SEGJ Technical Conference

Estimation of 3D S-wave velocity of sedimentary plain in the metropolitan area by applying surface-wave tomography to MeSO-net data

Abstract The estimation of S-wave velocity structure is essential to predict damage caused by earthquakes. We performed surface-wave tomography on the Metropolitan Seismic Observation network which is deployed around Kanto. To estimate surface wave dispersion curves, we applied the zero-crossing method based on the SPAC method. The zero-crossing method uses only zeros in the observed cross spectrum and zeros of the Bessel function to obtain phase velocity estimates at discrete frequencies. To estimate stable dispersion curves, we developed iterative phase-velocity picking algorithm. We then estimated the 3D S-wave velocity structure by applying a direct surface-wave tomography method. This surface-wave tomography method can estimate S-wave velocity directly with 3D sensitivity kernels updated iteratively. Our results show the low velocity anomaly in north Boso peninsula. This low velocity anomaly corresponds to the trend of depth of basement rock and Vs 1.5 km/s which were observed in previous study. To estimate more accurate S-wave velocity structure, we need to find optimal parameters for tomography and select stable dispersion curves manually.