Recursos de colección

Caltech Authors (160.010 recursos)

Repository of works by Caltech published authors.

Group = Seismological Laboratory

Mostrando recursos 1 - 20 de 299

  1. Stability of faults with heterogeneous friction properties and effective normal stress

    Luo, Yingdi; Ampuero, Jean-Paul
    Abundant geological, seismological and experimental evidence of the heterogeneous structure of natural faults motivates the theoretical and computational study of the mechanical behavior of heterogeneous frictional interfaces. Fault zones are composed of a mixture of materials with contrasting strength, which may affect the spatial variability of seismic coupling, the location of high-frequency radiation and the diversity of slip behavior observed in natural faults. To develop a quantitative understanding of the effect of strength heterogeneity on the mechanical behavior of faults, here we investigate a fault model with spatially variable frictional properties and pore pressure. Conceptually, this model may correspond to...

  2. Amplification and Attenuation across USArray using Ambient Noise Wavefront Tracking

    Bowden, Daniel C.; Tsai, Victor C.; Lin, Fan-Chi
    As seismic travel-time tomography continues to be refined using data from the vast USArray dataset, it is advantageous to also exploit the amplitude information carried by seismic waves. We use ambient noise cross correlation to make observations of surface-wave amplification and attenuation at shorter periods (8 – 32 seconds) than can be observed with only traditional teleseismic earthquake sources. We show that the wavefront tracking approach of [Lin et al., 2012a] can be successfully applied to ambient noise correlations, yielding results quite similar to those from earthquake observations at periods of overlap. This consistency indicates that the wavefront tracking approach...

  3. Effect of seismogenic depth and background stress on physical limits of earthquake rupture across fault step-overs

    Bai, Kangchen; Ampuero, Jean-Paul
    Earthquakes can rupture geometrically complex fault systems by breaching fault step-overs. Quantifying the likelihood of rupture jump across step-overs is important to evaluate earthquake hazard and to understand the interactions between dynamic rupture and fault growth processes. Here we investigate the role of seismogenic depth and background stress on physical limits of earthquake rupture across fault step-overs. Our computational and theoretical study is focused on the canonical case of two parallel strike-slip faults with large aspect ratio, uniform pre-stress and friction properties. We conduct a systematic set of 3D dynamic rupture simulations with different seismogenic depth, step-over distance and initial...

  4. Rapid Cenozoic Subsidence in the Gulf of Mexico Resulting From Hess Rise Conjugate Subduction

    Wang, Huilin; Gurnis, Michael; Skogseid, Jakob
    Enigmatic surface deflections occurred in North America starting from the Cretaceous, including the continental-scale drainage reorganization and the long-wavelength subsidence in the Western Interior Seaway. These surface undulations cannot be simply explained by sea level change or flexure loading. Coinciding with the large-scale surface deflection, the Gulf of Mexico (GOM) has an immense Paleocene sediment deposition probably caused by tectonic subsidence. Increasing evidence indicates a distinct seismic anomaly localized in the mantle below the GOM. With geodynamic models, we show that the Hess Rise conjugate coincides with the position of the seismic anomaly. The basalt-eclogite transition in the Hess conjugate...

  5. Pre- and post-seismic deformation related to the 2015, M_w 7.8 Gorkha earthquake, Nepal

    Gualandi, Adriano; Avouac, Jean-Philippe; Galetzka, John; Genrich, Joachim F.; Blewitt, Geoffrey; Adhikari, Lok Bijaya; Koirala, Bharat Prasad; Gupta, Ratnamani; Upreti, Bishal Nath; Pratt-Sitaula, Beth; Liu-Zeng, Jing
    We analyze time series from continuously recording GPS stations in Nepal spanning the pre- and post-seismic period associated to the M_w7.8 Gorkha earthquake which ruptured the Main Himalayan Thrust (MHT) fault on April 25th, 2015. The records show strong seasonal variations due to surface hydrology. After corrections for these variations, the time series covering the pre- and post-seismic periods do not show any detectable transient pre-seismic displacement. By contrast, a transient post-seismic signal is clear. The observed signal shows southward displacements consistent with afterslip on the MHT. Using additional data from stations deployed after the mainshock, we invert the time...

