Mantle flow velocity of East Asia

Abstract: Based on the high-resolution body wave tomographic images and relevant geophysical data the authors calculated the form and vertical and tangential velocities of mantle flow. Mantle flow in East Asia and the Western Pacific may fall into three patterns: (1) in the East-Asia marginal rift system and western Pacific marginal seas the mantle flow is marked by an upwelling mantle flow, characterized by flow convergence in the lower mantle and divergence in the upper mantle, especially for the South China Sea, where the structure of the upwelling mantle flow may be roughly outlined as a “工” shape in the upper mantle, a column shape in the middle and a divergent shape at the bottom; (2) in Siberia there is a “人”-shaped downwelling mantle flow, characterized by mantle material convergence in the upper mantle and divergence in the lower mantle; and (3) in the Qinghai-Tibet Plateau-Burma-Indonesia Tethys subduction zone, there is a “人”-shaped downwelling mantle flow, which is also characterized by flow convergence in the upper mantle and divergence in the lower mantle. The three regions of mantle convection beneath East Asia and the Western Pacific are in agreement with Western Pacific, Paleo-Asiatic and Tethyan tectonic domains. The material in the central part of East Asia shows no trend of flow in the deep interior of the mantle. The upwelling mantle flow originates from the core-mantle boundary and is mainly manifested in the lower mantle and lower part of the upper mantle. At the top of the upper mantle and at the surface, its location coincides with that of modern hot spots. The rate of vertical mantle flow is about 1 to 4 cm per year and the tangential rate is 1 to 10 cm per year.