A man-made earthquake was detected Wednesday morning near the nuclear testing in North Korea, followed by a claim by the North Korean government that they had successfully tested their first hydrogen bomb.

Preliminary data on the test was a 5.1 magnitude earthquake, which is within the range of the 2013 atomic test by North Korea, itself the largest so far and the result of a 7 kt bomb test.

While the earthquake suggests there was a significant test, it’s still not certain how big, nor whether it was a hydrogen bomb or another attempt at a conventional atomic bomb.

It is not unusual for North Korea to overstate its military capabilities, but whatever the size of the test it’s almost certain to lead to more emergency UN meetings and more regional acrimony, once it’s clear what, exactly has happened.