Variable Viscosity Whole Mantle Convection And Surface Plate Motions

During the course of looking after the real earth's mantle convection model, a fundamental thing is done in this paper. Only the seismic velocity structure in mantle is introduced to constrain our model, which is turned into temperature deviation and lateral variable viscosity in the mantle, and the convection patterns in the uppermost mantle are inverted. As a result, the relationships between convection patterns and global surface plate motion are discussed and the horizontal divergence and radial vorticity from our model and observations are compared and contrasted in detail.(1) Not only the poloidal field representing the vertical flow of but also the toroidal field representing the horizontal flow of the mantle's mass is obtained.(2) The magnitudes of poloidal field are comparable to but these of toroidal field are much smaller than those of the observations of plate motion.(3) The computed horizontal divergence and radial vorticity distribute wider than the observations limiting mainly to large tectonic zones, but the computed horizontal divergence can interprets the characteristics of main surface tectonic motion and its intensity. While probably because of the ignorance of the terms including lateral variable viscosity in computing poloidal field, the computed radial vorticity is symmetry to the meridian plane with 180°.(4) The poloidal convection patterns in the uppermost mantle have good correlations with global surface plate motions. We can interpret the divergent or convergent motive state of the plates close to large tectonic zones and then recognize and understand their formation in deep dynamics by our computed poloidal field. There are 2 composite rotating hemisphere-scale rolls in toroidal convection patterns, which is the possible reason of differential motion between Northern and Southern hemispheres. In addition, the large-scale convection tangent zone close to the equator is the possible deep dynamic origin of strong tangent zone and, as a result, strong earthquake occurrence in this zone.(5) In analysis, it is reasonable to use the results from R-F boundary for the continents while from F-F boundary for the oceans. However, if taken the continents as rigid...