Recursos de colección

Caltech Authors (163.728 recursos)

Repository of works by Caltech published authors.

Group = Seismological Laboratory

Mostrando recursos 1 - 20 de 364

  1. Empirical Site Classification of CSN Network Using Strong‐Motion Records

    Leyton, F.; Pastén, C.; Ruiz, S.; Idini, B.; Rojas, F.
    The National Seismological Center of the University of Chile (CSN, Centro Sismológico Nacional) has been operating more than 400 seismic stations throughout the country. The data collected from this network, from March 2012 to August 2017, includes more than 4000 Chilean strong‐motion records, from more than 1000 events (magnitudes ranging from 4.0 up to 8.3). In this study, we use this data set and classify 118 stations from this network, using the horizontal‐to‐vertical response spectral ratio (HVRSR) of strong‐motion records. This classification considers not only the predominant period obtained from the average HVRSR but also the peak amplitude from this...

  2. Systematic deficiency of aftershocks in areas of high coseismic slip for large subduction zone earthquakes

    Wetzler, Nadav; Lay, Thorne; Brodsky, Emily E.; Kanamori, Hiroo
    Fault slip during plate boundary earthquakes releases a portion of the shear stress accumulated due to frictional resistance to relative plate motions. Investigation of 101 large [moment magnitude (M_w) ≥ 7] subduction zone plate boundary mainshocks with consistently determined coseismic slip distributions establishes that 15 to 55% of all master event–relocated aftershocks with M_w ≥ 5.2 are located within the slip regions of the mainshock ruptures and few are located in peak slip regions, allowing for uncertainty in the slip models. For the preferred models, cumulative deficiency of aftershocks within the central three-quarters of the scaled slip regions ranges from...

  3. A multi-pixel time series analysis method accounting for ground motion, atmospheric noise and orbital errors

    Jolivet, R.; Simons, M.
    InSAR time series methods aim to reconstruct time-dependent ground displacements over large areas from sets of interferograms in order to detect transient, periodic or small amplitude deformation. Because of computational limitations, most existing methods consider each pixel independently, ignoring important spatial covariances between observations. We describe a framework to reconstruct time series of ground deformation while considering all pixels simultaneously, allowing us to account for spatial covariances, imprecise orbits and residual atmospheric perturbations. We describe spatial covariances by an exponential decay function dependent of pixel-to-pixel distance. We approximate the impact of imprecise orbit information and residual long wavelength atmosphere as...

  4. Transpressional Rupture Cascade of the 2016 M_w 7.8 Kaikoura Earthquake, New Zealand

    Xu, Wenbin; Feng, Guangcai; Meng, Lingsen; Zhang, Ailin; Ampuero, Jean Paul; Bürgmann, Roland; Fang, Lihua
    Large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults. The 2016 M_w 7.8 Kaikoura earthquake, New Zealand involved the rupture of at least 21 faults, propagating from southwest to northeast for about 180 km. Here we combine space geodesy and seismology techniques to study subsurface fault geometry, slip distribution and the kinematics of the rupture. Our finite-fault slip model indicates that the fault motion changes from predominantly right-lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the...

  5. Internal structure of the San Jacinto fault zone in the trifurcation area southeast of Anza, California, from data of dense seismic arrays

    Qin, L.; Ben-Zion, Y.; Qiu, H.; Share, P.-E.; Ross, Z. E.; Vernon, F. L.
    We image the internal structure of the San Jacinto fault zone (SJFZ) in the trifurcation area southeast of Anza, California, with seismic records from dense linear and rectangular arrays. The examined data include recordings from more than 20 000 local earthquakes and nine teleseismic events. Automatic detection algorithms and visual inspection are used to identify P and S body waves, along with P- and S-types fault zone trapped waves (FZTW). The location at depth of the main branch of the SJFZ, the Clark fault, is identified from systematic waveform changes across lines of sensors within the dense rectangular array. Delay...

  6. Mapping Mantle Transition Zone Discontinuities Beneath the Central Pacific With Array Processing of SS Precursors

    Yu, Chunquan; Day, Elizabeth A.; de Hoop, Maarten V.; Campillo, Michel; van der Hilst, Robert D.
    We image mantle transition zone (MTZ) discontinuities beneath the Central Pacific using ~120,000 broadband SS waveforms. With a wave packet-based array processing technique (curvelet transform), we improve the signal-to-noise ratio of SS precursors and remove interfering phases, so that precursors can be identified and measured over a larger distance range. Removal of interfering phases reveals possible phase shifts in the underside reflection at the 660, that is, S^(660)S, which if ignored could lead to biased discontinuity depth estimates. The combination of data quantity and improved quality allows improved imaging and uncertainty estimation. Time to depth conversions after corrections for bathymetry,...

