Abstract
It is essential to evaluate the subsurface structure properly and validate previously proposed ground structure models based on the geological data and boring exploration data with the observation of ground shaking for extensive and highly precise estimation of strong ground motions in urban areas. In this study, we observed microtremors in the southern part of the Osaka Plain in Japan where detailed geological information are comparatively less than the other areas of the Osaka Plain. We calculated H/V spectral ratios from observed microtremors data and compared predominant peak frequencies and amplitudes at these frequencies of the H/V spectral ratio with those calculated theoretically from our initial model. We searched for the 1-D structures at each site based on these predominant frequencies and amplitudes calculated from the recently proposed diffuse-field theory. As a result we identified the modified subsurface structures for each observation point along the two east-west lines in the southern part of the Osaka Plain. We also constructed a two-dimensional velocity structure for future strong motion prediction purposes.
