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Take a 3D tour of North Korea’s nuclear test site, thanks to open source intelligence

Experts suspect North Korea’s sixth nuclear test is coming soon

Screen grab of 3D reconstruction of North Korea’s nuclear test site.
The James Martin Center for Nonproliferation Studies and The Nuclear Threat Initiative

Rumors have been flying around about the possibility of a North Korean nuclear test, thanks in part to activity at North Korea’s nuclear test site. If it is, this will be the sixth known nuclear test in 11 years — and a clear sign that North Korean arms development is continuing.

Now, because it’s hard to get information in or out of North Korea, it’s not clear that will actually test a nuclear bomb. The next big thing might also be a new missile, or just the opening of a new street.

But enough intelligence experts are worried that a test could happen soon that we should probably take the possibility seriously. Despite the difficulty in figuring out what’s going on within the North Korean border, there are some things we do know. For instance, where the test will likely take place — because each explosion can be seen on the same seismographs used to detect earthquakes. That’s helped analysts locate North Korea’s test site in the far northeast of the country, called Punggye-ri.

Using that seismic information, along with satellite images and high-resolution topography data released by both NASA and Japan’s Ministry of the Economy, Trade, and Industry, Jeffrey Lewis and his colleagues at the Monterey Institute of International Studies have created a 3D model of what they think the tunnels stretching beneath the mountains of Punggye-ri look like. They filled in visual details based on photos of our own tunnels here in the US, and an animation released by North Korea, Lewis says in an article for the Nuclear Threat Initiative in December 2016. You can navigate through the tunnels in the 3D reconstruction, and even walk through them in VR (instructions here).

North Korea is already known to have conducted five underground nuclear explosions at Punggye-ri, and they have generally increased in magnitude over the last 11 years. The most recent test in September 2016 was the largest yet, measured to be roughly equivalent to between 15 and 20 kilotons of TNT. (For scale, the blast caused by the Little Boy atomic bomb at Hiroshima was 15 kilotons, and the Fat Man implosion bomb was 21 kilotons.)

Some of the reconstruction is very educated guess work, Lewis told The Verge. “I can’t see the exact layout of the tunnels, but I can see where the explosions were inside from the seismic data, and I can see the bearing of the tunnel going in,” he says. “It’s a heavily constrained guess — we’re making some assumptions that you dig tunnels in straight lines, and you try to build them as efficiently as possible, and there are probably air shafts because people like to breathe.”

Watch how the Comprehensive Test Ban Treaty Organization detects a nuclear test:

The reconstruction leaves us with a couple alarming takeaways. First, Lewis notes that this model of the test complex appears to resemble declassified plans of our own nuclear test tunnels in the United States.

Second, it’s possible that there’s room for a lot more, and a lot bigger, tests under Mount Mantap.

It’s a plausible scenario, agree analysts writing for 38 North, a site run by the Johns Hopkins University School of Advanced International Studies. Mount Mantap provides enough overlaying rock to contain a blast of 282 kilotons — more than 10 times larger than the September 2016 explosion.

If North Korea does conduct a nuclear test, the Comprehensive Test Ban Treaty Organization’s international network of monitoring stations will detect the seismic waves — probably before Kim Jong Un even announces it. It won’t be a good day, but this data will give both government and open-source intelligence analysts another window into North Korea’s nuclear weapons program.