The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Terry M Calloway - One of the best experts on this subject based on the ideXlab platform.
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Monitoring Surface Phenomena Created by an Underground Chemical Explosion Using Fully Polarimetric VideoSAR
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: David A Yocky, R. Derek West, Robert M. Riley, Terry M CallowayAbstract:Sandia National Laboratories flew its Facility for Advanced RF and Algorithm Development X-Band (9.6-GHz center frequency), fully polarimetric synthetic aperture radar (PolSAR) in VideoSAR mode to collect complex-valued SAR imagery before, during, and after the sixth Source Physics Experiment’s (SPE-6) underground Explosion. The VideoSAR products generated from the data sets include “movies” of single-and quad-polarization coherence maps, magnitude imagery, and polarimetric decompositions. Residual defocus, due to platform motion during data acquisition, was corrected with a digital elevation model-based autofocus algorithm. We generated and exploited the VideoSAR image products to characterize the surface movement effects caused by the underground Explosion. Unlike seismic sensors, which measure local area seismic waves using sparse spacing and subterranean positioning, these VideoSAR products captured high-spatial resolution, 2-D, time-varying surface movement. The results from the fifth SPE (SPE-5) used single-polarimetric VideoSAR data. In this paper, we present single-polarimetric and fully polarimetric VideoSAR results while monitoring the SPE-6 underground Chemical Explosion. We show that fully polarimetric VideoSAR imaging provides a unique, coherent, time-varying measure of the surface expression of the SPE-6 underground Chemical Explosion. We include new surface characterization results from the measured PolSAR SPE-6 data via $H/A/\alpha $ polarimetric decomposition.
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videosar collections to image underground Chemical Explosion surface phenomena
Proceedings of SPIE, 2017Co-Authors: David A Yocky, Terry M Calloway, Daniel E WahlAbstract:Fully-polarimetric X-band (9.6 GHz center frequency) VideoSAR with 0.125-meter ground resolution flew collections before, during, and after the fifth Source Physics Experiment (SPE-5) underground Chemical Explosion. We generate and exploit synthetic aperture RADAR (SAR) and VideoSAR products to characterize surface effects caused by the underground Explosion. To our knowledge, this has never been done. Exploited VideoSAR products are “movies” of coherence maps, phase-difference maps, and magnitude imagery. These movies show two-dimensional, time-varying surface movement. However, objects located on the SPE pad created unwanted, vibrating signatures during the event which made registration and coherent processing more difficult. Nevertheless, there is evidence that dynamic changes are captured by VideoSAR during the event. VideoSAR provides a unique, coherent, time-varying measure of surface expression of an underground Chemical Explosion.
Robert J Mellors - One of the best experts on this subject based on the ideXlab platform.
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Using Dense Array Waveform Correlations to Build a Velocity Model with Stochastic Variability
Bulletin of the Seismological Society of America, 2021Co-Authors: Arben Pitarka, Robert J MellorsAbstract:ABSTRACT 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. 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. 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 SPE were conducted to investigate the generation and propagation of seismic and acoustic waves from underground Explosions. 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. Using comparisons between recorded and simulated waveform cross correlations, we were able to recover sets of statistical properties of small-scale velocity perturbations in the velocity model that produce the best-fit between the recorded and simulated ground motion. The stochastic velocity fluctuations in the velocity model that produced the smallest misfits have a horizontal correlation distance of between 400 and 800 m, a vertical correlation distance between 100 and 200 m, and a standard deviation of 10% from the nominal model velocity in the alluvium basin layers. They also have a horizontal correlation distance of 1000 m, a vertical correlation distance of 250 m, and a standard deviation of 6% in the underlying and consolidated sedimentary layers, up to a depth of 4 km. Comparisons between observed and simulated wavefields were used to assess the proposed small-scale heterogeneity enhancements to the Yucca Flat basin model. We found that adding a depth-resolved stochastic variability to the geology-based velocity model improves the overall performance of ground-motion simulations of an SPE-5 Explosion in the modeled frequency range up to 10 Hz. The results may be applicable to other similar basins.
