Abstract

The seismogenetically active area of the Sele valley is characterized by a series of hot springs due to the peculiar hydrogeological structures of the area. Its low- and medium-enthalpy waters were geochemically sampled both before the earthquake of 23.11.80 (magnitude 6.8) in the Campania-Lucania Appennines, during earthquakes, and later, revealing correlations between geochemical parameters and seismic activity. Considerable variations in flow, emission temperatures, total salinity, increased gas activity and, in some cases, the hydrogen isotope ratio, were recorded throughout the area during the seismic period. In particular, the waters of Contursi Bagni rose in temperature by 10 degrees C, and at all water sampling points NH <sub>4</sub> contents more than 50 times higher than preearth-quake values were measured. At some sampling points, NH <sub>4</sub> contents were only recorded during seismic events of magnitude >4. Lastly, the high energy produced in the deep system, perhaps in a nonuniform way, probably triggered a mechanism of decomposition and reduction of the water, with the production of H <sub>2</sub> , before and during the earthquake. However, changes only took place over a relatively short period of time, indicating that the hydrogeological situation of the area was not profoundly modified by the earthquake, but that only temporary changes occurred, due to the main seismic events of November 1980-December 1981. Of particular interest among the examined parameters are emission temperatures and piezometric level which may represent useful markers for earthquake prediction in this area. Detailed studies in the period 1988-1990 showed that the hydrogeological conditions existing before 23.11.80 have been restored and also revealed the presence of numerous local aquifers at various piezometric levels, the waters of which are only slightly mineralized. The hydrogeological picture of the area could thus be completed.

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