Nearly nine months after a devastating earthquake in Sichuan province, China, left 80,000 people dead or missing, a growing number of American and Chinese scientists are suggesting that the calamity was triggered by a 4-year-old reservoir built close to the earthquake’s geological fault line.
A Columbia University scientist who studied the quake has said that it may have been triggered by the weight of 320 million tons of water in the Zipingpu Reservoir less than a mile from a well-known major fault. His conclusions, presented to the American Geophysical Union in December, coincide with a new finding by Chinese geophysicists that the dam caused significant seismic changes before the earthquake.
Scientists emphasize that the link between dam and the failure of the fault has not been conclusively proved, and that even if the dam acted as a trigger, it would only have hastened a quake that would have occurred at some point.
Nonetheless, any suggestion that a government project played a role in one of the biggest natural disasters in recent Chinese history is likely to be politically explosive.
Questions about the Zipingpu Dam are especially delicate because China is building many major hydroelectric dams in the southwest, a region which has abundant water resources but is considered prone to earthquakes.
In a petition to the government in July, a group of environmentalists and scholars said the fact that government scientists had underestimated the risk of the May earthquake raised questions about a host of other dams built in the same valley and along five other major rivers, according to an article published by Probe International, an environmental advocacy group.
Chinese authorities have steadfastly dismissed any notion that reservoir-building in Sichuan province placed citizens at any added risk, and they have blocked some Web sites of environmental groups that suggest dangers have been overlooked.
In a December article in the Chinese magazine Science Times, two scientists from the Chinese Academy of Sciences strongly denied that the dam played any role in the earthquake.
“The earthquake research community outside and inside China has widely accepted the notion that the May 12 Wenchuan earthquake was a huge natural disaster caused by massive crustal movement, because no reservoir triggered-quake with a magnitude eight has ever occurred in history,” said Pan Jiazheng, an expert in hydroengineering, according to a translation published by Probe International.
Scientists generally agree that a reservoir, no matter how big, cannot by itself cause an earthquake. But Leonardo Seeber, a senior scientist with the Lamont-Doherty Earth Observatory of Columbia University, said the impact of so much water could hasten an earthquake’s occurrence if geological conditions for a quake already existed. He said the best known example was a 1967 earthquake triggered by the Koyna Dam in a remote area of India, with a magnitude of about 6.5 and a death toll of about 180 people.