SPATIAL DISTRIBUTION FEATURES OF VELOCITY RESPONSES OF MW=8.0 EARTHQUAKE -CASE STUDY IN THE 2003 TOKACHI-OKI EARTHQUAKE-

摘要

The 2003 Tokachi-oki earthquake, a large (Mw=8.0) inter-plate earthquake, is the first earthquake with a magnitude of 8 after the nation wide high-density strong-motion network was installed. We make the spatial distribution maps and attenuation relationships for velocity responses. The spatial distribution maps show different features depending on the period. The short period (T:natural period =0.1) sec map shows strong attenuation of the response at back-arc side of the volcanic front; this can be explained by the S-wave attenuation structure beneath the northern Japan. The long-period (T~10sec) maps and relations are in part controlled by the source effect and the deep subsurface structure.