Analysis and Simulation of Near-Field Wave Motion Data from the Source Physics Experiment Explosions
LAWRENCE LIVERMORE NATIONAL LAB CA
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The Source Physics Experiment SPE-N at the Nevada National Security Site is planned as a series of chemical explosions under a variety of emplacement conditions. The goal of the SPE-N is to improve our physical understanding and ability to model explosively generated seismic waves, particularly S-waves. The first SPE explosion SPE1 consisted of a 100 kg shot at a depth of 60 meters in granite Climax Stock. The shot was well-recorded by an array of over 150 instruments, including both near-field wave motion measurements as well as far-field seismic measurements. This paper focuses on measurements and modeling of the near-field data. A complimentary study focusing on far-field seismic observations is the subject of a companion paper Mellors et al. these Proceedings. The near-field data included triaxial acceleration measurements at eighteen different locations azimuthally distributed around the explosive charge. Three triaxial accelerometers were embedded in each of six vertical boreholes, distributed in two concentric rings around the charge. The inner ring consisted of three equidistant boreholes at a radius of 10 m from the charge, and the outer ring consisted of another three equidistant boreholes at a radius of 20 m. In each borehole, the accelerometers were vertically distributed at depths of 60 m shot horizon, 50 m and 15 m. Surface accelerations were also recorded along a radial line centered at surface ground zero. A review of the SPE1 data shows that the peak radial velocity as a function of scaled range is consistent with previous nuclear explosion data but exhibits greater variability. The scaled peak radial displacement variation also exhibits greater variability but the mean values are significantly higher than exhibited in previous nuclear explosion data.