Fig. 2

a Continuous GPS velocity field (ellipses show 2 standard deviation uncertainties) in a stable North America reference frame, colored by latitude (Blewitt et al. 2018). The dashed line is the boundary at ~ 45° N that separates the region to the north where the velocity field primarily reflects loading from Cascadia subduction coupling, from the region to the south where the velocity field reflects the superposition of subduction coupling with NNW-directed tectonic processes. b GPS velocities in a, plotted on a half-rose diagram, colored by latitude. The relative motions of the Pacific–N. America, Pacific–SNGV, SNGV–N. America and Juan de Fuca–N. America plate/block pairs are shown. The Juan de Fuca–N. America relative motion changes with latitude. The shaded gray region shows the extent of directions represented by the NE (subduction) motions