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a study of the crustal stability in the yangtze three gorges area
Pages: 23-31,56
Year: Issue:  1
Journal: Engineering Sciences

Keyword:  GetLinkList(KeywordFilter('Three Gorges Dam on the Yangtze Huangling block strong seismogenic zone crustal stability')'kw''CJFQ');
Abstract: The Three Gorges Dam on the Yangtze River is situated on the intact rock mass composed of diorite granite at the southern termination of the Huangling block which, as a sub plate with a double layer structure (crystalline basement and sedimentary cover) in the Chinese inland, keeps a constant but slow uplift as a whole since its formation in the Indoncisia movement. Tectonic deformation within the block is not significant, with the exception of a slight southeastward tilt. The block is confined by many active structures, of which the sub longitudinal Yuanan and Xiannvshan ( Mount Fairy ) deep fault zones are the main strongly seismogenic zones. The Yuan'an fault zone represents a regional boundary among West Henan, West Hubei and West Hunan mountainous regions as well as the Nanyang, Jianghan and Dongting Lake basins, with a total length of more than 1,000 km. Two M 6 5 earthquakes (in Changde and Nanyang) occurred in the fault zone in historic time and the distance between the two epicenters is about 500 km. The Mount Fairy fault zone extends northward along the Xiangxi River and ends at the Qingfeng fault. It runs a total length of more than 220 km. southward across Yuyang Pass and then its trace is unknown. The fault zone has a tectonic condition for occurrences of M 6.0 earthquakes. The possible seismic risk for the dam may come from these two strong seismogenic zones. Thus the seismic intensity to influence the dam is estimated to be Ⅵ~Ⅶ and the horizontal peak acceleration to be 0 1~0 15 g.
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