Discussion on Deep Tectonic Background of Moderately Strong Earthquake in Anhui Province and Its Neighboring Areas Using Results of Seismic Tomography     

Zhang Jie 《中国地震研究》2006,20(2):138-147

INTRODUCTIONThe studied areaislocated mostlyinthe southeastern part of the North Chinafault block provinceat 28°~39°N, 112°~124°E, where the geologic tectonics is complex with frequent historicalmoderate-strong earthquakes .The 3Dvelocity images derived fromseismic tomography have enrichedthe knowledge about the deep structures of the crust and the upper mantle ,and by combining thespatial distribution of seismicity patterns ,we canfurther studythe relations of velocitystructure toth…  相似文献   

Experimental study on the effects of artificial bed roughness on turbidity currents over abrupt bed slope change     

《国际泥沙研究》2020,35(3):256-268

A series of experimental observations are presented in the current study to discuss the effects of artificial bed roughness on the turbidity current flowing in a rectangular channel with an abrupt change in bed slope.For this purpose,two different types of elements,sinusoidal and trapezoidal,with various heights and arrangements are considered as artificial bed roughness.A Vectrino velocity meter was used to measure the velocity and sediment concentration profiles.The effects of inlet sediment concentration on front velocity,body velocity,unit discharge,sediment concentration,and suspended load transport rate also were investigated.Accurate equations were developed for estimation of the velocity of a turbidity current over smooth and rough beds.The unexpected experimental results showed that unlike the effect of roughness height,a change in the roughness arrangement has no significant influence on the velocity of a turbidity current.Also,the effect of bed roughness on the front velocity of a denser current is more significant.  相似文献   

Quasi-stationary flow structure in turbidity currents     

《国际泥沙研究》2020,35(6):659-665

A turbidity current is a particle-laden current driven by density differences due to suspended sediment particles. Turbidity currents can transport large amounts of sediment down slopes over great distances, and play a significant role in fluvial, lake and submarine systems. To better understand the sediment transport process, the flow system of an experimentally produced turbidity current in an inclined flume was investigated using video processing. We observed that the current progresses with constant frontal velocity and maintains an unchanged global interface geometry. In addition, the spatio-temporal profiles of the inner mean and turbulence velocity obtained by ultrasound velocity profiler (UVP) showed that similar distributions were maintained, with low dissipation. The results indicate that the turbidity current progressed in a quasi-stationary state, which enabled long-distance sediment transport. To understand the mechanisms behind the quasi-stationary flow, we analyzed the forces acting on the turbidity current. We found that under particular densities of suspended particles, the gravitational force is balanced by the viscous forces along the slope direction. We conclude that this specific force balance induces the quasi-stationary flow structure, enabling the long-distance transport of a substantial amount of sediment downstream with low dissipation.  相似文献   

大同阳高震区及其邻区壳幔速度结构与深部构造   总被引：2，自引：1，他引：1       下载免费PDF全文

张成科  张先康  盖玉杰  赵金仁  聂文英  任青芳 《地震地质》1998,20(4):104

利用通过本区６条宽角反射／折射剖面资料对大同阳高震区及邻区地壳上地幔速度结构与构造进行了详细的研究。结果表明,地壳上地幔速度结构与构造在纵向和横向上具有明显的不均一性。浅部基底断裂发育,而在其深部,根据波组特征、壳内界面及速度等值线起伏变化和低速异常体的边界等推测有３处地壳深断裂带。本区最明显的上地壳低速体位于大同—阳原附近,其南界存在地壳深断裂,大同阳高地震群与该低速异常体和深断裂有关。  相似文献   

大同 阳高震区及其邻区壳幔速度结构与深部构造   总被引：8，自引：1，他引：7       下载免费PDF全文

张成科  张先康 《地震地质》1998,20(4):104-398

利用通过本区６条宽角反射／折射剖面资料对大同 阳高震区及邻区地壳上地幔速度结构与构造进行了详细的研究。结果表明,地壳上地幔速度结构与构造在纵向和横向上具有明显的不均一性。浅部基底断裂发育,而在其深部,根据波组特征、壳内界面及速度等值线起伏变化和低速异常体的边界等推测有３处地壳深断裂带。本区最明显的上地壳低速体位于大同—阳原附近,其南界存在地壳深断裂,大同 阳高地震群与该低速异常体和深断裂有关  相似文献   

