基于二次场二维起伏地形MT有限元数值模拟

通过计算二次场来进行二维大地电磁数值模拟;导出了二维大地电磁二次场的微分方程,利用有限单元法来解微分方程;对矩形网格进行对角线的二次剖分,更容易且真实地模拟起伏地形。对几个典型模型进行了试算,与前人总场法的计算结果做了比较,两者视电阻率曲线一致,证明本文算法是正确的;通过2个简单的算例说明复杂地表下2种极化模式的MT观测资料都有明显的异常,视电阻率在TM模式下比TE模式更易受地形影响,TE模式下视电阻率曲线形态与地形呈"正相关",TM模式下反之。

Secondary Field-Based Two-Dimensional Topographic Numerical Simulation in Magnetoteillurics by Finite Element Method

An efficient method has been presented which is named secondary field finite element method for two-dimentional magnetotelluric numerical modeling.The two-dimentional electromagnetic differential equations of secondary field have been derived,and the equations of secondary field can be solved by finite element method when the boundary conditions are simple;it is easier to simulate topographic earth by taking subdivision to the rectangle mesh.We have calculated several models and compared with previous researcher's results using total field method.The results obtained indicated that the algorithm provided in this paper was correct.And it can be confirmed that the topographic abnormalities both in TE mode and TM mode are obvious.The apparent resistivity of H-polarization is affected by terrain more easily than that of E-polarization.The shape of apparent resistivity is positive correlation with terrain in TE mode,but that is opposite in TM mode.