Portland's building industry slowly starts earthquake preparation

Daily Journal of Commerce (Portland, OR), Aug 16, 2006 by Libby Tucker

Earthquake preparation slowly is starting to shake in Portland's building industry. But it's not happening in response to the series of small- to medium-size earthquakes that have rattled the region over the last few months.

In June, the state began a systematic seismic assessment, mandated by the 2005 Oregon Legislature, of key public buildings such as schools, hospitals and fire and police stations. All told, $1.2 billion will be invested to improve seismic safety in Oregon based on the assessment's findings.

A more roundabout earthquake preparation is occurring in the private sector as well, dictated by market demands for renovated office buildings and condominiums and city and state building codes.

"A lot of warehouses and older, more industrial buildings are being converted to residential based on the need for infill," said Jay Wilson, earthquake, volcano and tsunami coordinator with the state's Office of Emergency Management. "And those older buildings in their rehabilitation have to meet seismic requirements in Portland. These are the kinds of permits (the city) has been issuing."

In 1993, the city of Portland amended its building code to require seismic design criteria and structural upgrades when a building's occupancy or use changes. Buildings designed and built before the change aren't necessarily safe in the event of a large earthquake, according to the city's Bureau of Development Services.

"The majority of the buildings in downtown Portland don't meet current seismic code," said Jed Sampson, chief structural engineer for the city of Portland. "There's never been any mandates for upgrading existing buildings."

But more contractors and engineers have been conducting seismic upgrades in Portland office and residential buildings recently, simply because the building market is strong, they say.

Shoring up history

The seven-story Crane Building, built in 1910 in Portland's historic warehouse district, used to be the structural equivalent of a stack of bricks.

"Unreinforced masonry, a brick wall mortared together, has historically not performed well in earthquakes," said Mark Tobin, an associate at KPFF, a structural engineering firm. "When they were built they weren't even designed for seismic forces."

Walsh Construction Co. recently finished installing steel reinforcement beams as part of the building's conversion from a former plumbing fixture showroom and warehouse to high-end condominiums for the Pearl District.

The building now contains a modern steel and concrete skeleton capable of withstanding an earthquake, Tobin said.

"There's a huge mat slab that's poured in the basement with a concrete shear tower ... that surrounds the elevator and the central stair, and all the existing structure gets tied back to the core with collector beams," said Geoff McGraw, a Walsh project manager.

"It's meant so that even if the brick falls down in an earthquake, the remaining structure will hold up and allow people to get out of the building," McGraw said.

Everybody's fault

Due to the high cost of seismic retrofitting, most buildings are upgraded to meet seismic standards only when they are renovated to comply with the city's building code.

"Not all corporations and certainly not all owner-developers of these downtown class A office buildings would necessarily have that attitude that they're willing to invest in (upgrades)," said Larry Sitz, president of Emerick Construction, a Portland-based general contractor that conducted seismic upgrades for Hewlett-Packard. "As long as they can rent their space, the market won't necessarily force them to do it."

However, some large companies such as Intel and Hewlett-Packard have upgraded their Oregon facilities without any other major renovations in order to protect their business investments, said Yumei Wang, geohazards section leader with the Oregon Department of Geology and Mineral Industries.

Such structural investments are a wise choice for Pacific Northwest companies, Wang said. The region is due for a magnitude 9.0 quake, Wang said, along the Cascadia Subduction Zone, a large offshore fault that runs from northern California to British Columbia and that has historically ruptured about every 500 years.

Each one-point increase on the earthquake magnitude scale represents an increase of about 30 times the amount of energy created by the quake.

"It's definitely going to snap, and we're definitely in the window of opportunity for it to snap," Wang said. "And so not to prepare for it would be a bad move."

A magnitude 3.8 earthquake shook Portland on Aug. 3, preceded by a magnitude 2.8 quake in the city in January. And a series of minor earthquakes continue to rumble under Mount St. Helens and Mount Hood.

"We're in a period of higher seismicity right now on small faults and unknown faults throughout this region," Wang said. "They're not predictors, and we can't say that those are foreshocks to something big that's going to happen, but we don't know enough to rule that out either."