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

Konca, A. Ozgun and Hjorleifsdottir, Vala and Song, Teh-Ru Alex and Avouac, Jean-Philippe and Helmberger, Don V. and Ji, Chen and Sieh, Kerry and Briggs, Richard and Meltzner, Aron (2007) Rupture Kinematics of the 2005 M_w 8.6 Nias–Simeulue Earthquake from the Joint Inversion of Seismic and Geodetic Data. Bulletin of the Seismological Society of America, 97 (1). S307-S322. ISSN 0037-1106. http://resolver.caltech.edu/CaltechAUTHORS:20101116-092441405

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Abstract

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, where the dip is determined to be 8° to 10° with corresponding moments of 1.24 x 10^(22) to 1.00 x 10^(22) N m, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long-period seismic waveforms (100–500 sec). Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/sec and long average rise time of up to 20 sec. The earthquake nucleated between two separate slip patches, one beneath Nias and the other beneath Simeulue Island. The gap between the two patches and the hypocentral location appears to be coincident with a local geological disruption of the forearc. Coseismic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accretionary prism. Using the models from joint inversions, we estimate the peak ground velocity on Nias Island to be about 30 cm/sec, an order of magnitude slower than for thrust events in continental areas. This study emphasizes the importance of utilizing multiple datasets in imaging seismic ruptures.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1785/0120050632 DOIUNSPECIFIED
http://www.bssaonline.org/cgi/content/abstract/97/1A/S307PublisherUNSPECIFIED
Additional Information:© 2007 Seismological Society of America. Manuscript received 13 February 2006. This research was partly funded by the Gordon and Betty Moore Foundation. This is Caltech Tectonic Observatory Contribution Number 38. We appreciate the processing of the SuGAr cGPS data at the Scripps Orbit and Permanent Array Center (SOPAC) by Michael Scharber, Linette Prawirodirdjo, and Yehuda Bock. This manuscript has benefited from helpful suggestions and comments by our reviewers, Roland Burgmann and David Wald.
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Sumatran Plate Boundary
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Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
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Caltech Tectonics Observatory38
Record Number:CaltechAUTHORS:20101116-092441405
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20101116-092441405
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20824
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Nov 2010 21:40
Last Modified:29 Jul 2014 21:42

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