The Pacific Tsunami Warning Centre said the quake generated a large tsunami with the biggest wave reported at about six feet. The Chilean navy said the first big wave hit the coast within 45 minutes.
Iquique is a key port, close to Chile’s main copper mines.
‘On high alert’
The area has been on high alert in recent weeks after an unusual number of tremors, and a series of aftershocks further frayed nerves in the early hours of Wednesday.
The city is more than 900 miles north of Chile’s capital Santiago, where the quake was not felt.
Video footage showed Chileans calmly evacuating coastal areas on foot, with policemen helping bundled-up elderly people and some residents loading up vehicles with their belongings.
Seismic Chile has strict tremor-proof construction regulations and most residents stay calm during quakes, which helps to limit harm.
The government evacuated Chile’s northern coast and President Michelle Bachelet declared the area a disaster zone, promising troops and police reinforcements to maintain public order while damage was repaired after landslides blocked roads.
Lauding Chile’s initial response to the quake, Ms Bachelet said in a televised address: “The government will work for as long as necessary to confront this emergency.”
The center-left president, who only returned to power last month, was due to travel to the north on Wednesday morning.
In 2010, at the end of Ms Bachelet’s first term as president, an 8.8-magnitude quake triggered a tsunami that devastated several coastal towns in central-south Chile, a disaster that killed 526 people.
State-owned miner Codelco and other major copper companies reported no harm to workers or mines and said operations in northern Chile were normal.
A tsunami warning was issued for the Pacific coast of Mexico through central and south America.
“An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines near the epicentre within minutes and more distant coastlines within hours,” the Pacific Tsunami Warning Center said.