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Caltech Authors (147.820 recursos)

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Group = Caltech Tectonics Observatory. Sumatran Plate Boundary

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  1. Sumatran Megathrust Earthquakes: From Science to Saving Lives

    Sieh, Kerry
    Most of the loss of life, property and well-being stemming from the great Sumatran earthquake and tsunami of 2004 could have been avoided and losses from similar future events can be largely prevented. However, achieving this goal requires forging a chain linking basic science—the study of why, when and where these events occur—to people's everyday lives. The intermediate links in this chain are emergency response preparedness, warning capability, education and infrastructural changes. In this article, I first describe our research on the Sumatran subduction zone. This research has allowed us to understand the basis of the earthquake cycle on the...

  2. Submergence and uplift associated with the giant 1833 Sumatran subduction earthquake: Evidence from coral microatolls

    Zachariasen, Judith; Sieh, Kerry; Taylor, Frederick W.; Edwards, R. Lawrence; Hantoro, Wahyoe S.
    The giant Sumatran subduction earthquake of 1833 appears as a large emergence event in fossil coral microatolls on the reefs of Sumatra's outer-arc ridge. Stratigraphic analysis of these and living microatolls nearby allow us to estimate that 1833 emergence increased trenchward from about 1 to 2 m. This pattern and magnitude of uplift are consistent with about 13 m of slip on the subduction interface and suggest a magnitude (M_w) of 8.8–9.2 for the earthquake. The fossil microatolls also record rapid submergence in the decades prior to the earthquake, with rates increasing trenchward from 5 to 11 mm/yr. Living microatolls...

  3. Neotectonics of the Sumatran fault, Indonesia

    Sieh, Kerry; Natawidjaja, Danny
    The 1900-km-long, trench-parallel Sumatran fault accommodates a significant amount of the right-lateral component of oblique convergence between the Eurasian and Indian/Australian plates from 10°N to 7°S. Our detailed map of the fault, compiled from topographic maps and stereographic aerial photographs, shows that unlike many other great strike-slip faults, the Sumatran fault is highly segmented. Cross-strike width of step overs between the 19 major subaerial segments is commonly many kilometers. The influence of these step overs on historical seismic source dimensions suggests that the dimensions of future events will also be influenced by fault geometry. Geomorphic offsets along the fault range...

  4. Paleogeodetic records of seismic and aseismic subduction from central Sumatran microatolls, Indonesia

    Natawidjaja, Danny Hilman; Sieh, Kerry; Ward, Steven N.; Cheng, Hai; Edwards, R. Lawrence; Galetzka, John; Suwargadi, Bambang W.
    We utilize coral microatolls in western Sumatra to document vertical deformation associated with subduction. Microatolls are very sensitive to fluctuations in sea level and thus act as natural tide gauges. They record not only the magnitude of vertical deformation associated with earthquakes (paleoseismic data), but also continuously track the long-term aseismic deformation that occurs during the intervals between earthquakes (paleogeodetic data). This paper focuses on the twentieth century paleogeodetic history of the equatorial region. Our coral paleogeodetic record of the 1935 event reveals a classical example of deformations produced by seismic rupture of a shallow subduction interface. The site closest...

  5. Crustal deformation at the Sumatran Subduction Zone revealed by coral rings

    Sieh, Kerry; Ward, Steven N.; Natawidjaja, Danny; Suwargadi, Bambang W.
    Analyses of coral rings grown in the interval 1970–1997 reveal a geographically distinct pattern of interseismic uplift off Sumatra's western coast. At distances less than 110 km from the Sumatran trench, coral reefs are submerging as fast as 5 mm/y. At 130 and 180 km distance from the trench, they are emerging at similar rates. We suggest that a locked, or partially locked patch, located above 30 km depth on the upper surface of the subducting oceanic plate, generates this pattern.

  6. Modern Vertical Deformation above the Sumatran Subduction Zone: Paleogeodetic Insights from Coral Microatolls

    Zachariasen, Judith; Sieh, Kerry; Taylor, Frederick W.; Hantoro, Wahyoe S.
    Coral microatolls from the coast and outer-arc islands of Western Sumatra retain a stratigraphic and morphologic record of relative sea-level change, which is due in large part to vertical tectonic deformation above the Sumatran subduction zone. Low water levels, whose fluctuations produce measurable changes in coral morphology, limit the upward growth of the microatolls. Annual rings, derived from seasonal variations in coral density, serve as an internal chronometer of coral growth. The microatolls act as natural long-term tide gauges, recording sea-level variations on time scales of decades. Field observations and stratigraphic analysis of seven microatolls, five from the outer-arc islands...

  7. A Comparative Study of the Sumatran Subduction-Zone Earthquakes of 1935 and 1984

    Rivera, Luis; Sieh, Kerry; Helmberger, Don; Natawidjaja, Danny
    A M_s 7.7 earthquake struck the western, equatorial coast of Sumatra in December 1935. It was the largest event in the region since the two devastating giant earthquakes of 1833 and 1861. Historical seismograms of this event from several observatories around the world provide precious information that constrains the source parameters of the earthquake. To more precisely quantify the location, geometry, and mechanism of the 1935 event and to estimate the coseismic deformation, we analyze the best of the available teleseismic historical seismograms by comparing systematically the records of the 1935 earthquake with those of a smaller event that occurred...

