2013年岷县—漳县6.6级地震前地磁日变化异常及机理分析

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

摘要:

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。

Abstract:

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.