With an absolutely innovative method, scientists managed to "see" the internal structure of the caldera
Obtain detailed images of the structure and level of fracture of the rocks of the Campi Flegrei caldera through the analysis of the variation in the speed of seismic waves over time. At the same time, investigate the main characteristics of the volcanic power system and the main changes between the ongoing instability (unrest) or bradyseism and the phenomenon that occurred between 1982 and 1984.
These are the objectives of the study "Tracking transient changes in the plumbing system at Campi Flegrei Caldera” conducted by a multidisciplinary team of researchers fromNational Institute of Geophysics and Volcanology (INGV) and University of Milan-Bicocca, just published on Earth and Planetary Science Letters by Elsevier.
This is the first seismic tomography study that integrates the microseismicity that occurred at the Campi Flegrei over a period of forty years, from 1982 to 2022. The researchers used a technique based on a non-linear probabilistic approach to solving the tomographic problem, analyzing the relationship between the speed of the so-called P waves (first or pressure) and their relationship with the so-called S waves (second or shear).
This innovative method has allowed us to shed light on the characteristics of crustal velocity up to a depth of 6 km, where traditional linearized techniques have always shown resolution limits. Furthermore, the use of this method made it possible to identify for the first time three main areas of accumulation of magmatic material under the resurgent area, corresponding to the sources of the bradyseismic deformations. While the central reservoirs, located at 2.5 and 3.5 km depth, reveal a prevalent accumulation of overpressured fluids, the deeper reservoir, located at 5 km, shows velocity values consistent with an accumulation of magma.
An important innovative element of the studied method is the possibility of identifying the main variations over time of the velocity anomalies and, therefore, of the evolution of the areas of accumulation of magmatic material. This was possible thanks to the intuition of the team of researchers who pioneered the 4-dimensional (space and time) seismic tomography method.
The results show that the two unrest episodes analyzed from 1982-1984 and from 2005 to 2022, although involving different volumes, were both characterized by episodes of ascent and accumulation in the central area mainly of magmatic gases under overpressure and at depth of magma , suggesting that both of these processes play an important role in inducing caldera unrest.
This approach can prove to be a useful tool for monitoring the evolution of the caldera's magmatic supply system over time and the researchers' desire is to extend the probabilistic model to the years after 2022 as soon as possible.
Link to the study: https://doi.org/10.1016/j.epsl.2024.118744
Citation: Giacomuzzi, G., Chiarabba, C., Bianco, F., De Gori, P. and Piana Agostinetti, N. Tracking transient changes in the plumbing system at Campi Flegrei Caldera. Earth. Planet. Sci. Lett., 637 (2024)
