利用全球电离层地图分析芦山地震电离层异常变化

Analysis of Seismo-ionospheric Anomalies in Vertical Total Electron Content of GIM for Lushan Earthquake

利用全球电离层地图（global ionosphere map,GIM）提供的垂直电子含量（vertical total electron content,VTEC）观测值,采用滑动四分位距法分析了芦山地震前后的电离层异常。为了探讨异常现象与地震之间的相关性,进一步确定了震中附近上空VTEC东向及北向梯度变化,并比较分析了2008-2012年相同时间段的VTEC变化。结果表明,2013年4月18-20日的负异常现象很可能与地震相关。通过分析震中附近电离层赤道异常的变化,发现赤道异常峰值在震前5d内明显减小,且峰值的位置向磁赤道方向移动。结合电离层负异常现象及赤道异常的变化,本文认为芦山地震孕震区内异常电场可能是引起电离层异常的主要原因之一。

In this paper, we analysed the seismo-ionospheric anomalies of the vertical total eletron content extracted from a global ionosphere map during the Lushan earthquake by adopting a quartilebased method. To confirm whether the ionospheric anomalies associated with the earthquake, VTEC gradients in the eastward and northward directions near the epicenter were further examined, and VTEC data during the same period in 2008-2012 were cross-compared. The results show that the neg- ative anomalies during 18 to 20 April are probably caused by Lushan earthquake. Analysis of equatorial anomaly near epicenter shows that the crests significantly decreased five days before the earthquake, and moved to magnetic equator. Combining ionospheric negative anomalies with the modification of the equatorial anomaly, we find that the anomalous electric field generated in the earthquake preparation might be a main cause of the observed ionospheric anomalies.