Source and path corrections, feature selection, and outlier detection applied to regional event discrimination in China

The authors are investigating techniques to improve regional discrimination performance in uncalibrated regions. These include combined source and path corrections, spatial path corrections, path-specific waveguide corrections to construct frequency-dependent amplitude corrections that remove attenuation, corner frequency scaling, and source region/path effects (such as blockages). The spatial method and the waveguide method address corrections for specific source regions and along specific paths. After applying the above corrections to phase amplitudes, the authors form amplitude ratios and use a combination of feature selection and outlier detection to choose the best-performing combination of discriminants. Feature selection remains an important issue. Most stations have an inadequate population of nuclear explosions on which to base discriminant selection. Additionally, mining explosions are probably not good surrogates for nuclear explosions. The authors are exploring the feasibility of sampling the source and path corrected amplitudes for each phase as a function of frequency in an outlier detection framework. In this case, the source identification capability will be based on the inability of the earthquake source model to fit data from explosion sources.