Characterization of the Vulcano’s active geothermal system: an integrated approach based on geophysical models and numerical simulations

The island of Vulcano belongs to the Aeolian Archipelago (Italy), and throughout its history, it has experienced many eruptions, including at least three phreatic events. After its last eruption (1888-1890 AD), Vulcano has been the site of various volcanic unrest crises, and a continuous fumarolic activity mainly concentrated within La Fossa crater and Baia Levante beach. In September 2021, Vulcano entered a new phase of unrest characterized by rising fumarole temperatures and changes in gas composition, as well as ground deformation and microseismicity, indicating an increased input of magmatic fluids in the geothermal system. We conducted a comprehensive study integrating geophysical models with numerical simulations to understand the fluid dynamics and mechanisms driving Vulcano’s active geothermal system. Specifically, a petrophysical model for the La Fossa Caldera area was derived from evidence gained through a magnetotelluric tomography (MT) carried out in 2022 [Di Giuseppe et al., 2023]. This provided fundamental information for characterizing the volcanic tectonic structures and geothermal fluid pathways down to 2.5 km depth. The geophysical highligths were also integrated with additional geochemical and geological constraints. To further investigate the thermodynamic state of the system, we employed the TOUGH2 numerical code to simulate fluid and heat flow in porous and fractured media. This powerful tool allowed us to model the complex dynamics of the Vulcano geothermal system, including its temporal evolution. The simulations provided estimates of the fluid distribution in terms of pressure, temperature, and gas saturation, ultimately elucidating the current state of the Volcano’s geothermal system.