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Education

What is an Earthquake?

Earthquakes are common occurrences due to plate tectonics; the slow movement of rock landmasses that are constantly grinding against one another, creating stress. Eventually, the stress builds up at points of rock weakness and result in a sudden release of stored energy, which create seismic waves and results in an earthquake.

We live in a seismically active region that is often forgotten and overlooked due to the lack of frequency and destruction our region has experienced. The Pacific Coast is known for its earthquakes and is considered the most seismically active region in North America. Though, we experience frequent earthquakes, most cannot be felt due to their magnitude and depth of occurrence and go unnoticed. The Pacific Northwest is compressed by geological forces that are unpredictable, and formed from it’s very active, and occasionally violent, natural environment.

The Ring of Fire

The Ring of Fire is a 25,000 mile long chain of volcanoes and earthquakes around the perimeter of the Pacific ocean coastlines. The Ring of Fire encapsulates several tectonic plates that are constantly moving inches per year due to the heating and cooling of these plates. Where these plates meet results in a collision zone of volcanic eruptions, earthquakes and oceanic trenches. These plates regularly skid past, colliding into, and move above or below each other, resulting in fault lines.

About 90% of all the worlds earthquakes and more than 75% of all the volcanic eruptions occur within the Ring of Fire. The largest earthquakes in our world’s history are known as subduction zone earthquakes. Most of the largest earthquakes in recent history have occurred within the Ring of Fire. Most prominently in the past decade, the 2010 Chile earthquake (8.8 magnitude) resulting in 525 deaths and the 2011 Japanese Tohoku earthquake (9.0 magnitude) resulting in 15,895 deaths and 2,539 still missing.

Earthquakes in the Pacific Northwest

The Pacific Northwest is host to three different types of earthquakes: subduction zone earthquakes; deep slab earthquakes; and shallow crustal earthquakes. Click the photo on the left for an expanded view of a detailed map of the three different types of earthquakes in our region.




In the Pacific Northwest, the Juan De Fuca plate is one of the smallest tectonic plates but plays a major role in developing our coastlines and geography. The Juan De Fuca plate is diving under the western side of the North American plate at the Cascadia subduction zone, a fault line 50 miles west of the Washington-Oregon coastline creating hundreds of small earthquakes each year, most of which cannot be felt.

In a 2015 article, entitled The Really Big One, Katheryn Shultz of the New Yorker, discusses the Cascadia subduction zone, which runs over 600 miles north to south, from northern Vancouver Island to Cape Mendocino in northern California. Her article has made many in our region aware of the extent to which we are in a seismically active zone, and led to a significant increase in the demand for seismic retrofit work.

Earthquakes that occur along subduction zones have been the most destructive in recent history, with many exceeding a magnitude of 9.0. In March 2011, the Tokuku earthquake and tsunami killed nearly 16,000 people, with a magnitude of 9.1. In 2010, the Chile earthquake had a magnitude of 8.8 with a death toll of 525.
The last Cascadia subduction zone earthquake of a significant magnitude occurred in 1700. Our history has shown that these earthquakes occur every 300-600 years.

Explore more news and resources about earthquake.

As previously mentioned, the Plate of Juan De Fuca is constantly subducting beneath the North American plate. In our region, deep slab earthquakes occur several miles below the Puget Sound, within the Plate of Juan De Fuca. As the subduction plate bends to dive more steeply beneath the Puget Sound, the upper part stretches and fractures in normal faults. Because the hypocenter of these types of earthquakes is so deep, typically miles below the surface, the forces of these earthquakes are dissipated and spread out across a wide area.
The Nisqually earthquake was an intraplate, or deep slab earthquake, which had anepicenter 30 miles deep near Olympia. Thankfully, this earthquake only claimed one life and very few were injured, but there was still plenty of monetary damage done; it was estimated that the Nisqually earthquake caused between $2-4 billion dollars in damage.
Most of us experienced the 2001 Nisqually earthquake, and very few rode through the 1965 and 1949 earthquakes without serious injury or damage. Most people do not realize that these earthquakes we experienced were relatively small or moderate in comparison to the more catastrophic events our region could be hit with. Washingtonian’s who experienced any of the three deep slab earthquakes, experienced the mildest of the three that could occur at any time in our region of the Pacific Northwest.

These types of earthquakes are the most frequent in our region and typically occur every 30-50 years.

