The Use of Gravity Gradient Tensor Eigenvectors to Recover the Basic Geometric Properties of 2D Density Boundaries

Abstract

Many geological structures such as faults, calderas, large intrusions, etc. can be approximated by a density boundary model that can be characterised by dip, edge position, depth and density contrast. Gravity gradiometry is a geophysical method that can be used to investigate some of the properties of such geological structures. In this study, we have tested a method for estimating the slope of the density boundary based on analysing the inclination angles of the gravity gradient tensor eigenvectors above the edge of the contact. We also introduced a new edge detection technique that uses the rate of change of the eigenvectors of the gravity gradient tensor. We found that the dip angle of a density boundary cannot be derived directly from the inclinations of the eigenvectors above the contact. On the other hand, we have found that the edge position given by the maximum rate of change of the eigenvector inclinations works better than the vertical and horizontal gradient methods in case the measurements are performed at a considerable height above the boundary. This new edge detection method may therefore be suitable for aerial gravity gradiometry data interpretation.