Unless the Norks have a Death Wish, they won’t dare do that.
Once atomic weapons have been used, all bets are off.
The other side can unleash the full power of a hydrogen barrage that will vaporize every city and military installation on their side of the peninsula.
People do not realize what a H-bomb can do. If there had been an H-Bomb dropped on Hiroshima, the damage would have bee a 1000 times more than what there was.
http://www.nationalterroralert.com/nuclear/
Seoul has a land area of about 233 square miles. While exploding a 20 KT device in it would improve no one’s health, it would most definitely NOT turn all of the city into a “sheet of glass.”
It’d do a lot of damage within a 1.2 mile radius of the blast epicenter (1.9 kilometers) - that’s the radius within which you’d have 5 lbs/sq. inch (PSI), which is enough to destroy most homes and other structures that aren’t very strong. 1 PSI only extends out to 5.9 km, which is about 2.4 miles. Beyond that, there wouldn’t be much damage or casualties. a circle with a diameter of 4.8 miles has an area of about 18.1 sq. miles, less than 10% of the area of Seoul.
Again, I’m not trying to minimize the damage that even a small nuke could do - it would be horrific for anyone within about 2.5 miles - but I think that we should stick with FACTS.
Here’s where I got the data: http://www.alternatewars.com/BBOW/ABC_Weapons/Nuke_Effects_Calculator.htm To me, the value of calculators like this is that they are factual...so that no one is able to be an overly-emotional idiot and claim that a single nuke could “literally destroy the nation” or even a whole city. They are powerful and destructive, to be sure, but here science trumps feelings.
FYI, going up to a 1 MT bomb (50 times the explosive force) “only” gives you 5 PSI out to 7 km, which is about 4.2 miles, and 1 PSI out to 21.4 km, which is a hair over 13 miles. IOW, NOT 50 times the distance for the same effects. The explosive force of a weapon diminishes considerably because of distance.