Burst-like swarms in the Campi Flegrei caldera accelerating unrest from 2021 to 2024
Flora Giudicepietro, Rosario Avino, Eliana Bellucci Sessa, Andrea Bevilacqua, Manuela Bonano, Stefano Caliro, Francesco Casu, Walter De Cesare, Claudio De Luca, Prospero De Martino, Federico Di Traglia, Mauro Antonio Di Vito, Mario Dolce, Antonietta M. Esposito, Riccardo Lanari, Giovanni Macedonio, Michele Manunta, Carmine Minopoli, Fernando Monterroso, Augusto Neri, Patrizia Ricciolino, Francesco Rufino, Alessandro Santi, Giovanni Scarpato, Pasquale Striano, Anna Tramelli, Giovanni Chiodini
Abstract
Since early 2021, peculiar Volcano-Tectonic (VT) seismic sequences with very short inter-event times have become increasingly frequent and evident in the Campi Flegrei caldera (Italy), which has been experiencing a long-term unrest since 2005. During the same period the ground deformation (uplift), seismicity and gas emission that characterize the current unrest showed an acceleration. Within this type of seismic sequence, we identify burst-like swarms, characterized by inter-event times so short that they are often not easily recognizable. Here we show that these sequences are located in an area encompassing the main hydrothermal field and a zone affected by a geodetic anomaly (a region that uplifts less rapidly than the surroundings), which became evident in 2021. This type of seismicity has been associated with phreatic explosions and critical phases of unrest in other volcanoes and currently characterizes the state of activity of Campi Flegrei caldera. During the long-term unrest of the Campi Flegrei caldera, burst-like seismic swarms are observed and associated with an increase in hydrothermal activity and an anomaly in the ground deformation pattern recorded since 2021.