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Monitoring the accelerating deformation and seismicity of the ongoing unrest of Campi Flegrei caldera (Italy)

Augusto Neri 1, Andrea Bevilacqua1, Prospero De Martino2, Flora Giudicepietro2, Giovanni Macedonio2, Patrizia Ricciolino2

  • Affiliations: 1Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Pisa, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy

  • Presentation type: Talk

  • Presentation time: Friday 09:00 - 09:15, Room R290

  • Programme No: 3.10.3

  • Theme 3 > Session 10

Abstract

Since 2005, the Campi Flegrei caldera has exhibited progressive ground inflation and intensified seismic activity. Using monitoring data collected from 2000 to 2023, we analyzed the temporal trends in geophysical data and the relationships between them. Our results identified a decadal accelerating trend accompanied by oscillations of varying frequencies. A parabolic acceleration in vertical uplift, estimated at approximately 0.7--0.8 cm/yr², was observed at the center of the caldera (RITE GNSS station). Additionally, a super-exponential increase in the number of earthquakes was detected. The primary oscillation periods ranged from about 2 to 5 months (shorter periods) to approximately 1.5 and 3 years (longer periods). Data inspection revealed a temporal correlation between deformation rate and seismicity, along with a robust exponential relationship between ground deformation and the cumulative number of earthquakes. This relationship has shown an inflection since around 2021, characterized by an increase in its exponent and heightened sensitivity of seismic activity to caldera inflation. These findings were interpreted as evidences of quasi-elastic behavior in the upper crust and a stress memory effect, reflecting the reaching of a stress level larger than the peak observed during the 1982--84 crisis. As of the time of writing, the described trends continue to persist with similar characteristics. The exponential relationship between vertical uplift and cumulative earthquake numbers remains valid. The May 20, 2024, Md 4.4 event fully aligns with the hypothesized behavior, raising concerns about the potential for new seismic crises if the bradyseism persists with the same trends and relationships.