Fig. 3

Hypocenter distribution in central Japan. The dots denote hypocenters of earthquakes shallower than 30 km that occurred in the period of 2006 to 2019. The dot colors indicate hypocenter depth. Predominant earthquake clusters related to large and moderate earthquakes in the last 170 years are shown by ellipsoids with years of earthquake occurrence. The Itoigawa-Shizuoka Tectonic Line active fault system (The Headquarters for Earthquake Research Promotion 2015) is indicated by the solid lines