[JPX2011]

Interesting. Well then I’d have to agree with you that seems pretty weak for a successful test.

[The Antiyuppie]

“Interesting. Well then I’d have to agree with you that seems pretty weak for a successful test.”

The US had numerous successful tests that small. The size of the bang isn’t always indicative of how well it worked.

[Gideon7]

WaPo just put up an article estimating it at 20-30 KT.

https://www.washingtonpost.com/world/north-korea-conducts-fifth-nuclear-test-as-regime-celebrates-national-holiday/2016/09/08/9332c01d-6921-4fe3-8f68-c611dc59f5a9_story.html

I am guessing they are estimating that only a fraction of the energy goes into shaking the earth with the rest going out as heat, light, gamma rays, etc. (In other words the higher yields come from tables based on previous tests, not from a simple energy conversion formula.)