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FEM model of surface deformation pattern applied to the Campi Flegrei caldera

^^ Pierdomenico Romano^^ , Bellina Di Lieto, Annarita Mangiacapra, Zaccaria Petrillo, Agata Sangianantoni

Abstract

Campi Flegrei is the largest active urbanized caldera in Europe. Since 2005, it has shown slow but progressive ground inflation and, in recent years, an increase in seismic activity. Deformation is characterized by transient reversals in rate, leading to episodes of monotonic uplift lasting from several weeks to a few years. Additionally, some aseismic transients have been detected using high-sensitivity strainmeters and long-baseline tiltmeters, with amplitudes typically below the noise level and durations shorter than the sampling frequency of most geodetic techniques. A shallow hydrothermal origin for the ongoing deformation may explain non-eruptive cycles of subsidence and uplift, driven by the balance between magmatic input and fluid discharge at the surface. However, separating signals from magmatic and hydrothermal sources is challenging due to the presence of both types of reservoirs. A detailed study of ground deformation using a finite element model is essential to understand the kinematics of both the aquifer and the plumbing system at different depths. In this study, we used COMSOL Multiphysics to examine how deep pressure and temperature changes influence surface deformation in the Campi Flegrei caldera. The Tough software, simulating multi-phase fluid and heat flows, was used to model the sources which, within the COMSOL model, has shown a good match with observed surface deformation data from GPS/GNSS and strainmeter time series, confirming the model's accuracy. Combining data and models makes it more feasible to forecast volcanic system parameters on relevant timescales. Data used contains valuable information for scientific community, following EPOS policies.