基于二次场算法的CSAMT二维正演研究

Research on Two-Dimensional CSAMT Forward Modeling Based on Secondary Field Algorithm

本文采用基于二次场的有限单元算法开展了二维可控源音频大地电磁CSAMT的数值模拟研究。研究工作从麦克斯韦方程组出发,导出了电阻率异常的二次场方程;采用了基于二叉树结构的三角单元剖分,推导了双线性的单元钢度矩阵表达式;对电阻率异常模型进行了试算。实践表明,二次场算法无需对场源区域剖分,可有效的减小计算区间,提高了计算效率;与总场算法相比,二次场算法边界处理简单;二次场算法有利于提高计算精度,解决了低频计算不稳定问题。

This paper, by adopting the finite element algorithm which is based on the secondary field, takes a numerical simulation research on the two-dimension Controlled Source Audio Magneto Telluric（CSAMT）. The research derives the secondary field equation of abnormal resistivity based on Maxwell equations, deduces the bilinear unit stiffness matrix expression by using a triangle element meshing which is based on binary tree structure,and tries to calculate the abnormal resistivity model. The practice shows that the secondary field algorithm can effectively reduce the computation space and increase the computational efficiency without subdividing sections on field source; by comparing with total field algorithm, the boundary treatment is simpler with secondary field algorithm; the algorithm solves the instability of low frequency calculation by improving computational accuracy.