[S-SS23_1AM2] Strong Ground Motion and Earthquake Disaster

[SSS23-08] Three-dimensional structure model for modeling strong motion around the Ryukyu arc

Akira FUJIOKA¹, *Hiroshi TAKENAKA², Nobuyuki YAMADA³, Takeshi NAKAMURA⁴, Taro OKAMOTO⁵, Hiroyuki FUJIWARA⁶ (1.Kyushu Univ., 2.Okayama Univ., 3.Kyushu Univ. of Education, 4.JAMSTEC, 5.Tokyo Institute of Technology, 6.NIED)

Keywords:Ryukyu arc, strong motion, simulation

The Ryukyu Islands have frequently been damaged by large earthquakes and tsunamis since ancient times. For instance, in 1771, gigantic tsunamis are occurred from an earthquake and more than 12000 people died in Yaeyamya Islands. From the point of view of disaster prevention, it is also important to improve the precision of strong ground motion prediction. Here we build a 3D numerical structure model for modeling of strong ground motion, which includes land and ocean-bottom topographies and a seawater layer as well as subsurface structures of the arc side and the PHS slab, partially based on the J-SHIS model for near-surface structure (NIED) and a slab-top depth model of the PHS (Headquarters for Earthquake Research Promotion, Japan). We then try to improve the near-surface structure model in the islands using our original microtremor surveys. We also conduct numerical simulations of seismic motions for three sub-oceanic earthquakes occurring near the Amami Islands, Okinawa Island and Miyako Island to confirm the applicability of the constructed structure model and to check the improvement of the near-surface model.