The amplitude and phase of the derivatives of the magnetic anomalies of thin dykes and contacts

Abstract

If the horizontal and vertical derivatives of the total field magnetic anomalies of thin dykes and contacts (and the magnetic anomaly from a thin dyke) are put into an amplitude-phase form, then this can aid in their interpretation. First, it allows derivatives of fractional order to be calculated analytically; second, estimates of the source dip can be made; and finally, the relationships between local wavenumber and source-distance semi-automatic interpretation methods are clarified. The approach is demonstrated on synthetic data and aeromagnetic data from South Africa.

If the horizontal and vertical derivatives of the total field magnetic anomalies of thin dykes and contacts are put into an amplitude-phase form, then this can aid in their interpretation. In addition, the relationships between local wavenumber and source-distance semi-automatic interpretation methods are clarified.

Key words::

• magnetics, semiautomatic interpretation, potential fields.

Acknowledgements

The National Research Foundation (Pretoria) is thanked for funding this project. Thanks also go to the Council for Geoscience, Pretoria, for the data shown in Figure 4, and to Dr M. A. G. Andreoli for helpful discussions.