Events such as earthquakes, explosions and releases of radionuclides produce signals and surface features that may be observed locally, nationally, regionally or globally. Such events can be located in time and space, and their characteristics can be estimated based on the data products collected. This theme covers the characterization of the source, the signals being emitted, and what these reveal about the event and its environment. Only if the source is well characterized can its associated signals and anomalies be correctly analysed and interpreted. To ensure compliance with the Treaty, it is essential to understand the full extent of signals that may be generated by a nuclear explosion, as well as to be familiar with any other seismic, acoustic, radionuclide or other signals that could be confused with those from a nuclear explosion.
The Treaty’s provision for OSI depends upon knowledge of the observables that may be expected after a nuclear test and how these could be identified as geophysical, radioactive, temperature or other anomalies or artefacts of testing. While such observations can help distinguish between inactive and active nuclear weapon test sites, the data recorded by International Monitoring System (IMS) stations also make it possible to differentiate nuclear tests from other human made or natural events, thereby serving as a unique reservoir of knowledge for better informed policy making.
One of the challenges facing an inspection team at a historic test site is the need to distinguish and identify observables generated by historic underground nuclear explosions (those conducted before the nuclear testing moratorium) and those resulting from a more recent event. Factors to consider could include recognizing features that may indicate a decommissioned and decontaminated site or those that may suggest an active or reopened site. The types of expertise and capabilities required for these purposes need to be elaborated and could become relevant in the case of any contingency operations that would call upon CTBTO technological capabilities, if requested and if approved by the States Signatories.
Theme 2. Topics
T2.1 Characterization of Treaty-Relevant Events
T2.2 Challenges of On-Site Inspection
T2.3 Seismoacoustic Sources in Theory and Practice
T2.4 Atmospheric and Subsurface Radionuclide Background and Dispersion
T2.5 Historical Data from Nuclear Test Monitoring