North Korea holds nuclear bomb tests the way other countries hold parades. It's a festive occasion, really. Or it would be if North Korea allowed festiveness.
Anyway, when North Korea announces that it has detonated a nuclear device -- as it did just recently -- intelligence agencies around the world go to work assessing the situation. Because, as Trace Dominguez points out it today's DNews special report, it's not like we can take North Korea's word for these things.
The best way to detect nuclear explosions is by listening, but in a high-tech sort of way. Efforts to do so are coordinated by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), an international group that hopes to outlaw all nuclear test explosions.
To detect underground explosions, the CTBTO uses a network of 42 primary seismic activity stations around the world, backed up by 107 secondary stations. These stations, otherwise researching earthquake activity, can detect underground explosions anywhere on the planet. By crunching the numbers on direction, speed and type of seismic waves, they can pinpoint the test site with pretty good accuracy.
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For underwater tests, the CTBTO has a network of underwater hydroacoustic stations deployed around the planet. Sound travels much more efficiently through water, so CTBTO needs only 10 of these stations to do the trick. Any detonations up in the atmosphere cause specific sound patterns that can be detected by infrasound stations -- there are currently 49 of these in use.
All of these detection methods can be tripped up by natural phenomena -- earthquakes, volcanoes -- or even conventional explosions of sufficient intensity. So the CTBTO also scans for radioactive elements that escape into the atmosphere after nuclear tests, even those that take place underground or underwater.
Thanks to these various detection methods -- together with satellite imagery and old-school espionage techniques -- intelligence officials are generally up to speed already whenever North Korea announces that it has lit up another nuke. We keep an eye on those parades, too.
-- Glenn McDonald
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