The conduit feeding the vents of Stromboli volcano is always open. For this reason, lava can easily rise driven by internal pressure, and this is why Stromboli volcano produces dozens of small eruptions every day with remarkable regularity. This regularity, however, is occasionally disrupted by much more energetic and dangerous explosions, the so-called "paroxysmal" eruptions.
Understanding when the volcano is preparing for one of these more energetic episodes is fundamental. For years, volcanologists have avidly investigated the signals collected by increasingly complex and powerful sensors in search of "warning" clues. In the INGV seminar held on Wednesday 22 November 2023, Bellina Di Lieto and Pierdomenico Romano presented research on this very topic. Let us make clear upfront that this research was conducted outside the UNO project, but it concerns the volcano UNO deals with, and thus we are happy to present it here. Bellina and Pierdomenico tried to interpret the signal collected by a specific instrument, a "strainmeter", which has been installed for years in a well dug at low altitude on the island of Stromboli. This instrument is capable of measuring imperceptible state variations in the subsoil, i.e. very small "tensions" induced by the activity of the volcano. Without going into detail about the characteristics of the signals captured by the strainmeter, let's mention the applied signal processing techniques and the obtained results.
The data collected was processed through "machine learning", i.e. an artificial intelligence technique in which the software, guided by researchers, learns "on its own" how to analyze a very large amount of data. This helps a lot because traditional methods can hardly manage such a large amount of data. The obtained results indicate that given changes in the shape of the signal recorded during the volcano's activity a few weeks before the paroxysmal events of summer 2019 could constitute a warning signal to be taken into account in the future. The trigger of these very energetic explosive events would be linked to a particular change in the state of the magma that rises into the volcanic conduit, and this change is recorded by the strainmeter set deep into the well.