Relationships between geological structure and earthquake source faults along the eastern margin of the Japan Sea

Abstract

This study reviews the relationship between geological structure and major earthquakes along the eastern margin of the Japan Sea, and con- siders the possibility of inferring the location and geometry of earth- quake source faults from geological structures. The source areas of major earthquakes in this region correspond to the locations of asym- metric anticlines that are 10−20 km wide and that have grown during the past 2−3 million years. These observations suggest that the anti- clines are fault-related folds located above the source faults. This hypothesis was partly confirmed by a comparison between a fault model based on fold geometry and the distribution of aftershocks in the source area of the 2004 Niigata Chuetsu Earthquake. It is impor- tant to assess whether this model of fault-related folding is widely applicable to folds at the eastern margin of the Japan Sea. If we could infer the location and geometry of future earthquake source faults based on analyses of geological structure, this would greatly improve our ability to evaluate ground motions due to earthquakes. Keywords: