GPS can locate hidden nuclear explosions

AUG 29, 2011

Physics Today

Bulletin of Atomic Scientists : When North Korea conducted its second known nuclear bomb test on 25 May 2009, the country’s leaders took extreme care to conceal the details of the event. They detonated the device a kilometer or so beneath the earth, so no radiation could escape and provide clues to the type and size of the bomb tested.

What the rest of the world knows about the bomb was learned from seismic waves. Tremors registering at 4.52 on the Richter scale suggested that the yield was on the order of a few kilotons.

Three researchers from Ohio State University detect a different unexpected signature however: an atmosphere shockwave spread out from the test site across the planet and high into the ionosphere. Writing in the Bulletin of Atomic Scientists they state that GPS radio waves suffer interference from atmospheric disturbances and by chance the North Korean test occur while they were testing equipment to reduce interference.

By timing when the shockwave from the test hit different GPS stations the three researchers were able to calculate the location of the initial explosion, which matched the seismic data. They suggest that the addition of GPS data to the monitoring stations spread about the world to watch for clandestine nuclear explosions, will strengthen the case for the US to ratify the Comprehensive Test Ban Treaty.