Strong Quake Hits off Japan, No Tsunami Alert

A strong 6.8 magnitude earthquake struck in waters off Okinawa island on Tuesday, but there were no concerns about a tsunami, the U.S. and Japanese agencies said.

The quake occurred in the East China Sea, 218 kilometers (136 miles) west of Naha, Okinawa prefecture, the U.S. Geological Survey said. The quake's depth was 222 kilometers (138 miles).

There were no immediate reports of injuries or damage from the quake, which happened at 11:59 am (0259 GMT).

Japan, located at the junction of four tectonic plates, experiences 20 percent of the strongest quakes recorded on earth each year.

A devastating tsunami on March 11 left about 22,000 people dead or missing and triggered an atomic crisis at the Fukushima Daiichi nuclear plant in the northeast of the country.