International Data Centre Research Articles

Interactive analysis of the results of NET-VISA, a Bayesian inference system, in CTBTO’s International Data Centre bulletin production

Interactive analysis of the results of NET-VISA, a Bayesian inference system, in CTBTO’s International Data Centre bulletin production

Infrasound analysis of the 2018-Dec-18 49 kiloton Bering Sea bolide: Misassociations and celerity-range models

Automatic detections at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) are often misassociated. This occasionally leads to single events being split into multiple events. Infrasound signals generated from a large bolide over the Bering Sea on 2018-Dec-18 were recorded on more than 15 of the CTBTO International Monitoring System (IMS) stations. The bolide was also reported by the Center for Near Earth Object Studies (http://cneos.jpl.nasa.gov/fireballs) with a calculated total impact energy value of 49 kt. Signals from this bolide were automatically detected and associated at the IDC, into two different events, with the origin time differing by approximately 7.5 minutes and location by ∼125 km. To investigate why detections from this bolide event were misassociated in the automatic bulletins, we analyze infrasound observations from the IMS infrasound arrays and compare our arrival time observations to the automatic detections from the IDC. We use the Bayesian Infrasonic Source Localisation method and employ different celerity-range models, to investigate signal association for this event. Through comparison with the associations based on IDC detections, we aim to improve our understanding of the causes of misassociations and identify potential improvements to future event association algorithms.

Beyond The Nuclear Explosion Verification Monitoring, the Comprehensive Nuclear-Test-Ban Treaty Offers A Strong Capacity Building System Support

Purpose: The United Nations (UN) General Assembly, as part of nuclear non-proliferation and disarmament measures to prohibit nuclear test explosions and any other nuclear explosions in all environments (in the atmosphere, oceans, and underground) adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Thus, it ultimately enhances international peace and security. It is an essential step aimed at making the world a safer place. States that agree to sign on to this Treaty will be contributing to the protection of human health and the environment against nuclear test explosions and their severe impacts. This paper seeks to demonstrate that the CTBT beyond its global prohibition measure against all nuclear explosions, is offering a strong Capacity Building System support to State Signatories such as the Republic of Ghana. The CTBT global verification regime is built to monitor States Signatories compliance with the Treaty. CTBT Organization (O) through the International Data Centre (IDC) provides States Signatories with technical assistance to support their verification responsibilities to ensure effective global monitoring.
 Methodology: The Republic of Ghana through the Capacity Building project under the IDC technical assistance to States Signatories is a beneficiary of equipment support commissioned in July 2021. Under this project the GCI-III/VSAT equipment set was received from the IDC, establishing a new communication link for forwarding IMS waveform data from some selected stations in Africa in near-real-time to the National Data Centre – Ghana (NDC – GH). The IMS seismic data also contributes to prompt access to information on seismic events within our respective geographic territories globally, thus playing a complementary role.
 Findings: The monitoring data generated provides essential civil and scientific applications to greatly support to mitigate the effects of natural or man-made disasters. This is an example of what the CTBT is providing to Member States beyond the Treaty’s main purpose.
 Unique contributor to theory, policy and practice: It is therefore important for the international community to fashion out other multilateral agreements considering the possibility of incorporating the potential additional benefits States can derived from such agreements.

Investigation on atmospheric radioactivity sample association using consistency with isotopic ratio decay over time at IMS radionuclide stations

For the enhancement of the International Data Centre's products, specifically the Standard Screened Radionuclide Event Bulletin, an important step is to establish methods to associate the detections of the Comprehensive Nuclear-Test-Ban Treaty-relevant nuclides in different atmospheric radioactivity samples with the same radionuclide release to characterize its source for the purpose of nuclear explosion monitoring. Episodes of anomalously high activity concentrations in samples at the International Monitoring System radionuclide stations are used as the primary assumption for being related to the same release. For multiple isotope observations, the consistency of their isotopic ratios in subsequent samples with radioactive decay is another plausible hint for one unique release. The radioxenon observations that are associated with the nuclear test announced by the Democratic People's Republic of Korea in 2013 serve as case study to demonstrate the effectiveness of this basic approach and how the additionally associated samples improve the source location. We use two distinct puff releases, both of short duration, for the atmospheric transport modelling simulations to gain further evidence and confidence in our sample association study by identifying the air masses that link the releases to multiple samples. This basic approach will support the definition of analysis procedures and criteria for automatic sample association to be implemented in the Standard Screened Radionuclide Event Bulletin, which is of relevance for an expert technical analysis.

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.

