Seismic Source Characteristics of Nuclear and Chemical Explosions in Granite from Hydrodynamic Simulations

Xu, Heming; Rodgers, Arthur R.; Lomov, I.; Vorobiev, O.

doi:10.1007/s00024-012-0623-0

Cited by 16 publications

(14 citation statements)

References 16 publications

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“…GEODYN has been used on a wide range of applications involving high-energy loading of earth materials (Antoun et al, 2001(Antoun et al, , 2004Antoun and Lomov, 2003;Lomov et al, 2003). Recently, Xu et al (2011) used GEODYN to model elastic source spectra from buried nuclear and chemical explosions in granite and showed excellent agreement with the widely accepted empirical elastic source model of Mueller and Murphy (1971) and Stevens and Day (1985). They also showed that chemical and nuclear explosions of equivalent yield have different seismic moments with chemical explosions having higher seismic moments by a factor of about two, consistent with empirical evidence from the 1992 Nonproliferation Experiment in hard rock (Denny, 1994).…”

Section: Computational Approachsupporting

confidence: 54%

“…Rougier et al (2011) used hydrodynamic modeling to constrain the trade-off between yield and depth-of-burial for the May 25, 2009 North Korean nuclear explosion. Recently, Xu et al (2011) showed that hydrodynamic modeling of buried explosions in a well-calibrated granite material model reproduces the elastic source spectra predicted by the widely accepted empirical source model of Mueller and Murphy (1971) and Stevens and Day (1985). These studies justify optimism that explosion generated waves for other emplacement geologies and conditions can be predicted by hydrodynamic modeling and the proposed approach can reduce uncertainties in NEM source estimates.…”

Section: Introductionmentioning

confidence: 81%

“…In this case we consider a simple dilatational volume source (isotropic moment tensor with a step waves and some mismatch for Rayleigh waves at the same location, presumably due to freesurface boundary condition effects as in Lamb's problem (discussed above). In addition, for this type of volume source the reduced velocity potential (Murphy, 1991;Xu et al, 2011) is conveniently derived in the linear elastic region from the GEODYN calculation then convolved with elastic Green's functions for a point source. These semi-analytical solutions are plotted as second traces and are also in good agreement with the analytical solutions.…”

Section: Coupling the Linear Near-source Response To Elastic Wave Promentioning

confidence: 99%

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Simulation of Explosion Ground Motions Using a Hydrodynamic-to-Elastic Coupling Approach in Three Dimensions

Xu¹,

Rodgers²,

Lomov³

et al. 2013

Bulletin of the Seismological Society of America

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Explosion motions in the solid earth or atmosphere are governed by hydrodynamics and must include non-linear material response effects. However, the numerical calculation of the hydrodynamic response is computationally intensive compared to linear (e.g. elastic and acoustic) wave propagation solvers due to non-linear constitutive behavior especially. In order to propagate explosion generated ground motions from the non-linear near-source region to the far-field we developed a hybrid modeling approach with one-way hydrodynamic-to-elastic coupling in three dimensions. Near source motions are computed with GEODYN, an Eulerian hydrodynamics code with adaptive mesh refinement for high-energy loading of earth materials.Motions on a dense grid of points are saved, resampled and then passed to WPP, an anelastic finite difference code for seismic wave modeling. Our coupling strategy is based on the uniqueness theorem where motions are introduced into WPP as a boundary source and continue Hydrodynamic-to-Elastic Coupling in Three-Dimensions2 to propagate as elastic waves at much lower computational cost than with GEODYN. We have developed and verified the methodology to compute GEODYN hydrodynamic responses in either two-or three-dimensions (2D and 3D) and pass these to WPP as 3D boundary motions on the faces of a cube. For the 2D case we compute the axisymmetric response with GEODYN and transform the elastic motions onto the cube faces (coupling interface) in 3D before introducing motions to WPP. The accuracy of the numerical calculations and the coupling strategy is demonstrated in cases with a purely elastic medium as well as non-linear medium. Importantly we show that GEODYN can accurately model motions for a linear elastic medium including surface waves, which is essential to insure that near-source motions are correct. An application of our hybrid modeling approach is shown for a problem involving scattering by 3D heterogeneity. Our strategy by design is capable of incorporating complex non-linear effects near the source as well as volumetric and topographic material heterogeneity along the propagation path to receiver, making it very powerful for modeling a wide variety of effects and providing new prospects for modeling and understanding explosion generated seismic waveforms.

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Section: Computational Approachsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 81%

Section: Coupling the Linear Near-source Response To Elastic Wave Promentioning

confidence: 99%

See 1 more Smart Citation

Simulation of Explosion Ground Motions Using a Hydrodynamic-to-Elastic Coupling Approach in Three Dimensions

Xu¹,

Rodgers²,

Lomov³

et al. 2013

Bulletin of the Seismological Society of America

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“…For example Rougier et al (2011) showed that historical cavity radius models don't fit numerical modeling for over--buried shots. Hydrodynamic calculations for 1--5 kt explosions in granite performed by Xu et al (2012) show higher corner frequencies and different low--frequency moment scaling with depth than MM and DJ.…”

