著者

川原谷 浩 安孫子 勤 松葉谷 治 KAWARAYA Hiroshi ABIKO Tsutomu MATSUBAYA Osamu

出版者

秋田大学大学院理工学研究科

雑誌

秋田大学大学院理工学研究科研究報告 = Scientific and technical reports of Graduate School of Engineering Science, Akita University (ISSN:24324108)

巻号頁・発行日

no.37, pp.31-36, 2016

---

At Noboribetsu, Hokkido, hydrogen and oxygen isotopic ratios (δD and δ18O) of precipitation collected in about one month interval were measured from 1979 to 1983. Although the easurement is rather old, it is useful to explain the isotopic characteristics of precipitation in the southern coast area of Hokkaido. δD, δ18O and d value (d=δD-8δ18O) of annual mean precipitation at Noboribetsu are -60‰, -8.9‰ and 11, respectively. The relationships of δD and δ18O show obvious difference between winter season and spring to fall season, and the d value is 21 in the winter season and higherthan the value of 9 in the spring to fall season, as like as the characteristics observed at Akita, Ryori and Rokkasho in thenorthern Honshu. The relationship in the spring to fall season is similar to those at Akita, Ryori and Rokkasho, and thisimplies that the Noboribetsu precipitation in the spring to fall season may be brought by the process similar to those in theabove three localities. On the contrary, the relationship in the winter season is different from those of above three localitiesimplying some difference in precipitation process. However, the d value of annual mean precipitation at Noboribetsu isthe same as Ryori located at the Pacific Ocean coast of northern Honshu, because the precipitation amount in the winterseason is fairly smaller than that in the spring to fall season at Noboribetsu as like as Ryori. The isotopic ratios of smallrevers in the Noboribetsu area are similar to those of several small rivers at the southern coast of Hokkaido, and thisimplies that the isotopic ratios of precipitation at the southern coast of Hokkaido have characteristics similar to those atNoboribetsu.Records monitoring the airflow's temperature and absolute humidity revealed a periodic nature of the variations. Suchseasonal changes had an approximate cycle length of six months and can be modeled by a harmonic vibration equation. The dewcondensation observed at the rock surface can be explained by the calculation results based on the measured values. Theconstraints of equation (6) are practically negligible at a Hyakumeishi level, which was apparent from the induction of theproposed theoretical formula. The seasonal thermal variations of the environment and the dew generation mechanism can beattributed to heat balance in the entire mining area. Finally, the primary results of this study are considered to be fundamentaldata to the case of variously utilized underground spaces.