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There were no immediate reports of damage or injuries in the
area around Adak, Amchitka and Kiska islands some 1,350 miles
(2,200 kilometers) west of Anchorage. Of the three remote
islands, only Adak Island, with a population of about 300
people, is inhabited.
Nine quakes measuring at least magnitude 5.0 struck on or near
the islands and in a cluster offshore to the south Sunday
morning and afternoon, according to the Alaska Earthquake
Center.
Three of the quakes measured 6.0 or stronger, with the biggest a
6.3 temblor offshore.
In a summary posted on its website Sunday night, the earthquake
center said the 6.3 magnitude quake at a depth of about 11 miles
(18 kilometers) did not raise concern on its own because of its
offshore location and the lack of damage reports, while the
events that followed within the hour above magnitude 5.0 were
expected aftershocks.
But two additional aftershocks above magnitude 6.0 that began
around 3 p.m. and spaced by 20 minutes were not normal. The
quake series constituted a swarm, or a cluster of earthquakes
with similar magnitudes, the center said.
Michael West, the Alaska Earthquake Center director and state
seismologist, said the swarm included quakes that were larger
than normal but should not alarm Alaska residents.
“Swarms of moderately large earthquakes are common in the
Aleutians and do not necessarily portend anything more
substantial,” West said in the summary. “Because this area has
been in, or on the edge, of numerous large historical
earthquakes, we are keeping close watch on it.”
There are small earthquake swarms every couple of years on
average in the subduction zone along the Aleutian chain. A swarm
occured in May about 350 miles (550 kilometers) east of Sunday's
activity, the center said.
The quakes on Sunday did not appear related to recent seismic
activity at a volcano near Anchorage that last erupted in 1992.
Much of Alaska including the Aleutian Islands is on the Ring of
Fire, a seismically and volcanically active zone that surrounds
most of the Pacific Ocean.
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