SEISMIC HAZARD ASSESSMENT OF THE THREE
GORGES PROJECT
Yao Yunsheng，Wang Qiuliang，Li Jinggang，Shen Xueling and Kong Yuyang
【摘 要】Abstract:Seismic monitoring data for the past 50 years in the Three Gorges Reservoir area show that the reservoir head area is a typical weak seismic region with low seismicity before impoundment and that the epicenters were concentrated in the east and west sides of the
Zigui
Basin，most
of
which
were
natural
tectonic
earthquakes．After impoundment，the seismic activity shifted to the segment between Badong and Zigui along the Yangtze River，mainly within 5 km of the reservoir bank．The seismogenesis was categorized into four types:Karst collapse earthquakes，earthquakes caused by Karst gas explosion，mining tunnel collapse earthquakes，and rock(terrane)slip earthquakes，all of which are related to the lithology，structure，and tectonics of nearsurface geological bodies of the area．Compared with the seismicity before impoundment，the seismic frequency increase was remarkable，with most of the magnitudes below M s2.0．Therefore，the intensity of the earthquakes remained at a low level．On November 22，2008，a magnitude 4．1 earthquake，the largest earthquake recorded since impoundment，occurred in Quyuan Town，Zigui County．The intensity and PGA of reservoir-
Seismic hazard assessment of the Three Gorges Project
