Conveners
T3.5 e-poster session: e-poster session - T3.5 - Data Analysis Algorithms
- Abdelhakim Gheddou (CTBTO Preparatory Commission, Vienna, Austria)
- Christos Saragiotis (CTBTO Preparatory Commission, Vienna, Austria)
T3.5 e-poster session: T3.5 - Data Analysis Algorithms
- Abdelhakim Gheddou (CTBTO Preparatory Commission, Vienna, Austria)
- Christos Saragiotis (CTBTO Preparatory Commission, Vienna, Austria)
- Ivan Kitov (CTBTO Preparatory Commission, Vienna, Austria)
Description
T3.5
The United Kingdom National Data Centre (UK NDC) has developed a novel tool for the analysis of radionuclide (RN) detection events on the International Monitoring System (IMS). An automated process for the fusion of RN and atmospheric transport modelling (ATM) data streams has been produced which efficiently compiles a wealth of information in a single source and puts interactive virtual maps...
A new algorithm for processing beta-gamma coincidence spectra based on the maximum likelihood and non-negative least squares (NNLS) methods is presented. The algorithm allows simultaneous processing of the signal in all regions of interest (ROI). This approach has a number of advantages over the net count calculation (NCC) algorithm and provides a solution to the problem of processing...
This research demonstrates a new accurate automated method for seismic first arrival picking that is based on a mathematical approach with considering the fractal dimension of seismic traces. Reliable and accurate detection of the first arrival is a key step for the determination of seismic parameters. In this work, we introduce an adaptive mathematical triggering algorithm by considering the...
Seismic signal processing aimed at extracting relevant information is often faced with the problem of the presence of disturbing signals, which can be generated by different sources of noise. This problem is all the more glaring when the seismic event of interest is so weak that it is drowned in noise, and can therefore pass without being noticed. We propose in this paper a new method which...
Seismic event depth is used for event characterization and location and is estimated using the vertical component of the velocity at the source and half the time interval between a direct P seismic phase and a similar shape echo, reflected from the surface, named depth phase or pP. The signal-echo separation can be estimated with cepstral methods designed for shallow-event cases when the P and...
Radioxenon analysis is a critical part of monitoring for underground nuclear explosions. Algorithms that determine the activity concentration of a sample were developed over many years and continue to be updated as lessons are learned from automated radioxenon analysis systems. During Xenon International testing in the U.S., a large activity 133Xe spike caused false positive hits for 133mXe...
This paper analyzes the possibility of applying higher - order statistics - third - order cumulants for isolation and autonomous determination of the moment of physical change in the observed environment. The proposed methods and algorithm make it possible to analyze all those phenomena: sound, infra sound, seismic and others that are essentially non-linear and non-Gaussian. As a result of the...
Magnitude measures the strength of an earthquake and is an important parameter for earthquake / underground test discrimination.
The IDC computes body magnitudes from the amplitude to period ratio recorded at network stations. Radzyner et al. (2017) showed that there was superior consistency of magnitudes across stations when the magnitude is computed as a linear function of the ratio, but...
Seismic event source identification is one of the vital and primordial tasks in seismic signal processing. Indeed, the first goal of seismic signal analyst is to recognize the source of each recorded seismogram. For example, one of the main goals of CTBTO is to identify nuclear explosion from natural seismic events. Several complex methods have been studied in the previous researches.
The aim...
The analysis system for CTBT radionuclide monitoring data is developed by the CNNDC. The system realizes the functions of automatic acquisition, database storage, automatic processing, interactive analysis and statistical query of IMS radionuclide monitoring data. A comprehensive assessment is carried out. The results show that the data analysis system has the capability of detection and...
This poster describes progress in 2020 of classifying IMS particulate radionuclide spectra into “likely normal” (Cat. 1,2) and “requires scrutiny” (Cat.3,4,5).The aim is to assist IDC radionuclide analysts by reducing their workload of “normal” spectra, which are the majority of IMS spectra.
The method described here is entirely ignorant of radionuclide science. The point of these efforts...
The International Monitoring System Division (IMS) of the CTBTO aims to maximize the data availability from the radionuclide monitoring systems. The detectors at the radionuclide stations require a calibration whenever a new detector is installed or the geometry is changed.
The maintenance unit of the IMS division is responsible for assisting the Station operator during calibration,...
