GNGTS 2022 - Atti del 40° Convegno Nazionale

102 GNGTS 2022 Sessione 1.2 • SiOrNet, managed by the Geodetic Group of the Geological Survey of Italy-ISPRA and consists of 5 cGNSS stations installed along the SE slope of Mt. Etna (yellow dots in Fig. 1). • Italpos, managed by Hexagon Geosystems (https://hxgnsmartnet.com/it-it) and developed to support commercial applications, such as mapping and cadastral purposes Only 2 stations are installed on the volcano edifice (red dots in Fig. 1). • NetGEO, a network developed by Geotop (http://www.netgeo.it ) since early 2012 to support commercial applications. Monuments consist on pillars or steel masts, anchored to buildings. Only 2 stations are installed on the volcano edifice (black dots in Fig. 1). All collected data were processed using the GAMIT/GLOBK software and referred to a local reference frame in order to isolate the Mt. Etna volcanic deformation from the background tectonic pattern. By inspecting the resulting time-series of some selected GNSS stations we detected 11 SSEs with duration grossly ranging from 2 to 67 days. For each recognized SSE, we determine the amount of displacements by averaging site position in the 3 days preceding and following the event. Observed surface deformation for most of the detected slow slip events, concentrates on the south-eastern edge of the unstable flank while the slow slip events involving the north-eastern edge are less frequent. Such a pattern highlights the existence of two distinct families of events, involving two contiguous sectors of the unstable flank, which occasionally slip together in large slow slip events. The displacement fields were used to constrain isotropic half-space elastic inversion models. To determine the spatial distribution of slip for each SSE, we adopted planar source (divided in 15 by 15 squared patches) with a fixed dip of 10°. Achieved results highlight that, for SSEs occurring more frequently, the slip distribution concentrates with values up to 6 cm on the southeastern sector of the planar source, ~10 km off-shore. Regarding the SSEs involving the north-eastern edge of the unstable flank, the slip distribution on the modelled surface concentrates ~12 km off-shore beneath the Riposto Ridge where a ~16-km-long tectonic lineament with a N102° attitude would represent the off-shore prolongation of the most active splay of the Pernicana fault. Finally, equivalent seismic moments of slow slip events occurred in the last ten years (corresponding to magnitudes in the range 5.4-5.9) are larger than those associated to seismic events observed in the last 200 years, suggesting that most of the deformation affecting the eastern flank occurs aseismically.