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.

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.

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.

Network-averaged teleseismic P-wave spectra for underground explosions. Part I. Definitions and examples

1989 ◽  
Vol 79 (1) ◽  
pp. 141-155
Author(s):  
J. R. Murphy ◽  
B. W. Barker ◽  
A. O'Donnell
Keyword(s):  
Test Site ◽  
P Wave ◽  
Spectral Amplitude ◽  
Scaling Analysis ◽  
Wave Spectra ◽  
Correction Factors ◽  
Station Correction ◽  
Wave Source ◽  
Amplitude Data ◽  
Short Period

Abstract A new procedure is described for estimating network-averaged P-wave spectra from short-period, teleseismic recordings of explosions. This procedure is then applied to a large sample of approximately 1000 digitized Nevada Test Site (NTS) explosion seismograms to simultaneously derive estimates of frequency-dependent station correction factors and network-averaged P-wave spectra for each of the 50 selected explosions. An analysis of the station correction factors is then presented which demonstrates that the Veith-Clawson (1972) B(Δ) curve for time domain mb adequately describes the teleseismic distance dependence of the spectral amplitude data over the entire short-period band extending from 0.50 to 2.25 Hz. A simplified scaling analysis of the network-averaged spectra is described and used to confirm the fact that the P-wave source coupling characteristics below the water table at the Yucca Flat and Pahute Mesa testing areas of NTS are essentially identical. We conclude that this new spectral measure can provide robust means for comparing different explosion testing areas.

Short-period Lg magnitudes: Instrument, attenuation, and source effects

1983 ◽  
Vol 73 (6A) ◽  
pp. 1835-1850
Author(s):  
Robert B. Herrmann ◽  
Andrzej Kijko
Keyword(s):  
United States ◽  
Epicentral Distance ◽  
P Wave ◽  
Magnitude Scale ◽  
Source Effects ◽  
Anelastic Attenuation ◽  
Basic Conclusion ◽  
Short Period ◽  
Central United States ◽  
Definition Of

Abstract The applicaton of the Nutli (1973) definition of the mbLg magnitude to instruments and wave periods other than the short-period WWSSN seismograph is examined. The basic conclusion is that the Nuttli (1973) definition is applicable to a wider range of seismic instruments if the log10(A/T) term is replaced by log10A. For consistency and precision, the notation mbLg should be applied only to magnitudes based upon 1.0 Hz observations. The mbLg magnitude definition was constrained to be consistent with teleseismic P-wave mb estimates from four Central United States earthquakes. In general, for measurements made at a frequency f, the notation mLg(f) should be used, where m L g ( f ) = 2.94 + 0.833 log ⁡ 10 ( r / 10 ) + 0.4342 γ r + log ⁡ 10 A , and r is the epicentral distance in kilometers, γ is the coefficient of anelastic attenuation, and A is the reduced ground amplitude in microns. Given its stability when estimated from different instruments, the mLg(f) magnitude is an optimum choice for an easily applied, standard magnitude scale for use in regional seismic studies.

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.

Lg magnitudes and yield estimates for underground Novaya Zemlya nuclear explosions

1988 ◽  
Vol 78 (2) ◽  
pp. 873-884
Author(s):  
Otto W. Nuttli
Keyword(s):  
Large Range ◽  
Test Site ◽  
Nevada Test Site ◽  
P Values ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Novaya Zemlya ◽  
Short Period ◽  
Lg Wave ◽  
Range Of Values

Abstract Lg-wave amplitudes of 30 Novaya Zemlya underground nuclear explosions, as recorded by short-period seismographs in Denmark, Finland, Germany, Norway, Spitsbergen, and Sweden, are used to determine mb(Lg) values. Assuming that the mb(Lg) versus explosion yield relation derived from Nevada Test Site data applies to all continental areas, the yields of the explosions are estimated. They cover a large range of values, from 2.5 to 4900 kt. The largest explosion since April 1976 had an estimated yield of 145 kt. The mb(Lg) values, when subtracted from the mb(P) values, can be used to estimate the mb(P) bias between two test sites. In this way, the mb(P) bias between Novaya Zemlya and the Nevada Test Site is estimated to be 0.20 magnitude units.