Detection of anomalous radioxenon concentrations: A distribution‐free approach

AbstractThe detection of anomalous atmospheric radioxenon concentrations plays a key role in detecting both underground nuclear explosions and radioactive emissions from nuclear power plants and medical isotope production facilities. For this purpose, the CTBTO's International Data Centre uses a procedure based on descriptive thresholds. In order to supplement this procedure with a statistical inference‐based method, we compared several non‐parametric change‐point control charts for detecting shifts above the natural radioxenon background. The results indicate that the proposed methods can provide valuable tools for the institutions responsible for the verification and classification of anomalous radioxenon concentrations.

International Data Centre Bulletin Events Triggered by Controlled Underwater Explosions of World War 2 Ordnances

This paper focuses on events linked to controlled underwater explosions of World War 2 (WW2) ordnances which were included in the Reviewed Event Bulletin (REB). Data used for the study were provided by seismic stations of the International Monitoring System (IMS) in 2020. Examined events were triggered by devices of different charge size and took place in several locations in Europe. There were also other, previously detected WW2 ordnance underwater explosions which could be compared to events in 2020. It is shown that these relatively small underwater explosions listed in the REB, with good coupling to the ground, are located by the IMS network within 20 km from the ground truth. Charge size of explosive material was related to event magnitude. Results were compared to magnitudes published for underwater explosions of larger sizes. The conclusion is that an in-water explosion will result in seismic waves with amplitudes equivalent to the amplitudes of seismic waves from an in-ground explosion with 17.2 times the yield in kT.

Overview of temporary radioxenon background measurement campaigns conducted for the CTBTO between 2008 and 2018

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) specifies that an overall network of at least 40 International Monitoring System (IMS) stations should monitor the presence of radioxenon in the atmosphere upon its entry into force. The measurement of radioxenon concentrations in the air is one of the major techniques to detect underground nuclear explosions. It is, together with radionuclide particulate monitoring, the only component of the network able to confirm whether an event originates from a nuclear test, leaving the final proof to on-site inspection.Correct and accurate interpretation of radioxenon detections by State Signatories is a key parameter of the verification regime of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). In this context, the discrimination between the highly variable radioxenon background generated by normal operations of nuclear facilities and CTBT-relevant events is a challenging, but critical, task. To this end, the radioxenon background that can be expected at IMS noble gas systems must be sufficiently characterized and understood. All activities conducted to study the global radioxenon background are focused on the calibration and performance of the verification system as described in the Treaty.The unique CTBTO noble gas system network is designed to optimally covering the globe. By the end of 2019, 31 systems were put in operation, 25 of which being already certified. It took two decades from the first experimental setup of noble gas system in the field to reach this stage of maturity. In the meantime, it was an urgent need to gain empirical evidence of atmospheric radioxenon concentrations with the full spectrum of characteristics that IMS noble gas systems may be observing. This experience was significantly advanced through temporary measurement campaigns. Their objective was to gain the additional necessary knowledge for a correct understanding and categorization of radioxenon detections. The site selection for these campaigns put emphasis on regions with low coverage by the initially few experimental noble gas systems at IMS locations or where potential interferences with normal background might be observed.Short-term measurements were first initiated in 2008. Sites of potential interest were identified, and campaigns up to few weeks were performed. Based on the findings of these short campaigns, transportable systems were procured by the CTBTO. Longer temporary measurement campaigns were started afterwards and operated by local hosts in different regions of the globe. Site selections were based on purely scientific criteria. Objectives of the measurement campaigns were continually reassessed, and projects were designed to meet the scientific needs for radioxenon background understanding as required for nuclear explosion monitoring.As of today, several thousands of samples have been collected and measured. Spectra of temporary measurement campaigns were (and are still) analysed in the International Data Centre (IDC). As they are not part of the CTBT monitoring system, no IDC product is generated. Analysis results are stored in a non-operational database of the CTBTO and made available, together with raw data, to authorized users of States Signatories through a Secure Web Portal (SWP) and to scientific institutions for approved research projects through a virtual Data Exploitation Centre (vDEC) after signing a cost-free confidentiality agreement (https://www.ctbto.org/specials/vdec).This paper aims at providing an overview of the temporary measurement campaigns conducted by the CTBTO since the very first field measurements. It lays out scientific results in a systematic approach. This overview demonstrates the asset of radioxenon background measurement data that have been collected with a wide variety of characteristics that may be observed at IMS stations. It bears a tremendous opportunity for development, enhancement and validation of methodologies for CTBT monitoring.In 2018, a campaign started in Japan with transportable noble gas systems in the vicinity of the IMS station RN38 in Takasaki. It will be described separately once the measurements are completed.

