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Let’s revisit WSDOT’s terrifying Alaskan Way Viaduct earthquake simulation

It’s almost gone, so let’s take another peek

WSDOT’s simulation of the Alaskan Way Viaduct collapse.

There’s been a lot of nostalgia around the Alaskan Way Viaduct lately. It’s been up for more than 60 years, and most of us either can’t remember or can barely remember a Seattle without it. For those that travel by car, the viaduct has some of the most gorgeous views of Elliott Bay in the public right-of-way.

But between the fraught history of choosing the viaduct’s replacement, years of delays, and nine figures of cost overruns, it’s sometimes easy to forget what got us into our present condition: earthquakes. In 2001, we all got a nasty reminder that we’re in a supremely earthquake-prone region when the 6.8 Nisqually quake hit the area, damaging the viaduct. WSDOT repaired and strengthened the viaduct, but for almost two decades, the highway has shut down twice a year for safety inspections.

This only contributed to growing tension around the viaduct’s stability—in 1989, the collapse of a similar structure, Oakland’s Cypress Street Viaduct, killed 42 people. Throughout the 1990s, we learned more and more about the danger of the Seattle fault and the Cascadia Subduction Zone.

Then one fateful day in 2009 (a week before election day!) WSDOT circulated a 2007 simulation video showing what would happen to the viaduct in an earthquake a little more potent than the Nisqually quake—longer, with a closer epicenter, or slightly greater in magnitude. We stared at our computer screens as we watched the viaduct and seawall collapse and eventually catch fire. Cars sink into Elliott Bay. The view pans out over the smoldering ruins to show a crack in unreinforced masonry nearby, although it’s mostly upstaged by the smoky, concrete soup in front of it. Ivar’s stays intact somehow.

“Alaskan Way street and viaduct are impassable,” reads the last blurb of clinical text narrating the video. “Colman Dock sustains damage. Half of city without power or communications.” But it ends on a high note, at least: “No tsunami expected.”

This decade-old video is revisited in another video released by WSDOT on Monday, interviewing experts about the viaduct’s earthquake vulnerability (and the tunnel’s comparative safety). Over a short clip of the simulation, UW civil and environmental engineering professor Steve Kramer remembers running models that told WSDOT what would happen to the earthquake and seawall right after the Oakland viaduct collapse: “The analysis took a week to run on the computer and it was just failing, tumbling essentially.”

We knew the viaduct was earthquake-vulnerable more than 10 years before the Nisqually quake. But the visual horror show of WSDOT’s dead-silent portrayal of cars being swallowed by Elliott Bay really drove the thing home.

Alaskan Way Viaduct

Alaskan Way Viaduct, , WA