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.

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.

Strain effects of nuclear explosions in Nevada

1971 ◽  
Vol 61 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Gary Boucher ◽  
Stephen D. Malone ◽  
E. Fred Homuth
Keyword(s):  
Body Wave ◽  
High Sensitivity ◽  
Test Site ◽  
Strain Effects ◽  
Underground Nuclear Explosions ◽  
Static Strain ◽  
Nuclear Explosions ◽  
Shot Point ◽  
A Minor ◽  
The University

abstract The University of Nevada's three-component quartz-rod strain meter installation at Round Mountain, Nevada (38°42.1′N, 117°04.6′W) has recorded a number of underground nuclear explosions at the Nevada Test Site, beginning with the megaton-sized JORUM event September 16 1969. Both that explosion and the larger HANDLEY event on March 26 1970 produced static strain offsets of a few parts in 109 at Round Mountain. These offsets did not decay within the first few hours after the explosions. In both cases, the strain offsets were in the sense of ground extension radial to the shot point, which is inconsistent with the assumption of a pure compressive source of strain. The strain-change ellipse for the HANDLEY event was found to have a major strain axis of 11 × 10−9 extensional, oriented N 34°W, and a minor axis of 7.4 × 10−9 compressional. A single-component strain meter at Mina, Nevada, (38°26.3′N, 118°9.3′W) was operated for the HANDLEY event, and recorded a strain offset of 2.6 × 10−9 in the direction N 74°E. Strain offsets at the time of the largest collapse events following HANDLEY were observed at Round Mountain. These offsets had the same sense on each component as those following the explosion itself. This is interpreted as support for the hypothesis that the strain changes are tectonic in origin, and the explosion initiates the strain release. Small offsets were observed for three smaller explosions out of a total of 13 studied. The relationship between body-wave magnitude mb and maximum dynamic strains at Round Mountain may be described empirically by the equation Log S = − 13.4 + 1.10 mb. Because of its high sensitivity and stability, the Round Mountain strain meter is capable of obtaining useful measurements of dynamic and static strain effects of intermediate- to large-sized explosions, at distances ranging from 160 to 200 km.

scholarly journals Seismological investigation of the 2016 January 6 North Korean underground nuclear test

2016 ◽  
Vol 206 (3) ◽  
pp. 1487-1491 ◽  
Author(s):  
Lian-Feng Zhao ◽  
Xiao-Bi Xie ◽  
Wei-Min Wang ◽  
Jin-Lai Hao ◽  
Zhen-Xing Yao
Keyword(s):  
Body Wave ◽  
Broad Band ◽  
Test Site ◽  
Nuclear Test ◽  
The Body ◽  
The North ◽  
Nuclear Tests ◽  
Master Event ◽  
Fully Coupled ◽  
Body Wave Magnitude

Abstract Seismology plays an important role in characterizing potential underground nuclear tests. Using broad-band digital seismic data from Northeast China, South Korea and Japan, we investigated the properties of the recent seismic event occurred in North Korea on 2016 January 6. Using a relative location method and choosing the previous 2006 explosion as the master event, the 2016 event was located within the North Korean nuclear test site, with its epicentre at latitude 41.3003°N and longitude 129.0678°E, approximately 900 m north and 500 m west of the previous event on 2013 February 12. Based on the error ellipse, the relocation uncertainty was approximately 70 m. Using the P/S spectral ratios, including Pg/Lg, Pn/Lg and Pn/Sn, as the discriminants, we identify the 2016 event as an explosion rather than an earthquake. The body-wave magnitude calculated from regional wave Lg is mb(Lg) equal to 4.7 ± 0.2. Adopting an empirical magnitude–yield relation, and assuming that the explosion is fully coupled and detonated at a normally scaled depth, we find that the seismic yield is about 4 kt, with the uncertainties allowing a range from 2 to 8 kt.

P-wave spectra of nevada test site events at near and very near distances: Implications for a near-regional body wave-surface wave discriminant

1976 ◽  
Vol 66 (3) ◽  
pp. 803-825
Author(s):  
William A. Peppin
Keyword(s):  
Scaling Laws ◽  
Body Wave ◽  
Test Site ◽  
P Wave ◽  
Spectral Amplitude ◽  
Source Spectrum ◽  
Wave Spectra ◽  
Nevada Test Site ◽  
Field Source ◽  
Source Spectra

abstract Some 140 P-wave spectra of explosions, earthquakes, and explosion-induced aftershocks, all within the Nevada Test Site, have been computed from wide-band seismic data at close-in (< 30 km) and near-regional (200 to 300 km) distances. Observed near-regional corner frequencies indicate that source corner frequencies of explosions differ little from those of earthquakes of similar magnitude for 3 < ML < 5. Plots of 0.8 to 1.0 Hz Pg spectral amplitude versus 12-sec Rayleigh-wave amplitude show a linear trend with unit slope over three orders of magnitude for explosions; earthquakes fail to be distinguished from explosions on such a plot. These spectra also indicate similar source spectra for explosions in different media (tuff, alluvium, rhyolite) which corroborates Cherry et al. (1973). Close-in spectra of three large explosions indicate that: (1) source corner frequencies of explosions scale with yield in a way significantly different from previously published scaling laws; (2) explosion source spectra in tuff are flat from 0.2 to 1.0 Hz (no overshoot); (3) the far-field source spectrum decays at least as fast as frequency cubed. Taken together, these data indicate that the following factors are not responsible for Peppin and McEvilly's (1974) near-regional discriminant: (a) source dimension, (b) source rise time, or (c) shape of the source spectrum.

