While it may seem that we know much about tectonics, faulting, and the processes that cause earthquakes, it is not safe to assume that we have the ability to accurately forecast earthquakes. A few examples of successful predictions have indeed occurred, but many have failed, and some powerful earthquakes have struck, with little to no warning, in settings similar to those where predictions had previously succeeded.
The world's first successful prediction took
place in China on February 4, 1975, when the Chinese government issued
a specific, immediate warning of a major earthquake in the area of
the city of Haicheng, and began a massive evacuation effort.
The earthquake, measuring magnitude 7.3, followed about nine hours
later, just as the evening chill was setting in -- which had residents
contemplating a return to the warmth of their homes. Thankfully, most
remained outside until the earthquake occurred, and thus while 90% of the
city's buildings were severely damaged or destroyed, casualties were few.
Haicheng is located in an area of frequent earthquakes, and was being extensively monitored at the time. The monitoring efforts resulted in the decision to announce an earthquake warning only after assembling circumstantial evidence for an imminent earthquake from many different sources using several different techniques and "warning signs". The success of the prediction ultimately hinged on good fortune and massive government-backed monitoring efforts.
Similar methods led to two more successful predictions in the Yunnan and Sichaun provinces of China in the year following the Haicheng prediction. However, several other predictions were made which did not come true, casting some doubt on the reliability of official predictions. Just seventeen months after the Haicheng prediction, a powerful and unexpected earthquake beneath the city of Tangshan, 150 kilometers east of Beijing, provided solid support for these doubts, and shattered hopes that regular earthquake prediction would soon become a reality.
