Amplitude-yield scaling for underground nuclear explosions

1973 ◽  
Vol 63 (2) ◽  
pp. 477-500 ◽  
Author(s):  
D. L. Springer ◽  
W. J. Hannon
Keyword(s):  
Rayleigh Wave ◽  
Statistical Tests ◽  
Test Site ◽  
Mean Value ◽  
P Wave ◽  
Source Population ◽  
Yield Data ◽  
P Waves ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions

abstract About 60 sets of seismic amplitude-yield data were examined using standard regression techniques to determine slopes of amplitude-yield scaling relations for explosions in water-saturated tuffs and rhyolites. Both P-wave amplitudes and Rayleigh-wave amplitudes were studied at selected stations located at regional and teleseismic distances. The source population included only those underground nuclear explosions fired near or below the level of the static water table at Pahute Mesa, Nevada Test Site, and covered about three orders of magnitude in yield. Statistical tests applied to the slope parameter (b) indicate that the slopes at regional and teleseismic distances are different. An estimated mean value of b for P-wave amplitude/period (A/T) was slightly greater than 0.6 for regional distances but was almost 1.0 for teleseismic distances. The estimated mean value of b for Rayleigh-wave A/T data was about 1.1. At a given distance the slopes seem to be independent of the yield range considered for both P-waves and Rayleigh-waves.

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.

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.

Seismic magnitudes of underground nuclear explosions

1973 ◽  
Vol 63 (1) ◽  
pp. 105-131 ◽  
Author(s):  
P. W. Basham ◽  
R. B. Horner
Keyword(s):  
Computational Procedure ◽  
Test Site ◽  
P Wave ◽  
Nevada Test Site ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Novaya Zemlya ◽  
Yield Information ◽  
Short Period ◽  
Propagation Effects

abstract Using an Ms computational procedure that minimizes path-propagation effects, and with Ms values found to be empirically independent of test site and detonation medium among consolidated rock explosions, available yield information is employed to illustrate that the seismic scaling of explosions in realistic detonation environments produces teleseismic Rayleigh-wave displacements proportional to the 1.2-power of yield over the range from low yields to greater than three megatons. Ms values independent of network, path, and site can be employed to estimate unknown yields at uncalibrated test sites to within average errors judged to be about 20 per cent. P-wave magnitudes, in the form of a calibrated teleseismic measure of short-period P-wave displacements, show a theoretically supported dependence of displacement on the 1.1-power of yield over the range from 6 kt to 1 mt. Studied explosions separate into two categories: the Nevada Test Site granite explosions, LONG SHOT, the Sahara February 1965 explosion and (by empirical inference) Novaya Zemlya and Eastern Kazakh explosions exhibit P-wave displacements about a factor of 3 greater than explosions of the same yield in tuff, rhyolite, and shale. P-wave magnitudes of explosions are subject to such a diversity of source, propagation, and measurement phenomena that any estimation of unknown yields without a closely controlled site and network calibration can be subject to large errors.

The stability of rms Lg measurements and their potential for accurate estimation of the yields of Soviet underground nuclear explosions

1990 ◽  
Vol 80 (6B) ◽  
pp. 2106-2126
Author(s):  
Roger A. Hansen ◽  
Frode Ringdal ◽  
Paul G. Richards
Keyword(s):  
Soviet Union ◽  
Signal To Noise Ratio ◽  
Test Site ◽  
P Wave ◽  
Accurate Estimation ◽  
Seismic Stations ◽  
Array Data ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Single Station

