I think it was natural and they came up with cover story to discredit Zeta's and the many internet groups that talk about earth geological events. Or you can take it at face value.

But what bothers me it that this news story about them testing explosions feels like it all of a sudden popped up. There was no build up it was just there all of a sudden. That could be just because I missed the news altogether concerning these tests. That's possible