A new algorithm for three dimensional magnetotelluric forward modeling

Due to the need for greater depth of investigation in petroleum and geothermal exploration and the complexity of the associated geological models often involved in any interpretation of magnetotelluric data, it would be inevitable to employ a more robust and effective 3-D forward modeling engine capable of incorporating complex geological models. The newlydeveloped algorithm presented in this paper uses the conventional finite difference technique of numerical methods but in a nonstaggeredscheme which enables solving the governing electromagnetic fields with the imposed boundary conditionssimultaneously. Through dividing the air and earth half space into discrete blocky model the governing magnetotelluric equationsare discretized to form a linear matrix equation which in turn is solved for the unknown magnetic and electric fields iteratively.Because of the frequency dependency of governing magnetic and electric fields and the finite size of the discretized model a number of problems such as oscillating phenomena in the final forward response in the course of solving such boundary value problems are observed. Also it happens that due to the conventional staggered scheme of forming discretized linear equations, a pseudo singularity appears which makes the iterative solvers to diverge. In order to address and remedy for these problems we have introduced an optimum mesh refining scheme to resolve the response oscillation problem. Also through using non staggered formalism which changes the shape of the final discretized matrix equation, it is shown that the pseudo singularity effect could be removed effectively.