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A VHF interferometry system for detecting anomalous propagation of FM radio broadcasting waves related to earthquakes and some preliminary results
Author(s) -
Ohno Nozomi,
Tone Yuka,
Hattori Katsumi,
Yamamoto Isao,
Shimakura Shin,
Takano Toshiaki
Publication year - 2013
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/eej.22303
Subject(s) - interferometry , transmitter , epicenter , radio wave , line of sight propagation , wave propagation , seismology , physics , geology , radio propagation , geodesy , acoustics , geophysics , ground wave propagation , telecommunications , optics , computer science , astronomy , channel (broadcasting) , quantum mechanics
Earthquake‐related anomalous electromagnetic phenomena have been reported in various frequency ranges over the past few decades. Investigation of the anomalous propagation of VHF transmitter waves is a promising approach to short‐term prediction and crustal activity monitoring. Anomalous propagation is believed to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over‐the‐horizon propagation has been received. A recent study shows that the appearance of anomalies was signicantly enhanced within 5 days of earthquakes with M ≥4.8. However, there is no information on the scattering location, that is, on the direction of wave arrival. Therefore, a simple interferometer system for VHF radio waves to identify the space‐time position of earthquake‐related atmospheric disturbances has been developed and installed at Chiba University. This paper describes the newly developed interferometer system and presents the results of fundamental tests to evaluate the performance of the new interferometer at Chiba. Data on over‐the‐horizon propagation of VHF radio waves obtained from 1‐year continuous measurement at Chiba are described. These are possible radio duct propagations and possible earthquake‐related anomalous propagations. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 16–24, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22303