The Impact of a North Korean Nuclear Weapon on the United States

Thanks to Alex Wallerstein and his Nukemap, we can get a sense of the impact of a current North Korean nuclear weapon on the United States should a ballistic missile penetrate U.S. airspace.

The first thing that you need to know about nuclear weapons is that they can be detonated in four ways; an air burst where the device is detonated at less than 30 km above the earth's surface, surface burst where the weapon is detonated at or slightly above the earth's surface, subsurface burst where the detonation takes place below the surface of the land or water or a high altitude burst where the weapon is detonated at an altitude above 30 km above the earth's surface.  For a ground burst or low altitude atmospheric burst, there are three types of destructive energy created:

1.) 50 percent of the energy is created by the blast itself.

2.) 35 percent of the energy is thermal radiation including infrared, visible, ultraviolet and soft x-ray.

3.) 15 percent of the energy is nuclear radiation including 5 percent ionizing radiation made up of neutrons and gamma rays and 10 percent residual nuclear radiation.

Air bursts are most likely to be used against ground forces since initial nuclear radiation is much higher than in a surface burst except in the region around the surface burst's ground zero.  High altitude bursts created ionizing radiation can be used to disrupt communication and electrical/electronic networks.  

Here is a graphic showing the chronological development of an air burst:

Obviously, the yield of a weapon has a significant impact on the damage that results from a nuclear detonation.  The yield of the "Little Boy" atomic bomb (airburst) dropped on Hiroshima was between 13 and 18 kilotons of TNT with John Malik at the Los Alamos National Laboratory calculating the yield at 15 kilotons with an uncertainty range of 20 percent.  The "Fat Man" which was dropped on Nagasaki had a yield of 21 kilotons with an uncertainty range of 10 percent.  Here is a table showing the total casualties for both cities:

In Hiroshima, 95 percent of deaths were because of burns, 30 percent because of falling debris and 10 percent were caused by other factors.  In Nagasaki, 95 percent of deaths were because of burns, 9 percent because of falling debris, 7 percent because of flying glass and 7 percent were caused by other factors.  

Now, let's look at North Korea's nuclear capabilities.  According to a summary by Larry Greenmeier at Scientific American, his calculations suggest that the 2016 North Korean nuclear test weapon had a yield of between 3.4 to 7 kilotons based on the amplitude of the seismic waves created by the blast.  Accurate estimates are nearly impossible because Western scientists are not privy to key information; the depth of the blast and the physical properties of the rock surrounding the explosion.  Other estimates of previous test detonations have varied widely with Russia's Defense Ministry stating that the blast in 2009 may have had a yield as high as 15 to 20 kilotons, the same size as the weapons used at the end of the Second World War.  According to the Nuclear Threat Initiative, the September 2016 test had a yield of 35 kilotons, more than twice the yields of the January 2016 and February 2013 tests.

Let's put the other part of the equation into play.  According to the Pentagon, North Korea's latest ICBM tests suggest that the North Koreans now have a missile with a potential range of 10,400 kilometres or 6500 miles.  Here is a table showing the distance of major American cities from North Korea:

Let's make the following reasonable assumptions:

1.) North Korea has developed a nuclear weapon with a 15 kiloton yield. 

2.) North Korea has developed a ballistic missile that is capable of reaching a distance of 10,000 kilometres but for the purposes of this posting, we'll assume that they are only targeting cities on the west coast.  This would mean that the missile could reach San Francisco, Los Angeles, Portland and Seattle.

Now, let's look at the damage that can be done with a 15 kiloton airburst weapon over the downtown core of each of the four previously mentioned West coast cities with the following effects radii:

1.) Los Angeles:

In total, there would be an estimated 88,540 fatalities and 186,830 injuries.

2.) San Francisco:

In total, there would be an estimated 158,050  fatalities and 200,380 injuries.

3.) Portland:

In total, there would be an estimated 57,920 fatalities and 95,210 injuries.

4.) Seattle:

In total, there would be an estimated 97,800 fatalities and 86,930 injuries.

At the present time, while the odds of a North Korean nuclear weapon actually making it to the North American coast and being successfully detonated are rather remote, as you can see from this posting, the results of a successful detonation over a densely populated urban area would be rather sobering.  Even worse than a surface or air burst is the prospect of an atmospheric burst and resulting electromagnetic pulse which would result in significant destruction of the North American electrical and communications infrastructure.  Either way, it would be a very different future than we've come to expect. 

...and, should the worst case scenario transpire, remember this: