Disaster mitigation

[DM-08] Earthquake ground motion prediction in the Fujikawa-kako fault zone, Japan, using 3D structural model of deep sedimentary layers

*Hiroaki Yamanaka¹, Kosuke Chimoto², Hiroe Miyake³, Seiji Tsuno⁴, Masahiro Korenaga⁴, Shigeki Senna⁵, Masayuki Yoshimi⁶ (1. Tokyo Institute of Technology (Japan), 2. Kagawa university (Japan), 3. Earthquake Research Institute, The University of Tokyo (Japan), 4. Railway Technical Research Institute (Japan), 5. National Research Institute for Earth Science and Disaster Resilience (Japan), 6. National Institute of Advanced Industrial Science and Technology (Japan))

Fujikawa-kako fault in central Japan is one of the most active faults in Japan. The fault is located in the northern extension area of the Philippine Sea plate in Suruga Bay. A research project had been conducted to obtain geoscientific data on earthquake mechanisms, geological features, and engineering-seismological knowledge on possible earthquakes. The research group consists of 6 sub-groups for geological and geomorphological studies on active faults, seismic activity, historical earthquake study, engineering seismological study and communication with local governments. We were contributed in the engineering seismological topics related with site characterization for seismic hazard in the area and prediction of earthquake ground motion for the possible earthquakes in the area. Many geophysical explorations have been conducted to know velocity structure of the shallow and deep sediments in the area. The results of the microtremor explorations were reported in Yamanaka et al. (2018) and Chimoto et al. (2020). This paper reports on some of the results of the engineering seismological researches in the project including strong motion prediction due to the future events in the area. The possible scenarios were assumed from discussions with geoscientific researchers in the project. A joint rupture of two segments of the Fujikawa-kako fault zone and the Philippine Sea plate boundary along the Suruga trough was used in the strong motion prediction. We conducted a hybrid simulation of broad-band strong ground motion in the eastern part of Shizuoka prefecture and the southern part of Yamanashi prefecture due to the scenario earthquake using a 3D subsurface structural model of deep sedimentary layers. Large ground motion can be identified in the southwestern part of the area. We also found large ground motion in the mouth of the Fujikawa river due to the rupture directivity effects of the segment of the Fujikawa-kako fault zone.