LLNL's Regional Model Calibration and Body-Wave Discrimination Research in the Former Soviet Union Using Peaceful Nuclear Explosions (PNEs)
LAWRENCE LIVERMORE NATIONAL LAB CA
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Long-range seismic profiles from Peaceful Nuclear Explosions PNE in the Former Soviet Union FSU provide a unique data set to investigate several important issues in regional Comprehensive Nuclear-Test-Ban Treaty CTBT monitoring. The recording station spacing approx. 15 km allows for extremely dense sampling of the propagation from the source to greater than or equal to 3300 km. This allows us to analyze the waveforms at local, near- and far-regional and teleseismic distances. These data are used to 1 study the evolution of regional phases and phase amplitude ratios along the profile 2 infer one-dimensional velocity structure along the profile and 3 evaluate the spatial correlation of regional and teleseismic travel times and regional phase amplitude ratios. We analyzed waveform data from four PNEs mb 5.1 - 5.6 recorded along profile KRATON, which is an east-west trending profile located in northern Siberia. Short-period regional discriminants, such as PS amplitude ratios, will be essential for seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty CTBT at small magnitudes mb4.0. However, PS amplitude ratios in the short-period band, 0.5 - 5.0 Hz, show some scatter. This scatter is primarily due to propagation and site effects, which arise from variability in the elastic and anelastic structure of the crustal waveguide. Preliminary results show that Pg and Lg propagate efficiently in north Siberia at regional distances. The amplitude ratios show some variability between adjacent stations that are modeled by simple distance trends. The effect of topography, sediment and crustal thickness, and upper mantle discontinuities on these ratios, after removal of the distance trends, will be investigated.
- Numerical Mathematics
- Computer Programming and Software
- Test Facilities, Equipment and Methods
- Seismic Detection and Detectors