Earthquakes in Tokyo: The 1923 Kanto Disaster & the Next Big One

Tokyo faces a very high earthquake risk and is often described as one of the most quake-prone megacities on Earth. The Japanese capital sits above the meeting point of three tectonic plates, the Pacific, Philippine Sea, and North American plates, whose grinding collision generates constant seismic activity. Scientists and the Japanese government warn of a long-anticipated great earthquake, sometimes called the "Big One," beneath or near the metropolitan region. Official projections put the probability of a major quake striking the greater Tokyo area within the next 30 years at around 70 percent, an event that could affect tens of millions of people.

History underlines the stakes. The 1923 Great Kanto earthquake, a magnitude 7.9 event, devastated Tokyo and Yokohama and, together with the firestorms that swept the wooden city, killed more than 100,000 people, still Japan's deadliest earthquake disaster. In 2011 the magnitude 9.0 Tohoku earthquake struck off the northeast coast and shook Tokyo strongly while triggering the tsunami and Fukushima nuclear crisis further north. In response Japan has built perhaps the world's most advanced earthquake defenses, from rigorous building codes and base-isolated skyscrapers to a nationwide early-warning system that can alert phones seconds before shaking arrives, yet the sheer density of Tokyo keeps the risk profound.