Explosive Sources Research Articles

Estimating Explosion Yields Using Moment Tensor Solutions and Seismic Moment

Abstract Seismic moment, a measurable and well-understood quantity of seismic sources, is used to estimate the yield of explosions. Application of such a method in the past, as in the manner of mb-derived yields, has been complicated by the effect of variations in the explosion working point, depth, and secondary source effects (such as spalling and tectonic release) on the observed moment. We start using the full (six-element) moment tensor solution, which can capture the relevant source physics and, at least in theory, better isolate the primary explosion source. The moment-to-yield ratio is then estimated using an explosion source model which, provided with emplacement conditions, can relate the two parameters. We discuss the major sources of uncertainty associated with the method, and calibrate it with chemical and nuclear explosions at the Nevada National Security Site. We then apply the method to published moment tensor solutions for the six declared North Korean nuclear explosions that occurred between 2006 and 2017. The results are mostly consistent with other yield estimates made using a variety of high-frequency methods. This technique is a new approach to estimating explosive yield and simple to implement, as much of the complexity is captured by the source models.

Relative Seismic Source Scaling Based on Pn Observations from the North Korean Underground Nuclear Explosions

ABSTRACT We estimate yields and source depths for the six North Korean underground nuclear explosions (UNEs) in 2006, 2009, 2013, 2016 (January and September), and 2017, based on regional seismic observations in South Korea. Spectral ratios of event pairs are calculated using seismograms from the six UNEs observed along the same propagation paths and at the same receivers. These relative seismic source scaling spectra for Pn provide a basis for a grid search source solution that estimates source yields and depths for each event pair based on assumed explosion source models by Mueller and Murphy (1971; MM71), Denny and Johnson (1991; DJ91), and Walter and Ford (2018; WF18). The grid search is used to identify the best fit to the empirical spectral ratios subject to the source models by minimizing the root mean square misfit in the frequency range of 0.2–15 Hz. To address the trade-off between depth and yield, a modified grid search was implemented that includes elastic propagation effects for different source depths using reflectivity Green’s functions, thus modeling slight differences in propagation path based on source depth. This addition reduces trade-offs between depth and yield, and results in better model fits to frequencies as high as 15 Hz compared with cases in which depth effects were not included. The modified grid search results indicate that both MM71 and WF18 models provide comparable source depth and yield estimates with good agreement between theoretical and observed spectral ratios matching both the long-period levels and the corner frequencies, whereas the DJ91 model estimates produce lower yields due to a difference in corner frequency scaling. The best grid search solutions produce yields from ∼0.9 kt for the first UNE and up to ∼290 kt for the explosion in 2017, with depths varying from ∼280 to ∼750 m.

Seismic and Infrasound Data Recorded at Regional Seismoacoustic Research Arrays in South Korea from the Six DPRK Underground Nuclear Explosions

Abstract Five seismoacoustic research arrays and one infrasound research array located across the southern Korean peninsula have been installed, maintained, and are cooperatively operated by Southern Methodist University and Korea Institute of Geoscience and Mineral Resources. The seismoacousitc arrays are each composed of 1–5 broadband seismometers spaced from 0.5 to 1.5 km and 4–16 infrasound sensors spaced from 0.1 to 1.5 km. The arrays—BRDAR, CHNAR, KSGAR, KMPAR, TJIAR, and YPDAR—have recorded regional seismic and infrasound signals from the six underground nuclear explosions conducted by Democratic People’s Republic of Korea. These seismoacoustic data are being made available for researchers interested in studying and quantifying the explosion source functions of these events as well as wave propagation effects in the solid earth and atmosphere as constrained by seismic and infrasound observations at regional distances.

