China has suffered some terrible earthquakes, and it isn’t surprising that China’s scientists want to find ways of forecasting them. In 1975, they were successful. They cleared the city of Haicheng two hours before a devastating quake and saved the city’s population. Earthquake forecasting is, however, still inexact; the Chinese have failed to predict several earthquakes since 1975, but they have advanced the science of earthquake prediction.
We now know that small tremors (foreshocks) often occur before a larger movement. Changes also occur in the electric and magnetic properties of rocks, and growing tension often causes swellings and cracks in the ground. When rocks cracks, a radioactive gas, radon, is often released. Radon dissolves in water and so, if the radon content in well water builds up, an earthquake may be on the way.
Chinese workers have also been asked to report strange behaviour by animals. Before quakes, dog may howl, nervous animals run from buildings and fish thrash about in water. Perhaps they sense changes which we can not detect.