Interesting GPS related issue with the New Zealand earthquake of earlier today.
According to http://geodesy.unr.edu/, the island moved quite around: The maximum displacements we found with GPS are at station CMBL near Clifford Bay, 1.3 meters east, 2.3 meters north, and 0.9 meters upward.
See http://geodesy.unr.edu/news_items/CMBL.png for the whole details.