地球重力场的精细频谱结构及其应用

综述了近年内在全球地球动力学合作观测和研究网络框架下开展的重力场观测、频谱结构和应用研究方面的成果. 内容涉及精密大气、海潮负荷信号检测, 重力潮汐和自由核章动参数测定, 海潮模型和重力固体潮模型有效性检验, 重力潮汐实验模型构制, 地球球型基频和低阶震型谱峰分裂现象和地球Chandler摆动等方面. 文章还介绍了综合现代大地测量技术, 全球超导重力仪的长期、连续观测在地表水循环、同震和震后形变、地球慢形变和地壳垂直运动等方面将发挥重要作用的情况.

Detail spectral structure of Earth's gravity field and its application

The achievements on study of the Earth's gravity field in the network of global geodynamical project(GGP) and its detail special structure as well as its application in geodynamics are summarized in this paper. The special attention is focused on the role of gravity changes recorded based on the superconducting gravimeters(SG) in the GGP network.By stacking the gravity signals from global SG in both frequency and time domains,the special background noise and systematical discrepancy in measurement of an individual instrument are effectively depressed.The noise levels,as well as the possibility of identification of some very weak gravity signals,are comprehensively analyzed.After available loading correction of barometric pressure and oceanic tides,the gravimetric parameters and resonance parameters of the Earth's free core nutation are accurately retrieved.The validation of Earth's gravity tidal models and ocean tidal models are investigated.The loading effects from the non-tidal ocean tides are successfully detected in SG observations.An accurate experimental model for global gravity tides is developed.It is shown that the SG plays an important role in structuring the long-period seismogram.The gravity signals,related to spheroidal fundamental modes with degrees less than 48 and the splitting of low-degree spheroidal modes,are discovered.The frequencies of these free oscillations are evaluated.In addition,the persistently excited free oscillations of the Earth are discovered in tidal gravity observations while no any earthquake occurs.Several global gravity signals,that may be related to the long-period free oscillations in Earth's fluid outer core,significantly emerge from station background noise.The gravity variations,caused by polar motion and by changes in continental water,are also analysis in this paper.The global tidal gravimetric parameters,including the amplitude factor and phase difference,are accurately determined.The paper introduces also the combination of the comprehensive modern space-geodetic techniques,the long-term continuous measurement of the global SG will play an significant role in study of global hydrologic cycle,the deformation associated with earthquake,the slow deformation after earthquake and the vertical displacement of the crust and so on.