First watch this illustration of the mechanics of the earthquake. You may even want to play it a few time to follow the action. (You may have to use your “back arrow” to return to this page.)
Then follow that up with a look at the next animation of the records from the many survey grade GPS/GNSS observation stations across the Islands recording their positions continually. It too may need more than one viewing to see what it happening. It happens quickly.
GPS/GNSS CORS displacements_0530-0630UTC Sendai
The movie shows the displacements due to the M9.0 and M7.9 earthquakes in Japan on March 11, 2011 (data, no model!). It shows body and surface waves, and static displacements.
Visualization: R. Grapenthin, Geophysical Institute, Univ. Alaska Fairbanks. Data: preliminary GPS positioning solutions provided by ARIA/HPL/Caltech. All original GEONET RINEX data were provided to Caltech by the Geospatial Information Authority (GSI) of Japan.