The analysis of the nuclear explosion effect on the state of the Earth crust, changes in the chemical composition of subterranean waters in places of testing were revealed along with other results. To check this assumption, logging potentiometric measurements of the chemical composition of the aqueous medium were carried out after calibrating non-nuclear explosions. The studies were performed in the former Semipalatinsk testing nuclear proving ground in September-October, 1997. Observations of changing hydrochemical parameters before and after the seismic event were carried out in the hydrogeological well N 4103 during 700 h, and two measurements with a week interval from the moment of the seismic event were performed on the residue of the structural well N 1349s (depth 55 m). A PZ-64 potentiometric sound developed in IEM RAS (Patent No.), which makes it possible to detect changes in pressure (P, atm), temperature (T, C), pH, Eh, and concentrations of Na (pNa), Cl (pCl), and S (pS), was used as the measuring technique.

The measurements performed confirm the assumption about the influence of explosions on the chemical composition of water at a distance to 1-5 km from the epicenter. Jumps of all parameters measured and pressure (to 20 atm) are observed at the moment of explosion.

According to preliminary data, short-time and smoother long-time changes in the parameters measured can be distinguished in the whole time range. The pronounced changes of the first kind were observed a day and ten days after the explosion (Table 1). In the first case, the pH value decreases sharply, and the concentrations of Cl and Na increase. Ten days after the explosion, the pH values increase along with those of Cl and Na.

Long-time changes are expressed as a smooth increase in the pH value and content of Cl during 5 days, while the content of Na has a smooth tendency to decrease. Then these processes change their character to the mirror one: the concentration of Na increases smoothly, and those of Cl and pH decrease (Fig. 1).

Table 1.