冲绳板块应力场数值模拟及其动力学特征

Numerical simulation of the stress field in Okinawa plate and its dynamic characteristics

冲绳板块位于菲律宾海板块向欧亚板块俯冲形成的西太平洋边缘活动带上,构造应力场图像及其动力学机制表现得相当复杂.采用伪三维有限元方法,以WSM2008观测应力场数据的应力取向和应力型两方面指标作为主要约束,对冲绳板块构造应力场进行了数值模拟.通过对计算结果的分析,对模型涉及的各种作用力作出了估计.在此基础上,对冲绳板块岩石层的状态,以及该地区的板块动力学特征进行了探讨,并得到了以下一些初步认识:①软流层静压推力控制着该地区构造应力场的基本形态;②冲绳海槽的演化过程,例如该地区的岩石层减薄与其下地幔流的上升等,也在很大程度上影响了该地区的板内应力场空间分布特征;③琉球俯冲带边界力的作用是分段的,不同区段作用力对板内应力场的影响有所不同.

The Okinawa plate is located on the Western Pacific active belt,which was created by northwestward subducting of the Philippine Sea plate with respect to the Eurasian plate. The tectonic stress field and its dynamic mechanism demonstrates a very complicated pattern in this region. Using the pseudo-3-D finite element method,this paper numerically simulated the tectonic stress field in the Okinawa plate area,with the orientation and regime indicators from WSM2008 data base as principal constraints. Based on the simulated result we try to understand the state of lithosphere and to explore dynamic characteristics of the intraplate stress in this region. We thus estimated the effect of boundary forces on the intraplate stress field,and got some preliminary conclusions：① The asthenospheric static push forces mainly control the general spatial pattern of the intraplate stress field. ② The evolution process of the Okinawa Trough,including the lithosphere thinning and moving up of the mantle flow in this region,also plays important role in constructing the stress pattern. ③ The boundary forces acting along the Ryukyu subduction zone show segment dependence,with different force acting on different segment.