Except for directivity effects, the epicenter does not matter. It is the rupture area that matters. News media kept worrying about the epicenter of the Sumatra quakes and that was really missing the point. So: I don't know where the epicenter was and I doubt that anyone can tell this 306 years later. I think pretty much the entire subduction zone failed in 1700...so the rupture area is probablt from northern California through northern Washington or southern B.C. For ground motion...the shaking will be more intense if the rupture starts far from you and ruptures towards you...but will last a little less. Chris