Full Moment Tensor Solutions of U.S. Underground Nuclear Tests for Event Screening and Yield Estimation

2021 ◽  
Author(s):  
Michael E. Pasyanos ◽  
Andrea Chiang
Keyword(s):  
Moment Tensor ◽  
Test Site ◽  
Event Identification ◽  
Nuclear Explosions ◽  
Explosion Monitoring ◽  
Yield Determination ◽  
Nuclear Tests ◽  
Chemical Explosions ◽  
Material Conditions ◽  
Full Moment Tensor

ABSTRACT Moment tensor (MT) solutions are proving increasingly valuable in explosion monitoring, especially now that they are more routinely calculated for the unconstrained, full (six component) MT. In this study, we have calculated MTs for U.S. underground nuclear tests conducted at the Nevada National Security Site using seismic recordings primarily from the Livermore Nevada Network. We are able to determine them for 130 nuclear explosions from 1970 to 1996 for a range of yields and under a variety of material conditions, which we have supplemented with 10 additional chemical explosions at the test site. The result is an extensive database of MTs that can be used to assess the performance of important monitoring tasks such as event identification and yield determination. We test the explosion event screening on the fundamental lune of the MT eigensphere and find MT screening to be a robust discriminant between earthquakes and explosions. We then explore the estimation of moment-derived yield, in which we find that material properties are the largest contributor to differences in the estimated moment-to-yield ratio. Further research conducted on this dataset can be used to develop, test, and improve various explosion monitoring methodologies.

Effects of Secondary Sources of Underground Nuclear Explosions on the mb : Ms Criterion and Implications for Discrimination of the DPRK’s Nuclear Tests

2020 ◽  
Author(s):  
Henglei Xu ◽  
Sidao Ni ◽  
Ping Jin ◽  
Shiban Ding ◽  
Hongchun Wang
Keyword(s):  
Body Wave ◽  
Test Site ◽  
Nuclear Test ◽  
Source Spectrum ◽  
Secondary Source ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Secondary Sources ◽  
Nuclear Tests ◽  
Recognition Criterion

ABSTRACT The mb :  Ms (mb vs. Ms) relationship is an important criterion for screening explosions from earthquakes and has been widely adopted in seismological monitoring by the Comprehensive Nuclear-Test-Ban Treaty Organization. In general, the earthquakes have larger Ms than the underground explosions with equivalent mb. However, it has been reported that this recognition criterion failed to identify some explosions at the North Korea nuclear test site. In this study, we investigate the potential effects of secondary source components, including the compensated linear vector dipole (CLVD) and double-couple (DC) sources, on mb and Ms magnitude measurements and the physical mechanism of the mb :  Ms recognition criterion by calculating synthetic seismograms. The results show an apparent critical body-wave magnitude of 5 when using the mb :  Ms method to discriminate North Korean underground nuclear explosions. The Ms measurements decrease as the CLVD components increase, whereas the effects from the DC source can be neglected. Small events, such as the first five North Korean nuclear tests, generate weak CLVD components, leading to the failure of mb :  Ms-based discrimination, whereas the last event, with a larger magnitude, caused extensive damage and hence can be successfully discriminated. In addition, the large difference between the source spectrum of explosions and those of earthquakes might be another important factor in the successful mb :  Ms-based discrimination of the sixth North Korean nuclear test.

scholarly journals THE FACTOR OF IONIZING RADIATION AND THYROID CANCER IN WOMEN IN THE ALTAI KRAI

2017 ◽  
Vol 22 (4) ◽  
pp. 224-228
Author(s):  
A. F Lazarev ◽  
Ya. N Shoikhet ◽  
L. F Pisareva ◽  
Valentina D. Petrova ◽  
S. A Terekhova
Keyword(s):  
Thyroid Cancer ◽  
Ionizing Radiation ◽  
Comparison Group ◽  
Test Site ◽  
Incidence Rates ◽  
Main Group ◽  
Female Population ◽  
Nuclear Explosions ◽  
Semipalatinsk Test Site ◽  
Nuclear Tests

The purpose of the study was to study the dynamics of the incidence of thyroid cancer in the female population of the Altai Territory during the period of 1992-2016. Studies were performed with the use of data of the patient register of thyroid cancer, including information on 3026 women, with the use of methods of modern medical statistics. Intensive and standardized indices were calculated for the female population, resided near to traces of nuclear explosions executed at the Semipalatinsk test site, in the zone of the most significant radiation doses (the Main group). As a comparison, incidence rates of the remaining population of the Altai Territory (the Comparison group) and average values for the region were used. The article presents results of a descriptive epidemiological study of the incidence of thyroid cancer in the Altai Territory over 25 years (1992-2016). The results of the probabilistic association of the incidence of thyroid cancer with the ionizing radiation factor due to nuclear tests at the Semipalatinsk test site were obtained. The dynamics of the incidence of thyroid cancer by the data for five-years periods (averaged data): 1992-1996; 1997-2001; 2002-2006; 2007-2011 and 2012-2016 was studied in various territories of the Altai Territory: both on the traces of nuclear explosions - the main group, and in the rest territory (the comparison group), indices of average values for the regions. There were revealed the dynamics of the incidence of thyroid cancer in tens of years after nuclear tests in the population living in the zone with the most significant doses of radiation and its gradual decrease, due to rehabilitation measures. New approaches to the formation of high cancer risk groups for thyroid cancer in the Altai Territory are substantiated.

