The earthquake that erupted below Wenchuan County took less than two minutes to kill some 70,000 people and injure several times that number, mostly in Sichuan Province. Shock turned to grief, and then to anger, as Chinese began looking for someone to blame.

Nature is a force that can't be held guilty. But human beings can, and the target of much anger has been the staff of the official institution known as the China Earthquake Administration (CEA). A key mission of the CEA Institute of Earthquake Science, founded on Jan. 1, 1980, was to make short- and medium-term earthquake predictions.

An accurate forecast, of course, could have saved many lives, and many Chinese wonder why, after almost 30 years in operation, the CEA institute didn't provide one. Some online conspiracy theories hold that there were predictions, which were suppressed because of the upcoming Olympic Games.

CEA experts spoke out to the media, expressing sorrow for the losses but defending their work and denying a cover-up.

Can it be done?

Short-term quake forecasts -- meaning days or hours, with an accurate description of area and magnitude -- are almost impossible with current technology, the CEA experts said. "We are unable to penetrate deep under the earth, the conception of an earthquake is very complicated, and the recurrence of big earthquakes in a given region takes a long time," said CEA China Earthquake Networks Center (CENC) deputy director Zhang Xiaodong.

Accurate earthquake predictions remain a problem for scientists around the world, including China, which has a long historical record of quakes.

What's considered to be the first successful quake forecast was made in China more than three decades ago, involving a 7.3-magnitude quake in Haicheng, Liaoning Province, in northeast China. The prediction was based chiefly on a spike in minor quakes in the region.

But the same method failed to predict a huge quake the following year in Tangshan, near Beijing, which killed some 240,000 people.

In the Wenchuan case, there was no such foreshadowing surge in small quakes, said Che Shi, deputy chief of the CEA Monitoring and Prediction Division. The minor quakes were all less than 1.0 on the Richter scale. And no prediction was made.