著者

Uyeda Seiya Kumamoto Atsumi

出版者

日本学士院

雑誌

Proceedings of the Japan Academy. Ser. B: Physical and Biological Sciences (ISSN:03862208)

巻号頁・発行日

vol.80, no.3, pp.140-147, 2004

被引用文献数

4

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Kushida and Kushida found that FM radio waves from stations at distances over-the-horizon are received before earthquakes. Based on this finding, since the mid-1990's, the Kushidas have been practicing "Earthquake Precursor Detection Experiment". The performance of the Kushida method during 2000-2003 has been evaluated by checking their predictions against the actual seismicity. During the period, there were 92 Kushida predictions mentioning the possibility of M &ge; 5.5 event, whereas there were 49 M &ge; 5.5 earthquakes in the Japanese region. If the criteria for successful prediction are set as: the errors in date is less than one day, epicentral position is roughly within specified area, and error in M is less than 0.5, the success rate was 20% and the alarm rate was 12%. If we relax the criteria to: the errors in dates within 10 days, epicenter within additional 100 km of specified area and the magnitude error less than 1.0, the success rate was 40% and the alarm rate was 27%. These rates may look insufficient for a practical prediction method. Considering, however, the fact that no other short-term prediction has ever been made in Japan so far it is a significant achievement. Moreover, it was found that in almost all failed predictions, meaningful signals were detected although the interpretations were incorrect. This indicates that the method is promising provided further investigation is carried out. The same evaluation at the M &ge; 6.0 level showed that the general performance was similar to the M &ge; 5.5 level, except that both success rate and alarm rate were lower at the M &ge; 6.0 level. If this unexpected finding is real, it might be inherent to the methodology using scattering of short-wave length radio waves as suggested by M. Hayakawa and may contain important information in understanding the earthquake physics and LAI-coupling. The results of the present study indicate strongly that the earthquake prediction research using anomalous transmission of VHF FM radio waves should be enhanced in parallel with complementary research in other frequency ranges.<br> <br> <br> (Contributed by Seiya UYEDA, M.J.A.)<br>