![]() Comparisons of decay rates of waveform cross correlations as function of interstation distance, computed for observed and synthetic seismograms from the SPE-5 chemical explosion, were used to constrain statistical properties of correlated stochastic velocity perturbations representing small-scale heterogeneities added to a geology-based velocity model of the Yucca Flat basin. The more » SPE were conducted to investigate the generation and propagation of seismic and acoustic waves from underground explosions. The array consisted of 996 geophones with a 50–100 m grid spacing, deployed at the SPE site at the north end of the Yucca Flat basin. The waveforms were recorded by a dense 2D seismic array deployed during the Source Physics Experiments for event number 5 (SPE-5) in a series of six underground chemical explosions, conducted at the Nevada National Security Site. In an ongoing effort to improve 3D seismic-wave propagation modeling for frequencies up to 10 Hz, we used cross correlations between vertical-component waveforms from an underground chemical explosion to estimate the statistical properties of small-scale velocity heterogeneities. This study shows that the HVSR method in conjunction with a large-N seismic array is a quick and effective method for investigating shallow structures. The 2D subsurface models support and extend previous understanding of the structure of the SPE phase II site. The deeper interface relates to the contrast between Tertiary volcanic rocks and the Paleozoic bedrock. The shallower interface relates to the contrast between Quaternary alluvium and Tertiary volcanic rocks. In this work the results clearly image two significant seismic impedance interfaces at ~150–500 and ~350–600 m depth. We obtain 2D seismic images of shear-wave velocities across the SPE phase II site for the shallow structure of the basin. Using ambient-noise recordings throughout the large-N seismic array, we calculate horizontal-to-vertical spectral ratios (HVSRs) across the array. The array is located in the Yucca Flat in the northeast corner of the NNSS, Nye County, more » Nevada. The deployment consists of 500 geophones and covers an area of, approximately, 2.5 × 2 km. Here, we utilize a large-N seismic array deployed at the SPE phase II site to generate a shallow subsurface model of shear-wave velocity. To understand explosion source physics, accurate geophysical models of the SPE site are needed. The Source Physics Experiment (SPE) is a series of chemical explosions at the Nevada National Security Site (NNSS) with the goal of understanding seismic-wave generation and propagation of underground explosions. An appendix is included that provides quantitative data on physical properties for each model layer. The GFM includes 7 model layers and 48 faults that cut and offset the layers. The Yucca Flat GFM helps address these challenges by providing more » the 3-D distribution of relevant geologic features and physical properties necessary to more effectively model seismic wave propagation. The geology in the Yucca Flat region is complex and diverse, which creates challenges to modeling seismic wave propagation from SPE tests. This report describes a 3-D GFM constructed for the Source Physics Experiment Phase II Dry Alluvium Geology test series located in Yucca Flat at the Nevada National Security Site. GFMs provide a three-dimensional (3-D), geology-based digital framework for developing and parametrizing meshes and evaluating model and simulation results. Geologic framework models (GFMs) provide a methodology for integrating geology into, and thus geologically informing, other modeling and simulation activities. An appendix is included that provides quantitative data on physical properties for each model = , The Yucca Flat GFM helps address these challenges by providing the 3-D distribution of relevant geologic features and physical properties necessary to more effectively model seismic wave propagation. GFMs provide a threedimensional (3-D), geology-based digital framework for developing and parametrizing meshes and evaluating model and simulation results.
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