At 1.5 to 3km

Heat would cause so many fires that a "firestorm" would be started. Rising hot air would suck in air from the surrounding area and stoke up a very hot and extensive fire. The blast would leave houses irrepairably damaged. Streets would be blocked by debris. Steel bridges would collapse. Vehicles would be thrown around by the intense wind.

Many people would die from third degree burns, which would char their skin. This would be made worse by radiation. Others would be crushed by buildings. The greatest killer in this zone would be the firestorm.

The area within this zone (1.5 - 3 kms) would be 20 square kms.