Site-effect analysis of four japanese kik-net stations using surface-to-borehole-spectral-ratios (Sbsrs)

In this study, we use horizontal ground-motion recordings gathered from KiK-net stations MYGH08, FKSH11, YMTH04 and IWTH12 to estimate deterministically particular site-effects and to identify nonlinear soil behavior with respect to different intensity measure types. The KiK-net database has a dense array of installed stations with a large amount of recordings for each site and the uniqueness of two three-component sensors, which are installed at soil surface and at borehole depth. Using this opportunity we employ the surface-to-borehole-spectral ratios (SBSRs), defined as the ratio of the response spectra at surface (PSASF) and the response spectra at borehole depth (PSABH) and estimate the site-effects. To model the nonlinear site effects more precisely, we investigate the effectiveness of PGA (peak-ground-acceleration), PGV (peak-ground-velocity) and PSA at given borehole depths. Our results show strong variations in non-linearity for different periods in spite of the fact that all selected stations are marked by similar Vs30 values (whereby all are lower than 400 m/s).