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991.
岩石节理粗糙度系数的分形特征 总被引:5,自引:0,他引:5
岩石节理粗糙度系数JRC是估算节理抗剪强度和变形指标最重要的参数。通过对简易纵剖面仪获取的节理表面轮廓曲线的分形研究,讨论了节理表面轮廓曲线的自相似性和JRC的自相似性,并根据实测统计资料的分析,指出了分形理论研究JRC的适用条件和有效的使用方法。由实测统计资料的JRC尺寸效应自相似性分析,认为JRC尺寸效应具分形结构。本文介绍了一种确定JRC尺寸效应分维数D的方法,由此确定的分维数D具有明确的物理意义。 相似文献
992.
993.
WANG Guixian WANG Xingkui GUO Jiachao Professor Sediment Research Laboratory Dept. of Hydraulic Engineering Tsinghua University Beijing China. Associate Professor Dept. of Hydraulic Engineering Tsinghua University. Assistant Dept. of Hydraulic Engineering Tsinghua University. 《国际泥沙研究》1993,(3)
I. INTRODUCTIONResistance to flow in alluvial streams is one of the crucial problems in fluvial hydraulics. Despite that large amount of studies have been conducted for centuries, no perfectmethod describing and calculating the resistance to flow in alluvial streams is availablehll now. Investigation on bed forms and resistance properties of light--weight bed materials is even more scarce. USWES (1936) has conducted systematic experiments onlight--weight materials in a flume & m long an… 相似文献
994.
应用放射性同位素x射线荧光分析仪测定各种元素含量在许多文献中均有报道。本文主要介绍84A86型轻便x射线荧光分析仪首次在福建省紫金山铜矿区测定粉末样、块状岩心、坑道壁中铜矿的含量及其所取得的经济效益。 相似文献
995.
In this paper we discuss two types of crust models with abnormal density, velocity of wave and certain geometrical structures.
The far-field synthetic seismograms of P and SH wave are calculated by the far-field vertical displacement formulas of P and
SH waves with the double couple point source and the formulas of reflection coefficient, radiation pattern and travelling
time difference derived from the models suggested in the paper. It is shown by the results that the effect of special crust
structures near focus on the far-field seismograms can be ignored if the densities and wave velocity of the special structure
are less than average those of the crust (model I). However the effect should be noticed if the densities and wave velosities
of the structure are large than average those of the crust (modelI). The effect of the special crust structure on the far-field seismograms has not been studied further before. Seismic records
of the Haicheng earthquake and the crust structure in Haicheng region are studied by the calculation method in the paper.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 1993. 相似文献
996.
The phase velocities of Rayleigh waves and the lateral variation of lithospheric structure in Tibetan Plateau 总被引:1,自引:0,他引:1
According to a Sino-U. S. joint project, eleven broadband digital PASSCAL seismometers had been deployed inside the Tibetan
Plateau, of which 7 stations were on the profile from Lhasa to Golmud and other 4 stations situated at Maxin, Yushu, Xigatze
and Linzhi. Dispersions and phase velocities of the Rayleigh surface waves (10s–120s) were obtained on five paths distributed
in the different blocks of Tibetan Plateau. Inversions of the S-wave velocity structures in Songpan-Ganzi block, Qiang-Tang
block, Lhasa block and the faulted rift zone were obtained from the dispersion data. The results show that significant lateral
variation of the S-wave velocity structures among the different blocks exists. The path from Wenquan to Xigatze (abbreviated
as Wndo-Xiga) passes through the rift-zone of Yadong-Anduo. The phase velocities of Rayleigh waves from 10s to 100s on this
path are significantly higher than that on other paths. The calculated mean crustal velocity on this path is 3.8 km/s, much
greater than that on other paths, where mean crustal velocities of 3.4–3.5 km/s are usually observed. Low velocity zones with
different thicknesses and velocities are observed in the middle-lower crust for different paths. Songpan-Ganzi block, located
in the northern part of Tibetan Plateau is characterized by a thinner crust of 65 km thick and a prominent low velocity zone
in the upper mantle. The low velocity zone with a velocity of 4.2 km/s is located at a depth form 115 km to 175 km. While
in other blocks, no low velocity zone in the upper mantle is observed. The value of Sn in Songpan-Ganzi is calculated to be
4.5 km/s, while those in Qiang-Tang and Lhasa blocks are about 4.6 km/s.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 566–573, 1992. 相似文献
997.
The terrestrial noise in the differencial data of geomagnetic total field recorded at 21h in North China was fitted by using
the geomagnetic vector data from Beijing Observatory. The terrestrial noise level and its spatial feature in this region was
discussed. A method, which may be useful for justifying the quality of fitting, was provided in this paper. The analysis indicates
that the terrestrial noise is one of the important noise in tectonomagnetic study. It is shown that the susceptibility effect
is quite small and the orientation effect is the main component in the terrestrial noise in North China. The rough spatial
feature of the magnetic anomaly in crustal substance was infered from the spatial feature of terrestrial noise. The measurement
precision and the source noise level of data at 21h in this region were obtained in the analysis of residual noise.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 441–447, 1993. 相似文献
998.
999.
光滑处理使得单界面成为非均匀薄层,界面反射转变为层反射.为了探讨光滑处理的影响,以平面波作为入射波场,首先利用过渡层反射系数推导了反射信号的理论公式,然后就非均匀薄层下反射系数的计算问题,给出了具体的实现算法,并通过与经典Epstein过渡层反射系数解析结果的对比说明了算法的精度.最后在单界面及其被光滑后界面的对比分析中,得出了几点重要结论:随着光滑次数的增加,反射信号的到时基本保持不变,而反射信号的主频与能量呈减少趋势,其中信号能量在低光滑次数的衰减速率明显大于高光滑次数. 相似文献
1000.
伴随层析成像(Adjoint Tomography)通过求解全波方程来准确模拟地震波在复杂介质中的传播,并利用波形信息来反演地下结构,是新一代的高分辨率成像方法.其中3-D伴随层析成像需要庞大的计算资源,而2-D反演相对更具计算效率.面波和远震体波是研究地壳上地幔速度结构的重要方法,它们对S波速度及Moho面的敏感度不同,通过联合反演,可以得到更为准确的S波速度结构及Moho面.通过两种数据的高度互补性,本文提出基于伴随方法的线性台阵背景噪声面波和远震体波联合成像方法,同时约束台阵下方S波速度结构及Moho面形态.我们将该方法应用到符合华北克拉通岩石圈典型结构特征的理论模型上,测试结果表明联合反演方法优势明显,相比于面波伴随层析成像,能获得更高分辨率的S波速度结构,同时能精准约束Moho面形态.相比于体波伴随层析成像,联合反演能有效压制高频假象,降低波形反演过程中的非线性化程度.本研究有望提供一种更为高效精准的线性台阵成像方法,搭建联合伴随层析成像理论框架,提升岩石圈成像分辨率,并为后续其他类型波形数据的引入提供思路和方法. 相似文献