........ published in NEWSLETTER # 57
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........ published in NEWSLETTER # 57
MONITORING A COMPREHENSIVE TEST BAN TREATY
by Professor E.S. Husebye, University, Bergen (Norway)
The issue of a Comprehensive Test Ban Treaty (CTBT) has been on the U.N. political agenda for almost 40 years. As this is being written, it is an active topic: the Conference on Disarmament (CD) is working to draft such a Treaty which will then be made available for any nation that wishes to sign. Negotiation of a CTBT was explicitly stated as a goal when the Non-Proliferation Treaty was recently renewed indefinitely. In the technical field, the Group of Scientific Experts (GSE), convened by the CD, is conducting its third Technical Test, known as GSETT-3. The intention of GSETT-3 is to produce a prototype system for seismological monitoring that, among other goals, can serve as a practical example for the negotiating community of what is technically feasible. Also, the CD has established special working groups on the non-seismic techniques of hydroacoustic, radionuclide, and infrasound monitoring, and on on-site inspection methods, as part of the process of drafting a CTBT.
In this book (NATO ASI SERIES E303), the main focus is on the scientific and technical aspects of seismic monitoring of underground nuclear tests. This particular topic was chosen because it is one of the main technical challenges of monitoring. However, we have also included political issues and non-seismic techniques. The overview section includes contributions about political background and developments, and technical reviews of the latest practice in testing and non-seismic monitoring methods, including on-site inspection. It must be born in mind that current testing practice is to contain tests underground, and any compliance system must contain provisions for monitoring such events; hence, the focus on seismic monitoring in this book.
Also, a CTBT is intended to be multilateral and worldwide rather than bilateral or trilateral, thus any monitoring system must cover the globe and all environments: underground, underwater, atmosphere and space. Second, and technically much more important, all tests of any size would be banned under a CTBT, including small events. To monitor small underground events, it is necessary to record seismograms at relatively short ranges of 100-2000 km from the event, known in seismology as the regional distance range. This is a major change from current operational procedure in monitoring which is based on monitoring at distances beyond 2000 km, the teleseismic distance range.
The structure of this book is designed to cover the problems listed above. Following the initial overview section on Principal Political and Technical Test Ban Issues, a section on Monitoring Technologies gives a summary of all the methods being considered for monitoring a CTBT. Following this, the section "Explosion and Earthquake Source Modelling" examines underground nuclear tests and other disturbances as seismic sources. This examination includes the problem of decoupling (i.e., decoupling the explosion from the solid earth by detonating it in a cavity), which is probably the most credible way in which monitoring might be defeated. Following this, the problem of monitoring such seismic sources is discussed in some detail, with sections on Seismic Networks, including detection and location of seismic events; Signal Processing and Seismic Wave Propagation, covering analysis methods specific to the seismic arrays used in regional monitoring and propagation of seismic waves at regional distances; and Seismic Source Discrimination Technologies, especially at regional distances. These topics cover three of the four classical steps of monitoring, namely, detection, location, and discrimination; signal analysis and wave propagation are included as the scientific basis for accomplishing this. A review paper on existing methods of yield estimation is included in the section on source modelling, but this topic has not been treated at greater length because in a CTBT, all tests of any size will be proscribed.
Reference books: 2-4, C144, C266, C74, E303