Study And Detection On The Geodynamic Effects Of The Earth's Fluid Outer Core

The long-term,continuous gravity data,recorded with superconducting gravimeters (SCO) at the Global Geodynamics Project (GGP) observatories including one at Wuhan,and the corresponding station atmospheric pressure records have been comprehensively processed and analyzed. Based on the study and detection on the geodynamical effects of the Earth's fluid outer core,the roles of the SCG distributed globally are especially emphasized on. We have investigated the data pre-processing,the deformation characteristics of the solid Earth,the Earth's nearly diurnal free wobble,the free oscillations of the fluid outer core and the translational oscillations of the solid inner core. The main results are listed as following:1. The Earth's deformation under the luni-solar tidal force and surface loads is investigated. The numerical results indicate that the deformation within the solid inner core is very small. However,in the fluid outer core,the changes of the displacement with relatively low spherical harmonic degree (n<10) is very complicated via the radius,due to the resonance near the eigenfrequenies of the core long-period oscillations. While the spherical harmonic degree of the loading is larger than 10,the deformation and the gravitational perturbation in the core are very small,and the Earth's deformation response is dominantly represented as the radial displacement in the elastic mantle. The displacement decreases sharply with the depth increasing. The surface load Love numbers weakly depend upon the signal frequencies. An acceptable approximate procedure for the body tide Love number calculation is developed in this dissertation.2. The internal load Love numbers,expressed as a general form in this dissertation,are employed to describe the deformation response of the Earth's solid parts to the dynamical behaviors of the fluid outer core. The spatial distribution and frequency-dependence characteristics of the internal load Love numbers are also investigated. The numerical results indicate that the internal load Love numbers decrease quickly with the spherical harmonic degree enhancement,and depend strongly upon the perturbation frequencies,especially upon relatively high those closed to the eigenfrequencies of the Earth's free oscillations.3. By stacking the high-precision tidal gravity observations recorded with international SCG at six stations located on different area,the influences of the barometric pressure,ocean tides and the local environmental perturbations around the stations are eliminated effectively,and lead to an accurate determination of the resonance parameters of the Earth's free core nutation (FCN). The final results indicate that the FCN period is about 429.0 sidereal days,in closed agreement with the corresponding results in the previous studies,and about 30 sidereal days less than one expected theoretically. It confirms that the real dynamical ellipticity of the fluid core is about 5% larger than one expected on assumption of the hydrostatic equilibrium. The quality factor is about 9543,which,compared with those determined based on the tidal gravity observations in the previous studies,more closes to those obtained by using the VLBI data. The complex resonance strength is (-6.10X10-4,-0.01X10-4). It can principally describe the deformation characteristics of an anelastic mantle.4. The tidal gravity observations,recorded with a SCG at Wuhan,are employed to investigate the influences of the ocean tide loading on the fitted FCN parameters and thelocal characteristics of the nearly diurnal resonance on the tidal gravity observations. It is found that the influence of different co-tides on the fitted eigenperiod and the real part of the resonance strength of the FCN is very small. The discrepancies are less than 1.5% for the eigenperiod and 7.7% for the real part of the resonance strength. Meanwhile,the fitted qualify factor Q and the imaginary part of the resonance strength of the FCN depends obviously on the chosen co-tides,and the influence of different co-tides on the fittin...