Results of the NTS Experiment: Phase II

Der, Zoltan A.; McElfresh, T.W.; Mrazek, C. P.; Racine, D. P. J.; Barker, B. W.

doi:10.21236/ada096761

Cited by 3 publications

(5 citation statements)

References 18 publications

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“…We have concluded (Der et al 1980a), however, that the level of high-frequency (f> 2 Hz) energy in the recordings of short-period signals is considerably above the level that could be attributed to non-linearity. Fourier analysis of steady state calibration signals, where the input level is considerably above the amplitude of most real signals, shows harmonics well below the spectral level of recorded teleseismic signals.…”

Section: Introductionmentioning

confidence: 68%

“…We corrected for this difference in the spectral analysis, but the trace amplitudes and dominant wave periods at this station are not directly comparable to the rest of the stations. For further details we refer the reader to a more complete report (Der et al 1980a). …”

Section: The S D C S E X P E R I M E N Tmentioning

confidence: 99%

“…Band pass filtering of teleseismic P-waves usually shows, however, that the envelope shape is essentially the same, within a factor of 2, for all bands in the 0.5-4 Hz range for the first 10s into the signal (Der, McElfresh & O'Donnell 1980a). Any variability introduced scattering would be small relative to the drastic effect of even moderate changes in t:.…”

Section: Introductionmentioning

confidence: 95%

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An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

Der

McElfresh

O’Donnell

1982

Geophysical Journal International

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Studies of teleseismic Pand S-wave amplitudes and spectra in the 0.5-4 Hz band show large variations in the attenuative properties of the upper mantle under the United States. The data indicate that attenuation is greatest under the south-western United States including, but not confined to, the Basin and Range province. The lowest attenuation prevails under the north central shield regions. The north-eastern part of the country, consisting of New England and possibly including a larger area along the eastern seaboard, is characterized by moderate attenuation in the mantle.The level of the high-frequency energy in short-period seismic waves and the differences between Q values derived from short-and long-period data indicate that Q is frequency dependent. The form of frequency dependence of t* compatible with the data in the 0.5-4 Hz range does not allow a rapid decrease of t * with increasing frequency. Rather it supports a gradual decrease covering the broader 0.1-4Hz range. The curves of t* versus frequency, for shield-to-shield and mixed shield-to-western United States type paths are parallel with an average difference of 0.2 s in t* in the short-period band, but may diverge towards the long-period band. For both curves t: is below 1 s. For shield-to-shield paths t: must be below 0.5 s at 1 Hz.

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Section: Introductionmentioning

confidence: 68%

Section: The S D C S E X P E R I M E N Tmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

Der

McElfresh

O’Donnell

1982

Geophysical Journal International

Self Cite

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“…These results generally do not appear to explain the anomalies (DER et al, 1980). For example, LRSM stations were established at FAULTLESS, RULISON, and GASBUGGY epicenters to measure the relative attenuation in order to explain dm b 's with respect to dt a dierences.…”

Section: O-test-site Eventsmentioning

confidence: 99%

Effects of Source RDP Models and Near-source Propagation: Implication for Seismic Yield Estimation

Saikia¹,

Helmberger

Stead³

et al. 2001

Pure appl. geophys.

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Ð It has proven dicult to uniquely untangle the source and propagation eects on the observed seismic data from underground nuclear explosions, even when large quantities of near-source, broadband data are available for analysis. This leads to uncertainties in our ability to quantify the nuclear seismic source function and, consequently the accuracy of seismic yield estimates for underground explosions. Extensive deterministic modeling analyses of the seismic data recorded from underground explosions at a variety of test sites have been conducted over the years and the results of these studies suggest that variations in the seismic source characteristics between test sites may be contributing to the observed dierences in the magnitude/yield relations applicable at those sites. This contributes to our uncertainty in the determination of seismic yield estimates for explosions at previously uncalibrated test sites. In this paper we review issues involving the relationship of Nevada Test Site (NTS) source scaling laws to those at other sites. The Joint Veri®cation Experiment (JVE) indicates that a magnitude (m b ) bias (dm b ) exists between the Semipalatinsk test site (STS) in the former Soviet Union (FSU) and the Nevada test site (NTS) in the United States. Generally this dm b is attributed to dierential attenuation in the upper-mantle beneath the two test sites. This assumption results in rather large estimates of yield for large m b tunnel shots at Novaya Zemlya. A re-examination of the US testing experiments suggests that this dm b bias can partly be explained by anomalous NTS (Pahute) source characteristics. This interpretation is based on the modeling of US events at a number of test sites. Using a modi®ed Haskell source description, we investigated the in¯uence of the source Reduced Displacement Potential (RDP) parameters w ¥ , K and B by ®tting short-and long-period data simultaneously, including the near-®eld body and surface waves. In general, estimates of B and K are based on the initial P-wave pulse, which various numerical analyses show to be least aected by variations in near-source path eects. The corner-frequency parameter K is 20% lower at NTS (Pahute) than at other sites, implying larger eective source radii. The overshoot parameter B appears to be low at NTS (although variable) relative to other sites and is probably due to variations in source conditions. For a low B, the near-®eld data require a higher value of w ¥ to match the long-period M S and short-period m b observations. This¯exibility in modeling proves useful in comparing released FSU yields against predictions based on m b and M S .

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“…This value has been in popular use since then, if only because there was no compelling evidence for a different value. More recent work using digital short period instruments peaked at a higher frequency than the WWSSN short period (which is peaked at 1.4 htz) seems to indicate that t* could be substantially lower than 1 (e.g., Der, et al 1979), perhaps 0.5-0.6, and in some cases values of Thus, at f = 1 hz., allowing the range t* = 0.1 to t* 1.0 introduces a factor of %17 uncertainty in the amplitude. As the amplitudes of the P-waves are used to determine the yield, clearly the value of t* is of primary importance.…”

Section: Introductionmentioning

confidence: 96%

Time Domain Waveform Inversion of Short-Period P-Waves for Nuclear Explosion Source Time Functions

Ruff¹

1981

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Continue on reverie side If necessary and identify by block nuhb.r) :-This research investigates the estimation of the source time parameters of .-of undergrou-td nuclear explosions from the waveforms of short-period teleseismic P-waves. In the simplest consideration, and when the source yield is unconstrained, there are only three source parameters, two that describe the source time function and one for the delay time of the (p)P phase. There are, of course, indications that the (p)P arrival may not have the same amplitude or shape as the direct P arrival, presumably due to anelastic or nonlinear effects OD , ,% 1473 EDITION OF I NOV65 IS OB 'D E-E UNCLASSIFLEs SEC-. A-SECURITY CLASfSIIICATION OF THIS PAGE(II7, hent Enf'red) between tile shot point and thle surface. Thus, we will also consider the effect on the waveforms of a decreased (p)P amplitude. Another parameter :.7b which has a significant influence upon the observed waveforms; is t (t travel time/Q(av). Accordingly, the variation in the source parameter estimates due to a varying t will also be addressed.

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Results of the NTS Experiment: Phase II

Cited by 3 publications

References 18 publications

An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

Effects of Source RDP Models and Near-source Propagation: Implication for Seismic Yield Estimation

Time Domain Waveform Inversion of Short-Period P-Waves for Nuclear Explosion Source Time Functions

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