Looks like you guys have answered your own questions, and that was a nice pix of the plate boundaries by the way.

In So Cal the San Andreas is moving laterally. Hence the slip is sidewards along the main earthquake fault. Geologists generally believe that this type of motion is a little more benign, compared to the big quake in Japan. The San Andreas is hung up on the southern section, running from (just north of) Palm Springs down past the Salton Sea. Expected quake magnitude might be an 8-something. This quake is overdue. Places like Palm Springs and Banning will be toast when this quake goes down.

In Oregon they have got a real problem with the small plate boundary called the Juan de Fuca. That is the type of motion where one plate slides under the other. Exact same motion that generated the big Japan quake. The southern section of Oregon is now overdue to trigger on that fault line. Very likely it will trigger a big tsunami along the OR coast and the coast of northern CA.

There is a geological theory that the activity on the San Andreas and the Cascadia fault (OR) is linked. This comes from studies looking at when quakes (historically) coincided. Hence, if the OR fault system triggers, that could mean that the San Andreas is at higher risk. I don't think that geologists are saying that everything would all rupture at the same time. That would be a nightmare.

However, that worst-case event cannot be ruled out. Needless to say, if there's a rupture along hundreds of miles of fault line from southern CA all the way to OR, the west coast of the USA would be a basket case. It's not worth thinking about :-(

Pete2