  8. Near-field propagation of tsunamis from megathrust earthquakes

    McCloskey, John; Antonioli, Andrea; Piatanesi, Alessio; Sieh, Kerry; Steacy, Sandy; Nalbant, Suleyman S.; Cocco, Massimo; Giunchi, Carlo; Huang, Jian Dong; Dunlop, Paul
    We investigate controls on tsunami generation and propagation in the near-field of great megathrust earthquakes using a series of numerical simulations of subduction and tsunamigenesis on the Sumatran forearc. The Sunda megathrust here is advanced in its seismic cycle and may be ready for another great earthquake. We calculate the seafloor displacements and tsunami wave heights for about 100 complex earthquake ruptures whose synthesis was informed by reference to geodetic and stress accumulation studies. Remarkably, results show that, for any near-field location: (1) the timing of tsunami inundation is independent of slip-distribution on the earthquake or even of its magnitude,...

  9. The Sumatra subduction zone: A case for a locked fault zone extending into the mantle

    Simoes, Martine; Avouac, Jean Philippe; Cattin, Rodolphe; Henry, Pierre
    A current view is that the portion of the subduction interface that remains locked in the time interval between large interplate earthquakes, hereinafter referred to as the locked fault zone (LFZ), does not extend into the mantle because serpentinization of the mantle wedge would favor stable aseismic sliding. Here, we test this view in the case of the Sumatra subduction zone where the downdip end of the LFZ can be well constrained from the pattern and rate of uplift deduced from coral growth and from GPS measurements of horizontal deformation. These geodetic data are modeled from a creeping dislocation embedded...

  10. Uplift and subsidence associated with the great Aceh-Andaman earthquake of 2004

    Meltzner, Aron J.; Sieh, Kerry; Abrams, Michael; Agnew, Duncan C.; Hudnut, Kenneth W.; Avouac, Jean-Philippe; Natawidjaja, Danny H.
    Rupture of the Sunda megathrust on 26 December 2004 produced broad regions of uplift and subsidence. We define the pivot line separating these regions as a first step in defining the lateral extent and the downdip limit of rupture during that great M_w ≈ 9.2 earthquake. In the region of the Andaman and Nicobar islands we rely exclusively on the interpretation of satellite imagery and a tidal model. At the southern limit of the great rupture we rely principally on field measurements of emerged coral microatolls. Uplift extends from the middle of Simeulue Island, Sumatra, at ~2.5°N, to Preparis Island,...

  11. Plate-boundary deformation associated with the great Sumatra–Andaman earthquake

    Subarya, Cecep; Chlieh, Mohamed; Prawirodirdjo, Linette; Avouac, Jean-Philippe; Bock, Yehuda; Sieh, Kerry; Meltzner, Aron J.; Natawidjaja, Danny H.; McCaffrey, Robert
    The Sumatra–Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M_w > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estimates of the ground displacement associated with this event, using near-field Global Positioning System (GPS) surveys in northwestern Sumatra combined with in situ and remote observations of the vertical motion of coral reefs. These data show that the earthquake was generated by rupture of the Sunda subduction megathrust over...

  12. Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls

    Natawidjaja, Danny Hilman; Sieh, Kerry; Chlieh, Mohamed; Galetzka, John; Suwargadi, Bambang W.; Cheng, Hai; Edwards, R. Lawrence; Avouac, Jean-Philippe; Ward, Steven N.
    Large uplifts and tilts occurred on the Sumatran outer arc islands between 0.5° and 3.3°S during great historical earthquakes in 1797 and 1833, as judged from relative sea level changes recorded by annually banded coral heads. Coral data for these two earthquakes are most complete along a 160-km length of the Mentawai islands between 3.2° and 2°S. Uplift there was as great as 0.8 m in 1797 and 2.8 m in 1833. Uplift in 1797 extended 370 km, between 3.2° and 0.5°S. The pattern and magnitude of uplift imply megathrust ruptures corresponding to moment magnitudes (M_w) in the range 8.5...

  13. Deformation and Slip Along the Sunda Megathrust in the Great 2005 Nias-Simeulue Earthquake

    Briggs, Richard W.; Sieh, Kerry; Meltzner, Aron J.; Natawidjaja, Danny; Galetzka, John; Suwargadi, Bambang; Hsu, Ya-Ju; Simons, Mark; Hananto, Nugroho; Suprihanto, Imam; Prayudi, Dudi; Avouac, Jean-Philippe; Prawirodirdjo, Linette; Bock, Yehuda
    Seismic rupture produced spectacular tectonic deformation above a 400-kilometer strip of the Sunda megathrust, offshore northern Sumatra, in March 2005. Measurements from coral microatolls and Global Positioning System stations reveal trench-parallel belts of uplift up to 3 meters high on the outer-arc islands above the rupture and a 1-meter-deep subsidence trough farther from the trench. Surface deformation reflects more than 11 meters of fault slip under the islands and a pronounced lessening of slip trenchward. A saddle in megathrust slip separates the northwestern edge of the 2005 rupture from the great 2004 Sumatra-Andaman rupture. The southeastern edge abuts a predominantly...

