Seismic event identification by negative evidence

1974 ◽  
Vol 64 (6) ◽  
pp. 1671-1683
Author(s):  
Eva Elvers
Keyword(s):  
Signal Amplitude ◽  
False Alarms ◽  
Negative Evidence ◽  
Event Identification ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Short Period ◽  
Seismic Discrimination ◽  
Period Detection ◽  
Period Data

abstract A decision-theoretical model for seismic discrimination between earthquakes and underground nuclear explosions is developed. The influence of long- and short-period detection thresholds on the probabilities to identify explosions and to make false alarms is discussed. The model includes identification by negative evidence. This kind of identification is considered in the case when only short-period data are available and when the long-period signal amplitude is supposed to be less than or equal to the seismic noise amplitude. For one set of data—obtained from North American events at the Hagfors Observatory in Sweden—the applicability of the m(M)-method is increased about half a magnitude by including identification by negative evidence.

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.

Seismic source and transmission functions from underground nuclear explosions

1974 ◽  
Vol 64 (4) ◽  
pp. 1275-1293
Author(s):  
Ola Dahlman
Keyword(s):  
Seismic Source ◽  
Theoretical Models ◽  
Test Site ◽  
Distance Curve ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Short Period ◽  
Source Models ◽  
Function Models ◽  
Relative Differences

abstract A model is presented for the simultaneous detemination of the relative variation in transmission properties to different stations and of the relative differences between the seismic sources for closely spaced underground nuclear explosions recorded by a fixed seismological station network. The model is applied to short-period data reported from 24 globally distributed stations from 12 underground nuclear explosions with known yields at Nevada Test Site. The obtained transmission functions vary within a factor of 10 between the different stations and show a weak decrease with epicenter distance and little correlation with the Gutenberg amplitude-distance curve. The relative source functions for 10 explosions in tuff and rhyolite, with yields in the range 16 to 1,200 kt, are with good correlation proportional to explosion yield to 0.9. Two theoretical source-function models, one by Haskell (1967) and one by Mueller and Murphy (1971a), are compared with each other and they agree well for frequencies around 1 Hz and for yields in the range 3 to 300 kt. The Haskell model for tuff is modified to be more compatible with the models for salt, granite and alluvium. The Haskell model predicts stronger variation of the source functions with frequency and yield than the Mueller-Murphy model. The observed relative source functions are compared with the theoretical source functions obtained from the two source models. The agreement is fairly good but the relative decrease of the source functions at yields above 300 kt predicted by the theoretical models is not observed.

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.

scholarly journals Discrimination of teleseismic events in Central Asia with a local network of short period stations

1994 ◽  
Vol 37 (3) ◽  
Author(s):  
T. Tiira ◽  
M. Tarvainen
Keyword(s):  
Spectral Ratio ◽  
Difficult Problem ◽  
P Wave ◽  
Local Network ◽  
Separation Function ◽  
Data Set ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Discrimination Capability ◽  
Short Period

The difficult problem of distinguishing underground nuclear explosions from earthquakes at teleseismie distances was approached using short period seismic data from 6 stations in South and Central Finland. The events were nuclear tests mostly from the Semipalatinsk and Lop Nor test sites and earthquakes from adjacent areas. The magnitude range of the events was from 4.1 to 6.6. The features of the two classes of events were examined by computing spectral ratio, third moment of frequency (TMF) and complexity from P wave signals. The spectral discrimination parameters were extracted from spectra computed in 5 different ways in order to obtain all possible information even from weak events. The standard FFT spectra were computed from. raw data, after noise adaption and data adaption, from correlograms and using combinations of adaption and correlation: methods. This was done to employ not only the spectral differences of the events but also the temporal variation of energy and lack of it as a function of frequency. The optimum frequeney windows for spectral ratio and TMF were defined using stacked spectra of about 10 events from both classes. No single discriminant could classify all the events. Their performance varied significanfly for different stations, but on average the spectral discriminants had slightly higher discrimination capability than complexity. The distributions of all discriminants were studied and a group separation function was formed using an optimum set of discriminants. Instead of discriminant values their relative positions in the corresponding distributions of nuelear tests and earthquakes were used as inputs to the function. A weight for each discriminant was derived from the amount of overlap in the distributions of earthquakes and nuelear tests. All 75 events in the data set were correctly classified with the method. The testing was performed with a jack knife method to create an independent test data base

