The nightmare facilitator helpfully color-codes the blast. Going outward from the hypocenter: the yellow  in the center is a deep crater of fuzed glass. This is the extent of the fireball itself and EVERYTHING here is utterly gone.  The green area has an instant death rate of 50-100 percent due to radiation. This is included in the simulator because it's important for smaller bombs but its really redundant here because the much larger red area overlaps it and experiences instant overpressures of 20PSI and above. Red is going to see the utter destruction of even many steel reinforced concrete buildings. The grey area, which will have overpressure down to 4,6 PSI will  see most structures destroyed except for the very strongest steel and concrete structures, which will be damaged. The death rate in the red and grey zones is going to be close to 100% even if NO radiation was present. Overlapping all of these zones,  and extending well beyond them the is orange area . Outside the grey area it will still experience some blast damage but the orange zone mainly experiences thermal effects. Any exposed skin gets 3rd degree burns and most everything flammable or combustible burst into flames. This will likely result in a firestorm stretching from Trenton NJ to Brentwood, to Fairfield CT and north almost to West Point. Note that this is a very simplistic map and takes into account dissipation of the blast and the curvature of the earth, but it does not take into account terrain or atmospheric conditions. For instance the facing slopes of hills might get higher level effects than their distance would indicate and info from the actual Tsar Bomba test indicates that scattered fires might be started in the Adirondacks

This blast does not have the vast range of the 1961 test because it is assumed to be a ground burst. Of course a ground burst is a VERY dirty explosion. The harbor is unusable for decades and very likely isn't a harbor any more.

Lets pull back a bit...


The major US harbors would have been destroyed and since the seismic effects would have been greater than 8.0,  there would have been earthquake-like damage up and down the eastern seaboard, which transmits seismic waves very efficiently. Remember each 100 MT bomb is roughly half a Krakatoa. Worse, radioactive tsunamis might have done additional damage. The bomb itself, wouldn't cause a real tsunami, but the vertical shaking the concussion would have caused could have precipitated avalanches in the undersea canyons outside many east coast ports. This could conceivably trigger tsunamis.

Note that those 'splody circles are the actual blast fields...to scale.

DC, Philadelphia and Baltimore as torpedo targets are a bit far fetched. One would have to assume torpedoes powered by RTGs or something so the Sub doesn't have to enter the Chesapeake or Delaware Bays. Chicago and Sacramento are rather unlikely targets for a torpedo.

However, the above simulation was done with a slightly different scenario in mind.

The weapon, as big as it was, was not as big as one might think. If you removed the fins, it could fit in an ISO shipping container. It was also not all that advanced in reality. The Soviet engineers designed it very quickly and it was reportedly a straightforward and very conservative scale-up from the U.S.S.R.s early hydrogen weapons. The Soviet engineers did not seem to find it terribly challenging. This means that once anyone gets the ability to produce hydrogen bombs, something like this weapon is a straightforward development, probably only a decade or so down the road.  (the Russians did it rather quicker in what by today's standards are primitive conditions, but they are very good at engineering)

Barring a catastrophic screw-up resulting in a nuclear exchange, the current nuclear threat is, at the very most, something along the scale of "Little Boy" (a firecracker by comparison). However, there is no more potent terror weapon than the 'King of Bombs' and the ability to do damage on that scale is demonstrably attainable. That such large weapons are wasteful and poisonous enough to cause massive contamination is of little deterrent to those who covet nukes for terror purposes. Fortunately, no one likely to try and sneak one of these things into the country will be able to develop or obtain them...for at least 10 or 12 years. 

UPDATE: Edited for clarity.

1 The tsunami effect of underwater nuclear explosions is much less than you might think.  Tsunamis form when a large section of the Earth's crust moves a small amount; while nowhere near as violent locally as a nuclear explosion, it's much, much bigger.  The shockwave of a nuke radiates out from a single point, so it's locally devastating but dissipates rapidly with distance.

I still don't want one in my back yard.

In other explodey news, Fractal Village go boom!  Snowflake Village arises from its ashes.

2

... it was a fission weapon lit off by a comparatively small fission pilot light.

I think you mean "fusion weapon lit off by a comparatively small fission pilot light."  Tsar Bomba was meant to test just how big a big nuclear explosion could get and the only way to get there is with the power of the sun's core:  nuclear fusion.

3 @JT: Yes. That is a typo. it should be fusion. I'll change it ASAP. 
@ Pixy:You are of course correct that the nuclear explosion itself would not produce much of a tsunami, but the FAS article estimated the seismic effects of a ground burst to be about 8.0 on the richter scale. This sudden sharp vertical jolt would be analogous to a brief thrust earthquake and might cause undersea avalanches in the marine canyons outside several east coast harbors . Either of these MIGHT spawn a tsunami. 

4 Fixed. Thanks JT!

5 Interesting.  I'd always thought that while Tsar Bomba was the largest device detonated, the USSR had actually deployed a small number of even larger warheads, intended to take out Cheyenne Mountain.  But I can't find any evidence to back that up.  I wonder where I originally got the idea?
The text where you describe the effects related to the colored circles was a bit confusing.  It would be easier to interpret if you ordered the effects either in or out, instead of just randomly describing areas.

6 I'd also read (but I do not recall where) that a 100 megaton warhead could destroy a soft target such as a city from low-Earth orbit.  Thus, if you convinced other nations that it was some sort of satellite and not a weapon, you could detonate it on some future date as it passed over the target, with no launch warning.

7 Umm...no. In space there would be no blast, though the EMP would be hellacious.

8 ACTUALLY that's probably what you read. Someone extrapolating what this thing would have done in the Hardtack Teak test.

That would be ugly...electrical grid shut down on a continent perhaps.