Japan's Meterological Agency says the quake struck near the uninhabited island of Torishima in the Pacific Ocean, about 370 miles south of Tokyo. Its epicenter was about 230 miles below the sea. It did not generate a tsunami.
Express trains in northern and central Japan were suspended temporarily for safety checks but later resumed. Public broadcaster NHK says no abnormalities have been reported at power plants, including the crippled nuclear power plant in northeast Japan hit by the March earthquake and tsunami.
A massive earthquake and tsunami March 11 left nearly 20,000 people dead or missing. Japan, which lies along the Pacific "Ring of Fire," is one of the world's most seismically active countries.
