Ack, there is a reason I have a rule about blogging before a cup of coffee. In an earlier post, I made a math mistake (actually several, including a data entry error in a spread sheet).

Anyway, here is the data on the North Korean nuclear test, with very simple yield estimates.

The US Geological Survey, NORSAR and the Geophysical Survey of Russian Academy of Sciences all cluster in an Mb range of 4.5-5.0 — about 2-6 kilotons.

Author ID Magnitude Yield (kt)
NAO 11473033 4.5 2
NEIC 11473034 4.7 3
MOS 11473087 5.0 6

International Seismological Center

You’ll want to double check these — I am taking the day off.

I’d love to see what AFTAC says.

Update: The Project for the CTBT has a calculation from Martin Kalinowski:

The U.S. Geological Survey readings indicate a seismic body wave of magnitude of 4.7, which is larger as compared to the value of 4.1±0.1 in 2006. According a preliminary assessment by Martin Kalinowski of the University of Hamburg, this corresponds to an explosive yield of about 3 to 8 kilotons TNT equivalent with a most likely yield of 4 kt. In 2006. The yield of the 2006 test explosion was approximately 0.5 to 0.8 kt TNT equivalent.

Later Update: Here is Kalinowski’s fact sheet.