I know, I know… it’s spooky season and you want your frights in the form of movie monsters and madmen, with a side of Pumpkin Spice. But, there is a real threat looming over all of us living in the Pacific states, and it is groundbreaking…
That’s right, earthquakes! A nightmare that crumbles buildings and shakes the ground more than any giant movie monster from Godzilla to Cloverfield. If you live anywhere North of the Bay Area in California, you might be wondering why you need to prepare for a Pacific Northwest earthquake, right? Isn’t that a southern California thing?
Well, maybe not. Earthquakes in the Pacific Northwest did historically occur, we’re still all living on an active fault, and, according to scientists, we might be long overdue for a big one.
Pacific Northwest Earthquake: Seismic Science
Let’s start with a little backstory on what earthquakes are and what causes them. We all probably know that the Earth’s surface is broken up into large tectonic plates that are slowly moving around all the time. The boundaries where these plates meet are the source of major geographical / geological formations and events, like mountains, volcanoes, and you guessed it: earthquakes.
There are three main types of plate boundaries:
- – Divergent Boundaries: This is where the plates are moving away from each other, creating a space between the two plates. When this occurs on the ocean floor, exposed magma rapidly cools to form new crust on the seafloor. Continental divergence does not have as clean of a break, instead forming rift valleys.
- – Transform Boundaries: Transforms are when two plates are sliding in opposite directions along their boundaries. A famous transform is the San Andreas Fault.
- – Convergent Boundaries: Convergent boundaries are what we’re sitting on in the PNW. That’s where two tectonic plates are moving toward each other and impact. When one plate gets pulled under the other and back into the magma-filled mantle, it’s called a “subduction zone,” and volcanoes and crustal deformation (like cliffs and mountains) occur here, and are the reason why a Pacific Northwest Earthquake is possible.
On these boundaries, where two plates meet will “stick” and build up stress, or potential force, as the plates continue to move. When the “stick” eventually breaks its hold, it creates a “slip” that releases the built up stress and causes what we feel as an earthquake. This is why the earthquake cycle is referred to as a “stick-slip” process.
The two main boundaries we have on the West Coast, Transform and Convergent, are known for creating earthquakes. Since we haven’t had a notable earthquake in about 20 years, but the plates keep on moving and building up stress along the faults, we all need to prepare for the inevitable Pacific Northwest earthquake and volcanic activity.
The History of Earthquakes in the Pacific Northwest
The San Andreas Fault here on the West Coast has gained notoriety because it has significant earthquakes (average M6.0) about every 22 years, but now it has built up a higher stress level for a much larger earthquake. Well, that and the movie with The Rock.
The San Andreas Fault stretches about 800 miles from Mendocino to the San Bernardino Mountains, and has had regular earthquakes since its discovery in 1857. That year saw the Fort Tejon earthquake, an estimated magnitude (M) of 7.9 that was able to move stream beds by as much as 29 feet.
Another earthquake occurred in 1888, and again in 1906. The M7.9 San Francisco earthquake caused a 250-mile long crack in the Earth and a fire that killed about 700 people. Less deadly seismic events followed in 1922, 1934, and 1966.
The next quake was expected to rock California sometime between 1988 and 1993, but it wouldn’t happen until the Parkfield Earthquake in 2004. With pressure along the fault building for 20 years now, that means we’re right about due for a Big One that could be felt all the way up in British Columbia.
Farther north, we’re sitting on the Cascadia Subduction Zone. This fault causes less earthquakes in the Pacific Northwest than the San Andreas does in California, with only 43 occurring in the last 10,000 years. However, with the unique topography of the Cascadia Subduction zone and longer times to build stress between slips, the resulting quakes can be catastrophic. Not only is a Pacific Northwest earthquake possible, it has already happened.
The last earthquake to hit the Cascadia Subduction Zone hit in 1700, with an estimated magnitude of 9.0. To put that in perspective, for every point that magnitude rises, an earthquake is 10 times more intense than the previous number. That means an M9.0 earthquake is about 11 times more powerful than the destructive San Francisco Earthquake’s M7.9!
The Cascadia earthquake in 1700 caused the coastline to drop several feet and created a tsunami, much like the 2011 Japanese earthquake. Scientists are now estimating Oregon will experience an earthquake in the next 50 years, with the potential of 9.0+ magnitude. That would cause 5 to 7 minutes of shaking and rolling along the coastline, and a tsunami over 100 feet tall.
