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1.
1.INTRODUCnONSAn~sizeplaysanimpo~roleinmanyfields,SUChasinndmeDt-laden~ordebrisflow.TheStateofsedimentmovementwhateVertheyaresugunded.jUInpingorbed-loading,isoftencloselyrelatedtOtheirSizes.Thebodyor~forcesbornacaglainareOftendiredproponionedtotheabcorSq~sizeofthisgrain.Thereforesedimentsizeisanimpohalltindextoesedimentcharacteristics.Besides,depositsizeanditsdistributionimplysome~infonnationdepositingfonnationenvironmentandcauseing~hyandgeqlogy.Ina~on.thesizeanditsdistributionareeac…  相似文献   

2.
I.m~UCrIONBedloadisthesedimentwhichmovesalongtheriverbedintheformofrolling,slidingandsaltation.BedloadmaycreatemanyproblemsintheoperationandmaintenanceofnavigationchannelandinthedevelOPmentofhydroelectricity.Dataofbedloaddischargearealsorequiredinthedesignofreservoir,inwhichtheinflowbedloadareallactuallytrapped.Thewaysofbedloadmotionaredifferentfordifferentsizes.Thus,itisextremelydifficulttodeterminethebedloaddischargeaccurately.Manyequationshavebeenproposedtocalculatethebedloaddischarge.H…  相似文献   

3.
I.INTRODUCTIONReseri,oirsonoverloadedriverswillreachthestateofrelativeequilibriumwithcontinuousdevelopmentofsedimentation.Insuchcase,thereisdePOsitinfrontofthedam.Thereforethesiltpressureonthedambodyisconsiderablylarge.Sedimentationelevationinfrontofthedamisoneofthefactorsofcalculatingthesiltpressure.Inaddition,tokeeplong-termworkingstorageinreservoif,itisnecessarytoinstallbottomoutlets.Asthereisapressureconduitinfrontoftheoperatinggateofthebottomoutlet,thesedimelltenteredtheconduitwill…  相似文献   

4.
I.I~rnoxTherearemanyproblemsfortheresearchondebrisflowmechanism.ThemostimPOrtantandmOSturgentoneisthecalculationofresistanceandvelocityOfdebrisflow.Inthisaspectmuchresearchhasbeencompletedfromtwoapproaches.Oneapproachisbasedonordinaryhydraulicsandmodifiedbyfieldobservationdata,andempiricalformulaeofdebrisflowresistanceandvelocitywereestablished.MOStoftheearlyresearch,suchascalculatingdebrisflowvelocitywiththemodifiedformOfMariningformula,belongedtothisscope.Theonlydifferenceisthattherough…  相似文献   

5.
根据中俄地震科学技术合作1993年度计划安排,1993年8月28日至9月4日在俄罗斯大地物理联合研究所“伯洛克”地球物理观象台(伯洛克科学城)举行了中俄地震预报研讨会。中方代表团由8人组成:团长孙其政,副团长张肇诚(兼翻译),团员有张国民、何世海(兼翻译)、罗兰格、陈立德、车兆宏、黄剑发;俄方代表团由9人组成:团长G.A.Sobolev,团员有A.G.Prozorov,A.D.Zavyalov,A.A.Avagimov,A.Ya.Sidorin,V.G.Gitis,V.I.Lykov,V.Petrov,A.O.Mostrjukov.  相似文献   

6.
时间:1992年10月30日至11月1日 地点:北京清华大学 议题:1.应用,2.认知科学,3.神经网络,4.语言识别,5.计算机视觉,6.数据抽取与传感技术,7.图象与语音处理及其压缩传输,8.石油勘探中的智能信息处理,9.智能信息系统,10.实现技术等  相似文献   