Theoretical response of a seismograph at Yellowknife, Northwest Territories, to an underground explosion at the Nevada test site

1969 ◽  
Vol 6 (3) ◽  
pp. 517-520 ◽  
Author(s):  
H. S. Hasegawa ◽  
K. Whitham
Keyword(s):  
Northwest Territories ◽  
Vertical Component ◽  
Test Site ◽  
Underground Explosion ◽  
Nevada Test Site ◽  
Short Period

A comparison of the theoretical response of the short-period, vertical-component seismograph at Yellowknife to an underground explosion originating at the Nevada Test Site with a real seismogram indicates that the prime contributors to complexity are likely due to the following: (a) complex crustal reverberations at the N.T.S., (b) different phase arrivals, and (c) signal-generated noise at Yellow knife.

Full-waveform matching of VP and VS models from surface waves

2019 ◽  
Vol 218 (3) ◽  
pp. 1873-1891 ◽  
Author(s):  
Farbod Khosro Anjom ◽  
Daniela Teodor ◽  
Cesare Comina ◽  
Romain Brossier ◽  
Jean Virieux ◽  
...  
Keyword(s):  
Surface Waves ◽  
Wave Velocity ◽  
Real Data ◽  
Test Site ◽  
P Wave ◽  
S Wave ◽  
Surface Wave Dispersion ◽  
Data Set ◽  
Near Surface ◽  
Velocity Models

SUMMARY The analysis of surface wave dispersion curves (DCs) is widely used for near-surface S-wave velocity (VS) reconstruction. However, a comprehensive characterization of the near-surface requires also the estimation of P-wave velocity (VP). We focus on the estimation of both VS and VP models from surface waves using a direct data transform approach. We estimate a relationship between the wavelength of the fundamental mode of surface waves and the investigation depth and we use it to directly transform the DCs into VS and VP models in laterally varying sites. We apply the workflow to a real data set acquired on a known test site. The accuracy of such reconstruction is validated by a waveform comparison between field data and synthetic data obtained by performing elastic numerical simulations on the estimated VP and VS models. The uncertainties on the estimated velocity models are also computed.

Monitoring nuclear test sites with GERESS

1996 ◽  
Vol 86 (1A) ◽  
pp. 172-190
Author(s):  
M. L. Jost ◽  
J. Schweitzer ◽  
H.-P. Harjes
Keyword(s):  
Test Site ◽  
Nevada Test Site ◽  
Data Set ◽  
Detection Thresholds ◽  
Novaya Zemlya ◽  
Tuamotu Archipelago ◽  
The Future ◽  
Nuclear Tests ◽  
Lop Nor ◽  
Eastern Kazakhstan

Abstract Since the installation of the 25-element GERman Experimental Seismic System (GERESS) array in southeastern Germany in 1990, 36 presumed nuclear tests were recorded by this system: 16 from Nevada, 12 from the Tuamotu Archipelago, 7 from Lop Nor, and 1 from Novaya Zemlya. Also, a chemical calibration experiment at Nevada Test Site (NPE) was observed at the array in 1993. In addition, two presumed nuclear events from Nevada, four from the Tuamotu Archipelago, and six from eastern Kazakhstan were recorded on temporary stations close to the GERESS array during the site survey (1988 to 1989). These latter 12 events were carefully included in this study to broaden the data set. This has been done since the number of underground nuclear tests observable at the GERESS site is not expected to increase significantly in the future because most nuclear powers have adhered to a moratorium on nuclear testing. In addition, we also do not expect that peaceful nuclear explosions (PNE) will be detonated in the future due to reasons of environmental hazard. Concentrating on Nevada Test Site and the Tuamotu Archipelago, a cross-correlation method and a cluster analysis indicate subgroups of the data. These empirical methods clearly discriminate presumed nuclear tests on the islands of Mururoa and Fangataufa. In addition, detection thresholds at GERESS were estimated based on bodywave magnitudes published by ISC: mb = 4.3 for the Nevada Test Site, mb = 3.9 for the Tuamotu Archipelago, mb = 4.6 for Lop Nor, mb = 4.3 for Novaya Zemlya, and mb = 4.4 for eastern Kazakhstan. Clearly, these path-specific detection thresholds deviate substantially from those derived from global amplitude-distance relations (i.e., Gutenberg-Richter). This indicates that a network of seismic stations used for global monitoring purposes may need careful calibration.

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