Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-SS Seismology

[S-SS13] Strong Ground Motion and Earthquake Disaster

Mon. May 27, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Masayuki Kuriyama(Central Research Institute of Electric Power Industry), Kazuhiro Somei(Geo-Research Institute)

[SSS13-P11] Estimation of Site Amplification Characteristics in Kumamoto plain by Spectral Separation Analysis Using Aftershock Records of the 2016 Kumamoto Earthquake

*Tomomi Iida1, Hiroaki Yamanaka1, Kosuke Chimoto1, Daiki Shinoyama8, Seiji Tsuno5, Masahiro Korenaga5, Nobuyuki Yamada7, Hiroe Miyake6, Tatsuo Kanno3, Michiko Shigefuji3, Masayuki Yoshimi2, Shinichi Matsushima4, Hiroshi Kawase4, Kimiyuki Asano4, Tomotaka Iwata4 (1.Tokyo institute of Technology, 2.National Institute of Advanced Industrial Science and Technology, 3.Kyushu University, 4.Kyoto University, 5.Railway Technical Research Institute, 6.The University of Tokyo, 7.Kochi Unicersity, 8.Central Research Institute of Electric Power Industry)

Keywords:Spectral inversion technique, the 2016 Kumamoto Earthquake, Site Amplification

The 2016 Kumamoto earthquake contains a foreshock with an Mj of 6.5 on April 14 and the main shock with an Mj of 7.3 on April 16. The earthquakes generated ground motions with a seismic intensity of 7 on the Japan Meteorological Agency scale twice in Mashiki, Kumamoto, Japan and many wooden houses were collapsed. In this study we estimated site amplification characteristics in Kumamoto plain by using ground motion records at strong motion stations of K-NET, KiK-net, seismic intensity-meters stations by local governments and aftershock observation stations by Yamanaka et al. (2016) through a spectral inversion technique. We choose the OITH08 station as the referential site in the inversion. The estimated frequency dependent Q and the source characteristics by the spectral inversion technique show similar features to those from previous studies (e.g. Somei et al, 2018). The site amplifications in the alluvium plain show large values in a frequency range of 0.5-2.0Hz. At high frequency the site amplifications of the mountain are larger than those of the plain area. We estimated S-wave velocity structures in Kumamoto plain by an inverse analysis of the site amplifications. The sediments are large in central area of the Kumamoto plain.
Acknowledgements: This work was conducted as a part of the Comprehensive Study on the Futagawa-Hinagu fault zone after the 2016 Kumamoto earthquake, MEXT.