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analysis of ground motion from an underground Chemical Explosion
Bulletin of the Seismological Society of America, 2015Co-Authors: Arben Pitarka, William R Walter, Robert J Mellors, Souheil Ezzedine, Oleg Y Vorobiev, Tarabay Antoun, Jeffery L Wagoner, Eric Matzel, Sean R Ford, Arthur J RodgersAbstract:We investigate the excitation and propagation of far‐field seismic waves from the 905 kg trinitrotoluene equivalent underground Chemical Explosion SPE‐3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far‐field ground motion at short and long distances is characterized by substantial shear‐wave energy, and large azimuthal variations in P ‐ and S ‐wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances <50 m suggests they were generated at or very near the source. The relative amplitude of the shear waves grows as the waves propagate away from the source. We analyze and model the shear‐wave excitation during the Explosion in the 0.01–10 Hz frequency range, at epicentral distances of up to 1 km. We used two simulation techniques. One is based on the empirical isotropic Mueller–Murphy (MM) (Mueller and Murphy, 1971) nuclear Explosion source model, and 3D anelastic wave propagation modeling. The second uses a physics‐based approach that couples hydrodynamic modeling of the Chemical Explosion source with anelastic wave propagation modeling. Comparisons with recorded data show the MM source model overestimates the SPE‐3 far‐field ground motion by an average factor of 4. The observations show that shear waves with substantial high‐frequency energy were generated at the source. However, to match the observations additional shear waves from scattering, including surface topography, and heterogeneous shallow structure contributed to the amplification of far‐field shear motion. Comparisons between empirically based isotropic and physics‐based anisotropic source models suggest that both wave‐scattering effects and near‐field nonlinear effects are needed to explain the amplitude and irregular radiation pattern of shear motion observed during the SPE‐3 Explosion.
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Chemical Explosion experiments to improve nuclear test monitoring
Eos Transactions American Geophysical Union, 2013Co-Authors: Catherine M Snelson, Robert J Mellors, Robert E Abbott, Scott Thomas Broome, Howard J Patton, A J Sussman, Margaret Townsend, William R WalterAbstract:A series of Chemical Explosions, called the Source Physics Experiments (SPE), is being conducted under the auspices of the U.S. Department of Energy’s National Nuclear Security Administration (NNSA) to develop a new more physics-based paradigm for nuclear test monitoring. Currently, monitoring relies on semi-empirical models to discriminate Explosions from earthquakes and to estimate key parameters such as yield. While these models have been highly successful monitoring established test sites, there is concern that future tests could occur in media and at scale depths of burial outside of our empirical experience. This is highlighted by North Korean tests, which exhibit poor performance of a reliable discriminant, mb:Ms (Selby et al., 2012), possibly due to source emplacement and differences in seismic responses for nascent and established test sites. The goal of SPE is to replace these semi-empirical relationships with numerical techniques grounded in a physical basis and thus applicable to any geologic setting or depth.
William R Walter - One of the best experts on this subject based on the ideXlab platform.
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analysis of ground motion from an underground Chemical Explosion
Bulletin of the Seismological Society of America, 2015Co-Authors: Arben Pitarka, William R Walter, Robert J Mellors, Souheil Ezzedine, Oleg Y Vorobiev, Tarabay Antoun, Jeffery L Wagoner, Eric Matzel, Sean R Ford, Arthur J RodgersAbstract:We investigate the excitation and propagation of far‐field seismic waves from the 905 kg trinitrotoluene equivalent underground Chemical Explosion SPE‐3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far‐field ground motion at short and long distances is characterized by substantial shear‐wave energy, and large azimuthal variations in P ‐ and S ‐wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances <50 m suggests they were generated at or very near the source. The relative amplitude of the shear waves grows as the waves propagate away from the source. We analyze and model the shear‐wave excitation during the Explosion in the 0.01–10 Hz frequency range, at epicentral distances of up to 1 km. We used two simulation techniques. One is based on the empirical isotropic Mueller–Murphy (MM) (Mueller and Murphy, 1971) nuclear Explosion source model, and 3D anelastic wave propagation modeling. The second uses a physics‐based approach that couples hydrodynamic modeling of the Chemical Explosion source with anelastic wave propagation modeling. Comparisons with recorded data show the MM source model overestimates the SPE‐3 far‐field ground motion by an average factor of 4. The observations show that shear waves with substantial high‐frequency energy were generated at the source. However, to match the observations additional shear waves from scattering, including surface topography, and heterogeneous shallow structure contributed to the amplification of far‐field shear motion. Comparisons between empirically based isotropic and physics‐based anisotropic source models suggest that both wave‐scattering effects and near‐field nonlinear effects are needed to explain the amplitude and irregular radiation pattern of shear motion observed during the SPE‐3 Explosion.
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Chemical Explosion experiments to improve nuclear test monitoring
Eos Transactions American Geophysical Union, 2013Co-Authors: Catherine M Snelson, Robert J Mellors, Robert E Abbott, Scott Thomas Broome, Howard J Patton, A J Sussman, Margaret Townsend, William R WalterAbstract:A series of Chemical Explosions, called the Source Physics Experiments (SPE), is being conducted under the auspices of the U.S. Department of Energy’s National Nuclear Security Administration (NNSA) to develop a new more physics-based paradigm for nuclear test monitoring. Currently, monitoring relies on semi-empirical models to discriminate Explosions from earthquakes and to estimate key parameters such as yield. While these models have been highly successful monitoring established test sites, there is concern that future tests could occur in media and at scale depths of burial outside of our empirical experience. This is highlighted by North Korean tests, which exhibit poor performance of a reliable discriminant, mb:Ms (Selby et al., 2012), possibly due to source emplacement and differences in seismic responses for nascent and established test sites. The goal of SPE is to replace these semi-empirical relationships with numerical techniques grounded in a physical basis and thus applicable to any geologic setting or depth.
