GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 - POSTER GNGTS 2023 Poroelastic interaction between the deep source and the hydrothermal system at Campi Flegrei caldera (Italy) M. Albano, E. Trasatti, M. Polcari Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna murata 605, 00143 Roma. Introduction The Campi Flegrei caldera (Italy) represents a unique test case, with an impressive dataset that describes ground deformation over a century, including three significant uplift phases starting in 1950, 1969, and 1982 (Del Gaudio et al., 2010) followed by a subsidence phase, interrupted by occasional, minor, and short-lasting uplift events. Uplift resumed after 2005 and it is still going on. The caldera is also characterised by significant gas discharge, mostly occurring through soil and fumaroles within the Solfatara crater, roughly at the caldera centre, and its eastern flank (Pisciarelli), with a typical CO 2 flux amounting to 1000–2000 t per day. The presence of fumaroles at this location has been known for centuries, and measurements of gas temperature began as early as the end of the 19 th century. The complex volcanic system has been analysed by several authors that provided different interpretations about the origin of ground deformation as caused by magmatic sources with the possible contribution of a shallower hydrothermal system (Amoruso et al., 2014; D’Auria et al., 2015; Trasatti et al., 2011). They showed by analytical and numerical modelling that both magmatic sources and hydrothermal circulation could cause some deformation. On the other hand, subsidence is often explained in terms of poroelastic relaxation, considering the extensive degassing characterising the caldera. Other authors have interpreted the subsequent uplift phase in terms of heating and pressurisation of the hydrothermal system (Aiuppa et al., 2013; Chiodini et al., 2015; Moretti et al., 2017). However, the origin of the pressurisation of the hydrothermal system and the possible interconnection between the deeper source (probably magmatic) and the shallow hydrothermal system has not been deeply investigated. In our work we develop Finite Element models to simulate the changes in pore pressure and the development of fluid diffusion. The models are tuned with the observed ground displacement, with the aim of assessing the relation between the mechanical deformation of the magma chamber, the development of excess pore pressures and fluid flow, and the possible fueling of the shallower hydrothermal system. To assess the poroelastic interaction, we realise an axisymmetric Finite Element Model (Figure 1), whose symmetry axis is centred on the Solfatara area. The poroelastic rheology accounts for the