the profile is thinner than observed elsewhere along the margin, possibly as a result of thinning during Jurassic rifting.

  10. Geographic boundary of the “Pacific Anomaly” near the Earth’s core-mantle boundary

    NASA Astrophysics Data System (ADS)

    He, Y.; Wen, L.

    2009-12-01

    Seismic tomography have revealed a broad, seismically low velocity anomaly in the Earth’s lower mantle beneath the Pacific (we term it the “Pacific Anomaly”), surrounded by the circum-Pacific high velocity zone. Here, we determine geographical boundary and average shear velocity structure of the Pacific Anomaly near the core-mantle boundary based on travel time analysis of ScSH-SH and ScS2-SS phases. We further constrain the detailed structure of the transition from the base of the Pacific Anomaly to the northern high velocity zone along two perpendicular cross sections on the basis of forward waveform modeling of the seismic data. Two cross-sections include one great arc across the Anomaly from New Zealand to Alaska and another from Solomon Islands to North America. Our seismic data are collected from those recorded in the China National Digital Seismographic Network, and many permanent and temporal arrays from the Incorporated Research Institutions for Seismology. The observed ScS-SH and ScS2-SS differential travel time residuals allow the entire geographic boundary of the anomaly to be clearly defined. The seismic data suggest that the average shear velocity reduction inside the anomaly reaches -5% in the lowermost 300 km of the mantle. Waveform analysis of the seismic data sampling the edge of the anomaly further validates the model of the boundary previously deduced by differential-travel-time-residual data, and suggests that the northern boundary is characterized by a shear velocity model with the low-velocity region accompanied by a high velocity structure.

  11. Modeling the Geometry of Plate Boundary and Seismic Structure in the Southern Ryukyu Trench Subduction Zone, Japan, Using Amphibious Seismic Observations

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Takahashi, T.; Ishihara, Y.; Kaiho, Y.; Arai, R.; Obana, K.; Nakanishi, A.; Miura, S.; Kodaira, S.; Kaneda, Y.

    2018-02-01

    Here we present the new model, the geometry of the subducted Philippine Sea Plate interface beneath the southern Ryukyu Trench subduction zone, estimated from seismic tomography and focal mechanism estimation by using passive and active data from a temporary amphibious seismic network and permanent land stations. Using relocated low-angle thrust-type earthquakes, repeating earthquakes, and structural information, we constrained the geometry of plate boundary from the trench axis to a 60 km depth with uncertainties of less than 5 km. The estimated plate geometry model exhibited large variation, including a pronounced convex structure that may be evidence of a subducted seamount in the eastern portion of study area, whereas the western part appeared smooth. We also found that the active earthquake region near the plate boundary, defined by the distance from our plate geometry model, was clearly separated from the area dominated by short-term slow-slip events (SSEs). The oceanic crust just beneath the SSE-dominant region, the western part of the study area, showed high Vp/Vs ratios (>1.8), whereas the eastern side showed moderate or low Vp/Vs (<1.75). We interpreted this as an indication that high fluid pressures near the surface of the slab are contributing to the SSE activities. Within the toe of the mantle wedge, P and S wave velocities (<7.5 and <4.2 km/s, respectively) lower than those observed through normal mantle peridotite might suggest that some portions of the mantle may be at least 40% serpentinized.

  12. Academia vs Industry: vanishing boundaries between global earthquake seismology and exploration seismics.

    NASA Astrophysics Data System (ADS)

    van der Hilst, R. D.

    2011-12-01

    Global seismology and exploration seismics have long lived in parallel universes, with little cross-fertilization of methodologies and with interaction between the associated communities often limited to company recruitment of students. Fortunately, this traditional separation of technology and people has begun to disappear. This is driven not only by continuing demands for human and financial resources (for companies and academia, respectively) but increasingly also by overlapping intellectual interest. First, 'waves are waves' (that is, the fundamental physics - and math to describe/handle it - is scale invariant) and many artificial boundaries are being removed by use of better wave theory, faster computers, and new data acquisition paradigms. For example, the development of dense sensor arrays (in USA, Europe, Asia - mostly China and Japan) is increasing the attraction (and need) of industry-style interrogation of massive data sets. Examples include large scale seismic exploration of Earth's deep interior with inverse scattering of teleseismic wavefields (e.g., Van der Hilst et al., Science, 2007). On the other hand, reservoir exploration and production benefits from expertise in earthquake seismology, both for better characterization of reservoirs and their overburden and for (induced) micro-earthquake analysis. Passive source methods (including but not restricted to ambient noise tomography) are providing new, economic opportunities for velocity analysis and monitoring, and studies of (micro)seismicity (e.g., source location, parameters, and moment tensor) allow in situ stress determination, tomographic velocity analysis with natural sources in the reservoir, and 4D monitoring (e.g., for hydrocarbon production, carbon sequestration, enhanced geothermal systems, and unconventional gas production). Second, the gap between the frequency ranges traditionally considered by both communities is being bridged by better theory, new sensor technology, and through

  13. Seismic Characterization of Oceanic Water Masses, Water Mass Boundaries, and Mesoscale Eddies SE of New Zealand

    NASA Astrophysics Data System (ADS)

    Gorman, Andrew R.; Smillie, Matthew W.; Cooper, Joanna K.; Bowman, M. Hamish; Vennell, Ross; Holbrook, W. Steven; Frew, Russell

    2018-02-01

    The Subtropical and Subantarctic Fronts, which separate Subtropical, Subantarctic, and Antarctic Intermediate Waters, are diverted to the south of New Zealand by the submerged continental landmass of Zealandia. In the upper ocean of this region, large volumes of dissolved or suspended material are intermittently transported across the Subtropical Front; however, the mechanisms of such transport processes are enigmatic. Understanding these oceanic boundaries in three dimensions generally depends on measurements collected from stationary vessels and moorings. The details of these data sets, which are critical for understanding how water masses interact and mix at the fine-scale (<10 m) to mesoscale (10-100 km), are inadequately constrained due to resolution considerations. Southeast of New Zealand, high-resolution seismic reflection images of oceanic water masses have been produced using petroleum industry data. These seismic sections clearly show three main water masses, the boundary zones (fronts) between them, and associated thermohaline fine structure that may be related to the mixing of water masses in this region. Interpretations of the data suggest that the Subtropical Front in this region is a landward-dipping zone, with a width that can vary between 20 and 40 km. The boundary zone between Subantarctic Waters and the underlying Antarctic Intermediate Waters is also observed to dip landward. Several isolated lenses have been identified on the three data sets, ranging in size from 9 to 30 km in diameter. These lenses are interpreted to be mesoscale eddies that form at relatively shallow depths along the south side of the Subtropical Front.

  14. Proterozoic crustal boundary in the southern part of the Illinois Basin

    USGS Publications Warehouse

    Heigold, P.C.; Kolata, Dennis R.

    1993-01-01

    Recently acquired COCORP and proprietary seismic reflection data in the southern part of the Illinois Basin, combined with other geological and geophysical data, indicate that a WNW-trending Proterozoic terrane boundary (40 km wide) lies within basement. The boundary is characterized by the termination of subhorizontal Proterozoic reflectors and associated diffraction patterns along a line coinciding with the major magnetic lineament in this region (South Central Magnetic Lineament). North of the boundary, where reflectors thought to represent a sequence of layered Proterozoic rocks in the upper crust are widespread and as much as 11 km thick, total magnetic intensity values are relatively high, suggesting layers of rock with high magnetic susceptibility. To the south, the Proterozoic rocks are acoustically transparent on seismic reflection sections and total magnetic intensity values are relatively low. Moreover, relatively high Bouguer gravity anomaly values to the south may be caused by a dense, altered, lower crustal layer similar to that interpreted from deep seismic refraction studies to underlie the northern Mississippi Embayment. The boundary lies along the projected trend of the northern margin of the Early Proterozoic Central Plains orogen and we suggest that it marks the convergent margin of this orogen. Reactivation of the boundary and the associated zone of weakness during late Paleozoic times apparently resulted in structural deformation in the southern part of the Illinois Basin, including movement along the Cottage Grove Fault System and Ste. Genevieve Fault Zone and igneous activity at Hicks Dome. In addition to the role played by this crustal boundary in the evolution of the Illinois Basin, its location between the Wabash Valley Seismic Zone to the northeast and the New Madrid Seismic Zone to the southwest may be a significant factor in present-day seismicity. ?? 1993.

  15. New insights into the kinematics and seismotectonics of the Adria-Eurasia boundary in the eastern Alps from geodetic and seismic data

    NASA Astrophysics Data System (ADS)

    Serpelloni, Enrico; Vannucci, Gianfranco; Bennett, Richard A.; Anderlini, Letizia; Cavaliere, Adriano

    2015-04-01

    In this work we describe a new kinematic and seismotectonic model of the eastern Alps, at the boundary between Italy, Austria, Slovenia and Croatia, obtained from the analysis of geodetic (GPS) and seismological data. We use a dense GPS velocity field, obtained from integration of continuous, semi-continuous and survey-mode networks (~200 GPS stations between longitude 10°E and 17°E and latitude 44.5°N and 47.5°N) and an updated seismic and focal mechanisms catalogue, with uniformly calibrated moment magnitudes from ~1000 B.C.. Improved accuracies and precisions of GPS motion rates have been obtained by filtering displacement time-series for the spatially correlated common mode errors. The eastern Alps mark the boundary between the Adriatic microplate and the Eurasian plate through a wide zone of distributed deformation. Geodetic deformation and seismic release are more localized, and characterized by larger earthquakes, along the southeastern Alps fold-and-thrust belt, which accommodates the large part of the ~N-S Adria-Eurasia convergence, and in Slovenia, where a transition from ~N-S shortening to the eastward escape of the Pannonian Basin units occurs through a complex pattern of crustal deformation. GPS velocities well describe the overall kinematics, with a transition from NNW-ward to NE-ward motion trends (in a Eurasian frame) across Slovenia and Austria, but also show small but significant crustal deformation far from the major blocks boundaries. This may suggest internal continuous deformation or a more complex configuration of interacting tectonic blocks in the eastern Alps. This second hypothesis is taken into account and tested in this work. We use seismic moment release rate maps, active faults databases and inspections of GPS velocities in different local frames to define the geometry of a kinematic block model, constrained by GPS horizontal velocities, in order to estimate blocks rotations and elastic strain at blocks bounding faults. The

  16. An economical educational seismic system

    USGS Publications Warehouse

    Lehman, J. D.

    1980-01-01

    There is a considerable interest in seismology from the nonprofessional or amateur standpoint. The operation of a seismic system can be satisfying and educational, especially when you have built and operated the system yourself. A long-period indoor-type sensor and recording system that works extremely well has been developed in the James Madison University Physics Deparment. The system can be built quite economically, and any educational institution that cannot commit themselves to a professional installation need not be without first-hand seismic information. The system design approach has been selected by college students working a project or senior thesis, several elementary and secondary science teachers, as well as the more ambitious tinkerer or hobbyist at home 

  17. 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

  18. The Advanced National Seismic System; management and implementation

    USGS Publications Warehouse

    Benz, H.M.; Shedlock, K.M.; Buland, R.P.

    2001-01-01

    What is the Advanced National Seismic System? The Advanced National Seismic System (ANSS) is designed to organize, modernize, and standardize operations of seismic networks in the United States to improve the Nation’s ability to respond effectively to damaging earthquakes, volcanoes, and tsunamis. To achieve this, the ANSS will link more than 7,000 national, regional and urban monitoring stations in real time

  19. Archaeological Graves Revealing By Means of Seismic-electric Effect

    NASA Astrophysics Data System (ADS)

    Boulytchov, A.

    [a4paper,12pt]article english Seismic-electric effect was applied in field to forecast subsurface archaeological cul- tural objects. A source of seismic waves were repeated blows of a heavy hammer or powerful signals of magnetostrictive installation. Main frequency used was 500 Hz. Passed a soil layer and reached a second boundary between upper clayey-sand sedi- ments and archaeological object, the seismic wave caused electromagnetic fields on the both boundaries what in general is due to dipole charge separation owe to an im- balance of streaming currents induced by the seismic wave on opposite sides of a boundary interface. According to theoretical works of Pride the electromagnetic field appears on a boundary between two layers with different physical properties in the time of seismic wave propagation. Electric responses of electromagnetic fields were measured on a surface by pair of grounded dipole antennas or by one pivot and a long wire antenna acting as a capacitive pickup. The arrival times of first series of responses correspond to the time of seismic wave propagation from a source to a boundary between soil and clayey-sand layers. The arrival times of second row of responses correspond to the time of seismic wave way from a source to a boundary of clayey-sand layer with the archaeological object. The method depths successfully investigated were between 0.5-10 m. Similar electromagnetic field on another type of geological structure was also revealed by Mikhailov et al., Massachusetts, but their signals registered from two frontiers were too faint and not evident in comparing with ours ones that occurred to be perfect and clear. Seismic-electric method field experi- ments were successfully provided for the first time on archaeological objects.

  20. Seismic Retrofit for Electric Power Systems

    DOE PAGES

    Romero, Natalia; Nozick, Linda K.; Dobson, Ian; ...

    2015-05-01

    Our paper develops a two-stage stochastic program and solution procedure to optimize the selection of seismic retrofit strategies to increase the resilience of electric power systems against earthquake hazards. The model explicitly considers the range of earthquake events that are possible and, for each, an approximation of the distribution of damage experienced. Furthermore, this is important because electric power systems are spatially distributed and so their performance is driven by the distribution of component damage. We also test this solution procedure against the nonlinear integer solver in LINGO 13 and apply the formulation and solution strategy to the Eastern Interconnection,more » where seismic hazard stems from the New Madrid seismic zone.« less

  1. Seismic constraints on the lithosphere-asthenosphere boundary

    NASA Astrophysics Data System (ADS)

    Rychert, Catherine A.

    2014-05-01

    The basic tenet of plate tectonics is that a rigid plate, or lithosphere, moves over a weaker asthenospheric layer. However, the exact location and defining mechanism of the boundary at the base of the plate, the lithosphere-asthenosphere boundary (LAB) is debated. The oceans should represent a simple scenario since the lithosphere is predicted to thicken with seafloor age if it thermally defined, whereas a constant plate thickness might indicate a compositional definition. However, the oceans are remote and difficult to constrain, and studies with different sensitivities and resolutions have come to different conclusions. Hotspot regions lend additional insight, since they are relatively well instrumented with seismic stations, and also since the effect of a thermal plume on the LAB should depend on the defining mechanism of the plate. Here I present new results using S-to-P receiver functions to image upper mantle discontinuity structure beneath volcanically active regions including Hawaii, Iceland, Galapagos, and Afar. In particular I focus on the lithosphere-asthenosphere boundary and discontinuities related to the base of melting, which can be used to highlight plume locations. I image a lithosphere-asthenosphere boundary in the 50 - 95 km depth range beneath Hawaii, Galapagos, and Iceland. Although LAB depth variations exist within these regions, significant thinning is not observed in the locations of hypothesized plume impingement from receiver functions (see below). Since a purely thermally defined lithosphere is expected to thin significantly in the presence of a thermal plume anomaly, a compositional component in the definition of the LAB is implied. Beneath Afar, an LAB is imaged at 75 km depth on the flank of the rift, but no LAB is imaged beneath the rift itself. The transition from flank of rift is relatively abrupt, again suggesting something other than a purely thermally defined lithosphere. Melt may also exist in the asthenosphere in these regions

  2. Seismic Hazard Analysis as a Controlling Technique of Induced Seismicity in Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Convertito, V.; Sharma, N.; Maercklin, N.; Emolo, A.; Zollo, A.

    2011-12-01

    The effect of induced seismicity of geothermal systems during stimulation and fluid circulation can cover a wide range of values from light and unfelt to severe and damaging. If the design of a modern geothermal system requires the largest efficiency to be obtained from the social point of view it is required that the system could be managed in order to reduce possible impact in advance. In this framework, automatic control of the seismic response of the stimulated reservoir is nowadays mandatory, particularly in proximity of densely populated areas. Recently, techniques have been proposed for this purpose mainly based on the concept of the traffic light. This system provides a tool to decide the level of stimulation rate based on the real-time analysis of the induced seismicity and the ongoing ground motion values. However, in some cases the induced effect can be delayed with respect to the time when the reservoir is stimulated. Thus, a controlling system technique able to estimate the ground motion levels for different time scales can help to better control the geothermal system. Here we present an adaptation of the classical probabilistic seismic hazard analysis to the case where the seismicity rate as well as the propagation medium properties are not constant with time. We use a non-homogeneous seismicity model for modeling purposes, in which the seismicity rate and b-value of the recurrence relationship change with time. Additionally, as a further controlling procedure, we propose a moving time window analysis of the recorded peak ground-motion values aimed at monitoring the changes in the propagation medium. In fact, for the same set of magnitude values recorded at the same stations, we expect that on average peak ground motion values attenuate in same way. As a consequence, the residual differences can be reasonably ascribed to changes in medium properties. These changes can be modeled and directly introduced in the hazard integral. We applied the proposed

  3. Development of Vertical Cable Seismic System

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2011-12-01

    In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by

  4. Tritium glovebox stripper system seismic design evaluation

    SciTech Connect

    Grinnell, J. J.; Klein, J. E.

    2015-09-01

    The use of glovebox confinement at US Department of Energy (DOE) tritium facilities has been discussed in numerous publications. Glovebox confinement protects the workers from radioactive material (especially tritium oxide), provides an inert atmosphere for prevention of flammable gas mixtures and deflagrations, and allows recovery of tritium released from the process into the glovebox when a glovebox stripper system (GBSS) is part of the design. Tritium recovery from the glovebox atmosphere reduces emissions from the facility and the radiological dose to the public. Location of US DOE defense programs facilities away from public boundaries also aids in reducing radiological dosesmore » to the public. This is a study based upon design concepts to identify issues and considerations for design of a Seismic GBSS. Safety requirements and analysis should be considered preliminary. Safety requirements for design of GBSS should be developed and finalized as a part of the final design process.« less

  5. Online monitoring of seismic damage in water distribution systems

    NASA Astrophysics Data System (ADS)

    Liang, Jianwen; Xiao, Di; Zhao, Xinhua; Zhang, Hongwei

    2004-07-01

    It is shown that water distribution systems can be damaged by earthquakes, and the seismic damages cannot easily be located, especially immediately after the events. Earthquake experiences show that accurate and quick location of seismic damage is critical to emergency response of water distribution systems. This paper develops a methodology to locate seismic damage -- multiple breaks in a water distribution system by monitoring water pressure online at limited positions in the water distribution system. For the purpose of online monitoring, supervisory control and data acquisition (SCADA) technology can well be used. A neural network-based inverse analysis method is constructed for locating the seismic damage based on the variation of water pressure. The neural network is trained by using analytically simulated data from the water distribution system, and validated by using a set of data that have never been used in the training. It is found that the methodology provides an effective and practical way in which seismic damage in a water distribution system can be accurately and quickly located.

  6. Boundary-layer mantle flow under the Dead Sea transform fault inferred from seismic anisotropy.

    PubMed

    Rümpker, Georg; Ryberg, Trond; Bock, Günter

    2003-10-02

    Lithospheric-scale transform faults play an important role in the dynamics of global plate motion. Near-surface deformation fields for such faults are relatively well documented by satellite geodesy, strain measurements and earthquake source studies, and deeper crustal structure has been imaged by seismic profiling. Relatively little is known, however, about deformation taking place in the subcrustal lithosphere--that is, the width and depth of the region associated with the deformation, the transition between deformed and undeformed lithosphere and the interaction between lithospheric and asthenospheric mantle flow at the plate boundary. Here we present evidence for a narrow, approximately 20-km-wide, subcrustal anisotropic zone of fault-parallel mineral alignment beneath the Dead Sea transform, obtained from an inversion of shear-wave splitting observations along a dense receiver profile. The geometry of this zone and the contrast between distinct anisotropic domains suggest subhorizontal mantle flow within a vertical boundary layer that extends through the entire lithosphere and accommodates the transform motion between the African and Arabian plates within this relatively narrow zone.

  7. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-01-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet.« less

  8. Micro-seismicity and seismic moment release within the Coso Geothermal Field, California

    USGS Publications Warehouse

    Kaven, Joern; Hickman, Stephen H.; Davatzes, Nicholas C.

    2014-01-01

    We relocate 16 years of seismicity in the Coso Geothermal Field (CGF) using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We expand on our previous results by doubling the number of relocated events from April 1996 through May 2012 using a new field-wide 3-D velocity model. Relocated micro-seismicity sharpens in many portions of the active geothermal reservoir, likely defining large-scale fault zones and fluid pressure compartment boundaries. However, a significant fraction of seismicity remains diffuse and does not cluster into sharply defined structures, suggesting that permeability is maintained within the reservoir through distributed brittle failure. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vs generally higher in the Main Field and East Flank and Vp remaining relatively uniform across the CGF, but with significant local variations. The Vp/Vs ratio appears to outline the two main producing compartments of the reservoir at depths below mean ground level of approximately 1 to 2.5 km, with a ridge of relatively high Vp/Vs separating the Main Field from the East Flank. Detailed analyses of spatial and temporal variations in earthquake relocations and cumulative seismic moment release in the East Flank reveal three regions with persistently high rates of seismic activity. Two of these regions exhibit sharp, stationary boundaries at the margins of the East Flank that likely represent barriers to fluid flow and advective heat transport. However, seismicity and moment release in a third region at the northern end of the East Flank spread over time to form an elongated NE to SW structure, roughly parallel both to an elongated cluster of seismicity at the southern end of the East Flank and to regional fault traces mapped at the surface. Our results indicate that high

  9. Real-time Seismic Alert System of NIED

    NASA Astrophysics Data System (ADS)

    Horiuchi, S.; Fujinawa, Y.; Negishi, H.; Matsumoto, T.; Fujiwara, H.; Kunugi, T.; Hayashi, Y.

    2001-12-01

    An extensive seismic network has been constructed nationwide composed of hi-sensitivity seismographic network, broadband seismographic network and strong motion seismographic network. All these data from some 3,000 sites belonging to NIED, JMA and universities are to be accumulated and distributed through NIED to any scientists and engineering through INTERNET under the coordination of the National Seismic Research Committee of MEXT. As a practical application of those data we are now developing a real-time seismic alert information system for the purpose of providing short-term warning of imminent strong grounds motions from major earthquakes from several seconds to a few days. The contents of information are seismic focal parameters (several seconds), seismic fault plane solutions (some 10 seconds), after-shock activities (several minutes-a few days ). The fundamental fault parameters are used to build specific information at sites for particular users for use of triggering automated and /or half-automated responses. The most important application is an immediate estimate of expected shaking distribution and damages in a district using synthetic database and site effects for local governments to initial proper measures of hazard mitigation. Another application is estimation of arrival time and shaking strength at any individual site for human lives to be safeguarded. The system could also start an automatic electrical isolation and protection of computer systems, protection of hazardous chronic systems, transportation systems and so on. The information are corrected successively as seismic ground motion are received at a larger number of sites in time with the result that more accurate and more sophisticated earthquake information is transmitted to any user. Besides the rapid determination of seismic parameters, one of essential items in this alert system is the data transmission means. The data transmission is chosen to assure negligibly small delay of data

  10. Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

    USGS Publications Warehouse

    Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

    2017-12-08

    sequence stratigraphic cycles that compose the Eocene to Miocene Oldsmar, Avon Park, and Arcadia Formations. The mapping of these seismic-reflection and well data has produced a refined Cenozoic sequence stratigraphic, seismic stratigraphic, and hydrogeologic framework of southeastern Florida. The upward transition from the Oldsmar Formation to the Avon Park Formation and the Arcadia Formation embodies the evolution from (1) a tropical to subtropical, shallow-marine, carbonate platform, represented by the Oldsmar and Avon Park Formations, to (2) a broad, temperate, mixed carbonate-siliciclastic shallow marine shelf, represented by the lower part of the Arcadia Formation, and to (3) a temperate, distally steepened carbonate ramp represented by the upper part of the Arcadia Formation.In the study area, the depositional sequences and seismic sequences have a direct correlation with hydrogeologic units. The approximate upper boundary of four principal permeable units of the Floridan aquifer system (Upper Floridan aquifer, Avon Park permeable zone, uppermost major permeable zone of the Lower Floridan aquifer, and Boulder Zone) have sequence stratigraphic and seismic-reflection signatures that were identified on cross sections, mapped, or both, and therefore the sequence stratigraphy and seismic stratigraphy were used to guide the development of a refined spatial representation of these hydrogeologic units. In all cases, the permeability of the four permeable units is related to stratiform megaporosity generated by ancient dissolution of carbonate rock associated with subaerial exposure and unconformities at the upper surfaces of carbonate depositional cycles of several hierarchical scales ranging from high-frequency cycles to depositional sequences. Additionally, interparticle porosity also contributes substantially to the stratiform permeability in much of the Upper Floridan aquifer. Information from seismic stratigraphy allowed 3D geomodeling of hydrogeologic units

  11. The Indirect Boundary Element Method (IBEM) for Seismic Response of Topographical Irregularities in Layered Media

    NASA Astrophysics Data System (ADS)

    Contreras Zazueta, M. A.; Perton, M.; Sanchez-Sesma, F. J.; Sánchez-Alvaro, E.

    2013-12-01

    The seismic hazard assessment of extended developments, such as a dam, a bridge or a pipeline, needs the strong ground motion simulation taking into account the effects of surface geology. In many cases the incoming wave field can be obtained from attenuation relations or simulations for layered media using Discrete Wave Number (DWN). Sometimes there is a need to include in simulations the seismic source as well. A number of methods to solve these problems have been developed. Among them the Finite Element and Finite Difference Methods (FEM and FDM) are generally preferred because of the facility of use. Nevertheless, the analysis of realistic dynamic loading induced by earthquakes requires a thinner mesh of the entire domain to consider high frequencies. Consequently this may imply a high computational cost. The Indirect Boundary Element Method (IBEM) can also be employed. Here it is used to study the response of a site to historical seismic activity. This method is particularly suited to model wave propagation through wide areas as it requires only the meshing of boundaries. Moreover, it is well suited to represent finely the diffraction that can occur on a fault. However, the IBEM has been applied mainly to simple geometrical configurations. In this communication significant refinements of the formulation are presented. Using IBEM we can simulate wave propagation in complex geometrical configurations such as a stratified medium crossed by thin faults or having a complex topography. Two main developments are here described; one integrates the DWN method inside the IBEM in order to represent the Green's functions of stratified media with relatively low computational cost but assuming unbounded parallel flat layers, and the other is the extension of IBEM to deal with multi-regions in contact which allows more versatility with a higher computational cost compared to the first one but still minor to an equivalent FEM formulation. The two approaches are fully

  12. Significant earthquakes on the Enriquillo fault system, Hispaniola, 1500-2010: Implications for seismic hazard

    USGS Publications Warehouse

    Bakun, William H.; Flores, Claudia H.; ten Brink, Uri S.

    2012-01-01

    Historical records indicate frequent seismic activity along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo fault system in the eighteenth century. An intensity magnitude MI 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and the accounts of the shaking in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the 18 October 1751 MI 7.4–7.5 earthquake, probably located near the eastern end of the fault in the Dominican Republic, followed by the 21 November 1751 MI 6.6 earthquake near Port-au-Prince, Haiti, and the 3 June 1770 MI 7.5 earthquake west of the 2010 earthquake rupture. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of seismic quiescence. The entire Enriquillo fault system appears to be seismically active; Haiti and the Dominican Republic should prepare for future devastating earthquakes.

  13. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-02-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.« less

  14. Definition and means of maintaining the supply ventilation system seismic shutdown portion of the PFP safety envelope

    SciTech Connect

    Keck, R.D.

    1997-01-21

    The purpose of this document is to record the technical evaluation of the Limiting Condition for Operation (LCO) described in the Plutonium Finishing Plant (PFP) Operational Safety Requirements, WHC-SD-CP-OSR- 010, Rev. 0. Kay 1994, Section 3.2.3, `Supply Ventilation System Seismic Shutdown.` This document, with its appendices, provides the following: 1. The system functional requirements for determining system operability (Section 3). 2. Evaluations of equipment to determine the safety boundary for the system (Section 4). 3. A list of annotated drawings which show the safety envelope boundaries (Appendix C). 4. A list of the safety envelope equipment (Appendix B). 5. Functionalmore » requirements for the individual safety envelope equipment, including appropriate setpoints and process parameters (Section 4.1). 6. A list of the operational, maintenance and surveillance procedures necessary to operate and maintain the system equipment within the safety envelope (Sections 5 and 6 and Appendix A).« less

  15. Seismic depth imaging of sequence boundaries beneath the New Jersey shelf

    NASA Astrophysics Data System (ADS)

    Riedel, M.; Reiche, S.; Aßhoff, K.; Buske, S.

    2018-06-01

    Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model.

  16. Optical seismic sensor systems and methods

    DOEpatents

    Beal, A. Craig; Cummings, Malcolm E.; Zavriyev, Anton; Christensen, Caleb A.; Lee, Keun

    2015-12-08

    Disclosed is an optical seismic sensor system for measuring seismic events in a geological formation, including a surface unit for generating and processing an optical signal, and a sensor device optically connected to the surface unit for receiving the optical signal over an optical conduit. The sensor device includes at least one sensor head for sensing a seismic disturbance from at least one direction during a deployment of the sensor device within a borehole of the geological formation. The sensor head includes a frame and a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path.

  17. Origins of a national seismic system in the United States

    USGS Publications Warehouse

    Filson, John R.; Arabasz, Walter J.

    2016-01-01

    This historical review traces the origins of the current national seismic system in the United States, a cooperative effort that unifies national, regional, and local‐scale seismic monitoring within the structure of the Advanced National Seismic System (ANSS). The review covers (1) the history and technological evolution of U.S. seismic networks leading up to the 1990s, (2) factors that made the 1960s and 1970s a watershed period for national attention to seismology, earthquake hazards, and seismic monitoring, (3) genesis of the vision of a national seismic system during 1980–1983, (4) obstacles and breakthroughs during 1984–1989, (5) consensus building and convergence during 1990–1992, and finally (6) the two‐step realization of a national system during 1993–2000. Particular importance is placed on developments during the period between 1980 and 1993 that culminated in the adoption of a charter for the Council of the National Seismic System (CNSS)—the foundation for the later ANSS. Central to this story is how many individuals worked together toward a common goal of a more rational and sustainable approach to national earthquake monitoring in the United States. The review ends with the emergence of ANSS during 1999 and 2000 and its statutory authorization by Congress in November 2000.

  18. Structure of the Lithosphere-Asthenosphere Boundary Onshore and Offshore the California Continental Margin from Three-Dimensional Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Gomez, C. D.; Escobar, L., Sr.; Rathnayaka, S.; Weeraratne, D. S.; Kohler, M. D.

    2016-12-01

    The California continental margin, a major transform plate boundary in continental North America, is the locus of complex tectonic stress fields that are important in interpreting both remnant and ongoing deformational strain. Ancient subduction of the East Pacific Rise spreading center, the rotation and translation of tectonic blocks and inception of the San Andreas fault all contribute to the dynamic stress fields located both onshore and offshore southern California. Data obtained by the ALBACORE (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) and the CISN (California Integrated Seismic Network) seismic array are analyzed for azimuthal anisotropy of Rayleigh waves from 80 teleseismic events at periods 16 - 78 s. Here we invert Rayleigh wave data for shear wave velocity structure and three-dimensional seismic anisotropy in the thee regions designated within the continental margin including the continent, seafloor and California Borderlands. Preliminary results show that seismic anisotropy is resolved in multiple layers and can be used to determine the lithosphere-asthenosphere boundary (LAB) in offshore and continental regions. The oldest seafloor in our study at age 25-35 Ma indicates that the anisotropic transition across the LAB occurs at 73 km +/- 25 km with the lithospheric fast direction oriented WNW-ESE, consistent with current Pacific plate motion direction. The continent region west of the San Andreas indicates similar WNW-ESE anisotropy and LAB depth. Regions east of the San Andreas fault indicate NW-SE anisotropy transitioning to a N-S alignment at 80 km depth north of the Garlock fault. The youngest seafloor (15 - 25 Ma) and outer Borderlands indicate a more complex three layer fabric where shallow lithospheric NE-SW fast directions are perpendicular with ancient Farallon subduction arc, a mid-layer with E-W fast directions are perpendicular to remnant fossil fabric, and the deepest layer

  19. Optimization of seismic isolation systems via harmony search

    NASA Astrophysics Data System (ADS)

    Melih Nigdeli, Sinan; Bekdaş, Gebrail; Alhan, Cenk

    2014-11-01

    In this article, the optimization of isolation system parameters via the harmony search (HS) optimization method is proposed for seismically isolated buildings subjected to both near-fault and far-fault earthquakes. To obtain optimum values of isolation system parameters, an optimization program was developed in Matlab/Simulink employing the HS algorithm. The objective was to obtain a set of isolation system parameters within a defined range that minimizes the acceleration response of a seismically isolated structure subjected to various earthquakes without exceeding a peak isolation system displacement limit. Several cases were investigated for different isolation system damping ratios and peak displacement limitations of seismic isolation devices. Time history analyses were repeated for the neighbouring parameters of optimum values and the results proved that the parameters determined via HS were true optima. The performance of the optimum isolation system was tested under a second set of earthquakes that was different from the first set used in the optimization process. The proposed optimization approach is applicable to linear isolation systems. Isolation systems composed of isolation elements that are inherently nonlinear are the subject of a future study. Investigation of the optimum isolation system parameters has been considered in parametric studies. However, obtaining the best performance of a seismic isolation system requires a true optimization by taking the possibility of both near-fault and far-fault earthquakes into account. HS optimization is proposed here as a viable solution to this problem.

  20. Korea Integrated Seismic System tool(KISStool) for seismic monitoring and data sharing at the local data center

    NASA Astrophysics Data System (ADS)

    Park, J.; Chi, H. C.; Lim, I.; Jeong, B.

    2011-12-01

    The Korea Integrated Seismic System(KISS) is a back-bone seismic network which distributes seismic data to different organizations in near-real time at Korea. The association of earthquake monitoring institutes has shared their seismic data through the KISS from 2003. Local data centers operating remote several stations need to send their free field seismic data to NEMA(National Emergency Management Agency) by the law of countermeasure against earthquake hazard in Korea. It is very important the efficient tool for local data centers which want to rapidly detect local seismic intensity and to transfer seismic event information toward national wide data center including PGA, PGV, dominant frequency of P-wave, raw data, and etc. We developed the KISStool(Korea Integrated Seismic System tool) for easy and convenient operation seismic network in local data center. The KISStool has the function of monitoring real time waveforms by clicking station icon on the Google map and real time variation of PGA, PGV, and other data by opening the bar type monitoring section. If they use the KISStool, any local data center can transfer event information to NEMA(National Emergency Management Agency), KMA(Korea Meteorological Agency) or other institutes through the KISS using UDP or TCP/IP protocols. The KISStool is one of the most efficient methods to monitor and transfer earthquake event at local data center in Korea. KIGAM will support this KISStool not only to the member of the monitoring association but also local governments.

  1. Seismic interpretation and thrust tectonics of the Amadeus Basin, central Australia, along the BMR regional seismic line

    NASA Astrophysics Data System (ADS)

    Shaw, Russell D.; Korsch, Russell J.; Wright, C.; Goleby, B. R.

    At the northern margin of the Amadeus Basin the monoclinal upturn (the MacDonnell Homocline) is interpreted to be the result of rotation and limited back-thrusting of the sedimentary sequence in front of a southerly-directed, imbricate basement thrust-wedge. This thrust complex is linked at depth to the crust-cutting Redbank Thrust Zone. In the northern part of the basin immediately to the south, regional seismic reflection profiling across the Missionary Plain shows a sub-horizontal, north-dipping, parautochthonous sedimentary sequence between about 8.5 km and 12.0 km thick. This sedimentary sequence shows upturning only at the northern and southern extremities, and represents an unusual, relatively undeformed region between converging thrust systems. In this intervening region, the crust appears to have been tilted downwards and northwards in response to the upthrusting to the north. Still farther to the south, the vertical uplift of the southern hanging wall of the Gardiner Thrust is about 6 km. Seismic reflection profiling in the region immediately south of the Gardiner Thrust indicates repetition of the sedimentary sequence. At the far end of the profile, in the Kernot Range, an imbricate thrust system fans ahead of a ramp-flat thrust pair. This thrust system (the Kernot Range Thrust System) occurs immediately north of an aeromagnetic domain boundary which marks the southern limit of a central ridge region characterized by thin Palaeozoic sedimentary cover and shallow depths to magnetic basement. A planar seismic event, imaged to a depth of at least 18 km, may correspond to the same boundary and is interpreted as a pre-basin Proterozoic thrust. Overall, the structure in the shallow sedimentary section in the central-southern region of the Amadeus Basin indicates that north-directed thrusting during the Dovonian-Carboniferous Alice Springs Orogeny was thin-skinned. During this orogeny an earlier thrust system, formed during the Petermann Ranges Orogeny and

  2. Pennsylvanian Tyler stratigraphic seismic concepts

    SciTech Connect

    Moore, C.E.; Archer, R.J.

    Recent drilling in the Rattler Butte area of central Montana has renewed interest in the Pennsylvanian Tyler Formation as a drilling objective. New production in this area, coupled with the surrounding well density, provides an ideal situation for further development of Tyler stratigraphic-seismic exploration concepts and methods. Both geologic and geophysical Tyler thickness maps have proven to be useful tools in delineating eroded Heath and subsequent lower Tyler deposition. Seismic modeling has revealed a series of possible Tyler-Heath erosional edge characteristics, providing another tool for Tyler-Heath boundary definition. In modeling specific seismic sand signatures, it was found that seismic charactermore » and amplitude are dependent upon both formation thickness and lithology. Detailed mapping of the study area also revealed a new environmental interpretation of the Tyler. Unlike the fluvial system to the north, the Tyler regime in the Rattler Butte area appears to have fluctuated among fluvial, deltaic, and marine systems. Two hydrocarbon occurrence patterns have been noted within the Tyler: (1) although reservoir quality sands are present throughout the Tyler, those within the lower Tyler are more likely to contain hydrocarbons, and (2) close proximity to the Tyler-Heath erosional edge increases the chances of discovering oil-filled Tyler sands. Combined use of these exploration tools should greatly enhance the chances for successful lower Tyler exploration.« less

  3. Imaging the SE Caribbean Accretionary Boundary: Results from the BOLIVAR Seismic Reflection and Refraction data at 65W

    NASA Astrophysics Data System (ADS)

    Magnani, M.; Zelt, C. A.; Sawyer, D.; Levander, A.

    2005-12-01

    We describe a N-S, ~550 km long onshore-offshore profile at approximately 65oW., which is one of the principal seismic reflection and refraction transects acquired in 2004 as part of the Broadband Ocean and Land Investigation of Venezuela and the Antilles arc Region (BOLIVAR) experiment. Goals of BOLIVAR are to understand the complex history of the progressive oblique collision between the Leeward Antilles arc and South America that has taken place since the late Cretaceous, and to unravel the mechanisms responsible for continental growth of the South American continent through arc accretion. The transect starts ~330 km offshore northern Venezuela, in the Venezuela Basin, crosses the South America/Caribbean incipient subduction zone, the Los Roques canyon, the ABC ridge, the Tuy-Cariaco Trough (bounded by the El Pilar-Moron dextral strike-slip system), and crosses the coast east of Barcelona, Ve., continues south 175 km through the Espino Graben, and the Eastern Venezuela Basin. Multi-channel seismic reflection data were acquired by the R/V Ewing along the offshore portion of the profile, while 7 ocean bottoms seismometers (offshore) and 485 Reftek Texans (onland) recorded the Ewing airgun shots. In addition two large land shots (600 kg and 1000 kg of pentanol) were recorded by the land stations, providing reversed refraction coverage. The profile is located in a unique position along the South America/Caribbean plate boundary as it lies astride a transfer zone between the Southern Caribbean Deformed Belt, where the Caribbean plate is subducting beneath South America, and the eastern Venezuela strike-slip boundary and modern Antilles volcanic arc, where the South American plate subducts beneath the Caribbean. The structure and motion across this apparent transfer zone are unknown. The seismic data show that this area is characterized by a basement high, with little sediment coverage and velocities as high as 6.5-6.7 km/s at a depth of 8-10 km. North of the coast

  4. On Mario Bunge's Definition of System and System Boundary

    ERIC Educational Resources Information Center

    Cavallo, Andrew M.

    2012-01-01

    In this short paper we discuss Mario Bunge's definition of system boundary. It is quickly discovered that Bunge's definition of system and system boundary are both deficient. We thus propose new definitions, which (hopefully) improve the situation. Our definition of system boundary works off the same intuition behind Bunge's.

  5. Marine Seismic System At-Sea-Test Deployment Operation

    DTIC Science & Technology

    1981-10-09

    ton crane can handle deck loads. An early version Deloo type ASK ( Automatic Stationkeeping) system is used to maintain position over a deployed short...b --- 00 - Ir RPT 006-007EV "A 126283 [ I iMIIE SEISMIC SYSTEM I AT-SEA-TEST DEP OYiN OFERATION I GLOBAL MARINE DEVELOPMENT INC 2302 Martin Street...Seismic System At-Sea-Test Deployment Operation 6. PERFORNING *o. REPORT NUMOER IPT 006-007 7. AUTNMORI) O. CONTRACT Ol GRANT NUMOERIa iR. Wallerstedt

  6. The Moho as a magnetic boundary. [Earth crust-mantle boundary

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Thomas, H. H.; Mayhew, M. A.

    1979-01-01

    Magnetism in the crust and the upper mantle and magnetic results indicating that the seismic Moho is a magnetic boundary are considered. Mantle derived rocks - peridotites from St. Pauls rocks, dunite xenoliths from the Kaupulehu flow, and peridotite, dunite, and eclogite xenoliths from Roberts Victor and San Carlos diatremes - are weakly magnetic with saturation magnetization values from 0.013 emu/gm to less than 0.001 emu/gm which is equivalent to 0.01 to 0.001 wt% Fe304. Literature on the minerals in mantle xenoliths shows that metals and primary Fe304 are absent, and that complex Cr, Mg, Al, and Fe spinels are dominant. These spinels are non-magnetic at mantle temperatures, and the crust/mantle boundary can be specified as a magnetic mineralogy discontinuity. The new magnetic results indicate that the seismic Moho is a magnetic boundary, the source of magnetization is in the crust, and the maximum Curie isotherm depends on magnetic mineralogy and is located at depths which vary with the regional geothermal gradient.

  7. Advanced Seismic While Drilling System

    SciTech Connect

    Robert Radtke; John Fontenot; David Glowka

    by TII. An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been

  8. Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

    NASA Astrophysics Data System (ADS)

    Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

    2003-11-01

    We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

  9. Seismic assessment of Technical Area V (TA-V).

    SciTech Connect

    Medrano, Carlos S.

    The Technical Area V (TA-V) Seismic Assessment Report was commissioned as part of Sandia National Laboratories (SNL) Self Assessment Requirement per DOE O 414.1, Quality Assurance, for seismic impact on existing facilities at Technical Area-V (TA-V). SNL TA-V facilities are located on an existing Uniform Building Code (UBC) Seismic Zone IIB Site within the physical boundary of the Kirtland Air Force Base (KAFB). The document delineates a summary of the existing facilities with their safety-significant structure, system and components, identifies DOE Guidance, conceptual framework, past assessments and the present Geological and Seismic conditions. Building upon the past information and themore » evolution of the new seismic design criteria, the document discusses the potential impact of the new standards and provides recommendations based upon the current International Building Code (IBC) per DOE O 420.1B, Facility Safety and DOE G 420.1-2, Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-Nuclear Facilities.« less

  10. Spatial organization of seismicity and fracture pattern at the boundary between Alps and Dinarides

    NASA Astrophysics Data System (ADS)

    Bressan, Gianni; Ponton, Maurizio; Rossi, Giuliana; Urban, Sandro

    2016-04-01

    The paper affords the study of the spatial organization of seismicity in the easternmost region of the Alps (Friuli, in NE Italy and W Slovenia), dominated by the interference between the Alpine and the Dinaric tectonic systems. Two non-conventional methods of spatial analysis are used: fractal analysis and principal component analysis (PCA). The fractal analysis helps to discriminate the cases in which hypocentres clearly define a plane, from the ones in which hypocenter distribution tends to the planarity, without reaching it. The PCA analysis is used to infer the orientation of planes fitting through earthquake foci, or the direction of propagation of the hypocentres. Furthermore, we study the spatial seismicity pattern at the shallow depths in the context of a general damage model, through the crack density distribution. The results of the three methods concur to a complex and composite model of fracturing in the region. The hypocentre pattern fills only partially a plane, i.e. has a fractal dimension close to 2. The three exceptions regard planes with Dinaric trend, without interference with Alpine lineaments. The shallowest depth range (0-10 km depth) is characterized by the activation of planes with variable orientations, reflecting the interference between the Dinaric and the Alpine tectonic structures, and closely bound to the variation of the mechanical properties of the crust. The seismicity occurs mostly in areas characterized by a variation from low to moderate crack density, indicating the sharp transition from zones of low damage to zones of moderate damage. Low crack density indicates the presence of more competent rocks capable of sustaining high strain energy while high crack density areas pertain to highly fractured rocks that cannot store high strain energy. Brittle failure, i.e. seismic activity, is favoured within the sharp transitions from low to moderate crack density zones. The orientation of the planes depicting the seismic activity

  11. Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

    NASA Astrophysics Data System (ADS)

    Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

    2014-09-01

    Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1-5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.

  12. The boundary between the Indian and Asian tectonic plates below Tibet

    PubMed Central

    Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Kumar, Prakash; Pei, Shunping; Kind, Rainer; Zhang, Zhongjie; Teng, Jiwen; Ding, Lin; Gao, Xing; Xu, Qiang; Wang, Wei

    2010-01-01

    The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy. PMID:20534567

  13. The boundary between the Indian and Asian tectonic plates below Tibet.

    PubMed

    Zhao, Junmeng; Yuan, Xiaohui; Liu, Hongbing; Kumar, Prakash; Pei, Shunping; Kind, Rainer; Zhang, Zhongjie; Teng, Jiwen; Ding, Lin; Gao, Xing; Xu, Qiang; Wang, Wei

    2010-06-22

    The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy.

  14. Improved Seismic Acquisition System and Data Processing for the Italian National Seismic Network

    NASA Astrophysics Data System (ADS)

    Badiali, L.; Marcocci, C.; Mele, F.; Piscini, A.

    2001-12-01

    A new system for acquiring and processing digital signals has been developed in the last few years at the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The system makes extensive use of the internet communication protocol standards such as TCP and UDP which are used as the transport highway inside the Italian network, and possibly in a near future outside, to share or redirect data among processes. The Italian National Seismic Network has been working for about 18 years equipped with vertical short period seismometers and transmitting through analog lines, to the computer center in Rome. We are now concentrating our efforts on speeding the migration towards a fully digital network based on about 150 stations equipped with either broad band or 5 seconds sensors connected to the data center partly through wired digital communication and partly through satellite digital communication. The overall process is layered through intranet and/or internet. Every layer gathers data in a simple format and provides data in a processed format, ready to be distributed towards the next layer. The lowest level acquires seismic data (raw waveforms) coming from the remote stations. It handshakes, checks and sends data in LAN or WAN according to a distribution list where other machines with their programs are waiting for. At the next level there are the picking procedures, or "pickers", on a per instrument basis, looking for phases. A picker spreads phases, again through the LAN or WAN and according to a distribution list, to one or more waiting locating machines tuned to generate a seismic event. The event locating procedure itself, the higher level in this stack, can exchange information with other similar procedures. Such a layered and distributed structure with nearby targets allows other seismic networks to join the processing and data collection of the same ongoing event, creating a virtual network larger than the original one. At present we plan to cooperate with other

  15. Geometric and thermal controls on normal fault seismicity from rate-and-state friction models

    NASA Astrophysics Data System (ADS)

    Mark, H. F.; Behn, M. D.; Olive, J. A. L.; Liu, Y.

    2017-12-01

    Seismic and geodetic observations from the last two decades have led to a growing realization that a significant amount of fault slip at plate boundaries occurs aseismically, and that the amount of aseismic displacement varies across settings. Here we investigate controls on the seismogenic behavior of crustal-scale normal faults that accommodate extensional strain at mid-ocean ridges and continental rifts. Seismic moment release rates measured along the fast-spreading East Pacific Rise suggest that the majority of fault growth occurs aseismically with almost no seismic slip. In contrast, at the slow-spreading Mid-Atlantic Ridge seismic slip may represent up to 60% of the total fault displacement. Potential explanations for these variations include heterogeneous distributions of frictional properties on fault surfaces, effects of variable magma supply associated with seafloor spreading, and/or differences in fault geometry and thermal structure. In this study, we use rate-and-state friction models to study the seismic coupling coefficient (the fraction of total fault slip that occurs seismically) for normal faults at divergent plate boundaries, and investigate controls on fault behavior that might produce the variations in the coupling coefficient observed in natural systems. We find that the seismic coupling coefficient scales with W/h*, where W is the downdip width of the seismogenic area of the fault and h* is the critical earthquake nucleation size. At mid-ocean ridges, W is expected to increase with decreasing spreading rate. Thus, the observed relationship between seismic coupling and W/h* explains to first order variations in seismic coupling coefficient as a function of spreading rate. Finally, we use catalog data from the Gulf of Corinth to show that this scaling relationship can be extended into the thicker lithosphere of continental rift systems.

  16. Hydrologically-driven crustal stresses and seismicity in the New Madrid Seismic Zone.

    PubMed

    Craig, Timothy J; Chanard, Kristel; Calais, Eric

    2017-12-15

    The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or 'stable' plate interiors, remains a subject of debate. Recent work in plate-boundary regions demonstrates the capacity for long-wavelength changes in continental water storage to produce observable surface deformation, induce crustal stresses and modulate seismicity rates. Here we show that a significant variation in the rate of microearthquakes in the intraplate New Madrid Seismic Zone at annual and multi-annual timescales coincides with hydrological loading in the upper Mississippi embayment. We demonstrate that this loading, which results in geodetically observed surface deformation, induces stresses within the lithosphere that, although of small amplitude, modulate the ongoing seismicity of the New Madrid region. Correspondence between surface deformation, hydrological loading and seismicity rates at both annual and multi-annual timescales indicates that seismicity variations are the direct result of elastic stresses induced by the water load.

  17. Seismological evidence for a localized mushy zone at the Earth's inner core boundary.

    PubMed

    Tian, Dongdong; Wen, Lianxing

    2017-08-01

    Although existence of a mushy zone in the Earth's inner core has been hypothesized several decades ago, no seismic evidence has ever been reported. Based on waveform modeling of seismic compressional waves that are reflected off the Earth's inner core boundary, here we present seismic evidence for a localized 4-8 km thick zone across the inner core boundary beneath southwest Okhotsk Sea with seismic properties intermediate between those of the inner and outer core and of a mushy zone. Such a localized mushy zone is found to be surrounded by a sharp inner core boundary nearby. These seismic results suggest that, in the current thermo-compositional state of the Earth's core, the outer core composition is close to eutectic in most regions resulting in a sharp inner core boundary, but deviation from the eutectic composition exists in some localized regions resulting in a mushy zone with a thickness of 4-8 km.The existence of a mushy zone in the Earth's inner core has been suggested, but has remained unproven. Here, the authors have discovered a 4-8 km thick mushy zone at the inner core boundary beneath the Okhotsk Sea, indicating that there may be more localized mushy zones at the inner core boundary.

  18. Numerical modeling of intraplate seismicity with a deformable loading plate

    NASA Astrophysics Data System (ADS)

    So, B. D.; Capitanio, F. A.

    2017-12-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  19. Seismic Fracture Characterization Methodologies for Enhanced Geothermal Systems

    SciTech Connect

    Queen, John H.

    2016-05-09

    Executive Summary The overall objective of this work was the development of surface and borehole seismic methodologies using both compressional and shear waves for characterizing faults and fractures in Enhanced Geothermal Systems. We used both surface seismic and vertical seismic profile (VSP) methods. We adapted these methods to the unique conditions encountered in Enhanced Geothermal Systems (EGS) creation. These conditions include geological environments with volcanic cover, highly altered rocks, severe structure, extreme near surface velocity contrasts and lack of distinct velocity contrasts at depth. One of the objectives was the development of methods for identifying more appropriate seismic acquisition parametersmore » for overcoming problems associated with these geological factors. Because temperatures up to 300º C are often encountered in these systems, another objective was the testing of VSP borehole tools capable of operating at depths in excess of 1,000 m and at temperatures in excess of 200º C. A final objective was the development of new processing and interpretation techniques based on scattering and time-frequency analysis, as well as the application of modern seismic migration imaging algorithms to seismic data acquired over geothermal areas. The use of surface seismic reflection data at Brady's Hot Springs was found useful in building a geological model, but only when combined with other extensive geological and geophysical data. The use of fine source and geophone spacing was critical in producing useful images. The surface seismic reflection data gave no information about the internal structure (extent, thickness and filling) of faults and fractures, and modeling suggests that they are unlikely to do so. Time-frequency analysis was applied to these data, but was not found to be significantly useful in their interpretation. Modeling does indicate that VSP and other seismic methods with sensors located at depth in wells will be the most

  20. On boundary-element models of elastic fault interaction

    NASA Astrophysics Data System (ADS)

    Becker, T. W.; Schott, B.

    2002-12-01

    We present the freely available, modular, and UNIX command-line based boundary-element program interact. It is yet another implementation of Crouch and Starfield's (1983) 2-D and Okada's (1992) half-space solutions for constant slip on planar fault segments in an elastic medium. Using unconstrained or non-negative, standard-package matrix routines, the code can solve for slip distributions on faults given stress boundary conditions, or vice versa, both in a local or global reference frame. Based on examples of complex fault geometries from structural geology, we discuss the effects of different stress boundary conditions on the predicted slip distributions of interacting fault systems. Such one-step calculations can be useful to estimate the moment-release efficiency of alternative fault geometries, and so to evaluate the likelihood which system may be realized in nature. A further application of the program is the simulation of cyclic fault rupture based on simple static-kinetic friction laws. We comment on two issues: First, that of the appropriate rupture algorithm. Cellular models of seismicity often employ an exhaustive rupture scheme: fault cells fail if some critical stress is reached, then cells slip once-only by a given amount, and subsequently the redistributed stress is used to check for triggered activations on other cells. We show that this procedure can lead to artificial complexity in seismicity if time-to-failure is not calculated carefully because of numerical noise. Second, we address the question if foreshocks can be viewed as direct expressions of a simple statistical distribution of frictional strength on individual faults. Repetitive failure models based on a random distribution of frictional coefficients initially show irregular seismicity. By repeatedly selecting weaker patches, the fault then evolves into a quasi-periodic cycle. Each time, the pre-mainshock events build up the cumulative moment release in a non-linear fashion. These

  1. Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

    NASA Astrophysics Data System (ADS)

    Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

    2007-05-01

    Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

  2. Quantitative Estimation of Seismic Velocity Changes Using Time-Lapse Seismic Data and Elastic-Wave Sensitivity Approach

    NASA Astrophysics Data System (ADS)

    Denli, H.; Huang, L.

    2008-12-01

    Quantitative monitoring of reservoir property changes is essential for safe geologic carbon sequestration. Time-lapse seismic surveys have the potential to effectively monitor fluid migration in the reservoir that causes geophysical property changes such as density, and P- and S-wave velocities. We introduce a novel method for quantitative estimation of seismic velocity changes using time-lapse seismic data. The method employs elastic sensitivity wavefields, which are the derivatives of elastic wavefield with respect to density, P- and S-wave velocities of a target region. We derive the elastic sensitivity equations from analytical differentiations of the elastic-wave equations with respect to seismic-wave velocities. The sensitivity equations are coupled with the wave equations in a way that elastic waves arriving in a target reservoir behave as a secondary source to sensitivity fields. We use a staggered-grid finite-difference scheme with perfectly-matched layers absorbing boundary conditions to simultaneously solve the elastic-wave equations and the elastic sensitivity equations. By elastic-wave sensitivities, a linear relationship between relative seismic velocity changes in the reservoir and time-lapse seismic data at receiver locations can be derived, which leads to an over-determined system of equations. We solve this system of equations using a least- square method for each receiver to obtain P- and S-wave velocity changes. We validate the method using both surface and VSP synthetic time-lapse seismic data for a multi-layered model and the elastic Marmousi model. Then we apply it to the time-lapse field VSP data acquired at the Aneth oil field in Utah. A total of 10.5K tons of CO2 was injected into the oil reservoir between the two VSP surveys for enhanced oil recovery. The synthetic and field data studies show that our new method can quantitatively estimate changes in seismic velocities within a reservoir due to CO2 injection/migration.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  4. The 2011 Virginia M5.8 earthquake: Insights from seismic reflection imaging into the influence of older structures on eastern U.S. seismicity

    USGS Publications Warehouse

    Pratt, Thomas L.; Horton, J. Wright; Spear, D.B.; Gilmer, A.K.; McNamara, Daniel E.

    2015-01-01

    The Mineral, Virginia (USA), earthquake of 23 August 2011 occurred at 6– 8 km depth within the allochthonous terranes of the Appalachian Piedmont Province, rupturing an ~N36°E striking reverse fault dipping ~50° southeast. This study used the Interstate Highway 64 seismic refl ection profi le acquired ~6 km southwest of the hypocenter to examine the structural setting of the earthquake. The profi le shows that the 2011 earthquake and its aftershocks are almost entirely within the early Paleozoic Chopawamsic volcanic arc terrane, which is bounded by listric thrust faults dipping 30°–40° southeast that sole out into an ~2-km-thick, strongly refl ective zone at 7– 12 km depth. Refl ectors above and below the southward projection of the 2011 earthquake focal plane do not show evidence for large displacement, and the updip projection of the fault plane does not match either the location or trend of a previously mapped fault or lithologic boundary. The 2011 earthquake thus does not appear to be a simple reactivation of a known Paleozoic thrust fault or a major Mesozoic rift basin-boundary fault. The fault that ruptured appears to be a new fault, a fault with only minor displacement, or to not extend the ~3 km from the aftershock zone to the seismic profi le. Although the Paleozoic structures appear to infl uence the general distribution of seismicity in the area, Central Virginia seismic zone earthquakes have yet to be tied directly to specifi c fault systems mapped at the surface or imaged on seismic profiles.

  5. Seismic Analysis Capability in NASTRAN

    NASA Technical Reports Server (NTRS)

    Butler, T. G.; Strang, R. F.

    1984-01-01

    Seismic analysis is a technique which pertains to loading described in terms of boundary accelerations. Earthquake shocks to buildings is the type of excitation which usually comes to mind when one hears the word seismic, but this technique also applied to a broad class of acceleration excitations which are applied at the base of a structure such as vibration shaker testing or shocks to machinery foundations. Four different solution paths are available in NASTRAN for seismic analysis. They are: Direct Seismic Frequency Response, Direct Seismic Transient Response, Modal Seismic Frequency Response, and Modal Seismic Transient Response. This capability, at present, is invoked not as separate rigid formats, but as pre-packaged ALTER packets to existing RIGID Formats 8, 9, 11, and 12. These ALTER packets are included with the delivery of the NASTRAN program and are stored on the computer as a library of callable utilities. The user calls one of these utilities and merges it into the Executive Control Section of the data deck to perform any of the four options are invoked by setting parameter values in the bulk data.

  6. Sub-crustal seismic activity beneath Klyuchevskoy Volcano

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  7. State of art of seismic design and seismic hazard analysis for oil and gas pipeline system

    NASA Astrophysics Data System (ADS)

    Liu, Aiwen; Chen, Kun; Wu, Jian

    2010-06-01

    The purpose of this paper is to adopt the uniform confidence method in both water pipeline design and oil-gas pipeline design. Based on the importance of pipeline and consequence of its failure, oil and gas pipeline can be classified into three pipe classes, with exceeding probabilities over 50 years of 2%, 5% and 10%, respectively. Performance-based design requires more information about ground motion, which should be obtained by evaluating seismic safety for pipeline engineering site. Different from a city’s water pipeline network, the long-distance oil and gas pipeline system is a spatially linearly distributed system. For the uniform confidence of seismic safety, a long-distance oil and pipeline formed with pump stations and different-class pipe segments should be considered as a whole system when analyzing seismic risk. Considering the uncertainty of earthquake magnitude, the design-basis fault displacements corresponding to the different pipeline classes are proposed to improve deterministic seismic hazard analysis (DSHA). A new empirical relationship between the maximum fault displacement and the surface-wave magnitude is obtained with the supplemented earthquake data in East Asia. The estimation of fault displacement for a refined oil pipeline in Wenchuan M S8.0 earthquake is introduced as an example in this paper.

  8. Seismicity of the Earth 1900–2010 Australia plate and vicinity

    USGS Publications Warehouse

    Benz, Harley M.; Herman, Matthew; Tarr, Arthur C.; Hayes, Gavin P.; Furlong, Kevin P.; Villaseñor, Antonio; Dart, Richard L.; Rhea, Susan

    2011-01-01

    This map shows details of the Australia plate and vicinity not presented in Tarr and others (2010). The boundary of the Australia plate includes all fundamental plate boundary components: mid-ocean ridges, subduction zones, arc-continent collisions, and large-offset transform faults. Along the southern edge of the plate the mid-ocean ridge separates the Australia and Antarctica plates and its behavior is straightforward. In contrast, the other boundary segments that ring the Australia plate represent some of the most seismically active elements of the global plate boundary system, and some of the most rapidly evolving plate interactions. As a result, there are some very complex structures which host many large and great earthquakes

  9. Seismic Constraints on the Lithosphere-Asthenosphere Boundary Beneath the Izu-Bonin Area: Implications for the Oceanic Lithospheric Thinning

    NASA Astrophysics Data System (ADS)

    Cui, Qinghui; Wei, Rongqiang; Zhou, Yuanze; Gao, Yajian; Li, Wenlan

    2018-01-01

    The lithosphere-asthenosphere boundary (LAB) is the seismic discontinuity with negative velocity contrasts in the upper mantle. Seismic detections on the LAB are of great significance in understanding the plate tectonics, mantle convection and lithospheric evolution. In this paper, we study the LAB in the Izu-Bonin subduction zone using four deep earthquakes recorded by the permanent and temporary seismic networks of the USArray. The LAB is clearly revealed with sP precursors (sdP) through the linear slant stacking. As illustrated by reflected points of the identified sdP phases, the depth of LAB beneath the Izu-Bonin Arc (IBA) is about 65 km with a range of 60-68 km. The identified sdP phases with opposite polarities relative to sP phases have the average relative amplitude of 0.21, which means a 3.7% velocity drop and implies partial melting in the asthenosphere. On the basis of the crustal age data, the lithosphere beneath the IBA is located at the 1100 °C isotherm calculated with the GDH1 model. Compared to tectonically stable areas, such as the West Philippine Basin (WPB) and Parece Vela Basin (PVB) in the Philippine Sea, the lithosphere beneath the Izu-Bonin area shows the obvious lithospheric thinning. According to the geodynamic and petrological studies, the oceanic lithospheric thinning phenomenon can be attributed to the strong erosion of the small-scale convection in the mantle wedge enriched in volatiles and melts.

  10. Development of Compact Seafloor Cabled Seismic and Tsunami Observation System Using ICT and Installation Plan to Off-Sanriku Region, Japan

    NASA Astrophysics Data System (ADS)

    Shinohara, M.; Yamada, T.; Sakai, S.; Shiobara, H.; Kanazawa, T.

    2014-12-01

    A seismic and tsunami observation system using seafloor optical fiber had been installed off Sanriku, northeastern Japan in 1996. The objectives of the system are to obtain exact seismic activity related to plate subduction and to observe tsunami on seafloor. The continuous real-time observation has been carried out since the installation. In March 2011, the Tohoku earthquake occurred at the plate boundary near the Japan Trench, and the system recorded seismic waves and tsunamis by the mainshock. These data are useful to obtain accurate position of the source faults and source region of tsunami generated by the event. However, the landing station of the system was damaged by huge tsunami, and the observation was suspended. Because the real-time seafloor observation by cabled system is important in this region, we decide to reconstruct a landing station and install newly developed Ocean Bottom Cabled Seismic and Tsunami (OBCST) observation system for additional observation and/or replacement of the existing system. From 2005, we have been developed the new compact Ocean Bottom Cabled Seismometer (OBCS) system using Information and Communication Technology (ICT). Our system is characterized by securement of reliability by using TCP/IP technology and down-sizing of an observation node using up-to-date electronics technology. In 2010, the first OBCS was installed near Awashima-island in the Japan Sea, and is being operated continuously. The new OBCST system is placed as the second generation of our system, and has two types of observation nodes. Both types have accelerometers as seismic sensors. One type of observation nodes equips a crystal oscillator type pressure gauge as tsunami sensor. Another type has an external port for additional observation sensor by using Power over Ethernet technology. Clocks in observation nodes can be synchronized through TCP/IP protocol with an accuracy of 300 ns (IEEE 1588). A simple canister for tele-communication seafloor cable is

  11. Fault geometries illuminated from seismicity in central Taiwan: Implications for crustal scale structural boundaries in the northern Central Range

    NASA Astrophysics Data System (ADS)

    Gourley, Jonathan R.; Byrne, Timothy; Chan, Yu-Chang; Wu, Francis; Rau, Ruey-Juin

    2007-12-01

    Data sets of collapsed earthquake locations, earthquake focal mechanisms, GPS velocities and geologic data are integrated to constrain the geometry and kinematics of a crustal block within the accreted continental margin rocks of Taiwan's northeastern Central Range. This block is laterally extruding and exhuming towards the north-northeast. The block is bound on the west-southwest by the previously recognized Sanyi-Puli seismic zone and on the east by a vertical seismic structure that projects to the eastern mountain front of the Central Range. Focal mechanisms from the Broadband Array of Taiwan Seismicity (BATS) catalog consistently show west-side-up reverse displacements for this fault zone. A second vertical structure is recognized beneath the Slate Belt-Metamorphic Belt boundary as a post-Chi-Chi relaxation oblique normal fault. BATS focal mechanisms show east-side-up, normal displacements with a minor left-lateral component. The vertical and lateral extrusion of this crustal block may be driven by the current collision between the Philippine Sea Plate and the Puli basement high indenter on the Eurasian Plate and/or trench rollback along the Ryukyu subduction zone. In addition, the vertical extent of the two shear zones suggests that a basal décollement below the eastern Central Range is deeper than previously proposed and may extend below the brittle-ductile transition.

  12. Deep seismic exploration into the Arctic Lithosphere: Arctic-2012 Russian wide-angle seismic experiment

    NASA Astrophysics Data System (ADS)

    Kashubin, S.

    2013-12-01

    Integrated geological and geophysical studies of the Earth's crust and upper mantle (the Russian project 'Arctic-2012') were carried out in 2012 in the Mendeleev Rise, central Arctic. The set of studies included wide-angle seismic observations along the line crossing the Mendeleev Rise in its southern part. The DSS seismic survey was aimed at the determination of the Mendeleev Rise crust type. A high-power air gun (120 liters or 7320 cu.in) and ocean stations with multi-component recording (X, Y, Z geophone components and a hydrophone) were used for the DSS. The line was studied using a dense system of observation: bottom station spacing was from 10 to 20 km, excitation point spacing (seismic traces interval) was 315 m. Observation data were obtained in 27 location points of bottom stations, the distance between the first and the last stations was 480 km, the length of the excitation line was 740 km. In DSS wave fields, in the first and later arrivals, there are refracted and reflected waves associated with boundaries in the sedimentary cover, with the top of the basement, and with boundaries in the consolidated crust, including its bottom (Moho discontinuity). The waves could be traced for offsets up to 170-240 km. The DSS line coincides with the near-vertical CMP line worked out with the use of a 4500-m-long seismic streamer and with a 50 m shot point interval that allowed essential detalization of the upper part of the section and taking it into account in the construction of a deep crust model. The deep velocity model was constructed using ray-trace modeling of compressional, shear, and converted waves with the use of the SeisWide program. Estimates were obtained for Vp/Vs velocity ratios, which played an important role in determining the type of crust. The results of the interpretation show that the Mendeleev Rise section corresponds to sections of a thin continental crust of shelf seas and a thinned continental crust of submarine ridges and rises.

  13. Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

    SciTech Connect

    Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

    2014-09-03

    Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift successionmore » is dominated by a thick (1–5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.« less

  14. The effect of plate-scale rheology and plate interactions on intraplate seismicity

    NASA Astrophysics Data System (ADS)

    So, Byung-Dal; Capitanio, Fabio A.

