长江三峡大坝座落于黄陵断块南端由闪长花岗岩组成的完整岩体上。黄陵断块作为中国内陆的次级板块具有典型的双层结构（结晶基底和沉积盖层），自印支运动形成以来一直呈持续、缓慢的整体抬升，断块除向东南轻微倾斜外，内部构造变形不明显。断块为多条活动构造所围限，其中近南北向的远安和仙女山两条深大断裂为主要强震发生带。远安断裂带为豫西、鄂西、湘西山地和南阳、江汉、洞庭盆地的一条区域性分界线，全长约1000 km，该断裂带历史上曾发生过两次6.5级地震（常德、南阳），两次地震震中相距约500km；仙女山断裂带沿香溪河向北延伸终止于青峰断裂，向南越过渔洋关后，形迹不明，全长达220 km，该断裂带具有发生6.0级地震的构造条件。大坝可能遭遇到的地震危险主要来自这两条强震发生带，对大坝的影响烈度预计为6°～7°，水平峰值加速度0.1～0.15g。

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. The Huangling block as a sub-plate having double-layer structure (crystalline basement and sedimentary cover) in China continent keeps constant and slow uplifting as a whole since its formation in the Indosinian movement. Tectonic deformation within the block is not significant, with exception of a slight southeastward tilting. The block is confined by many active structures, of which the sub-longitudinal Yuan*an and Xiannushan deep fault zones are the main strongly seismogenic zones. The Yuan´an fault zone represents a regional boundary between 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 1000 km. Two times M 6.5 earthquakes (the Changde and the Nanyang earthquakes) had occurred in the fault zone in historic time and the distance between the two epicenters is about 500 km. The Xiannushan fault one extends along the Xiangxi River northward and ends at the Qingfeng fault. It runs southward across Yuyangguan Pass and then its trace is unknown. Total length of the fault zone is more than 220 km. The fault zone has tectonic condition for occurrence of M 6 earthquake. The possible seismic risk for the dam may come from these two strong seismogenic zones, thus the seismic intensity influencing the dam was estimated to be 6°〜7° and the horizontal peak acceleration to be 0.1〜0.15 g.