scholarly journals Source Physics Experiment Phase II, Dry Alluvium Geology (DAG) Experiments Using Nitromethane

2016 ◽  
Author(s):  
Scott R. Traeger
Keyword(s):  
Phase Ii ◽  
Physics Experiment ◽  
Source Physics

Source Physics Experiment Phase II Dry Alluvium Geology (DAG) Experiments Design Reviews

2017 ◽  
Author(s):  
Peter Dickson ◽  
Gerald John Seitz ◽  
Kyle J. Deines ◽  
Robert C. Gentzlinger ◽  
Nathaniel Jordan Paul Mesick ◽  
...  
Keyword(s):  
Phase Ii ◽  
Physics Experiment ◽  
Source Physics

Imaging the Shallow Structure of the Yucca Flat at the Source Physics Experiment Phase II Site with Horizontal-to-Vertical Spectral Ratio Inversion and a Large-N Seismic Array

2021 ◽  
Author(s):  
Richard Alfaro-Diaz ◽  
Ting Chen
Keyword(s):  
Shear Wave ◽  
Phase Ii ◽  
Volcanic Rocks ◽  
Spectral Ratio ◽  
Seismic Array ◽  
Shallow Subsurface ◽  
Large N ◽  
Physics Experiment ◽  
Shallow Structure ◽  
Source Physics

Abstract 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. To understand explosion source physics, accurate geophysical models of the SPE site are needed. 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. The deployment consists of 500 geophones and covers an area of, approximately, 2.5×2  km. The array is located in the Yucca Flat in the northeast corner of the NNSS, Nye County, Nevada. Using ambient-noise recordings throughout the large-N seismic array, we calculate horizontal-to-vertical spectral ratios (HVSRs) across the array. We obtain 2D seismic images of shear-wave velocities across the SPE phase II site for the shallow structure of the basin. The results clearly image two significant seismic impedance interfaces at ∼150–500 and ∼350–600  m depth. The shallower interface relates to the contrast between Quaternary alluvium and Tertiary volcanic rocks. The deeper interface relates to the contrast between Tertiary volcanic rocks and the Paleozoic bedrock. The 2D subsurface models support and extend previous understanding of the structure of the SPE phase II site. 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.

Effect of Random 3D Correlated Velocity Perturbations on Numerical Modeling of Ground Motion from the Source Physics Experiment

2020 ◽  
Author(s):  
Michelle Scalise ◽  
Arben Pitarka ◽  
John N. Louie ◽  
Kenneth D. Smith
Keyword(s):  
Wave Propagation ◽  
Wave Scattering ◽  
Small Scale ◽  
Stochastic Perturbations ◽  
Near Surface ◽  
Velocity Models ◽  
Chemical Explosions ◽  
Shear Motion ◽  
Physics Experiment ◽  
Source Physics

ABSTRACT Explosions are traditionally discriminated from earthquakes, using the relative amplitude of compressional and shear waves at regional and teleseismic distances known as the P/S discriminant. Pyle and Walter (2019) showed this technique to be less robust at shorter distances, in detecting small-magnitude earthquakes and low-yield explosions. The disparity is largely due to ground motion from small, shallow sources being significantly impacted by near-surface structural complexities. To understand the implications of wave propagation effects in generation of shear motion and P/S ratio during underground chemical explosions, we performed simulations of the Source Physics Experiment (SPE) chemical explosions using 1D and 3D velocity models of the Yucca Flat basin. All simulations used isotropic point sources in the frequency range 0–5 Hz. We isolate the effect of large-scale geological structure and small-scale variability at shallow depth (<5  km), using a regional 3D geologic framework model (GFM) and the GFM-R model derived from the GFM, by adding correlated stochastic velocity perturbations. A parametric study of effects of small-scale velocity variations on wave propagation, computed using a reference 1D velocity model with stochastic perturbations, shows that the correlation length and depth of stochastic perturbations significantly impact wave scattering, near-surface wave conversions, and shear-wave generation. Comparisons of recorded and simulated waveforms for the SPE-5 explosion, using 3D velocity models, demonstrate that the shallow structure of the Yucca Flat basin contributes to generation of observed shear motion. The inclusion of 3D wave scattering, simulated by small-scale velocity perturbations in the 3D model, improves the fit between the simulated and recorded waveforms. In addition, a relatively low intrinsic attenuation, combined with small-scale velocity variations in our models, can confirm the observed wave trapping and its effect on duration of coda waves and the spatial variation of P/S ratio at basin sites.

