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1.
竖向与水平向地震动加速度反应谱比特性分析 总被引：2，自引：0，他引：2
本文采用全球范围128次地震的3235组三分量强地面运动记录,分析了其加速度竖向分量反应谱与水平分量反应谱的比值(V/H)的总体特征,研究了V/H随震级、震中距、局部场地条件和震源机制的变化关系。研究结果表明:(1)场地越硬,长周期段V/H越大,短周期段则相反;(2)震级越大,长周期段V/H越大,短周期段变化不明显;(3)短周期段V/H随震中距增大而减小;(4)对于大震(M7),长周期段V/H随震中距增大而减小;而对于中强震(M7),比值在近场(R60km)随震中距增加而增大,在远场则随震中距增加而减小;(5)V/H与震源机制也有一定的关系。 相似文献
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选取了1999年9月21日台湾集集7.6级地震主震中68组断层距在20km以内的近断层台站记录和46组断层距在40~70km的东部台站记录,按台站的上下盘位置、场地条件和断层距分组,对其竖向和水平加速度反应谱比值V/H进行了统计分析。研究表明:1)断层的滑动方向和断层破裂的传播方向对断层距在3km以内的台站上的地面运动谱比值V/H有一定影响,且主要体现在中短周期范围内,例如平行断层方向的谱比值要比垂直断层方向的谱比值大。在下盘断层距3~20km的范围内,场地条件对V/H基本没有影响。2)在集集地震中长周期(>3s)部分的谱比值通常>32,且有一个较高的峰值,表明其竖向运动加速度中的长周期分量大于其它地震。3)对于下盘的台站,地面运动在短周期(<0.2s)段的谱比值不随断层距的增加而减少。与中远(>40km)距离的台站相比较,近断层台站的V/H在工程界关心的周期范围内普遍较大。4)场地条件对谱比值V/H的影响在近断层处不显著。在远离断层的东部台站上,硬土场地谱比值V/H在长周期段大于软土场地 相似文献
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选取分布在北川-映秀中央断裂两侧断层距120 km以内的40个强震动台站的记录,对汶川地震近断层地震动竖向和水平向加速度峰值、速度峰值、竖向和水平向加速度反应谱及谱比值进行了统计分析.研究表明:(1)地震动加速度峰值有显著的上盘效应,经验衰减模型的结果表明,在距地表破裂3~60 km的范围内,龙门山发震断层上盘一侧竖向与水平向的加速度峰值要比衰减模型得到的平均值大30%~40%.上盘的加速度峰值残差大部分是正值,而断层下盘残差大部分为负;水平地震动的东西分量幅值总体要大于南北分量,东西分量衰减相对较慢.(2)地震动长周期成分较弱,加速度反应谱值随周期增大而迅速减小,在周期1.0 s 时,即使在靠近中央断裂的最大加速度反应谱值也只有0.5 g;地震动加速度反应谱谱比值(竖向/水平向)沿龙门山断层周围的分布,在较长周期(T=0.2 s, 0.5 s, 1.0 s)与短周期(T=0.05 s, 0.1 s)有明显的不同.(3)近断层竖向地震动显著,地震动加速度峰值比在(竖向/水平向)可达1.4.在龙门山发震断层的上盘,地震动加速度峰值比整体上比下盘要大,竖向地震动尤为剧烈.部分近断层记录的地震动谱比值(竖向/水平向)在短周期(< 0.1 s)甚至超过1.5,统计分析还表明谱比值在短周期段(< 0.1 s)随断层距的增大而减小. 相似文献
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液化土层对地表加速度反应谱的影响 总被引：4，自引：0，他引：4
采用一种改进的有效应力方法研究土层液化对地表加速度反应谱的影响，分析中考虑了砂层的厚度、埋深和输入地震波的幅值和波型等因素。分析结果表明，土层液化使地表加速度反应谱的特征周期至少延长0．1秒以上，使原Ⅱ类场地变为Ⅲ类场地，高烈度时易变成Ⅳ类场地，反应谱中周期0．8秒-1．0秒是液化砂层加震或减震的一个分界点，液化对反应谱短周期分量具有一定的减震作用，而对长周期分量有非常显著的放大作用。 相似文献
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我国现行规范谱的超越概率标准 总被引：1，自引：0，他引：1
工程场地的地震安全性评价给出的加速度反应谱在长周期部分一般均低于相应的规范谱。本文用Ⅰ类和Ⅲ类场地的地震动参数衰减规律,讨论加速度反应谱与不同周期规范谱值对应的重现期。结果表明,对加速度而言,基本情况是规范反应谱周期越长越保守。当峰值加速度对应的重现期为475年时,对于本文的工程算例,Ⅰ类和Ⅲ类场地的加速度反应谱分别于3.7s和5.2s以后超过重现期5000年。本文认为,对目前使用的衰减规律的可靠性,对一致概率谱与规范谱的关系,对按保守谱设计的工程在长周期地震波作用下的表现以及对速度、位移等在抗震设计中的作用等问题应作深入研究。 相似文献
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SMART-1台阵记录的长周期反应谱特性 总被引：3，自引：0，他引：3
利用台湾SMART－1台阵的数字强震仪加速度记录分析了同类场地上的地震动长周期分量特性，结果表明：同一次地震震中距基本相同的同类场地加速度反应谱短周期部分有较明显的差别，长周期部分则基本相同；震级和震中距对短周期反应谱影响明显，对长周期反应谱也有一定影响。最后将SMART－1台阳场地的平均谱与新的建筑抗震设计规范修订稿中提出的设计反应谱作了比较。 相似文献
