Theoretical Effect of Yield and Burst Height of Atmospheric Explosions on Rayleigh Wave Amplitudes

Abstract

Theoretical seismograms for fundamental mode Rayleigh waves were calculated for atmospheric point sources over oceanic and over continental Earth models, as recorded at an epicentral distance of 10000 km. Yields were uniformly distributed over the range 1 kT-10 MT, for source altitudes in the range 0.3-92.0 km. The Earth structures used were those of Gutenberg and of Anderson and Toksoz. The source models were point mass-injection and energy-injection sources at altitude, as well as a distributed pressure pulse at the surface of the Earth. It was found that: (1) as far as Rayleigh wave excitation is concerned, the mass-injection and energy-injection sources are equivalent; (2) for low altitudes the Rayleigh wave excitation is independent of source type, but at intermediate altitudes the surface overpressure source predicts greater amplitudes than the other two source models; (3) for most altitudes, the energy coupling from the atmosphere into Rayleigh waves is more efficient for the continental Earth structure than for the oceanic structure; (4) Rayleigh wave amplitude is more sensitive to yield than to burst height (5) dependence of Rayleigh wave amplitude is less than the cube root relation for low-yield explosions at intermediate altitudes but greater for high-yield explosions at near-surface altitudes; (6) spectral splitting ratios do not show a systematic variation with yield and burst height.