Three-dimensional Anisotropic Magnetotelluric Modelling using Edge-based Finite Element Method

This paper shows how electrical anisotropic affects the magnetotelluric (MT) responses over three-dimensional (3D) structures. We utilized the edge-based finite element method for numerical modeling. Tetrahedral mesh was used to better model the topography and the anomalous bodies. Our algorithm was tested for a one-dimensional (1D) model with an analytical solution. We study the influence of various anisotropy strike (0°-90°) and dip (0°-90°) on magnetotelluric responses. We found that, as the strike increases individually, the bigger the strike, the more influence from the principle resistivity along the y' direction (ρ_y') to the apparent resistivity (ρ_xy) and phase (φ_xy) of XY mode, and the more influence from the principle resistivity along the x' direction (ρ_x') to the apparent resistivity (ρ_yx) and phase (φ_yx) of YX mode. When only the dip changes, the change of ρ_xy and φ_xy depends on the ρ_x'. With the dip increasing individually, the influence from the principle resistivity along the z' direction (ρ_z') to the ρ_yx and φ_yx of YX mode increases.