GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 Afer checking the correctness of the developed thermo-poro-elastc displacement formulatons through a comparison with the fnite-element solutons (COMSOL, 2012), we verify whether the amplitude and extent of the deformaton recorded on Vulcano Island from September to mid- October 2021 are consistent with a thermo-poro-elastc response of the rock, applying both models (sphere and cylinder) in the inversion of the GPS daily monitoring data. The inversion results have suggested a deformaton source located below La Fossa crater at a depth of approximately 800 m from the ground surface undergoing a volume change of approximately 10 5 m 3 (Stssi et al., 2023). The modeling results support the hypothesis that the observed deformaton on the Island are induced by the circulaton of fuids (Figure 1), fed by the degassing of a deeper magmatc system (Aiuppa et al., 2022; Federico et al., 2023) without necessarily invoking the migraton of magma to shallow levels. We assume that a growing magmatc fuid input can explain both the source infaton and the simultaneous increase in gas emission from September to mid-October 2021. In partcular, both, the fast deformaton rate and the gas discharge, support the hypothesis that the infaton was engendered by the disequilibrium between the magmatc fuids entering the hydrothermal system and the hydrothermal-magmatc fuids released at the surface. Therefore, at the onset of the 2021 unrest, hot magmatc fuids raised from the deeper magmatc system, have reached the hydrothermal system at a shallower depth where they have generated a local overpressure, which produced the symmetric infaton patern centred in the La Fossa crater. The stop in the increase in deformaton startng from mid- October, and the contnued gas emission at a level above the background, can be interpreted as a change in the response of the porous medium. Indeed, the interacton between rocks and fuid could have altered the permeability, the increase of which has favoured the fuid release and has hindered a further increase in pore-pressure. Based on the observatons and the obtained results, we can state that, despite the introduced simplifcatons, the derived thermo-poro-elastc solutons can provide a frst-order approximaton of ground displacements and source parameters. Therefore, they represent an excellent method for a frst interpretaton of geodetc data during unrest periods and for a beter understanding of the evoluton of the hydrothermal systems, contributng to the hazard assessment during volcanic crises.