tsunami

Photo: Sabine Poux/KDLL

When an 8.2-magnitude earthquake hit near the Alaska Peninsula Wednesday, local alert systems sprang into action, beeping, buzzing and blaring to notify Alaskans in coastal communities they should get to higher ground.

Those notification systems require lots of preparation and funding well before a tsunami threat hits, explained Dan Nelson, emergency manager with the Kenai Peninsula Borough’s Office of Emergency Management.

Alaska Division of Geological and Geophysical Surveys

Geologists have been warning Alaskans for over a year about a tsunami that could hit Whittier following a potential landslide at Barry Arm in Prince William Sound.

They’re still ringing the alarm bells. But now, armed with more information about the area, they’re saying that wave will be a lot smaller than they originally expected.

Scientists have been scrambling for the last year and a half to wrap their heads around the risk posed by a potentially massive landslide on the steep slopes of Barry Arm in Prince William Sound. In a worst-case scenario a full slope failure could pummel Whittier with a tsunami wave as big as 30 feet.

State and federal researchers are working to get a better understanding of the size and factors that might cause the slope to fail, to help tsunami forecasters give boaters and coastal communities in the sound as much advance warning as possible.

Division of Geological and Geophysical Surveys

This summer is going to be busy in upper Prince William Sound. Not just for fishing, shrimping, kayaking and other recreational boating. But for scientists to continue research and modeling on a massive landslide threatening to crash into Barry Arm, and send a potentially devastating tsunami around the corner to Whittier.

NOAA

A magnitude-7.8 earthquake activated the national Tsunami Warning System late Tuesday night. The epicenter was 8 miles deep, south of Perryville and Chignik on the Alaska Peninsula. It was initially estimated at magnitude 7.4 but was revised upward.

The U.S. Tsunami Warning System activated about five minutes later, issuing an alert across coastal Alaska, from Seward to Unalaska, sending text messages to cellphones and triggering tsunami warning sirens in Kodiak, on the Alaska Peninsula and Aleutian Islands, as well as in Homer and Seward. 

Mike West, a seismologist and director of the Alaska Earthquake Center, said this type of earthquake is the kind they worry about for tsunamis. 

“It is the style of earthquake which tends to generate tsunamis,” West said. “All early signs indicate that this is on what we refer to as the subduction zone. It’s the interface, the plate boundary between where the Pacific Plate thrusts underneath North America. A very standard type of earthquake in this area.” 

An unstable slope caused by the retreat of Barry Glacier, northeast of Whittier in Prince William Sound, has geologists worried about a potential massive landslide and resulting tsunami.   
“It would be about the size of around 500 Empire State buildings falling into the fjord at once if it did release as a solid mass on the unstable slope.”
The resulting tsunami wave could be 30 feet or more in Whittier, arriving about 18 minutes after the landslide.

Division of Geological and Geophysical Surveys

The threat of a large tsunami is looming in Prince William Sound, where a landslide could generate a wave with devastating effects on fishermen and others frequenting the area.

Geologists say that the rapid retreat of Barry Glacier from Barry Amy, 28 miles northeast of Whittier, could release millions of tons of rock into Harriman Fjord, triggering a tsunami that could rival or exceed the largest slide-caused tsunamis in the state’s recorded history.

The loose slope is on the western side of the arm, now bare and hanging at a precarious angle since the retreat of the glacier. Steve Masterman, director of the Division of Geological and Geophysical Surveys, says the slope could release 10 times the amount of rock as the two most noteworthy, slide-triggered tsunamis in Alaska history.

Alaska Earthquake Center

  Kenai appears to have weathered the damage from the two strong earthquakes this morning.

Centered in and around Anchorage, the 7.0 and 5.7 earthquakes have triggered tsunami warnings for as far away as Prince William Sound, Kodiak, and all of the west coast of the Kenai Peninsula. All tsunami warnings were later cancelled with no waves reported.

Kenai Fire Department Battalion Chief Tony Prior said the department is responding to several calls.

Bjørn Olson

  Across Kachemak Bay from Homer, just up the coast from Halibut Cove, is Grewingk Lake, a popular daytrip destination for visitors. Just a short water taxi ride from Homer, the lake is fed by its namesake glacier.

The 7.9-magnitude earthquake which struck near Kodiak in January generated plenty of tsunami alerts -- though little in the way of actual tsunamis -- throughout coastal communities in the Gulf of Alaska, including here on the Kenai Peninsula.

Unfortunately, many people who needed to be notified of potential doom were not able to be reached because of limitations in the equipment the borough's Office of Emergency Management uses to contact citizens in times of crisis.

Last month’s 7.9 magnitude earthquake off Kodiak Island meant different things to different people on the Kenai Peninsula, and it all depended on where they lived. In areas closer to the open ocean of the Gulf of Alaska, it meant evacuation to high ground, while in the Central Peninsula, it was a midnight diversion, something to post about on Facebook for a few days.

For the people of the Kenai Peninsula Borough’s Office of Emergency Management, it was the time to swing into high gear to warn residents in vulnerable areas of possible tsunami danger.