Magnitude 5.2 earthquake strikes near Aleutian Islands; residents on alert for tsunami

A magnitude 5.2 earthquake struck off Alaska's Aleutian Islands early Monday, prompting concern among coastal communities though no immediate tsunami warning was issued.

The U.S. Geological Survey (USGS) recorded the initial quake at 1 a.m. local time (5:02 a.m. ET) near the uninhabited village of Nikolski. Less than two hours later the agency logged a magnitude 4.8 aftershock in the same region. The USGS reported a shallow depth of about 6.2 miles, a factor that typically produces stronger shaking at the surface than deeper events of similar magnitude.

Local authorities and residents on Alaska’s mainland assessed possible impacts despite the lack of an immediate tsunami alert. The USGS estimated a roughly 60% chance of at least one magnitude 3.0-or-greater quake near the same epicenter within the next week and placed the probability of another magnitude 5.0-or-greater event at approximately 2%.

The Alaska Earthquake Center said the seismic activity was driven by the Aleutian megathrust, a major subduction zone where the Pacific Plate is forced beneath the North American Plate. "It is a seismically active region, evidenced by the thousands of earthquakes occurring each year," the center said.

Because Nikolski is uninhabited, the USGS received no crowd-sourced shaking reports from the immediate area. Still, recent large earthquakes in the North Pacific have left communities on edge: in July, an 8.8-magnitude event off Russia's Kamchatka Peninsula and a separate magnitude 7.5 quake south of the Alaska Peninsula near the Shumagin Islands triggered tsunami alerts and precautionary evacuations across parts of Alaska.

Officials said alerts issued during the July events covered communities along the Aleutian chain, including Atka, Adak and the Pribilofs, and extended to more distant areas such as Hawaii and parts of the U.S. West Coast before being lifted. The largest measured wave in Alaska from that sequence was about 2.7 feet. David Snider, a tsunami warning coordinator at the National Oceanic and Atmospheric Administration, said a tsunami was generated by the July quake but "no longer poses a threat," with some locations continuing to experience only minor sea-level changes.

State and local officials have previously urged residents in low-lying coastal areas to move to higher ground when alerts are issued. During the July sequence, tens of thousands of people along Alaska’s coastline followed evacuation orders, sometimes resulting in heavy traffic as residents moved inland. Kodiak High School and North Star Elementary School were among facilities opened as emergency shelters during that period.

Emergency managers and scientists noted that the Aleutian megathrust remains one of the most active seismic zones in the world and that aftershocks and further activity are common following even moderate quakes. The USGS and the Alaska Earthquake Center will continue to monitor the area for additional seismicity and will update assessments and warnings as needed.

Monday’s events did not report injuries or structural damage in populated areas. Residents and officials in coastal communities remained vigilant for any new bulletins or advisory statements from federal and state agencies as they assess potential short-term seismic risk in the region.