    2017-11-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ =ηI /ηL, the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ =σY /σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  15. Measuring the seismic velocity in the top 15 km of Earth's inner core

    NASA Astrophysics Data System (ADS)

    Godwin, Harriet; Waszek, Lauren; Deuss, Arwen

    2018-01-01

    We present seismic observations of the uppermost layer of the inner core. This was formed most recently, thus its seismic features are related to current solidification processes. Previous studies have only constrained the east-west hemispherical seismic velocity structure in the Earth's inner core at depths greater than 15 km below the inner core boundary. The properties of shallower structure have not yet been determined, because the seismic waves PKIKP and PKiKP used for differential travel time analysis arrive close together and start to interfere. Here, we present a method to make differential travel time measurements for waves that turn in the top 15 km of the inner core, and measure the corresponding seismic velocity anomalies. We achieve this by generating synthetic seismograms to model the overlapping signals of the inner core phase PKIKP and the inner core boundary phase PKiKP. We then use a waveform comparison to attribute different parts of the signal to each phase. By measuring the same parts of the signal in both observed and synthetic data, we are able to calculate differential travel time residuals. We apply our method to data with ray paths which traverse the Pacific hemisphere boundary. We generate a velocity model for this region, finding lower velocity for deeper, more easterly ray paths. Forward modelling suggests that this region contains either a high velocity upper layer, or variation in the location of the hemisphere boundary with depth and/or latitude. Our study presents the first direct seismic observation of the uppermost 15 km of the inner core, opening new possibilities for further investigating the inner core boundary region.

  16. An assessment of seismic monitoring in the United States; requirement for an Advanced National Seismic System

    USGS Publications Warehouse

    ,

    1999-01-01

    This report assesses the status, needs, and associated costs of seismic monitoring in the United States. It sets down the requirement for an effective, national seismic monitoring strategy and an advanced system linking national, regional, and urban monitoring networks. Modernized seismic monitoring can provide alerts of imminent strong earthquake shaking; rapid assessment of distribution and severity of earthquake shaking (for use in emergency response); warnings of a possible tsunami from an offshore earthquake; warnings of volcanic eruptions; information for correctly characterizing earthquake hazards and for improving building codes; and data on response of buildings and structures during earthquakes, for safe, cost-effective design, engineering, and construction practices in earthquake-prone regions.

  17. Seismic attenuation system for a nuclear reactor

    SciTech Connect

    Liszkai, Tamas; Cadell, Seth

    A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel include a bottom head. Additionally, the system includes a base support to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device is located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vesselmore » are attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.« less

  18. Classifying seismic noise and sources from OBS data using unsupervised machine learning

    NASA Astrophysics Data System (ADS)

    Mosher, S. G.; Audet, P.

    2017-12-01

    The paradigm of plate tectonics was established mainly by recognizing the central role of oceanic plates in the production and destruction of tectonic plates at their boundaries. Since that realization, however, seismic studies of tectonic plates and their associated deformation have slowly shifted their attention toward continental plates due to the ease of installation and maintenance of high-quality seismic networks on land. The result has been a much more detailed understanding of the seismicity patterns associated with continental plate deformation in comparison with the low-magnitude deformation patterns within oceanic plates and at their boundaries. While the number of high-quality ocean-bottom seismometer (OBS) deployments within the past decade has demonstrated the potential to significantly increase our understanding of tectonic systems in oceanic settings, OBS data poses significant challenges to many of the traditional data processing techniques in seismology. In particular, problems involving the detection, location, and classification of seismic sources occurring within oceanic settings are much more difficult due to the extremely noisy seafloor environment in which data are recorded. However, classifying data without a priori constraints is a problem that is routinely pursued via unsupervised machine learning algorithms, which remain robust even in cases involving complicated datasets. In this research, we apply simple unsupervised machine learning algorithms (e.g., clustering) to OBS data from the Cascadia Initiative in an attempt to classify and detect a broad range of seismic sources, including various noise sources and tremor signals occurring within ocean settings.

  19. Geomorphology, active duplexing, and earthquakes within the Central Himalayan seismic gap

    NASA Astrophysics Data System (ADS)

    Morell, K. D.; Sandiford, M.; Rajendran, C. C.; Rajendran, K.

    2013-12-01

    The ~500 km long 'Central Himalayan seismic gap' of northwest India, is the largest section of the Himalaya that has not experienced a very large earthquake (Mw > 7.0) in the past 200-500 years. The slip deficit associated with this seismic quiescence has led many to suggest that the region is overdue for a great earthquake (Mw >8), an event which could be potentially devastating given the region's high population (>10 million). Despite the recognition that the region is under considerable seismic risk, the geometry of active fault structures that could potentially fail during large earthquakes remains poorly defined. This has arisen, to a certain extent, because moderate earthquakes, such as the Mw 6.3 1999 event near the city of Chamoli and the Mw 7.0 1991 earthquake near Uttarkashi (responsible for ~1000 deaths), have not produced obvious surface ruptures and do not appear to coincide with surficially mapped faults. We present new geomorphic and river longitudinal profile data that define a prominent ~400 km long distinctive geomorphic transition at the base of the high Himalaya in the seismic gap, defined as a sharp dividing line north of which there are significant increases in normalized river steepness (ksn), hillslope angles, and local relief. We interpret the morphologic changes across the geomorphic boundary to be produced due to a northward increase in rock uplift rate, given that the boundary cross-cuts mapped structures and lithologic contacts, yet coincides exactly with: 1) the axial trace of the geophysically-imaged ramp-flat transition in the Main Himalayan Thrust, 2) significant northward increases in instrumentally-recorded seismicity, and 3) an order of magnitude change in published Ar-Ar bedrock cooling ages. The available datasets suggest that such an increase in rock uplift rate is best explained by a ~400 km long by ~50 km wide active duplex along the Main Himalayan Thrust ramp, with the leading edge of the duplex giving rise to the

  20. Wireless acquisition of multi-channel seismic data using the Seismobile system

    NASA Astrophysics Data System (ADS)

    Isakow, Zbigniew

    2017-11-01

    This paper describes the wireless acquisition of multi-channel seismic data using a specialized mobile system, Seismobile, designed for subsoil diagnostics for transportation routes. The paper presents examples of multi-channel seismic records obtained during system tests in a configuration with 96 channels (4 landstreamers of 24-channel) and various seismic sources. Seismic waves were generated at the same point using different sources: a 5-kg hammer, a Gisco's source with a 90-kg pile-driver, and two other the pile-drivers of 45 and 70 kg. Particular attention is paid to the synchronization of source timing, the measurement of geometry by autonomous GPS systems, and the repeatability of triggering measurements constrained by an accelerometer identifying the seismic waveform. The tests were designed to the registration, reliability, and range of the wireless transmission of survey signals. The effectiveness of the automatic numbering of measuring modules was tested as the system components were arranged and fixed to the streamers. After measurements were completed, the accuracy and speed of data downloading from the internal memory (SDHC 32GB WiFi) was determined. Additionally, the functionality of automatic battery recharging, the maximum survey duration, and the reliability of battery discharge signalling were assessed.

  1. The INGV seismic monitoring system: activities during the first month of the 2016 Amatrice seismic sequence.

    NASA Astrophysics Data System (ADS)

    Scognamiglio, L.; Margheriti, L.; Moretti, M.; Pintore, S.

    2016-12-01

    At 01:36:32 UTC on August 24, 2016 an earthquake of ML=6.0 occurred in Central Italy, near Amatrice village; 21 s after the origin time, the first automatic location became available while the first magnitude estimate followed 47s after. The INGV seismologists on duty provided the alert to the Italian Civil Protection Department and thereby triggered the seismic emergency protocol In the hours after the earthquake, hundreds of events were recorded by the Italian Seismic Network of the INGV. SISMIKO, the coordinating body of the emergency seismic network, was activated few minutes after the mainshock. The main goal of this emergency group is to install temporary dense seismic network integrated with the existing permanent networks in the epicentral area to better constrain the aftershock hypocenters. From August the 24th to the 30th, SISMIKO deployed 18 seismic stations, generally six components (equipped with both seismometer and accelerometer), 13 of which were transmitting in real-time to the INGV seismic surveillance room in Rome. All data acquired are available at the European Integrated Data Archive (EIDA). The seismic sequence in the first month generated thousands of earthquakes which were processed and detected by the INGV automated localization system. We analyzed the performance of this system. Hundreds of those events were located by seismologists on shifts, the others were left to be analyzed by the Bollettino Sismico Italiano (BSI). The procedures of the BSI revise and integrate all available data. This allows for a better constrained location and for a more realistic hypocentral depth estimation. The first eight hours of August 24th were the most critical for the INGV surveillance room. Data recorded in these hours were carefully re-analyzed by BSI operators and the number of located events increased from 133 to 408, while the magnitude of completeness dropped significantly from about 3.5 to 2.7.

  2. An Experimental Seismic Data and Parameter Exchange System for Interim NEAMTWS

    NASA Astrophysics Data System (ADS)

    Hanka, W.; Hoffmann, T.; Weber, B.; Heinloo, A.; Hoffmann, M.; Müller-Wrana, T.; Saul, J.

    2009-04-01

    In 2008 GFZ Potsdam has started to operate its global earthquake monitoring system as an experimental seismic background data centre for the interim NEAMTWS (NE Atlantic and Mediterranean Tsunami Warning System). The SeisComP3 (SC3) software, developed within the GITEWS (German Indian Ocean Tsunami Early Warning System) project was extended to test the export and import of individual processing results within a cluster of SC3 systems. The initiated NEAMTWS SC3 cluster consists presently of the 24/7 seismic services at IMP, IGN, LDG/EMSC and KOERI, whereas INGV and NOA are still pending. The GFZ virtual real-time seismic network (GEOFON Extended Virtual Network - GEVN) was substantially extended by many stations from Western European countries optimizing the station distribution for NEAMTWS purposes. To amend the public seismic network (VEBSN - Virtual European Broadband Seismic Network) some attached centres provided additional private stations for NEAMTWS usage. In parallel to the data collection by Internet the GFZ VSAT hub for the secured data collection of the EuroMED GEOFON and NEAMTWS backbone network stations became operational and the first data links were established. In 2008 the experimental system could already prove its performance since a number of relevant earthquakes have happened in NEAMTWS area. The results are very promising in terms of speed as the automatic alerts (reliable solutions based on a minimum of 25 stations and disseminated by emails and SMS) were issued between 2 1/2 and 4 minutes for Greece and 5 minutes for Iceland. They are also promising in terms of accuracy since epicenter coordinates, depth and magnitude estimates were sufficiently accurate from the very beginning, usually don't differ substantially from the final solutions and provide a good starting point for the operations of the interim NEAMTWS. However, although an automatic seismic system is a good first step, 24/7 manned RTWCs are mandatory for regular manual verification

  3. Chaotic system detection of weak seismic signals

    NASA Astrophysics Data System (ADS)

    Li, Y.; Yang, B. J.; Badal, J.; Zhao, X. P.; Lin, H. B.; Li, R. L.

    2009-09-01

    When the signal-to-noise (S/N) ratio is less than -3 dB or even 0 dB, seismic events are generally difficult to identify from a common shot record. To overcome this type of problem we present a method to detect weak seismic signals based on the oscillations described by a chaotic dynamic system in phase space. The basic idea is that a non-linear chaotic oscillator is strongly immune to noise. Such a dynamic system is less influenced by noise, but it is more sensitive to periodic signals, changing from a chaotic state to a large-scale periodic phase state when excited by a weak signal. With the purpose of checking the possible contamination of the signal by noise, we have performed a numerical experiment with an oscillator controlled by the Duffing-Holmes equation, taking a distorted Ricker wavelet sequence as input signal. In doing so, we prove that the oscillator system is able to reach a large-scale periodic phase state in a strong noise environment. In the case of a common shot record with low S/N ratio, the onsets reflected from a same interface are similar to one other and can be put on a single trace with a common reference time and the periodicity of the so-generated signal follows as a consequence of moveout at a particular scanning velocity. This operation, which is called `horizontal dynamic correction' and leads to a nearly periodic signal, is implemented on synthetic wavelet sequences taking various sampling arrival times and scanning velocities. Thereafter, two tests, both in a noisy ambient of -3.7 dB, are done using a chaotic oscillator: the first demonstrates the capability of the method to really detect a weak seismic signal; the second takes care of the fundamental weakness of the dynamic correction coming from the use of a particular scanning velocity, which is investigated from the effect caused by near-surface lateral velocity variation on the periodicity of the reconstructed seismic signal. Finally, we have developed an application of the

  4. Seismic properties of fluid bearing formations in magmatic geothermal systems: can we directly detect geothermal activity with seismic methods?

    NASA Astrophysics Data System (ADS)

    Grab, Melchior; Scott, Samuel; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

    2016-04-01

    Seismic methods are amongst the most common techniques to explore the earth's subsurface. Seismic properties such as velocities, impedance contrasts and attenuation enable the characterization of the rocks in a geothermal system. The most important goal of geothermal exploration, however, is to describe the enthalpy state of the pore fluids, which act as the main transport medium for the geothermal heat, and to detect permeable structures such as fracture networks, which control the movement of these pore fluids in the subsurface. Since the quantities measured with seismic methods are only indirectly related with the fluid state and the rock permeability, the interpretation of seismic datasets is difficult and usually delivers ambiguous results. To help overcome this problem, we use a numerical modeling tool that quantifies the seismic properties of fractured rock formations that are typically found in magmatic geothermal systems. We incorporate the physics of the pore fluids, ranging from the liquid to the boiling and ultimately vapor state. Furthermore, we consider the hydromechanics of permeable structures at different scales from small cooling joints to large caldera faults as are known to be present in volcanic systems. Our modeling techniques simulate oscillatory compressibility and shear tests and yield the P- and S-wave velocities and attenuation factors of fluid saturated fractured rock volumes. To apply this modeling technique to realistic scenarios, numerous input parameters need to be indentified. The properties of the rock matrix and individual fractures were derived from extensive literature research including a large number of laboratory-based studies. The geometries of fracture networks were provided by structural geologists from their published studies of outcrops. Finally, the physical properties of the pore fluid, ranging from those at ambient pressures and temperatures up to the supercritical conditions, were taken from the fluid physics

  5. The Cottage Grove fault system (Illinois Basin): Late Paleozoic transpression along a Precambrian crustal boundary

    USGS Publications Warehouse

    Duchek, A.B.; McBride, J.H.; Nelson, W.J.; Leetaru, H.E.

    2004-01-01

    The Cottage Grove fault system in southern Illinois has long been interpreted as an intracratonic dextral strike-slip fault system. We investigated its structural geometry and kinematics in detail using (1) outcrop data, (2) extensive exposures in underground coal mines, (3) abundant borehole data, and (4) a network of industry seismic reflection profiles, including data reprocessed by us. Structural contour mapping delineates distinct monoclines, broad anticlines, and synclines that express Paleozoic-age deformation associated with strike slip along the fault system. As shown on seismic reflection profiles, prominent near-vertical faults that cut the entire Paleozoic section and basement-cover contact branch upward into outward-splaying, high-angle reverse faults. The master fault, sinuous along strike, is characterized along its length by an elongate anticline, ???3 km wide, that parallels the southern side of the master fault. These features signify that the overall kinematic regime was transpressional. Due to the absence of suitable piercing points, the amount of slip cannot be measured, but is constrained at less than 300 m near the ground surface. The Cottage Grove fault system apparently follows a Precambrian terrane boundary, as suggested by magnetic intensity data, the distribution of ultramafic igneous intrusions, and patterns of earthquake activity. The fault system was primarily active during the Alleghanian orogeny of Late Pennsylvanian and Early Permian time, when ultramatic igneous magma intruded along en echelon tensional fractures. ?? 2004 Geological Society of America.

  6. Is Microseismicity Relevant to Estimating Seismic Hazards in North Central New Mexico?

    NASA Astrophysics Data System (ADS)

    House, L.; Roberts, P.; Gardner, J. N.

    2003-12-01

    The Rio Grande rift extends south from southern Colorado through central New Mexico and into northern Mexico. It is a major tectonic feature in New Mexico, yet seismicity in the rift is comparable to or lower than in the adjacent stable Great Plains and Colorado Plateau provinces (Sanford, et al, 1991). In north-central New Mexico, thirty years of microearthquake monitoring have provided more than 650 epicenters in an area of about 28 000 sq km. The largest earthquake was about magnitude 3. Epicenters show only a slight association with recently active faults, and most lie away from faults (mislocation of epicenters could produce this scatter, though we think it is unlikely). The Pajarito fault system is presently the western boundary of the Rio Grande rift in the area of the Espanola Basin (from Santa Fe to Espanola), yet has little seismicity associated with it, and only for 15 km of its 50 km length. That seismicity includes five earthquakes that were been felt in the Los Alamos area since 1991 (most recently in April 2003). Paleoseismic studies (Gardner et al, 2001) found evidence for large slip events along that same 15 km portion of the Pajarito fault system as recently as 2 ka. Recurrence times of these events are not known, but may be 10 ka or longer. The remainder of the rift boundary in north-central New Mexico is not discernable from seismicity. A simple model of opening of the rift (at an assumed rate of 0.1 mm/yr) produces an estimate of seismic moment release that is several orders of magnitude greater than seen in the seismicity. Microseismicity seems to have little relation to the macroseismicity that may occur on long time intervals (perhaps thousands of years) and may not be relevant for understanding seismic hazards in this part of the Rio Grande rift. Sanford, A.R., L.H. Jaksha, and D.J. Cash (1991), Seismicity of the Rio Grande rift in New Mexico, in Slemmons, D.B., E.R. Engdahl, M.D. Zoback, and D.D. Blackwell (eds), Neotectonics of North

  7. Evaluation of Seismic Performance and Effectiveness of Multiple Slim-Type Damper System for Seismic Response Control of Building Structures

    PubMed Central

    Kim, David; Sung, Eun Hee; Park, Kwan-Soon; Park, Jaegyun

    2014-01-01

    This paper presents the evaluation of seismic performance and cost-effectiveness of a multiple slim-type damper system developed for the vibration control of earthquake excited buildings. The multiple slim-type damper (MSD) that consists of several small slim-type dampers and linkage units can control damping capacity easily by changing the number of small dampers. To evaluate the performance of the MSD, dynamic loading tests are performed with three slim-type dampers manufactured at a real scale. Numerical simulations are also carried out by nonlinear time history analysis with a ten-story earthquake excited building structure. The seismic performance and cost-effectiveness of the MSD system are investigated according to the various installation configurations of the MSD system. From the results of numerical simulation and cost-effectiveness evaluation, it is shown that combinations of the MSD systems can effectively improve the seismic performance of earthquake excited building structures. PMID:25301387

  8. Mantle dynamics and seismic tomography

    PubMed Central

    Tanimoto, Toshiro; Lay, Thorne

    2000-01-01

    Three-dimensional imaging of the Earth's interior, called seismic tomography, has achieved breakthrough advances in the last two decades, revealing fundamental geodynamical processes throughout the Earth's mantle and core. Convective circulation of the entire mantle is taking place, with subducted oceanic lithosphere sinking into the lower mantle, overcoming the resistance to penetration provided by the phase boundary near 650-km depth that separates the upper and lower mantle. The boundary layer at the base of the mantle has been revealed to have complex structure, involving local stratification, extensive structural anisotropy, and massive regions of partial melt. The Earth's high Rayleigh number convective regime now is recognized to be much more interesting and complex than suggested by textbook cartoons, and continued advances in seismic tomography, geodynamical modeling, and high-pressure–high-temperature mineral physics will be needed to fully quantify the complex dynamics of our planet's interior. PMID:11035784

  9. Integrating Social impacts on Health and Health-Care Systems in Systemic Seismic Vulnerability Analysis

    NASA Astrophysics Data System (ADS)

    Kunz-Plapp, T.; Khazai, B.; Daniell, J. E.

    2012-04-01

    This paper presents a new method for modeling health impacts caused by earthquake damage which allows for integrating key social impacts on individual health and health-care systems and for implementing these impacts in quantitative systemic seismic vulnerability analysis. In current earthquake casualty estimation models, demand on health-care systems is estimated by quantifying the number of fatalities and severity of injuries based on empirical data correlating building damage with casualties. The expected number of injured people (sorted by priorities of emergency treatment) is combined together with post-earthquake reduction of functionality of health-care facilities such as hospitals to estimate the impact on healthcare systems. The aim here is to extend these models by developing a combined engineering and social science approach. Although social vulnerability is recognized as a key component for the consequences of disasters, social vulnerability as such, is seldom linked to common formal and quantitative seismic loss estimates of injured people which provide direct impact on emergency health care services. Yet, there is a consensus that factors which affect vulnerability and post-earthquake health of at-risk populations include demographic characteristics such as age, education, occupation and employment and that these factors can aggravate health impacts further. Similarly, there are different social influences on the performance of health care systems after an earthquake both on an individual as well as on an institutional level. To link social impacts of health and health-care services to a systemic seismic vulnerability analysis, a conceptual model of social impacts of earthquakes on health and the health care systems has been developed. We identified and tested appropriate social indicators for individual health impacts and for health care impacts based on literature research, using available European statistical data. The results will be used to

  10. Investigating the Effects Fracture Systems Have on Seismic Wave Velocities at the Lajitas, Texas Seismic Station

    DTIC Science & Technology

    1989-05-01

    Victoria L. Sandidge-Bodoh % S Southern Methodist University Department of Geological Sciences Dallas, TX 75275 1 May 1989 Final Report 3 March 1987 - 2...Projects Agency or the U.S. Government. This technical report has been reviewed and is approved for publicj ion. JAME F. LEWKOW(CZ J/ S F. LEWKOWiC...Effects Fracture Systems Have on Seismic Wave Velocities at the Lajitas, Texas Seismic Station 12. PERSONAL AUTHOR( S ) Victoria L. Sandidge-Bodoh 13a. TYPE

  11. Five-day recorder seismic system

    USGS Publications Warehouse

    Criley, Ed; Eaton, Jerry P.; Ellis, Jim

    1978-01-01

    The 10-day recorder seismic system used by the USGS since 1965 has been modified substantially to improve its dynamic range and frequency response, to decrease its power consumption and physical complexity, and to make its recordings more compatible with other NCER systems to facilitate data processing. The principal changes include: 1. increasing tape speed from 15/160 ips to 15/80 ips (reducing running time from 10 days to 5 days with a 14' reel of 1 mil tape), 2. increasing the FM center frequency by a factor of 4, from 84.4 Hz to 337.6 Hz, 3. replacing the original amplifiers and FM modulators with new low-power units, 4. replacing the chronometer with a higher quality time code generator (with IRIG-C) to permit automation of data retrieval, 5. eliminating the amplifier/WWVB radio field case by incorporating these elements, along with the new TCG, in the weatherproof tape-recorder box, 6. reducing the power consumption of the motor-drive circuit by removal of a redundant component. In the new system, the tape-recorder case houses all components except the seismometers, the WWVB antenna, the 70-amp-hour 12-VDC battery (which powers the system for 5 days), and the cables to connect these external elements to the recorder box. The objectives of this report are: 1. to describe the new 5-day-recorder seismic system in terms of its constituent parts and their functions, 2. to describe modifications to parts of the original system that were retained and to document new or replacement components with appropriate circuit diagrams and constructional details, 3. to provide detailed instructions for the correct adjustment or alignment of the system in the laboratory, and 4. to provide detailed instructions for installing and operating the system in the field.

  12. The Seismic Alert System of Mexico (SASMEX): Performance and Evolution

    NASA Astrophysics Data System (ADS)

    Espinosa Aranda, J.

    2013-05-01

    Originally the Seismic Alert System of Mexico (SASMEX) was proposed to integrate the Seismic Alert System of Mexico City (SAS), operating since 1991, with the Seismic Alert System of Oaxaca City (SASO), in services since 2003. And today, after the intense big earthquake activity observed in our world during 2010 and 2011, local governments of Mexico City, Oaxaca Estate, and the Mexican Ministry of the Interior have been promoting the expansion of this technological EEW development. Until 2012 SASMEX better coverage includes 48 new field seismic sensors (FS) deployed over the seismic region of Jalisco, Colima, Michoacan and Puebla, with someone enhancements over Guerrero and Oaxaca, to reach 97 FS. During 2013, 35 new FS has been proposed to SASMEX enhancements covering the Chiapas and Veracruz seismic regions. The SASMEX, with the support of the Mexico Valley Broadcasters Association (ARVM) since 1993, automatically issue Public and Preventive earthquake early warning signals in the Cities of Mexico, Toluca, Acapulco, Chilpancingo, and Oaxaca. The seismic warning range in each case is seated in accordance with local Civil Protection Authorities: Public Alert, if they expect strong earthquake effects, and Preventive Alert one, the effect could be moderated. Now the SASMEX warning time opportunity could be different to the 60 sec. average typically generated when SAS warned earthquake effects coming from Guerrero to Mexico City valley. Mexican EEW issued today reach: 16 Public and 62 Preventive Alert in Mexico City; 25 Public and 19 Preventive Alerts in Oaxaca City; also 14 Public and 4 Preventive Alerts in Acapulco; 14 Public and 5 Preventive Alerts in Chilpancingo. The earthquakes events registered by SASMEX FS until now reach 3448. With the support of private and Federal telecommunications infrastructure like, TELMEX, Federal Electric Commission, and the Mexican Security Ministry, it was developed a redundant communication system with pads to link the different

  13. CRUSTAL TECTONICS AND SEISMICITY OF THE MIDDLE EAST

    NASA Astrophysics Data System (ADS)

    Ghalib, H. A.; Gritto, R.; Sibol, M. S.; Herrmann, R. B.; Aleqabi, G. I.; Caron, P. F.; Wagner, R. A.; Ali, B. S.; Ali, A. A.

    2009-12-01

    The Arabian plate describes a geological entity and a dynamic system that has been in continuous interaction with the African plate to the west and south and the Eurasian plate to the north and east. The western and southern boundaries are distinguished by see floor spreading along the Gulf of Aden and Red Sea and transform faulting along the Dead Sea, whereas the northern and eastern boundaries are portrayed by compressional suture zones under thrusting the Turkish and Iranian plateaus. Despite this favorable juxtaposition of continental land masses and the plethora of national seismic networks in every country of the Middle East, the majority of published research on the Arabian plate and surrounding tectonic blocks still depends primarily on global seismographic stations and occasional local networks. Since 2005, we deployed a number of seismic stations, and more recently a five elements array, in close proximity to the northeastern boundary of the Arabian plate. The primary objective of the effort is to better understand the regional seismicity and seismotectonics of the Arabian plate and surrounding regions. To date over a terabyte of high quality 100 sps continuous three-component broadband data have been collected and being analyzed to derive models representative of the greater Middle East tectonic setting. This goal is, in part, achieved by estimating local and regional seismic velocity models using receiver function and surface wave dispersion analyses, and by using these models to obtain accurate hypocenter locations and event focal mechanisms. The resulting events distribution reveals a distinct picture of the interaction between the seismicity and tectonics of the region. The highest seismicity rate seems to be confined to the active northern section of the Zagros thrust zone, while it decreases towards the southern end, before the intensity increases again in the Bandar Abbas region. Spatial distribution of the events and stations provide thorough

  14. Implications of a localized zone of seismic activity near the Inner Piedmont-Blue Ridge boundary

    SciTech Connect

    Douglas, S.; Powell, C.

    1994-03-01

    A small but distinct cluster of earthquake activity is located in Henderson County, NC, near the boundary of the Inner Piedmont and Blue Ridge physiographic provinces. Over twenty events have occurred within the cluster since 1776 and four had body-wave magnitudes exceeding 3.0. Average focal depth for instrumentally recorded events is 7.7 km. Epicenters plot within the Inner Piedmont, roughly 13 km from the surface expression of the Brevard fault zone. The reason for sustained earthquake activity in Henderson County is not known but the close spatial association of the events with the Brevard fault suggests a causal relationship. Themore » Brevard zone dips steeply to the SE and the events could be associated with the fault at depth. An even more intriguing possibility is that the events are associated with the intersection of the Brevard zone and the decollemont; this possibility is compatible with available information concerning the depth to the decollemont and the dip on the Brevard zone. An association of seismic activity with the Brevard zone at depth is supported by the presence of another small cluster of activity located in Rutherford County, NC. This cluster is located in the Inner Piedmont, roughly 30 km NE of the Henderson cluster and 16 km from the Brevard fault zone. Association of seismic activity with known faults is very rare in the eastern US and has implications for tectonic models and hazard evaluation. Additional research must be conducted to determine the feasibility that activity is associated with the Brevard zone.« less

  15. Global significance of a sub-Moho boundary layer (SMBL) deduced from high-resolution seismic observations

    USGS Publications Warehouse

    Fuchs, K.; Tittgemeyer, M.; Ryberg, T.; Wenzel, F.; Mooney, W.

    2002-01-01

    We infer the fine structure of a sub-Moho boundary layer (SMBL) at the top of the lithospheric mantle from high-resolution seismic observations of Peaceful Nuclear Explosions (PNE) on superlong-range profiles in Russia. Densely recorded seismograms permit recognition of previously unknown features of teleseismic propagation of the well known Pn and Sn phases, such as a band of incoherent, scattered, high-frequency seismic energy, developing consistently from station to station, apparent velocities of sub-Moho material, and high-frequency energy to distances of more than 3000 km with a coda band, incoherent at 10 km spacing and yet consistently observed to the end of the profiles. Estimates of the other key elements of the SMBL were obtained by finite difference calculations of wave propagation in elastic 2D models from a systematic grid search through parameter space. The SMBL consists of randomly distributed, mild velocity fluctuations of 2% or schlieren of high aspect ratios (???40) with long horizontal extent (???20 km) and therefore as thin as 0.5 km only; SMBL thickness is 60-100 km. It is suggested that the SMBL is of global significance as the physical base of the platewide observed high-frequency phases Pn and Sn. It is shown that wave propagation in the SMBL waveguide is insensitive to the background velocity distribution on which its schlieren are superimposed. This explains why the Pn and Sn phases traverse geological provinces of various age, heat flow, crustal thickness, and tectonic regimes. Their propagation appears to be independent of age. temperature, pressure, and stress. Dynamic stretching of mantle material during subduction or flow, possibly combined with chemical differentiation have to be considered as scale-forming processes in the upper mantle. However, it is difficult to distinguish with the present sets of Pn/Sn array data whether (and also where) the boundary layer is a frozen-in feature of paleo-processes or whether it is a response to

  16. Seismic Attenuation Structure and Intraplate Deformation

    NASA Astrophysics Data System (ADS)

    Bezada, M.; Kowalke, S.; Smale, J.

    2017-12-01

    It has been suggested that intraplate deformation and seismicity is localized at weak zones in the lithosphere and at rheological boundaries. Comparisons of intraplate deformation regions with mantle seismic velocity structure suggest a correlation, but are not universally accepted as compelling evidence. We present P-wave attenuation models built from records of teleseismic deep-focus earthquakes in three different regions that show significant correlation between attenuation structure and intraplate seismicity and deformation. In the eastern United States, the New Madrid, Wabash Valley, Eastern Tennessee, Central Virginia, and Carolina seismic zones all occur at or near the edges of high-Q (low attenuation) regions. In Spain, intraplate seismicity is absent from high-Q regions but relatively abundant in surrounding low-Q regions where intraplate orogeny is also observed. In Australia, where our model resolution is relatively poor owing to sparse and uneven station coverage, the Petermann and Alice Springs intraplate orogens occur near the edge of a high-Q feature roughly coinciding with the undeformed Amadeus basin. Our results suggest that lithospheric structure exerts important controls on the localization of intraplate deformation and seismicity and that seismic attenuation is a useful proxy for lithospheric strength.

  17. Seismic performance of arch dams on non-homogeneous and discontinuous foundations (a case study: Karun 4 Dam)

    NASA Astrophysics Data System (ADS)

    Ferdousi, A.

    2017-06-01

    The present study set out to investigate the nonlinear seismic response of the dam-reservoir-rock foundation system, taking into consideration the effects of change in the material properties of discontinuous foundation. To this end, it is important to provide the proper modeling of truncated boundary conditions at the far-end of rock foundation and reservoir fluid domain and to correctly apply the in situ stresses for rock foundation. The nonlinear seismic response of an arch dam mainly depends on the opening and sliding of the dam body's contraction joints and foundation discontinuities, failure of the jointed rock and concrete materials, etc. In this paper, a time domain dynamic analysis of the 3D dam-reservoir-foundation interaction problem was performed by developing a nonlinear Finite Element program. The results of the analysis of Karun-4 Dam revealed the essential role of modeling discontinuities and boundary conditions of rock foundation under seismic excitation.

  18. Reflection imaging of the Moon's interior using deep-moonquake seismic interferometry

    NASA Astrophysics Data System (ADS)

    Nishitsuji, Yohei; Rowe, C. A.; Wapenaar, Kees; Draganov, Deyan

    2016-04-01

    The internal structure of the Moon has been investigated over many years using a variety of seismic methods, such as travel time analysis, receiver functions, and tomography. Here we propose to apply body-wave seismic interferometry to deep moonquakes in order to retrieve zero-offset reflection responses (and thus images) beneath the Apollo stations on the nearside of the Moon from virtual sources colocated with the stations. This method is called deep-moonquake seismic interferometry (DMSI). Our results show a laterally coherent acoustic boundary around 50 km depth beneath all four Apollo stations. We interpret this boundary as the lunar seismic Moho. This depth agrees with Japan Aerospace Exploration Agency's (JAXA) SELenological and Engineering Explorer (SELENE) result and previous travel time analysis at the Apollo 12/14 sites. The deeper part of the image we obtain from DMSI shows laterally incoherent structures. Such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale (0.2-2.0 Hz).

  19. Shallow seismicity in volcanic system: what role does the edifice play?

    NASA Astrophysics Data System (ADS)

    Bean, Chris; Lokmer, Ivan

    2017-04-01

    Seismicity in the upper two kilometres in volcanic systems is complex and very diverse in nature. The origins lie in the multi-physics nature of source processes and in the often extreme heterogeneity in near surface structure, which introduces strong seismic wave propagation path effects that often 'hide' the source itself. Other complicating factors are that we are often in the seismic near-field so waveforms can be intrinsically more complex than in far-field earthquake seismology. The traditional focus for an explanation of the diverse nature of shallow seismic signals is to call on the direct action of fluids in the system. Fits to model data are then used to elucidate properties of the plumbing system. Here we show that solutions based on these conceptual models are not unique and that models based on a diverse range of quasi-brittle failure of low stiffness near surface structures are equally valid from a data fit perspective. These earthquake-like sources also explain aspects of edifice deformation that are as yet poorly quantified.

  20. Open Source Seismic Software in NOAA's Next Generation Tsunami Warning System

    NASA Astrophysics Data System (ADS)

    Hellman, S. B.; Baker, B. I.; Hagerty, M. T.; Leifer, J. M.; Lisowski, S.; Thies, D. A.; Donnelly, B. K.; Griffith, F. P.

    2014-12-01

    The Tsunami Information technology Modernization (TIM) is a project spearheaded by National Oceanic and Atmospheric Administration to update the United States' Tsunami Warning System software currently employed at the Pacific Tsunami Warning Center (Eva Beach, Hawaii) and the National Tsunami Warning Center (Palmer, Alaska). This entirely open source software project will integrate various seismic processing utilities with the National Weather Service Weather Forecast Office's core software, AWIPS2. For the real-time and near real-time seismic processing aspect of this project, NOAA has elected to integrate the open source portions of GFZ's SeisComP 3 (SC3) processing system into AWIPS2. To provide for better tsunami threat assessments we are developing open source tools for magnitude estimations (e.g., moment magnitude, energy magnitude, surface wave magnitude), detection of slow earthquakes with the Theta discriminant, moment tensor inversions (e.g. W-phase and teleseismic body waves), finite fault inversions, and array processing. With our reliance on common data formats such as QuakeML and seismic community standard messaging systems, all new facilities introduced into AWIPS2 and SC3 will be available as stand-alone tools or could be easily integrated into other real time seismic monitoring systems such as Earthworm, Antelope, etc. Additionally, we have developed a template based design paradigm so that the developer or scientist can efficiently create upgrades, replacements, and/or new metrics to the seismic data processing with only a cursory knowledge of the underlying SC3.

  1. Back-Projection Imaging of extended, diffuse seismic sources in volcanic and hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Kelly, C. L.; Lawrence, J. F.; Beroza, G. C.

    2017-12-01

    Volcanic and hydrothermal systems exhibit a wide range of seismicity that is directly linked to fluid and volatile activity in the subsurface and that can be indicative of imminent hazardous activity. Seismograms recorded near volcanic and hydrothermal systems typically contain "noisy" records, but in fact, these complex signals are generated by many overlapping low-magnitude displacements and pressure changes at depth. Unfortunately, excluding times of high-magnitude eruptive activity that typically occur infrequently relative to the length of a system's entire eruption cycle, these signals often have very low signal-to-noise ratios and are difficult to identify and study using established seismic analysis techniques (i.e. phase-picking, template matching). Arrays of short-period and broadband seismic sensors are proven tools for monitoring short- and long-term changes in volcanic and hydrothermal systems. Time-reversal techniques (i.e. back-projection) that are improved by additional seismic observations have been successfully applied to locating volcano-seismic sources recorded by dense sensor arrays. We present results from a new computationally efficient back-projection method that allows us to image the evolution of extended, diffuse sources of volcanic and hydrothermal seismicity. We correlate short time-window seismograms from receiver-pairs to find coherent signals and propagate them back in time to potential source locations in a 3D subsurface model. The strength of coherent seismic signal associated with any potential source-receiver-receiver geometry is equal to the correlation of the short time-windows of seismic records at appropriate time lags as determined by the velocity structure and ray paths. We stack (sum) all short time-window correlations from all receiver-pairs to determine the cumulative coherence of signals at each potential source location. Through stacking, coherent signals from extended and/or repeating sources of short-period energy

  2. Redox-influenced seismic properties of upper-mantle olivine

    NASA Astrophysics Data System (ADS)

    Cline, C. J., II; Faul, U. H.; David, E. C.; Berry, A. J.; Jackson, I.

    2018-03-01

    Lateral variations of seismic wave speeds and attenuation (dissipation of strain energy) in the Earth’s upper mantle have the potential to map key characteristics such as temperature, major-element composition, melt fraction and water content. The inversion of these data into meaningful representations of physical properties requires a robust understanding of the micromechanical processes that affect the propagation of seismic waves. Structurally bound water (hydroxyl) is believed to affect seismic properties but this has yet to be experimentally quantified. Here we present a comprehensive low-frequency forced-oscillation assessment of the seismic properties of olivine as a function of water content within the under-saturated regime that is relevant to the Earth’s interior. Our results demonstrate that wave speeds and attenuation are in fact strikingly insensitive to water content. Rather, the redox conditions imposed by the choice of metal sleeving, and the associated defect chemistry, appear to have a substantial influence on the seismic properties. These findings suggest that elevated water contents are not responsible for low-velocity or high-attenuation structures in the upper mantle. Instead, the high attenuation observed in hydrous and oxidized regions of the upper mantle (such as above subduction zones) may reflect the prevailing oxygen fugacity. In addition, these data provide no support for the hypothesis whereby a sharp lithosphere–asthenosphere boundary is explained by enhanced grain boundary sliding in the presence of water.

  3. An innovative seismic bracing system based on a superelastic shape memory alloy ring

    NASA Astrophysics Data System (ADS)

    Gao, Nan; Jeon, Jong-Su; Hodgson, Darel E.; DesRoches, Reginald

    2016-05-01

    Shape memory alloys (SMAs) have great potential in seismic applications because of their remarkable superelasticity. Seismic bracing systems based on SMAs can mitigate the damage caused by earthquakes. The current study investigates a bracing system based on an SMA ring which is capable of both re-centering and energy dissipation. This lateral force resisting system is a cross-braced system consisting of an SMA ring and four tension-only cable assemblies, which can be applied to both new construction and seismic retrofit. The performance of this bracing system is examined through a quasi-static cyclic loading test and finite element (FE) analysis. This paper describes the experimental design in detail, discusses the experimental results, compares the performance with other bracing systems based on SMAs, and presents an Abaqus FE model calibrated on the basis of experimental results to simulate the superelastic behavior of the SMA ring. The experimental results indicate that the seismic performance of this system is promising in terms of damping and re-centering. The FE model can be used in the simulation of building structures using the proposed bracing system.

  4. Seismicity in Azerbaijan and Adjacent Caspian Sea

    SciTech Connect

    Panahi, Behrouz M.

    2006-03-23

    So far no general view on the geodynamic evolution of the Black Sea to the Caspian Sea region is elaborated. This is associated with the geological and structural complexities of the region revealed by geophysical, geochemical, petrologic, structural, and other studies. A clash of opinions on geodynamic conditions of the Caucasus region, sometimes mutually exclusive, can be explained by a simplified interpretation of the seismic data. In this paper I analyze available data on earthquake occurrences in Azerbaijan and the adjacent Caspian Sea region. The results of the analysis of macroseismic and instrumental data, seismic regime, and earthquake reoccurrence indicatemore » that a level of seismicity in the region is moderate, and seismic event are concentrated in the shallow part of the lithosphere. Seismicity is mostly intra-plate, and spatial distribution of earthquake epicenters does not correlate with the plate boundaries.« less

  5. Development of real time monitor system displaying seismic waveform data observed at seafloor seismic network, DONET, for disaster management information

    NASA Astrophysics Data System (ADS)

    Horikawa, H.; Takaesu, M.; Sueki, K.; Takahashi, N.; Sonoda, A.; Miura, S.; Tsuboi, S.

    2014-12-01

    Mega-thrust earthquakes are anticipated to occur in the Nankai Trough in southwest Japan. In the source areas, we have deployed seafloor seismic network, DONET (Dense Ocean-floor Network System for Earthquake and Tsunamis), in 2010 in order to monitor seismicity, crustal deformations, and tsunamis. DONET system consists of totally 20 stations, which is composed of six kinds of sensors, including strong-motion seismometers and quartz pressure gauges. Those stations are densely distributed with an average spatial interval of 15-20 km and cover near the trench axis to coastal areas. Observed data are transferred to a land station through a fiber-optical cable and then to JAMSTEC (Japan Agency for Marine-Earth Science and Technology) data management center through a private network in real time. After 2011 off the Pacific coast of Tohoku Earthquake, each local government close to Nankai Trough try to plan disaster prevention scheme. JAMSTEC will disseminate DONET data combined with research accomplishment so that they will be widely recognized as important earthquake information. In order to open DONET data observed for research to local government, we have developed a web application system, REIS (Real-time Earthquake Information System). REIS is providing seismic waveform data to some local governments close to Nankai Trough as a pilot study. As soon as operation of DONET is ready, REIS will start full-scale operation. REIS can display seismic waveform data of DONET in real-time, users can select strong motion and pressure data, and configure the options of trace view arrangement, time scale, and amplitude. In addition to real-time monitoring, REIS can display past seismic waveform data and show earthquake epicenters on the map. In this presentation, we briefly introduce DONET system and then show our web application system. We also discuss our future plans for further developments of REIS.

  6. The damping of seismic waves and its determination from reflection seismograms

    NASA Technical Reports Server (NTRS)

    Engelhard, L.

    1979-01-01

    The damping in theoretical waveforms is described phenomenologically and a classification is proposed. A method for studying the Earth's crust was developed which includes this damping as derived from reflection seismograms. Seismic wave propagation by absorption, attenuation of seismic waves by scattering, and dispersion relations are considered. Absorption of seismic waves within the Earth as well as reflection and transmission of elastic waves seen through boundary layer absorption are also discussed.

  7. Noise analysis of the seismic system employed in the northern and southern California seismic nets

    USGS Publications Warehouse

    Eaton, J.P.

    1984-01-01

    The seismic networks have been designed and operated to support recording on Develocorders (less than 40db dynamic range) and analog magnetic tape (about 50 db dynamic range). The principal analysis of the records has been based on Develocorder films; and background earth noise levels have been adjusted to be about 1 to 2 mm p-p on the film readers. Since the traces are separated by only 10 to 12 mm on the reader screen, they become hopelessly tangled when signal amplitudes on several adjacent traces exceed 10 to 20 mm p-p. Thus, the background noise level is hardly more than 20 db below the level of largest readable signals. The situation is somewhat better on tape playbacks, but the high level of background noise set to accomodate processing from film records effectively limits the range of maximum-signal to background-earth-noise on high gain channels to a little more than 30 db. Introduction of the PDP 11/44 seismic data acquisition system has increased the potential dynamic range of recorded network signals to more than 60 db. To make use of this increased dynamic range we must evaluate the characteristics and performance of the seismic system. In particular, we must determine whether the electronic noise in the system is or can be made sufficiently low so that background earth noise levels can be lowered significantly to take advantage of the increased dynamic range of the digital recording system. To come to grips with the complex problem of system noise, we have carried out a number of measurements and experiments to evaluate critical components of the system as well as to determine the noise characteristics of the system as a whole.

  8. Enhanced Structural Interpretation Using Multitrace Seismic Attribute For Oligo-Miocene Target at Madura Strait Offshore

    NASA Astrophysics Data System (ADS)

    Pratama Wahyu Hidayat, Putra; Hary Murti, Antonius; Sudarmaji; Shirly, Agung; Tiofan, Bani; Damayanti, Shinta

    2018-03-01

    Geometry is an important parameter for the field of hydrocarbon exploration and exploitation, it has significant effect to the amount of resources or reserves, rock spreading, and risk analysis. The existence of geological structure or fault becomes one factor affecting geometry. This study is conducted as an effort to enhance seismic image quality in faults dominated area namely offshore Madura Strait. For the past 10 years, Oligo-Miocene carbonate rock has been slightly explored on Madura Strait area, the main reason because migration and trap geometry still became risks to be concern. This study tries to determine the boundary of each fault zone as subsurface image generated by converting seismic data into variance attribute. Variance attribute is a multitrace seismic attribute as the derivative result from amplitude seismic data. The result of this study shows variance section of Madura Strait area having zero (0) value for seismic continuity and one (1) value for discontinuity of seismic data. Variance section shows the boundary of RMKS fault zone with Kendeng zone distinctly. Geological structure and subsurface geometry for Oligo-Miocene carbonate rock could be identified perfectly using this method. Generally structure interpretation to identify the boundary of fault zones could be good determined by variance attribute.

  9. Topography at the inner core boundary

    NASA Astrophysics Data System (ADS)

    Lasbleis, M.; Forquenot, Q.; Deguen, R.

    2017-12-01

    Topography at the inner core boundary has been proposed to explain surprising seismic observations of some regional studies. Such observations are still debatted, and numerical values of possible inner core topography have been proposed ranging from no topography to "inner core mountains" (10km heigth over lengthscales of 20km, as in Dai et al. 2012). The inner core boundary is a peculiar boundary, as it is the place where the iron alloy constituting the core freezes. The existence of a significant topography on such a boundary is possible, but unlikely. At thermodynamic equilibrium, no topography is expected, as any material above the equilibrium radius would have melted and any below would have freezed. However, mechanical forcing may push the system out of equilibrium. Dynamical topography could be forced by convective flows in the inner core or by outer core heterogeneities. A topography induced by outer core convection would be short-lived when compared to geodynamical processes in the bulk of the inner core (τ ≈ 10-100 Myears), but long-lived compared to observations. Here, we would like to give a geodynamical perspective over inner core topography. We constrain plausible amplitude of inner core topography, and discuss the implications for seismic observations. We consider topography created by viscous flows in the bulk of the inner core and by variations of growth rate on regional lengthscale due to outer core convection. This approach allows us to consider both internal and external forcings on the topography. We treat topography forcings as stochastic processes, and calculate the probability of observing a given topography. Based on preliminary results, the high values for observed topography can not be interpreted as a normal behavior of core dynamics. If confirmed, the regions are likely to be anomalous and originated from outliers in the distribution of stochastic processes.

  10. Seismic and structural characterization of the fluid bypass system using 3D and partial stack seismic from passive margin: inside the plumbing system.

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Maestrelli, Daniele; Jihad, Ali; Bond, Clare; Bonini, Marco

    2017-04-01

    In recent years enormous attention has been paid to the understanding of the process and mechanism controlling the gas seepage and more generally the fluid expulsion affecting the earth system from onshore to offshore environment. This is because of their demonstrated impact to our environment, climate change and during subsea drilling operation. Several example from active and paleo system has been so far characterized and proposed using subsurface exploration, geophysical and geochemical monitoring technology approaches with the aims to explore what trigger and drive the overpressure necessary maintain the fluid/gas/material expulsion and what are the structure that act as a gateway for gaseous fluid and unconsolidated rock. In this contribution we explore a series of fluid escape structure (ranging from seepage pipes to large blowout pipes structure of km length) using 3D and partial stack seismic data from two distinctive passive margin from the north sea (Loyal field, West Shetland) and the Equatorial Brazil (Ceara' Basin). We will focuses on the characterization of the plumbing system internal architecture and, for selected example, exploring the AVO response (using partial stack) of the internal fluid/unconsolidated rock. The detailed seismic mapping and seismic attributes analysis of the conduit system helped us to recover some detail from the signal response of the chimney internal structures. We observed: (1) small to medium seeps and pipes following structural or sedimentary discontinuities (2) large pipes (probably incipient mud volcanoes) and blowup structures propagating upward irrespective of pre-existing fault by hydraulic fracturing and assisted by the buoyancy of a fluidised and mobilised mud-hydrocarbon mixture. The reflector termination observed inside the main conduits, the distribution of stacked bright reflectors and the AVO analysis suggests an evolution of mechanisms (involving mixture of gas, fluid and probably mud) during pipe birth and

  11. Deep Seismic Reflection Images of the Sumatra Seismic and Aseismic Gaps

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Hananto, N. D.; Chauhan, A.; Carton, H. D.; Midenet, S.; Djajadihardja, Y.

    2009-12-01

    The Sumatra subduction zone is seismically most active region on the Earth, and has been the site of three great earthquakes only in the last four years. The first of the series, the 2004 Boxing Day earthquake, broke 1300 km of the plate boundary and produced the devastating tsunami around the Indian Ocean. The second great earthquake occurred three months later in March 2005, about 150 km SE of the 2004 event. The Earth waited for three years, and then broke again in September 2007 at 1300 km SE of the 2004 event producing a twin earthquake of magnitudes of 8.5 and 7.9 at an interval of 12 hours, leaving a seismic gap of about 600 km between the second and third earthquake, the Sumatra Seismic Gap. Seismological and geodetic studies suggest that this gap is fully locked and may break any time. In order to study the seismic and tsunami risk in this locked region, a deep seismic reflection survey (Tsunami Investigation Deep Evaluation Seismic -TIDES) was carried out in May 2009 using the CGGVeritas vessel Geowave Champion towing a 15 long streamer, the longest ever used during a seismic survey, to image the nature of the subducting plate and associated features, including the seismogenic zone, from seafloor down to 50 km depth. A total of 1700 km of deep seismic reflection data were acquired. Three dip lines traverse the Sumatra subduction zone; one going through the Sumatra Seismic Gap, one crossing the region that broke during the 2007 great earthquake, and one going through the aseismic zone. These three dip profiles should provide insight about the locking mechanism and help us to understand why an earthquake occurs in one zone and not in aseismic zone. A strike-line was shot in the forearc basin connecting the locked zone with broken zone profiles, which should provide insight about barriers that might have stopped propagation of 2007 earthquake rupture further northward.

  12. Earthquake recurrence and risk assessment in circum-Pacific seismic gaps

    USGS Publications Warehouse

    Thatcher, W.

    1989-01-01

    THE development of the concept of seismic gaps, regions of low earthquake activity where large events are expected, has been one of the notable achievements of seismology and plate tectonics. Its application to long-term earthquake hazard assessment continues to be an active field of seismological research. Here I have surveyed well documented case histories of repeated rupture of the same segment of circum-Pacific plate boundary and characterized their general features. I find that variability in fault slip and spatial extent of great earthquakes rupturing the same plate boundary segment is typical rather than exceptional but sequences of major events fill identified seismic gaps with remarkable order. Earthquakes are concentrated late in the seismic cycle and occur with increasing size and magnitude. Furthermore, earthquake rup-ture starts near zones of concentrated moment release, suggesting that high-slip regions control the timing of recurrent events. The absence of major earthquakes early in the seismic cycle indicates a more complex behaviour for lower-slip regions, which may explain the observed cycle-to-cycle diversity of gap-filling sequences. ?? 1989 Nature Publishing Group.

  13. A seismic hazard overview of the Mitidja Basin (Northern Algeria)

    NASA Astrophysics Data System (ADS)

    Fontiela, J. F.; Borges, J.; Ouyed, M.; Bezzeghoud, M.; Idres, M.; Caldeira, B.; Boughacha, M. S.; Carvalho, J.; Samai, S.; Aissa, S.; Benfadda, A.; Chimouni, R.; Yalaoui, R.; Dias, R.

    2017-12-01

    The Mitidja Basin (MB) is located in N Algeria and it is filled by quaternary sediments with a length of 100 km on the EW direction and around 20 km width. The S and N limites comprise the Boumerdes-Larbaa-Blida, and the Thenia-Sahel active fault system, respectively. Both fault systems are of the reverse type with opposed dips and accommodate a general slip rate of ˜4 mm/year. In the basin occurred earthquakes that caused severe damage and losses such as the ones of Algiers (1365, Io=X; 1716, Io=X) and the Bourmedes earthquake (Mw 6.9; May 2003) that affected the area of Zemmouri and caused 2.271 deaths. The event was caused by the reactivation of the MB boundary faults. The earthquake generated a max uplift of 0.8m along the coast and a horizontal max. slip of 0.24m.Recent studies show that the Boumerdes earthquake overloaded the adjacent faults system with a stress increase between 0.4 and 1.5 bar. The stress change recommends a detailed study of mentioned faults system due to the increase of the seismic hazard. The high seismogenic potential of the fault system bordering the MB, increases the vulnerability of densely populated areas of Algiers and the amplification effect caused by the basin are the motivation of this project that will focus on the evaluation of the seismic hazard of the region. To achieve seismic hazard assessment on the MB, through realistic predictions of strong ground motion, caused by moderate and large earthquakes, it is important 1) develop a detailed 3D velocity/structure model of the MB that includes geological constraints, seismic reflection data acquired on wells, refraction velocities and seismic noise data, and determination of the attenuation laws based on instrumental records; 2) evaluate the seismic potential and parameters of the main active faults of the MB; 3) develop numerical methods (deterministic and stochastic) to simulate strong ground motions produced by extended seismic sources. To acquire seismic noise were used

  14. Structural and Tectonic Map Along the Pacific-North America Plate Boundary in Northern Gulf of California, Sonora Desert and Valle de Mexicali, Mexico, from Seismic Reflection Evidence

    NASA Astrophysics Data System (ADS)

    Gonzalez-Escobar, M.; Suarez-Vidal, F.; Mendoza-Borunda, R.; Martin Barajas, A.; Pacheco-Romero, M.; Arregui-Estrada, S.; Gallardo-Mata, C.; Sanchez-Garcia, C.; Chanes-Martinez, J.

    2012-12-01

    Between 1978 and 1983, Petróleos Mexicanos (PEMEX) carried on an intense exploration program in the northern Gulf of California, the Sonora Desert and the southern part of the Mexicali Valley. This program was supported by a seismic reflection field operation. The collected seismic data was 2D, with travel time of 6 s recording, in 48 channels, and the source energy was: dynamite, vibroseis and air guns. Since 2007 to present time, the existing seismic data has been re-processing and ire-interpreting as part of a collaboration project between the PEMEX's Subdirección de Exploración (PEMEX) and CICESE. The study area is located along a large portion of the Pacific-North America plate boundary in the northern Gulf of California and the Southern part of the Salton Trough tectonic province (Mexicali Valley). We present the result of the processes reflection seismic lines. Many of the previous reported known faults were identify along with the first time described located within the study region. We identified regions with different degree of tectonic activity. In structural map it can see the location of many of these known active faults and their associated seismic activity, as well as other structures with no associated seismicity. Where some faults are mist placed they were deleted or relocated based on new information. We included historical seismicity for the region. We present six reflection lines that cross the aftershocks zone of the El Mayor-Cucapah earthquake of April 4, 2010 (Mw7.2). The epicenter of this earthquake and most of the aftershocks are located in a region where pervious to this earthquake no major earthquakes are been reported. A major result of this study is to demonstrate that there are many buried faults that increase the seismic hazard.

  15. Necessary Conditions for Intraplate Seismic Zones in North America

    NASA Astrophysics Data System (ADS)

    Thomas, William A.; Powell, Christine A.

    2017-12-01

    The cause of intraplate seismic zones persists as an important scientific and societal question. Most intraplate earthquakes are concentrated in specific seismic zones along or adjacent to large-scale basement structures (e.g., rifts or sutures at ancient plate boundaries) within continental crust. The major intraplate seismic zones are limited to specific segments and are not distributed along the lengths of the ancient structures. We present a new hypothesis that major intraplate seismic zones are restricted to places where concentrated crustal deformation (CCD) is overprinted on large-scale basement structures. Examples where CCD affects the stability of specific parts of large-scale structures in response to present-day stress conditions include the most active seismic zones in central and eastern North America: Charlevoix, Eastern Tennessee, and New Madrid. Our hypothesis has important implications for the assessment of seismic hazards.

  16. Effects of volcano topography on seismic broad-band waveforms

    NASA Astrophysics Data System (ADS)

    Neuberg, Jürgen; Pointer, Tim

    2000-10-01

    Volcano seismology often deals with rather shallow seismic sources and seismic stations deployed in their near field. The complex stratigraphy on volcanoes and near-field source effects have a strong impact on the seismic wavefield, complicating the interpretation techniques that are usually employed in earthquake seismology. In addition, as most volcanoes have a pronounced topography, the interference of the seismic wavefield with the stress-free surface results in severe waveform perturbations that affect seismic interpretation methods. In this study we deal predominantly with the surface effects, but take into account the impact of a typical volcano stratigraphy as well as near-field source effects. We derive a correction term for plane seismic waves and a plane-free surface such that for smooth topographies the effect of the free surface can be totally removed. Seismo-volcanic sources radiate energy in a broad frequency range with a correspondingly wide range of different Fresnel zones. A 2-D boundary element method is employed to study how the size of the Fresnel zone is dependent on source depth, dominant wavelength and topography in order to estimate the limits of the plane wave approximation. This approximation remains valid if the dominant wavelength does not exceed twice the source depth. Further aspects of this study concern particle motion analysis to locate point sources and the influence of the stratigraphy on particle motions. Furthermore, the deployment strategy of seismic instruments on volcanoes, as well as the direct interpretation of the broad-band waveforms in terms of pressure fluctuations in the volcanic plumbing system, are discussed.

  17. Seismic Waves, 4th order accurate

    SciTech Connect

    2013-08-16

    SW4 is a program for simulating seismic wave propagation on parallel computers. SW4 colves the seismic wave equations in Cartesian corrdinates. It is therefore appropriate for regional simulations, where the curvature of the earth can be neglected. SW4 implements a free surface boundary condition on a realistic topography, absorbing super-grid conditions on the far-field boundaries, and a kinematic source model consisting of point force and/or point moment tensor source terms. SW4 supports a fully 3-D heterogeneous material model that can be specified in several formats. SW4 can output synthetic seismograms in an ASCII test format, or in the SAC finarymore » format. It can also present simulation information as GMT scripts, whixh can be used to create annotated maps. Furthermore, SW4 can output the solution as well as the material model along 2-D grid planes.« less

  18. Multiple plates subducting beneath Colombia, as illuminated by seismicity and velocity from the joint inversion of seismic and gravity data

    DOE PAGES

    Syracuse, Ellen M.; Maceira, Monica; Prieto, German A.; ...

    2016-04-12

    Subduction beneath the northernmost Andes in Colombia is complex. Based on seismicity distributions, multiple segments of slab appear to be subducting, and arc volcanism ceases north of 5° N. Here, we illuminate the subduction system through hypocentral relocations and Vp and Vs models resulting from the joint inversion of local body wave arrivals, surface wave dispersion measurements, and gravity data. The simultaneous use of multiple data types takes advantage of the differing sensitivities of each data type, resulting in velocity models that have improved resolution at both shallower and deeper depths than would result from traditional travel time tomography alone.more » The relocated earthquake dataset and velocity model clearly indicate a tear in the Nazca slab at 5° N, corresponding to a 250-km shift in slab seismicity and the termination of arc volcanism. North of this tear, the slab is flat, and it comprises slabs of two sources: the Nazca and Caribbean plates. The Bucaramanga nest, a small region of among the most intense intermediate-depth seismicity globally, is associated with the boundary between these two plates and possibly with a zone of melting or elevated water content, based on reduced Vp and increased Vp/Vs. As a result, we also use relocated seismicity to identify two new faults in the South American plate, one related to plate convergence and one highlighted by induced seismicity.« less

  19. Seismicity of the Earth 1900-2010 Mexico and vicinity

    USGS Publications Warehouse

    Rhea, Susan; Dart, Richard L.; Villaseñor, Antonio; Hayes, Gavin P.; Tarr, Arthur C.; Furlong, Kevin P.; Benz, Harley M.

    2011-01-01

    Mexico, located in one of the world's most seismically active regions, lies on three large tectonic plates: the North American plate, Pacific plate, and Cocos plate. The relative motion of these tectonic plates causes frequent earthquakes and active volcanism and mountain building. Mexico's most seismically active region is in southern Mexico where the Cocos plate is subducting northwestward beneath Mexico creating the deep Middle America trench. The Gulf of California, which extends from approximately the northern terminus of the Middle America trench to the U.S.-Mexico border, overlies the plate boundary between the Pacific and North American plates where the Pacific plate is moving northwestward relative to the North American plate. This region of transform faulting is the southern extension of the well-known San Andreas Fault system.

  20. Stability boundaries for command augmentation systems

    NASA Technical Reports Server (NTRS)

    Shrivastava, P. C.

    1987-01-01

    The Stability Augmentation System (SAS) is a special case of the Command Augmentation System (CAS). Control saturation imposes bounds on achievable commands. The state equilibrium depends only on the open loop dynamics and control deflection. The control magnitude to achieve a desired command equilibrium is independent of the feedback gain. A feedback controller provides the desired response, maintains the system equilibrium under disturbances, but it does not affect the equilibrium values of states and control. The saturation boundaries change with commands, but the location of the equilibrium points in the saturated region remains unchanged. Nonzero command vectors yield saturation boundaries that are asymmetric with respect to the state equilibrium. Except for the saddle point case with MCE control law, the stability boundaries change with commands. For the cases of saddle point and unstable nodes, the region of stability decreases with increasing command magnitudes.

  1. Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

    USGS Publications Warehouse

    Wardell, N.; Childs, J. R.; Cooper, A. K.

    2007-01-01

    The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

  2. Seismic hazard map of the western hemisphere

    USGS Publications Warehouse

    Shedlock, K.M.; Tanner, J.G.

    1999-01-01

    Vulnerability to natural disasters increases with urbanization and development of associated support systems (reservoirs, power plants, etc.). Catastrophic earthquakes account for 60% of worldwide casualties associated with natural disasters. Economic damage from earthquakes is increasing, even in technologically advanced countries with some level of seismic zonation, as shown by the 1989 Loma Prieta, CA ($6 billion), 1994 Northridge, CA ($ 25 billion), and 1995 Kobe, Japan (> $ 100 billion) earthquakes. The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures, due to an insufficient knowledge of existing seismic hazard. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. National, state, and local governments, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require seismic hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The seismic hazard map of the Americas is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful global seismic hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This seismic hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years for the western hemisphere. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include seismic provisions specify the

  3. Ray Tracing Methods in Seismic Emission Tomography

    NASA Astrophysics Data System (ADS)

    Chebotareva, I. Ya.

    2018-03-01

    Highly efficient approximate ray tracing techniques which can be used in seismic emission tomography and in other methods requiring a large number of raypaths are described. The techniques are applicable for the gradient and plane-layered velocity sections of the medium and for the models with a complicated geometry of contrasting boundaries. The empirical results obtained with the use of the discussed ray tracing technologies and seismic emission tomography results, as well as the results of numerical modeling, are presented.

  4. High-resolution seismic constraints on flow dynamics in the oceanic asthenosphere.

    PubMed

    Lin, Pei-Ying Patty; Gaherty, James B; Jin, Ge; Collins, John A; Lizarralde, Daniel; Evans, Rob L; Hirth, Greg

    2016-07-28

    Convective flow in the mantle and the motions of tectonic plates produce deformation of Earth's interior, and the rock fabric produced by this deformation can be discerned using the anisotropy of the seismic wave speed. This deformation is commonly inferred close to lithospheric boundaries beneath the ocean in the uppermost mantle, including near seafloor-spreading centres as new plates are formed via corner flow, and within a weak asthenosphere that lubricates large-scale plate-driven flow and accommodates smaller scale convection. Seismic models of oceanic upper mantle differ as to the relative importance of these deformation processes: seafloor spreading fabric is very strong just beneath the crust-mantle boundary (the Mohorovičić discontinuity, or Moho) at relatively local scales, but at the global and ocean-basin scales, oceanic lithosphere typically appears weakly anisotropic when compared to the asthenosphere. Here we use Rayleigh waves, recorded across an ocean-bottom seismograph array in the central Pacific Ocean (the NoMelt Experiment), to provide unique localized constraints on seismic anisotropy within the oceanic lithosphere-asthenosphere system in the middle of a plate. We find that azimuthal anisotropy is strongest within the high-seismic-velocity lid, with the fast direction coincident with seafloor spreading. A minimum in the magnitude of azimuthal anisotropy occurs within the middle of the seismic low-velocity zone, and then increases with depth below the weakest portion of the asthenosphere. At no depth does the fast direction correlate with the apparent plate motion. Our results suggest that the highest strain deformation in the shallow oceanic mantle occurs during corner flow at the ridge axis, and via pressure-driven or buoyancy-driven flow within the asthenosphere. Shear associated with motion of the plate over the underlying asthenosphere, if present, is weak compared to these other processes.

  5. A Methodology for Assessing the Seismic Vulnerability of Highway Systems

    SciTech Connect

    Cirianni, Francis; Leonardi, Giovanni; Scopelliti, Francesco

    2008-07-08

    Modern society is totally dependent on a complex and articulated infrastructure network of vital importance for the existence of the urban settlements scattered on the territory. On these infrastructure systems, usually indicated with the term lifelines, are entrusted numerous services and indispensable functions of the normal urban and human activity.The systems of the lifelines represent an essential element in all the urbanised areas which are subject to seismic risk. It is important that, in these zones, they are planned according to opportune criteria based on two fundamental assumptions: a) determination of the best territorial localization, avoiding, within limits, the placesmore » of higher dangerousness; b) application of constructive technologies finalized to the reduction of the vulnerability.Therefore it is indispensable that in any modern process of seismic risk assessment the study of the networks is taken in the rightful consideration, to be integrated with the traditional analyses of the buildings.The present paper moves in this direction, dedicating particular attention to one kind of lifeline: the highway system, proposing a methodology of analysis finalized to the assessment of the seismic vulnerability of the system.« less

  6. Coherent Waves in Seismic Researches

    NASA Astrophysics Data System (ADS)

    Emanov, A.; Seleznev, V. S.

    2013-05-01

    Development of digital processing algorithms of seismic wave fields for the purpose of useful event picking to study environment and other objects is the basis for the establishment of new seismic techniques. In the submitted paper a fundamental property of seismic wave field coherence is used. The authors extended conception of coherence types of observed wave fields and devised a technique of coherent component selection from observed wave field. Time coherence and space coherence are widely known. In this paper conception "parameter coherence" has been added. The parameter by which wave field is coherent can be the most manifold. The reason is that the wave field is a multivariate process described by a set of parameters. Coherence in the first place means independence of linear connection in wave field of parameter. In seismic wave fields, recorded in confined space, in building-blocks and stratified mediums time coherent standing waves are formed. In prospecting seismology at observation systems with multiple overlapping head waves are coherent by parallel correlation course or, in other words, by one measurement on generalized plane of observation system. For detail prospecting seismology at observation systems with multiple overlapping on basis of coherence property by one measurement of area algorithms have been developed, permitting seismic records to be converted to head wave time sections which have neither reflected nor other types of waves. Conversion in time section is executed on any specified observation base. Energy storage of head waves relative to noise on basis of multiplicity of observation system is realized within area of head wave recording. Conversion on base below the area of wave tracking is performed with lack of signal/noise ratio relative to maximum of this ratio, fit to observation system. Construction of head wave time section and dynamic plots a basis of automatic processing have been developed, similar to CDP procedure in method of

  7. Development of 3-axis precise positioning seismic physical modeling system in the simulation of marine seismic exploration

    NASA Astrophysics Data System (ADS)

    Kim, D.; Shin, S.; Ha, J.; Lee, D.; Lim, Y.; Chung, W.

