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Validating global hydrological models by ground and space gravimetry

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chinese Science Bulletin 2009年第9期54卷 1534-1542页

作者： zhou jiangcun1,2,3. sun heping1,2 & xu jianqiao1,{3., chinese academy of sciences, wuhan 43.077, China 2 Key Laboratory of dynamic geodesy, chinese academy of sciences, wuhan 43.077, China 3.Graduate University of chinese academy of sciences, Beijing 100049, China institute of geodesy and geophysics Chinese Academy of Sciences Wuhan China Key Laboratory of dynamic geodesy Chinese Academy of Sciences Wuhan China Graduate University of chinese academy of sciences Beijing China

The long-term continuous gravity observations obtained by the superconducting gravimeters (SG) at seven globally-distributed stations are comprehensively analyzed. After removing the signals related to the Earth's tides and variations in the Earth's rotation, the gravity residuals are used to describe the seasonal fluctuations in gravity field. Meanwhile, the gravity changes due to the air pressure loading are theoretically modeled from the measurements of the local air pressure, and those due to land water and nontidal ocean loading are also calculated according to the corresponding numerical models. The numerical results show that the gravity changes due to both the air pressure and land water loading are as large as 100×10-9 m s-2 in magnitude, and about 10×10-9 m s-2 for those due to the nontidal ocean loading in the coastal area. On the other hand, the monthly-averaged gravity variations over the area surrounding the stations are derived from the spherical harmonic coefficients of the GRACE-recovered gravity fields, by using Gaussian smoothing technique in which the radius is set to be 600 km. Com-pared the land water induced gravity variations, the SG observations after removal of tides, polar mo-tion effects, air pressure and nontidal ocean loading effects and the GRACE-derived gravity variations with each other, it is inferred that both the ground- and space-based gravity observations can effec-tively detect the seasonal gravity variations with a magnitude of 100×10-9 m s-2 induced by the land water loading. This implies that high precision gravimetry is an effective technique to validate the re-liabilities of the hydrological models.

关键词：重力测量水文模型模型验证和空间地面重力变化季节性波动空气压力

A review of tidal triggering of global earthquakes

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geodesy and Geodynamics 2023年第1期14卷 35-42页

作者： Ruyu Yan Xiaodong Chen heping sun jianqiao xu {3. zhou State Key Laboratory of geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of chinese academy of sciences Beijing 100049China

Earthquake prediction remains a challenging and difficult task for scientists all over the *** tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown that earthquakes are positively correlated with tides,and thus,tides provide a potential tool for earthquake prediction,especially for imminent *** this study,publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes,which were classified into three main types:tectonic,volcanic,and slow *** results reveal a high correlation between tectonic earthquakes and tides(mainly for semidiurnal and diurnal tides;14-day tides) before and after the occurrence of significant *** volcanic earthquakes,observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces,mostly those with semidiurnal and diurnal *** slow earthquakes,the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal *** conclusion,the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism,and thus,the prediction of these types of earthquakes should be ***,there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all *** main inadequacies are discussed in this paper from our point of view.

关键词： Tidal triggering Tectonic earthquakes Volcanic earthquakes Slow earthquakes Earthquake prediction

Theoretical calculation of tidal Love numbers of the Moon with a new spectral element method

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Earth and Planetary Physics 2022年第3期6卷 241-247页

作者： BinBin Liao XiaoDong Chen jianqiao xu jiangcun zhou {3. sun State Key Laboratory of geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China University of the chinese academy of sciences Beijing 100049China

The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial *** play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal *** this study,we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers:the spectral element ***,we explain the mathematical theory and advantages of this *** the basis of this new method,using 10 published lunar internal structure reference models,the lunar surface and lunar internal tidal Love numbers were calculated,and the influence of different lunar models on the calculated Love numbers was *** of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%,the influence on the maximum vertical displacement on the lunar surface could reach±8.5 mm,and the influence on the maximum gravity change could reach±6μ*** the influence on the Love numbers inside the Moon,different lunar models had a greater impact on the Love numbers h_(2) and l_(2) than on k_(2) in the lower lunar mantle and core.

