5月12日汶川8.0级地震强余震观测的电磁同震效应

2008年5月12日汶川8.0级大地震发生后,在武都汉王地震台及其附近地区进行了为期22d的余震序列电磁异常连续监测,观测到多次余震事件的电磁同震现象。通过与汉王强震台的地震记录数据比较发现,同震信号存在于所有的电场和磁场记录分量中,它们与地震波的到达同步,而不是在地震发生的时刻出现。地震发生时的电磁辐射信号似乎在记录数据中有所显示,但是与地震波到达观测点时的电磁信号相比幅度要小得多

COSEISMIC SIGNAL ASSOCIATED WITH AFTERSHOCK OF THE M_S 8.0 WENCHUAN EARTHQUAKE

The measurement of electromagnetic field for monitoring aftershock series has been done by continuous observation after the MS 8.0 Wenchuan earthquake on May 12,2008 in Hanwang Observatory,Longnan,Gansu Province and vicinity for 22 days since May 22,2008.Two V5-2000 instruments for MT measurement made by Phoenix Company were set up 2.5km away from each other near Hanwang Observatory where a geophone for strong earthquake recording was set up.The coseismic signals of aftershocks exist in all components of the magnetic and electric fields of the two electromagnetic sites.Comparing with the seismic data at Hanwang station,the signals arrive simultaneously with the seismic waves and do not at the origin time of the earthquake.The main frequency of both seismic waves and electromagnetic signals is almost the same.The signal produced at the origin time of the earthquake seems apparent in the EM data,but the signal amplitude is much smaller than those of seismic wave arrival.