    2017-12-01

    Seismic physical modeling is a laboratory-scale experiment that deals with the actual and physical phenomena that may occur in the field. In seismic physical modeling, field conditions are downscaled and used. For this reason, even a small error may lead to a big error in an actual field. Accordingly, the positions of the source and the receiver must be precisely controlled in scale modeling. In this study, we have developed a seismic physical modeling system capable of precisely controlling the 3-axis position. For automatic and precise position control of an ultrasonic transducer(source and receiver) in the directions of the three axes(x, y, and z), a motor was mounted on each of the three axes. The motor can automatically and precisely control the positions with positional precision of 2''; for the x and y axes and 0.05 mm for the z axis. As it can automatically and precisely control the positions in the directions of the three axes, it has an advantage in that simulations can be carried out using the latest exploration techniques, such as OBS and Broadband Seismic. For the signal generation section, a waveform generator that can produce a maximum of two sources was used, and for the data acquisition section, which receives and stores reflected signals, an A/D converter that can receive a maximum of four signals was used. As multiple sources and receivers could be used at the same time, the system was set up in such a way that diverse exploration methods, such as single channel, multichannel, and 3-D exploration, could be realized. A computer control program based on LabVIEW was created, so that it could control the position of the transducer, determine the data acquisition parameters, and check the exploration data and progress in real time. A marine environment was simulated using a water tank 1 m wide, 1 m long, and 0.9 m high. To evaluate the performance and applicability of the seismic physical modeling system developed in this study, single channel and

  8. Time-dependent boundary conditions for hyperbolic systems. II

    NASA Technical Reports Server (NTRS)

    Thompson, Kevin W.

    1990-01-01

    A general boundary condition formalism is developed for all types of boundary conditions to which hyperbolic systems are subject; the formalism makes possible a 'cookbook' approach to boundary conditions, by means of which novel boundary 'recipes' may be derived and previously devised ones may be consulted as required. Numerous useful conditions are derived for such CFD problems as subsonic and supersonic inflows and outflows, nonreflecting boundaries, force-free boundaries, constant pressure boundaries, and constant mass flux. Attention is given to the computation and integration of time derivatives.

  9. Time-dependent boundary conditions for hyperbolic systems. II

    NASA Astrophysics Data System (ADS)

    Thompson, Kevin W.

    1990-08-01

    A general boundary condition formalism is developed for all types of boundary conditions to which hyperbolic systems are subject; the formalism makes possible a 'cookbook' approach to boundary conditions, by means of which novel boundary 'recipes' may be derived and previously devised ones may be consulted as required. Numerous useful conditions are derived for such CFD problems as subsonic and supersonic inflows and outflows, nonreflecting boundaries, force-free boundaries, constant pressure boundaries, and constant mass flux. Attention is given to the computation and integration of time derivatives.

  10. Wireless boundary monitor system and method

    DOEpatents

    Haynes, H.D.; Ayers, C.W.

    1997-12-09

    A wireless boundary monitor system used to monitor the integrity of a boundary surrounding an area uses at least two housings having at least one transmitting means for emitting ultrasonic pressure waves to a medium. Each of the housings has a plurality of receiving means for sensing the pressure waves in the medium. The transmitting means and the receiving means of each housing are aimable and communicably linked. At least one of the housings is equipped with a local alarm means for emitting a first alarm indication whereby, when the pressure waves propagating from a transmitting means to a receiving means are sufficiently blocked by an object a local alarm means or a remote alarm means or a combination thereof emit respective alarm indications. The system may be reset either manually or automatically. This wireless boundary monitor system has useful applications in both indoor and outdoor environments. 4 figs.

  11. Wireless boundary monitor system and method

    DOEpatents

    Haynes, Howard D.; Ayers, Curtis W.

    1997-01-01

    A wireless boundary monitor system used to monitor the integrity of a boundary surrounding an area uses at least two housings having at least one transmitting means for emitting ultrasonic pressure waves to a medium. Each of the housings has a plurality of receiving means for sensing the pressure waves in the medium. The transmitting means and the receiving means of each housing are aimable and communicably linked. At least one of the housings is equipped with a local alarm means for emitting a first alarm indication whereby, when the pressure waves propagating from a transmitting means to a receiving means are sufficiently blocked by an object a local alarm means or a remote alarm means or a combination thereof emit respective alarm indications. The system may be reset either manually or automatically. This wireless boundary monitor system has useful applications in both indoor and outdoor environments.

  12. Seismic imaging of slab metamorphism and genesis of intermediate-depth intraslab earthquakes

    NASA Astrophysics Data System (ADS)

    Hasegawa, Akira; Nakajima, Junichi

    2017-12-01

    We review studies of intermediate-depth seismicity and seismic imaging of the interior of subducting slabs in relation to slab metamorphism and their implications for the genesis of intermediate-depth earthquakes. Intermediate-depth events form a double seismic zone in the depth range of c. 40-180 km, which occur only at locations where hydrous minerals are present, and are particularly concentrated along dehydration reaction boundaries. Recent studies have revealed detailed spatial distributions of these events and a close relationship with slab metamorphism. Pressure-temperature paths of the crust for cold slabs encounter facies boundaries with large H2O production rates and positive total volume change, which are expected to cause highly active seismicity near the facies boundaries. A belt of upper-plane seismicity in the crust nearly parallel to 80-90 km depth contours of the slab surface has been detected in the cold Pacific slab beneath eastern Japan, and is probably caused by slab crust dehydration with a large H2O production rate. A seismic low-velocity layer in the slab crust persists down to the depth of this upper-plane seismic belt, which provides evidence for phase transformation of dehydration at this depth. Similar low-velocity subducting crust closely related with intraslab seismicity has been detected in several other subduction zones. Seismic tomography studies in NE Japan and northern Chile also revealed the presence of a P-wave low-velocity layer along the lower plane of a double seismic zone. However, in contrast to predictions based on the serpentinized mantle, S-wave velocity along this layer is not low. Seismic anisotropy and pore aspect ratio may play a role in generating this unique structure. Although further validation is required, observations of these distinct low P-wave velocities along the lower seismic plane suggest the presence of hydrated rocks or fluids within that layer. These observations support the hypothesis that dehydration

  13. Synthesis of regional crust and upper-mantle structure from seismic and gravity data

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Lavin, P. M.

    1979-01-01

    Available seismic and ground based gravity data are combined to infer the three dimensional crust and upper mantle structure in selected regions. This synthesis and interpretation proceeds from large-scale average models suitable for early comparison with high-altitude satellite potential field data to more detailed delineation of structural boundaries and other variations that may be significant in natural resource assessment. Seismic and ground based gravity data are the primary focal point, but other relevant information (e.g. magnetic field, heat flow, Landsat imagery, geodetic leveling, and natural resources maps) is used to constrain the structure inferred and to assist in defining structural domains and boundaries. The seismic data consists of regional refraction lines, limited reflection coverage, surface wave dispersion, teleseismic P and S wave delay times, anelastic absorption, and regional seismicity patterns. The gravity data base consists of available point gravity determinations for the areas considered.

  14. Design and implementation of a unified certification management system based on seismic business

    NASA Astrophysics Data System (ADS)

    Tang, Hongliang

    2018-04-01

    Many business software for seismic systems are based on web pages, users can simply open a browser and enter their IP address. However, how to achieve unified management and security management of many IP addresses, this paper introduces the design concept based on seismic business and builds a unified authentication management system using ASP technology.

  15. Seismic Imaging and Characterization of Bright Spots in the West Bohemia Seismic Zone (Germany and Czech Republic)

    NASA Astrophysics Data System (ADS)

    Alexandrakis, C.; Schreiter, L.; Hlousek, F.; Jusri, T.; Buske, S.

    2017-12-01

    In crystalline environments, imaging faults, layer boundaries and small scale structures is challenging due to the complex geometry of the structures themselves and the influence of the hardrock environment on the seismic wavefield. Optimally designed active seismic surveys and careful processing can produce a clear image of the subsurface structures. However, if little is known about the local geology and tectonic state of the area, the imaged reflections can be difficult to interpret. This is the case in the West Bohemia Seismic Zone, located along the border of Germany and Czech Republic. This geodynamically active area is spotted with springs and gas vents, and frequently experiences low magnitude seismic swarms. The most active region is located in the Cheb basin and coincides with the junction of a northwest trending fault with a north-south trending shear zone, making for a structurally complex hardrock setting. In the early 1990s, two long-offset reflection seismic profiles were collected along the boundary of the Cheb basin: MVE-90 along the northern edge, and 9HR-91 in the east. These profiles were recently reprocessed using Kirchhoff PreStack Depth Migration, revealing high amplitude reflections, or bright spots, that correlate to nearby seismicity. Several studies have hypothesized that the 9HR-91 bright spots image a fluid trap, where mantle-sourced fluids accumulate, thereby facilitating slip on the faults and triggering the swarms. However, the exact nature of the bright spots remains an open question. They may be a change in lithology and/or porosity, an infilled vein or an impermeable fault. We aim to answer this question by first using Coherency-Based PreStack Depth Migration to produce detailed images of the bright spots. We then forward model the waveforms guided by the reflection coefficients in order to derive rock-physical parameters. Finally, the best-fitting models are interpreted in terms of their possible relationship to the West Bohemia

  16. Seismic hydraulic fracture migration originated by successive deep magma pulses: The 2011-2013 seismic series associated to the volcanic activity of El Hierro Island

    NASA Astrophysics Data System (ADS)

    Díaz-Moreno, A.; Ibáñez, J. M.; De Angelis, S.; García-Yeguas, A.; Prudencio, J.; Morales, J.; Tuvè, T.; García, L.

    2015-11-01

    In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011-2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.

  17. The Crustal Structure and Seismicity of Eastern Venezuela

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

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

  18. Effects of Bounded Fault on Seismic Radiation and Rupture Propagation

    NASA Astrophysics Data System (ADS)

    Weng, H.; Yang, H.

    2016-12-01

    It has been suggested that narrow rectangle fault may emit stopping phases that can largely affect seismic radiation and thus rupture propagation, e.g., generation of short-duration pulse-like ruptures. Here we investigate the effects of narrow along-dip rectangle fault (analogously to 2015 Nepal earthquake with 200 km * 40 km) on seismic radiation and rupture propagation through numerical modeling in the framework of the linear slip-weakening friction law. First, we found the critical slip-weakening distance Dc may largely affect the seismic radiation and other source parameters, such as rupture speed, final slip and stress drop. Fixing all other uniform parameters, decreasing Dc could decrease the duration time of slip rate and increase the peak slip rate, thus increase the seismic radiation energy spectrum of slip acceleration. In addition, smaller Dc could lead to larger rupture speed (close to S wave velocity), but smaller stress drop and final slip. The results show that Dc may control the efficiency of far-field radiation. Furthermore, the duration time of slip rate at locations close to boundaries is 1.5 - 4 s less than that in the center of the fault. Such boundary effect is especially remarkable for smaller Dc due to the smaller average duration time of slip rate, which could increase the high-frequency radiation energy and impede low-frequency component near the boundaries from the analysis of energy spectrum of slip acceleration. These results show high frequency energy tends to be radiated near the fault boundaries as long as Dc is small enough. In addition, ruptures are fragile and easy to self-arrest if the width of the seismogenic zone is very narrow. In other words, the sizes of nucleation zone need to be larger to initiate runaway ruptures. Our results show the critical sizes of nucleation zones increase as the widths of seismogenic zones decrease.

  19. Geometry of the Arabia-Somalia Plate Boundary into Afar: Preliminary Results from the Seismic Profile Across the Asal Rift (Djibouti)

    NASA Astrophysics Data System (ADS)

    Vergne, J.; Doubre, C.; Mohamed, K.; Tiberi, C.; Leroy, S.; Maggi, A.

    2010-12-01

    In the Afar Depression, the Asal-Ghoubbet Rift in Djibouti is a young segment on land at the propagating tip of the Aden Ridge. This segment represents an ideal laboratory to observe the mechanisms of extension and the structural evolutions involved, from the continental break-up to the first stage of oceanic spreading. However, we lack first order information about the crustal and upper mantle structure in this region, which for example prevent detailed numerical modeling of the deformations observed at the surface from GPS or InSAR. Moreover the current permanent network is not well suited to precisely constrain the ratio of seismic/aseismic deformation and to characterize the active deformation and the rifting dynamics. Since November 2009 we have maintained a temporary network of 25 seismic stations deployed along a 150 km-long profile. Because we expect rapid variations of the lithospheric structure across the 10 km-wide central part of the rift, we gradually decreased the inter-stations spacing to less than 1 km in the middle section of the profile. In order to obtain a continuous image of the plate boundary, from the topographic surface to the upper mantle, several techniques and methods will be applied: P and S wave receiver functions, tomographies based on body waves, surface waves and seismic noise correlation, anisotropy, and finally a gravity-seismic joint inversion. We present some preliminary results deduced from the receiver functions applied to the data acquired during the first months of the experiment. We migrate several sets of receiver functions computed in various frequency bands to resolve both mantle interfaces and fine scale structures within the thin crust in the center of the rift. These first images confirm a rapid variation of the Moho depth on both sides of the rift and a very complex lithospheric structure in the central section with several low velocity zones within the top 50km that might correspond to magma lenses.

  20. Tunnel Detection Using Seismic Methods

    NASA Astrophysics Data System (ADS)

    Miller, R.; Park, C. B.; Xia, J.; Ivanov, J.; Steeples, D. W.; Ryden, N.; Ballard, R. F.; Llopis, J. L.; Anderson, T. S.; Moran, M. L.; Ketcham, S. A.

    2006-05-01

    Surface seismic methods have shown great promise for use in detecting clandestine tunnels in areas where unauthorized movement beneath secure boundaries have been or are a matter of concern for authorities. Unauthorized infiltration beneath national borders and into or out of secure facilities is possible at many sites by tunneling. Developments in acquisition, processing, and analysis techniques using multi-channel seismic imaging have opened the door to a vast number of near-surface applications including anomaly detection and delineation, specifically tunnels. Body waves have great potential based on modeling and very preliminary empirical studies trying to capitalize on diffracted energy. A primary limitation of all seismic energy is the natural attenuation of high-frequency energy by earth materials and the difficulty in transmitting a high- amplitude source pulse with a broad spectrum above 500 Hz into the earth. Surface waves have shown great potential since the development of multi-channel analysis methods (e.g., MASW). Both shear-wave velocity and backscatter energy from surface waves have been shown through modeling and empirical studies to have great promise in detecting the presence of anomalies, such as tunnels. Success in developing and evaluating various seismic approaches for detecting tunnels relies on investigations at known tunnel locations, in a variety of geologic settings, employing a wide range of seismic methods, and targeting a range of uniquely different tunnel geometries, characteristics, and host lithologies. Body-wave research at the Moffat tunnels in Winter Park, Colorado, provided well-defined diffraction-looking events that correlated with the subsurface location of the tunnel complex. Natural voids related to karst have been studied in Kansas, Oklahoma, Alabama, and Florida using shear-wave velocity imaging techniques based on the MASW approach. Manmade tunnels, culverts, and crawl spaces have been the target of multi-modal analysis

  1. Epistemic uncertainty in California-wide synthetic seismicity simulations

    USGS Publications Warehouse

    Pollitz, Fred F.

    2011-01-01

    The generation of seismicity catalogs on synthetic fault networks holds the promise of providing key inputs into probabilistic seismic-hazard analysis, for example, the coefficient of variation, mean recurrence time as a function of magnitude, the probability of fault-to-fault ruptures, and conditional probabilities for foreshock–mainshock triggering. I employ a seismicity simulator that includes the following ingredients: static stress transfer, viscoelastic relaxation of the lower crust and mantle, and vertical stratification of elastic and viscoelastic material properties. A cascade mechanism combined with a simple Coulomb failure criterion is used to determine the initiation, propagation, and termination of synthetic ruptures. It is employed on a 3D fault network provided by Steve Ward (unpublished data, 2009) for the Southern California Earthquake Center (SCEC) Earthquake Simulators Group. This all-California fault network, initially consisting of 8000 patches, each of ∼12 square kilometers in size, has been rediscretized into Graphic patches, each of ∼1 square kilometer in size, in order to simulate the evolution of California seismicity and crustal stress at magnitude M∼5–8. Resulting synthetic seismicity catalogs spanning 30,000 yr and about one-half million events are evaluated with magnitude-frequency and magnitude-area statistics. For a priori choices of fault-slip rates and mean stress drops, I explore the sensitivity of various constructs on input parameters, particularly mantle viscosity. Slip maps obtained for the southern San Andreas fault show that the ability of segment boundaries to inhibit slip across the boundaries (e.g., to prevent multisegment ruptures) is systematically affected by mantle viscosity.

  2. Epistemic uncertainty in California-wide synthetic seismicity simulations

    USGS Publications Warehouse

    Pollitz, F.F.

    2011-01-01

    The generation of seismicity catalogs on synthetic fault networks holds the promise of providing key inputs into probabilistic seismic-hazard analysis, for example, the coefficient of variation, mean recurrence time as a function of magnitude, the probability of fault-to-fault ruptures, and conditional probabilities for foreshock-mainshock triggering. I employ a seismicity simulator that includes the following ingredients: static stress transfer, viscoelastic relaxation of the lower crust and mantle, and vertical stratification of elastic and viscoelastic material properties. A cascade mechanism combined with a simple Coulomb failure criterion is used to determine the initiation, propagation, and termination of synthetic ruptures. It is employed on a 3D fault network provided by Steve Ward (unpublished data, 2009) for the Southern California Earthquake Center (SCEC) Earthquake Simulators Group. This all-California fault network, initially consisting of 8000 patches, each of ~12 square kilometers in size, has been rediscretized into ~100;000 patches, each of ~1 square kilometer in size, in order to simulate the evolution of California seismicity and crustal stress at magnitude M ~ 5-8. Resulting synthetic seismicity catalogs spanning 30,000 yr and about one-half million events are evaluated with magnitude-frequency and magnitude-area statistics. For a priori choices of fault-slip rates and mean stress drops, I explore the sensitivity of various constructs on input parameters, particularly mantle viscosity. Slip maps obtained for the southern San Andreas fault show that the ability of segment boundaries to inhibit slip across the boundaries (e.g., to prevent multisegment ruptures) is systematically affected by mantle viscosity.

  3. Global Seismic Cross-Correlation Results: Characterizing Repeating Seismic Events

    NASA Astrophysics Data System (ADS)

    Vieceli, R.; Dodge, D. A.; Walter, W. R.

    2016-12-01

    Increases in seismic instrument quality and coverage have led to increased knowledge of earthquakes, but have also revealed the complex and diverse nature of earthquake ruptures. Nonetheless, some earthquakes are sufficiently similar to each other that they produce correlated waveforms. Such repeating events have been used to investigate interplate coupling of subduction zones [e.g. Igarashi, 2010; Yu, 2013], study spatio-temporal changes in slip rate at plate boundaries [e.g. Igarashi et al., 2003], observe variations in seismic wave propagation velocities in the crust [e.g. Schaff and Beroza, 2004; Sawazaki et al., 2015], and assess inner core rotation [e.g. Yu, 2016]. The characterization of repeating events on a global scale remains a very challenging problem. An initial global seismic cross-correlation study used over 310 million waveforms from nearly 3.8 million events recorded between 1970 and 2013 to determine an initial look at global correlated seismicity [Dodge and Walter, 2015]. In this work, we analyze the spatial and temporal distribution of the most highly correlated event clusters or "multiplets" from the Dodge and Walter [2015] study. We examine how the distributions and characteristics of multiplets are effected by tectonic environment, source-station separation, and frequency band. Preliminary results suggest that the distribution of multiplets does not correspond to the tectonic environment in any obvious way, nor do they always coincide with the occurrence of large earthquakes. Future work will focus on clustering correlated pairs and working to reduce the bias introduced by non-uniform seismic station coverage and data availability. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  4. a Borehole Seismic System for Active and Passive Seimsic Studies to 3 KM at Ptrc's Aquistore Project

    NASA Astrophysics Data System (ADS)

    Schmitt, D. R.; Nixon, C.; Kofman, R.; White, D. J.; Worth, K.

    2015-12-01

    We have constructed a downhole seismic recording system for application to depths of nearly 3 km and temperatures up to 135 °C at Aquistore, an independent research and monitoring project in which liquid CO2 is being stored in a brine and sandstone water formation. The key component to this system is a set of commercially available slim-hole 3-C sondes carrying 15 Hz geophones deployable in open and cased boreholes with diameters as small as 57 mm. The system is currently hosted on a 4-conductor wireline with digital information streamed to the surface recording unit. We have further incorporated these sondes into a mobile passive monitoring unit that includes a number of redundancies such as a multiple Tbyte network accessible RAID hard-drive system (NAS) and a self-designed uninterruptible power supply. The system can be remotely controlled via the internet. The system is currently deployed covering a range of depths from 2850 m to 2910 m. Ambient temperatures at this depth are approximately 110 °C with onboard tool temperatures running at 115 °C. Data is continuously streamed to the NAS for archiving, approximately 11 GBytes of data is recorded per day at the sampling period of 0.5 ms. The lack of noise at this depth allows short data snippets to be flagged with a simple amplitude threshold criteria. The greatly reduced data volume of the snippets allows for ready access via the internet to the system for ongoing quality control. Spurious events, mostly small amplitude tube waves originating at or near the surface, are readily discounted. Active seismic measurements are carried out simultaneously but these require that an appropriately accurate independent GPS based time synchronization be used. Various experiences with event detection, orientation of sondes using both explosives and seismic vibrator, potential overheating of the surface electronics, and issues related to loss of shore power provide for a detailed case study. Aquistore, managed by the

  5. Seismic Imaging of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude

    The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

  6. 100 years of seismic research on the Moho

    NASA Astrophysics Data System (ADS)

    Prodehl, Claus; Kennett, Brian; Artemieva, Irina M.; Thybo, Hans

    2013-12-01

    The detection of a seismic boundary, the “Moho”, between the outermost shell of the Earth, the Earth's crust, and the Earth's mantle by A. Mohorovičić was the consequence of increased insight into the propagation of seismic waves caused by earthquakes. This short history of seismic research on the Moho is primarily based on the comprehensive overview of the worldwide history of seismological studies of the Earth's crust using controlled sources from 1850 to 2005, by Prodehl and Mooney (2012). Though the art of applying explosions, so-called “artificial events”, as energy sources for studies of the uppermost crustal layers began in the early 1900s, its effective use for studying the entire crust only began at the end of World War II. From 1945 onwards, controlled-source seismology has been the major approach to study details of the crust and underlying crust-mantle boundary, the Moho. The subsequent description of history of controlled-source crustal seismology and its seminal results is subdivided into separate chapters for each decade, highlighting the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. Since the late 1980s, passive seismology using distant earthquakes has played an increasingly important role in studies of crustal structure. The receiver function technique exploiting conversions between P and SV waves at discontinuities in seismic wavespeed below a seismic station has been extensively applied to the increasing numbers of permanent and portable broad-band seismic stations across the globe. Receiver function studies supplement controlled source work with improved geographic coverage and now make a significant contribution to knowledge of the nature of the crust and the depth to Moho.

  7. Development of Vertical Cable Seismic System (2)

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Murakami, F.; Tsukahara, H.; Ishikawa, K.

    2012-12-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have carried out two field surveys in 2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, we have confirmed that the

  8. Seismic Design of ITER Component Cooling Water System-1 Piping

    NASA Astrophysics Data System (ADS)

    Singh, Aditya P.; Jadhav, Mahesh; Sharma, Lalit K.; Gupta, Dinesh K.; Patel, Nirav; Ranjan, Rakesh; Gohil, Guman; Patel, Hiren; Dangi, Jinendra; Kumar, Mohit; Kumar, A. G. A.

    2017-04-01

    The successful performance of ITER machine very much depends upon the effective removal of heat from the in-vessel components and other auxiliary systems during Tokamak operation. This objective will be accomplished by the design of an effective Cooling Water System (CWS). The optimized piping layout design is an important element in CWS design and is one of the major design challenges owing to the factors of large thermal expansion and seismic accelerations; considering safety, accessibility and maintainability aspects. An important sub-system of ITER CWS, Component Cooling Water System-1 (CCWS-1) has very large diameter of pipes up to DN1600 with many intersections to fulfill the process flow requirements of clients for heat removal. Pipe intersection is the weakest link in the layout due to high stress intensification factor. CCWS-1 piping up to secondary confinement isolation valves as well as in-between these isolation valves need to survive a Seismic Level-2 (SL-2) earthquake during the Tokamak operation period to ensure structural stability of the system in the Safe Shutdown Earthquake (SSE) event. This paper presents the design, qualification and optimization of layout of ITER CCWS-1 loop to withstand SSE event combined with sustained and thermal loads as per the load combinations defined by ITER and allowable limits as per ASME B31.3, This paper also highlights the Modal and Response Spectrum Analyses done to find out the natural frequency and system behavior during the seismic event.

  9. Block structure and geodynamics of the continental lithosphere on plate boundaries

    NASA Astrophysics Data System (ADS)

    Gatinsky, Yu. G.; Prokhorova, T. V.; Romanyuk, T. V.; Vladova, G. L.

    2009-04-01

    Division of the Earth lithosphere on large plates must be considered only as the first and most general approximation in its structure hierarchy. Some transit zones or difuuse boundaries after other authors take place in lithosphere plate boundaries. The tectonic tension of plate interaction is transferred and relaxed within these zones, which consist of blocks limited by seismoactive faults. Vectors of block horizontal displacements often don't coincide with vectors of main plates and change together with changing block rigidity. As a rule the intensity the seismic energy at plate and transit zone boundaries decreases linearly with distancing from these boundaries and correlates with decreasing of velocities of block horizontal displacements. But sometimes the maximum of the energy manifestation takes place in inner parts of transit zones. Some relatively tight interblock zones established in central and east Asia are the most seismically active. They limited such blocks as Pamir, Tien Shan, Bayanhar, Shan, Japanese-Korean, as well as the north boundary of the Indian Plate. A seismic energy intensity of these zones can be compared with the energy of Pacific subduction zones. It is worthy to note that the majority catastrophic earthquakes took place in Central Asia just within interblock zones. A level of block displacement is situated mainly in the bottom or inside the Earth crust, more rare in the lithosphere mantle. Blocks with the most thick lithosphere roots (SE China, Amurian) are the most rigid and weakly deformed.

  10. Along-strike variations in seismic structure of the locked-sliding transition on the plate boundary beneath the southern part of Kii Peninsula, southwestern Japan

    NASA Astrophysics Data System (ADS)

    Kurashimo, E.; Iidaka, T.; Iwasaki, T.; Saiga, A.; Umeyama, E.; Tsumura, N.; Sakai, S.; Hirata, N.

    2013-12-01

    The Nankai trough region, where the Philippine Sea Plate (PHS) subducts beneath the SW Japan arc, is a well-known seismogenic zone of interplate earthquakes. A narrow zone of nonvolcanic tremor has been found in the SW Japan fore-arc, along strike of the arc (Obara, 2002). The epicentral distribution of tremor corresponds to the locked-sliding transition estimated from thermal and deformation models (Hyndman et al., 1995). The spatial distribution of the tremor is not homogeneous in a narrow belt but is spatially clustered. Obara [2002] suggested fluids as a source for tremor because of the long duration and the mobility of the tremor activity. The behavior of fluids at the plate interface is a key factor in understanding fault slip processes. Seismic reflection characteristics and seismic velocity variations can provide important information on the fluid-related heterogeneity of structure around plate interface. However, little is known about the deeper part of the plate boundary, especially the transition zone on the subducting plate. To reveal the seismic structure of the transition zone, we conducted passive and active seismic experiments in the southern part of Kii Peninsula, SW Japan. Sixty 3-component portable seismographs were installed on a 60-km-long line (SM-line) nearly perpendicular to the direction of the subduction of the PHS with approximately 1 km spacing. To improve accuracy of hypocenter locations, we additionally deployed six 3-component seismic stations around the survey line. Waveforms were continuously recorded during a five-month period from December, 2009. In October of 2010, a deep seismic profiling was also conducted. 290 seismometers were deployed on the SM-line with about 200 m spacing, on which five explosives shots were fired as controlled seismic sources. Arrival times of local earthquakes and explosive shots were used in a joint inversion for earthquake locations and 3-D Vp and Vp/Vs structures, using the iterative damped least

  11. 1D Seismic reflection technique to increase depth information in surface seismic investigations

    NASA Astrophysics Data System (ADS)

    Camilletti, Stefano; Fiera, Francesco; Umberto Pacini, Lando; Perini, Massimiliano; Prosperi, Andrea

    2017-04-01

    1D seismic methods, such as MASW Re.Mi. and HVSR, have been extensively used in engineering investigations, bedrock research, Vs profile and to some extent for hydrologic applications, during the past 20 years. Recent advances in equipment, sound sources and computer interpretation techniques, make 1D seismic methods highly effective in shallow subsoil modeling. Classical 1D seismic surveys allows economical collection of subsurface data however they fail to return accurate information for depths greater than 50 meters. Using a particular acquisition technique it is possible to collect data that can be quickly processed through reflection technique in order to obtain more accurate velocity information in depth. Furthermore, data processing returns a narrow stratigraphic section, alongside the 1D velocity model, where lithological boundaries are represented. This work will show how collect a single-CMP to determine: (1) depth of bedrock; (2) gravel layers in clayey domains; (3) accurate Vs profile. Seismic traces was processed by means a new software developed in collaboration with SARA electronics instruments S.r.l company, Perugia - ITALY. This software has the great advantage of being able to be used directly in the field in order to reduce the times elapsing between acquisition and processing.

  12. Proxies of oceanic Lithosphere/Asthenosphere Boundary from Global Seismic Anisotropy Tomography

    NASA Astrophysics Data System (ADS)

    Burgos, Gael; Montagner, Jean-Paul; Beucler, Eric; Trampert, Jeannot; Capdeville, Yann

    2013-04-01

    Surface waves provide essential information on the knowledge of the upper mantle global structure despite their low lateral resolution. This study, based on surface waves data, presents the development of a new anisotropic tomographic model of the upper mantle, a simplified isotropic model and the consequences of these results for the Lithosphere/Asthenosphere Boundary (LAB). As a first step, a large number of data is collected, these data are merged and regionalized in order to derive maps of phase and group velocity for the fundamental mode of Rayleigh and Love waves and their azimuthal dependence (maps of phase velocity are also obtained for the first six overtones). As a second step, a crustal a posteriori model is developped from the Monte-Carlo inversion of the shorter periods of the dataset, in order to take into account the effect of the shallow layers on the upper mantle. With the crustal model, a first Monte-Carlo inversion for the upper mantle structure is realized in a simplified isotropic parameterization to highlight the influence of the LAB properties on the surface waves data. Still using the crustal model, a first order perturbation theory inversion is performed in a fully anisotropic parameterization to build a 3-D tomographic model of the upper mantle (an extended model until the transition zone is also obtained by using the overtone data). Estimates of the LAB depth are derived from the upper mantle models and compared with the predictions of oceanic lithosphere cooling models. Seismic events are simulated using the Spectral Element Method in order to validate the ability of the anisotropic tomographic model of the upper mantle to re- produce observed seismograms.

  13. Seismic structure and segmentation of the axial valley of the Mid-Cayman Spreading Center

    NASA Astrophysics Data System (ADS)

    Van Avendonk, Harm J. A.; Hayman, Nicholas W.; Harding, Jennifer L.; Grevemeyer, Ingo; Peirce, Christine; Dannowski, Anke

    2017-06-01

    We report the results of a two-dimensional tomographic inversion of marine seismic refraction data from an array of ocean-bottom seismographs (OBSs), which produced an image of the crustal structure along the axial valley of the ultraslow spreading Mid-Cayman Spreading Center (MCSC). The seismic velocity model shows variations in the thickness and properties of the young oceanic crust that are consistent with the existence of two magmatic-tectonic segments along the 110 km long spreading center. Seismic wave speeds are consistent with exhumed mantle at the boundary between these two segments, but changes in the vertical gradient of seismic velocity suggest that volcanic crust occupies most of the axial valley seafloor along the seismic transect. The two spreading segments both have a low-velocity zone (LVZ) several kilometers beneath the seafloor, which may indicate the presence of shallow melt. However, the northern segment also has low seismic velocities (3 km/s) in a thick upper crustal layer (1.5-2.0 km), which we interpret as an extrusive volcanic section with high porosity and permeability. This segment hosts the Beebe vent field, the deepest known high-temperature black smoker hydrothermal vent system. In contrast, the southern spreading segment has seismic velocities as high as 4.0 km/s near the seafloor. We suggest that the porosity and permeability of the volcanic crust in the southern segment are much lower, thus limiting deep seawater penetration and hydrothermal recharge. This may explain why no hydrothermal vent system has been found in the southern half of the MCSC.

  14. Locating seismicity on the Arctic plate boundary using multiple-event techniques and empirical signal processing

    NASA Astrophysics Data System (ADS)

    Gibbons, S. J.; Harris, D. B.; Dahl-Jensen, T.; Kværna, T.; Larsen, T. B.; Paulsen, B.; Voss, P. H.

    2017-12-01

    The oceanic boundary separating the Eurasian and North American plates between 70° and 84° north hosts large earthquakes which are well recorded teleseismically, and many more seismic events at far lower magnitudes that are well recorded only at regional distances. Existing seismic bulletins have considerable spread and bias resulting from limited station coverage and deficiencies in the velocity models applied. This is particularly acute for the lower magnitude events which may only be constrained by a small number of Pn and Sn arrivals. Over the past two decades there has been a significant improvement in the seismic network in the Arctic: a difficult region to instrument due to the harsh climate, a sparsity of accessible sites (particularly at significant distances from the sea), and the expense and difficult logistics of deploying and maintaining stations. New deployments and upgrades to stations on Greenland, Svalbard, Jan Mayen, Hopen, and Bjørnøya have resulted in a sparse but stable regional seismic network which results in events down to magnitudes below 3 generating high-quality Pn and Sn signals on multiple stations. A catalogue of several hundred events in the region since 1998 has been generated using many new phase readings on stations on both sides of the spreading ridge in addition to teleseismic P phases. A Bayesian multiple event relocation has resulted in a significant reduction in the spread of hypocentre estimates for both large and small events. Whereas single event location algorithms minimize vectors of time residuals on an event-by-event basis, the Bayesloc program finds a joint probability distribution of origins, hypocentres, and corrections to traveltime predictions for large numbers of events. The solutions obtained favour those event hypotheses resulting in time residuals which are most consistent over a given source region. The relocations have been performed with different 1-D velocity models applicable to the Arctic region and

  15. A Fiber-Optic Borehole Seismic Vector Sensor System for Geothermal Site Characterization and Monitoring

    SciTech Connect

    Paulsson, Bjorn N.P.; Thornburg, Jon A.; He, Ruiqing

    2015-04-21

    Seismic techniques are the dominant geophysical techniques for the characterization of subsurface structures and stratigraphy. The seismic techniques also dominate the monitoring and mapping of reservoir injection and production processes. Borehole seismology, of all the seismic techniques, despite its current shortcomings, has been shown to provide the highest resolution characterization and most precise monitoring results because it generates higher signal to noise ratio and higher frequency data than surface seismic techniques. The operational environments for borehole seismic instruments are however much more demanding than for surface seismic instruments making both the instruments and the installation much more expensive. The currentmore » state-of-the-art borehole seismic instruments have not been robust enough for long term monitoring compounding the problems with expensive instruments and installations. Furthermore, they have also not been able to record the large bandwidth data available in boreholes or having the sensitivity allowing them to record small high frequency micro seismic events with high vector fidelity. To reliably achieve high resolution characterization and long term monitoring of Enhanced Geothermal Systems (EGS) sites a new generation of borehole seismic instruments must therefore be developed and deployed. To address the critical site characterization and monitoring needs for EGS programs, US Department of Energy (DOE) funded Paulsson, Inc. in 2010 to develop a fiber optic based ultra-large bandwidth clamped borehole seismic vector array capable of deploying up to one thousand 3C sensor pods suitable for deployment into ultra-high temperature and high pressure boreholes. Tests of the fiber optic seismic vector sensors developed on the DOE funding have shown that the new borehole seismic sensor technology is capable of generating outstanding high vector fidelity data with extremely large bandwidth: 0.01 – 6,000 Hz. Field tests have

  16. Bed load transport and boundary roughness changes as competing causes of hysteresis in the relationship between river discharge and seismic amplitude recorded near a steep mountain stream

    NASA Astrophysics Data System (ADS)

    Roth, Danica L.; Finnegan, Noah J.; Brodsky, Emily E.; Rickenmann, Dieter; Turowski, Jens M.; Badoux, Alexandre; Gimbert, Florent