Section: Introductionmentioning

confidence: 84%

“…Since both models contain cube--root yield scaling (f c ~ 1/W 1/3 ) their ratio is not dependent on yield and we can plot their ratio versus DOB as is done in Figure 2b. Since MM was built with nuclear data only, we also show a comparison where the yield for MM is doubled as is predicted by chemical/nuclear equivalency studies (Denny, 1994) and numerical calculations (e.g., Xu et al, 2012). Note that DJ was built using both chemical and nuclear data, and DJ state "no evidence was found in this study to suggest that chemical and nuclear explosions are significantly different," so no change is made to the DJ model for chemical explosions.…”

Section: Introductionmentioning

confidence: 99%

An Explosion Model Comparison with Insights from the Source Physics Experiments

Ford¹,

Walter²

2013

Bulletin of the Seismological Society of America

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Seismic spectral models for chemical and nuclear explosions are used in many applications including network modeling and yield estimation. Here we compare the models presented in Denny and Johnson (1991) and Mueller and Murphy (1971) with each other and with new results from the Source Physics Experiments (SPE). We demonstrate analytically the two models are in substantial agreement for large and normally buried explosions, consistent with much of the historic data collected during nuclear testing. However for small and/or deeply buried explosions, the spectral predictions of the two models can differ significantly. For example, the predicted yield of a 1--km deep, MW 2 nuclear explosion differs by more than a factor of five, and for the same moment and depth chemical explosion, the difference is greater than a factor of ten. We compare the models with initial data from the Source Physics Experiments (SPE), which include small and over--buried chemical explosions. The corner frequency of the one--ton SPE explosion (SPE--2) is slightly higher than the Mueller and Murphy (1971) The ability to predict the expected seismic amplitudes from an explosion is important in a number of applications including exploration and nuclear test monitoring. An analytical model for P--waves was first developed by Sharpe (1942), based on pressure in a spherical cavity in an elastic medium. Since then a large number of explosion source spectral models have been developed based on empirical data and theoretical considerations (cf. Denny and Johnson, 1991). Such spectral models are used to determine network thresholds for nuclear test monitoring and to estimate source properties, such as yield and depth of burial from seismic data.With the signing of the Comprehensive nuclear Test--Ban Treaty (CTBT) in 1996, and the cessation of testing by the signatories, any future nuclear tests may be conducted outside of standard practices and it is important to predict seismic observables for new regions and testing conditions. The development and validation of physics--based explosion models that extend the range of the current, more empirically, derived models is a focus of the DOE/NNSA funded Source Physics Experiments (SPE) (e.g. NNSA, 2012). The SPE focuses on physics--based model development work supported by a new chemical explosion dataset.We focus here on two of the most widely used far--field explosion P--wave spectral models: Mueller and Murphy (1971), hereafter referred to as MM, and Denny and Johnson (1991), hereafter referred to as DJ. MM developed a spectral model for several different emplacement media as a function of depth and source size. They extended the Sharpe (1942) analytical elastic response and developed a new pressure function applied at the elastic radius (distance from the source where the media begins to respond elastically) that Rougier et al. (2011) showed that historical cavity radius models don't fit numerical modeling for over--buried shots. Hydrodynamic calculations for 1--5 kt explosions in granite pe...

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Seismic source functions from free‐field ground motions recorded on SPE: Implications for source models of small, shallow explosions

Rougier

Patton

2015

JGR Solid Earth

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Reduced displacement potentials (RDPs) for chemical explosions of the Source PhysicsExperiments (SPE) in granite at the Nevada Nuclear Security Site are estimated from free-field ground motion recordings. Far-field P wave source functions are proportional to the time derivative of RDPs. Frequency domain comparisons between measured source functions and model predictions show that high-frequency amplitudes roll off as ω À 2 , but models fail to predict the observed seismic moment, corner frequency, and spectral overshoot. All three features are fit satisfactorily for the SPE-2 test after cavity radius R c is reduced by 12%, elastic radius is reduced by 58%, and peak-to-static pressure ratio on the elastic radius is increased by 100%, all with respect to the Mueller-Murphy model modified with the Denny-Johnson R c scaling law. A large discrepancy is found between the cavity volume inferred from RDPs and the volume estimated from laser scans of the emplacement hole. The measurements imply a scaled R c of~5 m/kt 1/3 , more than a factor of 2 smaller than nuclear explosions. Less than 25% of the seismic moment can be attributed to cavity formation. A breakdown of the incompressibility assumption due to shear dilatancy of the source medium around the cavity is the likely explanation. New formulas are developed for volume changes due to medium bulking (or compaction). A 0.04% decrease of average density inside the elastic radius accounts for the missing volumetric moment. Assuming incompressibility, established R c scaling laws predicted the moment reasonable well, but it was only fortuitous because dilation of the source medium compensated for the small cavity volume.

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Seismic Source Characteristics of Nuclear and Chemical Explosions in Granite from Hydrodynamic Simulations

Cited by 16 publications

References 16 publications

Simulation of Explosion Ground Motions Using a Hydrodynamic-to-Elastic Coupling Approach in Three Dimensions

Simulation of Explosion Ground Motions Using a Hydrodynamic-to-Elastic Coupling Approach in Three Dimensions

An Explosion Model Comparison with Insights from the Source Physics Experiments

Seismic source functions from free‐field ground motions recorded on SPE: Implications for source models of small, shallow explosions

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