Investigation of over-horizon VHF radio signals associated with earthquakes

Y. Fukumoto (1) , M. Hayakawa (1) , H. Yasuda (2)

1 Department of Electronic Engineering [Tokyo]
2 Taiyo Musen Co.

This paper presents the preliminary results on the possible reception of over-horizon VHF radio signals from a FM (frequency modulation) transmitter during abnormal situations (probably in close association with earthquakes). The transmitter is FM Sendai (frequency = 77.1 MHz) and the receiving station is our university (UEC) at Chofu, Tokyo, with the transmitter-receiver distance being about 310 km. We first show a typical example of the reception of over-horizon VHF signals in which we present the amplitude behavior, azimuthal and incident angle estimation, etc. Then, we study the correlation between a signal anomaly and an earthquake and it seems that the over-horizon VHF signals observed are probably associated with earthquakes, observed about 7 to 0 days before an earthquake. The direction finding measurements have indicated that such signals are due to favorable tropospheric (but not ionospheric) conditions attributed to the effects of earthquakes.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

Y. Fukumoto, M. Hayakawa, H. Yasuda. Investigation of over-horizon VHF radio signals associated with earthquakes. Natural Hazards and Earth System Sciences, 2001, 1 (3), pp.107-112. ⟨hal-00298998⟩