“Collapsed structures and highway bridges kill or injure thousands of people. Communication links are swamped or broken … The earthquake will trigger fires …”
–– “Scenario for a Magnitude 6.7 Earthquake on the Seattle Fault,” June 2005
After years of speculation about a big earthquake in Seattle, voters will soon decide whether to pay billions of dollars to help shore up bridges, overpasses, a floating bridge and an elevated highway, much of it in the quake-threatened area of central Puget Sound.
“If the (2001) Nisqually earthquake had lasted a mere 15 seconds longer, the Alaskan Way Viaduct in Seattle and SR 520 (floating bridge) would have crumbled, and bridges all up and down the I-5 corridor would have been highly vulnerable,” Gov. Christine Gregoire said last month. Reinforcement of such structures is long overdue, she said.
“These are our levees, and the earthquake is our hurricane,” the governor said. “We are not going to be given a warning.”
The economic aftershocks of a severed transportation system would hurt the entire state, proponents of the new gas tax say. It’s in Eastern Washington’s self-interest, they argue, to help protect Puget Sound, the engine of the state’s economy.
Critics say the earthquake threat is being used as an excuse for a huge tax increase.
“I think it’s marketing,” said Brett Bader, a spokesman for Initiative 912, which would veto the gas tax increase. “No one denies that government has a responsibility to make sure roads and bridges are safe, but I think they (Seattle leaders) have neglected their opportunities.”
Instead of steering hundreds of millions of dollars in public money into two sports stadiums and proposed monorail and light rail systems in recent years, he said, local officials should have been focusing on basics like the viaduct, a decades-old elevated highway.
“They could have fixed the viaduct years ago, but they chose to spend the money on other things,” Bader said. “And now they have their hands in the air, saying everyone has to help them pay for a new viaduct.”
“A little after 3:15 o’clock yesterday afternoon a stream of people, hatless, coatless, some in an even worse state of dishabille rushed down the stairs or to the elevators of every one of the downtown buildings and onto the streets, their faces showing every sign of terror.”
– Earthquake report in the Seattle Post-Intelligencer, Dec. 1, 1891
Washington seismologists say that a Puget Sound quake is like death: you know it’s coming, you just don’t know when.
The region has a long history of deep earthquakes every few decades, like the 1891 quake and the 2001 Nisqually quake. They can be big – the Nisqually Earthquake was magnitude 6.8 – but since they’re deep, damage is usually minor.
According to U.S. Geological Survey studies, there is an 87 percent chance of such a quake in Puget Sound in the next 50 years.
“That’s as likely to certain as you’re going to get,” said Bill Steele, University of Washington seismology lab coordinator.
A greater worry – although a lower probability – are quakes right on the surface.
Before 1998, there was only one known Puget Sound fault, the Seattle Fault, according to Craig Weaver, the Pacific Northwest coordinator for the USGS earthquake program.
Since then, researchers have looked more closely. They set off explosions from ships in Puget Sound, using the reverberations to detect fault lines. They’ve built giant air guns, pounded on 4 by 4s with sledgehammers and fired shotguns into the ground. When the Kingdome was imploded, geologists rushed to set up seismometers, using the impact to help map undiscovered fault lines.
The upshot: today there are eight known faults in the area, including ones near Everett, Tacoma and Olympia. The USGS estimates that there’s a 15 percent chance of a magnitude 6.5 or greater surface quake on one of those faults by 2055.
About 1,100 years ago, a magnitude 7.3 quake on the Seattle Fault sent a 22-foot wave roaring across Seattle’s Elliott Bay, now crowded with piers, shops and office buildings.
“Nature is not necessarily our friend,” Steele said.
“The double-headed eagle flew over the pass and the giant serpent came up very angry. The two began to fight, and the earth shook and the water boiled … the people began to scream and cry until it was as loud as thunder.”
– From a Suquamish tribal story that University of Washington researchers believe is one of numerous Indian references to Puget Sound earthquakes.
