著者

島 坦 野村 文生

出版者

信州大学工学部

雑誌

信州大学工学部紀要 (ISSN:00373818)

巻号頁・発行日

no.31, pp.87-103, 1971-12

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The analysis was made of the microtremors which were observed at 13 stations in the area surrounding the Takabayama tunnel destroyed by the landslide in January, 1970. The predominant period of microtremors is determined from the spectra, which is used to illustrate the dynamic behavior of underground structure. As given in Table 1, the predominant period of about 0.3 to 0.5 sec. estimated in the shorter period range agrees to that generally observed in the mountains overlaying soft soil. Moreover, another predominant period is found to be about 1.0 to 1.2 sec. in the longer period range of the same spectra. From the correlation of the two predominant periods at each station shown in Fig. 4, it may be considered that the periods of about 0.3~0.5 sec. and about 1.0~1.2 sec. are corresponding to the first and the second mode oscillations in the underground structure respectively. The relative variation of spectral amplitude with the location of observation is discussed mainly for the two predominant periods, and is explained to be caused by the effect of viscosity in the superficial layer on the lower medium. It seems that the coefficient of viscosity varies from about 5 × 10v to 5 × 10v CGS on the boundary of the landslide area, the value in the moutain range being smaller than in the plain.

著者

森本 弥三八

出版者

信州大学工学部

雑誌

信州大学紀要 (ISSN:05598575)

巻号頁・発行日

no.6, pp.工学部157-170, 1956-12

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The radioactive intensity of the rain water which fell on Nagano-District from May 21,1954, to October 31,1956, was measured with the Radiation Counter (Model 32), manufactured at the Scientific Research Institute, LTD., Tokyo, Japan. In order that the measurements were to be carried out accurately, the Geiger-Muller counter tubes used in the measurements had been examined carefully and their characteristics were studied in conformity with the curves representing the relation between the applied voltage and counts per minute of the radiation-ray. The results of the measurements show that the radioactive intensity of the rain water in Nagano-District considerably increased at certain periods of time after the explosion experiments on the nuclear-missiles were made on the coral-reeves in the South Pacific Ocean by U. S. A. and in Siberia or its vicinity by U. S. S. R.. From the manner of the radioactive decay, it can be concluded that the intensely increased radioactivity was not due to the natural source, but to the artificial one. This paper is attached by numerical data on the measurements of the radioactive intensity of the rain water in Nagano-District.