2004年浅間山噴火活動に伴う傾斜変動について

概要

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The eruptive activity of Asamayama Volcano started at the summit crater on September 1, 2004. The first eruption was explosive and accompanied with very strong air shock. Before the explosion, significant tilt change was detected by a tiltmeter installed at the northeastern flank of the volcano by JMA. Tilting direction of the signal was in the sense of ground-up toward the west side of the station. BH-type volcanic earthquakes drastically increased at the same time as the start of the precursory tilt change. Including the first one, four remarkable explosive eruptions occurred. In all the cases, significant tilt change and the BH-type volcanic earthquake swarms were observed before the explosive eruptions. The starts of the precursory signals were about 3.5-29 hours before the explosions and the amounts of tilt change were 0.03-0.11μ radian. These features suggest that the prediction of explosion may be possible at Asamayama volcano. We estimated the crustal deformation source using the tilt data associated with the explosive eruption occurred on November 14. The location of the estimated dike intrusion source was about 1 km below sea-level at the summit area. The volume of dike was 4.6×10^4m^3.
2006-02-28