Multiscale Modeling of the European aeromagnetic field

In this research, the aim of the study is the interpretation of the main magnetic anomalies at the European scale. Being the field characterized by anomalies originating by sources at different depth within the crust, a multiscale approach is the most suitable method to take into account all the different components of the anomaly field. In fact, at different altitudes, say from 5 km to 350 km, the anomaly field is varies and there is no specific scale, which can be judged as the most relevant for the analysis. The multiscale analysis of aeromagnetic data is based on a multiscale dataset, which is generated by the upward continuation of the dataset of the European and Mediterranean Magnetic Project up to satellite altitudes. The interpretation of the magnetic anomalies was carried out following two main steps: a) producing the total gradient maps of the magnetic field at low and high altitudes, in order to identify the magnetic features through the whole crust. This technique has been particularly useful because of three main properties: i) the anomalies of the total gradient modulus are monopolar, so losing the dipolar aspect of the magnetic field, regardless the source and field magnetization directions; ii) the maxima of the total gradient modulus are placed above the source position, regardless of the source and field magnetization directions; iii) the areas where it reaches very low values may be safely regarded as regions with a low-magnetization crust; conversely magnetic lows of the magnetic field are not exclusively linked to low-magnetization areas, but depends mainly on the total magnetization of the sources, either normally or reversely magnetized. Our total gradient analysis showed that the origin of the Central European Magnetic Low (CEML) should be attributed to the strong differences in magnetization between the central European crust and the North-Eastern platform. However, due to the property i) some reversely magnetized sources were detected, in different regions of central Europe (Anglo-Brabant Massif, Bohemian Massif, Pannonian basin). b) using specific multiscale tools for the simultaneous interpretation of the field at many scales. In particular, the Multiridge method allows the multiscale magnetic field to be interpreted in terms of source depths and shape. By this method, a model is obtained of the crustal magnetic sources beneath the TESZ, the Bohemian Massif and the Adriatic magnetic anomalies, which are key anomalies for the magnetic field in Europe, no matter the altitude. In order to estimate the deepest source depths in the TESZ region, the Multiridge method was applied to the large scales (50-100 km altitude), obtaining a set of singular points at depths ranging between 35-40 km. Considering the trend of the heat flow and the geological models around the study areas, a meaningful correspondence was found among the location of the estimated singular points and the most abrupt variations and complex morphology features of the magnetic basement and the Moho boundary. The interpreted models are largely in agreement with geological models based on seismic surveys and contribute to the whole knowledge of the areas, since refer to a wider region, if compared to that covered by seismic. Multiscale methods contribute to a complete knowledge of the area since they refer to the wider region, when compared with that covered by the seismic models.