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Published April 2014 | Published + Supplemental Material
Journal Article Open

The 2013 M_w 7.7 Balochistan Earthquake: Seismic Potential of an Accretionary Wedge


Great earthquakes rarely occur within active accretionary prisms, despite the intense long‐term deformation associated with the formation of these geologic structures. This paucity of earthquakes is often attributed to partitioning of deformation across multiple structures as well as aseismic deformation within and at the base of the prism (Davis et al., 1983). We use teleseismic data and satellite optical and radar imaging of the 2013 M_w 7.7 earthquake that occurred on the southeastern edge of the Makran plate boundary zone to study this unexpected earthquake. We first compute a multiple point‐source solution from W‐phase waveforms to estimate fault geometry and rupture duration and timing. We then derive the distribution of subsurface fault slip from geodetic coseismic offsets. We sample for the slip posterior probability density function using a Bayesian approach, including a full description of the data covariance and accounting for errors in the elastic structure of the crust. The rupture nucleated on a subvertical segment, branching out of the Chaman fault system, and grew into a major earthquake along a 50° north‐dipping thrust fault with significant along‐strike curvature. Fault slip propagated at an average speed of 3.0  km/s for about 180 km and is concentrated in the top 10 km with no displacement on the underlying décollement. This earthquake does not exhibit significant slip deficit near the surface, nor is there significant segmentation of the rupture. We propose that complex interaction between the subduction accommodating the Arabia–Eurasia convergence to the south and the Ornach Nal fault plate boundary between India and Eurasia resulted in the significant strain gradient observed prior to this earthquake. Convergence in this region is accommodated both along the subduction megathrust and as internal deformation of the accretionary wedge.

Additional Information

© 2014 Seismological Society of America. Manuscript received 10 December 2013; Published Online 25 March 2014. Part of R. J. and L. R.'s funding were provided by the Tectonics Observatory. This research was supported by National Science Foundation (NSF) Grant EAR-1118239. This research was supported by the Southern California Earthquake Center (SCEC). SCEC is funded by NSF Cooperative Agreement EAR-0529922 and United States Geological Survey Cooperative Agreement 07HQAG0008. This is SCEC contribution 1899. This research was partly supported by the Gordon and Betty Moore Foundation. We thank the Canadian Space Agency for providing RADARSAT-2 data. TerraSAR-X original data are copyrighted by the German Aerospace Agency (DLR) and were provided under project Motagh-GEO1217. Part of this research was supported by the National Aeronautics and Space Administration Earth Surface and Interior focus area and performed by the Jet Propulsion Laboratory, California Institute of Technology. We thank J.-P. Avouac, J.-P. Ampuero, and H. Kanamori for their constructive comments and contributions. We thank the Associate Editor R. Bürgmann, R. Bilham (reviewer), and an anonymous reviewer for their constructive comments, which helped improve this manuscript.

Attached Files

Published - 1020.full.pdf

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Supplemental Material - BSSA_104_2,_Electronic_Supplement_to_Jolivet_et_al.pdf


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August 20, 2023
October 26, 2023