The spatial and temporal changes inV p /V s before strong earthquakes in Kamchatka     

G. A. Sobolev  L. B. Slavina 《Pure and Applied Geophysics》1977,115(4):1047-1060

A method was developed to obtain from a signal station the spatial and temporal distribution ofV _p /V _s ratios before earthquakes of magnitude>6. It was shown thatV _p /V _s values strongly depend upon the relative positions of the stations, the future large earthquake and the foci of the smaller earthquakes used forV _p /V _s determination. The appearance of a zone of anomalousV _p /V _s values with linear dimensions of the order of 100 km was noted at least 4 years before a deep earthquake of magnitude 7. Similar size anomalous zones were detected one year before some magnitude 6 earthquakes. V _p /V _s values decreased by a small but distinct amount during this time. Additionally, local short term minima inV _p /V _s ratios were observed some months before the major event. The epicenters of the large earthquakes were located within the 100 km size zone where the gradients of theV _p /V _s field were largest.  相似文献   

Slip line theory applied to a retaining wall–unsaturated soil interaction problem     

《Computers and Geotechnics》2014

An extension of slip line theory to unsaturated soils is presented and applied to the problem of a rigid retaining wall rotating about its toe into unsaturated soils. Suction is introduced using the effective stress concept. Soil–wall interface friction is defined carefully. The influence of suction on limiting passive earth pressures is analysed for two soils under steady state evaporation and infiltration. Suction increases the limiting passive stress at the soil–wall interface, with a dependence on the steady state flow type. The displacement of the retained soil is studied assuming the wall undergoes a rotation increment. The results show a clear difference in the displacement for evaporation and infiltration.  相似文献   

1989年8月17日太阳边缘耀斑和速度场研究     

敦金平 《天文研究与技术》1997,(1)

本文利用云南天文台二维光谱仪观测的１９８９年８月１７日耀斑的Ｈβ波段光谱资料，采用多云模型的方法，得到此耀斑的观测视向速度分布，并在一定的简化和假设下，采用ＭＨＤ理论计算了几种情况下耀斑环内物质运动的视向速度分布，与观测的视向速度分布加以比较，研究和探讨耀斑环中的物质运动情况。通过分析比较，得出此耀斑环内物质运动可能属于下述两种模式：物质从环顶沿两环腿螺旋下落和物质从环足沿一环腿螺旋上升到环顶后沿另一腿螺旋下落  相似文献   

水平风作用下雨滴水平速度的数值仿真   总被引：1，自引：0，他引：1  

苏小勇  高太长  刘西川  赵世军 《气象科学》2013,33(3):282-288

为了研究雨滴在水平风作用下的水平移动情况,在分析水平风作用下雨滴受力情况的基础上,通过对曳力系数与雷诺数对应关系的研究,采用数值仿真的方法分别对海平面大气条件和不同大气条件下雨滴水平运动速度进行仿真.结果表明:当有水平风作用时,雨滴的水平运动速度不等于风的速度,而是随雨滴直径和水平风速的变化而变化;在水平风作用下,雨滴的水平移动速度可以在较短的时间内(一般小于15 s)达到一个稳定的值;在水平风速相同的情况下,气压越高、温度越低,雨滴达到平衡时的水平移动末速度相对越大,反之则越小.这些结论对基于图像采集原理的光学降水自动观测仪器进行雨滴图像拼合有重要的应用价值.  相似文献   

Turbulent Kinetic Energy Dissipation in the Surface Layer     

D. Charuchittipan  J. D. Wilson 《Boundary-Layer Meteorology》2009,132(2):193-204

We estimated the turbulent kinetic energy (TKE) dissipation rate for thirty-two 1-h intervals of unstable stratification covering the stability range 0.12 ≤ −z/L ≤ 43 (z/L is the ratio of instrument height to the Obukhov length), by fitting Kolmogorov’s inertial subrange spectrum to streamwise spectra observed over a desert flat. Estimated values are compatible with the existence of local equilibrium, in that the TKE dissipation rate approximately equalled the sum of shear and buoyant production rates. Only in the neutral limit was the turbulent transport term in the TKE budget measured to be small.  相似文献