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Over the years, a range of methods and technologies for monitoring of nuclear tests have been developed and implemented. A nuclear explosion manifests itself through a number of features, or signals, some of which can be observed at large distances from the source, while others are detectable at short distances only. Nuclear explosions generate radioactive gases and particles that are transported in the atmosphere to sensitive detectors at recording stations. Seismic, hydroacoustic and infrasound signals are generated by nuclear explosions underground, in the oceans and in the atmosphere, and are observed at stations around the globe designed for optimum detection of such signals. A monitoring system of some kind is needed for adequate verification of compliance with agreed limitations on nuclear testing. Work at NORSAR has focused on seismic monitoring, but in the context of the verification regime for the Comprehensive Nuclear-Test-Ban Treaty (CTBT), NORSAR is also responsible for the operation and maintenance of radionuclide and infrasound monitoring stations.
Three major events have put NORSAR in the forefront of technical development and progress in the field of nuclear test monitoring:
- The 1968 Government-to-Government agreement between the United States of America and Norway, which is still in force, laid the foundation for the design and testing of advanced seismic recording stations of the array type, resulting in the establishment and subsequent operation of the large-aperture NORSAR array and the smaller aperture NORES and ARCES arrays in Norway. Extensive work on methods for processing of data from such array stations was undertaken in parallel with station development, and research was conducted in many areas of relevance to nuclear test monitoring.
- The negotiation of the CTBT in the Genova-based Conference on Disarmament (CD) during 1994-1996 and this treaty’s elaborate verification arrangements represented an opportunity for the international community to take advantage of developments in nuclear test monitoring over several decades. In this respect, technical contributions from NORSAR researchers are well represented in the seismic monitoring component of the CTBT verification arrangements, in particular in areas such as station design and methods and procedures for data processing. The verification regime of the CTBT also leans heavily on technical work conducted between 1976 and 1996 in CD's Group of Scientific Experts in which NORSAR researchers participated in leading roles.
- Following Norway’s ratification of the CTBT in 1999, Norwegian authorities designated NORSAR as the National Data Centre for Norway for CTBT-related matters.
These web pages provide material on various aspects of NORSAR’s involvement in nuclear test monitoring, especially with regard to the CTBT, and snaphots are provided of some of the research advances that have been achieved in recent years.
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