Improving the statistical correlations between low seismic events and CO2 variations subtracting the rain contribution

A correlation between low seismic activity and CO₂ measurements variations was observed at the Gallicano thermomineral spring, Tuscany, Italy, where an automatic monitoring multiparametric geochemical station is operative since 2003 (Pierotti et al., 2015). The above-mentioned correlation reported a time delay of about 2 days of small earthquakes with respect to CO₂ anomalies. Starting from this correlation a conditional probability of earthquake occurrence given the CO₂ anomaly detection was calculated, with a probability gain near 4 (Pierotti et al., 2022).  A statistical correlation was also calculated between rain events and CO₂ anomalies which was observed for rain vents ahead CO₂ anomalies of one days. This permitted to distinguish CO₂ anomalies due to meteorological versus tectonic activities.  Following this distinction, and subtracting the rain contribution to the CO₂ variations, a new correlation was observed between small earthquakes and CO₂ anomalies which confirmed the past results whit a better performance. The new correlation peak is better defined and concentrated in the time lag of 2 days. The p-values of both earthquake and rain to CO₂ correlations were calculated. The correspondent probability gain in an earthquake forecasting experiment, taking into account the rain events, increased from less than 4 to 4.5. 

     

 

Fidani, C. (2021). West Pacific Earthquake Forecasting Using NOAA Electron Bursts With Independent L-Shells and Ground-Based Magnetic Correlations. Front. Earth Sci. 9:673105.

Pierotti, L., Botti, F., D’Intinosante, V., Facca, G., Gherardi, F. (2015). Anomalous CO₂ content in the Gallicano thermo-mineral spring (Serchio Valley, Italy) before the 21 June 2013, Alpi Apuane earthquake (M= 5.2). Physics and Chemistry of the Earth, Parts A/B/C, 85, 131-140.

Pierotti, L., Fidani C., Facca, G., Gherardi, F. (2022). Local earthquake conditional probability based on long term CO₂ measurements. In 40^st GNGTS National Conference, Trieste, 27 - 29 June 2022.