Aplikasi Standar TIA-942 pada Data Center Disinfolahtaau dalam Meningkatkan Layanan Sistem Informasi TNI AU

This study analyzes the condition of the Disinfolahtaau data center whose construction was carried out in 2013 as a service for the Indonesian Air Force system. To maintain data security in the Management Information System (MIS) in the fields of operations, logistics, personnel, and management, currently there are still problems with data center operations that run 1 x 24 hours. For this reason, it is necessary to compare the condition of the data center with the data center standards that have been made with reference to the TIA-942 International data center standard. The purpose of this study is to analyze the condition of the Disinfolahta or data center in several aspects, namely the architectural aspect of the building, the electrical aspect, the telecommunication aspect and the mechanical aspect that implements it by applying the TIA-942 standard. The data of this research were collected through informants based on the methods of interview, observation and documentation study. Then the data was analyzed using the Countance Stake's Model analysis. Each aspect in the Countance Stake's Model is then analyzed the actual conditions of each aspect which are combined to produce conclusions about future policies in the Disinfolahtaau data center condition. The results showed that the results of the analysis of the Disinfolahtau data center from the architectural aspect of the building, the electrical aspect, the telecommunication aspect and the mechanical aspect of the data center construction in 2013. With some aspect analysis on the Disinfolahtaau data center will provide the real condition of the capabilities and capacity of the data center so as to know the current conditions. This is so that we can find out problems in the condition of the data center, this has an impact after if some deficiencies are corrected in the Disinfolahtaau data center. However, it can have a negative impact if the current condition of the data center is not immediately repaired, it will interfere with the non-operation of the data center so that information system services will be disrupted in providing information system services within 1 x 24 hours in operation. Looking at the current situation and conditions compared to the initial development in 2013, it is necessary to develop the Disinfolahtaau data center for evaluation and revitalization in improving the optimal Indonesian Air Force information system services.

Source Term Analysis of Xenon (STAX): An effort focused on differentiating man-made isotope production from nuclear explosions via stack monitoring

An overview of the hardware and software developed for the Source Term Analysis of Xenon (STAX) project is presented which includes the data collection from two stack monitoring systems installed at medical isotope production facilities, infrastructure to transfer data to a central repository, and methods for sharing data from the repository with users. STAX is an experiment to collect radioxenon emission data from industrial nuclear facilities with the goal of developing a better understanding of the global radioxenon background and the effect industrial radioxenon releases have on nuclear explosion monitoring. A final goal of this work is to utilize collected data along with atmospheric transport modeling to calculate the contribution of a peak or set of peaks detected by the International Monitoring System (IMS) to provide desired discriminating information to the International Data Centre (IDC) and National Data Centers (NDCs). Types of data received from the STAX equipment are shown and collected data was used for a case study to predict radioxenon concentrations at two IMS stations closest to the Institute for RadioElements (IRE) in Belgium. The initial evaluation of results indicate that the data is very valuable to the nuclear explosion monitoring community.

Democratizing Glacier Data – Maturity of Worldwide Datasets and Future Ambitions

The creation and curation of environmental data present numerous challenges and rewards. In this study, we reflect on the increasing amount of freely available glacier data (inventories and changes), as well as on related demands by data providers, data users, and data repositories in-between. The amount of glacier data has increased significantly over the last two decades as remote sensing techniques have improved and free data access is much more common. The portfolio of observed parameters has increased as well, which presents new challenges for international data centers, and fosters new expectations from users. We focus here on the service of the Global Terrestrial Network for Glaciers (GTN-G) as the central organization for standardized data on glacier distribution and change. Within GTN-G, different glacier datasets are consolidated under one umbrella, and the glaciological community supports this service by actively contributing their datasets and by providing strategic guidance via an Advisory Board. To assess each GTN-G dataset, we present a maturity matrix and summarize achievements, challenges, and ambitions. The challenges and ambitions in the democratization of glacier data are discussed in more detail, as they are key to providing an even better service for glacier data in the future. Most challenges can only be overcome in a financially secure setting for data services and with the help of international standardization as, for example, provided by the CoreTrustSeal. Therefore, dedicated financial support for and organizational long-term commitment to certified data repositories build the basis for the successful democratization of data. In the field of glacier data, this balancing act has so far been successfully achieved through joint collaboration between data repository institutions, data providers, and data users. However, we also note an unequal allotment of funds for data creation and projects using the data, and data curation. Considering the importance of glacier data to answering numerous key societal questions (from local and regional water availability to global sea-level rise), this imbalance needs to be adjusted. In order to guarantee the continuation and success of GTN-G in the future, regular evaluations are required and adaptation measures have to be implemented.

