A 6.6-magnitude and another 6.1- magnitude undersea earthquakes jolted south of Fiji late Sunday, the United States Geological Survey (USGS) said. The epicenter of the first quake, a 6.6-magnitude one which struck from a depth of 527.6 kilometers at 9:15 p.m. local time ( 0915 GMT), was traced 722 kilometers south of the Fijian capital of Suva, USGS data showed. The agency had initially reported the quake at 6.8 magnitude. The epicenter of the second quake, a 6.1-magnitude one which struck from a depth of 610.6 kilometers at 9:25 p.m. local time ( 0925 GMT), was traced 848 kilometers south of Suva. The Hawaii-based Pacific Tsunami Warning Center did not immediately issue a tsunami warning based on the two quakes, and there were no immediate reports of casualty or damage. Fiji lies on the so-called Pacific "Ring of Fire," an arc of earthquake and volcanic zones where continental plates collide producing frequent seismic activity.