Interpretation of magnetic anomaly profiles using a decomposition in Hilbert transform pairs

Abstract

ABSTRACT. We propose a simple transformation to aid the interpretation of magnetic anomalies generated by linear structures. The profile of such anomalies perpendicular to the strike can be decomposed into two signals, one symmetric and the other antisymmetric concerning the center of the source. The symmetric component serves as input data to various depth estimation techniques that often assume the anomaly is reduced to the pole. We use the fact that these components form a Hilbert transform pair to transform a skewed anomaly profile into a symmetric one. Unlike in previous works that rely on the decomposition into even and odd functions, the profile does not need to be shifted to the source's center of symmetry or limited to one isolated anomaly. Multiple effective magnetization directions presented by different dikes are modeled by a function representing the different local effective dip angles. We validate the method with synthetic data and ground magnetic survey data from a dike swarm at Ponta Grossa Arch, southern Brazil. We also illustrate the usefulness of reconstructed anomalies for depth estimation methods. The results also show that the method can handle interfering sources with distinct effective magnetization directions.