Vertical profiles of fluid velocity and suspended sediment concentration in nearshore   总被引：2，自引：0，他引：2  

Jun ZHENG  Rui-jie LI  Qing.FENG  Sha-sha LU 《国际泥沙研究》2013,28(3):406-412

Based on the power function of velocity and the friction velocity,a velocity profile is obtained.By solving the Schmidt’s diffusion equation,an equilibrium suspended sediment concentration profile is further deduced.The profiles of velocity and suspended sediment concentration agree well with the field data,and the profile of suspended sediment concentration avoids the unreasonableness of the classical Rouse profile such as a zero value at the water surface.According to these profiles,an expression which is easy to use for calculating the suspended sediment transport rate is derived.  相似文献   

High-resolution seismic tomography of the upper crust in the source region of the April 20, 2013 Lushan earthquake and its seismotectonic implications     

Baofeng Tian  Zhiwei Li  Sha Liu  Jiansi Yang 《地震学报(英文版)》2013,(3):213-221

Both P- and S-wave arrivals were collected for imaging upper crustal structures in the source region of the April 20, 2013 Lushan earthquake. High-resolution, three- dimensional P and S velocity models were constructed by travel-time tomography. Moreover, more than 3700 after- shocks of the Lushan earthquake were relocated via a grid search method. The P- and S-wave velocity images of the upper crust show largely similar characters, with high and low velocity anomalies, which mark the presence of sig- nificant lateral and vertical heterogeneity at the source region of the Lushan earthquake. The characteristics of the velocity anomalies also reflect the associated surface geo- logical tectonics in this region. The distributions of high velocity anomalies of both P- and S-waves to 18 km depth are consistent with the distributions of relocated after- shocks, suggesting that most of the ruptures were localized inside the high velocity region. In contrast, low P and S velocities were found in the surrounding regions without aftershocks, especially in the region to the northeast of the Lushan earthquake. For the relocated aftershocks of the Lushan earthquake from this study, we found that mostaftershocks were concentrated in a zone of about 40 km long and 20 km wide, and were located in the hanging wall of Dayi-Mingshan fault. The focal depths of aftershocks increase from the southeast to the northwest region in the direction perpendicular to the fault strike, suggesting that the fault ruptured at an approximate dip angle of 45°. The main depths of the aftershocks in the northwest of the main shock are significantly shallower than expected, revealing the different seismogenic conditions in the source region.  相似文献   

云南通海盆地的浅层速度结构   总被引：3，自引：3，他引：0       下载免费PDF全文

何正勤  胡刚  鲁来玉  张维  叶太兰  沈坤 《地球物理学报》2013,56(11):3819-3827

为了研究通海盆地的地震动场地效应,在强地面运动的数值模拟计算中需要提供该地区的浅层速度结构模型.为此,在通海盆地开展了10 km高分辨率反射地震勘探和30个测点的面波联合勘探工作.综合本次探测结果与褐煤普查中的电测深和钻孔资料,得到了通海盆地的基岩埋深分布图.结果表明,在通海盆地中部,新生界厚度为100~300 m,整体表现出西南厚东北薄的趋势,盆地沉积层厚度变化明显受到小江断裂南段分支断裂的控制.浅层速度随深度分布表现出在深度相同的情况下,盆地边缘的速度高于盆地中部.  相似文献   

Optimizing the design of in situ sediment oxygen demand measurement chambers     

Yun HE  Cheng LIU 《国际泥沙研究》2011,26(2):222-229

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登陆台风卡努(0515)内核区环流结构特征分析   总被引：6，自引：3，他引：3  

魏超时  赵坤  余晖 《大气科学》2011,35(1):68-80

本文采用地基雷达轨迹显示技术(Ground Based Velocity Track Display,简称GBVTD)反演的雷达风场资料,分析台风卡努(0515)在登陆期间近中心环流结构特征.轴对称环流结构分析表明,登陆前卡努轴对称切向风速最大值出现在眼墙区域2 km高度附近,最大风速半径随高度向外倾斜.轴对称径向入流...  相似文献   

A review of the equations used to predict the velocity distribution within a ship’s propeller jet     

