2019年9月16日甘肃张掖发生5.0级地震，地震发生前既有空间范围跨度较大的地磁低点位移异常，也有单台电磁扰动异常；既有震前2年开始出现的山丹台视电阻率的年变形态畸变，也有震前3个月之内出现的高台钻孔应变和高台大庄低频电磁扰动异常。本次地震震级不高却记录到丰富的电磁场的异常信号，表明该地区处于地震电磁异常的敏感区。高台钻孔应变在震前观测到同步的异常变化，揭示孕震区应力状态发生了显著的变化。

On September 16, 2019, when a M5.0 earthquake occurred in Zhangye, Gansu Province, the geophysical anomalies of multiple time and spatial scales were observed before the event, including "geomagnetic low-point displacement" that spanned an area of square kilometers and electromagnetic disturbance on a single observatory. In addition, there exist both annual distortion of apparent resistivity of Shandan observatory which lasted for 2 years and borehole strain anomalies and low frequency electromagnetic disturbance at Gaotai observatory which appeared within 3 months prior to the Zhangye earthquake. Abundant abnormal signals were observed although the magnitude of the Zhangye earthquake is not a very big one, which indicates that the fault of northern margin of the Qilian Mountain is a sensitive region of seismic electromagnetic signal. The synchronous abnormal changes of the borehole strain at Gaotai observatory revealed that the stress in the seismogenic region had changed significantly before the earthquake.

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2020年度震情跟踪定向工作任务(2020020404)、国家重点研发计划(2017YFC1500502)共同资助