The Magnetotelluric Field for a Two-Dimensional Earth Modeled by a Nonuniform Buried Thin Sheet

Magnetotellurics (MT) is an electromagnetic sounding technique used in electrical geophysics to obtain information about the subsurface resistivity structure of the Earth. This information is then used to infer the presence of various natural resources such as oil accumulations and sources of geothermal energy. Extensive research has been done in the area of modeling and interpretation of the Earth in terms of one-dimensional Earth models. Difficulties in both modeling and interpretation occur when the conductivity structure of the Earth is allowed to vary laterally as well as vertically. This paper extends the analysis of a particular class of two-dimensional Earth models characterized by the "thin sheet" approximation. Integral equations are developed for the forward going problem of a plane wave normally incident on the surface of an Earth represented by a uniform half-space containing a thin sheet buried at an arbitrary depth and having an integrated conductivity that varies in one lateral direction. Both E perpendicular and E parallel polarization of the incident electric field are analyzed. The integral equations are evaluated numerically, and several example calculations are presented.