Source Physics Experiment: Research in Support of Verification and Nonproliferation

The Source Physics Experiment (SPE-N) was designed to provide a carefully controlled seismic and strong motion data set from buried explosions at the Nevada National Security Site (NNSS). The first experiment in a series (SPE1) was conducted in May of this year. It consisted of a 100 kg high explosive stemmed for coupling at 180 feet below the surface. In preparation for this experiment, predictive hydrodynamic calculations were performed, strong ground motion free-field and surface gauges were fielded, and a dense network of seismometers and some complimentary infrasound sensors were deployed. The data return for a majority of these sensors was excellent. This paper reports on a finite element analysis of the observable effects of an explosion in realistic earth material with particular focus on predicted and observed strong ground motion patterns. The model correctly incorporates the near-field cavity dynamics, energy deposition partitioned into internal (heat and plastic strain) and kinetic (e.g., radiated seismic) energy, giving more confidence in predicted free-field displacement/velocities and measured attenuation of the free-field peak velocity with distance. The degree of source asymmetry is studied with predictions of the hydrodynamic calculations for close-in free-field particle velocities. We present progress in improving our near-source modeling and predictive capabilities. A number of material test are presented on the granodiorite for both intact and weathered/damaged rock samples. These were used to improve our material model for the near-source environment. Additionally, a detailed 3D geologic framework model was created to represent the complex heterogeneities in the near-source environment (topography, faults, lithology, saturation and weathering). Published in the Proceedings of the 2011 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 13-15 September 2011, Tucson, AZ. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License