The Continuous Geochemical Observation of Self Spouting Hot Spring at Moriyama, Shiga Prefecture, Japan

Abstract

Between July 1985 and December 1986 we measured electrical conductivity, water-temperatures at different depths, and flow rate of the water of Moriyama hot spring in Shiga Prefecture. At the estuary of the old Yasu River near the eastern side of Biwako-Ohashi the observation well was drilled up to 1000m depth. Continuous measurements were also made of the chemical compositions of the bubble gas emanated from the hot spring. These data were carefully compared with the water level data of Lake Biwa and the meteoric factors, to check any possible relationship. During the observation period, the flow rate, the water-temperatures and the chemical compositions of the bubble gas anomalously changed twice. The first one can be the precursor to the earthquake of M5.0, which occurred on October 3, 1985 near the Hanaore fault. However, the second one is considered to be caused by the local heavy rainfall on July 22, 1986.