关键词： lunar tidal Love numbers spectral element method solid lunar tides lunar internal structure reference models lunar tidal deformation theory

Study on characteristics of long-term gravity changes at wuhan station

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chinese Science Bulletin 2008年第13期53卷 2033-2040页

作者： xu jianqiao zhou jiangcun LUO ShaoCong {3. heping Key Laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

We consider the characteristics of long-term changes in non-tidal gravity and their implication to the local perturbations in barometric pressure and water storage and to the local vertical crustal movement using the long-term continuous gravity observations from a superconducting gravimeter (SG) at Wu-han station,together with the co-site measurements from a Global Positioning System (GPS) receiver and an absolute gravimeter FG5. The observation results indicate that there are obvious seasonal variations in the long-term gravity changes measured with the SG. About 70 percent of the whole sea-sonal changes come from the contribution of the local disturbances in air pressure and water storage,while over 95 percent of the annual changes are attributed to the loading effects of these environmental perturbations. Due to the absence of direct measurements of the local water storage,especially those of the underground water,the global assimilating models of land water LaD (Land Dynamics) and GLDAS (Global Land Data Assimilation System) cannot virtually describe the real hydrologic distur-bances around the station. The resulting gravity changes,which are simulated theoretically by means of convolution integration of the loading Green’s functions and water models LaD and GLDAS,show significantly time delay of about 55 days from those measured with the SG. Compared with the meas-urements of the absolute gravity with the FG5,the long-term drift rate of the SG is determined as about 17.13.nms-2/a. From the co-site GPS measurements,it is found that the local crust is slowly subsiding at a rate of 3.71±0.16 mm/a,and the related gravity variation is estimated as 13.88±0.22 nms-2/a. In other words,the ratio of the changes in gravity and altitude related to the local vertical crustal movement is about -3..41 nms-2/cm. It implies that a considerable mass adjustment may be associated with the local vertical crustal movement,and its dynamic mechanism should be investigated further.

关键词：超导重力计潮汐引力气压水储存量

Application of superconductive gravity technique on the constraints of core-mantle coupling parameters

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Science China Earth sciences 2012年第2期55卷 513-520页

作者： CUI XiaoMing sun heping xu jianqiao {3. jiangcun institute of geodesy and geophysics Chinese Academy of SciencesWuhan 430077China Key Laboratory of Dynamic geodesy Chinese Academy of SciencesWuhan 430077China Graduate University of chinese academy of sciences Beijing 100049China

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.

关键词： SG observations free core nutation core-mantle boundary viscosity conductivity dynamic ellipticity

Co-seismic change in ocean bottom topography:Implication to absolute global mean sea level change

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geodesy and Geodynamics 2019年第3期10卷 179-186页

作者： jiangcun zhou heping {3. jianqiao xu Xiaodong Chen Xiaoming Cui State Key Laboratory of geodesy and Earth’s Dynamics Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhan430077China University of chinese academy of sciences Beijing 100049China

Earthquakes perturb both the ocean bottom topography due to displacements of sea floor and the geoid due to mass redistribution, which induces the relative sea level(RSL) change. However, the relative global mean sea level(GMSL) change is zero in that sea water mass is conserved. But the absolute GMSL change is not zero because earthquakes displace total ocean mass with respect to the Earth’s center of mass(CM) which remains unchanged after an earthquake. This displacement, i.e. the absolute GMSL change, may be detectable by altimetry since the satellites are orbiting around CM. In this paper, we proposed a method to estimate co-seismic absolute GMSL change caused by earthquakes based on the point dislocation theory for a spherically symmetric, non-rotating, elastic and isotropic(SNREI) *** change can be directly connected to the perturbation of ocean bottom topography. We first computed co-seismic displacements as well as the change in geo-potential and solved the sea level equation to validate the insignificance of the oceans’ feedback, i.e. the loading effect due to RSL change, to co-seismic displacements. The results imply that the loading effect due to RSL change is negligible on displacements while is considerable on geoid. We then computed the absolute GMSL change caused by co-seismic vertical and horizontal displacements by making use of the integrated Green’s function method. The numerical results show that a large earthquake may raise the absolute GMSL by magnitude of sub-millimeter and the recent three large events cause GMSL to rise about one millimeter, in which the contribution from horizontal displacement is non-negligible.

