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Progress in anticipating crustal rupture during unrest at Campi Flegrei

Christopher Kilburn 1,5, Eric Newland1,5, Nicola Alessandro Pino2, Stefano Carlino3, Stefania Danesi4

  • Affiliations: 1UCL Hazard Centre, Department of Earth Sciences, UCL, London, UK; 2Università di Camerino, Scuola di Scienze e Tecnologie, Sezione di Geologia, Camerino, Italy; 3INGV-Sezione di Napoli, Osservatorio Vesuviano, Napoli, Italy; 4INGV-Sezione di Bologna, Bologna, Italy; 5Project FEVER, UKRI, UK.

  • Presentation type: Talk

  • Presentation time: Friday 08:45 - 09:00, Room R290

  • Programme No: 3.10.2

  • Theme 3 > Session 10

Abstract

The 2017-2024 volcano-tectonic (VT) crisis at Campi Flegrei has provided a remarkable dataset for relating changes in VT seismicity with time to the progress of crustal rupture. The rate of VT seismicity passed through four stages until early 2024: an exponential increase in 2017-2020, a constant rate in 2020-2022, a hyperbolic increase until November 2023 and a three-month decay until March 2024. The sequence was followed by a rapid increase in rate to the highest recorded value in April 2024, since when it has been in gentle decline. Throughout the sequence, the floor of the caldera was uplifted at rates of 1-2 cm a month in the zone of fastest movement. An energy balance between uplift and seismicity reveals an accumulation of stress until 2022 and a decrease thereafter. The highest VT event rates thus occurred while stress was being lost. Such a relation is counter-intuitive, because decreasing stress is commonly associated with an Omori-style decline in VT event rate while crust relaxes. We attribute the increase in event rate to a self-accelerated interlinking of fractures that, more speculatively, triggered a temporary redistribution of pore fluids in the zone of nascent rupture, resulting in the brief decrease in seismicity in late 2023-early 2024. If confirmed, our interpretation suggests that Campi Flegrei's crust today contains a major new discontinuity -- that is, a structural weakness now available to be exploited by magma or magmatic fluids during future episodes of uplift.