Stochastic relation between anomalous propagation in the line-of-sight VHF radio band and occurrences of earthquakes
This paper was intended to find out any relation between anomalous line-of-sight propagation on the very high frequency (VHF) band and occurrences of earthquakes near the VHF propagation paths. The television and FM radio broadcasting waves on the VHF band were monitored continuously over the long term. For that purpose, a multidirectional VHF band monitoring system was established and utilized. Anomalous line-of-sight propagation on the VHF band was distinguished from the monitored wave by using a statistical analysis. After the stochastic consideration, it was found out that earthquakes associated with anomalous propagation were characterized by magnitude of earthquakes M ≥ 4.5, and distances from epicenters L ≤ 75 km. The anomalous propagation was monitored on the VHF band a few days before the associated earthquakes occurred. Moreover, the anomaly appeared on multidirectional propagation paths simultaneously. The anomaly on the line-of-sight propagation indicates the possibility of narrowly focusing the area of the epicenter of earthquake.