P-wave coupling of underground nuclear explosions

1966 ◽  
Vol 56 (4) ◽  
pp. 861-876 ◽  
Author(s):  
Donald L. Springer
Keyword(s):  
P Wave ◽  
Propagation Path ◽  
Seismic Signals ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Scaling Relationships ◽  
Amplitude Data ◽  
Detonation Energy ◽  
Relationship Of ◽  
The Relationship

abstract P-wave amplitude data for underground nuclear explosions are correlated with detonation energy. Amplitudes are reproducible to 25 per cent when source media and propagation path differences are minimized. These data verify theoretical scaling relationships and establish relative coupling for various shot media. An empirical correlation of these amplitude data with dry porosity of the detonation medium indicates that a medium with 60 per cent dry porosity may couple explosive energy one-fourth or one-fifth as efficiently as does alluvium. The relationship of teleseismic magnitude to explosive yield for various types of low coupling shows that dry porous media give a significant reduction of seismic signals generated by underground nuclear explosions.

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.

The Fairbanks earthquakes of June 21, 1967; aftershock distribution, focal mechanisms, and crustal parameters

1969 ◽  
Vol 59 (1) ◽  
pp. 73-100
Author(s):  
Larry Gedney ◽  
Eduard Berg
Keyword(s):  
P Wave ◽  
Fault System ◽  
Crustal Layer ◽  
Near Surface ◽  
Fault Surface ◽  
True Value ◽  
Regional Tectonic ◽  
Tectonic System ◽  
Relationship Of ◽  
The Relationship

Abstract A series of moderately severe earthquakes occurred in the vicinity of Fairbanks, Alaska, on the morning of June 21, 1967. During the following months, many thousands of aftershocks were recorded in order to outline the aftershock zone and to resolve the focal mechanism and its relation to the regional tectonic system. No fault is visible at the surface in this area. Foci were found to occupy a relatively small volume in the shape of an ablate cylinder tilted about 30° from the vertical. The center of the zone lay about 12 kilometers southeast of Fairbanks. Focal depths ranged from near-surface to 25 kilometers, although most were in the range 9-16 km. In the course of the investigation, it was found that the Jeffreys and Bullen velocity of 5.56 km/sec for the P wave in the upper crustal layer is very near the true value for this arec, and that the use of 1.69 for the Vp/Vs ratio gives good results in most cases. The proposed faulting mechanism involves nearly equal components of right-lateral strike slip, and normal faulting with northeast side downthrown on a system of sub-parallel faults striking N40°W. The fault surface appears to be curved—dipping from near vertical close to the surface to less steep northeast dips at greater depths. The relationship of this fault system with the grosser aspects of regional tectonism is not clear.

THE p-WAVE THRESHOLD EFFECT AND QUASIRESONANT SCATTERING

2005 ◽  
Vol 20 (03) ◽  
pp. 187-201 ◽  
Author(s):  
CORNEL HATEGAN ◽  
GERHARD GRAW ◽  
HORIA COMISEL
Keyword(s):  
Reaction Mechanism ◽  
Single Particle ◽  
Strength Function ◽  
Direct Interaction ◽  
Threshold Effect ◽  
Scattering Matrix ◽  
P Wave ◽  
Threshold Models ◽  
Relationship Of ◽  
The Relationship

The p-wave threshold effect is described in terms of the reduced scattering matrix. The relationship of this approach to previous theoretical threshold models is established. We prove that this phenomenon is related to the reaction-mechanism of quasiresonant scattering: a single particle neutron threshold state and direct interaction coupling to open observed channels. Spectroscopic aspects of the threshold effect, both with respect to the magnitude and microstructure, are discussed in terms of the neutron strength function.

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 relative performance of mb and alternative measures of elastic energy in estimating source size and explosion yield

1984 ◽  
Vol 74 (5) ◽  
pp. 1863-1882
Author(s):  
J. T. Bullitt ◽  
V. F. Cormier
Keyword(s):  
Elastic Energy ◽  
P Wave ◽  
Reference Station ◽  
Small Data ◽  
Federal Republic Of Germany ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Short Period ◽  
Alternative Measures ◽  
The Stability

Abstract A comparison has been made of the relative scatter of classical mb and alternative measures of P-wave energy from underground nuclear explosions at test sites in East Kazakh, USSR. The scatter of the energy measures is observed in teleseismic arrays of short-period Global Digital Seismic Network (GDSN) stations and the local broadband array at Graefenburg, Federal Republic of Germany. Four measures of A in log(A/T), spectral magnitudes, peak velocity, rms coda, and integrated velocity-squared are compared. The measures are constructed to be in equivalent units of the flux rate of radiated elastic energy. All measures are assumed to have the same slope in a linear regression of log(yield) versus log(measure). Three independent tests were made of the stability of the yield estimators: the scatter of the measures using: (1) Graefenburg array data; (2) GDSN data normalized to a reference station; and (3) GDSN data normalized to a reference event. The differences among the standard deviations are small (≦ 0.1 mb units), making it difficult using a small data base to conclude whether the performance of one estimator is significantly better than another. The relative order in the performance of the yield estimators, however, is preserved in each of the three tests. The coda measure is the most stable, followed by the spectral and time-domain A/T measures. The relations observed at Graefenburg between (1) the amplitude of direct P versus P coda, (2) the apparent azimuth of direct P, and (3) complexity, suggest that amplitude variations across an array are a product of scattering along the entire ray path as well as scattering, focusing, and defocusing localized in the lithosphere beneath the source and receiver sites.

Amplitudes and energies of primary seismic waves near the hardhat, haymaker, and shoal nuclear explosions

1966 ◽  
Vol 56 (3) ◽  
pp. 643-653 ◽  
Author(s):  
Lynn D. Trembly ◽  
Joseph W. Berg
Keyword(s):  
Theoretical Model ◽  
Seismic Waves ◽  
Theoretical Data ◽  
Source Model ◽  
Similar Data ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Long Period ◽  
Radiation Fields ◽  
Amplitude Data

abstract Records of near-source (0.3 to 20 km) primary seismic waves generated by the Hardhat, Haymaker, and Shoal underground nuclear explosions were analyzed in terms of displacement amplitude and energy variations with distance. The observed data were compared to similar data from a theoretical source model to determine the adequacy of the theoretical model. There was evidence that a long-period displacement field existed near the explosions as predicted by the theoretical source. Scatter in the observed amplitude data made it difficult to distinguish between the long-period and the radiation fields. However, the variation of total energy of the observed primary seismic waves with distance showed the presence of the long-period field. The comparison of observed and theoretical data indicates that a theoretical elastic source model approximated the observed sources.

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.

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