San Francisco Example: 14 seconds after detonation
The shock wave will have moved out 1.2 miles in the 5 seconds as the ring of destruction is extended out to 3.5 miles. The overpressure at the edge of the ring, which covers about 16 square miles, will be 5 psi. Reinforced structures will be heavily damaged as well as unreinforced residential. Again, some structures will be shielded by the city's hills and thus receive reduced damage. Significant structures affected in this ring include the Golden Gate and Bay Bridges, the Civic Center and the Presidio. It is very likely that both bridges will be severely damaged or destroyed by the blast.
This ring contains roughly 90,000 people. Less than one half (25,000) of the indoor population will be killed inside buildings, mainly by flying debris. Many of the rest (40,000) will receive injuries to varying degrees. Those outside at this range escape serious direct injury from the blast overpressure but may be injured or killed by flying objects. The thermal pulse has been attenuated to well below 1 calorie per square centimeter, posing the danger of temporary flashblindness to those looking in the direction of the blast, but nothing more.
This region contains the most severe fire hazard, since fire ignition and spread are more likely in partly damaged buildings than in completely flattened areas. Perhaps 5% of the building would be initially ignited, with fire spread to adjoining buildings highly likely. Fires will continue to spread for at least 24 hours, ultimately destroying about half the buildings.