A Technique for Improving the Accuracy of Finite Element Solutions for Magnetotelluric Data

This paper develops a finite element method which gives accurate numerical approximations to magnetotelluric data over two-dimensional conductivity structures. The method employs a simple finite element technique to find the field component parallel to the strike of the structure and a new numerical differentiation scheme to find the field component perpendicular to strike. Examples show that the new numerical differentiation scheme is a significant improvement over the standard finite element procedure when meshes of poor quality are used. Algorithms for incorporating the differentiation scheme into the finite element matrix equation and for computing partial derivatives of magnetotelluric data with respect to mesh parameters are derived in order to simplify the computation needed to do the inverse problem.