Generation of seismic waves by underground explosions and the collapse of cavities

Abstract

The occurrence of large collapse features associated with contained underground nuclear tests in alluvial material provides an unusual opportunity to study the effect of source geometry and time history. The explosion is represented by a pressure pulse applied to a buried spherical cavity, and a collapse by a point force normal to the surface. If the time duration for these sources is 0.16 second and 4 seconds, respectively, the resulting spectral ratio for Rayleigh waves is consistent with the experimental data in the frequency range 0.5 to 3.0 cps. The spectral ratios for SH and SV waves indicate that the SH waves are not generated by near-source phenomena such as movement along joints, but by elastic wave conversion within a few wavelengths of the source.