Technical Issues Related to the Comprehensive Nuclear Test Ban Treaty (2002) / Chapter Skim
Currently Skimming:
2. CTBT Monitoring Capability
2. CTBT Monitoring Capability
Pages 35-60
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 35... ...
They can include ground-based or space-based detectors of the characteristic flash of a nuclear explosion in the atmosphere or in space. information on nuclear testing in any environment potentially can also be provided by signals intelligence.
|
From page 36... ...
In ~ 974, the United States and the Soviet Union signed a bilateral Threshold Test Ban Treaty, banning underground nuclear tests of yield greater than 150 kt,l which involved extensive, close cooperation between the two states, and led to mutual understanding of the relationship between seismic magnitudes and yield of tamped underground nuclear explosions at their respective test sites3—a subject in longstanding dispute.4 As an example of informal cooperation, in 1977 the Soviet Union called the ahention of the United States to apparent South African preparations for an underground test in the Kalahari desert that had been missed by U.S. intelligence and that led to actions that prevented further activity at the site.
|
From page 37... ...
(d) Monitoring tor underground nuclear explosions usually entails: detecting signals recorded by each sensor of a particular network; associating into a single group the various signals (from different sensors)
|
From page 38... ...
In this report we assess monitoring capabilities in two ways: first, against nuclear tests conducted in the manner typical of past practice by the Nuclear-Weapon States, with no effort to conceal signals; and second, against various evasion scenarios intended to reduce and/or mask the signals of a nuclear test, and thus to prevent detection, identification, and attribution. There is a considerable degree of consensus among experts on the capability of various networks to monitor the first type of nuclear testing.
|
From page 39... ...
The utility of regional waves is demonstrated by experience with monitoring the 340 underground nuclear tests now known to have been conducted at the Semipalatinsk test site of the Soviet Union in East Kazakhstan during the period 1961-1989. These explosions were mostly documented at the time by Western seismologists using teleseismic signals.
|
From page 40... ...
Nuclear explosions by France and China prior to their signing the CTBT in September 1996 were widely recorded and nromntiv sharer terized, as were nuclear explosions of India and Pakistan in May ~ 998.10 ~~~ r-~ _,,, The transfer of IDC operations to Vienna in February 2000 has been associated with a significant change in practice, namely that the daily Reviewed Event Bulletin is no longer being made openly available to the research community. The IDC makes this bulletin (and all IMS data upon which it is based)
|
From page 41... ...
Table 2-2 lists yields as a function of decreasing magnitude for two representative magnitude-yield relationships in hard rock. The first LYNN is based on a relationship derived from extensive studies of Soviet underground nuclear testing at Semipalatinsk, Kazakhstan.
|
From page 42... ...
An explosion in an underground cavity also couples less efficiently, raising the question of evasive testing, discussed below. Figure 2-3 is important as indicating that the detection capability of the IMS primary seismic network is very significantly better than ~ kt for nuclear explosions conducted in a fashion typical of past underground nuclear testing (i.e., tamped and without efforts to reduce signals)
|
From page 43... ...
Methods first developed and applied to seismic events in Northwestern Europe and North America entail caTibration of IMS stations in these regions, by developing station-specific information on the traveltimes of regional waves arriving from sources at different distances and azimuths. These methods are now being extended to TMS stations in North Africa, the Middle East, and throughout Europe and Asia.
|
From page 44... ...
that occurred near the Novaya Zemlya test site on December 3l, 1992, which after much effort lasting several months led to an improved understanding of regional waves from sources near this site, and identification of the event as a very small earthquake. For regional waves, it appears that identification thresholds may not be significantly different from detection thresholds.
|
From page 45... ...
. Recent Russian papers documenting Soviet nuclear testing state that all underground tests at Novaya Zemlya and about half the underground tests at the Semipalatinsk test site in Kazakhstan resulted in release of radioactivity.
|
From page 46... ...
Therefore, evasive testing in the underground environment is generally regarded as the most serious challenge to monitoring efforts. In the era of monitoring underground nuclear tests principally by use of teleseismic signals, serious consideration had to be given to the concept of hiding a nuclear explosion by testing shortly after a large earthquake.
|
From page 47... ...
Can the limited practical experience with nuclear tests in cavities in salt, and very lowyield chemical explosions in hard rock, be extrapolated to predict the signals associated with nuclear testing in cavities in hard rock? Can a decoupling factor as high as 70 be attained in practice for yields significantly higher than subkiloton?
|
From page 48... ...
