Abstract
We review studies of long-period ground motion and surveys of deep subsurface structure in Hokkaido. The long-period ground motion studies have been begun by using JMA strong-motion records. The records demonstrated excitation of basin surface waves at large plains such as the Tokachi and Yufutsu plains; basin-induced surface waves from nearby intermediate-depth events and basin-transduced surface waves from regional shallow events. A seismic array observation using a digital recorder elucidated wave types and propagation characteristics of the basin-induced and basin-transduced surface waves in the Tokachi plain. The deep subsurface structural surveys have been begun to explore oil and natural gas reservoirs in and around Hokkaido; a few surveys have been done to clarify the nature of long-period ground motion. Recently the National Research Institute for Earth Science and Disaster Prevention (NIED) constructed a three-dimensional subsurface structural model of Hokkaido by combining all the previous surveys. Finally we briefly review studies of long-period ground motion obtained by the dense strong-motion network, e.g., K-NET and KiK-net, during the 2003 Tokachi-oki earthquake (M8.0).
