The quake struck at a depth of 53 kilometers (33 miles) with an epicenter some 15 km southwest of Coquimbo, according to the USGS.
The earthquake, which hit at 0132 GMT (Sunday), was felt in Valparaiso, O'Higgins and the region of the capital Santiago, as well as in Atacama and Coquimbo up north.
Thousands of homes lost power, which showed how intense the quake was, according to Ricardo Toro of the National Emergency Office.
There were no immediate reports of injuries or damage.
Chile is one of the world's most earthquake-prone countries.
The 1960 Valdivia earthquake in Chile was the strongest ever recorded, at 9.5, on the magnitude scale, according to the USGS.
Chile lies on what is known as the Ring of Fire - an arc of fault lines that circles the Pacific Basin and is prone to frequent earthquakes and volcanic eruptions.
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