Radionuclide event formation needs reliable detections. Because of the relatively large uncertainty in atmospheric transport modelling, which radionuclide event formation relies on, radionuclide event formation benefits from higher quality measurement analysis, specifically minimizing the number of false positive and false negative detections. This work proposes a quality scale that...
The automatic classification of seismic events is an absolute necessity when dealing with an important amount of data. Moreover, the classificationneeds to be achieved almost in real time. Due to the importance of an automatic task, various approaches have been proposed in the literature. Numerous approachesare based on features related to time domain, when othersexploit the frequency...
NDC-in-a-Box is an independent software package developed, distributed, and supported by PTS, which is intended for NDCs to establish a verification regime with a number of functions including receiving, archiving, processing and analysing data from IMS stations. To simplify installation and configuration of NDC-in-a-Box package, most software tools and applications are provided via a...
IMS radionuclide concentration data is accessible through the CRTooL. It contains detected concentrations for all kinds of radionuclides, categorized as noble gas (Xenon) and particulates, standing for natural, activation and fission-products.
The ultimate role of these data is to find and then identify any event that is related to the verification regime of the CTBT. Identification of events...
Quantitative methods that enable multi-physics waveform fusion support explosion monitoring and general research in geophysical processes that comprises background emissions for explosion monitoring. We offer a constructive method to fuse statistics that we derive from multi-physics waveforms and improve our capability to detect small, above-ground explosions over methods that consume single...
Nuclear test event data as acquired by the sensors at the terminal ends can be used to create multiple possible simulations of the event using any basic model. Alternatively, events can be created in an simulation environment generating stimuli producing data as of the recorded event. This can be done by adjusting input variables like yield, surface condition coefficients, depth variations,...
Current techniques used for analyzing beta-gamma spectra measured by radioxenon systems are based on Regions-of-Interest (ROIs) covering relevant decay modes. The ROIs are set in the detector calibration procedure, and the same ROIs are used for all samples. However, the optimal ROI limits generally will be different for each sample. We present at new method where the optimal ROI settings are...
The International Monitoring System (IMS) is comprised of multiple types of sensors that provide verification information. While each piece of information is useful for verification, the full benefit of multi-technology measurements has not been fully taken advantage of. Data Fusion is an approach that seeks to integrate disparate sources of data into a unified and comprehensive event...
Selby, (2008, 2011) developed a Generalized-F method, (Gen-F), to enable application of an F-statistic detector to small-aperture arrays where correlated background noise would otherwise degrade performance; and in 2013, he introduced an innovative time-frequency approach that further enabled application of Gen-F to arrays independent of aperture. Tests of the method on the IMS arrays have...
This presentation is an overview on radionuclide analysis procedures at the IDC. There are three sets of approaches currently, the single channel analyser curve for particulate, the least squares regression on gamma- and X-rays peaks of xenon isotopes for high resolution spectra and the net count calculation method for beta-gamma coincidence spectra for noble gas, which are based on...
Seismology data analysis is becoming a challenge due to the exponential growth of continuous data being stored. In this study we present and compare two methods to massive detect earthquakes: the matched filter and fingerprinting. We have tested matched filter over several study zones of interest: in the Western part of Mexico to study general seismic activity, in the Isthmus of Tehuantepec in...
37Ar is an indicator of an underground nuclear explosion. This radioisotope is produced via 40Ca (n, α) 37Ar reaction through neutron activation of 40Ca included in the rocks near to the nuclear explosion location. The relatively long half-life of 35 days compared to CTBT-relevant radioxenon isotopes results into 37Ar activity becoming stronger than radioxenon activity approximately 50 days...
Radioxenon detection systems chemically separate and purify xenon from the collected atmospheric sample. These systems reject radon to a high degree during this processing step. On occasion, radon will make it to the nuclear detectors and its progeny will interfere with the radioxenon measurement. The minimum-detectable-concentration values of an atmospheric monitoring system will also be...
Activity ratios of paired isotopes detected at IMS radionuclide stations can be used to not only discriminate a nuclear test from civil nuclear releases, but also determine the explosion time under assumed scenarios. A function of the isotopic ratio with time from the explosion time up to the stop of collection can be derived, based on Bateman equations of given decay chains. It is not a...
Multivariate analyses of fission product activities have previously been successfully used to determine the history of spent nuclear fuel from gamma measurements. A high dimensional data-set is projected to a one- or two-dimensional space using e.g. Partial Least Squares (PLS) regression to the parameters of interest, such as reactor type, burnup, initial enrichment and cooling time. Previous...
