SANTIAGO (Reuters) - A powerful quake shook northern Chile on Friday causing widespread alarm in the port city of Antofagasta that serves the country's mining regions, local radio said. Radio Agricultura said the quake lasted one minute and registered an intensity of 6-7 on the Mercalli scale in the Antofagasta area. There were no immediate reports of deaths or injuries. "It started at 0917 (7:17 A.M. EST/1217 GMT) this morning and lasted about a minute. It shook houses here in Antofagasta and provoked alarm," a reporter for Radio Agricultura told the station. First indications were that the quake's epicenter was just off the coast of Antofagasta 850 miles (1,360 km) north of the capital, local radio said. Other northern Chile regions felt the quake. "The information I have is that it was felt between Iquique and Vallenar," another reporter for the station said. The two cities are 740 miles (1,184 km) apart. The Mercalli scale, which is often used in Chile, measures the intensity of an earthquake. The more common open-ended Richter scale measures magnitude.