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Caltech Authors (143.226 recursos)

Repository of works by Caltech published authors.

Group = Caltech Tectonics Observatory. Taiwan Tectonics and Seismicity

Mostrando recursos 1 - 18 de 18

  1. Lithological control on the deformation mechanism and the mode of fault slip on the Longitudinal Valley Fault, Taiwan

    Thomas, Marion Y.; Avouac, Jean-Philippe; Gratier, Jean-Pierre; Lee, Jian-Cheng
    The Longitudinal Valley Fault (LVF) in Taiwan is creeping at shallow depth along its southern half, where it is bounded by the Lichi Mélange. By contrast, the northern segment of the LVF is locked where it is bounded by forearc sedimentary and volcanoclastic formations. Structural and petrographic investigations show that the Lichi Mélange most probably formed as a result of internal deformation of the forearc when the continental shelf of South China collided with the Luzon arc as a result of the subduction of the South China Sea beneath the Philippine Sea Plate. The forearc formations constitute the protolith of...

  2. Horizontal coseismic deformation of the 1999 Chi-Chi earthquake measured from SPOT satellite images: Implications for the seismic cycle along the western foothills of central Taiwan

    Dominguez, Stéphane; Avouac, Jean-Philippe; Michel, Rémi
    The 1999 Chi-Chi earthquake, M_w = 7.6, broke a major thrust fault along the western foothills of the Central Range of Taiwan. We have measured the horizontal coseismic displacement field by correlating optical satellite images acquired before and after the earthquake. These data reveal the fault trace and a clockwise rotation of surface displacements toward the north with much larger displacements and strain in the hanging wall. At the surface, coseismic slip increases from 5–6 m near the epicenter to 10–11 m to the north. In the epicentral area, we observe a left-lateral strike-slip zone trending N125°E, and farther north,...

  3. Slip distribution and tectonic implication of the 1999 Chi‐Chi, Taiwan, Earthquake

    Ji, Chen; Helmberger, Donald V.; Song, Teh‐Ru Alex; Ma, Kuo‐Fong; Wald, David J.
    We report on the fault complexity of the large (M_w = 7.6) Chi‐Chi earthquake obtained by inverting densely and well‐distributed static measurements consisting of 119 GPS and 23 doubly integrated strong motion records. We show that the slip of the Chi-Chi earthquake was concentrated on the surface of a ”wedge shaped” block. The inferred geometric complexity explains the difference between the strike of the fault plane determined by long period seismic data and surface break observations. When combined with other geophysical and geological observations, the result provides a unique snapshot of tectonic deformation taking place in the form of very...

  4. A two-dimensional dislocation model for interseismic deformation of the Taiwan mountain belt

    Hsu, Ya-Ju; Simons, Mark; Yu, Shui-Beih; Kuo, Long-Chen; Chen, Horng-Yue
    We use a Global Positioning System (GPS)-derived surface velocity field of Taiwan for the time period between 1993 and 1999 to infer interseismic slip rates on subsurface faults. We adopt a composite elastic half-space dislocation model constrained by the observed horizontal velocities projected into the direction of plate motion (306°). The GPS data are divided into northern and southern regions and the velocities in each region are projected into single profiles. The model fault geometry includes a shallowly dipping décollement, based on the balanced geological cross-sections in the Coastal Plain and Western Foothills, and a two-segment fault representing the Longitudinal...

  5. Postseismic relaxation driven by brittle creep: A possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks, application to the Chi-Chi earthquake, Taiwan

    Perfettini, H.; Avouac, J.-P.
    We evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth, assuming a velocity-strengthening brittle creep rheology. We show that this model can help reconcile the time evolution of afterslip, as measured from geodesy, with aftershocks decay. We propose an analytical expression for slip of the brittle creeping fault zone (BCFZ) that applies to any dynamic or static stress perturbation, including shear stress and normal stress changes. The model predicts an initial logarithmic increase of slip with time. Postseismic slip rate decays over a characteristic time t_r = aσ/τ that does not depend on the amplitude...

  6. Tandem suturing and disarticulation of the Taiwan orogen revealed by its neotectonic elements

    Shyu, J. Bruce H.; Sieh, Kerry; Chen, Yue-Gau
    Taiwan's numerous active faults and folds demarcate distinct eastern and western neotectonic belts. The western belt results from the attachment and subsequent detachment of a sliver of continental lithosphere to the Eurasian continental margin. The eastern belt is the product of the same continental sliver docking with and then separating from the Luzon volcanic arc. Thus, the active Taiwan orogen is a tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin. This progressive suturing and separation is a superb, living demonstration of the fundamental weakness of lithospheric sutures. Furthermore,...

