The earthquake struck at 11:53 a.m. local 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 aftershocks measuring magnitude 6.0 and 5.8, occurring 18 and 37 minutes after the mainshock, respectively.