  6. A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (M_w = 6.4)

    Kanamori, Hiroo; Ye, Lingling; Huang, Bor-Shouh; Huang, Hsin-Hua; Lee, Shiann-Jong; Liang, Wen-Tzong; Lin, Yen-Yu; Ma, Kuo-Fong; Wu, Yih-Min; Yeh, Te-Yang
    Despite a moderate magnitude, M_w = 6.4, the 5 February 2016 Meinong, Taiwan, earthquake caused significant damage in Tainan City and the surrounding areas. Several seismograms display an impulsive S-wave velocity pulse with an amplitude of about 1 m s-1, which is similar to large S-wave pulses recorded for the past several larger damaging earthquakes, such as the 1995 Kobe, Japan, earthquake (M_w = 6.9) and the 1994 Northridge, California, earthquake (M_w = 6.7). The observed PGV in the Tainan area is about 10 times larger than the median PGV of M_w = 6.4 crustal earthquakes in Taiwan. We investigate...

  7. Rayleigh‐Wave H/V via Noise Cross Correlation in Southern California

    Muir, Jack B.; Tsai, Victor C.
    We study the crustal structure of southern California by inverting horizontal‐to‐vertical (H/V) amplitudes of Rayleigh waves observed in noise cross‐correlation signals. This study constitutes a useful addition to traditional phase‐velocity‐based tomographic inversions due to the localized sensitivity of H/V measurements to the near surface of the measurement station site. The continuous data of 222 permanent broadband stations of the Southern California Seismic Network (SCSN) were used in production of noise cross‐correlation waveforms, resulting in a spatially dense set of measurements for the southern California region in the 1–15 s period band. The fine interstation spacing of the SCSN allows retrieval...

  8. Rayleigh-Wave H/V via Noise Cross Correlation in Southern California

    Muir, Jack B.; Tsai, Victor C.
    We study the crustal structure of southern California by inverting horizontal‐to‐vertical (H/V) amplitudes of Rayleigh waves observed in noise cross‐correlation signals. This study constitutes a useful addition to traditional phase‐velocity‐based tomographic inversions due to the localized sensitivity of H/V measurements to the near surface of the measurement station site. The continuous data of 222 permanent broadband stations of the Southern California Seismic Network (SCSN) were used in production of noise cross‐correlation waveforms, resulting in a spatially dense set of measurements for the southern California region in the 1–15 s period band. The fine interstation spacing of the SCSN allows retrieval...

  9. Inertial Forces from Earthquakes on a Hyperloop Pod

    Heaton, Thomas H.
    High‐speed transit (1300  km/hr) using pods traveling in evacuated tubes has been proposed. This Short Note addresses how earthquake ground shaking is changed when it is experienced by a high‐speed pod that is confined to a track. In particular, earthquake motions can cause lateral deformations of the tube that cause centripetal forces in the pod. I discuss the nature of these forces for the cases of (1) a tube that crosses a fault offset, (2) a tube that is deformed by traveling waves in the Earth, and (3) a tube that resonates between fixed points (e.g., a simple bridge). I suggest...

  10. Subduction initiation with vertical lithospheric heterogeneities and new fault formation

    Mao, Xiaolin; Gurnis, Michael; May, Dave A.
    How subduction initiates with mechanically unfavorable lithospheric heterogeneities is important and rarely studied. We investigate this with a geodynamic model for the Puysegur Incipient Subduction Zone (PISZ) south of New Zealand. The model incorporates a true free surface, elasto-visco-plastic rheology and phase changes. Our predictions fit the morphology of the Puysegur Trench and Ridge and the deformation history on the overriding plate. We show how a new thrust fault forms and evolves into a smooth subduction interface, and how a preexisting weak zone can become a vertical fault inboard of the thrust fault during subduction initiation, consistent with two-fault system...

