GNGTS 2018 - 37° Convegno Nazionale

88 GNGTS 2018 S essione 1.1 an inversion of tectonic motion, from normal to reverse, on the N70-80 oriented fault planes of the Pedagaggi Agnone Fault System, starting from Upper Pleistocene. Even if further geological-structural investigation are required, preliminary geological and morphometric data support the hypothesis that AFFS is an active extensional system; whereas PVFS is an active reverse system that exploits ancient normal faults. From a geodynamic and structural point of view, the coeval coexistence of these two systems can be explained considering that both AFFS and PVFS are the expression on the surface of a deep left lateral wrench fault, that we named Sicilian Blind Wrench Fault (SBWF) (Fig. 3a). According to Riedel’s experiment, the crustal sector above a blind wrench fault can be affected by a multitude of structures reflecting the strain field, among which normal and reverse faults (Fig. 3b): AFFS could be the extensional system associated to the wrench fault, whereas PVFS could be the compressional one. Sicilian Blind Wrench Fault is compatible with the southern Sicily geodynamic, indeed it could play the same role of the Ragusa Scicli Fault System and the Malta Escarpment Fault System that separate crustal blocks of the foreland that move with different velocity in the context of the convergence between Eurasia and Africa Plates (Fig. 3a). We compared structural results (fault location, geometry and kinematics) with data coming from seismicity, both historical and instrumental, with the aim: (i) to define the activity and to constrain the geometry and kinematics of the faults investigated at surface; (ii) to observe evidence of the existence of SBWF; (iii) to relate active faults with the seismotectonic setting of southeastern Sicily. Fig. 3 - A) Main fault systems and Sicilian Blind wrench fault (SBWF); b) model of SBWF according to Riedel’s experiment; c) seismicity during 1994-2013, the blue line is SBWF and d) distribution in depth of shocks across SBWF (modified from Musumeci et al. , 2014)