Sitting on ground zero, you mean you were one mile or less from the headquarters and armory, or any worthwhile targets?
In both cities the blast totally destroyed everything within a radius of 1 mile from the center of explosion, except for certain reinforced concrete frames as noted above. The atomic explosion almost completely destroyed Hiroshima's identity as a city. Over a fourth of the population was killed in one stroke and an additional fourth seriously injured, so that even if there had been no damage to structures and installations the normal city life would still have been completely shattered. Nearly everything was heavily damaged up to a radius of 3 miles from the blast, and beyond this distance damage, although comparatively light, extended for several more miles. Glass was broken up to 12 miles.
In Nagasaki, a smaller area of the city was actually destroyed than in Hiroshima, because the hills which enclosed the target area restricted the spread of the great blast; but careful examination of the effects of the explosion gave evidence of even greater blast effects than in Hiroshima. Total destruction spread over an area of about 3 square miles. Over a third of the 50,000 buildings in the target area of Nagasaki were destroyed or seriously damaged. The complete destruction of the huge steel works and the torpedo plant was especially impressive. The steel frames of all buildings within a mile of the explosion were pushed away, as by a giant hand, from the point of detonation. The badly burned area extended for 3 miles in length. The hillsides up to a radius of 8,000 feet were scorched, giving them an autumnal appearance.
Next you're going to say that the russians would have used nukes way more powerful than that, because why not be extremely excessive.
I do not know exactly how far away Moffett Field was, but we could see the LTA hangers from my street, so yes, we were pretty damned close. In addition, the tract homes in our neighborhood were all wood-framed (they're still there) and would have quickly turned into toothpicks. The entire Bay Area is, of course, a prime target area...Mare Island, the Presidio, etc. , but none of that mattered to me - I was ten at the time.