Regional seismic discrimination in central Asia with emphasis on western China

In support of an anticipated Comprehensive Test Ban Treaty, the authors have started to evaluate regional seismic event discrimination capabilities for central Asia, emphasizing western China. The authors have measured noise and seismic phase amplitudes of over 250 earthquakes and 18 underground nuclear explosions recorded at the broadband, digital station WMQ in western China and over 100 earthquakes and 5 nuclear explosions at station AAK in Kyrgyzstan. The explosions are from the Kazakh Test Site (KTS) and Lop Nor, China. The earthquakes are mostly from northwest China. They have also evaluated a single suspected chemical explosion. Event magnitudes (m{sub b}) range between 2.5 and 6.5 and maximum event-station distance is about 1,700 km. Using these measurements the authors formed phase, spectral, cross-spectral, short-period/long-period, and long-period ratios to test many possible event discriminants. All ratios were corrected for distance effects before forming ratio-versus-magnitude discrimination plots. The authors found that all five classes of these discriminants are useful for separating earthquakes from explosions in central Asia, provided the right combinations of frequency bands and phases are selected. Results are described