Yield estimation using regional mb(Pn)

1990 ◽  
Vol 80 (3) ◽  
pp. 656-674 ◽  
Author(s):  
Eileen S. Vergino ◽  
Richard W. Mensing
Keyword(s):  
Large Population ◽  
Test Site ◽  
Yield Estimation ◽  
Nevada Test Site ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Threshold Test ◽  
Using Data ◽  
Yield Threshold ◽  
Test Ban

Abstract Seismic yield estimation at regional distances will become increasingly important in monitoring a Low-Yield Threshold Test Ban (LYTTB). In order to investigate seismic yield estimation using regional data, we have examined regional mb(Pn) values for a large population of Nevada Test Site (NTS) underground nuclear explosions that occurred in widely varying geologic media with a range of yields from less than 1 kt to 300 kt. Magnitude-yield relationships were developed using data from a set of pre-1985 events (calibration set). To obtain an independent estimate of the uncertainty in estimating yields of events at NTS using mb(Pn) alone, the calibrated relationships were applied to a set of post-1984 events (prediction set). We found that the average uncertainty in the yield estimate, based on a weighted combination of the yield estimates from the four Livermore NTS Network (LNN) seismic stations, is about 1.8 (at the 2σ level). If data are available from all four LNN stations, the uncertainty is about 1.7 (at the 2σ level). By including a term for the gas-filled porosity of the rock near the working point in the magnitude-yield relationship, we were able to develop a single relationship valid for events both above and below the water table, as well as those in alluvium and tuff. We have found, however, systematic differences in the relationships for events in Yucca Flat, Pahute Mesa, and Rainier Mesa.

Application of Nuttli's method to estimate yield of Nevada Test Site explosions recorded on Lawrence Livermore National Laboratory's Digital Seismic System

1988 ◽  
Vol 78 (5) ◽  
pp. 1759-1772
Author(s):  
H. J. Patton
Keyword(s):  
Source Region ◽  
Test Site ◽  
Nevada Test Site ◽  
Underground Nuclear Explosions ◽  
Threshold Test ◽  
Gas Porosity ◽  
Sigma Level ◽  
Source Regions ◽  
Test Ban ◽  
Seismic System

Abstract Methods utilizing Lg waves for estimating yields of underground nuclear explosions have attracted considerable attention for their accuracy, claims of portability, and suitability for low yield test ban verification. In this study, the method developed by Nuttli is applied to a large dataset of Nevada Test Site explosions recorded on Livermore's Digital Seismic System. The purpose was to check the reproducibility of Nuttli's results and to verify the accuracy of mb(Lg) to estimate yield at high and low yield levels. Portability of the method is examined from the perspective of variability of the magnitude-yield relations as a function of station site and source geology. The results of this study show accuracies of about a factor of 1.6 in yield at the two sigma level for shots below the water table in source regions exhibiting more or less uniform coupling. At Nevada Test Site, there are three such source regions: Pahute Mesa (areas 19 and 20), northern Yucca including areas 2 and 9, and southern Yucca including areas 3, 4, and 7. There is no apparent degradation in accuracies at low yields (1 to 10 kt). Variations in source coupling were observed as a function of shot location and as a function of the medium's gas porosity for shots in tuff. The effect of gas porosity was not observed for shots in alluvium, which have uniformly low coupling compared to shots in tuff. Variations in magnitude-yield relations were observed from station to station, while the four-station network-average magnitudes are more robust and agreed well with Nuttli's magnitude-yield relations. Thus, portability to other test sites should be considered guardedly optimistic, requiring geologic and seismic data related to coupling in each source region and sufficient numbers of stations (four or five) to estimate a robust network magnitude. Taken all together, the findings of this study lend support to this method as a viable means of monitoring a threshold test ban or low yield threshold test ban.

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 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 Importance of Regional Seismic Networks in Monitoring Nuclear Test-Ban Treaties

2019 ◽  
Vol 91 (2A) ◽  
pp. 573-580 ◽  
Author(s):  
Keith D. Koper
Keyword(s):  
Detection Threshold ◽  
Nuclear Test ◽  
Global Networks ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Using Data ◽  
Seismic Networks ◽  
Test Ban ◽  
Nuclear Test Ban

Abstract The Comprehensive Nuclear-Test-Ban Treaty (CTBT) prohibits the testing of all nuclear weapons, no matter how small. Although the CTBT is not yet in force, its verification is supported by the International Monitoring System (IMS), which is about 90% complete. Using IMS data, seismologists are able to detect well-coupled underground nuclear explosions with yields larger than ∼0.5–1  kt anywhere in the world with high confidence. Lowering the detection threshold significantly, say to yields of 10−4–10−1  kt fully coupled, will require augmenting IMS data with records from thousands of seismometers that are deployed in various regional, national, and global networks. It will also require routine analysis (detection, location, and characterization) of small seismic events (M 0–3) that are well recorded only at local distances (<150–200  km). This is the same problem faced by operators of regional seismic networks, who are tasked with developing earthquake catalogs as complete as possible without contamination from explosions and other nonearthquake sources. In the future, verification seismology is likely to become increasingly intertwined with the data, methods, and expertise of regional seismic network operators. Here, I highlight some of the important contributions to verification seismology that have recently been made using data recorded by regional seismic networks in North America, with a focus on small events recorded at local distances.

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