The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan statio...The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.展开更多
Measurements of non-tidal variations of gravity (Ag), which were obtained from 1992 to 2012 at the Talaya seismic station (located in the south-western part of the Baikal region), are interpreted together with GPS...Measurements of non-tidal variations of gravity (Ag), which were obtained from 1992 to 2012 at the Talaya seismic station (located in the south-western part of the Baikal region), are interpreted together with GPS (Global Position System) observation data, which were obtained from 2000 to 2013 at the same station. An absolute gravimeter was used for gravity observation. The strongest precision requirements concern tidal gravity prediction. It is the reason why we investigated tidal effect by LCR (LaCoste & Romberg) gravimeter from 1996 to 1997 at the same station. We use tested tidal model for correction of gravity change. The linear component of gravity variations corresponds to changes in the elevation of the site. The correlation coefficient is close to the normal value of the vertical gradient of gravity. At this site, coseismic gravity variations at the time of the Kultuk earthquake (August 27, 2008, Mw = 6.5) were caused by a combined effect of the change of the site's elevation and deformation of the crust. Our estimations of the coseismic effects are consistent with results obtained by modeling based on the available seismic data.展开更多
The parameters, i.e. the Period and the Quality factor, of the Earth's free core nutation (FCN) are closely related to the dissipative coupling between the core and the mantle. Based on the FCN parameters obtained...The parameters, i.e. the Period and the Quality factor, of the Earth's free core nutation (FCN) are closely related to the dissipative coupling between the core and the mantle. Based on the FCN parameters obtained from the actual observations and theoretical simulation, significantly constrained in this study were several key parameters near the core-mantle boundary (CMB), related to the core and mantle coupling, including viscosity at the top of liquid core, conductivity at the bottom of the mantle, and dynamic ellipticity of the CMB. In order to choose high quality observations from global stations of the superconducting gravimeters (SG) on the Global Geodynamics Project (GGP) network, we adopted two criteria, the standard deviations of harmonic analysis on tidal observations and the quality of the FCN parameters calculated with the observations from single station. After the mean ocean tidal effects of the recent ocean tidal models were removed, the FCN parameters were retrieved by stacking the tidal gravity observations from the GGP network. The results were in a good agreement with those in the recent research by using the SG and/or the VLBI observations. Combined with an FCN theoretical model deduced by angular momentum method, the viscous and electromagnetic coupling parameters near the CMB were evaluated. Numerical results indicated that the viscosity at the top of the liquid core was in the range from 6.6×102 to 2.6×103 Pa·s, which was in good agreement with those obtained from the Earth's nutation, the FCN and variations in the length of day (LOD). The conductivity at the bottom of the mantle should be as large as 2.6×106-1.0×107 S m-1 to match the FCN quality factors from the actual observations. The dissipative coupling had a little influence of 1-2 sidereal days for the FCN period.展开更多
The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite form...The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite's geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented.展开更多
基金sponsored by the Basic Scientific Research of Institute of Geophysics,CEA(DQJB12B20,DQJB12C03,DQJB12B14)
文摘The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.
文摘Measurements of non-tidal variations of gravity (Ag), which were obtained from 1992 to 2012 at the Talaya seismic station (located in the south-western part of the Baikal region), are interpreted together with GPS (Global Position System) observation data, which were obtained from 2000 to 2013 at the same station. An absolute gravimeter was used for gravity observation. The strongest precision requirements concern tidal gravity prediction. It is the reason why we investigated tidal effect by LCR (LaCoste & Romberg) gravimeter from 1996 to 1997 at the same station. We use tested tidal model for correction of gravity change. The linear component of gravity variations corresponds to changes in the elevation of the site. The correlation coefficient is close to the normal value of the vertical gradient of gravity. At this site, coseismic gravity variations at the time of the Kultuk earthquake (August 27, 2008, Mw = 6.5) were caused by a combined effect of the change of the site's elevation and deformation of the crust. Our estimations of the coseismic effects are consistent with results obtained by modeling based on the available seismic data.
基金supported by Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KZCX2-YW-133 and KZCX2-YW-Q08-2)National Natural Science Foundation of China (Grant Nos. 41021003, 41074053 and 40730316)
文摘The parameters, i.e. the Period and the Quality factor, of the Earth's free core nutation (FCN) are closely related to the dissipative coupling between the core and the mantle. Based on the FCN parameters obtained from the actual observations and theoretical simulation, significantly constrained in this study were several key parameters near the core-mantle boundary (CMB), related to the core and mantle coupling, including viscosity at the top of liquid core, conductivity at the bottom of the mantle, and dynamic ellipticity of the CMB. In order to choose high quality observations from global stations of the superconducting gravimeters (SG) on the Global Geodynamics Project (GGP) network, we adopted two criteria, the standard deviations of harmonic analysis on tidal observations and the quality of the FCN parameters calculated with the observations from single station. After the mean ocean tidal effects of the recent ocean tidal models were removed, the FCN parameters were retrieved by stacking the tidal gravity observations from the GGP network. The results were in a good agreement with those in the recent research by using the SG and/or the VLBI observations. Combined with an FCN theoretical model deduced by angular momentum method, the viscous and electromagnetic coupling parameters near the CMB were evaluated. Numerical results indicated that the viscosity at the top of the liquid core was in the range from 6.6×102 to 2.6×103 Pa·s, which was in good agreement with those obtained from the Earth's nutation, the FCN and variations in the length of day (LOD). The conductivity at the bottom of the mantle should be as large as 2.6×106-1.0×107 S m-1 to match the FCN quality factors from the actual observations. The dissipative coupling had a little influence of 1-2 sidereal days for the FCN period.
基金supported by the National Natural Science Foundation of China(Grant Nos.41174014 and D0401)
文摘The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite's geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented.