- © 2010 by the Seismological Society of America
On 25 May 2009, the Democratic People's Republic of Korea (North Korea) announced that it had conducted a second nuclear test, without providing information of exact time, location, and yield. On that day, the United States Geological Survey (USGS) reported detecting a magnitude 4.7 seismic tremor in an aseismic region in North Korea (http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009hbaf.php; also archived copy at http://geophysics.geo.sunysb.edu/wen/NK/usgs_north_korea_2009_test.webarchive). The seismic waveform features recorded at the seismic stations around the globe for the event exhibit characteristics of an explosion. However, the exact location of the test remains elusive.
Seismic monitoring of underground nuclear explosions relies on seismic observations recorded by seismometers around the globe. Because seismic observations are influenced by the seismic properties along the paths of the wave propagation from the source to the seismometers, the accuracy of determination of an event location and time depends on the degree of our knowledge of the seismic properties in the interior of the Earth. The challenge in accurately determining the location of North Korea's nuclear tests stems from the fact that, due to the lack of seismic stations and seismicity in the region, the seismic structure is not known in enough detail that its influence can be well calibrated. For example, the horizontal uncertainty of the 2009 event location reported by the USGS is about ±3.8 km (http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009hbaf.php).
While our knowledge of the seismic structure in the region is unlikely to improve soon, in this study we demonstrate a strategy that uses the forensic evidence registered by North Korea's 2006 nuclear test to determine the location of the 2009 test in high precision, and we present our determination of the location of the 2009 test.
SCIENTIFIC EVIDENCE, APPROACH, AND RESULTS
Scientific Evidence Registered by the 2006 Test
The possible location of North Korea's 2006 test is identified by satellite images (http://cryptome.org/eyeball/dprk-test/dprktest.htm; also an archived copy at http://geophysics.geo.sunysb.edu/wen/NK/eyeball.webarchive) (Table 1). High-quality …