【摘要】 依据卫星重力、大地水准面观测结果,对表示地球形状的大地水准面异常进行了不同阶次的球谐函数计算和分析,发现2~6阶大地水准面异常表现出了地球双重非对称的基本形状,而高于6阶的大地水准面异常只表示了地球形态的局部变化特征。另外,采用阻尼最小二乘方法,利用全球地震层析成像资料和大地水准面异常资料联合反演了三维全球地幔密度异常。结果显示了地幔密度异常不仅在横向上,而且在纵向上也存在着明显的不均匀性。对比分析低阶大地水准面异常和地幔密度异常结果表明,地球形状非对称性主要是由下地幔的物质密度不均匀引起的。更多还原

【Abstract】 Based on satellite gravity and geoid observation results, we calculated and analyzed different order and degree of harmonic function of geoid, which can express earth shape. It is found that 26 degree geoid anomaly shows the fundamental shape of earth shape asymmetry, and geoid anomaly of more than 6 degree only shows the local undulation character of the earth shape. Moreover, The authors inverted three dimensional global mantle density (anomaly) combining geoid data and seismic tomography data by means of damping least square method. The density anomaly result shows that mantle density is obviously inhomogeneity not only in horizontal direction, but also in radial direction. Comparing low degree geoid anomaly with mantle density anomaly, The authors think the earth shape asymmetry is mainly caused by lower mantle density inhomogeneity.更多还原