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Analysis, comparison, and modeling of radar interferometry, date of surface deformation signals associated with underground Explosions, mine collapses and earthquakes. Phase I: underground Explosions, Nevada Test Site
1999Co-Authors: William Foxall, P. Vincent, William R WalterAbstract:We have previously presented simple elastic deformation modeling results for three classes of seismic events of concern in monitoring the CTBT--underground Explosions, mine collapses and earthquakes. Those results explored the theoretical detectability of each event type using synthetic aperture radar interferometry (InSAR) based on commercially available satellite data. In those studies we identified and compared the characteristics of synthetic interferograms that distinguish each event type, as well the ability of the interferograms to constrain source parameters. These idealized modeling results, together with preliminary analysis of InSAR data for the 1995 mb 5.2 Solvay mine collapse in southwestern Wyoming, suggested that InSAR data used in conjunction with regional seismic monitoring holds great potential for CTBT discrimination and seismic source analysis, as well as providing accurate ground truth parameters for regional calibration events. In this paper we further examine the detectability and ''discriminating'' power of InSAR by presenting results from InSAR data processing, analysis and modeling of the surface deformation signals associated with underground Explosions. Specifically, we present results of a detailed study of coseismic and postseismic surface deformation signals associated with underground nuclear and Chemical Explosion tests at the Nevada Test Site (NTS). Several interferograms were formed from raw ERS-1/2 radar data covering different time spans and epochs beginning just prior to the last U.S. nuclear tests in 1992 and ending in 1996. These interferograms have yielded information about the nature and duration of the source processes that produced the surface deformations associated with these events. A critical result of this study is that significant post-event surface deformation associated with underground nuclear Explosions detonated at depths in excess of 600 meters can be detected using differential radar interferometry. An immediate implication of this finding is that underground nuclear Explosions may not need to be captured coseismically by radar images acquired before and after an event in order to be detectable. This has obvious advantages in CTBT monitoring since suspect seismic events--which usually can be located within a 100 km by 100 km area of an ERS-1/2 satellite frame by established seismic methods-can be imaged after the event has been identified and located by existing regional seismic networks. Key Words: InSAR, SLC images, interferogram, synthetic interferogram, ERS-1/2 frame, phase unwrapping, DEM, coseismic, postseismic, source parameters.
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Seismic Results from DOE’s Non-Proliferation Experiment: A Comparison of Chemical and Nuclear Explosions
Monitoring a Comprehensive Test Ban Treaty, 1996Co-Authors: Marvin D. Denny, Peter Goldstein, Kevin Mayeda, William R WalterAbstract:The basic results from the US Department of Energy`s (DOE`s) NonProliferation Experiment (NPE) for seismic signal generation are that the source function for a Chemical Explosion is equivalent to that of a nuclear Explosion of about twice the yield and that the seismic moment measurements are consistent between freefield, local, and regional measurements. In addition, evidence was found that Pn in the Basin and Range province of the western United States is a turning ray and is simply proportional to the source function while the transfer functions for Pg and Lg are low-pass in nature.
David A Yocky - One of the best experts on this subject based on the ideXlab platform.
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Monitoring Surface Phenomena Created by an Underground Chemical Explosion Using Fully Polarimetric VideoSAR
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: David A Yocky, R. Derek West, Robert M. Riley, Terry M CallowayAbstract:Sandia National Laboratories flew its Facility for Advanced RF and Algorithm Development X-Band (9.6-GHz center frequency), fully polarimetric synthetic aperture radar (PolSAR) in VideoSAR mode to collect complex-valued SAR imagery before, during, and after the sixth Source Physics Experiment’s (SPE-6) underground Explosion. The VideoSAR products generated from the data sets include “movies” of single-and quad-polarization coherence maps, magnitude imagery, and polarimetric decompositions. Residual defocus, due to platform motion during data acquisition, was corrected with a digital elevation model-based autofocus algorithm. We generated and exploited the VideoSAR image products to characterize the surface movement effects caused by the underground Explosion. Unlike seismic sensors, which measure local area seismic waves using sparse spacing and subterranean positioning, these VideoSAR products captured high-spatial resolution, 2-D, time-varying surface movement. The results from the fifth SPE (SPE-5) used single-polarimetric VideoSAR data. In this paper, we present single-polarimetric and fully polarimetric VideoSAR results while monitoring the SPE-6 underground Chemical Explosion. We show that fully polarimetric VideoSAR imaging provides a unique, coherent, time-varying measure of the surface expression of the SPE-6 underground Chemical Explosion. We include new surface characterization results from the measured PolSAR SPE-6 data via $H/A/\alpha $ polarimetric decomposition.
