Japan’s ‘mega-quake’ that never was, and the danger of false alarms

Kanako Hosomura was working in a clothing store in Yokohama when an alert on her phone warned of an imminent magnitude 9.9 earthquake. “We all rushed outside,” Hosomura said, recalling how people poured out of nearby shops and offices to watch tall buildings and power lines for signs of shaking. But no earthquake came. Eight minutes after issuing the warning on Friday, the Japan Meteorological Agency (JMA) cancelled the alert, leaving residents to wonder what had gone wrong. “These alarms do not...