Criticality analysis of 3-year-long VLF subionospheric propagation data possibly related to significant earthquake events in Japan

Ionospheric anomalies possibly related to significant earthquakes (EQs) have been extensively investigated in recent years and could be considered promising for short-term EQ prediction. In this work, we study the subionospheric propagation data recorded during a time period of 3 years (1/1/2014–28/02/2017) by a network of 8 VLF/LF receivers deployed throughout Japan, to identify possible signatures of pre-EQ processes. Specifically, we analyzed...