The Korea Herald


Estimates differ on size of N.K. blast

By Korea Herald

Published : Feb. 14, 2013 - 20:50

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The extent of North Korea’s nuclear capability is in question with the yield of the device used in the test estimated at between 6 and 40 kilotons.

Following the detonation in Punggye-ri, North Hamgyeong Province on Tuesday, South Korea’s Institute of Geo-science and Mineral Resources detected seismic activity with a magnitude of 4.9.

The Ministry of National Defense later announced that the magnitude of the seismic waves created by the detonation places the yield of the device between 6 and 9 kilotons using the Comprehensive Nuclear Test Ban Treaty Organization’s calculation method.

Seoul’s calculations put the yield of Pyongyang’s latest nuclear device higher than that of those used in 2006 and 2009, but far short of the atomic bombs used against Japan in 1945.

North Korean devices used in the 2006 test had a yield of 1 kiloton, while that used in 2009 is estimated to have had between a 2 kiloton and 6 kiloton output. In comparison, the bombs dropped on Nagasaki and Hiroshima respectively had 21 kiloton and 16 kiloton yield.

The German state-run geological research institute BER, however, announced through its website on Wednesday that North Korea used a device estimated to have a yield of 40 kilotons in the latest nuclear test.

In comparison, the U.S. estimates the yield to have been “several kilotons” while Russia calibrated it to be more than 7 kilotons.

Although the exact yield of the device remains to be calibrated, experts estimate that a nuclear device with an output similar to that of the one dropped on Hiroshima would generate seismic activity that would measure 4.7 or 4.8 on the Richter scale.

In addition to the yield estimate, there are disparities in the scale of the seismic activity detected by different countries.

South Korea recorded a measure of 4.9 on the Richter scale, the U.S. Geological Survey measured it to be 5.1, while BER and Japan’s measurements came in at 5.2.

For natural earthquakes, increase of 1 on the Richter scale represents a 32-fold rise in the energy released in a seismic event. For man-made seismic activity, a 10-fold increase in energy release is considered necessary to raise the Richter measurement by 1.

The exact yield of Pyongyang’s latest device will have significant implications for countries involved in the denuclearization of the Korean Peninsula.

Seoul’s maximum estimate of 7 kilotons, according to the Defense Ministry, would mean that Pyongyang has yet to develop devices that can be weaponized. Germany’s estimate, however, would imply that Pyongyang’s nuclear capabilities are closer to its claims of being a nuclear power.

By Choi He-suk (