Determination of depth to the magnetic sources using spectral analysis with application to Sicily, Southern Italy

Spectral analysis is among the most old and common techniques for the processing and interpretation of potential field data. This is related to the decay properties of the field power spectra which allows an easy estimation of the depths to the top and to the bottom of the sources of magnetic and gravity field anomalies. Such analysis can be accomplished however in different theoretical frameworks, assuming either a statistical ensemble of homogeneous sources or random fractal source distribution. Here, we present the many existing spectral analysis techniques to compare them with respect to estimating the depth to the source top and bottom. We evidence practical constraints on the depth estimation and inherent assumptions/limitations of the different approaches. Depth estimation using spectral methods requires a critical evaluation of window size, window location, and wavenumber range. Careful consideration of the merits and of the limitations of these different spectral techniques for different source distribution models may lead to robust and geologically meaningful outcomes. In fact, despite the several different approaches all the methods give quite consistent and often similar estimates of the source depths. However, due to ambiguities on the correction spectral factor, the best estimates are obtained if this factor is constrained by a priori information. Finally, we estimate the depth to the magnetic sources beneath Sicily, which may provide additional constraints to better understand the deep crustal geometry and thermal gradients of the region.