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Modeling the 2012 Wharton basin earthquakes off-Sumatra: Complete lithospheric failure

Wei, Shengji and Helmberger, Don and Avouac, Jean-Philippe (2013) Modeling the 2012 Wharton basin earthquakes off-Sumatra: Complete lithospheric failure. Journal of Geophysical Research. Solid Earth, 118 (7). pp. 3592-3609. ISSN 2169-9313. https://resolver.caltech.edu/CaltechAUTHORS:20131104-111155904

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Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20131104-111155904

Abstract

A sequence of large strike-slip earthquakes occurred west of Sunda Trench beneath the Wharton Basin. First reports indicate that the main shock was extremely complex, involving three to four subevents (M_w > 8) with a maze of aftershocks. We investigate slip models of the two largest earthquakes by joint inversion of regional and teleseismic waveform data. Using the M_w 7.2 foreshock, we developed hybrid Green's Functions for the regional stations to approximate the mixture of oceanic and continental paths. The main shock fault geometry is defined based on the back projection results, point-source mechanisms, aftershock distribution, and fine tune of grid searches. The fault system contains three faults, labeled F1 (89°/289° for dip/strike), F2 (74°/20°), and F3 (60°/310°). The inversion indicates that the main rupture consisted of a cascade of high-stress drop asperities (up to 30 MPa), extending as deep as 50 km. The rupture propagated smoothly from one fault to the next (F1, F2, and F3 in sequence) with rupture velocities of 2.0–2.5 km/s. The whole process lasted about 200 s, and the major moment release (>70%) took place on the N-S oriented F2. The M_w 8.2 aftershock happened about 2 h later on a N-S oriented fault with a relatively short duration (~60 s) and also ruptured as deep as 50 km. The slip distributions suggest that the earthquake sequence was part of a broad left-lateral shear zone between the Australian and Indian plates and ruptured the whole lithosphere. These earthquakes apparently reactivated existing fracture zones and were probably triggered by unclamping of the great Sumatran earthquake of 2004.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/jgrb.50267 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/jgrb.50267/abstractPublisherArticle
ORCID:
AuthorORCID
Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2013 American Geophysical Union. Received 12 February 2013; revised 18 June 2013; accepted 23 June 2013; published 25 July 2013. This research was supported by NSF Grant EAR-1142020 and USGS Award G10AP00048. The seismic data were downloaded from http://www.iris.edu/. The manuscript was improved by the constructive comments from an anonymous reviewer and the associate editor.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR-1142020
USGSG10AP00048
Subject Keywords:Wharton Basin Sumatra; Finite Fault; Lithosphere Strength; Cut and Paste; Stress Drop
Issue or Number:7
Record Number:CaltechAUTHORS:20131104-111155904
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131104-111155904
Official Citation:Wei, S., D. Helmberger, and J.-P. Avouac (2013), Modeling the 2012 Wharton basin earthquakes off-Sumatra: Complete lithospheric failure, J. Geophys. Res. Solid Earth, 118, 3592–3609, doi:10.1002/jgrb.50267
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42220
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Nov 2013 19:47
Last Modified:09 Mar 2020 13:18

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