The map above simulates a 300-kiloton nuclear airburst over Tokyo, Japan — roughly the size of a modern deployed warhead. The coloured rings show the estimated fireball, the zones of heavy, moderate and light blast damage, the reach of the thermal flash and the ionizing-radiation dose. Drag the marker or change the weapon in the full simulator to explore other scenarios.
The metropolitan area is home to about 37 million people — the rings above are drawn to real scale over their homes.
The marker sits in the western wards a few kilometres from Shinjuku, in the dense low-rise housing of Nakano and Suginami that burned so badly in 1945. The 1.9 km zone of total destruction is residential almost edge to edge; the 4.7 km collapse ring reaches Shinjuku's skyscraper district and station, the busiest in the world, together with Nakano Broadway and Koenji. Third-degree burns extend to about 7.5 km — Shibuya, Yoyogi Park, Ikebukuro's southern edge, Kichijoji — and the 14.5 km ring of broken windows covers the Imperial Palace, Ginza, Shinagawa and most of the 23 wards west of the Sumida.
Greater Tokyo holds about 37 million people and the inner wards are among the most crowded places on Earth, so even a single 300-kiloton warhead puts several million people inside the outer ring. The land is flat alluvial plain; the only shadows would come from the tall buildings themselves. Japan is the one country that has lived through nuclear attack, and the scale here is roughly twenty times Hiroshima.
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