Faculty of Science, Kyoto University
Earthquake Research Institute, University of Tokyo
抄録
Gravity survey at 446 points in an area of about 4300km2 over the Aso and Kuju volcanic region occupying the central part of Kyushu Island of Japan was made by use of Worden and LaCoste and Romberg Geodetic Gravimeters from 1965 to 1966. This survey was carried out as one of the branch projects of ""Combined Aeromagnetic-Gravity Studies of Calderas in Japan"". Bouguer gravity anomalies over this area are characterized by 1) a strong negative anomaly on the Aso caldera, 2) a circular negative anomaly over the Kuju volcano group on the north-eastern side of the Aso caldera, 3) positive anomalies on the south-western flank of somma of the Aso caldera and 4) a narrow belt of relatively high gravity running from Ooita to Kumamoto. The gravity low of the Aso caldera shows characteristic feature of the ""low anomaly type caldera"" as is pointed out by Yokoyama. The Kuju volcanic group also shows the similar feature of ""low anomaly type caldera"", though existence of caldera is not identified from topographical view point. This fact coincides with the geological presumption of buried existence of the Kuju caldera which was once as gigantic as that of the Aso caldera. On the south-western flank of the somma of the Aso caldera, the oldest formation consists of semi-shist (Sambagawa System) and the outcrop of basalt is also being found from geological surveys. The gravity high which reaches 22 mgal at the center coincides with the distribution of basaltic formation. It reveals, therefore, the high density material such as basaltic or metamorphic rocks. A narrow belt of relatively high gravity is remarkably observed. The tectonic line which is geologically presumed to run from Ooita westward to Kumamoto through the Kyushu Island just coincides with this belt.|阿蘇及び九重火山地域を含む,約4300平方キロメートルの面積における重力測定結果について述べる.この研究は,日米科学応力の一環として行われた研究「日本火山カルデラの航空磁気重力測量」の一部をなすものである.
雑誌名
東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
47
号
2
ページ
215 - 255
発行年
1969-07-31
ISSN
00408972
書誌レコードID
AN00162258
フォーマット
application/pdf
日本十進分類法
453
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
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13. Gravity Surveys on Aso and Kuju Volcanic Region, Kyushu District, Japan
ji0472003.pdf
(4.32MB)