Event identification for test ban control

1970 ◽  
Vol 60 (5) ◽  
pp. 1521-1546 ◽  
Author(s):  
Ulf A. Ericsson
Keyword(s):  
Body Wave ◽  
The Political ◽  
False Alarms ◽  
Operating Characteristics ◽  
Event Identification ◽  
Long Period ◽  
Short Period ◽  
High Incidence ◽  
Test Ban

Abstract This paper describes a method to determine the usefulness of seismological event identification criteria for underground test ban control with or without on-site inspection. The method rests upon the notion that such control should be deterrent, by confronting a prospective violator with a certain disclosure probability at a politically determined level. Simple decision theory is then applied to the statistical properties of identification measures, to find the required compromise between a sufficient probability to disclose explosions and a not too high incidence of false alarms about earthquakes. A clean separation between the political requirements and the seismological capabilities is obtained. The latter are expressed by identification curves similar to the receiver operating characteristics curves employed in telecommunications analysis. The political requirements appear as geometrical conditions on the identification curves, expressing the required deterrence, the number of yearly explosions and earthquakes to be considered and the permitted number and quality of inspections, in the case of control with inspection. In the case of control without inspection, the acceptable rate of false alarms is included. The method also shows how identification criteria are most efficiently exploited. Application to some published observations shows identification by short-period body-wave magnitudes and long-period surface-wave magnitudes to be most efficient. It remains, however, to extend the analysis to weak events and low signal-to-noise ratios. For applications the acquisition of proper statistics is essential.

Short-period seismic energy radiation patterns from underground nuclear explosions and small-magnitude earthquakes

1967 ◽  
Vol 57 (2) ◽  
pp. 249-267 ◽  
Author(s):  
George H. Sutton ◽  
Walter Mitronovas ◽  
Paul W. Pomeroy
Keyword(s):  
United States ◽  
Surface Wave ◽  
Total Energy ◽  
Seismic Energy ◽  
The United States ◽  
Radiation Patterns ◽  
Small Magnitude ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Short Period

abstract Azimuthal radiation patterns of short-period (0.5-2.0 cps) seismic energy obtained from integrals of the seismograms from two underground nuclear explosions and two earthquakes are used to study the propagation and source characteristics of the Pg and Lg phases in the United States. In addition, the energy spectrum is divided into two bands, greater than and less than 1.4 cps, and the ratio of higher-to-lower-frequency energy is mapped to study the nature of propagation as a function of frequency. Both the total energy and the ratio show large fluctuations with azimuth and distance. However, a general correlation is found between the energy and ratio contours and the major tectonic provinces of the United States. This correlation is attributed to focusing, resulting from lateral variations in velocity and to regional differences in attenuation of the seismic energy. The range in the Q values across the United States, based on the assumption of symmetrical surface wave propagation, is from 200 to 1000, about a factor of 5. The transverse (T) component shows about the same total energy and ratio contour patterns as the vertical (Z) and longitudinal (L) components. Also, energy contour maps are similar to maps obtained using the maximum amplitudes of the Pg and Lg phases. For the events examined, it seems that the nature and distribution of tectonic features along the propagation path are more important in detemining the resultant radiation patterns than the initial conditions at the source. The particle motion at most stations does not give direct proof for the surface wave nature of the Pg and Lg phases, except that Pg tends to be longitudinal or mixed and Lg transverse or mixed.

scholarly journals Discriminating underground nuclear explosions leading to late-time radionuclide gas seeps

2020 ◽  
Author(s):  
Dylan Robert Harp ◽  
Suzanne Michelle Bourret ◽  
Philip H. Stauffer ◽  
Ed Michael Kwicklis
Keyword(s):  
Late Time ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Gas Seeps
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