A Damage Mechanics Source Model for Underground Nuclear Explosions.
Abstract
Recent advances in the damage mechanics of brittle solids have made is possible to calculate stress-strain curves for the non-linear source regime of underground nuclear explosions where the rock is being actively fractured. It has been shown that the damage-based rheology can explain the anomalously broad source pulses observed in the free field of explosions in granite. It also offers a physical explanation for why such pulse broadening was not observed in laboratory experiments in terms of the scaling of rock strength with the size of preexisting fractures. In this report we discuss how damage mechanics may be used to modify the Mueller-Murphy source model to explicitly include the fracture distribution in the explacement medium thereby providing a physical interpretation of source parameters which specify the width of the pressure pulse at the elastic radius, and the elastic radius itself. These parameters are currently evaluated empirically using calibration shots of known yield for each site. The resultant improvement of our understanding of the relation between the source medium and seismic coupling at high frequencies is especially important in view of the recent trend toward the use of higher frequency regional phases for yield estimation and discrimination allowed by improved seismic accessibility to test sites.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1991
- Accession Number
- ADA240692
Entities
People
- Charles G. Sammis
Organizations
- University of Southern California