Models of downdip frictional coupling for the Cascadia megathrust

We have developed models of downdip frictional coupling along two transects across the Cascadia subduction zone in northern Washington and central Oregon. The models involve complicated downdip coupling profiles. Although not unique, our models closely predict available GPS shortening rates and vertical uplift data. We are able to explain relatively low horizontal shortening rates along the Washington coast and small vertical uplift rates in central Oregon. Our models depart from previous models by inclusion of a deeply coupled region assumed to be related to mafic rocks in both the upper and lower plates of the thrust.