Influencing Mechanism of Detonator Location on Blasting Vibration with Electronic Initiation Technology

Vibration velocity amplitude and frequency are the critical factors for assessing the adverse effects of blasting on surrounding structures. In this study, vibration signals were measured from a specially designed field test, in which blast holes were detonated by different initiation modes. Results of the field test indicate that the initiation mode has significant effects on blasting vibration. Then the influencing mechanism was revealed with the help of numerical simulation and theoretical analysis. Numerical simulation results show perfect accordance with filed test results. Five initiation modes to detonate the same explosion source, in descending orders of both velocity amplitude and vibration frequency, are the two initiation points, then the midpoint initiation and top and bottom initiation, followed by the bottom initiation and top initiation. By changing the location or increasing the number of detonators to reduce the length of subsource, the propagation path of detonation waves will be shrunk. Then the rising time of blast loading will be reduced and the rising rate will be accelerated, which lead to an increase in vibration frequency. In the meantime, the release and distribution of explosion energy will be accelerated unavoidably, which leads to an increase of vibration intensity. This study has considerable theoretical meaning and engineering value to guide for blasting construction.

An analytical method for the dynamic response prediction and produced test modes generated by vibro-shock test benches

This article describes a methodology for the computational forecasting of dynamic characteristics and test modes, implemented by vibro-shock stands of explosive action. Vibro-shock stands are widely used in ground-based experimental testing of onboard equipment of spacecraft for non-stationary broadband impact arising from the operation of pyrotechnic separation means. The principle of operation of these stands is based on the excitation of an intense non-stationary broadband vibration mode using an explosive energy source in a system of elastic-inertial elements (resonator), affecting the test object. The presented analytical technique is used to predict the test modes implemented by the vibro-shock stand in the form of a shock spectrum and for pre-test calculations in order to adjust the characteristics of the stand, ensuring the implementation of the necessary test modes. The reliability of the calculation results performed according to this technique is confirmed by experimental data. Key words: dynamic stiffness, method of initial parameters, shock loading, pyrotechnic separation means, ground experimental development, vibro-shock strength, vibro-shock stands of explosive action.

Inferring astrophysical parameters of core-collapse supernovae from their gravitational-wave emission

Nearby core-collapse supernovae (CCSNe) are powerful multimessenger sources for gravitational-wave, neutrino, and electromagnetic telescopes as they emit gravitational waves in the ideal frequency band for ground based detectors. Once a CCSN gravitational-wave signal is detected, we will need to determine the parameters of the signal and understand how those parameters relate to the source's explosion, progenitor, and remnant properties. This is a challenge due to the stochastic nature of CCSN explosions, which is imprinted on their time series gravitational waveforms. In this paper, we perform Bayesian parameter estimation of CCSN signals using an asymmetric chirplet signal model to represent the dominant high-frequency mode observed in spectrograms of CCSN gravitational-wave signals. We use design sensitivity Advanced LIGO noise and CCSN waveforms from four different hydrodynamical supernova simulations with a range of different progenitor stars. We determine how well our model can reconstruct time-frequency images of the emission modes and show how well we can determine parameters of the signal such as the frequency, amplitude, and duration. We show how the parameters of our signal model may allow us to place constraints on the protoneutron star mass and radius, the turbulent kinetic energy onto the protoneutron star, and the time of shock revival.

Hoop and axial plastic buckling modes of submerged cylindrical shells subjected to side-on underwater explosion shock wave

Cylindrical shells are widely used in marine structures from small-sized pipes to various immersed containers and large submarines. Dynamic plastic buckling of the shells could be caused by underwater explosion (UNEX) loads in industrial accidents or hostile attacks. Influential factors including non-dimensional hull shock factor reflecting the resilience of the material to shock intensity, slenderness ratio, localised ring stiffener and endcap are identified. Their impacts on the dynamic buckling modes are discussed relied on the finite element investigations. The results show that the global hoop and axial buckling modes are mainly determined by the hull shock factor and slenderness ratio, respectively. With the increase of hull shock factor, i) back-side buckling, ii) back- and front-side buckling with dominant buckles at the back-side, iii) back- and front-side buckling with dominant buckles at the front side, and iv) overall buckling with very large buckles at the front-side originating from the priority buckling modes can be observed in the circumferential direction. The competition between the front- and back-sides buckling is attributed to their different buckling mechanisms. The former one is caused by shock transmitted from the explosion source through the fluid, whereas the later one is due to striking of the structural hoop stress waves propagated from the front-side via the shell itself. Axial buckling modes consisted of primary and potential buckles alternating in the axial direction could be triggered for a large slenderness ratio, but be concealed by localised buckling modes for small slenderness ratio. The localised buckling modes are controlled by the ring-stiffener and endcap, because they alter the continuity of compression potential of shells.

