Great Kantō Earthquake

The Great Kantō Earthquake was a massive megathrust earthquake. This type of earthquake occurs when one tectonic plate is forced under another. It struck the Kantō Plain on the main Japanese island of Honshu. The event began at 11:58:32 JST on September 1, 1923. It had an approximate magnitude of 8.0 on the moment magnitude scale. This disaster devastated Tokyo and the port city of Yokohama. It also caused widespread damage across the surrounding prefectures.

The earthquake was actually a series of three consecutive shocks. These shocks happened within just a few minutes of each other. The first rupture occurred near Odawara in Kanagawa Prefecture. This was a dual rupture on a broad trench-type fault. About ten seconds later, a second shock hit near the Miura Peninsula. Three minutes later, a magnitude 7.2 earthquake hit northern Tokyo Bay. Two minutes after that, a magnitude 7.3 shock hit Yamanashi Prefecture.

Fires caused the majority of the devastation and loss of life. Within thirty minutes, more than 130 major fires broke out across Tokyo. These fires were fueled by overturned charcoal braziers and leaking gas lines. Strong winds from a nearby typhoon fanned the flames into massive firestorms. These firestorms swept through densely populated urban areas. In some areas, the air temperature reached extremely high levels. One massive firestorm at the Honjo Clothing Depot killed an estimated 40,000 people in minutes.

The physical destruction of the region was immense and widespread. In Tokyo, 44 percent of the main government buildings burned to the ground. This included the police headquarters and several important ministries. The earthquake also destroyed 362 bridges and 70 heavily damaged others in Tokyo. Roads buckled and train tracks twisted under the force of the earth. The sea floor in Sagami Bay dropped by over one meter. This movement triggered tsunamis that hit low-lying coastal communities.

The human toll of the disaster was catastrophic for the population. Modern research estimates the total number of fatalities at 105,385 people. About 87 percent of these deaths, or 91,781 people, were caused by fires. Another 10.5 percent died from collapsing buildings. In the seven affected prefectures, approximately 2.5 million people were left homeless. In Tokyo alone, about 1.38 million people lost their homes. The disaster also caused high unemployment, reaching 45 percent in some Tokyo wards.

Social unrest and false rumors caused great suffering during the aftermath. Communication lines were destroyed, which helped dangerous rumors spread quickly. False reports claimed that ethnic Koreans were committing acts of arson and violence. These rumors led to the formation of vigilante groups called kōmin. These groups used makeshift weapons like clubs and bamboo spears. They targeted Koreans and others they mistook for them. This period of lawlessness included the tragic Kantō Massacre.

In the years following the disaster, Japan began a massive reconstruction. Home Minister Gotō Shinpei led ambitious plans to rebuild Tokyo. He wanted to create a modern and resilient imperial capital. These grand visions faced political contestation and financial constraints. Despite these challenges, the reconstruction significantly improved the city's infrastructure. The event also changed how people thought about national identity and modernity. Today, Japan commemorates September 1 as Disaster Prevention Day.