Abstract:The GPS derived global ionosphere map(GIM) by international GNSS service is used to analyze the impending ionospheric anomalies before the MW7.6 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.
SHI Kunpeng,GUO Jinyun,LIU Zhimin et al. Detection of Ionospheric TEC Anomaly before Chile MW7.6 Earthquake on December 25, 2016[J]. jgg, 2018, 38(9): 979-985.