Automated Geochemical Monitoring Systems Laboratory

The study of earthquake precursors has attracted the scientific community's interest since the 1970s (Wakita et al., 1975; King, 1986, 1989; Thomas, 1988). The development of methods and instruments for geochemical monitoring accelerated after the 1966 Tashkent earthquake, which coincided with the first well-documented radon anomaly (Ulomov and Mavashev, 1967). However, the problem of earthquake forecasting is still far from being solved, and the usefulness of currently used monitoring methods and devices is still a matter of debate and active research (see, e.g., Albarello, 2015; Biagi and Tramutoli, 2015).
t is now universally recognized by most of the scientific community working in this field of research that collecting reliable time series data (validated using standardized procedures) with extended time coverage (so that the background values ​​of each parameter are precisely defined) represents an essential step in obtaining tangible results in earthquake forecasting. The operational protocol for geochemical monitoring involves the measurement of multiple independent parameters. It is believed that cross-interpretation of data series relating to these independent parameters allows for a better understanding of the geodynamic processes occurring at depth in the preparatory stages of an earthquake (Toutain & Baubron, 1999). Since variations in the monitored chemical-physical parameters can occur even over relatively short time intervals, even on the order of a few hours, it is necessary for geochemical monitoring to be carried out continuously and after appropriate calibration of the sampling time step.
The choice of parameters to be measured is generally guided by current knowledge of the possible physical and mechanical processes that occur at depth in the phases preceding an earthquake, that is, during the accumulation phase of seismic energy. It is believed that, as a consequence of the variation in permeability of the system, associated with the accumulation of seismic energy, variations in the concentration of He, Ar, Rn, H₂, CO₂, CH₄, H₂S in the gases in the soil and in deep waters, or mixing phenomena between waters of different origins due to the breaking of impermeable barriers, variations in temperature and/or salinity should be expected (e.g. Scholz et al., 1973; Thomas, 1988; Muir-Wood and King, 1993; Rojstaczer et al., 1995; Roeloffs, 1998; Brodsky et al., 2003; Wang et al., 2004; Elkhoury et al., 2006; Wang and Chia, 2008; Doglioni et al., 2014).
The availability of specific, high-precision instrumentation is another factor that can influence the choice of parameters to monitor.
Based on these general criteria, and as part of a collaborative protocol between the Tuscany Region's Seismic Prevention Sector and the Institute of Geosciences and Earth Resources of the CNR in Pisa, a network of continuous automatic monitoring stations has been established in Tuscany since 2002 to study possible relationships between changes in water chemistry and seismic events. Regional Law No. 58 of October 16, 2009, defines the regulatory framework with which the Tuscany Region regulates the "Rules for the prevention and reduction of seismic risk." This law establishes that, together with the other continuous monitoring networks active in the region (seismic network, accelerometric network, and geodetic network), the Tuscan geochemical network constitutes the primary tool for studying, analyzing, and researching seismic risk.

uscany's geochemical monitoring network currently consists of six operational stations installed in the region's highest seismic risk areas: Lunigiana, Garfagnana, Mugello, Alta Valtiberina, and the Amiata district. The selected sites are as follows:

• Equi Terme, in the province of Massa (thermal mineral spring that feeds the swimming pool of a local spa);
• Gallicano, in the province of Lucca (private thermal mineral spring);
• Vicchio, in the province of Florence (Postignana source)
• Caprese Michelangelo, in the province of Arezzo (Armenian source);
• Bagnore, in the province of Grosseto (public spring);
• Bagno Vignoni, in the province of Siena (thermal well, used to feed the pools of a local spa).