Comprehensive Nuclear Test Ban Research Articles

Seismic Discrimination Between Nuclear Explosions and Natural Earthquakes using Multi-Machine Learning Techniques

AbstractIn the field of seismic signal analysis, it is of utmost importance to accurately differentiate between earthquakes and underground nuclear explosions. As a contribution for the verification regime of the Comprehensive Nuclear Test Ban Treaty (CTBT), Various methods have been employed for this purpose, including Complexity, Spectral ratio, mb—Ms (body wave and surface wave magnitudes), and corner frequency of P and S waves. These discrimination techniques have been examined to manually identify natural seismic events from nuclear explosions across different regions worldwide, such as China, India, Pakistan, North Korea, and the United States. To gather the necessary data, a comprehensive dataset comprising nuclear explosions and earthquakes of the same magnitude range (4 ≤ mb ≤ 6.5) of 35 seismic events from 1945 to 2017 has been compiled from the International Research Institute for Seismology (IRIS) using broadband and long period seismic stations. The objective of this study is to employ a range of linear and nonlinear Machine Learning (ML) models with the aim of automatically distinguishing between underground nuclear explosions and large earthquakes to enhance the accuracy of manual feature extraction. For this purpose, time domain waveforms and different classifier techniques focused on feature extraction have been used. The ML models employed include logistic regression, K-nearest neighbours classifier, decision tree classifier, random forest classifier, voting classifier, and Naive Bayes. The outcomes of the ROC and AUC analyses were employed to validate the validity of our proposed discrimination algorithm. The results show that the Random Forest Classifier is the most effective model, obtaining 100% accuracy in the case of feature extraction, while the best model for the time domain waveform classifier that achieved 75.5% accuracy is the voting classifier.

Relocation of 3 April 2017 Moiyabana Earthquake in Botswana Using Seismological Data from Local Network of Autonomously Recording Seismographs and International Monitoring System Stations

AbstractOn the 3rd April 2017 a widely felt Moiyabana earthquake shook Botswana and the rest of southern Africa. Previous Moiyabana earthquake locations used mainly teleseismic or regional seismograms; and/or non-seismic methods which include Synthetic Aperture Radar (InSAR), and magnetotelluric (MT). These results did not agree, as evidenced by the depth of the earthquake that ranged from zero to 30 km (i.e. indicating either a man-made event or a natural event); thus motivating us to re-assess the location parameters. Unfiltered seismic waveform data from the recent project of the Network of Autonomously Recording Seismographs (NARS) in Botswana was complimented with stations from the International Monitoring System (IMS) to relocate the event. Relocated parameters are origin time, epicentre, focal depth, and magnitude. Geotool software from the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), and the Regional Seismic Travel Time model (RSTT) were used to process vertical components waveforms from 9 NARS and 32 IMS stations. Geotool results are: earthquake epicentre (22.645 °S: 25.220 °E); origin time of 17:40:16.9 (UTC); hypocentral depth range of 22 to 24 km; body magnitude (mb) and local magnitude (ml) of 6.3 ± 0.6 and 6.0 ± 0.8, respectively. RSTT results are: earthquake epicentre (22.667 °S: 25.257 °E); origin time of 17:40:16.95 (UTC); hypocentral depth of 25 km; and mb of 6.65 ± 0.03. The seismological location parameters from Geotool and RSTT, agree very well within experimental uncertainties with the non-seismic geophysical methods.

New confidence-building measures can reduce tensions around subcritical tests

ABSTRACT With rising tensions between the United States on one side, and China and Russia on the other, the three countries have grown mutually accusatory about some testing activities they conduct to maintain and modernize their nuclear arsenals, with allegations made by the United States focusing on very low-yield fission experiments. In a world where trust in the nonproliferation regime is weakening and most bilateral arms control measures have been suspended, many experts fear that recriminations over very low-yield tests could spark a new escalation spiral to full-scale nuclear tests. Transparency measures could diffuse the suspicions around these tests and strengthen the Comprehensive Nuclear Test Ban Treaty, which is largely being complied with but still not legally in force.

