Flexible approaches to grav/mag inversion at regional and continental scales

Abstract

Magnetic and gravity data have great potential to inform us about regional-scale features. Major fault zones, basin geometries, basement character, Moho, intra-crustal boundaries etc can all be imaged. However, modelling results are inherently non-unique and often highly uncertain. This feeds into the reliability of the method and its usefulness in resource exploration. Following Occam's razor, traditional methods have usually sought to find the simplest model possible, through use of maximum smoothness regularization (e.g. UBC-GIF), or through simplifying the model to an analytically unique problem (e.g. Parker-Oldenburg). More recent software packages allow the process to be constrained by the explicit incorporation of geological knowledge into the process, through a lithological model including property constraints. There are now two variables: lithology and the property within that lithology. This increased degree of freedom leads to greater flexibility, but also greater ambiguity in results, and a single result is clearly not adequate in these cases. Here we present some examples at regional and continental scales where the inclusion of variability measures has greatly increased the usefulness of the inversion process to understand 1) the architecture and properties of the features of interest and 2) the robustness of the solution.