Shallow crustal earthquakes differ from deep slap earthquakes in several important ways. First, shallow crustal earthquakes originate where the crustal plates of the earth’s surface move against one other, as opposed to the areas where tectonic plates move under one another, like deep slab earthquakes. Second, their focus is much nearer to the surface of the Earth, therefore, they generally cause greater damage at the earth’s surface than deep slab earthquakes. Though shallow crustal earthquakes tend to be of smaller magnitudes, the maximum of which is 7.5, and are rarely felt, about 75% of the world’s energy that is released during earthquakes is from shallow crustal earthquakes.

The constant load and release of energy from subduction zone earthquakes, occurring every 300-600 years for the last 16 million years, has created a permanent deformation of the North American plate. There are several fractures within the North American plate, just below the surface of the Puget Sound and cities and towns, to include South Whidbey and Tacoma. Seattle has the misfortune of sitting directly on top of one such fracture.

The 43-mile Seattle fault runs west from the Hood Canal through the Puget Sound and south Seattle, parallel


We Love Our Customers!

They did a wonderful job on the seismic retrofitting. Our 1926 house is noticeably more stable. The workers were very pleasant to have in our home, and they cleaned up shockingly well when they were done. If we could hire them for the rest of our home improvement job we would.


It’s a matter of time, experts say, before the Northwest shudders under another massive tectonic plate earthquake or the Puget Sound region succumbs to a big quake from one of its faults. Wood frame homes generally survive the earth shaking. But there’s a risk of them sliding off the foundation. Split-level homes also may crumble along the pony wall, sometimes called a cripple wall, that supports the upper level. Quake risks were not that well known when my home was built in Bothell in 1975. In the summer of 2022, Evergreen Seismic upgraded the house with a retrofit. This included installing anchor bolts and hold-downs into the foundation and bracing the walls in places with ¾-inch CDX plywood. Owner Matt Robinson and his crew worked in a tight crawlspace. They also removed some outside siding to brace the pony wall, upgrading the insulation before replacing the siding. Matt handled all the required engineering plans, permits and inspections. Matt showed he is skilled in retrofitting. He communicated clearly about scope of the work and scheduling. The site was cleaned after each day and neatly finished at the conclusion. The retrofit improved the safety of my home. I have documentation that I believe adds to its value. Of various people we’ve had in our home from time to time for repairs or remodeling, Matt Robinson is one of the best. I recommend Evergreen Seismic for its quality of work and service. Doug in Bothell


If you need to earthquake your home for seismic activity, then you can definitely trust these guys. Matt and his team at Evergreen Seismic are very knowledgeable and do a great job.


I loved Evergreen Seismic so much that I hardly know where to start this review. I got three bids to retrofit our 1962 home, which has a finished walkout basement and required structural engineering. All three companies were very professional and gave me comparable recommendations. Here’s why I’m so happy that I went with Matt: Quality and attention to detail: Notably, a respected competitor described Matt as “the best retrofitter I know.” During the bid process, Matt answered my extensive questions with sound, thorough information. On site, he was happy to show me the in-progress guts of the work, explaining the rationale and placement of all the hardware, additional framing, and shear panels. He also pointed out places where people sometimes cut corners and educated me on how to recognize correct, up-to-code work. Matt and Nick used high-quality materials, high-quality tools, and every element they added to our home was carefully and precisely placed. Their work passed all inspections without a hitch. Matt even paid thoughtful attention to aesthetic details, like staggering their cuts into our siding for a pleasing end result, and purchasing a color of caulk that would blend into our paint. In all matters of quality, Matt ran a tight ship. I feel safe and secure in our home, having witnessed his expertise and skill. Professionalism: Others have said it, and I’ll say it again: Matt is the consummate professional. He was easy to communicate with and responded quickly. He set clear expectations for any minor distress the siding of the house might incur during the project. He cheerfully dealt with tight spaces and a maddening tangle of defunct cables attached to the side of the house. He and Nick kept a tidy jobsite, cleaning up beautifully at the end of each day and truly leaving the interior cleaner than they found it at the end of the job. They appeared to even be packing out tiny pieces of trash like paper towels from washing their hands, rather than using the trash cans I placed out for them. Matt had to cut an old landline cable that we hadn’t planned to use, and he pointed it out right away and offered to pay to have it reconnected - a high-integrity move. Finally, he spoke very highly of his competitors without exception, which says a lot. Kindness and care: Matt is just a wonderful human to be around. He’s easygoing, straightforward, considerate, thoughtful, warm, and generous with his time. When I met Matt in the fall, I was experiencing a period of high anxiety, and I came to him with a long list of bothersome questions as I was deciding who to hire. Even though he was busy, he went far out of his way to write detailed answers, send me safety data sheets, and chat on the phone with me multiple times. Some of my questions and worries were probably ridiculous, but he treated them as if they were completely reasonable and even welcome. He never made me feel like an annoyance, and his willingness to meet me where I was at, with so much empathy and humanity, meant a lot. Oh - and he and Nick treated my five-year-old as a person worthy of as much attention and respect as an adult, which is rare! With all of that put together, we were so happy we went with Matt and honestly feel kind of bummed that we probably won’t ever get to hire him for anything else. A few final details: Matt’s bid was in the middle of the three we received, but it was within $40 of its closest neighbor, so basically identical. Contracts and payment were all quick and easy. And for anyone exercising extra caution during the pandemic, Evergreen Seismic was extremely covid-conscious. The team was fully-vaccinated and wore high-quality masks for the entire duration of the job. I don’t even know what their faces look like. Even though they were working outdoors in the fresh air with no one else around, they always had a mask around their neck to be pulled up within a moment’s notice when I popped over to greet them. A+!


