North Korea’s Nuclear Bomb Is Much Bigger than Previously Thought

Scientists looking anew at a 2017 North Korean nuclear test discovered that the explosion was likely about two-thirds more powerful than U.S. officials previously thought.

Earlier data put the yield somewhere between 30 and 300 kilotons; the U.S. intelligence community said 140 kilotons. That was already the most powerful device tested by North Korea, topping a 2016 test by about an order of magnitude. But a new look at seismological data suggests that the blast was between 148 and 328 kilotons, and probably around 250 kilotons.

That’s the conclusion from a group of researchers from the University of California, Santa Cruz; the Seismological Observatory of Costa Rica; and elsewhere, as published Monday in the Journal of Geophysical Research: Solid Earth. The team combined sound-wave data recorded during the blast with information about North Korean nuclear tests since 2006 and plugged it all into models showing how sound would travel through various types of rock at an estimated depth of 430 to 710 meters.

A 250-kiloton weapon would be about 16 times more powerful than the one that leveled Hiroshima. Detonated over Washington, D.C., it would have knocked down virtually every residential structure in the downtown area and inflicted third-degree burns on everyone within a three-mile radius.

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