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

Journal Article · Wed Apr 28 00:00:00 EDT 2021 · Seismological Research Letters

DOI:https://doi.org/10.1785/0220200381· OSTI ID:1804411

Alfaro-Diaz, Richard Alexander ^[1]; Chen, Ting ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

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. In this work 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.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• Grant/Contract Number: 89233218CNA000001; AC52-06NA25396
• OSTI ID: 1804411
• Report Number(s): LA-UR--20-27512
• Journal Information: Seismological Research Letters, Journal Name: Seismological Research Letters Journal Issue: 5 Vol. 92; ISSN 0895-0695
• Publisher: Seismological Society of America
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
Nevada
Nevada National Security Site
S-waves
Source Physics Experiment
United States
Yucca Flat
body waves
chemical explosions
data processing
elastic waves
explosions
geophones
geophysical methods
horizontal-to-vertical spectral ratio
imagery
propagation
seismic methods
seismic waves
underground explosions