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.

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.

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.

A method for relocating seismic events using surface waves

1973 ◽  
Vol 63 (4) ◽  
pp. 1305-1313
Author(s):  
S. T. Crough ◽  
R. Van der Voo
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Group Velocity Dispersion ◽  
Body Wave ◽  
Test Site ◽  
Seismic Events ◽  
Computer Technique ◽  
Nuclear Explosions ◽  
Reference Event

abstract Seismic events can be relocated relative to a reference event by using the group-velocity dispersion curves of surface waves. Since group velocity is a function of the travel path, surface waves from two events in the same locale should show identical group velocities when viewed at any one seismograph station. A computer technique has been developed for comparing the group-velocity curves of any event with the curves of a reference event and for determining the relocation which causes the curves to best coincide. The method is evaluated by relocating eight intermediate-size nuclear explosions of the Nevada Test Site series. With precise curve fitting, the surface-wave locations are slightly more accurate in southern Nevada than the standard body-wave determinations. The surface-wave origin times are considerably more accurate. In areas of sparse station coverage or of many small earthquakes, the surface-wave method can be expected to improve seismic locations significantly.

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 Induced seismic events on the territory of the former Semipalatinsk Test Site (STS) according to the data of field observations

2020 ◽  
Vol 2 (4) ◽  
pp. 7-15
Author(s):  
Inna Sokolova ◽  
Natalya Mikhailova ◽  
Alexandr Velikanov
Keyword(s):  
Test Site ◽  
Seismic Array ◽  
Low Energy ◽  
Seismic Events ◽  
Field Observations ◽  
Induced Earthquakes ◽  
Nuclear Explosions ◽  
Semipalatinsk Test Site

Seismicity in the area of the Semipalatinsk Test Site near the sites of previously conducted nu-clear tests, as well as on the territory of operating quarries in the STS area was investigated. To study man-made events at the test site, the data of field seismic observations for 2005-2010, and 2018-2020 was used. In addition, data from the Kurchatov-Cross permanent seismic array, the Kurchatov IRIS IDA three-component station, and the Kurchatov infrasound station were used. It is shown that during the period of UNE conduction on the territory of the Semipalatinsk Test Site, as well as in recent years in the area of nuclear explosions, induced earthquakes with low-energy were observed. In the area of mineral mines, where intensive blasts are carried out, technogene-ous earthquakes induced by the prolonged impact of industrial explosions have been recorded.

North Korea in 2016

Asian Survey ◽  
2017 ◽  
Vol 57 (1) ◽  
pp. 119-127
Author(s):  
Charles K. Armstrong
Keyword(s):  
Security Council ◽  
North Korea ◽  
Leadership Position ◽  
Un Security Council ◽  
Nuclear Tests

Kim Jong Un further consolidated his leadership position at the Seventh Congress of the Workers’ Party in May, the first congress since 1980. Pyongyang conducted two nuclear tests and made advances in missile delivery, eliciting strong sanctions resolutions from the UN Security Council, first in March and again in November.

Study of low-magnitude seismic events near the Novaya Zemlya nuclear test site

1997 ◽  
Vol 87 (6) ◽  
pp. 1563-1575
Author(s):  
Frode Ringdal
Keyword(s):  
Monitoring Network ◽  
Test Site ◽  
Nuclear Test ◽  
P Wave ◽  
Scaling Effects ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Novaya Zemlya ◽  
Source Scaling ◽  
Low Magnitude

Abstract A study of available seismic data shows that all but one of the 42 known underground nuclear explosions at Novaya Zemlya have been detected and located by stations in the global seismic network. During the past 30 years, only one seismic event in this area has been unambiguously classified as an earthquake (1 August 1986, mb = 4.3). Several other small events, most of which are thought to be either chemical explosions or aftereffects of nuclear explosions, have also been detected. Since 1990, a network of sensitive regional arrays has been installed in northern Europe in preparation for the global seismic monitoring network under a comprehensive nuclear test ban treaty (CTBT). This regional network has provided a detection capability for Novaya Zemlya that is shown to be close to mb = 2.5. Three low-magnitude events have been detected and located during this period, as discussed in this article: 31 December 1992 (mb = 2.7), 13 June 1995 (mb = 3.5), and 13 January 1996 (mb = 2.4). To classify the source types of these events has proved very difficult. Thus, even for the mb = 3.5 event in 1995, we have been unable to provide a confident classification of the source as either an earthquake or explosion using the available discriminants. A study of mb magnitude in different frequency bands shows, as expected, that the calculation of mb at regional distances needs to take into account source-scaling effects at high frequencies. Thus, when comparing a 4 to 8 or 8 to 16 Hz filter band to a “teleseismic” 2 to 4 Hz band, the smaller events have, relatively speaking, significantly more high-frequency energy (up to 0.5 mb units) than the larger events. This suggests that a P-wave spectral magnitude scale might be appropriate. The problem of accurately locating small events using a sparse array network is addressed using the 13 January 1996 event, which was detected by only two arrays, as an illustrative example. Our analysis demonstrates the importance of using accurately calibrated regional travel-time curves and, at the same time, illustrates how array processing can be used to identify an interfering phase from a local disturbance, thereby avoiding location errors due to erroneous phase readings.

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