Most people in California think of the San Andreas fault as the likely source of the Big One. But scientists point to the Cascadia subduction zone in the Pacific Northwest as a bigger threat to the West Coast.
The Cascadia zone extends 700 miles along the coast from near Eureka, Calif., to Vancouver, Canada, and is capable of producing a catastrophic 9.0 earthquake and tsunami, as happened Jan. 26, 1700.
A graphic below shows the tsunami that likely was produced by the large-magnitude quake more than 300 years ago and caused damage as far away as Japan. Shown here is how this subduction zone creates such large quakes and tsunamis.
Read the full story. A report done in 2005 by the USGS on the area can be found at the USGS.