Everett, Wash.
Published: Wednesday, May 14, 2008

Could an earthquake disaster like China's happen here?

The county sits on ground at risk for strong earthquakes.

By Krista J. Kapralos, Herald Writer

 As the death toll from Monday's 7.9- magnitude earthquake in China's central Sichuan province continues to rise to more than 12,000, there is a nagging question:

What if it happened here?

The Pacific Northwest is earthquake country, and Snohomish County is smack in the middle. Within a few dozen miles, the earth hides four separate faults and geologic formations known to trigger powerful earthquakes.

Scientists say they've long known that the Seattle Fault, which courses beneath the earth's crust beneath the King County city, will cause widespread damage when it heaves.

Now, a growing body of research suggests that the South Whidbey Island Fault, which runs beneath south Everett, could pose a greater threat than even the Seattle Fault.

"It's the combination you see all over the world," said Bill Steele, lab coordinator at the Pacific Northwest Seismograph Network at the University of Washington. "Soft soils will tend to amplify and trap energy, as the Everett basin will."

Add to the mix many buildings made from unreinforced brick and concrete, and the situation becomes "very dangerous," Steele said.

The situation in China has remarkable parallels to the geology of the Pacific Northwest, Steele said. The earthquake there occurred on the Tibetan plateau, where there are earthquake-prone faults overlain by soft soils.

In China, "the basin that the primary cities lie in to the east were shaken very strongly by this earthquake in part because of the proximity to the fault, but it was made worse by the basin effects," Steele said. "The energy was trapped in those softer soils under the cities."

The Seattle Fault can cause the same type of earthquake that occurred in China. A quake on the Seattle Fault would be expected to throw its energy right up into Redmond, Bellevue and Seattle. While a 7.9-magnitude quake isn't likely on that fault, a 6.7- or 6.8-magnitude quake would be devastating for the region, Steele said.

The South Whidbey Island Fault likely packs more power than the Seattle Fault, Steele said. Emerging research shows that it's much longer than originally thought.

The fault stretches from west of Whidbey Island, straight through Mukilteo and south Everett and under the Brightwater Sewage Treatment Plant near Maltby, which is under construction. King and Snohomish county officials say they're confident that the $1.7 billion plant, which will include chemical storage buildings, isn't at risk of earthquake damage.

The fault is similar to the one that caused the quake in China, said Brian Atwater,* a mud geologist with U.S. Geological Survey. It is shallow and breaks through the Earth's crust.

It's difficult to know exactly how much risk the fault poses to people in Snohomish County, Atwater said.

"Like the faults in that Chinese area, there is clear evidence for movement here since the ice sheets left, and that's within the past 15,000 years," Atwater said. "In geological terms, that's an instant."

The region's lack of written history prior to contact with European settlers means that geologists have a difficult time dating seismic activity from anything other than geologic tests.

It is known that the Cascadia Subduction Zone caused a 9-magnitude quake in 1700 that resulted in a 33-foot tsunami off the coast of Washington, and a tsunami reported to be 10 feet tall that reached Japan 10 hours after the quake. But when it comes to the South Whidbey fault, oral history hasn't offered much insight, Atwater said.

The South Whidbey fault is "rising to the top as the most hazardous in Washington," Steele said.

Everett city officials say most of the homes and buildings here aren't likely to be damaged in an earthquake. In one scenario, with a Whidbey fault quake at a magnitude of 7.1, 60 percent of the homes wouldn't be damaged at all, said Dave DeHaan, Everett's emergency preparedness director. Even so, more than 2,000 homes -- about 5 percent -- would be damaged extensively.

Most of the damage likely would come from fires or other events triggered by the temblor. Toppled water heaters can cause gas leaks that erupt in flames, flooring can be smashed if heavy furniture isn't strapped or bolted down, and electronics are likely to be lost if they shake off shelves and tabletops.

"Even way back in the San Francisco earthquake, most of the damage was caused by fire after the earthquake," DeHaan said.

People are injured during earthquakes most often when they try to move to what they think is a safer spot instead of ducking where they are and protecting their bodies, he said.

"Our buildings don't tend to fall down, but light fixtures fall off the ceiling or bookcases fall over," DeHaan said. "People should just duck, cover and hold, because chances are, in the United States, the building is going to survive the earthquake."

Scientists at the Pacific Northwest Seismic Network say recent research revealing the true strength of the region's fault lines show there's no guarantee that our buildings will stand any stronger than those in China. As long as old concrete and unreinforced brick buildings stand, there is danger that they'll collapse in a quake, Steele said.

Local governments should offer more incentives to retrofit buildings so they have a chance against earthquakes, he said.

"That's how we'll avoid the tragedy that we see in China," he said.

*Correction, May 19, 2008: This article originally used an incorrect name for Brian Atwater.
© 2009The Daily Herald Co., Everett, WA