The logic for US ratification of the Comprehensive Nuclear Test Ban Treaty

ABSTRACT The United States has accepted increasingly stringent limits on nuclear testing, culminating in the 1996 Comprehensive Nuclear Test Ban Treaty. However, the US Senate in 1999 failed to consent to ratification, given concerns about verifying the treaty and maintaining safe and reliable US nuclear weapons without testing. Since then, the US Stockpile Stewardship Program has matured and allowed certification that US nuclear weapons remain safe and reliable without nuclear explosive testing. Likewise, advances in the US Nuclear Detonation Detection System and the International Monitoring System make virtually all tests detectable. Bringing the Comprehensive Nuclear Test Ban Treaty into force is in the US interest, as it would lock in an American advantage in nuclear knowledge and expertise and hinder other states from developing more sophisticated nuclear arms. Unfortunately, however, American domestic politics and the difficult international environment make it unlikely that the treaty will enter into force in the near term.

Preserving the nuclear test ban after Russia revoked its CTBT ratification

ABSTRACT Russia’s withdrawal of its ratification of the Comprehensive Nuclear Test Ban Treaty in 2023 raised concerns about the possible end of the existing moratorium on nuclear explosions. But the moratorium continues to hold, largely thanks to the de facto norm against full-scale nuclear tests and the strength of institutional structures created by the treaty. Transparency of nuclear experiments demonstrated by the United States will be an important factor in upholding the moratorium, and Russia and China should be encouraged to be more transparent about their activities as well. Any disputes about the exact nature of their experiments and their adherence to the strict definition of a zero-yield nuclear explosion should not become reasons to question the value of the moratorium—or the ability of parties to verify and enforce the test ban once the treaty comes into force.

Tidal modulation of very-low-frequency and ultra-low-frequency ambient noise levels.

Several years of continuous low-frequency underwater ambient noise data from 0.1 to 125 Hz have been made available for examination by the United Nations Comprehensive Nuclear Test Ban Treaty Organization. Narrow-band noise time records between 0.5 and 10 Hz were selected for study, chosen deliberately to address noise sources tied primarily to the environment. Power spectra of the variable narrow-band time records were found to display sharp spectral lines at fluctuation frequencies that match lunar and solar diurnal and semidiurnal ocean tides.

Algorithm development for low level radioxenon 2D spectra analysis: A first case of study using spectral unmixing for a β-γ detector

In the scope of the verification regime of the Comprehensive nuclear Test Ban Treaty, the CEA/DAM is developing new β-γ measurement systems. In order to improve the analysis methods at low statistics, a new multiplicative spectral unmixing algorithm for full-spectrum analysis was tested on a particular setup for different types of mixtures. The reconstructed activities for simulated spectra and the characteristic limits found with this algorithm are compared to the classic ROI analysis method.

Long-range underwater acoustic detection of aircraft surface impacts—The influence of acoustic propagation conditions and impact parameters

The 2019 crash of an F35 fighter aircraft off the east coast of Japan was detected at a range of approximately 3000 km by a hydroacoustic station of the Comprehensive Nuclear Test Ban Treaty Organisation’s International Monitoring System. In this paper we compare the acoustic propagation conditions relating to that detection to those relating to the crash of Malaysian Airlines flight MH370 in the Indian Ocean in 2014 with a view to reassessing the likelihood that acoustic signals detected on a similar hydroacoustic station could have been related to the loss of MH370. Possible differences in source levels due to different assumptions about impact parameters are also considered. Despite several extensive searches, the location of the wreckage of MH370 remains unknown.

