A numerical approach to depth determination from residual gravity anomaly due to two structures

The residual anomaly expression due to two simple geologic structures can be represented by the sum of fields produced by two known source bodies whose depths are to be determined. For a few fixed characteristic points and distances along the residual anomaly profile, the depth to the upper structure is determined iteratively using a simple formula for each depth of the lower structure. The computed depths to the lower structure are plotted against the depths to the upper structure representing a depth curve. The solution for the depths to both structures is read at the common intersection of the depth curves. Procedures are also formulated to estimate the radii of the two buried structures. The method is a powerful technique for separating the composite residual anomaly into two residual components due to two structures. The method is applied to theoretical data with and without random errors and tested on a field example from U.S.A.