(Revises magnitude, adds no damage, changes dateline)
SANTIAGO, June 1 (Reuters) - An earthquake of 6.4 magnitude struck off Chile's Pacific coast on Wednesday, causing no damage or injuries in a region rocked by a massive tremor last year.
The quake's epicenter was 60 miles (96 km) southwest of Concepcion and occurred at a depth of nine miles (15 km), USGS said.
The U.S. agency initially reported the quake as 6.3 magnitude.
The temblor was felt with low intensity in Chile's south-central region, the same area that was devastated by a massive quake in February 2010. Chile's national emergency office said there were no reports of damage or injuries.
State-run oil company ENAP said the quake did not affect the country's largest oil refinery Bio Bio, which is near the region.
The epicenter of the new quake was far from the country's copper-producing region in the north. (Reporting by Santiago newsroom; Editing by Eric Beech)
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