Japan is reporting that North Korea has detonated a second nuke. But South Korea has not picked up seismic activity.

There is no report as to why Japan believes there has been a second explosion. Japan has a lot to worry about with North Korea right now.

UPDATE: FALSE ALARM!!
Turns out it was probably an earthquake. But like I wrote earlier, you can hardly blame Japan for being a little nervous these days.

Breitbart

A strong earthquake shook northern Japan on Wednesday and the Japanese government said it had detected tremors, leading it to suspect North Korea had conducted a second nuclear test.

However, Kyodo News quoted Japanese Prime Minister Shinzo Abe as saying he had no information to confirm a second North Korea test had taken place.

U.S. and South Korean monitors said they detected no new seismic activity Wednesday in North Korea.

In Washington, a Pentagon spokesman, Army Lt. Col. Brian Maka, said: “We have received no credible information to confirm any of that. No seismic activity has been detected on our part.”

White House spokesman Blair Jones said, “We have no independent confirmation of the second test.”