Stable Electromagnetic Modeling Using a Multigrid Solver on Stretching Grids: The Magnetotelluric Example

Electromagnetic (EM) surveys are widely used in geophysical study. Reliable 3-D forward modeling is required for the inversion and interpretation of geophysical data. We have introduced a novel method for 3-D EM modeling using stretching grids, which uses a multigrid iterative solver for solving the formed linear system of equations based on the staggered finite-difference method. The developed algorithm is applied for the simulation of the magnetotelluric fields. We have tested this new algorithm using synthetic geoelectric models. The proposed multigrid method using stretching grids is also compared with the preconditioned Krylov-subspace solvers, the biconjugate gradients stabilized method, and the generalized minimum residual method. The developed multigrid method is proved to be more stable and requires less iterations to converge