Groundwater helium content related to the Spitak (Armenia) and Karymski (Russia) earthquakes

The Spitak and Karymsky earthquakes occurred with M = 6.9 in Armenia and in Kamchatka (Russia), respectively. As regards the Spitak earthquake, we ana lysed the groundwater helium content data collected by three Georgian and o ne Armenian measurement sites; as regards the Karymsky earthquake, we analy sed the groundwater helium content data collected by two measurement sites in Kamchatka. The first analysis has pointed out that precursory anomalies appeared in the northern area with respect to the Spitak epicentre; on the contrary, only co-post seismic anomalies were revealed in the southern area . As regards the Karymsky earthquake, no pre-co-post seismic variation in t he groundwater helium content was revealed at both the measurement sites. T he analysis of other hydrogeochemical parameters, collected in these sites, revealed that one site does not show any anomaly; on the contrary, at the other measurement site clear preseimic anomalies appeared in some hydrogeoc hemical parameters. A possible explanation of the quoted results is present ed.