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Title: The cause of heavy damage concentration in downtown Mashiki inferred from observed data and field survey of the 2016 Kumamoto earthquake
Authors: Kawase, Hiroshi  kyouindb  KAKEN_id
Matsushima, Shinichi  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0001-8240-4305 (unconfirmed)
Nagashima, Fumiaki  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0002-9125-5871 (unconfirmed)
Baoyintu
Nakano, Kenichi
Author's alias: 川瀬, 博
松島, 信一
長嶋, 史明
仲野, 健一
Keywords: Structural damage
HVR
Site effects
Fling-step
Directivity
Issue Date: 3-Jan-2017
Publisher: Springer Nature
Journal title: Earth, Planets and Space
Volume: 69
Thesis number: 3
Abstract: To understand the cause of heavy structural damage during the mainshock (on April 16, 2016) of the 2016 Kumamoto earthquake sequence, we carried out a field survey from April 29 through May 1, 2016, in Mashiki where heavy damage concentration was observed. The heavy damage concentration in downtown Mashiki could be understood based on the observed strong motions with the Japan Meteorological Agency instrumental seismic intensity of VII and information collected by the field investigation. First, the fundamental features of the structural damage in downtown Mashiki were summarized. Then, a distribution map of peak frequencies was derived from horizontal-to-vertical spectral ratios of microtremors. We could not see any systematic correlation between the peak frequencies and spatial distribution of damage ratios. We also analyzed observed strong motion data at two sites to obtain fling-step-like motions in the displacement time histories through the double integration of unfiltered accelerograms. It turned out that at both strong motion observation sites in Mashiki, only the east–west (EW) components had very strong velocity pulses westward before the emergence of the fling-step-like motion eastward, which would be the primary cause of heavy structural damage in downtown Mashiki, not site effects nor the fling-step-like motion itself.
Rights: © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
URI: http://hdl.handle.net/2433/218661
DOI(Published Version): 10.1186/s40623-016-0591-1
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