The geological interpretation of gravity gradiometry data is a very challenging problem. With the exception of the vertical gradient, maps of the different gravity gradients are usually very complicated and cannot be directly correlated with geological structures. We introduce the concept of 3D potential field migration and demonstrate how it can be applied for rapid imaging of entire gravity gradiometry surveys. The method is based on a direct integral transformation of the observed gravity gradients into a 3D density model which can be used for interpretation, or as an a priori model for subsequent 3D regularized inversion. For regional-scale surveys, we show how migration runs on the order of minutes compared to hours for 3D inversion. We present a case study is for the 3D migration of a FALCON® airborne gravity gradiometry (AGG) survey from Broken Hill, Australia, and compare our results to 3D regularized inversion and previously mapped geology.

It is well known that magnetotelluric (MT) impedance can be distorted by near-surface inhomogeneities (NSI), which complicates the interpretation of MT data and the correct imaging of deep geoelectrical structures. This paper demonstrates that the inclusion of magnetovariational (MV) tipper data in a three-dimensional (3D) inversion jointly with MT impedance provides better resolution of deep conductive anomalies than stand-alone MT impedance. This is significant because MV data can be collected alongside the MT impedance data for virtually no additional cost. Electric and magnetic fields in forward modeling are determined using the integral equation (IE) method. The inverse problem is solved with the reweighted regularized conjugate gradient (RRCG) method with limited sensitivity domain. We present the results of both a synthetic model and case study using EarthScope data gathered in Southern Alberta, Canada. In both cases, the joint inversion provides more accurate information about deep conductive anomalies than the inversion of impedance stand-alone data.