The 1538 eruption at the Campi Flegrei resurgent caldera: implications for future unrest and eruptive scenarios

Abstract. The recent unrest in the Campi Flegrei caldera, which began several decades ago, poses high risk to a densely populated area due to significant uplift, very shallow earthquakes of intermediate magnitude and the potential for an eruption. Given the high population density, it is crucial, especially for civil defence purposes, to consider realistic scenarios for the evolution of these phenomena, particularly seismicity and potential eruptions. The eruption of 1538, the only historical eruption in the area, provides a valuable basis for understanding how unrest episodes in this caldera may evolve toward an eruption. In this paper, we provide a new historical reconstruction of the precursory phenomena of the 1538 eruption, analysed considering recent volcanological observations and results obtained in the last few decades. This allows us to build a coherent picture of the mechanism and possible evolution of the present unrest, including expected seismicity, ground uplift and eruptions. Our work identifies two main alternative scenarios, providing a robust guideline for civil protection measures and facilitating the development of effective emergency plans in this highly risky area.