Magnetic inversion constrained by probabilistic magnetotellurics models: methodology and application

We introduce a sequential inversion workflow where we integrate magnetotelluric and magnetic data. We first perform probabilistic MT inversions, from which we derive 2D or 3D probabilities of observing an interface between rock units of contrasting electrical resistivity. Secondly, we use these probabilities to partition the model into domains where different rock units, or combinations thereof, can be observed. Using these domains, we define constraints for magnetic data inversion where the corresponding intervals (joint or disjoint) of magnetic susceptibility are used as spatially varying bound constraints for inversion. After introducing the methodology, we investigate the proof-of-concept using a geologically realistic synthetic model and conclude that the proposed methodology is applicable to field data. We then present ongoing investigations in the Cloncurry area (Queensland) on a 2D line to image the thickness of the sedimentary cover and to reduce interpretation uncertainty.