Improved Modeling of Shallow Subsurface Structure in the Eastern Osaka Region and Amplification Characteristics Considering 3-D Shallow and Deep Subsurface Structure in the Osaka Plain

Abstract

Site amplification factors of ground motions are significantly large from the engineering bedrock to the ground surface in the Osaka plain, Japan. In the western Osaka region, including the Osaka Bay area, shallow soil layer is thick, while in the eastern Osaka region, high sensitivity clay layers are widely distributed. In this paper, we constructed a shallow soil model, including reverse layers, in the eastern Osaka region for the three-dimensional subsurface structure model. The proposed model, which considered both regions shallow portions, was verified by simulation analysis of small earthquake records using the 3-D finite difference method. Ground motions because of the hypothetical point source were examined by focusing on the coupling effects of shallow and deep subsurface structural influences in the Osaka plain, along with the effects of the reversed S-wave profile and one-dimensional ground amplification of shallow layers.