Cause of destructive strong ground motion within 1–2 s in Mukawa town during the 2018 M w 6.6 Hokkaido eastern Iburi earthquake

Nobuo Takai, Michiko Shigefuji, Jun Horita, Shingo Nomoto, Takahiro Maeda, Masayoshi Ichiyanagi, Hiroaki Takahashi, Hiroaki Yamanaka, Kosuke Chimoto, Seiji Tsuno, Masahiro Korenaga, Nobuyuki Yamada

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9 Citations (Scopus)


We investigated the cause of destructive ground motion during the 2018 Hokkaido eastern Iburi earthquake. We conducted strong motion observations of aftershocks and microtremors and the surface wave method in the damaged areas of the town of Mukawa, Hokkaido prefecture, Japan. The ground accelerations were continuously recorded during a period of approximately 3 months after the main shock on September 6, 2018. The heavily damaged buildings were mainly situated around the strong motion station (HKD126) in Mukawa town. Such concentration of damage can be explained by the strong power that was observed in the 1–2 s period of the response spectrum at this station. We estimated the S-wave velocity profiles of this station site and a temporary station site that was installed on a nearby hill. The estimated S-wave velocity, which was inverted from phase velocity structures with the microtremor array and the surface wave method observations explained the difference in the SH-wave amplification characteristics between the two sites. An analysis of HKD126 and the temporarily observed records clearly indicates the strong effects of the local geological conditions on the heavily damaged area of Mukawa. The strong ground motion power generated during the main shock in Mukawa for 1–2 s period was mainly amplified by this shallow underground velocity structure.[Figure not available: see fulltext.].

Original languageEnglish
Article number67
Journalearth, planets and space
Issue number1
Publication statusPublished - Dec 1 2019

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science


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