50 years might seem like plenty of time to start preparing, but remember how the San Andreas fault could quake much sooner? Oftentimes, a large enough quake can cause a chain reaction of other quakes from nearby faults. That means the clock is ticking to start preparing for a Pacific Northwest earthquake.
Damage by Earthquakes
Since we’re talking about the coming Pacific Northwest earthquake, let’s look at the foil to what we can expect from ours: the Japan Earthquake and Tsunami of 2011.
On March 11, 2011, Japan was struck by the most powerful earthquake ever recorded in the country. This seismic event triggered a massive tsunami that caused widespread destruction. The tsunami and earthquake damaged billions of dollars in property and left thousands dead or missing.
- – The Earthquake: The shaking from the earthquake damaged buildings, infrastructure, and transportation networks with its intensity. It also triggered a series of aftershocks, extending the damage toll.
- – The Tsunami: As if the damage from earthquake effects wasn’t enough, it caused a massive tsunami with waves as high as 133 feet. The tsunami destroyed entire towns and villages, leaving thousands homeless.
- – The Damage: The aftermath of the quake left thousands of people dead or missing, and destroyed countless homes, businesses, schools, and hospitals. It also decimated Japan’s infrastructure, including roads, bridges, and power plants.
The disaster even affected places as far away as the Oregon Coast. Japan has made incredible progress in the 13 years since then, but they are still recovering. If the Cascadia Subduction Zone experiences a similar tremor as is expected, we can also expect similar destruction.
How to Prepare for a Pacific Northwest Earthquake
When we’re talking about personal preparation for a Pacific Northwest earthquake, it’s a lot like preparing for our yearly Wildfire season: you’ll want to have an emergency plan and protect your home. But, instead of sealing off your vents and removing foliage, you can protect your home by securing heavy and breakable objects like refrigerators and TVs, make earthquake resistant building improvements if you can, and get earthquake insurance benefits for anything you can’t strap down.
Earthquake resistant building techniques are designed to mitigate damage by earthquakes by reducing structural vibration and increasing flexibility to withstand horizontal forces. While it’s not possible to totally earthquake proof buildings, you can prevent a lot of damage. Unfortunately, most building codes in the PNW don’t include these techniques because they haven’t accounted for a Pacific Northwest earthquake actually happening.
Some techniques for building earthquake-resistant structures include:
- – Solid Soil: Soft or loose soils would increase vibration in the event of a Pacific Northwest earthquake and cause structures on them to crumble. Deep-mixing to remove groundwater beneath a structure and compaction grouting that combines pressurized cement into the soil can create a solid foundation.
- – Base Isolators: These allow the foundation to move independently from the rest of the building, reducing the impact on the structure.
- – Seismic Dampers: Dampers are used to dissipate and absorb vibration, and are placed at key points of stress in a building’s structure.
- – Structural Reinforcements: Reinforcing flex points allows the building to move with seismic forces, without reducing their strength or integrity.
- – High Ductility Frames: High ductility means that the material can move and twist, but return to its original form without losing its strength. Steel and wood frames are generally considered the best for this, while masonry and concrete have low ductility.
New materials and techniques are being tested and will eventually become available to homeowners, but for now it’s best to make the structural improvements available. For everything you can’t reinforce, it’s important to make sure you’re covered with earthquake insurance benefits.
Unlike fire damage, standard homeowners insurance policies won’t cover you in the case of a Pacific Northwest earthquake or any resulting damage. You’ll need a separate earthquake insurance policy, like flood insurance (you’ll want both, in case we get a tsunami along with our earthquake). It can help cover the costs to repair or rebuild your home, or replace your belongings if anything is lost or damaged following an earthquake.
Earthquake insurance price for deductibles vary, but it’s a small price to pay in the event of a Pacific Northwest earthquake. Especially if you aren’t able to retrofit or reinforce your home before the damage is done, or if you’re worried about losing any of your home’s contents.
Here at Ashland Insurance, we can help guide you in getting an earthquake insurance policy that will cover all of your needs, while getting the most out of your money. However, with the risk we’re all now facing, it’s most important that you just get covered and stay safe, no matter who you get your policy through.
When you’re ready to review your earthquake insurance options, give us a call!
541.482.0831 Ashland
541.857.0679 Medford