Mysterious “Burst-Like”: New study reveals the presence of particular seismic swarms at the Flegrei fields

A land that trembles, not with a single earthquakebut with a burst of shocks that follow one another at a pressing rhythm. This is what is happening to Campi Flegreiwhere the “Burst-like” seismic swarms They reveal a complex underground dynamic. But what are these seismic swarms? And what do they tell us about the future of this volcanic caldera?

The seismic swarms called “burst-like”

The Campi Flegrei, a volcanic area located in the heart of Italy, have always been the subject of studies and monitoring due to their active nature and the potential risk for the surrounding population, about 500,000 people. A new study, the result of the collaboration between theNational Institute of Geophysics and Volcanology (Ingv) and theInstitute for electromagnetic detection of the environment of the National Research Council (CNR-IREA), has thrown light on a peculiar dynamic of this area: the presence of seismic swarms called “burst-like”.

The research, published in the magazine Nature Communicationsit focused on particular seismic volcano-tettonic sequences that intensified from 2021. These “burst-like” seismic swarms are distinguished by a peculiar feature: a series of close earthquakes, with extremely short time intervals between one event and another. This peculiarity makes the analysis of individual seismic events difficult through traditional techniques.
“These seismic swarms manifest themselves as a quick sequence of small earthquakes, which makes the distinction of individual events in the seismogram complex,” he explained Flora judgepietroingv researcher and first author of the study. “Parallel, We have observed acceleration in soil lifting phenomenain ordinary seismic activity and in gas emissions, typical of this phase of activity “.
The multidisciplinary analysis conducted by the researchers made it possible to locate these seismic swarms in a crucial area of ​​the Flegrei camps: the one that includes the main hydrothermal field.

“In this area, in particular at the Monte Olibanothere is a geodetic anomaly, which has been highlighted since 2021, which has been the subject of our recent studies, “he adds Francesco Casuresearch manager of CNR-AREA. “This anomaly is manifested as one region that rises less quickly than the surrounding areassuggesting complex dynamics related to the interaction between soil deformations, seismicity and hydrothermal activity “.

Studies conducted in other volcanic contexts have associated “burst-like” seismic swarms with agitation phenomena and frieze explosions. This suggests that the seismic phenomena observed at the Flegrei fields could be signs of significant changes in the physical conditions of the hydrothermal system.

A dynamic and constantly evolving area

The Flegrei fields are a caldera volcanic active, with a diameter of about 12 km, whose last eruption dates back to 1538 AD, with the formation of Mount New. The area is characterized by phenomena of bradisism, i.e. vertical soil movements, which manifest themselves as a lifting and lowering phases.
In recent decades, the Flegrei fields have crossed several stages of bradisism, with a significant lifting of the soil accompanied by an increase in seismic activity. The current phase of bradisism, which began in 2005, is characterized by a progressive increase in seismicity, with a rate of occurring of earthquakes in continuous growth.

Detailed analysis of “burst-like” seismic swarms

The researchers identified different types of “burst-like” seismic swarmscharacterized by different time intervals between events and by different magnitudes. For example, sequences have been recorded with time intervals of 7.2 seconds, 29.6 seconds and 15.5 seconds, with magnitudes maximum variables between 0.7 and 2.7.

Another type of “burst-like” seismic swarms is characterized by a series of overlapping seismic events, with very short and difficult time intervals. These shamans are often accompanied by a continuous background signal, with the same frequency of seismic events. In some cases, “burst-like” seismic swarms may include relatively high magnitude eventslike the one recorded on May 20, 2024, with a magnitude of 4.4.

The interaction between soil deformation, seismicity and hydrothermal activity

The researchers analyzed the space distribution of “burst-like” seismic swarms, highlighting a greater concentration of events in correspondence with the hydrothermal system of Solfatara-Pisciarelli. This observation suggests a close relationship between seismic activity and hydrothermal activity, with possible implications for understanding the soil deformation mechanisms.