Analysis and Interpretation of In-Phase Component of VLF-EM Data using Hilbert Transform and the Amplitude of Analytical Signal

Abstract

An interpretation of in-phase anomaly of very low frequency electromagnetic (VLF-EM) data was carried out using the analysis of the Hilbert transform of the in-phase component and the amplitude of its analytic signal. The analysis was used to delineate the source and depth to the top of a subsurface conductive body. The amplitude of the analytical signal of the data was observed to mimic the conventional Fraser-filtered operation and was used to locate the exact location of the anomalous body. The in-phase component with the Hilbert transform yields an approximate depth to the top of the conductor which agree with the result of the vertical electrical sounding conducted at the vicinity of the anomalous body.

Keywords: VLF-EM method, Hilbert transform, analytical signal, in-phase, Fraser filtering.