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The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault

Avouac, Jean-Philippe and Ayoub, Francois and Wei, Shengji and Ampuero, Jean-Paul and Meng, Lingsen and Leprince, Sebastien and Jolivet, Romain and Duputel, Zacharie and Helmberger, Don (2014) The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault. Earth and Planetary Science Letters, 391 . pp. 128-134. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20140509-070750779

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Abstract

We analyse the Mw 7.7 Balochistan earthquake of 09/24/2013 based on ground surface deformation measured from sub-pixel correlation of Landsat-8 images, combined with back-projection and finite source modeling of teleseismic waveforms. The earthquake nucleated south of the Chaman strike-slip fault and propagated southwestward along the Hoshab fault at the front of the Kech Band. The rupture was mostly unilateral, propagated at 3 km/s on average and produced a 200 km surface fault trace with purely strike-slip displacement peaking to 10 m and averaging around 6 m. The finite source model shows that slip was maximum near the surface. Although the Hoshab fault is dipping by 45° to the North, in accordance with its origin as a thrust fault within the Makran accretionary prism, slip was nearly purely strike-slip during that earthquake. Large seismic slip on such a non-optimally oriented fault was enhanced possibly due to the influence of the free surface on dynamic stresses or to particular properties of the fault zone allowing for strong dynamic weakening. Strike-slip faulting on thrust fault within the eastern Makran is interpreted as due to eastward extrusion of the accretionary prism as it bulges out over the Indian plate. Portions of the Makran megathrust, some thrust faults in the Kirthar range and strike-slip faults within the Chaman fault system have been brought closer to failure by this earthquake. Aftershocks cluster within the Chaman fault system north of the epicenter, opposite to the direction of rupture propagation. By contrast, few aftershocks were detected in the area of maximum moment release. In this example, aftershocks cannot be used to infer earthquake characteristics.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://www.sciencedirect.com/science/article/pii/S0012821X14000521PublisherArticle
http://dx.doi.org/10.1016/j.epsl.2014.01.036DOIArticle
ORCID:
AuthorORCID
Avouac, Jean-Philippe0000-0002-3060-8442
Ampuero, Jean-Paul0000-0002-4827-7987
Additional Information:© 2014 Elsevier B.V. Received 23 November 2013. Received in revised form 18January 2014. Accepted 24 January 2014. Available online 13 February 2014. Editor: P. Shearer. We thank Steve Wesnousky and one anonymous reviewer for their comments which helped clarify the manuscript. This research was partly supported by the Gordon and Betty Moore Foundation and NSF grant EAR 1147436. This is Tectonics Observatory contribution # 254.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
NSFEAR 1147436
Subject Keywords:Balochistan earthquake; Chaman fault; Makran megathrust; earthquake source model; image geodesy
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory 254
Record Number:CaltechAUTHORS:20140509-070750779
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140509-070750779
Official Citation:Jean-Philippe Avouac, Francois Ayoub, Shengji Wei, Jean-Paul Ampuero, Lingsen Meng, Sebastien Leprince, Romain Jolivet, Zacharie Duputel, Don Helmberger, The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault, Earth and Planetary Science Letters, Volume 391, 1 April 2014, Pages 128-134, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2014.01.036. (http://www.sciencedirect.com/science/article/pii/S0012821X14000521)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45621
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 May 2014 15:03
Last Modified:17 Sep 2015 20:08

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