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. 2023 Jul 10;13:11115. doi: 10.1038/s41598-023-38205-7

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© The Author(s) 2023

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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(a) Ratio of stacked spectra of seismic precursor (15 windows of 1-minute length) and tremor (20 windows of 1-minute length). The maximum of the stacked spectra ratio corresponds to the 0.4 Hz frequency. (b) Azimuth of the seismic signal polarization of the STRA station in the frequency band 0.2–0.5 Hz, relevant for the overflow episode of 9 October 2022 (from 5:00 to 10:00). The rectangle with the red border highlights the segment used for the rose diagram of panel d (purple rose). (c) Azimuth of the seismic signal polarization of the STRA station in the 0.2-0.5 Hz frequency band, related to the overflow episode of 16 November 2022 (from 4:00 to 9:00). The rectangle with the red border highlights the segment used for the rose diagram of panel d (green rose). (d) Rose diagrams of the polarization azimuth of the two overflow episodes superimposed on the Stromboli map. The positions of the STRA station and the active vents are shown on the map. The thermal precursor is located on vent N2.