Three-dimensional edge-based finite-element modeling of magnetotelluric data in anisotropic media with a divergence correction

Abstract When simulating a 3-D magnetotelluric (MT) response, the convergence rate slows at low frequencies. Previous works have shown that by implementing divergence correction, the convergence rate of the iterative solution can be accelerated, the computational accuracy can be enhanced. However, traditional correction schemes of MT are mostly based on isotropic modeling. Electrical anisotropy strongly affects the interpretation of MT data and anisotropic influence cannot be ignored. To our best knowledge, there has been no open literature to apply divergence correction in 3-D MT anisotropic modeling. In this study, based on the divergence-free property of the current density, a divergence correction technique is incorporated into the edge-based FE method to speed up the modeling process for 3-D MT problems with axial anisotropic earth. By applying the divergence scheme, the computation time and iteration number for MT numerical simulation are largely reduced. The effectiveness of the anisotropic divergence correction technique on MT modeling is verified by numerical experiments.