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Volcanic tremor and deformation during the 2012-2023 lava fountains at Etna unveiled by high-precision strain signal

Luigi Carleo, Gilda Currenti, Alessandro Bonaccorso

Abstract

Explosive eruptions mainly consist in the powerful ejection of gas and solid products up to kilometres above the sea level affecting civil aviation and infrastructures. Such eruptions show differences in terms of duration, intensity and amount of emitted products implying different degrees of associated hazard and pointing out that different eruptive styles and magma ascent dynamics can be involved. Magma ascent produces ground deformation and seismic vibration. Deformation at low frequencies (< 0.01 Hz) is typically associated with the withdrawal of magma that supplies the event from depth and captured by tiltmeters and strainmeters. Seismic vibration, recorded as volcanic tremor (> 0.5 Hz), is usually related to the fast interaction between magma and the rock and is detected by seismometers. In this work, we analyzed the signal recorded by Sacks Evertson strainmeters which measure the volumetric deformation of the ground at the highest resolution (10-11) and in a wide frequency band (0 to > 20 Hz) covering both the tiny slow deformation and the volcanic tremor generated by the eruptions. The use of only one sensor allows studying the possible connection between these two processes avoiding the effects of different instrumental responses. We focused on 84 lava fountains occurred at Etna volcano in the period 2012-2023. Machine learning methods were applied on the strain signal to analyze the relationship between deformation, tremor and eruptive style. The comparison between geophysical data, volcanological observations and petrological measurements gave new insights into the eruptive mechanisms involved during explosive eruptions.