Interpretation of Magnetic Anomalies Using Spectral Estimation Techniques*

Abstract

The depth of causative bodies may be derived from the power spectrum of their magnetic anomalies. After a short review of the theoretical basis of the method, several examples of its application to synthetic cases are shown. Disturbing effects due to improper choice of the sampling interval and to anomalies only partially contained in the examined segment of the profile are studied. The spectral method is then applied to real cases; the tapering of the anomalies, the application of non‐linear filters and the effects of anomaly superpositions are investigated. In conclusion, an appraisal of the method and of its possible practical impact has been given.

Spectral analysis of the 1976 aeromagnetic survey of Harrat Rahat, Kingdom of Saudi Arabia

“…Anomalies may be for a variety of idealsteps, prisms, and the ntegral. Much original of the method are reviews given by Bhattacharyya (1967Bhattacharyya ( , 1978, Cassano andRocca (1975), andSpector andParker (1979). Spector (1968) provides a valuable general guide to spectral analysis in aeromagnetic map interpretation, with emphasis on statistical treatment of the radial spectra of source ensembles.…”

“…Other examples of application of the method to aeromagnetic map interpretation include reports by Bhattacharyya (1969), Naidu (1969, Spector (1971), Sarma (1974), Sadek (1978), and Meshref and others (1980). Use of spectral analysis for depth estimation is the subject of papers by Lehmann (1970), Treital and others (1971), Mishra and Naidu (1974), Cassano and Rocca (1975), Curtis and Jain (1975), and Hahn and others (1976).…”

The role of geomagnetic methods in the detection of mineral deposits at El‐Hody area, south‐eastern Aswan, Egypt

“…Cassano and Rocca () developed a technique to deduce the source depths z from the dip angle of the straight (regression) line in the diagram versus the spatial frequency in the form:…”

“…This correction improves the Spector and Grant (1970) technique for estimating the source depth from magnetic-field power spectra (De Fedi et al 1997). Cassano and Rocca (1975) developed a technique to deduce the source depths z from the dip angle Φ of the straight (regression) line in the diagram versus the spatial frequency in the form:…”

2D dipping dike magnetic data interpretation using a robust particle swarm optimization

“…Ram Babu and Atchuta Rao, 1991), Euler deconvolution method (Reid et al, 1990), Gauss-Newton method (Won, 1981), complex gradient method (Atchuta Rao et al, 1981), relation diagrams (Ram Babu et al, 1982), the gradient methods (Rao et al, 1973;Abdelrahman et al, 2007;Essa and Elhussein, 2016b), damped least-square ridge regression (Johnson, 1969), Spectral analysis methods (Bhattacharya, 1971;Sengupta and Das, 1975;Cassano and Rocca, 1975), modular neural network inversion (Al-Garni, 2015), an automated numerical method (Keating and 40 Pilkington, 1990), a new semi-automatic technique (Cooper, 2012), a non-linear constrained inversion technique (Beiki and Pedersen, 2012). However, the drawbacks of these methods are that they are highly subjective where they can lead to substantial errors in parameter estimations, rely upon trial and error till achieve the best fit between the measured and computed anomaly, require initial starting models which are close enough to the true solution, depends on the precision of separation of regional and residual magnetic anomalies from the measured magnetic anomaly,…”