Analysis of rough data by Chinese geologist Fan Xiao, cited by the prominent scientific journal Nature, connects heightened seismic activity to August’s Ludian earthquake.
“When choosing the site of [a] hydropower station, our government would make [a] seismic safety evaluation,” Xu Xiwei, deputy director of China Earthquake Administration’s Institute of Geology in Beijing, told news portal thepaper.cn yesterday, “so the hydropower station would be sited away from [an] active fault and will not be constructed in an area that’s prone to earthquakes.”
Xu’s comment came after a report by Nature, a prominent scientific journal on September 10, cited an analysis by Fan Xiao, an engineer at the Sichuan Bureau of Geology and Mineral Resources in Chengdu, as saying that crude data he collected showed a rough correlation between a 6.5-magnitude earthquake in Ludian, Yunnan province last month in which more than 600 people were killed and the filling of Xiluodu reservoir on the upper Yangtze River.
Xu said some earthquakes – mostly of middle- or small-scale – might be possibly triggered by dams, “but the affected regions would be within 10 kilometres surrounding the reservoirs,” Xu told thepaper.cn, “as the distance between the epicentre of Ludian quake and the dam is about 40 kilometres, the influence would be not big”.
The Nature report cited Fan’s analysis, in which he said he took seismic readings from January 2010 to July this year and discovered that “small quakes became more frequent in late 2012 and continued until the end of the period… [when] heightened activity roughly correlates with the reservoirs being filled,” including Xiangjiaba [reservoir] on the Jinsha River.
Fan’s analysis said the most affected areas of reservoir filling include the one close to a fault whose rupture led to the Ludian earthquake.
His report was posted on a website of Probe International, a non-profit organisation focusing on large-scale water projects on the mainland.
But in the Nature report, Fan also acknowledged that his studies had limitations because of the lack of seismic data, which are tightly under control of hydropower companies.
As evidenced by the dispute between Xu and Fan, the latest earthquake in Ludian has renewed discussions among the mainland’s geologists and researchers, as some worry that the series of dam projects along the fault on the upper Yangtze River, especially Xiluodu dam and Xiangjiaba dam, might indeed bring huge risks to nearby regions.
“Although there’s no clear links [between earthquake and reservoir], there’s no doubt that the risks are there,” said Weng Lida, former head of the Yangtze River Water Resources Protection Commission. “Power companies and local government should keep closer monitoring and do more research before and after reservoir projects. Otherwise, the risks would be hard to [imagine].”
Heated discussions over the links between reservoir projects and earthquakes have been raised since 2008 when an 8.0-magnitude earthquake in Wenchuan, Sichuan province rocked the region and killed nearly 70,000 people, leading some geologists to say the quake might have been triggered by the filling of Zipingpu reservoir, which is 5km from the epicentre.