LATE QUATERNARY SLIP RATES ON THE ACIREALE-PIEDIMONTE NORMAL FAULTS AND TECTONIC ORIGIN OF MT. ETNA (SICILY)

Mt. Etna is located along the east coast of Sicily, near the boundary between the continental crust of the Hyblean Plateau and the Mesozoic oceanic crust of the Ionian basin. The main active faults near Mt. Etn a cut the base of its eastern flank, forming a 30 km long system of NN E- and NNW-trending, en echelon fault segments (the Acireale-Piedimont e system), showing dip-slip and oblique (right-lateral) motion. Most s egments are associated with shallow-depth seismicity and all have Late Pleistocene to Holocene vertical slip rates ranging between 1 and 2 m m/yr, typical of major active normal faults worldwide. Eruptive fissur es, arranged in NNE- to NE-trending zones, cut the highest slopes of t he volcano, on the footwall of the normal fault system. Structural ana lysis suggests that current motions along both the active faults and e ruptive fissures are kinematically compatible and simply linked with o ngoing, WNW-ESE-directed regional extension. Such extension characteri zes, at a greater scale, the active tectonics of southern Italy, where all large, shallow, historical earthquakes have remained confined wit hin a narrow normal fault belt or rift zone stretching from the northe rn Calabrian Are to southeastern Sicily. The southernmost, west-dippin g, faults of that rift zone in Calabria (Aspromonte) cut across the Ca labro-Peloritan thrust belt to join the mostly east-dipping, Acireale- Piedimonte faults, along the western boundary of Ionian oceanic lithos phere, which continues southwards as the Malta escarpment. We thus rel ate magmatism at Etna to dilational strain on the footwall of an east- facing, crustal-scale normal fault at the bend where the Siculo-Calabr ian rift zone veers approximate to 60 degrees eastwards as it begins t o cross the Calabrian Are, leaving the east-facing margin of the Ionia n Sea, to catch up with the west-facing margin of the Tyrrhenian Sea f arther north.