Great Kanto Earthquake (1923): Tokyo and Yokohama in Ruins

The Great Kanto earthquake struck the Kanto plain of Japan at 11:58 a.m. on 1 September 1923. With a magnitude of about 7.9, it shook Tokyo, Yokohama and the surrounding prefectures, and the fires that followed destroyed much of both cities. About 105,000 people died, and in the chaos that followed, thousands of Korean residents were murdered by vigilantes. The disaster reshaped Tokyo and left a lasting mark on Japanese society.

Background

The Kanto region lies above a complex meeting point of tectonic plates, where the Philippine Sea Plate slides beneath the plate carrying central Japan. Large earthquakes had struck the area before, including one in 1703 that caused great damage in Edo, as Tokyo was then called.

By 1923 Tokyo was the capital of a rapidly modernising empire, with a population of more than two million, and Yokohama was Japan’s leading port for foreign trade. Since the Meiji Restoration of 1868, both cities had grown quickly, but most homes were still made of wood and paper and packed tightly along narrow streets. Japan also ruled Korea, which it had annexed in 1910, and many Koreans had come to Japan to work, often facing discrimination.

Seismologists had debated the risk of a great earthquake. In 1905 Imamura Akitsune of Tokyo Imperial University warned that a major quake and fire could cause huge loss of life in Tokyo. His senior colleague Omori Fusakichi publicly called this alarmist. When the earthquake came, Omori was in Australia; he returned to Japan and died a few weeks later, in November 1923.

The country was also between governments. Prime Minister Kato Tomosaburo had died on 24 August 1923, and Admiral Yamamoto Gonnohyoe was in the process of forming a new cabinet when the earthquake struck.

The earthquake

At 11:58 a.m. on Saturday 1 September, the ground began to shake violently across the Kanto region. The epicentre lay beneath Sagami Bay, south-west of Tokyo, and the rupture extended under the Miura and Boso peninsulas. Strong shaking lasted for several minutes, and powerful aftershocks followed throughout the day.

Areas closest to the epicentre suffered the worst direct damage. In Kanagawa Prefecture, towns such as Kamakura, Odawara and Yokosuka were badly hit, and in Yokohama many brick and stone buildings collapsed. A tsunami up to about 10 to 12 metres high struck parts of the coast of Sagami Bay and the Izu Peninsula. Landslides buried villages, and at Nebukawa, west of Odawara, a landslide swept a train and the station into the sea, killing more than 100 people.

The fires

The timing of the earthquake, just before noon, proved catastrophic. Many families were preparing lunch over charcoal braziers or gas stoves, and fires broke out in many places almost at once. Broken water mains left firefighters with little water, and strong winds, linked to a typhoon passing over the Sea of Japan, drove the flames across neighbourhoods of wooden houses.

The fires burned for about two days and destroyed around 40 per cent of Tokyo, including much of the crowded eastern districts along the Sumida River. In Yokohama, the fires and collapse destroyed most of the city. Some fires merged into firestorms that created their own powerful winds.

The worst single tragedy occurred at the site of a former army clothing depot in the Honjo district of Tokyo. Tens of thousands of people had fled to this open ground with their belongings, believing it would be safe. In the afternoon a fire whirl, a spinning column of flame and hot air, swept across the site, and an estimated 38,000 people died there.

The massacre of Koreans

In the hours after the earthquake, false rumours spread that Koreans were setting fires, poisoning wells and planning attacks. Some of these rumours were repeated by police and officials, and martial law was declared in Tokyo on 2 September.

Local vigilante groups, known as jikeidan, set up checkpoints and attacked people they believed to be Korean, often testing them on the pronunciation of Japanese words. Thousands of Koreans were beaten or stabbed to death, sometimes with the involvement of police or soldiers. Several hundred Chinese residents, as well as some Japanese from other regions who were mistaken for Koreans, were also killed.

The number of Korean victims is still debated. Japanese government figures at the time recorded only a few hundred deaths, while a Korean investigation in 1923 counted more than 6,000. Most historians accept that the true number ran into the thousands. Only a small number of vigilantes were prosecuted, and many received light sentences.

