孙进忠1, 彭一民1, 赵鸿儒2. 1988: 北京凹陷地震地面运动超声模拟. 地震学报, 10(1): 98-109.
引用本文: 孙进忠1, 彭一民1, 赵鸿儒2. 1988: 北京凹陷地震地面运动超声模拟. 地震学报, 10(1): 98-109.
SUN JINZHONGup, PENG YIMINup, ZHAO HONCRUup2. 1988: SUPERSONIC MODELLING OF EARTHQUAKE GROUND MOTION IN THE BEIJING DEPRESSION. Acta Seismologica Sinica, 10(1): 98-109.
Citation: SUN JINZHONGup, PENG YIMINup, ZHAO HONCRUup2. 1988: SUPERSONIC MODELLING OF EARTHQUAKE GROUND MOTION IN THE BEIJING DEPRESSION. Acta Seismologica Sinica, 10(1): 98-109.

北京凹陷地震地面运动超声模拟

SUPERSONIC MODELLING OF EARTHQUAKE GROUND MOTION IN THE BEIJING DEPRESSION

  • 摘要: 1976年唐山大地震震害调查表明,北京城区震害异常带的分布与北京凹陷的西北及东南两翼相对应。 垂直于北京凹陷长轴切取场地剖面,分別将覆盖层和基岩简化为均质体,按相似性要求设计模型。设震源位于场地的东南方向,选择与天然地震震源辐射特征相似的发射换能器模拟之,同时采用对不同方向的振动具有不同灵敏度的换能器,来拾取模拟地震地面运动的各分量。 由模拟实验观测得到,在随震中距离增加而衰减的总趋势之上,天坛、前门和西四附近模拟地震地面运动大大加强,这与宏观震害的分布吻合较好。模拟地震地面运动表现为先颠后摇,并且铅垂向振动具有一定强度,水平振动的大能量段持续时间较长,其反应谱呈现双峰乃至多峰形。另外,同一时刻不同地点水平地震力存在差异,这是产生水平力偶的原因之一,1976年唐山大地震时北京城区的地震破坏与上述结果较为一致。 进一步的分析研究揭示了埋藏基岩面形态对地震地面运动影响的物理实质。 本文还就基岩面的变化对地震波影响的规律方面也进行了探讨。

     

    Abstract: The investigation of the earthquake damages during the Tangshan big earthquake of 1976 showed that the distribution of anomalous zones of shock calamities in Beijing City corresponds to the two wings of the Beijing depression.Taking a cross-section perpendicular to the long axis of the Beijing depression, and simplifying both the coverlayers and bedrocks into homogeneous bodies, a model is designed in the light of the requirements of simulation. It is presumed that the centrum lies in the southeastern part of the site and it is simulated by the transmitting transducer which has similar radiation characteristics with the centrum of nature earthquakes. At the same time receiving transducers with different receiving senstivity along different directions are used in order to pick up every component of seismic ground motion.It is observed in the experiment that on the general attenuation trend with increase of distance from the earthquake center, the simulated earthquake ground motion intensifies greatly near Tiantan, Qianmen and Xisi, and this coincides well with the earthquake damages. Simulation of earthquake ground motion shows that the shocks are in the manner of 'shaking after bumping'. The vertical component has a considerable intensity and the duration time of the most energetic part of the horizontal components is longer. The response spectrums of the horizontal components show the shapes of double or multiple peaks. In addtion at one time there are differences among the earthquake forces at different places, and this is one of the causes which produce the horizontal couple of the earthquake. The earthquake damages in Beijing City during the Tangshan big earthquake of 1976 are in good correspondence with the above results.Further analyses and investigations reveal the physical essence of the effects of underlying bedrock topography on earthquake motion, and the paper also inquire into the regularity of the effects of the varying of bedrock surface on seismic waves.Having considered the centrum, propagation paths and the geological structures of the site, the method of supersonic seismic model experiments is an ideal method for the synthetic investigation of the problems of earthquake ground motion. This paper is a priliminary attempt to introduce this method into the study of the problems about effects of the underlying bedrock topography on earthquake ground motion.

     

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