The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu

The relatively low damage in the Kathmandu Valley caused by the 2015 Mw 7.8 Gorkha earthquake has attracted much attention. To gain a deeper understanding of this phenomenon, we conduct broadband ground‐motion simulations for both the mainshock and the Mw 7.2 Dolakha aftershock through a hybrid meth...

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Main Authors: Chen, Meng, Wei, Shengji
Other Authors: Asian School of the Environment
Format: Article
Language:English
Published: 2021
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Online Access:https://hdl.handle.net/10356/151615
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spelling sg-ntu-dr.10356-1516152021-06-22T08:21:31Z The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu Chen, Meng Wei, Shengji Asian School of the Environment Earth Observatory of Singapore Science::Geology W 7.8 Gorkha Detailed Assessment The relatively low damage in the Kathmandu Valley caused by the 2015 Mw 7.8 Gorkha earthquake has attracted much attention. To gain a deeper understanding of this phenomenon, we conduct broadband ground‐motion simulations for both the mainshock and the Mw 7.2 Dolakha aftershock through a hybrid method that combines deterministic 3D synthetics at relatively low frequencies (⁠<0.3  Hz⁠) and semistochastic synthetics at higher frequencies (⁠>0.3  Hz⁠). Because they are summarized in a companion paper (Wei et al., 2018), the 3D deterministic synthetics were generated by embedding a finite‐fault rupture model in a 3D velocity model that is characterized by a simplified basin structure for the Kathmandu Valley. We tested different weighting schemes using a finite slip model and backprojection results to weight the high‐frequency sources. Our simulations were guided by fitting the observations from five strong‐motion stations in Kathmandu Valley and the intensity and mortality distributions. Site effects were handled by amplitude spectra ratio derived from the vertical component of a hard‐rock station (KTP). Our broadband ground‐motion simulations show that (1) the stress parameter (3.8 MPa) of the mainshock was much lower in comparison to the Mw 7.2 aftershock (23 MPa) that suggests the rupture process of the mainshock was relatively deficient in radiating high‐frequency energy and different fault friction property between the mainshock and the aftershock; (2) the soft deposits in the Kathmandu Valley experienced a pervasive nonlinear site response during the mainshock and the Mw 7.2 aftershock, which also contributed to the reduction of high‐frequency motions; and (3) the high‐frequency ground motions during the mainshock were primarily radiated from the down‐dip rupture. Hence, we suggest considering the difference in the distribution of high‐frequency radiation and fault slip in the broadband ground‐motion simulations for scenario and historical earthquakes. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) This work is supported by the Earth Observatory of Singapore (EOS), Nanyang Technological University through its funding (M4430239.B50). This research is partly supported by the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. 2021-06-22T08:21:31Z 2021-06-22T08:21:31Z 2019 Journal Article Chen, M. & Wei, S. (2019). The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu. Bulletin of the Seismological Society of America, 109(2), 672-687. https://dx.doi.org/10.1785/0120180174 0037-1106 https://hdl.handle.net/10356/151615 10.1785/0120180174 2-s2.0-85065926756 2 109 672 687 en M4430239.B50 Bulletin of the Seismological Society of America © 2019 Seismological Society of America. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Science::Geology
W 7.8 Gorkha
Detailed Assessment
spellingShingle Science::Geology
W 7.8 Gorkha
Detailed Assessment
Chen, Meng
Wei, Shengji
The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
description The relatively low damage in the Kathmandu Valley caused by the 2015 Mw 7.8 Gorkha earthquake has attracted much attention. To gain a deeper understanding of this phenomenon, we conduct broadband ground‐motion simulations for both the mainshock and the Mw 7.2 Dolakha aftershock through a hybrid method that combines deterministic 3D synthetics at relatively low frequencies (⁠<0.3  Hz⁠) and semistochastic synthetics at higher frequencies (⁠>0.3  Hz⁠). Because they are summarized in a companion paper (Wei et al., 2018), the 3D deterministic synthetics were generated by embedding a finite‐fault rupture model in a 3D velocity model that is characterized by a simplified basin structure for the Kathmandu Valley. We tested different weighting schemes using a finite slip model and backprojection results to weight the high‐frequency sources. Our simulations were guided by fitting the observations from five strong‐motion stations in Kathmandu Valley and the intensity and mortality distributions. Site effects were handled by amplitude spectra ratio derived from the vertical component of a hard‐rock station (KTP). Our broadband ground‐motion simulations show that (1) the stress parameter (3.8 MPa) of the mainshock was much lower in comparison to the Mw 7.2 aftershock (23 MPa) that suggests the rupture process of the mainshock was relatively deficient in radiating high‐frequency energy and different fault friction property between the mainshock and the aftershock; (2) the soft deposits in the Kathmandu Valley experienced a pervasive nonlinear site response during the mainshock and the Mw 7.2 aftershock, which also contributed to the reduction of high‐frequency motions; and (3) the high‐frequency ground motions during the mainshock were primarily radiated from the down‐dip rupture. Hence, we suggest considering the difference in the distribution of high‐frequency radiation and fault slip in the broadband ground‐motion simulations for scenario and historical earthquakes.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Chen, Meng
Wei, Shengji
format Article
author Chen, Meng
Wei, Shengji
author_sort Chen, Meng
title The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
title_short The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
title_full The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
title_fullStr The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
title_full_unstemmed The 2015 Gorkha, Nepal, earthquake sequence : II. broadband simulation of ground motion in Kathmandu
title_sort 2015 gorkha, nepal, earthquake sequence : ii. broadband simulation of ground motion in kathmandu
publishDate 2021
url https://hdl.handle.net/10356/151615
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