EARTH MOTION MEASUREMENTS
Several parameters of ground motion on two deep underground nuclear detonations (Evans and Blanca) were measured. Primary measurements included vertical acceleration and velocity in a deep hole over Evans zero, horizontal and vertical acceleration on the mesa surface, and horizontal surface strain. Additional data were obtained on vertical response spectra (reed gage), surface subsidence (liquid level), and aftershocks (geophone listening). Most of the primary objectives were not fulfilled because of the low yield of Evans (30 + 15 - -5 tons, 830:ft depth); only about one-third of the records of primary measurements are useful. For Blanca (19 kt at 830-ft depth from the nearest surface (slope)), the Evans gages were reactivated and usable records were obtained on about one-third of the primary measurements; also, the peak strain, liquidlevel, and reed gages all performed effectively. Despite the less than satisfactory over-all results, some conclusions were drawn on the basis of the data obtained. Arrival time studies seemed to confirm earlier indications of a high speed layer in the Area 12 mesa at 300-ft depth. This layer was found to preclude general conclusions as to propagation mechanism or amplitudes measured at the surface. Subsurface motions although very small were consistent with scaling methods applied to prediction of Hardtack-II events. The cavity-size determination by geophysical methods was abandoned because of exigencies of the crowded shot schedule. In situ seismic propagation velocities in the earth near several underground shot chambers were measured for use in analysis of diagnostic measurements. (auth)
- Research Organization:
- Stanford Research Inst., Menlo Park, Calif.
- NSA Number:
- NSA-15-030958
- OSTI ID:
- 4837659
- Report Number(s):
- WT-1702
- Country of Publication:
- United States
- Language:
- English
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