用二维有限元研究青藏块体东北缘地壳的水平运动

ON HORIZONTAL CRUST MOVEMENT IN NORTHEASTERN MARGIN OF QINGHAI-TIBET BLOCK WITH 2D FEM

将1999～2001年、2001～2004年两个时段中青藏块体东北缘GPS水平速度场进行参考框架的变换,扣除区域刚性整体平移和旋转,得到反映区域内部相对运动的水平速度场。利用这个速度场,通过构建该区二维有限元模型,结合最优化原理,反演区域分段边界位移。将反演结果作为边界约束并将变换参考框架后的水平速度场作为有限元节点载荷,模拟区域内部水平运动场并计算其主应变率场、最大剪应变率场,以分析这两个时段中这两种场的变化特征及其与地震孕育之间的关系。

By transforming the reference frame of the velocity field of horizontal movement observed by GPS during 1999 -2001 and 2001 -2004 in the northeastern margin of Qinghai-Tibet block and then deducting the holistic movement of the region from it, the result out velocity field reflecting relative movement in the region is gotten. On the basis of this velocity field and the optimization theory, the segmented displacement of the boundary of the studied area are deduced with two-dimensional finite element model of linear elasticity. Taking the results as boundary constraint and the velocity field of horizontal movement after transforming reference frame as the load of FEM node, the velocity field of horizontal movement in the region is simulated, the principal strain rate field and maximal shear strain rate field are calculated, the variety characteristics of the two rate fields and relation between the variety characteristics and strong earthquake preparation are analyzed.