    2017-05-01

    Hysteresis in the relationship between bed load transport and river stage is a well-documented phenomenon with multiple known causes. Consequently, numerous studies have interpreted hysteresis in the relationship between seismic ground motion near rivers and some measure of flow strength (i.e., discharge or stage) as the signature of bed load transport. Here we test this hypothesis in the Erlenbach stream (Swiss Prealps) using a metric to quantitatively compare hysteresis in seismic data with hysteresis recorded by geophones attached beneath steel plates within the streambed, a well-calibrated proxy for direct sediment transport measurements. We find that while both the geophones and seismometers demonstrate hysteresis, the magnitude and direction of hysteresis are not significantly correlated between these data, indicating that the seismic signal at this site is primarily reflecting hysteresis in processes other than sediment transport. Seismic hysteresis also does not correlate significantly with the magnitude of sediment transport recorded by the geophones, contrary to previous studies' assumptions. We suggest that hydrologic sources and changes in water turbulence, for instance due to evolving boundary conditions at the bed, rather than changes in sediment transport rates, may sometimes contribute to or even dominate the hysteresis observed in seismic amplitudes near steep mountain rivers.Plain Language SummaryAn increasing number of studies have recently observed changes in the amount of <span class="hlt">seismic</span> shaking (hysteresis) recorded near a river at a given discharge during floods. Most studies have assumed that this hysteresis was caused by changes in the amount of sediment being transported in the river and have therefore used the hysteresis to assess sediment transport rates and patterns. We examine concurrent <span class="hlt">seismic</span> and sediment transport data from a steep mountain stream in the Swiss Prealps and find that changes in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T42D..02F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T42D..02F"><span><span class="hlt">Seismicity</span> and lithospheric structure of Central Mozambique: implications for the southward propagation of the East African Rift <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fonseca, J. F. B. D.; Domingues, A.</p> <p>2017-12-01</p> <p>South of latitude 5ºS, there is scarce support for a single preferred location of continental rifting in SE Africa. Building on the complexity already displayed further north around the Victoria microplate, the structures associated with rifting activity are now distributed over three branches: one directed towards the SW through Zambia and into the Okawango rift in Botswana; one running offshore along the Mozambique Channel; and a central rift <span class="hlt">system</span> through lake Malawi and Central Mozambique. Our investigation focuses on this central branch, whose tectonic relevance was highlighted by the M7 Machaze earthquake in 2006. Through the temporary deployment of 30 broadband stations in central Mozambique we were able to document that the Shire and Urema grabens linking the Malawi rift to the Machaze epicentral area are <span class="hlt">seismically</span> active, correlating with a 300 km long narrow band of <span class="hlt">seismicity</span> reaching the lower crust. No significant <span class="hlt">seismicity</span> was recorded along the Mazenga graben, south of the Machaze epicentral area. A tomographic model derived from ambient noise analysis showed a strong correlation between the <span class="hlt">seismicity</span> and a sharp NNE-SSW <span class="hlt">boundary</span> between the fast crust of the Zimbabwe and Kaapvaal cratons and slower crust underneath the Mozambique Coastal Plains. The <span class="hlt">seismicity</span> shuts down were this trend rotates to a more N-S direction as the Lebombo monocline is approached. 20th Century <span class="hlt">seismicity</span> of SE Africa shows a clear cluster in time, with five M>6 earthquakes concentrated in the 1950's, distributed along the edges of the Zimbabwe craton and spanning distances of 600 km. Spatial correlation with such range is hard to reconcile with stress transmission in the crust and may point to the interaction of the cratonic root with asthenospheric flow. Under this light, the M6.5 Central Botswana earthquake of April 2017 and the M7 Machaze earthquake of 2006, both located in the vicinity of the borders of the Kaapvaal craton, may bear a similar correlation. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.S53A1461H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.S53A1461H"><span>An Experimental <span class="hlt">Seismic</span> Data and Parameter Exchange <span class="hlt">System</span> for Tsunami Warning <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoffmann, T. L.; Hanka, W.; Saul, J.; Weber, B.; Becker, J.; Heinloo, A.; Hoffmann, M.</p> <p>2009-12-01</p> <p>For several years GFZ Potsdam is operating a global earthquake monitoring <span class="hlt">system</span>. Since the beginning of 2008, this <span class="hlt">system</span> is also used as an experimental <span class="hlt">seismic</span> background data center for two different regional Tsunami Warning <span class="hlt">Systems</span> (TWS), the IOTWS (Indian Ocean) and the interim NEAMTWS (NE Atlantic and Mediterranean). The SeisComP3 (SC3) software, developed within the GITEWS (German Indian Ocean Tsunami Early Warning <span class="hlt">System</span>) project, capable to acquire, archive and process real-time data feeds, was extended for export and import of individual processing results within the two clusters of connected SC3 <span class="hlt">systems</span>. Therefore not only real-time waveform data are routed to the attached warning centers through GFZ but also processing results. While the current experimental NEAMTWS cluster consists of SC3 <span class="hlt">systems</span> in six designated national warning centers in Europe, the IOTWS cluster presently includes seven centers, with another three likely to join in 2009/10. For NEAMTWS purposes, the GFZ virtual real-time <span class="hlt">seismic</span> network (GEOFON Extended Virtual Network -GEVN) in Europe was substantially extended by adding many stations from Western European countries optimizing the station distribution. In parallel to the data collection over the Internet, a GFZ VSAT hub for secured data collection of the EuroMED GEOFON and NEAMTWS backbone network stations became operational and first data links were established through this backbone. For the Southeast Asia region, a VSAT hub has been established in Jakarta already in 2006, with some other partner networks connecting to this backbone via the Internet. Since its establishment, the experimental <span class="hlt">system</span> has had the opportunity to prove its performance in a number of relevant earthquakes. Reliable solutions derived from a minimum of 25 stations were very promising in terms of speed. For important events, automatic alerts were released and disseminated by emails and SMS. Manually verified solutions are added as soon as they become</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70021490','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70021490"><span><span class="hlt">Seismic</span> slope-performance analysis: from hazard map to decision support <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Miles, Scott B.; Keefer, David K.; Ho, Carlton L.</p> <p>1999-01-01</p> <p>In response to the growing recognition of engineers and decision-makers of the regional effects of earthquake-induced landslides, this paper presents a general approach to conducting <span class="hlt">seismic</span> landslide zonation, based on the popular Newmark's sliding block analogy for modeling coherent landslides. Four existing models based on the sliding block analogy are compared. The comparison shows that the models forecast notably different levels of slope performance. Considering this discrepancy along with the limitations of static maps as a decision tool, a spatial decision support <span class="hlt">system</span> (SDSS) for <span class="hlt">seismic</span> landslide analysis is proposed, which will support investigations over multiple scales for any number of earthquake scenarios and input conditions. Most importantly, the SDSS will allow use of any <span class="hlt">seismic</span> landslide analysis model and zonation approach. Developments associated with the SDSS will produce an object-oriented model for encapsulating spatial data, an object-oriented specification to allow construction of models using modular objects, and a direct-manipulation, dynamic user-interface that adapts to the particular <span class="hlt">seismic</span> landslide model configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6052G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6052G"><span>Effect of inherited structures on strike-slip plate <span class="hlt">boundaries</span>: insight from analogue modelling of the central Levant Fracture <span class="hlt">System</span>, Lebanon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghalayini, Ramadan; Daniel, Jean-Marc; Homberg, Catherine; Nader, Fadi</p> <p>2015-04-01</p> <p>Analogue sandbox modeling is a tool to simulate deformation style and structural evolution of sedimentary basins. The initial goal is to test what is the effect of inherited and crustal structures on the propagation, evolution, and final geometry of major strike-slip faults at the <span class="hlt">boundary</span> between two tectonic plates. For this purpose, we have undertaken a series of analogue models to validate and reproduce the structures of the Levant Fracture <span class="hlt">System</span>, a major NNE-SSW sinistral strike-slip fault forming the <span class="hlt">boundary</span> between the Arabian and African plates. Onshore observations and recent high quality 3D <span class="hlt">seismic</span> data in the Levant Basin offshore Lebanon demonstrated that Mesozoic ENE striking normal faults were reactivated into dextral strike-slip faults during the Late Miocene till present day activity of the plate <span class="hlt">boundary</span> which shows a major restraining bend in Lebanon with a ~ 30°clockwise rotation in its trend. Experimental parameters consisted of a silicone layer at the base simulating the ductile crust, overlain by intercalated quartz sand and glass sand layers. Pre-existing structures were simulated by creating a graben in the silicone below the sand at an oblique (>60°) angle to the main throughgoing strike-slip fault. The latter contains a small stepover at depth to create transpression during sinistral strike-slip movement and consequently result in mountain building similarly to modern day Lebanon. Strike-slip movement and compression were regulated by steady-speed computer-controlled engines and the model was scanned using a CT-scanner continuously while deforming to have a final 4D model of the <span class="hlt">system</span>. Results showed that existing normal faults were reactivated into dextral strike-slip faults as the sinistral movement between the two plates accumulated. Notably, the resulting restraining bend is asymmetric and segmented into two different compartments with differing geometries. One compartment shows a box fold anticline, while the second shows an</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.8478G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.8478G"><span>Protective <span class="hlt">system</span> for civil buildings and industrial structures subjected to the <span class="hlt">seismic</span> risk</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghica, D.; Grigore, A.; Ionescu, C.</p> <p>2009-04-01</p> <p>Romania is a European country with significant <span class="hlt">seismicity</span>. The most active <span class="hlt">seismic</span> zone is represented by the Vrancea area, located within the arch of the Carpathians Mountains. Vrancea <span class="hlt">seismicity</span> is characterized by intermediate depth earthquakes which occur in a narrow epicentral and hypocentral region. During the last 70 years, Romania experienced four strong Vrancea earthquakes: 10 November 1940 (Mw =7.7, 160 km depth), 4 March 1977 (Mw =7.5, 100 km depth), 30 August 1986 (Mw =7.2, 140 km depth), 30 May 30 1990 (Mw =6.9, 80 km depth). The 1977 event was characterized by catastrophic consequences: 1500 casualties and collapsing of 35 high-risk buildings, mostly occurring in Bucharest. The purpose of this paper is to present a protective <span class="hlt">system</span> designed to be installed in the civil buildings and industrial structures placed in the high <span class="hlt">seismic</span> regions, and therefore to contribute to the mitigation of the strong earthquake effects on human society. This <span class="hlt">system</span> proposes an efficient antiseismic protection, respectively shutting down the installations and equipments mounted in the building's infrastructure, which can become extremely dangerous in case of a major earthquake by appearing the possibility of explosions, deflagration, fires, toxic and polluting fluids leakage. The damages are strongly amplified by the fact that, simultaneously, water and electric energy lines distributions are damaged too, making impossible an efficient firemen intervention, for localizing the fire sources. Moreover, the installations of the individual heating stations which operate with open flame increase the risk of explosions inside the buildings during an earthquake. The protective <span class="hlt">system</span> consists of a <span class="hlt">seismic</span> switch used for activating through weak-electric-currents of the building's safety <span class="hlt">systems</span> in case of strong earthquake, especially designed for building's elevators, as well as for moving parts of installations, which require positioning in safety place areas. The originality</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRB..123.1736E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRB..123.1736E"><span>The Role of Oceanic Transform Faults in Seafloor Spreading: A Global Perspective From <span class="hlt">Seismic</span> Anisotropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eakin, Caroline M.; Rychert, Catherine A.; Harmon, Nicholas</p> <p>2018-02-01</p> <p>Mantle anisotropy beneath mid-ocean ridges and oceanic transforms is key to our understanding of seafloor spreading and underlying dynamics of divergent plate <span class="hlt">boundaries</span>. Observations are sparse, however, given the remoteness of the oceans and the difficulties of <span class="hlt">seismic</span> instrumentation. To overcome this, we utilize the global distribution of <span class="hlt">seismicity</span> along transform faults to measure shear wave splitting of over 550 direct S phases recorded at 56 carefully selected <span class="hlt">seismic</span> stations worldwide. Applying this source-side splitting technique allows for characterization of the upper mantle <span class="hlt">seismic</span> anisotropy, and therefore the pattern of mantle flow, directly beneath <span class="hlt">seismically</span> active transform faults. The majority of the results (60%) return nulls (no splitting), while the non-null measurements display clear azimuthal dependency. This is best simply explained by anisotropy with a near vertical symmetry axis, consistent with mantle upwelling beneath oceanic transforms as suggested by numerical models. It appears therefore that the long-term stability of seafloor spreading may be associated with widespread mantle upwelling beneath the transforms creating warm and weak faults that localize strain to the plate <span class="hlt">boundary</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917127A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917127A"><span><span class="hlt">Seismic</span> slip on clay nano-foliation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aretusini, Stefano; Plümper, Oliver; Spagnuolo, Elena; Di Toro, Giulio</p> <p>2017-04-01</p> <p>Deformation processes active at <span class="hlt">seismic</span> slip rates (ca. 1 m/s) on smectite-rich slipping zones are not well understood, although they likely control the mechanical behaviour of: i) subduction zone faults affected by tsunamigenic earthquakes and <span class="hlt">seismic</span> surface rupturing, and ii) landslide decollements. Here we present a set of rotary experiments performed on water-dampened 2 mm thick clay-rich (70% wt. smectite and 30% wt. opal) gouge layers sheared at slip rates V ranging from 0.01 to 1.5 m/s, for 3 m of displacement under 5 MPa normal stress. Microstructural analyses were conducted on pre- and post-sheared gouges using focused ion beam scanning electron and transmission electron microscopy. All sheared gouges were slip weakening in the first 0.1 m of displacement, with friction coefficient decreasing from 0.4-0.3 to 0.1-0.05. Then, with progressive slip, gouges evolved to slip-strengthening (final friction coefficient of 0.47-0.35) at V ≤0.1 m/s and slip-neutral (final friction of 0.05) at V=1.5 m/s. Despite the large difference in the imposed slip rate and frictional behaviour, the slipping zone always consisted of a nano-foliation defined by sub-micrometric smectite crystals wrapping opal grains. The microstructural differences were (1) the thickness of the slipping zone which decreased from 1.5 mm at V≤0.1 m/s to 0.15 mm at V=1.5 m/s, and (2) the structure of the foliated fabric, which was S/C'-type at V≤0.1 m/s and anastomosing-type at V=1.5 m/s. The presence of a similar nano-foliation in all the smectite-rich wet gouges suggests the activation of similar frictional processes, most likely grain <span class="hlt">boundary</span> and interlayer frictional sliding aided by water films, operating from sub-<span class="hlt">seismic</span> to <span class="hlt">seismic</span> strain rates ( 10-10000 1/s). Water films on crystal <span class="hlt">boundaries</span> and interlayers possibly control the micro- and nano-mechanics of smectite deformation, therefore influencing the bulk frictional behaviour during <span class="hlt">seismic</span> slip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T54A..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T54A..01G"><span>The April 2017 M6.7 Botswana Earthquake: Implications for African Intraplate <span class="hlt">Seismicity</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gardonio, B.; Calais, E.; Jolivet, R.</p> <p>2017-12-01</p> <p>The last decades have seen a rapidly increasing number of studies of interplate <span class="hlt">seismicity</span>, revealing for instance the fundamental relationship between <span class="hlt">seismic</span> and aseismic slip along plate <span class="hlt">boundary</span> faults. To the contrary, intraplate earthquakes, occurring far from plate <span class="hlt">boundaries</span> are still misunderstood and by far less studied. Key questions are the mechanisms through which elastic strain builds up and is released in the seismogenic crust in such contexts, in the absence of (yet) measurable intraplate strain rates. The April 2017 M6.7 Botswana earthquake was a surprise in many ways. This is the largest recorded event that struck this ordinarily <span class="hlt">seismically</span> quiet region, West to the East-African Rift <span class="hlt">system</span> where most of the usual southern <span class="hlt">seismicity</span> occurs. It may also be the largest intraplate event recorded since the 1988 Tennant Creek earthquake in central Australia. No active structure can be mapped at the surface. Active extension related to the east African rifting may occur several hundreds of kilometers to the north-east with low rates of a few mm per year. Closer to the event, the Okavango delta, located at 20° of latitude and 23° of longitude is considered by some as an incipient rift with very low deformation rates, similar to a large part of the southern African continent. Interestingly, <span class="hlt">seismic</span> activity in the area of the recent Botswana earthquake is more important than the world average intraplate activity, potentially due to rifting to the east and/or large stresses induced by lateral gradients in gravitational potential energy (this part of the world has an altitude of 1000 to 2000 m.). The aim of this study is to better constrain the tectonic setting and the dynamics of the Botswana earthquake area. To do so, we analyze a Sentinel 1 interferogram of the event to constrain the strike, dip, depth, magnitude and location of the earthquake. We also analyze continuous teleseismic signals during two months centered on the mainshock using a template</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S53A0660F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S53A0660F"><span>Identifying Conventionally Sub-<span class="hlt">Seismic</span> Faults in Polygonal Fault <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fry, C.; Dix, J.</p> <p>2017-12-01</p> <p>Polygonal Fault <span class="hlt">Systems</span> (PFS) are prevalent in hydrocarbon basins globally and represent potential fluid pathways. However the characterization of these pathways is subject to the limitations of conventional 3D <span class="hlt">seismic</span> imaging; only capable of resolving features on a decametre scale horizontally and metres scale vertically. While outcrop and core examples can identify smaller features, they are limited by the extent of the exposures. The disparity between these scales can allow for smaller faults to be lost in a resolution gap which could mean potential pathways are left unseen. Here the focus is upon PFS from within the London Clay, a common bedrock that is tunnelled into and bears construction foundations for much of London. It is a continuation of the Ieper Clay where PFS were first identified and is found to approach the seafloor within the Outer Thames Estuary. This allows for the direct analysis of PFS surface expressions, via the use of high resolution 1m bathymetric imaging in combination with high resolution <span class="hlt">seismic</span> imaging. Through use of these datasets surface expressions of over 1500 faults within the London Clay have been identified, with the smallest fault measuring 12m and the largest at 612m in length. The displacements over these faults established from both bathymetric and <span class="hlt">seismic</span> imaging ranges from 30cm to a couple of metres, scales that would typically be sub-<span class="hlt">seismic</span> for conventional basin <span class="hlt">seismic</span> imaging. The orientations and dimensions of the faults within this network have been directly compared to 3D <span class="hlt">seismic</span> data of the Ieper Clay from the offshore Dutch sector where it exists approximately 1km below the seafloor. These have typical PFS attributes with lengths of hundreds of metres to kilometres and throws of tens of metres, a magnitude larger than those identified in the Outer Thames Estuary. The similar orientations and polygonal patterns within both locations indicates that the smaller faults exist within typical PFS structure but are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25119049','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25119049"><span>Gradual unlocking of plate <span class="hlt">boundary</span> controlled initiation of the 2014 Iquique earthquake.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schurr, Bernd; Asch, Günter; Hainzl, Sebastian; Bedford, Jonathan; Hoechner, Andreas; Palo, Mauro; Wang, Rongjiang; Moreno, Marcos; Bartsch, Mitja; Zhang, Yong; Oncken, Onno; Tilmann, Frederik; Dahm, Torsten; Victor, Pia; Barrientos, Sergio; Vilotte, Jean-Pierre</p> <p>2014-08-21</p> <p>On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate <span class="hlt">Boundary</span> Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile <span class="hlt">seismic</span> gap, the last major segment of the South American plate <span class="hlt">boundary</span> that had not ruptured in the past century. Since July 2013 three <span class="hlt">seismic</span> clusters, each lasting a few weeks, hit this part of the plate <span class="hlt">boundary</span> with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These <span class="hlt">seismic</span> clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the <span class="hlt">seismic</span> gap accentuated by the foreshock activity in a zone of intermediate <span class="hlt">seismic</span> coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased <span class="hlt">seismic</span> hazard with the potential to host an earthquake with a magnitude of >8.5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRB..122.2173N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRB..122.2173N"><span><span class="hlt">Seismicity</span> of the rocky mountains and Rio Grande Rift from the EarthScope Transportable Array and CREST temporary <span class="hlt">seismic</span> networks, 2008-2010</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakai, J. S.; Sheehan, A. F.; Bilek, S. L.</p> <p>2017-03-01</p> <p>We developed a catalog of small magnitude (ML -0.1 to 4.7) <span class="hlt">seismicity</span> across Colorado and New Mexico from the EarthScope USArray Transportable Array and CREST (Colorado Rocky Mountains Experiment and <span class="hlt">Seismic</span> Transects) <span class="hlt">seismic</span> networks from 2008 to 2010 to characterize active deformation in the Rio Grande Rift. We recorded over 900 earthquakes in the Rio Grande Rift region, not including induced earthquakes and mine blasts, and find that the rift is actively deforming both broadly and in distinct regions. <span class="hlt">Seismic</span> events that are likely induced, mostly in the Raton Basin, make up 66% of the catalog (1837 earthquakes). Neogene faults in the northern rift in north central Colorado are <span class="hlt">seismically</span> active in the North Park Basin and northwestern Colorado. The central rift from the San Luis Basin (southern Colorado) to south of the Socorro Magma Body is the most <span class="hlt">seismically</span> active rift region, and <span class="hlt">seismicity</span> delineates the deformation in the Colorado Plateau transition zone, which is spatially correlated with volcanic vents, dikes, and faults within the western Jemez Lineament. The eastern Jemez Lineament is nearly aseismic and surrounded by a halo of <span class="hlt">seismicity</span> culminating in <span class="hlt">boundaries</span> defined by recent moderate (Mw 3.9 and Mw 3.3) earthquakes. The southern rift is characterized by diffuse <span class="hlt">seismicity</span> in Texas and Mexico. This study provides an updated <span class="hlt">seismic</span> catalog built with uniformity in seismometer coverage and low epicentral uncertainties ( 2 km) that allows for regional evaluation of <span class="hlt">seismicity</span>. During this time period, clusters of <span class="hlt">seismicity</span> and moderate magnitude earthquakes characterize deformation in a low-strain rate extensional environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982Tectp..87..355R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982Tectp..87..355R"><span><span class="hlt">Seismicity</span> of the Indo-Australian/Solomon Sea Plate <span class="hlt">boundary</span> in the Southeast Papua region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ripper, I. D.</p> <p>1982-08-01</p> <p><span class="hlt">Seismicity</span> and earthquake focal mechanism plots of the Southeast Papua and Woodlark Basin region for the period January 1960 to May 1979 show that: (a) the West Woodlark Basin spreading centre extends from the deep West Woodlark Basin, through Dawson Strait into Goodenough Bay, Southeast Papua; (b) a southeast <span class="hlt">seismic</span> trend in the West Woodlark Basin is associated with a left-lateral transform fault, but a gap exists between this zone and the <span class="hlt">seismic</span> East Woodlark Basin spreading centre; (c) Southeast Papua <span class="hlt">Seismicity</span> divides into a shallow earthquake zone in which the earthquakes occur mainly in the northeast side of the Owen Stanley Range, and an intermediate depth southwest dipping Benioff zone which extends almost from Mt. Lamington to Goroka. The Benioff zone indicates the presence of a southwest dipping slab of Solomon Sea Plate beneath the Indo-Australian Plate in the Southeast Papua and Ramu-Markham Valley region. This subduction zone has collided with the New Britain subduction zone of the Solomon Sea Plate along the Ramu-Markham Valley. The Solomon Sea Plate is now hanging suspended in the form of an arch beneath Ramu-Markham Valley, inhibiting further subduction beneath Southeast Papua.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAG....92...68P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAG....92...68P"><span>Geostatistics applied to cross-well reflection <span class="hlt">seismic</span> for imaging carbonate aquifers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parra, Jorge; Emery, Xavier</p> <p>2013-05-01</p> <p>Cross-well <span class="hlt">seismic</span> reflection data, acquired from a carbonate aquifer at Port Mayaca test site near the eastern <span class="hlt">boundary</span> of Lake Okeechobee in Martin County, Florida, are used to delineate flow units in the region intercepted by two wells. The interwell impedance determined by inversion from the <span class="hlt">seismic</span> reflection data allows us to visualize the major <span class="hlt">boundaries</span> between the hydraulic units. The hydraulic (flow) unit properties are based on the integration of well logs and the carbonate structure, which consists of isolated vuggy carbonate units and interconnected vug <span class="hlt">systems</span> within the carbonate matrix. The vuggy and matrix porosity logs based on Formation Micro-Imager (FMI) data provide information about highly permeable conduits at well locations. The integration of the inverted impedance and well logs using geostatistics helps us to assess the resolution of the cross-well <span class="hlt">seismic</span> method for detecting conduits and to determine whether these conduits are continuous or discontinuous between wells. A productive water zone of the aquifer outlined by the well logs was selected for analysis and interpretation. The ELAN (Elemental Log Analysis) porosity from two wells was selected as primary data and the reflection <span class="hlt">seismic</span>-based impedance as secondary data. The direct and cross variograms along the vertical wells capture nested structures associated with periodic carbonate units, which correspond to connected flow units between the wells. Alternatively, the horizontal variogram of impedance (secondary data) provides scale lengths that correspond to irregular <span class="hlt">boundary</span> shapes of flow units. The ELAN porosity image obtained by cokriging exhibits three similar flow units at different depths. These units are thin conduits developed in the first well and, at about the middle of the interwell separation region, these conduits connect to thicker flow units that are intercepted by the second well. In addition, a high impedance zone (low porosity) at a depth of about 275 m, after</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2000/0379/pdf/of00-379.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2000/0379/pdf/of00-379.pdf"><span>A filter circuit board for the Earthworm <span class="hlt">Seismic</span> Data Acquisition <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jensen, Edward Gray</p> <p>2000-01-01</p> <p>The Earthworm <span class="hlt">system</span> is a <span class="hlt">seismic</span> network data acquisition and processing <span class="hlt">system</span> used by the Northern California <span class="hlt">Seismic</span> Network as well as many other <span class="hlt">seismic</span> networks. The input to the <span class="hlt">system</span> is comprised of many realtime electronic waveforms fed to a multi-channel digitizer on a PC platform. The digitizer consists of one or more National Instruments Corp. AMUX–64T multiplexer boards attached to an A/D converter board located in the computer. Originally, passive filters were installed on the multiplexers to eliminate electronic noise picked up in cabling. It was later discovered that a small amount of crosstalk occurred between successive channels in the digitizing sequence. Though small, this crosstalk will cause what appear to be small earthquake arrivals at the wrong time on some channels. This can result in erroneous calculation of earthquake arrival times, particularly by automated algorithms. To deal with this problem, an Earthworm filter board was developed to provide the needed filtering while eliminating crosstalk. This report describes the tests performed to find a suitable solution, and the design of the circuit board. Also included are all the details needed to build and install this board in an Earthworm <span class="hlt">system</span> or any other <span class="hlt">system</span> using the AMUX–64T board. Available below is the report in PDF format as well as an archive file containing the circuit board manufacturing information.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMDI33B0404T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMDI33B0404T"><span>Three Types of Earth's Inner Core <span class="hlt">Boundary</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tian, D.; Wen, L.</p> <p>2017-12-01</p> <p>The Earth's inner core <span class="hlt">boundary</span> (ICB) is the site where the liquid outer core solidifies and the solid inner core grows. Thus, the fine-scale structure of the ICB is important for our understanding of the thermo-compositional state of the Earth's core. In this study, we collect a large set of <span class="hlt">seismic</span> records with high-quality pre-critical PKiKP and PcP phase pairs, recorded by two dense <span class="hlt">seismic</span> arrays, Hi-net in Japan and USArray in US. This dataset samples the ICB regions beneath East Asia, Mexico and the Bering Sea. We use differential travel times, amplitude ratios and waveform differences between PKiKP and PcP phases to constrain fine-scale structure of the ICB. The sampled ICB can be grouped into three types based on their <span class="hlt">seismic</span> characteristics: (1) a simple ICB with a flat and sharp <span class="hlt">boundary</span>, (2) a bumpy ICB with topographic height changes of 10 km, and (3) a localized mushy ICB with laterally varying thicknesses of 4-8 km. The laterally varying fine-scale structure of the ICB indicates existence of complex small-scale forces at the surface and a laterally varying solidification process of the inner core due to lateral variation of thermo-compositional condition near the ICB.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T53F..07R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T53F..07R"><span>Indo-Burmese subduction of the Bengal basin controlled by 90°E ridge collison imaged from deep <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rangin, C.; Maurin, T.</p> <p>2009-12-01</p> <p>As a result of the Indo Burmese active hyper-oblique subduction, part of the Bay of Bengal is presently subducting eastward below the Burmese microplate. We have conducted two deep penetration <span class="hlt">seismic</span> reflection surveys in the north-eastern Bay of Bengal, providing the first high resolution <span class="hlt">seismic</span> image of the Bengal basin fill and basement. On basis of these data, we are able to trace the 90°E ridge much more northward than previously thought, i.e. up to 20°N along the Indo-Burmese plate <span class="hlt">boundary</span>. We found out that the surface deformation, the deep structure of the subduction zone and the geometry of the plate <span class="hlt">boundary</span> could all be strongly influenced by the impact of a prominent asperity, the 90°E ridge. These effects are variable along the margin. Between 15°N and 18°N, the ridge asperity brushes the active burmese plate <span class="hlt">boundary</span> that strikes N10°E. At this latitude, all the structures framing the Indo-Burmese wedge have a similar N10°E trend. Deformation at the plate <span class="hlt">boundary</span> is mainly strike slip. This is confirmed by the absence of subducted slab at depth as indicated by both <span class="hlt">seismicity</span> and tomography. The small component of shortening along this plate <span class="hlt">boundary</span> is probably accommodated partly by the flexure of the ridge and partly within the deformed upper plate. North of 19°N, the ridge vanishes progressively. The absence of basement topography together with the large amount of sediments provided by the Brahmaputra delta facilitates the fast westward growth of the Indo-Burmese wedge. The <span class="hlt">seismicity</span> fits a well developed subducted slab at depth,. In the narrow transition zone between 18°N and 19°N, the 90°E ridge northern tips collides with the Burmese microplate. This collision could explain the rise of a subsuface flat and ramp <span class="hlt">system</span> offshore Ramree and Cheduba islands, and the strong uplift of the Indo-Burmese wedge in Mount Victoria area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T11C4565B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T11C4565B"><span>Tsujal Marine Survey: Crustal Characterization of the Rivera Plate-Jalisco Block <span class="hlt">Boundary</span> and its Implications for <span class="hlt">Seismic</span> and Tsunami Hazard Assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bartolome, R.; Danobeitia, J.; Barba, D. C., Sr.; Nunez-Cornu, F. J.; Cameselle, A. L.; Estrada, F.; Prada, M.; Bandy, W. L.</p> <p>2014-12-01</p> <p>During the spring of 2014, a team of Spanish and Mexican scientists explored the western margin of Mexico in the frame of the TSUJAL project. The two main objectives were to characterize the nature and structure of the lithosphere and to identify potential sources triggering earthquakes and tsunamis at the contact between Rivera plate-Jalisco block with the North American Plate. With these purposes a set of marine geophysical data were acquired aboard the RRS James Cook. This work is focus in the southern part of the TSUJAL survey, where we obtain <span class="hlt">seismic</span> images from the oceanic domain up to the continental shelf. Thus, more than 800 km of MCS data, divided in 7 profiles, have been acquired with a 6km long streamer and using an air-gun sources ranging from 5800 c.i. to 3540 c.i. Furthermore, a wide-angle <span class="hlt">seismic</span> profile of 190 km length was recorded in 16 OBS deployed perpendicular to the coast of Manzanillo. Gravity and magnetic, multibeam bathymetry and sub-bottom profiler data were recorded simultaneously with <span class="hlt">seismic</span> data in the offshore area. Preliminary stacked MCS <span class="hlt">seismic</span> sections reveal the crustal structure in the different domains of the Mexican margin. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate <span class="hlt">boundary</span> between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define the subduction plane (TS06b). These strong reflections which we interpret as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Another clear pattern observed within the first second of the MCS data shows evidences of a bottom</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.T41B2010N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.T41B2010N"><span>Precisely relocated <span class="hlt">seismicity</span> using 3-D <span class="hlt">seismic</span> velocity model by double-difference tomography method and orogenic processes in central and southern Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nagai, S.; Wu, Y.; Suppe, J.; Hirata, N.</p> <p>2009-12-01</p> <p>The island of Taiwan is located in the site of ongoing arc-continent collision zone between the Philippine Sea Plate and the Eurasian Plate. Numerous geophysical and geological studies are done in and around Taiwan to develop various models to explain the tectonic processes in the Taiwan region. The active and young tectonics and the associated high <span class="hlt">seismicity</span> in Taiwan provide us with unique opportunity to explore and understand the processes in the region related to the arc-continent collision. Nagai et al. [2009] imaged eastward dipping alternate high- and low-velocity bodies at depths of 5 to 25 km from the western side of the Central Mountain Range to the eastern part of Taiwan, by double-difference tomography [Zhang and Thurber, 2003] using three temporary <span class="hlt">seismic</span> networks with the Central Weather Bureau <span class="hlt">Seismic</span> Network(CWBSN). These three temporary networks are the aftershock observation after the 1999 Chi-Chi Taiwan earthquake and two dense linear array observations; one is across central Taiwan in 2001, another is across southern Taiwan in 2005, respectively. We proposed a new orogenic model, ’Upper Crustal Stacking Model’ inferred from our tomographic images. To understand the detailed <span class="hlt">seismic</span> structure more, we carry on relocating earthquakes more precisely in central and southern Taiwan, using three-dimensional velocity model [Nagai et al., 2009] and P- and S-wave arrival times both from the CWBSN and three temporary networks. We use the double-difference tomography method to improve relative and absolute location accuracy simultaneously. The relocated <span class="hlt">seismicity</span> is concentrated and limited along the parts of <span class="hlt">boundaries</span> between low- and high-velocity bodies. Especially, earthquakes occurred beneath the Eastern Central Range, triggered by 1999 Chi-Chi earthquake, delineate subsurface structural <span class="hlt">boundaries</span>, compared with profiles of estimated <span class="hlt">seismic</span> velocity. The relocated catalog and 3-D <span class="hlt">seismic</span> velocity model give us some constraints to reconstruct</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028275','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028275"><span>Characterizing a large shear-zone with <span class="hlt">seismic</span> and magnetotelluric methods: The case of the Dead Sea Transform</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Maercklin, N.; Bedrosian, P.A.; Haberland, C.; Ritter, O.; Ryberg, T.; Weber, M.; Weckmann, U.</p> <p>2005-01-01</p> <p><span class="hlt">Seismic</span> tomography, imaging of <span class="hlt">seismic</span> scatterers, and magnetotelluric soundings reveal a sharp lithologic contrast along a ???10 km long segment of the Arava Fault (AF), a prominent fault of the southern Dead Sea Transform (DST) in the Middle East. Low <span class="hlt">seismic</span> velocities and resistivities occur on its western side and higher values east of it, and the <span class="hlt">boundary</span> between the two units coincides partly with a <span class="hlt">seismic</span> scattering image. At 1-4 km depth the <span class="hlt">boundary</span> is offset to the east of the AF surface trace, suggesting that at least two fault strands exist, and that slip occurred on multiple strands throughout the margin's history. A westward fault jump, possibly associated with straightening of a fault bend, explains both our observations and the narrow fault zone observed by others. Copyright 2005 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820000009&hterms=industrial+Security&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dindustrial%2BSecurity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820000009&hterms=industrial+Security&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dindustrial%2BSecurity"><span>Scanning <span class="hlt">Seismic</span> Intrusion Detector</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, R. D.</p> <p>1982-01-01</p> <p>Scanning <span class="hlt">seismic</span> intrusion detector employs array of automatically or manually scanned sensors to determine approximate location of intruder. Automatic-scanning feature enables one operator to tend <span class="hlt">system</span> of many sensors. Typical sensors used with new <span class="hlt">system</span> are moving-coil <span class="hlt">seismic</span> pickups. Detector finds uses in industrial security <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.6009K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.6009K"><span>Validating induced <span class="hlt">seismicity</span> forecast models—Induced <span class="hlt">Seismicity</span> Test Bench</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Király-Proag, Eszter; Zechar, J. Douglas; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph</p> <p>2016-08-01</p> <p>Induced earthquakes often accompany fluid injection, and the <span class="hlt">seismic</span> hazard they pose threatens various underground engineering projects. Models to monitor and control induced <span class="hlt">seismic</span> hazard with traffic light <span class="hlt">systems</span> should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced <span class="hlt">Seismicity</span> Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed <span class="hlt">Seismicity</span> (SaSS) and Hydraulics and <span class="hlt">Seismics</span> (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the <span class="hlt">seismicity</span> rate better after shut-in but is only mediocre at forecasting the spatial distribution. On the other hand, SaSS forecasts the spatial distribution better and gives better <span class="hlt">seismicity</span> rate estimates before shut-in. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the <span class="hlt">seismicity</span> rate around, and shortly after, shut-in.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS43A1599A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS43A1599A"><span>Development of Vertical Cable <span class="hlt">Seismic</span> <span class="hlt">System</span> for Hydrothermal Deposit Survey (2) - Feasibility Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Mikada, H.; Takekawa, J.; Shimura, T.</p> <p>2010-12-01</p> <p>In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey <span class="hlt">system</span> development for Hydrothermal deposit. We proposed the Vertical Cable <span class="hlt">Seismic</span> (VCS), the reflection <span class="hlt">seismic</span> survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. . (1) VCS is an effective high-resolution 3D <span class="hlt">seismic</span> survey within limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of <span class="hlt">seismic</span> data quality. (4) Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.) , deep-towed or ocean bottom sources. (5) Autonomous recording <span class="hlt">system</span>. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN. in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. The result gives clearer image than the conventional surface <span class="hlt">seismic</span>. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Uncertainty of the source/receiver poisons in water causes the serious problem of the imaging. We used several transducer/transponder to estimate these positions. The VCS <span class="hlt">seismic</span> records themselves can also provide sensor position using the first break of each trace and we calibrate the positions. We are currently developing the autonomous recording VCS <span class="hlt">system</span> and planning the trial experiment in actual ocean to establish the way of deployment/recovery and the examine the position through the current flow in November, 2010. The second VCS survey will planned over the actual hydrothermal deposit with deep-towed source in February, 2011.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GGG....18.4016L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GGG....18.4016L"><span>GrowYourIC: A Step Toward a Coherent Model of the Earth's Inner Core <span class="hlt">Seismic</span> Structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lasbleis, Marine; Waszek, Lauren; Day, Elizabeth A.</p> <p>2017-11-01</p> <p>A complex inner core structure has been well established from <span class="hlt">seismic</span> studies, showing radial and lateral heterogeneities at various length scales. Yet no geodynamic model is able to explain all the features observed. One of the main limits for this is the lack of tools to compare <span class="hlt">seismic</span> observations and numerical models successfully. We use here a new Python tool called GrowYourIC to compare models of inner core structure. We calculate properties of geodynamic models of the inner core along <span class="hlt">seismic</span> raypaths, for random or user-specified data sets. We test kinematic models which simulate fast lateral translation, superrotation, and differential growth. We explore first the influence on a real inner core data set, which has a sparse coverage of the inner core <span class="hlt">boundary</span>. Such a data set is however able to successfully constrain the hemispherical <span class="hlt">boundaries</span> due to a good sampling of latitudes. Combining translation and rotation could explain some of the features of the <span class="hlt">boundaries</span> separating the inner core hemispheres. The depth shift of the <span class="hlt">boundaries</span>, observed by some authors, seems unlikely to be modeled by a fast translation but could be produced by slow translation associated with superrotation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3376H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3376H"><span>Autonomous telemetry <span class="hlt">system</span> by using mobile networks for a long-term <span class="hlt">seismic</span> observation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirahara, S.; Uchida, N.; Nakajima, J.</p> <p>2012-04-01</p> <p>When a large earthquake occurs, it is important to know the detailed distribution of aftershocks immediately after the main shock for the estimation of the fault plane. The large amount of <span class="hlt">seismic</span> data is also required to determine the three-dimensional <span class="hlt">seismic</span> velocity structure around the focal area. We have developed an autonomous telemetry <span class="hlt">system</span> using mobile networks, which is specialized for aftershock observations. Because the newly developed <span class="hlt">system</span> enables a quick installation and real-time data transmission by using mobile networks, we can construct a dense online <span class="hlt">seismic</span> network even in mountain areas where conventional wired networks are not available. This <span class="hlt">system</span> is equipped with solar panels that charge lead-acid battery, and enables a long-term <span class="hlt">seismic</span> observation without maintenance. Furthermore, this <span class="hlt">system</span> enables a continuous observation at low costs with flat-rate or prepaid Internet access. We have tried to expand coverage areas of mobile communication and back up Internet access by configuring plural mobile carriers. A micro server embedded with Linux consists of automatic control programs of the Internet connection and data transmission. A status monitoring and remote maintenance are available via the Internet. In case of a communication failure, an internal storage can back up data for two years. The power consumption of communication device ranges from 2.5 to 4.0 W. With a 50 Ah lead-acid battery, this <span class="hlt">system</span> continues to record data for four days if the battery charging by solar panels is temporarily unavailable.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..653W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..653W"><span>Comparative statistical and spectral studies of <span class="hlt">seismic</span> and non-<span class="hlt">seismic</span> sub-ionospheric VLF anomalies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolbang, Daniel; Biernat, Helfried; Schwingenschuh, Konrad; Eichelberger, Hans; Prattes, Gustav; Besser, Bruno; Boudjada, Mohammed Y.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Friedrich, Martin</p> <p>2013-04-01</p> <p>We present a comparative study of <span class="hlt">seismic</span> and non-<span class="hlt">seismic</span> sub-ionospheric VLF anomalies. Our method is based on parameter variations of the sub-ionospheric VLF waveguide formed by the surface and the lower ionosphere. The used radio links working in the frequency range between 10 and 50 kHz, the receivers are part of the European and Russian networks. Various authors investigated the lithopsheric-atmospheric-ionospheric coupling and predicted the lowering of the ionosphere over earthquake preparation zones [1]. The received nighttime signal of a sub-ionospheric waveguide depends strongly on the height of the ionospheric E-layer, typically 80 to 85 km. This height is characterized by a typical gradient of the electron density near the atmospheric-ionospheric <span class="hlt">boundary</span> [2]. In the last years it has been turned out that one of the major issues of sub-ionospheric seismo-electromagnetic VLF studies are the non-<span class="hlt">seismic</span> influences on the links, which have to be carefully characterized. Among others this could be traveling ionospheric disturbances, geomagnetic storms as well as electron precipitation. Our emphasis is on the analysis of daily, monthly and annual variations of the VLF amplitude. To improve the statistics we investigate the behavior and typical variations of the VLF amplitude and phase over a period of more than 2 years. One important parameter considered is the rate how often the fluctuations are falling below a significant level derived from a mean value. The temporal variations and the amplitudes of these depressions are studied for several years for sub-ionospheric VLF radio links with the receivers in Graz and Kamchatka. In order to study the difference between <span class="hlt">seismic</span> and non-<span class="hlt">seismic</span> turbulences in the lower ionosphere a power spectrum analysis of the received signal is performed too. We are especially interested in variations T>6 min which are typical for atmospheric gravity waves causing the lithospheric-atmospheric-ionospheric coupling [3]. All</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840065105&hterms=Gravitational+motion+system&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DGravitational%2Bmotion%2Bsystem','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840065105&hterms=Gravitational+motion+system&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DGravitational%2Bmotion%2Bsystem"><span>The <span class="hlt">boundary</span> of the solar <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smoluchowski, R.; Torbett, M.</p> <p>1984-01-01</p> <p>The shape of the <span class="hlt">boundary</span> of the solar <span class="hlt">system</span>, defined as the surface within which the gravitational attraction of the sun rather than that of the rest of the Galaxy controls the orbital motion of planets and comets, has been determined. Outside of this surface, the dominant factors are the radial tides due to the galactic center and the vertical tides caused by the galactic disk. Orbits which are direct with respect to the galactic plane have a <span class="hlt">boundary</span> which differs from that for retrograde orbits, both being 10-20 percent oblate and both larger than the present Oort cloud. The surface may have been the <span class="hlt">boundary</span> of the early cloud of comets which was later reduced by the passages of stars and molecular clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4101210','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4101210"><span>The Effect Analysis of Strain Rate on Power Transmission Tower-Line <span class="hlt">System</span> under <span class="hlt">Seismic</span> Excitation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Wenming</p> <p>2014-01-01</p> <p>The effect analysis of strain rate on power transmission tower-line <span class="hlt">system</span> under <span class="hlt">seismic</span> excitation is studied in this paper. A three-dimensional finite element model of a transmission tower-line <span class="hlt">system</span> is created based on a real project. Using theoretical analysis and numerical simulation, incremental dynamic analysis of the power transmission tower-line <span class="hlt">system</span> is conducted to investigate the effect of strain rate on the nonlinear responses of the transmission tower and line. The results show that the effect of strain rate on the transmission tower generally decreases the maximum top displacements, but it would increase the maximum base shear forces, and thus it is necessary to consider the effect of strain rate on the <span class="hlt">seismic</span> analysis of the transmission tower. The effect of strain rate could be ignored for the <span class="hlt">seismic</span> analysis of the conductors and ground lines, but the responses of the ground lines considering strain rate effect are larger than those of the conductors. The results could provide a reference for the <span class="hlt">seismic</span> design of the transmission tower-line <span class="hlt">system</span>. PMID:25105157</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T13D3037A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T13D3037A"><span>J-SHIS - an integrated <span class="hlt">system</span> for knowing <span class="hlt">seismic</span> hazard information in Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azuma, H.; Fujiwara, H.; Kawai, S.; Hao, K. X.; Morikawa, N.</p> <p>2015-12-01</p> <p>An integrated <span class="hlt">system</span> of Japan <span class="hlt">seismic</span> hazard information station (J-SHIS) was established in 2005 for issuing and exchanging information of the National <span class="hlt">Seismic</span> Hazard Maps for Japan that are based on <span class="hlt">seismic</span> hazard assessment (SHA). A simplified app, also named J-SHIS, for smartphones is popularly used in Japan based on the integrated <span class="hlt">system</span> of http://www.j-shis.bosai.go.jp/map/?lang=en. "Smartphone tells hazard" is realized on a cellphone, a tablet and/or a PC. At a given spot, the comprehensive information of SHA map can be easily obtained as below: 1) A SHA probability at given intensity (JMA=5-, 5+, 6-, 6+) within 30 years. 2) A site amplification factor varies within 0.5 ~ 3.0 and expectation is 1 based on surface geology map information. 3) A depth of <span class="hlt">seismic</span> basement down to ~3,000m based on deeper borehole and geological structure. 4) Scenario earthquake maps: By choosing an active fault, one got the average case for different parameters of the modeling. Then choose a case, you got the shaking map of intensity with color scale. "<span class="hlt">Seismic</span> Hazard Karte tells more hazard" is another app based on website of http://www.j-shis.bosai.go.jp/labs/karte/. (1) For every mesh of 250m x 250m, professional service SHA information is provided over national-world. (2) With five ranks for eight items, comprehensive SHA information could be delivered. (3) Site amplification factor with an average index is given. (4) Deeper geologic structure modeling is provided with borehole profiling. (5) A SHA probability is assessed within 30 and/or 50 years for the given site. (6) <span class="hlt">Seismic</span> Hazard curves are given for earthquake sources from inland active fault, subduction zone, undetermined and their summarization. (7) The JMA <span class="hlt">seismic</span> intensities are assessed in long-term averaged periods of 500-years to ~100,000 years. The app of J-SHIS can be downloaded freely from http://www.j-shis.bosai.go.jp/app-jshis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016621','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016621"><span>Circum-Pacific <span class="hlt">seismic</span> potential: 1989-1999</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Nishenko, S.P.</p> <p>1991-01-01</p> <p>The <span class="hlt">seismic</span> potential for 96 segments of simple plate <span class="hlt">boundaries</span> around the circum-Pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5, 10, and 20 years (i.e., 1989-1994, 1989-1999 and 1989-2009). This study represents the first probabilistic summary of <span class="hlt">seismic</span> potential on this scale, and involves the comparison of plate <span class="hlt">boundary</span> segments that exhibit varying recurrence times, magnitudes, and tectonic regimes. Presenting these data in a probabilistic framework provides a basis for the uniform comparison of <span class="hlt">seismic</span> hazard between these differing fault segments, as well as accounting for individual variations in recurrence time along a specific fault segment, and uncertainties in the determination of the average recurrence time. The definition of specific segments along simple plate <span class="hlt">boundaries</span> relies on the mapping of earthquake rupture zones as defined by the aftershock distributions of prior large and great earthquakes, and historic descriptions of felt intensities and damage areas. The 96 segments are chosen to represent areas likely to be ruptured by "characteristic" earthquakes of a specified size or magnitude. The term characteristic implies repeated breakage of a plate <span class="hlt">boundary</span> segment by large or great earthquakes whose source dimensions are similar from cycle to cycle. This definition does not exclude the possibility that occasionally adjacent characteristic earthquake segments may break together in a single, larger event. Conversely, a segment may also break in a series of smaller ruptures. Estimates of recurrence times and conditional probabilities for characteristic earthquakes along segments of simple plate <span class="hlt">boundaries</span> are based on 1) the historic and instrumental record of large and great earthquake occurrence; 2) paleoseismic evidence of recurrence from radiometric dating of Holocene features produced by earthquakes; 3) direct calculations of recurrence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.V53A3063L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.V53A3063L"><span>VLP <span class="hlt">seismicity</span> from resonant modes of acoustic-gravity waves in a conduit-crack <span class="hlt">system</span> filled with multiphase magma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.</p> <p>2016-12-01</p> <p>Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) <span class="hlt">seismic</span> signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP <span class="hlt">seismicity</span> using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack <span class="hlt">system</span> filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing <span class="hlt">system</span>, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack <span class="hlt">system</span> that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous <span class="hlt">boundary</span> layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.V21E..11S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.V21E..11S"><span>The <span class="hlt">Seismic</span> Velocity In Gas-charged Magma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sturton, S.; Neuberg, J. W.</p> <p>2001-12-01</p> <p>Long-period and hybrid events, seen at the Soufrière Hills Volcano, Montserrat, show dominant low frequency content suggesting the <span class="hlt">seismic</span> wavefield is formed as a result of interface waves at the <span class="hlt">boundary</span> between a fluid and a solid medium. This wavefield will depend on the impedance contrast between the two media and therefore the difference in <span class="hlt">seismic</span> velocity. For a gas-charged magma, increasing pressure with depth reduces the volume of gas exsolved, increasing the <span class="hlt">seismic</span> velocity with depth in the conduit. The <span class="hlt">seismic</span> radiation pattern along the conduit can then be modelled. Where single events merge into tremor, gliding lines can sometimes be seen in the spectra and indicate either changes in the <span class="hlt">seismic</span> parameters with time or varying triggering rates of single events.The differential equation describing the time dependence of bubble growth by diffusion is solved numerically for a stationary magma column undergoing a decompression event. The volume of gas is depth dependent and increases with time as the bubbles grow and expand. It is used to calculate the depth and time dependence of the density, pressure and <span class="hlt">seismic</span> velocity. The effect of different viscosities associated with different magma types and concentration of water in the melt on the rate of bubble growth is explored. Crystal growth, which increases the concentration of water in the melt, affects the amount of gas that can be exsolved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714315K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714315K"><span>The LUSI <span class="hlt">Seismic</span> Experiment: Deployment of a <span class="hlt">Seismic</span> Network around LUSI, East Java, Indonesia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karyono, Karyono; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Haryanto, Iyan; Masturyono, Masturyono; Hadi, Soffian; Rohadi, Suprianto; Suardi, Iman; Rudiyanto, Ariska; Pranata, Bayu</p> <p>2015-04-01</p> <p>The spectacular Lusi eruption started in northeast Java, Indonesia the 29 of May 2006 following a M6.3 earthquake striking the island. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault <span class="hlt">system</span> and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. Lusi is located few kilometres to the NE of the Arjuno-Welirang volcanic complex. Lusi sits upon the Watukosek fault <span class="hlt">system</span>. From this volcanic complex originates the Watukosek fault <span class="hlt">system</span> that was reactivated by the M6.3 earthquake in 2006 and is still periodically reactivated by the frequent <span class="hlt">seismicity</span>. To date Lusi is still active and erupting gas, water, mud and clasts. Gas and water data show that the Lusi plumbing <span class="hlt">system</span> is connected with the neighbouring Arjuno-Welirang volcanic complex. This makes the Lusi eruption a "sedimentary hosted geothermal <span class="hlt">system</span>". To verify and characterise the occurrence of <span class="hlt">seismic</span> activity and how this perturbs the connected Watukosek fault, the Arjuno-Welirang volcanic <span class="hlt">system</span> and the ongoing Lusi eruption, we deployed 30 <span class="hlt">seismic</span> stations (short-period and broadband) in this region of the East Java basin. The <span class="hlt">seismic</span> stations are more densely distributed around LUSI and the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. Fewer stations are positioned around the volcanic arc. Our study sheds light on the <span class="hlt">seismic</span> activity along the Watukosek fault <span class="hlt">system</span> and describes the waveforms associated to the geysering activity of Lusi. The initial network aims to locate small event that may not be captured by the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) <span class="hlt">seismic</span> network and it will be crucial to design the second phase of the <span class="hlt">seismic</span> experiment that will consist of a local earthquake tomography of the Lusi-Arjuno Welirang region and temporal variations of vp/vs ratios. Such variations will then be ideally related to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S41B0744L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S41B0744L"><span>Microzonation of <span class="hlt">Seismic</span> Hazard Potential in Taipei, Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, K. S.; Lin, Y. P.</p> <p>2017-12-01</p> <p>The island of Taiwan lies at the <span class="hlt">boundary</span> between the Philippine Sea plate and the Eurasia plate. Accordingly, the majority of <span class="hlt">seismic</span> energy release near Taiwan originates from the two subduction zones. It is therefore not surprising that Taiwan has repeatedly been struck by large earthquakes such as 1986 Hualien earthquake, 1999 Chi Chi and 2002 Hualien earthquake. Microzonation of <span class="hlt">seismic</span> hazard potential becomes necessary in Taipei City for the Central Geological Survey announced the Sanchiao active fault as Category II. In this study, a catalog of more than 2000 shallow earthquakes occurred from 1900 to 2015 with Mw magnitudes ranging from 5.0 to 8.2, and 11 disastrous earthquakes occurred from 1683-1899, as well as Sanchiao active fault in the vicinity are used to estimate the <span class="hlt">seismic</span> hazard potential in Taipei City for <span class="hlt">seismic</span> microzonation. Furthermore, the probabilities of <span class="hlt">seismic</span> intensity exceeding CWB intensity 5, 6, 7 and MMI VI, VII, VIII in 10, 30, and 50-year periods in the above areas are also analyzed for the <span class="hlt">seismic</span> microzonation. Finally, by comparing with the <span class="hlt">seismic</span> zoning map of Taiwan in current building code that was revised after 921 earthquakes, Results of this study will show which areas with higher earthquake hazard potential in Taipei City. They provide a valuable database for the <span class="hlt">seismic</span> design of critical facilities. It will help mitigate Taipei City earthquake disaster loss in the future, as well as provide critical information for emergency response plans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JSeis..18..731B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JSeis..18..731B"><span>Detailed <span class="hlt">seismicity</span> analysis revealing the dynamics of the southern Dead Sea area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braeuer, B.; Asch, G.; Hofstetter, R.; Haberland, Ch.; Jaser, D.; El-Kelani, R.; Weber, M.</p> <p>2014-10-01</p> <p>Within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. During 18 recording months, 648 events were detected. Based on an already published tomography study clustering, focal mechanisms, statistics and the distribution of the microseismicity in relation to the velocity models from the tomography are analysed. The determined b value of 0.74 leads to a relatively high risk of large earthquakes compared to the moderate microseismic activity. The distribution of the <span class="hlt">seismicity</span> indicates an asymmetric basin with a vertical strike-slip fault forming the eastern <span class="hlt">boundary</span> of the basin, and an inclined western <span class="hlt">boundary</span>, made up of strike-slip and normal faults. Furthermore, significant differences between the area north and south of the Bokek fault were observed. South of the Bokek fault, the western <span class="hlt">boundary</span> is inactive while the entire <span class="hlt">seismicity</span> occurs on the eastern <span class="hlt">boundary</span> and below the basin-fill sediments. The largest events occurred here, and their focal mechanisms represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. The vertical extension of the spatial and temporal cluster from February 2007 is interpreted as being related to the locking of the region around the Bokek fault. North of the Bokek fault similar <span class="hlt">seismic</span> activity occurs on both <span class="hlt">boundaries</span> most notably within the basin-fill sediments, displaying mainly small events with strike-slip mechanism and normal faulting in EW direction. Therefore, we suggest that the Bokek fault forms the border between the single transform fault and the pull-apart basin with two active border faults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.7525J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.7525J"><span>A <span class="hlt">seismic</span> network to investigate the sedimentary hosted hydrothermal Lusi <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Javad Fallahi, Mohammad; Mazzini, Adriano; Lupi, Matteo; Obermann, Anne; Karyono, Karyono</p> <p>2016-04-01</p> <p>The 29th of May 2006 marked the beginning of the sedimentary hosted hydrothermal Lusi <span class="hlt">system</span>. During the last 10 years we witnessed numerous alterations of the Lusi <span class="hlt">system</span> behavior that coincide with the frequent <span class="hlt">seismic</span> and volcanic activity occurring in the region. In order to monitor the effect that the <span class="hlt">seismicity</span> and the activity of the volcanic arc have on Lusi, we deployed a ad hoc <span class="hlt">seismic</span> network. This temporary network consist of 10 broadband and 21 short period stations and is currently operating around the Arjuno-Welirang volcanic complex, along the Watukosek fault <span class="hlt">system</span> and around Lusi, in the East Java basin since January 2015. We exploit this dataset to investigate surface wave and shear wave velocity structure of the upper-crust beneath the Arjuno-Welirang-Lusi complex in the framework of the Lusi Lab project (ERC grant n° 308126). Rayleigh and Love waves travelling between each station-pair are extracted by cross-correlating long time series of ambient noise data recorded at the stations. Group and phase velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions, and are tomographically inverted to provide 2D velocity maps corresponding to different sampling depths. 3D shear wave velocity structure is then acquired by inverting the group velocity maps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/5900198','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/5900198"><span>A multilevel preconditioner for domain decomposition <span class="hlt">boundary</span> <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bramble, J.H.; Pasciak, J.E.; Xu, Jinchao.</p> <p>1991-12-11</p> <p>In this note, we consider multilevel preconditioning of the reduced <span class="hlt">boundary</span> <span class="hlt">systems</span> which arise in non-overlapping domain decomposition methods. It will be shown that the resulting preconditioned <span class="hlt">systems</span> have condition numbers which be bounded in the case of multilevel spaces on the whole domain and grow at most proportional to the number of levels in the case of multilevel <span class="hlt">boundary</span> spaces without multilevel extensions into the interior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17799298','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17799298"><span><span class="hlt">Seismic</span> data from man-made impacts on the moon.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Latham, G; Ewing, M; Dorman, J; Press, F; Toksoz, N; Sutton, G; Meissner, R; Duennebier, F; Nakamura, Y; Kovach, R; Yates, M</p> <p>1970-11-06</p> <p>Unusually long reverberations were recorded from two lunar impacts by a <span class="hlt">seismic</span> station installed on the lunar surface by the Apollo 12 astronauts. <span class="hlt">Seismic</span> data from these impacts suggest that the lunar mare in the region of the Apollo 12 landing site consists of material with very low <span class="hlt">seismic</span> velocities near the surface, with velocity increasing with depth to 5 to 6 kilometers per second (for compressional waves) at a depth of 20 kilometers. Absorption of <span class="hlt">seismic</span> waves in this structure is extremely low relative to typical continental crustal materials on earth. It is unlikely that a major <span class="hlt">boundary</span> similar to the crustmantle interface on earth exists in the outer 20 kilometers of the moon. A combination of dispersion and scattering of surface waves probably explains the lunar <span class="hlt">seismic</span> reverberation. Scattering of these waves implies the presence of heterogeneity within the outer zone of the mare on a scale of from several hundred meters (or less) to several kilometers. <span class="hlt">Seismic</span> signals from 160 events of natural origin have been recorded during the first 7 months of operation of the Apollo 12 <span class="hlt">seismic</span> station. At least 26 of the natural events are small moonquakes. Many of the natural events are thought to be meteoroid impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70158981','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70158981"><span>Passive <span class="hlt">seismic</span> monitoring of natural and induced earthquakes: case studies, future directions and socio-economic relevance</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bohnhoff, Marco; Dresen, Georg; Ellsworth, William L.; Ito, Hisao; Cloetingh, Sierd; Negendank, Jörg</p> <p>2010-01-01</p> <p>An important discovery in crustal mechanics has been that the Earth’s crust is commonly stressed close to failure, even in tectonically quiet areas. As a result, small natural or man-made perturbations to the local stress field may trigger earthquakes. To understand these processes, Passive <span class="hlt">Seismic</span> Monitoring (PSM) with seismometer arrays is a widely used technique that has been successfully applied to study <span class="hlt">seismicity</span> at different magnitude levels ranging from acoustic emissions generated in the laboratory under controlled conditions, to <span class="hlt">seismicity</span> induced by hydraulic stimulations in geological reservoirs, and up to great earthquakes occurring along plate <span class="hlt">boundaries</span>. In all these environments the appropriate deployment of <span class="hlt">seismic</span> sensors, i.e., directly on the rock sample, at the earth’s surface or in boreholes close to the <span class="hlt">seismic</span> sources allows for the detection and location of brittle failure processes at sufficiently low magnitude-detection threshold and with adequate spatial resolution for further analysis. One principal aim is to develop an improved understanding of the physical processes occurring at the <span class="hlt">seismic</span> source and their relationship to the host geologic environment. In this paper we review selected case studies and future directions of PSM efforts across a wide range of scales and environments. These include induced failure within small rock samples, hydrocarbon reservoirs, and natural <span class="hlt">seismicity</span> at convergent and transform plate <span class="hlt">boundaries</span>. Each example represents a milestone with regard to bridging the gap between laboratory-scale experiments under controlled <span class="hlt">boundary</span> conditions and large-scale field studies. The common motivation for all studies is to refine the understanding of how earthquakes nucleate, how they proceed and how they interact in space and time. This is of special relevance at the larger end of the magnitude scale, i.e., for large devastating earthquakes due to their severe socio-economic impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16810252','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16810252"><span>Subcontinental-scale crustal velocity changes along the Pacific-North America plate <span class="hlt">boundary</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Davis, J L; Wernicke, B P; Bisnath, S; Niemi, N A; Elósegui, P</p> <p>2006-06-29</p> <p>Transient tectonic deformation has long been noted within approximately 100 km of plate <span class="hlt">boundary</span> fault zones and within active volcanic regions, but it is unknown whether transient motions also occur at larger scales within plates. Relatively localized transients are known to occur as both <span class="hlt">seismic</span> and episodic aseismic events, and are generally ascribed to motions of magma bodies, aseismic creep on faults, or elastic or viscoelastic effects associated with earthquakes. However, triggering phenomena and systematic patterns of <span class="hlt">seismic</span> strain release at subcontinental (approximately 1,000 km) scale along diffuse plate <span class="hlt">boundaries</span> have long suggested that energy transfer occurs at larger scale. Such transfer appears to occur by the interaction of stresses induced by surface wave propagation and magma or groundwater in the crust, or from large-scale stress diffusion within the oceanic mantle in the decades following clusters of great earthquakes. Here we report geodetic evidence for a coherent, subcontinental-scale change in tectonic velocity along a diffuse approximately 1,000-km-wide deformation zone. Our observations are derived from continuous GPS (Global Positioning <span class="hlt">System</span>) data collected over the past decade across the Basin and Range province, which absorbs approximately 25 per cent of Pacific-North America relative plate motion. The observed changes in site velocity define a sharp <span class="hlt">boundary</span> near the centre of the province oriented roughly parallel to the north-northwest relative plate motion vector. We show that sites to the west of this <span class="hlt">boundary</span> slowed relative to sites east of it by approximately 1 mm yr(-1) starting in late 1999.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T13C2620S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T13C2620S"><span><span class="hlt">Seismic</span> activity of Tokyo area and Philippine Sea plate under Japanese Islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakai, S.; Nakagawa, S.; Nanjo, K.; Kasahara, K.; Panayotopoulos, Y.; Tsuruoka, H.; Kurashimo, E.; Obara, K.; Hirata, N.; Kimura, H.; Honda, R.</p> <p>2012-12-01</p> <p>The Japanese government has estimated the probability of earthquake occurrence with magnitude 7-class during the next 30 years as 70 %. This estimation is based on five earthquakes that occurred in this area in the late 120 years. However, it has been revealed that this region is lying on more complicated tectonic condition due to the two subducted plates and the various types of earthquakes which have been caused by. Therefore, it is necessary to classify these earthquakes into inter-plate earthquakes and intra-plate ones. Then, we have been constructing a <span class="hlt">seismic</span> observation network since 5 years ago. Tokyo Metropolitan area is a densely populated region of about 40 million people. It is the center of Japan both in politics and in economy. So that human activities have been conducting quite busily, this region is unsuitable for <span class="hlt">seismic</span> observation. Then, we have decided to make an ultra high dense <span class="hlt">seismic</span> observation network. We named it the Metropolitan Seismometer Observation Network; MeSO-net. MeSO-net consists of 296 <span class="hlt">seismic</span> stations. Minimum interval is about 2km and average interval is about 5km.We picked the P- and S-wave arrival times manually. We applied double-difference tomography method to the dataset and estimated the velocity structure. We depicted the plate <span class="hlt">boundaries</span> from the newly developed velocity model. And, we referred to the locations of the repeating earthquakes, the distributions of normal hypocenters and the focal mechanisms. Our plate model became relatively flat and a little shallower than previous one.<span class="hlt">Seismicity</span> of Metropolitan area after the M9 event was compared to the one before M9 event. The <span class="hlt">seismic</span> activity is about 4 times as high as before the M9 event occurred. We examined spatial distribution of the activated <span class="hlt">seismicity</span> with respect to the newly developed plate configuration. The activated events are located on upper <span class="hlt">boundaries</span> and they have almost thrust type mechanisms. Recently, a slow slip event has occurred on October in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoJI.209..876J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoJI.209..876J"><span>Hydrostratigraphy characterization of the Floridan aquifer <span class="hlt">system</span> using ambient <span class="hlt">seismic</span> noise</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>James, Stephanie R.; Screaton, Elizabeth J.; Russo, Raymond M.; Panning, Mark P.; Bremner, Paul M.; Stanciu, A. Christian; Torpey, Megan E.; Hongsresawat, Sutatcha; Farrell, Matthew E.</p> <p>2017-05-01</p> <p>We investigated a new technique for aquifer characterization that uses cross-correlation of ambient <span class="hlt">seismic</span> noise to determine <span class="hlt">seismic</span> velocity structure of the Floridan aquifer <span class="hlt">system</span> (FAS). Accurate characterization of aquifer <span class="hlt">systems</span> is vital to hydrogeological research and groundwater management but is difficult due to limited subsurface data and heterogeneity. Previous research on the carbonate FAS found that confining units and high permeability flow zones have distinct <span class="hlt">seismic</span> velocities. We deployed an array of 9 short period seismometers from 11/2013 to 3/2014 in Indian Lake State Forest near Ocala, Florida, to image the hydrostratigraphy of the aquifer <span class="hlt">system</span> using ambient <span class="hlt">seismic</span> noise. We find that interstation distance strongly influences the upper and lower frequency limits of the data set. <span class="hlt">Seismic</span> waves propagating within 1.5 and 7 wavelengths between stations were optimal for reliable group velocity measurements and both an upper and lower wavelength threshold was used. A minimum of 100-250 hr of signal was needed to maximize signal-to-noise ratio and to allow cross-correlation convergence. We averaged measurements of group velocity between station pairs at each frequency band to create a network average dispersion curve. A family of 1-D shear-wave velocity profiles that best represents the network average dispersion was then generated using a Markov Chain Monte Carlo (MCMC) algorithm. The MCMC algorithm was implemented with either a fixed number of layers, or as transdimensional in which the number of layers was a free parameter. Results from both algorithms require a prominent velocity increase at ∼200 m depth. A shallower velocity increase at ∼60 m depth was also observed, but only in model ensembles created by collecting models with the lowest overall misfit to the observed data. A final round of modelling with additional prior constraints based on initial results and well logs produced a mean shear-wave velocity profile taken as the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JSeis.tmp...17K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JSeis.tmp...17K"><span>Updated earthquake catalogue for <span class="hlt">seismic</span> hazard analysis in Pakistan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, Sarfraz; Waseem, Muhammad; Khan, Muhammad Asif; Ahmed, Waqas</p> <p>2018-03-01</p> <p>A reliable and homogenized earthquake catalogue is essential for <span class="hlt">seismic</span> hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40-83° N and 20-40° E) includes 36,563 earthquake events, which are reported as 4.0-8.3 moment magnitude (M W) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude M W. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical <span class="hlt">boundaries</span> in <span class="hlt">seismic</span> hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, <span class="hlt">seismicity</span> parameters of the <span class="hlt">seismic</span> sources are reported, and recommendations are made for <span class="hlt">seismic</span> hazard assessment studies in Pakistan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S51D..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S51D..05M"><span>Effects of Strike-Slip Fault Segmentation on Earthquake Energy and <span class="hlt">Seismic</span> Hazard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Madden, E. H.; Cooke, M. L.; Savage, H. M.; McBeck, J.</p> <p>2014-12-01</p> <p>Many major strike-slip faults are segmented along strike, including those along plate <span class="hlt">boundaries</span> in California and Turkey. Failure of distinct fault segments at depth may be the source of multiple pulses of <span class="hlt">seismic</span> radiation observed for single earthquakes. However, how and when segmentation affects fault behavior and energy release is the basis of many outstanding questions related to the physics of faulting and <span class="hlt">seismic</span> hazard. These include the probability for a single earthquake to rupture multiple fault segments and the effects of segmentation on earthquake magnitude, radiated <span class="hlt">seismic</span> energy, and ground motions. Using numerical models, we quantify components of the earthquake energy budget, including the tectonic work acting externally on the <span class="hlt">system</span>, the energy of internal rock strain, the energy required to overcome fault strength and initiate slip, the energy required to overcome frictional resistance during slip, and the radiated <span class="hlt">seismic</span> energy. We compare the energy budgets of <span class="hlt">systems</span> of two en echelon fault segments with various spacing that include both releasing and restraining steps. First, we allow the fault segments to fail simultaneously and capture the effects of segmentation geometry on the earthquake energy budget and on the efficiency with which applied displacement is accommodated. Assuming that higher efficiency correlates with higher probability for a single, larger earthquake, this approach has utility for assessing the <span class="hlt">seismic</span> hazard of segmented faults. Second, we nucleate slip along a weak portion of one fault segment and let the quasi-static rupture propagate across the <span class="hlt">system</span>. Allowing fractures to form near faults in these models shows that damage develops within releasing steps and promotes slip along the second fault, while damage develops outside of restraining steps and can prohibit slip along the second fault. Work is consumed in both the propagation of and frictional slip along these new fractures, impacting the energy available</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T43D1667B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T43D1667B"><span>Preliminary Results from the North Anatolian Fault Passive <span class="hlt">Seismic</span> Experiment: <span class="hlt">Seismicity</span> and Anisotropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Biryol, C. B.; Ozacar, A.; Beck, S. L.; Zandt, G.</p> <p>2006-12-01</p> <p>The North Anatolian Fault (NAF) is one of the world's largest continental strike-slip faults. Despite much geological work at the surface, the deep structure of the NAF is relatively unknown. The North Anatolian Fault Passive <span class="hlt">Seismic</span> Experiment is mainly focused on the lithospheric structure of this newly coalescing continental transform plate <span class="hlt">boundary</span>. In the summer of 2005, we deployed 5 broadband <span class="hlt">seismic</span> stations near the fault to gain more insight on the background <span class="hlt">seismicity</span>, and in June 2006 we deployed 34 additional broadband stations along multiple transects crossing the main strand of the NAF and its splays. In the region, local <span class="hlt">seismicity</span> is not limited to a narrow band near the NAF but distributed widely suggesting widespread continental deformation especially in the southern block. We relocated two of the largest events (M>4) that occurred close to our stations. Both events are 40-50km south of the NAF in the upper crust (6-9 km) along a normal fault with a strike-slip component that previously ruptured during the June 6, 2000 Orta-Cankiri earthquake (M=6.0). Preliminary analysis of SKS splitting for 4 stations deployed in 2005 indicates <span class="hlt">seismic</span> anisotropy with delay times exceeding 1 sec. The fast polarization directions for these stations are primarily in NE-SW orientation, which remains uniform across the NAF. This direction is at a high angle to the surface trace of the fault and crustal velocity field, suggesting decoupling of lithosphere and mantle flow. Our SKS splitting observations are also similar to that observed from GSN station ANTO in central Turkey and stations across the Anatolian Plateau in eastern Turkey indicating relatively uniform mantle anisotropy throughout the region.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70018494','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70018494"><span>Misinterpretation of lateral acoustic variations on high-resolution <span class="hlt">seismic</span> reflection profiles as fault offsets of Holocene bay mud beneath the southern part of San Francisco Bay, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Marlow, M. S.; Hart, P.E.; Carlson, P.R.; Childs, J. R.; Mann, D. M.; Anima, R.J.; Kayen, R.E.</p> <p>1996-01-01</p> <p>We collected high-resolution <span class="hlt">seismic</span> reflection profiles in the southern part of San Francisco Bay in 1992 and 1993 to investigate possible Holocene faulting along postulated transbay bedrock fault zones. The initial analog records show apparent offsets of reflection packages along sharp vertical <span class="hlt">boundaries</span>. These records were originally interpreted as showing a complex series of faults along closely spaced, sharp vertical <span class="hlt">boundaries</span> in the upper 10 m (0.013 s two-way travel time) of Holocene bay mud. A subsequent survey in 1994 was run with a different <span class="hlt">seismic</span> reflection <span class="hlt">system</span>, which utilized a higher power source. This second <span class="hlt">system</span> generated records with deeper penetration (max. 20 m, 0.026 s two-way travel time) and demonstrated that the reflections originally interpreted as fault offsets by faulting were actually laterally continuous reflection horizons. The pitfall in the original interpretations was caused by lateral variations in the amplitude brightness of reflection events, coupled with a long (greater than 15 ms) source signature of the low-power <span class="hlt">system</span>. These effects combined to show apparent offsets of reflection packages along sharp vertical <span class="hlt">boundaries</span>. These <span class="hlt">boundaries</span>, as shown by the second <span class="hlt">system</span>, in fact occur where the reflection amplitude diminishes abruptly on laterally continuous reflection events. This striking lateral variation in reflection amplitude is attributable to the localized presence of biogenic(?) gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S41A2406A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S41A2406A"><span>Real-time estimation <span class="hlt">system</span> for <span class="hlt">seismic</span>-intensity exposed-population</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aoi, S.; Nakamura, H.; Kunugi, T.; Suzuki, W.; Fujiwara, H.