PSEUDO DEPTH SLICING

This name is used for a variety of processes which different companies apply to aeromagnetic (and sometimes gravity) data to approximately isolate the contribution of a particular depth horizon. The methodology used at EDCON-PRJ is that of Wiener filtering, which requires statistical models of the magnetization distribution at the horizon being mapped, and of the other contributions to the data. Appropriate models were first proposed by Spector and Grant (1970), and variants of these models are used in the pseudo-depth slice designs.

The particular model to be used in the filtering operation is obtained from an examination of the power spectrum of the data. This examination yields the apparent depth and RMS magnetization intensity for the horizon of interest and for the other depth horizons in the data set. A filter transfer function is then designed using the principles of least-squares optimal (Wiener) filtering (Gunn, 1972) to isolate as far as possible the contribution of the selected depth horizon. The map resulting from the application of this filter to the original data is called the pseudo-depth slice for that horizon.

Although the procedure just outlined never produces perfect results, the enhancements which can be achieved under favorable circumstances are very striking.

REFERENCES

Gunn, P.J., 1972, Application of Wiener filters to transformations of gravity and magnetic data: Geophysical Prospecting, v. 20, p. 860-871.

Spector, A. and Grant, F.S., 1970, Statistical models for interpreting aeromagnetic data: Geophysics, v. 35, p. 293-302.