On May 12, 2008, a magnitude- 8.0 earthquake rocked mainland China's Sichuan Province, killing more than 69,000 people and shaking the world. There were repeated reports of unusual animal migrations in Sichuan prior to the temblor, and a government agency even correctly predicted that a quake was imminent. Unfortunately, officials chose to suppress the information.

Then again, hindsight is always 20/20 and the officials were in a no-win situation. On the one hand, there is no scientific basis for claims that animal migrations augur the arrival of earthquakes. On the other, the Sichuan Earthquake Administration's repeated erroneous warnings about aftershocks following the quake put the public on edge and led to complaints that the agency should be renamed the Aftershock Administration.

Sichuan's experience shows just how hard it is to predict quakes. Nine years ago, Taiwan's inability to provide advance warning of the massive Chichi earthquake similarly led to huge casualties. More recently, scientists have begun seeking reliable indicators of imminent earthquake activity in an effort to reduce the huge financial and human costs of major quakes.

In early February 1975, frequent small earthquakes of magnitude 2-3 struck the Haicheng County-Yingkou County area of China's Liaoning Province. When seismologists suggested that a major quake was on the way, the provincial government began making preparations to minimize the damage. At 10 a.m. on 4 February, officials issued an emergency evacuation order.

The government's preparations succeeded in limiting the death toll from that evening's magnitude 7.3 quake to just 1,300 people.

According to the United Nations, the Haicheng quake was the first major temblor to be accurately predicted. Unfortunately, it remains the only one. China, then a technological laggard, was proud of its achievement. But the following year's Tangshan earthquake quickly laid to rest the myth that scientists had a firm grasp on quake forecasting. Unheralded by foreshocks, the magnitude 7.8 quake caught China's earthquake authorities napping and left them watching awestruck as it leveled Tangshan and killed more than 242,000 people.