Evidence of oceanic and atmospheric tides in underwater ambient noise time records

Multiyear time records of low-frequency ocean ambient noise show clear evidence of a modulating influence by major semi-diurnal and diurnal gravitational tides. These are displayed by means of a variance spectral analysis of noise time records obtained from the United Nations Comprehensive Nuclear Test Ban Treaty Organization for hydrophone stations at Wake Island, Ascension Island and Diego Garcia. Narrow-band noise frequencies ranged from ½ to 10 Hz. There is also evidence in the noise records of a diurnal atmospheric tide related to solar radiation and atmospheric loading. This same tidal presence is seen in wind speed records as well. Part of the challenge in the analysis is to distinguish between expected diurnal behavior in wind speed, with its accompanying effect on ambient noise, and the presence of actual tidal lines. A brief history of earlier observations of diurnal variation in underwater acoustics is presented, along with some suggestions of causal mechanisms.

Basin scale propagation modeling of MLS signals from the Kauai Beacon source

Long distance underwater acoustic propagation is of interest for a variety of applications including underwater navigation, yet modeling such propagation is challenging due to the large degree of environmental uncertainty. In this presentation, the propagation of 75Hz center frequency maximum length sequence (MLS) signals emitted from a submerged source near Kauai and received at various sites throughout the Pacific Ocean Basin is modeled with the Bellhop ray tracing [1] and Monterey-Newport Parabolic Equation [2] models. Sites such as the Monterey Accelerated Research System (MARS) observatory and the Comprehensive Nuclear Test Ban Organization (CTBTO) hydroacoustic monitoring station near Wake Island are included in the discussion. The range-dependent environment is based on historical profiles from the World Ocean Atlas database and reanalysis data from the hybrid coordinate ocean model (HYCOM) [3]. Bathymetry profiles along the axis of propagation are interpolated from the General Bathymetric Chart of the Oceans (GEBCO) 2021 database [4]. Simulated broadband channel impulse responses transmission loss levels in the modeled environment are compared to selected receptions of the signal at the hydrophone sites. Additionally, fluctuations of the modeled transmission loss in the presence of an internal wave model [5] are discussed.

A Statistical Approach to Estimate Seismic Monitoring Stations’ Biases and Error Levels

ABSTRACT Magnitudes are common and important measures for the size of seismic events. The International Data Centre (IDC) of the Comprehensive Nuclear-Test Ban Treaty Organization estimates an event magnitude by averaging the magnitudes calculated by individual stations that detected the event, excluding outliers. This approach assumes that all station magnitudes have the same error level and are unbiased, namely, they have no systematic errors. We show that the body-wave and surface-wave magnitudes published in the Reviewed Event Bulletin (REB) of the IDC are inconsistent with these assumptions. We thus consider a model where each station has an unknown bias and error level. Given a large collection of reported event magnitudes by a network of monitoring stations, we propose a novel approach to estimate each individual station’s bias and error level. From a statistical perspective, this is a challenging problem involving a huge number of variables, because in addition to the stations’ biases and error levels, the event magnitudes are also unknown. Our approach is based on analyzing differences between reported magnitude values at pairs of stations, which cancels out the unknown event magnitudes and allows us to derive a simple and computationally efficient algorithm. We use the estimated station biases as station correction terms and the estimated error levels to compute weights for event magnitude estimation. Using a large data set from the REB with millions of reported station magnitudes, we show that our approach yields more consistent station and event magnitudes.

Variability analysis of low-frequency and very low-frequency ambient ocean noise

Much of the information presented was made possible by the presence over the past several years of a collection of deep water hydroacoustic arrays with long-term, high data rate recorders of ocean ambient noise, deployed and maintained under the auspices of the United Nations Comprehensive Nuclear Test Ban Treaty Office (CTBTO). Not only does the long time span of the noise record allow high frequency resolution of annual and multi-year variability, but the high data rate supports as well the analysis of high temporal resolution minute-by-minute variability. The present analysis is directed at acoustic frequencies where the noise level and its variability are governed primarily by natural events : planetary—such as the influence of tides, oceanographic—such as the influence of El Nino, and meteorological—such as the influence of storms and routine weather. The analysis is focused on the fluctuations of a series of narrow band tonals at acoustic frequencies between 0.1 and 10 Hz. Results of the analysis display the time scales of the various processes that drive the fluctuations.

