GNSS TEC and Swarm Satellites for the detection of Ionospheric Anomalies Possibly associated with 2018 Alaska Earthquake

Abstract

Abstract In the hunt for seismic precursors with GNSS to detect earthquake-related anomalies in ionosphere are proved as an effective strategy. One method is to use GNSS TEC to distinguish between seismic anomalies in ionosphere and anomalies induced by geo magnetic storm. In this study, TEC data of four GNSS sites near the epicenter of November 30, 2018, Alaska earthquake (Mw 7.1) are examined. We also examined the TEC from Swarm satellites during the local day and nighttime to further support the EQ-induced perturbations in ionosphere. One to six days before the major EQ, the GNSS stations' TEC displayed considerable disturbance positive anomalies crossing the upper bound. The GNSS TEC from the four stations near the EQ epicenter detected ionosphere perturbations in 1 to 6 days prior to the EQ. The swarm satellites TEC data also confirmed these findings. On the other hand, retrieving TEC from all GNSS sites during the EQ preparation phase and weak geo magnetic storm (Kp 4, Dst − 50 nT), we discover evidence of low-intensity anomalies in ionosphere 25–30 days prior to the major shock. Further research shows that EQ-induced TEC anomalies are considerable between UTC 17:30 and 23:00 and that the storm-induced TEC anomaly (caused by Dst = -50 nT and Kp 4) predominates in all GNSS stations between UTC 17:00 and 23:30. In the EQ preparation phase, all of these anomalies before the primary shock are helpful in separating seismic from geomagnetic storm anomalies. Additionally, using TEC monitoring, this work contributes to the growing lithosphere-ionosphere connection concept.