[DCBryan1]

If you want to know, in layman terms, what nuclear weapon effects will do, just go HERE for NUKEMAP by Alex Wellerstein

[Fitzy_888]

Using the application, for a 40 Mt weapon (4,000 kt) airburst the over pressure is (pounds per square inch):

8 psi at a 4 mile radius, virtually no freestanding structure survives collapse. A moonscape of unrecognisable rubble that is 8 miles across.