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.

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.

scholarly journals Velocity Structure at the Source Physics Experiment Phase I Site Obtained with the Large‐N Array Data

2019 ◽  
Vol 91 (1) ◽  
pp. 304-309
Author(s):  
Ting Chen ◽  
Catherine M. Snelson ◽  
Robert Mellors
Keyword(s):  
Velocity Structure ◽  
Volcanic Rocks ◽  
Velocity Model ◽  
Seismic Array ◽  
P Wave ◽  
Low Velocity ◽  
Large N ◽  
Chemical Explosions ◽  
Physics Experiment ◽  
Source Physics

Abstract The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. The goal of the SPE is to understand and model seismic‐wave generation and propagation from these explosions. To achieve this goal, we need an accurate velocity model of the SPE site. A large‐N seismic array deployed at the SPE site during one of the chemical explosions (SPE‐5) provides great data for this purpose. The array consists of 996 geophones and covers an area of approximately 2×2.5  km. In addition to the SPE‐5 explosion, the array recorded 53 large weight drops. Using the large‐N seismic array recordings, we perform first‐arrival analysis and obtain a 2D P‐wave velocity model of the SPE site. We image a sharp transition from high‐velocity Cretaceous granite to low‐velocity Quaternary alluvium. Other geological units such as the Tertiary volcanic rocks and Paleozoic sedimentary rocks are also clearly shown. The results of this work provide important local geological information and will be incorporated into the larger 3D modeling effort of the SPE program to validate the predictive models developed for the site.

The LArge‐n Seismic Survey in Oklahoma (LASSO) Experiment

2019 ◽  
Author(s):  
Sara L. Dougherty ◽  
Elizabeth S. Cochran ◽  
Rebecca M. Harrington
Keyword(s):  
Vertical Component ◽  
Seismic Survey ◽  
Spatiotemporal Evolution ◽  
Wastewater Disposal ◽  
Event Sequences ◽  
Large N ◽  
Field Deployment ◽  
Stress Drops ◽  
Seismic Wavefield ◽  
Induced Seismic Activity

ABSTRACT In 2016, the U.S. Geological Survey deployed >1800 vertical-component nodal seismometers in Grant County, Oklahoma, to study induced seismic activity associated with production of the Mississippi limestone play. The LArge‐n Seismic Survey in Oklahoma (LASSO) array operated for approximately one month, covering a 25 km by 32 km region with a nominal station spacing of ∼400  m. Primary goals of the deployment were to detect microseismic events not captured by the sparser regional network stations and to provide nearly unaliased records of the seismic wavefield. A more complete record of earthquakes allows us to map the spatiotemporal evolution of induced event sequences and illuminates the structures on which the events occur. Dense records of the seismic wavefield also provide improved measurements of the earthquake source, including focal mechanisms and stress drops. Taken together, we can use these findings to glean insights into the processes that induce earthquakes. Here, we describe the array layout, features of the nodal sensors, data recording configurations, and the field deployment. We also provide examples of earthquake waveforms recorded by the array to illustrate data quality and initial observations. LASSO array data provide a significant resource for understanding the occurrence of earthquakes induced by wastewater disposal.

scholarly journals Source Separation and Medium Change of Contained Chemical Explosions from Coda Wave Interferometry

2021 ◽  
Vol 1 (1) ◽  
pp. 3-10
Author(s):  
Sean R. Ford ◽  
William R. Walter
Keyword(s):  
Coda Wave ◽  
Velocity Perturbation ◽  
Spherical Region ◽  
Seismic Coda ◽  
Chemical Explosions ◽  
Medium Change ◽  
Physics Experiment ◽  
Coda Wave Interferometry ◽  
Source Physics ◽  
Chemical Explosion

Abstract Differences in the seismic coda of neighboring events can be used to investigate source location offsets and medium change with coda wave interferometry (CWI). We employ CWI to infer the known relative location between two chemical explosions in Phase I of the Source Physics Experiment (SPE). The inferred displacement between the first, SPE-1, and second, SPE-2, chemical explosion is between 6 and 18 m, with an expectation of 9.2 m, where the known separation is close to 9.4 m. We also employ CWI to find any velocity perturbation due to damage from SPE-2, by comparing its coda with the collocated third SPE chemical explosion, SPE-3. We find that damage due to SPE-2 must be confined to a spherical region with radius less than 10 m and velocity perturbation less than 25%.

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
Sign in / Sign up

Export Citation Format

Share Document