Magnetic Crustal Thickness Estimations versus Models for Crustal Magnetization

Abstract:

Many studies have attempted to evaluate the magnetic crustal thickness because this can provide an estimate of the depth to Curie temperature isotherm in areas characterized by high heat flow and an estimate of the depth to the Moho in areas of low heat flow if the mantle is considered non magnetic. There are currently two families of methods used to estimate crustal magnetic thickness. Statistical methods are based on the analysis of the power spectrum of magnetic anomalies and assume a random or fractal model for crustal magnetization. Equivalent dipole methods assume that the crust contains only induced magnetization characterized by a constant magnetic susceptibility and that it can be approximated by a surface distribution of dipoles. Although the first family of methods is most often applied to airborne data and the second family of methods is most often applied to satellite data, they can potentially be applied to both types of data. Because these families of methods rely on very different assumptions, they are not expected to provide the same thickness estimates and depending on the study area one method may be more applicable than the other. In this study, we apply both a statistical method and a dipole equivalent method for estimating the magnetic crustal thickness using aeromagnetic compilations available in the Western US, Greenland, and Australia, and also using synthetic datasets. We compare results from both methods and discuss similarities and differences with respect to the geological context and the data quality.