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Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence

Rajaure, S. and Asimaki, D. and Thompson, E. M. and Hough, S. and Martin, S. and Ampuero, J. P. and Dhital, M. R. and Inbal, A. and Takai, N. and Shigefuji, M. and Bijukchhen, S. and Ichiyanagi, M. and Sasatani, T. and Paudel, L. (2016) Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence. Tectonophysics . ISSN 0040-1951. (In Press) http://resolver.caltech.edu/CaltechAUTHORS:20170509-141502347

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Abstract

We analyze strong motion records and high-rate GPS measurements of the M 7.8 Gorkha mainshock, M 7.3 Dolakha, and two moderate aftershock events recorded at four stations on the Kathmandu basin sediments, and one on rock-outcrop. Recordings on soil from all four events show systematic amplification relative to the rock site at multiple frequencies in the 0.1–2.5 Hz frequency range, and de-amplification of higher frequencies ( >2.5–10 Hz). The soil-to-rock amplification ratios for the M 7.8 and M 7.3 events have lower amplitude and frequency peaks relative to the ratios of the two moderate events, effects that could be suggestive of nonlinear site response. Further, comparisons to ground motion prediction equations show that 1) both soil and rock mainshock recordings were severely depleted of high frequencies, and 2) the depletion at high frequencies is not present in the aftershocks. These observations indicate that the high frequency deamplification is additionally related to characteristics of the source that are not captured by simplified ground motion prediction equations, and allude to seismic hazard analysis models being revised – possibly by treating isolated high frequency radiation sources separately from long period components to capture large magnitude near-source events such as the 2015 Gorkha mainshock.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.tecto.2016.09.030DOIArticle
http://www.sciencedirect.com/science/article/pii/S004019511630395XPublisherArticle
ORCID:
AuthorORCID
Asimaki, D.0000-0002-3008-8088
Ampuero, J. P.0000-0002-4827-7987
Inbal, A.0000-0001-8848-7279
Additional Information:© 2016 Elsevier B.V. Received 28 January 2016, Revised 1 September 2016, Accepted 27 September 2016, Available online 1 October 2016. The accelerometer record at station KATPN was provided by the USGS (http://www.strongmotioncenter.org/cgi-bin/CESMD/StaEvent.pl?stacode=NPKATNP); the GPS data were processed by ARIA (JPL) and the Scripps Orbit and Permanent Array Center. The strong motion data at stations KTP, PTN, TVU and THM were processed by Michiko Shigefuji and Subeg Bijukchhen; the mainshock acceleration time series can be downloaded from http://eprints.lib.hokudai.ac.jp/dspace/handle/2115/60622?locale=en&lang=en; the aftershock time-series should be made available soon through the same portal. We acknowledge partial support of this work from the USGS/Caltech Cooperative Agreement (Sponsor Award Number G14AC00109). We also wish to thank Daniel McNamara and two anonymous reviewers for providing comments that have improved this manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
USGSG14AC00109
Subject Keywords:Site effects; Kathmandu Valley; Strong motions; Shaking intensity
Record Number:CaltechAUTHORS:20170509-141502347
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170509-141502347
Official Citation:S. Rajaure, D. Asimaki, E.M. Thompson, S. Hough, S. Martin, J.P. Ampuero, M.R. Dhital, A. Inbal, N. Takai, M. Shigefuji, S. Bijukchhen, M. Ichiyanagi, T. Sasatani, L. Paudel, Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence, Tectonophysics, Available online 1 October 2016, ISSN 0040-1951, https://doi.org/10.1016/j.tecto.2016.09.030. (http://www.sciencedirect.com/science/article/pii/S004019511630395X)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77312
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:11 May 2017 21:37
Last Modified:12 May 2017 19:39

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