According to Smithsonian magazine, the Great Kanto earthquake was caused by a seismic fault line six miles below the floor of Sagumi Bay. Close to noon on September 1, 1923, a 60 square mile portion of the Philippine oceanic plate ruptured and smashed into the Eurasian continental plate. This event produced a burst of tectonic energy that traumatized Japan.
Considered one of the worst natural disasters in Japan's history, the Great Kanto earthquake damaged much of Tokyo and Yokohama. Smithsonian magazine explains that the earthquake's intense jolt triggered large tsunamis and widespread fires. With a death toll of 140,000 and extensive infrastructure damage, the earthquake is thought to have ignited intense nationalist and racist passions, which fueled right wing groups as the country struggled between military expansion and a quest towards democracy.
The initial tremors of the Great Kanto earthquake lasted for 14 seconds, according to Smithsonian magazine. The shaking brought down the majority of buildings in Tokyo and Yokohama, and the cities were unequipped to handle an earthquake of such magnitude. Since building were largely made of wood, intense fires, fanned by strong winds, burned nearly 45 percent of Tokyo to the ground before they were finally quelled two days later.