[SSS13-P08] Swarm Activity in the Hida Mountain Range, Central Japan, Started in April 2020.; Comparison with Past Activity
Keywords:Hida Mountain Range, Central Japan, Swarm Activity
Intense swarm activity took place in the southern part of Hida mountain range, central Japan, in April 2020. This activity started with an earthquake of Mjma=3.8 on April 22 in Nagano prefecture about 6km apart from the main ridge of Hida mountain range, followed by Mjma=5.5 earthquake on April 23. Focal region of the swarm gradually migrated to the main ridge, which is the prefectural border of Nagano and Gifu prefectures. On May 19, focal region reached to the main ridge and migrated to Gifu prefecture area with an earthquake of Mjma=5.4. As of May 25, 2020, focal area is still migrating to north in Gifu prefecture, which is western side of Hida mountain range. The total extent of the focal area is about 12 km in the NS direction and 8 km in the EW direction as of May 25.
Continual swarm activities have been observed in this region since early 1990’s. Prominent activities were observed in 1990, 1993, 1998, 2011, 2014, and 2018. One of the characteristic features of these swarm activities is that the focal region of each swarm has not overlapped to each other until 2018 activity. However, in the 2020 activity, the focal region overlaps on that of 1998 activity, which is a unique character of this activity.
In this presentation, we will compare these activities from the view points of focal region, source mechanism, and other phenomenon such as swarm of low frequency earthquakes that follow the shallow swarm activities.
Continual swarm activities have been observed in this region since early 1990’s. Prominent activities were observed in 1990, 1993, 1998, 2011, 2014, and 2018. One of the characteristic features of these swarm activities is that the focal region of each swarm has not overlapped to each other until 2018 activity. However, in the 2020 activity, the focal region overlaps on that of 1998 activity, which is a unique character of this activity.
In this presentation, we will compare these activities from the view points of focal region, source mechanism, and other phenomenon such as swarm of low frequency earthquakes that follow the shallow swarm activities.