SOUTH AMERICA - The earthquake struck more than 700 km (435 miles) southeast of Argentina's city of Ushuaia, with a population of about 57,000, the USGS said. There was no tsunami threat after Thursday's earthquake of magnitude 7.5 in the Drake Passage between South America and Antarctica, the Pacific Tsunami Warning Center said, following its brief warning for Chilean coastal areas. The United States Geological Survey (USGS) revised down the quake magnitude, initially reported at 8, adding that it hit at a depth of 11 km (7 miles).