  7. Neotectonic architecture of Taiwan and its implications for future large earthquakes

    Shyu, J. Bruce H.; Sieh, Kerry; Chen, Yue-Gau; Liu, Char-Shine
    The disastrous effects of the 1999 Chi-Chi earthquake in Taiwan demonstrated an urgent need for better knowledge of the island's potential earthquake sources. Toward this end, we have prepared a neotectonic map of Taiwan. The map and related cross sections are based upon structural and geomorphic expression of active faults and folds both in the field and on shaded relief maps prepared from a 40-m resolution digital elevation model, augmented by geodetic and seismologic data. The active tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the Eurasian continental margin have created two...

  8. Millennial slip rate of the Longitudinal Valley fault from river terraces: Implications for convergence across the active suture of eastern Taiwan

    Shyu, J. Bruce H.; Sieh, Kerry; Avouac, Jean-Philippe; Chen, Wen-Shan; Chen, Yue-Gau
    The Longitudinal Valley fault is a key element in the active tectonics of Taiwan. It is the principal structure accommodating convergence across one of the two active sutures of the Taiwan orogeny. To understand more precisely its role in the suturing process, we analyzed fluvial terraces along the Hsiukuluan River, which cuts across the Coastal Range in eastern Taiwan in the fault's hanging wall block. This allowed us to determine both its subsurface geometry and its long-term slip rate. The uplift pattern of the terraces is consistent with a fault-bend fold model. Our analysis yields a listric geometry, with dips...

  9. Geomorphic analysis of the Central Range fault, the second major active structure of the Longitudinal Valley suture, eastern Taiwan

    Shyu, J. Bruce H.; Sieh, Kerry; Chen, Yue-Gau; Chung, Ling-Ho
    Numerous landforms along the Longitudinal Valley suture of eastern Taiwan indicate that two opposing reverse faults currently dominate the suturing process between the Luzon volcanic arc and the Central Range of Taiwan. The east-dipping Longitudinal Valley fault, on the eastern flank of the valley, is well known. The west-dipping Central Range reverse fault, on the western flank of the valley, is more obscure. Nonetheless, it has produced many uplifted lateritic fluvial terraces along the eastern flank of the Central Range in the central reach of the valley, from just north of the Wuhe Tableland to near Chihshang. The fault appears...

  10. Re-evaluation of the surface ruptures of the November 1951 earthquake series in eastern Taiwan, and its neotectonic implications

    Shyu, J. Bruce H.; Chung, Ling-Ho; Chen, Yue-Gau; Lee, Jian-Cheng; Sieh, Kerry
    The earthquakes of November 1951 constitute the most destructive seismic episode in the recorded history of the Longitudinal Valley, eastern Taiwan. However, information about their source parameters is sparse. To understand the relationship between the 1951 ruptures and new interpretations of the regional neotectonic architecture of the Longitudinal Valley, we re-evaluated the November 1951 ruptures by analyzing old documents, reports and photographs, and by interviewing local residents who experienced the earthquake. As a result, we have revised significantly the rupture map previously published. We divide the surface ruptures from south to north into the Chihshang, Yuli, and Rueisuei sections. The...

  11. Slip rates on the Chelungpu and Chushiang thrust faults inferred from a deformed strath terrace along the Dungpuna river, west central Taiwan

    Simoes, Martine; Avouac, Jean Philippe; Chen, Yue-Gau
    The Chelungpu fault produced the September 1999 M_w = 7.6 Chi-Chi earthquake, central Taiwan. The shortening rate accommodated by this structure, integrated over several seismic cycles, and its contribution to crustal shortening across the Taiwanese range have remained unresolved. To address the issues, we focus our study on the Chelungpu and Chushiang thrust faults within the southernmost portion of the Chi-Chi rupture area. Structural measurements and available seismic profiles are used to infer the subsurface geometry of structures. The Chushiang and Chelungpu faults appear as two splay faults branching onto a common ramp that further north connects only to the...

  12. Geomorphology of the southernmost Longitudinal Valley fault: Implications for evolution of the active suture of eastern Taiwan

    Shyu, J. Bruce H.; Sieh, Kerry; Chen, Yue-Gau; Chuang, Ray Y.; Wang, Yu; Chung, Ling-Ho
    In order to understand fully the deformational patterns of the Longitudinal Valley fault system, a major structure along the eastern suture of Taiwan, we mapped geomorphic features near the southern end of the Longitudinal Valley, where many well-developed fluvial landforms record deformation along multiple strands of the fault. Our analysis shows that the Longitudinal Valley fault there comprises two major strands. The Luyeh strand, on the west, has predominantly reverse motion. The Peinan strand, on the east, has a significant left-lateral component. Between the two strands, late Quaternary fluvial sediments and surfaces exhibit progressive deformation. The Luyeh strand dies out...

