North Korea says it tested a hydrogen bomb on Wednesday. The U.S. Geological Survey reported a 5.1 magnitude earthquake early Wednesday (UTC) near the site of previous North Korean nuclear tests. The test site is in the mountainous northeastern part of the country, near the border with China. North Korea announced the test on its state-run broadcast. The announcer said the test was “a self-defensive measure to thoroughly protect our nation’s autonomy.” A spokesman from the National Security Council in the United States says it is too soon to confirm North Korea’s claim. But if the claim is true, he says the U.S. “will respond appropriately to any and all North Korean provocations.” The last confirmed nuclear test by North Korea came in 2013. If it was a nuclear test, an analyst from Korea Defense Network says, it was more powerful than previous tests based on the seismic activity it produced.