The dynamics of the Pernicana Fault System (Mt. Etna, Sicily) investigated by 4 decades of multiparametric ground deformation data: inferences on the interaction between flank and magma dynamics

Mt. Etna volcano is located along the eastern coast of Sicily. In this region, the general N-S compressive regime related to the Africa – Eurasia collision interacts with the WNW-ESE extensional regime associated to the Malta Escarpment dynamics, observable along the eastern coast of Sicily.

A general eastward motion of the eastern flank of the volcano has been measured with always increasing detail and its relationship with the eruptive and magmatic activity is being investigated. The complex interaction between regional stress, gravity forces and dike-induced rifting of Mount Etna, seems to have a role in the eastward movement of the Mt. Etna eastern flank. In this context the Pernicana Fault system identifies the northern boundary of the mobile sector.

It is formed by discrete segments, arranged in a right stepping en-échelon configuration, of a left-lateral shear zone that dissects the north-eastern flank of Etna. Its kinematics is related to shallow seismic crises (M ≈ 4.0) occurring along the western segment, with dip-slip displacement and left-lateral components. The eastern segment, ESE trending, shows only aseismic creep with purely left-lateral displacement.

The dynamics of the fault has been analyzed by a multi-disciplinary approach: levelling, tiltmeters, InSAR and GNSS.

The fault system shows clear traces on SAR interferograms and time series. InSAR data allows tracking the path of the Pernicana fault from the NE rift to the coastline; the eastwards motion abruptly disappears north of the fault, producing a left-lateral transcurrent kinematics at a rate of about 30 mm/y. Episodic accelerations are visible on GNSS and InSAR data from different sensors, related to seismic crises and eruptive activity. The dense GNSS network is measured periodically and has more than seventy benchmarks. The time series of this network began in 1988 and from then on its configuration has been continuously improved. Two GNSS networks lie across the eastern segment of the Pernicana fault. The first one, located in the “Rocca Campana” area, was installed in April 1997; the second one, located a few kilometers westward, in the “Rocca Pignatello” area, was measured for the first time in July 2002 upgrading an EDM network. The aim of these networks is to detail the structural framework and displacements along the aseismic sector of the Pernicana fault. Finally, the levelling route on Mt Etna, installed in 1980, is 150 km long and consists of 200 benchmarks. Part of the levelling route crosses the Pernicana fault, at an altitude of 1500 and 700 m asl. Measures on this network started on eighties and provide a high detail on the vertical kinematics allowing strong constraints in modelling the sources of slip episodes.

Integration of this wide spectrum of geodetic data allows strongly constrained ground deformation pattern to be defined and modeled. Furthermore, the very long time series available for the different datasets on the Pernicana fault, allows its behavior to be investigated in time and its role and relationships in the framework of flank instability and eruptive activity to better understood.