MAGNETOTELLURIC MODELING OF 3-DIMENSIONAL BODIES IN LAYERED EARTHS

In this paper, we have developed an algorithm based on the method of integral equations to simulate the MT responses of three-dimensional bodies in layered earths. It has two steps. First is to compute the equivalent scatter current distribution in inhomogeneous midia. The 3-D bodies are replaced by an equivalent current which is approximated by pulse basis funtions. The integral equations of unknown electrical fields in 3-D bodies are constructed using the tensor Green's functions appropriate to layered earths. Second step is to find the scattered fields on the surface of earth by integration electric and magnetic tensor Green's functions over the scattering currents. In order to reduce computation cost and storage, three kinds of processing methods are adopted. They are linear filtering and interpolation, group transformation, and sparse tensor Green's matrix. A comparison of our responses were over a 3-D body in uniform half space with that reported in literatures and reciprocity of Green's functions have verified our program. The distortions of 3-D MT curves are preliminarily discussed with some new conclusions.