GNGTS 2017 - 36° Convegno Nazionale

152 GNGTS 2017 S essione 1.2 tectonic lineament is of broad interest for both geodynamic and seismotectonic implications having a complex tectonic evolution in an area that is a key point for Central Mediterranean geodynamics and locally showing evidences of ongoing tectonic activity. Along this transfer zone the maximum stress directions reoriented through times (Mantovani et al. , 2014) and it separated different sectors of the Sicilian-Maghrebian Chain characterized by various tectonic evolution, deformation age and thrusts vergence. Moreover, it separates in two portions the Sicilian Channel Rifting Zone (a western area where the Pantelleria Graben took place and an eastern sector characterized by the presence of the Linosa and Malta troughs) where several recent submarine volcanic centers are present (Civile et al. , 2008; Lodolo et al. , 2012; Coltelli et al. , 2016). A well constrained 3D reconstruction of the Sciacca Fault (Fig. 2) allowed us to define (i) the present day tectonic setting of this fault, (ii) its tectonic evolution and (iii) a possible interpretation of the seismic activity along it. Regarding the present day, tectonic setting data show that this tectonic lineament consists of a system of faults composed by a sub-vertical NNE-SSW trending master fault with several splays. The evidence of transcurrent tectonics along this fault is observable at least for 70 km, from the Sicily coastline to the southern margin of the Terrible Bank (Fig.1). From reflection seismic profiles it is possible to reconstruct a complex tectonic evolution of the Sciacca Fault. This structure probably developed along the offshore continuation of an inherited weakness zone identified in western Sicily and interpreted as a carbonate platform margin developed in Permo-Triassic times. It was probably active up to Miocene as a high angle normal fault testified by the considerable thickness variations of the Miocene succession. Under a NE-SW oriented maximum stress direction, the previous normal fault was re-activated in theLower Pliocene as a right-lateral transcurrent fault with a compressive component producing positive flower structures. The maximum stress direction changed its orientation starting from the Late Pliocene (Mantovani et al. , 2014), so that the present-day main compressive horizontal stress in the area of the Sicilian Channel has a NW-SE direction. This change in the orientation of the maximum stress field produced a kinematic change from Fig. 1 - Structural sketch of the study area (from Fedorik et al., under review).