Here is what California just might look like when the Megathrust earthquake hits. This is being predicted to hit around the middle of September 2015. There is concern that it will hit in California and run north through Seattle and up into Vancouver, Canada and could decimate unprepared cities on the north-west coast of the US and Canada.
The Cascadia fault line is what the data researched by the Active Tectonics and Seafloor Mapping Laboratory at Oregon State University have studied, but the Cascadia fault line has lain dormant for 300 years. The fear is that the earthquake will last at least 5 minutes and they are looking at it being a 9+ magnitude earthquake. The time the earth is shaking is what will do the damage and could cause the Tsunamis.