ANCHORAGE, Alaska â An early morning earthquake that rattled Alaska has been followed by a second aftershock in the Cook inlet region. The Alaska Earthquake Center says preliminary reports put the latest aftershock at a magnitude-4.7. 1  A magnitude-7.1 earthquake that struck early Sunday knocked items off shelves and walls in south-central Alaska and jolted the nerves of residents in this earthquake-prone region. 2  The earthquake struck about 1:30 a.m. Alaska time and was centered 53 miles west of Anchor Point in the Kenai Peninsula, which is about 160 miles southwest of Anchorage, according to the U.S. Geological Survey. About two hours later, a magnitude-4.3 aftershock hit the Cook Inlet, the agency said.