SH WAVES FROM EXPLOSIVE SOURCES

Abstract

Horizontally polarized shear (SH) waves have been reported from nuclear explosions and very small explosions. This paper presents selected examples of SH waves from charges ranging up to 50 lb and detected by downhole three‐component seismometers. The examples include outgoing SH waves and SH reflections from faults and an escarpment. The SH waves usually can be identified wherever three‐component seismometers are used. The SH waves appear to be generated near the point of detonation in earth materials that have no apparent horizontal changes in lithology, but comprise layers with marked vertical velocity contrasts. The observations neither confirm theoretical explanations that require horizontal changes in material surrounding the charge nor contribute to a satisfactory theoretical explanation for the generation of SH waves from explosive sources.