Depth estimate of the DPRK's 2006-10-09, 2009-05-25 and 2013-02-12 underground nuclear tests using local and teleseismic arrays

The Democratic People's Republic of Korea (DPRK aka North Korea) conducted underground nuclear explosions on October 9, 2006 (M 4.3), May 25, 2009 (M 4.7) and February 12, 2013 (M 5.1). We expanded standard depth calculation methods to encompass full depth utilizing spectral nulls of spectra using body waves and Rayleigh waves from local and teleseismic arrays. The depths of burial were calculated from the fundamental-mode Rayleigh wave spectra as well as the average spectra of depth phase (pP + P/sP + P, pPn + Pn/sPn + Pn) considering take-off angles based on the flat Earth model. The average depths of the 2006, 2009 and 2013 nuclear tests were thus estimated at 2.12 km, 2.06 km and 2.05 km, respectively. It should be noted that those depths are significantly greater than expected from the standard experiment practice. The possibility of the over-buried nuclear tests would affect the interpretation of M_S-m_b discriminants as well as the estimation of the yield.