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タイトル: 伊豆弧衝突に伴う西南日本弧の地殻構造改変
その他のタイトル: Re-arrangement of the Shallow-level structure of Southwest Japan Arc due to the collision of the Izu-Bonin Arc
著者: 狩野, 謙一
著者(別言語): Kano, Ken-ichi
キーワード: Izu-Bonin Arc
Southwest Japan Arc
arc-arc collision
vertical-axis rotation
発行日: 2003年1月31日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第77冊第3号, 2003.1.31, pp. 231-248
抄録: The central part of the Honshu Arc collided in the South Fossa Magna (SFM) area with the crossing Izu-Bonin Arc (IBA), forming a cuspidate bend of the pre-Middle Miocene basement rocks of the Honshu Arc. This paper summarizes the effects of the collision on the basement rocks of the Southwest Japan Arc (SWJA), the southwestern segment of the Honshu Arc. The northward shift of the pre-Middle Miocene rocks in the Akaishi Mountains in the easternmost SWJA on the frontal side of the SFM collision zone reaches more than 160 km at a sub-vertical-axis, under counterclockwise rotation with N-S trending, left-lateral strike-slip faultings. The Mesozoic rocks of the Mino and Ryoke Belts to the north of the Akaishi Mountains at the rear side of the collision zone also shifted about 80 km northward about a sub-vertical rotation axis. These northward shifts also had some components of horizontal-axis rotation and resulted in the re-arrangement of geologic bodies in the shallow-crustal level of eastern SWJA. Chronological and paleomagnetic data clearly suggest that the northward bend occurred in a short period of the Middle Miocene around 15 Ma. This intra-arc bending originated from the combined effects of the clockwise rotation of SWJA in association with the rapid fan-shaped opening of the Sea of Japan, and the initial collision of SWJA with the northern tip of IBA, the Kushigatayama Block. The E-W compression due to the intra-arc bending of the eastern SWJA resulted in the formation of N-S trending, km-scale folds with the vertical axes at the inner side of the hinge area of this bending about 150-200 km west of the collision zone. These wide effects on the eastern SWJA probably occurred under a high geothermal regime that weakened its upper crust. Compared to the initial collision, the following Late Miocene and Pliocene collisions due to the north or northwestward advance of IBA did not severely affect the pre-existing structures in SWJA. The latest collision with the Izu Block since 1 Ma has caused a rapid uplift of left-stepping, en-echelon arranging mountain ranges on the eastern SWJA.
URI: http://hdl.handle.net/2261/13253
ISSN: 00408972


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