为了易于模拟野外复杂地形和地下任意形状地电体模型,将有限元单元网格设计为三角单元；并考虑到野外实际勘探中,地球介质的电性参数均是连续变化的情况,单元内的场值和电性参数被设计为双线性变化；推导出二维起伏地形条件下大地电磁法有限元数值模拟算法；根据单元节点主场值和线性插值形函数间的关系,计算出单元节点的辅助场值；在二维起伏地形情况下,定义TE、TM模式视电阻率和阻抗相位.4个模型的计算的结果与解析法的均方根误差小于1％,地形模拟与前人的计算结果相符,模拟倾斜界面异常体,能有效的反映出其异常形态.%To model arbitrarily shaped two-dimensional topography and structures in field work, triangular element grid was used in the finite element method (FEM). In view of the fact of continuous variation of the subterranean rock-mineral electric parameters, the electromagnetic field and some electric parameters of models are designed to bilinear variation within each triangular element in our numeric modeling method, and which is developed for modeling two-dimensional magnetotelluric (MT) under the field topography condition. The calculation formulae of the auxiliary field, and the definition of apparent resistivity and impedance phase are deduced according to the relationship between the main fields of the three nodes and the linear shape function within each element. By calculating a continuous medium model and two topography models set up by other scholars to test our method, the result of our method shows a high accuracy (the mean square error is less than 1%), and the results of modeling two topography models accord with other scholar' s, too. Through modeling a sloping interface abnormity body, we find that our method can model arbitrarily complicated terrain and geoelectric bodies preferably.
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