Abstract
In July and August 2019, Stromboli volcano underwent two dangerous paroxysms previously considered “unexpected” because of the absence of significant changes in usually monitored parameters. We applied a multidisciplinary approach to search for signals able to indicate the possibility of larger explosive activity and to devise a model to explain the observed variations. We analysed geodetic data, satellite thermal data, images from remote cameras and seismic data in a timespan crossing the eruptive period of 2019 to identify precursors of the two paroxysms on a medium-term time span (months) and to perform an in-depth analysis of the signals recorded on a short time scale (hours, minutes) before the paroxysm. We developed a model that explains the observations. We call the model “push and go” where the uppermost feeding system of Stromboli is made up of a lower section occupied by a low viscosity, low density magma that is largely composed of gases and a shallower section occupied by the accumulated melt. We hypothesize that the paroxysms are triggered when an overpressure in the lower section is built up; the explosion will occur at the very moment such overpressure overcomes the confining pressure of the highly viscous magma above it.
Highlights
The Stromboli volcano activity is characterized by continuous degassing accompanied with explosive transients of variable intensity
A final consideration needs to be made on the paroxysm that occurred on 28 August (Figure A6): the strain curve in the 90 min preceding this second paroxysm appears to be slightly similar to the one of 3 July, but is much smoother and more importantly there is a lack of significant strain VLPs
The paroxysm of 3 July 2019 prompts a general reflection: an impressive number of monitoring devices have been installed for many years on the island, such a paroxysm occurred without any meaningful variation of the geophysical parameters used for the evaluation of the activity of the volcano
Summary
Mario Mattia 1 , Bellina Di Lieto 2, * , Gaetana Ganci 1 , Valentina Bruno 1 , Pierdomenico Romano 2 , Francesco Ciancitto 1 , Prospero De Martino 2 , Salvatore Gambino 1 , Marco Aloisi 1 , Mariangela Sciotto 1 , Roberto Scarpa 3 and Carmelo Ferlito 4. Approach to Reveal Hidden Features of the “Unexpected” 3 July Paroxysm
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