Foreland segmentation along an active convergent margin: New constraints in southeastern Sicily (Italy) from seismic and geodetic observations

Abstract

We performed an in-depth analysis of the ongoing tectonics of a large sector of southern Sicily, including the Hyblean Foreland and the front of the Maghrebian Chain, as well as the Ionian Sea offshore, through the integration of seismic and GPS observations collected in the nearly two decades. In particular, a dataset consisting of more than 1100 small-to moderate-magnitude earthquakes (1.0 ≤ ML ≤ 4.6) has been used for local earthquake tomography in order to trace the characteristics of the faulting systems, and for focal mechanisms computation to resolve the current local stress field and to characterise the faulting regime of the investigated area. In addition, GPS measurements, carried out on both episodic and continuous stations, allowed us to infer the main features of the current crustal deformation pattern. Main results evidence that the Hyblean Plateau is subject to a general strike–slip faulting regime, with a maximum horizontal stress axis NW–SE to NNW–SSE oriented, in agreement with the Eurasia–Nubia direction of convergence. The Plateau is separated into two different tectonic crustal blocks by the left-lateral strike–slip Scicli–Ragusa Fault System. The western block moves in agreement with central Sicily while the eastern one accommodates part of the contraction arising from the main Eurasia–Nubia convergence. Furthermore, we provided evidences leading to consider the Hyblean–Maltese Escarpment Fault System as an active boundary characterised by a left-lateral strike–slip motion, separating the eastern block of the Plateau from the Ionian basin. All these evidences lend credit to a crustal segmentation of the southeastern Sicily.