Active tectonics along the Trecastagni-San Gregorio-Acitrezza fault system: southern boundary of Mt Etna unstable sector

In the last decades, several studies have clearly detected the seaward motion of the eastern flank of Mt. Etna volcano which is characterized by a network of active tectonic lineaments controlling its morphology and its kinematics. The comprehension of the tectonic processes affecting this unstable sector requires multidisciplinary investigations including: (i) relation between active deformation and surface processes through the integration of geomorphological – paleoseismological methods and high precision geodetic surveying (e.g., GPS measurements, InSAR interferograms); (ii) accurate characterization of the geometry and internal arrangement of seismogenic structures at depth by seismological and applied geophysics surveys by means of environmental noice samplings; (iii) investigation of the mechanical behavior of rocks under variable stress conditions; (iv) modelling of earthquake ruptures, fault dynamic stress fields and ground motion (e.g., peak acceleration) at the surface. In order to characterize the main features of the unstable flank of Mt. Etna, we performed a detailed study of the surface deformation along the Trecastagni-San Gregorio-Acitrezza fault system. Such a fault system is considered as the main southern boundary of the sliding flank and is constituted of a ~7 km long fault zone roughly E–W oriented and characterized by different kinematics (strike-slip, dip-slip and oblique) and different style of strain release (seismic and aseismic deformation). The fault traces are usually marked by active deformation stripes that are highlighted by the damages caused to buildings and infrastructures. To adequately survey this fault system and provide complementary information on the dynamic of the main fault segments, a local geodetic network has been recently established across the active deformation stripes of the fault system. This network consist of XXX benchmarks and has been measured with both GPS and EDM techniques at least three times since late 2014. In addition, to sample with high detail the active deformation stripes of the fault system, the observed ground deformation pattern has been integrated with available InSAR measurements. These extensive datasets has been used to constrain the kinematics of the fault system using a non-uniform slip distribution model inversion. Main findings evidence a good correlation with geological field observations highlighting as the active deformation stripes is mainly affected by a right lateral displacement coupled with secondary vertical motions. These findings point out the key role played by the Trecastagni-San Gregorio-Acitrezza fault system in the kinematics and seaward motion of the unstable eastern flank of Mt. Etna, and provides new hints to better constrain its timing and kinematics.