  13. Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills

    Simoes, Martine; Avouac, Jean Philippe
    The Taiwanese range has resulted from the collision between the Luzon volcanic arc and the Chinese continental margin, which started about 6.5 Myr ago in the north, and has since propagated southward. The building of the range has been recorded in the spatiotemporal evolution of the foreland basin. We analyze this sedimentary record to place some constraints on the kinematics of crustal deformation. The flexure of the foreland under the load of the growing wedge started with a 1.5 Myr long phase of rapid subsidence and sedimentation, which has migrated southward over the last 3.5 Myr at a rate of...

  14. Seismic tomography of Taiwan: Improved constraints from a dense network of strong motion stations

    Wu, Yih-Min; Chang, Chien-Hsin; Zhao, Li; Shyu, J. Bruce H.; Chen, Yue-Gau; Sieh, Kerry; Avouac, Jean-Philippe
    In this study, a large collection of 41,141 S-P times from the untapped records of the Taiwan Strong Motion Instrumentation Program (TSMIP) network is combined with the P and S wave arrival times from the Taiwan Central Weather Bureau Seismic Network (CWBSN) to image the V_p and V_p /V_s structures beneath Taiwan. The records from the 680 TSMIP stations throughout Taiwan in the past 15 years enhance the path coverage and the resolution in the tomography inversions tremendously. Our result for the V_p structure largely confirms previous studies but brings better constraint on the V_p /V_s structure. The colliding Luzon...

  15. Late Cenozoic metamorphic evolution and exhumation of Taiwan

    Beyssac, Olivier; Simoes, Martine; Avouac, Jean Philippe; Farley, Kenneth A.; Chen, Yue-Gau; Chan, Yu-Chang; Goffé, Bruno
    The Taiwan mountain belt is composed of a Cenozoic slate belt (Hsuehshan Range units, HR, and Backbone Slates, BS) and of accreted polymetamorphic basement rocks (Tananao Complex, TC). Ongoing crustal shortening has resulted from the collision between the Chinese continental margin and the Luzon volcanic arc, which initiated ~6.5 Ma ago. The grade and age of metamorphism and exhumation are a key record of the development of the orogenic wedge. Because the Taiwan mountain belt is mostly composed by accreted sediments lacking metamorphic index minerals, quantitative constraints on metamorphism are sparse. By contrast, these rocks are rich in carbonaceaous material...

  16. Mountain building in Taiwan: A thermokinematic model

    Simoes, Martine; Avouac, Jean Philippe; Beyssac, Olivier; Goffé, Bruno; Farley, Kenneth A.; Chen, Yue-Gau
    The Taiwan mountain belt is classically viewed as a case example of a critical wedge growing essentially by frontal accretion and therefore submitted to distributed shortening. However, a number of observations call for a significant contribution of underplating to the growth of the orogenic wedge. We propose here a new thermokinematic model of the Taiwan mountain belt reconciling existing kinematic, thermometric and thermochronological constraints. In this model, shortening across the orogen is absorbed by slip on the most frontal faults of the foothills. Crustal thickening and exhumation are sustained by underplating beneath the easternmost portion of the wedge (Tananao Complex,...

  17. Interseismic crustal deformation in the Taiwan plate boundary zone revealed by GPS observations, seismicity, and earthquake focal mechanisms

    Hsu, Ya-Ju; Yu, Shui-Beih; Simons, Mark; Kuo, Long-Chen; Chen, Horng-Yue
    We use GPS-derived surface velocities, seismicity, as well as estimates of earthquake focal mechanisms from the time period before the 1999 Chi-Chi earthquake to evaluate spatial variations of surface strain rate and crustal stress regime in the Taiwan plate boundary zone. We estimate strain rates with a new but simple approach that solves for surface velocity on a rectangular grid while accounting for the distance between observations and each grid node and the impact of a spatially variable density of observations. This approach provides stable and interpretable strain-rate estimates. In addition, we perform a stress tensor inversion using earthquake focal...

  18. Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties

    Hsu, Ya-Ju; Avouac, Jean-Philippe; Yu, Shui-Beih; Chang, Chien-Hsin; Wu, Yih-Min; Woessner, Jochen
    We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic...

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