Did you encounter any studies that even suggested the possibility of a 900 mile rupture? I did not, and such broad-scale cataclysmic thinking is not common in the geophysicists whom I knew. I had a professor who wrote papers on mega-shear events: imagine Montana lifting, moving and rotating as a whole.
Not specifically, just the culmination of reports/articles I read and some feedback from city disaster planning we researched. That is the worst of the worst kind of scenario, though history would indicate a rupture of that magnitude is highly unlikely, but not out of the realm of possibility. I'm no geophysicist, and don't claim to be an expert, so I must rely on what I read/hear from others.
Some of the information that was given to us in our research for the company indicated that the damage in the Portland area may not be as bad as some other reports suggested, meaning many more structures may be left standing than some are lead to believe. Again, is this trustworthy? I really don't know. Plan for the worst, hope for the best.