It is not a matter of if a major earthquake will strike the Pacific Northwest, but rather a question of when.
According to geologists, the longest earthquake-free interval along the Cascadia Subduction Zone in the past 10,000 years lasted 330 years. The current drought stands at 318 years, with the most recent large quake occurring on or about Jan. 26, 1700. All of which reminds us that while there is nothing that can prevent an earthquake, numerous steps can be taken to mitigate its damage.
That is the conclusion from an eye-opening report released last week by the Oregon Department of Geology and Mineral Industries. The analysis examined the Portland metro area in the event of a 9.0-magnitude offshore quake — but did not include Clark County — and estimated a worst-case scenario in which up to 1,400 people would be killed, 85,000 people would be displaced from homes, and damage to buildings would amount to $37 billion.
“We can look at the damage on a building-by-building basis,” said Ian Madin, the agency’s deputy director. “As far as we know, nobody has ever done this for more than 600,000 buildings.”
Phase 2 of the study, expected to be released in 2019, will include Clark County, but it is safe to say that damage here would be severe. With 467,000 people sitting in a mostly urban area across the Columbia River, people and buildings would experience devastation, with roads, bridges, utilities and communication systems likely compromised.
There is nothing new about such warnings. Numerous studies have highlighted the risk of a major temblor in this region — and with good reason. The Cascadia Subduction Zone runs along the floor of the Pacific Ocean from Vancouver Island to northern California, about 70 miles offshore. That zone has seen 43 major ruptures over the past 10 millennia — an average of one every 232 years.
In other words, we are pressing our luck, buoyed by the misguided confidence that comes with the fact that no major quakes have hit the area since European settlers first arrived. But preparations by officials and residents will be essential to limiting damage when the big one does hit.
On an individual level, the most important thing is to prepare an emergency kit with enough food, water, flashlights and batteries to last several weeks. Most preparedness guides recommend two-week supplies, but a more realistic recommendation is five or six weeks’ worth; if roads and communications are knocked out, there is no telling how long a family could be isolated. As Madin said: “All you have to do is knock out key parts of the power system and water lines and you’re hauling water with a bucket and living in the dark.” The American Red Cross offers handy tips for earthquake preparedness (https://tinyurl.com/ydy8vjal), as do other organizations skilled in disaster response.
Meanwhile, the report says homeowners should ensure that their structures are bolted to the foundation. “If your house falls off the foundation,” Madin said, “you’re going to a refugee camp.”
While preparation begins at the family level, local officials also must act with the assumption that a major earthquake is inevitable. The analysis found that moderate seismic upgrades to older buildings could slash structure repair costs from $24 billion to $6.5 billion while reducing the number of people killed or injured from 18,000 to about 2,000.
Eventually, the Northwest is going to be shaken. Preparing now should be viewed as an investment that will save money and lives in the long run.
