GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 1.2 108 UNDERSTANDING OF HYDROTHERMAL DYNAMIC AT VULCANO ISLAND (ITALY) S. C. Stissi 1 , R. Napoli 1 , G. Currenti 1 , A. Afanasyev 2 , G. Montegrossi 3 1 Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy 2 Institute of Mechanics, Moscow State University, Moscow, Russia 3 CNR - IGG, Institute of Geosciences and Earth Resources, Florence, Italy 1. Introduction In recent decades, numerous studies have been performed to understand the mechanical re- sponse of volcano edifice to the circulation of hydrothermal fluids (Chiodini et al., 2016; Currenti and Napoli, 2017; Peiffer et al., 2018; Rinaldi et al., 2010; Troiano et al., 2011). The perturbation of a hydrothermal system induces temperature and pore-pressure variations in the fluid which in turn cause changes in stress and strain and in density distribution, manifesting at surface in changes in ground deformation and gravity field. Therefore, the monitoring of geophysical obser- vables and the development of efficient mathematical models to simulate them constitute a crucial point for gaining insights into the dynamics of volcano-hydrothermal systems. To quantify the underlying processes and their effects at surface we coupled a hydrothermal model, which computes pressure, temperature and density variations following the perturbation of the hydro- thermal system with a thermo-pore-elastic model, which allows to compute ground deforma- tion and gravity changes in response to the quantities provided by the hydrothermal simulations (Currenti and Napoli, 2017). We apply the methodology to Vulcano Island, (Chiodini et al., 1996; Granieri et al., 2006; Federico et al., 2010; Napoli and Currenti, 2016), where in the last 30 years the episodes of Fig. 1 - Changes in temperature (∆T) and in pressure (∆P) and gas saturation distribution (S g ) during an unrest phase induced by the injection of a mixture of H 2 O and of CO 2 at a temperature of 600 °C. The unrest phase was simulated for three different sizes of inlet: 40 m (left panels), 100 m (central panels) and 200 m (right panels), maintaining the same permeability configuration. A zoom of the area affected by the most significant variations was carried out in ∆T plot to allow a better visualization.