【作者】 叶正仁；

【Author】 Ye Zhengren (Institute of Geophysics,Chinese Academy of Sciences)

【机构】 中国科学院地球物理研究所；

【摘要】 利用长波重力异常及板块速度场这二类独立的观测资料,本文反演得到地幔密度的横向差异.地幔被处理为一个自重的牛顿流体球壳.描述流体运动的一组偏微分方程被转化为常微分方程,其中,横向密度差异作为"源项"出现,进而作球谐展开.形式上,这组方程可利用传播子方法求解,在所有满足观测的重力位及表面速度场资料的内部密度分布中,有着最小粘滞损耗的一个被选取.在数值计算中,球谐系数展开到11阶.结果给出了在不同深度间隔的横向密度差异的分布,并与表面构造形态作比较,同时,密度的横向变化随深度减少.在上地幔,其量级约为1—3%,而在下地幔,减为0.5%左右.更多还原

【Abstract】 An inverse method to determine lateral density differences in the mantle has been developed using long wavelength geopotential anomalies and the plate velocity field.The mantle is treated as a self-gravitating shell of Newtonian fluid.The partial differential equations governing the flow of this shell are converted to a set of ordinary differential equations with the lateral density as a"source"item,and scalar representations of the velocity and viscous stress fields are expanded as harmonic series.These equations are formally solved using the propagator method. Among the many possible density distribution choices satisfying observational geopotential and plate velocity field,one is selected whose associated velocity field minimizes the viscous dissipation. In the numerical work the harmonic expansions have been taken to degree and order 11. The lateral density differences in different depth ranges are given and compared with surface tectonic features.The magnitude of the lateral density difference decreascs with depth,in the upper mantle,it is about 1-3%but reduces to about 0.5%in the lower mantle.更多还原