Analysis and Simulation of Far-Field Seismic 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 NNSS is planned as a series of chemical explosions under a variety of emplacement conditions. The SPE-N goal is to improve our physical understanding and ability to model how explosion generate seismic waves, particularly S-waves. The first SPE-N explosion SPE1 occurred in May 2011 and consisted of a 220 lb 100 kg chemical explosion at a depth of 180 ft 55 m in granite Climax Stock. This paper examines the far-field seismic observations and a complementary paper addresses the near-field wave-motion Antoun et al. these Proceedings. The shot was well-recorded by a assortment of over 150 instruments. The greatest density of instruments were located within 5 km of the source but some extended as far out as 20 km, and there are additional local and regional stations that are part of permanent networks. The majority of the SPE-N specific stations were installed as part of 5 radially oriented lines that emanate from the shot location. A variety of instruments were deployed, including high-frequency geophones accelerometers, broadband seismometers, and rotational sensors. Data recovery from the first shot was over 95. A review of the SPE1 waveforms shows variations with azimuth in both frequency content and amplitudes. Some of the variations correlated closely with known lateral changes in geology but the nearest stations, all of which were located on granite, also showed significant variations. Preliminary modeling of the SPE1 data using a 3D finite difference code and a 3D velocity model showed similarities in both arrival times and overall features at low frequencies. Further modeling will be conducted with emphasis on understanding the generation of shear waves and comparison of data with the synthetics.