Crust and upper mantle structural properties along the active Tyrrhenian rim

The volcanic complexes from the Eolian islands to the Campania/Roman regions and Tuscany further north, rest on lithospheric sectors which overlie the Adriatic continental lithosphere sinking along the Apennine-Maghrebian orogenic belt. Evidence for this stems from the melting, at mantle depth, of upper crustal material as evidenced by the widespread interaction of S-type and K-alkaline melts. The genesis of atypical magmas of the Roman Province (central-southern Italy) appears to be the result of an important block faulting and deep lithospheric rifting of the Apennine continental margin lying parallel and above relic sinking slabs. Intermediate and deep-focus earthquakes indicate that the lithospheric slab is still seismically active under the Eolian-Calabrian area and, sporadically, at the southern end of Campania. On the other end, in the Roman/Tuscan region, it seems to be almost inactive, few earthquakes having been located with hypocentral depths not exceeding 150 km. The existence of lithospheric slabs along the Tyrrhenian rim is supported by surface wave dispersion and scattering measurements as well as P-waves residuals, and is confirmed by the trend of long-wavelengths gravity anomalies, interpreted within the geometrical constraints imposed by aeromagnetic and seismic data. The analysis of the spectral content of seismic sources supports the existence of two zones of lithospheric shortening in correspondence of Tuscany and South Tyrrhenian sea which are separated by a tensional region extending from Latium to Calabry.