The animation below (press the buttons below to play)
shows an isosurface of 0.5% higher than
average P wavespeed for the entire mantle volume below the
Far East (Japan, eastern China). This isosurface approximately
describes the Pacific plate subducted in the Kuriles, Japan and
Izu-Bonin trenches. Two important observations can be made from
this animation. First, in the upper mantle most of the plate
material flattens on the upper-to-lower mantle transition.
Second, there is a narrow conduit connecting the upper mantle
plate material with a large volume in the lowermost mantle
(the so-called "graveyard").