应用有限单元法恢复冲绳海槽和付加体古构造应力场及其意义

冲绳海槽是欧亚板块内大陆地壳的扩张作用所形成的一个弧后盆地。以弹性学原理和库仑—莫尔准则为基础,应用二维(2D)有限单元法模拟大陆岩石圈上部的构造应力场和断层发育状况。模型中使用两种位移边界条件,并采用平面应变条件进行计算。扩张位移边界条件加载于冲绳海槽内大陆地壳的底部,俯冲位移边界条件加载于菲律宾海板块的俯冲带。数学模拟的结果表明,大陆地壳底部的扩张作用使得冲绳海槽内发育正断层,最后导致冲绳海槽这一弧后盆地的形成。菲律宾海板块的俯冲作用引起欧亚板块付加体中形成逆掩断层。

PALEOSTRESS FIELD OF OKINAWA TROUGH AND ACCRETIONARY PRISM BY MEANS OF 2D FINITE ELEMENT METHOD AND ITS TECTONIC SIGNIFICANCE

The Okinawa Trough is a back-arc basin opened by crustal extension within the Eurasia plate.Several two-dimensional (2D) finite-element models are presented to simulate the stress field and fault development in the upper continental lithosphere of the Eurasia plate.Linear elastic rheology with failure criterion under plane strain condition is adopted.Two types of displacement boundary condition are considered in the numerical model.The spreading displacement is applied along the crustal bottom beneath the Okinawa Trough.The convergence displacement is subjected along the upper side of the Philippine Sea (PHS) plate.From the simulated results,the spreading displacement along the crustal bottom generates normal faults in the trough,which finally leads to the formation of the Okinawa Trough.The subduction of the PHS plate causes the thrust development within the accretionary prism of the Eurasia plate.