山崎断層の塩田温泉における近年の水質・水温変化

Abstract

We have observed Cl^- concentration in spring water for the research for earthquake prediction since November, 1991. The study area is located in Shiota district, Hyogo prefecture, which is known as the Yamasaki Fault zone. Water samples are collected every day in principle. In this study, we paid attention to the short-term changes. To eliminate long-term fluctuation, we took the first order differential value of the time series of Cl^- concentration. As a result, remarkable changes in Cl^- concentration were recognized three times during the observation period. Two of them were probably caused by the plumbing.However the rest was attributable to neither artificial nor weather effects. As the electrical conductivity of spring water at Shiota and the water pressure at Yoshioka hot spring in Tottori prefecture changed simultaneously just after the East-Off Hokkaido earthquake (M 8.1), we conclude that the Cl^- concentration change was caused by the East-Off Hokkaido earthquake.