Investigating Mt. Etna lava fountains by seismic and infrasonic signals: 14-21 February 2021 case study

Infrasonic and seismic tremor are signals released by active volcanoes. These signals play a crucial role in monitoring volcanic activity and providing insights into volcanic dynamics and hazards. Between December 2020 and February 2022, Mount Etna was characterized by an intense eruptive period, during which monitoring efforts were employed to investigate the characteristics and source signals. Our work focuses on analyzing volcanic tremors in both seismic and infrasound signals to understand their behavior and relationship with the volcano’s dynamics. In particular, the interval 14‐21 February 2021, comprising 4 lava fountain episodes, was taken into account. Concerning the data analysis, amplitude, spectral content, seismic volcanic tremor and infrasonic explosion‐quakes source locations have been computed. The results reveal that the seismic amplitude is closely related to emitted magma volume during the lava fountains. The study finds that most of the energy in volcanic tremors is concentrated below 5.0 Hz. During eruptive episodes, both seismic and infrasound signals exhibit lower frequencies, with variations between different stations due to propagation effects. Finally, two different source mechanisms of the seismic tremor were suggested: i) flow of gasses through a shallower permeable solid layer is likely to be responsible for the generation of volcanic tremor during non‐eruptive periods; ii) magmatic flows along the shallow plumbing system and the consequent impact of particles on the walls of the conduit during eruptive periods.