Seismic discrimination of an underground nuclear explosion (UNE) based on regional waveforms in continental margins is challenging due to large variations among waveforms. The 2009 North Korean UNE test was conducted in the far eastern Eurasian plate. The UNE was recorded by densely-located regional seismic stations, and regional waveforms exhibit highly path-dependent amplitude and arrival time features due to complex crustal structures. Regional source spectra are calculated by correcting for the path effects on the waveforms. A two-step approach is proposed for stable inversion of source-spectral parameters and path parameters. Characteristic overshoot features are observed in the source spectra, particularly strong in Pn. The path parameter, Q, is determined uniquely regardless of the source-spectral model implemented, which suggests stable separation of path effects from waveform records. The estimated source spectra fit well to a theoretical UNE source-spectral model. The fitness between the estimated and theoretical source-spectral models allows us to discriminate UNEs from natural earthquakes. Also, the P/S source-spectral ratio is observed to be an effective discriminant of UNE.
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Acknowledgements I am grateful to the Korea Meteorological Administration, the Korea Institute of Nuclear Safety, the National Research Institute for Earth Science and Disaster Prevention in Japan, and the Incorporated Research Institutions for Seismology, for making seismic data available. I thank two anonymous reviewers and the associate editor, Dr. Thomas Braun, for valuable review comments and suggestions that improved the presentation of paper. This work was supported by the Korea Meteorological Administration Research and Development Program under Grant CATER 2012-8050.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology