A Scaling Analysis of Frequency Dependent Energy Partition for Local and Regional Seismic Phases from Explosions
Abstract
Seismic identification of small explosions relies on the application of discriminants that are effective in the regional distance range. The most reliable regional discriminants identified to date are those based on high frequency spectral ratios of the amplitudes of the regional shear phases Sn and Lg to those of the corresponding direct P phases Pn and Pg. However, the universal applicability of such discriminants remains in question because there is currently no physical model of S wave generation by explosions that has been shown to be quantitatively consistent with the range of available observations. The objectives of this research program have been to determine frequency dependent source scaling relations for observed regional P and S phases through statistical analysis of data recorded from underground nuclear explosions conducted at a variety of different test sites, and to apply these derived scaling relations to a quantitative evaluation of the credibility of various proposed source mechanisms for generation of the regional shear phases Sn and Lg observed from underground explosion sources. The source scaling results obtained have been found to be remarkably consistent, indicating that the observed Sn and Lg spectra scale with yield in a manner which is very comparable to that of the corresponding direct Pn spectra, generally differing significantly over narrow frequency bands defined by differences in the P and S wave corner frequencies. These results provide strong constraints which must be satisfied by any plausible proposed physical mechanism of explosion S wave generation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 31, 2007
- Accession Number
- ADA476377
Entities
People
- Brian W. Barker
- Jamil D. Sultanov
- John R. Murphy
Organizations
- Leidos