Infrasound Observations from the Source Physics Experiment (tests 1 and 2) at the Nevada National Security Site

The overall mission of the National Center for Nuclear Security (NCNS) Source Physics Experiment (SPE-N) at the Nevada National Security Site (NNSS) near Las Vegas, Nevada is to improve upon and develop new physics based models for underground nuclear explosions using scaled, underground chemical explosions as proxies. Infrasound has been used for many years to study explosive sources both above and below ground. For most of these studies, the explosions were single shot events located in different areas. With the SPE-N series of explosions, we have the unique and rare opportunity to study infrasound generated by a well-characterized source from the same borehole. This reduces the number of variables that must be accounted for when generating models using the acoustic data. At the time of submission, the first two explosive tests (SPE-N-1 and SPE-N-2) were successfully conducted on May 3 and October 25, 2011, respectively. SPE-N-1 had a yield of 0.1 tons at a depth of 60 m with a scaled depth of burial of 1,026 m. This explosion was used as a calibration shot as it was the first in the series. SPE-N-2 had a yield of 1 ton at a depth of 45 m, corresponding to a scaled depth of burial of 357 m. The acoustic amplitudes ranged from ~0.5 Pa at 225 m, to not being detected after 1 km for the 0.1 ton shot; and ~14 Pa at 225 m, to ~0.1 Pa at 5 km for the 1 ton shot. This paper will focus on detailed acoustic observations from both of these tests as well as describe future work, including detailed modeling of infrasound generation at the surface in the area above the explosion. 2012 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies