Explanation of the Animations:

We show 2 videos on Japan's movement over the 35 minutes following the
initiation of the Tohoku-Oki (M 9.0). These images are made possible because
of the density of GPS stations in Japan (about 1200 GPS stations, or a GPS
station every ~30 km). The preliminary GPS displacement data that these
animations are based on are provided by the ARIA team at JPL and Caltech.
All Original GEONET RINEX data provided to Caltech by the Geospatial
Information Authority (GSI) of Japan.

a) ARIA_GPSDisplacement.mp4

   This animation shows the cumulative displacements of the GPS stations
   relative to their position before the M9.0 Tohoku-Oki earthquake. The colors
   show the magnitude of displacement and the arrows indicate direction. We
   observe 2 kinds of motions, a permanent deformation in the vicinity of the
   earthquake (first red star) inmediatelly followed by a perturbation that
   travels about ~4 km/sec which are the surface waves generated by the
   earthquake.


b) ARIA_GPSvelocity.mp4

   This animation shows the estimated instantaneous velocities of the GPS
   stations. In this view, we only observe the transient motion caused by the
   earthquake. The first waves to propagate from the mainshock (red star) are
   the body waves (P and S) but they can be barely seen (look for a slight
   purple perturbation).  These are followed by the surface waves (Love and
   Rayleigh) propagating as 2 orange-red stripes, as surface waves generate
   larger velocities at the surface than the body waves. At about 25 minutes
   there is a subtle signal from seismic waves generated by a small aftershock
   in northern Japan. At around 30 minutes we observe the seismic waves from a
   M7.9 aftershock (smaller red star), the largest aftershock to date. Since
   this event is about 30 times smaller than the mainshock, the P and S waves
   from this earthquake are too small to be detected with these rapid GPS
   solutions, but we can observe the surface waves. The small patches of color
   that appear randomly across Japan show the noise level of the measurements and
   are not related to any significant ground motion.


				
						                  ARIA Project
                                                                  CALTECH / JPL