Three-dimensional magnetotelluric modeling in general anisotropic media using nodal-based unstructured finite element method

Magnetotelluric sounding is an efficient and economical method for detecting Earth's deep structure because of its large surveying depth. We use a finite element approach to solve magnetotelluric fields in three-dimensional general anisotropic media based on the vector-scalar potentials and unstructured meshes. The implementation of a three-dimensional unstructured mesh generator TetGen with high-quality local mesh refinement can easily handle complicated models with high performance. The electromagnetic field equations are expressed in terms of Coulomb-gauged vector-scalar potentials, and the nodal-based finite element method can be used to compute the electromagnetic fields with high efficiency. The symmetric successive over-relaxation preconditioned conjugate gradient solver is used to solve the resulting linear equation system. The magnetotelluric responses in one-, two-, and three-dimensional medias are computed through our proposed approach. These results are then compared with the analytical solutions, twoand three-dimensional adaptive finite element solutions. Numerical examples demonstrate that these results are in good agreement. Because an unstructured mesh is incorporated in this approach, it has great potential for simulating the magnetotelluric responses in geometrically complicated situations.

Automated summary

Magnetotelluric sounding is an efficient and economical method for detecting Earth's deep structure with large surveying depth. A finite element approach is used to solve magnetotelluric fields in three-dimensional anisotropic media, with an unstructured mesh generator handling complex models effectively. The method shows great potential for simulating magnetotelluric responses in geometrically complicated situations, as demonstrated through numerical examples.