Spectra of hidden periodicities of the geoelectromagnetic and seismic events

One of the manifestations of human impact on the magnetosphere and the lithosphere is a weak but strictly periodic modulation of the Pc1 electromagnetic waves and the earthquakes. This modulation is synchronized by the clock world time and day of week. Previously, we have studied the phenomenon of phase-matching by the method of superposed epochs. In the presented paper this phenomenon is investigated by another method, namely by the method of spectral analysis. The result of analysis indicates the presence of pronounced maxima at periods of 7 d, 1 hour and 15 minutes in the spectra of Pc1 activity and earthquakes. This result is consistent with what was found earlier by the superposed epoch analysis. At the same time, in the spectrum of seismic activity a strong peak at 54 min is observed, along with the peak at 1 h, having clearly anthropogenic origin. The value of 54 min coincides with the period of the fundamental mode of eigen spheroidal oscillations of the Earth. It is suggested that the global seismic activity is modulated by the oscillations of the Earth as a whole.