On January 5, as Tokyo's commuters were struggling back to work after their long New Year break, blaring sirens from every phone pierced the sleepy atmosphere: "strong" earthquake coming. The message delivered via the country's alert system, part of its much-hyped J-Alert mechanism, warned of a big one directly hitting the Japanese capital - potentially on the scale of the devastating 2011 earthquake that wrought massive destruction.
Millions braced for impact. but it never came. It turned out that the system, which aims to give a precious few seconds to find shelter before a major earthquake strikes, had been tricked by an unusual seismological coincidence. Two minor tremors struck at almost exactly the same time in separate locations, making the alert system mistakenly believe a massive jolt was on its way, the meteorological agency admitted.
Even Prime Minister Shinzo Abe was caught off-guard - with TV footage showing him checking his phone as alarms echoed in his office ahead of a cabinet meeting. It was not the first false alarm for the system, a major component of Japan's J-Alert launched with great fanfare in 2007 as a way to save lives in a country constantly under threat of earthquakes and - more recently - North Korean missiles.
Several countries have introduced similar early warning systems for major earthquakes, with most focused on a particular, quake-prone area. But Japan's system is unique in its breadth of coverage, said Issei Suganuma, a scientific officer at the meteorological agency. "Our system covers the entire country with some 1,000 observation points across the nation," he told AFP proudly.
At the agency's Tokyo headquarters, at least seven uniformed officers keep watch around the clock in the earthquake observation room. Large screens hang on the walls showing real-time seismic waveform data. In the case of a cataclysmic earthquake, they detect initial minor tremors through seismometers and immediately warn local governments via J-Alert seconds before the first strong jolt is felt.
The agency also directly sends SMS messages and whooping alarms to local residents' phones. Broadcasters receive signals to flash breaking news alerts and bullet train services are immediately suspended. When the 9.0-magnitude earthquake hit Japan in 2011, the system successfully warned residents between six and 40 seconds before the first major jolt. The J-Alert system also warns of missiles, particularly relevant during a rise in tensions with North Korea last year.