The authorities also used the confusion to act against political opponents. In the Kameido incident, labour activists were killed in police custody, and on 16 September the anarchists Osugi Sakae and Ito Noe, together with Osugi’s six-year-old nephew, were murdered by military police under Lieutenant Amakasu Masahiko.

Reconstruction

Goto Shinpei, the new Home Minister and a former mayor of Tokyo, led plans to rebuild the capital as a modern city. He proposed an ambitious scheme of wide avenues, parks and new bridges, but its budget was sharply reduced by the Diet. Even so, the reconstruction created new main roads, more than 50 small parks next to schools, larger parks such as Sumida Park, and many new steel and concrete bridges across the Sumida River.

The Dojunkai foundation built some of Japan’s first reinforced-concrete apartment blocks, and land readjustment straightened and widened streets in burned areas. The rebuilding was officially celebrated as complete in 1930. However, many of the dense wooden neighbourhoods that grew up again in eastern Tokyo would burn once more in the bombing of Tokyo in March 1945.

The disaster also had heavy economic costs. Special “earthquake bills” issued to support businesses left banks holding bad debts, which contributed to the Showa financial crisis of 1927.

The earthquake also had a direct effect on Japanese building law. In 1924 the Urban Building Law was revised to require larger buildings in major cities to be designed to resist earthquake forces, one of the first legal seismic design requirements in the world. Engineers had observed that well-designed reinforced-concrete and steel-framed buildings had generally survived better than brick structures, many of which had collapsed in Yokohama and central Tokyo.

The disaster also changed how Japan planned for fires and evacuation. Parks, wide roads and open spaces were designed partly as firebreaks and refuges, and fire services were expanded. These measures were tested again during later disasters, including the Kobe earthquake of 1995, which revealed both progress and remaining weaknesses in older buildings.

Myths and facts

A popular story holds that the Imperial Hotel in Tokyo, designed by the American architect Frank Lloyd Wright, was the only building to survive the earthquake. The hotel, which was being formally opened on the day of the disaster, did come through with relatively light damage, but many other buildings also survived, and its performance was exaggerated in later accounts.

Another common belief is that most victims were crushed by falling buildings. In fact, the great majority died in the fires, which is why the disaster led Japan to place heavy emphasis on fire prevention in later earthquake planning.

By the numbers

Timeline

• 1905: Imamura Akitsune warns of the danger of a great earthquake and fire in Tokyo.
• 1923, 24 August: Prime Minister Kato Tomosaburo dies.
• 1923, 1 September, 11:58 a.m.: The earthquake strikes; fires break out across Tokyo and Yokohama.
• 1923, 1 September, afternoon: A fire whirl kills about 38,000 people at the Honjo clothing depot site.
• 1923, 2 September: Martial law is declared; Yamamoto Gonnohyoe’s cabinet takes office.
• 1923, early September: Vigilantes and some police and soldiers kill thousands of Koreans.
• 1923, 16 September: Osugi Sakae, Ito Noe and a child are murdered by military police.
• 1930: Tokyo celebrates the completion of its reconstruction.
• 1960: 1 September is designated Disaster Prevention Day.

Legacy

The Great Kanto earthquake remains the deadliest earthquake in Japanese history. It shaped modern Japanese approaches to earthquake preparedness, from building codes to fire safety and public drills. Later disasters, including the Tohoku earthquake and tsunami of 2011, are often compared with it.

The victims are commemorated at the Tokyo Memorial Hall, completed in 1930 in Yokoamicho Park on the site of the former Honjo clothing depot, where the ashes of tens of thousands of victims were placed. The hall was later also dedicated to the victims of the air raids on Tokyo during the Second World War. Nearby, a reconstruction memorial museum displays objects damaged in the fires and records of the rebuilding of the city. In Yokohama, too, memorials recall the destruction of the port and its foreign settlement.

The killings of Koreans remain a painful and contested subject in Japan and Korea. Memorial services are held each year in Tokyo, and historians continue to research the scale of the violence and the role of the authorities.

Why it matters

The Great Kanto earthquake destroyed Japan’s capital and its main port, killing about 105,000 people and forcing the rebuilding of Tokyo. It also showed how fear and prejudice can turn a natural disaster into a human atrocity, a lesson that still shapes how Japan remembers 1923.