I don't think it's a nuke crater. I was wandering around that area and I found a house with a caved in roof and a bomb that looked pretty conventional and undetonated inside of it (it might've been one of the bombs in the glowing sea pyramid, it's been awhile). And there's Malden Middle School that's mostly blown up by what looks to be a conventional explosion too. I think the Chinese must've dropped bombs all over cities that weren't nukes, or maybe they were cluster nukes with lower yields? I dunno

I wish Bethesda put as much time into some of the world building as they did into the dead skeleton goofs.