A survey of the geological subsurface structure was conducted in the east of the Osaka basin in order to predict seismic motions. The reflection survey revealed a detailed P-velocity structure down to the basement rock embedded at a depth of 1.5km to 1.7km. The features appearing commonly in reflection profiles of the Osaka basin are comfirmed in the reflection profiles as well: the sediments are divided into a shallow layer composed of alternate stacks of marine and non-marine deposits and a deep layer composed of only non-marine deposits. The array analyses of microtremors also revealed S-velocity structures down to the basement rock, using the inversion of microtremor phase velocities. Furthermore, a two-dimensional east-west subsurface structure model of the Osaka basin is proposed, combining geological information obtained by present and past surveys.
