Deciphering magma dynamics controlling the 2020-22 lava fountain sequence at Mount Etna volcano using tilt deformation and volcanic tremor analysis

Between December 13, 2020, and February 21, 2022, a series of 62 lava fountains occurred at Mt. Etna volcano. Our study adopts a multidisciplinary approach, utilizing tilt deformation and volcanic tremor RMS amplitude time series data. Our investigation involved the assessment of deflations linked to the lava fountains, inflations occurring during intra-event intervals, the peak values of volcanic tremor RMS amplitudes, and a gradient parameter to gauge the rate of evolution for each phase and signal. We have identified three sub-periods reflecting the dynamics of magma storage and transport. During the initial period (February - April 2021), we consistently observed medium to high values across all considered parameters, suggesting the transfer of larger volumes of volatile-rich magma migrating from deeper reservoirs to upper portions of the plumbing system. In the subsequent period (May - June 2021), lava fountains exhibited shorter average durations, marking the lowest values throughout the eruptive sequence. This phenomenon may be attributed to reduced amounts of undegassed magma in the uppermost feeding system. In the third period (July - October 2021), there was a discernible uptrend of the aforementioned parameters, coinciding with reduction of the inflation velocity. Detailed analyses of tilt signals and volcanic tremor RMS amplitudes unveiled distinctive characteristics during episodes within the second period, marked by notable inflations contemporary with the beginning of lava fountains and periodic RMS amplitude patterns. This approach offers valuable insights into the evolutionary dynamics of paroxysmal events witnessed at Mt. Etna during the 2020-2022 timeframe.