Mar 12, 2012
Originally published March 10, 2012 at 4:14 PM | Page modified March 10, 2012 at 10:14 PM
On NW coast, potential for tsunami waves up to 100 feet now seems possible
Japan's megaquake and tsunami last year has Northwest emergency planners wondering whether a similar earthquake here would unleash a much larger tsunami than anticipated.
Seattle Times science reporter
A computer simulation shows how a tsunami generated by a magnitude 9 earthquake off the Northwest Coast would spread across the Pacific. Scientists are asking whether the massive waves triggered by last year's Japanese quake mean a quake here could create bigger-than-expected tsunamis. Darker colors indicate bigger waves.
Graphic: Cascadia subduction zone
The Cascadia subduction zone is the boundary where the Juan de Fuca plate dives beneath the North American plate. After last year's Japan megaquake, some scientists and emergency planners now wonder whether an earthquake along this zone could trigger a tsunami much larger than originally predicted.
The specter of 30-foot waves slamming into the Northwest coast used to be about the worst thing emergency managers in Washington and Oregon could imagine. Now, a year after Japan's megaquake and tsunami, they're wondering whether their nightmares were bad enough.
Scientists and planners are reconsidering the region's tsunami risk in light of the massive walls of water that swept nearly 20,000 people to their deaths on the day the Japanese simply call 3-11. The tsunami reached 130 feet high in some places, taking everyone by surprise.
Levels that extreme are unlikely in the Pacific Northwest, but experts say it's possible some parts of our coast could be hit by waves of up to 100 feet the next time the offshore fault called the Cascadia subduction zone snaps.
"That is definitely something we need to be prepared for," said Vasily Titov, head of tsunami modeling at the National Oceanic and Atmospheric Administration in Seattle. "Underestimating kills people ... and the Japan event emphasized that in a very vivid way."
Researchers are still unraveling the disaster and digesting its lessons. At the same time, the Obama administration proposes to cut $4.6 million from NOAA's tsunami programs as part of a push to reduce government spending and the deficit.
State officials fear the cuts could undermine the safety of seaside communities.
"There will be serious consequences for our continued ability to maintain the level of preparedness on the coast today," said John Schelling, earthquake and tsunami program manager for Washington's Emergency Management Division.
NOAA officials say the cuts will mostly affect funding for state programs, like tsunami education and evacuation signs, and won't affect the national tsunami detection and warning system.
The federal government boosted funding for tsunami programs after the 2004 Indian Ocean tsunami killed more than 230,000 people. Since then, researchers have improved computer models that simulate how tsunamis spread.
States used the results to map danger zones for scores of coastal communities in Washington, Oregon, Northern California and Alaska. Scenarios for the Pacific Northwest generally yield maximum wave heights of about 30 feet.
Japan's quake and tsunami originated on a fault similar to the Cascadia subduction zone — the boundary where the geologic plate that makes up the ocean floor is forced under the continent. What stunned scientists in Japan was how far the plates slipped past each other during the quake: More than 160 feet in some spots, about half the length of a football field.
"That's huge," Titov said. "That much slip was unthinkable before."
When submerged plates shift, they shove the water column up, initiating a tsunami.
The question scientists are trying to answer now is whether the Cascadia subduction zone might be capable of more slip than the 65 feet factored into most tsunami models.
"Obviously, more slip would make a bigger tsunami," said Tim Walsh, geologic hazards chief for the Washington State Department of Natural Resources (DNR).
Differences between Cascadia and Japan might lower the odds of such colossal slip here. Japan's magnitude 9 quake packed a lot of force into a short fault segment, which may at least partially explain why the plates moved so much.
In a similar-sized quake in the Northwest, the force would probably be spread along the entire, 700-mile length of the subduction zone, theoretically resulting in less slip at any single location. Cascadia also lacks the deep, underwater trench that may have aggravated seafloor displacements in Japan, said Harry Yeh, a tsunami researcher from Oregon State University.
But the Japanese disaster showed that a lot of what scientists thought they knew about subduction zones was wrong, said Yeh, who is currently in Japan to study the 2011 tsunami.
"What we have found out is that we do not really understand this Earth," he said.
Japanese seismologists grossly underestimated the magnitude of an earthquake their subduction zone could unleash. In the Northwest, planners already assume a worst-case scenario of magnitude 9, based on geologic records of more than 20 giant quakes over the past 10,000 years.
The most recent one, in 1700, is estimated at a 9 because the tsunami it triggered was powerful enough to flood villages in Japan. But there's evidence that a few of the ancient Cascadia quakes and tsunamis were nearly twice as powerful.
New evacuation plans
University of Rhode Island oceanographer Stéphan Grilli was one of the first researchers to model a magnitude 9.2 Cascadia quake and suggest waves up to 100 feet. What happened in Japan reinforces his earlier work, he said.
"People now see how it is possible for these large subduction zones to create much larger tsunamis than anyone anticipated," Grilli said.
