焼岳火山付近の群発地震観測

Abstract

Earthquake swarm activities have been occurring since January 1990 in the vicinity of Mount Yake-dake volcano in central Honshu, Japan.The volcano erupted frequently but it has been 30years since the last eruption in 1962.Temporary observation of microerarthquakes was conducted -near the volcano to survey the seismic activity.A station was set at about 1.5 km away from the summit crater in September, 1990 and five temporary stations were installed in the surrounding area of the volcano during the period from July to September, 1992. After that, three stations have been maintained to monitor the seismic activity.Although only a few events were located in the volcano during the period from July to September, 1992, the focal depths of the events were found to be very shallow as less than 3 km.In October and December, earthquake swarms occurred right beneath Yake-dake volcano.Earthquake swarms were also found in northeast, north and southeast of the volcano.Reviews of the studies on the volcano activity and earthquake swarms near the volcano are also given in this paper.