Cascadia Subduction Zone

Fast facts about the Cascadia Subduction Zone:

• The Cascadia Subduction Zone runs from the northern most part of California into southern British Columbia, Canada
• It has a history of rupturing along the entire subduction zone, resulting in massive M9+ events all along the Oregon and Washington coasts
• The last such Cascadia megathrust earthquake was on January 26, 1700, at approximately 9pm, and was a M9+ event
• It caused tsunamis in Japan and North America, and submerged & flooded coastal forests in Oregon and Washington
• The Cascadia Subduction Zone is nearly a twin of the Sumatra Subduction Zone (which caused the devastating 2004 Indian Ocean tsunami, produced a measurable wobble of the Earth, and left a gravity scar in the earth.)
• A Cascadia megathrust earthquake could last up to five minutes
• The subduction is causing the land between the coast and the Cascade mountains to bow upward; when a great quake hits, inland areas (like Portland) could lose as much as 6 feet elevation in less than five minutes, as the bow is released
• During these Cascadia earthquakes, the whole fault is in motion; it isn't a pinpoint event like most crustal earthquakes; all western Oregon and Washington will experience terrific shaking
• Aftershocks could themselves be major earthquakes, capable of substantial damage, further compounding the destruction; a large quake can produce hundreds of aftershocks, most of which occur in the weeks immediately following the event, often starting just a few hours after the initial event
• Although the average between Cascadia earthquakes is 500 years, that number is misleading
• Cascadia earthquakes come in clusters of typically three to five M9+ earthquakes, spaced approximately 300 years apart
• A long quiescent period between clusters typically lasts from 500 to a little over a 1000 years
• The 1700 earthquake was about the fourth event in its cluster; we're either overdue for the next one, or in a quiescent period
• New evidence suggests the southern half of the Cascadia subduction zone also produces M8+ events even during quiescent periods between the M9+ clusters; these quakes will shake Portland, but Seattle not as much
• If we include the smaller M8+ Oregon Cascadia earthquakes, the average between quakes shrinks to only 250 years
• The duration of our current quiet period has already exceeded 75% of the quiet periods between quakes in Cascadia's history
• Chris Goldfinger of OSU, who has studied Cascadia extensively, now says he expects either a M8+ or M9+ quake before 2060
• Portland's building codes are designed for M7 "major" quakes
• A M9 "great" quake is over 1000 times more energetic than a M7 quake
• A M8 "great" quake is about 32 times more energetic than a M7 quake
• Western Oregon's seismic codes aren't as strong as California's, which in turn aren't as strong as Japan's or Chile's
• A M9+ Cascadia earthquake will damage cities and towns between the Cascades and the coast, from Canada to California
• It's doubtful that FEMA is prepared for such an event
• A 72-hour kit isn't going to be enough after a Cascadia earthquake
• Earthquakes often liquify landfill or alluvial soils; most of the damage and loss of life from the M7.1 Loma Prieta (aka “World Series”) earthquake occurred on such soils, and it only lasted 15 seconds
• Earthquakes don’t kill many people; it’s the structures people are in, on, or around which kill most people
• Portland’s weak seismic codes will increase the death toll
• Cascadia will continue to kill people days, weeks and perhaps months after the initial event by depriving them of shelter, food, water, medicine, heat, etc.
• Many people get seriously injured because they don't know what to do (or not do) during an earthquake; advance training is your best protection during an earthquake, and for surviving the aftermath
• Briefly… during an earthquake: running is likely to result in serious injury; leaving a building may be fatal; sheltering in doorways may actually be dangerous (and no longer recommended). Get CERT/NET training so you know what to do.

The Japanese Seismic Analog to Cascadia

We can expect more damage and destruction in the Pacific Northwest from a large (total rupture) Cascadia megathrust earthquake than Japan experienced in their 2011 Sendai (Honshu) quake for two reasons: Cascadia routinely ruptures along a much longer fault, and our seismic building codes are significantly weaker than Japan’s (our building codes only anticipate a M7 quake, whereas Japan’s codes anticipate M9 quakes).

The Nova program “Japan's Killer Quake” documents the awesome power and destructiveness of a M9 earthquake. It also contains a short discussion about the Cascadia subduction zone and our region. The show is well worth watching (and you are encouraged to follow the link); it's a wake-up call to the Pacific Northwest.

While much of the graphic devastation in Japan was due to the tsunami, it’s important to remember that Japan’s much stronger seismic codes protected their inland areas in ways our inland areas won’t be. Their buildings are far more resilient and earthquake resistant than ours. A Cascadia quake is likely to do a great deal more damage inland in our region than the Sendai quake did to inland Japan.

