The convergence of the Juan de Fuca plate and the northwestward motion of the Pacific plate relative to North America result in active deformation of the North American margin several hundred kilometers into its interior. This deformation has the potential of producing large, damaging earthquakes and can be measured very accurately with the Global Positioning System (GPS) operating in the differential mode. The investigators will utilize pre-existing GPS data gathered by the US Geological Survey between 1991 and 1995 along with more recent measurements made by the National Geodetic Survey, local surveyors, and by the PIs to examine specific aspects of this deformation and their geological causes. In this study the PIs will focus on the rate of northward transport of the coastal regions of Oregon and Washington and the role this transport plays in the growth of coastal mountains, the variations in strain rates along the coast possibly related to segmentation of the dipping thrust fault separating the Juan de Fuca plate from North America, and the location of the boundary between the northward moving coastal region and North America. All of these features are observed in several other convergent margins globally and this focused study in the US Pacific Northwest will help us understand their underlying causes.
