Volcano-tectonic earthquake statistics for Campi Flegrei monitoring

The knowledge of the dynamic of the Campi Flegrei calderic system is essential to mitigate the volcanic risk in one of the most densely populated volcanic areas in the world. From 1950 to 1985 three bradyseismic crises occurred with a total uplift of almost 3 m (Del Gaudio et al., 2010). After more than 20 years of subsidence, at the end of 2005 the uplift started again accompanied by a low increment in the seismicity rate. In 2012 a further increment in the seismicity rate was observed and a variation in the gas composition of the fumaroles of Solfatara (central area of the caldera) revealed the injection of magmatic fluids into the hydrothermal system (Chiodini et al., 2017). This suggests that the investigation of the seismicity can represent a very useful tool for the risk mitigation. Here we analyze the seismic catalogue of Campi Flegrei (collected by INGV - Osservatorio Vesuviano) to check for any variation of the observed seismicity. This can be eventually associated with geochemical monitored parameters. In addition, we analyzed the most energetic swarms recorded in this period by comparing their locations, waveforms and source mechanisms. We find that occurrence rate, location and b-value change in time. The seismicity occurs in swarms, which, in the last years, tends to became closer but with a smaller number of events. The observed variations are correlated also with the geochemical monitoring parameters suggesting that the uplift process has probably modified the elastic and permeability properties of the shallow part of the crust.