![]()
ABSTRACT Strong ground motion with very high dense spatial location for a third same grid square in centre of Miyoshi City, Tokushima Prefecture, Japan, during the Nankai Trough Earthquake are predicted based on the SMGA models considering local site effects in this study. We conducted first microtremor measurements at 200 sites in a grid square of interest. Based on the obtained records, microtremor H/V spectra are calculated. Distribution of the ground shaking characteristics based on several indices of the H/V spectra are then illustrated. We also evaluated the site amplification factor at the 200 sites based on an empirical relationship. Finally, we predicted seismic waveforms at the 200 sites during the Nankai Trough Earthquake based on the SMGA models considering the site amplification effects. As a result, we can found that the predicted value of the strong motion indices, such as JMA seismic intensity, are heterogeneous in the grid square of interest.
INTRODUCTION The occurrence of "the 2011 Tohoku Earthquake (Mw9.0)" along the Japan Trench motivated us to hypothesize an equally gigantic earthquake along the Nankai Trough, which is another plate boundary close to the coast of Japan. The prediction of strong ground motions for such an earthquake has already been carried out for each same grid square by Japanese Cabinet Office, National Research Institute for Earth Science and Disaster Resilience (NIED), Local Government Office and so on. In other words, it is assumed that the ground shaking characteristics in a grid square of interest is uniform in the ground motion prediction. Furthermore, at present, dense strong motion observation networks have been constructed in Japan. One of the important findings based on these networks is that strong ground motions are quite site-dependent. Characteristics of the observed ground motions at nearby stations can exhibit significant variation due to difference of the ground shaking characteristics, even when the stations are within several hundred meters. Thus, ground motion prediction with very high density in a same grid square of interest during a scenario earthquake with Mw9.0 along the Nankai Trough considering ground shaking characteristics is very important.
Site News