A least-squares derivative analysis of gravity data applied in Senegal, west Africa

Abstract

A simple method to simultaneously determine the shape (shape factor or structural index) and the depth of a buried structure from second horizontal derivative anomalies obtained from gravity data using filters of successive window lengths has been developed. The method is similar to Euler deconvolution, but it solves for shape and depth independently. For a fixed window length, the depth is determined using the least-squares method for each shape factor. The computed depths are plotted against the shape factors representing a continuous window curve. The solution for the shape and depth of the buried structure is read at the common intersection of window curves. The method involves using simple models convolved with the same numerical horizontal second derivative filter as applied to observed gravity data. As a result, the method can be applied not only to true residuals but also to measured Bouguer data of a short profile length. Finally, the validity of the method is tested on theoretical examples with and without random errors and field data from Senegal, west Africa.