A new study conducted jointly by Cnr and INGV reveals peculiar seismic signals at Campi Flegrei: a key to understanding the current dynamics. The research is published in the journal Nature Communications.
An important collaboration between researchers of the National Institute of Geophysics and Volcanology (INGV) and Institute for Electromagnetic Sensing of the Environment of the National Research Council (CNR-IREA) has brought to light new and significant results on the seismicity of the Phlegraean Fields, an active volcanic area that since 2005 has been characterised by dynamic processes that show a gradual increase over time.
The study, published in the journal Nature Communications., has examined some volcano-tectonic seismic swarms become evident since 2021, observing an increase in their frequency of occurrence, characterized by extremely short time intervals between one event and another: “These seismic swarms, defined as "burst-like", manifest themselves with a rapid sequence of small earthquakes which makes it difficult to distinguish the individual events in the seismogram using the usual analysis techniques”, he says Flora Giudicepietro, INGV researcher and first author of the work. “In parallel, the phenomena of ground uplift, ordinary seismic activity and gas emissions, typical of this phase of activity, have shown an acceleration”.
The multidisciplinary analysis conducted allowed us to locate these seismic sequences in an area that includes the main hydrothermal field of Campi Flegrei: “In this area, in particular in correspondence with Monte Olibano, there is a geodetic anomaly, which has been highlighted since 2021, which has been the specific object of our recent studies”, he adds Francesco Casu, research director of CNR-IREA. “This anomaly manifests itself as a region that is uplifting less rapidly than surrounding areas, suggesting complex dynamics related to the interaction between ground deformation, seismicity and hydrothermal activity”.
In some studies conducted in other volcanic contexts, seismic swarms "burst like" have been associated with phreatic explosions and critical phases of unrest (agitation). This would suggest that The observed seismic phenomena could be potential indicators of significant changes in the physical conditions of the Phlegraean caldera hydrothermal system.
The research has allowed to integrate geophysical, geochemical, geodetic and satellite observation skills of the Earth, providing a broad and in-depth interpretative framework to understand the evolution of the volcanic system of Campi Flegrei: results that, in addition to enriching the scientific knowledge on the behavior of the volcano, also represent a further element to support the improvement of monitoring and management activities of volcanic risk in a densely populated area.
Image 1: Comparison between a "burst-like swarm" (panel d and red circles in panel b) and a generic seismic sequence characterized by short time intervals between successive events (panel c and blue circles in panel b). It is observed that the events belonging to the sequence of type "burst like" are mainly located in the Solfatara-Pisciarelli hydrothermal area, while the locations of the generic seismic sequence are found only in the most superficial sector of the seismogenic volume.
Image 2: Average velocity of vertical ground displacement (panel a) of the Campi Flegrei caldera for the period 2021-2024, where each color cycle corresponds to an increase in uplift of 4 cm/year. The zoom at the top right highlights the effect of the geodetic anomaly in correspondence with the Monte Olibano area, to which the diagram below (panel b) also refers, where the temporal evolution is shown, starting from 2015, of the uplift deficit that becomes evident from 2021.