关键词： Point dislocation theory SNREI earth Sea level equation Absolute GMSL Ocean bottom topography

Characteristics of tidal gravity changes in Lhasa,Tibet,China

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chinese Science Bulletin 2012年第22期57卷 2586-2594页

作者： xu jianqiao CHEN XiaoDong zhou jiangcun {3. heping State Key Laboratory of geodesy and Earth＇s Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077China

Tidal gravity changes arise from the response of the solid Earth to the tidal forces of the sun,Moon and planets close to the Earth,and are a comprehensive reflection of the structure and distribution of physical properties of the Earth's *** a result,observations of tidal gravity changes are the basis of studies on other global and/or regional dynamic *** characteristics of tidal gravity changes in the region of the Tibetan Plateau were investigated through continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa over a *** contrast measurements with a spring gravimeter LaCoste-Romberg ET20 at the same site,the gravity observations in Lhasa were scaled to the international tidal gravity reference in ***,the scale factor of the SG was determined accurately as-777.3.8 ± 0.13. nm s-2V-1,which is about 2.2% less than the value provided by the *** results indicate that the precision of the tidal gravity observations made with the SG in Lhasa was very *** standard deviation was 0.459 nm s-2,and the uncertainties of for the four main tidal waves (i.e.O 1,K 1,M 2 and S 2) were better than 0.006%.In addition,the observations of the diurnal gravity tides had an obvious pattern of nearly diurnal *** a result,it is affirmed that the Lhasa station can provide a local tidal gravity reference for gravity measurements on the Tibetan Plateau and its surrounding *** loading effects of oceanic tides on tidal gravity observations in Lhasa are so weak that the resulting perturbations in the gravimetric factors are less than 0.6%.However,the loading effects of the local atmosphere on either the tidal or nontidal gravity observations are significant,although no seasonal variations were *** removal of the atmospheric effects,the standard deviation of the SG observations in Lhasa decreased obviously from 2.009 to 0.459 nm *** removed the loading effects of ocea

关键词：超导重力仪潮汐变化拉萨国际重力潮汐基准青藏高原地区重力潮汐观测重力观测中国

Estimating local water storage change based on space-and groundbased gravimetry

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Estimating local water storage change based on space-and gro...

Research Progress in Surface and Marine Gravimetry

2016中国地球科学联合学术年会

作者： zhou jiangcun sun {3. xu jianqiao Zhang Weiming institute of Surveying and geophysics Chinese Academy of Sciences

＜正＞The launch of the twin satellites of gravity recovery and climate experiment mission（GRACE）provided us monthly time-variable gravity field of the Earth with unprecedented precision（Tapley et al.2004）.Specifically,it allows us to evaluate the water ***,due to the large errors in the GRACE-recovered gravity field of the high degrees’spherical harmonics,some special techniques such as Gaussian smoothing

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测绘学报:英文版 2023年第3期6卷 19-32页

作者： heping sun Lifeng BAO Shi CHEN Xiaoming CUI Qianqian LI Lulu JIA jianqiao xu {3. zhou Minzhang HU Yiqing ZHU Xiaodong CHEN Lin WU Jiancheng HAN Honglei LI Miaomiao ZHANG Linhai WANG Innovation academy for Precision Measurement Science and Technology Chinese Academy of SciencesWuhan 430077China State Key Laboratory of geodesy and Earth’s Dynamics Innovation Academy for Precision MeasurementUniversity of Chinese Academy of Sci-encesBeijing 100049China institute of geophysics China Earthquake AdministrationBeijing 100081China Beijing Baijiatuan Earth sciences National Observation and Research Station Beijing 100095China institute of Seismology China Earth-quake AdministrationWuhan 430071China Second Monitoring Center China Earthquake AdministrationXi’an 710054China

Gravity field is the most basic physical field generated by the material properties of the Earth *** reflects the spatial distribution,movement and change of materials determined by the interaction and dynamic process inside the *** the years,a variety of technical means have been used to detect the Earth’s gravity field and supported numerous studies on the global change,resource detection,geological structure movement,water resources change and other related fields of *** is part of the progress in surface and marine gravimetry obtained by chinese geodesy scientists from 2019 to 2023.from the following aspects,including:①Continuous gravity network in chinese mainland;②Application of superconducting gravity measurement;③Network adjustment for continental-scale gravity survey campaign and data quality control;④Regional time-variable gravity field and its application;⑤Research progress on novel technologies for gravity inversion;⑥Research progress on marine gravity field determination;⑦Application research on marine gravity field.

关键词： surface and marine gravimetry time-variable gravity field geodynamics gravity inversion