Officials reported one death in a town north of the capital and heavy waves and some flooding in a handful of coastal cities last night.
The tremor was so strong that people on the other side of the continent, in Buenos Aires, Argentina, reported feeling it.
Four aftershocks above magnitude-6 and other strong shakes rattled the region after the first major tremor since a powerful quake and tsunami killed hundreds in 2010 and leveled part of the city of Concepcion in south-central Chile.
"People started screaming that everything was shaking," he said.
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Officials ordered people to evacuate low-lying areas along the 2,400 miles (3,900 kilometres) of Chile's Pacific shore, from Puerto Aysen in the south to Arica in the north. Fishing boats headed out to sea and cars streamed inland carrying people to higher ground. Santiago's main airport was evacuated as a precaution and authorities announced classes would be suspended in the port city of Valparaiso today.
Chile state TV showed water flowing in streets of Concon, a coastal town known for its beautiful beaches that is close to Valparaiso. Higher water was also seen in other cities but no destructive high waves had been reported.
Illapel's mayor, Denis Cortes, told a local television station that a woman had been killed in the city but declined to give any details.
Electricity was knocked out, leaving the city in darkness. "We are very scared. Our city panicked," Cortes said.
The US Geological Survey initially reported the quake at a preliminary magnitude of 7.9 but quickly revised the reading upward to 8.3. Chilean authorities put the magnitude at 8.4. US officials said the quake struck just offshore in the Pacific at 2254 GMT and was centred about 141 miles (228 kilometres) north-northwest of Santiago. It said the quake was 7.4 miles (12 kilometres) below the surface.