These maps show how much damage a North Korean thermonuclear weapon could do to major American cities

ShutterstockAn illustration of a nuclear bomb exploding in a city.

Nuclear weapons may be humanity’s most terrifying creations, but most people would be hard-pressed to say what, exactly, such an explosion might do to their town or city.

To help the public get a handle on nuclear threats, Alex Wellerstein, a historian of science at Stevens Institute of Technology, created Nukemap: an interactive simulator that lets you set off a nuke anywhere on a world map.

A recent update even lets you predict where clouds of radioactive fallout might drift based on current weather.

“A realistic understanding of what nuclear weapons can and can’t do is necessary for any discussion that involves them,” Wellerstein previously told Business Insider. “People tend to have either wildly exaggerated views of the weapons, or wildly under-appreciate their power.”

Given rising public interest in North Korea’s intercontinental ballistic missile and nuclear test programs, Wellerstein recently added the isolated nation’s Sept. 3 underground blast — its most powerful yet — to a list of preset options in Nukemap.

The device may have been a thermonuclear bomb since it yielded an explosion of roughly 150 kilotons’ worth of TNT. That’s about 10 times as strong as the Hiroshima bomb blast of 1945, which inflicted some 150,000 casualties.

Although a nuclear-tipped North Korean missile couldn’t reach most of the continental US (yet), and casualties are notoriously tough to estimate, the images below show what could happen if a 150-kiloton warhead hit major American cities.

We chose the 10 following US cities because they are the most densely populated, and ranked them based on estimated loss of life.

We used Google Earth Pro to 3D-illustrate each scenario from Nukemap (which now has a convenient export feature to the app). Here's what the blast result colours mean:

Yellow: Fireball (0.9kms wide, 1.65kms high) -- In the area closest to the bomb's detonation site, flames would incinerate most buildings, objects, and people.

Green: Radiation (2kms wide) -- A nuclear bomb's gamma and other radiation are so intense in this zone that 50% or more of people die within 'several hours to several weeks,' according to Nukemap.

Blue-grey: Air blast (7.4kms wide) -- This shows a blast area with 5 pounds per square inch of pressure, which is powerful enough to collapse most residential buildings and rupture eardrums. 'Injuries are universal, fatalities are widespread,' Nukemap says.

Orange: Thermal radiation (10.5kms wide) -- This region is flooded with skin-scorching ultraviolet light, burning anyone within view of the blast. 'Third-degree burns extend throughout the layers of skin and are often painless because they destroy the pain nerves,' Nukemap says. 'They can cause severe scarring or disablement, and can require amputation.'

Tampa, Florida: 67,000 dead, 161,000 injured

The blasts we use to estimate deaths and injuries are 150-kiloton airbursts detonated about 1 mile above the ground. Nuclear weapons inflict the most damage as airbursts -- detonating the bombs hundreds or thousands of feet above a target spreads blast energy more efficiently. That makes a bomb more deadly than if it were detonated on the ground, since soil and structures can absorb or block some of that energy.

This 150-kiloton blast over Tampa could destroy:

- 54 hospitals and medical facilities

- Two fire stations

- 46 schools and educational facilities

- 74 churches, synagogues, mosques, and other places of worship

In the event of a 150-kiloton surface detonation in Tampa, the nearby city of St. Petersburg may get a deadly dose of fallout.

Airbursts create little radioactive fallout compared to surface blasts, which suck up debris, irradiate it, and spread it for hundreds of kilometres. An airburst strike isn't guaranteed, however, so we've included predictions of fallout clouds from ground detonations to provide a sense of how far this threat can travel.

We used Nukemap's estimation of where fallout would travel based on the prevailing winds on Thursday, October 12. We'll note, however, that fallout clouds usually take on a more complex shape due to high-altitude winds.

New Haven, Connecticut: 85,000 dead, 117,000 injured

This 150-kiloton blast over New Haven could destroy:

- 93 hospitals and medical facilities

- Seven fire stations

- 114 schools and educational facilities

- 160 churches, synagogues, mosques, and other places of worship

Parts of Long Island, Queens, and Brooklyn may not escape the deadly fallout effects of a ground attack on New Haven.

The strongest fallout would be toward the center (red), emitting about 1,000 rads per hour. The weakest fallout (yellow), emitting about 1 rad per hour, would spread the farthest.

Weaker fallout dissipates withing 24 hours, though radioactive debris close to a blast site can remain dangerous for 48 hours.

A person who stood outside in the 100-rad-per-hour zone (dark orange) for four hours would get 400 rads of radiation exposure -- enough to kill 50% of people by acute radiation syndrome.

Detroit, Michigan: 102,000 dead, 220,000 injured

This 150-kiloton blast over Detroit could destroy:

- 59 hospitals and medical facilities

- Seven fire stations

- 62 schools and educational facilities

- 56 churches, synagogues, mosques, and other places of worship

Evening winds would blow fallout debris 1160kms southwest of the city center.

Miami, Florida: 125,000 dead, 277,000 injured

This 150-kiloton blast over Miami could destroy:

- 50 hospitals and medical facilities

- Five fire stations

- 116 schools and educational facilities

- 97 churches, synagogues, mosques, and other places of worship

Radioactive fallout from a Miami ground blast might travel all the way across the tip of the Florida peninsula.

Honolulu, Hawaii: 151,000 dead, 165,000 injured

This 150-kiloton blast over Honolulu could destroy:

- 34 hospitals and medical facilities

- Six fire stations

- 147 schools and educational facilities

- 141 churches, synagogues, mosques, and other places of worship

Most fallout from a nuclear ground strike on Honolulu would blow into the Pacific Ocean.

Philadelphia, Pennsylvania: 301,000 dead, 465,000 injured

This 150-kiloton blast over Philadelphia could destroy:

- 113 hospitals and medical facilities

- 14 fire stations

- 181 schools and educational facilities

- 183 churches, synagogues, mosques, and other places of worship

Cities as distant as Baltimore could get sprayed with 1-rad-per-hour nuclear fallout from a ground blast in Philadelphia.

San Francisco, California: 305,000 dead, 361,000 injured

This 150-kiloton blast over San Francisco could destroy:

- 295 hospitals and medical facilities

- 10 fire stations

- 94 schools and educational facilities

- 47 churches, synagogues, mosques, and other places of worship

The area's East Bay region could get hit hard with intense fallout.

Boston, Massachusetts: 311,000 dead, 491,000 injured

This 150-kiloton blast over Boston could destroy:

- 79 hospitals and medical facilities

- 14 fire stations

- 190 schools and educational facilities

- 146 churches, synagogues, mosques, and other places of worship

Fallout from a Boston-based nuclear ground blast would penetrate deep into Massachusetts.

Chicago, Illinois: 351,000 dead, 492,000 injured

This 150-kiloton blast over Chicago could destroy:

- 98 hospitals and medical facilities

- 15 fire stations

- 263 schools and educational facilities

- 117 churches, synagogues, mosques, and other places of worship

Radioactive fallout from a blast on the ground in Chicago might spread across the western shores of Lake Michigan. Milwaukee could even be within range.

New York, New York: 959,000 dead, 1.5 million injured

This 150-kiloton blast over Manhattan could destroy:

- 226 hospitals and medical facilities

- 20 fire stations

- 432 schools and educational facilities

- 389 churches, synagogues, mosques, and other places of worship

A thick slice of central New Jersey, and perhaps cities as distant as Philadelphia, could get hit with dangerous fallout.

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