AMCHITKA ISLAND, Alaska — A cluster of moderate to significant earthquakes rattled the western Aleutian Islands and nearby offshore regions on Sunday, which scientists have identified as a “swarm.” However, earthquake monitoring officials in Alaska have reassured residents that there is no cause for alarm.
There were no immediate reports indicating damage or injuries in the regions around Adak, Amchitka, and Kiska islands, located roughly 1,350 miles (2,200 kilometers) west of Anchorage. Of these three remote islands, only Adak Island—home to approximately 300 residents—is occupied.
On Sunday morning and afternoon, the Alaska Earthquake Center recorded nine earthquakes with a magnitude of 5.0 or higher occurring in or around these islands, as well as in a clustered area off the southern coast. Among these tremors, three registered magnitudes of at least 6.0, with the strongest being a 6.3 quake positioned offshore.
In a report posted on its website Sunday evening, the earthquake center indicated that the 6.3 magnitude quake, which occurred at a depth of about 11 miles (18 kilometers), did not elicit concern on its own due to its offshore position and the absence of damage reports. Following this quake, the events that unfolded were deemed aftershocks, given they all exceeded magnitude 5.0.
However, two subsequent aftershocks exceeding magnitude 6.0, which occurred around 3 p.m. and were spaced 20 minutes apart, were noted as unusual. According to the center, the situation qualified as a swarm—evident in a series of earthquakes that clustered with similar magnitudes.
Michael West, the director of the Alaska Earthquake Center and the state’s seismologist, mentioned that while the swarm included larger quakes than usual, there was no need for residents to panic. “Swarms of moderately large earthquakes are typical in the Aleutians and don’t necessarily indicate any forthcoming significant activity,” he stated in the summary. “As this area has experienced numerous substantial historical earthquakes, we are closely monitoring the situation.”
Small earthquake swarms occur on average every couple of years in the subduction zone along the Aleutian chain, with a recent swarm happening in May about 350 miles (550 kilometers) east of the current seismic activity, according to the center.
The quakes that took place on Sunday were not associated with recent seismic disturbances at a volcano near Anchorage, which last erupted in 1992. Much of Alaska, including the Aleutian Islands, sits within the Ring of Fire—a seismically and volcanically active area that encircles a majority of the Pacific Ocean.