It was established on the basis of seismograms of nuclear explosions that t
he upper mantle up to the depth of 410 km is characterized by chemical diff
erentiation, which occurs as alternating layers with low and high body wave
velocities. In the upper mantle-lower mantle transition zone, a seismic in
terface is present at 520 km. The interface geometry in the transition zone
is evidence of mantle warming up to a depth of 350-660 km below the kimber
lite field.