Here's another graphic, which shows the relative motions of the west coast of the US. Note that the boundary between the Pacific Plate and the North American plate is not a subduction area. The San Andreas Fault is a transform fault, meaning that the boundary of the two plates is a zone where one plate is sliding against the other. North of Mendocino, you find the subduction of the Juan de Fuca plate, which leads to the formation of the Cascades, extending down clear to Mt. Lassen in CA. The Los Angeles area is actually atop the Pacific Plate, while the rest of CA is on the North American plate. For a very, very long time, the Pacific Plate has been moving northwards, which is why CA can't fall off the map. I hope this helps.
Ramon Martinez of Monterey Co. Public Works checks a crack in a bridge from an earthquake Tuesday, Sep. 28, 2004 in Parkfield, Calif. The bridge suffered some strutural damage including separating nearly six inches from the road.
Gloria VanHorn, a 60-year resident of Parkfield, Calif., reacts to the damage in her home following a 6.0- maginitude earthquake that struck the region on Tuesday, Sept. 28, 2004, in Parkfield, Calif.