ON THE CAUSE OF LOW INTENSITY ANOMALY IN YUTIAN DURING THE TANGSHAN EARTHQUAKE
Liu Zengwu, Kou Dianqin, Lu Genshcng, Wang Dongqiang, Wei Peiheng, Wang Qipin(Institute of Engineering Mechanics, Academia Sinica)Dong Enchang (Exploration Com pany , Thisd Ministry of Machine Building)
In this paper, average weighted shear modulus is used as an index for measuring the effect of ground soil in the study of intensity anomaly in Yutian during the 1976 Tangshan earthquake. The cause of low intensity anomaly is primarily correlated to the ground soil with higher average weighted shear modulus (twenty meters thick) and consists of high percentage of coarse grain of soil.The effect of the thickness of ground soil to damage is discussed by comparing the average weighted shear modulus of various thickness of ground soil (e. g. ten meters, twenty meters and thirty meters) and damage. In addition, we calculated earthquake response of ground surface at various sites, and the correlation between characteristics of earthquake response versus damage was established. Finally, reliability of microzoning, using the average weighted shear modulus is testified by the field dala.