斜俯冲板块边界变形分配的力学分析

本文研究斜俯冲板块边界由俯冲的逆掩断层和平行于火山弧的走滑断层所切割出的岩石层窄条的宏观力学状态．分析计算表明，当断层强度小而构造压应力大时，海沟处板块俯冲形成的逆掩断层地震滑动方向与斜收敛板块运动方向将不一致，震源机制反映的主压应力和断层错动方向变得近乎垂直于海沟；板块间的强耦合和大陆板块边缘软弱带的存在为窄条滑动提供了有利条件．给定俯冲倾角和震源机制滑动角的观测值，可以计算逆掩和走滑断层上的有效摩擦系数．计算结果表明，两种断层上的有效摩擦系数一般都不大于０．２，反映或存在着高孔隙水压，或存在断层泥之类弱物质，或两者兼而有之．

MECHANICS OF DEFORMATION PARTITIONING AT PLATE BOUNDARIES OF OBLIQUE SUBDUCTION

In this paper the mechanics of a forearc lithospheric sliver at convergent plate boundary bounded by a strike-slip fault and a thrust fault with oblique convergence is investigated.The results show that slip tends to become perpendicular to the trench when the frictional coefficients of faults become small and the tectonic compression becomes large.This conclusion is in agreement with observations,i.e,strong intraplate coupling and weak continental plate are favorite conditions for sliver slip.Given the observed subduction angles and slide angles,effective frictional coefficients of both thrust and strike-slip faults are found to be 0.2 or smaller.This suggests either the presence of high pore pressure,or a weak decollement,or both.Strike-slip fault is found usually weaker than thrus fault.