CЕЙСМИЧЕСКИЕ НЕОДНОРОДНОСТИ ВЕРХНЕЙ МАНТИИ ПОД СИБИРСКИМ КРАТОНОМ (профиль Метеорит) В.Д. Суворов, Е.А. Мельник, З.Р. Мишенькина, Е.В. Павлов, В.А. Кочнев*

The upper-mantle structure was studied from fi rst-arrival data along the Meteorite profi le, run using underground nuclear bursts. Unlike the layered, slightly inhomogeneous models in the previous works, emphasis was laid on lateral inhomogeneity at the minimum possible number of abrupt seismic boundaries. We used forward ray tracing of the traveltimes of refracted and overcritical refl ected waves. The model obtained is characterized by considerable velocity variations, from 7.7 km/s in the Baikal Rift Zone to 8.0–8.45 km/s beneath the Tunguska syneclise. A layer of increased velocity (up to 8.5–8.6 km/s), 30–80 km thick, is distinguished at the base of seismic lithosphere. The depth of the layer top varies from 120 km in the northern Siberian craton to 210 km in its southeastern framing. It has been shown that, with crustal density anomalies excluded, the reduced gravity fi eld is consistent with the upper-mantle velocity model.