The 9 October 2006 North Korean event: full moment tensor solution and seismic discrimination
Abstract
On 9 October 2006 an underground nuclear explosion took place at North Korea's Chik-Tong nuclear test site, in the Hamgyeong Province. The explosive signatures of this seismic event were captured over a broad frequency band at near-regional and regional distances (150 - 350 km). We present a full moment tensor solution for this nuclear test and compare its signatures with those produced by natural earthquakes and chemical explosions. The velocity model we used for the moment tensor inversion is a modified version of what had been used by the Jilin Provincial Seismological Bureau for location purposes. The modifications were based on minimization of the travel-time residuals. We used a total of 10 stations and tested different frequency bands for the moment tensor inversion. We achieved the highest variance reduction of 62.2% at the frequency band of 0.06 to 0.1 Hz. At frequencies below 0.06 Hz, low-frequency noise overwhelms the signal. The inverted Mw is 3.8, which is at the lower end of the estimated magnitude range of 3.8 to 4.3. With 72% isotropic component, but only 22% for the compensated linear vector dipole, and 6% for the double couple, the moment tensor solution is highly consistent with that of an underground explosion. For comparison, we also studied a similar-sized earthquake (16 December 2004), which was well recorded by our stations. Of the two, the earthquake is much closer to our seismic network than is the North Korea nuclear event. The full moment tensor solution with the greatest variance reduction (66.7% with five available stations) is also achieved in the 0.06-0.10 Hz frequency band. The Mw in this case is 3.9. The solution, being characterized by 37% double couple, 24% compensated linear vector dipole, and 39% isotropic, is ostensibly not that of a typical earthquake. This might be related with the fact that this earthquake is located near the Changbaishan Volcano.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S11B1745C
- Keywords:
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- 7203 Body waves;
- 7215 Earthquake source observations (1240);
- 7219 Seismic monitoring and test-ban treaty verification;
- 7294 Seismic instruments and networks (0935;
- 3025);
- 7299 General or miscellaneous