中部地方の火山活動と沈み込んだフィリピン海プレートの形状

概要

論文の詳細を見る
Geometry of the subducling plates in the central area of Japan is summarized and its relationships to the distribution of Quaternary volcanoes in the Chubu district of Japan are discussed. Philippine Sea plate is subducting along the southern coast of Japan. The surface of the subducting Philippine Sea plate in this region is identified mostly with the distribution of earthquakes in the uppermost mantle. There had been no evidence of slab existence beyond the northern bound of the seismic slab. Recently we identified the Sp phases of the deep-focus earthquakes beneath Chubu district as the waves converted at the upper surface of subducting Philippine Sea plate. The Sp phases are even observed at station HKJ on the Japan sea coast of the Chubu district, which is 100 km beyond the northern bound of seismic slab. The geometry of the subducting Philippine Sea plate is summarized as follows: Philippine Sea plate is torn apart to the northwest of Izu peninsular. On the other hand the subducting plates overlapped beneath the Nobi plain; the western part is overlain by the eastern part. This strange geometry results from the strong distortion of Philippine Sea plate around Izu Peninsular before subduction. The aseismic slab identified in the region between Ise bay and Wakasa bay are the extension of the eastern part of the slab. We do not have any evidence of aseismic slab for the extension of the eastern-most part. Quaternary volcanoes are located in the region where we could not find the aseismic slab. Two possibilities can be proposed on the origin of magma source for these volcanoes. (1) They are originated in the deeper part of the mantle, possibly from the subducting Pacific plate. The magma ascents and generates volcanoes where no slab blocks. (2) The eastern part of the slab subducts in larger dip angle to the north of the seismic area, generating magma where it subducts below 100km. The result of seismic tomography might supports the sccond possibility.
1997-04-25

中部地方の火山活動と沈み込んだフィリピン海プレートの形状

スポンサーリンク

概要

著者

関連論文

スポンサーリンク