A contribution towards the understanding of the “bradyseism” phenomenon at the Campi Flegrei volcanic area (Southern Italy)

Abstract

Following the recent unrest phase occurred at Campi Flegrei Caldera in the last years, the population’s demand for information on the “bradyseism” phenomenon has significantly increased. The bradyseism consists in a slow subsidence or uplift ground movement that always has characterized the dynamics of the Campi Flegrei volcanic area. Generally, seismic activity accompanied ground uplifts whereas no seismic activity occurred during ground subsidence. In order to contribute towards the understanding of this particular phenomenon for the population residing in the Campi Flegrei area, we created an exhibition panel, which shows the general trend of the bradyseism since the year 34 A.D. up to modern times. The central panel shows a graph created by merging information from historical sources, geodetic levelling and GNSS data published in recent papers. The altimetric reference “0” of this panel is that of the average see level referred to the year 1900. To make the exhibition panel more incisive, we insert in the graph copies of vintage prints and postcards of the ruins of a monument located in proximity of the city of Pozzuoli’s harbor: The Macellum, best known as Serapeum. The peculiarity of this ancient Roman market is the presence, at various heights on the three still erected columns, of lithodome holes that are an indication of the sea level in the past. The images of the vintage prints (since about 1730) and of the postcards (since about 1850), well show the Serapeum in the phase of subsidence or ground uplift being its floor flooded with water (below sea level) or dry (above sea level). The vintage prints and postcards, inserted in correspondence of the date when realized, well support the trend in the graph. The exhibition panel was presented at “Notte dei Ricercatori” event (Napoli 29 September 2023) and in occasion of the “Futuro Remoto” event (Napoli 22-27 November 2023), receiving notable public success for the accompanying images that well helped in understanding the bradyseism phenomena.