THE CRUST-TO-MANTLE TRANSITION IN THE BAIKAL RIFT ZONE AS CHARACTERIZED BY DIVING WAVES

An approximate algorithm has been developed for determining velocity in the lower crust based on calculation of a set of one-dimensional functions v(z) along a seismic route. The initial data were vertical sections t(l) of the times fields t(x,l) of diving waves from the upper crust and the lower crust recorded in their first arrivals, and diving waves from the lower crust recorded in subsequent arrivals of seismograms. For DSS profiles running through the Muya, Baunt and Konda Depressions, data were obtained providing that within the rift depressions in the lower crust, there is a gradient layer 3 to 6 km thick, where compression waves velocity increases from 6.8–7.0 to 7.5–7.8 km/s. This layer is evidently missing beneath the mountain structures dividing the depressions.