On Sunday, October 08, 2006 at 8:35:27 PM (EST), North Korea apparently detonated a nuclear device. This registered as a seismic event in South Korea and beyond. Ignoring the geo-political consequences of this event, let's look at what data currently exists.
The Announced Location
On October 3rd, the North Korean government announced the location of its long threatened nuclear test. Global Security.org has since published an article with that location: 41°16'00"N 129°06'00"E. That test site is easily found with Google Maps:
Announced Location
The Actual Location
According to the USGS the location of yesterday's North Korean test was 41.294°N, 129.134°E. That location has a horizontal uncertainty of 9.6 kilometers (5.9 miles).
Location in North Korea.
Actual Location
The interesting part of the incident is that the location has virtually zero proability of seismic activity. Here is a map of the region provided by the USGS that displays this fact.
Seismic Hazard Map
The Comparison
According to the Latitude/Longitude Distance Calculation applet from the Northern Arizona University:
Distance between 41 16' 0"N 129 6' 0"E and 41.294N 129.134E is
2.5880 statute miles. This calculation assumes the earth is a perfect sphere
with a radius of 3963.1 statute miles.
This puts the announced location of the test well within the uncertainty radius of the actual event.
Distance Comparison (Click to Enlarge)
The Venue
Articles prior to the actual test suggested that North Korea would use a mine shaft deep underground to test the nuke. The satellite evidence suggests that they used that or some form of a facility under a mountain to do so.
The Explosion
There are conflicting reports as to the strength of the test. The official North Korean source reported that the explosion was equivalent to 1000 Tons of TNT. According to an AP article, the Russian Defense Minister Sergei Ivanov said “it was far more powerful, equivalent to 5,000 to 15,000 tons of TNT.” The USGS extrapolation places the explosion at 550 tons of TNT.
However, if the USGS figured is compared with bombs of the past, it is a tiny device. According to Hyper Text Book The bomb dropped on Hiroshima was approximately 15,000 tons of TNT and the Nagasaki bomb was about 20,000 tons. In the case of the latter bomb, it had a fireball with a radius of .2 km (1/10 of a mile).
Note: If the device was detonated inside a large cavern, this would have a damping effect on the shockwaves. The actual yield could be much larger than current guess of 550 Tons and closer to either the stated yield or the Russian estimate. The Washington Post has a great FAQ about detecting nuclear blasts. I also wrote another article about detecting underground detonations.
The Investigation
The surprising part is that only the Russians and North Koreans are sure that it was actually a nuclear weapon. This could be an extremely convincing hoax acting as a deterrent and trying to buy some international leverage.
Updated 10-10-06 - If you have any additional information or insight please comment below.
