Abstract
Power spectrum of the diurnal variations of the quasi-electrostatic field Ez in the near-Earth atmosphere have been presented for the first time. The Ez power spectrum variations in the period of fine weather have been shown to exhibit two bands of the periods of natural atmospheric oscillations with T = 1-5 and 6-24 h. These oscillations are the modes of the internal gravity and tidal waves in the lower atmosphere. On the days under atmospheric precipitation, the spectral power of Ez increases by an order of magnitude. During the pre-earthquake period, when the diurnal Ez variation had an anomaly, the intensity of harmonics with T = 1.8, 2.2, and 3.8 h increased by an order of magnitude or more in comparison with the Ez spectra in fine weather. Two additional spectral bands with T = 0.6 and 1 h have appeared simultaneously.
Highlights
Anomalous variations in the quasi-static electrical field Ez in the near-Earth atmosphere before the M ≥ 4 earthquakes have been recorded in many seismo-active regions of the Earth.They usually occur at an interval of a few hours to a few days before the main shock and prove to be either a bay-like field intensity decrease or an oscillation train lasting a few hours
Ez variations in fine weather and at high precipitation were shown in the paper (Mikhailov et al, 2002)
The continuous measurements of quasi-static electric field Ez with the sampling rate ∆t = 1 min have made it possible to study the fine structure of the power spectra with periods from 4 min and longer
Summary
Anomalous variations in the quasi-static electrical field Ez in the near-Earth atmosphere before the M ≥ 4 earthquakes have been recorded in many seismo-active regions of the Earth. They usually occur at an interval of a few hours to a few days before the main shock and prove to be either a bay-like field intensity decrease (even to a sign reversal) or an oscillation train lasting a few hours. Power spectrum features of the near-Earth atmospheric electric field in Kamchatka pheric quasi-static electric field Ez in a period of the fine weather, under atmospheric precipitation and during the pre-earthquake period of anomalous diurnal variations Ez. riod 1997-2000 in 1-36 h before earthquakes (Smirnov, 2001).
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