A CLEARER VIEW OF THE CURRENT PHASE OF UNREST AT CAMPI FLEGREI CALDERA
Campi Flegrei is the most populated caldera in the world and is currently in an unrest phase since 2005. This unrest is characterized by a slow uplift, a change in the composition of fumarole emissions, and an increment in the seismicity. In particular, the rate of earthquakes with Md>=0 increased from 45 events/year between 2006 and 2018 to 573 events/year between 2019 and 2022, reaching 2699 events/year in 2023. Such an increment in seismicity calls for algorithms that can help with manual activities in detecting earthquakes. In this study, we applied a machine learning-based workflow to analyze Campi Flegrei caldera’s seismic activity recorded from 21/1/2022 –20/03/2025 using continuous waveforms from 49 seismic stations. We used a retrained version of PhaseNet, a deep learning-based phase picker, for phase picking, and GaMMA-1D to associate seismic events. We then used VELEST, and TomoDD to locate and relocate the events incorporating the local 3D velocity model. The final catalog includes 54000 events, including two Md4.6 earthquakes, the largest recorded at Campi Flegrei caldera in the past 40 years. The enriched catalog illuminated multiple faults, in particular the ones bordering the currently resurgent dome, and the fault system beneath Pozzuoli, Sofatara, and Pisciarelli. Notably, it evidence very shallow seismicity beneath Solfatara and Pisciarelli, likely connected to the hydrothermal system, characterized by a fault system extending in the SW-NE direction. In addition, the distribution of seismicity indicates that this ring fault system is shallower in the northern sector and deepens towards the southern sector.