2013年岷县—漳县6.6级地震前地磁日变化异常及机理分析

利用空间相关法对2013年岷县—漳县6.6级地震前后151个台站地磁垂直分量日变化进行分析,结果显示:(1)2013年7月3日、4日在震中附近分别出现16和17个台站的地磁Z分量日变化明显反相位异常,具有明显的分界线。(2)利用S变换方法对分界线两侧的天水和兰州台的Z分量日变化进行分频率相关系数计算,发现7月3日、4日的地磁Z分量的日变化均在6 h左右的周期出现负相关变化。其他时段未出现类似变化,认为岷县—漳县6.6级地震前地磁Z分量日变化异常产生的反相位异常主要在6 h左右。此外,还对异常产生的机理进行了解释。

Characteristics and Mechanism of Geomagnetic Diurnal Variation before the 2013 Minxian-Zhangxian MS6.6 Earthquake

In this paper, the spatial correlation method was used to analyze the diurnal variation anomalies of geomagnetic vertical components obtained from 151 stations before and after the Minxian-Zhangxian M_S6.6 earthquake in Gansu Province. The results showed that: (1) On July 3 and July 4, 2013, the diurnal variation of geomagnetic Z components of 16 and 17 stations near the epicenter appeared obvious anti-phase anomalies, respectively, and there was a clear boundary between the two anomalies; (2) The S-transform method was used to calculate the correlation coefficient of the daily variation of Z component at Tianshui and Lanzhou stations on both sides of the boundary, and it is found that the daily variation of geomagnetic Z component on July 3 and July 4 both had a negative correlation at about 6 h. Therefore, it is considered that the anti-phase anomaly caused by daily variation anomaly of geomagnetic Z component before the Minxian-Zhangxian M_S6.6 earthquake is mainly at about 6 h. In addition, the mechanism of the anomaly was explained.