Abstract
In this paper, we conducted microtremor exploration in Iwaki city hall in order to investigate the effect of inclined bedrock on microtremor H/V spectrum and obtained phase velocity. For the sake of comparison between observed and theoretical values, velocity structure model was constructed by taking into account both down-hole S-wave logging data and N-value distributions from standard penetration tests. From this study, the following conclusions are made: 1) It was found from the result that the H/V spectra from observation data are in good agreement with those calculated from the obtained 1-D structure models. 2) It has also revealed that observed phase velocities by applying CCA method show a tendency of accuracy degradation in the vicinity of peak frequencies of H/V spectra. On the other hand, the phase velocities are consistent with theoretical ones in the vicinity of frequencies of H/V spectral troughs and in higher frequencies than those. 3) It is also confirmed that the estimated bedrock depth by joint inversion analysis of H/V spectrum and phase velocity is deeper than that determined from geotechnical data, due to the accuracy degradation of phase velocity.
