【摘要】 将地幔地震波速度异常转换为地幔横向黏度变化(达到3个数量级),在球坐标系下计算了瑞雷数为106、上边界为刚性、下边界为应力自由等温边界条件下的岩石层底部的地幔对流极型和环型应力场.结果表明,地幔对流极型应力场与地表大尺度构造具有良好的对应关系:俯冲带和碰撞带的应力呈现挤压状态,而洋中脊处的应力则呈现拉张状态.地幔对流环型应力场表明南北半球的旋转方向相反:北半球为右旋,南半球为左旋;总体上北半球岩石层底部的环型应力较大,而南半球的较小,特别是在低纬度(环赤道)附近区域.这些结果可能表明了地幔对流是导致岩石层大尺度应力场分布及状态的一个重要因素.更多还原

【Abstract】 Converting the seismic wave velocity anomalies into lateral viscosity variation (up to 3 orders) in the mantle, we obtained the poloidal and toroidal convection stress field at the bottom of lithosphere in spherical coordinates. In the computation, Rayleigh number is taken to be 106, and the top and bottom boundary are set to be rigid and free-slip isothermal, respectively. The result suggests that the poloidal convection stress field has a good correspondence with surface large-scale tectonics:The stress at subduction and collision zones is in compression state, and the stress at oceanic ridges takes on extension state. The toroidal convection stress field shows opposite rotation in southern and northern hemisphere:the northern one rotates clockwise while the southern one rotates counterclockwise. On the whole, the stress values in northern hemisphere are larger than those in southern one, especially in the low-latitude zone around the equator. These results indicate that mantle convection is a possible important factor to affect the distribution and state of large-scale stress field in the lithosphere.更多还原