This spring, state officials and earthquake engineers released a 162-page study of what a shallow quake would look like. It would be much worse than the Nisqually one.
The report paints a picture of an urban disaster zone: hospitals overwhelmed by more than 24,000 injured people, hundreds of people trapped, more than 1,600 dead. Drinking water would be scarce. Scores of fires would rage through ruined buildings. Nearly 10,000 buildings would be destroyed, and three times that many would be severely damaged and unsafe to occupy. Property damage and economic losses would be about $33 billion.
An even bigger worry is the specter of a “Cascadia Subduction Zone” earthquake. These start with a tectonic plate about 100 miles offshore, stretching from Vancouver Island to Eureka, Calif. It’s being pushed under the North American plate.
Seven or eight times in recent millennia, the collision of the two plates has produced a massive magnitude 9 earthquake.
Such a quake today, experts say, would be horrific. The shuddering would last for probably four minutes, causing soft soils to behave like liquids, toppling supports for bridges.
“And out on the coast,” Weaver said, “we know there will be a tsunami not unlike what we saw on Dec. 27, 2004.”
Catastrophic Cascadia quakes happen, on average, every 500 years. Sometimes they recur as soon as 200 years.
The last one was on Jan. 26, 1700.
“In Colville glass ware was thrown from store shelves so frequently that merchants were compelled to either take down their goods of that kind or put a guard around the shelving to hold the crockery in. It was reported by Indians that two houses north of Colville were shaken down…”
– Portland Oregonian, Jan. 15, 1873
So what about Eastern Washington?
The region has occasional earthquakes, like the swarm of small ones that startled Spokane in 2001. But it’s mostly stable. Half a century ago, when the federal government was installing seismometers in geologically quiet areas to detect nuclear tests in the Soviet Union, one was put in Newport.
“Quite honestly, being a seismologist in Spokane would be considered kind of a dead-end job,” joked Tom Frost, the scientist in charge of the USGS field office in Spokane. “All signs point to the likelihood of a major quake within 50 miles of Spokane being pretty low.”
A Puget Sound quake would likely be felt in Spokane – as the 2001 Nisqually quake was. A massive Cascadia quake could cause some damage across Eastern Washington. But the biggest effect, experts say, would be the economic cloud that would settle over the entire region. Unable to move apples, airplanes or coffee, the state’s economy would stall.
“We think in terms of a political divide, conservative versus liberal, but in reality our economy is inextricably linked,” said Ken Casavant, a transportation economist at Washington State University.
Spokane’s hospitals would likely be swamped. Refugees and businesses would pile into the city, seeking temporary quarters.
“There are a lot of companies that are storing data in hot sites in the Spokane area and many communities east of the Cascades,” Steele said.
If much of Puget Sound’s transportation network is hardened – as gas tax proponents say their package would do – the region’s economy can recover much faster.
“If we don’t do it,” Steele said, “after the earthquake it will be too late.”
The state’s now spending about $4.5 million a year to harden bridges. At that rate, state bridge engineer Jugesh Kapur says, the work should be done in about 60 years.
If voters leave the new gas tax in place, he said, the retrofitting would be done within eight years.
Even some folks well acquainted with the earthquake risk, however, question the gas-tax project list. The viaduct is just 2.2 miles long, along Seattle’s waterfront. It parallels Interstate 5. Yet it’s slated to get $2 billion of the $8.5 billion the gas tax would raise by 2020.
“Certainly, the viaduct is in very bad shape, I’m not arguing that,” said Don Ballantyne, a seismic risk expert with ABS Consulting. But that much money would allow for extensive hardening of many key bridges, including shoring up their supports against liquefaction.
Others worry about Seattle’s preference for replacing the viaduct with a more-expensive tunnel.
“We can’t let it turn into a pork-laden boondoggle,” said Rep. Mark Schoesler, R-Ritzville.
Meanwhile, the seismologists at the University of Washington’s lab watch their machines and wait for the next big quake.
“It might be hundreds of years off,” Steele said. “It might be decades. It might be days.”