有珠火山2000年噴火に伴って伊達市で観測された地下水位異常(<特集>2000年有珠山噴火)

概要

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Remarkable hydrological anomalies occurred in relation to the 2000 eruption of Usu volcano, Japan. The groundwater level at DT1 in Date City rose more than 4 m, and the groundwater discharged one day before the eruption. The groundwater level at DT2 rose 0.95 m before the eruption. Based on the well's response to tide, the rises of groundwater level are corresponded to the crustal strain changes caused by a spherical inflation source with a volumetric change of 0.3-1.7×10^7 m^3 (Matsumoto et al., 2002). The depth of the spherical source on March 29 is estimated at above 4.3 km by using the ratio of groundwater-level changes at DT1 to DT2. Assuming a vertical line source with the bottom depth of 10 km, the depth of the top on March 29 is estimated to be above 1.6 km. The ratio of groundwater-level changes gradually increased before the eruption, which might show the rising process of the magma.
特定非営利活動法人日本火山学会の論文
2002-07-10