GPS velocity and strain fields in Sicily and southern Calabria, Italy: Updated geodetic constraints on tectonic block interaction in the central Mediterranean

We present an improved rendition of the geodetic velocity and strain fields in Sicilyand southern Calabria obtained through the analysis of 18 years of GPS observationsfrom continuous and survey station networks. The dense spatial coverage of geodetic dataprovides precise quantitative estimates of previously established first-order activekinematic features, including: i) a narrow east-west-elongated belt of contraction(1–1.5 mm/yr) extending offshore northern Sicily from Ustica to Stromboli across theAeolian Islands; ii) a narrow east-west-trending contractional belt located along the northernrim of the Hyblean Plateau in southern Sicily, with shortening at up to 4.4 mm/yr; iii) rightmotion (3.6 mm/yr) on the Aeolian-Tindari-Letojanni fault (ATLF) system, a main shearzone extending from the Aeolian Islands to the Ionian coast of Sicily, with significanttranspression and transtension partitioned between discrete sectors of the fault; iv)transtension (1 mm/yr) across the Sicily Channel between Sicily and North Africa. We usegeodetic observations coupled to geological constraints to better elucidate the interplayof crustal blocks revealed in the investigated area. In particular, we focus on the ATLF,which forms the primary boundary between the Sicilian and Calabrian blocks. The ATLFjuxtaposes north-south contraction between Sicily and the Tyrrhenian block withnorthwest-southeast extension in northeastern Sicily and Calabria. Contraction betweenSicily and Tyrrhenian blocks probably arises from the main Europe-Nubia convergence,although Sicily has a component of lateral motion away from Nubia. We found thatconvergence is not restricted to the northern offshore, as commonly believed, but is widelyaccommodated between the frontal belt and the northern rim of the Hyblean foreland insouthern Sicily. Geodetic data also indicate that active right shear on the ATLF occurs to thesoutheast of the mapped fault array in northern Sicily, suggesting the fault cuts through tillthe Ionian coast of the island. The small geodetic divergence between the Hyblean andApulian blocks rimming on both sides the Calabria block and subjacent Ionian slab, coupledwith marine geophysical evidences in the Ionian Sea lends credit to the proposed deep rootof the ATLF and to a fragmentation of the Ionian domain.