It hit at 7:21 am (2221 GMT Monday) in waters 96 kilometres (60 miles) east of Miyako on the main island of Honshu at a depth of just 9.7 kilometres, according to the US Geological Survey.

The quake was followed by a 5.1-magnitude jolt roughly 30 minutes later, which hit 107 kilometres east of Miyako. It was measured at a depth of 37.9 kilometres, the USGS said.

The area, badly damaged by the major earthquake and tsunami of March 2011, is located roughly 500 kilometres north of Tokyo.