Simulation Study of Gas Explosion Propagation Law in Coal Mining Face With Different Ventilation Modes

In ventilation working face, different ventilation way is one of the important factors affecting the propagation of gas explosion shock wave. In order to study the gas explosion shock wave propagation laws in coal mining faces with different ventilation methods, using Fluent simulation software, combined with pipeline gas explosion experiments and the actual situation of gas accumulation area explosion in the corner of 415 coal face in Chenjiashan coal mine, Shaanxi Province, and on the basis of building a three-dimensional mathematical and physical model, the gas explosion simulations under Y-type and W-type ventilation methods were carried out, respectively. The results are described as follows: (1) The attenuation trend of overpressure peak value of inlet roadway 1 and working face with Y-type ventilation conforms to the power function form. Intake airway 2 and return airway have the same peak overpressure attenuation trend, but the peak value of overpressure in return airway is generally 10.6% higher than that in intake airway 2, and its attenuation rate is a process from low to high and then to low. (2) The peak attenuation trend of overpressure in intake airways 1 and 2 with W-type ventilation conforms to the form of power function, and the peak attenuation trend of overpressure in return airway conforms to the form of exponential function. The peak value of overpressure decreases with the increase in the distance from the explosion source, and its attenuation rate decreases gradually. The research results have important theoretical significance for improving the prevention of gas explosion in coal mining face with different ventilation modes.

Seismic wavefield model excited by a finite long cylindrical charge

The amplitude-frequency characteristic of a seismic wave excited by explosion sources directly affects the accuracy of seismic exploration. To reveal the effect law related to a cylindrical charge, this research proposes a seismic wavefield model excited by a long cylindrical charge. According to the characteristics of the blasting cavity generated by a finite-length cylindrical charge, the seismic wavefield characteristics of a cylindrical charge excitation are obtained by superposing the seismic wavefield excited by a series of spherical charges. Numerical simulation results show that the calculation error of the blasting cavity characteristics of the theoretical model is within 10%. The comparison with field experimental results shows that the error of the model is within 9.4%. The velocity field of the excited seismic wave is almost the same as that of the spherical charge when the explosion distance to the cylindrical charge with finite length is 16–21 times longer than the charge length, but the frequency of the seismic wave is 30% higher than for a spherical charge. Moreover, the explosive velocity has a certain influence on the amplitude-frequency characteristic of the seismic wave excited by the cylindrical charge. The established theoretical model can accurately describe the amplitude-frequency characteristics of the seismic wavefield excited by a cylindrical charge with finite length.

Personality Traits and Escape Behavior in Traffic Accidents: Experiment and Modeling Analysis.

In this article, we tried to reveal the relationship between personality traits and escape behavior in traffic accidents. Different from common computer simulations, this study, for the first time, established a real database recording the escape behavior and personality traits of subjects when watching a first-person-view driving video with explosion. Then, we used a modeling method of general linear to establish a quantitative model of the influence of personality traits, explosion, and their interaction on escape behavior. In the model, we introduced escape response time, escape time, escape direction, escape speed, escape trajectory, and other motion characteristics to study individual escape behavior in accidents. Through the analysis, we concluded several conclusions, including that high neurotic individuals tend to escape with shorter response time and slower speed by choosing doors far from the explosion source. These conclusions may provide some references for the effective escape of the crowd and the successful escape of the individual under traffic accidents.

