Main constraints for siting monitoring networks devoted to the study of earthquake related hydrogeochemical phenomena in Italy

Criteria and data useful to select test sites in Italy suitable for monitoring earthquake related fluctuations in geofluid natural emissions are given. For this purpose, a catalogue of thermically anomalous natural springs was compiled on the basis of recent and old documentary sources. This catalogue, reporting more than 1200 localities, can be used to identify those sites where gas-fluid emissions are presumably representative of deep water circulation. A catalogue of CO2 gas reservoirs exploited in the past and at present for industrial extraction was also compiled to identify all the areas where strong degassing activity may affect spring sources and generate enhanced water-rock interaction processes. To complete this review, data were also collected on natural springs characterized, on the basis of documentary sources, by "anomalous" behaviour during past earthquakes. An independent constraint to select the most interesting test sites was obtained by the analysis of seismic activity in this century. In this way, a number of sites were identified where it is likely to observe at least one significant earthquake (with magnitude ³ 3.5 within 20 km) during a 3 year monitoring interval. These pieces of information were matched and three areas, respectively located in the Central Apennines, Southern Apennines and Sicily were identified as the most promising test sites for monitoring geofluid emissions as markers of active seismogenic processes.