[SSS04-08] Impact of Seismic Velocity Change on Ground Motion Modeling
Keywords:seismic hazard, ground motion, velocity change
We quantitatively investigate the impact of seismic velocity change on ground motion modeling. Using the coda interferometry method by Chen et al. (2017), the seismic velocity change more than 5% with respect to the average S-wave velocity was observed for both the 2003 Tokachi-oki earthquake and the 2018 Hokkaido Eastern Iburi earthquake at the KiK-net IBUH03 station (e.g., Taira et al., 2019; Chen et al., 2020). The seismic velocity drop occurred near surface between the sensors at uphole and at downhole with 153 m deep with S-wave velocity of 520 m/s. We estimate the seismic velocity drop made the increment of 0.15 at maximum on the JMA seismic intensity scale. Since the increment of seismic intensity is proportional to the input ground velocity at the engineering bedrock, the temporal velocity change is not negligible in time-dependent seismic hazard assessment for aftershock forecasting with significant ground motion, and has a potential to over the threshold as a final push.