THE NEXT MEGAQUAKE

On Boxing Day 2004 the world was shocked by one of the worst natural disasters of all time. The cause of so much devastation was the most powerful kind of earthquake on the planet - a megathrust. Megathrust earthquake only occur on a particular kind of fault. Scientists have now discovered that just such a fault could cause a huge megathrust earthquake and tsunami right off the coast of North America.

The subduction zones:

The surface of the earth is divided into giant plates of rock - and most earthquakes occur at faults where two of the plates meet. Where the plates are colliding one of the plates usually gets pushed down under the other - this is subduction.
Not surprisingly, the process of subduction can be very violent. The two plates can get stuck together and the result is that the area where subduction is occurring (the subduction zone) gets compressed. Eventually the strain on the fault becomes too much. The plates suddenly slip past each other. The result is a megathrust earthquake.
Subduction zones are mainly found in South East Asia (like the subduction zone that caused the Indian Ocean Tsunami) and around the Pacific Rim. It has long been known that a subduction zone runs along the Pacific northwest coast, from northern California all the way to Vancouver Island in Canada. It's called the Cascadia Subduction Zone, and is linked to the Cascade Range of volcanoes that includes Mt St Helens.

http://www.imdb.com/title/tt0819996/