Fig. 6
Distributions of the significant positive TEC anomaly occurrences during the PEIA period associated with the M7.0 earthquake (1–3 August 2018), the M6.s earthquakes (12, 14, 15, 17, and 18 August 2018), and the M7.0 + M6.s earthquakes. For each lattice, the proportion is the number of positive anomalies divided by the total timepoints of the period in percentage. a Overall proportion associated with the M7.0 earthquake. The top proportion associated with b the M7.0 earthquake of 65%, c the M6.s earthquakes of 60%, and d the M7.0 + M6.s earthquakes of 64%. e The overall and f top 75% proportions during the storm period of 26–28 August 2018. The thin black curve denotes the magnetic equator. The heavy black curves present the mid-latitude troughs in the northern and southern hemisphere. Anomalies around ± 65oN are most likely related to the mid-latitude trough. The black rectangular frame (25°S–5°N, 110°E–150°E) denotes the epicenter area of the M7.0 and M6.s earthquakes