3-D Radial Gravity Gradient Inversion Applied to the Interpretation of the Vinton Salt Dome, USA

We present a 3-D gravity-gradient inversion approach that retrieves the geometry of an isolated geological body with known density contrast and depth of the top. The geological body is approximated by an ensemble of vertically juxtaposed right prisms with pre-established thickness and horizontal cross-sections described by polygons. The horizontal coordinates defining the vertices of the polygonal horizontal cross-section of each prism are the parameters to be estimated by inversion. After run the inversion several times and produce a set of estimated sources having different bottom depths, the best one is chosen by a criterion based on the curve of the ℓ2-norm of the data-misfits and the estimated volumes. Applications to the gravity-gradient data over the Vinton salt dome, USA, show that our method is able to produce estimated 3-D sources that fit the observed data and are consistent with the prior geological knowledge at the study area. In comparison with methods that estimate the constant density contrast into each rectangular cell forming a regular 3-D grid in subsurface, our method is very computationally effective and does not require (1) the use of depth-weighting functions, and (2) the introduction of compactness.