An earthquake measuring 5.5 on the Richter scale jolted 180 km west of Brookings, U.S. state of Oregon at 03:19:42 GMT on Sunday, the U.S. Geological Survey (USGS) said. The epicenter, with a depth of 11.0 km, was initially determined to be at 41.761 degrees north latitude and 126.425 degrees west longitude.