2013年甘肃岷县漳县Ms6．6地震震电磁信号和同震信号观测

The Seismo-Electromagnetic Signal and Coseismic Signal of 2013 Minxian-Zhangxian Ms6.6 Earthquake

2013年岷县漳县Ms6．6地震发生时，位于距震中约286km外的固原地区的两个地点正在实施大地电磁测量，对这两个测点电磁仪器记录到的电磁场时间序列和邻近固原地震台站记录的地震波形进行了对比分析，并结合岷县漳县地震震源区的深部电性结构特征和震电场理论数值模拟研究等结果，探讨了震电磁信号的激发机理。结果表明：大地电磁仪器不仅记录到了该次地震的地震波传播过程中“地震波驱动同震电磁效应”产生的同震信号波形，而且记录到了地震破裂过程中所激发的震电磁信号波形；岷县漳县地震震源区和震中到观测点一线区域中下地壳存在的低阻层，构成了震电磁信号传播的“导电通道”；岷县漳县地震电磁震电磁信号早于地震P波38s左右到达，且持续了4s左右，如果能捕捉到震电磁信号并用于地震预警，将可以大大减少因地震导致的人员伤亡。

Magnetotelluric survey is ongoing at two sites in Lueyang and Guyuan aera, while 2013 Minxian-Zhangxian Ms6.6 earthquake happened. The survey sites are about 286km away from the epicenter. In this paper, we compared and analyed the time series data with the seismic waveform data recorded by three magnetotelluric instruments and the nearby Guyuan seismic station, and combined with the chatacteristics of earthquake source area＇s deep electric structure of Minxian earthquake and the results of theoretical simulation of seismic electric field in order to investigate the excitation machanism of the seismoelectromagnetic signal. Our findings suggest that magnetotelluric instruments at two sites detected not only the coseismic signal generated by the ＂coseismic electromagnetic effect driven by seismic wave＂ during the seismic wave＇s propagation of this earthquake, but also the notes of the seismoelectromagnetic signal produced by source rupture. The low resistivity layer in lower crust of the region of earthquake source and the line zone from epicenter to observation results in a ＂conductive channel＂ to seismoelectromagnetic signal propagation, which causes the seismoelectromagnetic signal arrived earlier 38 seconds than seismic P wave and last for 4 seconds. If the signal can be captured it will be great significant in earthquake early warning system to reduce casualties.