  7. Rupture Along 400 km of the Bering Fracture Zone in the Komandorsky Islands Earthquake (M_W 7.8) of 17 July 2017

    Lay, Thorne; Ye, Lingling; Bai, Yefei; Cheung, Kwok Fai; Kanamori, Hiroo; Freymueller, Jeffrey; Steblov, Grigory M.; Kogan, Mikhail G.
    The 17 July 2017 Komandorsky Islands M_W 7.8 earthquake involved arc-parallel right-lateral patchy strike-slip faulting along ~400 km of the Bering Fracture Zone (BFZ) in the westernmost Aleutian Islands back arc. The large size of the earthquake indicates that the BFZ serves regionally as the primary plate boundary extending from the Near Islands to Kamchatka, with the fore-arc Komandorsky Sliver translating rapidly parallel to the Aleutian Trench. The slip distribution is determined by analysis of seismic, tsunami, and geodetic observations. Fault displacements of 4 to 8.5 m, mostly in the upper 15 km, but with localized extension to 20 to...

  8. Zintl Ions within Framework Channels: The Complex Structure and Low-Temperature Transport Properties of Na_4Ge_(13)

    Stefanoski, Stevce; Finkelstein, Gregory J.; Ward, Matthew D.; Zeng, Tao; Wei, Kaya; Bullock, Emma S.; Beavers, Christine M.; Liu, Hanyu; Nolas, George S.; Strobel, Timothy A.
    Single crystals of a complex Zintl compound with the composition Na_4Ge_(13) were synthesized for the first time using a high-pressure/high-temperature approach. Single-crystal diffraction of synchrotron radiation revealed a hexagonal crystal structure with P6/m space group symmetry that is composed of a three-dimensional sp^3 Ge framework punctuated by small and large channels along the crystallographic c axis. Na atoms are inside hexagonal prism-based Ge cages along the small channels, while the larger channels are occupied by layers of disordered sixfold Na rings, which are in turn filled by disordered [Ge_4]^(4–) tetrahedra. This compound is the same as “Na_(1–x)Ge_(3+z)” reported previously, but...

  9. High-resolution seismic event detection using local similarity for Large-N arrays

    Li, Zefeng; Peng, Zhigang; Hollis, Dan; Zhu, Lijun; McClellan, James
    We develop a novel method for seismic event detection that can be applied to large-N arrays. The method is based on a new detection function named local similarity, which quantifies the signal consistency between the examined station and its nearest neighbors. Using the 5200-station Long Beach nodal array, we demonstrate that stacked local similarity functions can be used to detect seismic events with amplitudes near or below noise levels. We apply the method to one-week continuous data around the 03/11/2011 Mw 9.1 Tohoku-Oki earthquake, to detect local and distant events. In the 5–10 Hz range, we detect various events of natural...

  10. Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere

    Hager, Bradford H.
    Isostatic geoid anomalies are usually interpreted using a flat-earth, one-dimensional idealization. Isostatic anomalies on the spherical, self-gravitating earth differ from this idealization because: (1) degree one terms in the spherical harmonic expansion vanish; (2) each term in the spherical harmonic expansion is multiplied by (l + 2)/(l + 0.5) relative to the flat-earth case; (3) mass in cones rather than straight-sided columns is constant; and (4) further deformation of the earth is induced by the gravitational attraction of the deformation caused by the isostatic potential anomaly. When the effect of each of these is quantified, the second, third, and fourth...

  11. Global isostatic geoid anomalies for plate and boundary layer models of the lithosphere

    Hager, Bradford H.
    Isostatic geoid anomalies are usually interpreted using a flat-earth, one-dimensional idealization. Isostatic anomalies on the spherical, self-gravitating earth differ from this idealization because: (1) degree one terms in the spherical harmonic expansion vanish; (2) each term in the spherical harmonic expansion is multiplied by (l + 2)/(l + 0.5) relative to the flat-earth case; (3) mass in cones rather than straight-sided columns is constant; and (4) further deformation of the earth is induced by the gravitational attraction of the deformation caused by the isostatic potential anomaly. When the effect of each of these is quantified, the second, third, and fourth...

  12. Dissipative intraplate faulting during the 2016 M_w 6.2 Tottori, Japan earthquake

    Ross, Zachary E.; Kanamori, Hiroo; Hauksson, Egill; Aso, Naofumi
    The 2016 M_w 6.2 Tottori earthquake occurred on 2016-10-21 and produced thousands of aftershocks. Here we analyze high-resolution relocated seismicity together with source properties of the mainshock to better understand the rupture process and energy budget. We use a matched-filter algorithm to detect and precisely locate >10,000 previously unidentified aftershocks, which delineate a network of sharp subparallel lineations exhibiting significant branching and segmentation. Seismicity below 8 km depth forms highly-localized fault structures subparallel to the mainshock strike. Shallow seismicity near the main rupture plane forms more diffuse clusters and lineations that often are at a high angle (in map view)...

