Japan on high alert for 'huge' 2nd quake
Digest more
A large earthquake prompted a short-lived tsunami warning and a slightly higher-than-average risk of a mega-quake. The Cabinet Office, along with the Japan Meteorological Agency, said the risk of a mega-quake was increased from the typical .
Two hours after the tremor tsunami waves as high as 80 cm had been detected. A tsunami warning was later downgraded to a tsunami advisory.