An earthquake with a preliminary magnitude of 7.3 was registered off the South Sandwich Islands in the South Atlantic Ocean, the US Geological Survey reported Monday. The quake, centered 10 kilometers under the water some 345 kilometers (215 miles) southeast of Bristol Island in the South Sandwich Islands, a UK territory east of Argentina, struck at 5:10 a.m. local time (0610 GMT), the survey said on its Web site. The Japanese weather agency reported the same earthquake with magnitude 7.5. No further information was available. The agency said they did not any information about whether the quake had triggered a tsunami. Underwater quakes at low depths can cause a tsunami.