  14. Frictional Afterslip Following the 2005 Nias-Simeulue Earthquake, Sumatra

    Hsu, Ya-Ju; Simons, Mark; Avouac, Jean-Philippe; Galetzka, John; Sieh, Kerry; Chlieh, Mohamed; Natawidjaja, Danny; Prawirodirdjo, Linette; Bock, Yehuda
    Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (M_w) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a M_w 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and...

  15. Rupture Kinematics of the 2005 M_w 8.6 Nias–Simeulue Earthquake from the Joint Inversion of Seismic and Geodetic Data

    Konca, A. Ozgun; Hjorleifsdottir, Vala; Song, Teh-Ru Alex; Avouac, Jean-Philippe; Helmberger, Don V.; Ji, Chen; Sieh, Kerry; Briggs, Richard; Meltzner, Aron
    The 2005 M_w 8.6 Nias–Simeulue earthquake was caused by rupture of a portion of the Sunda megathrust offshore northern Sumatra. This event occurred within an array of continuous Global Positioning System (GPS) stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture. Thus, this earthquake provides a unique opportunity to assess the source characteristics of a megathrust event from the joint analysis of seismic data and near-field static co-seismic displacements. Based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip,...

  16. Coseismic Slip and Afterslip of the Great M_w 9.15 Sumatra–Andaman Earthquake of 2004

    Chlieh, Mohamed; Avouac, Jean-Philippe; Hjorleifsdottir, Vala; Song, Teh-Ru Alex; Ji, Chen; Sieh, Kerry; Sladen, Anthony; Hebert, Helene; Prawirodirdjo, Linette; Bock, Yehuda; Galetzka, John
    We determine coseismic and the first-month postseismic deformation associated with the Sumatra–Andaman earthquake of 26 December 2004 from near- field Global Positioning System (GPS) surveys in northwestern Sumatra and along the Nicobar-Andaman islands, continuous and campaign GPS measurements from Thailand and Malaysia, and in situ and remotely sensed observations of the vertical motion of coral reefs. The coseismic model shows that the Sunda subduction megathrust ruptured over a distance of about 1500 km and a width of less than 150 km, releasing a total moment of 6.7–7.0 x 10^(22) N m, equivalent to a magnitude M_w 9.15. The latitudinal distribution...

  17. 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...

  18. Heterogeneous coupling of the Sumatran megathrust constrained by geodetic and paleogeodetic measurements

    Chlieh, M.; Avouac, J. P.; Sieh, K.; Natawidjaja, D. H.; Galetzka, John
    Geodetic and paleogeodetic measurements of interseismic strain above the Sumatran portion of the Sunda subduction zone reveal a heterogeneous pattern of coupling. Annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century, and repeated GPS surveys between 1991 and 2001 and continuous measurements at GPS stations operated since 2002 provide horizontal velocities. Near the equator, the megathrust is locked over a narrow width of only a few tens of kilometers. In contrast, the locked fault zone is up to about 175 km wide in areas where great interplate earthquakes have occurred in the...

  19. Interseismic deformation above the Sunda Megathrust recorded in coral microatolls of the Mentawai islands, West Sumatra

    Natawidjaja, Danny Hilman; Sieh, Kerry; Galetzka, John; Suwargadi, Bambang W.; Cheng, Hai; Edwards, R. Lawrence; Chlieh, Mohamed
    The geomorphology and internal stratigraphy of modern coral microatolls show that all the outer arc Mentawai islands of West Sumatra have been subsiding over the past several decades. These same islands rose as much as 3 m during the giant megathrust earthquakes of 1797 and 1833, and the current subsidence probably reflects strain accumulation that will lead to future large earthquakes. Average subsidence rates over the past half century vary from 2 to 14 mm yr^(−1) and increase southwestward, toward the subduction trench. The pattern is consistent with rates of subsidence measured by a sparse network of continuously recording Global...

  20. Earthquake Supercycles Inferred from Sea-Level Changes Recorded in the Corals of West Sumatra

    Sieh, Kerry; Natawidjaja, Danny H.; Meltzner, Aron J.; Shen, Chuan-Chou; Cheng, Hai; Li, Kuei-Shu; Suwargadi, Bambang W.; Galetzka, John; Philibosian, Belle; Edwards, R. Lawrence
    Records of relative sea-level change extracted from corals of the Mentawai islands, Sumatra, imply that this 700-kilometer-long section of the Sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years. The moment magnitude 8.4 earthquake of September 2007 represents the first in a series of large partial failures of the Mentawai section that will probably be completed within the next several decades.

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