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タイトル: Geomagnetic Studies of Volcano Mihara. The 3rd paper. : Magnetic Survey and Continuous Observation of Changes in Geomagnetic Declination.
その他のタイトル: 三原山の地球磁氣學的研究 第3報 : 地磁氣三成分測量および偏角變化の連續觀測
著者: 力武, 常次
横山, 泉
岡田, 惇
菱山, よね子
著者(別言語): RIKITAKE, Tsuneji
OKADA, Atsushi
発行日: 1951年12月15日
出版者: 東京大学地震研究所
掲載誌情報: 東京大學地震研究所彙報. 第29冊第4号, 1951.12.15, pp. 583-604
抄録: Conducting surveys over Ooshima Island with a G. S. I. type magnetometer, the writers constructed magnetic charts of three components more complete than those ever obtained, the anomaly in the earth's magnetic field thus made clear being ascribed to the magnetization of Volcano Mihara as is the case in other volcanoes. A comparison of the observed values to those of the 1936 survey was made at the three stations and a local anomalous change of order of 100 gammas was found out though its distribution was not clear. Meanwhile, the writers set up a temporary station at the western skirt of the volcano, about 4 km distant from the crater, where changes in geomagnetic declination has been continuously recorded with a variometer since April this year. An anomalous eastward change in the declination of an order of 5 minutes of arc occurred during the period from the beginning of April to the end of May, while the activity of the volcano which continued from February became weaker during the period. And the westerly declination turned to increase slightly before the activity in June. These changes were also confirmed by the absolute measurements made just before the cave in which the changes were recorded. Although we have not yet obtained sufficient data to discuss the relation between anomalous change in geomagnetism and volcanic activity, it will be possible to get a more comprehensive relation by repeating the magnetic survey and continuing the observation with the variometer. In summary, the writers wishes to express their appreciations to Professor H. Tsuya, Professor T. Hagiwara and Dr. T. Nagata for their helpful advices. The G.S.I. type magnetometer became available through the courtesy of the Geographical Survey Institute, and the writers'hearty thanks are especially due to Mr. I. Tsubokawa of the Institute. Dr. S. Imamiti of the Kakioka Magnetic Observatory and Mr. S. Imai of the Hydrographic Department placed magnetic data at the writers'disposal, to whom the writers'cordial thanks are also due. In the course of the field-observation, Mr. T. Masaka of the Nomashi Village and Mr. T. Yanai of the Nomashi primary school assisted the writers kindly. The writers wish to express their sincere thanks to them. A part of this study was done with the financial aid of the research grant given to one of the writers from the Department of Education, and the writers wish to express many thanks for the grant received.
URI: http://hdl.handle.net/2261/11706
ISSN: 00408972


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