An earthquake struck the Kanto Plain at 11:58 a.m. on September 1, 1923, and killed somewhere between 105,385 and 142,800 people. The wide range exists because tens of thousands were never found. Most of the dead were burned, not crushed.
The quake measured about magnitude 7.9, with its focus beneath Sagami Bay along the trough where the Philippine Sea Plate dives under the plate carrying central Japan. It hit at lunchtime, when charcoal and wood stoves were lit all over Tokyo and Yokohama. Hundreds of small fires started within minutes. Strong winds from a typhoon offshore pushed them together, and in several districts the fires merged into firestorms that outran the people fleeing them.
The single worst loss of life happened in one place. Around 38,000 people had gathered their belongings and taken refuge in an open lot at the Army Clothing Depot in Honjo, a common evacuation point. A fire tornado swept the lot. Almost everyone in it died within minutes.
The shaking itself was destructive enough. More than half of Tokyo's brick buildings came down. Nearly all of Yokohama did. The Great Buddha at Kamakura, a bronze statue weighing about 121 tonnes and standing more than 60 km from the epicenter, shifted about 60 cm on its base. A tsunami reaching up to 12 m struck the coast at Atami. Roughly 2.5 million people lost their homes.
After the fires came a second disaster. Vigilante groups, acting on false rumors that ethnic Koreans were poisoning wells and setting fires, murdered several thousand people. The government declared martial law in the affected areas.
In 1960 Japan designated September 1 as Disaster Prevention Day. Schools, offices and local governments across the country still run evacuation drills on the date, and the annual commemoration centers on the Honjo site where the fire tornado struck.