Fast approximate 3D inversion of ground TEM data utilising the concept of magnetic moments

Abstract

A fast approximate three dimensional inversion scheme for interpreting ground transient electromagnetic (TEM) data is presented. The scheme relies on linear superposition of magnetic moments. The moment transform of TEM data is a time-weighted integral of the impulse response. In effect, the moment transformation converts the 3-D TEM inversion problem into a 3-D magnetic inversion problem, with accuracy traded for speed. A starting model is generated from conductivity-depth sections, and the inversion is conditioned using standard potential field inversion devices such as depth weighting.