Abstract
This study aims to confirm the effectiveness of considering attenuation characteristics (bedrock characteristics) of a deep bedrock layer from the upper crust to the seismic bedrock of the observation site in ground motion evaluation. To achieve this, we evaluated the bedrock ground motions using the stochastic Green's function method and also considered the bedrock characteristics of the observation site. The characterized source model of the 2016 Tottori-ken Chubu earthquake (Mj 6.6) was used for this purpose. We examined bedrock ground motions up to 50 Hz (high-frequency band) at depths of 300 m (Vs = 2.8 km/s) and 1000 m (Vs = 3.2 km/s) at the Tottori 1000-m-deep hard rock borehole array station. In addition, we also examined the ground motions up to 25 Hz at depths of 100 m (Vs = 2.1 km/s) at the KiK-net Sekigane station, 101 m (Vs = 2.8 km/s) at the KiK-net Hakuta station, and 100 m (Vs = 2.4 km/s) at the KiK-net Yubara station. Accordingly, we confirmed that high-accuracy evaluation of the bedrock ground motions at the target observation stations of the 2016 Tottori-ken Chubu earthquake up to high frequencies is possible by considering the bedrock characteristics of the observation site instead of applying high-cut filters based on the cut-off frequency fmax of earthquakes in the stochastic Green's function method. In other words, we proved that high-cut filters based on fmax correspond to the bedrock characteristics of the observation site.
