Great Kantō earthquake (1923)

Just before noon on 1 September 1923, a huge earthquake beneath Sagami Bay shook the Kantō Plain of central Japan, home to Tokyo and the port of Yokohama. The shock, of magnitude around 8.0, and the firestorms that followed killed somewhere between 105,000 and 140,000 people and left about 2.5 million homeless. In the chaos, vigilantes and some police and soldiers murdered thousands of Koreans living in the region, in what became known as the Kantō Massacre.

The quake struck at 11:58 local time, when the Philippine Sea Plate slipped beneath the plate carrying eastern Japan along the Sagami Trough. Modern studies show a sequence of ruptures: the main shock near Odawara, about 100 kilometres south-west of Tokyo, was followed within minutes by two further large tremors, one under Tokyo Bay and one in Yamanashi Prefecture. Buildings collapsed across the region, and tsunamis struck low-lying coasts.

Because it was midday, charcoal stoves were alight for lunch. Within half an hour more than 130 major fires had broken out in Tokyo, fed by broken gas pipes and wooden debris and driven by strong winds from a passing typhoon. Crowds fleeing with their belongings jammed streets and bridges. The worst single disaster came at the Honjo Clothing Depot, an open site where tens of thousands had taken refuge: a whirlwind of fire swept over it and killed an estimated 40,000 people. Roughly half of Tokyo and almost all of Yokohama were destroyed.

Early estimates put the death toll at up to 140,000. The official disaster report, used by modern researchers, gives 105,385 dead, around 87 per cent of them killed by fire; a further 13,275 people were still listed as missing a year later. Tokyo Prefecture lost 70,387 people and Kanagawa 32,838. Ministries, police stations, most bank offices, 117 of Tokyo's 196 primary schools and thousands of factories were lost.

With communications cut, rumours spread fast. False reports, which began when looting by Japanese in Yokohama was blamed on Koreans, claimed that Koreans were poisoning wells, setting fires and planning attacks. Some officials repeated these claims, and on 2 September the Tokyo police issued a statement accusing Koreans of arson and violence. Thousands of neighbourhood vigilante groups formed, and many attacked Koreans, as well as Chinese, Okinawans and Japanese whose accents marked them as outsiders, sometimes after testing victims on the pronunciation of Japanese words.

The number killed is disputed. Police confirmed 248 Korean deaths; an inquiry by the Government-General of Korea found 832 killed or missing; an investigation by Korean students counted 2,613; and some modern estimates are as high as 6,000. Some police and soldiers protected Koreans while others took part or looked away, and few killers were punished. The military police also used the confusion to murder the anarchist Ōsugi Sakae, his partner Itō Noe and his six-year-old nephew.

The disaster struck during a change of government, after the prime minister had died in August. The new cabinet of Admiral Yamamoto Gonnohyōe, sworn in outdoors on 2 September, declared martial law the same day. More than 52,000 troops were eventually sent to Tokyo and Yokohama, where they distributed food and water, disarmed vigilante groups and took over 23,000 Koreans into so-called protective custody. Martial law lasted until 15 November.

Home Minister Gotō Shinpei proposed a grand reconstruction costing ¥3 billion, more than twice the national budget, but opponents cut it to ¥468 million. Even so, the rebuilding brought wider paved roads, new steel bridges and new parks before it was declared complete in 1930. Within days of the disaster the regent, Crown Prince Hirohito, had called for a capital that was not merely restored but renewed. Many commentators treated the catastrophe as divine punishment for luxury and moral decline, and an imperial rescript of November 1923 urged the nation towards thrift and spiritual renewal. Since 1960, 1 September has been marked in Japan as Disaster Prevention Day.

Our 1920 map shows the Empire of Japan, including Korea, which it then ruled, at the time of the disaster.