  11. Reconstruction of northeast Asian deformation integrated with western Pacific plate subduction since 200 Ma

    Liu, Shaofeng; Gurnis, Michael; Ma, Pengfei; Zhang, Bo
    The configuration and kinematics of continental deformation and its marginal plate tectonics on the Earth's surface are intrinsic manifestations of plate-mantle coupling. The complex interactions of plate boundary forces result in plate motions that are dominated by slab pull and ridge push forces and the effects of mantle drag; these interactions also result in continental deformation with a complex basin-mountain architecture and evolution. The kinematics and evolution of the western Pacific subduction and northeast Asian continental-margin deformation represent a first-order tectonic process whose nature and chronology remains controversial. This paper implements a “deep-time” reconstruction of the western Pacific subduction, continental...

  12. Toward automated directivity estimates in earthquake moment tensor inversion

    Huang, Hsin-Hua; Aso, Naofumi; Tsai, Victor C.
    Rapid estimates of earthquake rupture properties are useful for both scientific characterization of earthquakes and emergency response to earthquake hazards. Rupture directivity is a particularly important property to constrain since seismic waves radiated in the direction of rupture can be greatly amplified, and even moderate magnitude earthquakes can sometimes cause serious damage. Knowing the directivity of earthquakes is important for ground shaking prediction and hazard mitigation, and is also useful for discriminating which nodal plane corresponds to the actual fault plane particularly when the event lacks aftershocks or outcropped fault traces. Here, we propose a 3-D multiple-time-window directivity inversion method...

  13. Oceanic residual topography agrees with mantle flow predictions at long wavelengths

    Yang, Ting; Moresi, Louis; Müller, R. Dietmar; Gurnis, Michael
    Dynamic topography, the surface deflection induced by sub-lithosheric mantle flow, is an important prediction made by geodynamic models, but there is an apparent disparity between geodynamic model predictions and estimates of residual topography (total topography minus lithospheric and crustal contributions). We generate synthetic global topography fields with different power spectral slopes and spatial patterns to investigate how well the long-wavelength (spherical degree 1 to 3) components can be recovered from a discrete set of samples where residual topography has been recently estimated. Analysis of synthetic topography, along with observed geoid and gravity anomalies, demonstrates the reliability of signal recovery. Appropriate...

  14. The 2016 Kumamoto M_w = 7.0 earthquake: a significant event in a fault-volcano system

    Yue, Han; Ross, Zachary E.; Liang, Cunren; Michel, Sylvain; Fattahi, Heresh; Fielding, Eric; Moore, Angelyn; Liu, Zhen; Jia, Bo
    The 2016 Kumamoto earthquake sequence occurred on the Futagawa-Hinagu fault zone near the Aso volcano on Kyushu island. The sequence was initiated with two major (M_w ≥ 6.0) foreshocks and the mainshock (M_w=7.0) occurred 25 hours after the second major foreshock. We combine GPS, strong motion, Synthetic Aperture Radar (SAR) images and surface offset data in a joint inversion to resolve the kinematic rupture process of the mainshock and co-seismic displacement of the foreshocks. The joint inversion results reveal a unilateral rupture process for the mainshock involving sequential rupture of four major asperities. The slip area of the foreshocks and...

  15. An M_w = 7.7 slow earthquake in 1960 near the Aysén Fjord region, Chile

    Kanamori, Hiroo; Rivera, Luis
    We re-examine the source characteristics of an M_s = 6.9 earthquake in Chile which occurred on 1960 June 6, near the Aysén Fjord region where a remarkable earthquake swarm occurred in 2007 with more than 7000 earthquakes and hundreds of landslides. The June 6 event occurred during the aftershock activity of the 1960 May 22, M_w = 9.5 great Chilean earthquake. A recently found well-calibrated strain seismogram of the June 6 event recorded at Isabella (ISA), California, is the impetus to this study. We confirm that this event is a slow earthquake caused by a source process extending at least...

