The map above simulates a 300-kiloton nuclear airburst over Osaka, 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 19 million people — the rings above are drawn to real scale over their homes.
The marker is on Nakanoshima, the island between the Dojima and Tosabori rivers that holds City Hall and the Bank of Japan. The 1.9 km zone of total destruction covers Nakanoshima, Kitahama, Yodoyabashi and the Umeda station complex's southern half; the 4.7 km collapse ring reaches Osaka Castle, Shinsaibashi, Umeda's skyscrapers and Fukushima ward. Third-degree burns extend to about 7.5 km over Namba, Dotonbori, Tennoji, Kyobashi and Shin-Osaka station; the 14.5 km ring of broken windows reaches Osaka Bay's reclaimed islands, Amagasaki, Higashiosaka and Sakai's northern edge.
The Keihanshin region — Osaka, Kobe and Kyoto — is home to about 19 million people and Osaka city itself is flat delta land, densely built from the bay to the Ikoma hills. Osaka was spared the atomic bomb in 1945 only because it had already been devastated by firebombing; Kokura, the original target for the second bomb, lies 500 km west. The Hiroshima and Nagasaki article tells that story.
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