W. Lam  G.A. Hamil  Y.C. Song  S. Raghunathan 《Ocean Engineering》2011,38(1):1-10

Predicting the velocity within the ship’s propeller jet is the initial step to investigate the scouring made by the propeller jet. Albertson et al. (1950) suggested the investigation of a submerged jet can be undertaken through observation of the plain water jet from an orifice. The plain water jet investigation of Albertson et al. (1950) was based on the axial momentum theory. This has been the basis of all subsequent work with propeller jets. In reality, the velocity characteristic of a ship’s propeller jet is more complicated than a plain water jet. Fuehrer and Römisch (1977), Blaauw and van de Kaa (1978), Berger et al. (1981), Verhey (1983) and Hamill (1987) have carried out investigations using physical model. Current paper reviews the state-of-art of the equations used to predict the time-averaged axial, tangential and radial components of velocity within the zone of flow establishment and the zone of established flow of a ship’s propeller jet.  相似文献   

Assessment of liquefaction potential based on peak ground motion parameters   总被引：1，自引：0，他引：1  

Rolando P. Orense   《Soil Dynamics and Earthquake Engineering》2005,25(3):225-240

Conventionally, evaluation of liquefaction potential of loose saturated cohesionless deposits as specified in Japanese design codes employs peak ground acceleration (PGA). However, recent large-scale earthquakes in Japan revealed that liquefaction at some sites did not occur even though large PGAs were recorded at or near these sites. As an alternative approach, an evaluation procedure based on peak ground motion parameters, i.e. incorporating both PGA and the peak ground velocity (PGV), is proposed. By performing parametric studies using one-dimensional seismic response analysis and formulating regression models, seismic-induced shear stresses within the deposit are expressed in terms of peak ground motion parameters at the surface, and these are used to calculate the factor of safety against liquefaction. Application to case histories in Japan indicates that the proposed two-parameter equation can adequately account for the occurrence and non-occurrence of liquefaction at various sites as compared to the conventional PGA-based approach. Moreover, analyses of several strong motion records at various sites show that liquefaction may occur when PGA≥150 gal and PGV≥20 kine, indicating that these values can serve as thresholds in assessing the possible occurrence of liquefaction.  相似文献   

苍山地震与新沂台前兆异常   总被引：1，自引：0，他引：1  

李飞  杨冯威 《东北地震研究》2002,18(2):37-41

根据新沂台前兆资料，运用加卸载响应比、差分法对地磁场Z分量进行分析；运用滑动平均对短水准资料进行分析；运用速率法对视电阻率进行分析；结果表明：在苍山地震前，新沂台前兆资料具有良好的中、短期异常，并有进入临震的异常标志。  相似文献   

火山岩地震屏蔽层的转换波叠前时间偏移成像   总被引：6，自引：4，他引：2       下载免费PDF全文

谢飞  常旭  刘伊克 《地球物理学报》2008,51(6):1899-1908

在反射地震转换波资料处理中,准确求取共转换点一直是一个难题,采用叠前时间偏移技术能避免共转换点道集的抽取,而且能够使转换波归位到真正的反射点上,实现准确成像.本文针对火山岩地震屏蔽层的转换波成像问题,通过对转换波共近似转换点道集进行速度分析,建立了转换波叠前时间偏移的初始速度场,通过速度扫描和纵、横波速度比值扫描确定最佳的偏移速度场和纵、横波速度比值,实现了在火山岩高速层覆盖区域的转换波偏移成像.实际资料的成像结果表明,本文采用的近似转换点计算以及转换波叠前时间偏移方法是有效的.  相似文献   

隔震桥梁子结构拟动力实验中加载速率的影响因素研究     

袁涌  熊世树  资道铭  庞军 《震灾防御技术》2008,3(1):37-44

本研究运用DSP高速数字信号处理器的实时信号处理与控制技术,研究了基于速度控制法、OS数值积分法和相应的实验误差控制法的子结构拟动力实验系统。该试验系统对动力加载装置采用速度控制,在加载过程中考虑了加载速率对实验结果的影响,使隔震橡胶支座的速度相关性能在试验中得到充分体现,同时采用OS数值积分法,充分地减少了试验的时滞误差,提高了试验精度。并通过不同加载速率的子结构拟动力实验研究了天然橡胶支座、高阻尼橡胶隔震支座和超高阻尼橡胶隔震支座对桥梁的隔震效果,在对实验结果进行分析对比后,定量地研究了不同的加载速率对隔震桥梁子结构拟动力实验结果的影响。  相似文献