GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Thermo-poro-viscoelastc deformaton sources M. Nespoli 1 , M. E. Belardinelli 1 , M. Bonafede 1 1 Department of Physics and Astronomy, Alma Mater Studiorum, Università di Bologna, Bologna, Italy 1. Introducton. Thermo-poro-elastc (TPE) deformaton sources allow to explain seismicity and deformaton induced by pore-pressure ( p ) and temperature ( T ) changes in geothermal and volcanic environments. In the last years, TPE inclusions have been applied to model the displacement and the stress feld in the caldera of Campi Flegrei (Italy), where pore-pressure and temperature changes are assumed to derive from the exsoluton of fuids from a deep magmatc chamber. In the literature both analytcal and numerical models of TPE inclusions with diferent geometries exist (Belardinelli et al., 2019, Mantloni et al., 2020, Belardinelli et al., 2022, Nespoli et al., 2021 and 2022). While previous works were focused on TPE induced statc deformaton paterns, in the present work we show how to model the transient efects on displacement, strain and stress. Such transient efects can be modeled by extending the TPE models to the Thermo-Poro-ViscoElastc (TPVE) ones. 2. Method. The inclusion method allows us to model the statc mechanical efects of pore-pressure and temperature changes occurring inside a closed volume (i.e. an inclusion) embedded in an elastc medium (Eshelby, 1957). To model transient mechanical efects one can include the efects of viscoelastcity. A viscoelastc behavior should be expected in high temperature and fuid saturated rocks, due to thermally actvated and pressure-soluton creep. The analytcal thermo- poro-viscoelastc (TPVE) solutons for a disc-shaped inclusion embedded in a uniform viscoelastc medium can be obtained through the correspondence principle (Fung 1965, Nespoli et al., 2023a) assuming that the medium is a homogeneous Maxwell half space. 3. Discussion and Conclusions. The TPVE analytcal solutons indicate that including the viscoelastc behavior inclusion can explain a decrease in seismicity rate accompanied by an increase of surface uplif, as was observed in the late stage of the 1982-84 unrest phase at Campi Flegrei. This behavior is in contrast with what is expected according to the elastc response, in which the seismicity increases during the uplif and decreases during the subsidence. Our approach allows us to extend the relevance of hot and pressurized inclusion models to the interpretaton of transient mechanical efects, which can be observed in several areas of the World.