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Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake

Elliott, J. R. and Jolivet, R. and González, P. J. and Avouac, J.-P. and Hollingsworth, J. and Searle, M. P. and Stevens, V. L. (2016) Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake. Nature Geoscience, 9 (2). pp. 174-180. ISSN 1752-0894. http://resolver.caltech.edu/CaltechAUTHORS:20160225-105620266

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Abstract

The Himalayan mountain range has been the locus of some of the largest continental earthquakes, including the 2015 magnitude 7.8 Gorkha earthquake. Competing hypotheses suggest that Himalayan topography is sustained and plate convergence is accommodated either predominantly on the main plate boundary fault, or more broadly across multiple smaller thrust faults. Here we use geodetic measurements of surface displacement to show that the Gorkha earthquake ruptured the Main Himalayan Thrust fault. The earthquake generated about 1 m of uplift in the Kathmandu Basin, yet caused the high Himalaya farther north to subside by about 0.6 m. We use the geodetic data, combined with geologic, geomorphological and geophysical analyses, to constrain the geometry of the Main Himalayan Thrust in the Kathmandu area. Structural analyses together with interseismic and coseismic displacements are best explained by a steep, shallow thrust fault flattening at depth between 5 and 15 km and connecting to a mid-crustal, steeper thrust. We suggest that present-day convergence across the Himalaya is mostly accommodated by this fault—no significant motion on smaller thrust faults is required. Furthermore, given that the Gorkha earthquake caused the high Himalayan mountains to subside and that our fault geometry explains measured interseismic displacements, we propose that growth of Himalayan topography may largely occur during the ongoing post-seismic phase.


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http://dx.doi.org/10.1038/ngeo2623DOIArticle
http://www.nature.com/ngeo/journal/v9/n2/full/ngeo2623.htmlPublisherArticle
http://rdcu.be/gxnWPublisherFree ReadCube access
ORCID:
AuthorORCID
Avouac, J.-P.0000-0002-3060-8442
Additional Information:© 2016 Macmillan Publishers Limited. Received 30 June 2015; Accepted 26 November 2015; Published online 11 January 2016. This work was supported by the UK Natural Environmental Research Council (NERC) through the Looking Inside the Continents (LiCS) project (NE/K011006/1), the Earthquake without Frontiers (EwF) project (EwF_NE/J02001X/1_1), and the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, GA/13/M/031, http://comet.nerc.ac.uk). The Sentinel-1A interferograms presented are a derived work of Copernicus data, subject to the ESA use and distribution conditions. R.J. is supported by the Marie Curie FP7 Initial Training Network iTECC (investigating Tectonic Erosion Climate Couplings). We are grateful to E. Lindsey and colleagues for making ALOS-2 displacements available at http://topex.ucsd.edu/nepal. We thank A. Copley, S. K. Ebmeier, P. England, A. Hooper, J. Jackson, B. Parsons, R. Walters and T. Wright for discussions. Most figures were made using the public domain Generic Mapping Tools. Contributions: The first two authors each contributed equally to the study. J.R.E. wrote the manuscript and processed Sentinel offset data. R.J. performed the fault modelling. P.J.G. processed the Sentinel interferograms. J.-P.A. conceived the research idea. J.H. processed the optical offset data. M.P.S. constructed the geologic cross-section. V.L.S. produced the interseismic coupling map. All authors took part in finalizing the manuscript. The authors declare no competing financial interests.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Natural Environmental Research Council (NERC)NE/K011006/1
Earthquake without Frontiers (EwF)EwF_NE/J02001X/1_1
Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET)GA/13/M/031
Marie Curie FP7UNSPECIFIED
Record Number:CaltechAUTHORS:20160225-105620266
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160225-105620266
Official Citation:Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake J. R. Elliott, R. Jolivet, P. J. González, J.-P. Avouac, J. Hollingsworth, M. P. Searle & V. L. Stevens Nature Geoscience 9, 174–180 (2016) doi:10.1038/ngeo2623
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64757
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Feb 2016 19:16
Last Modified:25 Feb 2016 19:16

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