Estimative of the gravity-gradient data from vertical component of gravitational attraction by using the equivalent-layer and fast Fourier transform techniques

We present a comparison between the computing of gravity gradient tensor components from the vertical component of the gravitational attraction using the fast Fourier transform and the equivalent-layer techniques. In this comparison, we consider that the observed data consist of: (1) the residual gravity field (produced by local sources) and (2) the overlapping of regional and residual gravity fields. Applications to synthetic data show that the fast Fourier transform technique amplifies the noise to calculate the six components of the tensor. Comparing the FFT and the equivalent-layer results with the true gravity gradient components produced by local source without regional gravity field, the equivalent-layer result yields a better result because it shows a smaller residual. However, when the observed data have a regional gravity field overlapped to the residual gravity field both techniques yield unacceptable results, indicating the need of new methodologies to deal with regional field.