</p> <p>2013-12-01</p> <p>For an appropriate first-action to an earthquake, risk (damage) information evaluated in real-time are important as well as hazard (ground motion) information. To meet this need, we are developing real-time estimation <span class="hlt">system</span> (J-RISQ) for exposed population and earthquake damage on buildings. We plan to open the web page of estimated exposed population to the public from autumn. When an earthquake occurs, <span class="hlt">seismic</span> intensities are calculated at each observation station and sent to the DMC (Data Management Center) in different timing. For rapid estimation, the <span class="hlt">system</span> does not wait for the data from all the stations but begins the first estimation when the number of the stations observing the <span class="hlt">seismic</span> intensity of 2.5 or larger exceeds the threshold amount. Estimations are updated several times using all the available data at that moment. Spatial distribution of <span class="hlt">seismic</span> intensity in 250 m meshes is estimated by the site amplification factor of surface layers and the observed data. By using this intensity distribution, the exposed population is estimated using population data of each mesh. The exposed populations for municipalities and prefectures are estimated by summing-up the exposures of included meshes for the area and are appropriately rounded taking estimation precision into consideration. The estimated intensities for major cities are shown by the histograms, which indicate the variation of the estimated values in the city together with the observed maximum intensity. The variation is mainly caused by the difference of the site amplification factors. The intensities estimated for meshes with large amplification factor are sometimes larger than the maximum value observed in the city. The estimated results are seen on the web site just after the earthquake. The results of the past earthquakes can be easily searched by keywords such as date, magnitudes, <span class="hlt">seismic</span> intensities and source areas. The summary of the results in the one-page report of Portable Document Format</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..240G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..240G"><span>Numerical model for the evaluation of Earthquake effects on a magmatic <span class="hlt">system</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garg, Deepak; Longo, Antonella; Papale, Paolo</p> <p>2016-04-01</p> <p>A finite element numerical model is presented to compute the effect of an Earthquake on the dynamics of magma in reservoirs with deformable walls. The magmatic <span class="hlt">system</span> is hit by a Mw 7.2 Earthquake (Petrolia/Capo Mendocina 1992) with hypocenter at 15 km diagonal distance. At subsequent times the <span class="hlt">seismic</span> wave reaches the nearest side of the magmatic <span class="hlt">system</span> <span class="hlt">boundary</span>, travels through the magmatic fluid and arrives to the other side of the <span class="hlt">boundary</span>. The modelled physical <span class="hlt">system</span> consists in the magmatic reservoir with a thin surrounding layer of rocks. Magma is considered as an homogeneous multicomponent multiphase Newtonian mixture with exsolution and dissolution of volatiles (H2O+CO2). The magmatic reservoir is made of a small shallow magma chamber filled with degassed phonolite, connected by a vertical dike to a larger deeper chamber filled with gas-rich shoshonite, in condition of gravitational instability. The coupling between the Earthquake and the magmatic <span class="hlt">system</span> is computed by solving the elastostatic equation for the deformation of the magmatic reservoir walls, along with the conservation equations of mass of components and momentum of the magmatic mixture. The characteristic elastic parameters of rocks are assigned to the computational domain at the <span class="hlt">boundary</span> of magmatic <span class="hlt">system</span>. Physically consistent Dirichlet and Neumann <span class="hlt">boundary</span> conditions are assigned according to the evolution of the <span class="hlt">seismic</span> signal. <span class="hlt">Seismic</span> forced displacements and velocities are set on the part of the <span class="hlt">boundary</span> which is hit by wave. On the other part of <span class="hlt">boundary</span> motion is governed by the action of fluid pressure and deviatoric stress forces due to fluid dynamics. The constitutive equations for the magma are solved in a monolithic way by space-time discontinuous-in-time finite element method. To attain additional stability least square and discontinuity capturing operators are included in the formulation. A partitioned algorithm is used to couple the magma and thin layer of rocks. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.U13B..01K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.U13B..01K"><span><span class="hlt">Seismic</span> belt in the upper plane of the double <span class="hlt">seismic</span> zone extending in the along-arc direction at depths of 70-100km beneath NE Japan, and its relation with the dehydration embrittlement hypothesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kita, S.; Okada, T.; Nakajima, J.; Matsuzawa, T.; Hasegawa, A.</p> <p>2006-12-01</p> <p>1. Introduction Dehydration embrittlement or CO2¨Cbearing devolatization embrittlement hypothesis has been proposed as a possible cause of intraslab earthquakes in several studies [e.g., Peacock, 2001; Kirby et al., 1996; Meade and Jeanloz, 1991]. Precise location of intraslab <span class="hlt">seismicity</span> is needed to discuss its cause in these studies. Recently, a very dense nationwide <span class="hlt">seismic</span> network (Hi-net) has been constructed by NIED in Japan. In this study, we relocate microearthquakes more precisely by using data obtained by this dense <span class="hlt">seismic</span> network to detect the characteristic distribution of the <span class="hlt">seismicity</span> within the Pacific slab beneath Hokkaido and Tohoku, NE Japan. 2. Data and method In the present study, we relocated events at depths of 20¨C300 km for the period from January 2002 to August 2005 from the JMA earthquake catalog. Hypocenter locations and arrival time data in the JMA catalog were used as the initial hypocenters and data for relocations. We applied the double-difference hypocenter location method (DDLM) by Waldhauser and Ellsworth (2000) to the arrival time data of the events. We also checked spatial distribution of the focal mechanisms of the events in the <span class="hlt">seismic</span> belts and the surrounding upper <span class="hlt">seismic</span> plane. We used focal mechanism solutions determined by Igarashi et al. (2001). 3. Results and discussion 1) There exist earthquakes occurring in the area between the upper and lower <span class="hlt">seismic</span> planes (interplane earthquakes), and their focal mechanisms tend to be the down-dip compressional (DC-) type like those of upper plane events. 2) We found a <span class="hlt">seismic</span> "belt" which is parallel to the iso-depth contour of the plate interface beneath the forearc area at depths of 80¨C100 km. The location of the <span class="hlt">seismic</span> belt seems to correspond to one phase <span class="hlt">boundary</span> (from jadeite lawsonite blueschist (H2O content: 5.4 wt% ) to lawsonite amphibole eclogite (3.0wt %) (Hacker et al., 2003)) with dehydration reaction. 3) The location of the deeper limit of <span class="hlt">seismicity</span> of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSM.S52A..02P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSM.S52A..02P"><span><span class="hlt">Seismic</span> sequences in the Sombrero <span class="hlt">Seismic</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.</p> <p>2007-05-01</p> <p>The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, <span class="hlt">seismicity</span> has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero <span class="hlt">Seismic</span> Zone by the Puerto Rico <span class="hlt">Seismic</span> Network (PRSN). In the combined <span class="hlt">seismicity</span> catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of <span class="hlt">seismicity</span> in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of <span class="hlt">seismic</span> hazard, and the tsunamigenic potential of <span class="hlt">seismic</span> events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse <span class="hlt">system</span> of faults? A careful analysis of <span class="hlt">seismicity</span> patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify <span class="hlt">seismic</span> sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault <span class="hlt">systems</span> as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same <span class="hlt">system</span> within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JSeis.tmp....7M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JSeis.tmp....7M"><span>Multi scenario <span class="hlt">seismic</span> hazard assessment for Egypt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mostafa, Shaimaa Ismail; Abd el-aal, Abd el-aziz Khairy; El-Eraki, Mohamed Ahmed</p> <p>2018-01-01</p> <p>Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic <span class="hlt">boundaries</span> of African, Eurasian, and Arabian plates. The study area is characterized by northward increasing sediment thickness leading to more damage to structures in the north due to multiple reflections of <span class="hlt">seismic</span> waves. Unfortunately, man-made constructions in Egypt were not designed to resist earthquake ground motions. So, it is important to evaluate the <span class="hlt">seismic</span> hazard to reduce social and economic losses and preserve lives. The probabilistic <span class="hlt">seismic</span> hazard assessment is used to evaluate the hazard using alternative seismotectonic models within a logic tree framework. Alternate seismotectonic models, magnitude-frequency relations, and various indigenous attenuation relationships were amended within a logic tree formulation to compute and develop the regional exposure on a set of hazard maps. Hazard contour maps are constructed for peak ground acceleration as well as 0.1-, 0.2-, 0.5-, 1-, and 2-s spectral periods for 100 and 475 years return periods for ground motion on rock. The results illustrate that Egypt is characterized by very low to high <span class="hlt">seismic</span> activity grading from the west to the eastern part of the country. The uniform hazard spectra are estimated at some important cities distributed allover Egypt. The deaggregation of <span class="hlt">seismic</span> hazard is estimated at some cities to identify the scenario events that contribute to a selected <span class="hlt">seismic</span> hazard level. The results of this study can be used in <span class="hlt">seismic</span> microzonation, risk mitigation, and earthquake engineering purposes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JSeis..22..669M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JSeis..22..669M"><span>Multi scenario <span class="hlt">seismic</span> hazard assessment for Egypt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mostafa, Shaimaa Ismail; Abd el-aal, Abd el-aziz Khairy; El-Eraki, Mohamed Ahmed</p> <p>2018-05-01</p> <p>Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic <span class="hlt">boundaries</span> of African, Eurasian, and Arabian plates. The study area is characterized by northward increasing sediment thickness leading to more damage to structures in the north due to multiple reflections of <span class="hlt">seismic</span> waves. Unfortunately, man-made constructions in Egypt were not designed to resist earthquake ground motions. So, it is important to evaluate the <span class="hlt">seismic</span> hazard to reduce social and economic losses and preserve lives. The probabilistic <span class="hlt">seismic</span> hazard assessment is used to evaluate the hazard using alternative seismotectonic models within a logic tree framework. Alternate seismotectonic models, magnitude-frequency relations, and various indigenous attenuation relationships were amended within a logic tree formulation to compute and develop the regional exposure on a set of hazard maps. Hazard contour maps are constructed for peak ground acceleration as well as 0.1-, 0.2-, 0.5-, 1-, and 2-s spectral periods for 100 and 475 years return periods for ground motion on rock. The results illustrate that Egypt is characterized by very low to high <span class="hlt">seismic</span> activity grading from the west to the eastern part of the country. The uniform hazard spectra are estimated at some important cities distributed allover Egypt. The deaggregation of <span class="hlt">seismic</span> hazard is estimated at some cities to identify the scenario events that contribute to a selected <span class="hlt">seismic</span> hazard level. The results of this study can be used in <span class="hlt">seismic</span> microzonation, risk mitigation, and earthquake engineering purposes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T13C1474M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T13C1474M"><span>BOLIVAR: the Caribbean-South America plate <span class="hlt">boundary</span> between 60W and 71W as imaged by <span class="hlt">seismic</span> reflection data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Magnani, M.; Mann, P.; Clark, S. A.; Escalona, A.; Zelt, C. A.; Christeson, G. L.; Levander, A.</p> <p>2007-12-01</p> <p>We present the results of ~6000km of marine multi-channel <span class="hlt">seismic</span> (MCS) reflection data collected offshore Venezuela as part of the Broadband Ocean Land Investigation of Venezuela and the Antilles arc Region project (BOLIVAR). The imaged area spans almost 12 degrees of longitude and 5 degrees of latitude and encompasses the diffuse plate <span class="hlt">boundary</span> between South America (SA) and the SE Caribbean plate (CAR). This plate <span class="hlt">boundary</span> has been evolving for at least the past 55My when the volcanic island arc that borders the CAR plate started colliding obliquely with the SA continent: the collision front has migrated from west to east. BOLIVAR MCS data show that the crustal architecture of the present plate <span class="hlt">boundary</span> is dominated by the eastward motion of the Caribbean plate with respect to SA and is characterized by a complex combination of convergent and strike-slip tectonics. To the north, the reflection data image the South Caribbean Deformed Belt (SCDB) and the structures related to the thrusting of the CAR plate under the Leeward Antilles volcanic arc region. The data show that the CAR underthrusting continues as far east as the southern edge of the Aves ridge and detailed stratigraphic dating of the Venezuela basin and trench deposits suggests that the collision began in the Paleogene. The amount of shortening along the SCDB decreases toward the east, in part due to the geometry of plate motion vectors and in part as a result of the NNE escape of the Maracaibo block in western Venezuela. South of the SCDB the MCS profiles cross the Leeward Antilles island arc and Cenozoic sedimentary basins, revealing a complex history of Paleogene-Neogene multiphase extension, compression, and tectonic inversion, as well as the influence of the tectonic activity along the right-lateral El Pilar - San Sebastian fault <span class="hlt">system</span>. East of the Bonaire basin the MCS data image the southern end of the Aves Ridge abandoned volcanic island arc and the southwestern termination of the Grenada basin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5560K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5560K"><span><span class="hlt">Seismic</span> anisotropy and the state of stress in volcanic <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kendall, Michael</p> <p>2017-04-01</p> <p>The active magmatic and hydrothermal <span class="hlt">systems</span> of volcanoes can lead to complicated stress patterns that can vary over short spatial and temporal scales. An attractive approach to studying the state of stress in such <span class="hlt">systems</span> is to investigate <span class="hlt">seismic</span> anisotropy using shear-wave splitting in upper-crustal earthquakes. Anisotropy can be caused by a range of mechanisms, including crystal preferred orientation and fine scale layering, but the dominant mechanism in volcanic <span class="hlt">systems</span> is likely the preferred alignment of fluid-filled cracks and fractures. In general, cracks and fractures in the near surface tend to align parallel to the dominant direction of maximum horizontal stress. However, the observed patterns in volcanoes indicate more complicated stress patterns, which sometimes even change in time. A challenge is to untangle the magmatic versus hydrothermal control on stress. Here I summarise observations of <span class="hlt">seismic</span> anisotropy across several volcanoes in different settings. <span class="hlt">Seismic</span> anisotropy of the upper crust in the vicinity of the Soufrière Hills volcano - on the island of Montserrat in the Lesser Antilles - has been studied using shear wave splitting (SWS) analysis of shallow volcano-tectonic events. Clear spatial variations in anisotropy are observed, which are consistent with structurally controlled anisotropy resulting from a left-lateral transtensional array of faults that crosses the volcanic complex. Corbetti and Aluto are two volcanoes located roughly 100 km apart in the Main Ethiopian Rift. Their evolution is strongly controlled by pre-existing structural trends. In the case of Aluto, the anisotropy follows the Wonji fault belt in a rift parallel nearly N-S direction, but significantly oblique to the older border faults. In contrast, the shear-wave splitting at Corbetti is more complicated and supports ideas of the influence of a much-older pre-existing cross-rift structure known as the Goba-Bonga fault. Ontake volcano in Japan is another arc volcano. It</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.8998G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.8998G"><span><span class="hlt">Seismic</span> detection <span class="hlt">system</span> for blocking the dangerous installations in case of strong earthquake occurrence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghica, Daniela; Corneliu Rau, Dan; Ionescu, Constantin; Grigore, Adrian</p> <p>2010-05-01</p> <p>During the last 70 years, four major earthquakes occurred in the Vrancea <span class="hlt">seismic</span> area affected Romania territory: 10 November 1940 (Mw = 7.7, 160 km depth), 4 March 1977 (Mw = 7.5, 100 km depth), 30 August 1986 (Mw = 7.2, 140 km depth), 30 May 30 1990 (Mw = 6.9, 80 km depth). Romania is a European country with significant <span class="hlt">seismicity</span>. So far, the 1977 event had the most catastrophic consequences: about 33,000 residences were totally destroyed or partially deteriorated, 1,571 people dies and another 11,300 were injured. Moreover, 61 natural-gas pipelines were damaged, causing destructive fires. The total losses were estimated at 3 mld. U.S. dollars. Recent studies clearly pointed out that in case of a strong earthquake occurrence in Vrancea region (Ms above 7), the biggest danger regarding the major cities comes from explosions and fires started immediately after the earthquake, and the most important factor of risk are the natural gas distribution networks. The damages are strongly amplified by the fact that, simultaneously, water and electric energy lines distributions are damaged too, making impossible the efficient firemen intervention, for localizing the fire sources. Presently, in Romania safe and efficient accepted solutions for improving the buildings securing, using antiseismic protection of the dangerous installations as natural-gas pipelines are not available. Therefore, we propose a <span class="hlt">seismic</span> detection <span class="hlt">system</span> based on a <span class="hlt">seismically</span> actuated gas shut-off valve, which is automatically shut down in case of a <span class="hlt">seismic</span> shock. The device is intended to be installed in the natural-gas supply line outside of buildings, as well at each user (group of users), inside of the buildings. The <span class="hlt">seismic</span> detection <span class="hlt">system</span> for blocking the dangerous installations in case of a strong earthquake occurrence was designed on the basis of 12 criteria enforced by the US regulations for <span class="hlt">seismic</span> valves, aimed to eliminate the critical situations as fluids and under pressure gases leakage</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/869651','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/869651"><span><span class="hlt">Seismic</span> event classification <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Dowla, Farid U.; Jarpe, Stephen P.; Maurer, William</p> <p>1994-01-01</p> <p>In the computer interpretation of <span class="hlt">seismic</span> data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a <span class="hlt">seismic</span> event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S33A2310Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S33A2310Y"><span>Geoazur's contribution in instrumentation to monitor <span class="hlt">seismic</span> activity of the Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yates, B.; Hello, Y.; Anglade, A.; Desprez, O.; Ogé, A.; Charvis, P.; Deschamps, A.; Galve, A.; Nolet, G.; Sukhovich, A.</p> <p>2011-12-01</p> <p><span class="hlt">Seismic</span> activity in the earth is mainly located near the tectonic plate <span class="hlt">boundaries</span>, in the deep ocean (expansion centers) or near their margins (subduction zones). Travel times and waveforms of recorded seismograms can be used to reconstruct the three-dimensional wave speed distribution in the earth with <span class="hlt">seismic</span> tomography or to image specific <span class="hlt">boundaries</span> in the deep earth. Because of the lack of permanent sea-bottom seismometers these observation are conducted over short period of time using portable ocean bottom seismometers. Geaozur has a long experience and strong skills in designing and deploying Ocean Bottom Seismometers all over the world. We have developed two types of ocean bottom instruments. The "Hippocampe" for long deployment and "Lady bug" for aftershock monitoring or for fast overlaps during wide angle experiments. Early warning <span class="hlt">systems</span> for tsunamis and earthquakes have been developed in recent years but these need real time data transmission and direct control of the instrument. We have developed a permanent real time Broad Band instrument installed in the Mediterranean Sea and connected to the Antares Neutrinos telescope. This instrument offers all the advantages of a very heavy and costly installation, such as the ability to do real-time seismology on the seafloor. Such real-time seafloor monitoring is especially important for <span class="hlt">seismic</span> hazard. Major earthquakes cause human and economic losses directly related to the strong motion of the ground or by induced phenomena such as tsunamis and landslides. Fiber optical cables provide a high-capacity lightweight alternative to traditional copper cables. Three-component sensors analyze permanently the noise signal and detect the events to record. Major events can force the network to transmit data with almost zero lag time. The optical link also allows us to retrieve events at a later date. However, OBSs alone can never provide the density and long term, homogeneous data coverage needed for local and global</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.V24A..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.V24A..03W"><span>Anatomy of Old Faithful hydrothermal <span class="hlt">system</span> from subsurface <span class="hlt">seismic</span> imaging of the Yellowstone Upper Geyser Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, S. M.; Lin, F. C.; Farrell, J.; Ward, K. M.; Karplus, M. S.; Smith, R. B.</p> <p>2017-12-01</p> <p>The Upper Geyser Basin (UGB) in Yellowstone National Park contains one of the highest concentrations of hydrothermal features on Earth including the iconic Old Faithful Geyser (OFG). Although this <span class="hlt">system</span> has been the focus of many geological, geochemical, and geophysical studies, the shallow (<200 m) subsurface structure and the hydrothermal tremor behavior remain poorly characterized. To probe the detailed structure that relates to the hydrothermal plumbing of the UGB, we deployed dense arrays of 3-C 5-Hz geophones in both November of 2015 and 2016, composed of 133 stations with 50 m spacing, and 519 station locations, with an 20 m spacing, respectively. By applying <span class="hlt">seismic</span> interferometry techniques, we extracted Rayleigh-wave signals between 1-10 Hz via <span class="hlt">seismic</span> signals excited by nearby hydrothermal features (e.g. geysers and pools). We observe a clear lateral velocity <span class="hlt">boundary</span> at 3.3 Hz frequency that delineates a higher phase velocity of 1.6 km/sec in the NE and a lower phase velocity of 1.0 km/sec in the SW corresponding to the local geologic formation of rhyolitic and glacial deposits, respectively. We also image a relatively shallow (20-60 m deep) large reservoir with an estimated porosity 30% located 100 meters southwest of the OFG from the significant spatial-dependent waveform distortions and delays between 5-10 Hz frequency. This reservoir is likely controlled by the local geology with a rhyolitic deposit in the NE acting as a relatively impermeable barrier to vertical fluid ascent. To understand the pre-eruption tremor signals from OFG, we first study the <span class="hlt">seismic</span> waveforms recorded at the closest station to the OFG cone. Many highly repetitive <span class="hlt">seismic</span> pulses associated with bubble collapse, which compose the tremor signal, can be identified. Using a reference event template and the cross-correlation method, we can determine the onset of each individual bubbling event using a cross-correlation coefficient threshold of 0.8. Based on the detected timing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMDI21A0391S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMDI21A0391S"><span>Small aperture <span class="hlt">seismic</span> arrays for studying planetary interiors and <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmerr, N. C.; Lekic, V.; Fouch, M. J.; Panning, M. P.; Siegler, M.; Weber, R. C.</p> <p>2017-12-01</p> <p><span class="hlt">Seismic</span> arrays are a powerful tool for understanding the interior structure and <span class="hlt">seismicity</span> across objects in the Solar <span class="hlt">System</span>. Given the operational constraints of ground-based lander investigations, a small aperture <span class="hlt">seismic</span> array can provide many of the benefits of a larger-scale network, but does not necessitate a global deployment of instrumentation. Here we define a small aperture array as a deployment of multiple seismometers, with a separation between instruments of 1-1000 meters. For example, small aperture <span class="hlt">seismic</span> arrays have been deployed on the Moon during the Apollo program, the Active <span class="hlt">Seismic</span> Experiments of Apollo 14 and 16, and the Lunar <span class="hlt">Seismic</span> Profiling Experiment deployed by the Apollo 17 astronauts. Both were high frequency geophone arrays with spacing of 50 meters that provided information on the layering and velocity structure of the uppermost kilometer of the lunar crust. Ideally such arrays would consist of instruments that are 3-axis short period or broadband seismometers. The instruments must have a sampling rate and frequency range sensitivity capable of distinguishing between waves arriving at each station in the array. Both terrestrial analogs and the data retrieved from the Apollo arrays demonstrate the efficacy of this approach. Future opportunities exist for deployment of <span class="hlt">seismic</span> arrays on Europa, asteroids, and other objects throughout the Solar <span class="hlt">System</span>. Here we will present both observational data and 3-D synthetic modeling results that reveal the sensing requirements and the primary advantages of a small aperture <span class="hlt">seismic</span> array over single station approach. For example, at the smallest apertures of < 1 m, we constrain that sampling rates must exceed 500 Hz and instrument sensitivity must extend to 100 Hz or greater. Such advantages include the improved ability to resolve the location of the sources near the array through detection of backazimuth and differential timing between stations, determination of the small-scale structure</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT.......216M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT.......216M"><span><span class="hlt">Seismic</span> and infrasonic source processes in volcanic fluid <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matoza, Robin S.</p> <p></p> <p>Volcanoes exhibit a spectacular diversity in fluid oscillation processes, which lead to distinct <span class="hlt">seismic</span> and acoustic signals in the solid earth and atmosphere. Volcano <span class="hlt">seismic</span> waveforms contain rich information on the geometry of fluid migration, resonance effects, and transient and sustained pressure oscillations resulting from unsteady flow through subsurface cracks, fissures and conduits. Volcanic sounds contain information on shallow fluid flow, resonance in near-surface cavities, and degassing dynamics into the atmosphere. Since volcanoes have large spatial scales, the vast majority of their radiated atmospheric acoustic energy is infrasonic (<20 Hz). This dissertation presents observations from joint broadband <span class="hlt">seismic</span> and infrasound array deployments at Mount St. Helens (MSH, Washington State, USA), Tungurahua (Ecuador), and Kilauea Volcano (Hawaii, USA), each providing data for several years. These volcanoes represent a broad spectrum of eruption styles ranging from hawaiian to plinian in nature. The catalogue of recorded infrasonic signals includes continuous broadband and harmonic tremor from persistent degassing at basaltic lava vents and tubes at Pu'u O'o (Kilauea), thousands of repetitive impulsive signals associated with <span class="hlt">seismic</span> longperiod (0.5-5 Hz) events and the dynamics of the shallow hydrothermal <span class="hlt">system</span> at MSH, rockfall signals from the unstable dacite dome at MSH, energetic explosion blast waves and gliding infrasonic harmonic tremor at Tungurahua volcano, and large-amplitude and long-duration broadband signals associated with jetting during vulcanian, subplinian and plinian eruptions at MSH and Tungurahua. We develop models for a selection of these infrasonic signals. For infrasonic long-period (LP) events at MSH, we investigate <span class="hlt">seismic</span>-acoustic coupling from various buried source configurations as a means to excite infrasound waves in the atmosphere. We find that linear elastic <span class="hlt">seismic</span>-acoustic transmission from the ground to atmosphere is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910005047','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910005047"><span>Specification goals for a Mars <span class="hlt">seismic</span> network</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, Paul M.</p> <p>1990-01-01</p> <p>A <span class="hlt">seismic</span> network on Mars should have enough stations (e.g., 24) to characterize the <span class="hlt">seismicity</span> of the planet for comparison with a diversity of structural features; be comprised of low noise stations, preferably underground, 3 to 4 orders of magnitude more sensitive than those used on Viking; record over a sufficient band-width (DC-30 Hz) to detect micro-earthquakes to normal modes; and record for a sufficient duration (10 years) and data rate (10(exp 8) Mb/day/station) to obtain a data set comparable to that from the Apollo mission to the Moon so that locations of major internal <span class="hlt">boundaries</span> can be inferred, such as those in the Earth, i.e., crust - lithosphere - asthenosphere - upper - lower phase transitions - outer - inner core. The proposed Mars Global Network Mission provides an opportunity to sense the dynamics and probe the interior of the planet. The <span class="hlt">seismic</span> objectives, the availability of the instrumentation and trade-offs to meet them are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037507','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037507"><span><span class="hlt">Seismic</span> imaging of a fractured gas hydrate <span class="hlt">system</span> in the Krishna-Godavari Basin offshore India</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Riedel, M.; Collett, T.S.; Kumar, P.; Sathe, A.V.; Cook, A.</p> <p>2010-01-01</p> <p>Gas hydrate was discovered in the Krishna-Godavari (KG) Basin during the India National Gas Hydrate Program (NGHP) Expedition 1 at Site NGHP-01-10 within a fractured clay-dominated sedimentary <span class="hlt">system</span>. Logging-while-drilling (LWD), coring, and wire-line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500m transect. Three-dimensional (3D) <span class="hlt">seismic</span> data were subsequently used to image the fractured <span class="hlt">system</span> and explain the occurrence of gas hydrate associated with the fractures. A <span class="hlt">system</span> of two fault-sets was identified, part of a typical passive margin tectonic setting. The LWD-derived fracture network at Hole NGHP-01-10A is to some extent seen in the <span class="hlt">seismic</span> data and was mapped using <span class="hlt">seismic</span> coherency attributes. The fractured <span class="hlt">system</span> around Site NGHP-01-10 extends over a triangular-shaped area of ~2.5 km2 defined using <span class="hlt">seismic</span> attributes of the seafloor reflection, as well as " <span class="hlt">seismic</span> sweetness" at the base of the gas hydrate occurrence zone. The triangular shaped area is also showing a polygonal (nearly hexagonal) fault pattern, distinct from other more rectangular fault patterns observed in the study area. The occurrence of gas hydrate at Site NGHP-01-10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source. The triangular-shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits. Additionally, the fault-associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone. It is proposed that there are additional locations in the KG Basin with possible gas hydrate accumulation of similar tectonic conditions, and one such location was identified from the 3D <span class="hlt">seismic</span> data ~6 km NW of Site NGHP-01-10. ?? 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMGP21A0110G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMGP21A0110G"><span>Paleomagnetic Data Bearing on the Eastern and Southern <span class="hlt">Boundaries</span> of the Walker Lane Belt Transfer <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grow, J. S.; Geissman, J. W.; Oldow, J. S.</p> <p>2007-12-01</p> <p>In west-central Nevada, a transfer zone, which initiated in the mid-Miocene, presently links, via the Mina Deflection, right-lateral faults of the Eastern California Shear Zone to the south and the Central Nevada <span class="hlt">Seismic</span> Belt and Walker Lane to the north. This transfer zone, the early inception of which is characterized by moderate (20-30°) clockwise crustal rotations previously identified (e.g., Candelaria Hills and surrounding ranges), along with right-lateral structures to the south and north, are part of a diffuse zone of intracontinental deformation that accommodates some 25 percent of the motion between the Pacific and North American plates. Although the northern and western <span class="hlt">boundaries</span> of the transfer zone are relatively well defined by paleomagnetic data, the eastern and southeastern <span class="hlt">boundaries</span> remain poorly constrained. Additional paleomagnetic data are being obtained from mid-to-late Tertiary volcanic rocks, presumably lying within (e.g., Montezuma Range, Palmetto Mountains, Monte Cristo Range) and outside (e.g., Goldfield Hills, San Antonio Mountains, Slate Ridge) of the transfer zone. Areas outside of the transfer zone are inferred to have not undergone any appreciable rotation since its inception. Volcanic rocks as well as shallow intrusions ranging in age from Oligocene to mid-Pliocene have been sampled (N=187) from inside and outside of the inferred southern and eastern <span class="hlt">boundaries</span> of the transfer zone. Overall, the collection responds very favorably to progressive demagnetization; initial results are tentatively interpreted as suggesting the absence of appreciable rotation of the San Antonio Range (Tonopah, Nevada area and farther north). The extent to which areas near the eastern and southeastern <span class="hlt">boundaries</span> have been rotated is under investigation. These data will aid in a better understanding of differential block rotation and tilting throughout the development of the west-central Nevada transfer <span class="hlt">system</span> from the mid-Miocene to late Pliocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NHESS..17.2365G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NHESS..17.2365G"><span>Planar <span class="hlt">seismic</span> source characterization models developed for probabilistic <span class="hlt">seismic</span> hazard assessment of Istanbul</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gülerce, Zeynep; Buğra Soyman, Kadir; Güner, Barış; Kaymakci, Nuretdin</p> <p>2017-12-01</p> <p>This contribution provides an updated planar <span class="hlt">seismic</span> source characterization (SSC) model to be used in the probabilistic <span class="hlt">seismic</span> hazard assessment (PSHA) for Istanbul. It defines planar rupture <span class="hlt">systems</span> for the four main segments of the North Anatolian fault zone (NAFZ) that are critical for the PSHA of Istanbul: segments covering the rupture zones of the 1999 Kocaeli and Düzce earthquakes, central Marmara, and Ganos/Saros segments. In each rupture <span class="hlt">system</span>, the source geometry is defined in terms of fault length, fault width, fault plane attitude, and segmentation points. Activity rates and the magnitude recurrence models for each rupture <span class="hlt">system</span> are established by considering geological and geodetic constraints and are tested based on the observed <span class="hlt">seismicity</span> that is associated with the rupture <span class="hlt">system</span>. Uncertainty in the SSC model parameters (e.g., b value, maximum magnitude, slip rate, weights of the rupture scenarios) is considered, whereas the uncertainty in the fault geometry is not included in the logic tree. To acknowledge the effect of earthquakes that are not associated with the defined rupture <span class="hlt">systems</span> on the hazard, a background zone is introduced and the <span class="hlt">seismicity</span> rates in the background zone are calculated using smoothed-<span class="hlt">seismicity</span> approach. The state-of-the-art SSC model presented here is the first fully documented and ready-to-use fault-based SSC model developed for the PSHA of Istanbul.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4201Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4201Y"><span><span class="hlt">Seismic</span> Tomography of Siyazan - Shabran Oil and Gas Region Of Azerbaijan by Data of The <span class="hlt">Seismic</span> Stations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yetirmishli, Gurban; Guliyev, Ibrahim; Mammadov, Nazim; Kazimova, Sabina; Ismailova, Saida</p> <p>2016-04-01</p> <p>The main purpose of the research was to build a reliable 3D model of the structure of <span class="hlt">seismic</span> velocities in the earth crust on the territory of Siyazan-Shabran region of Azerbaijan, using the data of <span class="hlt">seismic</span> telemetry stations spanning Siyazan-Shabran region (Siyazan, Altiagaj, Pirgulu, Guba, Khinalig, Gusar), including 7 mobile telemetry <span class="hlt">seismic</span> stations. Interest to the problem of research <span class="hlt">seismic</span> tomography caused by applied environmental objectives, such as the assessment of geological risks, engineering evaluation (stability and safety of wells), the task of exploration and mining operations. In the study region are being actively developed oil fields, and therefore, there is a risk of technogenic earthquakes. It was performed the calculation of first arrival travel times of P and S waves and the corresponding ray paths. Calculate 1D velocity model which is the initial model as a set of horizontal layers (velocity may be constant or changed linearly with depth on each layer, gaps are possible only at the <span class="hlt">boundaries</span> between the layers). Have been constructed and analyzed the horizontal sections of the three-dimensional velocity model at different depths of the investigated region. By the empirical method was proposed density model of the sedimentary rocks at depths of 0-8 km.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810043543&hterms=collection+evaluation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcollection%2Bevaluation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810043543&hterms=collection+evaluation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcollection%2Bevaluation"><span>A <span class="hlt">seismic</span> signal processor suitable for use with the NOAA/GOES satellite data collection <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Webster, W. J., Jr.; Miller, W. H.; Whitley, R.; Allenby, R. J.; Dennison, R. T.</p> <p>1981-01-01</p> <p>Because of the high data-rate requirements, a practical <span class="hlt">system</span> capable of collecting <span class="hlt">seismic</span> information in the field and relaying it, via satellite, to a central collection point is not yet available. A <span class="hlt">seismic</span> signal processor has been developed and tested for use with the NOAA/GOES satellite data collection <span class="hlt">system</span>. Performance tests on recorded, as well as real time, short period signals indicate that the event recognition technique used is nearly perfect in its rejection of environmental noise and other non-<span class="hlt">seismic</span> signals and that, with the use of solid state buffer memories, data can be acquired in many swarm situations. The design of a complete field data collection platform is discussed based on the prototype evaluation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111040S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111040S"><span>The International Plate <span class="hlt">Boundary</span> Observatory Chile (IPOC) in the northern Chile <span class="hlt">seismic</span> gap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schurr, B.; Asch, A.; Sodoudi, F.; Manzanares, A.; Ritter, O.; Klotz, J.; Chong-Diaz, G.; Barrientos, S.; Villotte, J.-P.; Oncken, O.</p> <p>2009-04-01</p> <p>Fast convergence between the oceanic Nazca and the continental South American plate is accommodated by recurrent rupture of large segments of the two plates' interface. The resulting earthquakes are among the largest and, for their sizes, most frequent on Earth. Along the Chilean and southern Peruvian margin, all segments have ruptured at least once in the past 150 years for which there exist historic and/or instrumental records. The one segment that is most mature for re-rupture stretches for more than 500 km along the northernmost Chilean coast between roughly -23° and -18° latitude. It last broke in 1877 in a magnitude ~8.8 earthquake, triggering a major Tsunami. From the historical record, it has been known to have a recurrence cycle of approximately 110 years. The adjoining segments to the north and south broke rather recently in 1995 and 2001 in M>8 earthquakes and an M 7.7 earthquake encroached the southern part of the gap in 2007. The IPOC project intends to investigate this segment of the Nazca-South American plate <span class="hlt">boundary</span>, on which a strong to devastating earthquake is expected to occur within the next years, by monitoring at a variety of time-scales deformation, <span class="hlt">seismicity</span>, and magnetotelluric fields in the subduction zone at the closing stages of the interseismic cycle before and possibly during occurrence of a big earthquake. For that purpose, installation of long-term observatories in Northern Chile started in 2006 in a close cooperation of the Universidad de Chile (Santiago, Chile), the Universidad Catolica del Norte (Antofagasta, Chile), the Institut de Physique du Globe de Paris (Paris, France), and the German Research Centre for Geosciences (GFZ, Potsdam, Germany). Currently we are operating 14 modern seismological stations equipped with STS-2 broadband seismometers and accelerometers (EPI sensor). At least two more stations will be installed in the near future. To cope with the high resolution and dynamic of the sensors and data acquisition</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JVGR..343..192F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JVGR..343..192F"><span>Numerical simulations (2D) on the influence of pre-existing local structures and <span class="hlt">seismic</span> source characteristics in earthquake-volcano interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farías, Cristian; Galván, Boris; Miller, Stephen A.</p> <p>2017-09-01</p> <p>Earthquake triggering of hydrothermal and volcanic <span class="hlt">systems</span> is ubiquitous, but the underlying processes driving these <span class="hlt">systems</span> are not well-understood. We numerically investigate the influence of <span class="hlt">seismic</span> wave interaction with volcanic <span class="hlt">systems</span> simulated as a trapped, high-pressure fluid reservoir connected to a fluid-filled fault <span class="hlt">system</span> in a 2-D poroelastic medium. Different orientations and earthquake magnitudes are studied to quantify dynamic and static stress, and pore pressure changes induced by a <span class="hlt">seismic</span> event. Results show that although the response of the <span class="hlt">system</span> is mainly dominated by characteristics of the radiated <span class="hlt">seismic</span> waves, local structures can also play an important role on the <span class="hlt">system</span> dynamics. The fluid reservoir affects the <span class="hlt">seismic</span> wave front, distorts the static overpressure pattern induced by the earthquake, and concentrates the kinetic energy of the incoming wave on its <span class="hlt">boundaries</span>. The static volumetric stress pattern inside the fault <span class="hlt">system</span> is also affected by the local structures. Our results show that local faults play an important role in earthquake-volcanic <span class="hlt">systems</span> dynamics by concentrating kinetic energy inside and acting as wave-guides that have a breakwater-like behavior. This generates sudden changes in pore pressure, volumetric expansion, and stress gradients. Local structures also influence the regional Coulomb yield function. Our results show that local structures affect the dynamics of volcanic and hydrothermal <span class="hlt">systems</span>, and should be taken into account when investigating triggering of these <span class="hlt">systems</span> from nearby or distant earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JOUC...17...46W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JOUC...17...46W"><span>Application of <span class="hlt">seismic</span> interferometric migration for shallow <span class="hlt">seismic</span> high precision data processing: A case study in the Shenhu area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Jia; Liu, Huaishan; Xing, Lei; Du, Dong</p> <p>2018-02-01</p> <p>The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine <span class="hlt">seismic</span> exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow <span class="hlt">seismic</span> structure imaging is assessed by building a complex model, and differences between the <span class="hlt">seismic</span> interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The <span class="hlt">seismic</span> interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure <span class="hlt">boundary</span>. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037485','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037485"><span><span class="hlt">Seismic</span> analysis of clinoform depositional sequences and shelf-margin trajectories in Lower Cretaceous (Albian) strata, Alaska North Slope</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Houseknecht, D.W.; Bird, K.J.; Schenk, C.J.</p> <p>2009-01-01</p> <p>Lower Cretaceous strata beneath the Alaska North Slope include clinoform depositional sequences that filled the western Colville foreland basin and overstepped the Beaufort rift shoulder. Analysis of Albian clinoform sequences with two-dimensional (2D) <span class="hlt">seismic</span> data resulted in the recognition of <span class="hlt">seismic</span> facies inferred to represent lowstand, transgressive and highstand <span class="hlt">systems</span> tracts. These are stacked to produce shelf-margin trajectories that appear in low-resolution <span class="hlt">seismic</span> data to alternate between aggradational and progradational. Higher-resolution <span class="hlt">seismic</span> data reveal shelf-margin trajectories that are more complex, particularly in net-aggradational areas, where three patterns commonly are observed: (1) a negative (downward) step across the sequence <span class="hlt">boundary</span> followed by mostly aggradation in the lowstand <span class="hlt">systems</span> tract (LST), (2) a positive (upward) step across the sequence <span class="hlt">boundary</span> followed by mostly progradation in the LST and (3) an upward backstep across a mass-failure d??collement. These different shelf-margin trajectories are interpreted as (1) fall of relative sea level below the shelf edge, (2) fall of relative sea level to above the shelf edge and (3) mass-failure removal of shelf-margin sediment. Lowstand shelf margins mapped using these criteria are oriented north-south in the foreland basin, indicating longitudinal filling from west to east. The shelf margins turn westward in the north, where the clinoform depositional <span class="hlt">system</span> overstepped the rift shoulder, and turn eastward in the south, suggesting progradation of depositional <span class="hlt">systems</span> from the ancestral Brooks Range into the foredeep. Lowstand shelf-margin orientations are consistently perpendicular to clinoform-foreset-dip directions. Although the Albian clinoform sequences of the Alaska North Slope are generally similar in stratal geometry to clinoform sequences elsewhere, they are significantly thicker. Clinoform-sequence thickness ranges from 600-1000 m in the north to 1700-2000 m in the south</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70027524','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70027524"><span>Delineation of tectonic provinces of New York state as a component of <span class="hlt">seismic</span>-hazard evaluation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fakundiny, R.H.</p> <p>2004-01-01</p> <p><span class="hlt">Seismic</span>-hazard evaluations in the eastern United States must be based on interpretations of the composition and form of Proterozoic basement-rock terranes and overlying Paleozoic strata, and on factors that can cause relative movements among their units, rather than Phanerozoic orogenic structures, which may be independent of modern tectonics. The tectonic-province concept is a major part of both probabilistic and deterministic <span class="hlt">seismic</span>-hazard evaluations, yet those that have been proposed to date have not attempted to geographically correlate modern earthquakes with regional basement structure. Comparison of basement terrane (megablock) <span class="hlt">boundaries</span> with the spatial pattern of modern <span class="hlt">seismicity</span> may lead to the mechanically sound definition of tectonic provinces, and thus, better <span class="hlt">seismic</span>-hazard evaluation capability than is currently available. Delineation of megablock <span class="hlt">boundaries</span> will require research on the many factors that affect their structure and movement. This paper discusses and groups these factors into two broad categories-megablock tectonics in relation to <span class="hlt">seismicity</span> and regional horizontal-compressive stresses, with megablock tectonics divided into subcategories of basement, overlying strata, regional lineaments, basement tectonic terranes, earthquake epicenter distribution, and epeirogeny, and compressive stresses divided into pop-ups and the contemporary maximum horizontal-compressive stress field. A list presenting four to nine proposed research topics for each of these categories is given at the end.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V41B2780O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V41B2780O"><span>Updated Tomographic <span class="hlt">Seismic</span> Imaging at Kilauea Volcano, Hawaii</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okubo, P.; Johnson, J.; Felts, E. S.; Flores, N.</p> <p>2013-12-01</p> <p>Improved and more detailed geophysical, geological, and geochemical observations and measurements at Kilauea, along with prolonged eruptions at its summit caldera and east rift zone, are encouraging more ambitious interpretation and modeling of volcanic processes over a range of temporal and spatial scales. We are updating three-dimensional models of <span class="hlt">seismic</span> wave-speed distributions within Kilauea using local earthquake arrival time tomography to support waveform-based modeling of <span class="hlt">seismic</span> source mechanisms. We start from a tomographic model derived from a combination of permanent <span class="hlt">seismic</span> stations comprising the Hawaiian Volcano Observatory (HVO) seismographic network and a dense deployment of temporary stations in the Kilauea caldera region in 1996. Using P- and S-wave arrival times measured from the HVO network for local earthquakes from 1997 through 2012, we compute velocity models with the finite difference tomographic <span class="hlt">seismic</span> imaging technique implemented by Benz and others (1996), and applied to numerous volcanoes including Kilauea. Particular impetus to our current modeling was derived from a focused effort to review <span class="hlt">seismicity</span> occurring in Kilauea's summit caldera and adjoining regions in 2012. Our results reveal clear P-wave low-velocity features at and slightly below sea level beneath Kilauea's summit caldera, lying between Halemaumau Crater and the north-facing scarps that mark the southern caldera <span class="hlt">boundary</span>. The results are also suggestive of changes in <span class="hlt">seismic</span> velocity distributions between 1996 and 2012. One example of such a change is an apparent decrease in the size and southeastward extent, compared to the earlier model, of the low VP feature imaged with the more recent data. However, we recognize the distinct possibility that these changes are reflective of differences in earthquake and <span class="hlt">seismic</span> station distributions in the respective datasets, and we need to further populate the more recent HVO <span class="hlt">seismicity</span> catalogs to possibly address this concern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70174838','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70174838"><span>Tracking changes in volcanic <span class="hlt">systems</span> with <span class="hlt">seismic</span> Interferometry</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Haney, Matt; Alicia J. Hotovec-Ellis,; Bennington, Ninfa L.; Silvio De Angelis,; Clifford Thurber,</p> <p>2014-01-01</p> <p>The detection and evaluation of time-dependent changes at volcanoes form the foundation upon which successful volcano monitoring is built. Temporal changes at volcanoes occur over all time scales and may be obvious (e.g., earthquake swarms) or subtle (e.g., a slow, steady increase in the level of tremor). Some of the most challenging types of time-dependent change to detect are subtle variations in material properties beneath active volcanoes. Although difficult to measure, such changes carry important information about stresses and fluids present within hydrothermal and magmatic <span class="hlt">systems</span>. These changes are imprinted on <span class="hlt">seismic</span> waves that propagate through volcanoes. In recent years, there has been a quantum leap in the ability to detect subtle structural changes systematically at volcanoes with <span class="hlt">seismic</span> waves. The new methodology is based on the idea that useful <span class="hlt">seismic</span> signals can be generated “at will” from <span class="hlt">seismic</span> noise. This means signals can be measured any time, in contrast to the often irregular and unpredictable times of earthquakes. With <span class="hlt">seismic</span> noise in the frequency band 0.1–1 Hz arising from the interaction of the ocean with the solid Earth known as microseisms, researchers have demonstrated that cross-correlations of passive <span class="hlt">seismic</span> recordings between pairs of seismometers yield coherent signals (Campillo and Paul 2003; Shapiro and Campillo 2004). Based on this principle, coherent signals have been reconstructed from noise recordings in such diverse fields as helioseismology (Rickett and Claerbout 2000), ultrasound (Weaver and Lobkis 2001), ocean acoustic waves (Roux and Kuperman 2004), regional (Shapiro et al. 2005; Sabra et al. 2005; Bensen et al. 2007) and exploration (Draganov et al. 2007) seismology, atmospheric infrasound (Haney 2009), and studies of the cryosphere (Marsan et al. 2012). Initial applications of ambient <span class="hlt">seismic</span> noise were to regional surface wave tomography (Shapiro et al. 2005). Brenguier et al. (2007) were the first to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Tectp.721..462A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Tectp.721..462A"><span>The new Central American <span class="hlt">seismic</span> hazard zonation: Mutual consensus based on up to day seismotectonic framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alvarado, Guillermo E.; Benito, Belén; Staller, Alejandra; Climent, Álvaro; Camacho, Eduardo; Rojas, Wilfredo; Marroquín, Griselda; Molina, Enrique; Talavera, J. Emilio; Martínez-Cuevas, Sandra; Lindholm, Conrad</p> <p>2017-11-01</p> <p>Central America is one of the most active <span class="hlt">seismic</span> zones in the World, due to the interaction of five tectonic plates (North America, Caribbean, Coco, Nazca and South America), and its internal deformation, which generates almost one destructive earthquakes (5.4 ≤ Mw ≤ 8.1) every year. A new seismological zonation for Central America is proposed based on seismotectonic framework, a geological context (tectonic and geological maps), geophysical and geodetic evidence (gravimetric maps, magnetometric, GPS observations), and previous works. As a main source of data a depurated earthquake catalog was collected covering the period from 1522 to 2015. This catalog was homogenized to a moment magnitude scale (Mw). After a careful analysis of all the integrated geological and seismological information, the seismogenic zones were established into <span class="hlt">seismic</span> areas defined by similar patterns of faulting, <span class="hlt">seismicity</span>, and rupture mechanism. The tectonic environment has required considering <span class="hlt">seismic</span> zones in two particular seismological regimes: a) crustal faulting (including local faults, major fracture zones of plate <span class="hlt">boundary</span> limits, and thrust fault of deformed belts) and b) subduction, taking into account the change in the subduction angle along the trench, and the type and location of the rupture. The <span class="hlt">seismicity</span> in the subduction zone is divided into interplate and intraplate inslab <span class="hlt">seismicity</span>. The regional <span class="hlt">seismic</span> zonation proposed for the whole of Central America, include local <span class="hlt">seismic</span> zonations, avoiding discontinuities at the national <span class="hlt">boundaries</span>, because of a consensus between the 7 countries, based on the cooperative work of specialists on Central American seismotectonics and related topics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/951160','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/951160"><span>Short-Period <span class="hlt">Seismic</span> Noise in Vorkuta (Russia)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kishkina, S B; Spivak, A A; Sweeney, J J</p> <p></p> <p> <span class="hlt">seismic</span> array will considerably improve the recording capacity of regional and local <span class="hlt">seismic</span> events. It will allow detection of signatures of <span class="hlt">seismic</span> waves propagating in submeridional and sublatitudinal directions. The latter is of special interest not only to access the influence of the Urals on propagation patterns of <span class="hlt">seismic</span> waves, but also to address other questions, such as the structure and dynamic characteristics of the internal dynamo of the Earth [9,13]. Recording <span class="hlt">seismic</span> waves at low angular distances from <span class="hlt">seismically</span> active subpolar zones will allow us to collect data on vortical and convective movements in subpolar lithosphere blocks and at the <span class="hlt">boundary</span> of the inner core of the Earth, possibly giving essential clues to the modeling of the Earth's electromagnetic field [3,13]. The present study considers basic features of <span class="hlt">seismic</span> noise at the Vorkuta station obtained through the analysis of <span class="hlt">seismic</span> records from March, 2006 till December, 2007.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8278B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8278B"><span>The MITMOTION Project - A <span class="hlt">seismic</span> hazard overview of the Mitidja Basin (Northern Algeria)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borges, José; Ouyed, Merzouk; Bezzeghoud, Mourad; Idres, Mouloud; Caldeira, Bento; Boughacha, Mohamed; Carvalho, João; Samai, Saddek; Fontiela, João; Aissa, Saoussen; Benfadda, Amar; Chimouni, Redouane; Yalaoui, Rafik; Dias, Rui</p> <p>2017-04-01</p> <p>The Mitidja Basin (MB) is located in northern Algeria and is filled by quaternary sediments with a length of about 100 km on the EW direction and approximately 20 km width. This basin is limited to the south by the Boumerdes - Larbaa - Blida active fault <span class="hlt">system</span> and to the north by the Thenia - Sahel fault <span class="hlt">system</span>. Both fault <span class="hlt">systems</span> are of the reverse type with opposed dips and accommodate a general slip rate of 4 mm/year. This basin is associated with important <span class="hlt">seismic</span> events that affected northern Algeria since the historical period until the present. The available earthquake catalogues reported numerous destructive earthquakes that struke different regions, such as Algiers (1365, Io= X; 1716, Io = X). Recently, on May 2003 the Bourmedes earthquake (Mw = 6.9) affected the area of Zemmouri and caused 2.271 deaths. The event was caused by the reactivation of the MB <span class="hlt">boundary</span> faults. The epicenter was located offshore and generated a maximum uplift of 0.8 m along the coast with a horizontal maximum slip of 0.24 m. Recent studies show that the Boumerdes earthquake overloaded the <span class="hlt">system</span> of adjacent faults with a stress increase between 0.4 and 1.5 bar. This induced an increase of the <span class="hlt">seismic</span> hazard potential of the region and recommends a more detailed study of this fault <span class="hlt">system</span>. The high seismogenic potential of the fault <span class="hlt">system</span> bordering the MB, the exposure to danger of the most densely populated region of Algiers and the amplification effect caused by the basin are the motivation for this project proposal that will focus on the evaluation of the <span class="hlt">seismic</span> hazard of the region. The general purpose of the project is to improve the <span class="hlt">seismic</span> hazard assessment on the MB producing realistic predictions of strong ground motion caused by moderate and large earthquakes. To achieve this objective, it is important to make an effort in 3 directions: 1) the development of a detailed 3D velocity/structure model of the MB that includes geological constraints, <span class="hlt">seismic</span> reflection data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.671...56Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.671...56Z"><span>Stress development in heterogenetic lithosphere: Insights into earthquake processes in the New Madrid <span class="hlt">Seismic</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhan, Yan; Hou, Guiting; Kusky, Timothy; Gregg, Patricia M.</p> <p>2016-03-01</p> <p>The New Madrid <span class="hlt">Seismic</span> Zone (NMSZ) in the Midwestern United States was the site of several major M 6.8-8 earthquakes in 1811-1812, and remains <span class="hlt">seismically</span> active. Although this region has been investigated extensively, the ultimate controls on earthquake initiation and the duration of the <span class="hlt">seismicity</span> remain unclear. In this study, we develop a finite element model for the Central United States to conduct a series of numerical experiments with the goal of determining the impact of heterogeneity in the upper crust, the lower crust, and the mantle on earthquake nucleation and rupture processes. Regional <span class="hlt">seismic</span> tomography data (CITE) are utilized to infer the viscosity structure of the lithosphere which provide an important input to the numerical models. Results indicate that when differential stresses build in the Central United States, the stresses accumulating beneath the Reelfoot Rift in the NMSZ are highly concentrated, whereas the stresses below the geologically similar Midcontinent Rift <span class="hlt">System</span> are comparatively low. The numerical observations coincide with the observed distribution of <span class="hlt">seismicity</span> throughout the region. By comparing the numerical results with three reference models, we argue that an extensive mantle low velocity zone beneath the NMSZ produces differential stress localization in the layers above. Furthermore, the relatively strong crust in this region, exhibited by high <span class="hlt">seismic</span> velocities, enables the elevated stress to extend to the base of the ancient rift <span class="hlt">system</span>, reactivating fossil rifting faults and therefore triggering earthquakes. These results show that, if <span class="hlt">boundary</span> displacements are significant, the NMSZ is able to localize tectonic stresses, which may be released when faults close to failure are triggered by external processes such as melting of the Laurentide ice sheet or rapid river incision.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26ES..106a2003S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26ES..106a2003S"><span>Intelligent <span class="hlt">seismic</span> risk mitigation <span class="hlt">system</span> on structure building</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suryanita, R.; Maizir, H.; Yuniorto, E.; Jingga, H.</p> <p>2018-01-01</p> <p>Indonesia located on the Pacific Ring of Fire, is one of the highest-risk <span class="hlt">seismic</span> zone in the world. The strong ground motion might cause catastrophic collapse of the building which leads to casualties and property damages. Therefore, it is imperative to properly design the structural response of building against <span class="hlt">seismic</span> hazard. <span class="hlt">Seismic</span>-resistant building design process requires structural analysis to be performed to obtain the necessary building responses. However, the structural analysis could be very difficult and time consuming. This study aims to predict the structural response includes displacement, velocity, and acceleration of multi-storey building with the fixed floor plan using Artificial Neural Network (ANN) method based on the 2010 Indonesian <span class="hlt">seismic</span> hazard map. By varying the building height, soil condition, and <span class="hlt">seismic</span> location in 47 cities in Indonesia, 6345 data sets were obtained and fed into the ANN model for the learning process. The trained ANN can predict the displacement, velocity, and acceleration responses with up to 96% of predicted rate. The trained ANN architecture and weight factors were later used to build a simple tool in Visual Basic program which possesses the features for prediction of structural response as mentioned previously.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890046331&hterms=1041&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231041','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890046331&hterms=1041&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231041"><span>Time dependent inflow-outflow <span class="hlt">boundary</span> conditions for 2D acoustic <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Watson, Willie R.; Myers, Michael K.</p> <p>1989-01-01</p> <p>An analysis of the number and form of the required inflow-outflow <span class="hlt">boundary</span> conditions for the full two-dimensional time-dependent nonlinear acoustic <span class="hlt">system</span> in subsonic mean flow is performed. The explicit predictor-corrector method of MacCormack (1969) is used. The methodology is tested on both uniform and sheared mean flows with plane and nonplanar sources. Results show that the acoustic <span class="hlt">system</span> requires three physical <span class="hlt">boundary</span> conditions on the inflow and one on the outflow <span class="hlt">boundary</span>. The most natural choice for the inflow <span class="hlt">boundary</span> conditions is judged to be a specification of the vorticity, the normal acoustic impedance, and a pressure gradient-density gradient relationship normal to the <span class="hlt">boundary</span>. Specification of the acoustic pressure at the outflow <span class="hlt">boundary</span> along with these inflow <span class="hlt">boundary</span> conditions is found to give consistent reliable results. A set of <span class="hlt">boundary</span> conditions developed earlier, which were intended to be nonreflecting is tested using the current method and is shown to yield unstable results for nonplanar acoustic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EEEV...16..263P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EEEV...16..263P"><span><span class="hlt">Seismic</span> passive earth resistance using modified pseudo-dynamic method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pain, Anindya; Choudhury, Deepankar; Bhattacharyya, S. K.</p> <p>2017-04-01</p> <p>In earthquake prone areas, understanding of the <span class="hlt">seismic</span> passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical <span class="hlt">seismic</span> passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. <span class="hlt">Seismic</span> forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the <span class="hlt">boundary</span> conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the <span class="hlt">seismic</span> passive earth pressure coefficient. The effect of different parameters on the <span class="hlt">seismic</span> passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.9754R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.9754R"><span>Detailed <span class="hlt">seismicity</span> analysis in the SE of Romania (Dobrogea region)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rogozea, Maria; Radulian, Mircea; Ghica, Daniela; Popa, Mihaela</p> <p>2014-05-01</p> <p>The purpose of this paper is to analyze the <span class="hlt">seismicity</span> in the south-eastern part of Romania, in the Dobrogea region (namely the Predobrogean Depression and Black Sea area). Predobrogean Depression is the name attributed to the structures belonging to the Scythian Platform. The <span class="hlt">seismic</span> activity is moderate with most significant earthquakes at the <span class="hlt">boundary</span> between the North Dobrogea Orogen and Scythian Platform (Sf. Gheorghe fault). The largest magnitude event was recorded in 02.11.1871 (Mw = 5.3). Other events with magnitude above 4 were observed close to Tulcea city (13.11.1981, Mw = 5.1, 03.09.204, Mw =5.1) and Galati city (11.09.1980, Mw = 4.2). Recently, an earthquake swarm of 406 events extended over two months and a half (23 September - 5 December 2013) was produced in the Galati area (maximum magnitude 3.9). The deformation field has an extensional regime, as resulted from fault plane solutions and geotectonic investigations. The maximum expected magnitude in this area is estimated at Mw = 5.5. The <span class="hlt">seismic</span> activity in the Black Sea area, close to Romania seashore and north-east Bulgarian seashore, concentrates along Shabla fault <span class="hlt">system</span>. Large shocks (magnitude above 7) are reported here at intervals of a few centuries. The most recent major shock was recorded on 31 January 1901 (Mw = 7.2) in Shabla region, Bulgaria. To characterize <span class="hlt">seismicity</span> parameters, the Romanian catalogue of the National Institute of Earth Physics was used as a basic input. The catalogue was revised as concerns historical information by reanalyzing macroseismic data and for the recent events, by applying up-to-date tools to relocate and re-parametrize the <span class="hlt">seismic</span> sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860017517','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860017517"><span>Regularity estimates up to the <span class="hlt">boundary</span> for elliptic <span class="hlt">systems</span> of difference equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strikwerda, J. C.; Wade, B. A.; Bube, K. P.</p> <p>1986-01-01</p> <p>Regularity estimates up to the <span class="hlt">boundary</span> for solutions of elliptic <span class="hlt">systems</span> of finite difference equations were proved. The regularity estimates, obtained for <span class="hlt">boundary</span> fitted coordinate <span class="hlt">systems</span> on domains with smooth <span class="hlt">boundary</span>, involve discrete Sobolev norms and are proved using pseudo-difference operators to treat <span class="hlt">systems</span> with variable coefficients. The elliptic <span class="hlt">systems</span> of difference equations and the <span class="hlt">boundary</span> conditions which are considered are very general in form. The regularity of a regular elliptic <span class="hlt">system</span> of difference equations was proved equivalent to the nonexistence of eigensolutions. The regularity estimates obtained are analogous to those in the theory of elliptic <span class="hlt">systems</span> of partial differential equations, and to the results of Gustafsson, Kreiss, and Sundstrom (1972) and others for hyperbolic difference equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812319K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812319K"><span>Evaluation of induced <span class="hlt">seismicity</span> forecast models in the Induced <span class="hlt">Seismicity</span> Test Bench</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan</p> <p>2016-04-01</p> <p>Induced earthquakes often accompany fluid injection, and the <span class="hlt">seismic</span> hazard they pose threatens various underground engineering projects. Models to monitor and control induced <span class="hlt">seismic</span> hazard with traffic light <span class="hlt">systems</span> should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced <span class="hlt">Seismicity</span> Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and <span class="hlt">Seismics</span> (HySei). SiS is based on three pillars: the <span class="hlt">seismicity</span> rate is computed with help of the seismogenic index and a simple exponential decay of the <span class="hlt">seismicity</span>; the magnitude distribution follows the Gutenberg-Richter relation; and <span class="hlt">seismicity</span> is distributed in space based on smoothing <span class="hlt">seismicity</span> during the learning period with 3D Gaussian kernels. The HySei model describes <span class="hlt">seismicity</span> triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the <span class="hlt">seismicity</span> rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the <span class="hlt">seismicity</span> rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the <span class="hlt">seismicity</span> rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2010/1083/l/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2010/1083/l/"><span><span class="hlt">Seismicity</span> of the Earth 1900-2012 Sumatra and vicinity</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hayes, Gavin P.; Bernardino, Melissa; Dannemann, Fransiska; Smoczyk, Gregory; Briggs, Richard W.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio</p> <p>2013-01-01</p> <p>The plate <span class="hlt">boundary</span> southwest of Sumatra is part of a long tectonic collision zone that extends over 8,000 km from Papua, New Guinea, in the east to the Himalayan front in the west. The Sumatra-Andaman part of the collision zone forms a subduction zone plate <span class="hlt">boundary</span>, which accommodates convergence between the Indo-Australia and Sunda plates. This convergence is responsible for the intense <span class="hlt">seismicity</span> in Sumatra. The Sumatra Fault, a major transform structure that bisects Sumatra, accommodates the northwest-increasing lateral component of relative plate motion. Most strain accumulation and release between the two plates occurs along the Sunda megathrust. The increasingly oblique convergence moving northwest is accommodated by crustal <span class="hlt">seismicity</span> along several transform and normal faults, including the Sumatra Fault. Plate-<span class="hlt">boundary</span> related deformation is also not restricted to the subduction zone and overriding plate: the Indo-Australian plate actually comprises two somewhat independent plates (India and Australia) that are joined along a broad, actively deforming region that produces <span class="hlt">seismicity</span> up to several hundred kilometers west of the trench. This deformation is exemplified by the recent April 2012 earthquake sequence, which includes the April 11 M 8.6 and M 8.2 strike-slip events and their subsequent aftershocks. Since 2004, much of the Sunda megathrust between the northern Andaman Islands and Enggano Island, a distance of more than 2,000 km, has ruptured in a series of large subduction zone earthquakes—most rupturing the plate <span class="hlt">boundary</span> south of Banda Aceh. These events include the great M 9.1 earthquake of December 26, 2004; the M 8.6 Nias Island earthquake of March 28, 2005; and two earthquakes on September 12, 2007, of M 8.5 and M 7.9. On October 25, 2010, a M 7.8 on the shallow portion of the megathrust to the west of the Mentawai Islands caused a substantial tsunami on the west coast of those islands.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG21A0138D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG21A0138D"><span>The Influence of Heat Flux <span class="hlt">Boundary</span> Heterogeneity on Heat Transport in Earth's Core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davies, C. J.; Mound, J. E.</p> <p>2017-12-01</p> <p>Rotating convection in planetary <span class="hlt">systems</span> can be subjected to large lateral variations in heat flux from above; for example, due to the interaction between the metallic cores of terrestrial planets and their overlying silicate mantles. The <span class="hlt">boundary</span> anomalies can significantly reorganise the pattern of convection and influence global diagnostics such as the Nusselt number. We have conducted a suite of numerical simulations of rotating convection in a spherical shell geometry comparing convection with homogeneous <span class="hlt">boundary</span> conditions to that with two patterns of heat flux variation at the outer <span class="hlt">boundary</span>: one hemispheric pattern, and one derived from <span class="hlt">seismic</span> tomographic imaging of Earth's lower mantle. We consider Ekman numbers down to 10-6 and flux-based Rayleigh numbers up to 800 times critical. The heterogeneous <span class="hlt">boundary</span> conditions tend to increase the Nusselt number relative to the equivalent homogeneous case by altering both the flow and temperature fields, particularly near the top of the convecting region. The enhancement in Nusselt number tends to increase as the amplitude and wavelength of the <span class="hlt">boundary</span> heterogeneity is increased and as the <span class="hlt">system</span> becomes more supercritical. In our suite of models, the increase in Nusselt number can be as large as 25%. The slope of the Nusselt-Rayleigh scaling also changes when <span class="hlt">boundary</span> heterogeneity is included, which has implications when extrapolating to planetary conditions. Additionally, regions of effective thermal stratification can develop when strongly heterogeneous heat flux conditions are applied at the outer <span class="hlt">boundary</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMDI12A..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMDI12A..05S"><span><span class="hlt">Seismic</span> Velocity Anomalies in the Outer Core: The Final Frontier</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stevenson, D. J.</p> <p>2008-12-01</p> <p>Variation in density along outer core geoid surfaces must be very small (of order one part in a billion) since the resulting fluid motions and buoyancy fluxes would otherwise be prohibitively large for any reasonable choice of outer core viscosity. In any situation where <span class="hlt">seismic</span> velocity variations are proportional to density variations (a generalized Birch's "law") this means that the resulting <span class="hlt">seismic</span> travel time variations in the outer core would be unobservable. The largest lateral variations in the outer core are thus likely to arise from the distortion of geoid surfaces caused by density anomalies in the mantle or inner core. However, these do not change on decadal timescales and would be very difficult to separate from the inner core or mantle variations that cause them. Nonetheless, a recent study (Dai and Song, GRL, vol. 35, L16311, doi:10.1029/2008GL034895) provides evidence for time-variable outer core <span class="hlt">seismic</span> velocity at the level of ten parts per million. Assuming this is real, I argue that the best candidate explanation is that all or part of the outer core is a two-phase medium consisting of a small mass fraction of small (ten or 100 micron-sized) particles of exsolving silicate material suspended in the convecting liquid. The <span class="hlt">seismic</span> velocity of this two phase medium can vary at the desired level should the size distribution of particles vary from place to place (and with time) as one would expect in a convecting <span class="hlt">system</span>, even though the mean density of the medium is invariant at the level of a part per billion, as required by dynamical considerations (thus invalidating Birch's "law"). The <span class="hlt">seismic</span> velocity variation depends on the ratio of diffusion times to <span class="hlt">seismic</span> periods, where the diffusion times are thermal or compositional for the particles or the particle spacing. This idea is not new (cf. Stevenson, JGR, 1983) but gains increased impetus from recent work on the nature of core formation and the desirability of an additional energy source for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.U23B..04G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.U23B..04G"><span>Improvement of real-time <span class="hlt">seismic</span> magnitude estimation by combining <span class="hlt">seismic</span> and geodetic instrumentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goldberg, D.; Bock, Y.; Melgar, D.</p> <p>2017-12-01</p> <p>Rapid <span class="hlt">seismic</span> magnitude assessment is a top priority for earthquake and tsunami early warning <span class="hlt">systems</span>. For the largest earthquakes, <span class="hlt">seismic</span> instrumentation tends to underestimate the magnitude, leading to an insufficient early warning, particularly in the case of tsunami evacuation orders. GPS instrumentation provides more accurate magnitude estimations using near-field stations, but isn't sensitive enough to detect the first <span class="hlt">seismic</span> wave arrivals, thereby limiting solution speed. By optimally combining collocated <span class="hlt">seismic</span> and GPS instruments, we demonstrate improved solution speed of earthquake magnitude for the largest <span class="hlt">seismic</span> events. We present a real-time implementation of magnitude-scaling relations that adapts to consider the length of the recording, reflecting the observed evolution of ground motion with time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6640467','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/6640467"><span><span class="hlt">Seismic</span> event classification <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Dowla, F.U.; Jarpe, S.P.; Maurer, W.</p> <p>1994-12-13</p> <p>In the computer interpretation of <span class="hlt">seismic</span> data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a <span class="hlt">seismic</span> event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities. 21 figures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H11E0850J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H11E0850J"><span>Joint inversion of <span class="hlt">seismic</span> refraction and resistivity data using layered models - applications to hydrogeology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Juhojuntti, N. G.; Kamm, J.</p> <p>2010-12-01</p> <p>We present a layered-model approach to joint inversion of shallow <span class="hlt">seismic</span> refraction and resistivity (DC) data, which we believe is a seldom tested method of addressing the problem. This method has been developed as we believe that for shallow sedimentary environments (roughly <100 m depth) a model with a few layers and sharp layer <span class="hlt">boundaries</span> better represents the subsurface than a smooth minimum-structure (grid) model. Due to the strong assumption our model parameterization implies on the subsurface, only a low number of well resolved model parameters has to be estimated, and provided that this assumptions holds our method can also be applied to other environments. We are using a least-squares inversion, with lateral smoothness constraints, allowing lateral variations in the <span class="hlt">seismic</span> velocity and the resistivity but no vertical variations. One exception is a positive gradient in the <span class="hlt">seismic</span> velocity in the uppermost layer in order to get diving rays (the refractions in the deeper layers are modeled as head waves). We assume no connection between <span class="hlt">seismic</span> velocity and resistivity, and these parameters are allowed to vary individually within the layers. The layer <span class="hlt">boundaries</span> are, however, common for both parameters. During the inversion lateral smoothing can be applied to the layer <span class="hlt">boundaries</span> as well as to the <span class="hlt">seismic</span> velocity and the resistivity. The number of layers is specified before the inversion, and typically we use models with three layers. Depending on the type of environment it is possible to apply smoothing either to the depth of the layer <span class="hlt">boundaries</span> or to the thickness of the layers, although normally the former is used for shallow sedimentary environments. The smoothing parameters can be chosen independently for each layer. For the DC data we use a finite-difference algorithm to perform the forward modeling and to calculate the Jacobian matrix, while for the <span class="hlt">seismic</span> data the corresponding entities are retrieved via ray-tracing, using components from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990008176','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990008176"><span>Global <span class="hlt">Seismicity</span>: Three New Maps Compiled with Geographic Information <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lowman, Paul D., Jr.; Montgomery, Brian C.</p> <p>1996-01-01</p> <p>This paper presents three new maps of global <span class="hlt">seismicity</span> compiled from NOAA digital data, covering the interval 1963-1998, with three different magnitude ranges (mb): greater than 3.5, less than 3.5, and all detectable magnitudes. A commercially available geographic information <span class="hlt">system</span> (GIS) was used as the database manager. Epicenter locations were acquired from a CD-ROM supplied by the National Geophysical Data Center. A methodology is presented that can be followed by general users. The implications of the maps are discussed, including the limitations of conventional plate models, and the different tectonic behavior of continental vs. oceanic lithosphere. Several little-known areas of intraplate or passive margin <span class="hlt">seismicity</span> are also discussed, possibly expressing horizontal compression generated by ridge push.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T13A2587B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T13A2587B"><span>Actively dewatering fluid-rich zones along the Costa Rica plate <span class="hlt">boundary</span> fault</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Kluesner, J. W.; Ranero, C. R.; von Huene, R.</p> <p>2012-12-01</p> <p>New 3D <span class="hlt">seismic</span> reflection data reveal distinct evidence for active dewatering above a 12 km wide segment of the plate <span class="hlt">boundary</span> fault within the Costa Rica subduction zone NW of the Osa Peninsula. In the spring of 2011 we acquired a 11 x 55 km 3D <span class="hlt">seismic</span> reflection data set on the R/V Langseth using four 6,000 m streamers and two 3,300 in3 airgun arrays to examine the structure of the Costa Rica margin from the trench into the seismogenic zone. We can trace the plate-<span class="hlt">boundary</span> interface from the trench across our entire survey to where the plate-<span class="hlt">boundary</span> thrust lies > 10 km beneath the margin shelf. Approximately 20 km landward of the trench beneath the mid slope and at the updip edge of the seismogenic zone, a 12 km wide zone of the plate-<span class="hlt">boundary</span> interface has a distinctly higher-amplitude <span class="hlt">seismic</span> reflection than deeper or shallower segments of the fault. Directly above and potentially directly connected with this zone are high-amplitude, reversed-polarity fault-plane reflections that extend through the margin wedge and into overlying slope sediment cover. Within the slope cover, high-amplitude reversed-polarity reflections are common within the network of closely-spaced nearly vertical normal faults and several broadly spaced, more gently dipping thrust faults. These faults appear to be directing fluids vertically toward the seafloor, where numerous seafloor fluid flow indicators, such as pockmarks, mounds and ridges, and slope failure features, are distinct in multibeam and backscatter images. There are distinctly fewer seafloor and subsurface fluid flow indicators both updip and downdip of this zone. We believe these fluids come from a 12 km wide fluid-rich segment of the plate-<span class="hlt">boundary</span> interface that is likely overpressured and has relatively low shear stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711588H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711588H"><span><span class="hlt">Seismic</span> stratigraphic architecture of the Disko Bay trough-mouth fan <span class="hlt">system</span>, West Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hofmann, Julia C.; Knutz, Paul C.</p> <p>2015-04-01</p> <p>Spatial and temporal changes of the Greenland Ice Sheet on the continental shelf bordering Baffin Bay remain poorly constrained. Then as now, fast-flowing ice streams and outlet glaciers have played a key role for the mass balance and stability of polar ice sheets. Despite their significance for Greenland Ice Sheet dynamics and evolution, our understanding of their long-term behaviour is limited. The central West Greenland margin is characterized by a broad continental shelf where a series of troughs extend from fjords to the shelf margin, acting as focal points for trough-mouth fan (TMF) accummulations. The sea-ward bulging morphology and abrupt shelf-break of these major depositional <span class="hlt">systems</span> is generated by prograding depocentres that formed during glacial maxima when ice streams reached the shelf edge, delivering large amounts of subglacial sediment onto the continental slope (Ó Cofaigh et al., 2013). The aim of this study is to unravel the <span class="hlt">seismic</span> stratigraphic architecture and depositional processes of the Disko Bay TMF, aerially the largest single sedimentary <span class="hlt">system</span> in West Greenland, using 2D and 3D <span class="hlt">seismic</span> reflection data, seabed bathymetry and stratigraphic information from exploration well Hellefisk-1. The south-west Disko Bay is intersected by a deep, narrow trough, Egedesminde Dyb, which extends towards the southwest and links to the shallower and broader cross-shelf Disko Trough (maximum water depths of > 1000 m and a trough length of c. 370 km). Another trough-like depression (trough length of c. 120 km) in the northern part of the TMF, indicating a previous position of the ice stream, can be distinguished on the seabed topographic map and the <span class="hlt">seismic</span> images. The Disko Bay TMF itself extends from the shelf edge down to the abyssal plain (abyssal floor depths of 2000 m) of the southern Baffin Bay. Based on <span class="hlt">seismic</span> stratigraphic configurations relating to reflection terminations, erosive patterns and <span class="hlt">seismic</span> facies (Mitchum et al., 1977), the TMF</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CQGra..34f5002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CQGra..34f5002B"><span>Passive-performance, analysis, and upgrades of a 1-ton <span class="hlt">seismic</span> attenuation <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bergmann, G.; Mow-Lowry, C. M.; Adya, V. B.; Bertolini, A.; Hanke, M. M.; Kirchhoff, R.; Köhlenbeck, S. M.; Kühn, G.; Oppermann, P.; Wanner, A.; Westphal, T.; Wöhler, J.; Wu, D. S.; Lück, H.; Strain, K. A.; Danzmann, K.