Cascadia: Day of Destiny

Unknown to most people in the beautiful Pacific Northwest, they are already doomed!

There was an earthquake in Beaverton, Oregon last Friday morning on 4/21/2013 at 7:21 AM, just before school started. Beaverton is a bustling suburb of Portland in the USA’s Pacific Northwest.

At the surface, the earthquake was a few feet from the front door of houses at the corner of SW 135th and Hialeah Drive.

The earthquake epicenter was 900 feet from Hiteon Elementary School; 1,800 feet from Southridge High School and 3,700 feet from Conestoga Middle School. Total student enrollment: about 3,500.

Oregonians were lucky… this time.

Few knew it happened and its doubtful anyone felt it. It was 15 miles down and only 2.5 on the Richter Scale.

But make no mistake, the real “Big One” is coming; not to California’s San Andreas Fault, but to the Pacific Northwest’s Cascadia Subduction Zone. The tick of the clock is the only remaining unknown.

Newly assembled research shows the Pacific Northwest is already 70 years overdue for its own demise! The danger lurks just offshore under the Pacific Ocean.

Introducing Cascadia

The 15 largest earthquakes ever recorded in the lower-48 U.S. states (Source: USGS)

In terms of property damage and human loss of life, earthquakes are historically the single most cataclysmic events on Earth.

A “great quake” is in a special destructive class all its own. It is the worst of the worst. According to Stanford seismologist Gregory Berozo, a great quake has a Richter magnitude of 8.5 or higher.

Only one known great quake has ever struck the continental United States. It was a 9.0 magnitude Cascadia.

Cascadia last assaulted the northwest United States 313 years ago at 9 PM on January 26th, 1700. The date and time are precisely known because the tsunami it generated was recorded, not in the Pacific Northwest, but in Japan… over five thousand miles away!

Cascadia in 1700 is tied for the 4th largest earthquake ever measured on Earth.

It didn’t get attention because it occurred 105 years before Lewis and Clark. Evidence of it’s massive effect on Pacific Northwest shorelines started cropping up in the 1980s.

The 2nd largest earthquake ever in the continental USA, 33 times smaller, is California’s 7.9 magnitude Fort Tejon quake in January 1857. That one was in the hills just north of present day Los Angeles. It wasn’t a “great quake”.

By Beroza’s definition, Earth experiences only 1 great quake every 8 years.

The Cascadia Subduction Zone goes from Cape Mendocino, CA to southern British Columbia

Note on the map above that south of Cape Mendocino in California there are a lot of little yellow dots. Those are recent earthquakes. Note there isn’t much activity along the Cascadia megathrust fault shown as a thin blue line just off the Oregon/Washington coasts.

Cascadia is locked up tighter than a virgin’s chastity belt.

Since 1700, 42 feet of accumulated downward stress has again built up along the Cascadia Subduction Zone. That is a lot.

Complicating matters, the Pacific Plate has chugged 104 feet to the northwest at about 4 inches a year while the San Juan de Fuca Plate wants to push under North America. It causes a  twisting, pinching motion around the south end of Cascadia at a point called the Mendocino Triple Junction. It’s where all Cascadia earthquakes originate that begins a tear in the ocean floor that can extend as far as 600 miles north.

What happened on Japan’s northeast coast in 2011 and Sumatra in December 2004, will soon be repeated by Cascadia in the United States and Canada.

After that, life in the Pacific Northwest will be permanently altered… forever.

Long History of Cascadia Earthquakes

Cascadia averages 1 giant quake every 243 years over 10,000 years. Last quake: 313 years ago

The Pacific Northwest is 70 years overdo for its next massive earthquake. There have been 41 monster quakes along the Cascadia Subduction Zone in the last 10,000 years.

Scientists discovered the earthquakes from studies of ocean and lake sediment core samples taken all along the Oregon and Washington coasts. They reveal Cascadia “inundations”.

Turbidites is the quaint term geologists cleverly give large seabed landslides and ocean-side lake beds inundated by tsunamis debris.

19 full-length Cascadia Subduction Zone “turbidite” events (EQ mag 9+)

Cascadia quakes are categorized into two general types:

  1. Full-length rupture (680 miles)
  2. Partial rupture (<680 miles)

The partials usually occur in the southern section and range from 8.2 to 8.6. Full-length Cascadia’s start at 8.8 and then get bigger!

By Cascadia standards, the 9.0 earthquake of 1700 is classified as “medium”. According to the experts, Cascadia sizes range up to “extra-extra-large”.

Galveston Island’s September 8th, 1900 Great Storm is the loss of life record holder for worse natural disaster in the United States. In it 6,000 died and 3,600 structures were destroyed on the Gulf coast near Houston, Texas.

Cascadia will dwarf that. If unlucky, Oregon alone will see upwards of 10,00 dead.

