Simulation of Infrasound Spectrum Generated by Sea Surface Waves

Sea surface waves create pressure waves of the infrasound range that do not fade with depth, which have a noticeable effect on the processes occurring in the earth's crust. The connection between the energy of surface waves and microseisms makes it possible to solve the inverse problem and reconstruct wave characteristics based on seismic measurement data. These studies require information on the physical factors that cause ambiguity in the relationship between wave spectra and the spectra of infrasound generated by them. In this paper, the change in the shape of the infrasound spectrum is analyzed within the framework of numerical simulation. Well-known surface sea wave spectral models are used for analysis. It is shown that the main factors influencing the shape and peak value of the infrasound spectrum are the difference in the frequencies of the spectral peaks of swell ωw1 and wind waves ωw2, as well as the change in the angle between the directions of their propagation. For the same spectrum of surface waves, when ωw1 ≈ ωw2, the maximum value of the infrasound spectrum peak occurs at the opposite direction of wave propagation, it decreases by more than 5 times when the directions are mutually orthogonal, it decreases by two orders of magnitude, when the directions coincide. With an increase in the difference between ωw1 and ωw2, the frequency range where the generation of infrasound is determined by the interaction of swell and wind waves narrows.