Hydrothermal instability and ground displacement at the Campi Flegrei caldera

Ground deformation is commonly observed at active volcanoes, where it represents a reliable sign of unrest and a potential precursor of eruptive activity. The source of deformation, however, is not always unequivocally constrained. Magma ascent and differentiation are involved, but hydrothermal fluids may play a role, due to temperature and pore pressure acting on rocks. The identification of mechanisms driving ground displacement bears important consequences for hazard evaluation. Aim of this work is to evaluate mechanical effects associated with pressurization and heating of hydrothermal fluids. We first simulate the heat and fluid flow driven by the arrival of magmatic fluids from greater depth. Then, we calculate the rock deformation arising from simulated pressure and temperature changes, employing a mathematical model, based the linear theory of thermo-poro-elasticity and on a system of distributed equivalent forces. Results show that stronger degassing of a magmatic source may cause several centimetres of uplift.