青藏高原东北缘现代构造应力场数值模拟

摘要

In order to reveal the special tectonic stress field in the northeastern margin of Qinghai-Tibetan Plateau and explore its forming reason,we analyze the tectonic stress field based on structure unit divisions and fault distri-butions that some researchers made before.According to the structure unit division principle and the active fault dis-tributions,we set up a geological model.First according to the regional dynamic geological background,we define the boundary condition of load in the model and then use the subroutine FORCEN of MSC in the finite element method program to do the numerical simulation.In the numerical simulation calculation we use the 2-D finite ele-ment numerical method to calculate the modern tectonic stress field and analyze the characteristics of the modern tectonic stress field in the Qinghai-Tibetan Plateau.Our simulation calculating results on this region tectonic stress field distribution and change characteristics are well consistent with the previous.The maximum principle stress vec-tors rotating clockwise with the position from northwest to southeast is caused by the cooperation of two factors.The first factor is the decreasing gradually of pushing forces from Indian plate moving northward.The second factor is crustal material flowing horizontally and the crustal material is pushed out southeastward which are caused by both the Qinghai -Tibetan block pushing northward and the barrier of Alxa &Erdos boundary blocks.%为进一步揭示青藏高原东北缘区特殊构造应力场特征并探索其形成原因，本文在分析前人有关该地区构造应力场特征的基础上，依据活动块体构造单元划分原则及活动断裂分布规律建立地质模型，采用有限元数值软件 MSC．Marc 子程序 FORCEN 语句，并结合区域动力地质背景定义边界荷载，采用二维有限元数值方法计算模拟了青藏高原东北缘区现代构造应力场并对其特征进行了成因分析。通过模拟获得了研究区构造应力场分布特征及其变化规律，其结果与前人研究结论一致性很好。研究表明区内最大主应力矢量在空间位置（由北西至南东）上发生顺时针偏转是两种因素共同作用的结果：第一，印度板块由南向北的推挤作用逐渐减弱；第二，在青藏地块北东向推挤与阿拉善及鄂尔多斯地块边界阻挡的作用下，研究区内地壳物质发生纵向压缩横向流动并向东南方向逃逸挤出。