On September 1, 1923, just before noon, one of the darkest chapters in Japan’s modern history began.

At 11:58 a.m., a massive earthquake struck the Kanto region, devastating Tokyo, Yokohama and surrounding areas. But the shaking itself was only the beginning. Fires erupted almost immediately across densely populated neighborhoods, merging into enormous conflagrations and deadly firestorms.

More than a century later, the Great Kanto Earthquake of 1923 remains one of the most important disasters in Japanese history — and, by Japan’s modern official accounting, its deadliest earthquake disaster.

Japanese government assessments put the number of dead and missing at approximately 105,000 people, with around 90% of the victims killed by fire. Older historical estimates, still widely cited internationally, place the death toll closer to 140,000–143,000.

The Earthquake Struck at 11:58 a.m.

According to the Japan Meteorological Agency (JMA), the Great Kanto Earthquake struck at 11:58 a.m. on September 1, 1923.

Japan estimates its magnitude at 7.9, with the hypocenter in western Kanagawa Prefecture at a depth of approximately 23 kilometers. Extremely strong shaking affected Tokyo, Kanagawa, Chiba, Saitama and Yamanashi, while the earthquake was felt across a much wider part of Japan.

Modern analysis suggests that some areas around Sagami Bay and the southern Boso Peninsula experienced shaking comparable to seismic intensity 7 on Japan’s current scale.

The earthquake caused more than 100,000 homes to collapse, but what followed transformed an enormous seismic disaster into an almost unimaginable urban catastrophe.

The Fires Became Deadlier Than the Earthquake

Timing played a devastating role.

The earthquake struck around lunchtime, when countless households were preparing food using open flames and cooking stoves. Fires broke out simultaneously across Tokyo and other cities as buildings collapsed and combustible material ignited.

Those individual fires rapidly expanded.

Japan’s Cabinet Office notes that fire dramatically increased the scale of the disaster and ultimately became the principal cause of death.

According to the Japanese government’s 2023 Disaster Management White Paper, approximately 90% of the roughly 105,000 people killed or missing died from burns and fire-related causes.

This is one of the defining characteristics of the Great Kanto Earthquake: the majority of victims were not killed by collapsing buildings, but by the infernos that followed.

Tokyo Turned Into a Sea of Fire

Tokyo at the beginning of the 20th century was extraordinarily vulnerable to urban fire.

Large sections of the capital consisted of densely packed wooden buildings. Once numerous fires began simultaneously, firefighting resources were overwhelmed.

The earthquake had also damaged water supplies, roads and other essential infrastructure, making suppression operations even more difficult.

Historical accounts describe fires spreading at extraordinary speed through Tokyo and Yokohama.

Within minutes, dozens of individual fires had been reported. As winds pushed the flames through densely built neighborhoods, separate fires merged into enormous burning areas.

The result was not simply an earthquake followed by ordinary urban fires.

Parts of Tokyo experienced conditions resembling a firestorm.

The Terrifying Fire Whirl at the Army Clothing Depot

One of the most horrific events occurred at the former Army Clothing Depot in Honjo, Tokyo, where a huge number of people had gathered in what they believed was an open and relatively safe area.

They had brought belongings rescued from their homes.

Instead, the site became a death trap.

At approximately 3:30 p.m., an enormous fire whirl — sometimes described as a fire tornado — swept through the area.

A scientific study by Japan’s Meteorological Research Institute estimated that around 40,000 people were burned to death there in a very short period of time. The study concluded that the phenomenon was generated primarily by the enormous surrounding fires rather than by the passage of a cold front, as had once been suggested.

It remains one of the deadliest individual fire-related events associated with an earthquake in recorded history.

Tsunami Waves Struck Coastal Communities

Fire was not the only secondary disaster.

The earthquake also generated a tsunami in Sagami Bay.

USGS historical data indicate tsunami heights reaching approximately 12 meters on Oshima, while waves of around six meters affected portions of the Izu and Boso peninsulas.

