Insights from the Source Physics Experiments on Seismic Waves Generated by Explosions
Session: Explosion Seismology Advances
Type: Oral
Date: 4/29/2020
Time: 09:15 AM
Room: 240
Description:
The Source Physics Experiments (SPE) are a large, multi-institutional (LANL, LLNL, SNL, MSTS and UNR) endeavor to improve our understanding of how explosions generate seismic waves, particularly shear waves, to improve nuclear monitoring capabilities. The SPE includes a series of chemical explosions in southern Nevada in two different boreholes in contrasting geologies. The explosions vary in size and depth and for each borehole they are recorded on a common network, allowing ratios between events to be formed, canceling path and site effects and illuminating near source effects. In Phase I, six chemical explosions from about 0.1 to 5 tons in TNT equivalent yield were detonated between 2011 and 2016 in the same granite borehole. In Phase II, four chemical explosions from about 1 to 50 tons were detonated in 2018-2019 in the same dry alluvium geology (DAG) borehole.
Near-field observations of chemical SPE and historic nuclear data show high frequency tangential motion is 20-30% of radial amplitudes, although the mechanisms that cause this vary with emplacement media. Within a few kilometers, far-field seismic amplitudes at 1-10 Hz are comparable across the 3 components, requiring rapid scattering and conversion to explain. The largest granite and DAG explosions, the 5-ton SPE-5 and the 50-ton DAG-2 have very comparable far-field seismic 1-5 Hz amplitudes, but the DAG had relatively less high frequency energy, showing the importance of material effects on wave generation. Spectral ratios of small to large events confirm these effects are effectively very near source. We show the spectral ratios are not well matched by existing explosion models and that the dry alluvium geology produces smaller amplitudes and appears deficient in high frequency energy relative to explosions in granite. We are examining factors such as absolute depth, scale depth effects and material effects on shear wave generation, P/S and low/high frequency amplitude discrimination performance and correlation behavior. These results are being used to develop a new explosion spectral model.
Presenting Author: William R. Walter
Authors
William R Walter walter5@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States Presenting Author
Corresponding Author
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Sean R Ford ford17@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Arben Pitarka pitarka1@llnl.gov Lawrence Livermore National Laboratory, Lawrence Livermore National Laboratory, California, United States |
Moira Pyle pyle4@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Michael E Pasyanos pasyanos1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Gene Ichinose ichinose1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Andrea Chiang chiang4@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Robert J Mellors mellors1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Souheil M Ezzedine ezzedine1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Oleg Y Vorobiev vorobiev1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Douglas A Dodge dodge1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Eric Matzel matzel1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Jeff Wagoner wagoner1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Insights from the Source Physics Experiments on Seismic Waves Generated by Explosions
Category
Explosion Seismology Advances