  16. Imbricated slip rate processes during slow slip transients imaged by low-frequency earthquakes

    Lengliné, O.; Frank, W. B.; Marsan, D.; Ampuero, J.-P.
    Low Frequency Earthquakes (LFEs) often occur in conjunction with transient strain episodes, or Slow Slip Events (SSEs), in subduction zones. Their focal mechanism and location consistent with shear failure on the plate interface argue for a model where LFEs are discrete dynamic ruptures in an otherwise slowly slipping interface. SSEs are mostly observed by surface geodetic instruments with limited resolution and it is likely that only the largest ones are detected. The time synchronization of LFEs and SSEs suggests that we could use the recorded LFEs to constrain the evolution of SSEs, and notably of the geodetically-undetected small ones. However,...

  17. Lag and mixing during sediment transfer across the Tian Shan piedmont caused by climate-driven aggradation-incision cycles

    Malatesta, Luca C.; Avouac, Jean-Philippe; Brown, Nathan D.; Breitenbach, Sebastian F. M.; Pan, Jiawei; Chevalier, Marie-Luce; Rhodes, Edward; Saint-Carlier, Dimitri; Zhang, Wenjing; Charreau, Julien; Lavé, Jérôme; Blard, Pierre-Henri
    Transient sediment storage and mixing of deposits of various ages during transport across alluvial piedmonts alters the clastic sedimentary record. We quantify buffering and mixing during cycles of aggradation-incision in the north piedmont of the Eastern Tian Shan. We complement existing chronologic data with 20 new luminescence ages and one cosmogenic radionuclide age of terrace abandonment and alluvial aggradation. Over the last 0.5 Myrs, the piedmont deeply incised and aggraded many times per 100 kyr. Aggradation is driven by an increased flux of glacial sediment accumulated in the high range and flushed onto the piedmont by greater water discharge at...

  18. Correspondence: Reply to ‘Numerical modelling of the PERM anomaly and the Emeishan large igneous province’

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.
    Tectonic plates and plate boundaries migrate substantially through time and mantle plumes are generally accepted to be mobile within the convecting mantle, but it has been proposed that large low shear velocity provinces (LLSVPs) could have been fixed and rigid for as much as 540 million years (Myr). The hypotheses of fixed and rigid LLSVPs cannot be easily tested in the absence of constraints on the past location of lowermost mantle structures. We evaluated the hypothesis9of lower mantle thermochemical structure fixity with numerical experiments. As in earlier studies, we argue that the location of lower mantle thermochemical structures has changed...

  19. Correspondence: Reply to ‘Numerical modelling of the PERM anomaly and the Emeishan large igneous province’

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.
    Tectonic plates and plate boundaries migrate substantially through time and mantle plumes are generally accepted to be mobile within the convecting mantle, but it has been proposed that large low shear velocity provinces (LLSVPs) could have been fixed and rigid for as much as 540 million years (Myr). The hypotheses of fixed and rigid LLSVPs cannot be easily tested in the absence of constraints on the past location of lowermost mantle structures. We evaluated the hypothesis9of lower mantle thermochemical structure fixity with numerical experiments. As in earlier studies, we argue that the location of lower mantle thermochemical structures has changed...

  20. Stress- and Structure-Induced Anisotropy in Southern California From Two Decades of Shear Wave Splitting Measurements

    Li, Zefeng; Peng, Zhigang
    We measure shear wave splitting (SWS) parameters (i.e., fast direction and delay time) using 330,000 local earthquakes recorded by more than 400 stations of the Southern California Seismic Network (1995–2014). The resulting 232,000 SWS measurements (90,000 high-quality ones) provide a uniform and comprehensive database of local SWS measurements in Southern California. The fast directions at many stations are consistent with regional maximum compressional stress σ_(Hmax). However, several regions show clear deviations from the σ_(Hmax) directions. These include linear sections along the San Andreas Fault and the Santa Ynez Fault, geological blocks NW to the Los Angeles Basin, regions around the...

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