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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/5898
Title: A comparison of observed and predicted ground motions from the 2015 MW7.8 Gorkha, Nepal, earthquake
Authors: Hough S.E.
Martin S.S.
Gahalaut V.
Joshi A.
Landes M.
Bossu R.
Published in: Natural Hazards
Abstract: We use 21 strong motion recordings from Nepal and India for the 25 April 2015 moment magnitude (MW) 7.8 Gorkha, Nepal, earthquake together with the extensive macroseismic intensity data set presented by Martin et al. (Seism Res Lett 87:957–962, 2015) to analyse the distribution of ground motions at near-field and regional distances. We show that the data are consistent with the instrumental peak ground acceleration (PGA) versus macroseismic intensity relationship developed by Worden et al. (Bull Seism Soc Am 102:204–221, 2012), and use this relationship to estimate peak ground acceleration from intensities (PGAEMS). For nearest-fault distances (RRUP < 200 km), PGAEMS is consistent with the Atkinson and Boore (Bull Seism Soc Am 93:1703–1729, 2003) subduction zone ground motion prediction equation (GMPE). At greater distances (RRUP > 200 km), instrumental PGA values are consistent with this GMPE, while PGAEMS is systematically higher. We suggest the latter reflects a duration effect whereby effects of weak shaking are enhanced by long-duration and/or long-period ground motions from a large event at regional distances. We use PGAEMS values within 200 km to investigate the variability of high-frequency ground motions using the Atkinson and Boore (Bull Seism Soc Am 93:1703–1729, 2003) GMPE as a baseline. Across the near-field region, PGAEMS is higher by a factor of 2.0–2.5 towards the northern, down-dip edge of the rupture compared to the near-field region nearer to the southern, up-dip edge of the rupture. Inferred deamplification in the deepest part of the Kathmandu valley supports the conclusion that former lake-bed sediments experienced a pervasive nonlinear response during the mainshock (Dixit et al. in Seismol Res Lett 86(6):1533–1539, 2015; Rajaure et al. in Tectonophysics, 2016. Ground motions were significantly amplified in the southern Gangetic basin, but were relatively low in the northern basin. The overall distribution of ground motions and damage during the Gorkha earthquake thus reflects a combination of complex source, path, and site effects. We also present a macroseismic intensity data set and analysis of ground motions for the MW7.3 Dolakha aftershock on 12 May 2015, which we compare to the Gorkha mainshock and conclude was likely a high stress-drop event. © 2016, Springer Science+Business Media Dordrecht (outside the USA).
Citation: Natural Hazards (2016), 84(3): 1661-1684
URI: https://doi.org/10.1007/s11069-016-2505-8
http://repository.iitr.ac.in/handle/123456789/5898
Issue Date: 2016
Publisher: Springer Netherlands
Keywords: Earthquake
Gorkha
Ground motions
Nepal
ISSN: 0921030X
Author Scopus IDs: 7006052961
7404841376
6602495527
55682260000
24778526300
6603240474
Author Affiliations: Hough, S.E., United States Geological Survey (USGS), Pasadena, 525 South Wilson Avenue, Pasadena, CA 91106, United States
Martin, S.S., Earth Observatory of Singapore (EOS), Nanyang Technological University, 50 Nanyang Avenue, N2-01a-14, Singapore, 639798, Singapore
Gahalaut, V., National Centre for Seismology (NCS), Delhi, Ministry of Earth Sciences, Lodhi Road, New Delhi, 110003, India
Joshi, A., Department of Earth Sciences, Indian Institute of Technology (IIT) Roorkee, Roorkee, 247667, India
Landes, M., European-Mediterranean Seismic Centre, c/o Commissariat à l’Energie Atomique Centre DAM Ile de France, Arpajon CEDEX, 91297, France
Bossu, R., European-Mediterranean Seismic Centre, c/o Commissariat à l’Energie Atomique Centre DAM Ile de France, Arpajon CEDEX, 91297, France
Funding Details: We are thankful for helpful conversations with Pablo Ampuero, Domniki Asimaki, Aron Meltzner, and Sudhir Rajaure, to Eric Thompson for providing predicted PGA values for the BSSA14 GMPE, to Gail Atkinson for providing predicted PGA values for the Ghofrani and Atkinson (2014 ) GMPE, and to Christina Widiwijayanti for providing us a copy of Ohsumi et al. (2016 ). We are further grateful to Aron Meltzner and Bruce Worden for constructive reviews of an earlier version of this manuscript, and to two anonymous reviewers for their constructive reviews. SEH was supported by the Office of US Foreign Disaster Assistance (OFDA), a branch of the US Agency for International Development (USAID). SSM was supported by Kerry Sieh through the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. This work comprises Earth Observatory of Singapore contribution no. 116.
Corresponding Author: Hough, S.E.; United States Geological Survey (USGS), Pasadena, 525 South Wilson Avenue, United States; email: hough@usgs.gov
Appears in Collections:Journal Publications [ES]

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