After watching waves overrun supposedly safe areas in Japan, officials in Grays Harbor County — which includes Ocean Shores and other coastal towns — revamped their evacuation plans. Assembly points were switched to higher elevations and away from possible landslides, said Chuck Wallace, deputy director for emergency management.
"What's paramount to me right now is to know whether what we've modeled for is enough," he said.
Walsh, of Washington's DNR, hopes to revise the state's tsunami hazard maps and expand mapping to the Strait of Juan de Fuca and the San Juan Islands. A coastal tsunami isn't expected to cause serious flooding in Puget Sound. But a quake on the Seattle Fault, which runs through the city to the Eastside, could set off underwater landslides and cause localized tsunamis.
Walsh wants to model a scenario for Lake Washington, but like the other map revisions, that work could be derailed by NOAA's proposed budget cuts.
The cuts would also end funding to test and maintain tsunami warning sirens and replace tsunami evacuation signs, a common target for thieves. Also on the chopping block is federal money for community workshops, evacuation drills and programs to train hotel and business owners on the coast.
NOAA has funneled more than $40 million to states over the past several years to ramp up education, outreach and preparedness, but never intended to fund the programs indefinitely, said Jane Hollingsworth, the agency's tsunami program manager.
Local governments can't afford to pick up the slack, countered Wallace, who constitutes a one-person operation.
"These jurisdictions, they're bare bones now," he said.
NOAA's top priority
Facing its own tight budget, NOAA's top priority is a network of 40 tsunami detection buoys and the tsunami warning centers in Alaska and Hawaii, Hollingsworth said. The proposed budget would reduce buoy maintenance by $1 million, but the system has enough redundancy that it won't impair performance, she added.
Initial tsunami warnings are based on earthquake signals. The buoys add detail about tsunami size, direction and duration.
While the buoys are useful for tsunamis generated by distant earthquakes, they won't do much good for the Northwest coast when the Cascadia fault slips, Schelling said. Waves will hit within 30 minutes or less in many places, leaving little time for official warnings. NOAA may move some buoys closer to the fault so a detailed forecast could be issued more quickly. But people on the coast need to be conditioned to head for high ground as soon as the earth stops shaking — which is why public education is so crucial, he said.
"It's only having a trained and prepared population that's going to save lives," he said.
Despite Japan's staggering death toll, 90 percent of the people in the inundation zones made it to safety, because they knew what to do, said University of Washington tsunami expert Jody Bourgeois.
In the Northwest, where preparedness is not ingrained, she suspects the survival rate wouldn't be nearly that high.
Mary Ellen and I are both extremely pleased with the work that Matt and Richard did. Please pass on my personal "thank you" to each of them.
We were pleased with the amount of clean-up that was done at the end of each day.
Even with your discovery of unforeseen conditions that necessitated additional framing, it was still done within a very reasonable time-frame. My overall experience with Sound Seismic has been very positive and we will recommend your services to our circle of friends and family.
Again, thank you for a very "enjoyable" experience!
Mark and Mary Ellen Whitesell, Ballard, Seattle
I wish to praise SOUND SEISMIC for the earthquake retrofit they completed on my home. From the estimate to the finished job, Leif and his crew were professional, hard working, pleasant and exceptionally CLEAN. They handled the permit and inspections seamlessly. Office support from Elizabeth was equally professional, reliable and fast. I can't describe everything so I'll just say the whole experience was great.
Kristin Hill, Wallingford, Seattle
We recently had Sound Seismic do our earthquake retrofit. I cannot compliment enough the very professional job they did. Leif Jackson, the owner, sat with us for two hours answering questions and explaining how earthquakes work. He was completely above board, not promising more than he could deliver. He left interesting reading material so that we could evaluate and decide for ourselves. The most compelling was from FEMA warning people in the Puget Sound area to do everything they could to protect their homes because of our earthquake risk.
Once we were in contract, Leif sent our information to a structural engineer who drew up the plans. The bid was fair and complete. The crew showed up on the date the job started and completely it quickly. It looks great. Our new pony walls are gorgeous and the bolts and clamps very reassuring. City inspections were completed for the bolting and then for the finished job. This company is certified and high quality. Our house will be sticking around on the foundation. I encourage you to get over gambling about retrofitting and hire these guys. They are great.
Emily Elliott, Queen Anne
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Martin Muller, Olympic Manor, Seattle
Sound Seismic was the most professional group of contractors/employees I have ever dealt with. They were knowledgable, dependable, and skilled. The project lead was obviously well trained and knew what he was doing, was able to effectively manage and direct his crew and subcontractors. A quality job. Discovered an area behind my walls were my house was not up to code. Worked well will me to correct the problem and professional and reasonable about the change order.
Grateful homeowner, Mercer Island
The Sound Seismic crew arrived on time and got started on this structurally engineered and contracted job. It was estimated to take approximately one week to complete this work. The job was completed in 4 days with great professionalism and dedication to the work completed. The work passed a city inspection with no additional work required. The quality of work is excellent with great attention to detail.
