[PapaBear3625]

The Tsar Bomba was scaled back because after about 50-60 MT yield the energy produced would be mostly wasted. It was detonated at about 15,000 feet and the fireball touched the ground and the top of the fireball was at the tropopause. A larger bomb could be built but what is the point? It is a very inefficient use of weapon material.

As an air-burst, yes, most of the energy would go into the upper atmosphere.

Let's say a 100MT bomb detonated on the sea floor. Say, 60 miles offshore from Los Angeles, where Google Earth shows places up to 5,000 feet deep. The tamping effect of the water above it would let a lot of the shock-wave energy go into the shelf.

What would be the effect of that on the San Andreas fault?

[17th Miss Regt]

What would be the effect of that on the San Andreas fault?

The fault probably would not 'notice' it much at that range. That's a lot of earth and rock to move.