Effects of shock‐induced tensile failure on m b ‐ M s discrimination: Contrasts between historic nuclear explosions and the North Korean test of 9 October 2006

Rayleigh wave excitation is studied for an explosion source model consisting of a superposition of isotropic (monopole), tensile failure, and tectonic release point sources. The body‐force representation for shock‐induced, deep‐seated tensile failure is a compensated linear vector dipole CLVD, where the relative strength of the CLVD is given by an index K . Rayleigh wave amplitudes are reduced owing to destructive interference between an explosive monopole and a CLVD source with vertical axis of symmetry in extension ( K > 1). The effect of tensile failure on M s is to enhance the explosion‐like characteristics on a plot of m b ‐ M s . This model suggests that the success of the m b ‐ M s discriminant results from the fact that nuclear tests were conducted under containment practices for which tensile failure is ubiquitous, while the North Korean nuclear test of 9 October 2006 is a harbinger of poor m b ‐ M s performance when tensile failure is completely suppressed.