It’s a little difficult to imagine such an event but I want to wrap my mind around the significance of such a thing happening. Let’s say a hydrogen bomb was dropped right in the center of New York City.
What would be the approximate blast radius?
About how many fatalities would there be?
What would New York City look like afterwards?
How would American civilians as a whole cope with such a unprecedented event?
You’re going to need to be more specific as to: the yield of the bomb, height above the ground and define your location more precisely.
Well, for shits and giggles until the OP returns to answer, let’s say the most potent thermonuclear device ever tested–reputed to be capable of a 100-megaton yield, and a maximally-destructive airburst of, oh, around 2 miles up. Ground zero is directly over the Empire State Building.
Napkins ready…GO!
I would assume that if it were the beginning of World War 3, America’s enemy would choose the hydrogen bomb, height above the ground and location that would cause maximum damage.
Here’s an old BBC documentary using London as an example. I found it pretty interesting.
It both describes the effects and some points about survival after the explosion.
This site might be of interest:
http://meyerweb.com/eric/tools/gmap/hydesim.html
Probably a safe assumption. It’s not much harder to make a big H-bomb than a small one, and anyone with the tech to make any H-bomb probably also has a variety of ways of delivering it available to them, too.
I’ll take a WAG.
I’m going to crawl under the covers with my dogie now.
Oh, I forgot; the good news is that this is New York and not Los Angeles so most of the fallout blows out to sea.
Actually, at the beginning of WWII, the enemy would use whatever sized weapon either fit inside the missile they launched, or was easily smuggled into the country.
If it was a terrorist bomb, it would be highly unlikely that it was a hydrogen bomb, as those are significantly bigger and more complex than fission bombs. If it’s an SS-25 coming from Russia or equivalent, it’s got a 250kt warhead.
A warhead this size would create a zone of total destruction of about a mile, and knock down most buildings within 2 miles but there would be survivors between 1 and 2 miles away if they were protected. At about five miles, you’ve got blown out windows and other light damage, but most people would survive the initial blast. Radiation effects are a craphoot, depending on the wind direction, etc.
If it’s a terrorist bomb, it’s very likely it would be low yield - maybe 1 ton and up to 10kt, depending on design, size, and how well it goes off.
A 10 kt bomb, about half the size of Hiroshima’s bomb, would obliterate an area about 500 meters across, and do a lot of destruction for the next mile or two. Most of New York would survive such a bombing.
This picture shows an arial view of Hiroshima after the bombing. 69% of Hiroshima’s buildings were destroyed by the bomb. Hiroshima today is roughly the size of of New York City proper, but in WWII before the bomb it was about 1/3 the size in population. But I don’t know how that translates to area.
Anyway, there’s a reasonable comparison: about 70% of a city about 1/3 the size of modern New York was destroyed by a 20 kt bomb.
The New York Metro area is about 15 times larger than the city proper, however. So a 20kt bomb might destroy 5% of the metro area of new York. The majority of the population would survive. The city is very densely populated, so it would be an immense tragedy. Maybe 5 million people killed or seriously injured.
Well, but a hypothetical low-yield terrorist nuke would likely be detonated at ground level (probably in the harbour) which would significantly decrease the damage. The Hiroshima bomb was detonated at about 2000 feet.
Still, the OP is asking about a fusion bomb, not a fission bomb, and so it seems reasonable to presume a much higher yield, a proper delivery system, and an aerial detonation.
If we posit that the bomb dropped was the biggest Russia dropped, in effect a repeat of the Tsar Bomba test, it would be ugly. (Yes, I know it’s unrealistic, but this is at the OP’s posit)
The Tsar Bomba had a neutered yield of 50 megaton, weighed 27 tonnes.
It was detonated at 4km altitude - 2.5 miles. The fireball alone was 8 kilometres (5 miles) in diametre and would have caused third degree burns at a distance of 62 kilometres away. The mushroom cloud itself went 64 kilometres (40 miles) high and 40 kilometres (25mi) wide. The seizmic wave it created registered as a 5,25 on Richter’s and blew out windows in Finland. It was still detectable after having travelled around the earth three times.
On the upside, the Tsar Bomba was one of the cleanest (in terms of fallout) bombs ever designed. So if you survived the initial blast and the following destruction, you would have a good chance of getting away alive.
Eta: A comparative fireball size chart I found on the Wiki article: http://upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Comparative_nuclear_fireball_sizes.svg/250px-Comparative_nuclear_fireball_sizes.svg.png
I knew these formulas would come in handy some day!
According to these formulas which I found somewhere, for a 250 kt warhead, you’d be getting third-degree burns out to 6.6 km, and a 500 rem dose (sufficient to cause acute radiation poisoning) out to 2.4 km.
For the Tsar Bomba, you would be getting third degree burns 58 km away, and acute radiation poisoning out to 6.5 km.
One thing to consider. Most of Japans buildings at that time were both pretty flimsy and fairly flammable.
I have heard some say the nuclear bombs in Japan did more damage by the fact the whole town was set on fire than actual nuclear “blast” effects.
Or in other words, if we had airdropped a couple hundred well coordinated Ninja (american breed of course) arsonists, the results would have been almost as bad.
Then do a little research on firestorms and WW2 bombings for more info.
Modern New York building would probably fair much better.
Here’s a google maplet that lets you detonate nuclear bombs of varying yield wherever you so chose.
No, no, you forget the Inverse Ninja Law; the more Ninja there are, the weaker they are. Drop a few hundred and they’d be beaten to death by kids with sticks. You want to drop ONE Ninja arsonist; with just one you won’t even need to give him a parachute; just fire the plane’s machineguns and let him run down the bullets to the ground.
Oh, the joys and wonders of the interwebs! 
No problem, we did something like this a little while ago:
The terrain of Hiroshima and Nagasaki (slightly more rugged than New York) also affected both the population dispersal (and vulnerability) and the effects of the blast.
Comparing Hiroshima to New York shouldn’t be a straight linear equation.
That just seems to show thermal damage. What about the shockwave and radiation?
There should also be a “Chuck Norris roundhouse kick” option
