(Eugene, OR) -- A cluster of strong earthquakes struck off the coast of Oregon this morning. According to the U.S. Geological Survey, a 4.3 magnitude quake hit at about 3:25 a.m.  Five minutes later the strongest quake of the morning, a 5.5 hit. Five minutes after that a 5.4, and about 20 minutes later another 5.4. The U.S. Tsunami Warning System does not indicate any threat to Oregon's coast.