Filtering marine magnetic anomalies

Abstract

The fast Fourier transform algorithm is used for fast and accurate manipulation of magnetic anomalies over two-dimensional structures confined by horizontal planes. In such manipulations, operations such as upward and downward continuation and inverse filtering of magnetic anomalies, as well as the synthesis of theoretical anomalies, are simply linear filtering operations. Multiplication in the transform domain performs this filtering with more than order-of-magnitude increase in efficiency. Phase shifting the transform of anomalies can remove the skewing effect of the magnetization and of earth's field direction for easier comparison and identification of the anomalies. Inverse filters applied to anomaly sections of the Eltanin 41 track across an asymmetrically spreading ridge south of Australia produce highly correctable fine-scale magnetization distributions.