TOKYO – North Korea conducted its fifth nuclear test Friday. Here’s what we know so far:

What happened? Was it really a nuclear test, like North Korea claims, or was it just an earthquake?

Yes, it really was a nuclear test. The U.S. Geological Survey said the 5.3 magnitude seismic event it recorded had “explosion-like characteristics” and occurred where North Korea has detonated nuclear devices in the past. The North's first nuclear test was in 2006, and three have been carried out since Kim Jong Un took power in late 2011.

The quake had all the hallmarks of an explosion: the waveform is sudden, unlike an earthquake, and the depth is shallow. Plus, it happened at a known North Korean nuclear test site.

Here's a good explanation:

So this means they really have a nuclear warhead capable of being fitted on a long-range missile?

Not necessarily. North Korea announced that they had conducted a “nuclear explosion test” and that they had “standardized” a nuclear warhead. Just because they’re right on the former doesn’t mean they’re right on the latter.

Making a nuclear warhead small and light enough to attach to a missile is a difficult thing. Analysts and military chiefs think North Korea is well on the way to this capability, but there’s no sign they are there yet.

And, even if they do manage to “miniaturize” a nuclear device and stick it on a missile, there’s still a whole lot more steps to go through. A nuclear missile goes through extremes of heat and cold, shakes with vibrations during launch, and has to survive re-entry and hit its target. There’s a lot of things that can go wrong there.

But North Korea is making a lot of progress on its missile program. And its latest nuclear test does constitute another step down the path to what some people think is Pyongyang’s ultimate aim: being able to send a nuclear-tipped missile to the U.S. mainland.

If that was supposed to make me feel better, it hasn’t worked.

Sorry about that. But it’s true that this is a pretty scary situation. Kim Jong Un has made it clear that he’s determined to make North Korea a nuclear state – and he’s certainly shown no inclination to return to diplomatic negotiations aimed at persuading him to give up his weapons programs. The example always cited in North Korea analyst circles is Libya. Moammar Gaddafi gave up his nukes and look what happened to him.

But here's a nice graphic from the AFP news agency, putting North Korea's nuclear blasts in historical perspective:

Where are the Chinese when we need them?

Well, China is one country that has real leverage over North Korea, given that it provides economic aid to its neighbor and is its main route for trading with the rest of the world. China is always concerned about stability on its borders and has shown itself to prioritize keeping North Korea afloat over punishing Kim and his cronies.

That said, China seems pretty angry right now. North Korea fired three missiles on Monday while Chinese president Xi Jinping was hosting the Group of 20 summit in Hangzhou – and those missiles were technically capable of hitting Hangzhou. Not a subtle message.

On Friday, China’s foreign ministry released a statement condemning the test and saying it would work with the international community to urge North Korea to return to talks and give up its nukes.

The question now is whether China gets serious about enforcing sanctions.

Why is all this happening now?

Friday marks the “Day of the Foundation of the Republic” – a public holiday commemorating the 68th anniversary of the formation of the North Korean government by Kim Il Sung, North Korea’s founding president and the current leader’s grandfather. So it’s an important day for the regime.

But the test could also have been timed to push back at speculation that the regime is showing cracks after a handful of high-level defections, including the deputy ambassador to Britain and a couple of officials involved in making money for the Kim family.

It could also be a signal to the outside world that North Korea won’t be cowed. The United States will send an anti-missile battery to South Korea, and China has been supporting U.N. statements “deploring” North Korea’s recent actions. This is Kim Jong Un’s way of saying, “you’re not the boss of me.”


South Korean army soldiers ride on a military truck towing the artillery in Paju, South Korea, Friday, Sept. 9, 2016. (Im Byung-shik/Yonhap via AP)

What happens next?

Japanese "sniffer" planes went up Friday and there are probably some American ones flying around, too. They’ll be trying to measure radiation levels and capture gases so nuclear scientists can draw some conclusions about the test. “Let's see if any gases escape the test tunnel that would give away the nature of the device,” says Joshua Pollack, editor of the Nonproliferation Review.

Then, it will be back to the U.N. Security Council. We can expect meetings and harshly worded statements out of the United Nations, and a push for more sanctions. But the question is: What else can the international community do? There have been lots of new sanctions imposed this year – a crackdown on mineral exports, increased cargo inspections, tougher financial limitations – and clearly none of them have made Kim Jong Un stop with the missiles and the nuclear tests.

There aren’t many other options. A military strike is out – no one has any appetite for another war, and striking North Korea would probably unleash a volley of artillery by the North across the Demilitarized Zone at Seoul, home to 20 million people.

There’s another option: flooding North Korea with trade and investment and information and trying that way to convince them to change. But with all this defiance, there’s even less appetite for engagement than there is for military action.

How was the nuclear test announced to the North Koreans?

It's a classic North Korean announcement. This is Ri Chun Hee, a veteran newsreader who was brought out of retirement in January to announce the fourth nuclear test. When she shows up, you know it's big.

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