Tsunami Planning

Tsunami Evacuation Map for the popular resort town of Cannon Beach, Oregon

Special colored overlays for Google Maps are used to identify coastal tsunami hazard areas:

  • Orange: Distant tsunami (non-Cascadia)
  • Yellow: Local tsunami (Cascadia)
  • Green: No hazard

The State of Oregon’s Department of Geology and Mineral Industries (DOGAMI) is the leader in Pacific Northwest earthquake preparedness. Since 2011 it has built tsunami hazard maps for the entire Oregon Coast.

Maps can be explored with a fascinating interactive online northwest oceanography tool called the Nanoos Visualization System (NVS) using its Pacific Northwest Tsunami Evacuation Zones product.

That product is intended to help coastal citizens plan their own personal tsunami escape routes before inevitable earthquakes.

A distant tsunami is patterned after the 1964 Prince William sound 9.2 quake 1,200 miles away that caused considerable damage in Oregon.

DOGAMI has assembled a lot of scientific research on Cascadia since the great Sumatra and Japanese subduction zone quakes. Their tsunamis caused 240,000 deaths and tremendous destruction.

One of DOGAMI’s important early outcomes is Special Paper 43 – “SIMULATING TSUNAMI INUNDATION AT BANDON, COOS COUNTY, OREGON, USING HYPOTHETICAL CASCADIA AND ALASKA EARTHQUAKE SCENARIOS“.

The result of Special Paper 43 was development of scientific techniques for calculating tsunami evacuation zones. Those provide municipalities badly needed information necessary for disaster and city planning.

Oregon Outcomes of a 9.0 Cascadia Earthquake

Cascadia Projection vs. the March 2011 Japanese earthquake and tsunami

Reacting to the 2011 Japanese earthquake, the State of Oregon commissioned a study of earthquake and tsunami preparedness for a 9.0 Cascadia earthquake. It is called the Oregon Resiliency Plan. The final report was published in February 2013.

It’s chilling findings apply only to Oregon:

  • 1,250 to 10,000 killed
  • Severe shaking lasting 5-6 minutes
  • 10s of thousands of structures destroyed
  • $32 billion in property damage
  • Parts of northwest Oregon near Astoria could drop 4-8 feet in elevation
  • 10s of thousands left homeless
  • Severe infrastructure damage causing permanent economic slowdown

Strong ground motion of 1 foot or more affects everywhere in western Oregon

And that is just Oregon. Cascadia will affect the entire Pacific Northwest from Vancouver, British Columbia to northern California.

Conclusions

The past predicts the future. Simply put, the next Cascadia earthquake will be the most destructive natural disaster ever to strike the United States.

Shocked Pacific Northwest survivors will ask, “How could such a thing happen here? Why weren’t we warned?” while the dead are stacked like cord-wood and teetering buildings fall in strong aftershocks.

They have been warned. According to geologists, there is a 37% chance of a mega-quake in the next 50 years. People just need to be aware.

Oregonians might want to keep this in mind: 8 of the 15 largest earthquakes ever to strike the lower-48 states were in the winter months of December, January and February.

Every municipality, city planner, builder and citizen west of the Cascade Mountains should study the Oregon Resiliency Plan. It is a matter of life and death.

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About azleader

Learning to see life more clearly... one image at a time!

Posted on Apr 25, 2013, in earthquake, earthquakes, economics, Geography, geology, news, plate techtonics, Politics, science, Thoughts. Bookmark the permalink. 2 Comments.

  1. Given the nature of this narrative, how can one press the like button? I did find this an interesting article. But, how should the humans listen? The only thing I can think of is to move away and depopulate. But that will never happen as folks think there is only a 37 percent chance something will happen in 50 years. Most in Oregon or even elsewhere will interpret that to mean the liklihood on any given day is still so small as to stay living right where they are. I do not brag as living in Wisconsin I always wonder what the Madrid fault is up to. It may be ready too to pull off a large earthquake. If it happens in Winter, the natural gas pipelines we rely on for winter heating will rupture and we will literally freeze to death even using shelters. I wonder if earthquakes hit in the Winter more often because the Earth is nearer the sun then? In sum, I pray and hope nothing like this ever happens.

  2. Here is food for thought…
    There is a 1 in 365 (0.27%) chance that the next person you talk to will have the same birthday as you. Yet, a classroom with only 23 students has a 50% chance that two students sharing the same birthday. Up that to 57 and the probability is 99%.

    A 37% chance for Cascadia means it is likely that many people living in the Pacific Northwest today will still be alive when it strikes.

    In action movies it sometimes boils down to a tense race against the clock for the hero to disarm a ticking bomb before it explodes. They usually succeed.

    Cascadia is a ticking bomb that gets bigger and stronger with each tick of the clock and no hero can ever disarm it in time to keep it from exploding.

    Education is the only defense against Cascadia. Forewarned is forearmed.

    Folks living west of the Cascade Mountains need to be made fully aware of the danger. Nothing can prevent destruction and the loss of life, but reasonable precautions will greatly reduce both.

    I’m a ‘lower taxes, less government and less government intrusion into its citizen’s lives’ kinda guy.

    In this case, I think the State of Oregon did its citizens a great service commissioning the Oregon Resiliency Plan.

    Citizens have been forewarned; now they need to forearm.

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