Estimation of Vs30 Based on the Japanese KiK-Net P-Wave Seismograms

Session: Alpine-Himalayan Alpide Shallow Earthquakes and the Current and the Future Hazard Assessments
Type: Oral
Date: 4/30/2020
Time: 02:30 PM
Room: 215 + 220
Description: 

An automated procedure based on initial P-wave seismogram amplitudes in the radial and vertical directions is proposed to rapidly and objectively determine time-averaged shear wave velocities in the upper 30-m of soil deposits (V_S30). This procedure performs sequential eight steps, such as preprocessing of raw signal in a form of acceleration-time series by filtering and baseline corrections for removing background noises, converting the preprocessed acceleration-time series into velocity-time series, rotating seismograms in horizontal directions (east–west and north–south) to the radial direction, computing P-wave arrival time by utilizing an automatic algorithm for picking p-phase, applying local baseline correction, calculating the ratio of radial to vertical components of particle velocity (U'_R/U'_Z), verifying noise levels and determining V_S30 from estimated V_SZ. This procedure is applied to 630 Kiban-Kyoshin network stations (KiK-net) in Japan to estimate V_S30 using 9,207 ground motion records. It is observed that the V_S30 estimates are comparable to actual V_S30 measurements. Application of signal-to-noise ratio (SNR) thresholds for filtering records results in slight improvement of V_S30 estimation. However, the number of records used for estimating V_S30 decreases at certain sites. Bias correction models are proposed based on SNR thresholds and take-off angles to allow estimating V_S30 at lots of sites accompanied with accurate prediction performance. It is clear that the prediction performance of the automated procedure is comparable with that of methods using different types of proxies for several regions. The proposed method is successfully applied to Kyoshin network using available 18,454 records at 989 stations and a V_S30 map is provided for the entire Japan area.

Presenting Author: Sinhang Kang

Authors