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www.nat-hazards-earth-syst-sci.net/1/107/2001/
© Author(s) 2001. This work is licensed
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Investigation of over-horizon VHF radio signals associated with earthquakes
1Dept. of Electronic Engineering, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu Tokyo 182-8585, Japan
2Taiyo Musen Co., Ltd., Ebisu-nishi 2-20-7, Shibuya, Tokyo, Japan
Abstract. 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.
Full Article (PDF, 313 KB)
Citation: Fukumoto, Y., Hayakawa, M., and Yasuda, H.: Investigation of over-horizon VHF radio signals associated with earthquakes, Nat. Hazards Earth Syst. Sci., 1, 107-112, 2001. Bibtex EndNote Reference Manager
