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タイトル: The Accomodation of Plate Collision by Deformation in the Izu Block, Japan.
その他のタイトル: 伊豆ブロック内の変形によるプレートの衝突の緩和
著者: Somerville, Paul
発行日: 1978年12月25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53冊第3号, 1978.12.25, pp. 629-648
抄録: A model is proposed which explains the intraplate deformation of the Izu block as resulting from the collision between the Philippine Sea plate and the Eurasian plate along the southern Fossa Magna. The collision produces two stress domains having contrasting orientations. The northeast Izu block whose motion is impeded by the collision accomodates as much as 0.4cm/yr of the resulting NW-SE shortening by left lateral slip on the N-S striking Tanna fault and conjugate right lateral slip on the E-W striking Izu-Oshima fault. A further shortening of as much as 0.8cm/yr, calculated from geodetic measurements, is accomodated directly by deformation across the collision zone. The combined effect of these two processes can adequately explain the convergence rate, measured along the Sagami trough using coastal terrace data and historical seismicity, of as little as 1.2cm/yr, without resort to the subduction zone off the NE coast of the Izu Peninsula proposed by ISHIBASHI (1978). In the southwest Izu block, the difference in convergence rate between the outer Suruga trough (3cm/yr) and the collision zone (approximately 1cm/yr) produces shear strain parallel to the direction of relative plate motion. This shear strain is accomodated by slip on the network of NW striking faults in the Izu Peninsula and subduction along the inner Suruga trough which decreases northwards. The sense and rate of this shear strain are clearly reflected in the geodetically measured deformation of the Izu Peninsula during the past hundred years. The proposed model suggests explanations for various mechanical correlations between tectonic features of the Izu block, such as the presence of the Tanna fault, the Hiekawa Pass uplift region, and the Izu-Oshima fault in front of the zone of direct plate collision, and the observation that great earthquakes on the Sagami trough are followed by rupture on the Tanna fault.
URI: http://hdl.handle.net/2261/12679
ISSN: 00408972


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