7.
《国际泥沙研究》2007,22(4):327-328
No. 1, 2007 Prediction of the Grain Size of Suspended Sediment: Implications for Calculating Suspended Sediment Concentrations Using Single Frequency Acoustic Backscatter R. A. KUHNLE, D. G. WREN, and J. P. CHAMBERS (pp. 1-15) Numerical Modeling of Heavy Metal Pollutant Transport-Transformation in Fluvial Rivers:A Review S. L. HUANG, Z. H. WAN, and P. SMITH (pp. 16-26) Sediment Transport Capacity-An Improved Bagnold Formula Shu-Qing YANG, Sung-Cheol KOH, In-So…  相似文献   

8.
IINTRODUCTIONTheYellowRiverisfamousforitsheaVysedimentloadandcompledpluvialprocessesobviousadvanceshavebeenmadeinthetwo-dimensionalsedimentmathematicalmodel.Amongtile1llodelscreatedbeforethemechanismofsedimenttransportandrelatedphysicalparametel's,suchassedimentvelocity,sedimentcan'yingcapacityandriverfi.ictionetc.arenotyetundel.stoodvery\veil.Thesynchronousobserveddataoftheflowwithsediment,especiallyathyperconcentration,arenotenougllforthemodelcalibration.Thereforethedevelopmentoftwo-di…  相似文献   

9.
I.INTRODUCTIONhiverchannelsaresubjecttocontinuouschangeingeometryduetoillteraCtionbetWeentheflowanderodibleboundaries.Ofconcerntothedesignersofoilpipelinesacrossariver,bridgesandhydraulicworksistheproblemofscourwhichcanunderminetheStructures.Scouratsiteofbridgesandhydraulicworksoccursduetoconstrictedflowandexistenceofbridgepiers.SuchatabOfscouroccursonlyinashortsection,usuallyillthesameorderofthelengthofthehydraulicworksorbridges.Therefore,thispatternofscouriscalledlocalscour.Man}rresea…  相似文献   

10.
I. Soil erosion and sediment yieldDevelopment of Soil Erosion Index Model in Taiwan WatershedsVol. 16, No. 1, pp. 80-90 Modeling of Sediment Yield and Nonpoint Source Pollutant YieldVol. 16, No. 3, pp. 416-420 Runoff Generation Characteristics in Typical Erosion Regions on the Loess PlateauVol. 16, No. 4, pp. 473-485II. Environmental and ecological sedimentationLong Term Effects of Rehabilitation Measures on Bed Load Transport at the Salzach River Vol. 16, No. 2, pp. 95-102 Th…  相似文献   

11.
武定6.5级地震前后环境剪应力场动态变化   总被引:3,自引:1,他引:2  
王绍晋  龙晓帆 《地震研究》2000,23(3):298-306
采用陈培善等从断裂力学观点研究地震破裂过程,提出的由地震波和地震基本参数等资料估算地震震源处剪切应力强度值的方法,对发生在武定震区及其附近的中小地震测算了剪切应力值,据此对武定6.5级地震前后环境剪应力场动态变化作了追踪分析。结果表明,武定地震发生在环境剪应力场具有高值分布背景的地区。强震孕育经历了环境应力场由低-高-低-高的多次起伏变化,反复增强的过程。震后环境剪应力场逐渐减弱,最终回复到正常状  相似文献   

12.
川滇地区7级大震前中强震震源机制变化   总被引:7,自引:0,他引:7  
分析了 70年代以来 ,川滇地区发生的 8次 7级大震前 5年内 ,发生在大震孕震区和震源区内的中强震震源机制解时空分布。结果表明 ,最早中强震发生在大震震源区或其附近 ,其发震应力场与区域构造应力场一致 ,与大多数大震发震应力场一致或接近。大多数中强震震源破裂特征与大震明显不同。之后有多次中强震发生在距大震震源区较远的大震孕震区内其他地方 ,它们的发震应力场往往经历了与区域构造应力场和大震应力场一致与不一致的多次交替变化。大震前最后 1个中强震也发生在距大震震源区较近的地方 ,其发震应力场与大震发震应力场明显不一致 ,偏转了 30°~ 5 0° ,或更多 ,大多数也与区域构造应力场不一致 ,有的中强震发震断裂破裂特征与大震不一致。大震前中强震震源机制的变化 ,反映了大震孕育过程的不同阶段 ,区域构造应力场的时空调整变化和增强过程 ,以及由此引发的构造断裂异常活动 ,揭示出与大震发生有关的应力场和震源破裂特征信息  相似文献   

13.
    
