The seismicity of Campi Flegrei in the contest of the current unrest

Abstract

The knowledge of the dynamic of the Campi Flegrei calderic system is a primary goal to mitigate the volcanic risk in one of the most densely populated volcanic areas in the world. From 1950 to 1990 Campi Flegrei suffered three bradyseismic crises with a total uplift of 4.3 m. After 20 years of subsidence, the uplift started again in 2005 accompanied by a low increment of the seismicity rate. In 2012 an increment in the seismic energy release and a variation in the gas composition of the fumaroles of Solfatara/Pisciarelli (in the central area of the caldera) were recorded. Since then, a slow and progressive increase in phenomena continued until today. We analyzed the Campi Flegrei seismic catalogue from 2000 and the main seismic swarms in order to look for any variation in the seismic parameters and compare them with other geophysical information. A remarkable correlation between earthquake cumulative number, CO/CO2 values and vertical ground deformation is evidenced. Moreover, the focal mechanisms show an agreement with the tensional stress induced by the caldera uplift. Most of the swarms and remaining seismicity delineate a highly fractured volume extending vertically below the Solfatara/Pisciarelli vents, where gases find preferential paths to the surface triggering earthquakes. The main swarms are located below this volume where the presence of a rigid caprock is still debated.The correlation between the seismological, geochemical and geodetic observables can be interpreted in terms of injection of magmatic fluids into the hydrothermal system or its pressurization. The comparison between the geophysical information and the seismicity leads us to interpreted the current unrest in term of a gradual increment in the activity of the wide hydrothermal system whose most evident manifestation is the enlargement of the fumarolic field of Pisciarelli.This contribution was funded by the MIUR project PRIN-2017 WZFT2p “Stochastic forecasting in complex systems” and by the INGV Project LOVE-CF.