Changes in the Eruptive Style of Stromboli Volcano before the 2019 Paroxysmal Phase Discovered through SOM Clustering of Seismo-Acoustic Features Compared with Camera Images and GBInSAR Data

Abstract

Two paroxysmal explosions occurred at Stromboli on July 3 and August 28, 2019, the first of which caused the death of a young tourist. After the first paroxysm an effusive activity began from the summit vents and affected the NW flank of the island for the entire period between the two paroxysms. We carried out an unsupervised analysis of seismic and infrasonic data of Strombolian explosions over 10 months (15 November 2018–15 September 2019) using a Self-Organizing Map (SOM) neural network to recognize changes in the eruptive patterns of Stromboli that preceded the paroxysms. We used a dataset of 14,289 events. The SOM analysis identified three main clusters that showed different occurrences with time indicating a clear change in Stromboli’s eruptive style before the paroxysm of 3 July 2019. We compared the main clusters with the recordings of the fixed monitoring cameras and with the Ground-Based Interferometric Synthetic Aperture Radar measurements, and found that the clusters are associated with different types of Strombolian explosions and different deformation patterns of the summit area. Our findings provide new insights into Strombolian eruptive mechanisms and new perspectives to improve the monitoring of Stromboli and other open conduit volcanoes.

Seismic and thermal precursors of crater collapses and overflows at Stromboli volcano

“…These phenomena typically exhibit variations in the degassing processes preceding them, which can be detected through seismic data analysis, and interpreted by comparing seismic parameters with camera and deformation data. This was also observed in Giudicepietro et al (2022) 55 , where an anomalous period dominated by gas explosions that had begun more than a month before the 2019 paroxysmal phase at Stromboli was discovered through machine learning analysis of seismic data. However, Stromboli experiences continuous changes in the summit area’s morphology 56 , resulting in variations of the active vents and the slope of the Sciara del Fuoco 4 .…”

“…This study confirms that seismic measurements are highly sensitive to outgassing processes, as research in this field had already extensively highlighted 39 , 43 , 45 – 54 . In the case of Stromboli, which is a natural laboratory due to its persistent activity and easy accessibility, seismic methods combined with thermal and deformation measurements are making it possible to recognize precursors to potentially hazardous eruptive phenomena, such as paroxysms 43 , 55 and lava overflows 11 , 55 . These phenomena typically exhibit variations in the degassing processes preceding them, which can be detected through seismic data analysis, and interpreted by comparing seismic parameters with camera and deformation data.…”

“…These factors can influence the dynamics of the possible precursors. The properties of the seismic signals generated by outgassing processes are influenced by various factors, including magma viscosity, gas flux velocity, and conduit roughness 55 , 57 – 59 . Standardizing monitoring based on specific parameter thresholds is therefore challenging.…”

Multi-parametric study of an eruptive phase comprising unrest, major explosions, crater failure, pyroclastic density currents and lava flows: Stromboli volcano, 1 December 2020–30 June 2021

“…The most recent eruptive activity at Stromboli was characterized by two powerful paroxysmal explosive episodes occurring on 3 July and 28 August 2019 (Giudicepietro et al, Frontiers in Earth Science frontiersin.org 2019; Inguaggiato et al, 2019;Giudicepietro et al, 2020;Inguaggiato et al, 2020;Calvari et al, 2021;Giordano and De Astis, 2021;Inguaggiato et al, 2021;Giudicepietro et al, 2022) with a lava flow output starting on 3 July and ending on 30 August 2019 (Andronico et al, 2021). Both paroxysms of 3 July and 28 August were characterized by the ejection of gasrich, low porphyritic LP magma of deep origin rising up quickly along the conduit (Métrich et al, 2005;Bertagnini et al, 2011;Plank et al, 2019;Giordano and De Astis, 2021;Métrich et al, 2021).…”

Multi‐Temporal InSAR, GNSS and Seismic Measurements Reveal the Origin of the 2021 Vulcano Island (Italy) Unrest

“…In our work, we expanded the analysis of seismic signals beyond just VLP occurrence rates, also considering VLP amplitude. This approach builds upon the method introduced by Giudicepietro et al (2020) for defining the VLP size parameter in seismic signals associated with Stromboli explosions (Calvari et al, 2021;Di Traglia et al, 2014), a highly sensitive parameter to volcanoes' degassing processes (Giudicepietro et al, 2022). We analyzed the period from 1 July to 31 December 2021.…”