Nuclear Disarmament: Some Aspects of International Legal Regulation

The subject of the study of this article is some aspects of the problem of nuclear disarmament, which are highlighted, among other things, from the perspective of the ongoing military special operation in Ukraine. The history of the creation of the nuclear disarmament regime is traced. The main documents regulating the procedure of nuclear disarmament are characterized. The ways of strengthening and finding a compromise in the issues of nuclear disarmament in the world have been identified. The analysis of the problem of nuclear disarmament, which is at the center of international relations and is relevant in the theory of international law, is given. The author has studied the international legal regulation of nuclear disarmament, identified its problematic aspects. The main documents in the field of legal regulation of nuclear disarmament are the Treaties on the Non-Proliferation of Nuclear Weapons, the Comprehensive Nuclear Test Ban Treaty, as well as the International Monitoring System created for its implementation. The existing international legal system of control over nuclear disarmament, non-nuclear testing, and the use of atomic energy exclusively for peaceful purposes does not always prove its effectiveness, as a result of which countries with unstable political situation possess nuclear weapons, which entails an additional threat to the world community. As a result of the analysis, it was concluded that the current system of international monitoring of nuclear tests and the system of international regulation of nuclear disarmament need to be modernized in order to eliminate the threat of proliferation and use of nuclear weapons. Currently, the development of technologies for the enrichment of radioactive substances, the emergence of new threats and other factors create significant obstacles to the preservation of the nuclear disarmament regime.

Application Prospects of Distributed Optical Fiber Sensing Technique in Comprehensive Nuclear Test Ban Treaty

Application Prospects of Distributed Optical Fiber Sensing Technique in Comprehensive Nuclear Test Ban Treaty

Impact of industrial nuclear emissions on nuclear explosion monitoring

In 1995, the development of a global radioactive xenon monitoring network was discussed in the Conference on Disarmament as part of a nuclear explosion verification regime. Discussions considered different network densities and different possible source magnitudes. The Comprehensive Nuclear Test Ban Treaty was subsequently written to initially include 40 locations for noble gas (radioxenon) samplers, and to consider using a total of 80 locations for noble gas samplers in its International Monitoring System (IMS) after the treaty enters into force. Since 2000, a global network of noble gas monitoring locations has been built as part of the IMS. This network, currently with 31 locations, is of sufficient sensitivity to discover that the Earth's atmosphere contains a complex anthropogenic radioactive xenon background. In this work, the impact of calculated xenon backgrounds on IMS radionuclide stations is determined by atmospheric transport modeling over a period of two years using global average values. The network coverage for potential nuclear explosions is based on a proposed method for finding anomalies among frequent background signals. Even with the addition of background radioxenon sources and using a conservative anomaly-based approach, this work shows that various network configurations have higher xenon coverage than the estimates developed when the IMS network was designed in 1995. While these global xenon coverage figures are better than expected when the network was designed in 1995, the regional impact of background radioxenon sources is large, especially for smaller source magnitudes from potential nuclear explosions, and in some cases the xenon background vastly reduces the coverage value of individual sampling locations. The results show the detection capability and presents an optimal installation order of noble gas sampling locations, e.g. from 40 to 80, after the treaty enters into force.

Phase II testing of Xenon International on Mount Schauinsland, Germany

Station RN33 on Mount Schauinsland near Freiburg, Germany, is part of the International Monitoring System monitoring radioxenon in air (131mXe, 133Xe, 133mXe, and 135Xe) for verification of the Comprehensive Nuclear Test Ban Treaty. Here, we present data from phase II testing of a new system, Xenon International at RN33, July 14th, 2021 to Jan 22nd, 2022, together with SPALAX data from the same time period. Radioxenon could be detected in 473 of 719 samples, among them many multiple isotope detections. Activity concentrations of spiked and selected environmental samples were verified by laboratory reanalysis. The sensitivity of Xenon International for radioxenons is up to one order of magnitude better for the metastable isotopes than that of the SPALAX, with a shorter sampling duration of 6 h.