</p> <p>2017-03-01</p> <p>The 10 m prototype facility at the Albert-Einstein-institute (AEI) in Hanover, Germany, employs three large <span class="hlt">seismic</span> attenuation <span class="hlt">systems</span> to reduce mechanical motion. The AEI <span class="hlt">seismic-attenuation-system</span> (AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5 Hz. This <span class="hlt">system</span> provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4 Hz and in the vertical direction at 9 Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the <span class="hlt">system</span>. These dampers reduce RMS motion substantially in the frequency range between 10 and 100 Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1977/0224/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1977/0224/"><span>Factors limiting the sensitivity and dynamic range of a <span class="hlt">seismic</span> <span class="hlt">system</span> employing analog magnetic tape recording and a <span class="hlt">seismic</span> amplifier with adjustable gain settings and several output levels</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Eaton, Jerry P.; Van Schaack, John R.</p> <p>1977-01-01</p> <p>In the course of modernizing the low-speed-tape-recorder portable <span class="hlt">seismic</span> <span class="hlt">systems</span> and considering the possibilities for the design of a cassette-tape-recorder <span class="hlt">seismic</span> refraction <span class="hlt">system</span>, the factors that limit the sensitivity and dynamic range of such <span class="hlt">systems</span> have been reviewed. These factors will first be stated briefly, and then their influence on <span class="hlt">systems</span> such as the new 5-day-tape <span class="hlt">seismic</span> <span class="hlt">system</span> will be examined in more detail. To fix ideas, we shall assume that the <span class="hlt">system</span> consists of the following elements: 1. A <span class="hlt">seismic</span> sensor: usually a moving coil inertial seismometer with a period of about 1 second, a coil resistance of about 5000 ohms, and an effective motor constant of 1.0 V/cm/sec (across a 10K load terminating the seismometer sensitivity-and-damping-adjustment resistive network). 2. A <span class="hlt">seismic</span> amplifier/voltage controlled oscillator unit made up of the following components: a) A fixed gain preamplifier with an input resistance of 10K and an internal noise level of 0.5 muVpp referred to the preamp input (0.1 Hz <= freq. <= 30 hz). b) An adjustable gain (0 to 42 db in 6 db steps) intermediate amplifier c) One or more fixed gain output amplifiers. d) Two sections of 6 db/octave bandpass filter serving to couple the 3 amplifier stages together. e) Voltage controlled oscillators for each output amplifier to produce modulated FM carriers for recording on separate tape tracks or modulated FM subcarriers for subsequent multiplexing and direct recording on tape in the California Network format. 3. An analog magnetic tape recorder: e.g. the PI 5100 (15/80 ips recording in the FM mode or in the direct mode with the 'broad-band' variant-of the Cal Net multiplex <span class="hlt">system</span>, or 15/16 ips recording in the direct mode with the standard Cal Net multiplex <span class="hlt">system</span>), or the Sony TC-126 cassette recorder operating in the direct record mode with the standard Cal Net multiplex <span class="hlt">system</span>. 4. Appropriate magnetic tape playback equipment: e.g., the Bell and Howell 3700-B for the PI-5100 or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710641V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710641V"><span>SEISVIZ3D: Stereoscopic <span class="hlt">system</span> for the representation of <span class="hlt">seismic</span> data - Interpretation and Immersion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>von Hartmann, Hartwig; Rilling, Stefan; Bogen, Manfred; Thomas, Rüdiger</p> <p>2015-04-01</p> <p>The <span class="hlt">seismic</span> method is a valuable tool for getting 3D-images from the subsurface. <span class="hlt">Seismic</span> data acquisition today is not only a topic for oil and gas exploration but is used also for geothermal exploration, inspections of nuclear waste sites and for scientific investigations. The <span class="hlt">system</span> presented in this contribution may also have an impact on the visualization of 3D-data of other geophysical methods. 3D-<span class="hlt">seismic</span> data can be displayed in different ways to give a spatial impression of the subsurface.They are a combination of individual vertical cuts, possibly linked to a cubical portion of the data volume, and the stereoscopic view of the <span class="hlt">seismic</span> data. By these methods, the spatial perception for the structures and thus of the processes in the subsurface should be increased. Stereoscopic techniques are e. g. implemented in the CAVE and the WALL, both of which require a lot of space and high technical effort. The aim of the interpretation <span class="hlt">system</span> shown here is stereoscopic visualization of <span class="hlt">seismic</span> data at the workplace, i.e. at the personal workstation and monitor. The <span class="hlt">system</span> was developed with following criteria in mind: • Fast rendering of large amounts of data so that a continuous view of the data when changing the viewing angle and the data section is possible, • defining areas in stereoscopic view to translate the spatial impression directly into an interpretation, • the development of an appropriate user interface, including head-tracking, for handling the increased degrees of freedom, • the possibility of collaboration, i.e. teamwork and idea exchange with the simultaneous viewing of a scene at remote locations. The possibilities offered by the use of a stereoscopic <span class="hlt">system</span> do not replace a conventional interpretation workflow. Rather they have to be implemented into it as an additional step. The amplitude distribution of the <span class="hlt">seismic</span> data is a challenge for the stereoscopic display because the opacity level and the scaling and selection of the data have to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950025817','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950025817"><span>A <span class="hlt">seismic</span> data compression <span class="hlt">system</span> using subband coding</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kiely, A. B.; Pollara, F.</p> <p>1995-01-01</p> <p>This article presents a study of <span class="hlt">seismic</span> data compression techniques and a compression algorithm based on subband coding. The algorithm includes three stages: a decorrelation stage, a quantization stage that introduces a controlled amount of distortion to allow for high compression ratios, and a lossless entropy coding stage based on a simple but efficient arithmetic coding method. Subband coding methods are particularly suited to the decorrelation of nonstationary processes such as <span class="hlt">seismic</span> events. Adaptivity to the nonstationary behavior of the waveform is achieved by dividing the data into separate blocks that are encoded separately with an adaptive arithmetic encoder. This is done with high efficiency due to the low overhead introduced by the arithmetic encoder in specifying its parameters. The technique could be used as a progressive transmission <span class="hlt">system</span>, where successive refinements of the data can be requested by the user. This allows seismologists to first examine a coarse version of waveforms with minimal usage of the channel and then decide where refinements are required. Rate-distortion performance results are presented and comparisons are made with two block transform methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.U41A..06J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.U41A..06J"><span>Ambient <span class="hlt">seismic</span> noise applications for Titan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, J. M.; Zhan, Z.; Clayton, R. W.; Helmberger, D. V.; Tsai, V. C.</p> <p>2010-12-01</p> <p>Titan is Saturn’s largest moon and is host to a myriad of surface, crustal, and perhaps interior dynamic processes (e.g., Lunine & Lorenz 2009; Sotin et al. 2009). Although recent gravity data put constraints on the nature of Titan’s deep interior (Iess et al. 2010), details regarding the layering and crustal structure remain poorly constrained. For example, the crustal thickness derived from modeling of the gravity data suggests a value ~100 km, but with a large uncertainty. There may exist a subsurface ocean or reservoirs of liquid that actively connects with Titan’s hyrdrocarbon-bearing lakes and atmosphere. Cross-correlation of ambient <span class="hlt">seismic</span> noise is an emerging method to study crustal structures (e.g., Shapiro et al. 2005). Recent results show that under certain conditions, such as post-critical reflections, the Moho-reflected shear wave (SmS) can be clearly identified with ambient <span class="hlt">seismic</span> noise [Zhan et al. 2010]. Titan may represent a plausible planetary body to apply the methods of ambient <span class="hlt">seismic</span> noise, thereby providing a unique opportunity to better understand the interior of an icy body in our solar <span class="hlt">system</span>. We will explore the use of ambient <span class="hlt">seismic</span> noise on Titan and assess its application to determine interior structures, such as signals expected for different crust-(ocean)-mantle <span class="hlt">boundary</span> depths. References: Iess, L. et al. (2010), Science 327: 1367-1369 Lunine, J.I. and Lorenz, R.D. (2009), Ann. Rev. Earth Planet. Sci. 37: 299-320. Shapiro et al. (2005), Science 307: 1615-1618. Sotin et al. (2009), in Titan from Cassini-Huygens: 61-73. R.H. Brown, J.-P. Lebreton, J. Hunter Waite, Eds. Zhan, Z. et al. (2010), Geophys. J. Int. doi: 10.1111/j/1365-246X.2010.04625.x Acknowledgments: Parts of this work grew out of discussions during a mini study at the Keck Institute for Space Studies, which is funded by the W. M. Keck Foundation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036467','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036467"><span>Structure of the San Fernando Valley region, California: implications for <span class="hlt">seismic</span> hazard and tectonic history</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Langenheim, V.E.; Wright, T.L.; Okaya, D.A.; Yeats, R.S.; Fuis, G.S.; Thygesen, K.; Thybo, H.</p> <p>2011-01-01</p> <p>Industry <span class="hlt">seismic</span> reflection data, oil test well data, interpretation of gravity and magnetic data, and <span class="hlt">seismic</span> refraction deep-crustal profiles provide new perspectives on the subsurface geology of San Fernando Valley, home of two of the most recent damaging earthquakes in southern California. <span class="hlt">Seismic</span> reflection data provide depths to Miocene–Quaternary horizons; beneath the base of the Late Miocene Modelo Formation are largely nonreflective rocks of the Middle Miocene Topanga and older formations. Gravity and <span class="hlt">seismic</span> reflection data reveal the North Leadwell fault zone, a set of down-to-the-north faults that does not offset the top of the Modelo Formation; the zone strikes northwest across the valley, and may be part of the Oak Ridge fault <span class="hlt">system</span> to the west. In the southeast part of the valley, the fault zone bounds a concealed basement high that influenced deposition of the Late Miocene Tarzana fan and may have localized damage from the 1994 Northridge earthquake. Gravity and <span class="hlt">seismic</span> refraction data indicate that the basin underlying San Fernando Valley is asymmetric, the north part of the basin (Sylmar subbasin) reaching depths of 5–8 km. Magnetic data suggest a major <span class="hlt">boundary</span> at or near the Verdugo fault, which likely started as a Miocene transtensional fault, and show a change in the dip sense of the fault along strike. The northwest projection of the Verdugo fault separates the Sylmar subbasin from the main San Fernando Valley and coincides with the abrupt change in structural style from the Santa Susana fault to the Sierra Madre fault. The Simi Hills bound the basin on the west and, as defined by gravity data, the <span class="hlt">boundary</span> is linear and strikes ~N45°E. That northeast-trending gravity gradient follows both the part of the 1971 San Fernando aftershock distribution called the Chatsworth trend and the aftershock trends of the 1994 Northridge earthquake. These data suggest that the 1971 San Fernando and 1994 Northridge earthquakes reactivated portions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T31D0664C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T31D0664C"><span>Is the Local <span class="hlt">Seismicity</span> in Haiti Capable of Imaging the Northern Caribbean Subduction?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corbeau, J.; Clouard, V.; Rolandone, F.; Leroy, S. D.; de Lepinay, B. M.</p> <p>2017-12-01</p> <p>The <span class="hlt">boundary</span> between the Caribbean (CA) and North American (NAM) plates in the Hispaniola region is the western prolongation of the NAM plate subduction evolving from a frontal subduction in the Lesser Antilles to an oblique collision against the Bahamas platform in Cuba. We analyze P-waveforms arriving at 27 broadband <span class="hlt">seismic</span> temporary stations deployed along a 200 km-long N-S transect across Haiti, during the Trans-Haiti project. We compute teleseismic receiver functions using the ETMTRF method, and determine crustal thickness and bulk composition (Vp/Vs) using the H-k stacking method. Three distinctive crustal domains are imaged. We relate these domains to crustal terranes that have been accreted along the plate <span class="hlt">boundary</span> during the northeastwards displacement of the CA plate. We propose a N-S crustal profile across Haiti accounting for the surface geology, shallow structural history and these new seismological constraints. Local <span class="hlt">seismicity</span> recorded by the temporary network from April 2013 to June 2014 is used to relocate the <span class="hlt">seismicity</span>. A total of 593 events were identified with magnitudes ranging from 1.6 to 4.5. This local <span class="hlt">seismicity</span>, predominantly shallow (< 20 km) and situated in the southern part of Haiti along the major Enriquillo-Plantain-Garden strike-slip fault zone (EPGFZ) and offshore in Gonâve Bay, helps us to image deep active structures. Moment tensors for earthquakes with magnitudes between 3 and 4 were calculated by full waveform inversion using the ISOLA software. The analysis of the new moment tensors for the Haiti upper lithosphere indicates that normal, thrust and strike-slip faulting are equitably distributed. We found strike-slip events along the EPGFZ, near the location of the January 12th, 2010 earthquake. Most of the normal events are located in the area of Enriquillo and Azuei lakes, while the thrust events are located on both sides of the southern Peninsula of Haiti. The preliminary <span class="hlt">seismic</span> data of our Haitian network, even noisy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000EOSTr..81..397A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000EOSTr..81..397A"><span>Reassessing the New Madrid <span class="hlt">Seismic</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atkinson, Gail; Bakun, Bill; Bodin, Paul; Boore, David; Camer, Chris; Frankel, Art; Gasperini, Paulo; Gomberg, Joan; Hanks, Tom; Hermann, Bob; Hough, Susan; Johnston, Arch; Kenner, Shelley; Langston, Chuck; Linker, Mark; Mayne, Paul; Petersen, Mark; Powell, Christine; Prescott, Will; Schweig, Eugene; Segall, Paul; Stein, Seth; Stuart, Bill; Tuttle, Martitia; VanArsdale, Roy</p> <p></p> <p>The central enigma of the mid-continent region in the United States known as the New Madrid <span class="hlt">seismic</span> zone (NMSZ; Figure 1) involves the mechanisms that give rise to recurrent great earthquakes far from plate <span class="hlt">boundaries</span>. Given the lack of significant topographic relief that is the hallmark of tectonic activity in most actively deforming regions, most of us feel a need to “pinch ourselves to see if we're dreaming” when confronted with evidence that, at some probability levels, the earthquake hazard throughout the NMSZ is comparable to that estimated for the San Francisco Bay region.Although assessing the hazard in the NMSZ is in many ways more challenging than in the western United States, and the uncertainties are much greater, careful scientific study has led to a consensus on the issues most critical to <span class="hlt">seismic</span> hazard assessment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1183763','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1183763"><span>Development of <span class="hlt">Seismic</span> Isolation <span class="hlt">Systems</span> Using Periodic Materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yan, Yiqun; Mo, Yi-Lung; Menq, Farn-Yuh</p> <p></p> <p>Advanced fast nuclear power plants and small modular fast reactors are composed of thin-walled structures such as pipes; as a result, they do not have sufficient inherent strength to resist <span class="hlt">seismic</span> loads. <span class="hlt">Seismic</span> isolation, therefore, is an effective solution for mitigating earthquake hazards for these types of structures. Base isolation, on which numerous studies have been conducted, is a well-defined structure protection <span class="hlt">system</span> against earthquakes. In conventional isolators, such as high-damping rubber bearings, lead-rubber bearings, and friction pendulum bearings, large relative displacements occur between upper structures and foundations. Only isolation in a horizontal direction is provided; these features are notmore » desirable for the piping <span class="hlt">systems</span>. The concept of periodic materials, based on the theory of solid-state physics, can be applied to earthquake engineering. The periodic material is a material that possesses distinct characteristics that prevent waves with certain frequencies from being transmitted through it; therefore, this material can be used in structural foundations to block unwanted <span class="hlt">seismic</span> waves with certain frequencies. The frequency band of periodic material that can filter out waves is called the band gap, and the structural foundation made of periodic material is referred to as the periodic foundation. The design of a nuclear power plant, therefore, can be unified around the desirable feature of a periodic foundation, while the continuous maintenance of the structure is not needed. In this research project, three different types of periodic foundations were studied: one-dimensional, two-dimensional, and three-dimensional. The basic theories of periodic foundations are introduced first to find the band gaps; then the finite element methods are used, to perform parametric analysis, and obtain attenuation zones; finally, experimental programs are conducted, and the test data are analyzed to verify the theory. This procedure shows that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.T43H..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.T43H..04C"><span>Subduction Zone Dewatering at the Southern End of New Zealand's Hikurangi Margin - Insights from 2D <span class="hlt">Seismic</span> Tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crutchley, G. J.; Klaeschen, D.</p> <p>2016-12-01</p> <p>The southern end of New Zealand's Hikurangi subduction margin is characterised by highly-oblique convergence as it makes a southward transition into a right-lateral transform plate <span class="hlt">boundary</span>. Long-offset <span class="hlt">seismic</span> data that cross part of the offshore portion of this transition zone give new insight into the nature of the margin. We have carried out two-dimensional pre-stack depth migrations with an iterative reflection tomography to update the velocity field on two <span class="hlt">seismic</span> lines in this area. The depth-migrated sections show much-improved imaging of faulting within the wedge, and the <span class="hlt">seismic</span> velocities themselves give clues about the distribution of gas and/or overpressured regions at the plate <span class="hlt">boundary</span> and within the overlying wedge. A fascinating observation is a major splay fault that has been (or continues to be) a preferred dewatering pathway through the wedge, evidenced by a thermal anomaly that has left its mark on the overlying gas hydrate layer. Another interesting observation is a thick and laterally extensive low velocity zone beneath the subduction interface, which might have important implications for the long-term mechanical stability of the interface. Our on-going work on these data is focused on amplitude versus offset analysis in an attempt to better understand the nature of the subduction interface and also the shallower gas hydrate <span class="hlt">system</span>. This study is an example of how distinct disturbances of the gas hydrate <span class="hlt">system</span> can provide insight into subduction zone fluid flow processes that are important for understanding wedge stability and ultimately earthquake hazard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780021730','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780021730"><span>Application of normal mode theory to <span class="hlt">seismic</span> source and structure problems: <span class="hlt">Seismic</span> investigations of upper mantle lateral heterogeneity. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Okal, E. A.</p> <p>1978-01-01</p> <p>The theory of the normal modes of the earth is investigated and used to build synthetic seismograms in order to solve source and structural problems. A study is made of the physical properties of spheroidal modes leading to a rational classification. Two problems addressed are the observability of deep isotropic <span class="hlt">seismic</span> sources and the investigation of the physical properties of the earth in the neighborhood of the Core-Mantle <span class="hlt">boundary</span>, using SH waves diffracted at the core's surface. Data sets of <span class="hlt">seismic</span> body and surface waves are used in a search for possible deep lateral heterogeneities in the mantle. In both cases, it is found that <span class="hlt">seismic</span> data do not require structural differences between oceans and continents to extend deeper than 250 km. In general, differences between oceans and continents are found to be on the same order of magnitude as the intrinsic lateral heterogeneity in the oceanic plate brought about by the aging of the oceanic lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V43B3132L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V43B3132L"><span>Storage of fluids and melts at subduction zones detectable by <span class="hlt">seismic</span> tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luehr, B. G.; Koulakov, I.; Rabbel, W.; Brotopuspito, K. S.; Surono, S.</p> <p>2015-12-01</p> <p>During the last decades investigations at active continental margins discovered the link between the subduction of fluid saturated oceanic plates and the process of ascent of these fluids and partial melts forming a magmatic <span class="hlt">system</span> that leads to volcanism at the earth surface. For this purpose the geophysical structure of the mantle and crustal range above the down going slap has been imaged. Information is required about the slap, the ascent paths, as well as the reservoires of fluids and partial melts in the mantle and the crust up to the volcanoes at the surface. Statistically the distance between the volcanoes of volcanic arcs down to their Wadati Benioff zone results of approximately 100 kilometers in mean value. Surprisingly, this depth range shows pronounced <span class="hlt">seismicity</span> at most of all subduction zones. Additionally, mineralogical laboratory investigations have shown that dehydration of the diving plate has a maximum at temperature and pressure conditions we find at around 100 km depth. The ascent of the fluids and the appearance of partial melts as well as the distribution of these materials in the crust can be resolved by <span class="hlt">seismic</span> tomographic methods using records of local natural <span class="hlt">seismicity</span>. With these methods these areas are corresponding to lowered <span class="hlt">seismic</span> velocities, high Vp/Vs ratios, as well as increased attenuation of <span class="hlt">seismic</span> shear waves. The anomalies and their time dependence are controlled by the fluids. The <span class="hlt">seismic</span> velocity anomalies detected so far are within a range of a few per cent to more than 30% reduction. But, to explore plate <span class="hlt">boundaries</span> large and complex amphibious experiments are required, in which active and passive <span class="hlt">seismic</span> investigations should be combined to achieve best results. The <span class="hlt">seismic</span> station distribution should cover an area from before the trench up to far behind the volcanic chain, to provide under favorable conditions information down to 150 km depth. Findings of different subduction zones will be compared and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2008/1262/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2008/1262/"><span>Instrumentation Guidelines for the Advanced National <span class="hlt">Seismic</span> <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Working Group on Instrumentation, Siting</p> <p>2008-01-01</p> <p>This document provides guidelines for the <span class="hlt">seismic</span>-monitoring instrumentation used by long-term earthquake-monitoring stations that will sense ground motion, digitize and store the resulting signals in a local data acquisition unit, and optionally transmit these digital data. These guidelines are derived from specifications and requirements for data needed to address the nation's emergency response, engineering, and scientific needs as identified in U.S. Geological Survey Circular 1188 (1999). Data needs are discussed in terms of national, regional, and urban scales of monitoring in section 3. Functional performance specifications for instrumentation are introduced in section 4.3 and discussed in detail in section 6 in terms of instrument classes and definitions described in section 5. <span class="hlt">System</span> aspects and testing recommendations are discussed in sections 7 and 8, respectively. Although U.S. Geological Survey Circular 1188 (1999) recommends that the Advanced National <span class="hlt">Seismic</span> <span class="hlt">System</span> (ANSS) include portable instrumentation, performance specifications for this element are not specifically addressed in this document. Nevertheless, these guidelines are largely applicable to portable instrumentation. Volcano monitoring instrumentation is also beyond the scope of this document. Guidance for ANSS structural-response monitoring is discussed briefly herein but details are deferred to the ANSS document by the ANSS Structural Response Monitoring Committee (U.S. Geological Survey, 2005). Aspects of station planning, siting, and installation other than instrumentation are beyond the scope of this document.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70001345','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70001345"><span>Recurrence of <span class="hlt">seismic</span> migrations along the central California segment of the San Andreas fault <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wood, M.D.; Allen, S.S.</p> <p>1973-01-01</p> <p>VERIFICATIONS of tectonic concepts1 concerning seafloor spreading are emerging in a manner that has direct bearing on earthquake prediction. Although the gross pattern of worldwide <span class="hlt">seismicity</span> contributed to the formulation of the plate tectonic hypothesis, it is the space-time characteristics of this <span class="hlt">seismicity</span> that may contribute more toward understanding the kinematics and dynamics of the driving mechanism long speculated to originate in the mantle. If the lithosphere is composed of plates that move essentially as rigid bodies, then there should be <span class="hlt">seismic</span> edge effects associated with this movement. It is these interplate effects, especially <span class="hlt">seismic</span> migration patterns, that we discuss here. The unidirectional propagation at constant velocity (80 km yr-1 east to west) for earthquakes (M???7.2) on the Antblian fault for the period 1939 to 1956 (ref. 2) is one of the earliest observations of such a phenomenon. Similar studies3,4 of the Alaska Aleutian <span class="hlt">seismic</span> zone and certain regions of the west coast of South America suggest unidirectional and recurring migrations of earthquakes (M???7.7) occur in these areas. Between these two regions along the great transform faults of the west coast of North America, there is some evidence 5 for unidirectional, constant velocity and recurrent migration of great earthquakes. The small population of earthquakes (M>7.2) in Savage's investigation5 indicates a large spatial gap along the San Andreas <span class="hlt">system</span> in central California from 1830 to 1970. Previous work on the <span class="hlt">seismicity</span> of this gap in central California indicates that the recurrence curves remain relatively constant, independent of large earthquakes, for periods up to a century6. Recurrence intervals for earthquakes along the San Andreas Fault have been calculated empirically by Wallace7 on the basis of geological evidence, surface measurements and assumptions restricted to the surficial <span class="hlt">seismic</span> layer. Here we examine the evidence for recurrence of <span class="hlt">seismic</span> migrations along</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApGeo..12...79Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApGeo..12...79Z"><span>Three-component <span class="hlt">seismic</span> data in thin interbedded reservoir exploration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Li-Yan; Wang, Yan-Chun; Pei, Jiang-Yun</p> <p>2015-03-01</p> <p>We present the first successful application of three-component <span class="hlt">seismic</span> data to thin interbedded reservoir characterization in the Daqing placanticline of the LMD oilfield. The oilfield has reached the final high water cut stage and the principal problem is how to recognize the <span class="hlt">boundaries</span> of sand layers that are thicker than 2 m. Conventional interpretation of single PP-wave <span class="hlt">seismic</span> data results in multiple solutions, whereas the introduction of PS-wave enhances the reliability of interpretation. We analyze the gas reservoir characteristics by joint PP- and PS-waves, and use the amplitude and frequency decomposition attributes to delineate the gas reservoir <span class="hlt">boundaries</span> because of the minimal effect of fluids on S-wave. We perform joint inversion of PP- and PS-waves to obtain V P/ V S, λρ, and µ ρ and map the lithology changes by using density, λρ, and µ ρ. The 3D-3C attribute λρ slices describe the sand layers distribution, while considering the well log data, and point to favorable region for tapping the remaining oil.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S51A4388T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S51A4388T"><span><span class="hlt">Seismic</span> Characterization of EGS Reservoirs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Templeton, D. C.; Pyle, M. L.; Matzel, E.; Myers, S.; Johannesson, G.</p> <p>2014-12-01</p> <p>To aid in the <span class="hlt">seismic</span> characterization of Engineered Geothermal <span class="hlt">Systems</span> (EGS), we enhance the traditional microearthquake detection and location methodologies at two EGS <span class="hlt">systems</span>. We apply the Matched Field Processing (MFP) <span class="hlt">seismic</span> imaging technique to detect new <span class="hlt">seismic</span> events using known discrete microearthquake sources. Events identified using MFP are typically smaller magnitude events or events that occur within the coda of a larger event. Additionally, we apply a Bayesian multiple-event <span class="hlt">seismic</span> location algorithm, called MicroBayesLoc, to estimate the 95% probability ellipsoids for events with high signal-to-noise ratios (SNR). Such probability ellipsoid information can provide evidence for determining if a <span class="hlt">seismic</span> lineation could be real or simply within the anticipated error range. We apply this methodology to the Basel EGS data set and compare it to another EGS dataset. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT........50A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT........50A"><span>Teleseismic Array Studies of Earth's Core-Mantle <span class="hlt">Boundary</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexandrakis, Catherine</p> <p>2011-12-01</p> <p>The core mantle <span class="hlt">boundary</span> (CMB) is an inaccessible and complex region, knowledge of which is vital to our understanding of many Earth processes. Above it is the heterogeneous lower-mantle. Below the <span class="hlt">boundary</span> is the outer-core, composed of liquid iron, and/or nickel and some lighter elements. Elucidation of how these two distinct layers interact may enable researchers to better understand the geodynamo, global tectonics, and overall Earth history. One parameter that can be used to study structure and limit potential chemical compositions is <span class="hlt">seismic</span>-wave velocity. Current global-velocity models have significant uncertainties in the 200 km above and below the CMB. In this thesis, these regions are studied using three methods. The upper outer core is studied using two <span class="hlt">seismic</span> array methods. First, a modified vespa, or slant-stack method is applied to <span class="hlt">seismic</span> observations at broadband <span class="hlt">seismic</span> arrays, and at large, dense groups of broadband <span class="hlt">seismic</span> stations dubbed 'virtual' arrays. Observations of core-refracted teleseismic waves, such as SmKS, are used to extract relative arrivaltimes. As with previous studies, lower -mantle heterogeneities influence the extracted arrivaltimes, giving significant scatter. To remove raypath effects, a new method was developed, called Empirical Transfer Functions (ETFs). When applied to SmKS waves, this method effectively isolates arrivaltime perturbations caused by outer core velocities. By removing raypath effects, the signals can be stacked further reducing scatter. The results of this work were published as a new 1D outer-core model, called AE09. This model describes a well-mixed outer core. Two array methods are used to detect lower mantle heterogeneities, in particular Ultra-Low Velocity Zones (ULVZs). The ETF method and beam forming are used to isolate a weak P-wave that diffracts along the CMB. While neither the ETF method nor beam forming could adequately image the low-amplitude phase, beam forms of two events indicate precursors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.2641B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.2641B"><span><span class="hlt">Seismic</span> waves in a self-gravitating planet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brazda, Katharina; de Hoop, Maarten V.; Hörmann, Günther</p> <p>2013-04-01</p> <p>The elastic-gravitational equations describe the propagation of <span class="hlt">seismic</span> waves including the effect of self-gravitation. We rigorously derive and analyze this <span class="hlt">system</span> of partial differential equations and <span class="hlt">boundary</span> conditions for a general, uniformly rotating, elastic, but aspherical, inhomogeneous, and anisotropic, fluid-solid earth model, under minimal assumptions concerning the smoothness of material parameters and geometry. For this purpose we first establish a consistent mathematical formulation of the low regularity planetary model within the framework of nonlinear continuum mechanics. Using calculus of variations in a Sobolev space setting, we then show how the weak form of the linearized elastic-gravitational equations directly arises from Hamilton's principle of stationary action. Finally we prove existence and uniqueness of weak solutions by the method of energy estimates and discuss additional regularity properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70034610','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70034610"><span>On the composition of earth's short-period <span class="hlt">seismic</span> noise field</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Koper, K.D.; Seats, K.; Benz, H.</p> <p>2010-01-01</p> <p>In the classic microseismic band of 5-20 sec, <span class="hlt">seismic</span> noise consists mainly of fundamental mode Rayleigh and Love waves; however, at shorter periods <span class="hlt">seismic</span> noise also contains a significant amount of body-wave energy and higher mode surface waves. In this study we perform a global survey of Earth's short-period <span class="hlt">seismic</span> noise field with the goal of quantifying the relative contributions of these propagation modes. We examined a year's worth of vertical component data from 18 <span class="hlt">seismic</span> arrays of the International Monitoring <span class="hlt">System</span> that were sited in a variety of geologic environments. The apertures of the arrays varied from 2 to 28 km, constraining the periods we analyzed to 0.25-2.5 sec. Using frequency-wavenumber analysis we identified the apparent velocity for each sample of noise and classified its mode of propagation. The dominant component was found to be Lg, occurring in about 50% of the noise windows. Because Lg does not propagate across ocean-continent <span class="hlt">boundaries</span>, this energy is most likely created in shallow water areas near coastlines. The next most common component was P-wave energy, which accounted for about 28% of the noise windows. These were split between regional P waves (Pn=Pg at 6%), mantle bottoming P waves (14%), and core-sensitive waves (PKP at 8%). This energy is mostly generated in deep water away from coastlines, with a region of the North Pacific centered at 165?? W and 40?? N being especially prolific. The remainder of the energy arriving in the noise consisted of Rg waves (28%), a large fraction of which may have a cultural origin. Hence, in contrast to the classic micro-<span class="hlt">seismic</span> band of 5-20 sec, at shorter periods fundamental mode Rayleigh waves are the least significant component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS33B1774A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS33B1774A"><span>Development of Vertical Cable <span class="hlt">Seismic</span> <span class="hlt">System</span> (3)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asakawa, E.; Murakami, F.; Tsukahara, H.; Mizohata, S.; Ishikawa, K.</p> <p>2013-12-01</p> <p>The VCS (Vertical Cable <span class="hlt">Seismic</span>) is one of the reflection <span class="hlt">seismic</span> methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because VCS is an efficient high-resolution 3D <span class="hlt">seismic</span> survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS <span class="hlt">system</span>, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of the survey are from 100m up to 2100m. The target of the survey includes not only hydrothermal deposit but oil and gas exploration. Through these experiments, our VCS data acquisition <span class="hlt">system</span> has been completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation <span class="hlt">system</span> are available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed another approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In the data acquisition stage, we estimate the position of VCS location with slant ranging method from the sea surface. The deep-towed source or ocean bottom source is estimated by SSBL/USBL. The water velocity profile is measured by XCTD. After the data acquisition, we pick the first break times of the VCS recorded data. The estimated positions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036294','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036294"><span>A bayesian approach for determining velocity and uncertainty estimates from <span class="hlt">seismic</span> cone penetrometer testing or vertical <span class="hlt">seismic</span> profiling data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pidlisecky, Adam; Haines, S.S.</p> <p>2011-01-01</p> <p>Conventional processing methods for <span class="hlt">seismic</span> cone penetrometer data present several shortcomings, most notably the absence of a robust velocity model uncertainty estimate. We propose a new <span class="hlt">seismic</span> cone penetrometer testing (SCPT) data-processing approach that employs Bayesian methods to map measured data errors into quantitative estimates of model uncertainty. We first calculate travel-time differences for all permutations of <span class="hlt">seismic</span> trace pairs. That is, we cross-correlate each trace at each measurement location with every trace at every other measurement location to determine travel-time differences that are not biased by the choice of any particular reference trace and to thoroughly characterize data error. We calculate a forward operator that accounts for the different ray paths for each measurement location, including refraction at layer <span class="hlt">boundaries</span>. We then use a Bayesian inversion scheme to obtain the most likely slowness (the reciprocal of velocity) and a distribution of probable slowness values for each model layer. The result is a velocity model that is based on correct ray paths, with uncertainty bounds that are based on the data error. ?? NRC Research Press 2011.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011Tectp.507...47C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011Tectp.507...47C"><span>Arc segmentation and <span class="hlt">seismicity</span> in the Solomon Islands arc, SW Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Ming-Chu; Frohlich, Cliff; Taylor, Frederick W.; Burr, George; van Ufford, Andrew Quarles</p> <p>2011-07-01</p> <p>This paper evaluates neotectonic segmentation in the Solomon Islands forearc, and considers how it relates to regional tectonic evolution and the extent of ruptures of large megathrust earthquakes. We first consider regional geomorphology and Quaternary vertical displacements, especially uplifted coral reef terraces. Then we consider geographic <span class="hlt">seismicity</span> patterns, aftershock areas and vertical displacements for large earthquakes, focal mechanisms, and along-arc variations in <span class="hlt">seismic</span> moment release to evaluate the relationship between neotectonically defined segments and <span class="hlt">seismicity</span>. Notably, one major limitation of using <span class="hlt">seismicity</span> to evaluate arc segmentation is the matter of accurately defining earthquake rupture zones. For example, shoreline uplifts associated with the 1 April 2007 M w 8.1 Western Solomons earthquake indicate that the along-arc extent of rupture was about 50 km smaller than the aftershock area. Thus if we had relied on aftershocks alone to identify the 2007 rupture zone, as we do for most historical earthquakes, we would have missed the rupture's relationship to a major morphologic feature. In many cases, the imprecision of defining rupture zones without surface deformation data may be largely responsible for the poor mismatches to neotectonic <span class="hlt">boundaries</span>. However, when a precise paleoseismic vertical deformation history is absent, aftershocks are often the best available tool for inferring rupture geometries. Altogether we identify 16 segments in the Solomon Islands. These comprise three major tectonic regimes or supersegments that correspond respectively to the forearc areas of Guadalcanal-Makira, the New Georgia island group, and Bougainville Islands. Subduction of the young and relatively shallow and buoyant Woodlark Basin and spreading <span class="hlt">system</span> distinguishes the central New Georgia supersegment from the two neighboring supersegments. The physiographic expression of the San Cristobal trench is largely absent, but bathymetric mapping of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S12A..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S12A..06P"><span>Volcanic Centers in the East Africa Rift: Volcanic Processes with <span class="hlt">Seismic</span> Stresses to Identify Potential Hydrothermal Vents</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patlan, E.; Wamalwa, A. M.; Kaip, G.; Velasco, A. A.</p> <p>2015-12-01</p> <p>The Geothermal Development Company (GDC) in Kenya actively seeks to produce geothermal energy, which lies within the East African Rift <span class="hlt">System</span> (EARS). The EARS, an active continental rift zone, appears to be a developing tectonic plate <span class="hlt">boundary</span> and thus, has a number of active as well as dormant volcanoes throughout its extent. These volcanic centers can be used as potential sources for geothermal energy. The University of Texas at El Paso (UTEP) and the GDC deployed <span class="hlt">seismic</span> sensors to monitor several volcanic centers: Menengai, Silali, and Paka, and Korosi. We identify microseismic, local events, and tilt like events using automatic detection algorithms and manual review to identify potential local earthquakes within our <span class="hlt">seismic</span> network. We then perform the double-difference location method of local magnitude less than two to image the <span class="hlt">boundary</span> of the magma chamber and the conduit feeding the volcanoes. In the process of locating local <span class="hlt">seismicity</span>, we also identify long-period, explosion, and tremor signals that we interpret as magma passing through conduits of the magma chamber and/or fluid being transported as a function of magma movement or hydrothermal activity. We used waveform inversion and S-wave shear wave splitting to approximate the orientation of the local stresses from the vent or fissure-like conduit of the volcano. The microseismic events and long period events will help us interpret the activity of the volcanoes. Our goal is to investigate basement structures beneath the volcanoes and identify the extent of magmatic modifications of the crust. Overall, these <span class="hlt">seismic</span> techniques will help us understand magma movement and volcanic processes in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1067878','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1067878"><span><span class="hlt">Seismic</span> Technology Adapted to Analyzing and Developing Geothermal <span class="hlt">Systems</span> Below Surface-Exposed High-Velocity Rocks Final Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hardage, Bob A.; DeAngelo, Michael V.; Ermolaeva, Elena</p> <p></p> <p>The objective of our research was to develop and demonstrate <span class="hlt">seismic</span> data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component <span class="hlt">seismic</span> test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. <span class="hlt">Seismic</span> contractors have not succeeded in creating good-quality <span class="hlt">seismic</span> data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sedimentmore » were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the <span class="hlt">boundaries</span> of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled <span class="hlt">seismic</span> data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the <span class="hlt">boundaries</span> of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave <span class="hlt">seismic</span> data for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAfES.132...27G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAfES.132...27G"><span>Aptian-Albian <span class="hlt">boundary</span> in Central Southern Atlas of Tunisia: New tectono-sedimentary facts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghanmi, Mohamed Abdelhamid; Barhoumi, Amine; Ghanmi, Mohamed; Zargouni, Fouad</p> <p>2017-08-01</p> <p>The Aptian-Albian <span class="hlt">boundary</span> preserves one of the most important events in Central-Southern Atlas of Tunisia, which belongs to the Southern Tethyan margin. A major sedimentary break was recorded between Early Aptian and Albian series in Bouhedma-Boudouaou Mountains. This major hiatus probably linked to the ''Austrian phase'' and to the Aptian and Albian ''Crisis'' testify a period of major tectonic events. In this paper, field observations on the Mid-Cretaceous stratigraphy combined with <span class="hlt">seismic</span> profile interpretation were used for the first time to characterize the Aptian-Albian <span class="hlt">boundary</span> in Central-Southern Atlas of Tunisia. Our new results reveal that Aptian-Albian <span class="hlt">boundary</span> marks a critical interval not only in Maknassy-Mezzouna orogenic <span class="hlt">system</span> but also in the Tunisian Atlas. Furthermore, Aptian-Albian series outcrop is marked by the important sedimentary gaps as well as a dramatic thickness change from West to East and predominately from North to South. This is linked to the extensional tectonic features which characterize all the Central-Southern Atlas of Tunisia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036303','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036303"><span><span class="hlt">Seismic</span> and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.</p> <p>2011-01-01</p> <p>We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and <span class="hlt">seismic</span> modes as along crustal- and plate-scale <span class="hlt">boundaries</span>. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station <span class="hlt">seismic</span> network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of <span class="hlt">seismic</span> signals, nearly all of which originated outside the monitoring network <span class="hlt">boundaries</span> or from the side-bounding strike-slip faults. The landslide basal surface beneath our <span class="hlt">seismic</span> network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as <span class="hlt">seismically</span> radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S12C..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S12C..01W"><span>A High-Resolution View of Global <span class="hlt">Seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waldhauser, F.; Schaff, D. P.</p> <p>2014-12-01</p> <p>We present high-precision earthquake relocation results from our global-scale re-analysis of the combined <span class="hlt">seismic</span> archives of parametric data for the years 1964 to present from the International Seismological Centre (ISC), the USGS's Earthquake Data Report (EDR), and selected waveform data from IRIS. We employed iterative, multistep relocation procedures that initially correct for large location errors present in standard global earthquake catalogs, followed by a simultaneous inversion of delay times formed from regional and teleseismic arrival times of first and later arriving phases. An efficient multi-scale double-difference (DD) algorithm is used to solve for relative event locations to the precision of a few km or less, while incorporating information on absolute hypocenter locations from catalogs such as EHB and GEM. We run the computations on both a 40-core cluster geared towards HTC problems (data processing) and a 500-core HPC cluster for data inversion. Currently, we are incorporating waveform correlation delay time measurements available for events in selected regions, but are continuously building up a comprehensive, global correlation database for densely distributed events recorded at stations with a long history of high-quality waveforms. The current global DD catalog includes nearly one million earthquakes, equivalent to approximately 70% of the number of events in the ISC/EDR catalogs initially selected for relocation. The relocations sharpen the view of <span class="hlt">seismicity</span> in most active regions around the world, in particular along subduction zones where event density is high, but also along mid-ocean ridges where existing hypocenters are especially poorly located. The new data offers the opportunity to investigate earthquake processes and fault structures along entire plate <span class="hlt">boundaries</span> at the ~km scale, and provides a common framework that facilitates analysis and comparisons of findings across different plate <span class="hlt">boundary</span> <span class="hlt">systems</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915914M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915914M"><span>A <span class="hlt">seismicity</span> <span class="hlt">boundary</span> in the low-strain region of Alentejo, south Portugal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matos, Catarina; Zahradník, Jirí; Arroucau, Pierre; Silveira, Graça; Custódio, Susana</p> <p>2017-04-01</p> <p>Mainland Portugal lays on a stable continental setting characterized by low strain rates (convergence velocities < 1 mm/yr). However, the region has been the source of documented moderate magnitude earthquakes. The Alentejo region (south Portugal) presents belts of high epicenter density, the two main ones being (1) the Viana do Alentejo cluster in the south and (2) the NW-SE oriented Arraiolos alignment in the north. The latter appears as a sharp transition between a nearly aseismic area to the north and a <span class="hlt">seismically</span> active area to the south. Active fault studies based on geological observations have not identified tectonic features able to explain the observed <span class="hlt">seismicity</span> patterns. Our objective is to contribute to the understanding of the deformation pattern in south Portugal. Several hypotheses need to be addressed: (1) Are those clusters the expression of a broad region of distributed deformation?; (2) Do they mark structures that might have the potential to generate moderate magnitude events? We use a high-quality dataset recorded by a temporary array deployed in the area to produce a robust image of earthquake locations and to compute focal mechanisms. Newly detected events match well the previously identified earthquake alignments. The local network provides good control of the focal depths. We observe a spatial variation in the depth distribution. The Arraiolos alignment seems to produce deeper earthquakes than the Viana do Alentejo cluster. Earthquake locations inferred using 1D and 3D velocity models show a persistent concentration of <span class="hlt">seismicity</span> at middle to lower crust depths (15 - 30 km) in the SE section of that alignment. We also present relocation of instrumental <span class="hlt">seismicity</span> for the period (1970-2016). Previous studies show that a strike-slip faulting regime dominates mainland Portugal. IPMA (Instituto Português do Mar e da Atmosfera) routinely computes focal mechanisms for earthquakes with reported local magnitudes of 3.5 or greater using the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14..452Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14..452Z"><span>The influence of the mining operation on the mine <span class="hlt">seismicity</span> of Vorkuta coal deposit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zmushko, T.; Turuntaev, S. B.; Kulikov, V. I.</p> <p>2012-04-01</p> <p>The mine <span class="hlt">seismicity</span> of Vorkuta coal deposit was analyzed. <span class="hlt">Seismic</span> network consisting of 24 <span class="hlt">seismic</span> sensors (accelerometers) cover the area of "Komsomolskaya" and "North" mines of Vorkuta deposit. Also there is <span class="hlt">seismic</span> station of IDG RAS with three-component seismometer near this mines for better defining energy of the <span class="hlt">seismic</span> events. The catalogs of <span class="hlt">seismic</span> events contain 9000 and 7000 events with maximum magnitude M=2.3 for "Komsomolskaya" and "North" mines respectively and include the period from 01.09.2008 to 01.09.2011. The b-value of the magnitude-frequency relation was -1.0 and -1.15 respectively for the mines, meanwhile b-value for the nature <span class="hlt">seismicity</span> was -0,9. It was found, that the number of <span class="hlt">seismic</span> events per hour during mine combine operation is higher in 2.5 times than the number of <span class="hlt">seismic</span> events during the break in the operation. Also, the total energy of the events per hour during the operation is higher in 3-5 times than during the break. The study showed, that the number and the energy of the <span class="hlt">seismic</span> events relate with the hours of mine combine operation. The spatial distribution of the <span class="hlt">seismic</span> events showed, that 80% of all events and 85% of strong events (M>1.6) were located in and near the longwall under development during the mine combine operations as well asduring the breaks. The isoclines of <span class="hlt">seismic</span> event numbers proved that the direction of motion of the <span class="hlt">boundary</span> of <span class="hlt">seismic</span> events extension coincides with the direction of development, the maximum number of events for any period lies within the wall under operation. The rockburst with M=2.3 occurring at the North mine at July 16, 2011 was considered. The dependences of the energy and of the number of events with different magnitudes on the time showed that the number of events with M=1 and especially M=0.5 before the rockburst decreased, which corresponds to the prognostic <span class="hlt">seismic</span> quietness, described in the research works. The spatial distribution of the events for the 6 month before the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNH53B0148S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNH53B0148S"><span>Submarine Landslide Hazards Offshore Southern Alaska: <span class="hlt">Seismic</span> Strengthening Versus Rapid Sedimentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sawyer, D.; Reece, R.; Gulick, S. P. S.; Lenz, B. L.</p> <p>2017-12-01</p> <p>The southern Alaskan offshore margin is prone to submarine landslides and tsunami hazards due to <span class="hlt">seismically</span> active plate <span class="hlt">boundaries</span> and extreme sedimentation rates from glacially enhanced mountain erosion. We examine the submarine landslide potential with new shear strength measurements acquired by Integrated Ocean Drilling Program Expedition 341 on the continental slope and Surveyor Fan. These data reveal lower than expected sediment strength. Contrary to other active margins where <span class="hlt">seismic</span> strengthening enhances slope stability, the high-sedimentation margin offshore southern Alaska behaves like a passive margin from a shear strength perspective. We interpret that <span class="hlt">seismic</span> strengthening occurs but is offset by high sedimentation rates and overpressure within the slope and Surveyor Fan. This conclusion is supported because shear strength follows an expected active margin profile outside of the fan, where background sedimentation rates occur. More broadly, <span class="hlt">seismically</span> active margins with wet-based glaciers are susceptible to submarine landslide hazards because of the combination of high sedimentation rates and earthquake shaking</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNH23B..01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNH23B..01C"><span>Toward uniform probabilistic <span class="hlt">seismic</span> hazard assessments for Southeast Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chan, C. H.; Wang, Y.; Shi, X.; Ornthammarath, T.; Warnitchai, P.; Kosuwan, S.; Thant, M.; Nguyen, P. H.; Nguyen, L. M.; Solidum, R., Jr.; Irsyam, M.; Hidayati, S.; Sieh, K.</p> <p>2017-12-01</p> <p>Although most Southeast Asian countries have <span class="hlt">seismic</span> hazard maps, various methodologies and quality result in appreciable mismatches at national <span class="hlt">boundaries</span>. We aim to conduct a uniform assessment across the region by through standardized earthquake and fault databases, ground-shaking scenarios, and regional hazard maps. Our earthquake database contains earthquake parameters obtained from global and national <span class="hlt">seismic</span> networks, harmonized by removal of duplicate events and the use of moment magnitude. Our active-fault database includes fault parameters from previous studies and from the databases implemented for national <span class="hlt">seismic</span> hazard maps. Another crucial input for <span class="hlt">seismic</span> hazard assessment is proper evaluation of ground-shaking attenuation. Since few ground-motion prediction equations (GMPEs) have used local observations from this region, we evaluated attenuation by comparison of instrumental observations and felt intensities for recent earthquakes with predicted ground shaking from published GMPEs. We then utilize the best-fitting GMPEs and site conditions into our <span class="hlt">seismic</span> hazard assessments. Based on the database and proper GMPEs, we have constructed regional probabilistic <span class="hlt">seismic</span> hazard maps. The assessment shows highest <span class="hlt">seismic</span> hazard levels near those faults with high slip rates, including the Sagaing Fault in central Myanmar, the Sumatran Fault in Sumatra, the Palu-Koro, Matano and Lawanopo Faults in Sulawesi, and the Philippine Fault across several islands of the Philippines. In addition, our assessment demonstrates the important fact that regions with low earthquake probability may well have a higher aggregate probability of future earthquakes, since they encompass much larger areas than the areas of high probability. The significant irony then is that in areas of low to moderate probability, where building codes are usually to provide less <span class="hlt">seismic</span> resilience, <span class="hlt">seismic</span> risk is likely to be greater. Infrastructural damage in East Malaysia during the 2015</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM23D..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM23D..01M"><span>Magnetopause <span class="hlt">Boundary</span> Processes Throughout the Solar <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masters, A.</p> <p>2014-12-01</p> <p>Earth is not the only planet in the Solar <span class="hlt">System</span> with a natural magnetic shield. Mercury, Jupiter, Saturn, Uranus, and Neptune are similarly protected from the solar wind and cosmic rays. However, like our planet, the magnetic shielding of each of these magnetized planets can break down, driving energy flow through each planetary magnetosphere. Although studies of the magnetopause <span class="hlt">boundary</span> of Earth's magnetosphere have shed considerable light on the processes that lead to this breakdown, the extent to which we can apply this understanding to the diverse space plasma environments surrounding other planets remains unclear. Here we review what we have learnt so far about the operation of magnetopause <span class="hlt">boundary</span> processes at all the magnetized planets in the Solar <span class="hlt">System</span>, and outline some of the relevant outstanding questions. We start by consolidating present understanding of terrestrial magnetopause processes, which is our reference when considering other <span class="hlt">boundaries</span>. We focus on selected processes (magnetic reconnection, Kelvin-Helmholtz instability), compare how we expect them to operate at each planetary magnetopause, and assess whether or not this is consistent with in situ spacecraft observations. For each planetary magnetosphere we then discuss the nature of the total interaction with the solar wind, and whether this is expected to be dominant over internal drivers of magnetospheric dynamics. A combination of further spacecraft exploration and dedicated numerical modeling is required in order to address the many outstanding questions concerning this topic. Progress in this direction would have broad implications for other space plasma <span class="hlt">systems</span>, in our solar <span class="hlt">system</span> and beyond.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.V12B1419N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.V12B1419N"><span>Pressure changes of volcanic <span class="hlt">systems</span> derived from <span class="hlt">seismic</span> signals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neuberg, J. W.; Sturton, S.</p> <p>2002-12-01</p> <p><span class="hlt">Seismic</span> low-frequency events from Soufriere Hills volcano in Montserrat are a superposition of single interface waves travelling along the conduit and leaking into teh volcanic edifice at the upper end of a conduit section where magma properties change rapidly. These low-frequency signals are largely characterised by the intermittency of the interface waves, as well as by the dispersion effects they encounter. Using finite difference modelling of the <span class="hlt">seismic</span> wavefield together with simultaneous modelling of magma properties in time and at depth, allows us to link the <span class="hlt">seismic</span> signature directly to magma and conduit parameters. We retrieve a relationship between frequency content of <span class="hlt">seismic</span> signals and governing pressure in the magma which enables us to determine the pressure changes in the magma from spectral characteristics and their temporal changes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850058885&hterms=plate+tectonics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dplate%2Btectonics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850058885&hterms=plate+tectonics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dplate%2Btectonics"><span>A diffuse plate <span class="hlt">boundary</span> model for Indian Ocean tectonics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wiens, D. A.; Demets, C.; Gordon, R. G.; Stein, S.; Argus, D.</p> <p>1985-01-01</p> <p>It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse <span class="hlt">boundary</span>. The <span class="hlt">boundary</span> is a zone of concentrated <span class="hlt">seismicity</span> and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050217107','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050217107"><span>Development of a Real-Time GPS/<span class="hlt">Seismic</span> Displacement Meter: Applications to Civilian Infrastructure in Orange and Western Riverside Counties, California</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bock, Yehuda</p> <p>2005-01-01</p> <p> develop both the wireless networks and the integrated, seamless, and transparent information management <span class="hlt">system</span> that will deliver <span class="hlt">seismic</span>, geodetic, oceanographic, hydrological, ecological, and physical data to a variety of end users in real-time in the San Diego region. CSRC is interested in providing users access to real-time, accurate GPS data for a wide variety of applications including RTK surveying/GIS and positioning of moving platforms such as aircraft and emergency vehicles. SCIGN is interested in upgrading sites to high-frequency real-time operations for rapid earthquake response and GPS seismology. The successful outcome of the project will allow the implementation of similar <span class="hlt">systems</span> elsewhere, particularly in plate <span class="hlt">boundary</span> zones with significant populations and civilian infrastructure. CSRC would like to deploy the GPS/<span class="hlt">Seismic</span> <span class="hlt">System</span> in other parts of California, in particular San Diego, Los Angeles County and the San Francisco Bay Area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51G3016G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51G3016G"><span>Characteristics of <span class="hlt">seismicity</span> in Eritrea (2011-2012): Implications for rifting dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goitom, B.; Hammond, J. O. S.; Kendal, M. J.; Ogubazghi, G.; Keir, D.; Ayele, A.; Illsley-Kemp, F.</p> <p>2015-12-01</p> <p>Eritrea hosts the final stages of on-land East-African rifting, yet questions remain about how rifting transits from the Afar Depression to the Red Sea. In this study, we use data from recent deployments of 6 broadband seismometers in Eritrea together with deployments in Ethiopia to locate <span class="hlt">seismicity</span> and determine the current focus of strain. Over 1000 events have been located with local magnitudes 0.7-5.0. A significant period of <span class="hlt">seismicity</span> was observed on 1 July 2012 around Nabro volcano and is associated with the biggest event of mL 5 preceded by 33 events in the previous two days. It may be related to magma movement below Nabro. Other significant <span class="hlt">seismicity</span> was observed on 25 December 2011 and is correlated with an earthquake of mL 4.2 and associated with 13 other events on the same day. This event is located around Hayli Gubbi and Ale Bagu volcanoes and could be related to the activities around these volcanoes. We use double difference relocations to improve accuracy and show two main clusters of <span class="hlt">seismicity</span>, one oriented NW-SE in the Bada-Alid axis along the north-western <span class="hlt">boundary</span> of the Danakil microplate and the other NE-SW, following the trend of the Biddu-Nabro volcanic complex. Our new estimates of <span class="hlt">seismicity</span> demarcate the <span class="hlt">boundary</span> between the Nubian, Somalian, and Danakil Microplate and suggest that the Danakil microplate may be broken in two along the Biddu-Nabro Volcanic complex. We estimate b-values for the different clusters of events and show that close to the major border faults near Massawa, average b-values are lower (0.65) than that found near the volcanic centres (1.2 - Bada-Alid, 0.81 - Biddu-Nabro). This may indicate that the stress is less in the volcanic regions and the <span class="hlt">seismicity</span> is due to movement of magma fluids and strain is accommodated by the injection of magma. In contrast the earthquakes around Massawa occur in relatively stronger rocks suggesting strain may be accommodated by movement on larger faults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/421039-facies-log-signatures-sequence-boundaries-sembakung-area-tarakan-basin-east-kalimantan-indonesia','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/421039-facies-log-signatures-sequence-boundaries-sembakung-area-tarakan-basin-east-kalimantan-indonesia"><span>Facies and log signatures of sequence <span class="hlt">boundaries</span> in Sembakung area, Tarakan Basin, East Kalimantan, Indonesia</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bambang, P.; Hardjono, M.; Silalahi, L.</p> <p>1996-08-01</p> <p>Tarakan basin is one of the basins in East Kalimantan having a complicated geological condition. Tectonic repetition developed in this area constructed various stratigraphic traps. Sedimentary development in log data shows continuous regression in Meliat and Tabul Formations (Middle Meocene), Santul Formation (Late Miocene), Tarakan Formation (Pliocene) and Bunyu Formation (Pleistocene), Supported by <span class="hlt">seismic</span> data, stratigraphic sequence in the basin is obvious, especially in Sembakung-Bangkudulis area. The sequence <span class="hlt">boundaries</span>, mainly {open_quotes}lowstand{close_quotes} distribution as good prospective trap, can be mapped by applying tract <span class="hlt">systems</span> and studying wavelet extract as <span class="hlt">seismic</span> expression character of a reservoir. Subtle changes in pattern of stratigraphicmore » sequences can become a hint of sedimentary environment and its lithology content, supporting both exploration and exploitation planning.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMDI33B0402O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMDI33B0402O"><span>Reconsideration of F-layer <span class="hlt">seismic</span> model in the south polar region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ohtaki, T.; Kaneshima, S.</p> <p>2017-12-01</p> <p>Previously, we analyzed the <span class="hlt">seismic</span> structure near the inner core <span class="hlt">boundary</span> beneath Antarctica (Ohtaki et al., 2012). In the study, we determined the velocity of the lowermost outer core (F-layer) using amplitude ratio observations between the inner-core phase (PKIKP) and the inner-core grazing/diffracted phase (PKPbc/c-diff). Because the observations are not so sensitive to the F-layer structure, a constant velocity is assumed in the layer to simplify the model. The obtained model (SPR) has a flat velocity zone with a 75 km thick on the inner core <span class="hlt">boundary</span>. With this F-layer structure and using travel times of these phases as well as the phase that reflects at the <span class="hlt">boundary</span>, we determined the <span class="hlt">seismic</span> structure of the inner core in the south polar region. However, a constant velocity layer is unrealistic, although it is reasonable assumption.Recently, we determined F-layer velocity structures more accurately using the combined observations of PKiKP-PKPbc differential travel times and of PKPbc/c-diff dispersion (Ohtaki et al., 2015, 2016). The former observation is sensitive to average velocity in the F-layer; the latter to velocity gradient in the layer. By analyzing these two observations together, we can determine the detailed velocity structure in the F-layer. The surveyed areas are beneath the Northeast Pacific and Australia. The <span class="hlt">seismic</span> velocity models obtained are quite different between the two regions. Thus our results require laterally heterogeneous F-layer, and show that F-layer is more complicated than we ever imagined.Then there is one question; which structure is that of the south polar region close to? Unfortunately, the <span class="hlt">seismic</span> waveforms that we analyzed in the previous study may not have quality high enough to analyze the PKiKP-PKPbc or PKPbc dispersion. However, it would be meaningful to reanalyze the amplitude data and reconsider the F-layer velocity there. And we also estimate how large slope of velocity can be acceptable for the F-layer velocity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Tectp.726..100K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Tectp.726..100K"><span>Micro-<span class="hlt">seismicity</span> and seismotectonic study in Western Himalaya-Ladakh-Karakoram using local broadband <span class="hlt">seismic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kanna, Nagaraju; Gupta, Sandeep; Prakasam, K. S.</p> <p>2018-02-01</p> <p>We document the <span class="hlt">seismic</span> activity and fault plane solutions (FPSs) in the Western Himalaya, Ladakh and Karakoram using data from 16 broadband seismographs operated during June 2002 to December 2003. We locate 206 earthquakes with a local magnitude in the range of 1.5 to 4.9 and calculate FPSs of 19 selected earthquakes based on moment tensor solutions. The earthquakes are distributed throughout the study region and indicate active tectonics in this region. The observed <span class="hlt">seismicity</span> pattern is quite different than a well-defined pattern of <span class="hlt">seismicity</span>, along the Main Central Thrust zone, in the eastern side of the study region (i.e., Kumaon-Garhwal Himalaya). In the Himalaya region, the earthquakes are distributed in the crust and upper mantle, whereas in the Ladakh-Karakoram area the earthquakes are mostly confined up to crustal depths. The fault plane solutions show a mixture of thrust, normal and strike-slip type mechanisms, which are well corroborated with the known faults/tectonics of the region. The normal fault earthquakes are observed along the Southern Tibet Detachment, Zanskar Shear Zone, Tso-Morari dome, and Kaurik-Chango fault; and suggest E-W extension tectonics in the Higher and Tethys Himalaya. The earthquakes of thrust mechanism with the left-lateral strike-slip component are seen along the Kistwar fault. The right-lateral strike-slip faulting with thrust component along the bending of the Main <span class="hlt">Boundary</span> Thrust and Main Central Thrust shows the transpressional tectonics in this part of the Himalaya. The observed earthquakes with right-lateral strike-slip faulting indicate <span class="hlt">seismically</span> active nature of the Karakoram fault.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAESc..64..125Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAESc..64..125Y"><span>Nonlinear dynamic failure process of tunnel-fault <span class="hlt">system</span> in response to strong <span class="hlt">seismic</span> event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Zhihua; Lan, Hengxing; Zhang, Yongshuang; Gao, Xing; Li, Langping</p> <p>2013-03-01</p> <p>Strong earthquakes and faults have significant effect on the stability capability of underground tunnel structures. This study used a 3-Dimensional Discrete Element model and the real records of ground motion in the Wenchuan earthquake to investigate the dynamic response of tunnel-fault <span class="hlt">system</span>. The typical tunnel-fault <span class="hlt">system</span> was composed of one planned railway tunnel and one <span class="hlt">seismically</span> active fault. The discrete numerical model was prudentially calibrated by means of the comparison between the field survey and numerical results of ground motion. It was then used to examine the detailed quantitative information on the dynamic response characteristics of tunnel-fault <span class="hlt">system</span>, including stress distribution, strain, vibration velocity and tunnel failure process. The intensive tunnel-fault interaction during <span class="hlt">seismic</span> loading induces the dramatic stress redistribution and stress concentration in the intersection of tunnel and fault. The tunnel-fault <span class="hlt">system</span> behavior is characterized by the complicated nonlinear dynamic failure process in response to a real strong <span class="hlt">seismic</span> event. It can be qualitatively divided into 5 main stages in terms of its stress, strain and rupturing behaviors: (1) strain localization, (2) rupture initiation, (3) rupture acceleration, (4) spontaneous rupture growth and (5) stabilization. This study provides the insight into the further stability estimation of underground tunnel structures under the combined effect of strong earthquakes and faults.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGE....14.1535S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGE....14.1535S"><span>Unsupervised <span class="hlt">seismic</span> facies analysis with spatial constraints using regularized fuzzy c-means</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Chengyun; Liu, Zhining; Cai, Hanpeng; Wang, Yaojun; Li, Xingming; Hu, Guangmin</p> <p>2017-12-01</p> <p><span class="hlt">Seismic</span> facies analysis techniques combine classification algorithms and <span class="hlt">seismic</span> attributes to generate a map that describes main reservoir heterogeneities. However, most of the current classification algorithms only view the <span class="hlt">seismic</span> attributes as isolated data regardless of their spatial locations, and the resulting map is generally sensitive to noise. In this paper, a regularized fuzzy c-means (RegFCM) algorithm is used for unsupervised <span class="hlt">seismic</span> facies analysis. Due to the regularized term of the RegFCM algorithm, the data whose adjacent locations belong to same classification will play a more important role in the iterative process than other data. Therefore, this method can reduce the effect of <span class="hlt">seismic</span> data noise presented in discontinuous regions. The synthetic data with different signal/noise values are used to demonstrate the noise tolerance ability of the RegFCM algorithm. Meanwhile, the fuzzy factor, the neighbour window size and the regularized weight are tested using various values, to provide a reference of how to set these parameters. The new approach is also applied to a real <span class="hlt">seismic</span> data set from the F3 block of the Netherlands. The results show improved spatial continuity, with clear facies <span class="hlt">boundaries</span> and channel morphology, which reveals that the method is an effective <span class="hlt">seismic</span> facies analysis tool.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S23B0807D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S23B0807D"><span>Statistical Analysis and ETAS Modeling of <span class="hlt">Seismicity</span> Induced by Production of Geothermal Energy from Hydrothermal <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dinske, C.; Langenbruch, C.; Shapiro, S. A.</p> <p>2017-12-01</p> <p>We investigate <span class="hlt">seismicity</span> related to hydrothermal <span class="hlt">systems</span> in Germany and Italy, focussing on temporal changes of <span class="hlt">seismicity</span> rates. Our analysis was motivated by numerical simulations The modeling of stress changes caused by the injection and production of fluid revealed that <span class="hlt">seismicity</span> rates decrease on a long-term perspective which is not observed in the considered case studies. We analyze the waiting time distributions of the <span class="hlt">seismic</span> events in both time domain (inter event times) and fluid volume domain (inter event volume). We find clear indications that the observed <span class="hlt">seismicity</span> comprises two components: (1) <span class="hlt">seismicity</span> that is directly triggered by production and re-injection of fluid, i.e. induced events, and (2) <span class="hlt">seismicity</span> that is triggered by earthquake interactions, i.e. aftershock triggering. In order to better constrain our numerical simulations using the observed induced <span class="hlt">seismicity</span> we apply catalog declustering to seperate the two components. We use the magnitude-dependent space-time windowing approach introduced by Gardner and Knopoff (1974) and test several published algorithms to calculate the space-time windows. After declustering, we conclude that the different hydrothermal reservoirs show a comparable <span class="hlt">seismic</span> response to the circulation of fluid and additional triggering by earthquake interactions. The declustered catalogs contain approximately 50 per cent of the number of events in the original catalogs. We then perform ETAS (Epidemic Type Aftershock; Ogata, 1986, 1988) modeling for two reasons. First, we want to know whether the different reservoirs are also comparable regarding earthquake interaction patterns. Second, if we identify systematic patterns, ETAS modeling can contribute to forecast <span class="hlt">seismicity</span> during production of geothermal energy. We find that stationary ETAS models cannot accurately capture real <span class="hlt">seismicity</span> rate changes. One reason for this finding is given by the rate of observed induced events which is not constant over time. Hence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1612541D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1612541D"><span>High-precision relocation of induced <span class="hlt">seismicity</span> in the geothermal <span class="hlt">system</span> below St. Gallen (Switzerland)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diehl, Tobias; Kraft, Toni; Eduard, Kissling; Nicholas, Deichmann; Clinton, John; Wiemer, Stefan</p> <p>2014-05-01</p> <p>From July to November 2013 a sequence of more than 850 events, of which more than 340 could be located, was triggered in a planned hydrothermal <span class="hlt">system</span> below the city of St. Gallen in eastern Switzerland. <span class="hlt">Seismicity</span> initiated on July 14 and the maximum Ml in the sequence was 3.5, comparable in size with the Ml 3.4 event induced by stimulation below Basel in 2006. To improve absolute locations of the sequence, more than 1000 P and S wave arrivals were inverted for hypocenters and 1D velocity structure. Vp of 5.6-5.8 km/s and a Vp/Vs ratio of 1.82-1.9 in the source region indicate a limestone or shale-type composition and a comparison with a lithological model from a 3D <span class="hlt">seismic</span> model suggests that the <span class="hlt">seismically</span> active streak (height up to 400 m) is within the Mesozoic layer. To resolve the fine structure of the induced <span class="hlt">seismicity</span>, we applied waveform cross-correlation and double-difference algorithms. The results image a NE-SW striking lineament, consistent with a left-lateral fault plane derived from first motion polarities and moment tensor inversions. A spatio-temporal analysis of the relocated <span class="hlt">seismicity</span> shows that, during first acid jobs on July 17, microseismicity propagated towards southwest over the entire future Ml 3.5 rupture plane. The almost vertical focal plane associated with the Ml 3.5 event of July 20 is well imaged by the <span class="hlt">seismicity</span>. The area of the ruptured fault is approximately 675x400 m. <span class="hlt">Seismicity</span> images a change in focal depths along strike, which correlates with a kink or bend in the mapped fault <span class="hlt">system</span> northeast of the Ml 3.5 event. This change might indicate structural differences or a segmentation of the fault. Following the Ml 3.5 event, <span class="hlt">seismicity</span> propagated along strike to the northeast, in a region without any mapped faults, indicating a continuation of the fault segment. <span class="hlt">Seismicity</span> on this segment occurred in September and October. A complete rupture of the NE segment would have the potential to produce a magnitude larger than 3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSM.S43C..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSM.S43C..04C"><span>The Aysen (Southern Chile) 2007 <span class="hlt">Seismic</span> Swarm: Volcanic or Tectonic Origin?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Comte, D.; Gallego, A.; Russo, R.; Mocanu, V.; Murdie, R.; Vandecar, J.</p> <p>2007-05-01</p> <p>The Aysen <span class="hlt">seismic</span> swarm began January 23, 2007, with a magnitude 5.2 (USGS) earthquake and, after an apparent decrease in activity, continued with a magnitude 5.6 event on February 26. The swarm is characterized by numerous felt earthquakes of small to moderate magnitude, located at crustal depths beneath the Aysen Canal, a prominent fiord of the Chilean littoral. The region is characterized by the subduction of an active oceanic spreading ridge: the Chile Ridge, the divergent Nazca-Antarctic plate <span class="hlt">boundary</span>, is currently subducting beneath continental South America along the Chile Trench at approximately 46.5°S, forming a plate triple junction in the vicinity of the Taitao Peninsula, somewhat south and west of the swarm. Also, the Liquine-Ofqui dextral strike- slip fault traverses the Aysen Canal in the vicinity of the swarm. This fault has been interpreted as a 1000 km long dextral intra-arc strike-slip fault zone, consisting of two major strands which extend north from the Chile Margin triple junction. The Liquiñe-Ofqui <span class="hlt">system</span> is marked by several pull-apart basins along its trace through the area. <span class="hlt">Seismic</span> activity along the Liquiñe-Ofqui fault zone has been poorly studied to date, largely because teleseismic events clearly related to the fault have been few, and southern hemisphere <span class="hlt">seismic</span> stations are lacking. However, we deployed a dense temporary broad-band <span class="hlt">seismic</span> network both onland and on the islands in the Aysen region, which allowed us to capture the initial phases of the swarm on some 20 stations, and to determine the background <span class="hlt">seismicity</span> patterns in this area for the two years preceding the swarm. The swarm could be caused by several processes: the spatial and depth distribution of the events suggests that they are well correlated with reactivation of the southern end of the Liquiñe-Ofqui fault, as defined by geologic studies and onshore gravity data collected in southern Chile. The swarm may be related to formation of new volcanic center between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.2674R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.2674R"><span>The <span class="hlt">seismic</span> traffic footprint: Tracking trains, aircraft, and cars <span class="hlt">seismically</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riahi, Nima; Gerstoft, Peter</p> <p>2015-04-01</p> <p>Although naturally occurring vibrations have proven useful to probe the subsurface, the vibrations caused by traffic have not been explored much. Such data, however, are less sensitive to weather and low visibility compared to some common out-of-road traffic sensing <span class="hlt">systems</span>. We study traffic-generated <span class="hlt">seismic</span> noise measured by an array of 5200 geophones that covered a 7 × 10 km area in Long Beach (California, USA) with a receiver spacing of 100 m. This allows us to look into urban vibrations below the resolution of a typical city block. The spatiotemporal structure of the anthropogenic <span class="hlt">seismic</span> noise intensity reveals the Blue Line Metro train activity, departing and landing aircraft in Long Beach Airport and their acceleration, and gives clues about traffic movement along the I-405 highway at night. As low-cost, stand-alone <span class="hlt">seismic</span> sensors are becoming more common, these findings indicate that <span class="hlt">seismic</span> data may be useful for traffic monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T11C4583G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T11C4583G"><span>Subduction zone locking, strain partitioning, intraplate deformation and their implications to <span class="hlt">Seismic</span> Hazards in South America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galgana, G. A.; Mahdyiar, M.; Shen-Tu, B.; Pontbriand, C. W.; Klein, E.; Wang, F.; Shabestari, K.; Yang, W.</p> <p>2014-12-01</p> <p>We analyze active crustal deformation in South America (SA) using published GPS observations and historic <span class="hlt">seismicity</span> along the Nazca Trench and the active Ecuador-Colombia-Venezuela Plate <span class="hlt">boundary</span> Zone. GPS-constrained kinematisc models that incorporate block and continuum techniques are used to assess patterns of regional tectonic deformation and its implications to <span class="hlt">seismic</span> potential. We determine interplate coupling distributions, fault slip-rates, and intraplate crustal strain rates in combination with historic earthquakes within 40 <span class="hlt">seismic</span> zones crust to provide moment rate constraints. Along the Nazca subduction zone, we resolve a series of highly coupled patches, interpreted as high-friction producing "asperities" beneath the coasts of Ecuador, Peru and Chile. These include areas responsible for the 2010 Mw 8.8 Maule Earthquake and the 2014 Mw 8.2 Iquique Earthquake. Predicted tectonic block motions and fault slip rates reveal that the northern part of South America deforms rapidly, with crustal fault slip rates as much as ~20 mm/a. Fault slip and locking patterns reveal that the Oca Ancón-Pilar-Boconó fault <span class="hlt">system</span> plays a key role in absorbing most of the complex eastward and southward convergence patterns in northeastern Colombia and Venezuela, while the near-parallel <span class="hlt">system</span> of faults in eastern Colombia and Ecuador absorb part of the transpressional motion due to the ~55 mm/a Nazca-SA plate convergence. These kinematic models, in combination with historic <span class="hlt">seismicity</span> rates, provide moment deficit rates that reveal regions with high <span class="hlt">seismic</span> potential, such as coastal Ecuador, Bucaramanga, Arica and Antofagasta. We eventually use the combined information from moment rates and fault coupling patterns to further constrain stochastic <span class="hlt">seismic</span> hazard models of the region by implementing realistic trench rupture scenarios (see Mahdyiar et al., this volume).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MarGR..36..343M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MarGR..36..343M"><span>Using <span class="hlt">seismic</span> reflection data to reveal high-resolution structure and pathway of the upper Western <span class="hlt">Boundary</span> Undercurrent core at Eirik Drift</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller-Michaelis, Antje; Uenzelmann-Neben, Gabriele</p> <p>2015-12-01</p> <p>The method of <span class="hlt">seismic</span> oceanography was applied to identify fine structure and pathways of the Western <span class="hlt">Boundary</span> Undercurrent (WBUC) at Eirik Drift, 200 km south of Greenland. Three high-velocity cores of the WBUC were distinguished: a deep core in depths >2600 m which carries Denmark Strait Overflow Water, an upper core in depths between ~1900 and 3000 m transporting Iceland-Scotland Overflow Water, and a split-off of this upper core, which crosses the main crest of Eirik Drift at depths between ~1900 and 2400 m. For the upper WBUC core a detailed analysis of the structure was conducted. The WBUC core has as a domed structure, which changes in style, width and height above seafloor along the lines of the changing topography. We proved not only the influence of the topography on pathway and structure of the WBUC core but also that this information cannot be gained by measuring the overflow waters with discrete CTD stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.S52A..07B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.S52A..07B"><span><span class="hlt">Seismic</span> Catalogue and <span class="hlt">Seismic</span> Network in Haiti</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.