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SINGAPORE April 15 (Reuters) - A magnitude-6.1 shallow quake struck off Indonesia's Sumatra island early on Thursday, but there were no reports of casualties, officials said.
The U.S. Geological Survey said the depth of the quake was 8.5 km (5.3 miles), although it was "poorly constrained." It had earlier estimated the magnitude at 6.6.
The Indonesian meteorological agency bureau said the quake did not trigger a tsunami and no casualties had yet been reported.
It struck 210 km northwest of the Sumatra town of Bengkulu at 3:01 a.m. on Thursday.
It followed a magnitude-5.5 earthquake in the same area two and a half hours earlier.
The quakes, at least 620 miles (1,000 km) south of the devastating 2005 Sumatra tsunami, did not trigger a tsunami warning but could cause small local waves, USGS geophysicist John Bellini said earlier.
The Indonesian archipelago suffers frequent earthquakes, lying in an area of intense seismic activity where several tectonic plates collide.
Reporting by Sandra Maler in Washington and Harry Suhartono in Singapore; Writing by Sanjeev Miglani
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