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!

Evergreen Seismic was amazing to work with. Matt was quick to respond to our initial query, and took the time to walk us through the process and answer questions when he came out to look at the house. His bid was very clear and thorough. He's also a great communicator and made the whole process extremely smooth once we decided to go forward. We really appreciated that nothing felt rushed or unexpected. The crew here doing the work was considerate, patient with any questions we had, and kept us updated every day about what was going on. They did a really great job retrofitting our basement and crawl space and took care of some necessary repairs as well. We were lucky enough to have Evergreen recommended to us, so passing on the recommendation now! We would hire them again with zero reservations.

Evergreen Seismic and Matt were such blessings to us during our seismic retrofit on a Bellevue home we just bought! Matt and his crew, Phil and Nick, were all equally tremendous and beyond helpful to us and my inlaws! We were hell bent on seismically retrofitting by removing drywall interiorally vs sidings exteriorally. And Matt was accommodating to our request. As a hedge though, we knew we wanted a contractor who knows how to retrofit by both methods should a need arises during the retrofit peocess! And Matt fits the bill with his extensive knowledge and years working in earthquake retrofitting. They say never open up drywall if you don't want to find out what deep dark secrets lie underneath. And boy, did we unearthed a structurally problematic framing job on most all the studs holding up an exterior wall of the house, which threw my husband and I in a loop thinking of the scope creep. But Matt stuck with us, helped to sister in all new 2x4s on the compromised studs, and best yet didnt charge us an arm and a leg to fix the framing issue because he truly cares about doing the best job at the most economical rate. The framing job along with the seismic retrofit all easily passed various round of inspections. What started as out as contractor/client relationship became friendship based on what transpired with our house framing issue. We can only hope to find contractors as knowledgeable and honest as Matt and crew!

I would hire Matt again in a heartbeat. Not only do he and his crew perform good work (in my case, seismic retrofit) at a fair price, he combines his core competencies with great people skills and clear, timely, winsome communication. I am especially grateful to Matt because he was ever so patient with me when I suffered long COVID a few weeks after signing the contract, prompting me to delay the project a few months while I recovered. Matt turned what I expected to be a stressful experience into a very good experience. I encourage anyone considering a seismic retrofit to invite Matt to visit you and give you an estimate. I expect that you, too, will be highly satisfied with the result.

Matt did a fantastic job on the earthquake retrofit for our home. Our garage had never been so clean as it was after he was done with his work. Matt had the utmost professionalism through every step of the project. The contract clearly explained everything he was going to do, and he completed every step exactly as described. He thoroughly answered each of my questions during his initial visit in a way where he not only answered the question I asked, but gave background information to educate me on the topic of seismic retrofit. It's great to have the peace of mind that not only is my home now better able to withstand the "big one" that will eventually come to the PNW, but also that the work was done by a great company.

Matt is knowledgeable and competent, and he communicates clearly before and during the job. He made sure that we knew what our options were, and that we understood them. Matt is a friendly, likable person and obviously cares about doing a professional job. He wants his customers to be happy. It was soon clear that we could count on Matt and his team to show up on time and also to clean the site each day before they left. They worked all day each day until the project was finished. I would certainly recommend Evergreen Seismic to anyone who wishes to retrofit their home. I have confidence now that my 1901 home is in much better shape to withstand a significant earthquake without coming off the foundation.

Matt came out to see if our house needs a retrofit and I was absolutely blown away by his honesty, knowledge and professionalism. He advised against retrofitting our house due to the newer age of the home but did provide me with a tonne of useful information that I did not come across during my research and while speaking with other retrofit companies.

I was extremely pleased with the seismic retrofitting job Matt and his team completed for me. The entire experience was seamless. Matt was extremely informative during the bidding process and everything was completed on time and to a high standard. The work site was cleaned everyday and work plans and schedules were clearly communicated. It's obvious that Matt and his team really care about performing quality work. To echo another review, if I could hire them for all my home renovations, I would.

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.

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