Clearly our coastal areas will experience large tsunamis every bit as powerful as Japan’s. What is unclear is how far up the Columbia River a tsunami wave might travel, and how much water it might carry. Also unclear is whether Columbia River damns might breach. Portland has enough to worry about even if we don’t ponder breaching damns and monster inland tsunamis (scenarios which could occur, but hopefully won’t).

We already know that Cascadia quakes of the past — such as the 1700 quake — have caused costal areas to subside and flood. Japan experienced this in the 2011 Sendai quake (it was a factor in some of the tsunami wall breaches). We would be fools not to consider the Sendai quake as a preview of what to expect in the Pacific NW. We need to prepare, become better educated about hazards and how to respond, and we need to build stronger, more resilient buildings and structures.

How The Earth Was Made

An episode of the History Channel’s How The Earth Was Made TV series, titled Tsunami, has an in-depth discussion of the Cascadia subduction zone, an account of the history of the initial research into its geology, and graphically illustrates the magnitude of threat it poses to our area. Follow the link to watch the full episode.

[Embedded on the right is a segment of a Nova episode: Deadliest Earthquakes. Follow the link to watch the full episode.]

Emergency Preparedness Kit (aka 72-Hour Kits)

Everybody should have an Emergency Preparedness Kit.

In California, they call this a 72-Hour kit because that is the typical time it takes for government and utilities to rebound after a typical California earthquake.

Here in Oregon, we face a different kind of earthquake. One which potentially will do a lot more damage, and devastate a much larger region (about 84,000 square miles west of the Cascades, from southern Canada to northern California). One which will cause a measurable wobble in the Earth's orbit, and create a gravity scar on the Earth. This is a disaster far larger in scope than hurricane Katrina. As was the case in New Orleans, we can reasonably expect to be on our own for much longer than 72 hours before outside help begins to trickle in (Portland will be just one of many cities affected by a Cascadia Megathrust Earthquake). At a minimum, we recommend 240-Hour kits (10 days). Even a 30-day kit may not be enough.

A 72-Hour kit should include everything you, your family and pets would need in order to spend 72 hours on your own. Scale that up for 240-Hour or 30-day kits. This is not always straightforward. For food, it is a simple matter of storing more. While it may not be practical to store a 30-day supply of water, having as large a reservoir as practical, along with the knowledge and means to collect rainwater, make a solar still, treat and filter water, etc. is invaluable in an emergency. You may find there are things you cannot easily do without for 30-days which you can easily omit for three days.

By now you may be thinking you’ll just evacuate the area if help doesn’t arrive soon. How? There will be no commercial air traffic in or out. Roads and rail lines are likely to be impassible, and fuel will likely be limited to what you have in your tank. A tsunami ravaged coast may be impassible, even on foot. Columbia river shipping channels would need dredging, once the waters settle down, before shipping lanes can be reopened. And it’s a long walk to get east of the Cascades. For most people, evacuation is unlikely to be feasible for weeks or months after a M9+ quake.

Here are some resources on the web to get you started in creating your own Emergency Preparedness Kit:

• READYAmerica – US Department of Homeland Security’s “Get a kit; Make a plan; Be informed” website
• 72 Hour Emergency Preparedness Kit – Colorado Office of Emergency Management
• Are You Prepared? – San Francisco Office of Emergency Services
• 72-Hour Family Emergency Kit – Colorado Division of Emergency Management
• Disaster Preparedness – American Red Cross
• Pacific NW Earthquake resource page

Disaster-Resistant Community

What does it mean to build a disaster-resistant community? It means raising citizen awareness of the dangers we face, the importance of preparing for disaster, knowledge of how to respond, and insisting that our elected officials do what they can to create a disaster-resistant infrastructure (e.g. building disaster-resistant fire stations and schools – which can serve as emergency shelters – in every community in our city, beefing up seismic building codes, etc.)

A prepared citizenry is the most important component of a disaster-resistant community! One need look no further than New Orleans in the wake of hurricane Katrina to see the effect an unprepared citizenry. Wholesale reliance on government to prepare for (or respond to) disaster can be a fatal mistake. Government planning is critical, but citizen preparation is essential. If every citizen is prepared to deal with disaster, our community will fare far better than if we rely on government alone.

