Multivariate approach to evaluate the relationship among geophysical and geochemical variables during an unrest period at Campi Flegrei caldera (Italy)

Campi Flegrei is a caldera in Southern Italy, which has manifested signs of significant unrest in the last years. Indeed, during volcanic crises, the ground of Campi Flegrei caldera begin to grow steadily, the earthquake swarms become more common and strong variations in the chemical composition of fumaroles are observed. In the Campi Flegrei volcanic area there is a spread ground deformation monitoring network. In the years 1983–1985 the bradiseism showed an increasing trend of ground uplift with a fairly fast velocity. In the following years (1986–2014) the phenomenon tends to decrease: the earthquakes number is near to zero, the vertical ground displacement decreases, the fumaroles modify the gas emissions, the soil temperature decreases. The main object of this study is to evaluate, by means of variables comparison, in a counterclockwise periods, the relationship among geochemical data of fumaroles, earthquakes and ground deformations, to discover which variables can be considered signals (geochemical indicator) of the bradyseismic events during an unrest period.