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Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake

Avouac, Jean-Philippe and Meng, Lingsen and Wei, Shengji and Wang, Teng and Ampuero, Jean-Paul (2015) Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake. Nature Geoscience, 8 (9). pp. 708-711. ISSN 1752-0894. doi:10.1038/ngeo2518.

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Large earthquakes are thought to release strain on previously locked faults. However, the details of how earthquakes are initiated, grow and terminate in relation to pre-seismically locked and creeping patches is unclear. The 2015 M_w 7.8 Gorkha, Nepal earthquake occurred close to Kathmandu in a region where the prior pattern of fault locking is well documented. Here we analyse this event using seismological records measured at teleseismic distances and Synthetic Aperture Radar imagery. We show that the earthquake originated northwest of Kathmandu within a cluster of background seismicity that fringes the bottom of the locked portion of the Main Himalayan Thrust fault (MHT). The rupture propagated eastwards for about 140 km, unzipping the lower edge of the locked portion of the fault. High-frequency seismic waves radiated continuously as the slip pulse propagated at about 2.8 km s^(−1) along this zone of presumably high and heterogeneous pre-seismic stress at the seismic–aseismic transition. Eastward unzipping of the fault resumed during the M_w 7.3 aftershock on 12 May. The transfer of stress to neighbouring regions during the Gorkha earthquake should facilitate future rupture of the areas of the MHT adjacent and updip of the Gorkha earthquake rupture.

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Avouac, Jean-Philippe0000-0002-3060-8442
Meng, Lingsen0000-0003-2428-0548
Ampuero, Jean-Paul0000-0002-4827-7987
Additional Information:© 2015 Macmillan Publishers Limited. Received 13 May 2015; accepted 21 July 2015; published online 6 August 2015. Sentinel-1A data are provided by the European Space Agency. T.W. thanks J. Kim from SMU for help in processing the SAR data. We also thank R. Bürgmann for comments on an earlier version of this study. J.-Ph.A. thanks the BP Foundation and the Royal Society for support. Contributions: J.-Ph.A. coordinated the research and wrote the article. L.M. and J.-P.A. carried out the back-projection. S.W. carried out the finite source modelling. T.W. carried out the SAR offset measurements. All authors contributed to the interpretation and writing of the article. Competing financial interests: The authors declare no competing financial interests.
Group:Seismological Laboratory
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Issue or Number:9
Record Number:CaltechAUTHORS:20150721-143815662
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58970
Deposited By: George Porter
Deposited On:06 Aug 2015 22:06
Last Modified:10 Nov 2021 22:13

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