W.M.D.'s

Apparently, North Korea has tested a nuclear weapon.

China decries the act as a "brazen" development.
America condemns the "provocative act."
South Korea will react "sternly" with "appropriate measures."

I'm wondering what the actions this will provoke.
I'm wondering what a "stern" reaction is.
I'm wondering what "appropriate measures" look like.

And I don't think I like any of the answers any more than I like the reality that North Korea has tested a nuclear weapon.