ANCHORAGE, Alaska -- A 6.6 magnitude earthquake has rocked buildings in Anchorage, prompting people to run out of offices and seek shelter under office desks. The U.S. Geological Survey says the earthquake was centered about 7 miles north of Alaska's largest city. Officials issue tsunami warning for coastal areas of southern Alaska after earthquake. There was a tsunami alert for Cook Inlet, the National Weather Service in Anchorage said on Twitter.