Shear velocity structure in the Aegean area obtained by inversion of Rayleigh waves   总被引：2，自引：0，他引：2  

E. E. Karagianni  C. B. Papazachos  D. G. Panagiotopoulos  P. Suhadolc  A. Vuan  G. F. Panza 《Geophysical Journal International》2005,160(1):127-143

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The seismic structure of the Saurashtra crust in northwest India and its relationship with the Réunion Plume     

G. Surya Prakasa Rao  H. C. Tewari 《Geophysical Journal International》2005,160(1):319-331

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Shallow seismic trapping structure in the San Jacinto fault zone near Anza, California   总被引：3，自引：0，他引：3  

M. A. Lewis  Z. Peng †  Y. Ben-Zion  F. L. Vernon 《Geophysical Journal International》2005,162(3):867-881

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Transport rate of calcareous sand in unidirectional flow     

DAVID A. SMITH  KWOK FAI CHEUNG 《Sedimentology》2005,52(5):1009-1020

This paper examines the transport of calcareous sand in unidirectional flow and its prediction through existing sediment transport models. A flume experiment of four sand samples collected on Oahu, Hawaii, provides 29 sets of sediment transport data in the bed-form and suspended transport stages. The measured transport data are compared with direct predictions from four energy-based transport models developed for siliceous particles. Corrections for the grain-size, fall velocity, and critical velocity of calcareous sand based on recent research are applied to the models and the results are compared with the direct calculations and measured data. The comparison illustrates the important role particle shape plays in the transport of calcareous sand. All four sediment transport models give consistent predictions and good agreement with the majority of the measured data. Two of the models respond positively to the corrections in both the bed-form and suspended transport stages indicating that such an approach may provide an interim solution for the transport of calcareous sand.  相似文献   

Intrusion and its implication for subsidence: A case from the Baiyun Sag, on the northern margin of the South China Sea   总被引：12，自引：0，他引：12  

Xiaobin Shi  Evgenii Burov  Sylvie Leroy  Xuelin Qiu  Bin Xia 《Tectonophysics》2005,407(1-2):117-134

We develop a series of simple numerical models to explain the anomalous subsidence and deposition phenomena on the northern continental margin of the South China Sea, in particular in the Baiyun Sag. The results suggest that a short-period high rate deposition of around 17 Ma is related to a rapid subsidence event, which may be due to episodic emplacement of a dense intrusion. Necking and gravity models indicate that in the basement of the Baiyun Sag, there is a dense zone that is 100–200 kg/m³ more dense than the surrounding country rock. Considering its high magnetic intensity and regional igneous activity, the dense zone is thought to be related to a phase of basalt intrusion that may have taken place around 17 Ma. Thermal and subsidence models indicate that a hot denser intrusion can cause significant subsidence immediately after the intrusion. The subsidence rate then slows down with cooling, thus becoming consistent with the observed subsidence curves at around 17 Ma. The results also indicate that the lithospheric strength under the Baiyun Sag is negligible, and that the high-velocity layer in the lowermost crust may be not an original part of the pre-rift crust. Instead, it is thought to be underplated intrusion emplaced at around 30 Ma when the continental margin broke up.  相似文献   

Simplified Method for the Assessment of the Stiffness Anisotropy of Rocks at Small Strains     

K. Shin 《Rock Mechanics and Rock Engineering》2005,38(1):41-58

Summary A new, practically applicable method for characterizing the stiffness anisotropy of rocks is presented. The anisotropy of geo-materials is often ignored in engineering applications, with potentially serious ramifications, because of the number of parameters required for characterization. The elastic anisotropy has often been considered to be a function of mathematical symmetry, and the restrictions due to layering, microcracking and granularity of the materials have not been considered in the assessment of the anisotropy. The practicality of the method proposed here is achieved by rationally reducing the number of independent anisotropy parameters, typically 9 for orthotropic anisotropy, to a system of 4 independent parameters through a systematic theoretical and experimental analysis of these structural restrictions. These 4 parameters are shown to be sufficient for describing the anisotropy of some rocks and sands at small strains, and parameter determination by back-analysis is demonstrated to be stable using appropriate measurement systems involving 9 elastic wave velocities even when the directions of anisotropic axes are unknown and the velocity data contains appreciable error.  相似文献   

