Analysis of satellite and in situ ground deformation data integrated by the SISTEM approach: The April 3, 2010 earthquake along the Pernicana fault (Mt. Etna - Italy) case study

Etna is known worldwide as one of the most studied and monitored active volcanoes. Flank instability along the eastern and southern portions of Mt. Etna has been observed and measured thanks to geodetic networks and InSAR data analysis. The spreading area is bordered to the north by the east-west Pernicana Fault System (PFS) whose dynamics is often linked with the eruptive activity, as recently observed during the 2002-2003 eruption. A seismic sequence occurred from April 2-3, 2010, along the PFS with very shallow (a few hundred meters) mainshocks of magnitude 4.3 and 3.6. Explosions and ash emissions at the summit craters followed this swarm culminating a few days later (April 7-8). Despite their small magnitude, the earthquakes caused damage and significant surface fracturing along the PFS. In order to investigate and measure the deformations in the near field of the earthquakes, the SISTEM integration approach has been exploited. The SISTEM enabled integrating geodetic in situ ground deformation measurements (GPS and leveling) with satellite interferometric measurements (ENVISAT and ALOS), in order to obtain high resolution 3D displacement maps, allowing to overcome the limitations of each technique and take advantage of the particular features of each of them. The integrated ground deformation field evidenced that the medium behave elastically. We inverted the SISTEM results using an optimization algorithm based on the Genetic Algorithm (GA) in order to model the kinematics of the PFS associated to seismic swarm; the results are in good agreement with the field evidence and improved the knowledge on the kinematics of the PFS and Mt. Etna's unstable flank. (C) 2011 Elsevier B.V. All rights reserved.