After processed with periodical filtering method we find fixed leveling anomalies have different phases in development,which can be divided into early term,medium term and imminent term three stages,and it has distinct sign turni.
本文应用周期滤波方法对短水准资料进行了处理 ,发现短水准异常地震前有明显的阶段性 ,异常发展可分为初期、中期、临震三个阶段 ,且具有明显的由中期向短临转化标志。