  This paper illustrated the possible relationship between the occurrences of
the earthquake and the anomalous line-of-sight propagations in the very high
frequency band by the fast Fourier transform spectral analysis. Despite many
anomalous propagations appear in the different very high frequency band during
the earthquake occurrences, the majority of these abnormal signals contain
similar frequency distributions in the frequency domain. For the 31 anomalous
propagation spectral distributions, 30 of them present the same curve peaks,
within a frequency range of (0-0.5)Hz. Furthermore, for the first time, we
found that the spectral maximum of all anomalous propagations are below the
characteristic Brunt-Vaisala frequency (period T larger than 6 min), which
happens to be the frequency range of the internal gravity waves, which might
evidence that the atmospheric gravity waves should be responsible for the
indirect coupling between lithosphere and ionosphere. These novel results might
provide direct evidence to the relationship between the anomalous propagations
in the very high frequency band and the occurrences of earthquakes.
