2002年5月伊豆半島東部群発地震活動に伴った地殻変動の開口断層モデル

概要

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From May 8 to 13 in 2002, a small-scale earthquake swarm took place off Ito City, eastern Izu Peninsula, central Japan. Associated with the swarm, changes in the ground tilt as much as 2.8 μrad were detected by several tiltmeters near the swarm area. The change can be approximately interpreted by a tensile fault in the vicinity of the swarm area. We estimated the fault parameters from the tilt and GPS data, assuming that the fault length is 2 km. The depth of the upper bound of the tensile fault and the width are 10 km and 2 km, respectively. The estimated volumetric increase is 7 × 10^-3 km^3. This tensile fault is confirmed to be a dike intrusion from a deep seated magma reservoir, that is, the same process which had been observed in 1980's to 1990's. The tilt vectors of stations ITO and YOS are quite similar in shape in the period from May 8 to 11, suggesting thickening of the dike without upward elongation during the period.
特定非営利活動法人日本火山学会の論文
2003-12-25