Experienced Weapons Team Reviews New Satellite Image for Clues

WASHINGTON (October 13, 2006) -- The Natural Resources Defense Council (NRDC) today released an exclusive satellite photograph of the suspected North Korean nuclear test site taken just two days before the test took place on October 9 (see figure 2 at An analysis of the new photo shows little observable activity at the site and no significant changes to buildings and roads compared with a commercial satellite photograph taken of the same site in early 2005 (see figure 3 at

"The two photos show that the North Koreans probably did not rush the test," said Matthew McKinzie, a nuclear physicist and NRDC consultant. "A February 2005 satellite photo suggests construction or excavation activity at this location, indicating that the North Koreans planned in advance for the test. Given that the yield of the nuclear test from seismic measurements appears to measure only about half a kiloton, something went wrong, but it wasn't due to haste."

The satellite photo of the suspected North Korean nuclear test location was taken by the Dulles, Virginia-based GeoEye's Orbview-3 satellite from 423 miles in space on October 7, 2006.

Regardless of its size or capability, the fact that North Korea detonated a nuclear device could trigger a nuclear arms race in Asia, and prompt Japan to overcome its historic "nuclear allergy" and begin to build a nuclear weapons force, McKinzie said. "We would disagree with the White House questioning whether the test was 'a big deal event.' The fact that it happened is, unfortunately, a very big deal."

Detailed View of Roads, Rails and Buildings

On October 3, the North Korean government announced it would conduct a nuclear weapons test. Less than a week later, the U.S. Geological Survey (USGS) determined that a seismic event of magnitude 4.2 was detected at 10:35:27 AM (October 9 local time; October 8, 9:35 PM EDT) at a mountainous location in North Korea's northeast province of Hamgyong-bukto (41.294°N, 129.134°E). The USGS reported that the epicenter of the seismic event had a location uncertainty of 6 miles (9.6 kilometers) (see

The epicenter of the October 9 seismic event lies along a deep valley, 28 miles (about 45 kilometers) northwest of the North Korean city of Kilchu. The North Korean Highway 80 extends 14.5 miles (about 23 km) from Kilchu to the town nearest the suspected test site, Punggye-ri (also referred to as Chaedok). A rail line also connects Kilchu to a train station at Punggye-ri. An unpaved road extends 12 miles (about 19 km) from Punggye-ri along the Namdae River in the valley north to Mant'ap mountain (see figure 1 at, which is derived from the 1:250,000 scale U.S. Joint Operations Graphics (JOG) military map series).

Along the length of road heading north through the valley from the town of Punggye-ri are several clusters of buildings, any of which may be related to the North Korean nuclear test site. The Orbview-3 photograph taken on October 7 (see figure 2 at captured the cluster of buildings closest to the seismic epicenter - about 2.5 miles (4 km) directly southwest. The accompanying figures contrast the Orbview-3 image (1 meter resolution, black & white) with a February 15, 2005, satellite photo of this site acquired by DigitalGlobe's QuickBird satellite (70 cm resolution, color) (see figure 3 at

The images have been annotated to highlight a cluster of building structures and parking area to the south and a winding, connecting road leading to a construction or excavation site to the north. In the QuickBird image from 2005 the snowy landscape contrasts with the muddy, cluttered-looking excavation site. In the Orbview-3 image the excavation site appears somewhat cleaned up and finished. An additional satellite image of the North Korean test site was obtained by DigitalGlobe on October 13, 2006

Why Not a Bigger Bang?

A number of preliminary estimates of the explosion's yield placed it at approximately 500 tons, or a half kiloton. (A kiloton is equivalent to 1,000 tons (2,000,000 pounds) of TNT.) There are reports that the North Koreans told the Chinese that they were going to test imminently and that the yield was going to be 4 kilotons. If this is true, then it is likely that the test was not completely successful.

The reason or reasons for this are unknown, but it is possible that the detonators igniting the high explosive that compresses the plutonium did not fire simultaneously and thus only produced a partial yield. By historical standards, even 4 kilotons is small for a first test, but the North Koreans may have deliberately kept it small for safety reasons. They might not have been able to contain a larger yield explosion inside the mountain tunnel. The table below puts the North Korean test in perspective.

The last nuclear test was on May 30, 1998, when Pakistan tested a 4-kiloton bomb. For more information about known nuclear tests worldwide, see the NRDC Nuclear Notebook column in the November/December 1998 issue of the Bulletin of Atomic Scientists at

NRDC Nuclear Experts Have Long Monitored North Korean Nuclear Activities

NRDC nuclear experts have been monitoring North Korea's nuclear program for years. Dr. McKinzie wrote a report in 2004 that detailed the impact of a nuclear bomb on South Korea. McKinzie also gave a presentation at the Carnegie Endowment for International Peace in January 2005 featuring satellite images of North Korean military installations (see

McKinzie's long-time colleague, Robert S. Norris, also has been following developments on the Korean peninsula. In his essay, "North Korea's nuclear program, 2005," in the May/June 2005 issue of the Bulletin of the Atomic Scientists, Dr. Norris and his co-author Hans M. Kristensen offer a tightly written overview of what was known about North Korea's nuclear capability at the time, the historical background, and the threats a nuclear-armed North Korea poses to the region and the rest of the world. (See