SUMMARY REPORT OF STRONG-MOTION MEASUREMENTS, UNDERGROUND NUCLEAR DETONATIONS
Subsurface and surface motion measurements were made on six underground nuclear detonations in the Oak Springs tuff of Nevada Test Site in Operation Hardtack II: Shots Mars ( approximately 13 tons), Tamalpais ( approximately 77 tons), Neptune ( approximately 155 tons), Logan ( approximately 5 kt), Evans ( approximately 30 tons), and Blanca ( approximately 19 kt). Freefield peak radial acceleration decreased as the inverse third or fourth power of slant range, as for Rainier. Particle velocities attenuated at a rate between the inverse square and inverse cube. Maximum radial and tangential subsurface stress varied as the inverse cube of radial range. Observed peak strain suggested attenuation at a rate between inverse cube and inverse square of range. Maximum upheaval at Blanca surface zero was about 25.5 feet; approximately 2.5 feet at 750 feet radial range; and 1.5 feet at 910 feet. Reed gage spectra indicated a shift of maximum energy to lower frequencies with increasing ground range. All components of surface acceleration followed an empirical equation of the form A(g) = 3.2 x lO/sup 6/W/sup o.7/(kt)R/sup -2/(ft). All components of surface displacement did not follow a comparable relationship. Displacement was more precisely predicted than acceleration. The velocity of the tuff was determined to be 6200 ft/sec, with the velocity of the underlying dolomite 11,700 ft/sec. Assuming a two-layer model for the crust beneath the Nevada Test Site, appropriate values for the thicknesses and velocities were 24 km and 5.69 km/sec for the top layer, and 36 km and 7.65 km/sec for the intermediate layer. The top of the mantle beginning at a depth of 60 km had a velocity of 8.12 km/sec and dipped eastward. (auth)
- Research Organization:
- California Univ., Livermore
- NSA Number:
- NSA-15-014058
- OSTI ID:
- 4054253
- Journal Information:
- J. Geophys. Research, Journal Name: J. Geophys. Research Vol. Vol: 66
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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