Ground uplift and seismic activity at Campi Flegrei caldera (south Italy) during the unrest episodes: an overview

A wide-ranging overview on the ground uplift and seismic activity during the 1969-1972, 1982-1984, and 2005-ongoing unrest episodes at Campi Flegrei caldera is delivered using data reported in literature and those contained in the OV-INGV databases and surveillance reports. In this study, an attempt to correlate the increase of the ground uplift rate and the occurrence of seismic events with M ≥ 1.5 is made also by reporting some general features on the ground deformations and seismic activity of the 1969-1972 and 1982-1984 unrest episodes. The original graphs, created to compare the ground uplift with the seismic activity, highlight that the increment of the seismic activity, both in number but especially in magnitude, occurs when in the presence of an increment of the ground uplift rate. This feature appears to be common to both the large uplift episodes (1969-1972, 1982-1984, and 2005-ongoing) and the mini-uplift ones (e.g. 2000). Based on our observations on the occurrence of the seismic events with M ≥ 3.5, we hypothesise that, following an uplift rate of approximately 5 mm/day for a few days, seismic events with
M ≥ 4.5 may occur. Under such hypothesis, also considering the approximate migration of the epicentres of the seismic events with M ≥ 2.5 of the ongoing unrest, we believe that a reassessment of the seismic hazard for the area of Campi Flegrei could be useful.