Dams and Earthquakes

Earthquake hits Three Gorges area

Three Gorges Probe
January 4, 2002

An earthquake with a magnitude of 4.1 shook an area 40 kilometres upstream of the Three Gorges dam last month, the Three Gorges Project Daily (Sanxia gongcheng bao) reported.

The tremor, which occurred at 1:43 p.m. on Dec. 13, was the biggest to hit Hubei province in the past 10 years. It was centred on a tributary of the Yangtze – the Xiangxi – and was felt across 20 square kilometres of the river valley.

No injuries were reported in the affected counties of Xingshan and Zigui. However, in one village alone – Jiajiadian village in Zigui county – the quake caused structural damage to 26 houses. In addition, a crack in a stone bridge halted traffic on the highway linking Xingshan and Zigui.

Seismic experts have warned that the quake-prone Xiangxi River basin is likely to experience stronger and more frequent tremors after the Three Gorges dam reservoir is filled in 2003.

Experts from China and Taiwan who gathered at a conference in October 2000 at the dam site concluded that the reservoir is likely to cause quakes of magnitudes ranging from 4 to 5.5, the Guangzhou Daily (Guangzhou Ribao) reported at the time.

The Xiangxi River is located in one of the two sections of the Yangtze that are expected to be most affected by these reservoir-induced quakes. This section, stretching from the dam upstream to Miaohe in Hubei province, is prone to weak earthquakes, generally with magnitudes of less than 4, which the experts said would have no significant impact on the safety of the dam.

They predicted that the next section of the Yangtze, stretching from Miaohe to Baidicheng in Fengjie county, Chongqing municipality, will be most at risk of the strongest of the reservoir-induced quakes.

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