The Bradyseism Crisis of 1982 - 1984

The term "bradyseism" comes from the Greek and means "slow movement". This geological phenomenon, typical of the Phlegraean Fields region, manifests itself through the lowering or rising of the ground caused by underground volcanic activity. During the 1980s, this slow but constant movement reached an unprecedented level of activity, causing a series of problems that drew the attention of the international scientific community.

The current bradyseismic crisis situation in the Phlegraean Fields is comparable to that experienced between 1982 and 1984, the last one known chronologically for the frequency and strength of the earthquakes. During that period, around 10,000 earthquakes occurred, with a maximum magnitude of 4.0. By comparison, the earthquake of 27 September 2023 reached a magnitude of 4.2. That crisis led to the evacuation of part of the population of Pozzuoli due to the danger of collapses.

The main difference between the current situation and that of the past is the extent of the ground uplift. In the two-year period 1982-1984, the uplift reached 180 cm in just two years, whereas since 2005, when the uplift started again, it has reached a maximum of 113 cm.

The bradyseismic crisis of 1982 began with an anomaly in ground uplift in the Phlegraean Fields area, a region that hosts a supervolcano. During this crisis, earthquakes occurred as a result of the ground uplift, while during the phases of lowering, tremors were almost absent. The crisis began in earnest in the summer of 1982 and led to a series of significant seismic tremors, culminating in the evacuation of entire areas of Pozzuoli.

The earthquake of 4 September 1983 caused an alarming exodus of the inhabitants of Pozzuoli, who took refuge in temporary camps set up along the Licola coastline. Another earthquake, on 4 October 1983, led to the evacuation of the entire historic centre of Pozzuoli, making an evacuation plan for over 20,000 people necessary.

The crisis continued into 1984, leading to a long seismic swarm and fears of a volcanic eruption similar to that of Monte Nuovo in 1538. Fortunately, however, the crisis eased towards the end of the year and the ground uplift ceased, marking the beginning of a phase of subsidence that would last until 2005.