Abstract
AbstractOn October 9, 2006, a seismic event (mb3.9) occurred in North Korea, which was later announced as a nuclear test. We studied the seismic event from the viewpoint of seismological discrimination withouta prioriinformation of the source. This paper presents a compound discriminant method that enhances the ability to distinguish between earthquakes and explosions on the Korean Peninsula. The method includes four single discriminants based on seismic spectral amplitude ratios. These discriminants are used as single variables in a multivariate statistical analysis to derive a compound linear discriminant function that optimally separates the two populations. Short-period vertical component seismograms recorded by seismo-acoustic array (CHNAR) are used for the method. Combining the mutually complementary discrimination abilities of the single methods improves the discriminant power and lowers the probability of misclassification to 1.7% for the data sets. Using this compound method, we were able to identify the North Korea seismic event as explosion-induced. This discrimination technique can be applied automatically to new observations and extended to other seismic arrays or networks. The combination of these seismic discriminants with infrasound observations will increase our ability to detect surface explosions on the Korean Peninsula.
Highlights
This paper presents a compound discriminant method that enhances the ability to distinguish between earthquakes and explosions on the Korean Peninsula
The Korea Institute of Geoscience and Mineral Resources (KIGAM), the Korean National Data Center (NDC) under the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), operates a high-quality seismic network consisting of 32 stations
Based on the spectral characteristics of seismic phases at local and regional distances, a multivariate discriminant analysis was performed to derive a compound linear discriminant method applicable to small-magnitude seismic events occurring on the Korean Peninsula
Summary
Seismo-acoustic analysis has identified about 10% of the total number of seismic events that have occurred on the Korean Peninsula as surface explosions; many unidentified seismograms have explosion characteristics. Another discriminant method is needed that can directly use the seismograms, thereby supplementing seismo-acoustic analysis and increasing the power of discrimination. Two training datasets representing earthquakes and surface explosions that occurred on the Korean Peninsula were constructed and used in deriving the discriminant functions. To derive reliable discriminant functions and conduct effective discriminant analyses, we constructed training datasets representing natural earthquakes and surface explosions. For each of the single methods, the LDF could be formulated
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