By Tim Gibbins
In the past twenty years, geologists have determined that the Cascadia Subduction Zone, a 600-mile-long fault off the Northwest coast, is overdue for a major earthquake. The last major quake was on January 26th, 1700 on the fault, where the oceanic Juan de Fuca Plate rumbles beneath the North American Plate; geologists have found repeated historical records of major earthquakes occurring at the Cascadia Subduction Zone every 250 years.
The question is not if a major earthquake will hit Oregon, but when.
And our ability to think and plan around this reality — to mobilize and prepare for a threat that is rare but potentially devastating —is one of the region’s toughest resilience challenges. It must be tackled, but how?
Since 1993, the Oregon Structural Specialty Codes for Portland’s buildings have required architects and engineers to construct buildings that can withstand significant seismic forces. Many of our schools, offices, bridges, and homes, however, were built before 1993.
A major earthquake at the Cascadia Subduction Zone could leave many of Portland and the Pacific Northwest’s buildings in rubble.
A report from the Oregon Department of Geology and Minerals Industry concludes that over 1,000 of Portland’s schools, hospitals, and other emergency facilities are at high to very high risk of significant structural damage during an earthquake.
In a place like California where the San Andreas Fault produces numerous minor to moderate earthquakes, the antiquated buildings get weeded out through a Darwinian process – they receive damage and are then retrofitted or demolished. But in Oregon, our buildings are vulnerable to a major quake because we have not had many earthquakes testing the foundations of our older buildings, says Ted Wolf of the Portland Earthquake Project – an informal collaborative group between members of Mercy Corps, the US Geological Survey, the Oregon Red Cross, and the Portland Bureau of Emergency Management.
The group formed to tackle Portland’s earthquake resilience through education. They noticed a knowledge gap between what geologists and engineers were finding and what the public understood. If policies to retrofit our buildings and funds to update our infrastructure are needed, then the public must clearly understand the geologic region in which it lives.
This spring the Portland Earthquake Project began the Cascadia Lecture Series to increase the public’s awareness of living in this dynamic geological region.
On Tuesday June 12th ,Yumei Wang, an engineer with the Oregon Department of Geology and Mineral Industries, will lead the Portland Earthquake Walking Tour past four Old Town historic structures in downtown Portland, to address how each structure will fare in a major earthquake. The tour reprises one Wang took with media and Mayor Sam Adams earlier this spring.
Activities like the tour are a necessary reminder, says Ted Wolf, because we have a blind spot for active geology in the Northwest. We view our mountains and our coast as scenery instead of as a dynamic geologic force that shapes the place we live.
Tim Gibbins is an environmental writer living in Portland.