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Assessment of teleseismically-determined source parameters for the April 25, 2015 M_W 7.9 Gorkha, Nepal earthquake and the May 12, 2015 M_W 7.2 aftershock

Lay, Thorne and Ye, Lingling and Koper, Keith D. and Kanamori, Hiroo (2017) Assessment of teleseismically-determined source parameters for the April 25, 2015 M_W 7.9 Gorkha, Nepal earthquake and the May 12, 2015 M_W 7.2 aftershock. Tectonophysics, 714-715 . pp. 4-20. ISSN 0040-1951. doi:10.1016/j.tecto.2016.05.023.

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On April 25, 2015 a major (M_W 7.9) thrust earthquake ruptured the deeper portion of the seismogenic plate boundary beneath Nepal along which India is underthrusting Eurasia. An M_W 7.2 aftershock on May 12, 2015 extended the eastern, down-dip edge of the rupture. These destructive events caused about 9000 fatalities and 23,000 injuries. The overall rupture zone is about 170 km long and 40–80 km wide. This region of the plate boundary previously experienced a large earthquake in 1833, and in 1934 a larger M_S 8.0 event located to the east ruptured all the way to the surface. The Main Himalayan Thrust (MHT) on which slip occurred in 2015 has a very low dip angle of ~ 6°, and the depth of the mainshock slip distribution is very shallow, extending from ~ 7 to ~ 18 km. The shallow dip and depth present challenges for resolving faulting characteristics using teleseismic data. We analyze global teleseismic signals for the mainshock and aftershock to estimate source parameters, evaluating the stability of various procedures used for remotely characterizing kinematics of such shallow faulting. Back-projection and finite-fault slip inversion are used to assess the spatio-temporal rupture history and evidence for frequency-dependent radiation along dip. Slip zone width constraints from near-field geodetic observations are imposed on the preferred models to overcome some limitations of purely teleseismic methods. Radiated energy, stress drop and moment rate functions are determined for both events.

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URLURL TypeDescription
Lay, Thorne0000-0003-2360-4213
Ye, Lingling0000-0002-8739-2072
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2016 Elsevier B.V. Received 31 January 2016, Revised 3 April 2016, Accepted 11 May 2016, Available online 13 May 2016. This work made use of GMT and SAC software. Finite-fault inversion programs were derived from M. Kikuchi and H. Kanamori ( and have been extensively augmented. We thank Luis Rivera for his program for calculating stress drop for variable slip models. Guest editor Gavin Hayes, reviewer Martin Vallée, and an anonymous reviewer provided thoughtful comments that improved the manuscript. The IRIS DMS data center was used to access the seismic data from Global Seismic Network and Federation of Digital Seismic Network stations. This work was supported by NSF grant EAR1245717 (T. L.).
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Subject Keywords:2015 Gorkha, Nepal earthquake; Himalayan seismic gaps; Rupture process; Seismic rupture parameters
Record Number:CaltechAUTHORS:20161104-104920768
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Official Citation:Thorne Lay, Lingling Ye, Keith D. Koper, Hiroo Kanamori, Assessment of teleseismically-determined source parameters for the April 25, 2015 MW 7.9 Gorkha, Nepal earthquake and the May 12, 2015 MW 7.2 aftershock, In Tectonophysics, Volumes 714–715, 2017, Pages 4-20, ISSN 0040-1951, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71746
Deposited By: Tony Diaz
Deposited On:04 Nov 2016 18:26
Last Modified:11 Nov 2021 04:50

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