地球自由振荡谱峰分裂及其对侧向非均匀结构的约束

Determining the internal structure of the Earth has been one of the main focuses of seismology, since it can be related to the composition, dynamics and evolution of planet. The anomaly splitting of the Earth's free oscillations plays an extremely important role in exploring the lateral heterogeneity of the Earth. The global geodynamics projects(GGP) provides a platform for us to cooperate with international organizations in terms of its high precision and resolution data which are generated by the superconducting gravimeters. We will adopt the techniques of stacking in time and frequency domain, digital filtering, statistical methods, spectral analysis of high accuracy and numerical simulation in order to extract the signatures of free oscillations with high signal-to-noise ratio, especially those of their splitting of low spherical harmonic orders. As a result, the long period seismograms should be improved and refined through researching the free oscillations and their splitting characteristics. The focus of this project is to investigate the lateral structure within the Earth through the normal mode splitting. The ranges of sensitive depth of the normal modes with different overtone numbers and spherical harmonic orders will be identified. The technique of small parameter perturbation will be utilized to simulate theoretically normal splitting due to the Earth's rotation and ellipticity and anomaly splitting due to lateral heterogeneity, and then the splitting function will be deduced. The spectra of anomaly splitting will be obtained by removing the effects of rotation and ellipticity from the observed signatures of normal mode splitting. According the sensitive depth of the corresponding normal modes, the physical properties of the medium in the related depth range will be modified for the simulated theoretically splitting functions matching the observed ones. Finally, the Earth model including lateral heterogeneity will be revised.

地球自由振荡的异常谱峰分裂的探测与研究是探索了解地球内部侧向非均匀结构的有效手段。在全球地球动力学（GGP）国际合作的总体框架下，利用GGP观测网络中高精度高分辨率超导重力仪观测数据，采用在时间域和频率域的迭积技术、数字滤波和高精度的谱分析方法，结合数值模拟技术，系统研究地球自由振荡及其谱峰分裂特征。提取高信噪比的自由振荡及低阶振型的谱峰分裂信号，完善和精化地球的长周期地震图；研究不同泛频数、不同球谐阶数简正模的敏感深度范围；采用"小参数扰动"理论模拟地球自转和椭率导致的低阶简正模正常谱峰分裂，和内部介质结构侧向非均匀性异常谱峰分裂，计算分裂函数；将观测的简正模波谱扣除椭率和旋转的影响，得到残差图谱，估计观测的异常谱峰分裂函数；分析比较观测和理论模拟的谱峰分裂函数，根据相关简正模的敏感深度，调整相应区域的介质参数，从而修正现有的侧向非均匀地球模型。

地球自由振荡的异常谱峰分裂的探测与研究是探索了解地球内部侧向非均匀结构的有效手段。在全球地球动力学（GGP）国际合作的总体框架下，利用GGP观测网络中高精度高分辨率超导重力仪观测数据，采用在时间域和频率域的迭积技术、数字滤波和高精度的谱分析方法，结合数值模拟技术，系统研究地球自由振荡及其谱峰分裂特征。提取高信噪比的自由振荡及低阶振型的谱峰分裂信号，完善和精化地球的长周期地震图；研究不同泛频数、不同球谐阶数简正模的敏感深度范围；采用“小参数扰动”理论模拟地球自转和椭率导致的低阶简正模正常谱峰分裂，和内部介质结构侧向非均匀性异常谱峰分裂，计算分裂函数；将观测的简正模波谱扣除椭率和旋转的影响，得到残差图谱，估计观测的异常谱峰分裂函数；分析比较观测和理论模拟的谱峰分裂函数，根据相关简正模的敏感深度，调整相应区域的介质参数，从而修正现有的侧向非均匀地球模型。