Computer modeling in gravity and magnetic interpretation

Abstract

Abstract Computation of anomalous gravity and magnetic fields generated by various models is a necessary step if techniques of curve-matching are to be used for quantitative interpretation of potential field data. Recently developed methods show that anomalous magnetic and gravity fields are completely determined by the divergence of magnetization and the first vertical derivative of density, respectively. Using these methods, efficient algorithms can be developed for computing potential field anomalies caused by arbitrary distribution of magnetization and density in an irregularly shaped body.Automatic iterative procedures are normally employed in the space domain for estimating parameters of the selected model that yield a best-fit anomaly curve for a set of discrete observed data. Examples of application of the Newton-Raphson method, Marquardt method, and the Powell algorithm to the interpretation of magnetic data are presented and discussed.Amplitude and energy spectra of the anomalous fields are also used conveniently in many cases for systematic estimation of average and individual depths, horizontal and vertical extents, and density or magnetization contrasts of causative bodies in a bounded region. Some of these frequency-domain approaches are found to have many useful applications.