Summary:
A strong earthquake has struck off the coast of Japan, triggering a tsunami warning.

Full article:
(CNN) -- A strong earthquake with a magnitude of 6.8 struck off the coast of Japan on Sunday, the U.S. Geological Survey reported. The earthquake hit 468 kilometers (302 miles) south-southwest of Tokyo at a depth of 348 kilometers, according to the USGS. There were no immediate reports of injuries or damage. The Pacific Tsunami Warning Center did not issue a tsunami warning. The USGS gave the quake a preliminary magnitude of 7.0 before downgrading it to 6.8. Ohio looks into quakes' possible link to fracking . Japan lies along the Pacific "ring of fire," an area of high seismic and volcanic activity stretching from New Zealand in the South Pacific up through Japan, across to Alaska and down the west coasts of North and South America. Last year, a devastating earthquake and tsunami hit northeastern Japan, leaving thousands of people dead or missing. The March 11 earthquake triggered powerful tsunami waves and sparked a nuclear crisis.