The Pacific Geoscience Centre (part of the Geological Survey of Canada) is responsible for studying and understanding earthquake activity in western Canada, and for determining the risk of future damaging earthquakes. Part of their work involves making careful measurements of deformation of the crust using a network of GPS stations on Vancouver Island and adjacent areas. (6 of these stations are in the coastal region. Another, which is situated at the Dominion Radio Astronomical Observatory just south of Penticton (DRAO), is used as a stationary reference point.) This network is called the Western Canada Deformation Array (WCDA).

Your assignment is to go to the PGC website (www.pgc.nrcan.gc.ca) and find out what you need to know about the Geodynamics Program and the WCDA GPS network.  For each station there are graphs showing the east, north and vertical components of the displacement (relative to DRAO) over several years. Measure the relative displacements from the graphs, and calculate them in mm/y. 

To save you some time, copies of the graphs are available from here:

You can use the diagram below to determine the directions of motion. For each site plot the EAST and NORTH components (in mm/y) on the E and N axes, and then use that to determine the overall direction and rate of motion.  (You can also do this mathematically - the results will be more accurate.)

Then plot the results on the map below, using arrows to show the direction and rate of horizontal motion at each location, plus numbers to show the rates of horizontal and vertical motion (mm/y). (You should also express the rate of horizontal motion using the arrow length, as determined from the scale shown at the lower-left corner of the map.)

An example is shown to the left.

When you're finished, your map should have five arrows showing different orientations and rates of horizontal motion, plus ten numbers showing the rates of horizontal and vertical motion. 

Comment on what the observed deformation tells us about what's happening to the North America Plate in our area.