两次4.0级地震前高邮台和盐城台地磁谐波振幅比异常分析

Analysis on the Seismic Anomaly of Geomagnetic Harmonic Wave Amplitude Ratios of Gaoyou Station and Yancheng Station before Two Earthquakes with M4.0

摘要:

使用江苏地区9个地磁台站2009年1月~2016年10月的分钟值数据，计算得到各台站的地磁谐波振幅比时间序列变化曲线。分析发现，2012年7月20日高邮4.9级地震、2016年10月20日射阳4.4级地震前，高邮台和盐城台地磁谐波振幅比Y_ZHx和Y_ZHy分别出现了长短周期不同步的异常变化。其异常特征表现为：①异常的长期变化形态为“下降—转折—恢复”，在恢复过程中出现不同步现象，异常持续时间近3年，异常幅度为0.02~0.17；②Y_ZHy向的异常幅度大于Y_ZHx向，同时，2次地震主震的主压应力方向为EW向，存在异常幅度较大方向与主压应力方向一致的特点。

Abstract:

The series of geomagnetic harmonic wave amplitude ratios are calculated in this paper,by using minute sampling data of 9 stations in Jiangsu from January 2009 to October 2016. The asynchronous changes of the long period and the short period of geomagnetic harmonic wave amplitude ratios are considered anomalous observed before earthquake. The geomagnetic harmonic wave amplitude ratio anomaly of Gaoyou station was found before the Gaoyou M4.9 earthquake,July 20,2012. And that of Yancheng station was found before the Sheyang M4.4 earthquake,October 20,2016. There are three anomaly features. The first one is asynchronous changes in the anomaly recovery period. The duration of anomaly is about 3 years and the amplitude of anomaly is between 0.02 and 0.17. The second,the amplitude of Y_ZHy is larger than Y_ZHx in two anomalies. The E-W direction is the principal compressive stress direction in the Gaoyou earthquake and the Sheyang earthquake. The direction of larger amplitude is considered to be consistent with the principal compressive stress direction.