Coastal settlements were inundated, buildings were swept away and additional lives were lost.

The disaster therefore involved several destructive processes almost simultaneously: catastrophic ground shaking, building collapses, fires, firestorms, tsunami waves and landslides.

Landslides Buried Entire Communities

Mountainous areas surrounding the Kanto region experienced another deadly consequence.

Earthquake-triggered landslides and debris flows occurred across Kanagawa and neighboring areas.

One of the worst disasters occurred around Nebukawa, now part of Odawara, where a massive debris flow buried 64 homes and killed 406 people, according to Japan’s Cabinet Office historical assessment.

These events received considerably less attention than the destruction of Tokyo and Yokohama but demonstrate the enormous geographical extent of the catastrophe.

Around 105,000 Dead and Missing – Why Some Sources Say 140,000

Different death tolls for the Great Kanto Earthquake continue to appear in historical sources.

Modern Japanese government material generally uses a figure of approximately 105,000 dead or missing. The Cabinet Office’s detailed assessment records 105,385 deaths, while Japan’s Geospatial Information Authority similarly gives approximately 105,000 dead and missing.

Older assessments produced considerably higher figures.

For example, the USGS historical earthquake database lists approximately 142,800 deaths, while other historical accounts commonly refer to roughly 140,000 fatalities.

The difference reflects changes in historical records and later reassessments of victims rather than a newly discovered change in the disaster itself.

For contemporary reporting, the approximately 105,000 dead and missing figure used by modern Japanese authorities is the more appropriate reference, while acknowledging that older estimates reached around 140,000–143,000.

Nearly 300,000 Homes Destroyed, Burned or Swept Away

The physical destruction was staggering.

Japan’s Cabinet Office records 293,387 homes completely collapsed, burned or washed away. Electricity, water, roads, railways and other critical infrastructure suffered extensive damage.

More than 212,000 buildings were destroyed by fire alone, according to Japanese government historical figures.

Tokyo and Yokohama were transformed.

Entire neighborhoods disappeared, hundreds of thousands of people were left homeless and Japan faced an enormous humanitarian and reconstruction challenge.

The Disaster Changed Japan

The Great Kanto Earthquake was more than a geological event.

It became a defining moment in modern Japanese history, influencing urban planning, disaster preparedness and the reconstruction of Tokyo.

It also produced severe social consequences. Amid the chaos, false rumors spread about ethnic Koreans poisoning wells or committing attacks. Those rumors contributed to massacres of Koreans and others by vigilante groups, a tragic part of the disaster’s history that Japan continues to confront.

The catastrophe demonstrated how a natural hazard can develop into a much larger societal disaster when infrastructure failure, fire, misinformation and social instability occur simultaneously.

Why September 1 Became Disaster Prevention Day in Japan

The legacy of September 1 remains deeply embedded in Japanese society.

The anniversary of the Great Kanto Earthquake is observed in Japan as Disaster Prevention Day, when authorities, schools, businesses and communities conduct earthquake and emergency preparedness exercises.

The date serves as a reminder that Japan’s extraordinary exposure to earthquakes requires constant preparation.

Japan’s Geospatial Information Authority emphasizes another fundamental lesson from the disaster: major earthquakes can recur in the same tectonic regions over long periods of time.

More Than a Century Later, the Lesson Remains

The Great Kanto Earthquake was not the strongest earthquake ever recorded in Japan.

The magnitude 9.0 Great East Japan Earthquake of March 11, 2011 was vastly more powerful.

But the catastrophe of September 1, 1923 demonstrated that magnitude alone does not determine how deadly an earthquake becomes.

The combination of violent shaking, densely built wooden cities, simultaneous fires, damaged water infrastructure, strong winds, firestorms, tsunami waves and landslides created one of the most destructive chains of natural hazards in modern history.

More than a century later, the Great Kanto Earthquake remains a powerful lesson in how an earthquake can trigger a cascading disaster — and why preparation for what happens after the shaking stops can be just as important as preparation for the earthquake itself.