</p> <p>2013-05-01</p> <p>The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address <span class="hlt">seismic</span> phenomena. At the moment of the earthquake, there was no <span class="hlt">seismic</span> network operating in the country, and only a partial control of the past <span class="hlt">seismicity</span> was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a <span class="hlt">seismic</span> catalogue providing the necessary input for <span class="hlt">seismic</span> Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a <span class="hlt">seismic</span> catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the <span class="hlt">seismic</span> network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian <span class="hlt">System</span> CARINA. In 2012, the Spanish IGN together</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H33C1333P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H33C1333P"><span>Anisotropic analysis for <span class="hlt">seismic</span> sensitivity of groundwater monitoring wells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, Y.; Hsu, K.</p> <p>2011-12-01</p> <p>Taiwan is located at the <span class="hlt">boundaries</span> of Eurasian Plate and the Philippine Sea Plate. The movement of plate causes crustal uplift and lateral deformation to lead frequent earthquakes in the vicinity of Taiwan. The change of groundwater level trigged by earthquake has been observed and studied in Taiwan for many years. The change of groundwater may appear in oscillation and step changes. The former is caused by <span class="hlt">seismic</span> waves. The latter is caused by the volumetric strain and reflects the strain status. Since the setting of groundwater monitoring well is easier and cheaper than the setting of strain gauge, the groundwater measurement may be used as a indication of stress. This research proposes the concept of <span class="hlt">seismic</span> sensitivity of groundwater monitoring well and apply to DonHer station in Taiwan. Geostatistical method is used to analysis the anisotropy of <span class="hlt">seismic</span> sensitivity. GIS is used to map the sensitive area of the existing groundwater monitoring well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tecto..35.1249Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tecto..35.1249Y"><span>A new view for the geodynamics of Ecuador: Implication in seismogenic source definition and <span class="hlt">seismic</span> hazard assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yepes, Hugo; Audin, Laurence; Alvarado, Alexandra; Beauval, Céline; Aguilar, Jorge; Font, Yvonne; Cotton, Fabrice</p> <p>2016-05-01</p> <p>A new view of Ecuador's complex geodynamics has been developed in the course of modeling <span class="hlt">seismic</span> source zones for probabilistic <span class="hlt">seismic</span> hazard analysis. This study focuses on two aspects of the plates' interaction at a continental scale: (a) age-related differences in rheology between Farallon and Nazca plates—marked by the Grijalva rifted margin and its inland projection—as they subduct underneath central Ecuador, and (b) the rapidly changing convergence obliquity resulting from the convex shape of the South American northwestern continental margin. Both conditions satisfactorily explain several characteristics of the observed <span class="hlt">seismicity</span> and of the interseismic coupling. Intermediate-depth <span class="hlt">seismicity</span> reveals a severe flexure in the Farallon slab as it dips and contorts at depth, originating the El Puyo <span class="hlt">seismic</span> cluster. The two slabs position and geometry below continental Ecuador also correlate with surface expressions observable in the local and regional geology and tectonics. The interseismic coupling is weak and shallow south of the Grijalva rifted margin and increases northward, with a heterogeneous pattern locally associated to the Carnegie ridge subduction. High convergence obliquity is responsible for the North Andean Block northeastward movement along localized fault <span class="hlt">systems</span>. The Cosanga and Pallatanga fault segments of the North Andean Block-South American <span class="hlt">boundary</span> concentrate most of the <span class="hlt">seismic</span> moment release in continental Ecuador. Other inner block faults located along the western border of the inter-Andean Depression also show a high rate of moderate-size earthquake production. Finally, a total of 19 <span class="hlt">seismic</span> source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S43A2475L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S43A2475L"><span>The Great Maule earthquake: <span class="hlt">seismicity</span> prior to and after the main shock from amphibious <span class="hlt">seismic</span> networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lieser, K.; Arroyo, I. G.; Grevemeyer, I.; Flueh, E. R.; Lange, D.; Tilmann, F. J.</p> <p>2013-12-01</p> <p>The Chilean subduction zone is among the <span class="hlt">seismically</span> most active plate <span class="hlt">boundaries</span> in the world and its coastal ranges suffer from a magnitude 8 or larger megathrust earthquake every 10-20 years. The Constitución-Concepción or Maule segment in central Chile between ~35.5°S and 37°S was considered to be a mature <span class="hlt">seismic</span> gap, rupturing last in 1835 and being <span class="hlt">seismically</span> quiet without any magnitude 4.5 or larger earthquakes reported in global catalogues. It is located to the north of the nucleation area of the 1960 magnitude 9.5 Valdivia earthquake and to the south of the 1928 magnitude 8 Talca earthquake. On 27 February 2010 this segment ruptured in a Mw=8.8 earthquake, nucleating near 36°S and affecting a 500-600 km long segment of the margin between 34°S and 38.5°S. Aftershocks occurred along a roughly 600 km long portion of the central Chilean margin, most of them offshore. Therefore, a network of 30 ocean-bottom-seismometers was deployed in the northern portion of the rupture area for a three month period, recording local offshore aftershocks between 20 September 2010 and 25 December 2010. In addition, data of a network consisting of 33 landstations of the GeoForschungsZentrum Potsdam were included into the network, providing an ideal coverage of both the rupture plane and areas affected by post-<span class="hlt">seismic</span> slip as deduced from geodetic data. Aftershock locations are based on automatically detected P wave onsets and a 2.5D velocity model of the combined on- and offshore network. Aftershock <span class="hlt">seismicity</span> analysis in the northern part of the survey area reveals a well resolved <span class="hlt">seismically</span> active splay fault in the accretionary prism of the Chilean forearc. Our findings imply that in the northernmost part of the rupture zone, co-<span class="hlt">seismic</span> slip most likely propagated along the splay fault and not the subduction thrust fault. In addition, the updip limit of aftershocks along the plate interface can be verified to about 40 km landwards from the deformation front. Prior to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1818444F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1818444F"><span><span class="hlt">Seismic</span> attenuation and scattering tomography of rock samples using stochastic wavefields: linking seismology, volcanology, and rock physics.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fazio, Marco; De Siena, Luca; Benson, Phillip</p> <p>2016-04-01</p> <p><span class="hlt">Seismic</span> attenuation and scattering are two attributes that can be linked with porosity and permeability in laboratory experiments. When measuring these two quantities using <span class="hlt">seismic</span> waveforms recorder at lithospheric and volcanic scales the areas of highest heterogeneity, as batches of melt and zones of high deformation, produce anomalous values of the measured quantities, the <span class="hlt">seismic</span> quality factor and scattering coefficient. When employed as indicators of heterogeneity and absorption in volcanic areas these anomalous effects become strong indicators of magma accumulation and tectonic <span class="hlt">boundaries</span>, shaping magmatic chambers and conduit <span class="hlt">systems</span>. We perform attenuation and scattering measurements and imaging using <span class="hlt">seismic</span> waveforms produced in laboratory experiments, at frequencies ranging between the kHz and MHz. As attenuation and scattering are measured from the shape of the envelopes, disregarding phases, we are able to connect the observations with the micro fracturing and petrological quantities previously measured on the sample. Connecting the imaging of dry and saturated samples via these novel attributes with the burst of low-period events with increasing saturation and deformation is a challenge. Its solution could plant the seed for better relating attenuation and scattering tomography measurements to the presence of fluids and gas, therefore creating a novel path for reliable porosity and permeability tomography. In particular for volcanoes, being able to relate attenuation/scattering measurements with low-period micro <span class="hlt">seismicity</span> could deliver new data to settle the debate about if both source and medium can produce <span class="hlt">seismic</span> resonance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAG...143...31P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAG...143...31P"><span>Capabilities of <span class="hlt">seismic</span> and georadar 2D/3D imaging of shallow subsurface of transport route using the Seismobile <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pilecki, Zenon; Isakow, Zbigniew; Czarny, Rafał; Pilecka, Elżbieta; Harba, Paulina; Barnaś, Maciej</p> <p>2017-08-01</p> <p>In this work, the capabilities of the Seismobile <span class="hlt">system</span> for shallow subsurface imaging of transport routes, such as roads, railways, and airport runways, in different geological conditions were presented. The Seismobile <span class="hlt">system</span> combines the advantages of <span class="hlt">seismic</span> profiling using landstreamer and georadar (GPR) profiling. It consists of up to four <span class="hlt">seismic</span> measuring lines and carriage with a suspended GPR antenna. Shallow subsurface recognition may be achieved to a maximum width of 10.5 m for a distance of 3.5 m between the measurement lines. GPR measurement is performed in the axis of the construction. Seismobile allows the measurement time, labour and costs to be reduced due to easy technique of its installation, remote data transmission from geophones to accompanying measuring modules, automated location of the <span class="hlt">system</span> based on GPS and a highly automated method of <span class="hlt">seismic</span> wave excitation. In this paper, the results of field tests carried out in different geological conditions were presented. The methodologies of acquisition, processing and interpretation of <span class="hlt">seismic</span> and GPR measurements were broadly described. Seismograms and its spectrum registered by Seismobile <span class="hlt">system</span> were compared to the ones registered by Geode seismograph of Geometrix. <span class="hlt">Seismic</span> data processing and interpretation software allows for the obtaining of 2D/3D models of P- and S-wave velocities. Combined <span class="hlt">seismic</span> and GPR results achieved sufficient imaging of shallow subsurface to a depth of over a dozen metres. The obtained geophysical information correlated with geological information from the boreholes with good quality. The results of performed tests proved the efficiency of the Seismobile <span class="hlt">system</span> in <span class="hlt">seismic</span> and GPR imaging of a shallow subsurface of transport routes under compound conditions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70189606','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70189606"><span>Analysis of induced <span class="hlt">seismicity</span> in geothermal reservoirs – An overview</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Zang, Arno; Oye, Volker; Jousset, Philippe; Deichmann, Nicholas; Gritto, Roland; McGarr, Arthur F.; Majer, Ernest; Bruhn, David</p> <p>2014-01-01</p> <p> fluid injected) when induced events start to occur far away from the <span class="hlt">boundary</span> of the <span class="hlt">seismic</span> cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020063483','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020063483"><span>New <span class="hlt">Boundary</span> Constraints for Elliptic <span class="hlt">Systems</span> used in Grid Generation Problems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaul, Upender K.; Clancy, Daniel (Technical Monitor)</p> <p>2002-01-01</p> <p>This paper discusses new <span class="hlt">boundary</span> constraints for elliptic partial differential equations as used in grid generation problems in generalized curvilinear coordinate <span class="hlt">systems</span>. These constraints, based on the principle of local conservation of thermal energy in the vicinity of the <span class="hlt">boundaries</span>, are derived using the Green's Theorem. They uniquely determine the so called decay parameters in the source terms of these elliptic <span class="hlt">systems</span>. These constraints' are designed for <span class="hlt">boundary</span> clustered grids where large gradients in physical quantities need to be resolved adequately. It is observed that the present formulation also works satisfactorily for mild clustering. Therefore, a closure for the decay parameter specification for elliptic grid generation problems has been provided resulting in a fully automated elliptic grid generation technique. Thus, there is no need for a parametric study of these decay parameters since the new constraints fix them uniquely. It is also shown that for Neumann type <span class="hlt">boundary</span> conditions, these <span class="hlt">boundary</span> constraints uniquely determine the solution to the internal elliptic problem thus eliminating the non-uniqueness of the solution of an internal Neumann <span class="hlt">boundary</span> value grid generation problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.T43D2696B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.T43D2696B"><span>Plate <span class="hlt">boundary</span> and major fault <span class="hlt">system</span> in the overriding plate within the Shumagin gap at the Alaska-Aleutian subduction zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Becel, A.; Shillington, D. J.; Nedimovic, M. R.; Keranen, K. M.; Li, J.; Webb, S. C.; Kuehn, H.</p> <p>2013-12-01</p> <p>Structure in the overriding plate is one of the parameters that may increase the tsunamigenic potential of a subduction zone but also influence the seismogenic behavior and segmentation of great earthquake rupture. The Alaska-Aleutian margin is characterized by along-strike changes in plate interface coupling over relatively small distances. Here, we present trench normal multichannel <span class="hlt">seismic</span> (MCS) profiles acquired across the Shumagin gap that has not broken in many decades and appears to be weakly coupled. The high fold, deep penetration (636 channel, 8-km long streamer, 6600 cu.in airgun source) MCS data were acquired as part of the ALEUT project. This dataset gives us critical new constraints on the interplate <span class="hlt">boundary</span> that can be traced over ~100 km distance beneath the forearc with high variation in its reflection response with depth. These profiles also reveal the detailed upper plate fault structure and forearc morphology. Clear reflections in the overriding plate appear to delineate one or more large faults that cross the shelf and the upper slope. These faults are observed 75 km back from the trench and seem to branch at depth and connect to the plate interface within this gap at ~11 s twtt. We compare the reflective structure of these faults to that of the plate <span class="hlt">boundary</span> and examine where it intersects the megathrust with respect of the expected downdip limit of coupling. We also compare this major structure with the <span class="hlt">seismicity</span> recorded in this sector. The imaged fault <span class="hlt">system</span> is associated with a large deep basin (~6s twt) that is an inherited structure formed during the pre-Aleutian period. Basins faults appear to have accommodated primarily normal motion, although folding of sediments near the fault and complicated fault geometries in the shallow section may indicate that this fault has accommodated other types of motion during its history that may reflect the stress-state at the megathrust over time. The deformation within the youngest sediment also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S52A..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S52A..08W"><span>Eclogitization-induced mechanical instanility in granulite: Implications for deep <span class="hlt">seismicity</span> in southern Tibet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y.; Shi, F.; Yu, T.; Zhu, L.; Zhang, J.; Gasc, J.; Incel, S.; Schubnel, A.; Li, Z.; Liu, W.; Jin, Z.</p> <p>2017-12-01</p> <p>Southern Tibet is the most active orogenic region on Earth where the Indian plate thrusts under the Eurasian continent, pushing the Moho to unusual depths of 80 km. <span class="hlt">Seismicity</span> is wide spread, reaching 100 km depth. Mechanisms of these deep earthquakes remain enigmatic. Here we examine the hypothesis of metamorphism induced mechanical instability in granulite-facies rocks, which are the dominant constituent in subducted Indian lower crust. We conducted deformation experiments on natural and nominally dry granulite in a DDIA apparatus within the stability fields of both granulite and eclogite. The <span class="hlt">system</span> is interfaced with an acoustic emission (AE) monitoring <span class="hlt">system</span>, allowing in-situ detection of mechanical instability along with the progress of eclogitization. We found that granulite deformed within its own stability field behaved in a ductile fashion without any AE activity. In contrast, numerous AE events were observed during deformation of metastable granulite in the eclogite field. The observed AE activities were episodic. Correlating closely to the AE burst episodes, measured differential stresses rose and fell during deformation, suggesting unstable fault slip. Microstructural observation shows that strain is highly localized around grain <span class="hlt">boundaries</span>, which are decorated by eclogitization products. Time-resolved event location analysis showed large episodes corresponded to the growth of branches of macroscopic faults in recovered samples. It appears that ruptures originate from weakened grain <span class="hlt">boundaries</span>, propagate through grains, and self-organize into macroscopic fault zones. No melting is required in the fault zones to facilitate brittle failure. This process may be responsible for the deep crustal <span class="hlt">seismicity</span> in Southern Tibet and other continental-continental subduction regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JAESc...4..147V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JAESc...4..147V"><span><span class="hlt">Seismicity</span> and deep structure of the Indo-Burman plate margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vaněk, J.; Hanuš, V.; Sitaram, M. V. D.</p> <p></p> <p>Two differently inclined segments of the Wadati-Benioff zone beneath the Chin Hills and Naga Hills segments of the Indo-Burman Ranges were verified on the basis of the geometrical analysis of distribution of 566 earthquakes. The Wadati-Benioff zone and young calc-alkaline volcanism point to the existence of a Mio-Pliocene subduction with the trench at the western <span class="hlt">boundary</span> of the Oligocene Indo-Burman orogenic belt. A <span class="hlt">system</span> of ten <span class="hlt">seismically</span> active fracture zones was delineated in the adjacent Indian and Burman plates, the tectonic pattern of which represents the eastern manifestation of the continental collision of the Indian and Eurasian plates. The position of historical disastrous earthquakes confirms the reality of this pattern.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..185W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..185W"><span>Kernel Smoothing Methods for Non-Poissonian <span class="hlt">Seismic</span> Hazard Analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woo, Gordon</p> <p>2017-04-01</p> <p>For almost fifty years, the mainstay of probabilistic <span class="hlt">seismic</span> hazard analysis has been the methodology developed by Cornell, which assumes that earthquake occurrence is a Poisson process, and that the spatial distribution of epicentres can be represented by a set of polygonal source zones, within which <span class="hlt">seismicity</span> is uniform. Based on Vere-Jones' use of kernel smoothing methods for earthquake forecasting, these methods were adapted in 1994 by the author for application to probabilistic <span class="hlt">seismic</span> hazard analysis. There is no need for ambiguous <span class="hlt">boundaries</span> of polygonal source zones, nor for the hypothesis of time independence of earthquake sequences. In Europe, there are many regions where seismotectonic zones are not well delineated, and where there is a dynamic stress interaction between events, so that they cannot be described as independent. From the Amatrice earthquake of 24 August, 2016, the subsequent damaging earthquakes in Central Italy over months were not independent events. Removing foreshocks and aftershocks is not only an ill-defined task, it has a material effect on <span class="hlt">seismic</span> hazard computation. Because of the spatial dispersion of epicentres, and the clustering of magnitudes for the largest events in a sequence, which might all be around magnitude 6, the specific event causing the highest ground motion can vary from one site location to another. Where significant active faults have been clearly identified geologically, they should be modelled as individual <span class="hlt">seismic</span> sources. The remaining background <span class="hlt">seismicity</span> should be modelled as non-Poissonian using statistical kernel smoothing methods. This approach was first applied for <span class="hlt">seismic</span> hazard analysis at a UK nuclear power plant two decades ago, and should be included within logic-trees for future probabilistic <span class="hlt">seismic</span> hazard at critical installations within Europe. In this paper, various salient European applications are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985RpESc.......71K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985RpESc.......71K"><span>Relationship between <span class="hlt">seismic</span> status of Earth and relative position of bodies in sun-earth-moon <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kulanin, N. V.</p> <p>1985-03-01</p> <p>The time spectrum of variations in <span class="hlt">seismicity</span> is quite broad. There are <span class="hlt">seismic</span> seasons, as well as multiannual variations. The range of characteristic times of variation from days to about one year is studied. <span class="hlt">Seismic</span> activity as a function of the position of the moon relative to the Earth and the direction toward the Sun is studied. The moments of strong earthquakes, over 5.8 on the Richter scale, between 1968 and June 1980 are plotted in time coordinates relating them to the relative positions of the three bodies in the sun-earth-moon <span class="hlt">system</span>. Methods of mathematical statistics are applied to the points produced, indicating at least 99% probability that the distribution was not random. a periodicity of the earth's <span class="hlt">seismic</span> state of 413 days is observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S41C0813D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S41C0813D"><span><span class="hlt">Seismic</span> Wave Velocity in the Subducted Oceanic Crust from Autocorrelation of Tectonic Tremor Signals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ducellier, A.; Creager, K.</p> <p>2017-12-01</p> <p>Hydration and dehydration of minerals in subduction zones play a key role in the geodynamic processes that generate <span class="hlt">seismicity</span> and that allow tectonic plates to subduct. Detecting the presence of water in the subducted plate is thus crucial to better understand the seismogenesis and the consequent <span class="hlt">seismic</span> hazard. A landward dipping, low velocity layer has been detected in most subduction zones. In Cascadia, this low velocity zone is characterized by a low S-wave velocity and a very high Poisson's ratio, which has been interpreted as high pore-fluid pressure in the upper half part of the subducted oceanic crust. Most previous studies were based on <span class="hlt">seismic</span> reflection imaging, receiver function analysis, or body wave tomography, with <span class="hlt">seismic</span> sources located far from the low velocity zone. In contrast, the sources of the tectonic tremors generated during Episodic Tremor and Slip (ETS) events are located on the plate <span class="hlt">boundary</span>. As the sources of the tremors are much closer to the low velocity zone, <span class="hlt">seismic</span> waves recorded during ETS events should illuminate the area with greater precision. Most methods to detect and locate tectonic tremors and low-frequency earthquakes are based on the cross correlation of <span class="hlt">seismic</span> signals; either signals at the same station for different events, or the same event at different stations. We use the autocorrelation of the <span class="hlt">seismic</span> signal recorded by eight arrays of stations, located in the Olympic Peninsula, Washington. Each tremor, assumed to be on the plate <span class="hlt">boundary</span>, generates a direct wave and reflected and converted waves from both the strong shear-wave velocity contrast in the mid-oceanic crust, and from the Moho of the subducted oceanic crust. The time lag between the arrivals of these different waves at a <span class="hlt">seismic</span> station corresponds to a peak of amplitude on the autocorrelation signals. Using the time lags observed for different locations of the tremor source, we intend to invert for the <span class="hlt">seismic</span> wave velocity of the subducted oceanic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EEEV...15...19S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EEEV...15...19S"><span>Response of a 2-story test-bed structure for the <span class="hlt">seismic</span> evaluation of nonstructural <span class="hlt">systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soroushian, Siavash; Maragakis, E. "Manos"; Zaghi, Arash E.; Rahmanishamsi, Esmaeel; Itani, Ahmad M.; Pekcan, Gokhan</p> <p>2016-03-01</p> <p>A full-scale, two-story, two-by-one bay, steel braced-frame was subjected to a number of unidirectional ground motions using three shake tables at the UNR-NEES site. The test-bed frame was designed to study the <span class="hlt">seismic</span> performance of nonstructural <span class="hlt">systems</span> including steel-framed gypsum partition walls, suspended ceilings and fire sprinkler <span class="hlt">systems</span>. The frame can be configured to perform as an elastic or inelastic <span class="hlt">system</span> to generate large floor accelerations or large inter story drift, respectively. In this study, the dynamic performance of the linear and nonlinear test-beds was comprehensively studied. The <span class="hlt">seismic</span> performance of nonstructural <span class="hlt">systems</span> installed in the linear and nonlinear test-beds were assessed during extreme excitations. In addition, the dynamic interactions of the test-bed and installed nonstructural <span class="hlt">systems</span> are investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMP....56g1705V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMP....56g1705V"><span><span class="hlt">Boundary</span> transfer matrices and <span class="hlt">boundary</span> quantum KZ equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlaar, Bart</p> <p>2015-07-01</p> <p>A simple relation between inhomogeneous transfer matrices and <span class="hlt">boundary</span> quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable <span class="hlt">systems</span> with reflecting <span class="hlt">boundary</span> conditions, analogous to an observation by Gaudin for periodic <span class="hlt">systems</span>. Thus, the <span class="hlt">boundary</span> quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin's <span class="hlt">boundary</span> transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110946M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110946M"><span>The SISMA Project: A pre-operative <span class="hlt">seismic</span> hazard monitoring <span class="hlt">system</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Massimiliano Chersich, M. C.; Amodio, A. A. Angelo; Francia, A. F. Andrea; Sparpaglione, C. S. Claudio</p> <p>2009-04-01</p> <p>Galileian Plus is currently leading the development, in collaboration with several Italian Universities, of the SISMA (<span class="hlt">Seismic</span> Information <span class="hlt">System</span> for Monitoring and Alert) Pilot Project financed by the Italian Space Agency. The <span class="hlt">system</span> is devoted to the continuous monitoring of the <span class="hlt">seismic</span> risk and is addressed to support the Italian Civil Protection decisional process. Completion of the Pilot Project is planned at the beginning of 2010. Main scientific paradigm of SISMA is an innovative deterministic approach integrating geophysical models, geodesy and active tectonics. This paper will give a general overview of project along with its progress status and a particular focus will be put on the architectural design details and to the software implementation choices. SISMA is built on top of a software infrastructure developed by Galileian Plus to integrate the scientific programs devoted to the update of <span class="hlt">seismic</span> risk maps. The main characteristics of the <span class="hlt">system</span> may be resumed as follow: automatic download of input data; integration of scientific programs; definition and scheduling of chains of processes; monitoring and control of the <span class="hlt">system</span> through a graphical user interface (GUI); compatibility of the products with ESRI ArcGIS, by mean of post-processing conversion. a) automatic download of input data SISMA needs input data such as GNSS observations, updated <span class="hlt">seismic</span> catalogue, SAR satellites orbits, etc. that are periodically updated and made available from remote servers through FTP and HTTP. This task is accomplished by a dedicated user configurable component. b) integration of scientific programs SISMA integrates many scientific programs written in different languages (Fortran, C, C++, Perl and Bash) and running into different operating <span class="hlt">systems</span>. This design requirements lead to the development of a distributed <span class="hlt">system</span> which is platform independent and is able to run any terminal-based program following few simple predefined rules. c) definition and scheduling of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T41B4614R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T41B4614R"><span>Tracking the India-Arabia Transform Plate <span class="hlt">Boundary</span> during Paleogene Times.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rodriguez, M.; Huchon, P.; Chamot-Rooke, N. R. A.; Fournier, M.; Delescluse, M.</p> <p>2014-12-01</p> <p>The Zagros and Himalaya mountain belts are the most prominent reliefs built by continental collision. They respectively result from Arabia and India collision with Eurasia. Convergence motions at mountain belts induced most of plate reorganization events in the Indian Ocean during the Cenozoic. Although critical for paleogeographic reconstructions, the way relative motion between Arabia and India was accommodated prior to the formation of the Sheba ridge in the Gulf of Aden remains poorly understood. The India-Arabia plate-<span class="hlt">boundary</span> belongs to the category of long-lived (~90-Ma) oceanic transform faults, thus providing a good case study to investigate the role of major kinematic events over the structural evolution of a long-lived transform <span class="hlt">system</span>. A <span class="hlt">seismic</span> dataset crossing the Owen Fracture Zone, the Owen Basin, and the Oman Margin was acquired to track the past locations of the India-Arabia plate <span class="hlt">boundary</span>. We highlight the composite age of the Owen Basin basement, made of Paleocene oceanic crust drilled on its eastern part, and composed of pre-Maastrichtian continental crust overlaid by Early Paleocene ophiolites on its western side. A major transform fault <span class="hlt">system</span> crossing the Owen Basin juxtaposed these two slivers of lithosphere of different ages, and controlled the uplift of marginal ridges along the Oman Margin. This transform <span class="hlt">system</span> deactivated ~40 Ma ago, coeval with the onset of ultra-slow spreading at the Carlsberg Ridge. The transform <span class="hlt">boundary</span> then jumped to the edge of the present-day Owen Ridge during the Late Eocene-Oligocene period, before seafloor spreading began at the Sheba Ridge. This migration of the plate <span class="hlt">boundary</span> involved the transfer of a part of the Indian oceanic lithosphere accreted at the Carlsberg Ridge to the Arabian plate. The episode of plate transfer at the India-Arabia plate <span class="hlt">boundary</span> during the Late Eocene-Oligocene interval is synchronous with a global plate reorganization event corresponding to geological events at the Zagros and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhyB..459..105C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhyB..459..105C"><span>Modulus spectroscopy of grain-grain <span class="hlt">boundary</span> binary <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Peng-Fei; Song, Jiang; Li, Sheng-Tao; Wang, Hui</p> <p>2015-02-01</p> <p>Understanding various polarization mechanisms in complex dielectric <span class="hlt">systems</span> and specifying their physical origins are key issues in dielectric physics. In this paper, four different methods for representing dielectric properties were analyzed and compared. Depending on the details of the <span class="hlt">system</span> under study, i.e., uniform or non-uniform, it was suggested that different representing approaches should be used to obtain more valuable information. Especially, for the grain-grain <span class="hlt">boundary</span> binary non-uniform <span class="hlt">system</span>, its dielectric response was analyzed in detail in terms of modulus spectroscopy (MS). Furthermore, it was found that through MS, the dielectric responses between uniform and non-uniform <span class="hlt">systems</span>, grain and grain <span class="hlt">boundary</span>, Maxwell-Wagner polarization and intrinsic polarization can be distinguished. Finally, with the proposed model, the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics were studied. The colossal dielectric constant of CCTO at low frequency was attributed to the pseudo relaxation process of grain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....13070V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....13070V"><span>Modernization of the Slovenian National <span class="hlt">Seismic</span> Network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vidrih, R.; Godec, M.; Gosar, A.; Sincic, P.; Tasic, I.; Zivcic, M.</p> <p>2003-04-01</p> <p>The Environmental Agency of the Republic of Slovenia, the Seismology Office is responsible for the fast and reliable information about earthquakes, originating in the area of Slovenia and nearby. In the year 2000 the project Modernization of the Slovenian National <span class="hlt">Seismic</span> Network started. The purpose of a modernized <span class="hlt">seismic</span> network is to enable fast and accurate automatic location of earthquakes, to determine earthquake parameters and to collect data of local, regional and global earthquakes. The modernized network will be finished in the year 2004 and will consist of 25 Q730 remote broadband data loggers based <span class="hlt">seismic</span> station subsystems transmitting in real-time data to the Data Center in Ljubljana, where the Seismology Office is located. The remote broadband station subsystems include 16 surface broadband seismometers CMG-40T, 5 broadband seismometers CMG-40T with strong motion accelerographs EpiSensor, 4 borehole broadband seismometers CMG-40T, all with accurate timing provided by GPS receivers. The <span class="hlt">seismic</span> network will cover the entire Slovenian territory, involving an area of 20,256 km2. The network is planned in this way; more <span class="hlt">seismic</span> stations will be around bigger urban centres and in regions with greater vulnerability (NW Slovenia, Krsko Brezice region). By the end of the year 2002, three old <span class="hlt">seismic</span> stations were modernized and ten new <span class="hlt">seismic</span> stations were built. All <span class="hlt">seismic</span> stations transmit data to UNIX-based computers running Antelope <span class="hlt">system</span> software. The data is transmitted in real time using TCP/IP protocols over the Goverment Wide Area Network . Real-time data is also exchanged with <span class="hlt">seismic</span> networks in the neighbouring countries, where the data are collected from the <span class="hlt">seismic</span> stations, close to the Slovenian border. A typical <span class="hlt">seismic</span> station consists of the <span class="hlt">seismic</span> shaft with the sensor and the data acquisition <span class="hlt">system</span> and, the service shaft with communication equipment (modem, router) and power supply with a battery box. which provides energy in case</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S41F..05T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S41F..05T"><span>GISMO: A MATLAB toolbox for <span class="hlt">seismic</span> research, monitoring, & education</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, G.; Reyes, C. G.; Kempler, L. A.</p> <p>2017-12-01</p> <p>GISMO is an open-source MATLAB toolbox which provides an object-oriented framework to build workflows and applications that read, process, visualize and write <span class="hlt">seismic</span> waveform, catalog and instrument response data. GISMO can retrieve data from a variety of sources (e.g. FDSN web services, Earthworm/Winston servers) and data formats (SAC, Seisan, etc.). It can handle waveform data that crosses file <span class="hlt">boundaries</span>. All this alleviates one of the most time consuming part for scientists developing their own codes. GISMO simplifies <span class="hlt">seismic</span> data analysis by providing a common interface for your data, regardless of its source. Several common plots are built-in to GISMO, such as record section plots, spectrograms, depth-time sections, event count per unit time, energy release per unit time, etc. Other visualizations include map views and cross-sections of hypocentral data. Several common processing methods are also included, such as an extensive set of tools for correlation analysis. Support is being added to interface GISMO with ObsPy. GISMO encourages community development of an integrated set of codes and accompanying documentation, eliminating the need for seismologists to "reinvent the wheel". By sharing code the consistency and repeatability of results can be enhanced. GISMO is hosted on GitHub with documentation both within the source code and in the project wiki. GISMO has been used at the University of South Florida and University of Alaska Fairbanks in graduate-level courses including <span class="hlt">Seismic</span> Data Analysis, Time Series Analysis and Computational Seismology. GISMO has also been tailored to interface with the common <span class="hlt">seismic</span> monitoring software and data formats used by volcano observatories in the US and elsewhere. As an example, toolbox training was delivered to researchers at INETER (Nicaragua). Applications built on GISMO include IceWeb (e.g. web-based spectrograms), which has been used by Alaska Volcano Observatory since 1998 and became the prototype for the USGS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA569487','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA569487"><span><span class="hlt">Seismic</span> and Geophysical Characterization of Northern Asia</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-09-01</p> <p><span class="hlt">seismic</span> networks in Russia and Japan. The geographic scope of this project covers Russia from the Urals to the Bering Strait and from the Arctic Ocean to...Russia and Japan. The geographic scope of this project covers Russia from the Urals to the Bering Strait and from the Arctic Ocean to the North Korean...between these somewhat correspond to the <span class="hlt">boundaries</span> of the microplates , it is our intention to use significantly more data from the region to define</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1870d0069S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1870d0069S"><span>The analytical solution for drug delivery <span class="hlt">system</span> with nonhomogeneous moving <span class="hlt">boundary</span> condition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saudi, Muhamad Hakimi; Mahali, Shalela Mohd; Harun, Fatimah Noor</p> <p>2017-08-01</p> <p>This paper discusses the development and the analytical solution of a mathematical model based on drug release <span class="hlt">system</span> from a swelling delivery device. The mathematical model is represented by a one-dimensional advection-diffusion equation with nonhomogeneous moving <span class="hlt">boundary</span> condition. The solution procedures consist of three major steps. Firstly, the application of steady state solution method, which is used to transform the nonhomogeneous moving <span class="hlt">boundary</span> condition to homogeneous <span class="hlt">boundary</span> condition. Secondly, the application of the Landau transformation technique that gives a significant impact in removing the advection term in the <span class="hlt">system</span> of equation and transforming the moving <span class="hlt">boundary</span> condition to a fixed <span class="hlt">boundary</span> condition. Thirdly, the used of separation of variables method to find the analytical solution for the resulted initial <span class="hlt">boundary</span> value problem. The results show that the swelling rate of delivery device and drug release rate is influenced by value of growth factor r.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T11A4544W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T11A4544W"><span>Updated mapping and <span class="hlt">seismic</span> reflection data processing along the Queen Charlotte fault <span class="hlt">system</span>, southeast Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walton, M. A. L.; Gulick, S. P. S.; Haeussler, P. J.; Rohr, K.; Roland, E. C.; Trehu, A. M.</p> <p>2014-12-01</p> <p>The Queen Charlotte Fault (QCF) is an obliquely convergent strike-slip <span class="hlt">system</span> that accommodates offset between the Pacific and North America plates in southeast Alaska and western Canada. Two recent earthquakes, including a M7.8 thrust event near Haida Gwaii on 28 October 2012, have sparked renewed interest in the margin and led to further study of how convergent stress is accommodated along the fault. Recent studies have looked in detail at offshore structure, concluding that a change in strike of the QCF at ~53.2 degrees north has led to significant differences in stress and the style of strain accommodation along-strike. We provide updated fault mapping and <span class="hlt">seismic</span> images to supplement and support these results. One of the highest-quality <span class="hlt">seismic</span> reflection surveys along the Queen Charlotte <span class="hlt">system</span> to date, EW9412, was shot aboard the R/V Maurice Ewing in 1994. The survey was last processed to post-stack time migration for a 1999 publication. Due to heightened interest in high-quality imaging along the fault, we have completed updated processing of the EW9412 <span class="hlt">seismic</span> reflection data and provide prestack migrations with water-bottom multiple reduction. Our new imaging better resolves fault and basement surfaces at depth, as well as the highly deformed sediments within the Queen Charlotte Terrace. In addition to re-processing the EW9412 <span class="hlt">seismic</span> reflection data, we have compiled and re-analyzed a series of publicly available USGS <span class="hlt">seismic</span> reflection data that obliquely cross the QCF. Using these data, we are able to provide updated maps of the Queen Charlotte fault <span class="hlt">system</span>, adding considerable detail along the northernmost QCF where it links up with the Chatham Strait and Transition fault <span class="hlt">systems</span>. Our results support conclusions that the changing geometry of the QCF leads to fundamentally different convergent stress accommodation north and south of ~53.2 degrees; namely, reactivated splay faults to the north vs. thickening of sediments and the upper crust to the south</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17..441N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17..441N"><span>Development of <span class="hlt">seismic</span> tomography software for hybrid supercomputers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikitin, Alexandr; Serdyukov, Alexandr; Duchkov, Anton</p> <p>2015-04-01</p> <p><span class="hlt">Seismic</span> tomography is a technique used for computing velocity model of geologic structure from first arrival travel times of <span class="hlt">seismic</span> waves. The technique is used in processing of regional and global <span class="hlt">seismic</span> data, in <span class="hlt">seismic</span> exploration for prospecting and exploration of mineral and hydrocarbon deposits, and in <span class="hlt">seismic</span> engineering for monitoring the condition of engineering structures and the surrounding host medium. As a consequence of development of <span class="hlt">seismic</span> monitoring <span class="hlt">systems</span> and increasing volume of <span class="hlt">seismic</span> data, there is a growing need for new, more effective computational algorithms for use in <span class="hlt">seismic</span> tomography applications with improved performance, accuracy and resolution. To achieve this goal, it is necessary to use modern high performance computing <span class="hlt">systems</span>, such as supercomputers with hybrid architecture that use not only CPUs, but also accelerators and co-processors for computation. The goal of this research is the development of parallel <span class="hlt">seismic</span> tomography algorithms and software package for such <span class="hlt">systems</span>, to be used in processing of large volumes of <span class="hlt">seismic</span> data (hundreds of gigabytes and more). These algorithms and software package will be optimized for the most common computing devices used in modern hybrid supercomputers, such as Intel Xeon CPUs, NVIDIA Tesla accelerators and Intel Xeon Phi co-processors. In this work, the following general scheme of <span class="hlt">seismic</span> tomography is utilized. Using the eikonal equation solver, arrival times of <span class="hlt">seismic</span> waves are computed based on assumed velocity model of geologic structure being analyzed. In order to solve the linearized inverse problem, tomographic matrix is computed that connects model adjustments with travel time residuals, and the resulting <span class="hlt">system</span> of linear equations is regularized and solved to adjust the model. The effectiveness of parallel implementations of existing algorithms on target architectures is considered. During the first stage of this work, algorithms were developed for execution on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.8435S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.8435S"><span>Submarine landslide and tsunami hazards offshore southern Alaska: <span class="hlt">Seismic</span> strengthening versus rapid sedimentation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sawyer, Derek E.; Reece, Robert S.; Gulick, Sean P. S.; Lenz, Brandi L.</p> <p>2017-08-01</p> <p>The southern Alaskan offshore margin is prone to submarine landslides and tsunami hazards due to <span class="hlt">seismically</span> active plate <span class="hlt">boundaries</span> and extreme sedimentation rates from glacially enhanced mountain erosion. We examine the submarine landslide potential with new shear strength measurements acquired by Integrated Ocean Drilling Program Expedition 341 on the continental slope and Surveyor Fan. These data reveal lower than expected sediment strength. Contrary to other active margins where <span class="hlt">seismic</span> strengthening enhances slope stability, the high-sedimentation margin offshore southern Alaska behaves like a passive margin from a shear strength perspective. We interpret that <span class="hlt">seismic</span> strengthening occurs but is offset by high sedimentation rates and overpressure. This conclusion is supported by shear strength outside of the fan that follow an active margin trend. More broadly, <span class="hlt">seismically</span> active margins with wet-based glaciers are susceptible to submarine landslide hazards because of the combination of high sedimentation rates and earthquake shaking.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25653000','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25653000"><span>A <span class="hlt">seismic</span> reflection image for the base of a tectonic plate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stern, T A; Henrys, S A; Okaya, D; Louie, J N; Savage, M K; Lamb, S; Sato, H; Sutherland, R; Iwasaki, T</p> <p>2015-02-05</p> <p>Plate tectonics successfully describes the surface of Earth as a mosaic of moving lithospheric plates. But it is not clear what happens at the base of the plates, the lithosphere-asthenosphere <span class="hlt">boundary</span> (LAB). The LAB has been well imaged with converted teleseismic waves, whose 10-40-kilometre wavelength controls the structural resolution. Here we use explosion-generated <span class="hlt">seismic</span> waves (of about 0.5-kilometre wavelength) to form a high-resolution image for the base of an oceanic plate that is subducting beneath North Island, New Zealand. Our 80-kilometre-wide image is based on P-wave reflections and shows an approximately 15° dipping, abrupt, <span class="hlt">seismic</span> wave-speed transition (less than 1 kilometre thick) at a depth of about 100 kilometres. The <span class="hlt">boundary</span> is parallel to the top of the plate and <span class="hlt">seismic</span> attributes indicate a P-wave speed decrease of at least 8 ± 3 per cent across it. A parallel reflection event approximately 10 kilometres deeper shows that the decrease in P-wave speed is confined to a channel at the base of the plate, which we interpret as a sheared zone of ponded partial melts or volatiles. This is independent, high-resolution evidence for a low-viscosity channel at the LAB that decouples plates from mantle flow beneath, and allows plate tectonics to work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.S33G2925E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.S33G2925E"><span>The results of the <span class="hlt">Seismic</span> Alert <span class="hlt">System</span> of Mexico SASMEX, during the earthquakes of 7 and 19 of September 2017</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Espinosa Aranda, J. M., Sr.; Cuellar Martinez, A.</p> <p>2017-12-01</p> <p>The <span class="hlt">Seismic</span> Alert <span class="hlt">System</span> of Mexico, SASMEX began in 1991, is integrated by the <span class="hlt">seismic</span> alert <span class="hlt">system</span> of Mexico City and the <span class="hlt">seismic</span> alert <span class="hlt">system</span> of Oaxaca. SASMEX has 97 <span class="hlt">seismic</span> sensors which are distributed in the <span class="hlt">seismic</span> regions of the Pacific coast and the South of the Trans-Mexican Volcanic Belt of states of Jalisco, Colima, Michoacán, Guerrero, Oaxaca and Puebla. The alert dissemination covers the cities of: Acapulco, Chilpancingo, Morelia, Puebla, Oaxaca, Toluca and Mexico City, reaching the earthquake warnings to more than 25 millions of people. SASMEX has detected correctly more than 5600 earthquakes and warned 156. Mexico City has different alert dissemination <span class="hlt">systems</span> like several Radio and Tv commercial broadcasters, dedicated radio receivers, EAS-SAME-SARMEX radio receivers and more tha 6700 public loud speakers. The other cities have only some of those <span class="hlt">systems</span>. The Mw 8.2 Chiapas earthquake on September 7, despite the epicentral distance far of the first <span class="hlt">seismic</span> detections (more than 180 km) and the low amplitudes of the P waves, the earthquake warning time gave more than 90 seconds to Mexico City before the arrivals of S waves with minor damages to the city in contrast with high damages in towns in the coast. This earthquake offered an opportunity to show the developments and lacks to reduce the risk, such as the need to increase the <span class="hlt">seismic</span> detection coverage and the earthquake warning dissemination in towns with high <span class="hlt">seismic</span> vulnerability. The Mw 7.1 Morelos earthquake on September 19 caused thousands of damages and hundreds of deaths and injuries in Mexico City, this earthquake is the second with the most damages after the Mw 8.1 Michoacán earthquake of September 19 on 1985. The earthquake early warning gave 11 seconds after the arrivals of S waves, however the activation occurred few seconds after the P waves arrives to Mexico City, and due to the <span class="hlt">seismic</span> focus was near to the city, the P waves were felt for the people. The Accelerographic Network</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037142','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037142"><span>Time-dependent <span class="hlt">seismic</span> tomography</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Julian, B.R.; Foulger, G.R.</p> <p>2010-01-01</p> <p>Of methods for measuring temporal changes in <span class="hlt">seismic</span>-wave speeds in the Earth, <span class="hlt">seismic</span> tomography is among those that offer the highest spatial resolution. 3-D tomographic methods are commonly applied in this context by inverting <span class="hlt">seismic</span> wave arrival time data sets from different epochs independently and assuming that differences in the derived structures represent real temporal variations. This assumption is dangerous because the results of independent inversions would differ even if the structure in the Earth did not change, due to observational errors and differences in the <span class="hlt">seismic</span> ray distributions. The latter effect may be especially severe when data sets include earthquake swarms or aftershock sequences, and may produce the appearance of correlation between structural changes and <span class="hlt">seismicity</span> when the wave speeds are actually temporally invariant. A better approach, which makes it possible to assess what changes are truly required by the data, is to invert multiple data sets simultaneously, minimizing the difference between models for different epochs as well as the rms arrival-time residuals. This problem leads, in the case of two epochs, to a <span class="hlt">system</span> of normal equations whose order is twice as great as for a single epoch. The direct solution of this <span class="hlt">system</span> would require twice as much memory and four times as much computational effort as would independent inversions. We present an algorithm, tomo4d, that takes advantage of the structure and sparseness of the <span class="hlt">system</span> to obtain the solution with essentially no more effort than independent inversions require. No claim to original US government works Journal compilation ?? 2010 RAS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70195140','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70195140"><span>Quake warnings, <span class="hlt">seismic</span> culture</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Allen, Richard M.; Cochran, Elizabeth S.; Huggins, Tom; Miles, Scott; Otegui, Diego</p> <p>2017-01-01</p> <p>Since 1990, nearly one million people have died from the impacts of earthquakes. Reducing those impacts requires building a local <span class="hlt">seismic</span> culture in which residents are aware of earthquake risks and value efforts to mitigate harm. Such efforts include earthquake early warning (EEW) <span class="hlt">systems</span> that provide seconds to minutes notice of pending shaking. Recent events in Mexico provide an opportunity to assess performance and perception of an EEW <span class="hlt">system</span> and highlight areas for further improvement. We have learned that EEW <span class="hlt">systems</span>, even imperfect ones, can help people prepare for earthquakes and build local <span class="hlt">seismic</span> culture, both beneficial in reducing earthquake-related losses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JSAES..83...96E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JSAES..83...96E"><span>Geometry and structure of the pull-apart basins developed along the western South American-Scotia plate <span class="hlt">boundary</span> (SW Atlantic Ocean)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esteban, F. D.; Tassone, A.; Isola, J. I.; Lodolo, E.; Menichetti, M.</p> <p>2018-04-01</p> <p>The South American-Scotia plate <span class="hlt">boundary</span> is a left-lateral fault <span class="hlt">system</span> which runs roughly E-W for more than 3000 km across the SW Atlantic Ocean and the Tierra del Fuego Island, reaching to the west the southern Chile Trench. Analyses of a large dataset of single- and multi-channel <span class="hlt">seismic</span> reflection profiles acquired offshore has allowed to map the trace of the plate <span class="hlt">boundary</span> from Tierra del Fuego to the Malvinas Trough, a tectonic depression located in the eastern part of the fault <span class="hlt">system</span>, and to reconstruct the shape and geometry of the basins formed along the principal displacement zone of the fault <span class="hlt">system</span>. Three main Neogene pull-apart basins that range from 70 to 100 km in length, and from 12 to 22 km in width, have been identified along this segment of the plate <span class="hlt">boundary</span>. These basins have elongated shapes with their major axes parallel to the ENE-WSW direction of the fault zone. The sedimentary architecture and the infill geometry of the basins suggest that they represent mostly strike-slip dominated transtension basins which propagated from E to W. The basins imaged by <span class="hlt">seismic</span> data show in some cases geometrical and structural features linked to the possible reactivation of previous wedge-top basins and inherited structures pertaining to the external front of the Magallanes fold-and-thrust compression belt, along which the South American-Scotia fault <span class="hlt">system</span> has been superimposed. It is suggested that the sequence of the elongated basins occur symmetrically to a thorough going strike-slip fault, in a left-stepping geometrical arrangement, in a manner similar to those basins seen in other transcurrent environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999GeoRL..26.1501C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999GeoRL..26.1501C"><span>Can lower mantle slab-like <span class="hlt">seismic</span> anomalies be explained by thermal coupling between the upper and lower mantles?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Čížková, Hana; Čadek, Ondřej; van den Berg, Arie P.; Vlaar, Nicolaas J.</p> <p></p> <p>Below subduction zones, high resolution <span class="hlt">seismic</span> tomographic models resolve fast anomalies that often extend into the deep lower mantle. These anomalies are generally interpreted as slabs penetrating through the 660-km <span class="hlt">seismic</span> discontinuity, evidence in support of whole-mantle convection. However, thermal coupling between two flow <span class="hlt">systems</span> separated by an impermeable interface might provide an alternative explanation of the tomographic results. We have tested this hypothesis within the context of an axisymmetric model of mantle convection in which an impermeable <span class="hlt">boundary</span> is imposed at a depth of 660 km. When an increase in viscosity alone is imposed across the impermeable interface, our results demonstrate the dominant role of mechanical coupling between shells, producing lower mantle upwellings (downwellings) below upper mantle downwellings (upwellings). However, we find that the effect of mechanical coupling can be significantly weakened if a narrow low viscosity zone exists beneath the 660-km discontinuity. In such a case, both thermally induced ‘slabs’ in the lower mantle and thermally activated plumes that rise from the upper/lower mantle <span class="hlt">boundary</span> are observed even though mass transfer between the shells does not exist.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1978/0287/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1978/0287/"><span>FORTRAN programs for calculating nonlinear <span class="hlt">seismic</span> ground response in two dimensions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Joyner, W.B.</p> <p>1978-01-01</p> <p>The programs described here were designed for calculating the nonlinear <span class="hlt">seismic</span> response of a two-dimensional configuration of soil underlain by a semi-infinite elastic medium representing bedrock. There are two programs. One is for plane strain motions, that is, motions in the plane perpendicular to the long axis of the structure, and the other is for antiplane strain motions, that is motions parallel to the axis. The <span class="hlt">seismic</span> input is provided by specifying what the motion of the rock-soil <span class="hlt">boundary</span> would be if the soil were absent and the <span class="hlt">boundary</span> were a free surface. This may be done by supplying a magnetic tape containing the values of particle velocity for every <span class="hlt">boundary</span> point at every instant of time. Alternatively, a punch card deck may be supplied giving acceleration values at every instant of time. In the plane strain program it is assumed that the acceleration values apply simultaneously to every point on the <span class="hlt">boundary</span>; in the antiplane strain program it is assumed that the acceleration values characterize a plane shear wave propagating upward in the underlying elastic medium at a specified angle with the vertical. The nonlinear hysteretic behavior of the soil is represented by a three-dimensional rheological model. A <span class="hlt">boundary</span> condition is used which takes account of finite rigidity in the elastic substratum. The computations are performed by an explicit finite-difference scheme that proceeds step by step in space and time. Computations are done in terms of stress departures from an unspecified initial state. Source listings are provided here along with instructions for preparing the input. A more detailed discussion of the method is presented elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70176403','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70176403"><span>Slab tears and intermediate-depth <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Meighan, Hallie E.; ten Brink, Uri S.; Pulliam, Jay</p> <p>2013-01-01</p> <p>Active tectonic regions where plate <span class="hlt">boundaries</span> transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well-documented slab tears that are associated with high rates of intermediate-depth <span class="hlt">seismicity</span> are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. <span class="hlt">Seismicity</span> at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid-related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950054992&hterms=plate+tectonics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dplate%2Btectonics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950054992&hterms=plate+tectonics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dplate%2Btectonics"><span>Topography and tectonics of the central New Madrid <span class="hlt">seismic</span> zone: Results of numerical experiements using a three-dimensional <span class="hlt">boundary</span> element program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gomberg, Joan; Ellis, Michael</p> <p>1994-01-01</p> <p>We present results of a series of numerical experiments designed to test hypothetical mechanisms that derive deformation in the New Madrid <span class="hlt">seismic</span> zone. Experiments are constrained by subtle topography and the distribution of <span class="hlt">seismicity</span> in the region. We use a new <span class="hlt">boundary</span> element algorithm that permits calcuation of the three-dimensional deformation field. Surface displacement fields are calculated for the New Madrid zone under both far-field (plate tectonics scale) and locally derived driving strains. Results demonstrate that surface displacement fields cannot distinguish between either a far-field simple or pure shear strain field or one that involves a deep shear zone beneath the upper crustal faults. Thus, neither geomorphic nor geodetic studies alone are expected to reveal the ultimate driving mechanism behind the present-day deformation. We have also tested hypotheses about strain accommodation within the New Madrid contractional step-over by including linking faults, two southwest dipping and one vertical, recently inferred from microearthquake data. Only those models with step-over faults are able to predict the observed topography. Surface displacement fields for long-term, relaxed deformation predict the distribution of uplift and subsidence in the contractional step-over remarkably well. Generation of these displacement fields appear to require slip on both the two northeast trending vertical faults and the two dipping faults in the step-over region, with very minor displacements occurring during the interseismic period when the northeast trending vertical faults are locked. These models suggest that the gently dippling central step-over fault is a reverse fault and that the steeper fault, extending to the southeast of the step-over, acts as a normal fault over the long term.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017P%26SS..144...89M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017P%26SS..144...89M"><span>Probing the internal structure of the asteriod Didymoon with a passive <span class="hlt">seismic</span> investigation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murdoch, N.; Hempel, S.; Pou, L.; Cadu, A.; Garcia, R. F.; Mimoun, D.; Margerin, L.; Karatekin, O.</p> <p>2017-09-01</p> <p>Understanding the internal structure of an asteroid has important implications for interpreting its evolutionary history, for understanding its continuing geological evolution, and also for asteroid deflection and in-situ space resource utilisation. Given the strong evidence that asteroids are <span class="hlt">seismically</span> active, an in-situ passive <span class="hlt">seismic</span> experiment could provide information about the asteroid surface and interior properties. Here, we discuss the natural <span class="hlt">seismic</span> activity that may be present on Didymoon, the secondary component of asteroid (65803) Didymos. Our analysis of the tidal stresses in Didymoon shows that tidal quakes are likely to occur if the secondary has an eccentric orbit. Failure occurs most easily at the asteroid poles and close to the surface for both homogeneous and layered internal structures. Simulations of <span class="hlt">seismic</span> wave propagation in Didymoon show that the <span class="hlt">seismic</span> moment of even small meteoroid impacts can generate clearly observable body and surface waves if the asteroid's internal structure is homogeneous. The presence of a regolith layer over a consolidated core can result in the <span class="hlt">seismic</span> energy becoming trapped in the regolith due to the strong impedance contrast at the regolith-core <span class="hlt">boundary</span>. The inclusion of macro-porosity (voids) further complexifies the wavefield due to increased scattering. The most prominent <span class="hlt">seismic</span> waves are always found to be those traveling along the surface of the asteroid and those focusing in the antipodal point of the <span class="hlt">seismic</span> source. We find also that the waveforms and ground acceleration spectra allow discrimination between the different internal structure models. Although the science return of a passive <span class="hlt">seismic</span> experiment would be enhanced by having multiple <span class="hlt">seismic</span> stations, one single <span class="hlt">seismic</span> station can already vastly improve our knowledge about the <span class="hlt">seismic</span> environment and sub-surface structure of an asteroid. We describe several <span class="hlt">seismic</span> measurement techniques that could be applied in order to study the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatGe..10..935V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatGe..10..935V"><span>Past <span class="hlt">seismic</span> slip-to-the-trench recorded in Central America megathrust</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vannucchi, Paola; Spagnuolo, Elena; Aretusini, Stefano; Di Toro, Giulio; Ujiie, Kohtaro; Tsutsumi, Akito; Nielsen, Stefan</p> <p>2017-12-01</p> <p>The 2011 Tōhoku-Oki earthquake revealed that co-<span class="hlt">seismic</span> displacement along the plate <span class="hlt">boundary</span> megathrust can propagate to the trench. Co-<span class="hlt">seismic</span> slip to the trench amplifies hazards at subduction zones, so its historical occurrence should also be investigated globally. Here we combine structural and experimental analyses of core samples taken offshore from southeastern Costa Rica as part of the Integrated Ocean Drilling Program (IODP) Expedition 344, with three-dimensional <span class="hlt">seismic</span> reflection images of the subduction zone. We document a geologic record of past co-<span class="hlt">seismic</span> slip to the trench. The core passed through a less than 1.9-million-year-old megathrust frontal ramp that superimposes older Miocene biogenic oozes onto late Miocene-Pleistocene silty clays. This, together with our stratigraphic analyses and geophysical images, constrains the position of the basal decollement to lie within the biogenic oozes. Our friction experiments show that, when wet, silty clays and biogenic oozes are both slip-weakening at sub-<span class="hlt">seismic</span> and <span class="hlt">seismic</span> slip velocities. Oozes are stronger than silty clays at slip velocities of less than or equal to 0.01 m s-1, and wet oozes become as weak as silty clays only at a slip velocity of 1 m s-1. We therefore suggest that the geological structures found offshore from Costa Rica were deformed during <span class="hlt">seismic</span> slip-to-the-trench events. During slower aseismic creep, deformation would have preferentially localized within the silty clays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5605151','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/5605151"><span>Down-hole periodic <span class="hlt">seismic</span> generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hardee, H.C.; Hills, R.G.; Striker, R.P.</p> <p>1982-10-28</p> <p>A down hole periodic <span class="hlt">seismic</span> generator <span class="hlt">system</span> is disclosed for transmitting variable frequency, predominantly shear-wave vibration into earth strata surrounding a borehole. The <span class="hlt">system</span> comprises a unitary housing operably connected to a well head by support and electrical cabling and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The <span class="hlt">system</span> further comprises a variable speed pneumatic oscillator and a self-contained pneumatic reservoir for producing a frequency-swept <span class="hlt">seismic</span> output over a discrete frequency range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/867904','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/867904"><span>Advanced downhole periodic <span class="hlt">seismic</span> generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hardee, Harry C.; Hills, Richard G.; Striker, Richard P.</p> <p>1991-07-16</p> <p>An advanced downhole periodic <span class="hlt">seismic</span> generator <span class="hlt">system</span> for transmitting variable frequency, predominantly shear-wave vibration into earth strata surrounding a borehole. The <span class="hlt">system</span> comprises a unitary housing operably connected to a well head by support and electrical cabling and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The <span class="hlt">system</span> further comprises a variable speed pneumatic oscillator and a self-contained pneumatic reservoir for producing a frequency-swept <span class="hlt">seismic</span> output over a discrete frequency range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/866847','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/866847"><span>Down hole periodic <span class="hlt">seismic</span> generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hardee, Harry C.; Hills, Richard G.; Striker, Richard P.</p> <p>1989-01-01</p> <p>A down hole periodic <span class="hlt">seismic</span> generator <span class="hlt">system</span> for transmitting variable frequency, predominantly shear-wave vibration into earth strata surrounding a borehole. The <span class="hlt">system</span> comprises a unitary housing operably connected to a well head by support and electrical cabling and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The <span class="hlt">system</span> further comprises a variable speed pneumatic oscillator and a self-contained pneumatic reservoir for producing a frequency-swept <span class="hlt">seismic</span> output over a discrete frequency range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T33F..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T33F..03B"><span>Plateau subduction, intraslab <span class="hlt">seismicity</span> and the Denali Volcanic Gap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bostock, M. G.; Chuang, L. Y.; Wech, A.; Plourde, A. P.</p> <p>2017-12-01</p> <p>Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative network matched filtering and stacking. The timing of impulsive P (compressional) wave and S (shear) wave arrivals on template waveforms places LFEs at 40-58 km depth, near the upper envelope of intraslab <span class="hlt">seismicity</span> and immediately updip of increased levels of intraslab <span class="hlt">seismicity</span>. S waves at near-epicentral distances display polarities consistent with shear slip on the plate <span class="hlt">boundary</span>. We compare characteristics of LFEs, <span class="hlt">seismicity</span>, and tectonic structures in central Alaska with those in warm subduction zones, and propose a new model for the region's unusual intraslab <span class="hlt">seismicity</span> and the enigmatic Denali volcanic gap (i.e., an area of no volcanism where expected). We argue that fluids in the Yakutat plate are confined to its upper crust, and that shallow subduction leads to hydromechanical conditions at the slab interface in central Alaska akin to those in warm subduction zones where similar LFEs and tremor occur. These conditions lead to fluid expulsion at shallow depths, explaining strike-parallel alignment of tremor occurrence with the Denali volcanic gap. Moreover, the lack of double <span class="hlt">seismic</span> zone and restriction of deep intraslab <span class="hlt">seismicity</span> to a persistent low-velocity zone are simple consequences of anhydrous conditions prevailing in the lower crust and upper mantle of the Yakutat plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009CG.....35.1460Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009CG.....35.1460Z"><span>Use of raster-based data layers to model spatial variation of seismotectonic data in probabilistic <span class="hlt">seismic</span> hazard assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zolfaghari, Mohammad R.</p> <p>2009-07-01</p> <p>Recent achievements in computer and information technology have provided the necessary tools to extend the application of probabilistic <span class="hlt">seismic</span> hazard mapping from its traditional engineering use to many other applications. Examples for such applications are risk mitigation, disaster management, post disaster recovery planning and catastrophe loss estimation and risk management. Due to the lack of proper knowledge with regard to factors controlling <span class="hlt">seismic</span> hazards, there are always uncertainties associated with all steps involved in developing and using <span class="hlt">seismic</span> hazard models. While some of these uncertainties can be controlled by more accurate and reliable input data, the majority of the data and assumptions used in <span class="hlt">seismic</span> hazard studies remain with high uncertainties that contribute to the uncertainty of the final results. In this paper a new methodology for the assessment of <span class="hlt">seismic</span> hazard is described. The proposed approach provides practical facility for better capture of spatial variations of seismological and tectonic characteristics, which allows better treatment of their uncertainties. In the proposed approach, GIS raster-based data models are used in order to model geographical features in a cell-based <span class="hlt">system</span>. The cell-based source model proposed in this paper provides a framework for implementing many geographically referenced seismotectonic factors into <span class="hlt">seismic</span> hazard modelling. Examples for such components are <span class="hlt">seismic</span> source <span class="hlt">boundaries</span>, rupture geometry, <span class="hlt">seismic</span> activity rate, focal depth and the choice of attenuation functions. The proposed methodology provides improvements in several aspects of the standard analytical tools currently being used for assessment and mapping of regional <span class="hlt">seismic</span> hazard. The proposed methodology makes the best use of the recent advancements in computer technology in both software and hardware. The proposed approach is well structured to be implemented using conventional GIS tools.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987Tectp.144..323S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987Tectp.144..323S"><span><span class="hlt">Seismic</span> crustal structure of the Limpopo mobile belt, Zimbabwe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuart, G. W.; Zengeni, T. G.</p> <p>1987-12-01</p> <p>A 145 km N-S <span class="hlt">seismic</span> traverse was deployed to determine the crustal structure of the Limpopo mobile belt in southern Zimbabwe and the nature of its northern <span class="hlt">boundary</span> with the Zimbabwean craton. Rockbursts from South African gold mines to the south and regional <span class="hlt">seismicity</span> from the Kariba-South Zambia belt to the north were used as <span class="hlt">seismic</span> sources. P-wave relative teleseismic residuals were also measured to assess whether any velocity contrast between the craton and the mobile belt extended into the upper mantle. Interpretation of reduced travel times from the local Buchwa iron-ore mine blasts, which were broadside to the traverse, revealed an upper crustal interface in the Limpopo mobile belt at a depth of 5.8 ± 0.6 km, dividing material with a velocity of about 5.8 km/s from that of about 6.4 km/s. On the craton, arrivals from the same source showed a 4.4 ± 0.5 km thick 5.5 km/s layer overlying crust of about velocity 6.5 km/s. P-wave arrivals from the regional <span class="hlt">seismicity</span> were used to construct a crustal cross-section. Absolute crustal thickness was tentatively estimated from the identification of a Moho reflection on the mine blast recordings. To the south of Rutenga, the crust thins from around 34 km to 29 km in association with a positive gravity anomaly centred over the late-Karoo Nuanetsi Igneous Province and Karoo Tuli Syncline. North of Rutenga to the <span class="hlt">boundary</span> with the Zimbabwean craton, the crust is about 34 km thick. The craton <span class="hlt">boundary</span> was found to be a steeply southerly dipping zone associated with high-velocity material, which could either be deep-seated greenstones or mafic material associated with the margin in the region studied. This zone divides cratonic crust, which was found to be about 40 km thick, from that typical of the mobile belt and implies a step in the Moho of around 6 km. Analysis of relative teleseismic residuals showed that the velocity contrasts are not confined to the crust but extend into the uppermost upper mantle with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.T51D0516B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.T51D0516B"><span>Gravity and <span class="hlt">Seismic</span> Investigations of the Northern Rio Grande Rift Area, New Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braile, L. W.; Deepak, A.; Helprin, O.; Kondas, S.; Maguire, H.; McCallister, B.; Orubu, A.; Rijfkogel, L.; Schumann, H.; Vannette, M.; Wanpiyarat, N.; Carchedi, C.; Ferguson, J. F.; McPhee, D.; Biehler, S.; Ralston, M. D.; Baldridge, W. S.</p> <p>2017-12-01</p> <p>Participants in the Summer of Applied Geophysical Experience (SAGE, a research and education program in applied geophysics for undergraduate and graduate students) program have studied the northern Rio Grande rift (RGR) area of New Mexico for the past thirty-five years. In recent years, the SAGE program has focused on the western edge of the Española basin and the transition into the Santo Domingo basin and the Valles caldera. During this time, we have collected about 50 km of <span class="hlt">seismic</span> reflection and refraction data along approximately East-West profiles using a 120 channel data acquisition <span class="hlt">system</span> with a 20 m station interval and a Vibroseis source. We also have access to several energy-industry <span class="hlt">seismic</span> reflection record sections from the 1970s in the study area. During SAGE 2017, new gravity measurements north of the Jemez Mountains and a <span class="hlt">seismic</span> reflection profile (Rio de Truchas Profile) in the Valarde graben adjacent to the eastern <span class="hlt">boundary</span> of the RGR have added new constraints to a west-to-east transect in area of the northern RGR. The recorded near-vertical and wide-angle <span class="hlt">seismic</span> refection data were processed to produce a CMP (common midpoint) stacked record section. Bandpass filtering, muting, deconvolution, and F-K velocity filtering were found to be effective in enhancing the <span class="hlt">seismic</span> reflections. Modeling and interpretation of the northern RGR west-to-east geophysical profile indicates that the sedimentary rock fill in the Velarde graben is at least 3 km near the center of the graben. Gravity modeling also suggests the presence of a high-density intrusion at the top of the crystalline basement in an area to the north and west of Abiquiu, NM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.S31A2004S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.S31A2004S"><span><span class="hlt">Seismic</span> Tomography of the South Carpathian <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stuart, G. W.; Ren, Y.; Dando, B. D.; Houseman, G.; Ionescu, C.; Hegedus, E.; Radovanovic, S.; South Carpathian Project Working Group</p> <p>2010-12-01</p> <p>The South Carpathian Mountain Range is an enigmatic <span class="hlt">system</span>, which includes one of the most <span class="hlt">seismically</span> active regions in Europe today. That region, Vrancea in the SE Carpathians, is well studied and its deep structure may be geologically unique, but the mantle structures beneath the western part of the South Carpathian Range are not well resolved by previous tomographic studies. The South Carpathian Project (SCP) is a major temporary deployment (2009-2011) of <span class="hlt">seismic</span> broadband <span class="hlt">systems</span> extending across the eastern Pannonian Basin and the South Carpathian Mountains. In this project we aim to map the upper mantle structure in central Europe with the objective of testing geodynamic models of the process that produced extension in the Pannonian, synchronous with convergence and uplift in the Carpathians. Here, we describe initial results of finite-frequency tomography using body waves to image the mantle of the region. We have selected teleseismic earthquakes with magnitude greater than 5.9, which occurred between 2005 and 2010. The data were recorded on 57 temporary stations deployed in the South Carpathian Project, 56 temporary stations deployed in the earlier Carpathian Basins Project (CBP), and 41 permanent broadband stations. The differential travel times are measured in high, intermediate and low frequencies (0.5-2.0 Hz, 0.1-0.5 Hz and 0.03-0.1 Hz for both P-wave, 0.1-0.5 Hz, 0.05-0.1 Hz and 0.02-0.05 Hz for S-wave), and are inverted to produce P and S-wave velocity maps at different depths in the mantle. An extensive zone of high <span class="hlt">seismic</span> velocities is located in the Mantle Transition zone beneath the Pannonian Basin, and is related to down-welling associated with an earlier phase of continental convergence in the Pannonian region. These results will be used in conjunction with 3D geodynamical modelling to help understand the geological evolution of this region. SCP working group: G. Houseman, G. Stuart, Y. Ren, B. Dando, P. Lorinczi, School of Earth and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.198...55C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.198...55C"><span><span class="hlt">Seismic</span> waveform inversion for core-mantle <span class="hlt">boundary</span> topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colombi, Andrea; Nissen-Meyer, Tarje; Boschi, Lapo; Giardini, Domenico</p> <p>2014-07-01</p> <p>The topography of the core-mantle <span class="hlt">boundary</span> (CMB) is directly linked to the dynamics of both the mantle and the outer core, although it is poorly constrained and understood. Recent studies have produced topography models with mutual agreement up to degree 2. A broad-band waveform inversion strategy is introduced and applied here, with relatively low computational cost and based on a first-order Born approximation. Its performance is validated using synthetic waveforms calculated in theoretical earth models that include different topography patterns with varying lateral wavelengths, from 600 to 2500 km, and magnitudes (˜10 km peak-to-peak). The source-receiver geometry focuses mainly on the Pdiff, PKP, PcP and ScS phases. The results show that PKP branches, PcP and ScS generally perform well and in a similar fashion, while Pdiff yields unsatisfactory results. We investigate also how 3-D mantle correction influences the output models, and find that despite the disturbance introduced, the models recovered do not appear to be biased, provided that the 3-D model is correct. Using cross-correlated traveltimes, we derive new topography models from both P and S waves. The static corrections used to remove the mantle effect are likely to affect the inversion, compromising the agreement between models derived from P and S data. By modelling traveltime residuals starting from sensitivity kernels, we show how the simultaneous use of volumetric and <span class="hlt">boundary</span> kernels can reduce the bias coming from mantle structures. The joint inversion approach should be the only reliable method to invert for CMB topography using absolute cross-correlation traveltimes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817441P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817441P"><span>Active normal fault network of the Apulian Ridge (Eastern Mediterranean Sea) imaged by multibeam bathymetry and <span class="hlt">seismic</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pellegrini, Claudio; Marchese, Fabio; Savini, Alessandra; Bistacchi, Andrea</p> <p>2016-04-01</p> <p>The Apulian ridge (North-eastern Ionian margin - Mediterranean Sea) is formed by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a NNW-SSE penetrative normal fault <span class="hlt">system</span> and is part of the present foreland <span class="hlt">system</span> of both the Apennine to the west and the Hellenic arc to the east. The geometry, age, architecture and kinematics of the fault network were investigated integrating data of heterogeneous sources, provided by previous studies: regional scale 2D <span class="hlt">seismics</span> and three wells collected by oil companies from the '60s to the '80s, more recent <span class="hlt">seismics</span> collected during research projects in the '90s, very high resolution <span class="hlt">seismic</span> (VHRS - Sparker and Chirp-sonar data), multi-beam echosounder bathymetry and results from sedimentological and geo-chronological analysis of sediment samples collected on the seabed. Multibeam bathymetric data allowed in particular assessing the 3D continuity of structures imaged in 2D <span class="hlt">seismics</span>, thanks to the occurrence of continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides), revealing the vertical extent and finite displacement associated to fault scarps. A penetrative network of relatively small faults, always showing a high dip angle, composes the NNW-SSE normal fault <span class="hlt">system</span>, resulting in frequent relay zones, which are particularly well imaged by seafloor geomorphology. In addition, numerous fault scarps appear to be roughly coeval with quaternary submarine mass-wasting deposits colonised by Cold-Water Corals (CWC). Coral colonies, yielding ages between 11 and 14 kA, develop immediately on top of late Pleistocene mass-wasting deposits. Mutual cross-cutting relationships have been recognized between fault scarps and landslides, indicating that, at least in places, these features may be coeval. We suppose that fault activity lasted at least as far as the Holocene-Pleistocene <span class="hlt">boundary</span> and that the NNW-SSW normal fault network in the Apulian Plateau can be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMOS53B1195T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMOS53B1195T"><span>Baseline <span class="hlt">seismic</span> survey for the 2nd offshore methane hydrate production test in the Eastern Nankai Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Teranishi, Y.; Inamori, T.; Kobayashi, T.; Fujii, T.; Saeki, T.; Takahashi, H.; Kobayashi, F.</p> <p>2017-12-01</p> <p>JOGMEC carries out <span class="hlt">seismic</span> monitoring surveys before and after the 2nd offshore methane hydrate (MH) production test in the Eastern Nankai Trough and evaluates MH dissociation behavior from the time-lapse <span class="hlt">seismic</span> response. In 2016, JOGMEC deployed Ocean Bottom Cable (OBC) <span class="hlt">system</span> provided by OCC in the Daini Atsumi Knoll with water depths of 900-1100 m. The main challenge of the <span class="hlt">seismic</span> survey was to optimize the cable layout for ensuring an effective time-lapse <span class="hlt">seismic</span> detectability while overcoming the following two issues: 1. OBC receiver lines were limited to only two lines. It was predicted that the imaging of shallow reflectors would suffer from lack of continuity and resolution due to this limitation of receiver lines. 2. The seafloor and shallow sedimentary layers including monitoring target are dipping to the Northwest direction. It was predicted that the refection points would laterally shift to up-dip direction (Southeast direction). In order to understand the impact of the issues above, the <span class="hlt">seismic</span> survey was designed with elastic wave field simulation. The reflection <span class="hlt">seismic</span> survey for baseline data was conducted in August 2016. A total of 70 receiver stations distributed along one cable were deployed successfully and a total of 9952 shots were fired. After the baseline <span class="hlt">seismic</span> survey, the hydrophone and geophone vertical component datasets were processed as outlined below: designaturing, denoising, surface consistent deconvolution and surface consistent amplitude correction. High-frequency imaging with Reverse Time Migration (RTM) was introduced to these data sets. Improvements in imaging from the RTM are remarkable compared to the Kirchhoff migration and the existing Pre-stack time migration with 3D marine surface <span class="hlt">seismic</span> data obtained and processed in 2002, especially in the following parts. The MH concentrated zone which has complex structures. Below the Bottom Simulating Reflector (BSR) which is present as a impedance-contrast <span class="hlt">boundary</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.S23D..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.S23D..01T"><span>Expert agreements and disagreements on induced <span class="hlt">seismicity</span> by Enhanced Geothermal <span class="hlt">Systems</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trutnevyte, E.; Azevedo, I. L.