On the possibility of the 2011 Tohoku-oki earthquake reactivating Shinmoe-dake volcano, southwest Japan: insights from strain data measured in vaults
- 1Miyazaki Observatory, Disaster Prevention Research Institute, Kyoto University, 3884, Kaeda, Miyazaki 889-2161, Japan
- 2Research Center for Earthquake Prediction, Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan
- 3Division of Technical Affairs, Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan
Abstract. The Shinmoe-dake volcano in southwest Japan, which produced its first major eruption in 52 yr on 26 January 2011 but had been quiescent since 1 March, re-erupted on 13 March. It was only two days after the occurrence of the M = 9.0 Tohoku-oki earthquake in eastern Japan. The coincidence of the two events raises the question of whether the earthquake triggered the volcanic activity. As a provisional but rapid assessment of this question, we examined high-resolution strain data at a site located 18 km from Shinmoe-dake. In terms of the Tohoku-oki earthquake, three points can be drawn from the strain data: (1) static strain changes were less than 0.05 × 10−6, which is too small to trigger an eruption; (2) the amplitudes of dynamic strain changes are on the order of 10−6, which may trigger seismicity or volcanic eruption; and (3) strain rates were not accelerated, which indicates no significant change in magma pressure. Comparing these results with reports of other eruptions coincident with seismic events, and considering a scenario in which a seismic event triggered an eruption, we tentatively conclude that the eruption on 13 March was not a triggered event. However, this conclusion may be revised after analyzing seismic data.