Automated procedure for estimating V_S30 utilizing P-wave seismograms and its application to Japan

We develop an automated procedure to estimate time-averaged shear wave velocities in the upper 30 m of soil deposits (V_S30) rapidly and objectively based on initial P-wave seismogram amplitudes in the radial and vertical directions. We apply this procedure to 630 Kiban-Kyoshin network stations in Japan utilizing 9207 records. It is clear that the estimates are in good agreement with real-world measurements. Filtering records based on signal-to-noise ratio (SNR) thresholds slightly improves V_S30 estimation, but a decrease in the number of records results in an inability to estimate V_S30 at certain sites. We propose bias correction models based on SNRs and take-off angles to facilitate V_S30 estimation at numerous sites while maintaining suitable prediction performance. We observe that the performance of the proposed method is similar to that of methods utilizing different types of proxies for various regions. We successfully apply the proposed method to 989 Kyoshin network stations utilizing 18,454 records and create a V_S30 map for the entire area of Japan.