An analysis based on over 5000 teleseisms (seismic waves generated by distant earthquakes) recorded between 2016 and 2022 has allowed us to reconstruct in detail the deep structure of the Campi Flegrei caldera, the volcanic area located west of Naples, providing new details on the seismicity and the presence of an area interpreted as a possible zone of partial melting of the crust and upper mantle.
A new international study has provided the First image of the deep magma feeder zone of the Campi Flegrei pushing the observation to a depth of about 50 km. The research, Magma storage depths and crustal-upper mantle structure of Campi Flegrei caldera (Southern Italy) revealed through receiver functions analysis, is fruit of the collaboration between theCanary Volcano Institute (INVOLCAN), the Istituto Nazionale di Geofisica e Vulcanologia (INGV), the Complutense University of Madrid andUniversity of Geneva, and was published in the magazine Scientific Reports (Nature).
Although the Campi Flegrei have been extensively investigated in their most superficial part in recent decades, this new analysis allows us to extend the investigation to the entire deep structure of the volcanic system.
The reconstruction was possible thanks to the analysis of seismograms produced by distant earthquakes, the teleseisms, recorded by the INGV permanent seismic network in the Phlegraean Fields. Through the technique of “receiver functions”, which allows us to interpret the seismic waves reflected and converted within the Earth, researchers have analyzed over 5000 seismic events.
As illustrated in the study, when an earthquake occurs at a great distance, the waves travel through the planet's interior and, encountering variations in the properties of the rocks, are reflected and converted. Analysis of these signals allows us to reconstruct the depth and characteristics of the main discontinuities in the subsurface. explains Víctor Ortega-Ramos, researcher at INVOLCAN and first author of the study.
The main result achieved concerns The identification, at depths greater than 16-20 km, of a layer characterized by "very low seismic wave velocities." This data suggests that up to 30% of the rocks in that area are in a molten state..
According to the authors, this area represents the source of the primitive magma of the Campi Flegrei, which, during their ascent in the Earth's crust, cool and evolve towards compositions richer in silicon.
“At depths between 8 and 10 km, The study also highlights the presence of further less intense seismic characteristics, which could indicate the presence of smaller quantities of magma, in continuity with previous observations”, continues Luca D'Auria, Director of the INVOLCAN volcanic surveillance area.
"The results contribute to improving the understanding of the magmatic system of the Campi Flegrei, its recent evolution and the processes that regulate the volcanic activity of the area.The next steps will be aimed at better understanding how the different parts of the magmatic system are connected and how the transfer of magma from the depths to the surface occurs, also through the integration of different methodologies.”, concludes Lucia Pappalardo, director of the Vesuvius Observatory of the INGV (INGV -OV).
Link to the study: https://doi.org/10.1038/s41598-026-51786-3.
Links
Canary Volcano Institute (INVOLCAN)
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Complutense University of Madrid
Deep structure of the Campi Flegrei volcano, up to 50 km deep, along an EW section passing through the center of the caldera. The low-velocity seismic wave zone, shown in red, is located beneath the volcano. This area is the source of the magma that fuels the Campi Flegrei volcano's activity.
Animation showing the extent of the low-velocity zone beneath the Phlegraean Fields. The red dots indicate the hypocenters of earthquakes recorded in recent years.
Monitoring magmatic degassing in the Solfatara area, Campi Flegrei.