Evergreen Seismic recently completed an earthquake retrofit on our home. We chose the company in part because of great online reviews and we were not disappointed. Matt clearly explained the entire process and patiently responded to all of our questions. The work went smoothly and efficiently, was completed ahead of schedule, and the daily cleanup was amazing. Most importantly (for us anyway), the person who sold us on the job (Matt) was also part of the working crew. I wholeheartedly recommend Evergreen Seismic for earthquake retrofitting. From start to finish, this was by far the smoothest construction job we have experienced during the twenty years that we have lived in our home.


We used Evergreen Seismic to do an earthquake retrofit on our 1979 build home in Kent, WA based upon great customer reviews. We were not disappointed! Matt and his crew were very professional and showed up as promised. We were promptly informed when on one occasion they were a bit late due to traffic congestion. The work was performed to our satisfaction. The daily cleanup was impeccable. Matt was able to answer all questions that the inspector asked to his satisfaction. The Company actually went over and above what the structural analysis indicated was needed (additional bracing was installed). The majority of the retrofit was done on the exterior of the house in pouring rain! However, to our amazement, this did not in any way slow down the crew! A truly professional Company. We can recommend Evergreen Seismic without any hesitation.


Exceptional service from Evergreen Seismic. I met Matt at an info session on seismic retrofitting hosted by the city of Seattle. It took me a year or so to reach out to him. I was impressed form the start. Matt was more than willing to coach me on doing the project myself, if I wanted to take it on. But in given the complexity of our project, I preferred to hire Matt and his crew. They did a great job, and even did some prep that I was supposed to do but couldn't because of a recent back injury. Very straightforward, informative, and considerate service. I'd hire Matt again without hesitation.


Matt did the seismic retrofit of our single-family residence back in January when we were finishing our basement. I cannot speak highly enough of him and Evergreen Seismic. Matt has undoubtedly been one of the best contractors we've worked with. He's an excellent communicator and really goes above and beyond on all fronts. He does what he says he's going to do, when he says he's going to do it, and finishes when he says he's going to finish, all at an extremely competitive price. He's knowledgeable of seismic retrofitting and has a very streamlined process nailed down. If you are thinking of doing a seismic retrofit, Evergreen Seismic is DEFINITELY the way to go!


Matt and crew performed a larger earthquake retrofit project for us that took the entire month of May. The project involved building out a new foundation /wall to connect between posts on the back half of the house to prevent lateral shear, as well as all of the hardware to attach the rest of the house to the foundation. We had a similar experience to the other positive reviews here - Matt has a truly exceptional work ethic and clearly takes a lot of pride in his work, and expects the same of his crew. Matt is very knowledgeable and was more than happy to answer all of our questions. Communication and timeliness were well above par from start to finish, and they were also competitive on pricing (slightly lower than other bids of the same scope). They were a pleasure to have around the house (actually, outside the house, because they were able to take off the siding and do the work from the outside, while a competing bidder was planning on going inside to remove drywall), and were always available for questions. A nice extra touch was that they installed new insulation in 2 of our walls which was not part of the fixed price bid (another reason we went with Evergreen - no risk of cost overrun). Thanks Matt and crew, truly appreciate your work!


Evergreen Seismic did an outstanding job on my retrofit. They fit my project in right away, provided a clear and thorough bid and scope of work, and completed the project on time. Absolutely a pleasure working with them. Highly recommended!

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