The ground deformation monitoring on volcanic areas makes use of tilt networks that continuously measure the local surface inclination by using tiltmeters.On Mt. Etna, the INGV-OE manages a permanent tilt network, first installed in the 1990s and then gradually improved, which actually includes 17 bore-hole sensors and one long-base instrument located at the Pizzi Deneri Volcanological Observatory at 2850 m a.s.l.Tiltmeters measure with high accuracy very small ground deformations, such as those recorded during the short-lived lava fountains episodes. In the last 30 years, Mt. Etna has been characterized by occurrence of hundreds lava fountains, taking place at the summit craters. This activity, known as paroxysms, consist in strong Strombolian to lava fountaining activity producing high dispersing ash plumes and fall-out deposits, which can represent a danger to aviation and more generally to the population.Here we report the results of the analysis on more than 100 lava fountains recorded since 1998, when the first episode was observed by tilt signals. We have estimated tilt moduli and directions at the different stations, thus obtaining long time-series of these values. Our analyses evidenced as tilt changes, for different episodes, show generally similar shapes but different amplitude; we also focused the tilt behavior during the paroxysms sequences i.e. periods (weeks-months) in which lava fountain episodes occurred repeatedly in a brief time (e.g. 2011, 2021). We finally report the estimates of the ground deformation source positions obtained by tilt data inversion to assess their stability over time.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)