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文中将921台湾集集地震主震的404组强震记录按照不同震中距和场地类别分组,对加速度水平分量和垂直分量的持时、峰值加速度(PGA)、包络线、反应谱比值进行了统计分析。结果表明,场地条件对不同分量加速度时间历程的若干特征有显著的影响,而且比较复杂。此外,断层方向对地震动水平特性也有一定的影响。具体研究结果为:1)地震动水平分量的持时随着场地依次变软而增大;2)断层方向对PGA衰减特征有一定影响;3)不同震中距离和场地条件下集散的时间里程的包线基本上都是单峰点的时间函数;地震动加速度水平分量包络线与竖向分量包络线有明显的不同;4)在震中距相同的条件下,场地愈软弱,周期愈短,谱比值EW/SN愈接近1。场地愈软,在短周期(<0.1s)段,V/H谱比值是变大的趋势,而在长周期(>特征周期)段则是变小的趋势;而且相对来说V/EW谱比值随场地变软而减小的趋势相对要强一些 相似文献
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为考查远场地震动的场地相关性并评价一些场地特性分析方法的适用性,采用不同方法对汶川地震山东省12个远场台站的强震记录进行了分析.选取台站分别位于按建筑抗震设计规范(CBC)场地划分中的Ⅰ—Ⅲ类场地上.地震动记录的分析方法包括傅里叶幅值谱法,地震反应谱法,水平与竖向谱比率法,参考点谱比率法,以及尾波分析等.结果表明,按傅里叶幅值谱法,地震反应谱法,水平与竖向谱比法计算得到的卓越周期均远大于台站场地的卓越周期,不同方法得到的结果之间也有较大差别,且主要反映长周期地震动的卓越频率;参考点谱比率法的结果未反映地震动的卓越周期,也与场地的卓越周期差别较大;对完整记录尾波分析所得的结果比较接近场地的卓越周期.希望本文能为考虑远场地震作用时设计谱的建立,以及场地特性估计时地震动分析方法的选取提供参考依据. 相似文献
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本文收集了从南北地震带川滇甘陕地区263个有详细场地资料的强震台站获得的802组强震动记录,按照场地、震级和震中距等因素统计分析了竖向与水平向加速度反应谱比的形状以及不同场地、震级和震中距下不同周期段内的谱比平均值,并与建筑抗震规范GB50011—2010规定的0.65进行了比较。结果表明:竖向与水平向加速度反应谱比受场地、震级和震中距等因素的影响; Ⅰ类和Ⅱ类场地在全周期段的谱比均值基本上大于0.65;无论何种分组情况谱比均值在0.1—1.0 s周期范围内基本低于定值0.65,周期大于1.0 s的谱比均值基本上远高于0.65。因此对于大部分抗震规范直接把竖向地震作用取为水平向地震作用的0.65倍,有待商榷。本文建议根据水平向反应谱的标定方式来确定现有竖向强震动记录的竖向地震作用。 相似文献
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选取日本熊本MW7.0地震断层距小于200 km的82个近场KiK-net台站记录到的三分量记录数据进行基线校正后,获得近场地面运动水平向的峰值加速度PGA、峰值速度PGV及周期为0.2,1,2,3,5和10 s的加速度反应谱数据,并与美国NGA-West2的地震动预测模型相比较,研究熊本地震地表和井下地震动峰值及反应谱的衰减特征,通过比较KiK-net台站地表与井下记录结果,探讨浅层场地放大效应的影响。研究结果表明:① 对于井下观测结果,NGA-West2的地震动模型对PGA和短周期0.2 s的反应谱的预测值与井下观测值相比整体偏高,而PGV和较长周期地震动（如1,2和3 s的反应谱）的预测值与井下观测值较为吻合;② 地表观测记录的PGA,PGV和周期为0.2—3 s的反应谱残差整体上随vS30对数值的增大呈线性减小的趋势,而周期为5 s和10 s的长周期部分,其场地效应的影响很小;③ 相对于井下记录,地表记录的地震动PGA,PGV和周期为0.2,1和2 s的反应谱有明显的放大,这种放大作用随浅层场地剪切波速的增大而减小;周期为3,5和10 s时长周期地震动的放大效应很小。 相似文献
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《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
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《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
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Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored. 相似文献
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《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
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K.-G. Malle 《洁净——土壤、空气、水》1992,20(4):196-204
Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m3 zinc. Apart from civilization air contains 1–10 ng zinc per m3. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters. 相似文献