Prediction of Flow around a Vertical Circular Pier in a Discordant Bed Channel Confluence

Water Resources - Understanding the flow dynamics around the hydraulic structure caused by complex junction flow is still a major challenge. In order to gain a better insight of impact of junction...     

Two-Dimensional Horizontal Numerical Model of Open Flow over a Bed with Obstacles

An explicit numerical algorithm for solving two-dimensional system of shallow-water equations is presented. The algorithm is based on the control volume method with recording mass and momentum fluxes through the faces of the volume with the use of an approximate solution of the Riemann problem. A numerical solution is compared with analytical solutions for a flow over a bottom step and with data of laboratory experiments in a flume with a sloped bed or a bed with an obstacle.__________Translated from Vodnye Resursy, Vol. 32, No. 3, 2005, pp. 282–294.Original Russian Text Copyright © 2005 by Prokofev.     

On the Critical Velocities and Depths in a Nonuniform Steady Flow in an Open Channel

The results of experiments discussed in this paper show that some characteristics of gravity waves in finite-depth water can be used in the case of steady flows with a pronounced nonuniformity in open channels. In particular, in addition to the classical critical velocity and depth, the higher (second) critical velocity and (second) critical depth can be used.     

汶川大地震前后电离层电子含量的扰动分析

为了分析地震前后电离层电子含量的变化,本文选取四川汶川发生8.0级地震前后10天电离层中的电子含量作为研究对象,使用IGS网站提供的VTEC数据,采取统计学分析方法,结合太阳和地磁活动信息,对此次地震前后电离层VTEC资料进行了详细的统计分析和讨论,数据分析结果表明大地震前电离层电子含量会出现明显扰动,电离层中电子含量的异常变化有可能是地震发生的前兆信息.     

Fracture of a Liquefied Crack and the Physics of Rayleigh Waves

The standard free-surface boundary conditions for in-plane crack dynamics are shown to be identical to the conditions for crack dynamics on a liquefied crack. The surfaces of both the free and liquefied cracks do not separate during faulting and hence the static normal stress is not relaxed by the faulting. A crack with either free or liquid boundary conditions deforms in the transverse direction during slip. It follows that both the free and liquefied cracks may represent solutions to the heat-flow paradox. As an application of the proof, we derive a physical understanding of the properties of harmonic Rayleigh waves on a uniform elastic half-space without solving a cubic equation.     

Waves in the diapir tail as a mechanism of hotspot pulsations

The one-dimensional (1D) problem of magma rising through a volcanic channel is identical in its statement to the problem of chemical-density or thermo-chemical convection in an unbounded medium. The present work demonstrates how the rise of a low-viscous, buoyant material through an ambient environment with significantly higher viscosity can be successively described as a 1D problem of viscous fluid dynamics. The suggested analytical model is applied to describe the upwelling of a less dense material in the tail of a diapir through the mantle to the Earth??s surface. The linear study of wave disturbances in the shape of the conduit shows that the buoyant material tends to uprise by portions, which probably accounts for the pulsed activity of the hotspots appearing on the surface above the diapir.     

汶川8.0级地震前后宏观异常现象分析

文章对2008年5月12日汶川8.0级大地震前后(2008年2月1日至6月10日)出现的宏观异常现象进行了收集整理。 较为可靠的异常做为地震宏观异常, 并对其时空分布特征进行了研究。 研究结果表明, 在时间分布上, 地震宏观异常的数量在临震前形成一次峰值, 震后出现两次峰值; 在空间分布上, 大震前后宏观异常的空间展布方向趋于一致。 文章还对宏观异常的映震机理以及对地震预测可能发挥的作用等问题进行了讨论。     

Study of the Gravity Changes before and after the Jingtai Ms 5.9 Earthquake

By systematically analyzing the data of gravity reiteration in the Hexi region and taking a dynamic viewpoint.we have studied the evolution characters of gravity field during the preparation-occurrence of the Jingtai Ms5.9 earthquake of June 6,2000,The patterns of dynamic change of the gravity field clearly reflected how the gravity field evolved from the quasi-homogeneous state to non-homogeneous state for earthquake preparation and then the earthquake occurred.Besides,we have also studied the relation between the characteristic gravity change and strong earthquake activity.     

Lake Baikal and the Angara River before and after the Construction of Reservoirs

Variations in the regime of the Angara River flow fluctuations and in the components of the water balance of Lake Baikal are discussed.     

Tar ball concentrations in the ocean around the Cape of Good Hope before and after a major oil spill

Measurement of tar ball concentrations of samples taken on twelve monthly cruises from 120 stations around the south-western coast of South Africa shows that this area is relatively free of floating tar. A tanker collision resulted in a major oil spill halfway through the programme, allowing the movement and dispersion of tar balls to be followed.     