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videosar collections to image underground Chemical Explosion surface phenomena
Proceedings of SPIE, 2017Co-Authors: David A Yocky, Terry M Calloway, Daniel E WahlAbstract:Fully-polarimetric X-band (9.6 GHz center frequency) VideoSAR with 0.125-meter ground resolution flew collections before, during, and after the fifth Source Physics Experiment (SPE-5) underground Chemical Explosion. We generate and exploit synthetic aperture RADAR (SAR) and VideoSAR products to characterize surface effects caused by the underground Explosion. To our knowledge, this has never been done. Exploited VideoSAR products are “movies” of coherence maps, phase-difference maps, and magnitude imagery. These movies show two-dimensional, time-varying surface movement. However, objects located on the SPE pad created unwanted, vibrating signatures during the event which made registration and coherent processing more difficult. Nevertheless, there is evidence that dynamic changes are captured by VideoSAR during the event. VideoSAR provides a unique, coherent, time-varying measure of surface expression of an underground Chemical Explosion.
Arben Pitarka - One of the best experts on this subject based on the ideXlab platform.
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Using Dense Array Waveform Correlations to Build a Velocity Model with Stochastic Variability
Bulletin of the Seismological Society of America, 2021Co-Authors: Arben Pitarka, Robert J MellorsAbstract:ABSTRACT 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. 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. 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 SPE were conducted to investigate the generation and propagation of seismic and acoustic waves from underground Explosions. 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. Using comparisons between recorded and simulated waveform cross correlations, we were able to recover sets of statistical properties of small-scale velocity perturbations in the velocity model that produce the best-fit between the recorded and simulated ground motion. The stochastic velocity fluctuations in the velocity model that produced the smallest misfits have a horizontal correlation distance of between 400 and 800 m, a vertical correlation distance between 100 and 200 m, and a standard deviation of 10% from the nominal model velocity in the alluvium basin layers. They also have a horizontal correlation distance of 1000 m, a vertical correlation distance of 250 m, and a standard deviation of 6% in the underlying and consolidated sedimentary layers, up to a depth of 4 km. Comparisons between observed and simulated wavefields were used to assess the proposed small-scale heterogeneity enhancements to the Yucca Flat basin model. We found that adding a depth-resolved stochastic variability to the geology-based velocity model improves the overall performance of ground-motion simulations of an SPE-5 Explosion in the modeled frequency range up to 10 Hz. The results may be applicable to other similar basins.
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analysis of ground motion from an underground Chemical Explosion
Bulletin of the Seismological Society of America, 2015Co-Authors: Arben Pitarka, William R Walter, Robert J Mellors, Souheil Ezzedine, Oleg Y Vorobiev, Tarabay Antoun, Jeffery L Wagoner, Eric Matzel, Sean R Ford, Arthur J RodgersAbstract:We investigate the excitation and propagation of far‐field seismic waves from the 905 kg trinitrotoluene equivalent underground Chemical Explosion SPE‐3 recorded during the Source Physics Experiment (SPE) at the Nevada National Security Site. The recorded far‐field ground motion at short and long distances is characterized by substantial shear‐wave energy, and large azimuthal variations in P ‐ and S ‐wave amplitudes. The shear waves observed on the transverse component of sensors at epicentral distances <50 m suggests they were generated at or very near the source. The relative amplitude of the shear waves grows as the waves propagate away from the source. We analyze and model the shear‐wave excitation during the Explosion in the 0.01–10 Hz frequency range, at epicentral distances of up to 1 km. We used two simulation techniques. One is based on the empirical isotropic Mueller–Murphy (MM) (Mueller and Murphy, 1971) nuclear Explosion source model, and 3D anelastic wave propagation modeling. The second uses a physics‐based approach that couples hydrodynamic modeling of the Chemical Explosion source with anelastic wave propagation modeling. Comparisons with recorded data show the MM source model overestimates the SPE‐3 far‐field ground motion by an average factor of 4. The observations show that shear waves with substantial high‐frequency energy were generated at the source. However, to match the observations additional shear waves from scattering, including surface topography, and heterogeneous shallow structure contributed to the amplification of far‐field shear motion. Comparisons between empirically based isotropic and physics‐based anisotropic source models suggest that both wave‐scattering effects and near‐field nonlinear effects are needed to explain the amplitude and irregular radiation pattern of shear motion observed during the SPE‐3 Explosion.