Geologically Constrained 2D and 3D Airborne EM Inversion Through Cross-Gradient Regularization and Multi-Grid Efficiency

Abstract

With a goal of increasing the geological reliability of single and joint domain inversion, including those set in rugged terrain, we present an expanded scope for cross-gradient regularized inversion. The basic application covers the usual structural similarity objective — comparing the gradient fields of distinct property volumes derived from different geophysical domains — but a particular advantage comes when including gradients derived a priori, from geology or any ancillary property set, providing reference gradient control during single or joint inversions.

In the first example, straightforward cross-gradient joint inversion of synthetic datasets of airborne EM (AEM) and airborne gravity-gradiometry (AGG) improves both the lateral and vertical definition of closely adjacent but distinct bodies.

Two further AEM examples include surface and subsurface geology in the cross-gradient inversion; a) complex foothills setting, and b) buried massive sulphide. Both outputs demonstrate a marked improvement in interpretability over the standard smooth model approach.