“Directly overhead?”
Probably, so long as it’s not actually detonated on the surface. 45 feet deep is pretty far, and any appreciable altitude will mitigate crater depth. 20kT is about equal to the Hiroshima blast, which did leave buildings standing near ground zero.
200 PSI Overpressure? Think the vault doors will still work?
It would have left more standing if it had not been detonated at approx. 1900 feet above the surface. That maximized the design's destructive potential.