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An ancient shallow slip event on the Mentawai segment of the Sunda megathrust, Sumatra

Philibosian, Belle and Sieh, Kerry and Natawidjaja, Danny H. and Chiang, Hong-Wei and Shen, Chuan-Chou and Suwargadi, Bambang W. and Hill, Emma M. and Edwards, R. Lawrence (2012) An ancient shallow slip event on the Mentawai segment of the Sunda megathrust, Sumatra. Journal of Geophysical Research B, 117 (B5). Art. No. B05401. ISSN 0148-0227.

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The outer-arc islands of western Sumatra rise during great megathrust earthquakes, due to large slip on the underlying megathrust. In contrast, the islands subsided up to a few centimeters during the recent tsunamigenic earthquake of October 2010, due to slip far updip, near the trench. Coral microatolls on one of the islands recorded a much larger subsidence, at least 35 cm, during an event in approximately A.D. 1314. We calculate a suite of slip models, slightly deeper and/or larger than the 2010 event, that are consistent with this large amount of subsidence. Sea level records from older coral microatolls suggest that these events occur at least once every millennium, but likely far less frequently than their great downdip neighbors. The revelation that shallow slip events are important contributors to the seismic cycle of the Mentawai segment further complicates our understanding of this subduction megathrust and our assessment of the region's exposure to seismic and tsunami hazards.

Item Type:Article
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Philibosian, Belle0000-0003-3138-4716
Sieh, Kerry0000-0002-7311-2447
Additional Information:© 2012 by the American Geophysical Union. Received 7 December 2011; revised 15 March 2012; accepted 19 March 2012; published 1 May 2012. We thank Dudi Prayudi, Imam Suprihanto, John Galetzka, and all the crew members of the K.M. Andalas for field support, Ke (Coco) Lin for assistance with U-Th disequilibrium dating at the HISPEC Laboratory at the National Taiwan University, and Aron Meltzner, Jean-Philippe Avouac, and Mark Simons for helpful discussions. This paper was improved thanks to thoughtful reviews by Harvey Kelsey and an anonymous reviewer. This project was supported by National Science Foundation grants 0208508, 0530899, 0538333, and 0809223 to K.S.; Sumatran Paleoseismology grant M58B50074.706022; the Earth Observatory of Singapore; the Research Center for Geotechnology at the Indonesian Institute of Sciences (LIPI); the Caltech Tectonics Observatory, and the Gordon and Betty Moore Foundation. U-Th disequilibrium dating was supported by the Taiwan ROC National Science Council grants 99- 2611-M-002-006, 99-2628-M-002-012, and NSC100-3113-M-002-002 to C.-C.S., and by National Science Foundation grants EAR-0207686 and 0537973 to R.L.E. This is Earth Observatory of Singapore contribution 36 and Caltech Tectonics Observatory contribution 189.
Group:Caltech Tectonics Observatory
Funding AgencyGrant Number
Sumatran Paleoseismology GrantM58B50074.706022
Earth Observatory of SingaporeUNSPECIFIED
Indonesian Institute of Sciences (LIPI)UNSPECIFIED
Caltech Tectonics ObservatoryUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Taiwan ROC National Science Council99-2611-M-002-006
Taiwan ROC National Science Council99-2628-M-002-012
Taiwan ROC National Science CouncilNSC100-3113-M-002-002
Subject Keywords:Sumatra; coral; megathrust; paleoseismology; seismic cycle; subduction zone
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Other Numbering System NameOther Numbering System ID
Earth Observatory of Singapore 36
Caltech Tectonics Observatory189
Issue or Number:B5
Record Number:CaltechAUTHORS:20120529-105400699
Persistent URL:
Official Citation:Philibosian, B., K. Sieh, D. H. Natawidjaja, H.-W. Chiang, C.-C. Shen, B. W. Suwargadi, E. M. Hill, and R. L. Edwards (2012), An ancient shallow slip event on the Mentawai segment of the Sunda megathrust, Sumatra, J. Geophys. Res., 117, B05401, doi:10.1029/2011JB009075
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31675
Deposited By: Tony Diaz
Deposited On:05 Jun 2012 21:38
Last Modified:03 Oct 2019 03:53

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