Excitation of seismic surface waves by atmospheric nuclear explosions

The Rayleigh waves generated by nuclear explosions in the atmosphere and by earthquakes are investigated to determine the relative effects of the source and the propagation medium on the observed amplitude spectrums. It is found that when the waves from a given source propagate along different paths the shapes of the spectrums change markedly. Comparison of earthquake- and explosion-generated waves leads to the conclusion that the source characteristics are obscured by the propagation effects. The theoretical expression for the spectrum of the Rayleigh wave displacement is derived for an explosion in a homogeneous atmosphere. The yield of the explosion introduces a frequency-dependent factor into the equations. Using this frequency dependence, the relative yields of explosions are computed from the amplitude-spectrum ratios of Rayleigh waves recorded at a distant station.