scholarly journals Seismic moment tensor event screening

2020 ◽  
Vol 221 (1) ◽  
pp. 77-88
Author(s):  
Sean R Ford ◽  
Gordon D Kraft ◽  
Gene A Ichinose
Keyword(s):  
Seismic Moment ◽  
Moment Tensor ◽  
Test Site ◽  
Seismic Moment Tensor ◽  
Data Set ◽  
New Approach ◽  
Moment Tensors ◽  
Explosion Monitoring ◽  
Langevin Distribution ◽  
Monitoring Practice

SUMMARY Event screening is an explosion monitoring practice that aims to identify an event as an explosion (‘screened in’) or not (‘screened out’). Confidence in event screening can be increased if multiple independent approaches are used. We describe a new approach to event screening using the seismic moment tensor and its representation on the hypersphere, specifically the 5-sphere of 6-degree unit vectors representing the normalized symmetric moment tensor. The sample of moment tensors from an explosion data set is unimodal on the 5-sphere and can be parametrized by the Langevin distribution, which is sometimes referred to as the Normal distribution on the hypersphere. Screening is then accomplished by finding the angle from the explosion population mean to any newly measured moment tensor and testing if that angle is in the tail of the Langevin distribution (conservatively quantified as greater than 99.9 per cent of the cumulative density). We apply the screen to a sample of earthquakes from the Western USA and the September 2017 explosion and subsequent collapse at the Pungyye-Ri Test Site in North Korea. All the earthquakes and the collapse screen out, but the explosion does not.

Regional Seismic Characteristics of Chemical Explosions on the Eastern Margin of the Junggar Basin, Northwest China, and of Historical Semipalatinsk Nuclear Tests

2020 ◽  
Author(s):  
Xiao Ma ◽  
Lian-Feng Zhao ◽  
Xiao-Bi Xie ◽  
Xi He ◽  
Zhen-Xing Yao
Keyword(s):  
Junggar Basin ◽  
Test Site ◽  
Northwest China ◽  
Eastern Margin ◽  
The North ◽  
Semipalatinsk Test Site ◽  
Semipalatinsk Nuclear Test Site ◽  
Nuclear Tests ◽  
Chemical Explosions ◽  
Natural Earthquakes

ABSTRACT The applicability of the empirical magnitude–yield relations developed for northeast China and Korean Peninsula explosions was investigated for data from northwest China. We collected regional broadband digital seismic data from 13 chemical explosions (CEx) detonated between 6 September and 10 October 2018, on the eastern margin of the Junggar basin, northwest China, five nuclear tests at the Semipalatinsk nuclear test site, and eight natural earthquakes. Both Lg and Rayleigh-wave magnitudes (mb(Lg) and Ms, respectively) were estimated for these events. Similar to the North Korean test site, the mb(Lg)–Ms discriminant did not properly distinguish explosions from natural earthquakes at the Semipalatinsk test site. However, network-averaged P/S spectral ratios (Pg/Lg, Pn/Lg, and Pn/Sn) did successfully discriminate explosions from earthquakes at both the North Korean and the Semipalatinsk test sites at frequencies above 2.0 Hz. Based on 13 known-yield CEx, we selected an empirical magnitude–yield relation to constrain the explosive yields of five historical nuclear tests at the Semipalatinsk test site. The resulting yields are lower than those previously obtained from teleseismic observations.

scholarly journals Discrimination of Small Earthquakes and Buried Single-Fired Chemical Explosions at Local Distances (<150  km) in the Western United States from Comparison of Local Magnitude (ML) and Coda Duration Magnitude (MC)

2020 ◽  
Author(s):  
Keith D. Koper ◽  
Monique M. Holt ◽  
Jonathan R. Voyles ◽  
Relu Burlacu ◽  
Moira L. Pyle ◽  
...  
Keyword(s):  
United States ◽  
High Frequency ◽  
Characteristic Curve ◽  
Moment Tensor ◽  
Western United States ◽  
Local Magnitude ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Duration Magnitude ◽  
Chemical Explosions