The International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty: vision and progress

Abstract The mission of the Comprehensive Nuclear-Test-Ban Treaty International Data Centre (IDC) is to: (a) acquire data over a Global Communications Infrastructure from a global network of 337 facilities of the International Monitoring Systems (IMS), (b) to process and analyze these data, and (c) to provide the IMS data, IDC products and services to Member States. In effect, the IDC symbolizes a new brand of arms control for the information age, leveraging Internet communications, knowledge-based data fusion, graphical decision support systems and Web-based user interfaces to achieve its mission. During 2000, the IDC was disseminating products based on data from about 90 seismic, hydroacoustic, infrasound and radionuclide stations of the future network. The number of events in the reviewed seismo-acoustic bulletins ranged from 40 to 360 each day. On average, some 200 radionuclide spectra were processed and analysed each month. Users from 45 Member States received an average of close to 18,000 data and product deliveries per month from the IDC. As the IDC continues to prepare for entry-into-force of the CTBT, it will continue to integrate the state-of-the-art in science and technology in order to meet the demands of the increasing volume of new types of IMS data, expanded IDC services, and a growing base of users.

Atmospheric transport modelling related to radionuclide monitoring in support of the Comprehensive Nuclear-Test-Ban Treaty verification

Abstract Global monitoring for relevant radionuclides in the atmosphere serves as part of the International Monitoring System to verify compliance with the Comprehensive Nuclear-Test-Ban-Treaty (CTBT). Atmospheric transport modelling can be applied to support these measurements and to get indications for possible source locations of detected relevant anthropogenic nuclides. This paper puts a focus on those issues that are of relevance to the International Data Centre (IDC). Possible methods of atmospheric transport modelling are outlined. The current tentative implementation at the IDC is described here.

Evaluation of the International Monitoring System and International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty Organization

Abstract Evaluation and quality assurance activities of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) are reviewed with special emphasis on radionuclide technologies. The CTBTO carries out detailed evaluation in all fields of technical verification of the Treaty. The goal is to provide States Signatories with confidence in the quality of data from the International Monitoring System and data products of the International Data Centre. The largest technical evaluation effort has been the quality assessment of the operational software. About 1.3 million lines of source code and scripts were checked. Software characteristics, such as maintainability, were assessed using automated tool-based techniques and improvements were suggested. Specific to radionuclide technologies, several methods have been developed to cope with the large amounts of spectra produced each day by 80 radionuclide monitoring stations around the world. Some of the key evaluation results, such as the peak detection capability of the operational software are presented in detail.

Hydroacoustic monitoring system for the Comprehensive Nuclear-Test-Ban Treaty

Abstract Hydroacoustics is one of the four monitoring technologies of the International Monitoring System (IMS') established under the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The hydroacoustic network, designed to monitor the major world oceans, contains eleven stations located with an emphasis on the vast ocean areas of the Southern Hemisphere. Two different sensing techniques are employed; hydrophone sensors, which effectively cover large ocean areas, but are quite complex and expensive, and seismic detectors on small islands which are less effective, but considerably simpler and cheaper. The hydroacoustic stations transmit data in real time via satellite to the International Data Centre (IDC). The IDC analyses the hydroacoustic data in combination with the other three technologies to produce bulletins of detected events for the States Party to the Treaty.

Comprehensive Nuclear-Test-Ban Treaty: relevant radionuclides

Abstract With the first version of the IDC IDC is the acronym for the International Data Centre, IMS for the International Monitoring System and CTBT for the Comprehensive Nuclear-Test-Ban Treaty. software all known radionuclides, less the natural ones and one “naturalised” man-made one, caused a spectrum measured in the IMS* network to be characterised as interesting from a CTBT* point of view. But this is really not true for the majority of nuclides, so a change has been made to let only nuclides from a limited set of so called CTBT relevant nuclides have an impact on the characterization scheme. In the present paper the concept of CTBT relevance is analysed and a set of 96 relevant nuclides are defined. Out of these 51 are fission products and 41 are neutron activation products. There are also 4 nuclides which are residues from the nuclear fuel itself or added tracers.

