Determination of source parameters of explosions and earthquakes by amplitude equalization of seismic surface waves: 1. Underground nuclear explosions

Abstract

A method of determining the source parameters of explosions and earthquakes from the amplitude spectrums of seismic surface waves is described. The method, called amplitude equalization, involves the correction of the ground displacement spectrum for the propagation effect. This is accomplished by multiplying it numerically with the inverse of the frequency response of the layered medium. The result is the amplitude spectrum of the source function, which may be interpreted by itself or jointly with the initial phase spectrum to determine the source-time variation. The spectrums of the Rayleigh waves from underground nuclear explosions are compared and the source-time function is interpreted using the amplitude equalization method. The time variation of the pressure pulse at the boundary of the elastic zone is found to be of the form p(t) = P_0te^(−ηt), where η is a parameter which depends on the yield of the explosion and on the medium. For the events studied, the breadth of the pulse increased (η decreased) with the yield of the explosion.