June 5, 2008
U.S. engineer Dr. Philip Williams has added his voice to concerns expressed by a Chinese expert that the Zipingpu reservoir, now cracked and damaged as a result of China’s devastating May 12 earthquake, could actually have induced the earthquake.
In a recent interview, Dr. Williams said: “I think there are substantial grounds for connecting the triggering of the earthquake to the filling of the reservoir as a Reservoir-Induced Seismicity event (RIS).” The dam’s reservoir is just 5 kilometres from the earthquake’s epicenter and it was filled only about 18 months ago, he pointed out. Both conditions are consistent with the phenomena of reservoir-induced seismicity in which increased pressure from water infiltrating into micro-cracks and fissures in the ground under and near a reservoir lubricates faults and induces slippage.
Dr. Williams echoes the concerns of Fan Xiao, chief engineer of the Regional Geology Investigation Team of the Sichuan Geology and Mineral Bureau who agrees that Zipingpu has all the conditions that provoke reservoir-induced earthquakes and who last week called for an investigation of whether the dam could have contributed to the temblor.
If Zipingpu, part of China’s dam building spree of the last decade, actually induced the May 12th earthquake then China’s dam building industry, consisting primarily of state agencies, can expect unprecedented and intense scrutiny. To date, many of China’s dams have been built without receiving official environmental approval, often with no public knowledge, and certainly without public oversight. Even if no link between the recent earthquake and Zipingpu is conclusively drawn, public concern about dam safety in the event of earthquakes will take on a whole new life as approximately one-third of China’s 88,000 dams are thought to be poorly constructed or dangerous.
According to Dr. Williams, the lesson from this earthquake is that “dams and their reservoirs should not be built on major active faults.” Moreover, he says, the planning of all dams must be transparent, so that issues like RIS can be scientifically assessed and weighed in the benefit-cost analysis so affected people can be properly informed of the implications.
As for dams that are already built, Dr. Williams adds, emergency evacuation contingency plans must be prepared, including the publication and dissemination of potential dam failure inundation maps. In all cases, Dr. Williams argues, dams must be designed to make sure that outlet structures can withstand maximum ground accelerations to allow for rapid reservoir drawdown in the event of damage to the dam.
Environmental groups in China voiced similar worries some three years ago when they signed a petition calling for an earthquake warning system around large dams and a stricter assessment of the vulnerability to earthquakes of dams proposed for China’s southwest region. In fact, during the planning of Zipingpu, Chinese authorities heard these concerns from their own officials including Fan Xiao, the Earthquake Bureau, and the Chinese Academy of Geological Science. Their collective concerns should be more seriously heeded now.
So far, public reviews by the country’s environmental regulator, the State Environmental Protection Agency, have been narrowly focused on environmental impacts and less on dam safety and emergency preparedness in the event of catastrophic failure. Now, the State Electricity Regulatory Commission can be expected to step in too as it has the mandate to review all costs and financial risks associated with project proposals that affect consumers electricity rates. And, whether induced or not by Zipingpu, China’s May 12 earthquake has pointed out just how costly the interrelationship can be between dams and earthquakes.