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Title: Modelling of wave propagation and attenuation in the Osaka sedimentary basin, western Japan, during the 2013 Awaji Island earthquake
Authors: Asano, Kimiyuki  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0002-8530-4198 (unconfirmed)
Sekiguchi, Haruko  kyouindb  KAKEN_id
Iwata, Tomotaka  kyouindb  KAKEN_id
Yoshimi, Masayuki
Hayashida, Takumi
Saomoto, Hidetaka
Horikawa, Haruo
Author's alias: 浅野, 公之
関口, 春子
岩田, 知孝
吉見, 雅行
林田, 拓己
竿本, 英貴
堀川, 晴央
Keywords: Earthquake ground motions
Seismic attenuation
Site effects
Computational seismology
Wave propagation
Issue Date: 1-Feb-2016
Publisher: Oxford University Press (OUP)
Journal title: Geophysical Journal International
Volume: 204
Issue: 3
Start page: 1678
End page: 1694
Abstract: On 2013 April 13, an inland earthquake of Mw 5.8 occurred in Awaji Island, which forms the western boundary of the Osaka sedimentary basin in western Japan. The strong ground motion data were collected from more than 100 stations within the basin and it was found that in the Osaka Plain, the pseudo velocity response spectra at a period of around 6.5 s were significantly larger than at other stations of similar epicentral distance outside the basin. The ground motion lasted longer than 3 min in the Osaka Plain where its bedrock depth spatially varies from approximately 1 to 2 km. We modelled long-period (higher than 2 s) ground motions excited by this earthquake, using the finite difference method assuming a point source, to validate the present velocity structure model and to obtain better constraint of the attenuation factor of the sedimentary part of the basin. The effect of attenuation in the simulation was included in the form of Q(f) = Q0(f/f0), where Q0 at a reference frequency f0 was given by a function of the S-wave velocity, Q0 = αVS. We searched for appropriate Q0 values by changing α for a fixed value of f0 = 0.2 Hz. It was found that values of α from 0.2 to 0.5 fitted the observations reasonably well, but that the value of α = 0.3 performed best. Good agreement between the observed and simulated velocity waveforms was obtained for most stations within the Osaka Basin in terms of both amplitude and ground motion duration. However, underestimation of the pseudo velocity response spectra in the period range of 5–7 s was recognized in the central part of the Osaka Plain, which was caused by the inadequate modelling of later phases or wave packets in this period range observed approximately 2 min after the direct S-wave arrival. We analysed this observed later phase and concluded that it was a Love wave originating from the direction of the east coast of Awaji Island.
Rights: This article has been accepted for publication in 'Geophysical Journal International' © The Authors 2016. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
URI: http://hdl.handle.net/2433/226323
DOI(Published Version): 10.1093/gji/ggv543
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