极低频台站同震电磁信号特征分析  

ANALYSIS OF ELECTROMAGNETIC CO-SEISMIC PHENOMENA OBSERVED IN CSELF STATIONS

作　　者：韩冰[1] 汤吉[1] 赵国泽[1] 王立凤[1] 董泽义[1] 范晔[1] 孙贵成 HAN Bing;TANG Ji;ZHAO Guo-ze;WANG Li-feng;DONG Ze-yi;FAN Ye;SUN Gui-cheng(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Chengde Central Seismic Station,Hebei Earthquake Agency,Chengde 067000,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]承德地震监测中心站,河北067000

出　　处：《地震地质》2022年第3期753-770,共18页Seismology and Geology

基　　金：国家重大科学技术设施项目(1512Z0000001);中国地震局地质研究所基本科研业务专项(IGCEA1919)共同资助。

摘　　要：文中对景谷台站记录到的7次同震电磁现象及2次较强地震在周围几个极低频台站引起的同震电磁现象进行了研究,发现了总体形态与地震波相近的电磁波,其幅度远大于地球感应产生的背景信号,且垂直磁场强度约为水平磁场的10倍。对于同一台站记录到的多次同震电磁信号,幅值与震级在对数域基本满足线性关系,同时也受震源深度与震中距影响。在同一地震中,震中距越大,台站记录到的同震电磁信号出现的时间越晚,持续时间也相对较长,但信号的幅值不仅受到震中距的影响,还与观测点的近地表介质有关。通过小波能量谱可以看出,同震电磁信号的主要频率为1~2Hz,在同震信号初始阶段高频成分较多,并表现出随震中距增加频率降低的特点;同时相对于电场,磁场记录的高频信息更加丰富。2014年景谷M6.6地震发生时,在距离震中很近的台站记录到比同震信号更强的尖峰信号,其在地震波到达之初出现。推测偶然的电磁强干扰与地面震动互相叠加是引起电磁信号强烈变化的原因。With the support of the wireless electro-magnetic method(WEM)project,the control source extremely low frequency(CSELF)continuous observation network,which includes 30 electromagnetic stations in Beijing capital area(BCA)and the southern section of the North-South Seismic Belt in China,was built for recording the artificial and nature source singles.The natural source observation of the network was started in July 2013 and December 2013 in batches and the electromagnetic field was recorded continually with a sampling rate of 16Hz.Until now,the co-seismic electromagnetic signals have been recorded repeatedly in several stations.In this paper seven co-seismic electromagnetic signals recorded at Jinggu station and co-seismic electromagnetic signals associated with two strong earthquakes recorded at different stations surrounding the epicenter are studied.It is found that the variation of the EM filed is similar to the seismogram,and the amplitude of the co-seismic EM signal is much larger than the background signal generated by earth induction,and the intensity of the vertical magnetic field is about ten times as big as the horizontal electromagnetic field.For co-seismic EM signals recorded at the same station,the relationship between the amplitude of electromagnetic field and the magnitude of the earthquake is basically linear in logarithmic domain.Meanwhile,the amplitude of electromagnetic field is also affected by focal depth of the earthquake and distance between the stations and the epicenter.When the epicenter distance is close,the amplitude of the co-seismic signal caused by the earthquake with shallow focal depth is higher.When the focal depth is similar,the amplitude of electromagnetic co-seismic signal caused by the earthquake closer to the station is larger.For the co-seismic EM signals associated with a same earthquake recorded by different stations,the larger the epicenter distance is,the later the signal appears and the longer the duration is.However,the signal amplitude is not only affected by the epic

关 键 词：极低频电磁台网 同震电磁信号 小波变换 

分 类 号：P315.722[天文地球—地震学]