A magnitude 6.0 earthquake struck early Tuesday off the coast of northern Chile, but there were no reports of damage.      The U.S. Geological Survey said the quake was recorded at 3:46 a.m. local time at a moderate depth of 32 kilometers (20 miles). It was centered 37 kilometers (23 miles) west-southwest of the city of Arica.The biggest recent quake to hit Chile came in 2010, when a magnitude 8.8 quake caused a tsunami blamed for more than 500 deaths. 
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