|
There is a belt of abnormally high seismic intensity along the line of Sanlihe-Xisi-Deshengmen in Beijing city during the Tangshan earthquake. Various hypothesis as to the cause of this abnormal belt have been suggested.Because the earthquake risk of Beijing city is not negligble and more and more highrise buildings are being erected,it might be necessary to find out the cause resulting in this belt of high seismic risk.Through detailed researches on a typical geological profile and its earthquake response by... There is a belt of abnormally high seismic intensity along the line of Sanlihe-Xisi-Deshengmen in Beijing city during the Tangshan earthquake. Various hypothesis as to the cause of this abnormal belt have been suggested.Because the earthquake risk of Beijing city is not negligble and more and more highrise buildings are being erected,it might be necessary to find out the cause resulting in this belt of high seismic risk.Through detailed researches on a typical geological profile and its earthquake response by using the extended SAP 5 program,the following main results are obtained:1.It is found that a depression of the underlying bedrock to a depth of 1000-1500 meters plays a dominant role in causing the belt of abnoralty intense earthquake damage in Beijing.2.The calculated predominant periods of the response spectra at different sites above the depression are from 0.85-0.95 see.These conclusions are likely to be helpful to the earthquake-resistant design of high-rise builings in the urban area of Beijing or other similar zones. 北京市区沿三里河—西四—德胜门有一条地震高烈度异常带,其产生异常的原因众说不一。目前北京地区仍存在中等强度地震的波及与威胁,同时该区高层建筑正在日新月异的发展,因而探明这条高烈度异常的成因看来是很必要的。本文回顾了有关场地工程地质条件对地震动的影响的研究进展,详细分析了该区的工程地质和基岩构造情况,利用经作者扩展的SAP 5程序计算了典型剖面的地震反应。结果表明深度在1000—1500米的基岩凹陷对这一高烈度异常似有着控制性的影响。由于地面振动的卓越周期在1.0秒左右,将对该区的长周期结构(如高层建筑和烟囱等)带来不利影响。 The results of analysing the age distribution of antibody against hepatitis A virus (HAV) of urban and suburban populations in Beijing and Shanghai showed that the infectivity of HAV in urban Beijing population began to decrease since 1968, that the tendency of decrease of the infectivity of HAV in urban and suburban Shanghai populations began earlier, around 1955, and it continued to decrease singnificantly since 1968, while the infectivity of HAV in suburban Beijing population remained constant for several... The results of analysing the age distribution of antibody against hepatitis A virus (HAV) of urban and suburban populations in Beijing and Shanghai showed that the infectivity of HAV in urban Beijing population began to decrease since 1968, that the tendency of decrease of the infectivity of HAV in urban and suburban Shanghai populations began earlier, around 1955, and it continued to decrease singnificantly since 1968, while the infectivity of HAV in suburban Beijing population remained constant for several decades. 本文应用催化模型拟合京沪城乡甲型肝炎(HA)流行率的年龄分布,发现北京市区人群的HA感染力自1968年起开始降低;上海城乡人群的HA感染力下降趋势开始得更早,约在1955年,1968年后其感染力更进一步降低;但北京市郊区人群的HA感染力几十年来却一直保持恒定。 Seismic effect on ground motion is a problem of common interest by seismo-engineer and engineering - seismologist The former stresses to study the effect of seismic ground motion on uPPer structure of buildings, but the latter mainly considers the effect of seismic ground motion on engineering geological conditions of site foundations. 地震地面效应是地震工程和工程地震工作者共同关心的问题.前者着重研究地震动对上部结构的影响,后者则主要从事研究地震动对场地地基工程地质条件的影响.1979年对北京市区所作的一维地震反应分析,得出了土层厚度是影响地震地面运动的主要因素.输入地震动的卓越周期及其加速度峰值对反应谱形状的影响较时程曲线的影响明显.但一维方法只反映有界水平层及地震垂向上传.二维动力有限元地震反应分析改进了上述局限性,它可以研究任意形状的地基地质结构,能够反映埋藏基岩地形对地震波的折射、反射所产生的能量聚、散效应,埋藏基岩地形对地震地面效应的影响比上复松软土层土质不均匀的影响要大.超声地震模型实验首次引入工程地震学的研究课题中,得到了与上述数值分析方法相似的结果,并提出若干新问题.它提供了一种能够全面模拟震源—传播途径—场地地质结构的综合研究方法.
|