Rotation and plate locking at the southern Cascadia subduction zone

Global Positioning System vectors and surface tilt rates are inverted simul taneously for the rotation of western Oregon and plate locking on the south ern Cascadia subduction thrust fault. Plate locking appears to be largely o ffshore, consistent with earlier studies, and is sufficient to allow occasi onal great earthquakes inferred from geology. Clockwise rotation of most of Oregon about a nearby pole is likely driven by collapse of the Basin and R ange and results in shortening in NW Washington State. The rotation pole li es along the Olympic - Wallowa Lineament and explains the predominance of e xtension south of the pole and contraction north of it.