Rotation and plate locking at the southern Cascadia subduction zone

Abstract

Global Positioning System vectors and surface tilt rates are inverted simultaneously for the rotation of western Oregon and plate locking on the southern Cascadia subduction thrust fault. Plate locking appears to be largely offshore, consistent with earlier studies, and is sufficient to allow occasional great earthquakes inferred from geology. Clockwise rotation of most of Oregon about a nearby pole is likely driven by collapse of the Basin and Range and results in shortening in NW Washington State. The rotation pole lies along the Olympic - Wallowa lineament and explains the predominance of extension south of the pole and contraction north of it. Copyright 2000 by the American Geophysical Union.