人工地震探査による霧島火山群の地震波速度構造 : はぎとり法による解析

概要

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Seismic velocity structures beneath Kirishima volcanoes are estimated down to 3 km from the surface with the differential analysis of refraction from the explosion experiment. Three layers are interpreted in the central and northern part of the volcanoes and two layers are interpreted in the southern part of the volcanoes. Through the northern and middle part of the volcanoes, the first layer whose velocity is 2.1 km/s is almost constant thickness of 0.5 km. The second layer whose velocity is 3.6 km/s is 0.5 km thickness at the end of the northern volcanoes and thicken northwestward into 3 km thickness. The third layer whose velocity is 5.8 km/s is estimated. In the southern part of the volcanoes, all velocities are higher than those of the northern or middle part. Several features appear in the profiles; a discontinuity around Takachiho-gawara in the south part of the volcanoes, north-westward declination of the third layer as a basement, and no low velocity zone beneath recent active craters down to 3 km depth. These results are consistent with the results of Magnetotelluric survey.
1996-11-30