Adak, Alaska – A magnitude 5.5 earthquake struck early Sunday south-southwest of Adak, shaking portions of the central Aleutian Islands before sunrise. The U.S. Geological Survey recorded the quake at 8:21 a.m. UTC (late Saturday night local time), centered about 59 kilometers SSW of Adak at a depth of 54.8 kilometers.
According to USGS, light shaking was reported across the region, with two “Did You Feel It?” responses submitted as of Sunday morning. The agency classified the event with green PAGER alerts, indicating low likelihood of significant injuries or economic losses.
The earthquake occurred along one of the most seismically active corridors in the United States, where the Pacific Plate subducts beneath the North American Plate. While quakes of this magnitude are common in the Aleutians, USGS notes that aftershocks are likely. The agency estimates an 85% chance of at least one aftershock of magnitude 3.0 or higher this week and a 47% chance of an aftershock of magnitude 4.0 or higher.
No damage, tsunami alerts, or service interruptions have been reported for Adak or nearby communities, which remain sparsely populated but host critical military and scientific infrastructure.
USGS ShakeMap imagery shows that the strongest intensities were located offshore, with weak to light shaking extending across Adak Island. Regional seismicity maps indicate consistent activity over the past several weeks within 250 kilometers of the event.
Residents of the Aleutians who felt the quake are encouraged to submit reports to the USGS “Did You Feel It?” system to assist with ground-level intensity mapping.
Have you felt shaking in the Aleutians today? Tell us where you were and how strong it felt.
