The Next Big One

Japan is preparing for a massive earthquake

The centenary of the Great Kanto earthquake brings angst, and lessons for the world

EVERY YEAR on September 1st, Japan’s ministers trek by foot to the prime minister’s office to take part in a crisis simulation. Across the country, local officials and schoolchildren drill for disasters. The date marks the Great Kanto earthquake, a 7.9-magnitude tremor that struck near the capital back in 1923. The ensuing disaster killed at least 105,000 people, including around 70,000 in Tokyo itself, destroyed 370,000 homes and changed the course of Japanese history.

This year’s centenary of the disaster has occasioned much commemoration—and angst. What will happen when the next Big One hits? Seismologists cannot predict earthquakes, but their statistical models, which are based on past patterns, can estimate the likelihood of one. The city government’s experts reckon there is a 70% chance of a magnitude 7 or higher quake hitting the capital within the next 30 years. Far fewer people will probably die than during the disaster in 1923, thanks to better technology and planning: the worst case foresees some 6,000 deaths in the city. But millions of lives will be upended.

Another, similarly likely scenario could be much worse. A Nankai Trough earthquake, envisaged south of Kansai, Japan’s industrial heartland, could trigger a tsunami; as many as…