2020年7月12日唐山古冶5.1级地震的电磁现象  

THE ELECTROMAGNETIC ANOMALY OF TANGSHAN GUYE M_(S)5.1 EARTHQUAKE ON JULY 12, 2020

作　　者：范晔[1] 汤吉[1] 缪杰[3] 叶青[2] 崔腾发 董泽义[1] 韩冰[1] 孙贵成 FAN Ye;TANG Ji;MIAO Jie;YE Qing;CUI Teng-fa;DONG Ze-yi;HAN Bing;SUN Gui-cheng(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;China Earthquake Networks Center,Beijing 100045,China;Lingyang Seismic Station,Shandong Earthquake Agency,Lingyang 276521,China;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;Chengde Earthquake Monitoring Center Station,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]中国地震台网中心,北京100045 [3]山东省地震局陵阳地震台,陵阳276521 [4]中国地震局地震预测研究所,北京100036 [5]承德地震监测中心站,承德067000

出　　处：《地震地质》2022年第3期669-685,共17页Seismology and Geology

基　　金：国家自然科学基金(41674081);中国地震科技计划项目(3JH-202001113);北京市自然科学基金(8212045)共同资助。

摘　　要：文中使用时间域波形分析、滑动傅式去年变分析、归一化变化速率方法和矢量方位角方法处理分析了2020年7月12日古冶M_(S)5.1地震震中距400km范围内的地电阻率、地电场、极低频观测数据。在排除各台站仪器运行、台站观测环境、空间电磁活动等影响因素后,认为有6个地电阻率台站于震前出现了“趋势性下降—加速下降—震后恢复”的变化过程,7个地电阻率台站在震前1a内的归一化变化速率超过±2.4阈值;滦县地电场NS和NW向测道于震前3个月出现先下降后回升的变化,且矢量方位角在震前向古冶地震方向偏移,后恢复为沿滦县-乐亭断裂方向;文安和丰宁极低频台清晰地记录到16hz天然源磁场同震变化,磁场垂直分量的变化超过水平分量的2倍,由于台站的地下结构存在巨大差异,2个台站的电场观测值差别较大,且电场同震扰动淹没在背景噪声中。文中利用首都圈极低频台站观测数据反演了地下电性结构,发现古冶地震的震源位于电性发生变化的边界附近,北边为高阻区,西南方向为低阻区,宝坻和文安处于局部低阻区,并据此初步分析了古冶地震的电磁现象特征。针对异常空间选择性问题,认为可能与京津唐地区NEE和NW向2个主要共轭构造方向有关。对地震电磁异常机理开展研究时,应从地震电磁同震现象入手,从地震电磁信号产生的源和传播路径2方面展开相关工作。On July 12,2020,an M_(S)5.1 occurred in Guye,Hebei Province,and as the largest earthquake in the capital circle in recent years,its unique geographical location has attracted more attention.During an earthquake,the electromagnetic properties of underground media will change,so dense electromagnetic observation stations were arranged in the capital circle.In this study,the data of geoelectric resistivity,geoelectric field,and extremely low frequency(ELF)observation within 400km of the Guye earthquake are analyzed using a combination of time-domain waveform analysis,sliding Fourier analysis with annual variation removed,normalized variation rate method(NVRM),and geo-electric azimuthal method.After eliminating the influencing factors such as operation status,observational environment,and the spatial electromagnetic effect,we analyzed the characteristics of electromagnetic phenomena that may be related to the Guye earthquake preliminarily and found that there was a variation process of“trend decrease—accelerated decrease—postseismic recovery”observed in 6 geoelectric resistivity stations and that the normalized variation rate exceeded the threshold value of±2.4 in 7 stations within one year before the earthquake.In Luanxian station,the intensity of the geoelectric field in the north-south and north-western directions decreased and then rose back before the earthquake.In addition,the azimuth shifted to the direction of the Guye earthquake in the preseismic period,and then returned to the direction of the Luanxian-Laoting Fault.The ELF stations in Wen′an and Fengning precisely recorded the coseismic change of the 16Hz natural magnetic field,in which the variation of the vertical component is twice larger than that of the horizontal component.Under the condition of large subsurface structure difference beneath the stations,the observed electric values from the two stations are distinctively different;moreover,the coseismic disturbance is submerged by the background noise.The subsurface electric structure was

关 键 词：古冶M_(S)5.1地震 地电阻率 地电场 极低频 电磁异常 

分 类 号：P315.721[天文地球—地震学]