Megathrust Earthquake Mega-Scary

by Tim on May 9, 2008

Around these parts, we all pretty much accept that it’s only a matter of time until The Big One hits.

An earthquake, I mean. A devastating earthquake.

We all know it’s supposed to be bad, and I haven’t really given it much thought, other than to store food and water to get my family through the first week or so.

But then I spotted this page over at Natural Resources Canada, and…yikes! Potentially five meters of lateral movement for the southeast coast of Vancouver Island?

Here’s a map showing how the strain is building up.

Using the Global Positioning System (GPS) of satellites, and a network of permanent GPS receivers, the relative motion of points on the earth’s surface can be monitored at the level of a few millimetres per year. The arrows in this diagram show the measured annual rates and directions of motion of specific sites of the Western Canada Deformation Array (WCDA) relative to a reference site located at the Dominion Radio Astrophysical Observatory (DRAO) south of Penticton. Points on the outer coast of the North American Margin, which overly the locked portion of the Cascadia Subduction Zone, move at rates of over 10 mm/yr in a north-easterly direction. The fact that inland sites move at half that rate, or less, indicates that the outer margin is slowly being compressed like a giant spring. At the time of the next great earthquake it is expected that the accumulated compression will be totally released and that the outer coast of southern Vancouver Island will move up to 5 metres to the south-west.

You know, it’s so easy for us to sit here in the Pacific Northwest and look down our noses at those silly people who live in places where hurricanes tend to come ashore, or those trailer parks that seem to attract all the tornados. What silly people! What silly places to live!

Just don’t ask us about volcanoes or earthquakes. :-)

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