MODEL STUDY OF EXPLOSION-GENERATED SEISMIC WAVES
Final rept. 1 Oct 1962-1 Oct 1965
SAINT LOUIS UNIV MO INST OF TECH
Pagination or Media Count:
The generation of seismic waves by an explosive source in homogeneous media was investigated by two-dimensional models. The size of the effective source for compressional waves agrees well with the outer limits of the zone of circumferential cracking in a brittle medium. Prominent shear waves appear only when the source produces long radial cracks, is located near the free surface of the model, or the source is elongated. The radiation of both types of body waves is strongly modified when the source is near the surface. The P-wave spectrum can be modified by surrounding the shot with a different material. A cavity, filled with air or a solid substance, affects the signal through both its geometric configuration and the properties of the material in the cavity. The evidence from Rayleigh waves indicates that the effect of an explosion changes from a vertically applied source pulse to a buried center of compression when the source depth exceeds the radius of the zone of nonelastic behavior. When the medium is statically stressed before the shot, the body waves are modified. A low velocity wedge modifies wave propagation by creating a shadow zone. Diffractions into this shadow zone from the wedge tip were observed.
- Seismic Detection and Detectors