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顾及起始数据误差影响时单位权中误差的估值 总被引:1,自引:0,他引:1
黄加纳 《武汉大学学报(信息科学版)》1986,(4)
本文推导了在附有条件的间接平差和附有未知数的条件平差两种方法中,顾及起始数据误差影响时,计算单位权中误差估值(?)的公式,并以两个实例说明,平差时应该考虑起始数据误差对(?)的影响。 相似文献
63.
印度与欧亚大陆碰撞构造变形数值分析 总被引:8,自引:0,他引:8
在全面考虑了大陆构造变形三重非线性特征的基础上,用动态有限元法研究了藏东对印度与欧亚大陆碰撞作用的大变形响应。数值模拟结果显示了明显的纵向收缩变形,变形主轴多具有顺时针转动的趋势,但横向位移在总体上并不显著。其最大值正位于红河和鲜水河断裂之间,这一结果论证了印度板块对欧亚大陆的碰撞可能是川滇菱形块体向南东运动的动力来源。红河、鲜水河、昆仑及阿尔金活断层在碰撞作用下发生了顺时针的旋转变形;而且,计算结果模拟出了红河断裂由左旋变为右旋,另3条断裂始终左旋的运动特征 相似文献
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Ian Douglas 《地球表面变化过程与地形》1987,12(5):481-495
The variety of active, exhumed, and buried limestone landforms of northern England, North Wales, and the Isle of Man arises in part from the way in which Dinantian (Lower Carboniferous) sedimentation was affected by a tilt-block basement structure evolved during the closure of the Iapetus Ocean suture to the north, and partly to subsequent plate tectonic movements associated with the closure of the proto-Tethys ocean, the opening of the Atlantic Ocean and the Alpine orogeny. Landforms created during the Dinantian now form important exhumed and buried landscape features. The Permian half-graben structures of the eastern Irish Sea-Cheshire-Worcester Basins account for many of the contrasts between the upland karsts of the Pennines and the lowland karsts of coastal areas. 相似文献
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Abstract: 3–D velocity images of the crust beneath the northern margin of the North China Plate have been constructed using P-wave travel time residuals of the latest earthquakes, with the data supplied by Chinese seismic networks.
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
70.
Masayuki Hyodo Noritaka Aramaki Masayuki Itoh Adrian F.L. Hyde 《Soil Dynamics and Earthquake Engineering》1996,15(5):331-336
Cyclic triaxial tests have been carried out on a skeletal carbonate sand from the west coast of Eire. Results are presented for undrained cyclic shear tests on samples with 80% of relative density consolidated under both isotropic and anisotropic conditions. Failure was defined as a 5% double amplitude cyclic strain and a 5% peak axial strain for stress-reversal and non-reversal stress conditions, respectively. Using this definition the cyclic strength for isotropically consolidated samples was affected by the confining pressure although the angular platey nature of the sand resulted in higher cyclic strengths than for a comparable silica sand. For anisotropically consolidated samples the cyclic strength increased with increasing initial static shear stress while on the other hand the cyclic strength normalised in the usual way with respect to the initial confining pressure decreased as this pressure increased. 相似文献