Apr 15, 2011
Seattle Times science reporter
First came 2004's killer quake and tsunami off Sumatra. Then a year ago, Chile was rocked almost as hard. Now Japan is reeling from its biggest quake in recorded history.
The juxtaposition of three of the world's most powerful earthquakes within a span of seven years has some scientists asking the question: Are we in an age of megaquakes?
Few corners of the world are more keen to know the answer than the Pacific Northwest, where an offshore fault is cocked to unleash a quake and tsunami on a par with the magnitude 9.0 that devastated Japan last month.
Most geologists are skeptical that monster quakes come in clusters. But some are convinced they do — though no one can explain how quakes separated by several thousand miles could be linked.
On its face, the lineup of very large quakes over the past century seems to fall into two peaks of activity: Between 1950 and 1965, when there were seven earthquakes of magnitude 8.5 or greater; and 2004 to now, with three megaquakes (and two big aftershocks) so far.
The nearly four decades preceding the disaster off Sumatra (one of the main islands in Indonesia) didn't see a single great earthquake, U.S. Geological Survey scientist Charles Bufe said Thursday, from the Seismological Society of America's annual meeting, in Memphis, Tenn.
When Bufe, of Denver, and his USGS colleague David Perkins analyzed the clustering, they concluded it's not coincidental when it comes to the small subset of truly monstrous quakes: those of magnitude 9.0 or greater.
"It's very statistically significant," Bufe said. "We think we're in an increased hazard situation for these very large earthquakes."
If they're right, Bufe and Perkins estimate there's a 63 percent chance that another magnitude 9.0 or greater quake will strike somewhere in the world within the next six years. If monster quakes strike randomly, the chance is about 24 percent.
The random interpretation is backed by several other scientists who subjected the earthquake records to more extensive statistical tests.
"Seismologists are in a very difficult situation, because we can't run experiments," said Andrew Michael, of the USGS Science Center in Menlo Park, Calif. The best they can do is parse the existing data in multiple ways, then compare it against random scenarios to tease out any meaningful patterns.
It's well known that quakes beget other quakes, Michael pointed out. Japan has been rattled by hundreds of aftershocks since the main event on March 11.
A big quake on one segment of a fault can also prime adjacent segments to rupture, as happened twice after the magnitude 9.1 Indian Ocean quake in 2004. And large quakes can trigger small quakes more than 1,000 miles away. A magnitude 7.9 earthquake in Alaska touched off rattles and rearranged the plumbing in geyser fields in Yellowstone National Park in 2002.
But could a megaquake in the Indian Ocean lead to the rupture of a giant fault off the coast of Chile more than five years later and 9,000 miles away?
Michael doesn't think so.
When aftershocks were factored out, he and his colleagues found no pattern in the timing of quakes of magnitudes 7.5 to 8.5 that couldn't be explained by random fluctuation. There have been only five magnitude 9 or greater quakes over the past century — far too few to draw any conclusions, he said.
Michael also found no evidence that a higher number of quakes occur in the five years following giant quakes.
Aaron Velasco, of the University of Texas, El Paso, examined quakes of magnitude 7.0 or greater, and found there's a limit to their geographical reach in terms of setting off other destructive quakes. Big quakes do spawn daughter quakes of moderate size, 5.0 or greater, but not beyond about 600 miles, he said.
With only about 100 years of data and an understanding of earthquakes that's far from complete, it's important to keep asking questions about possible links between megaquakes, said Rick Aster, outgoing president of the seismological society.
The conventional wisdom can turn out to be wrong, as it did when the faults off Japan and Indonesia fractured with unexpected force.
"We used to think many of these subduction-zone segments were not capable of magnitude 9," said Aster, of the New Mexico Institute of Mining and Technology. "That confidence has really been shattered by these earthquakes."
Scientists who drill sediment cores and dig trenches looking for evidence of ancient quakes in the Pacific Northwest do see signs of clustering through time.
The shallow faults that crisscross the Puget Sound region appear to have gone through active and quiet periods. The same is true of the Cascadia Subduction Zone, the menacing fault where the ocean floor dives under the continent off Washington, Oregon and Northern California.
Chris Goldfinger, of Oregon State University, finds evidence there for three to four earthquake clusters in the last 10,000 years on one fault segment.
"The clusters are real," he wrote in an email. "They are not just a random product, and therefore they mean something."
He doesn't yet know what, or whether it has any bearing on global earthquake clusters.
A plausible explanation for the way megaquakes might link up over great distances would give scientists a better starting point for future analyses, Michael said.
The Japanese quake sent small vibrations around the globe and tilted the Earth's axis several inches.
"After a very big earthquake, we have the Earth ringing like a bell ... and this can go on for days, weeks, months," Bufe said.
The motions are tiny, but widespread. Big earthquakes also deform the taffylike mantle layer that underlies the planet's rocky crust, and those ripples spread slowly.
Maybe these slight motions can further weaken a fault that's already on the edge, Bufe speculated.
Michael and others remain unconvinced.
But geologists can't really explain how earthquakes like the one in Alaska in 2002 trigger smaller quakes as far away as Yellowstone, Velasco pointed out.
"We still have a long way to go as far as understanding the earthquake process."
Sandi Doughton: 206-464-2491 or firstname.lastname@example.org
Mary Ellen and I are both extremely pleased with the work that your crew 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
The crew kept me informed of their progress and plans all the time. They told me what their plans were, and delivered every time. Very satisfying knowing I could count on them doing what they promised - when they promised it!
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.
Andrew Austin, Phinney Ridge
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.
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.
I would highly recommend Sound Seismic to anyone -- they were fantastic!
Rachel Opel, Ballard, Seattle
Thanks for the great work on the house - you've done an outstanding job of prompt, low-impact work - and leaving the job site in excellent shape. Appreciate the attention to detail."
Wayne Dodge, Ravenna, Seattle
"I wanted to follow up and thank you for your good communication, strong planning and flexibility.
Your foreman was great. Very professional, low key, friendly and efficient."
Urs Koenig, Madrona, Seattle
Sound Seismic gave a very competitive bid, clearly explained everything they were going to do, accomodated my schedule, and produced a very high quality outcome. I highly recommend them.
Gary Johnson, Wallingford, Seattle
Your crew did a great job! It was a pleasure to meet them. And as soon as I met your lead carpenter, 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.
Paul Gustie, Fremont
Sound Seismic performed an engineered retrofit on our house built in 1928. I've never had a better experience working with a contractor - thoroughly professional (truly experienced and knowledgeable in their craft), they were also excellent communicators throughout the engagement. And the cleanup afterwards was amazing. I would recommend them without reservation!
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.
Patrick Murphy, Mount Baker
I can't think of a single way you could improve the service of your company. Yours is one of the VERY best companies I've worked with on this home.
Jeannie Macri, West Seattle
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.
Harriet B., Ballard
"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."
Sound Seismic exhibited a great combination of skill, hard work, and professionalism. You treated our home and our project as though you were doing it on your own house.
Everything looks good. Thanks for the all the work your guys did, very professional.
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