Three-Dimensional Forward Modeling for TEM by Vector Finite Element Method

Abstract

Transient electromagnetic method has gradually became a popular geophysical prospecting method in recent years in China and rest of the world. Considering the complexity of the transient electromagnetic theory, the theory of technology is still imperfect, especially in the area of 3D inversion processing and interpretation, which is far from practical level. With this situation, this paper studies the three-dimensional forward modeling for transient electromagnetic method by vector finite element method. And we use quadratic field method as a way to load source, then the frequency domain of three-dimensional forward modeling is realized. In the process, the sparse matrix is stored by the CSR format and the equations are solved by the parallel solver PARDISO in the MKL library. Then we transform the solution form frequency domain to time domain. We discrete frequency by the logarithmic interval. And we obtain the frequency domain response that we need by using cubic spline function, and then realize the transformation of time domain by cosine transform. By comparing the results of typical layered model analysis, the validity of the vector finite element method is proved. The three-dimensional model test shows the accuracy of the vector finite element method. It can objectively reflect the scale and the position of the underground abnormal body. Keywords—transient electromagnetic method; vector finite element method; three-dimensional forward modeling