Modeling the influence of settling velocity on cohesive sediment transport in Tanshui River estuary     

Wen−Cheng Liu 《Environmental Geology》2005,47(4):535-546

Settling velocities of suspended cohesive sediment in estuaries vary over a range of several orders in magnitude. Variations in the suspended sediment concentration are often considered as the principal cause. Turbulence and the suspended sediment concentration, as well as other factors such as salinity, dissolved organic substances, flocculation ability, and the rate of floc growth affect setting velocities. A laterally–averaged finite difference model for hydrodynamics and cohesive sediment transport is developed and applied in the Tanshui River estuary, Taiwan. The model has been calibrated and verified with water surface elevation, longitudinal velocity, salinity, and cohesive sediment measured. The overall performance of the model is in qualitative agreement with the available data. The model is used to investigate the influence of settling velocity on cohesive sediment transport dynamics. The simulation indicates that the turbidity maximum zone is near Kuan–Du. When settling velocities increase the surface cohesive sediment concentration at Kuan–Du station trends to decrease and bottom cohesive sediment concentration increases. Both surface and bottom cohesive sediment concentrations decrease at Taipei Bridge and Pa–Ling Bridge. This implies that suspended sediment advected seaward and deposited. There is consequently a net seaward flux of suspended sediment near surface, and a net landward flux near the bed.  相似文献   

Quantum-thermodynamic treatment of intrinsic anharmonicity; Wallace’s theorem revisited   总被引：1，自引：0，他引：1  

Michel H.G. Jacobs  Bernard H.W.S. de Jong 《Physics and Chemistry of Minerals》2005,32(8-9):614-626

Wallace (in Thermodynamics of crystals, 1972) developed a theorem, rooted in rigid lattice dynamics, which incorporates intrinsic anharmonic effects in solids. The practical application of this theorem in mineral physics is computationally involved and this is the main reason for the theorem not getting the attention it deserves. Because intrinsic anharmonicity is an important issue at the extreme conditions in planetary mantles, we derived a method which removes the computational obstacles in applying this theorem. We extended the theorem to incorporate details of the phonon spectrum and tested our algorithm on forsterite (Mg₂SiO₄). Using a least squares inversion technique applied to all available experimental data, we show that it results in an accurate representation of thermodynamic properties and sound wave velocities of Mg₂SiO₄ in its complete pressure–temperature stability range. We also show that the accuracy of our results is not significantly affected by the use of a different equation of state.  相似文献   

拉萨地体内低速异常成因的探讨--壳内局部熔融的地震层析证据   总被引：2，自引：0，他引：2       下载免费PDF全文

薛光琦  王有学  宿和平 《地球学报》2005,26(5):411-415

青藏高原南部天然地震体波的层析反演图像描绘出拉萨地体内在15～90km深度内低速异常的分布特征。在研究速度结构的基础上，根据熔融程度与纵波波速呈倒数衰减的特性，论证了拉萨地体中低速体的出现与壳内的局部熔融有关。壳内局部熔融则来源于板块俯冲、地壳增厚产生的热而非幔源侵入所造成。同时，也发现了在拉萨以东中下地壳低速体有向东发展的趋势。大面积部分熔融层分布的深度范围约在15～35km处。另外，据藏南地区的SKS波分裂时间延迟很小的特点，推测藏南地幔中可能不存在各向异性，也就是没有足够的热源使各向异性矿物的品格重新定位。这从另一方面佐证了部分熔融仅存在于地壳内而不是地幔中。  相似文献   

滑坡监测的新方法——PMP测量方法     

孙园  李大心 《中国地质灾害与防治学报》2005,16(B12):15-18

文章从国内外滑坡灾害、滑坡灾害的危害及现有滑坡监测方法等方面，论述了滑坡灾害带来的危害性，从而验证了滑坡监测的重要性。但目前现行的滑坡监测手段各有不足之处。针对这种情况，提出了新的测量方法改进其不足之处。位相测量剖面术的测量原理是将LCD投影仪安装于滑坡体上，在滑坡体外稳定地带放置监测系统，CCD光束中心垂直于滑坡体位移方向，监测系统由望远镜头和CCD组成，CCD输出的视频信号进入计算机。通过软件对图像进行处理，绘制出滑坡整体的三维面貌，并计算出滑动的距离，从而有效的观测滑坡体的运动过程。  相似文献