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We develop a 3D gravity anomaly inversion to estimate a 3D density-contrast distribution that gives rise to a complex, interfering gravity field. Our approach estimates the 3D density-contrast distribution that fits the observed anomaly within the measurement errors and favors compact gravity sources closest to pre-specified geometric elements such as lines and points. This method retrieves the geometry of multiple gravity sources with prescribed density contrasts (positive and negative values) assigned to each geometric element. In this way, each geometric element operates as the first-guess skeletal outline of a particular, homogeneous section of the gravity source to be reconstructed. Based on an iterative learning scheme, the number of parameters, the number of geometric elements, their spatial positions and the associated target density contrasts may increase automatically. Tests on synthetic data from geometrically complex bodies and on field data collected over a granitic pluton, located in the Carajas province of the eastern Amazonian Craton, Brazil, illustrate that our method makes its possible to reconstruct a sharp image of multiple and closely located gravity sources.

We present a new gravity interpretation method to delineate the basement relief and the shape of homogeneous salt domes and salt sills within sediments whose densities increase with depth. The interpretation model consists of juxtaposed 2D vertical prisms for thebasement, and 2D prisms with polygonal cross sections for the domes and sills. We presume that the physical properties of all sources are known a priori. The estimation of the basement relief is stabilized by the global and weighted smoothness constraints whereas the estimation of the domes and sills is stabilized by concentrating the estimated anomalous mass about known directions. We applied the method to synthetic data to demonstrate its utility in delineating salt structures in marginal basins, whose basement is formed by horsts, grabens, and step faults. We also applied the method to a real gravity profile perpendicular to the coast line in the Campos Basin, Brazil.

We present a gravity inversion method for estimating the 3D basement relief of a sedimentary basin. We assume that the density contrast between the basement and the sediments decreases with depth according to a parabolic law. We discretize the sedimentary section into a grid of 3D vertical, juxtaposed prisms in both horizontal directions. The prisms’ thicknesses represent the depths to the basement relief and are the parameters to be estimated from the gravity data. To produce a stable solution we maximize the smoothness of the estimated relief using the overall smoothness regularization. We apply our method to synthetic data from simulated complex 3D basement relief and the results show well-resolved estimated relief, starting at different initial guesses. These results are obtained if the values defining the parabolic decay of the density contrast with depth are known. We conducted a numerical analysis to investigate the solution sensitivity to the effects caused by: (1) random noise in data, (2) the depth to the true basement relief, and (3) the density-contrast decay with depth according to the parabolic law. We show that, if the density contrast in the deepest portion of the basin is above a threshold, our method retrieves the 3D geometry of the basement relief regardless of the true basement depths and regardless of the pseudorandom noise sequences.