Repeated reactivation in the Apennine-Maghrebide system, Italy: a possible example of fault-zone weakening?

Italy owes its complex geological structure to a double switch in tectonic regime, which involved the opening of the Tethys Ocean during Early Mesozoic time, its closure leading to development of the Apennine-Maghrebide fold-and-thrust belt during the Eocene-Recent interval, and the post-orogenic opening of the Tyrrhenian Sea since Miocene time. This history of tectonic inversion is partly preserved within two major fault zones, the Valnerina Line, in the central Apenmnes, and the Gratteri-Mount Mufara Line, in central-northern Sicily, which were repeatedly reactivated with different kin- ematic characters. The relatively long life of these structures indicates that strain was localized along anisotropies inherited from early deformation episodes. However, the pro- gressive widening of both fault zones through time may result from strain-hardening fault-rock behaviour during subsequent deformations, thus suggesting that fault reactiva- tion does not imply fault-zone weakening as is often assumed.