There have been 36,337 earthquakes reported in Alaska so far in 2020. Most were just small rumblings of the North American and Pacific Plates grinding together along the fault line that runs south of the Aleutian chain. Only one, a 7.8-magnitude earthquake near Simeonoff Island in July, caused much alarm.
It may be years, months or even days before an earthquake large enough to cause a tsunami strikes coastal Alaska again. But whenever it does, Kodiak’s villages of Akhiok, Old Harbor, Chiniak, Port Lions and Ouzinkie will be a little better prepared.
At last week’s Kodiak Island Borough Assembly meeting, Elena Suleimani, a tsunami modeler with the Alaska Earthquake Center, presented inundation maps for the five communities.
Previous maps only showed how far a worst-case-scenario wave might reach. The newer maps were first published last year in a report. This year, they’ve been updated with more detailed information about where water would flow and how deep it might be.
The process of making such maps takes several years. First, data modelers with the Alaska Earthquake Center create nine different scenarios based on previous knowledge of how tsunamis have struck coastal Alaska. Then, they create a line based on the worst-case scenario that runs around or through the community they are modeling.
That line represents the danger zone. A big wave could potentially reach anything between it and the water. The line represents more than just the first wave, but all those that come after it.
The first wave isn’t always the most dangerous, Suleimani told the borough. The tides play a role too. In the Good Friday earthquake of 1964, the biggest wave hit Valdez 11 hours after the first quake. The first earthquake struck at low tide, and as the tide came in, the waves rose higher and higher.
The updated maps show more. Beyond just the line where the water could reach, they show how deep water could get in certain areas. This was done by walking around the various villages in question with survey equipment and doing more modeling on computers. The result shows, for example, much of the town center of Ouzinkie under deep water.
This squares with what was already known about tsunami risk in the village. In the 1964 tsunami, Ouzinkie suffered $500,000 in damage. The cannery, post office and company store were all destroyed, the waterfront was extensively damaged and commercial fishing gear was damaged beyond repair.
The maps can serve as guides for identifying better places to build emergency shelters. Suleimani said that in 2016, she presented very early stage maps to rural communities in Kodiak. Chiniak used them to decide where to build its new tsunami shelter after the old one burned down.
Still, the key to surviving tsunamis, as most Alaskans know, is preparedness. The first wave, Suleimani said, would likely arrive within 22 to 30 minutes after the earthquake strikes. That doesn’t leave much time for those in the inundation zone to flee to higher ground.
“You don’t have time to think about what to do at 4 a.m. when the alarm sounds. You all know this. You’ve had that experience before, ” she said.
Having a backpack full of emergency food, a radio, water, flashlight and other emergency supplies on hand is the best way to be prepared.
Suleimani said she is also working on maps for Karluk, Larsen Bay and Pasagshak.