5月12日汶川8.0级地震强余震观测的电磁同震效应
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摘要
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。
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.
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.
引文
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苏巍,刘财,陈晨.2006.震电效应理论及其研究进展[J].地球物理学进展,21(2):379-385.SU Wei,LIU Cai,CHEN Chen.2006.Progress of seismoelectrics in theory and research[J].Progress in Geophysics,21(2):379-385(in Chinese).
Bernardi A,Fraser-Smith A C,McGill P R,et al.1991.Magnetic field measurements near the epicenter of theMS7·1Loma Prieta earthquake[J].Phys Earth Planet Interiors,68:45-63.
Fraser-Smith A C,Bernardi A,McGill P R,et al.1990.Low-frequency magnetic field measurements near the epicenterof theMS7·1Loma Prieta earthquake[J].Geophys Res Lett,17:1465-1468.
Gokhberg M B,Morgounov V A,Yoshino T,et al.1982.Experimental measurement of electromagnetic emissions possi-bly related to earthquakes in Japan[J].J Geophys Res,87:7824-7828.
Haartsen M W and Pride S R.1997.Electroseismic waves from point sources in layered media[J].J Geophys Res,102:24745-24769.
Haines S.2003.Development of experimental methods in electroseismics[A].In:Proceedings of the73Annual In-ternational Meeting.SEG Expanded Abstracts,22.557-559.
Johnston M J S,Mueller R J and Sasai Y.1994.Magnetic field observation in the near-field the28June1992MW7·3Landers,California,earthquake[J].Bull Seis Soc Am,84:792-798.
Karakelian D,Beroza G C,Simon L.2002.Analysis of ultra lowfrequency electromagnetic field measurements associat-ed with the1999M7·1Hector Mine earthquake sequence[J].Bull Seism Soc Am,92:1513-1524.
Kinoshita M,Uyeshima M and Uyeda S.1989.Earthquake prediction research by means of telluric potential monito-ring,progress report No.1:Installation of monitoring network[J].Bull Earthq Res Inst,Univ Tokyo,64:255-311.
Matsushima M,Honkura Y,Oshiman N,et al.2002.Seismoelectromagnetic effect associated with the Izmit Earthquakeand its aftershocks[J].Bull Seism Soc Am,92:350-360.
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