Leon Young, Issaquah
Based in Ballard, the 2 man crew of Sound Seismic did a very clean, professional job of installing the earthquake retrofit. I was very happy with quality of the work and the way the crew kept the site clean and organized every day. They stick to a firm 8-hour work day for their employees and offer health benefits, a rarity in the contract world, it would seem. So their bid was not the lowest, however was comparable to a number of other firms, within 5-10%. Very punctual and professional in all coordination and in handling the 2 inspections reqd. by the city. No surprises or additional costs. I would recommend this contractor overall.
Jennifer Dovey, Broadview, Seattle
Sound Seismic did such a thorough job. Looking at their work lets me sleep better at night knowing my house is now very unlikely to shift off its foundations in an earthquake.
P. Kiraly, Madrona, Seattle
We thank you for the very professional work done by all of your people that we have had contact with. The crew working here were outstanding, and we were charmed by your lead carpenter, Matt.
Our basement has not been this clean in 70 years (the house is 70 years old)!
Bryant neighborhood, Seattle
We had a wonderful experience with Sound Seismic. After the devastating earthquake in Japan my husband and I were quite worried about our 3 story brick home and decided to retrofit our basement as a way to ease our anxiety and protect our family.
Sound Seismic's estimate was more reasonable than any of the others we got and we felt very confident knowing that Leif and his team have done many retrofits, including our friend's basement. Leif was able to explain the process to me, answer my questions, and gave me the estimate within an hour of coming to the house.
The hardest part of the process was moving our furniture and boxes out of the way to prepare the basement - after that things just moved along smoothly. I had been expecting huge holes in the walls and dust everywhere but the work was really tidy and not nearly as disruptive as I had feared. My kids and I were able to stay in the house the whole time, only playing out in the backyard a couple times when the banging was loud. The baby was even able to take naps in the midst of the demolition!
Matt was very professional and friendly, he always arrived on time and he communicated well, checking in with us at the end of each day to show us the progress of the work. He was able to finish the work a half-day sooner than planned and there were no hidden costs or extra changes when the invoice arrived.
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Wayne Dodge, Ravenna, Seattle
"I wanted to follow up and thank you for your good communication, strong planning and flexibility.
Matt was great. Very professional, low key, friendly and efficient."
Urs Koenig, Madrona, Seattle
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Matt and Richard did a great job! It was a pleasure to meet them. And as soon as I met Matt, I knew that everything would be done 'right.'
They took extra care at every level: and left everything better than ever. They were able to remove the siding without cutting it, which is great, too.
I am glad that I got to see how substantial the anchors, fasteners, etc. are - and how robustly the plywood panels are nailed in. ( It was hard for me to tell from the blueprints alone.)
I am very happy with all aspects of the plan and the work, Leif.
David Rosenbaum, Sand Point, Seattle
All in all, we felt the project went extremely well. Given the number of earthquakes worldwide of late, we are pleased to have had the work done. We’d rather not have it tested, but we know we are in as good a position as possible if the ground starts shaking!
I wanted to let you know what a great job that your crew did on our earthquake retrofit. They were very knowledgeable about the whole process and answered any questions we had without hesitation. Their work was excellent and they finished the job quickly. I have done my share of remodeling in the past and I can say that they cleaned up after each day’s work more thoroughly than anyone I’ve ever encountered. They took obvious pride in the retrofit work they did but also in the cleanup. They saw that as an integral part of the Sound Seismic service. All in all, it was a fast and painless experience.
Thanks for assigning those fine young men to our job.
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George Murphy, Northgate, Seattle
I wanted to thank you for the wonderful job you did retrofitting my home in South Seattle. I was aware that it would be a challenge and it proved to offer more problems than we expected. You met them all and did a great job correcting the rot and damage that happened over the years since 1927, when the house was built.
When I arrived home yesterday the basement was clean and organized. It was the first time I did not have to spend hours cleaning up after a contractor. Your lead carpenter and his assistant were a great team. Thanks for all your efforts.
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Sound Seismic completed a earthquake retrofit on our house. Their explanation about what to expect and what we'd get was clear and straightforward; the work was completed as described, as scheduled and exactly on time; clean-up: spotless.
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"The experience with Sound Seismic was possibly the finest I have had in my dealings with any of my trade contractors. Your crew was knowledgable, well informed, hard working, tidy, as well as a pleasure to have on my job."
Thank you very much for your excellent work on retrofitting our house. We appreciated your careful oversight of the project, ongoing contact with the engineering firm, attention to detail, and clean and timely work. You really rose to the challenges presented by "this old house."
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Stuart Jamieson, Montlake
Sound Seismic did an excellent job of the seismic retrofit on my two-story house, which entailed quite a lot of siding work as I don't have a basement. The workmen were punctual, neat and meticulous. I feel safer because of their work.
Pippa Kiraly., Madrona
Just wanted to send you a note to express how pleased we are with the work your firm recently completed. You did exactly what you said you would and the quality of the work is first rate. Also, please tell Matt how much we enjoyed him. Thanks,
Gary Johnson, Wallingford