China's Haicheng earthquake on February 5, 1975 is the only earthquake that was accurately predicted. The earthquake measuring 7.3 on Richter scale was predicted on the basis of observations of change in land elevation and groundwater levels. Study of animal behaviours prior to the earthquake was a part of the prediction exercise.
Scientists conducted an elaborate study of this region's seismic activities. After this, as a part of the medium-term prediction, scientists monitored the changes in geophysical precursors. For example, in late 1973 and 1974, a number of changes and variations in geophysical precursors were reported: ground surface rose at 20 times its normal rate. Based on these observations, it was predicted that an earthquake would strike within two years. On December 20, 1974, an earthquake warning was issued based on changes in the geophysical precursors. Two days later, an earthquake of magnitude 4.8 struck the Liaoning Province convincing the scientists that another larger earthquake was about to strike. Carrying forward their observation, it was noticed that many foreshocks were striking the region and geological changes were prominent. Based on these, a warning was issued on February 4, 1975. The next day the earthquake struck. The warning saved the lives of about 100,000 people. Despite this, there was no warning of the Tangshan earthquake in 1976 that killed 250,000 people.