2018年云南通海MS5.0和墨江MS5.9地震前地磁垂直强度极化异常时空特征研究

Spatial-temporal Variations of Geomagnetic Vertical Intensity Polarization Value Associated with the 2018 Tonghai MS5.0 and Mojiang MS5.9 Earthquake in Yunnan Province

摘要:

利用云南11个地磁台站的秒采样观测数据，计算和分析了地磁垂直强度极化值Y_zh在2019年8月13日、14日通海M_S5.0地震前及2019年9月8日墨江M_S5.9地震前的时空变化特征。研究表明，地磁台站Y_zh值的幅度在震前会出现同步增强现象。而与以往的极化震例研究相比，Y_zh值的高值异常在震前出现时间要更早些，可能会在震前2~5个月出现，距发震时间越近，产生的异常幅值可能越大，异常持续时间也越长。同时，研究还发现2次地震主要发生在异常空间等值线的高值区内，尤其在零值阈值线附近，这可能对今后发震地点的预测有一定的指示意义。对比异常产生时段内的D_st指数，认为该高值异常并非由空间电流体系所引起。

Abstract:

Based on the 1-second sampling data derived from 11 geomagnetic stations in Yunann Province,we calculated and analyzed spatial-temporal variations of vertical geomagnetic intensity polartzation value (Y_zh) before Tonghai M_S5.0 on August 13th and 14th,2018 and Mojiang M_S5.9 on September 8th,2019. The result shows that there exists an obvious enhancement of Y_zh' amplitude in most geomagnetic stations before the earthquakes. However,compared with the previous studies of earthquake cases,the high-value anomaly of polarization value appeared even earlier,probably 2~5 months before the earthquake. The closer the time is to the earthquake,the larger the amplitude of the anomaly may have and the longer the duration of the anomaly will be. Moreover,it is found that these two earthquakes mainly occur near the zero threshold line of the spatial contour. This may be of significance of indication for the prediction of the earthquake location in the future. Compared with the D_st index in the period of anomaly generation,the high-value anomaly was not caused by the space current system.