GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 Thermo-poro-elastc modeling of the infaton phase during the 2021 Vulcano Island (Italy) unrest S. C. Stssi 1 , G. Current 1 , F. Cannavò 1 , R. Napoli 1 1 Isttuto Nazionale di Geofsica e Vulcanologia (Catania, Italy) Startng from September 2021, Vulcano Island has been afected by an unrest episode, characterised by the increase in gas emission, seismic actvity, and edifce infaton (Aiuppa et al., 2022; Federico et al., 2023). The contnuous and stable radial expansion of the volcano edifce contnuing untl mid-October 2021, that afected the GPS statons closer to the summit crater, suggested a deformaton source located below La Fossa crater. The temporal evoluton of the deformaton patern is indicatve of a spatally statonary source. The deformaton patern and the lack of shallow VT seismicity ruled out a possible involvement of shallow magmatc intrusion. Therefore, it is likely that the observed displacements have been generated by the thermo-poro- elastc response of the rocks to the increase of hot fuid fow at shallow depth originatng from the degassing of a deeper magma source. With this in mind, we review and develop (semi-)analytcal formulatons to calculate the ground deformaton induced by homogeneous distributons of pore-pressure and/or temperature changes within thermo-poro-elastc sources with simple geometries, embedded in an elastc, isotropic and homogeneous half-space. We investgate two models: spherical (Davies, 2003; Rinaldi et al., 2011) and cylindrical. For homogeneous and isotropic distributons of rock elastc parameters and irrotatonal displacement felds, the deformatons related to hydrothermal actvity are given by the gradient of a potental that obeys a Poisson equaton, establishing a mathematcal analogy between displacement and gravitatonal problems in an infnite space (Wang, 2000). The semi-analytc formulaton for the cylindrical source is derived as a functon of this analogy startng from the soluton to calculate the gravity changes due to homogeneous distributons of the density variatons (Hemmings et al., 2016).