GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 GNGTS 2023 The hot topic of Thermo-Poro-Elastic deformation sources in volcanic and geothermal fields M. Nespoli 1 , M. E. Belardinelli 1 , M. Bonafede 1 1 Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna, Italy Introduction Thermo-poro-elastic (TPE) inclusions provide a mechanism to explain seismicity and deformation induced by pore-pressure ( p ) and temperature ( T ) changes in volcanic contexts. They are also suitable to represent the mechanical effects due to fluid extraction and re-injection in geothermal fields. Since the pioneering work of Segall (1989) it is well known that TPE inclusions can explain the different fault mechanisms induced by oil and gas production inside and around the reservoirs. Recently, the inclusion method was applied to volcanic environments, where pore-pressure and temperature changes derive from the exsolution of fluids of magmatic origin (Fig. 1). Some recent work show how to obtain analytical and numerical representations of the mechanical effects of TPE inclusions with different geometries (Belardinelli et al., 2019, Mantiloni et al., 2020, Belardinelli et al., 2022, Nespoli et al., 2021 and 2022). Several of the recent applications of TPE inclusion models in a volcanological context refer to the 1982-1984 unrest phase at the caldera of Campi Flegrei (Italy). Method The inclusion method described by Eshelby (1957) and Aki and Richards (1980) allows us to model the mechanical effects of pore-pressure and temperature changes occurring inside a closed volume (i.e. an inclusion) embedded in an elastic medium. Significant simplifications are obtained if an unbounded medium is considered (Belardinelli et al., 2021 and 2022). Semi-analytical approaches, instead, allow us to model the presence of the free-surface, thus making it possible to compare the model results with the displacement data measured on the surface of the Earth (Mantiloni et al., 2020, Nespoli et al., 2021). Furthermore, numerical computations allow modeling the effects of the elastic layering of the medium and accounting for an arbitrary complex geometry of the inclusion. Numerical approaches are based on the fact that the mechanical effects of a TPE inclusion can be represented by an equivalent distribution of single forces acting normally on its surface boundaries. The mechanical effects of preassigned distributions of single forces in a layered elastic medium can be computed with the EFGRN ∕ EFCMP (Elastic Forces GReeN functions/Elastic Forces CoMPutation) code (Nespoli et al, 2022), which is based on the