It is real.
Here is the short version of the detonation:
And the longer, archival footage version:
The National Interest had a story earlier this year about the October 30, 1961 event.
It's already the day after on Novaya Zemlya.
I think I read that the camera that filmed the first video was about 50 miles from the explosion, and it still got shaken pretty good by the shock wave.
