THE MANGAI AND GONGHE EARTHQUAKES AND THE DYNAMIC ANOMALY OF FAULT GAS
He Genqiao Chang Qiujun Guo Yuying Song Yulan(Earthquake Research Institute of Lanzhou, SSB,China)
Observing the dynamic state of fault gas to study the interrelation of its anomalous variation and earthquakes is a new method for short-term and impending earthquake prediction. In this paper,the anomalous changes of fault gas Rn and Hg before the Mangai earthquake(M6. 7)and Gonghe earthquake (M 6. 9)of Qinghai province in 1990 are emphatically introduced. During the Mangai earthquake,anomalies occurred at four observing points, the farthest of which is Shibalipu,Gulang county,960 km from the epicenter. At the nearest Changcaogou point,Akesai county,260 km from the epicenter, the anomaly of gas Rn appeared 115 days before the earthquake. There is a certain interrelaton between the time appearing anomaly and epicentral distance. At Hongsihu .Shandan county,300 km from Gonghe,the short-term and impending anomaly variation of fault gas is very prominent, gas Rn suddenly decreased by 108%, 12 days before the earthquake occurrence,and gas Hg suddenly increased by 146%, 7 days before the earthquake occurrence. It is pointed out that the fault gas anomaly before earthquakes shows a better reappearance . Fault gases have the following prominent characteristics the variation range immediately before event is big and the area of anomaly is wide.