D6 International monitoring and surveillance networks

Topic

Detecting a nuclear event anywhere in the world requires combining four technologies that observe distinct physical phenomena and reinforce one another. Seismic monitoring detects the mechanical waves that an underground detonation transmits through the Earth's crust, much like a seismograph detects an earthquake. Infrasound monitoring detects the very low-frequency waves generated in the atmosphere by the same type of energy release described in the first model of this catalog—specifically, when the event occurs in the open air.

Radionuclide monitoring detects characteristic radioactive particles or gases transported through the atmosphere—the very same cloud described by the fallout and regional dispersion models—while hydroacoustics detects underwater acoustic signals typical of an underwater detonation. Each technology has distinct strengths and limitations depending on the type of detonation and geographical conditions; consequently, no single technology performs well in every scenario.

What makes the entire network reliable is correlation: when multiple stations and technologies converge to indicate the same event, that coincidence allows for confirmation and localization with a level of confidence far greater than what any single technology could provide. For this reason, this model—which introduces four technologies observing distinct phenomena—serves as the technical foundation for the international treaty verification systems described later in this catalog.

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