(Adds details on ocean levels, evacuation)
Santiago, March 16 (Reuters) - A strong quake struck off northern Chile on Sunday evening, triggering a preventive evacuation of part of the coastal area but not causing any injuries or damage to the country's crucial copper mines.
The magnitude 6.7 quake, originally measured as a 7.0, was centered 37 miles (60 km) west-northwest of Iquique and hit at a depth of 12.4 miles (20 km), the U.S. Geological Survey said.
The ONEMI emergency office said that preliminarily no damage or injuries had been reported after the shake, which struck at 6:16 p.m. local time (2116 GMT).
Chile's massive mines, clustered in the mineral-rich North, appeared to be fine. Collahuasi, a partnership between Glencore Xstrata and Anglo American, located in the area, said operations were normal.
The Pacific Tsunami Warning Center said there was no tsunami expected.
But Chile's navy said there was a possibility of what it called "a minor tsunami," so authorities ordered a preventive evacuation of part of the coastline after the quake.
Local media showed footage of people in Iquique calmly evacuating on foot to nearby hills.
A press officer at the ONEMI said sea levels in Iquique had risen a negligible 18 centimeters.
The officer said it was unclear how many people had evacuated, and that it depended on each local authority when they would return to their homes. (Reporting by Peter Cooney; and Alexandra Ulmer; Editing by Jim Loney and Chris Reese)