GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 Cross-correlation between seismic events, rain and CO 2 anomalies in spring waters: insights from geochemical monitoring in Northern Tuscany, Italy L. Pierotti 1 , C. Fidani 2,3 , G. Facca 1 , F. Gherardi 1 1 Istituto di Geoscienze e Georisorse CNR, Pisa, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy 3 Central Italy Electromagnetic Network, Fermo, Italy Located in Garfagnana Valley, northern Tuscany, Italy, the Gallicano thermomineral spring (temperature = 23.4 - 25.2 °C, salinity = 2.4 - 4.2 g/l) is considered a suitable site to study correlations between seismic events and CO 2 anomalies (Pierotti et al., 2022). Under the auspices of the Regional Government of Tuscany, and the technical and scientific management of CNR-IGG-Pisa, since 2003 this site is monitored for hydrogeochemical precursors of earthquakes by means of a continuous automatic monitoring station (Cioni et al., 2007). Garfagnana Valley is one of the areas with the highest seismic risk of Tuscany. The region was shaken by a Mw 6.53 earthquake in 1920 (Garfagnana earthquake; Rovida et al., 2022), and is characterized by a quite high Peak Ground Acceleration value (0.175g<PGA<0.200g, Stucchi et al., 2011). The Gallicano thermomineral spring is fed by a major, fractured carbonate aquifer. After long underground circulation paths, thermal waters emerge in correspondence with neotectonic structures belonging to one of the seismogenic structures identified by the DISS Working group of INGV (2021). These conditions reflect the essential criteria required for the successful monitoring of preseismic gas-geochemical signals (Martinelli and Albarello, 1997; Weinlich et al., 2006; King et al. 2006; Martinelli and Tamburello, 2018). Temperature (T), pH, electrical conductivity (EC), redox potential (ORP), and CO 2 dissolved concentrations are simultaneously measured every 5 minutes. A data logger is used to sends the recorded data, by router GPRS, to the CNR–IGG elaboration center in Pisa. The elaboration of long-term time series acquired by the automatic station allowed for an accurate definition of the geochemical background, and the recognition of CO 2 anomalies in concomitance with the most energetic seismic event (e.g. 21 June 2013, Alpi Apuane earthquake Mw = 5.1) occurred during the last years (Pierotti et al., 2015).