Accession Number : ADA516259

Title :   Explosion Source Model Development in Support of Seismic Monitoring Technologies: New Models Accounting for Shock-Induced Tensile Failure

Descriptive Note : Conference paper


Personal Author(s) : Patton, Howard J

Full Text :

Report Date : Sep 2008

Pagination or Media Count : 10

Abstract : The traditional source model for long-period seismic waves from nuclear explosions consists of a monopole releasing tectonic strain. Tectonic release has been studied since the 1960's, and numerous studies have shown that linear superposition of monopole + double-couple sources can explain many observations of Rayleigh and Love waves. Free surface interactions and the dynamics of shock-wave rebound are responsible for modes of tensile failure which can also lead to permanent deformations affecting long-period excitation. Indeed, the vast majority of nuclear explosions worldwide were conducted under containment conditions that facilitated shock-induced, deep-seated tensile failure. A new source model, which is a superposition of monopole + tectonic release + shock-induced tensile failure, is proposed, the latter source represented by a compensated-linear-vector dipole (CLVD) with vertical axis of symmetry. This CLVD source does not excite Love waves. I draw upon the Toksoz-Kehrer (1972) model for tectonic release where F is an index measuring long-period source strength of the release relative to monopole moment MI. A new index K, analogous to F, is introduced, providing a relative measure of MCLVD, the source strength of tensile failure. MCLVD vanishes for K = 1, and is 0 in the case of extensional deformation along the vertical axis, e.g., K 1. Rayleigh waves from the CLVD destructively interfere with waves from the monopole, and polarity reversals occur on all azimuths for K 3 in Poisson media. Most Nevada Test Site (NTS) observations support 1 K 3, and as such the new model predicts lower Ms compared to the traditional model involving just tectonic release. This effect of tensile failure on Ms improves mb - Ms discrimination and suggests that anomalously large Ms compared to mb for the North Korean test of 9 October 2006 is due to the absence of tensile failure on this explosion.


Subject Categories : Seismic Detection and Detectors
      Nuclear Explosions and Devices(non-military)

Distribution Statement : APPROVED FOR PUBLIC RELEASE