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Published September 13, 2017 | Supplemental Material
Journal Article Open

Depth varying rupture properties during the 2015 Mw 7.8 Gorkha (Nepal) earthquake


On April 25th 2015, the Mw 7.8 Gorkha (Nepal) earthquake ruptured a portion of the Main Himalayan Thrust underlying Kathmandu and surrounding regions. We develop kinematic slip models of the Gorkha earthquake using both a regularized multi-time-window (MTW) approach and an unsmoothed Bayesian formulation, constrained by static and high rate GPS observations, synthetic aperture radar (SAR) offset images, interferometric SAR (InSAR), and teleseismic body wave records. These models indicate that Kathmandu is located near the updip limit of fault slip and approximately 20 km south of the centroid of fault slip. Fault slip propagated unilaterally along-strike in an ESE direction for approximately 140 km with a 60 km cross-strike extent. The deeper portions of the fault are characterized by a larger ratio of high frequency (0.03–0.2 Hz) to low frequency slip than the shallower portions. From both the MTW and Bayesian results, we can resolve depth variations in slip characteristics, with higher slip roughness, higher rupture velocity, longer rise time and higher complexity of subfault source time functions in the deeper extents of the rupture. The depth varying nature of rupture characteristics suggests that the up-dip portions are characterized by relatively continuous rupture, while the down-dip portions may be better characterized by a cascaded rupture. The rupture behavior and the tectonic setting indicate that the earthquake may have ruptured both fully seismically locked and a deeper transitional portions of the collision interface, analogous to what has been seen in major subduction zone earthquakes.

Additional Information

© 2016 Elsevier B.V. Received 24 February 2016, Revised 11 July 2016, Accepted 12 July 2016, Available online 16 July 2016. Data analysis made use of GMT, SAC, and Matlab. The IRIS data management center was used to access the seismic data from Global Seismic Network and Federation of Digital Seismic Network stations. Original ALOS-2 radar images are copyright 2014-2015 by the Japanese Aerospace Exploration Agency (JAXA) and were provided under JAXA ALOS RA4 projects P1385, P1372, and P1303 and through the CEOS Disasters Seismic Pilot. This work contains Copernicus data from the Sentinel-1A satellite provided by the European Space Agency (ESA). Original RADARSAT-2 data and products are copyright 2015 McDonald, Dettweiler and Associates Ltd. (MDA)–all rights reserved. RADARSAT is an official trademark of the Canadian Space Agency (CSA). RADARSAT-2 data products were provided under the CSA Science and Operational Applications Research and development program (SOAR) Geohazard Project number 5320. Array was funded by Caltech and DASE (to J.-P. Avouac) and by the Gordon and Betty Moore Foundation. This work was partly supported by the Initiative d'Excellence (IDEX) funding framework (Université de Strasbourg) and the CNRS international program for scientific cooperation (PICS). Part of this research was supported by the NASA Earth Surface and Interior focus area and performed at the Jet Propulsion Laboratory, California Institute of Technology. We thank the Associate Editor and reviewers XX and XX for their valuable comments and suggestions. This work was supported in part by NSF grant 1447107 awarded to Mark Simons and Jean Paul Ampuero.

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