The subject of this NATO Advanced Study Institute was seismic monitoring under a nuclear test ban - an application of scienti fic knowledge and modern technology for a political purpose. The international political objective of a comprehensive nuclear test ban provided in turn the motivation for our technical and scientific discussions. In order to obtain a historical perspec tive on the progress of the work towards a comprehensive test-ban treaty (CTB), it is necessary to go back to 1958, when a confer ence of scientific experts in Geneva made the first steps toward an international seismic monitoring system. However, agreement on actual capabilities of a monitoring system for verifying compliance with such a treaty was not achieved, and thus the conference did not lead to immediate political results. After the Partial Test Ban Treaty of 1963, which banned nuclear explosions in the atmosphere, outer space and under the seas, renewed interest in the seismological verification of a CTB took place. A number of countries initiated large-scale research efforts toward detecting and identifying underground nuclear explosions, and it was in this context that the large aperture seismic arrays NORSAR and LASA were established. This type of development resulted in excellent seismic data in digital form and was thus of great irnprotance to the seismological com munity.

An international treaty banning the testing of any nuclear device in any environment - a comprehensive test ban treaty (CTBT) - has been on the political agenda for nearly 40 years. Objections to a CTBT have been political, technical, or a combination of both. However, the possibilities seem better after the end of the Cold War. In the prevailing, cooperative disarmament climate a CTBT appears likely to be approved by most countries in 1996. Hence the great current interest in monitoring technologies and capabilities. Such issues are comprehensively addressed here, a preamble being devoted to the political developments and setbacks over the past 40 years. Since seismic means are considered the dominant monitoring element, they are explored in detail. Contributions cover network deployments, advanced signal processing, wave propagation in heterogeneous media, and seismic source representations, and a variety of techniques for source classification (including neural networks). Complementary monitoring techniques, such as hydroacoustics, radionuclides and infrasound, are also summarised. The IAEA operation for monitoring compliance with the Non-Proliferation Treaty is also presented. The book also includes eyewitness accounts of the Soviet 50 Mt megabomb development and test, as well as the efforts made by the state to monitor the nuclear test programmes of the western powers. Includes some 33 articles written by distinguished scientists active in CTBT monitoring research for decades.

Reprint from Pure and Applied Geophysics (PAGEOPH), Volume 147 (1996), No. 2

The Workshop on the Seismicity and Seismic Risk in the Off shore North Sea Area was intended to bring together experts from a variety of disciplines as well as interest groups with involve ment in siting, design and construction of offshore structures in the region. Participants came from the fields of geology, seismology, oceanography, geotechnical and structural engineering and risk analysis. The wide range of participant affiliations included institutes, Observatories, universities, oil companies, consultants and insurance firms. All nationalities around the North Sea were present, in addition to some experts from outside the region. All participants were present on the basis of personal invitation. The idea of organizing the Workshop stemmed from conside- tions, such as: the rapidly increasing material and personel investments and versatility of type of structures in the basin.during the past decade; - the present-day important role Jf the North Sea oil and gas production in the economy of Western Europe; and - the increase of potential environmental risks in the region. Although devastating earthquakes are almost unknown in the area and seismic hazard is not great, the seismic risk grows with the growing size and number of structures in the area. The study of the potential seismic risks, therefore, cannot be neglected any more. The siting and design of offshore platforms and submarine pipelines are controlled by the degree of their vulnerability as well as the seismic hazard. in the region.