Chapter 5: Assessing Monitoring Requirements
Chapter 5 Footnotes
1. See Chapter 1: "Effect of a Test Ban on Developing Nuclear Weapons.", pages I-1 to I-5.
2. A possible exception to this generalization is the explosion recorded by the U.S. Vela satellite on September 22, 1979. If this signal was produced by a first time test, it may have had a yield of less than three kilotons. See "The 22 September 1979 Event", Interagency Intelligence Memorandum, Directorate of Central Intelligence, December 1979, Obtained through the Freedom of Information Act by the Natural Resources Defense Council, Washington, D.C.
3. From "Nuclear Notebook" by R.S. Norris, The Bulletin of Atomic Scientists, p.48-49, May 1993.
4. Alternatively (from the perspective of the monitoring nation) these two questions could be asked as "What are we sure we will see?" and "What are we likely to miss?"
5. This network simulation was based on the requirement of detecting a P-wave with 90% probability at four or more seismic stations assuming a network maximum of 128 existing, planned, or proposed open global seismic stations. The results assume data availability of 95%, and the worst case noise at stations for which noise spectra are available. An average noise is associated with stations for which noise estimates are not available. The propagation models are region dependent. This figure is courtesy of Dr. John Claassen, Sandia National Laboratory, ("The Potential Monitoring Contribution of the Open Worldwide Networks", Report SAND 93-1931).
6. Because a seismic signal must be clearly detected before it is identified, the identification threshold is generally higher that the detection threshold. The standard rule-of-thumb to account for this difference is to add 0.5 magnitude units to the detection threshold.
7. The conversion of seismic magnitude to yield must be corrected to account for the difference in efficiency with which various parts of the Earth transmit seismic signals.
8. The most credible scenario for evading a seismic monitoring system is by "decoupling" the explosion in a large underground cavity. The size of the seismic signal produced by such muffling can be reduced by approximately a factor of 70 based on U.S. extrapolations from small explosions and Soviet experiments.
9. At this level, the limit is constrained by the feasibility of constructing an underground cavity of sufficient size and characteristics to decouple an explosion of this magnitude.
10. This network simulation was based on the requirement of detecting a P-wave with 10% probability at four or more seismic stations assuming a network of 128 of the either existing, planned, or proposed open global seismic stations. All other assumptions are the same as in Case 1. This figure is courtesy of Dr. John Claassen, Sandia National Laboratory, ("The Potential Monitoring Contribution of the Open Worldwide Networks", Report SAND 93-1931).
11. It can be argued that it would be difficult for a first time proliferator to have confidence in a hypothetical evasion scenario extrapolated over an order of magnitude, especially when they might have a device of uncertain yield, have never tested before, and are testing in a geological area with no prior experience.
12. As discussed in Chapter 1, it is unclear that there would be any technically compelling reason to test a first generation fission weapon of simple design.
13. For instance, the PLATO (Permanent Large Array of Terrestrial Observatories) concept developed in the National Academy of Sciences study Mission to Planet Earth (NAS, 1988) was an early version of the proposal. More recently the NASA-proposed FLINN (Fiducial Laboratories for an International Natural science Network) concept was examined in International Global Network of Fiducial Stations: Science and Implementations Issues (NAS, 1991).
14. See for example, "The Politics of Verification: Limiting the Testing of Nuclear Weapons" by Gregory E. van der Vink and Christopher Paine, Science & Global Security, vol. 3, pp.261-288, 1993. For example, the U.S. made false allegations of Soviet violations of the 150 kiloton limit of the 1974 Threshold Test Ban Treaty and a poor presentation of seismic monitoring capabilities during the ratification debate of the Threshold Test Ban Treaty and the Peaceful Nuclear Explosions Treaty.
Nuclear Testing and Nonproliferation
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