Atmospheric anomalies observed during earthquake occurrences

Appearance of anomalies in the atmosphere before earthquakes (EQs) has been verified, through observation of anomalous transmission of VHF electromagnetic (EM) waves beyond line‐of‐sight. Anomalous increase of the received intensity for a few minutes ‐ several hours on a day was identified by the previous 15‐day running median and its inter‐quartile range. The cross‐correlation between the EQ occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before M ≥ 4.8 EQs. The one‐day average number of the anomaly appearance within 5 days was found 2.4 times larger than that of other days. Through the polarization measurement of the received EM waves, the anomalies were found to occur in the atmosphere.