A short, sharp quake of magnitude 4.5 jolted Tokyo on Friday, but there were no immediate reports of damage and the Japan Meteorological Agency said no tsunami warning was issued.
The tremor was centred in western Tokyo, 40 km (25 miles) below the surface of the earth, the Agency said.
Japanese broadcaster NHK said trains and highways were operating as usual.
Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.
In October 2004, an earthquake with a magnitude of 6.8 struck the Niigata region in northern Japan, killing 65 people and injuring more than 3,000.
That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400.