Skip to main content


We’d like to understand how you use our websites in order to improve them. Register your interest.

A compound linear discriminant method for small-magnitude seismic events and its application to the North Korea seismic event of October 9, 2006


On October 9, 2006, a seismic event (mb 3.9) occurred in North Korea, which was later announced as a nuclear test. We studied the seismic event from the viewpoint of seismological discrimination without a priori information 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.


  1. Che, I.-Y., M.-S. Jun, J.-S. Jeon, and K. D. Min, Analysis of local seismo-acoustic events in the Korean Peninsula, Geophys. Res. Lett., 29, 1589, doi:10.1029/2001GL014060, 2002.

  2. Chung, T. W., M. H. Noh, and S. Matsumoto, The attenuation structure of South Korea: a review, J. Korean Geophys. Soc, 9, 199–207, 2006.

  3. Gupta, I. N., W. W. Chan, and R. A. Wagner, A comparison of regional phases from underground nuclear explosions at East Kazakh and Nevada test sites, Bull. Seismol. Soc. Am., 82, 352–382, 1992.

  4. Kim, W. Y, V. Aharonian, A. L. Lerner-Lam, and P. G. Richards, Discrimination of earthquakes and explosions in southern Russia using regional high-frequency three-component data from the IRIS/JSP Caucasus Network, Bull. Seismol. Soc. Am., 87, 569–588, 1997.

  5. Koch, K., Seismic event identification of earthquakes and explosions in Germany using spectral Lg ratios, Pure Appl. Geophys., 159, 759–778, 2002.

  6. Koch, K. and D. Fäh, Identification of earthquakes and explosions using amplitude ratios: the Vogtland area revisited, Pure Appl. Geophys., 159, 735–757, 2002.

  7. Murphy, J. R. and T. J. Bennett, A discrimination analysis of short-period regional seismic data recorded at Tonto Forest Observatory, Bull. Seismol. Soc. Am., 72, 1351–1366, 1982.

  8. Patton, H. J. and S. R. Taylor, Analysis of spectral ratios from NTS explosions: implications for the source mechanisms of spall and the generation of Lg waves, Bull. Seismol. Soc. Am., 85, 220–236, 1995.

  9. Rodgers, A. J. and W. R. Walter, Seismic discrimination of the May 11, 1998 Indian nuclear test with short-period regional data from Station NIL (Nilore, Pakistan), Pure Appl. Geophys., 159, 679–700, 2002.

  10. Taylor, S. R., N. W Sherman, and M. D. Denny, Spectral discrimination between NTS explosions and western United States earthquakes at regional distances, Bull. Seismol. Soc. Am., 78, 1563–1579, 1988.

Download references

Author information



Corresponding author

Correspondence to Il-Young Che.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Che, I., Jun, M. & Jeon, J. A compound linear discriminant method for small-magnitude seismic events and its application to the North Korea seismic event of October 9, 2006. Earth Planet Sp 59, e41–e44 (2007).

Download citation

Key words

  • Linear discriminant method
  • small-magnitude seismic events
  • seismic spectral ratio