MODELING 3-D SUBSURFACE STRUCTURE FOR STRONG GROUND MOTION ESTIMATION IN THE TOTTORI PLAIN

Abstract

 In this study, we constructed a 3D subsurface structure model for ground motion simulation in the Tottori plain. Therefore, we set common physical properties (ρ, V_P, V_S) for sedimentary layers in the target area and thickness of each sedimentary layer is estimated through inversion analysis from observed phase velocity data at the microtremor array observation sites. Depth estimation of seismic basement is supported by gravity anomaly data under an assumption of two-layered homogeneous medium. 3-D subsurface structure model is constructed from spatial interpolation of the layer boundary depths with 2-D 3rd-order B-spine function. Strong ground motions due to the 1943 Tottori earthquake (M7.2) is simulated by the 3-D finite difference method with the 3-D subsurface structure model. The model was well verified by comparing the distribution of peak ground velocity with the damage distribution under the 1943 Tottori earthquake.