I used to digest BSSA articles, but I can't afford it any more. :( Anyway, the triggering of landslides is 100% correlated with PGV (peak ground velocity), since that is directly related to induced shear strain. In a happy world, this would put an end to PGA, blah.
Had this earthquake happened under Montreal, Boston, or New York, we wouldn't have even looked at Sandy. Luckily it was in the middle of nowhere, and we don't have to learn a thing, as Homer would say. As to whether it was unusual in the historic sense, I doubt it. It was just in a place where you could get a lot of rock falls. In other places, the 'power' or PGV is measured by looking at liquefaction. For an M6 you would get rock falls, for an M7 you would get soft soil deformation. New Madrid and Charleston are in that class.
Update: Now they are finally getting the idea there is soil amplification.