[S-SS15] [JJ] Strong Ground Motion and Earthquake Disaster

[SSS15-P21] 3D velocity structure of Oita prefecture, Kyushu, Japan for strong ground motion simulation

*Masayuki Yoshimi¹, Hisanori Matsuyama², Haruhiko Suzuki², Atsushi Yatagai², Takumi Hayashida³, Shinichi Matsushima⁴, Hiroshi Takenaka⁵, Hiroe Miyake⁶, Keiji Takemura⁷ (1.Geological Survey of Japan, AIST, 2.Oyo Corporation, 3.Building Research Institute, 4.DPRI, Kyoto University, 5.Okayama University, 6.Tokyo University, 7.Kyoto University)

Keywords:shear wave velocity structure model, ground motion prediction, site amplification, microtremor observation

For reliable strong ground motion prediction, valid velocity structure is essential. We constructed a 3D velocity structure of Oita prefecture up to engineering bedrock (Vs > 500 m/s) and finer 3d structure for Oita Plain additionally. In this study, we observed, collected, and compiled data obtained from microtremor surveys, ground motion observations, boreholes etc., and constructed velocity structure by modifying published one. Velocity structure up to the engineering bedrock is modified so as to reproduce the observed phase velocity and H/V ratio. Finer structure of the Oita Plain is modeled, as 250m-mesh model, with empirical relation among N-value, lithology, depth and Vs, using borehole data, then validated with the phase velocity data obtained by the dense microtremor array observation (Yoshimi et al., 2016).

This work is supported by the Comprehensive Research on the Beppu-Haneyama Fault Zone funded by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.