[struggle]

A bit strange. Looks like an initial explosion and a secondary, not a clear fade like the Indian and Paki explosions.

[Crazieman]

I would think if its an underground test, it would be an initial explosion, followed by the collapse of the surrounding ground.

[Afterguard]

I’ve always understood that a hydrogen detonation is a twin-pulse event. A smaller origination detonation followed by the main pulse. Possibly a failed hydrogen bomb test?