The goal of the project is to develop a quantitative predictive capability for explosion-generated Lg phases with a sound and unambiguous physical basis. The research program consists of a theoretical investigation of explosiongenerated Lg combined with an observational study. The specific question addressed by this research program is how the Lg phase is generated by underground nuclear explosions. This question is fundamental to how Lg phases are interpreted for use in explosion yield estimation and earthquake/explosion discrimination.
READ INSTRUCTIONS REPORT__ DOCUMENTATIONPAGE BEFORE COMPLETING FORM 1. REPORT NUMBER Z. GOQVT ACCESSION NO. 3. RECIPIENTS CATALOG NUMBER 2. Comparison between SALMON gauge 1El4-20 AR at a range of 274 m and calculated velocity. .. .. .. .. . 5 3. Comparison between SALMON velocity gauge E6-27URH at 318 m and calculated velocity.. .. .. .. .. .. .. 6 4. Comparison between SALMON velocity gauge E14C-39 at 402 m and calculated velocity.. .. .. .. .. .. .. 7 5. Comparison between SALMON velocity gauge Ell-27URH at 620 m and calculated velocity.. .. .. .. .. .. .. 8 6. Comparison between SALMON velocity gauge Ell-34URB at 658 m and calculated velocity.. .. .. .. .. .. .. 9 7. Comparison between SALMON velocity gauge E5-27URH at 742 m and calculated velocity.. .. .. .. .. .. . .10 8. Comparison between calculated and observed peak velocity and displacements for SALMON. .
Ð During the period from 1975 to 1979, the former Soviet Union conducted a series a six nuclear explosions in a water-®lled cavity in salt which was created in 1968 by a tamped 27 kt explosion at a depth of 597 m at the Azgir test site at the north end of the Caspian Sea. Broadband, near-regional seismic data recorded from these tests have been processed and analyzed in an attempt to characterize the seismic source characteristics of these explosions and assess their relevance to the cavity decoupling evasion scenario. The results of these analyses indicate that the explosions in the water-®lled cavity were not decoupled, but rather show evidence of enhanced seismic coupling with respect to that which would be expected from tamped explosions of the same yields in salt. Theoretical ®nite dierence simulations of these tests have been conducted in which the complex, nonlinear interactions between the shock eects in both the water and surrounding salt medium have been explicitly modeled. The results of these simulations indicate that the most prominent yield dependent features of the observed seismic source functions can be largely explained by the dynamic interactions between the expanding and contracting steam bubbles generated by the explosions in water and the shock-wave re¯ections from the cavity wall. More speci®cally, it has been found that the shock-wave re¯ection from the cavity wall retards the expansion of the steam bubble in a yield dependent fashion relative to that expected in the open ocean, resulting in a smaller maximum bubble radius and a shorter bubble oscillation period.
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