Iterative Fast Equivalent-layer Technique

Abstract

We have developed a new iterative scheme for processing gravity data using a fast equivalent-layer technique. This scheme estimates a 2D mass distribution on a fictitious layer composed by a set of point masses, one directly beneath each gravity station. Our method starts from an initial mass distribution that is proportional to the observed gravity data. Iteratively, our approach updates the mass distribution by adding mass corrections that are proportional to the gravity residuals. At each iteration, the computation of the residual is accomplished by the forward modelling of the vertical component of the gravitational attraction produced by all point masses setting up the equivalent layer. Our method is grounded on the excess of mass and on the positive correlation between the observed gravity data and the masses on the equivalent layer. The algorithm requires neither matrix multiplications nor the solution of linear systems. The desired processed data is obtained by multiplying the matrix of Green's functions associated with the desired processing by the estimated 2D mass distribution. Tests on synthetic and field gravity data from the Vinton salt dome, USA, confirms the potential of our approach in processing large gravity data set over on undulating surface.