ABSTRACT

The authors determined the chemical composition of ground water which gushed out in connection with swarm earthquakes in the Matsushiro area (Nagano Pref., Central Japan), from September 1966 to December 1968. This paper shows the variation in the chemical composition of the ground water with time and the remarkable increase in the calcium, chloride and carbon dioxide contents with increasing activity of the swarm earthquakes. A hypothesis on the origin of the waters is also presented.