A strong earthquake registering 6.1 on the Richter scale deep under the sea shook northeastern Japan Wednesday, officials said. The U.S. Geological Survey said the quake was centered 68 miles north-northeast of Hachinoche on the island of Honshu and 74 miles east-southeast of Hakodate on the island of Hokkaido. The earthquake was at a depth of 25 miles and had a preliminary magnitude of 6.1, USGA said. No tsunami alert was issued. There were no immediate reports of damage or injuries.