North Korea’s nuclear threats reached new heights when the country claimed to have successfully tested a hydrogen bomb underground on Tuesday night. Regional measurements confirmed a seismic event took place in North Korea, but the estimated size of the disruption cast doubt that the secretive nation had in fact detonated a thermonuclear weapon. Such a device would be hundreds of times more powerful than the bombs Pyongyang detonated during its previous three nuclear weapon tests. The estimated size of this disruption is about the same as those from previous tests, however.

Researchers can estimate the yield of a nuclear explosion based on the amplitude of the seismic waves it creates. Data collected at a Global Seismographic Network Station in Mudanjiang, China, however, suggest roughly a 3.4- to seven-kiloton blast, says Won-Young Kim, a senior research scientist at Columbia University’s Lamont–Doherty Earth Observatory. (A kiloton is equal to 1,000 tons of TNT.) Kim calculated this yield based on the magnitude 5.1 body waves the detonation sent rippling through Earth. This was more powerful than North Korea’s previous nuclear test, a 2.2- to four-kiloton blast in 2013 that set off waves equivalent to a magnitude 4.5 to 4.7 earthquake, but not nearly enough to confirm the use of a thermonuclear bomb.

To read more, click here.