Influences of the burden on the fracture behaviour of rocks by using electric explosion of wires

The burden is one of the most important parameters in the blasting operation of rock engineering, so it is essential to evaluate its influences on the fracture behaviours of rocks. In this work, blasting experiments on cement mortar samples were conducted with different burdens by taking the electric explosion of wires as the explosion source. Then, the fracture process of samples was revealed based on images captured by an ultra-high-speed camera. Changes in the scope of the fractured zone with the burden were quantitatively evaluated. Experimental results indicate that fractures on the free face are composed of transverse, longitudinal, oblique, and circular cracks. As the burden increases, the initiation time of cracks on the surface delays, accompanied by a decreased degree of fracturing on the free face. Meanwhile, the explosive load causes formation of a crater-shaped fractured zone in the samples. With the increase of the burden, the short axis, perimeter, and volume of the fractured zone all tend to increase, then decrease. The finite element program ANSYS/LSDYNA was used to perform numerical simulations. The simulation results were compared with the fracture mode of the free face and the fractured zone in samples in the experiments. Besides, the damage and fracturing patterns inside the samples were further investigated based on the numerical simulation results.

Study on Dominant Frequency Attenuation of Blasting Vibration for Ultra-Small-Spacing Tunnel

The middle rock pillar in ultra-small-spacing tunnels is significantly narrow, and the stability of the primary support and lining are easily influenced by the blasting vibration wave from an adjacent tunnel. Therefore, understanding the vibration frequency characteristics is essential for the blasting vibration control. Based on the blasting works on a double-track roadway tunnel (Jiuwuji tunnel in Guizhou, China), this study investigates the dominant frequency attenuation in the preceding tunnel with the middle rock pillar spacing ranging from 4.0 m to 9.4 m. The results show that the ranges of the dominant frequency distributions on the primary support and lining are widely within 200 Hz, but there are varieties in their propagation laws. The distribution of the dominant frequencies on the primary support is broader than that on the lining; and the dominant frequencies are concentrated on a specific range when the lining is far from the blast face beside a particular value, which is not present on the primary support. As the presence of cavity and changing medium between the lining and the primary support, it made a significant contribution to the filtering the vibration waves. Furthermore, on the primary support, the high-frequency part of the vibration waves attenuates rapidly with distance, and then, the practical prediction equations describing dominant frequency attenuation were proposed. The comparison on frequency characteristics per delay for the millisecond delay blasting shows that multiple delay sequences blast contributes to a multi-structured amplitude spectrum of blast vibration waves; and the varies of the equivalent explosion sources dimensions and numbers of free surfaces in each blast delay resulting in diverse vibration waveforms. Finally, the dominant frequencies determined by different methods were compared, and the results show a nonlinear relationship between the ZCFs and DFs. The above research conclusion expands the understanding of blasting vibration in tunnel engineering, particularly in the frequency distribution.

Failure analysis for concrete gravity dam subjected to underwater explosion: A comparative study

The failure analysis of concrete gravity dams subjected to noncontact underwater explosions (UNDEXs) plays a significant role in evaluating the safety of dams. In this paper, two types of numerical models were developed to predict the failure behavior of a typical concrete gravity dam, i.e., the fully-coupled and semi-coupled model, which can provide a cross validation of the analysis results. The two models were verified by the experimental data and then adopted for the failure analysis. The results show that the shock wave can produce peak value in the blast responses and concentrated damage directly opposite to the explosive source. Even after the energy transmission at the fluid–structure interface, the UNDEX load still had influence on the failure behavior of the dam and can induce a total swelling in the velocity response.

CO2 Emission Accounting Model in Nonferrous Mining Industry

The policy of carbon peak in 2030 address the question of how to account CO2 emissions of Nonferrous Mining. The aim of this study is to establish CO2 emissions accounting model, focused on usual activities, e.g. fuel combustion emission, process emission, emission from purchased and exported electricity and heat. And also to discuss explosive and urea emission sources to identify the significant process that contribute the most to climate change. Moreover, the accounting model is chosen to evaluate emissions of one mine in china, and explosive explosion and urea use of CO2 emissions accounting for 4.61% and 3.97%, respectively.

