3-D Finite Difference Forward Modeling Based on the Balance Method

We present a new 3-D finite difference approach for EM field simulation for different excitation sources. It is based on the balance method, which solves for the anomalous electric field and automatically takes into account the conservation laws of Maxwell's equa- tions. The linear system of finite difference equa- tions is solved using the GMRES iterative solver. We suggest applying a new pre-conditioner and bound- ary conditions based on the quasi-analytical approxi- mation and series in order to decrease the mesh size and speed up the convergence rate. The developed 3-D finite difference code can be used in different geo- physical applications, including magnetotelluric (MT), controlled source magnetotelluric (CSMT), airborne, and borehole EM methods in the frequency domain. The new algorithm was tested on several models and demonstrated good agreement with the integral equa- tion solution.