Within this zone, which stretches 11.4 square kilometres, people would suffer third degree burns extending throughout the layers of the skin. Many would be left disabled or severely scarred and some would require amputation. Within the nine-square-kilometre outer air blast zone (overpressure 5 psi), shown by the orange ring, fatalities are widespread and injuries universal. Most residential buildings would collapse. A representation of the Hiroshima Bomb damage if it fell on the Melbourne CBD. In Sydney, roughly 17,000 residents would fall within the radiation area, the green ring stretching 4.5 square kilometres across the CBD, The Rocks and part of Pyrmont and Ultimo.

Without medical treatment, between 50 and 90 per cent of people could expect to die from the acute effects of radiation poisoning alone. Some would die within hours; others up to several weeks later. Bear in mind that these numbers are based on residents only, so don't take into account the tens of thousands of city workers who would be starting to arrive just as the bomb was detonated, assuming this occurred at the same time as in Hiroshima - 8.15am local time. A representation of the Hiroshima Bomb damage if it fell on the Canberra CBD. Fatalities approach 100 per cent within the pink ring, which indicates the air blast radius at an overpressure of 20 psi. Within this area, which covers one-third of a square kilometre, even heavily reinforced concrete buildings would be demolished or significantly damaged. The red, innermost ring shows the maximum size of the nuclear fireball. Everything inside this fireball - people, buildings, even soil and water - is instantly vaporised.

These maps and the description of the effects within each zone are based on NukeMap, a tool developed by nuclear historian Alex Wellerstein, from the Stevens Institute of Technology in New Jersey. A representation of the Hiroshima Bomb damage if it fell on the Brisbane CBD. The tool allows you drop a bomb (you can specify the size or select from a menu of current and past bombs) anywhere in the world and visualise its effects. The horrific effects of the two atomic bombs dropped on Hiroshima and Nagasaki continue to be felt today. The 15-kiloton bomb dropped on Hiroshima on August 6, code-named "Little Boy", killed 66,000 people and injured 69,000 more, according to US Army estimates made in 1946.