Journal of Japan Association for Earthquake Engineering Vol. 17(2017) No. 3
The English Issue

The earthquake and associated aftershocks that occurred off the Pacific coast of Tohoku, Japan on March 11, 2011 caused liquefaction over a large area in the mouth of the Tone River. This study aims to establish a spatial relationship between sand-boiling and the damage done to buried pipelines in the zones of concentrated liquefaction-induced damage in the Kashima region. The pipeline repair rate in the sand-boiling area was roughly 10 times as high as that in the liquefaction-induced pipeline-damage concentration zones. As the pipeline within the sand-boiling area enlarges, percentage of damage occurrence increased and its damage occurred more near the boundaries of the sand-boiling area.

We developed a method to simulate strong ground motions using a combination of the stochastic Green's function and three-dimensional attenuation structures, and succeeded in reproducing the strong motions of the 2003 Tokachi-Oki earthquake (M8) and the 2011 off the Pacific Coast of Tohoku, Japan earthquake (M9). The response spectra using this method well reproduced actual observations of both earthquakes. Our findings show it is necessary to consider the three-dimensional (3-D) S-wave attenuation (Qs) structure in evaluating the ground motion over a broad area.

This study used strong-motion records from the three-dimensional-dense-array observation network at the Hamaoka Nuclear Power Plant to evaluate the spatial variation (coherency and variation in Fourier amplitude ratio between points) of seismic motion in hard soil. The evaluated spatial variation characteristics of seismic motion were used to derive statistical models based on regression analysis. The results showed that coherency decreased with increasing frequency and distance. Meanwhile, variation in Fourier amplitude ratio increased with increasing frequency and distance below 5 Hz.

In this study, we structured the disaster risk communication method that assists disaster prevention activities in the local community and applied the method to the earthquake disaster prevention activities in the elementary school district to verify its effectiveness in improving the capability of the local community to respond to disasters. As a result, with the disaster risk communication among a variety of concerned parties in the community, we confirmed that the viable disaster prevention system that utilizes diversified social resources accumulated in the local community was restructured.