A magnitude 7.9 earthquake struck the Aleutian Islands of Alaska Monday, prompting tsunami warnings and evacuations for the islands near the epicenter. The warning was later downgraded to an advisory as experts ruled out the potential of a destructive tsunami for other Pacific coastlines. The earthquake struck at 12:53 p.m. Alaska Daylight Time 4:53 p.m. Eastern time near Little Sitkin Island in the far western part of the Aleutian Island chain, just west of the International Date Line. According to the U.S. Geological Survey, the main jolt was followed by a series of aftershocks. Two significant aftershocks, measuring magnitude 6.0 and 5.8, occurring 18 and 37 minutes after the mainshock, respectively. About four hours after the 7.9 temblor, a magnitude-6.9 aftershock rocked the same area. Alaska Earthquake: Tsunami Warning Prompts Evacuations As Magnitude 8.0 Earthquake Strikes Aleutian Islands – weather.com Massive 8.0 Earthquake.