FEM model of surface deformation pattern and a first application on real data at Campi Flegrei caldera

Campi Flegrei Caldera is an active volcano located westward of Naples, Italy. Despite its volcanic activity spanning over 39,000 years, the area is densely populated and poses a significant threat to the inhabitants due to ongoing seismicity, ground uplift, and hydrothermal activity resulting from increased pressure due to fluid injections and thermal variations at depth. These factors highlight the potential for a major volcanic eruption. Being able to model the processes that lead to ground deformation could be of vital importance in predicting an imminent eruption and enabling the evacuation of the resident population in the area.

Such models are being schematized and analyzed using specific Finite Element Method (FEM) software capable of solving complex mathematical problems involving partial differential equations. In this manuscript, we utilized COMSOL Multiphysics, configured with the structural mechanics module, to examine how deep changes in pressure and temperature influence the observed surface deformation field within the Campi Flegrei caldera. To simulate these deep changes, we employed the Tough software, an open-source numerical simulation program designed for multi-dimensional fluid and heat flows of multiphase and multicomponent fluid mixtures in porous and fractured media. The output of Tough served as an input for the COMSOL model, representing the source at depth. By using the structural mechanics module, we were able to assess the accuracy of the proposed model in comparison to analytical solutions. Furthermore, we were able to model the geometry of the deep source in more detail and verify that the surface deformation pattern aligned with the measurements obtained from sensors. By leveraging COMSOL Multiphysics, therefore, we have constructed a mathematical model that accurately captures the intricate interplay of fluid injections, thermal variations, and rock mechanics, enabling us to simulate volcanic crustal deformations with remarkable fidelity: the surface deformations obtained through simulation aligns with those observed through GPS/GNSS, strain and tilt time series recorded by the Osservatorio Vesuviano monitoring networks.

Valuable information are embedded in the data used in the current work, which could be used not only for scientific purposes but also from civil protection for monitoring reasons. Such a variety of possible usage needs the setting of principles and legal arrangements to be implemented in order to ensure that data will be properly and ethically managed and in turn can be used and accessed from the scientific community.