Abstract Data on underground nuclear explosions have recently become available from modern digital seismic stations installed within the Soviet Union and China. Observations of root mean square (rms) Lg-wave signals for Soviet underground nuclear explosions at the Shagan River Test Site in East Kazakhstan show that the relative amplitudes of the rms signals at stations in Norway, the USSR, and China are very similar for different explosions, the standard deviation of the differences being only about 0.03 in logarithmic units (i.e., magnitude units). This is consistent with earlier observations comparing NORSAR and Graefenberg array data, and the observed scatter is significantly lower than has been reported for Lg data from Nevada Test Site explosions. In view of the excellent correspondence found by Nuttli (1986) and Patton (1988) for Lg versus yield at Nevada, this indicates that rms Lg has a potential for yield estimation with very high accuracy at Shagan River. Our study has shown that: (a) selected stations in the USSR and China, situated at regional distances, provide a much improved signal-to-noise ratio of the Lg phase for events at Shagan River, as compared to NORSAR array data; (b) the scaling of rms Lg amplitudes between different-sized events recorded at the same single station site appears to be consistent with that of NORSAR, indicating a remarkable degree of precision in single station measurements of Lg signal; (c) rms Lg amplitude measurements for the best of these stations may be made at 1.5 to 2.0 magnitude units lower than at NORSAR or Graefenberg, allowing a much lower threshold for Lg-based yield determination; and (d) the P-wave detection capabilities of these single stations do not match those of the NORESS and ARCESS arrays; thus, teleseismic signals continue to be important for detection of small nuclear explosions. Our conclusion is that Lg signals appear to provide an excellent basis for supplying estimates of the yields of nuclear explosions even down to below 1 kt when such signals are recorded at high-quality, digital in-country seismic stations, and when calibrated by access to independent (nonseismic) yield information for a few nuclear explosions at the test sites of interest. In the context of monitoring a low-yield threshold test ban treaty, it will, in addition, be important to take into consideration various environmental conditions in the testing area, such as the possible presence of cavities, and to devise appropriate procedures for on-site observations in this regard.

Measurements of Rayleigh-wave phase velocities in Nevada: Implications for explosion sources and the Massachusetts Mountain earthquake

1982 ◽  
Vol 72 (4) ◽  
pp. 1329-1349
Author(s):  
H. J. Patton
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Moment Tensor ◽  
Test Site ◽  
P Wave ◽  
Stress Axis ◽  
Phase Velocities ◽  
Wave Phase ◽  
Single Station ◽  
Source Phase

abstract Single-station measurements of Rayleigh-wave phase velocity are obtained for paths between the Nevada Test Site and the Livermore broadband regional stations. Nuclear underground explosions detonated in Yucca Valley were the sources of the Rayleigh waves. The source phase φs required by the single-station method is calculated for an explosion source by assuming a spherically symmetric point source with step-function time dependence. The phase velocities are used to analyze the Rayleigh waves of the Massachusetts Mountain earthquake of 5 August 1971. Measured values of source phase for this earthquake are consistent with the focal mechanism determined from P-wave first-motion data (Fischer et al., 1972). A moment-tensor inversion of the Rayleigh-wave spectra for a 3-km-deep source gives a horizontal, least-compressive stress axis oriented N63°W and a seismic moment of 5.5 × 1022 dyne-cm. The general agreement between the results of the P-wave study of Fischer et al. (1972) and this study supports the measurements of phase velocities and, in turn, the explosion source model used to calculate φs.

Seismic effects of the MILROW and CANNIKIN nuclear explosions

1972 ◽  
Vol 62 (6) ◽  
pp. 1411-1423 ◽  
Author(s):  
E. R. Engdahl
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
High Gain ◽  
High Yield ◽  
Upper Crust ◽  
Seismic Effects ◽  
Underground Nuclear Explosions ◽  
Low Level ◽  
Nuclear Explosions

abstract Seismic effects of the underground nuclear explosions MILROW (October 1969, about 1 megaton) and CANNIKIN (November 1971, under 5 megatons) were monitored by a network of continuously recording, high-frequency, high-gain seismographs located on Amchitka and nearby islands. Each explosion was immediately followed by hundreds of small, discrete events (mB < 4), of similar focal mechanism and with a characteristic low-frequency signature, which were apparently related to the deterioration of the explosion cavity. This activity intensified, then terminated within minutes of a large, complex multiple event and concurrent formation of a surface subsided area that signaled complete collapse of the explosion cavity (MILROW, 37 hr; CANNIKIN, 38 hr). A number of small explosion-stimulated tectonic events, apparently unrelated to the collapse phenomenon, occurred intermittently for several weeks following each explosion—near the explosion cavity and up to 13 km southeast of CANNIKIN ground zero along the Island. These events were confined to the upper crust of the Island, had characteristic high-frequency signatures, and, near the Rifle Range Fault, had focal mechanisms which could be correlated with pre-existing faulting. The evidence points to a short-term interaction of the explosions with local ambient tectonic stresses. Because these stresses are of relatively low level on Amchitka, the observed seismic effects were significantly less extensive and smaller than similar effects reported from high-yield explosions at the Nevada Test Site. Continuous monitoring of the natural seismicity of the Amchitka region since 1969 has not revealed other evidence for an interaction between either MILROW or CANNIKIN and natural tectonic processes. The structural stability and apparent low level of stress in the upper crust of Amchitka suggest that the Island effectively is seismically decoupled from the active subduction zone below.

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