Normal mode model for electromagnetic propagation in the earth crust waveguide

Propagation of modes in an idealized model of the earth-crust waveguide is considered. The two-layer region is bounded above and below by a perfectly conducting plane. For this structure, there are an infinite number of discrete modes without any contribution from a continuous spectrum. The excitation factor for the structure is derived for voltage-type and electric, current line sources. Specific numerical results for 1 to 1000 Hz are given for the case where the lower conductive region is effectively of infinite depth. It is found that the conductivity of the upper region is the main controlling factor on the attenuation rate.