SURFACE MOTION FROM AN UNDERGROUND DETONATION
Surface and near-surface acceleration and strain were measured on a deep undergreund nuclear burst to permit extrapolation of results to nuclear detonations of other yields under different test or employment conditions. Results indicate that a large earth cap, probably including more than one chunk, separated from the mesa over the charge and subsequently fell back into place. The only significant vertical displacement occurred at or near ground zero and reached a maximum of approximately 0.9 feet. Both acceleration and horizontal surface strain measurements suggest that the principal disturbance on the mesa surface was confined to a small region around ground zero; however, the measurements on the slope indicate significant earth motion. Velocity data indicate that the layering characteristics of the medium exert a great influence upon the severity of the ground motion. The displacement-time data at surface zero agrees well with photographic data. In general, the peak displacements indicate that the cap rock moved up and away from surface zero, whereas the permanent displacements on the mess show that the final positions of the stations are downward and inward toward surface zero, relative to preshot position. From the preshot seismic survey and average velocities computed from the arrival time data, it is concluded that the medium of the Rainier mesa is many-layered with seismic velocities that are widely different. A reasonable profile is 5000 ft/ sec from the surface to 200 feet, 10,000 ft/sec to 300 feet, and 6600 ft/sec to 1000 foot depth. Although predicted strains were higher than those observed, horizontal surface strain results support the conclusion that the principal disturbance on the mesa was confined to a relatively small radius around surface zero. Peak strains measured on the slope are significantly larger than expected at comparable ranges on the mesa. (auth)
- Research Organization:
- Stanford Research Inst., Menlo Park, Calif.
- NSA Number:
- NSA-14-018033
- OSTI ID:
- 4148113
- Report Number(s):
- WT-1528
- Country of Publication:
- United States
- Language:
- English
Similar Records
SUBSURFACE MOTION FROM A CONFINED UNDERGROUND DETONATION. PART I
EARTH MOTION MEASUREMENTS. PART I. SEISMIC STUDIES AND CAVITY STUDIES. Preliminary Report