A powerful earthquake of 6.4 magnitude hit the coast of Japan but no immediate tsunami warning was issued. Japan's meteorologists have said the underwater quake is likely to trigger some "slight sea-level changes in coastal regions".
The USGS said the tremor was centred about 230km southeast of capital Tokyo and struck at a depth of 10km. Tokyo's official meteorological agency said the quake that struck in the early hours of Friday (23 September), did not cause any "damage to Japan".
As the country sits on top of three tectonic plates — North America, Pacific and Philippine Sea — Japan frequently experiences such tectonic movements resulting in powerful quakes. Devastating earthquakes have struck Japan in the past claiming tens of thousands of lives.