Theme 2: Events and their characterization

Theme 2: Events and their characterization

Events such as earthquakes, explosions or radionuclide releases produce signals and surface features that may be observed locally, regionally or globally. The events can be located in time and space and their characteristics can be estimated from the data that are 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 analyzed and interpreted. To ensure compliance with the Treaty, it is essential to understand the way that nuclear explosions generate the full variety of signals, as well as being familiar with any other seismic, acoustic or radionuclide signals that could be confused with those of a nuclear explosion.

The Treaty’s provision for on-site inspections depends on a priori knowledge of the observables (telltale signs) that can be expected after a nuclear test and how these might be identified as geophysical anomalies or testing artefacts. The increasing database of recorded events and historical observables also establishes an asset for research on a wide range of scientific applications.


  • Location of seismic events using realistic Earth models
  • Location of infrasound events using realistic atmospheric models
  • Constraining the source location of multiple atmospheric radionuclide observations
  • Estimating source characteristics using global, regional and local networks
  • Identification of well-characterized (ground truth) events
  • Observation and evaluation of the effects of nuclear accidents
  • Anthropogenic events and observables with relevance for on-site inspections
  • Civil applications of event characterization and on-site inspection procedures