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

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%.

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

Bulletin of the Seismological Society of America ◽

10.1785/0120200160 ◽

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.

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Hanging glacier monitoring with icequake repeaters and seismic coda wave interferometry: a case study of the Eiger hanging glacier

10.5194/nhess-2021-205 ◽

2021 ◽

Author(s):

Małgorzata Chmiel ◽

Fabian Walter ◽

Lukas Preiswerk ◽

Martin Funk ◽

Lorenz Meier ◽

...

Keyword(s):

Large Scale ◽

Wave Attenuation ◽

Seismic Velocity ◽

Swiss Alps ◽

Coda Wave ◽

Diurnal Cycles ◽

Ice Surface ◽

Novel Approach ◽

Seismic Coda ◽

Coda Wave Interferometry

Abstract. Driven by the force of gravity, hanging glacier instabilities can lead to catastrophic rupture events. Reliable forecasting remains a challenge as englacial damage leading to large-scale failure is masked from modern sensing technology focusing on the ice surface. The Eiger hanging glacier, located in the Swiss Alps, was intensely monitored between April and August 2016 before a moderate 15,000 m3 break-off event from the ice cliff. Among different instruments, such as an automatic camera and interferometric radar, four 3-component seismometers were installed on the glacier. A single seismometer operated throughout the whole monitoring period. It recorded over 200,000 repeating icequakes showing strong englacial seismic coda waves. We propose a novel approach for hanging glacier monitoring by combining repeating icequake analysis, coda wave interferometry, and attenuation measurements. Our results show a seasonal 0.1 % decrease in relative englacial seismic velocity dv/v and an increase in coda wave attenuation Qc−1 (Qc decreases from ~50 to ~30). Comparison of dv/v and Qc with air temperature suggests that these changes are driven by a seasonal increase in the glacier’s ice and firn pack temperature that might affect the top 20 m of the glacier. Diurnal cycles of Qc−1, repeating icequake activity, and the velocity of the glacier front shift from cosinusoidal to sinusoidal variations under the presence of meltwater. The proposed approach extends the monitoring of the hanging glacier beyond the ice surface and allows for a better understanding of the glacier’s response to time-dependent external forcing, which is an important step towards improved break-off forecasting systems.

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

Bulletin of the Seismological Society of America ◽

10.1785/0120180296 ◽

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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Detection of Velocity Perturbation Based on Coda Wave Interferometry

Proceedings 76th EAGE Conference and Exhibition 2014 ◽

10.3997/2214-4609.20140887 ◽

2014 ◽

Author(s):

J. Li ◽

J. Tang ◽

C. Sun ◽

J. Xie ◽

B. Fang ◽

...

Keyword(s):

Coda Wave ◽

Velocity Perturbation ◽

Coda Wave Interferometry

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Aftershocks of a Chemical Explosion in Granite from the Source Physics Experiment Phase I

10.2172/1668470 ◽

2020 ◽

Author(s):

Sean Ford

Keyword(s):

Phase I ◽

Physics Experiment ◽

Source Physics ◽

Chemical Explosion

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Coda-wave interferometry and the Marchenko method

10.5194/egusphere-egu2020-20123 ◽

2020 ◽

Author(s):

Kees Wapenaar ◽

Johno van IJsseldijk

Keyword(s):

Fluid Flow ◽

Propagation Velocity ◽

High Sensitivity ◽

Body Waves ◽

Coda Wave ◽

Local Perturbation ◽

Local Velocity ◽

Velocity Perturbation ◽

Flow Process ◽

Coda Wave Interferometry

Coda-wave interferometry, introduced by Snieder and co-workers, employs the relative high sensitivity of the scattering coda in an acoustic or seismic response to time-lapse changes of the propagation velocity and/or structure. It has been successfully applied at many scales, ranging from inferring temperature changes in granite samples, via structural health monitoring of bridges, to monitoring the minute changes in the interior of a volcano prior to eruption. Whereas in most situations the velocity changes are assumed to take place in a large region, it has been shown that coda-wave interferometry can also be used to image a local perturbation of the propagation velocity or structure. The latter approach assumes diffuse waves and employs an array of receivers that surrounds the perturbation.We investigate the application of coda-wave interferometry for monitoring of fluid-flow processes in aquifers, geothermal reservoirs, CO2-storage reservoirs and hydrocarbon reservoirs. In these applications the velocity perturbation is local, but the medium is probed with deterministic seismic body waves from the surface only. The location of the velocity perturbation is usually reasonably well known, but it is practically impossible to identify events in the coda that are directly related to the local perturbation. Recently we introduced the Marchenko method, which retrieves information about multiple scattering from reflection data at the surface in a data-driven way. Here we propose to use the Marchenko method to remove the response from the areas above and below the local velocity perturbation. In this way we isolate the scattering coda of the local velocity perturbation, which enables the application of coda-wave interferometry to monitor the fluid-flow process.

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

Seismological Research Letters ◽

10.1785/0220190104 ◽

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.

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