The strong earthquakes in western Yunnan area, mainly occur along great interplate strike-slip faults and have a dominant depth-layer about 10–20 km; the seismic rupture is characterized by strike-slip rupture. Considering the Yunnan lithospheric structure and dynamic background, we think that earthquakes occurring at this area might have such a kind of nucleation process: because of the multi-layers and heterogeneities of lithospheric structure, a zone of concentrated shear strain or of slip might be formed at the moderate or deep portions of lithosphere, and spread upward along faulting boundary, toward the earth’s surface under the background field of tectonic movement of lithospheric plates. The slip front will encounter the maximum shear resistance zone on the fault surface in this process, be barried and blocked, and form a seismic gap. With the increase of tectonic load, this slip zone will continuously spread forward, traverse and lead to instable crack of the whole blocked zone, and cause a great earthquake. We have derived an approximate integral equation describing this seismic process; the numerical results show that the model has an instable nonlinear accelerating evolution period which might have important significance for the generation of earthquake precursors. This paper is supported by the Eight Five-Year Target of the State Seismological Bureau, China.  相似文献   

14.
1996年3月19日新疆阿图什6.9级地震震源破裂特征的研究   总被引:4,自引:0,他引:4  
通过对1996年3月19日新疆阿图什6.9级地震余震分布特征的研究,分析了这次地震震源破裂过程.并结合柯坪断裂带的构造运动、区域应力场的分布特征以及1972年以来该带的另外3次6级地震的余震分布方向,探讨了柯坪断裂带附近地区不同构造部位震源破裂扩展方向与强震活动的迁移方向.结果表明,本次地震震源破裂为明显的单侧破裂.柯坪断裂带的阿图什震区和柯坪震区,余震分布具有一定规律性,震源破裂基本都为单侧破裂;震源断错以逆断层为主.区内主要受NW向压应力。不同地段强震震源破裂扩展具有明显的区域特征,强余震分布方向是应力集中的体现,它标志着同一构造断裂带附近近期强震活动的迁移方向.在柯坪断裂带上这种规律更为明显。  相似文献   

15.
According to the fracture mechanics rupture model of earthquakes put forward by us, several equations to compute tectonic ambient shear stress value τ0 have been derived [equations (1), (2), (3), (5)]. τ0 values for intermediate and small earthquakes occurred in Chinese mainland and Southern California have been calculated by use of these equations. The results demonstrate that the level and distribution of τ0 are closely related to the location where large earthquakes will occur, i.e. the region with higher level of τ0 will be prone to occur large earthquakes and the region with lower level will usually occur small earthquakes. According to the spatial distribution of τ0, the seismic hazard regions or the potential earthquake source regions can in some degree be determined. According to the variation of τ0 with time, the large earthquake occurrence time can be roughly estimated. According to the distribution of τ0 in Southern California and variation with time, three high stress level regions are determined, one (Goldfield area) of them is the present seismic hazard region. Contribution No. 98A02023, Institute of Geophysics, State Seismological Bureau, China  相似文献   

16.
澜沧江断裂带环境剪应力场与地震活动分析   总被引:1,自引:0,他引:1  
利用地震波资料,测算了1990~2003年沿澜沧江断裂带上中小地震震源处的相对剪应力强度值,分析了该断裂带环境剪应力场的空间分布及其与地震活动的关系。结果表明,澜沧江断裂带总体上处于环境剪应力场的相对低值分布区,但在断裂带局部段落及其附近出现一定时段的高剪应力值分布,这主要是受断裂带附近区域高剪应力状态的影响。沿澜沧江断裂带地震活动性较弱,这与沿断裂带环境剪应力场的低值状态基本一致。  相似文献   

