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Spectral Line Variability in Volcanic Tremor as a Proxy for Subsurface Changes: Observations from Etna Volcano

Alexander Yates 1,2, Sonia Heuninck1, Hazal Bektas1, Andres Barajas3, Corentin Caudron1,2, Silvio De Angelis4,5, Luciano Zuccarello5,4

  • Affiliations: 1 G-Time, Université libre de Bruxelles, Brussels, Belgium 2WEL Research Institute, Wavre, Belgium 3ISTerre, CNRS, IRD, Université Grenoble Alpes, Université Savoie Mont Blanc, Université Gustave Eiffel, Grenoble, France 4Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, UK 5Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, via Cesare Battisti, Pisa, Italy

  • Presentation type: Talk

  • Presentation time: Friday 14:15 - 14:30, Room S160

  • Programme No: 2.1.8

  • Theme 2 > Session 1

Abstract

Episodes of volcanic tremor provide valuable insights into the dynamics of subsurface processes at active volcanoes. Previous studies have suggested that evolution in tremor properties, such as frequency and amplitude, may relate to changes in the stress conditions of the plumbing system. However, a strong causative link has remained elusive. At Etna volcano, we observe changes in the frequency of broadband tremor during a prolonged seven-month episode of unrest and eruptive activity in 2020. A comparison with seismic velocity changes computed at multiple stations using passive seismic interferometry reveals an intriguing consistency between the evolution of tremor spectra and seismic velocities. Furthermore, variability in seismic velocity changes across different stations, with closely matching spectra evolution, suggests that these phenomena are not simply related to a change in seismic source frequency. Instead, we propose that the spectra are evolving in response to a phase velocity change within the medium, as evidenced by our measurements of seismic velocity. These findings highlight the sensitivity of tremor spectra to changes in subsurface conditions, thus providing a new perspective on the relationship between spectral evolution and medium properties. Our results confirm that monitoring spectral changes offers a promising approach for tracking subsurface conditions within volcanic plumbing systems.