Seismic Activity In North Korea Indicates Possible Fifth Nuclear Test

A magnitude 5.3 earthquake shook parts of northeastern North Korea Friday morning, possibly indicating North Korea has conducted a fifth nuclear test. South Korea and Japan's leadership immediately convened emergency meetings in response, with Seoul indicating the shallow depth of the quake indicates it's artificial and likely caused by a bomb detonating underground.

Analysts are still working on determining the yield of the potential bomb. The U.S. National Security Council says it's "aware of seismic activity on the Korean Peninsula" and "monitoring and continuing to assess the situation in close coordination with our regional partners."

This test, if confirmed, follows the January detonation of a device the North claimed was a hydrogen bomb, which led to wide condemnation and tougher international sanctions. Pyongyang previously tested at Punggye-ri in 2006, 2009 and 2013. The Associated Press reported that South Koreans' measurements indicated this would be the North's largest test thusfar.

North Korea is the only nation to conduct any nuclear tests in the 21st century. Friday's suspected test falls on a North Korean holiday: the 68th anniversary of North Korea's founding as a state.

The move comes against numerous calls from North Korea's allies and antagonists to refrain from more "provocative acts" following January's test and a February rocket launch.

In March, the United Nations Security Council passed Resolution 2270, which the U.S. calls the toughest package of sanctions on the North in two decades. China, a longtime ally of Pyongyang, signed on, signaling it too was weary of the North's threats on the security in the Northeast Asia region. Six months after those sanctions, North Korea is only increasing its missile launches and test frequency.

If the provocation-condemnation cycle seems like a Groundhog Day situation, it is. President Barack Obama acknowledged as much Thursday in a press conference before heading home from a trip to Laos, saying "when it comes to changing Pyongyang's behavior, it's tough."

"We will continue to put some of the toughest pressure North Korea has ever been under as a consequence of this behavior," Obama said. "Can I guarantee that it works? No. But it's the best options that we have available to us right now and we will continue to explore with all parties involved — including China — the means by which we can bring about a change in behavior."

With the latest test, talk of heightening and expanding the current sanctions surely will begin. But numerous rounds of sanctions so far only have seemed to strengthen Kim Jong Un's resolve to show off his military might. Alongside the nuclear test, the North Korean military has sent a number of projectiles and missiles into the sea since March and kept up its anti-American and anti-South Korean rhetoric.

Some Korean observers say that because Kim Jong Un's regime is underpinned by being a full-fledged nuclear state, no amount of financial squeeze will stop him.

"It's pretty incredible that we've come this far since the first nuclear crisis back in 1994" says Hahm Chaibong, head of the Asan Institute, a Seoul-based independent think tank. "Things just got worse and much worse, and we don't seem to see a way to reverse that trend."

Beyond casting out North Korea financially, other options include diplomatic ostracization: Katharine Moon, Brookings Institution's SK Korea Chair, has floated throwing North Korea out of the United Nations altogether, and written that nations with diplomatic ties with Pyongyang ought to pull their ambassadors. Asan Institute's Hahm says the "politically incorrect" option is all-out regime change, an option few are openly talking about just yet.

Haeryun Kang contributed to this story.