Fast geodetic strain-rates in eastern Sicily (southern Italy): New insights into block tectonics and seismic potential in the area of the great 1693 earthquake

Abstract

Along the ∼500 km long Sicily–Calabria segment of the Nubia–Eurasia plate boundary GPS data highlight a complex, and debated, kinematic pattern. We focus on eastern Sicily, where the style of crustal deformation rapidly changes in the space of few tens of kilometers. In southeastern Sicily, struck by the 1693 MW∼7.4 earthquake, GPS measurements highlight a steep velocity gradient, with ∼2.4 mm/yr of ∼N–S shortening in ∼10 km, changing to broader extension (∼3 mm/yr in ∼60 km) in northern Sicily and shortening in the southern Tyrrhenian Sea. GPS data and kinematic elastic block models highlight a complex fragmentation of the Sicilian domain into three tectonic blocks, which move independently from Nubia, describing an overall clockwise rotation of this crustal domain with respect to Eurasia. Shortening in southeastern Sicily is associated with a system of high-angle reverse faults resulting from tectonic inversion of extensional faults at the northern tip of the Hyblean plateau. Extension in northern Sicily occurs on a broader deformation belt, developed on the former Kumeta–Alcantara line, extending west of Mount Etna toward the southwestern Tyrrhenian Sea, accommodating the faster rotation of the northeastern Sicily block with respect to central Sicily. Although the seismic potential of inland faults is not negligible, our results strengthen the hypothesis that the Malta escarpment is the likely source of the large 1693 earthquake and tsunami. The observed kinematics appears only subordinately driven by the Nubia–Eurasia convergence and the dynamics of the Mediterranean subduction system is likely playing a major role in governing block motions and active tectonics in Sicily.