Observations of Love Waves from the HUMBLE REDWOOD Explosions with Implications for P/S Ratios at Local Distances
Abstract
The ratio of 6-8 Hz P/S energy is a robust discriminant between earthquakes and explosions at regional distances (e.g., Taylor et al., 1989; Walter et al., 1995; Hartse et al., 1997; Pasyanos et al., 2009). We have examined the P/S discriminant at regional and local distances for simultaneously-detonated chemical explosions conducted for the Non-Proliferation Experiment (NPE), Source Phenomenology Experiments in Arizona (SPE Black Mesa and Morenci), Alaska Frozen Rock Experiments (FRE Frozen and Unfrozen) and the New England Damage Experiment (NEDE). These shots were conducted at various scaled depths of burial in lithology ranging from granite to alluvium. Several of these datasets have delay-fired mining explosions detonated in close proximity to the dedicated shots for comparison. During the past year, we have added additional datasets to our analysis of P/S ratios from explosions: HUMBLE REDWOOD (HR) I and II. The HR I and II experiments (Foxall et al., 2008,2010) provide a unique opportunity to study local phase generation, in particular S-waves, from above- and below-ground explosions. We have identified P-waves higher and fundamental-mode Rayleigh (Rg) waves, and Love (specifically SH, the horizontally polarized shear wave) waves from 656 kg ANFO explosions detonated above and in alluvium in the Albuquerque Basin, New Mexico. Identification of P and Rg was relatively simple based on arrival times and rectilinear and retrograde elliptical particle motion, respectively. Identification of higher mode Rayleigh waves required particle motion (prograde elliptical) and synthetic modeling. The candidate SH arrivals from the above-ground shots are difficult to positively identify as Love waves due to small amplitudes and complex particle motion.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2011
- Accession Number
- ADA568898
Entities
People
- Bill Foxall
- Brian W. Stump
- Howard J. Patton
- Jessie L. Bonner
- Mark Leidig
- Robert E. Reinke
- Sean R. Ford
- William R. Walter
- Xiaoning D. Yang