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In Earth Science, GPS receivers embedded in bedrock are used to measure the deformation of the surface over time. In this video, I show the GPS-measured surface deformation of Japan from late 2002 to late 2015. The data are courtesy of the Geospatial Information Authority of Japan (http://datahouse1.gsi.go.jp/terras/te....

Black arrows are average *velocities* over the previous 100 days. There are two very large earthquakes in this video (the 2003 Hokkaido earthquake and the 2011 Tohoku earthquake). During these events, the arrows turn blue, and represent the earthquake-generated **displacements**. For those of you who haven't taken physics recently, displacement is position of the ground relative to the pre-earthquake position (not taking time into account). Velocity is how fast the ground is moving.

Interesting features:
Most of the time before 2011, the arrows point west. This is interpreted to be a result of the Pacific ocean pushing against Japan as it descends westward beneath the island.
During an earthquake, the arrows usually move in the opposite direction as Japan rebounds to the east.
After the 2003 and 2011 earthquakes, parts of Japan continue moving to the east for a while after the earthquake. In fact, most of the main island continues to move eastward today.
When small earthquakes occur, the velocity arrows change and then return to their previous direction. This is an artifact of fitting a line through an abrupt step in the GPS position caused by the earthquake, not a real velocity change.