LAS: A combination of the analytic signal amplitude and the generalised logistic function as a novel edge enhancement of magnetic data

Abstract

In the evaluation of magnetic field data, edge enhancement and detection
techniques are important treatments for the interpretation of geological structures. In
general geological sense, contiguity of deep and shallow magnetic sources leads to weak
and intense anomalies that complicates the interpretation to disclose adjacent anomalous
sources. Many of the existing filters for edge detection in magnetics mostly have the disadvantage
that they require a reduction to pole transformation as the pre-process of the
data or they cannot balance weak and intense anomalies and therefore fail in detecting
edges of deep and shallow sources simultaneously. This study presents an improved edge
detection filter LAS (logistic function of the analytical signal), based on the generalised
logistic function configured by the ratio of derivatives of the analytical signal. This novel
approach has the capability of reducing the dependence on the direction of the magnetization
and also balancing anomalies of sources at different levels of depth. The feasibility of
the method is examined on both theoretical and real data cases comparatively with some
other methods that utilize the analytical signal in their basis. In comparison, the results
demonstrate that the LAS method provides more accurate estimation of edge localization.