Monitoring of spectral parameters of longitudinal waves from the strongest earthquakes in Honshu Island, Japan in 2011

Results of the retrospective analysis of spectral parameters of earthquakes off the coast of Honshu Island, in the area of the catastrophic Tohoku-Oki event of March 11, 2011, are presented. Spectra of longitudinal waves on teleseismic distances are considered. The increase in the ratio between the spectral amplitude of fluctuations at frequencies f = 0.1 Hz and f = 1 Hz some months prior to the catastrophic earthquake is studied. That is, by the time of the approach of the main shock, the share of high-frequency fluctuations in the spectrum decreases, which can testify to a change of the strain of the environment in the source zone of strong events.