ABSTRACT Seismologists distinguish underground nuclear explosions from more commonly occurring earthquakes using moment tensor inversion, high-frequency P/S amplitude ratios, mb:Ms comparisons, and P-pP differential travel times. These methods are generally successful for large seismic events (M&gt;3–4) well recorded at regional-to-teleseismic distances (&gt;150  km); however, it is unclear whether they can be modified to work for small events (M&lt;3) well recorded only at local distances (&lt;150  km). Here, we evaluate a recently proposed, local-distance seismic source discriminant—the difference between local magnitude (ML) and coda duration magnitude (MC)—using seismograms of earthquakes and buried, single-fired chemical explosions recorded in three regions of the western United States. The quantity ML–MC was previously found to be sensitive to source depth, effectively discriminating mine blasts, induced earthquakes, and very shallow tectonic earthquakes from deeper crustal earthquakes. In this study, we report the first evaluation of ML–MC as a depth discriminant using data from buried, single-fired explosions that, unlike the seismic sources studied earlier, are good analogs for underground nuclear explosions. We find that even when using generic, uncalibrated methods of assigning magnitudes, ML–MC separates single-fired explosions and earthquakes. The area under the receiver operating characteristic curve is 0.92 for 19 explosions and 14 earthquakes in Washington, 0.90 for 22 explosions and 90 earthquakes in Wyoming, and 0.99 for three explosions and 149 earthquakes in Nevada. ML:MC comparisons have the potential to enhance discrimination based on high-frequency P/S amplitudes ratios—which perform less well at local than regional distances—because the two metrics have complementary sensitivities.

scholarly journals Moment Tensor Inversion for Nuclear Explosions: What Can We Learn from the 6 January and 9 September 2016 Nuclear Tests, North Korea?

2017 ◽  
Vol 88 (2A) ◽  
pp. 300-310 ◽  
Author(s):  
Simone Cesca ◽  
Sebastian Heimann ◽  
Marius Kriegerowski ◽  
Joachim Saul ◽  
Torsten Dahm
Keyword(s):  
North Korea ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Nuclear Explosions ◽  
Nuclear Tests

scholarly journals An evaluation of generalized likelihood ratio outlier detection to identification of seismic events in western China

1997 ◽  
Vol 87 (4) ◽  
pp. 824-831
Author(s):  
Steven R. Taylor ◽  
Hans E. Hartse
Keyword(s):  
Outlier Detection ◽  
Likelihood Ratio ◽  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
Detection Technique ◽  
Western China ◽  
Generalized Likelihood Ratio ◽  
Event Identification ◽  
Nuclear Explosions

Abstract The generalized likelihood ratio outlier detection technique for seismic event identification is evaluated using synthetic test data and frequency-dependent Pg/Lg measurements from western China. For most seismic stations that are to be part of the proposed International Monitoring System (IMS) for the Comprehensive Test Ban Treaty (CTBT), there will be few or no nuclear explosions in the magnitude range of interest (e.g., mb &lt; 4) on which to base an event-identification system using traditional classification techniques. Outlier detection is a reasonable alternative approach to the seismic discrimination problem when no calibration explosions are available. Distance-corrected Pg/Lg data in seven different frequency bands ranging from 0.5 to 8 Hz from the Chinese Digital Seismic Station WMQ are used to evaluate the technique. The data are collected from 157 known earthquakes, 215 unknown events (presumed earthquakes and possibly some industrial explosions), and 18 known nuclear explosions (1 from the Chinese Lop Nor test site and 17 from the East Kazakh test site). A feature selection technique is used to find the best combination of discriminants to use for outlier detection. Good discrimination performance is found by combining a low-frequency (0.5 to 1 Hz) Pg/Lg ratio with high-frequency ratios (e.g., 2 to 4 and 4 to 8 Hz). Although the low-frequency ratio does not discriminate between earthquakes and nuclear explosions well by itself, it can be effectively combined with the high-frequency discriminants. Based on the tests with real and synthetic data, the outlier detection technique appears to be an effective approach to seismic monitoring in uncalibrated regions.

Discrimination of Seismic Events (2006–2020) in North Korea Using P/Lg Amplitude Ratios from Regional Stations and a Bivariate Discriminant Function

2021 ◽  
Author(s):  
Rigobert Tibi
Keyword(s):  
Discriminant Function ◽  
North Korea ◽  
Test Site ◽  
Seismic Events ◽  
Triggered Earthquakes ◽  
Nuclear Explosions ◽  
Cavity Collapse ◽  
Tectonic Earthquakes ◽  
Nuclear Tests ◽  
Discriminant Power

Abstract Two events of magnitude (mb) 3.6–3.8 occurred in southern North Korea (NK) on 27 June 2019 and 11 May 2020. Although these events were located ∼330–400  km from the known nuclear test site, the fact that they occurred within the territory of NK, a country with a recent history of underground nuclear tests, made them events of interest for the monitoring community. We used P/Lg ratios from regional stations to categorize seismic events that occurred in NK from 2006 to May 2020, including these two recent events, the six declared NK nuclear tests, and the cavity collapse and triggered earthquakes that followed the 3 September 2017 nuclear explosion. We were able to separate the cavity collapse from the population of nuclear explosions. However, based on P/Lg ratios, the distinction between the earthquakes and the cavity collapse is ambiguous. The performed discriminant analyses suggest that combining Pg/Lg and Pn/Lg ratios results in improved discriminant power compared with any of the ratio types alone. We used the two ratio types jointly in a quadratic discriminant function and successfully classified the six declared nuclear tests and the triggered earthquakes that followed the September 2017 explosion. Our analyses also confirm that the recent southern events of June 2019 and May 2020 are both tectonic earthquakes that occurred naturally.

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