Estimating Yield and Depth of Burial from Rg (POSTPRINT) Annual Report 2
Abstract
We have examined the feasibility of using short-period, fundamental-mode surface waves (Rg) to estimate the yields and depths of burial (DOB) of small chemical explosions recorded at local distances. Rg and other surface wave arrivals were recorded from the HUMBLE REDWOOD I and II (HR I and II) experiments. The experiments were conducted in and above the dry alluvium of Kirtland AFB, NM near the eastern margin of the Albuquerque Basin, and were recorded by extensive local seismic and acoustic networks. Our Rg analysis technique includes developing a velocity model using inversion of Rg group velocity dispersion data and estimating a frequency-dependent Q model for Rg. The velocity and Q models developed for the region show two distinct regions separated by the Hubbell Springs normal fault. To the west of the fault (graben), upper crustal Rg velocities are slow (0.3 to 0.7 km/sec) and are indicative of dry alluvium. East of the fault (horst), the Rg velocities are faster (0.8 to 2 km/sec) and are representative of more competent bedrock (limestone). Similarly, the Q is lower (2 to 15) to the west of the fault than to the east (15 to 50). The fault also acts as an intense scattering mechanism for Rg. The Rg wave packets west of the fault are easy to identify and process, while, east of the fault, the fundamental model is not easily differentiated from scattered waves. We developed a method that examines the tradeoffs between depth of burial (DOB), Rg excitation, and yield estimation. Our new technique includes 1) development of a velocity and attenuation model using inversion of Rg group velocity dispersion data, 2) propagation of synthetics with isotropic moments through these models to determine the best fit to the observed Rg spectral amplitudes, and 3) estimation of a range of DOB and yields that fit these moments using the Denny and Johnson (1991) explosion source model and near-source material properties.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 20, 2012
- Accession Number
- ADA565906
Entities
People
- Aaron Ferris
- Elizabeth Lenox
- Jessie Bonner
- Robert Reinke