Seismic quiescence and foreshock activity preceding the 2007 Niigata-ken Chuetsu-oki earthquake (M6.8) in Japan

On June 16, 2007, a moderate shallow earthquake (M6.8) occurred along the NW coast of central Honshu, Japan and caused severe damage. After the occurrence of this earthquake, many studies have described its mechanism and other related topics, but significant discussion about the precursory phenomena related to the earthquake have not been presented. In this study, the regional seismicity prior to the earthquake was examined using high-quality seismic data from the JMA Unified Earthquake Catalog. The results show that the 2007 earthquake was preceded by seismic quiescence that began about 7 years before the main shock. There was also an M4.8 foreshock at a slightly greater depth in November 2005. The observed results for the case of the 2007 earthquake suggest that useful information for forecasting earthquake can be obtained from prior earthquake activity.