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Preparing for the Cascadia Earthquake Disaster

Updated on September 25, 2012

Earthquake timing

The last known great earthquake in the northwest was the 1700 Cascadia earthquake. Geological evidence indicates that great earthquakes may have occurred at least seven times in the last 3,500 years, suggesting a return time of 300 to 600 years. There is also evidence of accompanying tsunamis with every earthquake, and one line of evidence for these earthquakes is tsunami damage, and through Japanese records of tsunamis.

The next rupture of the Cascadia Subduction Zone is anticipated to be capable of causing widespread destruction throughout the Pacific Northwest.

Other similar subduction zones in the world usually have such earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip.

Works Cited

The Juan De Fuca Plate and North American Plate Subduction Zone

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The Cascadia Problem

We have all heard about the proverbial "BIG ONE", the massive 8.0 earthquake that is supposed to rock and roll poor old California from the Mexico border all the way up to San Francisco Bay. Theories say it will cause California to fall into the ocean, others say it will be like setting off a series of forest fires where one quake causes many many more. But really it just means that the San Andreas fault is going to cause a big earthquake one day. The scientists know this because the evidence shows it happens pretty regularly, and so far amazingly enough the California coast is still attached to the rest of the North American continent.

Well the same can be said for the northern half of the west coast from Northern California to British Columbia the North American plate is being pushed on by the Juan De Fuca plate creating a subduction zone and a bulge which is ready to snap and release an tremendous amount of pent up energy. The problem is that the fault is locked, there is no give as the plates move against each other. So the pressure is building. Predictions say this earthquake has the makings of a 9.0. We have seen the powerful destruction of a 9.0 in the 2004 Indian Ocean tsunami and in the 2011 Japanese earthquake and tsunami. The issue isn't a matter of can it happen but more of when and how bad will it be?

In 1700 a massive tsunami raced across the Pacific Ocean to wreak havoc on the coast of Japan. A Cascadian quake caused massive waves several meters high to wash up along the thousand mile length of the coast of Honshu in Japan. A computer graphic shows how the tsunami was made by the Cascadian earthquake of 1700 six hours after initiation. Massive waves slammed the west coast less than 30 minutes after the shaking ceased. These disasters happen periodically. The evidence from past great cascadian earthquakes shows that they happen about every 500 years on average. These quakes are often the cause of massive tsunamis. There is evidence of at least 13 other events from the years 600 BC all the way up to 1700 AD.

So what does this mean? Well these quakes can happen any time between 300 and 600 years. Here we are 312 years in. The cascadian bulge is growing, the plates are in a position of locked, this is the danger zone of earthquake volatility. As the plates push on each other the subduction zone builds and builds pressure. Soon the plates will slip and then the land under the ocean will drop several yards. This causes massive shaking on the surface and displaces unimaginable amounts of water. If you drop a swimming pool several feet the water would splash down with great force and splash out of the basin. The ocean will do the same but on the coast of the pacific northwest and any other land masses like Japan and Hawaii. The tsunamis will cause the most damage. But a 9.0 + will also create wide spread damage as well.

What to Do in an Earthquake

When Inside a Building:

The U.S. Emergency Management Agencies use the D.C.H.O. or Duck Cover and Hold On method. The idea is to get low by crouching into a ball and then getting under something sturdy like a desk, table, or even a chair. If in a doorway then brace yourself against the frame, these are load bearing beams and should hold up until it is safe to move again.

When Caught Outside:

If you are outside try to get away from bridges, over-passes, buildings, power-lines, and steep terrain that may be a risk when it comes to rock-slides or landslides. Once the shaking has stopped take personal inventory, check out your surroundings in your general vicinity. Note the least amount of debris and see if you can get to an exit or if you are outside see if you can safely navigate the terrain.

What Next?

  • If you are at home, if it is night time locate a flashlight.
  • Have a pair of shoes at the side of your bed that you can slip on.
  • Get a tool kit and head outside and turn off the main gas and water lines to your home. This is important as it can lead to a fire or water damage. If you don't think you need to just assume there are gas and water leaks and turn off them off; better safe than sorry.
  • If you have a disaster supply kit or a 72 hour kit this is the time to get it out and set up camp outside the home.

To learn more visit: Understanding Earthquakes What to Do

Tsunami Evacuation Sign

What to Do to Escape a Tsunami?

Tsunami Preparedness:

Well if you live anyplace along the pacific northwest coastline this is critical information. Once an earthquake is felt the first thing to do is move inland and preferably to high ground. You want to get out of homes, businesses, and buildings that sit right on the shoreline. If you have a boat in harbor the best place to be is off the shoreline. Take your boat out into the ocean to brave the swell. Ships at sea will barely even notice anything has happened. Ships in port will be destroyed along with piers and other coastal properties.

Oregon Coast Evacuation Routes

Oregon CERT (Community Emergency Response Team)

Know your escape routes, find out where your local disaster teams and first responders have set up and designated as safe areas for people. Have a plan to meet up and contact family. If the area is heavily damaged try to stay clear of downed power lines and other debris. Help injured family and coworkers but not at the cost of your own life. You may only have minutes to reach minimum safe distance. If at all possible find a first responder to help get out your trapped family members. When trying to flee a tsunami you must move fast get to safe ground,.


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