Megathrust Earthquakes: Is The West Coast Next?

Posted: March 12, 2011 in disaster

After the Quake event in Japan yesterday people have been wondering “Can an earthquake that big hit Canada and the USA?” The answer to this question is yes an earthquake can hit Canada and the USA, more specifically Alaska, British Columbia and the Western Coast of the USA. Can the Quake register a 9 or higher on the Richter scale? Yes.

There is a Fault line known as the Juan du Fuca plate. This is a Subduction plate, the exact same type of fault line that caused yesterday’s quake in Japan. A Megathrust earthquake has not happened in some time, in fact the last one to hit BC was in the 1700’s.  Scientists can only speculate that it was between a 8.7 and 9.2 based on Carbon dating of Tsunami deposits. There was a tsunami and it was big, possibly bigger than the one that hit Japan. Japan’s records state that there was a Tsunami on January 26 1700 so the quake that occurred on the Juan de Fuca plate likely caused it.

Earthquakes for quite some time have not been caused from the Subduction zone(Where the two plates meet), Scientists are stumped. Usually at a subduction zone the plates stick to one another causing pressure and earthquakes as the pressure is released. The Juan de Fuca plate has not released any pressure for a very long time. The Juan de Fuca is moving under the North American plate and probably storing up a lot of pressure but it has not released this pressure as of yet. Thousands of Quakes are recorded each year from the fault but none have been recorded at the point where the Juan de Fuca and North American plates meet.The Actual name of the Subduction zone is called the Cascadia Subduction zone.

So if the Juan de Fuca plate is slowly moving beneath the North American plate, when will the next earthquake be? Is the fault line storing up energy? What happens when the fault finally gives? We can only guess until it happens but if a magnitude 9 or higher occurs there will be without a doubt  lots of shaking and then a Tsunami. BC has a building code for large quakes but will it be good enough? Make a building strong all you want but it will not withstand the ocean’s Wrath. This is what worries the people who reside on the West Coast. Yes they face earthquakes all the time but these quakes are not a result of the Subduction zone giving out. It has not given out since 1700. The Second largest quake to hit BC occurred offshore of Queen Charlotte BC and registered an 8.1.

As of now, BC is worried about onshore earthquakes which can also do a lot of damage. While they don’t cause Tsunamis a 7.0 magnitude quake can cause alot of infrastructure damage. Onshore Earthquakes can do more structure damage than a Ocean quake because the quakes tend to be more shallow. These Earthquakes can turn the ground into liquid (It doesn’t actually turn into liquid but the sediments take on a liquid form). The Earthquake that hit Kobi japan in 1995 caused 200 Billion in damages and it was only a 6.9 on the Richter scale.

It’s not a matter of IF BC will experience a Megathrust Earthquake like the one that Hit Japan but WHEN. When will it happen and how much devastation will it cause?

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