Seismotectonics and present seismic hazard in theTuscany–Romagna–Marche–Umbria Apennines (Italy)

tThe Tuscany–Romagna–Marche–Umbria Apennines host major seismic zones that have generated severalstrong earthquakes. We argue that such activity is an effect of the relative motion between the outer-most sector of the Romagna–Marche–Umbria units and the surrounding zones. This interpretation isconsistent with the pattern of post-early Pleistocene deformation and the present velocity field, inferredfrom geodetic observations. The last evidence, being derived by a fairly dense network of permanent GPSstations, allows a good definition of the outer Apennine sector which is characterized by a significantlyhigher velocity (4–6 mm/y, roughly NE ward) with respect to the inner belt (1–2 mm/y, roughly NNWward). The fact that the main seismic zones are just located along the inner and outer boundaries of theextruding wedge is compatible with the proposed seismogenetic mechanism. Taking into account thetectonic setting in the Apennine belt and the possible effects, in terms of post seismic deformation, of therecent (since 1930) seismicity distribution in that zone, an attempt is made at recognizing which faultsystems in the northern Apennines may be most prone to next major shocks (M > 5.5).