COLLISION OF FOREARCS AND OVERLAPPED DEEP SEISMIC ZONE IN THE TRANSITIONAL ZONE BETWEEN THE NORTHERN HONSHU AND KURILE ARCS
COLLISION OF FOREARCS AND OVERLAPPED DEEP SEISMIC ZONE IN THE TRANSITIONAL ZONE BETWEEN THE NORTHERN HONSHU AND KURILE ARCS
复制标题
北本州岛弧与千岛岛弧过渡带前弧与重叠深震带的碰撞
DOI：
10.4294/jpe1952.34.supplement_s175
复制
发表时间：
1986
期刊：
影响因子：
--
通讯作者：
T. Moriya
中科院分区：
文献类型：
--
作者：
T. Moriya
阐述了北海道过渡带下碰撞弧前和下降岩石圈之间的构造关系。根据日高山脉和浦川地区的构造和应力状态推断，北方本州前弧的地壳可能正在日高山脉--千岛前弧的西南端下冲。1982年发生在前弧结合区的浦川冲地震（日本地震协会震级7.1）就是这种碰撞运动的结果。碰撞的主要原因是太平洋板块斜向俯冲到千岛群岛前弧之下，造成千岛群岛前弧向西南方向运动。为了解日高山碰撞构造与浦川近海构造的关系及中深地震带的形态，重新确定了4200多个震源。为了更详细地了解深地震带的结构，将震源投影到垂直于倾斜深地震带的垂直平面和不同的倾斜平面上。中深地震带的震源分布表明，北方本州弧和千岛群岛弧的地震带在两弧的过渡带之下重叠。推测这种超覆是由于斜俯冲的太平洋板块在千岛群岛前弧下向西南方向的异常迁移所致，并认为在弧结前弧下，地壳结构、扭曲板块的几何形状和应力状态可能明显地受大洋板块运动方向的控制。
Tectonic relation between the colliding forearc and descending lithosphere beneath the Hokkaido transition zone is presented. Structure and state of stress inferred beneath Hidaka mountains and off Urakawa regions show a possibility that the crust of the northern Honshu forearc is downthrusting beneath Hidaka mountains-the southwestern end of the Kurile forearc. Urakawa-oki earthquake of 1982 (JMA magnitude 7.1) which occurred in the forearc-junction region is concluded to be a result of this colliding movement. The collision is inferred to be mainly ascribed to southwestward movement of the Kurile forearc which may be originated from oblique subduction of the Pacific plate beneath the Kurile forearc. To understand the tectonic relation between colliding structure of Hidaka mountains and off Urakawa regions, and configuration of intermediate-depth seismic zone, more than 4, 200 hypocenters were redetermined. To look through the configuration of the deep seismic zone in detail, the hypocenters were projected on vertical planes and on different slant planes perpendicular to the dipping deep seismic zone. Hypocenter distribution in the intermediate-depth seismic zone shows that the seismic zones of the northern Honshu and the Kurile arcs are overlapping beneath the transitional zone of the two arcs. It is inferred that the overlap is ascribed to anomalous southwestward migration of the obliquely subducted Pacific plate beneath the Kurile forearc.It is concluded that beneath the forearcs in the arc-junctions, crustal structure, geometry of the contorted plate and state of the stress may be significantly controlled by the direction of the oceanic plate motion.