Interaction between compressional and transcurrent structures: insights from the Sicilian Channel and SW Sicily

Abstract:

The Sicilian Channel presents a very remarkable structural complexity due to the presence and superposition of compressional, extensional and transcurrent structures. In particular, the SW Sicily and its offshore area are affected by two different tectonic processes: (1) compressional, responsible of the Late Miocene Maghrebian Fold-Thrust Belt; (2) transcurrent, responsible of the NS trending lineaments modeled offshore.

A geophysical data set composed by seismic reflection profiles (VIDEPI, MS, CROP, OGS profiles) and GEBCO bathymetric data, in addition with analog models, have been used here to shed light on the interaction between the thrust belt and transcurrent deformation.We use clay box with thrust front precut and an undergoing mobile plate for the simulation of the transcurrent movement. Through this setup the interaction angle between the thrust belt and transcurrent displacement was varied in order to check the influence of the interaction angle on the newly formed structures. From the 3D model, we have seen that the region is dominated by N-NE transpressional structure called Sciacca structural high. In the southern part of this structure some faults are still active, as they deform the sea-floor. Lateral branches composing positive flower structures form an open horsetail splays. The plate on the eastern side of the Sciacca high is uplifted due a transpressional displacement and shortening in front of Maghrebian Fold-Thrust Belt. The analog modelling supports the structural setting of Sciacca high, where we equally observe comparable positive flower structures, horsetail splays, and uplift of the moving plate.

From the offshore dataset we have seen that these two geodynamic processes coexist independently, but from the onshore structural map, the transcurrent strike-slip deformation affects the Maghrebian Fold-Thrust Belt. These two coexisting geodynamic processes can help in interpreting the 1968 Belice earthquake sequence, where both right-lateral strike–slip and compressive focal mechanisms have been observed.