Radon anomaly and earthquakes in Sichuan Province

In the early period of observing the content of water radon in Sichuan Province,the value of water radon in some of observing points presented changes relative to medium-strong earthquakes occurred around.The water radon anomaly is taken as an important index to the earthquake prediction of Songpan-Pingwu in 1976.Analyzing the changes of water radon in the whole period from the beginning of water radon observation,we find that the whole corresponding rate(the water radon changes to earthquakes)is low.Further studies indicate that the anomaly changes are complicated and the water radon is only one index for the prediction of medium-strong earthquake in Sichuan Province.