Abstract

A series of nuclear [MINERAL QUARRY (MQ), HUNTERS TROPHY (HT)] and chemical [NON-PROLIFERATION EXPERIMENT (NPE) and NPECAL] explosions were detonated in the same geological material at Rainier Mesa, Nevada Test Site. These sources were extensively instrumented with the same near-source, free-surface instrumentation array. The data from these explosions allow the establishment of empirical source scaling relations as well as investigation of possible chemical and nuclear source differences. Even in the near-source region at common receivers, the data display propagation path effects resulting from slight differences in source locations. These effects are effectively taken into account by smoothing the source comparisons across the different stations in the receiver array. As many as 30 individual waveforms from each source are used in this smoothing process. Comparison of HT and NPE at near-source distances indicates that within the bandwidth of the data (0.36 to 100 Hz), there is no apparent spectral difference between the nuclear and single-fired chemical source. The smoothed spectral ratio between the NPE and NPE CAL is consistent with the long-period source spectral difference (104), corner frequencies (2 to 3 Hz/NPE and 40 to 60 Hz/NPE CAL), and high-frequency decay (ƒ−2) similar to the Mueller-Murphy source model for wet tuff after modifying the cavity radius to scale as the cube root of yield. Comparison of the two nuclear sources, HT and MQ, indicates that at long periods, the HT/MQ ratio is 0.4 to 0.6 with the spectra from the two explosions merging above 5 Hz, which is consistent with the 0.3 magnitude difference observed for the two sources. In all the source comparisons, the spectral ratios of the transverse components of motion are indistinguishable from those produced by either the vertical or radial components. This fact argues that the transverse component of motion from an explosion is generated at very close-in distances, in this case on the order of 1 to 2 km. These observations are in agreement with some type of linear scattering mechanism.

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