2016-12-25智利M_W7.6地震震前电离层TEC异常探测

Detection of Ionospheric TEC Anomaly before Chile M_W7.6 Earthquake on December 25,2016

使用IGS发布的GIM数据,利用奇异谱(singular spectrum analysis,SSA)和四分位距法(inter quartile range,IQR)对2016-12-25智利MW7.6地震进行震前电离层异常探测。研究表明,2种方法探测到的电离层主要异常特征基本一致,在震前4d和震前7d分别探测到明显的正异常和负异常,电离层异常自东向西移动,峰值点出现在震中附近,且震前4d共轭区域出现明显的电离层正异常变化。相较于IQR探测,SSA探测突出了电离层主要的异常时间段和空间异常特征,但幅度和范围偏小,两者互为补充,可以探测出更加明显的地震电离层异常效应特征。由于距发震时间较短,在排除外界环境干扰因素后,认为此次电离层异常可能由智利地震引起。

The GPS derived global ionosphere map(GIM)by international GNSS service is used to analyze the impending ionospheric anomalies before the M W7.6 earthquake in Chile on December 25,2016.The singular spectrum analysis(SSA)and sliding inter quartile range(IQR)method are used to detect the ionospheric anomaly preceding great earthquake,respectively.The results show the main feature of ionosphere anomalies detected by the two methods are basically the same.There are significant positive anomalies and negative anomalies on the 4th and 7th day prior to the earthquake,respectively.The ionospheric anomalies had the movement tendency from east to west in the two days,with its peak points appearing near the epicenter.The positive TEC anomalies had also been found in the conjugate area 4 days before earthquake.Compared to IQR detection,although the SSA detection highlights the main anomalous periods and spatial anomaly feature of the ionosphere,the TEC abnormal amplitude and range are smaller at the same time.Therefore,we can combine with two methods to detect the more obvious characteristics of seismic-ionospheric coupling effect.Due to the closer time to the moment of the earthquake occurrence,the results show that the ionospheric anomalies are possibly related to the earthquake,excluding other possible factors.