Three-dimensional Finite-Element Forward Modeling and Response Characteristic Analysis of Multifrequency Electromagnetic

The research on three-dimensional (3D) forward modeling of complex models and the analysis of response characteristics are key factors that restrict the development of multifrequency electromagnetic induction exploration technology and inversion methods. Therefore, investigating the 3D multifrequency electromagnetic forward modeling method and the characteristics of the resulting responses is important and has practical value. This paper presents an investigation of a 3D multifrequency electromagnetic forward modeling method based on the vector finite-element theory. The technique employs a regular hexahedral grid for the model's discretization. It utilizes a MUMPS (MUltifrontal Massively Parallel sparse direct Solver) solver to directly solve an extensive sparse linear system of equations, which enables high-precision forward modeling of the 3D multifrequency electromagnetic method. Theoretical models were used to verify the reliability and accuracy of the forward modeling results. On this basis, the multifrequency electromagnetic response characteristics of the 3D model were further studied, and the action rules of the measurement configuration and the geometric shape of the anomaly on the multifrequency electromagnetic response signal were preliminarily analyzed. The above work lays a theoretical foundation for subsequent research on optimizing observation technology and inversion methods.