(December 16, 2013) A 5.1-magnitude earthquake struck a mountainous and populous area of China’s Hubei Province today, 100 kilometres from the Three Gorges Dam site. Officials have been quick to reassure the public that the dam has remained intact and is operating normally after the event, which occurred at 1:04 p.m. in Enshi Tujia and Miao Autonomous Prefecture, Badong County. Aftershocks and quake-triggered landslides are expected. What more could there be to this story?
By Lisa Peryman for Probe International
A strangely well-timed report entitled “Experts hail Three Gorges project, deny link to disasters,” published two days before today’s earthquake by China’s state-run Xinhua news agency, strived at length to counter concerns the country’s Three Gorges Dam might be the cause of alarming impacts, such as earthquakes, as a result of its operations; an article likely prompted by growing fears regarding large dams in seismic-prone areas, which has generated a fair amount of media interest in China this year [see Are dams triggering China’s earthquakes?].
Emphasizing the successful operation of the controversial Three Gorges Dam for the past decade, Xinhua News quotes Gao Anze*, a former chief engineer with the Ministry of Water Resources, who says, “it is normal to have different views on such a massive project,” and that accusations of the project’s negative environmental and climate impact, and its role as a trigger for geological disasters and even earthquakes, did “not have scientific basis and will not help nurture objective evaluations on the impacts of the Three Gorges project.”
But fears are justified and, contrary to Gao Anze’s claim, they do have a scientific basis.
A 2011 Chinese study by seismologists at the China Earthquake Administration, a government agency, found that the massive Three Gorges Dam — which sits atop two major fault lines, the Jiuwanxi and the Zigui-Badong — had triggered around 3,000 earthquakes and numerous landslides in the dam’s reservoir (in the six years after inundation began in 2003), representing a 30-fold increase over pre-dam seismic activity in the area. The study concluded that the Three Gorges Dam on the Yangtze River had “significantly increased” seismic activity along the dam’s reservoir and also helped to explain a spate of landslides that have caused havoc in the region.
Man-made dam reservoirs, particularly large reservoirs built on fault lines where a vast amount of water would add substantial pressure to any existing fractures, prompted alarm in China’s southwestern Sichuan Province earlier this year in April when a magnitude-7 earthquake struck Lushan County in Ya’an City. Some experts believe the April quake may have been an aftershock of Sichuan’s major 2008 earthquake disaster, which they argue may have been triggered by the Zipingpu Dam reservoir – due to a phenomenon known as “Reservoir-induced Seismicity (RIS).” Scientists have observed that reservoir impoundment (the filling of the reservoir) may not only increase the risk of strong earthquakes, especially in areas already vulnerable to high-intensity seismic activity, but may represent a more pronounced risk in the first few years after a dam is filled. [See also Did the Zipingpu Dam Trigger China’s 2008 Earthquake? The Scientific Case].
Meanwhile, today’s earthquake in Badong County, described as “moderate but dangerous,” is reported to have injured three people so far, flattened 79 houses and left 1,543 houses severely damaged. The total cost of damage to property in rural areas has been estimated at around 16 million yuan (2.6 million U.S. dollars). Reports on the quake’s impacts remain ongoing.
Hu Xing’e, vice head of the Three Gorges dam project’s management bureau with the China Three Gorges Corporation, told Xinhua News, that although the earthquake today ranked as the largest in recent years to have occurred near to the project site, the event had not impacted the dam.
The Land and Resources Department of Hubei Province said the earthquake had already caused several large landslides, and had collapsed and cracked houses within close proximity, reports Xinhua News.
According to the China News Service, residents in the Three Gorges reservoir region report having clearly felt the earthquake.
Although today’s tremblor, with its relatively shallow depth of around 3 miles below the surface, is considered moderate, it may portend further risk to the region. According to John Jackson, a geologist with a detailed knowledge of western China, shallow earthquakes (less than 10 km deep) indicate active faults that could be reactivated by routine practices, such as the filling of a reservoir to accommodate flood waters and its drawdown to generate power. The location of large dams near clusters of recorded earthquakes with magnitudes greater than 4.9, and especially when the earthquake focal points are also close to the surface, “is cause for grave concern,” he said. [See Feverish Chinese dam building could trigger tsunami].
With files from Mu Lan, the editor of Three Gorges Probe (Chinese language edition).
* Gao, however, did express concern in regards to the dam project’s sedimentation problem, first illuminated by Probe International in 2003, the year the dam began operation [see Three Gorges sedimentation concerns build up].
For a succinct overview of the dangers China’s dam fever represents to its waterways, ecosystems, agriculture and fisheries, traditional livelihoods, species survival and even to its geological stability, see China’s great dam boom: A major assault on its rivers.
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Categories: China's Dams, Dams and Earthquakes, Dams and Landslides, RIS, Three Gorges, Three Gorges Probe, Zipingpu
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