The Thyrrenian Sea is commonly considered as the back arc basin connected to the west-directed subduction of the Apennines chain. Here the tectonic regime is mainly extensional and trans-extensional and involves both continental and oceanic crust.
The Messina Strait is probably where the fault system responsible of the earthquake of 1908 and of the subsequent tsunami is located ARGNANITAO2009. This structure can be described as a semi-graben characterized by a complex kinematics. If is formed by faults trending ENE-WSW in the northern part with a dip slip kinematics and by N-S and NNE-SSW faults in the south, with a trans-extensional direction of movement. This kinematic configuration can be deduced by the relative motion between the Sicilian structures in the west and the Calabrian arc in the east, resulting this latter more advanced due to the southeastward migration of the subduction arc. This two sector have in fact a different geodynamic behaviour: in the east of the strait the subduction hinge is progressively moving away from the upper plate, whereas in the western sector the same hinge approaches it DEVOTI2008. Nevertheless, few evidences are available about the geometry and the position of the fault plane connected to the 1908 Messina earthquake. Growing geometries of Late Pleistocene deposits recognized in the area are not enough to reconstruct the geometry along strike of the main fault plane.
A definition of the length of the plane and of its dip, combined with a rheological profile can provide information in order to better define the seismic parameters of the seismogenic source and, also, the role of these fault system in the geodynamic setting of the area.
The Pontine islands escarpment is one of the most relevant morphological structure in the Tyrrhenian Sea, and, likely, of the Mediterranean area. It has a NW-SE direction, and is the boundary between the continental crust to the North-East and the supposed oceanic crust in the South-West. Its nature is almost unknown; is possible to hypotise the occurrence of a normal fault system that controls the escarpment, which should have a mainly trans-extensional kinematic. The very well development slope (from -200 to -3000 m meters in less than 10 km) suggests the occurrence of recent tectonic activity. Based on the length of this supposed fault zone (150-200 km) this structure could potentially generate earthquakes with very high magnitude, even if the occurrence of an high heat flow reduce the elastic thickness and the differential stress in the area.
Finally, the volcanic area of the Phylgrean Field , located at the northern boundary of the Campana Plain, is a tectonically depressed area along the Tyrrhenian margin of the Southern Apennines. The tectono-volcanic activity is very important and, consequently, this area has an elevated volcanic risk as it densely populated DIVITO2008. A peculiar character of this activity is the bradisism, a periodicity of relative speed uplifting and slow subsidence episodes. The most recent crisis due to bradisism occurred in 1969-1972 [e.g., CORRADO1977] and in 1982-1984 [e.g. DENATALE1999]. In the last decades the need to better define this processes associated to volcanic risk become progressively higher.