Buildings shook briefly in Tokyo and smartphone alerts could be heard going off in offices.
Update 05:38 UTC: Magnitude M5.6 at a depth of 590 km. Epicenter : Saitama-ken Hokubu
Update 05:41 UTC : JMA reports a max intensity of JMA 5-, just below what we see as the damage potential. Slight damage is however always possible.
Updates coming soon