  13. Convective instability of thickening mantle lithosphere

    Conrad, Clinton P.
    Mantle lithosphere, being colder and therefore denser than the underlying mantle, is prone to convective instability that can be induced by horizontal shortening. Numerical experiments on a cold layer with imposed horizontal shortening are carried out to examine the relative importance of mechanical thickening, thermal diffusion and gravitational instability in deforming the layer. This analysis is then used to develop a method for determining which of these styles dominates for a layer thickening at a given rate. If viscosity is non-Newtonian, the imposition of shortening decreases the lithospheric strength, which causes perturbations to the lithosphere’s temperature structure to grow exponentially...

  14. Teleseismic evidence for lateral heterogeneities in the northeastern Japan arc

    Zhao, Dapeng; Hasegawa, Akira
    We have measured and analyzed 4211 P wave first-arrival times from 100 teleseismic events recorded by 67 high-sensitivity seismic stations in the northeastern Japan arc. The relative travel time residuals show regional variations of about 1.6 s. The mean relative residuals averaged for all 100 events produce a spatial pattern of early arrivals at stations near the Pacific coast and delayed arrivals in the central part of the island arc and along the Japan Sea coast. Large delayed arrivals are observed at stations in volcanic areas. This pattern is generally consistent with the heat flow distribution and the major structural...

  15. Teleseismic evidence for lateral heterogeneities in the northeastern Japan arc

    Zhao, Dapeng; Hasegawa, Akira
    We have measured and analyzed 4211 P wave first-arrival times from 100 teleseismic events recorded by 67 high-sensitivity seismic stations in the northeastern Japan arc. The relative travel time residuals show regional variations of about 1.6 s. The mean relative residuals averaged for all 100 events produce a spatial pattern of early arrivals at stations near the Pacific coast and delayed arrivals in the central part of the island arc and along the Japan Sea coast. Large delayed arrivals are observed at stations in volcanic areas. This pattern is generally consistent with the heat flow distribution and the major structural...

  16. Teleseismic evidence for lateral heterogeneities in the northeastern Japan arc

    Zhao, Dapeng; Hasegawa, Akira
    We have measured and analyzed 4211 P wave first-arrival times from 100 teleseismic events recorded by 67 high-sensitivity seismic stations in the northeastern Japan arc. The relative travel time residuals show regional variations of about 1.6 s. The mean relative residuals averaged for all 100 events produce a spatial pattern of early arrivals at stations near the Pacific coast and delayed arrivals in the central part of the island arc and along the Japan Sea coast. Large delayed arrivals are observed at stations in volcanic areas. This pattern is generally consistent with the heat flow distribution and the major structural...

  17. Structural Health Monitoring of Buildings Using Smartphone Sensors

    Kong, Qingkai; Allen, Richard M.; Kohler, Monica D.; Heaton, Thomas H.; Bunn, Julian
    This article presents the results of a shaker test of the Millikan Library in Pasadena, California, using sensors inside smartphones to demonstrate their potential usage as a way to monitor health states of buildings. This approach to structural health monitoring could allow many more commercial and residential buildings to be monitored because it removes the cost prohibitive nature of traditional seismic arrays and the complexity of deploying the instruments. Recordings from the smartphones during the shaking show high correlation with those from a reference sensor in the building, illustrating that the phones can capture the shaking even when not fully...

  18. Vital Signs: Seismology of Icy Ocean Worlds

    Vance, Steven D.; Kedar, Sharon; Panning, Mark P.; Stähler, Simon C.; Bills, Bruce G.; Lorenz, Ralph D.; Huang, Hsin-Hua; Pike, W. T.; Castillo, Julie C.; Lognonné, Philippe; Tsai, Victor C.; Rhoden, Alyssa R.
    Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with...

  19. Vital Signs: Seismology of Icy Ocean Worlds

    Vance, Steven D.; Kedar, Sharon; Panning, Mark P.; Stähler, Simon C.; Bills, Bruce G.; Lorenz, Ralph D.; Huang, Hsin-Hua; Pike, W. T.; Castillo, Julie C.; Lognonné, Philippe; Tsai, Victor C.; Rhoden, Alyssa R.
    Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with...

  20. Vital Signs: Seismology of Icy Ocean Worlds

    Vance, Steven D.; Kedar, Sharon; Panning, Mark P.; Stähler, Simon C.; Bills, Bruce G.; Lorenz, Ralph D.; Huang, Hsin-Hua; Pike, W. T.; Castillo, Julie C.; Lognonné, Philippe; Tsai, Victor C.; Rhoden, Alyssa R.
    Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with...

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