## 3 Data and Methods
### Magnetics  
In the framework of the qualitative analysis of the Tyrrhenian crustal magnetic anomaly field, the magnetic map of Italy [53] is presented in Figure 4. The analysis aims to describe the general pattern of the field and to identify potentially productive areas from a  
Figure 3: Detailed morphology of the SE Tyrrhenian Sea. PVC: Palinuro Volcanic Chain; MS: Marsili Seamount; AS: Alcioni Seamount; LS: Lametini Seamount SI: Stromboli Island. LI: Lipari Island; VI: Volcano Island; Sal: Salina Island; FI: Filicudi Island; AI: Alicudi Island.  
mining perspective, as defined by their magnetic properties. The map here reported represents the integration of various marine and terrestrial surveys and was created using data acquired by the OGS between 1965 and 1972, as well as data from measurement campaigns conducted by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) within the framework of the Geodynamics Finalized Project of the National Research Council from 1977 to 1981. The marine dataset used for the compilation of the map refers to oceanographic campaigns organized by the National Research Council (CNR) between 1965 and 1972 in the Mediterranean and conducted by the National Institute of Oceanography (OGS). The surveys in the Tyrrhenian Sea and in the study area form a dense set of acquisition lines striking mostly in the NS and EW directions. Measurements were taken at a speed of 10-12 knots using a proton precession magnetometer whose sensor, mounted on a fish, is towed 200-300 m below the boat. The Loran C system was used for positioning the measurements. Data processing involved the reduction of the diurnal variations using the geomagnetic observatory of L'Aquila (centrally located with respect to the extent of the marine surveys) and data reduction to a common epoch (1979.0). The magnetic anomaly is then obtained by removing the core magnetic main field (CMT) using the [PERSON], 1987, model (HGRF) [54]. Measurement leveling and the removal of the residual line errors were applied by using a crossover analysis and filtering of the total magnetic intensity field (TMI).  
Digital enhancement of the magnetic anomaly field involves operations aimed at highlighting its variations and extracting components that improve the ability to derive geological information from geophysical data. To achieve this, a series of filters are typically applied, such as field derivatives, regional and local field separation, and anomaly source edge detection. In this work, we successfully applied the analytic signal tool.  
Figure 4: Shaded relief of SE Tyrrhenian Sea (gray scale) overlayed by magnetic map.  
The analytic signal (the square root of the sum of the squares of the total field derivatives, hereafter AS; Equation (1)) combines the horizontal and vertical derivatives of potential field data [55]. The horizontal derivative enhances the location of the source edges, while the vertical derivative narrows the anomaly width. As a result, this filter exhibits its maximum values above the magnetization contrast, regardless of the inducing field's direction, the magnetization directions, and without requiring prior information about the source.  
\[\text{Analytic}\,\text{Signal}=\sqrt{(\mathbb{Z}\text{dx}\,\mathbb{Z}+ \mathbb{Z}\text{dy}\,\mathbb{Z}\,\mathbb{Z}+\mathbb{Z}\,\mathbb{Z}\,\mathbb{Z} \,\mathbb{Z})} \tag{1}\]  
Therefore, geological contacts or faults characterized by significant magnetization contrast can be efficiently mapped using AS features. These features are located directly over the edges of causative structures (Figure 5).