Approximate 2D Inversion of AEM Data

Abstract

Airborne electromagnetic (AEM) data are presently inverted with one-dimensional (1D) models either as Conductivity Depth Images (CDI) or with full non-linear inversion to build model sections of concatenated 1D models. If lateral conductivity changes are small, 1D models are justified. However, AEM investigations are often carried out specifically to find localised conductors and in this case 1D inversion is insufficient and will often produce artefacts in the model section. We have developed an approximate inversion method that deals with laterally inhomogeneous sections. The method is based on the Adaptive Born Approximation previously applied by one of the authors (NBC) to the interpretation of central-loop ground EM profiles. The technique reproduces synthetic models of moderate conductivity contrasts without the artefacts typically seen in CDI sections. The computing speed is comparable to that of stitched 1D inversions. An example of processing field data over a massive Nickel Sulphide deposit shows promising results for routine application on large AEM data sets.