Determination of Design Seismic Motion by Considering Inland and Interplate Earthquakes

摘要

To determine the seismic ground motion for aseismic design after the Hyogoken-Nanbu Earthquake, it is required to take into consideration the earthquakes which occur either at the boundary of intercontinent plate or at the inland faults, although the return period Of the latter for every inland fault may be longer than a thousand years. The seismic motion on bedrock with a shear wave speed over 400m/s is determined according to sta- tistical analyses of strong seismic records observed in major earthquakes which occurred both in Japan and in the United States during recent years. In order to reduce deviation of recorded ground motion in statistics, influences of surface soil and topography have been avoided according to the information of the site of observation, and all records have been adjusted with respect to either the Closest Distance to Fault or the Equivalent Hypo- central Distance by attenuation function. Regarding the site where the seismic source can not be located, seismic risk factor is employed to determine the seismic ground motion. The factor is determined by seismic risk analysis based on the data of historical earth- quakes as well as inland active faults.