Evidence of tectonic release from underground nuclear explosions in long-period P waves

1983 ◽  
Vol 73 (2) ◽  
pp. 593-613
Author(s):  
Terry C. Wallace ◽  
Donald V. Helmberger ◽  
Gladys R. Engen
Keyword(s):  
Upper Mantle ◽  
High Stress ◽  
Test Site ◽  
Strike Slip ◽  
Body Waves ◽  
Release Time ◽  
P Waves ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Long Period

abstract In this paper, we study the long-period body waves at regional and upper mantle distances from large underground nuclear explosions at Pahute Mesa, Nevada Test Site. A comparison of the seismic records from neighboring explosions shows that the more recent events have much simpler waveforms than those of the earlier events. In fact, many of the early events produced waveforms which are very similar to those produced by shallow, moderate-size, strike-slip earthquakes; the phase sP is particularly obvious. The waveforms of these explosions can be modeled by assuming that the explosion is accompanied by tectonic release represented by a double couple. A clear example of this phenomenon is provided by a comparison of GREELEY (1966) and KASSERI (1975). These events are of similar yields and were detonated within 2 km of each other. The GREELEY records can be matched by simply adding synthetic waveforms appropriate for a shallow strike-slip earthquake to the KASSERI observations. The tectonic release for GREELEY has a moment of 5 ՠ1024 dyne-cm and is striking approximately 340°. The identification of the sP phase at upper mantle distances indicates that the source depth is 4 km or less. The tectonic release time function has a short duration (less than 1 sec). A comparison of these results with well-studied strike-slip earthquakes on the west coast and eastern Nevada indicate that, if tectonic release is triggered fault motion, then the tectonic release is relatively high stress drop, on the order of several hundred bars. It is possible to reduce these stress drops by a factor of 2 if the tectonic release is a driven fault; i.e., rupturing with the P velocity. The region in which the stress is released for a megaton event has a radius of about 4 km. Pahute Mesa events which are detonated within this radius of a previous explosion have a substantially reduced tectonic release.

scholarly journals A Multi-Technology Analysis of the 2017 North Korean Nuclear Test

2018 ◽  
Author(s):  
Peter Gaebler ◽  
Lars Ceranna ◽  
Nima Nooshiri ◽  
Andreas Barth ◽  
Simone Cesca ◽  
...  
Keyword(s):  
Monitoring System ◽  
Body Wave ◽  
Test Site ◽  
Nuclear Test ◽  
International Monitoring System ◽  
Seismic Stations ◽  
Technology Analysis ◽  
Tnt Equivalent ◽  
International Monitoring ◽  
Strong Surface

Abstract. On September 3rd 2017 official channels of the Democratic People's Republic of Korea announced the successful test of a thermonuclear device. Only seconds to minutes after the alleged nuclear explosion at the Punggye-ri nuclear test site in the mountainous region in the country's northeast at 03:30:02 (UTC) hundreds of seismic stations distributed all around the globe picked up strong and distinct signals associated with an explosion. Different seismological agencies reported body wave magnitudes of well above 6.0, consequently estimating the explosive yield of the device in the order of hundreds of kilotons TNT equivalent. The 2017 event can therefore be assessed being multiple times larger in energy than the two preceding events in January and September 2016. This study provides a multi-technology analysis of the 2017 North Korean event and its aftermath using a wide array of geophysical methods. Seismological investigations locate the event within the test site at a depth of approximately 0.8 km below surface. The radiation and generation of P- and S-wave energy in the source region is significantly influenced by the topography of the Mt. Mantap massif. Inversions for the full moment tensor of the main event reveal a dominant isotropic component accompanied by significant amounts of double couple and compensated linear vector dipole terms, confirming the explosive character of the event. Analysis of the source mechanism of an aftershock that occurred around eight minutes after the test in the direct vicinity suggest a cavity collapse. Measurements at seismic stations of the International Monitoring System result in a body wave magnitude of 6.2, which translates to an yield estimate of around 400 kilotons TNT equivalent. The explosive yield is possibly overestimated, since topography and depth phases both tend to ehance the peak amplitudes of teleseismic P-waves. Interferometric Synthetic-Aperture-Radar analysis using data from the ALOS-2 satellite reveal strong surface deformations in the epicenter region. Additional multispectral optical data from the Pleiades satellite show clear landslide activity at the test site. The strong surface deformations generated large acoustic pressure peaks, which were observed as infrasound signals with distinctive waveforms even in distances of 400 km. In the aftermath of the 2017 event atmospheric traces of the fission product 133Xe have been detected at various locations in the wider region. While for 133Xe measurements in September 2017 the Punggye-ri test site is disfavored as source by means of atmospheric transport modeling, detections in October 2017 at the International Monitoring System station RN58 in Russia indicate a potential delayed leakage of 133Xe at the test site from the 2017 North Korean nuclear test.

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