Discrimination Among Small Magnitude Events on Nevada Test Site
CALIFORNIA UNIV BERKELEY DEPT OF GEOLOGY AND GEOPHYSICS
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Broadband data .02 to 20 Hz from the University of California Lawrence Livermore Laboratory four-station seismic array, deployed at close range less than 500 km azimuthally about Nevada Test Site NTS, allow investigation of the body wave-surface wave discriminant between explosion and earthquakes for small events confined to NTS, extending previous results to magnitudes around 3.5. It is found that natural earthquakes, explosion collapses, and explosion aftershocks all are distinct from explosions, and that the populations do not seem to converge at the low magnitudes. Also, for explosions, there is no change in the slope of the Pn versus Rayleigh wave amplitude relation over more than three orders of magnitude. Since the non- explosion events are shallow, of low magnitude, and of different source types, differences in source dimension, focal depth, and focal mechanism appear inadequate to explain the discriminant at small magnitudes.
- Seismic Detection and Detectors