Active faulting in the Calabrian arc and eastern Sicily

Abstract

The Calabrian arc and eastern Sicily are areas of the central Mediterranean where the effects of Quaternary tectonics are well preserved. The most impressive tectonic feature in this region is represented by a major normal fault belt that runs more or less continuously along the inner side of the Calabrian arc, extending through the Strait of Messina along the Ionian coast of Sicily as far as the Hyblean Plateau. The distinct normal fault segments within the belt, which during Pleistocene times have controlled the evolution of major marine sedimentary basins, have lengths ranging from 10 to 45 km. They exhibit huge fault scarps which defines the fronts of the main mountain ranges of the region (Catena Costiera, Aspromonte, Serre, Peloritani and Hyblean). Morphological features of fault scarps, and the age of the faulted rocks, suggest slip rates of 0.5–1.2 mm/year for the last 700 kyear (Middle Pleistocene-Holocene), reaching values of about 2.0 mm/year in the areas of active volcanism. From a seismological point a view, the Calabrian arc and eastern Sicily represent a very active area which is characterized by crustal earthquakes, the largest of which reached in the last nine centuries an intensity of X–XI (6 < M ≤ 7.4). The occurrence of intermediate and deep focus earthquakes located along the inner side of the arc, beneath the southern Tyrrhenian Sea, is associated to the existence of a slab of Ionian lithosphere. The distribution of crustal seismicity shows that most of the events which have occurred in the area, are located in the hangingwalls of the main Quaternary normal faults hence suggesting a strong relationship between seismic activity and the growth of extensional structures. Geological observations, together with seismological data, indicate that normal faulting in the area results from the development of a main rift zone, related to an overall ESE–WNW extension, which also controls the evolutionary history of the magmatism in this sector of southern Italy.