The 6.9 magnitude temblor off Hokkaido Island's southeastern coast caused tidal changes that prompted some communities to issue evacuation orders for seaside residents.
But the relatively small ocean surge caused no damage or injuries to the region hit hard last year by Japan's record 9.0 magnitude quake and giant tsunami.
The Japan Meteorological Agency reported that Wednesday's undersea quake struck about 450 miles northeast of Tokyo at 7:08 p.m. local time/
Three hours later, a 5.7 magnitude jolt centered 55 miles east of Tokyo was felt throghout the capital.
There were no injuries or damage reported from that shaking.