The discrimination between the highly variable radioxenon background caused by normal operations of nuclear facilities and CTBT-relevant events is a challenging but crucial task. For this reason, the radioxenon background at IMS noble gas systems must be sufficiently characterized and understood. The scientific methods and software tools to do this can still be significantly enhanced. This...
Quality Control (QC) measurements are taken to monitor and correct for gain drifts in radioxenon nuclear detectors. The measurement is performed by placing a $^{137}$Cs source near the detector and measuring the position of the 662-keV photoelectric peak in the NaI detector and determining the endpoint for the Compton scatter distribution, but there is much more information that can be...
An extensive phase identification (i.e. Pg,Pn,Sg,Sn,Lg) and analysis is still pending in order to better precise the location and nature of the main seismic events (5.1 and 4.8 Mw) that took place within the two branches of the Boconó fault in Las Gonzalez sector in Western Venezuela. Along with these two events (Nov 14th and 11th) in 2015, an intense aftershock sequence of almost one thousand...
Development of methods to track beta-gamma detector gains is important to the accuracy of radioxenon system measurements. Typical gain monitoring and correction is done using a mixed 137Cs/154Eu source, which results in several gamma-ray lines that can be fit by Gaussian distributions, and gain adjustments made to bring the peaks into the expected channel. The beta detector on the other hand...
The evolution of the SPALAX systems, now equipped with a high resolution beta/gamma detection equipement (PIPSBox/HPge), led CEA/DAM to develop dedicated spectrum analysis algorithms. The first developments were presented to CTBTO noble gas experts during the “Paris equation” meeting in March 2018.
Lately, CEA/DAM conducted a computer-based study to evaluate those algorithms. A large low...
Shallow earthquakes with Mw>8-9 usually create extensive aftershock activity with thousands of events with mb>3.5. This is a tremendous challenge for IDC automatic and interactive processing, with the Tohoku-2011 earthquake being a prime example. The SHI IDC processing is fine-tuned to find the smallest events (with fixed human resources), and thousands of similar events within a very short...
The Reviewed Event Bulletin (REB) of the IDC is the final product of interactive analysis, but also represents a set of seismic (S), infrasound (I), and SI events, which can be used for the analysis of the REB consistency. Continuous comparison of the event hypotheses obtained in routine automatic and interactive analysis with these historical events also helps to improve the REB completeness....
Radioxenon measurements use the net-count method to determine the activity for the radioxenon isotopes of interest. Detected decay events are plotted on a beta-gamma coincidence histogram and events are tallied inside regions-of-interest specific to a given radioxenon isotope. The boundaries of these regions are based on both the resolution of the detector and the physics of the emitted...
The recently developed open source FREAR tool improves nuclear event analysis by using Bayesian inference principles to estimate key source term parameters using measurements from distant radionuclide monitoring equipment in combination with Atmospheric Transport and Dispersion Models (ATDM). Trials on real world reconstructions have demonstrated clear and dramatic improvements over...
The materials relative to impulse source detection from SnT 2015, 2017 and 2019 were summarized using methods of maximal likelihood ratio according on information collected at the infrasonic IMS stations.
New criteria of infrasound IMS station efficiency were defined according on priority areas of network selection method control.
The present work reveals the influence of the signal...
The vast majority of International Monitoring System (IMS) seismic detections are associated with small events that are detected by only one station. Large numbers of small-event detections at each IMS station increases the probability of the International Data Centre (IDC) automatic system building false events. We test whether detections of small, repeating local events (e.g., mines) can be...
The coda magnitude method of Mayeda and Walter (1996) provides stable source spectra and moment magnitudes (Mw) for local to regional events from as few as one station that are virtually insensitive to source and path heterogeneity. The method allows for a consistent measure of Mw over a broad range of event sizes rather than relying on empirical magnitude relationships that attempt to tie...
This method allows us to determine the most reliable OSI area coordinates and the probability of the infrasound source occurrence by using the signal detection results, time of signal event and an azimuth of the signal according to information from IMS stations.
The method is based on the construction of the complex probability map and furthers its analysis according to CTBT OSI area limits....
Waveform cross correlation uses template waveforms from historical seismic events to detect recurring events from the same seismic source. Waveform cross correlation works well for dense regional networks, so research challenges arise when applying similar techniques to a sparse network such as the International Monitoring System (IMS). Effective waveform cross correlation requires templates...
