A geophysical study of the Mount Etna volcanic area

A geophysical model of the Mt. Etna volcanic area (Sicily, Italy) is outlined by an integrated analysis of gravity, geoelectrical, magnetotelluric and seismic data. New 3D tomography and visualization systems are applied in order to extract the aximum information and to define, connect and assemble structures and related physical properties. All geophysical methods concur to single out a dense, rigid and resistive structure in the central part of the study area, about 10 km long in E-W direction, about 4 km wide in N-S direction and extending from near surface down to about 30 km of depth. The resistivity pattern shows also two conductive zones on both sides of the E-W barrier, in the depth range 15-30 km. Resistivities of a few Wm and a few tens Wm are estimated in the southern and northern conductive zone, respectively. A non-uniform feeding system is thus assumed to exist, instead of the ellipsoid-like uniform magma reservoir previously deduced from regional seismological data in the depth range 15-25 km. Moreover, the comparison with seismic tomographies from local earthquakes allows a central high velocity nucleus to be distinguished inside the upper portion of the resistive barrier, which is thus ascribed to a system of compact dikes tending to become highly fractured along the western and eastern edges. Finally, the impedivity analysis gives no support to the existence of any permanent shallower magma chambers, contributing, instead, to argue the presence of a plumbing system hydrothermally altered at medium-to-low temperatures.