A Comparative Study of Regional Phases from Underground Nuclear Explosions at East Kazakh and Nevada Test Sites
Abstract
The spectral characteristics of regional phases from East Kazakh, USSR underground nuclear explosions are studied for their dependence on parameters such as m sub b (generally related to shot depth) and spatial location (Shagan versus Degelen). The observed results are compared with those of the Nevada Test Site (NTS), where the near-source conditions are better known. Pn and Lg from 25 Soviet nuclear shots recorded at the Chinese Digital Seismic Network (CDSN) station WMQ are analyzed by obtaining spectral and time domain measurements on each phase. The average amplitude ratio Pn/Lg is found to be stable with mb but to vary strongly with frequency. For both Shagan and Yucca Flat explosions of similar yield, the reduction in amplitude with frequency is considerably larger for Lg than for Pn. At higher frequencies (3-7 Hz), the amplitude ratios Pn/Lg for explosions from Shagan, Degelen, Pahute Mesa, and Yucca Flat test sites show significant differences that appear to be due to variations in their source medium velocities. Over the frequency range of about 0.5 to 5.0 Hz, Pn/Lg increases by almost two orders of magnitude for the USSR shots and considerably less for the NTS shots. A possible explanation for the observed Lg spectra varying systematically with shot medium velocity is that Lg from USSR explosions is dominated by S* whereas that from NTS shots includes contributions from both pS and S.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1990
- Accession Number
- ADA230567
Entities
People
- I. N. Gupta
- R. A. Wagner
- W. W. Chan