Yield estimation from spectral amplitudes of direct P and P coda recorded by the wake island deep ocean hydrophone array

1987 ◽  
Vol 77 (5) ◽  
pp. 1748-1766
Author(s):  
Charles S. McCreery
Keyword(s):  
Body Wave ◽  
Relative Yield ◽  
Deep Ocean ◽  
Test Site ◽  
Spectral Amplitude ◽  
Stable Measure ◽  
Regression Techniques ◽  
Shape Characteristics ◽  
Hydrophone Array ◽  
Epicentral Location

Abstract Spectral amplitudes of direct P and P coda between 0.5 and 6 Hz have been measured for 14 Eastern Kazakh test explosions using 8 hydrophones of the Wake Island Array, and a new model for these data has been developed to estimate relative yields of those explosions. Each log spectral amplitude is considered to be the sum of four parameters and an error term. Three parameters are frequency-dependent and represent: (1) the average Eastern Kazakh spectrum at the Wake Island Array; (2) the spectral shape characteristics unique to each event; and (3) the station or hydrophone corrections. The fourth parameter represents relative yield. A total of 346 parameters, including the 14 relative yields, were needed to model all 901 spectral amplitudes that were measured, and first-order linear regression techniques were used to invert the data for these parameters. Standard deviations of the computed relative yields are very small, averaging only 0.015 mb units. Deviations between the relative yields and their corresponding relative NEIS body-wave magnitudes, however, are larger, averaging 0.14 mb units. This difference is interpreted to be an indicator of the level of inhomogeneity in the worldwide pattern of energy radiated from Eastern Kazakh tests. There is evidence that this pattern can be correlated with the precise epicentral location of each explosion within the test site and is due to focusing and defocusing near the source. It is proposed that the yield of a large explosion might be disguised by siting the explosion at a location that selectively defocuses energy towards continents where most seismic stations are located. The precision with which a relative yield is determined from the data of any single hydrophone averages 0.035 mb units. Thus, the model appears to provide a very stable measure of yield. Errors associated with frequencies greater than 2 Hz are only slightly greater than errors associated with frequencies less than 2 Hz, verifying the utility of using the higher frequencies observed in direct P and P coda to estimate yield.

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.

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.

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.

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.

A discrimination analysis of short-period regional seismic data recorded at Tonto Forest Observatory

1982 ◽  
Vol 72 (4) ◽  
pp. 1351-1366
Author(s):  
J. R. Murphy ◽  
T. J. Bennett
Keyword(s):  
Epicentral Distance ◽  
Test Site ◽  
P Wave ◽  
Set Cover ◽  
Spectral Amplitude ◽  
Nevada Test Site ◽  
Data Set ◽  
Short Period ◽  
Single Station ◽  
Regional Phases

abstract A new seismic discriminant based on spectral differences of regional phases from earthquakes and explosions recorded at a single station has been tested and found to work remarkably well. The test data consisted of a well-constrained set of 30 Nevada Test Site (NTS) explosions and 21 earthquakes located within about 100 km of NTS which were recorded on short-period seismographs at the Tonto Forest Observatory in central Arizona at an epicentral distance averaging 530 km. The events in the data set cover a magnitude range from 3.3 to 4.8 (mb) for which Pn, Pg, and Lg phases have been analyzed. We found that, although Lg phases from earthquakes are typically more prominent than for explosions with comparable P-wave amplitude levels, simple time-domain Lg/P amplitude ratios do not result in a separation of the earthquake and explosion samples consistent enough to provide reliable discrimination. However, spectral analyses of the data over the frequency band from 0.5 to 5.0 Hz revealed significant differences in the spectra of certain regional phases which proved to be a quite reliable discriminant. In particular, both the Pg and Lg spectra from earthquakes have been found to be richer in high-frequency content than corresponding explosion spectra. A discriminant measure, defined as the ratio of average Lg spectral amplitude level in the 0.5- to 1.0-Hz passband to that in the 2.0- to 4.0-Hz passband, provides good separation of earthquake and explosion populations.

Potential effect of seasonally varying station thresholds on joint-maximum-likelihood magnitude estimates from bulletin data 

2021 ◽  
Author(s):  
Sheila Peacock
Keyword(s):  
Maximum Likelihood ◽  
Body Wave ◽  
Monitoring Network ◽  
Test Site ◽  
Potential Effect ◽  
Likelihood Method ◽  
Different Seasons ◽  
Noise Threshold ◽  
Test Ban ◽  
Magnitude Estimates

<div> <div> <div> <p>Accurate seismic body-wave magnitudes (m<sub>b</sub>) are important in nuclear test-ban treaty verification.  Network mean magnitudes are known to be biased when the effect of noise obscuring signal at some stations in the monitoring network is ignored.  To overcome this bias a joint-maximum-likelihood method is used to invert bulletin amplitude and period measurements at a network of stations from a number of closely spaced sources, to estimate unbiased network m<sub>b</sub> values and station corrections. For each station a noise threshold is determined independently using the Kelly & Lacoss (1969) method, assuming that large samples of amplitudes reported in a bulletin (in this case from the International Seismological Centre, ISC) follow a Gutenberg-Richter distribution. Where stations report arrivals sufficiently frequently, the noise threshold can be estimated separately for different seasons, to highlight variations caused by, for instance, storms or freezing of nearby ocean.  The noise thresholds at some stations differ by up to 0.4 magnitude units between seasons.  Sensitivity of maximum-likelihood magnitude estimates of a group of announced explosions at the Nevada Test Site to variations in threshold at Canadian Arctic stations (compared with using the annual mean) is generally small (<∼0.01-0.02 units), and greatest for low-magnitude events in the “noisy” season, when the station magnitudes are below the seasonal threshold but above the annual average threshold.</p> <p>UK Ministry of Defence © Crown copyright 2021/AWE</p> </div> </div> </div>

Surface-wave constraints on the August 1, 1975, Oroville earthquake

1977 ◽  
Vol 67 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Robert S. Hart ◽  
Rhett Butler ◽  
Hiroo Kanamori
Keyword(s):  
Surface Wave ◽  
Rayleigh Waves ◽  
Body Wave ◽  
Source Parameters ◽  
The Body ◽  
Wave Radiation ◽  
Spectral Amplitude ◽  
Surface Wave Magnitude ◽  
Long Period ◽  
Short Period

abstract Observations of Love and Rayleigh waves on WWSSN and Canadian Network seismograms have been used to place constraints upon the source parameters of the August 1, 1975, Oroville earthquake. The 20-sec surface-wave magnitude is 5.6. The surface-wave radiation pattern is consistent with the fault geometry determined by the body-wave study of Langston and Butler (1976). The seismic moment of this event was determined to be 1.9 × 1025 dyne-cm by both time-domain and long-period (T ≥ 50 sec) spectral amplitude determinations. This moment value is significantly greater than that determined by short-period studies. This difference, together with the low seismic efficiency of this earthquake, indicates that the character of the source is intrinsically different at long periods from those aspects which dominate the shorter-period spectrum.

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