Synthetic Evaluation of Infrasonic Multipole Waveform Inversion

AbstractAcoustic source inversions estimate the mass flow rate of volcanic explosions or yield of chemical explosions and provide insight into potential source directionality. However, the limitations of applying these methods to complex sources and their ability to resolve a stable solution have not been investigated in detail. We perform synthetic infrasound waveform inversions that use 3‐D Green’s functions for a variety of idealized and realistic deployment scenarios using both a flat plane and Yasur volcano, Vanuatu as examples. We investigate the ability of various scenarios to retrieve the input source functions and relative amplitudes for monopole and multipole (monopole and dipole) inversions. Infrasound waveform inversions appear to be a robust method to quantify mass flow rates from simple sources (monopole) using deployments of infrasound sensors placed around a source, but care should be taken when analyzing and interpreting results from more complex acoustic sources (multipole) that have significant directional components. In the examples we consider the solution is stable for monopole inversions with a signal‐to‐noise ratio greater than five and the dipole component is small. For most scenarios investigated, the vertical dipole component of the multipole explosion source is poorly constrained and can impact the ability to recover the other source term components. Because multipole inversions are ill‐posed for many deployments, a low residual does not necessarily mean the proper source vector has been recovered. Synthetic studies can help investigate the limitations and place bounds on information that may be missing using monopole and multipole inversions for potentially directional sources.

Direct Estimation of Explosion Pn Green’s Functions Applied to Teleseismic P-wave Intercorrelations for North Korean Nuclear Tests

Abstract Seismic yields and explosion source time functions for the six declared underground nuclear tests at the North Korean test site are estimated using teleseismic waveform equalization (intercorrelation) incorporating improved source structure inferred from regional distance Pn phases. Explosion source time functions estimated by previous modeling efforts are deconvolved from the broadband Pn observations to extract direct estimates of the Pn Green’s functions. Very consistent signals are found for station MDJ (to the north) for all but the 2006 event, and a 1D layered elastic model is determined that matches the corresponding pPn signals for the larger events. The much simpler Pn Green’s functions found for INCN (to the south) are well modeled using a half-space structure. The 1D structures are incorporated into intercorrelations for teleseismic P observations. Very similar results are found using the layered MDJ model for all azimuths, or when azimuthally varying the source velocity model to have a half-space structure for stations to the south, and/or using a half-space structure for the 2006 event at all azimuths. The relative yield estimates from intercorrelation are thus stable with respect to specific 1D source structures; the full effects of 3D elastic and nonelastic structures are yet to be considered.

Exploring the Effects of Emplacement Conditions on ExplosionP/SRatios across Local to Regional Distances

AbstractHigh-frequency (∼> 2 Hz) seismic P/S amplitude ratios are well-established as a discriminant to distinguish between natural earthquakes and underground explosions at regional distances (∼200–1500 km). As research shifts toward identifying lower-yield events, work has begun to investigate the potential of this discriminant for use at local distances (<200 km), in which initial results raise questions about its effectiveness. Here, we utilize data from several chemical explosion experiment series at the Nevada National Security Site in southern Nevada in the United States to study explosion Pg/Lg ratios across the range of local to regional distances. The experiments are conducted over differing emplacement conditions, with contrasting geologies and a variety of yields and depths of burial, including surface explosions. We first establish the similarities of Pg/Lg ratios from chemical explosions to those from historic nuclear tests and conclude that, as previous data have suggested, chemical explosion ratios are good proxies for nuclear tests. We then examine Pg/Lg ratios from the new experiment series as functions of distance, yield, depth of burial, and scaled depth of burial (SDOB). At far-local and regional distances, we observe consistently higher ratios from hard-rock explosions compared to ones in a weaker dry alluvium medium, consistent with prior regional distance results. No other trends with yield, depth of burial, or SDOB are strongly evident. Scatter in the observed ratios is very high, particularly at the shortest event-to-station distances, suggesting that small-scale path effects play a significant role. On average, the local distance explosion Pg/Lg ratios show remarkable consistency across all the variations in emplacement. Explosion source models will need to reproduce these results.

