| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | January 17, 2008 |
| Latest Amendment Date: | February 18, 2010 |
| Award Number: | 0738299 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | May 1, 2008 |
| End Date: | April 30, 2013 (Estimated) |
| Total Intended Award Amount: | $234,841.00 |
| Total Awarded Amount to Date: | $234,841.00 |
| Funds Obligated to Date: |
FY 2010 = $81,220.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1608 4TH ST STE 201 BERKELEY CA US 94710-1749 (510)643-3891 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1608 4TH ST STE 201 BERKELEY CA US 94710-1749 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Geophysics |
| Primary Program Source: |
01001011DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The December 26, 2004 Sumatra-Andaman earthquake was the largest event since the 1960s and the first magnitude > 9 earthquake to occur in the era of modern space geodesy and broadband seismology. This earthquake produced measurable static surface displacements at distances as large as 4500 km. Given the tremendous size of the 2004 earthquake, a ?second wave? of accelerated asthenospheric flow has developed that is going to perturb the regional deformation field for many decades. In addition, other postseismic deformation processes such as localized afterslip and poroelastic rebound, will also affect the regional deformation field. In fact, deformation measurements of the first few months following the Sumatra-Andaman earthquake can be explained quite well by either kinematic models of localized afterslip along and mostly below the rupture, or by viscoelastic relaxation. The 2004 earthquake was followed three months later by a great magnitude 8.7 event on an adjoining segment of the subduction zone, and again in 2007 by a magnitude 8.4 earthquake. This earthquake sequence provide the rare opportunity to fundamentally improve our understanding of the earthquake cycle of megathrust ruptures and the constitutive properties of the adjoining oceanic and continental crust and upper mantle. The knowledge the research team is gaining from this work will be applied towards improved stress models of how earlier ruptures influenced the timing and nature of subsequent events.
This study includes a comprehensive analysis of GPS-measured deformation, seismicity changes and other geophysical data in order to develop well-constrained models of regional deformation and stress transients. The main goals of the project are to (1) differentiate the contributions from the various postseismic deformation processes, (2) to quantify the reach and distribution of transient deformation and stress across the region, especially from deep-seated relaxation in the upper mantle, and (3) to determine the extent, magnitude and pattern of time dependent stress perturbations affecting active seismicity throughout the region. In their modeling, the investigators rely on analytical viscoelastic normal mode solutions for post-earthquake relaxation on a spherically symmetric, compressible, self-gravitating Earth and on numerical finite element techniques. The finite element techniques allow for consideration of lateral heterogeneity across the subduction plate boundary zone and for the role of the subducting slab. The most important impact of this work is to contribute to earthquake hazard assessments for the Burma-Andaman-Sumatra-Java plate boundary zone by improving the accuracy of earthquake scenarios and probabilities.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Starting with the 2004 Mw 9.2 megathrust event, Southeast Asia has been home to an exceptional amount of seismic activity over the past eight years. The series of megathrust earthquakes have been imperfect dominoes, rupturing the northernmost section of the Sunda subduction zone in 2004, then the Nias segment next in line to the south in 2005, followed by the Bengkulu earthquake 750 km further south in 2007. The Bengkulu earthquake skipped over the northern Mentawai segment, which has not ruptured in a great event since 1797. However, the subduction zone has not been silent is this section. Analysis of focal mechanisms and geodetic data reveals the reactivation of the Mentawai backthrust system in the overriding plate, and a large, deep earthquake near the city of Padang in 2009 is shown through finite fault inversions and aftershock analysis to have obliquely ruptured the subducting slab. At the same time, the entire region spanning from the Indian Ocean, through the trench and forearc islands, and throughout Thailand has been aseismically deforming in response to the stress changes in the mantle following the megathrust earthquakes. Geode- tic observations of postseismic deformation during the first five years following the 2004 earthquake have shown that the far-field regions of Thailand and the Malay Peninsula have moved more postseismically than coseismically, peaking at 0.4 m of horizontal displacement in Phuket. In 2012, the stress changes associated with this continued postseismic deformation, along with the initial push from the megathrust earthquakes, appear to have triggered the largest instrumentally recorded M=8.6 strike-slip earthquake in the Indian Ocean. This was a complex earthquake, consisting of four conjugate fault segments, that ruptured the diffuse India-Australia plate boundary zone. Understanding how the faults interact throughout the subduction system, from the incoming plate, to the slab, to the megathrust interface, and overriding plate is an essential part of determining the future seismic hazard for Southeast Asia.
Last Modified: 06/03/2013
Modified by: Roland Burgmann
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