</p> <p>2016-12-01</p> <p>Enhanced or Engineered Geothermal <span class="hlt">Systems</span> (EGS) are at an early stage of development and only a handful of projects exist worldwide. In face of limited empirical evidence on EGS induced <span class="hlt">seismicity</span>, expert elicitation provides a complementary view to quantitative assessments and basic science. We present the results of an international expert elicitation exercise with 14 experts from 6 countries. The elicitation aimed at evaluating induced <span class="hlt">seismicity</span> hazard and risk for EGS and characterizing associated uncertainty. The state-of-the-art expert elicitation method was used: it combines technical analysis with behavioral science-informed elicitation of expert judgement in order to minimize subjectivity. The experts assessed a harmonized scenario of an EGS plant, its operational characteristics, geological context, and surrounding buildings and infrastructures. The experts provided quantitative estimates of exceedance probabilities of induced M>=3 and M>=5, maximum magnitudes that could be observed, and made judgements on economic loss, injuries, and fatalities in the case of M=3 and M=5. The experts also rated the importance of factors that influence induced <span class="hlt">seismicity</span> hazard and risk (e.g. reservoir depth, injected volumes, exposed building stock etc.) and the potential uncertainty reductions through future research. We present the findings of this elicitation and highlight the points of expert agreements and disagreements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.3509M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.3509M"><span>Bayesian identification of multiple <span class="hlt">seismic</span> change points and varying <span class="hlt">seismic</span> rates caused by induced <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montoya-Noguera, Silvana; Wang, Yu</p> <p>2017-04-01</p> <p>The Central and Eastern United States (CEUS) has experienced an abnormal increase in <span class="hlt">seismic</span> activity, which is believed to be related to anthropogenic activities. The U.S. Geological Survey has acknowledged this situation and developed the CEUS 2016 1 year <span class="hlt">seismic</span> hazard model using the catalog of 2015 by assuming stationary <span class="hlt">seismicity</span> in that period. However, due to the nonstationary nature of induced <span class="hlt">seismicity</span>, it is essential to identify change points for accurate probabilistic <span class="hlt">seismic</span> hazard analysis (PSHA). We present a Bayesian procedure to identify the most probable change points in <span class="hlt">seismicity</span> and define their respective <span class="hlt">seismic</span> rates. It uses prior distributions in agreement with conventional PSHA and updates them with recent data to identify <span class="hlt">seismicity</span> changes. It can determine the change points in a regional scale and may incorporate different types of information in an objective manner. It is first successfully tested with simulated data, and then it is used to evaluate Oklahoma's regional <span class="hlt">seismicity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSM.S33A..06C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSM.S33A..06C"><span>Ancestral Structure of the Neuquén Basin, Supported by an Innovative Deep <span class="hlt">Seismic</span> Reprocessing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Comínguez, A. H.; Franzese, J. R.</p> <p>2007-05-01</p> <p><span class="hlt">Seismic</span>-tracings comprising both the eastern and western sectors of Sierra de los Chihuidos, showed the deep structure of the Neuquén basin, Argentina. Deep reprocessing of historical industrial <span class="hlt">seismic</span>-lines supplied interpretive information down to about 30-33 km. Consequently, <span class="hlt">seismic</span> data reprocessed with "self-truncating extended correlation" confirmed an objective way for acquiring deep-<span class="hlt">seismic</span> information where standard Vibroseis records are available. In addition, the FMED algorithm was an appreciated nonlinear mathematical tool to improve <span class="hlt">seismic</span> resolution. Original results accomplished with the above emphasized techniques, revealed a list of concepts summarized along the subsequent comments. An acoustic contrast at about 24 km depth must be the top of the lower Crust. An oblique reflector between 16 and 18 km depth must be assumed as the local image of the master shear that controlled the extension <span class="hlt">system</span> during the Late Triassic-Early Jurassic period. A sub-master fault dipping about 8° W, surely have been controlling the evolution of `Las Cárceles' area. An important inversion event initiated during the Bathonian-Callovian, sensibly affected the western sector of `Las Cárceles' (that is the site contiguous to the Neuquén river). Significant deposition of synrift sediments (Precuyo Group) originated in contiguous scarp degradation was detected on the western side of `Los Chihuidos' arch, at about 7 km depth. A Pliensbachian-Toarcian bipolar inversion developed during the transition to the Cuyo Group was evidenced in the western area. In the same sector, a middle Jurassic postrift episode is characterized by a deltaic depositional <span class="hlt">system</span> prograding to the west with accentuate high energy. A deep discontinuity was related with the ancestral origin of the Basin, its <span class="hlt">seismic</span> tracing permitted to match field results with a scale tank experiment simulating orogenic collapse. Bulk extension of the ancestral thickened crust could be only justified if a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/392223-deepwater-seismic-acquisition-technology','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/392223-deepwater-seismic-acquisition-technology"><span>Deepwater <span class="hlt">seismic</span> acquisition technology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Caldwell, J.</p> <p>1996-09-01</p> <p>Although truly new technology is not required for successful acquisition of <span class="hlt">seismic</span> data in deep Gulf of Mexico waters, it is helpful to review some basic aspects of these <span class="hlt">seismic</span> surveys. Additionally, such surveys are likely to see early use of some emerging new technology which can improve data quality. Because such items as depth imaging, borehole <span class="hlt">seismic</span>, 4-D and marine 3-component recording were mentioned in the May 1996 issue of World Oil, they are not discussed again here. However, these technologies will also play some role in the deepwater <span class="hlt">seismic</span> activities. What is covered in this paper are somemore » new considerations for: (1) longer data records needed in deeper water, (2) some pros and cons of very long steamer use, and (3) two new commercial <span class="hlt">systems</span> for quantifying data quality.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.429..122L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.429..122L"><span>Landslide <span class="hlt">seismic</span> magnitude</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.</p> <p>2015-11-01</p> <p>Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time <span class="hlt">system</span> has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period <span class="hlt">seismic</span> signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide <span class="hlt">seismic</span> magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one <span class="hlt">seismic</span> station and Δ is its distance (km) from the landslide. We conclude that both the location and <span class="hlt">seismic</span> magnitude of large landslides can be rapidly estimated from broadband <span class="hlt">seismic</span> networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S53A2749I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S53A2749I"><span>Inter-plate aseismic slip on the subducting plate <span class="hlt">boundaries</span> estimated from repeating earthquakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Igarashi, T.</p> <p>2015-12-01</p> <p>Sequences of repeating earthquakes are caused by repeating slips of small patches surrounded by aseismic slip areas at plate <span class="hlt">boundary</span> zones. Recently, they have been detected in many regions. In this study, I detected repeating earthquakes which occurred in Japan and the world by using seismograms observed in the Japanese <span class="hlt">seismic</span> network, and investigated the space-time characteristics of inter-plate aseismic slip on the subducting plate <span class="hlt">boundaries</span>. To extract repeating earthquakes, I calculate cross-correlation coefficients of band-pass filtering seismograms at each station following Igarashi [2010]. I used two data-set based on USGS catalog for about 25 years from May 1990 and JMA catalog for about 13 years from January 2002. As a result, I found many sequences of repeating earthquakes in the subducting plate <span class="hlt">boundaries</span> of the Andaman-Sumatra-Java and Japan-Kuril-Kamchatka-Aleutian subduction zones. By applying the scaling relations among a <span class="hlt">seismic</span> moment, recurrence interval and slip proposed by Nadeau and Johnson [1998], they indicate the space-time changes of inter-plate aseismic slips. Pairs of repeating earthquakes with the longest time interval occurred in the Solomon Islands area and the recurrence interval was about 18.5 years. The estimated slip-rate is about 46 mm/year, which correspond to about half of the relative plate motion in this area. Several sequences with fast slip-rates correspond to the post-<span class="hlt">seismic</span> slips after the 2004 Sumatra-Andaman earthquake (M9.0), the 2006 Kuril earthquake (M8.3), the 2007 southern Sumatra earthquake (M8.5), and the 2011 Tohoku-oki earthquake (M9.0). The database of global repeating earthquakes enables the comparison of the inter-plate aseismic slips of various plate <span class="hlt">boundary</span> zones of the world. I believe that I am likely to detect more sequences by extending analysis periods in the area where they were not found in this analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T11D2126A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T11D2126A"><span>Stress Transfer Processes during Great Plate <span class="hlt">Boundary</span> Thrusting Events: A Study from the Andaman and Nicobar Segments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andrade, V.; Rajendran, K.</p> <p>2010-12-01</p> <p>The response of subduction zones to large earthquakes varies along their strike, both during the interseismic and post-<span class="hlt">seismic</span> periods. The December 26, 2004 earthquake nucleated at 3° N latitude and its rupture propagated northward, along the Andaman-Sumatra subduction zone, terminating at 15°N. Rupture speed was estimated at about 2.0 km per second in the northern part under the Andaman region and 2.5 - 2.7 km per second under southern Nicobar and North Sumatra. We have examined the pre and post-2004 <span class="hlt">seismicity</span> to understand the stress transfer processes within the subducting plate, in the Andaman (10° - 15° N ) and Nicobar (5° - 10° N) segments. The <span class="hlt">seismicity</span> pattern in these segments shows distinctive characteristics associated with the outer rise, accretionary prism and the spreading ridge, all of which are relatively better developed in the Andaman segment. The Ninety East ridge and the Sumatra Fault <span class="hlt">System</span> are significant tectonic features in the Nicobar segment. The pre-2004 <span class="hlt">seismicity</span> in both these segments conform to the steady-state conditions wherein large earthquakes are fewer and compressive stresses dominate along the plate interface. Among the pre-2004 great earthquakes are the 1881 Nicobar and 1941 Andaman events. The former is considered to be a shallow thrust event that generated a small tsunami. Studies in other subduction zones suggest that large outer-rise tensional events follow great plate <span class="hlt">boundary</span> breaking earthquakes due to the the up-dip transfer of stresses within the subducting plate. The <span class="hlt">seismicity</span> of the Andaman segment (1977-2004) concurs with the steady-state stress conditions where earthquakes occur dominantly by thrust faulting. The post-2004 <span class="hlt">seismicity</span> shows up-dip migration along the plate interface, with dominance of shallow normal faulting, including a few outer rise events and some deeper (> 100 km) strike-slip faulting events within the subducting plate. The September 13, 2002, Mw 6.5 thrust faulting earthquake at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41.1514F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41.1514F"><span><span class="hlt">Seismic</span> anisotropy of the Archean crust in the Minnesota River Valley, Superior Province</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferré, Eric C.; Gébelin, Aude; Conder, James A.; Christensen, Nik; Wood, Justin D.; Teyssier, Christian</p> <p>2014-03-01</p> <p>The Minnesota River Valley (MRV) subprovince is a well-exposed example of late Archean lithosphere. Its high-grade gneisses display a subhorizontal layering, most likely extending down to the crust-mantle <span class="hlt">boundary</span>. The strong linear fabric of the gneisses results from high-temperature plastic flow during collage-related contraction. <span class="hlt">Seismic</span> anisotropies measured up to 1 GPa in the laboratory, and <span class="hlt">seismic</span> anisotropies calculated through forward-modeling indicate ΔVP ~5-6% and ΔVS ~3%. The MRV crust exhibits a strong macroscopic layering and foliation, and relatively strong <span class="hlt">seismic</span> anisotropies at the hand specimen scale. Yet the horizontal attitude of these structures precludes any substantial contribution of the MRV crust to shear wave splitting for vertically propagating shear waves such as SKS. The origin of the regionally low <span class="hlt">seismic</span> anisotropy must lie in the upper mantle. A horizontally layered mantle underneath the United States interior could provide an explanation for the observed low SWS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.S41B2446G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.S41B2446G"><span><span class="hlt">Seismic</span> databases of The Caucasus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunia, I.; Sokhadze, G.; Mikava, D.; Tvaradze, N.; Godoladze, T.</p> <p>2012-12-01</p> <p>The Caucasus is one of the active segments of the Alpine-Himalayan collision belt. The region needs continues <span class="hlt">seismic</span> monitoring <span class="hlt">systems</span> for better understanding of tectonic processes going in the region. <span class="hlt">Seismic</span> Monitoring Center of Georgia (Ilia State University) is operating the digital <span class="hlt">seismic</span> network of the country and is also collecting and exchanging data with neighboring countries. The main focus of our study was to create <span class="hlt">seismic</span> database which is well organized, easily reachable and is convenient for scientists to use. The seismological database includes the information about more than 100 000 earthquakes from the whole Caucasus. We have to mention that it includes data from analog and digital <span class="hlt">seismic</span> networks. The first analog <span class="hlt">seismic</span> station in Georgia was installed in 1899 in the Caucasus in Tbilisi city. The number of analog <span class="hlt">seismic</span> stations was increasing during next decades and in 1980s about 100 analog stations were operated all over the region. From 1992 due to political and economical situation the number of stations has been decreased and in 2002 just two analog equipments was operated. New digital <span class="hlt">seismic</span> network was developed in Georgia since 2003. The number of digital <span class="hlt">seismic</span> stations was increasing and in current days there are more than 25 digital stations operating in the country. The database includes the detailed information about all equipments installed on <span class="hlt">seismic</span> stations. Database is available online. That will make convenient interface for <span class="hlt">seismic</span> data exchange data between Caucasus neighboring countries. It also makes easier both the <span class="hlt">seismic</span> data processing and transferring them to the database and decreases the operator's mistakes during the routine work. The database was created using the followings: php, MySql, Javascript, Ajax, GMT, Gmap, Hypoinverse.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/962316','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/962316"><span><span class="hlt">Seismic</span> fragility formulations for segmented buried pipeline <span class="hlt">systems</span> including the impact of differential ground subsidence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pineda Porras, Omar Andrey; Ordaz, Mario</p> <p>2009-01-01</p> <p>Though Differential Ground Subsidence (DGS) impacts the <span class="hlt">seismic</span> response of segmented buried pipelines augmenting their vulnerability, fragility formulations to estimate repair rates under such condition are not available in the literature. Physical models to estimate pipeline <span class="hlt">seismic</span> damage considering other cases of permanent ground subsidence (e.g. faulting, tectonic uplift, liquefaction, and landslides) have been extensively reported, not being the case of DGS. The refinement of the study of two important phenomena in Mexico City - the 1985 Michoacan earthquake scenario and the sinking of the city due to ground subsidence - has contributed to the analysis of the interrelation ofmore » pipeline damage, ground motion intensity, and DGS; from the analysis of the 48-inch pipeline network of the Mexico City's Water <span class="hlt">System</span>, fragility formulations for segmented buried pipeline <span class="hlt">systems</span> for two DGS levels are proposed. The novel parameter PGV{sup 2}/PGA, being PGV peak ground velocity and PGA peak ground acceleration, has been used as <span class="hlt">seismic</span> parameter in these formulations, since it has shown better correlation to pipeline damage than PGV alone according to previous studies. By comparing the proposed fragilities, it is concluded that a change in the DGS level (from Low-Medium to High) could increase the pipeline repair rates (number of repairs per kilometer) by factors ranging from 1.3 to 2.0; being the higher the <span class="hlt">seismic</span> intensity the lower the factor.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.493...47F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.493...47F"><span>Progressive reactivation of the volcanic plumbing <span class="hlt">system</span> beneath Tolbachik volcano (Kamchatka, Russia) revealed by long-period <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frank, William B.; Shapiro, Nikolaï M.; Gusev, Alexander A.</p> <p>2018-07-01</p> <p>After lying dormant for 36 yr, the Tolbachik volcano of the Klyuchevskoy group started to erupt on 27 November 2012. We investigate the preparatory phase of this eruption via a statistical analysis of the temporal behavior of long-period (LP) earthquakes that occurred beneath this volcanic <span class="hlt">system</span>. The LP <span class="hlt">seismicity</span> occurs close to the surface beneath the main volcanic edifices and at 30 km depth in the vicinity of a deep magmatic reservoir. The deep LP earthquakes and those beneath the Klyuchevskoy volcano occur quasi-periodically, while the LP earthquakes beneath Tolbachik are clustered in time. As the <span class="hlt">seismicity</span> rate increased beneath Tolbachik days before the eruption, the level of the time clustering decreased. We interpret this as a manifestation of the evolution of the volcano plumbing <span class="hlt">system</span>. We suggest that when a plumbing <span class="hlt">system</span> awakes after quiescence, multiple cracks and channels are reactivated simultaneously and their interaction results in the strong time clustering of LP earthquakes. With time, this network of channels and cracks evolves into a more stable state with an overall increased permeability, where fluids flow uninhibited throughout the plumbing <span class="hlt">system</span> except for a few remaining impediments that continue to generate <span class="hlt">seismic</span> radiation. The inter-<span class="hlt">seismic</span> source interaction and the level of earthquake time clustering in this latter state is weak. This scenario suggests that the observed evolution of the statistical behavior of the shallow LP <span class="hlt">seismicity</span> beneath Tolbachik is an indicator of the reactivation and consolidation of the near-surface plumbing <span class="hlt">system</span> prior to the Tolbachik eruption. The parts of the plumbing <span class="hlt">system</span> above the deep magmatic reservoir and beneath the Klyuchevskoy volcano remain in nearly permanent activity, as demonstrated by the continuous occurrence of the deep LP earthquakes and very frequent Klyuchevskoy eruptions. This implies that these parts of the plumbing <span class="hlt">system</span> remain in a stable permeable state and contain a few</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/fs/2006/3050/fs2006-3050.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/fs/2006/3050/fs2006-3050.pdf"><span>Earthquake information products and tools from the Advanced National <span class="hlt">Seismic</span> <span class="hlt">System</span> (ANSS)</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wald, Lisa</p> <p>2006-01-01</p> <p>This Fact Sheet provides a brief description of postearthquake tools and products provided by the Advanced National <span class="hlt">Seismic</span> <span class="hlt">System</span> (ANSS) through the U.S. Geological Survey Earthquake Hazards Program. The focus is on products specifically aimed at providing situational awareness in the period immediately following significant earthquake events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUSM.S23A..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUSM.S23A..06H"><span>The Budget Guide to <span class="hlt">Seismic</span> Network Management</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hagerty, M. T.; Ebel, J. E.</p> <p>2007-05-01</p> <p>Regardless of their size, there are certain tasks that all <span class="hlt">seismic</span> networks must perform, including data collection and processing, earthquake location, information dissemination, and quality control. Small <span class="hlt">seismic</span> networks are unlikely to possess the resources -- manpower and money -- required to do much in-house development. Fortunately, there are a lot of free or inexpensive software solutions available that are able to perform many of the required tasks. Often the available solutions are all-in-one turnkey packages designed and developed for much larger <span class="hlt">seismic</span> networks, and the cost of adapting them to a smaller network must be weighed against the ease with which other, non-<span class="hlt">seismic</span> software can be adapted to the same task. We describe here the software and hardware choices we have made for the New England <span class="hlt">Seismic</span> Network (NESN), a sparse regional <span class="hlt">seismic</span> network responsible for monitoring and reporting all <span class="hlt">seismicity</span> within the New England region in the northeastern U.S. We have chosen to use a cost-effective approach to monitoring using free, off-the-shelf solutions where available (e.g., Earthworm, HYP2000) and modifying freeware solutions when it is easier than trying to adapt a large, complicated package. We have selected for use software that is: free, likely to receive continued support from the <span class="hlt">seismic</span> or, preferably, larger internet community, and modular. Modularity is key to our design because it ensures that if one component of our processing <span class="hlt">system</span> becomes obsolete, we can insert a suitable replacement with few modifications to the other modules. Our automated event detection, identification and location <span class="hlt">system</span> is based on a wavelet transform analysis of station data that arrive continuously via TCP/IP transmission over the internet. Our <span class="hlt">system</span> for interactive analyst review of <span class="hlt">seismic</span> events and remote <span class="hlt">system</span> monitoring utilizes a combination of Earthworm modules, Perl cgi-bin scripts, Java, and native Unix commands and can now be carried out via</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914761M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914761M"><span>Data Analysis of <span class="hlt">Seismic</span> Sequence in Central Italy in 2016 using CTBTO- International Monitoring <span class="hlt">System</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mumladze, Tea; Wang, Haijun; Graham, Gerhard</p> <p>2017-04-01</p> <p>The <span class="hlt">seismic</span> network that forms the International Monitoring <span class="hlt">System</span> (IMS) of the Comprehensive Nuclear-test-ban Treaty Organization (CTBTO) will ultimately consist of 170 <span class="hlt">seismic</span> stations (50 primary and 120 auxiliary) in 76 countries around the world. The Network is still under the development, but currently more than 80% of the network is in operation. The objective of <span class="hlt">seismic</span> monitoring is to detect and locate underground nuclear explosions. However, the data from the IMS also can be widely used for scientific and civil purposes. In this study we present the results of data analysis of the <span class="hlt">seismic</span> sequence in 2016 in Central Italy. Several hundred earthquakes were recorded for this sequence by the <span class="hlt">seismic</span> stations of the IMS. All events were accurately located the analysts of the International Data Centre (IDC) of the CTBTO. In this study we will present the epicentral and magnitude distribution, station recordings and teleseismic phases as obtained from the Reviewed Event Bulletin (REB). We will also present a comparison of the database of the IDC with the databases of the European-Mediterranean Seismological Centre (EMSC) and U.S. Geological Survey (USGS). Present work shows that IMS data can be used for earthquake sequence analyses and can play an important role in seismological research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/6019099','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/6019099"><span>Analytical simulation of nonlinear response to <span class="hlt">seismic</span> test excitations of HDR-VKL (Heissdampfreaktor-Versuchskreislauf) piping <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Srinivasan, M.G.; Kot, C.A.; Mojtahed, M.</p> <p></p> <p>The paper describes the analytical modeling, calculations, and results of the posttest nonlinear simulation of high-level <span class="hlt">seismic</span> testing of the VKL piping <span class="hlt">system</span> at the HDR Test Facility in Germany. One of the objectives of the tests was to evaluate analytical methods for calculating the nonlinear response of realistic piping <span class="hlt">systems</span> subjected to high-level <span class="hlt">seismic</span> excitation that would induce significant plastic deformation. Two out of the six different pipe-support configurations, (ranging from a stiff <span class="hlt">system</span> with struts and snubbers to a very flexible <span class="hlt">system</span> with practically no <span class="hlt">seismic</span> supports), subjected to simulated earthquakes, were tested at very high levels. Themore » posttest nonlinear calculations cover the KWU configuration, a reasonably compliant <span class="hlt">system</span> with only rigid struts. Responses for 800% safe-shutdown-earthquake loading were calculated using the NONPIPE code. The responses calculated with NONPIPE were found generally to have the same time trends as the measurements but contained under-, over-, and correct estimates of peak values, almost in equal proportions. The only exceptions were the peak strut forces, which were underestimated as a group. The scatter in the peak value estimate of displacements and strut forces was smaller than that for the strains. The possible reasons for the differences and the effort on further analysis are discussed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MsT.........37S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MsT.........37S"><span><span class="hlt">Seismic</span> investigation of the Kunlun Fault: Analysis of the INDEPTH IV 2-D active-source <span class="hlt">seismic</span> dataset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seelig, William George</p> <p></p> <p>The Tibetan Plateau has experienced significant crustal thickening and deformation since the continental subduction and collision of the Asian and Indian plates in the Eocene. Deformation of the northern Tibetan Plateau is largely accommodated by strike-slip faulting. The Kunlun Fault is a 1000-km long strike-slip fault near the northern <span class="hlt">boundary</span> of the Plateau that has experienced five magnitude 7.0 or greater earthquakes in the past 100 years and represents a major rheological <span class="hlt">boundary</span>. Active-source, 2-D <span class="hlt">seismic</span> reflection/refraction data, collected as part of project INDEPTH IV (International Deep Profiling of Tibet and the Himalaya, phase IV) in 2007, was used to examine the structure and the dip of the Kunlun fault. The INDEPTH IV data was acquired to better understand the tectonic evolution of the northeastern Tibetan Plateau, such as the far-field deformation associated with the continent-continent collision and the potential subduction of the Asian continent beneath northern Tibet. <span class="hlt">Seismic</span> reflection common depth point (CDP) stacks were examined to look for reflectivity patterns that may be associated with faulting. A possible reflection from the buried North Kunlun Thrust (NKT) is identified at 18-21 km underneath the East Kunlun Mountains, with an estimated apparent dip of 15°S and thrusting to the north. Minimally-processed shot gathers were also inspected for reflections off near-vertical structures such as faults and information on first-order velocity structure. Shot offset and nearest receiver number to reflection was catalogued to increase confidence of picks. Reflections off the North Kunlun (NKF) and South Kunlun Faults (SKF) were identified and analyzed for apparent dip and subsurface geometry. Fault reflection analysis found that the North Kunlun Fault had an apparent dip of approximately 68ºS to an estimated depth of 5 km, while the South Kunlun Fault dipped at approximately 78ºN to an estimated 3.5 km depth. Constraints on apparent dip and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5626S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5626S"><span>The <span class="hlt">seismic</span> signatures of the solar <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stähler, Simon C.; Kedar, Sharon; van Driel, Martin; Vance, Steven D.; Panning, Mark P.</p> <p>2017-04-01</p> <p>Seismology is a powerful tool to image the interior of planetary bodies. At the same time, its results are often difficult to visualize. The spectral-element solver AxiSEM (Nissen-Meyer et al. 2014) enables calculations of the broadband <span class="hlt">seismic</span> response of terrestrial bodies with solid crusts and mantles, as well as icy moons with solid ice crusts overlying liquid oceans. In its database mode, Instaseis (van Driel et al. 2015), AxiSEM can efficiently calculate the <span class="hlt">seismic</span> response for earthquakes at arbitrary distances and depths. We use this method to present a set of global stacks of seismograms, similar to the iconic global stack that Astiz and Shearer (1996) created for IRIS from thousands of seismograms on Earth. We present these stacks for models of Europa, Enceladus, Ganymede, Mercury, Venus, Moon and - for comparison - Earth. The results are based on thermodynamical modeling for the icy moons and orbital observations for the terrestrial planets. The results visualize how each planet and moon has its own unique <span class="hlt">seismic</span> wavefield and which observables exist to infer its detailed structure by future lander missions. Astiz, L., P. Earle and P. Shearer, Global stacking of broadband seismograms, Seis. Res. Lett., 67, 8-18, 1996. M. van Driel, L. Krischer, S.C. Stähler, K. Hosseini, and T. Nissen-Meyer (2015), "Instaseis: instant global seismograms based on a broadband waveform database," Solid Earth, 6, 701-717, doi:10.5194/se-6-701-2015. Nissen-Meyer, T., van Driel, M., Stähler, S. C., Hosseini, K., Hempel, S., Auer, L., … Fournier, A. (2014). AxiSEM: broadband 3-D <span class="hlt">seismic</span> wavefields in axisymmetric media. Solid Earth, 5(1), 425-445. https://doi.org/10.5194/se-5-425-2014</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830048402&hterms=Physical+Review&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DPhysical%2BReview','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830048402&hterms=Physical+Review&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DPhysical%2BReview"><span><span class="hlt">Boundary</span>-fitted coordinate <span class="hlt">systems</span> for numerical solution of partial differential equations - A review</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, J. F.; Warsi, Z. U. A.; Mastin, C. W.</p> <p>1982-01-01</p> <p>A comprehensive review of methods of numerically generating curvilinear coordinate <span class="hlt">systems</span> with coordinate lines coincident with all <span class="hlt">boundary</span> segments is given. Some general mathematical framework and error analysis common to such coordinate <span class="hlt">systems</span> is also included. The general categories of generating <span class="hlt">systems</span> are those based on conformal mapping, orthogonal <span class="hlt">systems</span>, nearly orthogonal <span class="hlt">systems</span>, <span class="hlt">systems</span> produced as the solution of elliptic and hyperbolic partial differential equations, and <span class="hlt">systems</span> generated algebraically by interpolation among the <span class="hlt">boundaries</span>. Also covered are the control of coordinate line spacing by functions embedded in the partial differential operators of the generating <span class="hlt">system</span> and by subsequent stretching transformation. Dynamically adaptive coordinate <span class="hlt">systems</span>, coupled with the physical solution, and time-dependent <span class="hlt">systems</span> that follow moving <span class="hlt">boundaries</span> are treated. References reporting experience using such coordinate <span class="hlt">systems</span> are reviewed as well as those covering the <span class="hlt">system</span> development.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1330358','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1330358"><span>Advances in Rotational <span class="hlt">Seismic</span> Measurements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pierson, Robert; Laughlin, Darren; Brune, Robert</p> <p>2016-10-19</p> <p>Rotational motion is increasingly understood to be a significant part of <span class="hlt">seismic</span> wave motion. Rotations can be important in earthquake strong motion and in Induced <span class="hlt">Seismicity</span> Monitoring. Rotational <span class="hlt">seismic</span> data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational <span class="hlt">seismic</span> applications. Initial focus is onmore » induced <span class="hlt">seismicity</span> monitoring, particularly for Enhanced Geothermal <span class="hlt">Systems</span> (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020920','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020920"><span><span class="hlt">Seismic</span> hazard map of North and Central America and the Caribbean</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shedlock, K.M.</p> <p>1999-01-01</p> <p>Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of <span class="hlt">seismic</span> hazard. National, state, and local government, decision makers, engineers, planners, emergency response organizations, builders, universities, and the general public require <span class="hlt">seismic</span> hazard estimates for land use planning, improved building design and construction (including adoption of building construction codes), emergency response preparedness plans, economic forecasts, housing and employment decisions, and many more types of risk mitigation. The <span class="hlt">seismic</span> hazard map of North and Central America and the Caribbean is the concatenation of various national and regional maps, involving a suite of approaches. The combined maps and documentation provide a useful regional <span class="hlt">seismic</span> hazard framework and serve as a resource for any national or regional agency for further detailed studies applicable to their needs. This <span class="hlt">seismic</span> hazard map depicts Peak Ground Acceleration (PGA) with a 10% chance of exceedance in 50 years. PGA, a short-period ground motion parameter that is proportional to force, is the most commonly mapped ground motion parameter because current building codes that include <span class="hlt">seismic</span> provisions specify the horizontal force a building should be able to withstand during an earthquake. This <span class="hlt">seismic</span> hazard map of North and Central America and the Caribbean depicts the likely level of short-period ground motion from earthquakes in a fifty-year window. Short-period ground motions effect short-period structures (e.g., one-to-two story buildings). The highest <span class="hlt">seismic</span> hazard values in the region generally occur in areas that have been, or are likely to be, the sites of the largest plate <span class="hlt">boundary</span> earthquakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/1977/0671/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/1977/0671/"><span>A FORTRAN program for calculating nonlinear <span class="hlt">seismic</span> ground response</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Joyner, William B.</p> <p>1977-01-01</p> <p>The program described here was designed for calculating the nonlinear <span class="hlt">seismic</span> response of a <span class="hlt">system</span> of horizontal soil layers underlain by a semi-infinite elastic medium representing bedrock. Excitation is a vertically incident shear wave in the underlying medium. The nonlinear hysteretic behavior of the soil is represented by a model consisting of simple linear springs and Coulomb friction elements arranged as shown. A <span class="hlt">boundary</span> condition is used which takes account of finite rigidity in the elastic substratum. The computations are performed by an explicit finite-difference scheme that proceeds step by step in space and time. A brief program description is provided here with instructions for preparing the input and a source listing. A more detailed discussion of the method is presented elsewhere as is the description of a different program employing implicit integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900002914','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900002914"><span>Convergence results for pseudospectral approximations of hyperbolic <span class="hlt">systems</span> by a penalty type <span class="hlt">boundary</span> treatment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Funaro, Daniele; Gottlieb, David</p> <p>1989-01-01</p> <p>A new method of imposing <span class="hlt">boundary</span> conditions in the pseudospectral approximation of hyperbolic <span class="hlt">systems</span> of equations is proposed. It is suggested to collocate the equations, not only at the inner grid points, but also at the <span class="hlt">boundary</span> points and use the <span class="hlt">boundary</span> conditions as penalty terms. In the pseudo-spectral Legrendre method with the new <span class="hlt">boundary</span> treatment, a stability analysis for the case of a constant coefficient hyperbolic <span class="hlt">system</span> is presented and error estimates are derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915979B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915979B"><span>Earthquakes along the Azores-Iberia plate <span class="hlt">boundary</span> revisited</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batlló, Josep; Matos, Catarina; Torres, Ricardo; Cruz, Jorge; Custódio, Susana</p> <p>2017-04-01</p> <p>The plate <span class="hlt">boundary</span> that separates the Eurasian and African plates between the Azores triple junction and Gibraltar has unleashed some of the highest magnitude earthquakes in Europe in the historical and instrumental periods, including the 1755 great Lisbon earthquake with an estimated magnitude of M8.5-8.7, a M8.3 earthquake in 1941 in a transform oceanic fault, a M8.1 fault in 1975 in an oceanic intraplate domain, and a M7.9 earthquake in 1969 offshore SW Portugal. The plate <span class="hlt">boundary</span> evolves from a divergent <span class="hlt">boundary</span> in the east - the Azores domain - through a strike-slip domain at the center - the Gloria fault domain - to an oblique convergence domain in the west - west Iberia and its oceanic margin. A proper mapping of the <span class="hlt">seismicity</span> along this plate <span class="hlt">boundary</span> is key to better understanding it. Prior to the early eighties, many earthquakes with epicentre in the Atlantic and even in mainland Portugal were undetected or not located instrumentally. However knowledge of the occurrence and location of earthquakes prior to this period is critical to understanding the <span class="hlt">seismicity</span> of the region and for the assessment of <span class="hlt">seismic</span> hazard and risk. The relocation of events recorded instrumentally until 1960 is particularly difficult due to the poor sensitivity of the seismographs, few available stations, incompleteness of the reports and lack of accuracy of station chronometers. Thus, different catalogues often provide different locations for the same event, with no information about how they were obtained. On the other hand, there are also conspicuous gaps in the instrumental records of some Portuguese stations. For many earthquakes of the studied period records rely solely on felt effects. In general, a good control on the accuracy or quality of epicenters lacks. Here we present a review of the locations of instrumental earthquakes of the Azores-west Iberia region in the period 1900-1960. In total, we reviewed around 350 earthquakes. More than 160 additional events have</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title41-vol3/pdf/CFR-2014-title41-vol3-sec128-1-8004.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title41-vol3/pdf/CFR-2014-title41-vol3-sec128-1-8004.pdf"><span>41 CFR 128-1.8004 - <span class="hlt">Seismic</span> Safety Coordinators.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-01-01</p> <p>... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false <span class="hlt">Seismic</span> Safety... Management Regulations <span class="hlt">System</span> (Continued) DEPARTMENT OF JUSTICE 1-INTRODUCTION 1.80-<span class="hlt">Seismic</span> Safety Program § 128-1.8004 <span class="hlt">Seismic</span> Safety Coordinators. (a) The Justice Management Division shall designate an...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title41-vol3/pdf/CFR-2012-title41-vol3-sec128-1-8004.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title41-vol3/pdf/CFR-2012-title41-vol3-sec128-1-8004.pdf"><span>41 CFR 128-1.8004 - <span class="hlt">Seismic</span> Safety Coordinators.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-01-01</p> <p>... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false <span class="hlt">Seismic</span> Safety... Management Regulations <span class="hlt">System</span> (Continued) DEPARTMENT OF JUSTICE 1-INTRODUCTION 1.80-<span class="hlt">Seismic</span> Safety Program § 128-1.8004 <span class="hlt">Seismic</span> Safety Coordinators. (a) The Justice Management Division shall designate an...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title41-vol3/pdf/CFR-2013-title41-vol3-sec128-1-8004.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title41-vol3/pdf/CFR-2013-title41-vol3-sec128-1-8004.pdf"><span>41 CFR 128-1.8004 - <span class="hlt">Seismic</span> Safety Coordinators.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-07-01</p> <p>... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false <span class="hlt">Seismic</span> Safety... Management Regulations <span class="hlt">System</span> (Continued) DEPARTMENT OF JUSTICE 1-INTRODUCTION 1.80-<span class="hlt">Seismic</span> Safety Program § 128-1.8004 <span class="hlt">Seismic</span> Safety Coordinators. (a) The Justice Management Division shall designate an...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title41-vol3/pdf/CFR-2011-title41-vol3-sec128-1-8004.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title41-vol3/pdf/CFR-2011-title41-vol3-sec128-1-8004.pdf"><span>41 CFR 128-1.8004 - <span class="hlt">Seismic</span> Safety Coordinators.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-01-01</p> <p>... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false <span class="hlt">Seismic</span> Safety... Management Regulations <span class="hlt">System</span> (Continued) DEPARTMENT OF JUSTICE 1-INTRODUCTION 1.80-<span class="hlt">Seismic</span> Safety Program § 128-1.8004 <span class="hlt">Seismic</span> Safety Coordinators. (a) The Justice Management Division shall designate an...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811106M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811106M"><span>Causality between expansion of <span class="hlt">seismic</span> cloud and maximum magnitude of induced <span class="hlt">seismicity</span> in geothermal field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus</p> <p>2016-04-01</p> <p>Occurrence of induced <span class="hlt">seismicity</span> with large magnitude is critical environmental issues associated with fluid injection for shale gas/oil extraction, waste water disposal, carbon capture and storage, and engineered geothermal <span class="hlt">systems</span> (EGS). Studies for prediction of the hazardous <span class="hlt">seismicity</span> and risk assessment of induced <span class="hlt">seismicity</span> has been activated recently. Many of these studies are based on the seismological statistics and these models use the information of the occurrence time and event magnitude. We have originally developed physics based model named "possible <span class="hlt">seismic</span> moment model" to evaluate <span class="hlt">seismic</span> activity and assess <span class="hlt">seismic</span> moment which can be ready to release. This model is totally based on microseismic information of occurrence time, hypocenter location and magnitude (<span class="hlt">seismic</span> moment). This model assumes existence of representative parameter having physical meaning that release-able <span class="hlt">seismic</span> moment per rock volume (<span class="hlt">seismic</span> moment density) at given field. <span class="hlt">Seismic</span> moment density is to be estimated from microseismic distribution and their <span class="hlt">seismic</span> moment. In addition to this, stimulated rock volume is also inferred by progress of microseismic cloud at given time and this quantity can be interpreted as the rock volume which can release <span class="hlt">seismic</span> energy due to weakening effect of normal stress by injected fluid. Product of these two parameters (equation (1)) provide possible <span class="hlt">seismic</span> moment which can be released from current stimulated zone as a model output. Difference between output of this model and observed cumulative <span class="hlt">seismic</span> moment corresponds the <span class="hlt">seismic</span> moment which will be released in future, based on current stimulation conditions. This value can be translated into possible maximum magnitude of induced <span class="hlt">seismicity</span> in future. As this way, possible <span class="hlt">seismic</span> moment can be used to have feedback to hydraulic stimulation operation in real time as an index which can be interpreted easily and intuitively. Possible <span class="hlt">seismic</span> moment is defined as equation (1), where D</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSM.S23A..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSM.S23A..01W"><span><span class="hlt">Seismic</span> Constraints on Geometry, <span class="hlt">Seismic</span> Velocity and Anisotropy of the "African Anomaly"</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y.; Wen, L.</p> <p>2006-05-01</p> <p><span class="hlt">Seismic</span> evidence shows that the "African Anomaly", a prominent low-velocity structure in the lower mantle beneath Africa, has a broad base near the core-mantle <span class="hlt">boundary</span> (CMB) and extends at least 1000 km upward into the mid-lower mantle. Waveform modeling results indicate that its base is a very-low velocity province (VLVP) in the lowermost 200-300 km of the Earth's mantle with rapidly varying geometries and a strong Vs reduction gradient of -2% - -12% from top to bottom. These features unambiguously indicate the VLVP is compositionally distinct and can be best explained by partial melting driven by a compositional change produced in the early Earth's history [Wen, 2001; Wen et. al, 2001; Wang and Wen, 2004]. <span class="hlt">Seismic</span> structure for the mid-lower mantle portion of the "African Anomaly" and the anisotropic behavior related to the VLVP remain unclear. In this presentation, we will present <span class="hlt">seismic</span> data to constrain geometry and both P- and S- velocity perturbations for the "African Anomaly" along the great arc from the East Pacific Rise to the Japan Sea, and discuss <span class="hlt">seismic</span> anisotropic behavior inside the VLVP and in the surrounding areas. We collected direct S, ScS, SKS, and SKKS waveforms data sets for 9 earthquakes recorded at the temporary broadband Kaapvaal, Tanzania, and Ethiopia/Kenya <span class="hlt">seismic</span> arrays in Africa. These <span class="hlt">seismic</span> data provide reasonably good coverage for the "African Anomaly" along a great circle path in opposite directions. We corrected for the effects of the earthquake mislocation and the <span class="hlt">seismic</span> heterogeneities outside the anomaly. <span class="hlt">Seismic</span> data suggest that the "African Anomaly" exhibits a "cusp-like" shape along the great arc and continuously extends from the CMB to about 1300 km above the CMB with both sides tilting toward its center beneath southern Africa. The magnitude of these travel time residuals can be best explained by a shear velocity structure with average Vs reductions of -5% for the basal layer and -2% - -3% for the portion in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P41F1981S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P41F1981S"><span>The Cretaceous-Paleogene <span class="hlt">boundary</span> unit in the Gulf of Mexico: Large-scale oceanic basin response to the Chicxulub impact</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanford, J. C.; Gulick, S. P.; Snedden, J.</p> <p>2013-12-01</p> <p>The prevailing theory for the Cretaceous-Paleogene (K-Pg) extinction event cites the Chicxulub asteroid impact on the Yucatán Peninsula as the catalyst for the global climatologic and ecologic crisis. This theory has been corroborated by a multitude of K-Pg <span class="hlt">boundary</span> deposits observed globally in both boreholes and outcrops. The change in character of these deposits with proximity to the crater, from a millimeter-scale clay layer to a hectometer-scale carbonate sequence, supports a causal link between the <span class="hlt">boundary</span> unit and the asteroid impact. Due to its passive marine setting and proximity to the Chicxulub crater, the Gulf of Mexico is the premier locale in which to study the near-field geologic effect of a massive bolide impact. Until recently, investigation of the K-Pg <span class="hlt">boundary</span> deposit within the Gulf has been largely confined to outcrops and boreholes on the periphery of the basin due to the difficulty of observation of the <span class="hlt">boundary</span> unit in the deep water. However, hydrocarbon exploration in the past decade has yielded significant borehole and <span class="hlt">seismic</span> data that can be used to better understand the deep-water response to the impact and to gain a comprehensive regional understanding impact-related processes in the Gulf. Based on roughly 100 offshore and 300 onshore Cretaceous well penetrations, the K-Pg <span class="hlt">boundary</span> is interpreted to range from a strictly erosional surface in shallow-water and coastal regimes to a mass transport deposit up to ~400 meters thick. Depth-converted <span class="hlt">seismic</span> data throughout the Gulf corroborate such thicknesses and reveal that the deposit is virtually ubiquitous throughout the deep water. For the first time, the K-Pg <span class="hlt">boundary</span> deposit has been tied from the central Gulf to the Chicxulub crater, further establishing a causative link between the two. Biostratigraphic data in wells confirm the age of the deposit and document the presence of the 'K-Pg <span class="hlt">boundary</span> cocktail.' <span class="hlt">Seismic</span> data reveals areas of extensive debris flows and slump deposits on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/988391','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/988391"><span>Cell <span class="hlt">boundary</span> fault detection <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Archer, Charles Jens [Rochester, MN; Pinnow, Kurt Walter [Rochester, MN; Ratterman, Joseph D [Rochester, MN; Smith, Brian Edward [Rochester, MN</p> <p>2009-05-05</p> <p>A method determines a nodal fault along the <span class="hlt">boundary</span>, or face, of a computing cell. Nodes on adjacent cell <span class="hlt">boundaries</span> communicate with each other, and the communications are analyzed to determine if a node or connection is faulty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.T53A1113A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.T53A1113A"><span>Crustal features along the southern Kuril Trench, Japan, obtained by a refraction/reflection <span class="hlt">seismic</span> survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azuma, R.; Hino, R.; Machida, Y.; Murai, Y.; Takanami, T.; Mochizuki, K.; Yamada, T.; Shinohara, M.; Kanazawa, T.; Sato, T.</p> <p>2007-12-01</p> <p>The seismogenic zone in the southern Kuril Trench can be divided into two segments by the Kushiro Canyon, the Nemuro segment to the east and the Tokachi segment to the west. Except for the giant compound earthquake in 17th century, [e.g. Sawai et al., 2002], M8 class earthquakes have occurred repeatedly within each of these segments. The 1952 and 2003 Tokachi earthquakes are considered to be repeated rupture of the asperity of the Tokachi-oki segment. In order to reveal the <span class="hlt">seismic</span> velocity structure related to the rupture propagation or suspension along the plate <span class="hlt">boundary</span>, we made a <span class="hlt">seismic</span> survey across the segment <span class="hlt">boundary</span> between the Nemuro and Tokachi segments. In the experiment, we deployed 16 OBSs along a <span class="hlt">seismic</span> line with about 180 km length and shot 75 liter airgun to correct wide-angle <span class="hlt">seismic</span> data, and MCS survey was also made simultaneously. The profile ran through the focal areas of the 2003 Tokachi and the 1973 Nemuro earthquakes along the strike of the Kuril Trench. The first arrival times observed by the OBSs are inverted for 2-D P-wave velocity distribution and locations of major reflectors are imaged by using traveltime mapping method (TMM) [Fujie et al., 2005]. In the obtained crustal velocity model, sedimentary layers with Vp < 4.8 km/s shows significant variation along the profile. In the rupture area of the 2003 Tokachi earthquake, their total thickness is about 8 km, it decrease to about 4 km in the segment <span class="hlt">boundary</span> zone around the Kushiro Canyon. In the Vp model obtained by Nakanishi et al [2004], the layer with Vp of about 5~6 km/s was interpreted as the upper crustal layer of the Kuril arc. But the present result of the TMM shows that there is a distinct reflective <span class="hlt">boundary</span> within the layer, which separating the layer into upper and lower units. Judging from its large vertical velocity gradient, the upper unit may be old sedimentary unit. Wells et al [2003] pointed out the correlation between the low gravity anomaly (LGA) zones and areas</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G53A1126P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G53A1126P"><span>Salton Trough Post-<span class="hlt">seismic</span> Afterslip, Viscoelastic Response, and Contribution to Regional Hazard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, J. W.; Donnellan, A.; Lyzenga, G. A.</p> <p>2012-12-01</p> <p>The El Mayor-Cucapah M7.2 April 4 2010 earthquake in Baja California may have affected accumulated hazard to Southern California cities due to loading of regional faults including the Elsinore, San Jacinto and southern San Andreas, faults which already have over a century of tectonic loading. We examine changes observed via multiple <span class="hlt">seismic</span> and geodetic techniques, including micro <span class="hlt">seismicity</span> and proposed <span class="hlt">seismicity</span>-based indicators of hazard, high-quality fault models, the Plate <span class="hlt">Boundary</span> Observatory GNSS array (with 174 stations showing post-<span class="hlt">seismic</span> transients with greater than 1 mm amplitude), and interferometric radar maps from UAVSAR (aircraft) flights, showing a network of aseismic fault slip events at distances up to 60 km from the end of the surface rupture. Finite element modeling is used to compute the expected coseismic motions at GPS stations with general agreement, including coseismic uplift at sites ~200 km north of the rupture. Postseismic response is also compared, with GNSS and also with the CIG software "RELAX." An initial examination of hazard is made comparing micro <span class="hlt">seismicity</span>-based metrics, fault models, and changes to coulomb stress on nearby faults using the finite element model. Comparison of <span class="hlt">seismicity</span> with interferograms and historic earthquakes show aseismic slip occurs on fault segments that have had earthquakes in the last 70 years, while other segments show no slip at the surface but do show high triggered <span class="hlt">seismicity</span>. UAVSAR-based estimates of fault slip can be incorporated into the finite element model to correct Coloumb stress change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70030773','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70030773"><span>Numerical investigation of implementation of air-earth <span class="hlt">boundary</span> by acoustic-elastic <span class="hlt">boundary</span> approach</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Xu, Y.; Xia, J.; Miller, R.D.</p> <p>2007-01-01</p> <p>The need for incorporating the traction-free condition at the air-earth <span class="hlt">boundary</span> for finite-difference modeling of <span class="hlt">seismic</span> wave propagation has been discussed widely. A new implementation has been developed for simulating elastic wave propagation in which the free-surface condition is replaced by an explicit acoustic-elastic <span class="hlt">boundary</span>. Detailed comparisons of seismograms with different implementations for the air-earth <span class="hlt">boundary</span> were undertaken using the (2,2) (the finite-difference operators are second order in time and space) and the (2,6) (second order in time and sixth order in space) standard staggered-grid (SSG) schemes. Methods used in these comparisons to define the air-earth <span class="hlt">boundary</span> included the stress image method (SIM), the heterogeneous approach, the scheme of modifying material properties based on transversely isotropic medium approach, the acoustic-elastic <span class="hlt">boundary</span> approach, and an analytical approach. The method proposed achieves the same or higher accuracy of modeled body waves relative to the SIM. Rayleigh waves calculated using the explicit acoustic-elastic <span class="hlt">boundary</span> approach differ slightly from those calculated using the SIM. Numerical results indicate that when using the (2,2) SSG scheme for SIM and our new method, a spatial step of 16 points per minimum wavelength is sufficient to achieve 90% accuracy; 32 points per minimum wavelength achieves 95% accuracy in modeled Rayleigh waves. When using the (2,6) SSG scheme for the two methods, a spatial step of eight points per minimum wavelength achieves 95% accuracy in modeled Rayleigh waves. Our proposed method is physically reasonable and, based on dispersive analysis of simulated seismographs from a layered half-space model, is highly accurate. As a bonus, our proposed method is easy to program and slightly faster than the SIM. ?? 2007 Society of Exploration Geophysicists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JAG...152..118Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JAG...152..118Z"><span>Properties of <span class="hlt">seismic</span> absorption induced reflections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Haixia; Gao, Jinghuai; Peng, Jigen</p> <p>2018-05-01</p> <p><span class="hlt">Seismic</span> reflections at an interface are often regarded as the variation of the acoustic impedance (product of <span class="hlt">seismic</span> velocity and density) in a medium. In fact, they can also be generated due to the difference in absorption of the <span class="hlt">seismic</span> energy. In this paper, we investigate the properties of such reflections. Based on the diffusive-viscous wave equation and elastic diffusive-viscous wave equation, we investigate the dependency of the reflection coefficients on frequency, and their variations with incident angles. Numerical results at a <span class="hlt">boundary</span> due to absorption contrasts are compared with those resulted from acoustic impedance variation. It is found that, the reflection coefficients resulted from absorption depend significantly on the frequency especially at lower frequencies, but vary very slowly at small incident angles. At the higher frequencies, the reflection coefficients of diffusive-viscous wave and elastic diffusive-viscous wave are close to those of acoustic and elastic cases, respectively. On the other hand, the reflections caused by acoustic impedance variation are independent of frequency but vary distinctly with incident angles before the critical angle. We also investigate the difference between the seismograms generated in the two different media. The numerical results show that the amplitudes of these reflected waves are attenuated and their phases are shifted. However, the reflections obtained by acoustic impedance contrast, show no significant amplitude attenuation and phase shift.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5544G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5544G"><span>Detection capability of the IMS <span class="hlt">seismic</span> network based on ambient <span class="hlt">seismic</span> noise measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaebler, Peter J.; Ceranna, Lars</p> <p>2016-04-01</p> <p>All nuclear explosions - on the Earth's surface, underground, underwater or in the atmosphere - are banned by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty, a verification regime was put into place to detect, locate and characterize nuclear explosion testings at any time, by anyone and everywhere on the Earth. The International Monitoring <span class="hlt">System</span> (IMS) plays a key role in the verification regime of the CTBT. Out of the different monitoring techniques used in the IMS, the <span class="hlt">seismic</span> waveform approach is the most effective technology for monitoring nuclear underground testing and to identify and characterize potential nuclear events. This study introduces a method of <span class="hlt">seismic</span> threshold monitoring to assess an upper magnitude limit of a potential <span class="hlt">seismic</span> event in a certain given geographical region. The method is based on ambient <span class="hlt">seismic</span> background noise measurements at the individual IMS <span class="hlt">seismic</span> stations as well as on global distance correction terms for body wave magnitudes, which are calculated using the <span class="hlt">seismic</span> reflectivity method. From our investigations we conclude that a global detection threshold of around mb 4.0 can be achieved using only stations from the primary <span class="hlt">seismic</span> network, a clear latitudinal dependence for the detection threshold can be observed between northern and southern hemisphere. Including the <span class="hlt">seismic</span> stations being part of the auxiliary <span class="hlt">seismic</span> IMS network results in a slight improvement of global detection capability. However, including wave arrivals from distances greater than 120 degrees, mainly PKP-wave arrivals, leads to a significant improvement in average global detection capability. In special this leads to an improvement of the detection threshold on the southern hemisphere. We further investigate the dependence of the detection capability on spatial (latitude and longitude) and temporal (time) parameters, as well as on parameters such as source type and percentage of operational IMS stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSMG14A1891L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSMG14A1891L"><span><span class="hlt">Seismic</span> geomorphology of the Lobed-channel <span class="hlt">System</span> of Upper Miocene Huangliu Formation, Yinggehai Basin, Northwestern South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, H.</p> <p>2016-02-01</p> <p>Three-dimensional <span class="hlt">seismic</span> data have been widely used in interpreting ancient river <span class="hlt">systems</span> and their associated sediment deposits. Thin-bed reservoirs of lobed-channel <span class="hlt">system</span> in lithostratigraphic units of Dongfang (DF) area are one of the major study areas for reservoir growth in the Yinggehai basin of northwestern South China Sea. Although it is understood that the transport mechanics of parent substrate and alluvium determine the morphology of channel for lobed-channel <span class="hlt">system</span>, the transport mechanism and regional gradient are relatively poorly understood. This study is focused on the application of various techniques in <span class="hlt">seismic</span> geomorphology to the Yinggehai Basin at paleo-water-depth of 120m to assess influences of regional gradient and relative sea level change on lobed-channel palaeogeomorphology in shallow-water environments. The Vietnam paleo-Blue River, which located at south of modern Red River, flowed through DF area and transported turbidity deposit to DF area in the coastal environment. In 3-D <span class="hlt">seismic</span> survey area, four fifth-order sequences in first member of upper Miocene Huangliu formation were identified using well and <span class="hlt">seismic</span> data. <span class="hlt">Seismic</span> inversion and 90° phasing of <span class="hlt">seismic</span> data were used to convert <span class="hlt">seismic</span> traces to pseudolithologic logs. Stratal slicing made it possible to interpolate and extrapolate well-data-derived sequence and identify submarine fan, channel fill, lobes and overbank deposit. Strata slices suggested that sea-floor slopes exerted main influence on channel morphology. Specifically, DF13-1 block had high gradient, which mainly distributed mud-sand-rich lobes. However, DF13-2 block established low gradient, which mostly indicated sand-rich braided channels. The values of sinuosity, channel widths, meander-belt widths in DF13-2 block are all greater than these in DF13-1 block. In addition, results of carbon isotope measurements and foraminiferal research of two blocks suggest that paleo sea level in DF13-2 block (30m 150m) was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S51A4418G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S51A4418G"><span>A probabilistic assessment of waste water injection induced <span class="hlt">seismicity</span> in central California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goebel, T.; Hauksson, E.; Ampuero, J. P.; Aminzadeh, F.; Cappa, F.; Saleeby, J.</p> <p>2014-12-01</p> <p>The recent, large increase in <span class="hlt">seismic</span> activity within the central and eastern U.S. may be connected to an increase in fluid injection activity since ~2001. Anomalous <span class="hlt">seismic</span> sequences can easily be identified in regions with low background <span class="hlt">seismicity</span> rates. Here, we analyze <span class="hlt">seismicity</span> in plate <span class="hlt">boundary</span> regions where tectonically-driven earthquake sequences are common, potentially masking injection-induced events. We show results from a comprehensive analysis of waste water disposal wells in Kern county, the largest oil-producing county in California. We focus on spatial-temporal correlations between <span class="hlt">seismic</span> and injection activity and <span class="hlt">seismicity</span>-density changes due to injection. We perform a probabilistic assessment of induced vs. tectonic earthquakes, which can be applied to different regions independent of background rates and may provide insights into the probability of inducing earthquakes as a function of injection parameters and local geological conditions. Our results show that most earthquakes are caused by tectonic forcing, however, waste water injection contributes to <span class="hlt">seismic</span> activity in four different regions with several events above M4. The <span class="hlt">seismicity</span> shows different migration characteristics relative to the injection sites, including linear and non-linear trends. The latter is indicative of diffusive processes which take advantage of reservoir properties and fault structures and can induce earthquakes at distances of up to 10 km. Our results suggest that injection-related triggering processes are complex, possibly involving creep, and delayed triggering. Pore-pressure diffusion may be more extensive in the presence of active faults and high-permeability damage zones thus altering the local <span class="hlt">seismic</span> hazard in a non-linear fashion. As a consequence, generic "best-practices" for fluid injections like a maximum distance from the nearest active fault may not be sufficient to mitigate a potential <span class="hlt">seismic</span> hazard increase.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026567','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026567"><span><span class="hlt">Seismic</span> hazard maps of Mexico, the Caribbean, and Central and South America</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tanner, J.G.; Shedlock, K.M.</p> <p>2004-01-01</p> <p>The growth of megacities in <span class="hlt">seismically</span> active regions around the world often includes the construction of <span class="hlt">seismically</span> unsafe buildings and infrastructures due to an insufficient knowledge of existing <span class="hlt">seismic</span> hazard and/or economic constraints. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of <span class="hlt">seismic</span> hazard. We have produced a suite of <span class="hlt">seismic</span> hazard estimates for Mexico, the Caribbean, and Central and South America. One of the preliminary maps in this suite served as the basis for the Caribbean and Central and South America portion of the Global <span class="hlt">Seismic</span> Hazard Map (GSHM) published in 1999, which depicted peak ground acceleration (pga) with a 10% chance of exceedance in 50 years for rock sites. Herein we present maps depicting pga and 0.2 and 1.0 s spectral accelerations (SA) with 50%, 10%, and 2% chances of exceedance in 50 years for rock sites. The <span class="hlt">seismicity</span> catalog used in the generation of these maps adds 3 more years of data to those used to calculate the GSH Map. Different attenuation functions (consistent with those used to calculate the U.S. and Canadian maps) were used as well. These nine maps are designed to assist in global risk mitigation by providing a general <span class="hlt">seismic</span> hazard framework and serving as a resource for any national or regional agency to help focus further detailed studies required for regional/local needs. The largest <span class="hlt">seismic</span> hazard values in Mexico, the Caribbean, and Central and South America generally occur in areas that have been, or are likely to be, the sites of the largest plate <span class="hlt">boundary</span> earthquakes. High hazard values occur in areas where shallow-to-intermediate <span class="hlt">seismicity</span> occurs frequently. ?? 2004 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1018214','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1018214"><span>Cell <span class="hlt">boundary</span> fault detection <span class="hlt">system</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Archer, Charles Jens [Rochester, MN; Pinnow, Kurt Walter [Rochester, MN; Ratterman, Joseph D [Rochester, MN; Smith, Brian Edward [Rochester, MN</p> <p>2011-04-19</p> <p>An apparatus and program product determine a nodal fault along the <span class="hlt">boundary</span>, or face, of a computing cell. Nodes on adjacent cell <span class="hlt">boundaries</span> communicate with each other, and the communications are analyzed to determine if a node or connection is faulty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13c4004T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13c4004T"><span>Induced <span class="hlt">seismicity</span> hazard and risk by enhanced geothermal <span class="hlt">systems</span>: an expert elicitation approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trutnevyte, Evelina; Azevedo, Inês L.</p> <p>2018-03-01</p> <p>Induced <span class="hlt">seismicity</span> is a concern for multiple geoenergy applications, including low-carbon enhanced geothermal <span class="hlt">systems</span> (EGS). We present the results of an international expert elicitation (n = 14) on EGS induced <span class="hlt">seismicity</span> hazard and risk. Using a hypothetical scenario of an EGS plant and its geological context, we show that expert best-guess estimates of annualized exceedance probabilities of an M ≥ 3 event range from 0.2%-95% during reservoir stimulation and 0.2%-100% during operation. Best-guess annualized exceedance probabilities of M ≥ 5 event span from 0.002%-2% during stimulation and 0.003%-3% during operation. Assuming that tectonic M7 events could occur, some experts do not exclude induced (triggered) events of up to M7 too. If an induced M = 3 event happens at 5 km depth beneath a town with 10 000 inhabitants, most experts estimate a 50% probability that the loss is contained within 500 000 USD without any injuries or fatalities. In the case of an induced M = 5 event, there is 50% chance that the loss is below 50 million USD with the most-likely outcome of 50 injuries and one fatality or none. As we observe a vast diversity in quantitative expert judgements and underlying mental models, we conclude with implications for induced <span class="hlt">seismicity</span> risk governance. That is, we suggest documenting individual expert judgements in induced <span class="hlt">seismicity</span> elicitations before proceeding to consensual judgements, to convene larger expert panels in order not to cherry-pick the experts, and to aim for multi-organization multi-model assessments of EGS induced <span class="hlt">seismicity</span> hazard and risk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018IJEaS.tmp...41K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018IJEaS.tmp...41K"><span>Long-term <span class="hlt">seismic</span> observations along Myanmar-Sunda subduction margin: insights for 2004 M w > 9.0 earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, Prosanta Kumar; Banerjee, Jayashree; Shamim, Sk; Mohanty, Manoranjan</p> <p>2018-03-01</p> <p>The present study investigates the temporal variation of few <span class="hlt">seismic</span> parameters between the Myanmar (Zone I), Andaman-Nicobar-Northwest Sumatra (Zone II), Southeast Sumatra-West Indonesia (Zone III) and East Indonesia (Zone IV) converging <span class="hlt">boundaries</span> in reference to the generation of 26 December 2004 M w > 9.0 off-Sumatra mega-earthquake event. The four segments are distinguished based on tectonics parameters, distinct geological locations, great earthquake occurrences, and the Wadati-Benioff zone characteristics. Two important <span class="hlt">seismic</span> parameters such as <span class="hlt">seismic</span> energy and b values are computed over a time-window of 6-month period during the entire 1976-2013 period for these segments. The b values show a constant decrease in Zones II, III, and IV, whereas the Zone I does not show any such pattern prior to the 2004 mega-event. The release of <span class="hlt">seismic</span> energy was also gradually decreasing in Zones II and III till the 2004 event, and little similar pattern was also noted in Zone IV. This distinct observation might be indicating that the stress accumulation was dominant near the Sumatra-Java area located towards southeast of Zone II and northwest of Zone III. The released strain energy during the 2004 event was subsequently migrated towards north, rupturing 1300 km of the <span class="hlt">boundary</span> between the Northwest Sumatra and the North Andaman. The occurrence of 2004 mega-event was apparently concealed behind the long-term <span class="hlt">seismic</span> quiescence existing near the Sumatra and Nicobar margin. A systematic study of the patterns of <span class="hlt">seismic</span> energy release and b values, and the long-term observation of collective behaviour of the margin tectonics might have had given clues to the possibility of the 2004 mega-event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMEP13C3537S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMEP13C3537S"><span><span class="hlt">Seismic</span> features and evolution of a late Miocene submarine channel <span class="hlt">system</span> in the Yinggehai basin, northwestern South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, H.; Jiang, T.; Wang, Z.; Zhang, Y.</p> <p>2014-12-01</p> <p>Submarine channel is one of key conduits for coarse terrigenous clastic sediments to abyssal plain, which provides the possibility for deepwater hydrocarbon exploration. Recently, a new high-quality 3D <span class="hlt">seismic</span> data is acquired in south Yinggehai basin (YGHB) and the detailed interpretations on those <span class="hlt">seismic</span> profiles as well as RMS amplitude attributes and variance slices reveal a submarine channel <span class="hlt">system</span> developed in late Miocene, which could be supplied from Hainan Island via turbidity currents so that it would be filled with sand-rich turbidites as good hydrocarbon reservoir. Based on the integration between regional <span class="hlt">seismic</span> survey and some boreholes, the investigations on its infilling architectures and depositional processes are carried out. The results show that it composes two converged submarine channels with two channelized submarine fans to their west and the main submarine channel (MSC) is characterized by a downstream increasing width and is infilled by sediments with high amplitude <span class="hlt">seismic</span> facies, which could be originated from channelized submarine fans. Furthermore, the complicated depositional processes around the confluence region of these two channels are pointed out and the interactions between the submarine channel <span class="hlt">system</span> and nearby channelized submarine fans are discussed. The detailed illustration on the <span class="hlt">seismic</span> features and depositional processes of the subsurface submarine <span class="hlt">system</span> provides us better understanding deepwater sedimentary dynamics and would be more benefit for the hydrocarbon exploration in similar deepwater area around the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21380919','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21380919"><span>Determining the depositional pattern by resistivity-<span class="hlt">seismic</span> inversion for the aquifer <span class="hlt">system</span> of Maira area, Pakistan.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Akhter, Gulraiz; Farid, Asim; Ahmad, Zulfiqar</p> <p>2012-01-01</p> <p>Velocity and density measured in a well are crucial for synthetic <span class="hlt">seismic</span> generation which is, in turn, a key to interpreting real <span class="hlt">seismic</span> amplitude in terms of lithology, porosity and fluid content. Investigations made in the water wells usually consist of spontaneous potential, resistivity long and short normal, point resistivity and gamma ray logs. The sonic logs are not available because these are usually run in the wells drilled for hydrocarbons. To generate the synthetic seismograms, sonic and density logs are required, which are useful to precisely mark the lithology contacts and formation tops. An attempt has been made to interpret the subsurface soil of the aquifer <span class="hlt">system</span> by means of resistivity to <span class="hlt">seismic</span> inversion. For this purpose, resistivity logs and surface resistivity sounding were used and the resistivity logs were converted to sonic logs whereas surface resistivity sounding data transformed into <span class="hlt">seismic</span> curves. The converted sonic logs and the surface <span class="hlt">seismic</span> curves were then used to generate synthetic seismograms. With the utilization of these synthetic seismograms, pseudo-<span class="hlt">seismic</span> sections have been developed. Subsurface lithologies encountered in wells exhibit different velocities and densities. The reflection patterns were marked by using amplitude standout, character and coherence. These pseudo-<span class="hlt">seismic</span> sections were later tied to well synthetics and lithologs. In this way, a lithology section was created for the alluvial fill. The cross-section suggested that the eastern portion of the studied area mainly consisted of sandy fill and the western portion constituted clayey part. This can be attributed to the depositional environment by the Indus and the Kabul Rivers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGP32A..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGP32A..06R"><span>Central Atlantic Lithosphere-Asthenosphere <span class="hlt">Boundary</span> Study (CAL-LAB): Massive Coast effects in MT data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reyes Ortega, V.; Constable, S.; Bassett, D.</p> <p>2017-12-01</p> <p>The Lithosphere-Asthenosphere <span class="hlt">Boundary</span> (LAB) is the largest plate <span class="hlt">boundary</span> on Earth yet is still poorly understood, with temperature, hydration, composition, melting, strain rate, and anisotropy all candidates to explain the location and behavior of this transition from convecting asthenosphere to rigid lithosphere. Electrical conductivity, estimated from magnetotelluric (MT) data and combined with <span class="hlt">seismic</span> measurements, is increasingly being seen as a way to improve our understanding of the LAB. The Integrated LAB (iLAB) experiment brings together three institutions from three countries to collect MT data along with passive and active <span class="hlt">seismic</span> data in the central equatorial Atlantic, over lithosphere from 0 to 80 My old. Thirty-nine seafloor MT instruments were deployed alongside ocean-bottom seismometers for over one year, and recorded data for 70 to 100 days before the batteries expired. Good quality MT responses were obtained from 10 to nearly 100,000 seconds period, but many sites exhibited up to -180 degree phase shifts at the highest frequencies. Forward modeling shows that this behavior is consistent with a coast effect from the African coastline 500-1500 kilometers away. The conductive mid-ocean ridge <span class="hlt">system</span> modifies the coast effect for sites west of the ridge. Inverting these data for LAB geology in the presence of such a strong coast effect presents a considerable challenge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S33D2816T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S33D2816T"><span>The ANSS Station Information <span class="hlt">System</span>: A Centralized Station Metadata Repository for Populating, Managing and Distributing <span class="hlt">Seismic</span> Station Metadata</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, V. I.; Yu, E.; Acharya, P.; Jaramillo, J.; Chowdhury, F.</p> <p>2015-12-01</p> <p>Maintaining and archiving accurate site metadata is critical for <span class="hlt">seismic</span> network operations. The Advanced National <span class="hlt">Seismic</span> <span class="hlt">System</span> (ANSS) Station Information <span class="hlt">System</span> (SIS) is a repository of <span class="hlt">seismic</span> network field equipment, equipment response, and other site information. Currently, there are 187 different sensor models and 114 data-logger models in SIS. SIS has a web-based user interface that allows network operators to enter information about <span class="hlt">seismic</span> equipment and assign response parameters to it. It allows users to log entries for sites, equipment, and data streams. Users can also track when equipment is installed, updated, and/or removed from sites. When <span class="hlt">seismic</span> equipment configurations change for a site, SIS computes the overall gain of a data channel by combining the response parameters of the underlying hardware components. Users can then distribute this metadata in standardized formats such as FDSN StationXML or dataless SEED. One powerful advantage of SIS is that existing data in the repository can be leveraged: e.g., new instruments can be assigned response parameters from the Incorporated Research Institutions for Seismology (IRIS) Nominal Response Library (NRL), or from a similar instrument already in the inventory, thereby reducing the amount of time needed to determine parameters when new equipment (or models) are introduced into a network. SIS is also useful for managing field equipment that does not produce <span class="hlt">seismic</span> data (eg power <span class="hlt">systems</span>, telemetry devices or GPS receivers) and gives the network operator a comprehensive view of site field work. SIS allows users to generate field logs to document activities and inventory at sites. Thus, operators can also use SIS reporting capabilities to improve planning and maintenance of the network. Queries such as how many sensors of a certain model are installed or what pieces of equipment have active problem reports are just a few examples of the type of information that is available to SIS users.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/880010','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/880010"><span>Method Apparatus And <span class="hlt">System</span> For Detecting <span class="hlt">Seismic</span> Waves In A Borehole</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>West, Phillip B.; Sumstine, Roger L.</p> <p>2006-03-14</p> <p>A method, apparatus and <span class="hlt">system</span> for detecting <span class="hlt">seismic</span> waves. A sensing apparatus is deployed within a bore hole and may include a source magnet for inducing a magnetic field within a casing of the borehole. An electrical coil is disposed within the magnetic field to sense a change in the magnetic field due to a displacement of the casing. The electrical coil is configured to remain substantially stationary relative to the well bore and its casing along a specified axis such that displacement of the casing induces a change within the magnetic field which may then be sensed by the electrical coil. Additional electrical coils may be similarly utilized to detect changes in the same or other associated magnetic fields along other specified axes. The additional sensor coils may be oriented substantially orthogonally relative to one another so as to detect <span class="hlt">seismic</span> waves along multiple orthogonal axes in three dimensional space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70195500','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70195500"><span>Plateau subduction, intraslab <span class="hlt">seismicity</span>, and the Denali (Alaska) volcanic gap</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chuang, Lindsay Yuling; Bostock, Michael; Wech, Aaron; Plourde, Alexandre</p> <p>2018-01-01</p> <p>Tectonic tremors in Alaska (USA) are associated with subduction of the Yakutat plateau, but their origins are unclear due to lack of depth constraints. We have processed tremor recordings to extract low-frequency earthquakes (LFEs), and generated a set of six LFE waveform templates via iterative network matched filtering and stacking. The timing of impulsive P (compressional) wave and S (shear) wave arrivals on template waveforms places LFEs at 40–58 km depth, near the upper envelope of intraslab <span class="hlt">seismicity</span> and immediately updip of increased levels of intraslab <span class="hlt">seismicity</span>. S waves at near-epicentral distances display polarities consistent with shear slip on the plate <span class="hlt">boundary</span>. We compare characteristics of LFEs, <span class="hlt">seismicity</span>, and tectonic structures in central Alaska with those in warm subduction zones, and propose a new model for the region’s unusual intraslab <span class="hlt">seismicity</span> and the enigmatic Denali volcanic gap (i.e., an area of no volcanism where expected). We argue that fluids in the Yakutat plate are confined to its upper crust, and that shallow subduction leads to hydromechanical conditions at the slab interface in central Alaska akin to those in warm subduction zones where similar LFEs and tremor occur. These conditions lead to fluid expulsion at shallow depths, explaining strike-parallel alignment of tremor occurrence with the Denali volcanic gap. Moreover, the lack of double <span class="hlt">seismic</span> zone and restriction of deep intraslab <span class="hlt">seismicity</span> to a persistent low-velocity zone are simple consequences of anhydrous conditions prevailing in the lower crust and upper mantle of the Yakutat plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRC..118.2329P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRC..118.2329P"><span><span class="hlt">Seismic</span> reflection imaging of shallow oceanographic structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piété, Helen; Marié, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-André</p> <p>2013-05-01</p> <p>Multichannel <span class="hlt">seismic</span> (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow <span class="hlt">seismic</span> oceanography (SO), we reprocessed and analyzed four multichannel <span class="hlt">seismic</span> reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. <span class="hlt">Seismic</span> data processing dedicated to SO was also investigated. Conventional <span class="hlt">seismic</span> acquisition <span class="hlt">systems</span> were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large offsets and <span class="hlt">seismic</span> trace lengths, and sources that typically cannot provide both a high level of emission and fine vertical resolution. We considered a test case, the imagery of the seasonal thermocline on the western Brittany continental shelf. New oceanographic data acquired in this area allowed simulation of the <span class="hlt">seismic</span> acquisition. Sea trials of a specifically designed <span class="hlt">system</span> were performed during the ASPEX survey, conducted in early summer 2012. The <span class="hlt">seismic</span> device featured: (i) four <span class="hlt">seismic</span> streamers, each consisting of six traces of 1.80 m; (ii) a 1000 J SIG sparker source, providing a 400 Hz signal with a level of emission of 205 dB re 1 μPa @ 1 m. This survey captured the 15 m thick, 30 m deep seasonal thermocline in unprecedented detail, showing images of vertical displacements most probably induced by internal waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.S41D..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.S41D..04Z"><span><span class="hlt">Seismic</span> imaging of the oil and geothermal reservoirs using the induced <span class="hlt">seismicity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, H.; Toksoz, M. N.; Fehler, M.</p> <p>2011-12-01</p> <p>It is known that microseismicity can be induced in the oil field due to the stress change caused by oil/gas production. Similarly, injection of high-pressure fluids into the reservoir can also induce microseismicity. Due to the proximity of induced <span class="hlt">seismicity</span> to the reservoir, in some cases, it may be advantageous to use induced <span class="hlt">seismicity</span> to image the reservoir. The <span class="hlt">seismic</span> stations for monitoring the induced <span class="hlt">seismicity</span> are usually sparse. Conventional travel time tomography using travel times from <span class="hlt">seismic</span> events to stations may not be applicable because of poor ray coverage outside the source region. In comparison, the double-difference tomography method of Zhang and Thurber (2003) that uses the differential travel times is able to image the reservoir by avoiding determining the velocity structure outside the source region. In this study, we present two case studies of applying double-difference tomography to induced <span class="hlt">seismicity</span> monitored by borehole stations. In the case of an oil field in Oman, five closely spaced monitoring wells are used to monitor microseismicity induced by gas production. In each well, multiple <span class="hlt">seismic</span> sensors are positioned from depths 750 m - 1250 m and about 2000 events are selected for tomography. Reservoir imaging shows encouraging results in identifying structures and velocity changes within reservoir layers. Clear velocity contrast was seen across the major northeast-southwest faults. Low Vp, low Vs and low Vp/Vs anomalies are mainly associated with the gas production layer. For the case of the Soultz Enhanced Geothermal <span class="hlt">System</span> at Soultz-sous-Forets, France, we used travel time data from the September and October 1993 hydraulic stimulations, where only four borehole stations are available. The results showed that the S-wave velocity structure correlated well with <span class="hlt">seismicity</span> and showed low velocity zones at depths between 2900 and 3300 meters, where fluid was believed to have infiltrated the reservoir. We also attempt time</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29350212','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29350212"><span>Defining <span class="hlt">System</span> <span class="hlt">Boundaries</span> of an Institution Nitrogen Footprint.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de la Reguera, Elizab