Upending previous understanding of Anchorage’s tsunami vulnerability, researchers said Wednesday that a “rare but real risk” exists that a confluence of conditions could lead an earthquake-produced tsunami to inundate parts of coastal Anchorage, including the Port of Alaska and much of Ship Creek.
The findings, presented by researchers from the Alaska Earthquake Center and the state Division of Geological and Geophysical Surveys, are the result of a first-time effort to model earthquake scenarios’ potential tsunami impact on Anchorage.
“A rare combination of earthquake magnitude, location, and timing must be satisfied for tsunami wave energy to reach upper Cook Inlet coincident with a natural high tide,” the study found. …
Part of the reasoning that Anchorage was “immune” to tsunami destruction, the researchers said, was that during the 1964 earthquake — with a magnitude of 9.2 — there was no observation of a tsunami in Anchorage. But the earthquake, researchers found through modeling, did produce a 10-foot tsunami — which went unnoticed because it arrived at 2 a.m. during a minus-16-foot low tide, which meant the water level stayed below normal high tide levels. …
A potential worst-case scenario tsunami in Anchorage would affect some waterfront homes but largely parkland and infrastructure — like the port, Loach said. And the dynamics of the Upper Cook Inlet mean a destructive wave would probably be hours away, so people could be warned in advance, she said.