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The 2015 Gorkha (Nepal) earthquake sequence: I. Source modeling and deterministic 3D ground shaking

Wei, Shengji and Chen, Meng and Wang, Xin and Graves, Robert and Lindsey, Eric and Wang, Teng and Karakaş, Çağıl and Helmberger, Don (2018) The 2015 Gorkha (Nepal) earthquake sequence: I. Source modeling and deterministic 3D ground shaking. Tectonophysics, 722 . pp. 447-461. ISSN 0040-1951. https://resolver.caltech.edu/CaltechAUTHORS:20180314-105805436

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Abstract

To better quantify the relatively long period (< 0.3 Hz) shaking experienced during the 2015 Gorkha (Nepal) earthquake sequence, we study the finite rupture processes and the associated 3D ground motion of the Mw7.8 mainshock and the Mw7.2 aftershock. The 3D synthetics are then used in the broadband ground shaking in Kathmandu with a hybrid approach, summarized in a companion paper (Chen and Wei, 2017, submitted together). We determined the coseismic rupture process of the mainshock by joint inversion of InSAR/SAR, GPS (static and high-rate), strong motion and teleseismic waveforms. Our inversion for the mainshock indicates unilateral rupture towards the ESE, with an average rupture speed of 3.0 km/s and a total duration of ~ 60 s. Additionally, we find that the beginning part of the rupture (5–18 s) has about 40% longer rise time than the rest of the rupture, as well as slower rupture velocity. Our model shows two strong asperities occurring ~ 24 s and ~ 36 s after the origin and located ~ 30 km to the northwest and northeast of the Kathmandu valley, respectively. In contrast, the Mw7.2 aftershock is more compact both in time and space, as revealed by joint inversion of teleseismic body waves and InSAR data. The different rupture features between the mainshock and the aftershock could be related to difference in fault zone structure. The mainshock and aftershock ground motions in the Kathmandu valley, recorded by both strong motion and high-rate GPS stations, exhibited strong amplification around 0.2 Hz. A simplified 3D basin model, calibrated by an Mw5.2 aftershock, can match the observed waveforms reasonably well at 0.3 Hz and lower frequency. The 3D simulations indicate that the basin structure trapped the wavefield and produced an extensive ground vibration. Our study suggests that the combination of rupture characteristics and propagational complexity are required to understand the ground shaking produced by hazardous earthquakes such as the Gorkha event.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.tecto.2017.11.024DOIArticle
https://www.sciencedirect.com/science/article/pii/S0040195117304869PublisherArticle
Additional Information:© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). Received 1 September 2017, Revised 14 November 2017, Accepted 18 November 2017, Available online 21 November 2017. This work was supported by Earth Observatory of Singapore grant M4430240.B50.706022 and partially supported by the USGS grant G15AP00005. We thank Gavin Hayes, Art Frankel and Susan Hough for their constructive reviews. We also thank two anonymous reviewers for their reviews. Figures were made by GMT, the strong motion and teleseismic waveform data were downloaded from strongmotioncenter.org and IRIS, respectively.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Earth Observatory of SingaporeM4430240.B50.706022
USGSG15AP00005
Subject Keywords:Gorkha earthquake; Finite fault; 3D ground shaking; Joint inversion; Basin structure
Record Number:CaltechAUTHORS:20180314-105805436
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180314-105805436
Official Citation:Shengji Wei, Meng Chen, Xin Wang, Robert Graves, Eric Lindsey, Teng Wang, Çağıl Karakaş, Don Helmberger, The 2015 Gorkha (Nepal) earthquake sequence: I. Source modeling and deterministic 3D ground shaking, Tectonophysics, Volume 722, 2018, Pages 447-461, ISSN 0040-1951, https://doi.org/10.1016/j.tecto.2017.11.024. (http://www.sciencedirect.com/science/article/pii/S0040195117304869)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85307
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:15 Mar 2018 03:36
Last Modified:03 Oct 2019 19:29

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