A GEOMETRIC TECHNIQUE FOR STUDYING SURFACE MOTIONS FROM UNDERGROUND NUCLEAR EXPLOSIONS IN REAL GEOLOGIC LAYERED MEDIA.
Technical rept. Apr-Jul 66,
AIR FORCE WEAPONS LAB KIRTLAND AFB NM
Pagination or Media Count:
A Semiempirical technique, utilizing the methods of geometrical optics, is used to examine the effect of geologic layering on the surface peak particle velocity associated with the direct compressional wave produced by underground nuclear explosions. This geometric technique is different from former ray techniques in that it accounts for the curvature of the wave front, i.e., the divergence of the rays, as well as the distance the wave travels. Data from contained nuclear explosions in homogeneous media are used to determine the relationship between the peak particle velocity and the divergence of the rays. This empirical relationship is then used for layered media, where the divergence of the rays is determined by the methods of geometrical optics, to predict the free-surface peak particle velocity. The required transmission and reflection factors are currently taken from the theory of elastic wave propagation. Several parametric studies and comparisons with data from experiments in layered media are presented. It is found that a number of previously unexplained departures from what was measured and what might intuitively be expected are qualitatively and sometimes quantitatively predicted by this technique. It is emphasized that layering between the source and the free surface which usually occurs can have a profound and deceiving effect on the surface motion, and, therefore, it should not be neglected in any prediction technique. Author