The Great Kantō Earthquake (Japanese: 関東大地震, Kantō daijishin, or 関東大震災, Kantō daishinsai) was a megathrust earthquake that struck the Kantō Plain on the main Japanese island of Honshu at 11:58:32 JST (02:58:32 UTC) on Saturday, 1 September 1923. It had an approximate magnitude of 8.0 on the moment magnitude scale (Mw), with its epicenter located some 100 km (62 mi) southwest of the capital Tokyo. The earthquake devastated Tokyo, the port city of Yokohama, and the surrounding prefectures of Kanagawa, Chiba, and Shizuoka, causing widespread damage throughout the Kantō region.
The event was a complex disaster, with modern research indicating it consisted of three consecutive shocks in the span of several minutes. The initial megathrust event in Kanagawa Prefecture was followed three minutes later by a magnitude 7.2 earthquake centered beneath Tokyo Bay, and two minutes after that by a magnitude 7.3 shock in Yamanashi Prefecture. Fires, exacerbated by strong winds from a nearby typhoon, spread rapidly through the densely populated urban areas, accounting for the majority of the devastation and casualties. The death toll is estimated to have been between 105,000 and 140,000 people, including tens of thousands who went missing and were presumed dead. Over half of Tokyo and nearly all of Yokohama were destroyed, leaving approximately 2.5 million people homeless. The disaster triggered widespread social unrest, including the Kantō Massacre, in which ethnic Koreans and others mistaken
Why this event still matters
Historical incidents shape the rules that protect people today — building codes, evacuation policy, warning systems and inspection regimes almost always trace back to a specific disaster. Studying 1923 Great Kantō Earthquake alongside current events is how preparedness improves.
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