[S-SS12] Statistical seismology and underlying physical processes

[SSS12-13] Linear Structure Observed in Shallow Volcanic Swarms near Izu Oshima

*Hinako Arakawa¹, Naofumi Aso¹ (1.TOKYO UNIVERSITY OF SCIENCE)

The relationship between earthquakes and volcanic activities is very important. To capture ongoing volcanic swarms in Izu Oshima, where active seismic activity has been observed for several decades, we installed two seismometers in September 2023. We applied a matched filter method to detect small earthquakes, using four NIED V-net stations and eleven ERI stations in addition to our stations. We chose a total of ten template earthquakes. As a result, we detected about ten times more earthquakes than the JMA catalog between September 12 and February 18. Most earthquakes were observed during September 22–23 and October 2–4, whose overall pattern is also recognized in the JMA catalog. During these periods, we detected small earthquakes of magnitude zero or less, while the JMA catalog mainly consists of events of magnitude one or greater. We also relocate the hypocenters using the double difference method to investigate the spatiotemporal distribution of swarm events. The obtained hypocenters were found to be distributed in a straight line in the NNW-SSE direction. The lineation is slightly tilted toward NNW. We also discuss the dependency on station coverage and the subsurface structure, as well as the potential migration.