Just after 2:46 p.m. on Friday, March 11, an earthquake warning buzzed on the cell phone belonging to Professor Kensuke Watanabe. He knew it was time for everyone in his class to bolt under their desks. The university building in Sendai, the biggest city hit by the quake and subsequent tsunami, began to shake violently. But Watanabe and his students, with that small warning, were able to use the sturdy desks as protection against falling objects. Shortly after, they fled the building for open ground. None in the group was hurt by Japan’s worst earthquake on record. “It was terrifying,” says Watanabe, “but the mobile warning really helped.”
Japan has the most advanced earthquake early-warning system in the world. A nationwide online system launched in 2007, it detects tremors, calculates an earthquake’s epicenter and sends out brief warnings from its 1,000-plus seismographs scattered throughout the country, one of the most earthquake-prone nations on the planet.