The Site Amplification Ratio Regression Equation of PGA and PGV Obtained from Earthquake Records of KiK-net

In the conventional Ground Motion Prediction Equations (GMPE), site amplification term is represented by average S-wave velocity near surface at a site (AVS30) or by ground type(type I, II or III). However, there has been pointed out that large variation of the site amplification factor by earthquake magnitude. In order to solve this problem, we used borehole data and velocity structures provided by KiK-net and tried to create a regression equation of site amplification ratio of PGA and PGV from the surface to bedrock as the new site amplification term. We investigated the effect of source parameters and wave propagation parameters, in addition to the number of layers, the average S-wave velocity and thickness of each layer, on the ground amplification ratios of PGA and PGV of the horizontal components. As a result, we created a high precision regression formula of the site amplification ratio that can evaluate the dispersion due to each individual earthquake by introducing magnitude, dominant periods and soil parameters that reflect deep subsurface structure, instead of the AVS30 site amplification term used in conventional regression equations.