Seismological monitoring of the Comprehensive Nuclear-Test-Ban Treaty

Seismological monitoring is one of the four technologies used by the Intern ational Monitoring System to verify compliance with the Comprehensive Nucle ar-Test-Ban Treaty. When fully operational, two seismic networks, one prima ry (50 stations) and one auxiliary (120 stations), will enable global detec tion and event characterisation of sources with equivalent magnitude as low as 4. The basic principles of seismological theory and practice applied to verification are summarised below, with particular emphasis on the new req uirements imposed by the needs of the Treaty.