葛根田地熱地域において遠隔自然地震の前後に観測した微小地震の発生数と大きさの解析

抄録

Both number and amplitude of microearthquakes in the Kakkonda geothermal field before and after arrival of remote earthquakes are investigated. Earthquakes occurring when a remote earthquake arrives has been reported in some journal papers. On the other hand, earthquakes felt by people can hinder geothermal development. Quantitative analysis on the response of a geothermal reservoir when remote earthquakes arrive is necessary to understand the effect of remote earthquakes in geothermal development. Twenty-nine remote earthquakes arrived in the Kakkonda geothermal field during the three-year period from 2017 to 2019. 809 microearthquakes were observed in the 24 hours after the arrival of those remote earthquakes. There was no significant increase in the number of microearthquakes after the remote earthquake. In addition, the maximum instantaneous value of 75% of the microearthquakes was almost same or 1/10 smaller than that of the remote earthquakes. Nine in the 809 microearthquakes had a maximum instantaneous value greater than that of a remote natural earthquake. The largest of those nine microearthquakes was about 39 times larger than the remote earthquake.