Influence of CO2 as quench gas on the characteristics of the proportional counter in MARDS

The Movable 37Ar Rapid Detection System (MARDS) was first developed by the Institute of Nuclear Physics and Chemistry (INPC) of the China Academy of Engineering Physics (CAEP) in 2006, and it has been continually upgrading and serving for On-site Inspections (OSI) under the Comprehensive Nuclear Test Ban Treaty (CTBT) to this day. To make MARDS more suitable for OSI, we have tried to use CO2 as the quench gas of the proportional counter. The feasibility was confirmed by using a 1 L proportional counter and energy spectrum analysis method. The characteristics influence of the proportional counter in MARDS has been studied with different CO2 concentration and different operating voltage. The results show that the 37Ar peak shape can be improved when the CO2 concentration is about 2% to 6%, and the resolution of 37Ar energy peak becomes worse when the CO2 concentration is above 6%. Meanwhile, the operating voltage almost linearly increases with the CO2 concentration, and it is proportional to the gas pressure when the CO2 concentration is constant.

Evaluating the Intersection of Technology and Nuclear Escalation in South Asia

There are range of factors that are shaping nuclear issues in South Asia. Among these, India and Pakistan remain outside the Treaty on the Non-proliferation of Nuclear Weapons and the Comprehensive Nuclear-Test-Ban Treaty. Further, their religious conflicts, ethnic disputes, military confrontations and territorial disputes remain fierce and acute. The confluence of these factors means that when a crisis occurs, India and Pakistan are more likely to misjudge the situation due to poor communication, or to even face the use of tactical nuclear weapons. This essay examines the convergence of technology and nuclear escalation. It concludes by offering some conclusions about external powers that are often involved in the technological procurement and their both stabilising and destabilising impacts on South Asia. Keywords: Nuclear Escalation, Treaty on the Non-proliferation of Nuclear Weapons, Comprehensive Nuclear Test Ban Treaty, South Asia

Evaluation and Uncertainty of Radioxenon Transport with a Mesoscale Model after the February 2013 Underground Test in North Korea

Abstract The transport of radioxenon released from the February 2013 underground nuclear weapons test in North Korea was analyzed at two receptors—one at the Comprehensive Nuclear Test Ban Treaty site Rn58 in Russia (400 km downwind) and a second at Rn38 in Japan (1000 km downwind). Transport was modeled with two ensembles of mesoscale simulations, one generated with varying initial and lateral boundary conditions taken from the Global Forecasting System uncertainty ensemble, and a second created from different parameterizations and surface conditions. The wind variability was similar for the two ensembles and consistent with observations at 925 mb (1 mb = 1 hPa) but not at the surface. Biases in calculated surface winds and the radioxenon concentration in the ensembles were attributed mainly to poor simulation of the sea breeze at both locations and mountain lee affects at Rn38 in Japan. These wind regimes affected the timing of the surface radioxenon plume at Rn58 and its duration at Rn38. Surface wind variability induced by terrain and land–sea contrast (the sea breeze) also had a significant effect on the surface winds and plume dynamics, including blocking of flow approaching elevated terrain near Vladivostok and the west side of Japan. Increased plume uncertainty was seen at night because of surface wind variability. Measured surface chemical variability was larger than found in the first European Tracer Experiment in central Europe. The study found that horizontal model resolution contributes to uncertainty but not as much as vertical resolution, boundary layer parameterizations, and assimilation of surface meteorological data near the receptor.

SAUNA field - A sensitive system for analysis of radioxenon in soil gas samples

A high throughput system for processing and detection of low levels of radioxenon in soil gas samples has been developed. Processing and analysis of sub-soil noble gas samples puts high demands on the gas separation part of the system since the samples might contain high levels of Rn, CO2 as well as other gases. The gas process is optimized to remove all CO2, H2O and Rn with a high recovery yield of the xenon in the sample to ensure a high sensitivity even for small samples. The system is designed to handle multiple samples per day with a high level of automation and sample traceability to be suitable for use in an on-site inspection (OSI) an important component in the verification of the Comprehensive Nuclear Test Ban Treaty. To ensure a rapid deployment the system could be pre-installed in a flight container.