A big earthquake could hit Seattle in the next 50 years. That got KUOW listener Derek Hanson wondering: What would happen to our most prominent landmark?
“The Space Needle seems really tall and tippy, and as a layperson looking at it, it seems like maybe it would fall over if there was an earthquake,” Hanson asked. “What would really happen in that case?”
It turns out the Space Needle will probably be just fine.
We’ve got nothing to worry about when it comes to our beloved landmark. Or its tall, slender neighbors in the Seattle skyline.
Instead, look lower.
Look at our old brick buildings built before World War II. They're just a few stories tall. Called unreinforced masonry buildings, they are much riskier.
In an unreinforced masonry building, the brick walls aren’t reliable when it comes to resisting the back and forth motion of an earthquake. The city has a list of these buildings — there are more than 1,150 of them — and they surround us daily.
Even when we belt Karaoke "Rock Lobster" on Capitol Hill.
On a recent Saturday evening, Rock Box karaoke bar manager Monchaya Paitoonnerarmit pointed up at the thick wooden support beams in the hallway between private singing rooms. New, flat metal braces on top of the wood secure the beams together.
“We wanted to make sure everybody is safe here, so when we talked to them, they sent their team in to take a look at this and they came up with a solution.”
Unreinforced masonry is even more ubiquitous than you may think. When structural engineer Dave Swanson came in for an interview, we showed him the KUOW newsroom. Fun fact: We are also in an unreinforced masonry building.
Swanson pointed out our exposed brick walls — a lush red hue — and their alternating rows of bricks stacked short and long. “Here’s a good telltale sign for you,” he said. (The short and long brick faces mean there aren’t other support beams inside the wall.)
Luckily, our building has been upgraded. The city estimates more than half of these buildings have not been retrofitted at all.
Swanson tells us one more thing. There is yet another type of building that we should be even more concerned about. More than the Space Needle. More than unreinforced masonry.
Nonductile concrete buildings.
Those buildings are from around the 1920s to the 70s. They’re vulnerable to quakes.
“A lot of them are warehouses and industrial functions that now, given our urbanization, have turned into lofts and other areas for people to work and sleep and have retail and commerce in,” Swanson said.
Researchers have inventoried these buildings in Los Angeles. But in our region, we don’t know how many there are. So, where is the best place to be during an earthquake?
On a clear day, KUOW listener Derek Hanson and Karen Olson, head of marketing for the Space Needle, went up to the Space Needle's observation deck.
“If we were up here during an earthquake, we probably would need a little motion sickness medicine after, because we would be moving,” Olson said.
Contrary to Hanson’s initial impression, the Space Needle is actually not tippy at all. Its bones are flexible steel and well rooted in a massive foundation.
Below the ground, the Space Needle weighs around 7,000 tons. Compare that to what’s above ground: about 4,000 tons. And, right now, the tower is undergoing seismic renovations to make it even stronger.
“So, it’s probably one of the best places you can be during an earthquake,” Olson said.
Really, the Space Needle?
Structural engineer Dave Swanson agrees: “I would say that's a relatively fair statement.”
Tall buildings are designed to be flexible, he said, and landmark buildings benefit from extra design attention.
“The Space Needle is going to want to act like an inverted pendulum and sort of bend left and right, kind of like wheat in a wheat field during a windstorm.”
Bending but not breaking.