How can we know that North Korea and Iran (to name a few) are exploding nuclear weapons if no inspectors have ever been granted access to suspected nuclear sites in these countries?

How can we passively detect a secret detonation of a nuclear warhead? What are the telltale signs of a nuclear detonation?

  • $\begingroup$ I am surprise this question is not duplicated. I can't find any. $\endgroup$
    – TBBT
    Commented Sep 21, 2015 at 9:29
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    $\begingroup$ That's classified, but the US has a satellite network for air bursts and there is a seismic network for underground tests. Don't worry, they know when a nuke goes off. They even know how much energy the explosion had. :-) $\endgroup$
    – CuriousOne
    Commented Sep 21, 2015 at 9:30
  • $\begingroup$ What about the IAEA? $\endgroup$
    – user83391
    Commented Sep 21, 2015 at 9:31
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    $\begingroup$ I'm not sure about IAEA, but there is an organization called the Comprehensive Nuclear-Test-Ban Treaty Organization that are monitoring nuclear activities. $\endgroup$
    – TBBT
    Commented Sep 21, 2015 at 9:32
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    $\begingroup$ Please leave out personal feelings in questions "..are terrifying." Not everyone agrees, for one thing. $\endgroup$ Commented Sep 21, 2015 at 12:07

2 Answers 2


There are many ways to detect a nuclear explosion, and there are people working to detect it. The Comprehensive Nuclear-Test-Ban Treaty Organization or CTBTO is one such organization. They are using a global network called the International Monitoring System. This is capable of detecting any nuclear detonations anywhere on the Earth (underwater, or in the atmosphere, or deep underground).

First of all, please note that a nuclear explosion releases a lot of energy, and I mean a lot of energy. Ionizing radiation, shock-waves, and heat are all generated in a nuclear explosion.

Let's talk first about how to detect shock waves from a nuclear detonation. These waves can travel through the air, water, and ground at the relative speed of sound in each medium. The CTBTO use an Infrasound Monitoring System to detect shock waves traveling through the atmosphere. Infrasound is generated in exploding volcanoes, earthquakes, meteors, storms and auroras; nuclear, mining and large chemical explosions, as well as aircraft and rocket launches in the man-made arena. Nuclear generated shock waves in the air are easily detected since a nuclear explosion is much much more powerful then pretty much anything else in the natural world.

Underwater nuclear explosion can be detected using a Hydroacoustic Monitoring System. They are kind of microphones at the bottom of the ocean. Theses microphones also pick up sounds from underwater earthquakes, underwater volcanoes eruptions, submarines, whale, and of course, nuclear detonation. Like an above ground explosion, nothing beats nuclear generated shock waves in terms of intensity. Therefore, an underwater nuclear explosion is also quite easy to detect.

Underground nuclear detonations can be detected using seismometers. Seismometers are used mainly to detect earthquakes. Different from the Infrasound Monitoring System, which detects sounds in the air, seismometers detect sounds in the ground. Scientists have documented the various characteristics of shock waves created by earthquakes to volcanic activities to even planes crashing. Thus, if powerful unrecognized waves are detected, they can link their observations to nuclear detonation.

Shock waves can be detected by multiple sensors as described above. Scientists can use this result to triangulate and correctly pinpoint the site of a nuclear explosion. This is how we know that North Korea secretly detonated nuclear weapons in 2006, 2009, and 2013.

Lastly, to be sure if an explosion is nuclear, scientists need to confirm the presence of a radioactive dust cloud using Radionuclide Detection. However, in the case of a perfectly contained nuclear detonation, radioactive dust cannot be detected. Therefore, teams of inspectors have to be sent to the suspected site.

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    $\begingroup$ "is much much more powerful then pretty much anything else in the natural world." Really? I mean I don't know, whereas you have clearly done some research, but it surprises me that nukes out sound earthquakes or volcanic explosions. Thanks for the summary BTW: good piece of work. $\endgroup$ Commented Sep 21, 2015 at 10:11
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    $\begingroup$ @WetSavannaAnimalakaRodVance: Volcanoes are pretty annoying because a whole lot of hot molten rock suddenly moves up to our altitude. But it was already molten; there's not that much energy conversion. Earthquakes on the other hand convert mechanical stress into movement on a large scale. But the energy density is fairly limited compared to nuclear. Underground nuclear explosions suddenly create a lot of thermal energy in one specific position, and that is rather unique. $\endgroup$
    – MSalters
    Commented Sep 21, 2015 at 11:44
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    $\begingroup$ @WetSavannaAnimalakaRodVance MSalters explains clearly on the matter. Indeed, total energy output of a volcanic eruption or an earthquake is massive. However, energy releases in nuclear detonation is sudden and confined. $\endgroup$
    – TBBT
    Commented Sep 21, 2015 at 12:13
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    $\begingroup$ minutephysics has a good video about this: youtube.com/watch?v=daZ7IQFqPyA $\endgroup$
    – DLeh
    Commented Sep 21, 2015 at 14:41
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    $\begingroup$ @WetSavannaAnimalakaRodVance, the 1960 Valdiva earthquake released a half-million times as much energy as the largest nuclear weapon, but it did so over the course of ten minutes, spread out over 800 km of faultline. The 1980 Mt. St. Helens eruption, the most explosive in recorded history, released 24 MT of energy, but took 30 seconds to do so. The defining characteristic of nuclear weapons is how incredibly concentrated the energy release is. $\endgroup$
    – Mark
    Commented Sep 21, 2015 at 22:02

I've heard that the military has satellites orbiting earth with gamma detectors installed in them. The phenomenon of Gamma Ray Bursts was discovered when these satellites kept detecting gamma rays when no nuclear weapons were going off.

See here: https://en.wikipedia.org/wiki/Vela_(satellite)

  • $\begingroup$ Yes, but these won't detect anything if the explosion is underground. $\endgroup$
    – user10851
    Commented Nov 16, 2015 at 20:32

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