Challenge to Prediction of Crustal Deformation by geochemical compositions of Non-volcanic Hot spring water, Shikoku, Japan

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K13893
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Ehime University
• Principal Investigator: Hori Rie 愛媛大学, 理工学研究科(理学系), 教授 (30263924)
• Co-Investigator(Kenkyū-buntansha): 山本 明彦 愛媛大学, 理工学研究科(理学系), 教授 (80191386)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 道後温泉 / 東道後温泉 / pH / 潮汐振動 / 地殻変動

Outline of Final Research Achievements

We have conducted to study secular changes of pH value and spring temperature of hot spring water from Dogo and Higashi Dogo Hot springs, which are famous and old non-volcanic hot springs in western Shikoku, Japan, to clarify whether the geochemical composition of hot spring water is changed due to crustal deformation and/or earthquake activity. Through this research, the following results were obtained. (1) The pH value of these hot springs shows a short-term fluctuation of approximate one day, while the long-term value decreases and rises every few months. (2) The analyses such as FFT and other methods revealed that there is a strong tidal response to the change of pH value of Dogo and Higashi Dogo hot spring water examined. We conclude that the pH value of hot spring water can be used as a sensor that is changing in response to crustal movements, however it is necessary to search the critical mechanism in the future.

Free Research Field

地質学、地球環境学

Academic Significance and Societal Importance of the Research Achievements

本研究成果によって、西南日本の非火山性温泉水の化学組成地殻にかかる応力によって変化している事実を初めて証明した学術的意義は大きい。温泉水のpH 値は、おおまかに温泉水の組成変化を代表していると判断され、且つ簡便に測定出来る事から、簡便な地殻変動検出法として、非火山性の温泉水におけるpH値のモニタリングが使える可能性を示唆した社会的意義は大きい。この様なモニタリング井を地域別に設置し、ネットワーク化すれば、安価で感度の良い地殻変動予測が可能となる事を本研究は示した。