Earthquake catalog improvements and their seismic hazard impacts for the Arabian Peninsula

The Reviewed Event Bulletin (REB) issued through the International Data Centre (IDC) using the International Monitoring System (IMS) network of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is a seismo-acoustic bulletin distributed to the Member States of the CTBTO for the purpose of verifying the Treaty. The REB is partially available within a few days on the public site of the International Seismological Center (ISC), where the REB events are labeled ‘IDC’. This study focuses on the seismicity of the Arabian Peninsula and its adjacent regions, but the conclusions would be similar for regions that include good quality seismic stations of the IMS auxiliary seismic network, which has no weight in the current Event Definition Criteria (EDC). It is indicated that the consideration of the confidence ellipse factors (semi-major a-axis, semi-minor b-axis, and the epicentral area (A) as alternative EDC would significantly improve the completeness of the REB for the Arabian Peninsula, which consequently enhance the quality of the ISC bulletin.The Arabian Peninsula has been chosen as a study region not only because it is surrounded by the IMS auxiliary seismic stations but also due to its increasing population, rapid urbanization, and strong economic growth in recent years. It has attracted many mega-projects (e.g., Multinational NEUM in Saudi Arabia, Expo 2020 in Dubai, the Special Economic Zone at Duqm in Oman, and the World Cup 2022 in Qatar). The earthquake hazards impact for the big cities in Saudi Arabia, such as Dammam in the east, and Jeddah, Tabuk, and Jizan in the west and the nearby cities are reviewed. The completeness catalog of the revised earthquakes may serve to improve the calculation of earthquake hazards threatening big cities in and around Saudi Arabia.

Contributions to the Improvement of Climate Data Availability and Quality for Sub-Saharan Africa

Reliable weather observations are the basis to assess climate change and variability. Compared to other regions of the world, long time series of weather observations are sparse in many countries of Sub-Saharan Africa. Various activities at national or international level are ongoing to improve the availability and quality of climate databases. Here, we present ongoing international contributions with a focus on representative examples hosted at Germany's national meteorological service DWD (Deutscher Wetterdienst). The international exchange of monthly climate reports (CLIMAT) is monitored within the Monitoring Centre of the GCOS Surface Network (Global Climate Observing System). In that context also quality control is performed and data are made publicly available. Recent climate observations can be complemented by digitization of historical hand-written weather observations which are available in distributed archives. International data centers, such as the Global Precipitation Climatology Centre (GPCC), collect international data. They perform quality-control of these observations and provide derived products in support of global and regional climate assessments. These activities can also contribute to the improvement of national climate databases, as e.g., demonstrated in a cooperation among selected countries with the SASSCAL initiative (Southern African Science Service Centre for Climate Change and Adaptive Land Management). Satellite-based observations are an additional source that can provide climatological information for selected parameters. In particular, the METEOSAT satellite series provides valuable data for the African continent. The Satellite Application Facility on Climate Monitoring (CM SAF) provides high resolution climate data covering the last decades derived from observations of such meteorological satellites. Based on these examples the paper illustrates the variety of ongoing international efforts in support of regional observation-based climate information, but also identifies the needs for further activities.

The International Data Centre infrasound processing system, a 25 years travel

In 2001, when the first data from an International Monitoring System infrasound station started to arrive in near real-time at the International Data Centre (IDC), its infrasound processing system was in a premature state. The IDC embarked for a multi-year design and development of its dedicated processing system, which led to operational IDC automatic processing and interactive analysis systems in 2010. In the next ten years the IDC produced over 40,000 infrasound events reviewed by expert analysts. In an effort to continue advancing its methods, improving its automatic system and providing software packages to Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) users, the IDC focused on several projects. First, the automatic system for the identification of valid signals was redesigned with the development of DTK-(G)PMCC (Progressive Multi-Channel Correlation), which is made available to CTBTO users within NDC-in-a-Box. And second, an infrasound model was developed for automatic waveform network processing software NET-VISA with an emphasis on the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. Ongoing and future improvements of the IDC processing system are planned to further reduce analyst workload that includes atmospheric propagation modeling and enhancements of the automatic pipeline components.

Applying Waveform Correlation to Reduce Seismic Analyst Workload Due to Repeating Mining Blasts

ABSTRACT Agencies that monitor for underground nuclear tests are interested in techniques that automatically characterize mining blasts to reduce the human analyst effort required to produce high-quality event bulletins. Waveform correlation is effective in finding similar waveforms from repeating seismic events, including mining blasts. We report the results of an experiment to detect and identify mining blasts for two regions, Wyoming (U.S.A.) and Scandinavia, using waveform templates recorded by multiple International Monitoring System stations of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO PrepCom) for up to 10 yr prior to the time of interest. We discuss approaches for template selection, threshold setting, and event detection that are specialized for characterizing mining blasts using a sparse, global network. We apply the approaches to one week of data for each of the two regions to evaluate the potential for establishing a set of standards for waveform correlation processing of mining blasts that can be generally applied to operational monitoring systems with a sparse network. We compare candidate events detected with our processing methods to the Reviewed Event Bulletin of the International Data Centre to assess potential reduction in analyst workload.