ESTIMATION OF SUBSURFACE STRUCTURE USING SURF ACE-WAVE DISPERSION DATA AND ITS APPLICATION TO GROUND MOTION EVALUATION

Abstract

It is important to estimate effects of deep subsurface structures to long-period ground motion. In this study, the mean subsurface structures between a observatory at Kashiwazaki, Niigata prefecture and epicenters are estimated as a multi-layered model by an inversion of the group velocities using a genetic algorithm. The estimated models for the events located around Niigata have deep pre-Neogene basement and the depth of basement estimated from the epicenter near Toyama trough is especially deep. These features of the models agree with the regional variation of geological data and gravity anomaly. Furthermore, long-period ground motions at the observatory are evaluated by normal mode theory using the estimated models and existing fault parameters. Over whole features of the records were reconstructed by synthetics. It is concluded that the subsurface structure estimated from single station data is so useful to evaluate long-period ground motions.