Tokyo jolted by third quake in four days

 An intensity map made available by the US Geological Survey shows the location where a preliminary 4.8 magnitude earthquake occured near Mobara, Japan on July 19.
An intensity map made available by the US Geological Survey shows the location where a preliminary 4.8 magnitude earthquake occured near Mobara, Japan on July 19.PHOTO: EPA

TOKYO (AFP) - Tokyo was struck by a third quake in four days on Wednesday (July 20), but there were no reports of damage or casualties.

The 5.0 magnitude jolt struck Tokyo and areas of eastern Japan at 7.25am (6.25am Singapore time), the US Geological Survey said.

The quake's epicentre was east of the capital in Ibaraki at a depth of about 44km, 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 on Tuesday 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 north-east coast, leaving more than 18,000 people dead or missing, and sending three reactors into meltdown at the Fukushima nuclear plant.