Seismic Activity near the Border Between Nagano and Gifu Prefectures (the Central Nagano Prefecture and the Hida Region, Gifu Prefecture) (1)

Near the border between Nagano and Gifu prefectures (the central Nagano prefecture and the Hida region, Gifu prefecture), within the crust (Area a) a series of seismic activity continues since April 2020. In July there occurred 43 earthquakes with maximum seismic intensity 1 or over (maximum seismic intensity: number of earthquakes, 3: 2, 2: 9, 1: 31). The maximum magnitude earthquake in Area a occurring in July was the earthquake in the central Nagano prefecture on July 5 at 15:09 (JST) (M4.8, maximum seismic intensity 3, earthquake ① in the figure). The focal mechanism (CMT solution) of this event showed a strike-slip fault type with a compression axis in an NNW-SSE direction. Also, in the vicinity of this event, at almost the same time there were 2 earthquakes in the central Nagano prefecture (M3.8 and M3.6), and on the same day at 15:10 (JST) an earthquake in the Hida region, Gifu prefecture (M4.0).

Japan Meteorological Agency
[Evaluation of Seismic Activities for July 2020 (August 12, 2020)]