3D multiscale analysis method for explosion problems based on the substructure of the explosion source

When using the explicit finite element method to solve explosion problems at engineering sites, high-density meshes are usually adopted near the explosion source to calculate the high-frequency components of the explosion response. However, the critical time step in an explicit algorithm is usually controlled by the minimum mesh size. The resulting poor computational efficiency will restrain the application of the overall explosion source-engineering site model in explosion problems for large-scale numerical systems, especially in 3D conditions. In this study, a 3D multiscale analysis method based on the substructure of explosion sources is proposed. This method computationally separates the process of explosion initiation and the propagation of shock waves by dividing the model of engineering sites under explosion loads into a small-scale near-source model and a large-scale site-structure model, and the substructure of explosion source is used as an approach for explosion action transmission and mesh transition between different models, thereby progressively completing the explosion analysis of the entire explosion source-site-structure system from the near-source region to the far-field region. The proposed multiscale method adopts appropriate mesh sizes and numerical techniques in different calculation stages and avoids the use of irregularly shaped elements that are employed in traditional mesh transition methods, thereby reducing the calculation cost and modeling difficulties while ensuring accuracy. In addition, the proposed method provides a convenient approach for calculating standard explosion loads for a given explosion equivalent, which can be further applied in multiload-case explosion response analyses of large-scale complex site-structure systems.

PS interferometric imaging condition for microseismic source elastic time-reversal imaging

SUMMARYThe time-reversal imaging method utilizes the wave equation to back-propagate recorded seismic data and a proper imaging condition to locate a passive seismic source. For an explosive source, the reconstructed wavefield is focused at the seismic source location and origin time. Although the elastic time-reversal wavefield for a moment tensor source may not exhibit a maximum at the true location at the origin time, it does exhibit a quasi-symmetrical spatial distribution around the source location that represents the radiation pattern of the moment tensor source. We propose the use of an interferometric imaging condition to solve the radiation pattern problem, which is combined with elastic PS cross-correlation imaging condition (referred to as the PS interferometric cross-correlation imaging condition) to locate a moment tensor source using elastic time-reversal imaging method. 2-D and 3-D numerical tests demonstrate that our proposed method can identify the moment tensor source location in complex velocity models with a high noise level. In tests of the sensitivity of the method to the accuracy of the velocity model, we find that the method can still get focused images under about 10–25 per cent random perturbations in P- and S-wave velocities, but only under about 5 per cent correlated perturbation of global P- and S-wave velocities with a potential bias in the location.

Constructing a Gas Explosion Inversion Model in a Straight Roadway Using the GA-BP Neural Network.

When the location and intensity of the source of an explosion are determined, the severity and impact of the explosion can be analyzed and predicted, such as the overpressure, temperature, and toxic gas propagation. Determining the location and intensity of the explosion source can also provide a theory for emergency rescue work, improve rescue efficiency, and ensure the safety of rescue personnel. Therefore, the location and intensity of the source of the explosion through field data inversion are of great significance. Based on a genetic algorithm (hereinafter GA) to improve back propagation (BP) neural network theory, the location and intensity of the roadway gas explosion source were inverted through a gas explosion experiment and simulated overpressure data. When all parameters reached the optimal iteration, MATLAB was used to realize the final inversion model of the roadway gas explosion disaster. Compared with the real results, this model has high precision in determining the location of the explosion source and has a high reference value. The overall accuracy of the roadway gas explosion disaster inversion model results is high and reliable, and the inversion model of the roadway gas explosion disaster is established to provide data support for emergency rescue and accident investigation.