Physical models of spall zone ground motions and the determination of spatial decay rates. Los Alamos Source Region Project
- Southern Methodist Univ., Dallas, TX (United States). Dept. of Geological Sciences
- Los Alamos National Lab., NM (United States)
Spall, the tensile failure of near-surface layers, which is observed above contained explosions, has been identified as a possible secondary seismic source contributing to teleseismic and regional signals. The relative importance of this secondary source can be constrained if the motion field in the spall zone is characterized. Spall zone motions from nuclear explosions detonated above the water table at Pahute Mesa are analyzed to develop these models. Acceleration, velocity, displacement, and dwell time measurements are made from gauges placed directly above the explosion, most often at the free surface. Decay of peak motions are strongly affected by the free surface with little change in amplitude out to a free surface range of 100 m/kt{sup l/3} followed by rapid decay beyond. Free surface interactions are assessed with first-order elastic spherical wave calculations that match observed peak velocity decays. These results indicate that the spall zone motions may be strongly affected by the scaled depth of burial of the explosion. Spall zone velocities, displacements and dwell times are compared for consistency with a gravitational model. The data is in agreement with the functional form of theoretical models although observed displacements may be as much as a factor of two to four greater than the model predicts for observed velocities and dwell times. These differences may reflect the continuous nature of the spall process and/or the role of material strength in these phenomena.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Southern Methodist Univ., Dallas, TX (United States). Dept. of Geological Sciences
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10182162
- Report Number(s):
- LA-UR-92-451; ON: DE93040506; CNN: Contract F19628-89-K-0025
- Resource Relation:
- Other Information: PBD: 24 Jan 1992
- Country of Publication:
- United States
- Language:
- English
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