How prepared are Washington’s buildings for a big earthquake?
Wed., Feb. 15, 2023
In the span of nine hours on Feb. 6, 7.8 and 7.5 magnitude earthquakes hit southeastern Turkey and northern Syria, killing tens of thousands and flattening some newer buildings that were supposedly built to modern U.S. standards.
While Turkish officials continue to investigate whether some of those collapses were caused by unscrupulous contractors, the question remains: Could Washington’s own buildings withstand a similar disaster?
“There really is no such thing as an earthquake-proof building,” said Jeff Berman, civil and environmental engineering professor at the University of Washington. “There are buildings with a lower probability of collapse.”
Washington has many seismic risks, some of which have only become well understood in recent decades. The existence of the Seattle Fault was only definitively recognized in 1992, and the extent of the risks posed by the Cascadia Subduction Zone came to light later that decade.
In particular, the Cascadia Subduction Zone, where three tectonic plates are slowly sliding underneath the West Coast of the much larger North American Plate, has the potential to trigger monstrous earthquakes and tsunamis.
FEMA projects that a 9 magnitude earthquake could produce a tsunami up to 80 feet tall, reaching the coast 10 to 30 minutes after the earthquake began. An estimated 8,000 people in Washington and Oregon would die from the tsunami, and another 5,800 from the earthquake itself. Another 100,000 would be injured, and 1 million people would be displaced.
Infrastructure would be devastated. A 2019 study by state and federal officials found that much of Western Washington’s roads, rail networks, ports and airports would be extensively damaged.
The study found that of the roughly 3,500 bridges operated by the state Department of Transportation only 13% could be made somewhat operable within a month after the earthquake. Nearly 29% of bridges would take more than a year.
As for the state’s buildings, newer construction in Washington follows some of the best standards in the world, Berman said.
“Again, they aren’t earthquake proof,” he said. “We design for a certain standard of reliability.”
That standard is that a building has no more than a 10% chance of collapsing every 2,500 years, given the understood seismic risks in the area.
Berman admits an expected risk of collapse might not feel entirely comforting. But when the design life of a building is roughly 50 years, 2,500 years is a long time.
“It’s risk,” he said. “We all assume risk in our daily life, when we get into our cars, when we get onto the highway.
“We wouldn’t have a city if you designed every building to withstand the strongest possible earthquakes,” he added.
Berman acknowledges that those calculated risks sometimes fall short. In some areas of Turkey, the seismic shock appears to have been worse than the buildings were designed to withstand.
“Even if buildings were designed to code, this earthquake exceeded the code design,” he said. “In Seattle or other locations, could we have earthquakes that exceed what we design for? Absolutely.”
Those risk calculations are also based on best available data. While the basics of how to build a building to withstand a powerful shake have been relatively similar for decades, Berman said, our understanding of the likeliness and severity of those quakes has changed radically during that time.
The concept of tectonic plates was considered controversial until the 1960s. Until the 1990s, many scientists expressed skepticism that the Cascadia Subduction Zone had as violent a past as it does.
It took many years for the threat posed by the Cascadia Subduction Zone to be baked into building codes, said Corina Allen, Chief Hazards Geologist for the state Department of Natural Resources.
As a result, many of the older buildings in Seattle and elsewhere in Western Washington are not built to withstand the Big One. Buildings made of unreinforced masonry, like many of Spokane’s older brick buildings, or inflexible concrete are particularly susceptible to collapse.
Efforts are underway to try to make up for lost time. In 2020, the state Legislature passed a bill that provides loans that can be used for seismic retrofitting with a focus for the state’s nearly 4,500 unreinforced masonry buildings.
Last year, the Legislature passed a law establishing a grant program for seismic retrofitting of schools. Approximately 800 schools across the state are in need of significant upgrades, according to a 2021 study by the state Department of Natural Resources.
These efforts cannot come fast enough, said Peter Nitze, CEO of investment firm and co-founder of the Alliance for Safety, Affordability and Preservation, which has advocated for seismic retrofitting in Seattle.
“The concern is that we suffer something like Christchurch or Turkey,” Nitze said, referring to the 2011 earthquake in New Zealand, where collapsing unreinforced masonry killed dozens. “This is a public safety issue.”
The primary obstacle to making progress is, of course, cost, Nitze notes. He estimates retrofitting can run anywhere from $5 to $100 per square foot.
While the loan program passed by the state in 2020 is a good first step, Nitze argues more incentives and financing is needed to make seismic retrofitting more economically feasible.
Efforts are also well underway to harden the state’s transportation infrastructure, particularly its bridges. The state Department of Transportation has 585 bridges in need of seismic retrofitting, with an estimated price tag of $1.5 billion. Of those, 114 bridges have been partially retrofitted but still need additional work.
There have been success stories, Berman notes. The demolition of the Alaska Way Viaduct, which was at risk of collapse in a major earthquake, was an important step forward for Seattle, he said.
But there is more work to be done.
“I think it’s super important that the Pacific Northwest doesn’t lose sight of its seismic hazard,” Berman said. “There is no shortage of problems to solve, but we have a sizable seismic hazard here, a lot of older buildings, and it’s a big concern.”
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