Hydrogeochemical seismic precursors: pilot study for future hydrogeochemical networks

The aim of this thesis is to illustrate the importance of establishing a method of investigation of seismic precursors based on the investigation of possible relationships between groundwater and earthquakes, through hydrogeological, hydrogeochemical and seismic monitoring of the territory under consideration. This will be done through a detailed and systematic study of hydrogeological and hydrogeochemical factors that can be potentially influenced by seismic activity, such as: piezometric levels, temperature, electrical conductivity, chemical composition of groundwater and dissolved gases in solution. The analysis of these factors will allow to verify the existence and the modalities of manifestation of a cause / effect relationship between the hydrogeological, hydrogeochemical and seismic signals. The objective of this PhD project is therefore the study of potential geochemical precursors that will allow the short-term forecast (from days to months) of seismic phenomena of medium-high magnitude (M ≥ 5.0) in order to initiate an effective preventive action. In particular, through this study, I want to highlight the importance of collecting data from a network of monitoring stations spread over a seismic territory and for a long time, with the construction of a national hydrogeochemical monitoring network. The advances in identifying the earthquakes hydrogeochemical precursors depends on the systematic and patient acquisition of long-term multiparametric data set. Long records are therefore essential to identify precursor signals of earthquake responses, especially in regions with abundant seismicity. Well-developed documentation is required to assess the uniqueness and statistical significance of possible precursor signals and to identify and screen out meteorological and seasonal signals. The solid statistical significance of the results therefore depends on the length of the time series, that is the observations of more than one seismic event and the multiparametric nature of the recorded data (Ingebritsen and Manga, 2014). The aim of this PhD project is therefore the better understanding of seismic precursors of hydrogeochemical nature and the related processes to facilitate the understanding of site-specific phenomena and their possible applicability to other sites or their general and global value.