海洋大地电磁二维正演及结果分析

摘要

The algorithm to do the marine magnetotelluric two-dimensionalforward modeling using finite element method (FEM) is developed in this paper.Apparent resistivity and phase of each node on the seafloor are calculated from electromagnetic fields.In order to estimate the precision of the algorithm,the expression to calculate the response of one-dimensional (1D) layer model is derived according to Cagniard's theory.The comparison of analytic result with numerical result from FEM for 1D layer model shows the FEM algorithm has high precision.Some results of different models show that FEM algorithm is a useful tool for the research on seafloor magnetotellurics.%研究了海洋大地电磁法的二维正演并编制了相应程序，程序采用有限单元法求出海底各节点处的电磁场值，进一步计算得到视电阻率。为了验证程序的正确性与有效性，根据卡尼亚理论推导出计算一维海洋模型的阻抗公式，并得到视电阻率的解析解，将其与有限元法得出的数值解进行了对比，表明了此方法的正确性。通过对正演结果的分析，表明海洋大地电磁测深能够成功地反映海底的电性结构。