3.淺間火山の精密水準測量結果

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It is well known that the eruption of a volcano is often attended by the swelling and subsidence of the volcano itself as well as of the region surrounding it. In order to study both the spatial and time distribution of such crustal deformations related to eruptions, precise levelling was clone this summer at volcano Asama, one of the most active in Japan. The new line of levels, which is shown in Fig.1, which begins from bench mark No.551 previously established at Miyota, goes up the western slope of the volcano, and after passing arround the southern brink of the crater at the summit, descends the eastern slope down to the Asama Volcano Observatory, ending at bench mark No.547 previously established at Kutukake, the whole forming a loop 48km long. The observations were made by Mr. Tiyozo Urano of the Japanese Land Survey. A Zeiss geodetic level was used. The observation conditions were extremely severe owing to the abnormal bad weather this summer, to the long and steep slopes of the mountain, and also to the frequent violent eruptions that occurred during the observations. Thanks to the ability of the observer, the closing error was surprisingly small. The results are given in Table I, This being the first observation, naturally crustal deformations cannot yet be known, but upon comparing these results with the heights given in the topographic map of 1912, we may conclude that there has been no crustal deformations exceeding 5m, except for the central cone, the eastern brink of the crater of which seems to have risen about 18m. Undoubtedly, this elevation is partly due to the volcanic bombs and ashes that have accumulated since 1912, although there are evidences that true upheavals of the central cone take place during active periods of the volcano.
東京帝国大学地震研究所,Earthquake Research Institute, Tokyo Imperial University,地震研究所の論文
1936-03-20

3.淺間火山の精密水準測量結果

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東京帝国大学地震研究所,Earthquake Research Institute, Tokyo Imperial University,地震研究所 | 論文

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