THE MAIN FEATURES OF THE INTERFACE BETWEEN THE CRUST AND THE UPPER-MANTLE IN THE MIDDLE URALS (IN THE VICINITY OF THE DEEP DRILLHOLE SC-4)

Analysis of both P- and S-wave seismic data from the Middle Urals supp orts the existence of a multi-layered crust-mantle transition zone and a deep crustal root along the central axis of the Urals, Data from de ep seismic sounding (DSS) nuclear explosions (Rubin I and Quartz), qua rry blasts from industrial sources, and wide-angle experiments (Krasno uralsky and UWARS) are integrated to form the basis for this study. Th e crust-mantle transitional complex begins in the eastern par? of the Pre-Uralian foredeep where it consists of relatively thin layers (thic kness similar to 3-5 km) with alternating high- and low-velocity layer s. Toward the axis of the Urals the transition zone thickens to 10-15 km beneath the Tagil are before thinning toward the East Uralian zone. The average interval P wave velocity for the transition zone varies f rom 7.3-7.8 km/s. The thickness of the crust is found to reach a maxim um of 55-60 km in the vicinity of the super deep borehole SG4. In the area of SG-4, the Moho shallows from the Tagil zone west to the Centra l Urals uplift and Western Urals fold zone. The upper mantle is charac terized by a nearly uniform velocity of 8.5 km/s.