Earthquakes - The Pacific Northwest Still Isn't Ready for "the Big One"By Hildi Flores
The last time the Cascadia Subduction Zone shifted was around 1700. The only human accounts of the event were made by indigenous people who passed them down several generations until the arrival of European settlers in the mid-1800s. In her book Full Rip 9.0: the Next Big Earthquake in the Pacific Northwest, science writer Sandi Doughton documents the modern discovery of the Cascadia Subduction Zone and how over several decades, scientists concluded that a single megaquake rearranged the landscape of Puget Sound and produced a tsunami that decimated the Northwest coastline. "For Northwesterners, the images from Japan of doomed men and women running from the waves and tall buildings engulfed by water resonated in a visceral way," writes Doughton. "Even the world's most earthquake-ready nation was no match for the kind of blow that had struck the Pacific Northwest more than three centuries ago - and which geologists now know will strike again someday. When it does, it will roil a human landscape that has undergone a tectonic shift of its own. The region called Cascadia is now home to more than fifteen million people and several of North America's most vibrant cities, businesses, and ports." Geologists estimate the Cascadia Subduction Zone to slip roughly every 100-1,100 years, with an average spacing of 550 years, according to the state Department of Natural Resources website. It has been 314 years since the last megaquake. It can be difficult to wrap one's mind around the level of region-wide destruction an earthquake of this magnitude can produce. Not knowing when it could strike, whether it be tomorrow or several centuries down the line, can make it all the more difficult to commit to adequate preparations. Damaging earthquakes of lesser magnitude have occurred in the Puget Sound throughout the historic record, the most recent being the Nisqually deep quake in 2001. As a magnitude 6.8 quake, it did significant damage to structures throughout Thurston County. Some of the most memorable include the 4th Avenue Bridge, Deschutes Parkway, and the Capitol Dome. Chimneys fractured and unreinforced masonry buildings in downtown Olympia began to crumble, unable to withstand the half minute of intense shaking. The Cascadia Subduction Zone is expected to produce around a magnitude 9.0 earthquake. Measured on a logarithmic scale, this is several orders of magnitude larger than the Nisqually quake, with the most noticeable difference being the duration. It is estimated the region will experience several minutes of intense shaking. Apart from principle damages from shaking, the Olympia area has a number of infrastructural facilities subject to collateral damage, primarily from liquefaction. The Port Peninsula, Deschutes Parkway, the isthmus, and much of Olympia's water front is built on fill. With intense ground shaking, water-saturated sand, silt, and gravel layers behave like a liquid instead of a solid, causing the ground to be unstable. Experts Speak Washington State Chief Geologist Tim Walsh sat down with the Green Pages to discuss some of the seismic-related threats to the Olympia area. "When you have liquefaction, that commonly causes underground utilities to break," said Walsh. "Gas, water, and sewer lines can rupture. If you have gas lines rupturing, there is a significant probability they could catch fire." Walsh explained the damage caused by liquefaction is dependent upon a number of factors: the quality of building construction, the strength of the ground, and level of ground shaking in any given area. "The Port Penninsula had quite a bit of liquefaction in the Nisqually earthquake," said Walsh. "The isthmus surprises me that it performed as well as it did. You would think there would have been heightened ground motions there, but apparently the fill that it's on was better compacted than some of these other fills." Deschutes Parkway is an area notorious for liquefaction, bearing damage from earthquakes in 1965 and 2001. Walsh admits the repair is not built to withstand another earthquake. He said because Deschutes Parkway is part of the Capitol Campus and under state jurisdiction, "the money to repair it came from the Federal Highway Administration, and they would only pay to restore it to the condition it was in before the earthquake. To harden it would have cost an extra couple of million dollars." While the Thurston region suffered considerable damage from the 2001 earthquake, some believe impact will pale in comparison to what a Cascadia Subduction Zone quake could bring. Former Olympia Mayor Bob Jacobs has taken a particular interest in urging public officials to prepare for "the Big One," but said he felt they were "generally not interested." He took it upon himself to interview experts, including Walsh. "A Cascadia earthquake will be orders of magnitude larger than Nisqually," said Jacobs. "I've been trying to convince local officials to give us a description of what we will face. People need mental preparation. Without awareness, there will be total panic." In a brief interview with the Green Pages, Joan Gomberg of the U.S. Geological Survey in Seattle commented on the impact of a Cascadia earthquake. "There will certainly be major impacts. Bridges will fail, gas lines will break," said Gomberg. "There will be areas that get cut off, but there will be other areas that will be functional. It's not going to be total destruction by any means." Walsh also provided his speculation as to what can be expected. "When we have a Cascadia event, a lot of bad things will happen, and response will be initially uncoordinated," he said. "One of the things that always happens in a big disaster is that you start out with your communications disrupted, and it takes a while to figure out what actually happened so you can respond to it. Given that it's an event that would affect cities from Vancouver, BC to Redding, California, communications will be knocked out over a wide area, so it will take a long time for what emergency managers call a common operating picture to emerge." "A lot of people will not be able to occupy their houses," Walsh continued. "Depending on the time of year, you might have to stay outside for long periods of time. The Red Cross and other outfits will set up shelters, but after a really big earthquake you would need to do a lot of inspections to be sure a building is sound enough to use as a shelter." The report Resilient Washington State: A Framework for Minimizing Loss and Improving Statewide Recovery after an Earthquake published by the Washington State Seismic Safety Committee, estimates the recovery time for each economic sector. Water and sewer systems are estimated to take the longest to repair, especially in areas of liquefaction, where they are expected to take one month to one year to return to full operation. "In terms of governmental preparations," said Walsh, "there are plans for what to do, there are exercises that we do periodically. We have an exercise coming up next year that's going to be exercising a Cascadia event. We'll pretend it happened and mobilize various emergency responders." Preparation is Key Transition Olympia invited Thurston County Emergency Management Coordinator Vivian Eason to speak about earthquake preparedness during its April 14 meeting. "Elderly folks are generally more interested in getting prepared than younger folks," she said. Eason invited people to participate in the Map Your Neighborhood Train-the-Trainer program at the Emergency Management Center (see page 4 for details), which teaches individuals how to coordinate their neighborhood to respond to disaster situations. "There will be power outages and first responders will be overwhelmed," said Eason. "Check up on your neighbors and prepare to be on your own for a longer period of time without power." Eason also recommends having an out-of-area contact and food and water supplies for at least three days or more. Walsh recommended having at least a weekfs worth of supplies in the event of a Cascadia earthquake. Jacobs speculates the situation to be rather bleak. "There is going to be a lot of evacuation," he said. "It will cease to be life as we know it. Ifm really trying not to be alarmist, but this is the picture I build. But if we prepare for 'the Big One,' everything in between is covered." Hildi Flores is Managing Editor of the South Sound Green Pages and a graduate of The Evergreen State College.
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Of all the known earthquake zones, the people of the Pacific Northwest have been late to realize the seismic capabilities of the region. Not only is Cascadia riddled with fault structures located near or running underneath major cities including Seattle, Tacoma, and Olympia, but just offshore is a 684 mile subduction zone. The Cascadia Subduction Zone extends from Vancouver Island to Northern California, where the plate of Juan de Fuca subducts beneath the North American plate. These faults are capable of producing the most destructive quakes, like the magnitude 9 that struck off the coast of Japan in 2011, triggering a tsunami that brought the region to its knees.