Earlier this week, an analysis from US intelligence officials revealed that North Korea has figured out how to fit nuclear warheads on missiles, and that the country may have up to 60 nuclear weapons. (Some independent experts estimate the figure is much smaller).

On Monday, North Korea issued a stark warning to the US: If you attack us, we will retaliate with nuclear weapons.

Several American cities, including New York, San Francisco, and Honolulu, have response plans for terrorist attacks, including so-called "dirty bombs" containing radioactive material. But few have publicized plans to deal with a real nuclear explosion.

One exception is Ventura County, a suburb about 60 miles northwest of Los Angeles. In 2003, the local government launched a PSA campaign called "Ready" that aims to educate Americans how to survive a nuclear attack. The goal, according to the campaign site, is to "increase the level of basic preparedness across the nation."

One of the more recent PSA videos is the one below, published in 2014. It opens with a short message from Ventura County public health officer Dr. Robert Levin, then cuts to a little girl with an ominous expression around the one-minute mark.

"Mom, I know you care about me," she says. "When I was five, you taught me how to stop, drop, and roll ... But what if something bigger happens?" The video then flashes to the girl walking down empty streets alone.



The Ventura County Health Care Agency has published several guides on what to do in the event of a nuclear bomb hitting the area. As the girl says in the video above, the agency's focus is to "go in, stay in, tune in."

The scenario assumes a terrorist-caused nuclear blast of about 10 kilotons' worth of TNT or less. Few people would survive within the immediate damage zone, which may extend up to one or two miles wide, but those outside would have a chance.

Brooke Buddemeier, a health physicist and radiation expert at Lawrence Livermore National Laboratory, previously told Business Insider that he likes Ventura County's PSAs because they're simple and easy to remember. "There is a ton of guidance and information out there," he said, but "it's kind of too hard to digest quickly."

Buddemeier said you'd have about 15 minutes — maybe a little bit longer, depending on how far away you are from the blast site — to get to the center of a building to avoid devastating exposure to radioactive fallout. Going below-ground is even better.

"Stay in, 12 to 24 hours, and tune in — try to use whatever communication tools you have. We’re getting better about being able to broadcast messages to cell phones, certainly the hand-cranked radio is a good idea — your car radio, if you’re in a parking garage with your car," he said.

The protection factor that various buildings, and locations within them, offer from the radioactive fallout of a nuclear blast. The higher the number, the greater the protection. Brooke Buddemeier/Lawrence Livermore National Laboratory

Buddemeier adds, however, that you shouldn't try to drive away or stay in your car for very long, because it can't really protect you. Today's vehicles are made of glass and very light metals, and offer almost no shielding from damaging radiation.

In large cities, hundreds of thousands of people would be at risk of potentially deadly exposure. But fallout casualties are preventable, Buddemeier said.

"All of those hundreds of thousands of people could prevent that exposure that would make them sick by sheltering. So, this has a huge impact: Knowing what to do after an event like this can literally save hundreds of thousands of people from radiation illness or fatalities," he said.