The so-called "big one" in the Pacific Northwest – a potentially catastrophic earthquake caused by a fault off the Oregon Coast – happens on average every 500 years, with the last event occurring in January 1700.
"That means we're 300 years into what is usually a 500-year cycle," said Craig Weaver, Pacific Northwest coordinator for the U.S. Geological Service's Earthquake Program. "The problem is sometimes nature can be really early – or really late."
That's where structural engineering firms like Miyamoto International come in.
"People are under the misconception that Oregon and Washington are under a lower seismic risk than California," said Scott Nyseth, a principal at the Vancouver office of Miyamoto. "The biggest risk is seismic."
According to Weaver, if an earthquake of the magnitude of the 1700 event occurred today, much of brick-and-mortar Vancouver and Portland would be severely damaged, the highways and bridges quickly compromised and the Columbia riverfront turned to quicksand.
Along with fellow firm principal, Brian Knight, Nyseth leads a team designing structures built to withstand potentially catastrophic earthquakes in seismically active zones from New Zealand to the Pacific Northwest. Their latest project, a four-story classroom complex at Clark College in Vancouver, continues Miyamoto's emphasis on "high performance" engineering that strictly adhere to local, state and international building codes, according to Knight.
Opening their Vancouver office in April 2008, Miyamoto has grown from three to eight engineers, with about 60 percent of their work focused on reducing seismic risk to new and existing building owners and utilities – all while trying to combat a sense of complacency among businesses and the general public about earthquakes.
"Typically, things don't get fixed if nothing happens," Nyseth said. "Because earthquakes happen infrequently here, it doesn't seem like a real threat – it becomes ethereal."
However, other fault lines in the regions cause earthquakes far more frequently than the Cascadia subduction zone, which caused the last major quake in 1700.
For instance, the 2001 Nisqually earthquake, located just northeast of Olympia and registering 6.8 on the Richter Scale, caused significant property damage to homes and businesses in the Puget Sound area and closed Boeing Field in Seattle for nearly two weeks. In 2007, another temblor hit the Scotts Mills area south of Portland and was felt as far north as Seattle.
While these moderate earthquakes occurring elsewhere in the region are less common in Southwest Washington, smaller seismic events from the nearby Portland Hills and St. Helen's fault zones still present serious risks to residences, businesses and infrastructure, according to Weaver.
Adding to the risk, Weaver said, is the high number of brick buildings without steel structural supports in the Vancouver-Portland metro area, as well as a belief that earthquakes are not as serious a threat to life and property compared to other locations on the West Coast.
According to Nyseth at Miyamoto, one of the biggest challenges for his firm is assessing and mitigating seismic risk to existing structures, especially in facilities critical to an emergency response should an earthquake hit, such as hospitals and fire stations.
"The building code is like a cookbook – it will tell you exactly what you need to do," he said. "That falls apart when you are dealing with existing buildings."
Other challenges come from protecting structures built on sandy, unstable soil like the Columbia riverbank, the site of a future $1.2 billion waterfront redevelopment project in downtown Vancouver. According to Weaver, in a Cascadia earthquake event, the riverbank's sandy soil could potentially start to liquefy and flow toward the water, taking any structures along with it.
"You can plan and prepare for events like these," he said. "The hard part is predicting when they are going to happen."
