https://www.youtube.com/watch?v=-3IriKR6tRo#t=14
The Sedan Crater is approximately 1,300ft long in diameter. Looking at the video, I'd say where the MP nuke is dropped is about half that distance or roughly the center of said diameter. Thus, the NT bomb hit ~700ft away from Nuketown. Now I'm not saying that the nuke alone caused the hole; what if the nuke was dropped WHILE the Sedan nuke was already buried underneath the ground? A nuke, detonating another nuke? KABOOM!
That's when things get nice for us: Nuketown is destroyed. We have a large-ass crater, with the remains of NT sitting on the edge. A mushroom cloud has formed. Radiation team is sent out, but they die off minus one particular scientist. Distress signal was released, and CIA coming but also the CDC. Then, the V2 Moon rocket hits NT and practically obliterates it to nothingness.