A viscous layer at the crust-mantle boundary in the Far East of Russia

Geophysical indications, spatial parameters, and localization of the crustal and subcrustal viscous layers in the Far East of Russia are considered. The low-viscosity zones and layers are correlated equally distinctly with the Jurassic-Cretaceous plutonic and Cretaceous, Early Cenozoic, and Recent volcanic belts in tectonic domains of different age and geographic position, testifying to the long-term (up to 100–120 Ma) existence of viscous layers permanently fed by mantle-derived energy and mass flows through a deep fault zone and central-type structures of plume nature. The widespread low-viscosity zones in the lower crust and the uppermost mantle provided in the past and are providing now favorable conditions for lateral displacements of overlying tectonic sheets and fast relaxation of elastic stress in the Earth’s crust, provoking earthquakes.