The results are described the following publication:
Gao, S. S., and K. H. Liu (2014),
Mantle transition zone discontinuities beneath the
contiguous United States,
Journal of Geophysical Research, volume 119,
6452-6468,
doi: 10.1002/2014JB011253 .
PDF
and supporting info:
26 E-W cross-sections with velocity anomalies.