2.5D modelling of Somma–Vesuvius structure by aeromagnetic data

This paper deals with the analysis of aeromagnetic data on the Somma–Vesuvius area. An inverse 2.5D method is used, its main features being a variable strike length and a data set relative to a vertical plane. This last provides a depth resolution, so that the result consists in a magnetic tomography along a vertical section. The magnetic model shows that magnetized rocks extend up to carbonate basement depths (about 2 km). The stronger magnetizations (>6 A/m) are concentrated in the emerged part of the volcano, but high magnetizations are still present down to about 1800 m b.s.l. The magnetization distribution found is then compared to the distribution of the hypocenters of Vesuvian earthquakes and for shallow depth a positive correlation is noted. At depths greater than about 2 km, i.e. at the level where a geothermal well started to encounter dolomites, the model shows no magnetization, while hypocenters form a nearly continuous vertical belt. This pattern leads to the conclusion that this evidence may be considered as being due to a small volume of the feeding system at these depths or eventually as an indication of strong alteration processes of magnetic rocks.