- A nuclear attack on US soil would most likely target one of six cities, according to one expert: New York, Chicago, Houston, Los Angeles, San Francisco, or Washington, DC.
- Simulations show how each of the cities would be affected by a 15-kiloton blast — the kind detonated over Hiroshima.
- New York City would have the most fatalities. San Francisco would have the least.
It's the disaster for which no city is prepared: A nuclear bomb strikes the US, triggering a blinding flash of light, a giant orange fireball, building-toppling shockwaves, and dangerous nuclear fallout.
"There isn't a single jurisdiction in America that has anything approaching an adequate plan to deal with a nuclear detonation," Irwin Redlener, a public-health expert at Columbia University who specializes in disaster preparedness, told Business Insider.
The US Federal Emergency Management Agency has some simple advice for those catastrophic circumstances: Get inside, stay inside, and stay tuned.
But Redlener said the overall federal guidelines weren't enough.
He thinks even the six most likely targets — New York, Chicago, Houston, Los Angeles, San Francisco, and Washington, DC — wouldn't be ready with a sufficient response. Those cities would be particularly at risk, he said, because they're some of the largest and densest in the country. They're also home to critical infrastructure like energy plants, financial hubs, government facilities, and wireless transmission systems.
To help people understand how a nuke would affect large cities around the world, the nuclear-weapons historian Alex Wellerstein created an interactive tool called NukeMap that allows users to simulate the consequences based on customizable variables. Using updated Cold War models of nuclear explosions, Wellerstein's simulator can roughly predict the number of casualties and injuries from a nuclear bomb in a given place, big or small. The data is meant to be "evocative, not definitive," he wrote on the simulation website, since nuclear attacks are difficult to model.
The following images created using Wellerstein's simulation tool show how each of the six cities Redlener named would be affected by a 15-kiloton blast — the kind detonated over Hiroshima during World War II.
Wellerstein's NukeMap tool lets you detonate a hypothetical nuclear bomb over any major city in the world.
The simulations use data from the Oak Ridge National Laboratory (which is sponsored by the US Department of Energy) that shows how many people are likely to inhabit an area within a 24-hour period.
Wellerstein previously told Business Insider that his tool was meant to give people "a realistic understanding of what nuclear weapons can and can't do." But it comes with some limitations. The models, for instance, don't take into account weather conditions, which can affect the altitude of a mushroom cloud.
Here's a key to help you understand his tool:
Yellow: Fireball (590-foot radius) — Less than one-millionth of one second after a bomb exploded, it would emit a giant orange fireball filled with hot air and weapon debris. Any buildings, objects, and people caught within this radius would likely burst into flames.
Green: Radiation (0.74-mile radius) — Within at least 15 minutes of a blast, clouds of dust and sandlike radioactive particles — what's referred to as nuclear fallout — would reach the ground. Nuclear fallout can expose people to radiation poisoning, which can damage the body's cells and prove fatal. Wellerstein estimated that between 50 and 90% of people within this radius could die from the acute effects of radiation.
Blue-gray: Air blast (1.04-mile radius) — Air blasts are powerful enough to topple residential buildings. There would likely also be widespread injuries and fatalities within this radius.
Orange: Thermal radiation (1.18-mile radius) — People caught within this radius could experience third-degree burns, severe scarring, or disablement.
In the event of a 15-kiloton blast, 64,000 people in San Francisco could die — but that's the smallest number of any city on this list.
The city could also see about 172,00 injuries — more than Houston, LA, or Washington, DC.
If a fireball were to hit the city's Mission District, the Golden Gate Bridge would remain standing.
That blast would also miss two of the city's iconic waterside landmarks: the Ferry Building and Fisherman's Wharf.
If Houston were attacked, 90,000 people could die.
About 65,000 Houston residents could also be injured from a Hiroshima-like blast — the smallest total of injuries on this list.
The Johnson Space Center and Space Center Houston would both be safe from damage if the bomb were detonated near the city's downtown.
The Houston Zoo would likely escape air blasts as well.
In Los Angeles, 100,000 people would be killed.
About 151,000 people would be injured.
In the simulation below, LA's historic center is directly within the fireball, so everyone there would likely be killed.
Since Los Angeles is a sprawling city, Beverly Hills and neighborhoods like West Hollywood would be relatively safe in this simulation.
A 15-kiloton explosion could cause 120,000 deaths in Washington, DC.
Nearly 169,000 people would be injured.
The Pentagon and Ronald Reagan Airport might escape thermal radiation if a bomb were detonated over the National Mall.
The air blast could be strong enough to damage the White House and Washington Monument, according to Wellerstein's simulation.
In Chicago, a nuclear bomb could kill 151,000 people — almost as many as Houston's and San Francisco's death counts combined.
About 209,000 residents would be injured.
People at the University of Chicago and Willis Tower would be exposed to severe doses of radiation under this simulation, according to an explosion simulation above the South Loop neighborhood.
Those visiting the Cloud Gate sculpture (better known as "The Bean") could experience third-degree burns.
nuclear bomb dropped on New York City could kill 264,000 people — the most of any city on this list.
The city's total injury count would also be harrowing: About 512,000 people would be hurt.
If the blast were to strike lower Manhattan, most of Brooklyn and Queens would be safe, but some windows there might still shatter.
If the fireball were centered near SoHo, as shown above, Chinatown and the area around Washington Square Park would be exposed to radiation. Parts of the Financial District would also see thermal radiation.
Read next on Business Insider: If A Nuclear Bomb Is Dropped On Your City, Here's What You Should (And Shouldn't) Do To Stay Alive