采用伪魏格纳-维勒分布对静日和扰日的地磁场Z分量数据进行时频分析,结果表明周期为6～24h的静日变化在静日和扰日的各个台站都存在;而2～6h部分既受外源场影响,也反映了区域信息,表现出感应磁场和地壳磁场的特征。采用平滑伪魏格纳-维勒分布对汶川8.0级地震前各台的Z分量数据进行时频分析,结果显示震中附近的地磁台站在震前记录到了周期约为4.4h的异常信号,其振幅随震中距增大而减小。

Using Pseudo Wigner-Ville Distribution （PWVD） in time-frequency analysis of geomagnetic Z-component on magnetically quiet and disturbed days, we discover geomagnetic daily variations with period 6 - 24 hour in all stations. The part with period 2 - 6 hour is not only influenced by external field, but also contains regional information, which shows the characteristics of crustal and induction field. Using Smoothed Pseudo Wigner-Ville Distribution （SPWVD） in time-frequency analysis of geomagnetic Z-component before the Wenchuan MsS. 0 earthquake, we found that the geomagnetic stations near the epicenter recorded an abnormal signal with period 4.4 hour before the major earthquake, and the amplitudes of the signal in different stations decreased with epicentral distance increased.

“十二五”国家科技支撑项目（2012BAK19804-01-04）和中国地震局青年震情跟踪课题（2012020401）共同资助