利用HHT方法，对汾渭地震带1965一2011年度最大地震时间序列进行逐级分解，得到4个本征模态函数（IMF）项和一个趋势项，分析了各个IMF分量不同周期成份，结果显示，汾渭地震带地震活动既存在比较稳定的周期，也具有一定的时变性。1965年以来,在IMF1-IMF4的时间尺度上汾渭地震带Ms ≥4.0地震一共有5个活跃期。同时M ≥4.0地震存在3年和7年左右的活动周期,还存在16年、23年、44年左右的弱活动期。

With 1965 a 2011 annual maximum seismic time series utilize the HHT method Fenwei earthquake the gradual decomposition the four intrinsic mode functions (IMF) items and a trend item, Analysis the different cycles ingredients of each IMF component, results showthe seismic zones Fenwei activities stable cycle exists, but also has a certain time-varying. Since 1965 in the time scale IMF1-IMF4 Fenwei the earthquake with Ms ≥ 4.0 earthquake, a total of five active period.Exists M ≥ 4.0 earthquake activity cycle of about three years and seven years, there are still 16 years, 23 years, 44 years or so weak activity period.