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

Chlieh, Mohamed and Avouac, Jean-Philippe and Hjorleifsdottir, Vala and Song, Teh-Ru Alex and Ji, Chen and Sieh, Kerry and Sladen, Anthony and Hebert, Helene and Prawirodirdjo, Linette and Bock, Yehuda and Galetzka, John (2007) Coseismic Slip and Afterslip of the Great M_w 9.15 Sumatra–Andaman Earthquake of 2004. Bulletin of the Seismological Society of America, 97 (1). S152-S173. ISSN 0037-1106. doi:10.1785/0120050631.

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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 of released moment in our model has three distinct peaks at about 4° N, 7° N, and 9° N, which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated T waves. Our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very-long-period surface waves. The tsunami predicted from this model fits relatively well the altimetric measurements made by the JASON and TOPEX satellites. Neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave. The near-field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500-sec-long seismic rupture. The postseismic geodetic moment of about 2.4 x 10^(22) N m (M_w 8.8) is equal to about 30 ± 5% of the coseismic moment release. Evolution of postseismic deformation is consistent with rate-strengthening frictional afterslip.

Item Type:Article
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URLURL TypeDescription DOIArticle
Avouac, Jean-Philippe0000-0002-3060-8442
Hjorleifsdottir, Vala0000-0003-3275-108X
Song, Teh-Ru Alex0000-0003-3697-5881
Ji, Chen0000-0002-0350-5704
Sieh, Kerry0000-0002-7311-2447
Sladen, Anthony0000-0003-4126-0020
Additional Information:© 2007 Seismological Society of America. Manuscript received 16 February 2006. The Gordon and Betty Moore Foundation and the National Science Foundation EAR0530899 supported this research. Thanks to R. W. Briggs for his helpful readings. We are grateful to the two anonymous reviewers for comments and suggestions. This is Caltech Tectonics Observatory contribution no. 31.
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Sumatran Plate Boundary, Seismological Laboratory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory31
Caltech Tectonics Observatory39
Issue or Number:1
Record Number:CaltechAUTHORS:20101116-091058235
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20823
Deposited By: Tony Diaz
Deposited On:17 Nov 2010 21:43
Last Modified:09 Nov 2021 00:03

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