Update | June 24, 2014 at 5:43 a.m.
The tsunami advisory in Unalaska has ended, after a powerful underwater earthquake in the Western Aleutians triggered tsunami alerts for parts of the Aleutian Islands Monday afternoon.
No damages were reported after the magnitude 8.0 quake, recorded just before 1 p.m. on Monday. It happened about 30 miles northwest of Amchitka, about 60 miles underwater.
Residents in the Western Aleutians reported feeling shaking during the quake, according to the Alaska Earthquake Information Center. And the quake has set off a series of aftershocks, some as strong as a magnitude 6.
The earthquake also generated a tsunami warning from Attu to Nikolski and in the Pribilof Islands for about two hours Monday. It was then downgraded to an advisory.
The Unalaska area, from Nikolski to Unimak Pass, was also under an advisory for part of Monday afternoon. It ended around 4 p.m.
The tsunami alerts stemmed from the force of the quake. But the Earthquake Center’s Natasha Ruppert says tremors at such a depth don’t often create tsunamis.
“Based on its magnitude, there is definitely potential for tsunami in the Aleutian Islands,” she said Monday afternoon, while the alerts were in effect. “But based on its depth, I do not expect that there will be a significant tsunami from this earthquake.”
The National Oceanic and Atmospheric Administration observed tsunami waves about a foot in height or less in Unalaska, Adak and other islands in the region. Those waves are measured at the highest water level above the tide level. They weren’t high enough to do any damage.
Unalaska’s Department of Public Safety told residents to avoid beaches and harbors during the advisory, but there was no full-scale evacuation to high ground.
Original Post | June 23, 2014 at 2:00 p.m.
A tsunami warning is in effect for part of the Western Aleutians, from Attu to Nikolski, and for the Pribilof Islands.
There’s also a tsunami advisory in place for the Unalaska area — from Unimak Pass to Nikolski, just east of the warning area. The Department of Public Safety says residents in Unalaska do not need to take any action at this time.
People in the tsunami warning area should move to high ground and steer clear of the coast in case of high waves, and heed instructions from their local emergency personnel.
The tsunami warning stems from an underwater earthquake recorded just before 1 p.m. today, about 30 miles northwest of Amchitka Island in the Western Aleutians. The quake happened at a depth of about 60 miles. Preliminary magnitude estimates are between 7 and 8.
That’s a powerful quake, which automatically triggers a tsunami warning. But the Alaska Earthquake Information Center says there’s very little tsunami risk from a quake so deep underwater.
They also say the quake does not have anything to do with the volcano on watch in that area. Semisopochnoi has been experienced a series of small tremors over the past couple of weeks. But the AEIC’s Natasha Ruppert says it’s not related.
“Earthquakes that are related to volcanos are very shallow, right beneath the surface,” she says. “This one is about 100 kilometers deep.”
Again, the tsunami advisory in Unalaska does not mean residents have to take any action. A tsunami warning is in effect for coastal areas from Attu to Nikolski and in the Pribilof Islands, St. Paul and St. George.
— NWS Alaska Region (@NWSAlaska) June 23, 2014