17.
The strong earthquakes in western Yunnan area, mainly occur along great interplate strike-slip faults and have a dominant depth-layer about 10–20 km; the seismic rupture is characterized by strike-slip rupture. Considering the Yunnan lithospheric structure and dynamic background, we think that earthquakes occurring at this area might have such a kind of nucleation process: because of the multi-layers and heterogeneities of lithospheric structure, a zone of concentrated shear strain or of slip might be formed at the moderate or deep portions of lithosphere, and spread upward along faulting boundary, toward the earth’s surface under the background field of tectonic movement of lithospheric plates. The slip front will encounter the maximum shear resistance zone on the fault surface in this process, be barried and blocked, and form a seismic gap. With the increase of tectonic load, this slip zone will continuously spread forward, traverse and lead to instable crack of the whole blocked zone, and cause a great earthquake. We have derived an approximate integral equation describing this seismic process; the numerical results show that the model has an instable nonlinear accelerating evolution period which might have important significance for the generation of earthquake precursors.  相似文献   

18.
The spatial distribution of the stress field around a fault, before its failure, depends on the focal mechanism of the ensuing rupture. In the preseismic stage, the main fault is locked and background seismicity is distributed in the surrounding area along small faults due to the raise of the stress level. This distribution is well correlated with changes of the stress field, when these are calculated considering the fault slipping on the opposite sense (back-slip model), before the incoming strong event. Studies of the seismicity around faults with known geometry, dimensions and slip properties could contribute in the seismic hazard assessment. In the present work, the spatio-temporal distribution of the smaller magnitude seismic activity before the occurrence of the four most recent (1995–2008) strong (M ≥ 6.4) shallow earthquakes in Greece is compared with the stress pattern necessary for the generation of the strong earthquakes. Studying the annual rate of occurrence it is found that in areas of positive pre-stress changes a sharp increase of the number of earthquakes is observed several years before the occurrence of the main shock. This increase lasts for a few years and then for several years before the main shock the occurrence rate declines but usually remains higher than it was before the sharp increase. Seismicity distribution in the respective areas of negative pre-stress changes shows a rather stable occurrence rate.  相似文献   

19.
Source parameters of the earthquakes of the Baikal rift system   总被引:1,自引:0,他引:1  
The dynamic parameters of the earthquake source—the seismic moment, the moment magnitude, the source radius, the stress drop, and the amplitude of displacement—are determined by the amplitude Fourier spectra of the body shear waves (S-waves) for 62 earthquakes of the Baikal rift system with the energy class of K P = 9.1–15.7. In the calculations I used the classical Brune model. The seismic moment of the earthquakes being investigated changes from 3.65 × 1011 N m to 1.35 × 1018 N m, and the radii of earthquake sources vary from 390 m to 1.84 km. The values of the drop in stress Δσ grow with an increase in the seismic moment up to 1.7 × 108 Pa. For the group of weak earthquakes (M w = 1.7–3.3), extremely low values of the drop in stress 103–104 Pa are observed. The maximum amplitude of displacement in the source amounts to 5.95 m. The empirical equations between the seismic moment and the other dynamic parameters of the source are determined. The regional dependence of the seismic moment and energy class is obtained: log M 0 ± 0.60 = 1.03K P + 3.17. The character of the relationship between the seismic moment and the corner frequency indicates that the classical scaling law of the seismic spectrum for the earthquakes in question is not fulfilled. The obtained estimates of the dynamic parameters are in satisfactory agreement with the published data concerning the analogous parameters of the other rift zones, which reflects the general regular patterns of the destruction of the lithosphere and the seismicity in the extension zones of the lithosphere.  相似文献   

20.
应用P波初动半周期直接测定环境剪应力值的方法,测定了北部湾6.1,6.2级地震前后中小地震的环境剪应力值τ0,由此分析了北部湾地震过程的环境应力场特征。结果表明,北部湾6.1级地震后平均剪应力值较高,达18MPa左右;6.2级地震及两次5级余震后剪应力值下降很快,降至目前的6MPa左右。在此基础上对北部湾地震活动趋势作了初步分析。  相似文献   

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