It is important to understand that as bad as Katrina was, the devastation of a Cascadia subduction zone earthquake will be far, far worse. It will affect 84,000 square miles of the Pacific Northwest! “Don’t be scared, be prepared” is Alaska’s emergency preparedness motto. Wise words. It should be our motto too. We need to start planning and preparing now, today. Every one of us. Individual citizen, school principal, business owner, elected official, government agency, all of us.

Portland’s Feeble Seismic Codes

Seismologists often say: “Earthquakes don't kill people… buildings do.”

Portland is retrofitting fire stations and bridges to meet seismic code. While this might sound comforting, not all seismic standards are created equally. The fact is, our seismic code standards aren't as strong as they need to be. We live in an area known to regularly experience M9+ Cascadia subduction zone megathrust earthquakes. But our seismic codes are designed for M7 earthquakes. M9 earthquakes are a thousand times more energetic, and last longer. Our seismic codes won't protect us from “the big one.” We need seismic standards on par with Chile & Japan. This will save lives and speed recovery.

Portland’s zone 3 seismic code standards, which only anticipate a M7 earthquake, are weaker than California’s zone 4 standards. Even zone 4 standards aren't intended to withstand a sustained M9+ event. Both Chile & Japan have stronger seismic building code standards than California's M8 standards. In Portland we're only building to withstand M7 earthquakes, but a M9 earthquake is 1024 times more energetic. A building which might withstand a M7 earthquake may pancake in a M9+ Cascadia megathrust earthquake.

It is important to understand that seismic standards are intended only to protect lives by preventing total structural collapse; the building may not be safe or usable afterward. For earthquakes larger (or lasting longer) than the seismic code zone anticipates, total collapse may occur. So a school or fire station built to meet Portland’s seismic code has no assurances it will remain standing nor protect life, much less remain functional and safe, after a Cascadia subduction zone megathrust earthquake.

So why are our seismic codes so lax? Two reasons: 1) It is only in recent years we have come to understand the severity of the earthquake threat we face here in the Pacific Northwest, and 2) Money. In general, stronger seismic standards mean higher building costs. And that often leads to political push-back from developers. However there are economical ways to build stronger, if you think outside the box… literally.

Conventional box shaped buildings contain many joints between walls, roof & foundation. During an earthquake these joints are subjected to enormous stresses. If the stress is great enough or prolonged enough, the joint fails and the building collapses. Creating stronger joints can rapidly escalate construction costs, yet failure of the joint is still possible. A better and more economical approach is to reduce the number of joints in a building. A building without any would distribute seismic loads evenly across the entire structure. A wood framed geodesic dome reduces the number of joints, and has intrinsically stronger joints. A thin-shelled one-piece (i.e. monolithic) dome made of steel- & fiber-reinforced concrete would have few, if any, consequential joints an earthquake could damage. This type of building has by far the best chance of surviving Portland’s greatest seismic threat. Amazingly, a large monolithic dome structure is less costly to build, heat or maintain than similar sized conventional structures.

Even skyscrapers can be built with fewer joints, or intrinsically stronger joints (as found in the pyramid design).

If most of Portland's buildings become unusable after the next M9+ Cascadia megathrust earthquake, and if it comes in the dead of winter as the last one did, where will the survivors go to take refuge from the elements? And what if, as is common after large earthquakes, fires burn uncontrollably afterward? Might we lose serviceable building to fires? Shouldn't we be building schools, fire stations and public buildings as fire & earthquake resistant monolithic domes? Wouldn't it be wise to encourage churches and homeowners to consider such structures as well? Serviceable buildings after a M9+ Cascadia megathrust earthquake will be valuable assets to the survivors, and may be essential to surviving the aftermath.

Click here to watch the full episode of this Nova program: Deadliest Earthquakes.

Resources on the Web

Various Links & Resources

Monolithic Domes

Pacific NW Earthquake resource page Cascadia Earthquake Possibly Imminent What Businesses Learned From The 2001 Nisqually Earthquake Earthquake Mitigation Information for Homeowners NET Directory Oregon Emergency Management – Earthquakes Oregon Emergency Management – Living on Shaky Ground: How to Survive Earthquake & Tsunami in Oregon FEMA – Earthquake Living with Earthquakes in the Pacific Northwest: A Survivor's Guide

A Monolithic Dome Indestructible Fire Station Building Survivability: The Strength of the Monolithic Dome FEMA -- Design and Construction for Community Shelters and Its Application to Domes Monolithic Dome Videos – These videos are a good way to learn about these domes Man Survives Hurricane Ivan in a Monolithic Dome house – YouTube video