文安5.1级地震前后地壳形变特征研究

应用文安地震200km范围内的定点形变观测资料,在研究断层活动性质的基础上,进一步综合分析在文安地震前后地壳形变的时空演化特征及其与地震活动的关系,结果表明：（1）部分测项在震前均出现张性或者压性转折变化,或者阶跃变化;（2）地表潮汐平面应变状态在中强地震前后表现出不同的变化特征;（3）平面应变参数曲线2011年前后发生同步转折变化,且变化幅度很大,但首都圈及附近地区并没有中强以上地震发生,可能与引发2011年3月日本9.0级特大地震的板块构造应力场变化有关。     

The mechanism of regional gravity changes before and after the Tangshan earthquake

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小北湖火山台迁建前后观测数据对比分析

小北湖火山台原址位于原始森林保护区,按照林区防火要求,2019年选址迁建.选取迁建前后小北湖火山台观测数据,通过计算不同频段范围内背景噪声记录的加速度功率谱密度,分析了迁建前后地震观测台站的噪声特征.结果 表明,在1-20 Hz频段内,迁建后功率谱噪声值普遍降低10-20 dB;从RMS值来看,UD向降低22.0％,E...     

Analyses on gravity variation before and after the Lijiang earthquake based on a finite rectangular dislocation model

The methods were discussed to calculate the gravity variation due to crustal deformation based on a model of dis-location on a finite rectangular plane.Taking the Lijiang Ms=7.0 earthquake as an example the calculating princi-ple of fault parameters were determined,and the results were given.Of particular interests were the characteristics of the gravity variations in different dislocation types.With comparison between the calculated results and the practical measurements,it was found that the model could to some extent account for the observations.But it failed to give explanations to the more far spatial gravity variation.     

Pressure Energy Diffusion Rates in the Wall-Wake Region of Immobile Solid Sphere in Open Channel Flows-Numerical Simulation and Experimental Study

Water Resources - Present study elucidates the near-bed pressure energy diffusion rates in the wall-wake region of flowpast a stationary solid sphere in open channel. Vertical distributions of...     

地震前后岩石圈磁场变化特征分析

本文以九江—瑞昌M_s5.7级地震和汶川M_s8.0级地震为研究对象,根据两个震区地震后观测所得地磁场三分量数据和“2005.0中国地磁图”项目所积累的地磁场三分量数据,建立了两个震区的岩石圈磁场模型.通过对比分析两个震区岩石圈磁场总强度、磁偏角、磁倾角三个独立分量地震前后的时空变化特征,初步探讨地震与岩石圈磁场变化关系,寻找有效震磁变化信息.结果表明：（1）两次震中均位于岩石圈磁场的磁偏角和磁倾角零值线附近;（2）震后震中百公里范围内岩石圈磁场分量均出现了不同程度的异常变化;（3）震中附近岩石圈磁场出现了明显的与地震相关的变化,该变化在两个震区表现出相近的规律性.     

Seismicity before and after the two great Sumatra earthquakes of 2004 and 2005

The Harvard CMT catalogue contains 481 shallow earthquakes that occurred between 1 January 1977 and 30 November 2005 within a broad region defined by the geographical latitude from 3°S to 14°N and by the longitude from 91°E to 102°E. There are 230 events that occurred before the great earthquake of 26 December 2004. Their surface distribution is not uniform and the source area of the 2004 great event appears as an area of seismic quiescence with a radius of about 100 km. There are 186 events that occurred between the two great earthquakes of 26 December 2004 and 28 March 2005. Practically all of them are located to the northwest from the great earthquake of 2005, that in turn was followed by 63 events, mostly located to the southeast. The cumulative seismic moment from earthquakes before the occurrence of the great event of 2004 increased rather regularly with time, with sudden increase about twenty years and two years before the occurrence of the great event. The seismic moment of earthquakes between the two great events increased rapidly during the first ten-fifteen days, then flattened out and increased slowly with time. After the great event of 2005 the seismic moment shows quiet increase during some 115 days, then sudden jump, followed by very small activity till the end of our observations. From the spatial distribution of seismic moment of earthquakes that occurred before the great event of 2004 it follows that its largest release appeared to the southeast from the great event, around the rupture area of the great earthquake of 2005. The largest release of seismic moment from earthquakes between the two great events is observed in the vicinity of the 2004 event and further up to the north. The seismic moment from earthquakes that occurred after the great event of 2005 was mostly released in its vicinity and further down to the south.     

大同─阳高2次地震前后震源应力场的变化过程

利用１９８９、１９９１年大同－阳高两次地震前后几年的地震记录资料，详细分析了其震源应力场的变化，结果表明，６．１级地震前震源应力场中两个主应力轴的方向曾发生逆转，主压应力袖逆转时间约１０个月，主张应力轴逆转时间为２个月。６．１级主震前４个月，两个主应力轴的方向、仰角都恢复到正常状态，且与华北区域应力场的特征某本一致，而１９９１年５．８级地震前却没有出现上述现象。说明大同－阳高２次地震是在同一震源应力场作用之下孕育、发展的，亦说明５．８级地震是６．１级地震的晚期强余震。指出山西地震带６级以上地震的孕育发生似是在华北区域应力场的作用之下完成的。     

汶川地震前后水位频谱特征分析

以频谱分析方法作为理论基础,采用周期图法计算汶川地震前后距震中500 km以内10口观测井水位（包括动水位与静水位）的功率谱,对比分析2009年无大震年份同时期的数据,研究结果表明：水位的频域特征受制于观测井的地质构造背景、观测方式和观测深度;水位的波动能量主要集中于大于4天与小于0.5天周期,震后水位波动能量则集中在大于8天的周期;动水位频谱更加丰富.另外,不同井水位的频域响应特征与该井观测层岩性有关,需进一步研究.