The Pollino 2012 seismic sequence: clues from continuous radon monitoring
Abstract. The 2012 Pollino (Calabria, Italy) seismic sequence, culminating in the Mw 5.2 earthquake of October 25, 2012, is investigated exploiting data collected during a long term continuous radon monitoring experiment performed in the epicentral area from late 2011 to the end of 2014. We analyze data collected both using a phenomenological approach based on quantitative evidence and a purely numerical analysis including: i) correlation and cross-correlation investigations; ii) an original approach aimed to limit the impact of meteorological parameters variations on the interpretation of measured radon levels; iii) a change point analysis; iv) the implementation of an original detection algorithm aimed to highlight the connections between radon emission variations and major seismic events occurrence. Results from both approaches suggest that radon monitoring stations can be subject to massive site effects, especially regarding rainfall, making data interpretation harder. The availability of long term continuous measurements is crucial to precisely assess those effects. Nevertheless, statistical analysis shows a viable approach for quantitatively relating radon emanation variations to seismic energy release. Although much work is still needed to make radon timeseries analysis a robust complement to traditional seismological tools, this work has identified a characteristic variation in radon exhalation during the preparation process of large earthquakes.