2018年阿拉斯加Mw7.9级地震同震电离层扰动研究

Study of the 2018 Mw7.9 Alaska Earthquake Coseismic Ionospheric Disturbance Based on GPS Detection

2018年1月23日,阿拉斯加湾科迪亚克岛东南部海域发生了Mw7.9级地震,这是由于太平洋板块浅层岩石圈内的走滑断层造成的。采用美国连续运行参考站(CORS)的GPS观测数据(采样间隔为15s),解算孕震区上空高精度的倾斜总电子含量(STEC),利用奇异谱分析(SSA)的方法提取电离层扰动信息,对阿拉斯加地震同震电离层扰动(CID)进行分析。结果表明,在震后1h内,STEC探测到了明显的“N”形波扰动,扰动振幅超过了0.16个总电子含量单位(TECU),持续时间近15min。CID传播速度为2.62km/s,在距震中600km的范围内传播,结合扰动信号频率,判断是由瑞利波向上传播至电离层引起的。由于受到地震破裂带和地磁场影响,CID传播具有明显的方向差异性,探测到的CID点主要位于震中西南方向。此外,在SWARM卫星的垂直总电子含量(VTEC)数据中发现,震发当天震中上空区域TEC明显减小。

On January 23,2018,a Mw7.9 earthquake occurred in the southeast of Kodiak Island in the Gulf of Alaska,which was caused by strike slip faults in the shallow lithosphere of the Pacific plate.In this paper,the high-frequency GPS observations(sampling interval of 15s)of the continuously operating reference station(CORS)in the United States are used to solve the high-precision slate total electron content(STEC)over the earthquake preparation area.And the ionospheric disturbance information is extracted by using the method of singular spectrum analysis(SSA),and the coseismic ionospheric disturbances(CID)of Alaska earthquake are analyzed.The results show that the STEC shows an obvious"N"wave disturbance within 1h after the earthquake,the disturbance amplitude exceeds 0.16 TECU and lasts for nearly 15 minutes.The CID propagates within 600km from the epicenter with a propagation speed of 2.62km/s.Combined with the disturbance signal frequency,it is judged that the CID is caused by the upward propagation of Rayleigh wave to the ionosphere.Due to the influence of seismic rupture zone and geomagnetic field,CID propagation has obvious directional differences,and the detected CID points are mainly located in the southwest of the epicenter.In addition,in the vertical total electron content(VTEC)data of SWARM satellites,it is found that the TEC in the area above the epicenter decreases significantly on the day of the earthquake.