Referring to the studies by Shimazu and Kono (1963, '64), two dimensional stress distributions within the unsteady convection cell and their secular variations are calculated. The results obtained are as follows: (1) The stress distribution is strongly affected by the type of boundary conditions at the upper and lower surface, i. e. fixed (rigid) or free. When the upper surface (Moho) is stress free, the stress is concentrated at the rising and sinking areas. When the upper surface is rigid, it is concentrated in the middle of the rising and sinking areas. (2) The patterns and magnitudes of stress within the cell are not significantly varied with time.
Based upon the stress distributions thus obtained, the distribution of the deep focus earthquakes and the elastic anisotropy of the upper mantle are discussed.
Furthermore, a possibility of stirring of the mantle by convection current is checked. It is concluded that the upper mantle is nearly completely stirred during the one cycle of the convection.