Conclusions on the possible variations of chemical and isotopic composition of groundwater systems in response to changed hydrodynamic conditions (based on investigations of deep groundwater systems and thermal-mineral waters and brines in tectonic active areas)

To establish an observation network of possible parameters to be used as precursors of earthquakes or volcanic eruptions it is necessary first to understand the natural conditions of a given groundwater system and the possible variations of groundwater chemistry and isotopic composition. In the presented study three sites within tectonic active areas in Western Turkey were discussed and compared with the situation of the deep groundwaters in Northern Switzerland. (author). 35 refs, 19 figs