An Approach to the Geometric 3D Inversion of Airborne EM Data for Detection and Geometrization of Local targets Overlapped by Laterally Inhomogeneous Layers

Summary The paper proposes an approach to performing geometric 3D inversions of airborne EM data, which allows the detection and geometrization of local targets in complex geoelectrical media, i.e. in situations, when the targets response in the signals is mixed with the responses from other inhomogeneities, such as changing conductivity of overburdens, elevations of relief, etc. The approach is based on the use of special parametrizations of the background medium and target objects and step-by-step recovery of a geoelectrical model. At the first stage, 3D conductivity distribution is recovered in the overburdens, and, on the basis of the remaining residuals between the observed and calculated data, the areas potentially corresponding to targets positions are localized. At the second stage, in these areas, the geometric (including inclinations) and electrophysic characteristics of the targets are determined. The workability of the proposed approach is demonstrated on the data synthesized for a 3D medium, which is obtained as a result of airborne EM data processing measured by the HeliTem system in the Ural region. It is shown, that the boundaries, depth and inclination of the stratified local body, which is overlapped by a significantly laterally inhomogeneous layer, are recovered confidently and quite adequately.