Аннотация:A description is given of a graphical method of mapping a horizontal upper mantle velocity
inhomogeneity, by projecting discrepancies in the travel times of waves from distant earthquakes to a given depth and smoothing the resulting numerical field. The differences in the velocity cross sections of neighboring mantle blocks are estimated by the magnitude of the
discrepancies for rays intersecting the contact surface between blocks at various depths. A
map of the horizontal velocity inhomogeneity of Pamir-Hindu-Kush is constructed. The intermediate-depth seismicity of the region is closely related to a high-velocity body detected
at depths down to 300 km. The dimensions of this body and its relation to outcroppings of
Precambrian rocks enable us to hypothesize that it represents the downward continuation of
the edge of the old shield. The intermediate-depth seismicity is caused by the rigidity of the
high-velocity body and by a concentration of tectonic stress in its narrowest part.