A study of magnetotelluric fields in laterally inhomogeneous Earth models

The effect of arbitrary lateral variations in the resistivity of the Earth dimensional Earth models which can be represented by the thin sheet approximation. An integral equation solution is obtained for the forward going problem of a plane wave normally incident on the surface of an Earth modeled by a uniformly conducting half-space containing a laterally varying thin sheet buried at an arbitrary depth. Numerical results are obtained by using a variation of the method of moments for thin sheets changing in both one and two lateral directions. Numerical results for the two dimensional case are confined to E Parallel polarization and a surface thin sheet. The effect of lateral resistivity variations on magnetotelluric data is considered. An examination of the surface electric field in wave number space yields a procedure for the interpretation of magnetotelluric data in the presence of a three dimensional Earth.