SEISMIC EVENTS

In 2025, seismicity in Italy did not reach high magnitudes, in fact, of the 1,768 events of magnitude equal to or greater than 2 recorded by the INGV National Seismic Network (Figure 1), the most energetic event was of Magnitude Mw 4.8, which occurred at sea in front of the Gargano coast, without causing damage. However, the sequence of earthquakes that is affecting the Campi Flegrei area continued, with the release of more energy than last year. In fact, two events reached Md 4.6, a consequence of the persistence of the uplift phenomenon that is affecting the Phlegraean area. Unfortunately, these events are causing localized damage to the building stock, with falling cornices, rubble, false ceilings, but also structural damage, with the consequent need to evacuate the affected homes, and therefore inconvenience for the population. Overall, the events of magnitude equal to or greater than 4, which occurred in Italy and across the border up to a distance of 100 km were 20 (Table 1). The hypocentral depths were between 2.3 kilometers and 184 kilometers, although most fall within the first 30 km, where crustal earthquakes are generally located. The most superficial earthquakes were recorded in the volcanic area of the Campi Flegrei, while the deepest ones in the southern Tyrrhenian Sea. The intensification of the seismic sequence at the Campi Flegrei is due to the continuation of the caldera uplift phase, which began in 2005, with acceleration phases in 2025. In some periods, the uplift speed reached values above 30 mm/month, and then returned to lower values, generally around 20 mm/month or lower. Since 2018, the uplift has been accompanied by a gradual increase in seismic activity, both in the number of earthquakes and in their magnitude. During 2023, a new increase in the frequency of earthquakes was recorded, which continued in 2024 and intensified in 2025. The intensification of the bradyseismic crisis has made it necessary to strengthen the monitoring activities of the volcano and the strengthening of the prevention actions carried out by the Civil Protection System. The Major Risks Commission, convened several times, has noted that the set of scientific results reinforces the evidence of the presence of magma at depth as the trigger of the current bradyseismic crisis. However, in the absence of evidence of magmatic rise, it was decided to confirm "the yellow alert level for volcanic risk". It was therefore considered appropriate that both the monitoring activities by the Competence Centres and the prevention activities by the various components of the National Service be further intensified and prepared for the possible need to raise the alert level. Recent research has made it possible to reconstruct a subsurface model composed of a first surface layer of 2 kilometers that acts as a natural seal, an intermediate reservoir between 2 and 4 kilometers deep, containing a mixture of water, steam and pressurized carbon dioxide that exerts strong thrusts on the overlying rocks, and finally a stable deep carbonate basement (De Landro et al., 2025). The study confirmed the absence of magma in the first 4.5 kilometers of depth. As far as seismicity on a national scale is concerned, since there have been no earthquakes of magnitude 6 and higher, which are generally associated with long sequences of replications, in 2025, as in previous years up to and including 2018, the number of events with a magnitude greater than or equal to 2 is lower than, for example, in 2016 (Figure 2). As can be seen, the years with the highest number of earthquakes are those in which the paroxysmal events of Molise (2002), L'Aquila (2009), Emilia-Romagna (2012) and Central Italy (2016) occurred, which were followed by numerous aftershocks. As mentioned, in Central Italy a lot of low-magnitude seismicity is still due to the tail end of the 2016-2017 sequence. Furthermore, it can be observed that the number of earthquakes in 2016 is more than double those of both 2009 and 2012 and about three times that of 2002, demonstrating that the energy release of the Central Italy sequence was far higher than that of the other sequences. In fact, in 2016, unlike the other three years, there was also a mainshock of Magnitude 6.5, preceded by another event of Magnitude 6 (there are 4 events of Magnitude greater than or equal to 5.5; Figure 3). The number of events of Magnitude equal to or greater than 4 in 2025 is significantly lower than in the years in which the most destructive sequences occurred: in 2016 there were 66 events of Magnitude equal to or greater than 4 and in 2012 55 events. It can be seen that the years in which there were more events of Magnitude greater than or equal to 4 are also those in which there were more events of Magnitude greater than or equal to 5.5 (4 in 2016 and 2 in 2012). Figures 2 and 3 show that from 2002 to 2016 destructive events occurred from once every 7 years to once every 3 years. Instead, more than 9 years have now passed since the last destructive event in 2016. Furthermore, looking at the past, our seismic history tells of periods in which, unfortunately, there have been series of destructive earthquakes even with an annual frequency such as, for example, the series of 14 strong earthquakes that occurred from 1688 to 1706, or the series of 6 strong earthquakes that occurred from 1915 to 1920. To prepare good prevention policies and to be ready to face the next emergency, it is necessary to consider these seismic characteristics of our country.