图37  共和7.0级地震前乐都水氡异常曲线

      （a）月均值曲线；（b）日测值指数窗速率曲线

Fig. 37  Curves of  radon amomalies in groundwater before

         the M7.0 Gonghe earthquake at Ledu station

      （a）Monthly mean value；

      （b）Velocity curve of daily observation exponential window