We have obtained the velocities at more than 200 sites in Greece using GPS data from epoch campaigns spanning up to 10 years , under the assumption that short-term inter-seismic velocities are steady and therefore reference frame biases can be estimated. Over 20 of the sites are coincident with or close to pillars in 20- and 100-year-old triangulation networks. By extrapolating a minimal subset of the GPS pillar velocities, we estimate the scale and orientation of the triangulation networks. We find that the coordinate fit of the GPS and triangulation networks fits our model of steady-state velocities well within 95% confidence limits, and observe that the velocity field is generally smooth spatially as well as temporally.
By interpolating our velocity field we calculate the strain tensor field and associated derived quantities. We note that the current and recent orientations of faults are consistent with those predicted from the velocity field but oblique to earlier crustal trends. This observation, coupled with the temporal and spatial smoothness of the crustal velocity field, is suggestive of a dynamic model in which brittle-elastic crustal deformation is driven by the ductile lower lithosphere. Further densification and expansion of the GPS network is currently in progress (Cross et al, this volume).