| 我国西北地区地壳中的高速夹层 |
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| 引用本文： | 曾融生,滕吉文,阚荣举,张家茹.我国西北地区地壳中的高速夹层[J].地球物理学报,1965,14(2):94-106. |
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| 作者姓名： | 曾融生 滕吉文 阚荣举 张家茹 |
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| 作者单位： | 中国科学院地球物理研究所 |
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| 摘 要： | 在我国西北地区的柴达木盆地东部和甘肃地区,在距离炮点40互100公里处,能够接收到不少能量较强的地壳深界面反射波。另外还发现一种与一般反射波性质不同的波,其视速度特大,视速度随距离的变化不大,而且有较明显的终点;其吋距曲线与一般深界面反射波的时距曲线相交。根据它的特征可以判断地壳中存在具有速度梯度的高速夹层.求得的夹层参数为: 甘肃地区柴达木盆地东部覆盖层厚度 18.8公里 30.5公里覆盖层平均速度 5.5公里/秒 5.3公里/秒夹层厚度 6.0公里 3.2公里夹层速度 7.5-8.5公里/秒 7.5-8.0公里/秒夹层的上下界面均为强反射面,可以产生多次反射波。分別利用相邻两个反射波可以求得各层参数,并能避免射线折射的影响。甘肃地区和柴达木盆地东部的地壳厚度分別为51和52公里。地壳中有高速夹层的存在,可以更好地说明P~*速度分散的原因,而且也能够解释Lg波的传播机制。
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| 关 键 词： | 柴达木盆地东部 多次反射波 甘肃地区 西北地区 夹层厚度 地壳构造 下界面 地壳厚度 高速 速度梯度 |
THE HIGH VELOCITY IMBEDDED LAYER IN THE CRUST OF NORTHWESTERN CHINA |
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| TSENG JUNG-SHENG,TENG CHI-WEN,KAN YUNG-CH AND CHANG CHIA-JU.THE HIGH VELOCITY IMBEDDED LAYER IN THE CRUST OF NORTHWESTERN CHINA[J].Chinese Journal of Geophysics,1965,14(2):94-106. |
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| Authors: | TSENG JUNG-SHENG TENG CHI-WEN KAN YUNG-CH AND CHANG CHIA-JU |
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| Institution: | Institute of Geophysics and Meteorology, Academia Sinica |
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| Abstract: | During the past several years, an investigation of the earth's crust using seismic reflection method has been carried out in Eastern Chai Dam Basin and Kansu. At the distances of 40-100kms from the shot point, ordinary reflections from the deep boundaries in the earth's crust can be identified. Apart from these ordinary reflections, another kind of phases with different properties have been discovered. Their apparent velocities are noticeably greater than that of the ordinary reflections. Their apparent velocities do not change regularly with distances. Their travel time curves intersect with the ordinary reflections and disappear suddenly at a distance of about 80-90 kms from the shot point. From their properties, it can be shown that a high velocity imbedded layer with continuously increasing velocities must exist in the earth's crust of these regions. The calculated parameters of this high velocity layer in these two regions are: Kansu Eastern Chai Darn Basin Total thickness of overburden layers 18.8 kms 30.5 kms Average velocity of overburden layers 5.5 km/sec 5.3 km/sec Thickness of high velocity layer 6.0kms 3.2kms Velocity of high velocity layer 7.5-8.5km/sec 7.5-8.0km/sec Both the upper and lower boundaries of this high velocity layer are shown to have good reflectivity, and are apt to produce multiples. The parameters of succeeding layers in the earth's crust can be calculated from their corresponding reflection arrivals. The depths of Mohorovii discontinuities from the earth's surface are calculated to be 51 and 52 kms in Kansu and Eastern Chai Dam Basin respectively. It is also argued that if this high velocity layer as discovered in Northwestern China exists extensively in the continental earth's crust, the scatterly distributed velocities of P~* and the mechanism of propagation of Lg waves can be more properly explained. |
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