Effects of Soil Amplification on Ground Motion Response Spectra with High-Frequency Contents at Generic Soil Sites for Nuclear Facilities in Korea

Abstract

Ground motion response spectra (GMRS) at rock/soil sites in regions where earthquake ground motions have dominant contents at high frequencies of 10 Hz or more are evaluated and the effects of soil amplification on the GMRS are studied. The seismic hazard levels at the soil sites are estimated from soil amplification functions and hazard curves for rock outcrop motions. The soil amplification functions are obtained using modified earthquake ground motions which match the uniform hazard response spectra (UHRS) for rock outcrop motions with various mean annual frequencies of exceedance in order to consider the effects of earthquake ground motions consistently in a site response analysis. UHRS at soil sites are determined from the calculated seismic hazard curves. Subsequently, design factors, which will be applied to UHRS, and the corresponding GMRS are evaluated such that the seismic risk for the structures, systems, and components of nuclear facilities would be equal to a target seismic risk. It can be observed from example applications that the UHRS and GMRS at soil sites have peaks at the natural frequencies of the soil, where the soil responses are amplified. Amplification at soil sites depends on the frequency contents of rock outcrop motions.