A somewhat technical news article at the BBC. This recap-translation may contain errors, and corrections are welcome.
A reservoir 5.5 kilometers away from the epicenter of the Wenchuan Earthquake of last year may have caused the disaster, some geologists say. In a telephone interview with the BBC’s Chinese website, Sichuan Geological Bureau’s regional geological survey team chief engineer Fan Xiao (范晓) said that the pressure of more than 300 mn tons of water stored up by the Zipingpu Dam (紫坪铺大坝) potentially influenced the time and magnitude of the earthquake. But he also said that it would take more analysis of the collected data before a conclusion could be made. Science (科学) last month’s edition published the remarks of several earthquake experts who expressed concern about the possible link, writes the BBC. [The 科学 online edition apparently doesn't contain the article.]
The BBC also quotes a researcher of geophysical disasters at Colombia University saying that the hundreds of millions tons of waters created an unnatural pressure on the neighboring Beichuan fault. Although he didn’t draw a direct link with any dam, he said that the storage multiplied the natural pressure on crustal movements by 25 times.
There are other experts who do not agree with this theory, although some of them do think of the reservoir as one factor. National Seismological Bureau geophysicist Lei Xinglin (雷兴林) says that osmosis from the reservoir to the fault and the water level from December 2007 to May 2008 were a factor in shaping the earthquake, but that it was too early for final conclusions. Also, the idea that dam itself created the earthquake was somewhat ridiculous. His view is supported by an earthquake researcher (Chinese name transcription: 马森 or Masen) of the British Geological Survey who says that the earthquake was a result of tectonic activity. If at all, one could say that the dam made the earthquake happen earlier.
Fan Xiao, during the telephone interview with the BBC, agreed that the earthquake would have happened anyway. But he also said that the idea of reservoirs inducing earthquakes was that when they were built in potential earthquake zones, they did interfere with earthquake activities, and the result of that was that they made earthquakes happen some time after the storage of water. Also, with an epicenter close to the reservoir, the magnitude of the quake could by far exceed that of a merely natural earthquake.