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タイトル: Modes of Secular Vertical Movements of the Earth's Crust : Part 1.
その他のタイトル: 地殻の永年的上下変動の様式について : その1
著者: Mizoe, Megumi
著者(別言語): 溝上, 恵
発行日: 1968年2月10日
出版者: 東京大学地震研究所
掲載誌情報: 東京大学地震研究所彙報. 第45冊第4号, 1968.2.10, pp. 1019-1090
抄録: Modes of secular vertical movements of the earth's crust along the various levelling routes in the different tectonic regions are investigated on the bases of the original materials of the crustal movements obtained through the precise re-levellings carried out in Japan, U.S.A. and U.S.S.R. Numerical filtering mothod is used for the analysis of the modes of movements in space and time correlating them with topographical features, geological patterns and gravity anomalies, the results of which are interpreted from the view-point of geotectonics. The map of secular vertical movements of the earth's crust in Japan is compiled to clarify the two-dimensional modes of movements. Comparative study of modes of movement in various tectonic regions is made by using Fourier's analysis method. The numerical filtering method of sin X/X function is available for classifying the modes of movements into the three groups of horizontal wave-length ranges, e.g. the shorter (<20km), intermediate (20~100km) and the longer (≥100km). The prominent modes of shorter wave-length movements are generally found in subsiding coastal plains and intermountain basins, and are especially intensive in subsiding alluvial plains. In these areas, the amplitude (A half of the peak to trough amplitude is merely noted as "amplitude" in this paper unless otherwise stated.) of these modes of movement generally amounts to 0.5~3.0mm/year in both wave-length ranges of 4~10km and 10~20km. These modes of movement confirmed on the Quaternary plains throughout Japan independently of the geologic difference of the basement under the plains seem to depend upon the physical nature of plains, though they may reflect, of course, the tectonic history of the place. In addition to the movements of natural origin, ground depressions of artificial origin in urban and mining areas include the intensive movements of the shorter wave-length range, too. The movements of the intermediate wave-length range of 20~100km are progressive in the U-etsu geosynclinal zone (the Inner Zone of North-eastern Japan) as manifested by the upheaval of the basement blocks and the subsidence of coastal or intermountain basins. These are closely correlated with geology and gravity anomalies. The amplitudes of the movement on the routes across and along the Inner Zone of NE Japan are 1.0~1.5mm/year and 2.0~4.0mm/year, respectively. The movements of the longer wave-length (≥100km) are found on the various routes in Japan. In the Chugoku district (South-western Honshu), up-warping of the back-bone range exists as a progressive mode of the longer wave-length ranging 100~200km, though the intensity of the movement changes with time. On the other hand, the movement of this wave-length range on the routes across the Inner Zone of NE Japan seems to be progressive with more complicated patterns. Movements of still longer wave-length superposed on the movements of wave-length of 100~200km are also noticed on the cross routes in both NE and SW Japan, though their natures are not quite clear. The general upheaval of the central highland of Honshu Island belongs to the movement of the wave-length more than 100km and seems to be to be progressive with a certain connection with deep tectonics. A map of secular vertical movements of the earth's crust in Japan for the period 1900~1928 is compiled using the results of N. Miyabe (1952). The maximum amplitudes of the secular upheaval and subsidence on the map are as large as 160mm (5.7mm/year) and -160mm/year (-5.7mm/year), respectively. The regional modes of movements shown on the map are interpreted with special concern to geotectonics. Fourier's analysis method is used to investigate the modes of movements on several lines of 300km length along Honshu Island correlating with gravity anomalies. Spectral modes of movements for the wave-length ranging 100~500km on the routes of Japan, U.S.A. and U.S.S.R. represent large velocity gradients of 5×10-8~2×10-7/year in the tectonically active regions, showing remarkable contrast to the small velocity gradients of 10-9~2×10-8/year in the tectonically stable regions.
水準測量によってえられた地殻の永年的な上下変動の様式の地域的な特性を要約すると以下のようになる.A) 日本島孤(本州)における変動の特性
URI: http://hdl.handle.net/2261/12368
ISSN: 00408972


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