There is a subduction zone off the coast (beginning just north of where the RECENT 6.0 quake hit) the fuels the Cascade volcanos. Geologists have been able to figure out that in the past, quakes in the 9 range have occured - possibly historically (before the country moved west). It is similar to the boxer day quake that hit indoneasa a couple years back.
San Andreas and affiliated faults are long over due for a big'en
Oh my.... I suppose it will not surprise you that I have never ever heard of a NINE earthquake, I had no idea that such a magnitude even existed.
That is absolutely frightening, but it is VERY interesting to me that perhaps there have been major cataclysms in the area, say in the 1500s, 1600s, early 1700s -- well before settlement in the area.
Is there anything in the Lewis & Clarke journals which may substantiate the recent geologic record?