scholarly journals The Effects of Atmospheric Models on the Estimation of Infrasonic Source Functions at the Source Physics Experiment

2020 ◽  
Vol 110 (3) ◽  
pp. 998-1010 ◽  
Author(s):  
Christian Poppeliers ◽  
Lauren Bronwyn Wheeler ◽  
Leiph Preston
Keyword(s):  
Green's Functions ◽  
Time Window ◽  
Green’S Functions ◽  
Atmospheric Model ◽  
Weather Data ◽  
Atmospheric Models ◽  
Data Set ◽  
Model Type ◽  
Physics Experiment ◽  
Source Physics

ABSTRACT We invert infrasound signals for an equivalent seismoacoustic source function using different atmospheric models to produce the necessary Green’s functions. The infrasound signals were produced by a series of underground chemical explosions as part of the Source Physics Experiment (SPE). In a previous study, we inverted the infrasound data using so-called predictive atmospheric models, which were based on historic, regional-scaled, publicly available weather observations interpolated onto a 3D grid. For the work presented here, we invert the same infrasound data, but using atmospheric models based on weather data collected in a time window that includes the approximate time of the explosion experiments, which we term postdictive models. We build two versions of the postdictive models for each SPE event: one that is based solely on the regional scaled observations, and one that is based on both regional scaled observations combined with on-site observations obtained by a weather sonde released at the time of the SPE. We then invert the observed data set three times, once for each atmospheric model type. We find that the estimated seismoacoustic source functions are relatively similar in waveform shape regardless of which atmospheric model that we used to construct the Green’s functions. However, we find that the amplitude of the estimated source functions is systematically dependent on the atmospheric model type: using the predictive atmospheric models to invert the data generally yields estimated source functions that are larger in amplitude than those estimated using the postdictive models.

scholarly journals Azimuthally Dependent Seismic‐Wave Coherence at the Source Physics Experiment Large‐N Array

2019 ◽  
Vol 109 (5) ◽  
pp. 1935-1947
Author(s):  
Andréa Darrh ◽  
Christian Poppeliers ◽  
Leiph Preston
Keyword(s):  
Seismic Wave ◽  
Vertical Component ◽  
Linear Arrays ◽  
Seismic Scattering ◽  
Large N ◽  
2D Arrays ◽  
Physics Experiment ◽  
Seismic Wavefield ◽  
Source Physics ◽  
Chemical Explosion

Abstract We document azimuthally dependent seismic scattering at the Source Physics Experiment (SPE) using the large‐N array. The large‐N array recorded the seismic wavefield produced by the SPE‐5 buried chemical explosion, which occurred in April 2016 at the Nevada National Security Site, U.S.A. By selecting a subset of vertical‐component geophones from the large‐N array, we formed 10 linear arrays, with different nominal source–receiver azimuths as well as six 2D arrays. For each linear array, we evaluate wavefield coherency as a function of frequency and interstation distance. For both the P arrival and post‐P arrivals, the coherency is higher in the northeast propagation direction, which is consistent with the strike of the steeply dipping Boundary fault adjacent to the northwest side of the large‐N array. Conventional array analysis using a suite of 2D arrays suggests that the presence of the fault may help explain the azimuthal dependence of the seismic‐wave coherency for all wave types. This fault, which separates granite from alluvium, may be acting as a vertically oriented refractor and/or waveguide.

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