Seismic activity starts to grow slightly again Phlegraean Fields after last week’s brief respite. If the bulletin of the previous week (8-14 December) had recorded the monthly minimum with 34 events, the new update of the INGV Vesuvian Observatory – referring to the week from 15 to 21 December 2025 – marks a reversal of the trend, earthquakes have more than doubled, rising in altitude 76two accomplices seismic swarms distinct. However, the parameter remains unchanged, and at high values bradyseism: the ground continues to rise at the speed of 25 ± 3 mm/monthbringing the total deformation to approximately 21.5cm year to date. Based on the current framework, INGV does not highlight elements that suggest significant short-term developments.
76 earthquakes and two swarms in the last week
In the reference week (15-21 December) they were located 76 earthquakes. However, the maximum magnitude recorded remains limited to 2.0.
Ten tremors occurred during two seismic swarms:
- Swarm of December 15: started at 07:47, recorded 5 earthquakes in the Pozzuoli area with maximum magnitude 1.9.
- Swarm of December 19th: started at 04:42, counted 5 earthquakes with maximum magnitude 2.0.
Among the most significant events of the week, in addition to those of the swarms, we note a tremor from M 1.6 on December 19th (3.50 am) and one from M 1.5 on December 18 at 5.16pm.
Ground deformation continues at 25 mm/month
The data confirms that, starting from October 10, 2025the average monthly uplift velocity in the zone of maximum deformation is stable at approximately 25 ± 3 mm/month.
The cumulative effect of this constant speed brought about the total lift registered at the Rione Terra GNSS station (RITE) a about 21.5cm from January 2025.
The geochemical parameters confirm the long-term warming trend of the hydrothermal system. In particular, the temperature of the main fumarole (BG) in the Solfatara crater shows an increasing trend, with a confirmed average value of approximately 173°C. In the Pisciarelli area, the average temperature is around 94thCshowing a slight decrease compared to past values.
Summary of the INGV bulletin
In summary, the data from the latest bulletin:
- Seismicity: increasing, with 76 earthquakes (maximum magnitude 2.0).
- Swarms: two episodes recorded compared to zero the previous week.
- Bradyseism: Stable speed a 25 ± 3 mm/month with total lift of 2025 to 21.5cm.
- Temperatures: Solfatara stable at high values (~173°C).
