SEISMIC MOTION LEVEL IN ACCELERATION RESPONSE SPECTRA ON ENGINEERING BEDROCK

摘要

On determination of seismic ground motion for aseismic design, it was proposed to take earthquakes into consideration, which occur either at the boundary of intercontinent plate or at the inland fault, although the return period of the latter for each inland fault may be longer than a thousand years. Seismic motion on bedrock with shear wave speed over 400m/s was worked out according to the statistical analyses of strong seismic records observed in major earthquakes occurred in both Japan and United States in recent years. To reduce deviation of recorded ground motion in statistics, the influences of surface soil and topography have been avoided based on the information of sites of observation, and all records have been adjusted with respect to either the shortest distance from fault or the equivalent hypocenter distance by attenuation equation. For sites where the seismic source can not be located, seismic risk factors are employed in determination of seismic ground motion, which were determined by seismic risk analysis based on the information of historical earthquakes as well as inland active faults.