A study on the progressive fracturing of the crust of the Phlegrean Caldera has just been published
The succession of uplift episodes in recent decades has caused a progressive weakening of the crust of the Campi Flegrei caldera.
This is the main result of the study "Potential for rupture before eruption at Campi Flegrei caldera in southern Italy” published in Nature's 'Communications Earth and Environment', conducted by researchers from University College London (UCL) and the National Institute of Geophysics and Volcanology (INGV).
The research shows that the crust of the Phlegrean caldera is going through a progressive transition from an "elastic" to an "inelastic" phase.
"In this last phase”, says Christopher Kilburn of UCL, “any increase in effort associated with continued lifting is immediately released in the form of earthquakes. Based on our previous research," recalls Kilburn, “in 2016 we hypothesized the increase in seismicity, which actually occurred starting from 2019. This result has encouraged us to continue on the path taken and demonstrates how important it is to study the Campi Flegrei through this new approach which gives us information on the level of fracturing of the crust".
"I study", says Stefano Carlino of the INGV Vesuvius Observatory (INGV-OV), “evidence that, although the ground level reached today is more than 10 cm higher than that reached during the bradyseismic crisis of 1984, the inelastic deformation is taking place with a lower stress level than in 1984. This result suggests that, during the episodes of uplift of the caldera in the past decades have progressively produced changes in the physical state of the crust and that these changes cannot be neglected in the study of the volcanic dynamics in progress and in its future evolutions".
The activity of the caldera is caused by movements of fluids which are said to be about 3 km deep and which could be made up of both magma and gases of a volcanic nature. According to many authors, including those of the present work, the cause of the current uplift could be of hydrothermal origin, but a possible magmatic contribution cannot be completely excluded.
“In the studio”, says Stefania Danesi of the Bologna Section of INGV, "we demonstrate that the uplift episodes in Campi Flegrei from 1950 to today must be considered as phases of a single long-term process in which the recent transition from an "elastic" to an "inelastic" regime marks a significant step".
The authors therefore hypothesize different evolutions of the current phase.
“Our results”, observes Nicola Alessandro Pino of the INGV Vesuvius Observatory (INGV-OV), “They are based on the elaboration of a scientific model in which the observed parameters allow us to hypothesize evolution scenarios of rock fracturing and therefore of seismicity. In the most critical scenario, the persistence of the inelastic regime could lead to the rapid fracturing of the more superficial crustal layers, with precursors that could be less intense than generally expected in case of magma upwelling. However, the progressive and widespread reactivation of fractures could cause the depressurization of the hydrothermal system, with an arrest of ground uplift and, therefore, the resumption of slow subsidence".
Finally, the authors underline how their study indicates the need for increasingly quantitative analyzes of the relationships between the signals recorded on the surface by the monitoring networks and the processes that determine them, which are essential to provide more reliable assessments of volcanic hazards.
The published research has an essentially scientific value, currently devoid of immediate implications regarding the aspects of civil protection, representing a potentially useful contribution in the future to refine the forecasting and prevention tools of civil protection. At the moment the research results have no direct implication on measures affecting the safety of the population.
Links to work: Kilburn, CRJ, Carlino, S., Danesi, S. & Pino, NA (2023). Potential for rupture before eruption at Campi Flegrei caldera in southern Italy. Communications Earth & Environment, doi: 10.1038/s43247-023-00842-1.
Useful links: INGV Vesuvius Observatory, UCL Hazard Centre
Photo - Solfatara crater.