A country considering this approach would need to face some of the general problems outlined above for a cavity-decoupled nuclear test, including containment of radionuclides, imposition of secrecy on many people, and the capability of seismic monitoring. As for mine masking, chemical explosions in mines are typically ripple-fired and thus relatively inefficient at generating seismic signals compared to single explosions of the same total yield.
|
From page 49... ...
If their data along with data from the IMS primary seismic network were continuously examined for detections, the monitoring thresholds shown in Figure 2-2 (three station detection capability) would drop generally by about 0.25 magnitude units in Europe, Asia, and North Africa, and by about 0.5 magnitude units in 22 Both of these approaches are developed in National Research Council, Seismic Signalsfrom Mining Operations and the Comprehensive Test Ban Tread: Comments on a Draft Report by a Department of Energy Working Group, (Washington, DC: National Academy Press, 1998)
|
From page 50... ...
(2) More generally, detection capability can be improved by any augmentation of the IMS primary seismic network, to the extent that the additional data streams are continuously examined for detections, along with IMS data streams.
|
From page 51... ...
Its magnitude was about 3.5, which according to Table 2-2 would correspond to about ~ 00 tons tamped in hard rock, but corresponds to only a few tons yield for an explosion in water. At the IMS and non-IMS stations which recorded regional signals, correlation analysis permits clear seismic detection of the first and much smaller explosion, with yield about 26 This organization, with headquarters in the United Kingdom, has served research communities for decades with authoritative information on seismic source locations, estimated on the basis of detections reported voluntarily by hundreds of institutions operating seismic networks at the national or regional or local scale.
|
From page 52... ...
Monitoring Nuclear Explosions in the Atmosphere Nuclear tests in the atmosphere are best monitored with radionuclide, infrasound, and electromagnetic systems (including satellite-based optical detection, which is not part of the IMS)
|
From page 53... ...
Even though the radionucTide system can give proof of a nuclear explosion, backtracking the path of detected radionuclides is imprecise and does not provide an accurate estimate of the explosion location.32 Detection of the characteristic radionuclides of a nuclear explosion would trigger searches for confirming evidence, and information on the location, based on other IMS elements and on NTM. Monitoring Nuclear Explosions in Space Nuclear tests in space are best monitored with a variety of electromagnetic sensors, which also have a major role in monitoring explosions in the atmosphere.
|
From page 54... ...
Thus monitoring of space explosions depends on national technical means. Sensors involved in observing space explosions serve the dual role of treaty monitoring and detecting and locating nuclear explosions should they be used in actual combat.
|
From page 55... ...
The Role of Conficience-Building Measures and On-Site Inspections Confidence-building measures have already been mentioned in the context of potential problems with mine blasting. The CTBT also specifies that confidence-building measures assist in calibration of IMS stations; and that each State Party undertakes to cooperate with the CTBTO and other states party to the treaty, in carrying out chemical calibration explosions or to provide relevant information on chemical explosions planned for other purposes.
|
From page 56... ...
it provides a mechanism for the innocent to clear the record. Research and Development in Support of CTBT Monitoring Following the first CTBT negotiations, the need to develop a scientific basis for monitoring nuclear testing in all environments was explicitly recognized in ~ 959.
|
From page 57... ...
Events determined to be at this depth, or greater, can only be earthquakes. Conclusions on CTBT Monitoring Capability Detection, identification, and attribution of nuclear explosions rest on a combination of methods, some being deployed under the international Monitoring System established under the CTBT, some deployed as National Technical Means, and some relying on other methods of intelligence collection together with openly-available data not originally acquired for treaty monitoring.
|
From page 58... ...
And evaders must reckon with the high sensitivity of the global IMS, with the possibility of detection by regional seismic networks operated for scientific purposes, and with the chance that a higher-thanexpected yield will lead to detection because their cavity was sized for a smaller one. As for mine masking, chemical explosions in mines are typically ripple-f~red and thus relatively inefficient at generating seismic signals compared to single explosions of the same total yield.
|
From page 59... ...
CTBTMONITOR1NG CAPABILITY 59 It can be expected, in future decades, that monitoring capabilities wall significantly improve beyond those described here, as instrumentation, communications, and methods of analysis improve, as data archives expand and experience increases, and as the limited regions associated with serious evasion scenarios become the subject of close attention and better understanding.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.