太平洋卫星测高重力场与地球动力学特征

通过多卫星测高数据的综合处理，获得西太平洋卫星测高重力场，进行不同尺度、深度构造动力信息的分离，探讨诸边缘海盆的地球动力学问题。测高大地水准面反映了研究区板块相互作用的特点，其高频成分可以刻画各海盆的构造特征。测高空间重力异常也可刻画陆架构造及盆地分布，由其推算出的海底地形含有大量的海底构造信息。各边缘海盆的莫霍面埋深具有往南变浅的趋势，与菲律宾海各海盆的莫霍面埋深大致相当，说明岛弧两侧的构造动力强度基本相似。大尺度地幔流应力场总体上反映了欧亚板块向东南蠕散和太平洋板块向北西扩张的特点；日本海北侧和南海巽他陆架的中尺度上地幔对流与地幔柱之间有着密切关系，西菲律宾海的上地幔对流强化了日本-琉球-台湾-菲律宾岛弧的活动强度；小尺度地幔流主要限于软流圈层内部，在各海盆分散，而在冲绳海槽和马里亚纳海槽则会聚，可与均衡重力异常类比。还讨论了大、中、小地幔流体系的特点及相互之间的关系，籍以阐明海盆及海槽演化的地球动力学过程。

THE SATELLITE ALTIMETRY GRAVITY FIELD AND THE GEODYNAMIC FEATURE IN THE WEST PACIFIC

Through synthetic processing of altimetry data from Geosat, ERS 1/2 and Topex/Poseidon, the satellite altimetry gravity field has been calculated in the West Pacific and tectonic information for different scales and depths is separated and extracted from the gravity field in order to probe into geodynamics in marginal sea basins. The altimetry geoid undulation is mainly conducted by convergence between two or three plates, and its components at short wavelength characterize tectonics within basins. The altimetry free air gravity anomaly can describe structure and basin on continental shelves, and its derived submarine topography contains lots of submarine tectonic information. The Moho depth among marginal sea basins goes shallower southward, and it is similar to that of the Philippine Sea. Such a case means that strength of tectonic activities is almost the same in either side of the arc. The stress field from large scale of mantle convection is consistent with the southeastward rift of the Eurasian plate and the northwestward spread of the Pacific plate. Middle scale of mantle convection is closely related to the mantle plumes north of the Japan Sea and southwest of the South China Sea, and middle scale of mantle convection in the Philippine Sea has upgraded strength of the arc tectonic activities. Small scale of mantle convection restricted in asthenosphere diverges in sea basins, converges in Okinawa Trough and Mariana Trough, and it can be generally analogized with isostatic gravity anomaly. Features and relationships among large, middle and small scales of mantle convection systems are discussed to elucidate the geodynamic process of evolution of sea basins and troughs.