Follow this link for a GPS vector map of the Western U.S.
 You can click on the map to zoom in and use your browser back button to zoom out (or use the 'Zoom out' button in the button bar to the top left.)

What am I seeing here?
The map has a number of arrows called GPS vectors, mostly along the west coast of the United States.

For this image, we have set the frame of reference to be North America, which means middle-North America is not moving and the rest of world is moving in comparison to the stable part of North America.

In the upper left of the image is a scale bar; approximately one inch is equivalent to a GPS station moving 50mm/year.

Along the coast in the Pacific Northwest, the GPS motion vectors show the North American plate moving slightly to the northeast (about 5mm/yr).

The Juan de Fuca plate (the area between the orange line and blue line) is subducting under Washington and Oregon; however, rather than sliding under the North American plate smoothly, the two plates are momentarily 'stuck' together which is causing the North American plate's crust near the plate boundary to be dragged along with the Juan de Fuca plate. Eventually a very large earthquake will occur and the North American plate will snap back to the west and the Juan de Fuca plate will slide down to the east (subduct). There are many interesting phenomena going on here... to learn more about this, take a look at our activities: Using GPS to Visualize Plate Tectonics in the Pacific Northwest and ETS: The Case of the Mystery Earthquakes.

Take a look at the animation called ETS Animation near subduction zones
More animations
 
Along the coast of California, the vectors are pointing to the Northwest and are relatively long near the coast (approx 50mm/yr) and become shorter further inland (5mm/yr to no motion).

The San Andreas fault (the blue line) runs through the thick cluster of arrows and is a strike-slip fault.

California west of the San Andreas is moving to the Northwest ~50mm/yr while California east of the San Andreas is also moving to the Northwest more slowly (about 5 mm/yr).  The west side is moving faster than the east side which still makes this a strike slip motion.  If we could change our frame of reference to be the middle of the San Andreas fault, we would see the traditional view with each side slipping past each other.


The basin and range region (Nevada) into Utah is also moving slightly to the west. This area is under extension.


Quick directions to make this map
Go to the EarthScope Voyage JR map tool
(http://jules.unavco.org/VoyagerJr/EarthScope)

Under Add a base Map
    Click on Gray Topography

Under Add Features,
    Hold the Ctrl key (or Apple key) and click on 'Tectonic Plates' and  ‘Political, Lat/Long’

Under the ‘Add velocities’ menu
    Click on ‘N. America’ and the ‘Obs’ button.

Click the ‘Make changes’ once. In a few seconds, the map will reload with plate motion vectors (arrows) in purple.

Now, click on the map on west coast of the U.S. twice.

Your final map should look like this: