A Preliminary Analysis Of Seismic Variability At The Shagan River Nuclear Test Site PDF Download

Large volumes of teleseismic P wave amplitude and arrival time data recorded from explosions at this test site were collected and statistically analyzed in an attempt to define any systematic trends which correlate with source location. The results of the analysis of the teleseismic m sub b data have been shown to provide strong evidence of systematic geophysical variations within the Shagan River testing area. In particular, the m sub b station corrections have been shown to vary with source location in a manner which depends on source-to-station azimuth. Results of detailed comparisons of m sub b residual data at common stations from selected pairs of nearby explosions have been used to conclude that the observed variations in the azimuthal patterns of the m sub b residuals are related to event location rather than tectonic release effects. Results of this preliminary analysis suggest that the observed m sub b differences may be associated with changes in the near-source portions of the teleseismic P wave propagation paths. In contrast to the m sub b residual data, the reduced P wave travel-time residuals were found to show no obvious correlation with event location, and this has been interpreted as an indication that the available bulletin data are not precise enough to resolve the rather small travel-time variations which might be expected to accompany the observed m sub b variations. Keywords: Underground nuclear explosions; Seismic detection; Numerical analysis of seismic data; USSR; Geophysically distinct seismic waves; Least squares matrix factorization.