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Mega-thrust Earthquakes

Fault line and water build-up

What are mega-thrust earthquakes?

Mega- thrust earthquakes are the most intense and destructive types of earthquakes that occur along a fautine in a subduction zone (the result of the convergence between continetal and oceanic plates) (Natural Resources Canada). When the oceanic plate subducts and pushes against the continental plate the tip of the continental plate makes a move to try and subduct as well,  and as a consequence, the two plates lock up. Pressure builds over time and when released, it results in a very powerful and destructive earthquake (see image). The continental plate springs back to its original state, pushing along with it the water that has built up in the formed fault, thus generating a tsunami (see image).

Why do these pose a threat to Canada?

These megathrust earthquakes have been observed to occur repeatedy in Canada's geological history. As megathrust earthquakes occur due to the locking up of one oceanic plate subducting under a continental plate, and  the resulting build-up of pressure that requires a release in the form of an earthquake, these are bound to occur repeatedly over the course of time. The last so-called "mega-earthquake" was documented to have occurred 313 years ago in Canada. Research shows that these types of earthquakes are inevitable in the region of British Coumbia (CBC News). As time has gone by, pressure in the subduction zone that is the result of the collision between Juan de Fuca and North American Plates has increased, thus making the fault tine situated just off of the West Coast of Canada overdue for a very destructive mega- thrust earthquake (see 'Earthquake Hazard map').

Map citation: "Earthquake Hazard Map." Map. The Canadian Press (2015). Natural Resources Canada. Web. 3 Feb. 2016. 

Citaion: Kieffer, Susan "Illustration of the elastic rebound part of volcanic arc subsidence after a megathrust earthquake." Geology in Motion. N.p., 31 July 2013. Web. 3 Feb. 2016.

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