Tokyo: Tokyo was struck by a third quake in four days on today, but there were no reports of damage or casualties.
The 5.0 magnitude jolt struck Tokyo and areas of eastern Japan at 7:25 am (2225 GMT yesterday), the US Geological Survey said.
The quake's epicentre was east of the capital in Ibaraki at a depth of about 44 kilometres (27 miles), the USGS said.
There was no threat of a tsunami.
It was the third to shake the capital's high-rise buildings this week, after a 4.8 magnitude quake yesterday and a 5.0 on Sunday.
Japan sits at the junction of four tectonic plates and experiences a number of relatively violent quakes every year, but rigid building codes and strict enforcement mean even powerful tremors frequently do little damage.
A massive undersea quake that hit in March 2011 sent a tsunami barrelling into Japan's northeast coast, leaving more than 18,000 people dead or missing, and sending three reactors into meltdown at the Fukushima nuclear plant.
