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Earth's deformation due to the dynamical perturbations of the fluid outer core

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Acta Seismologica Sinica(English Edition) 2002年第4期15卷 414-424页

作者： XU Jian-qiao (徐建桥) SUN He-ping (孙和平) Key laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

The elasto-gravitational deformation response of the Earths solid parts to the perturbations of the pressure and gravity on the core-mantle boundary (CMB) and the solid inner core boundary (ICB), due to the dynamical behaviors of the fluid outer core (FOC), is discussed. The internal load Love numbers, which are formulized in a general form in this study, are employed to describe the Earths deformation. The preliminary reference Earth model (PREM) is used as an example to calculate the internal load Love numbers on the Earths surface, CMB and ICB, respectively. The characteristics of the Earths deformation variation with the depth and the perturbation periods on the boundaries of the FOC are also investigated. The numerical results indicate that the internal load Love numbers decrease quickly with the increasing degree of the spherical harmonics of the displacement and depend strongly on the perturbation frequencies, especially on the high frequencies. The results, obtained in this work, can be used to construct the boundary conditions for the core dynamics of the long-period oscillations of the Earths fluid outer core.

关键词： dynamical effect of the fluid outer core boundaries of the fluid outer core internal load Love

Tri-frequency spectrum method and results for resolving the parameters of Earth's liquid core free nutation

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Science China Earth Sciences 2002年第4期45卷 325-336页

作者：雷湘鄂许厚泽 laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China

The parameters of Earth free core nutation (FCN) are two relatively significant geophysical parameters. Sasao et al. (1980) and Wahr and Bergen (1986) provided the theoretical estimation values of FCN parameters. Gwinn, Herring and Shapiro (1987) first obtained the observational values of FCN parameters by very long base Interference (VLBI) at Cambridge University. In the same year, Neuberg and Zurn in former West Germany and Hinderer in France began to retrieve FCN parameters by the observation of gravity tides and introduced the stacking method. The other scholars who researched into the same geophysical problems by applying the data of gravity tides basically followed the stacking method. The results they reached were similar to the observational result of FCN parameters given by Neuberg et al. in 1987. But the observational results of FCN parameters gained from gravity tides were not identical with those from VLBI, mainly because of the large difference of quality of FCN. So there was not an affirmative observational result of FCN parameters since then. In this paper, The authors firstly introduce the tri-frequency spectrum method with clearly geometrical and geophysical meaning for the resolution of FCN parameters , and the observational results of FCN parameters obtained from tide data at three superconducting gravity stations were accordant with those from VLBI, which will be relatively important to arriving at a certain observational result of FCN parameters.

关键词： gravity tides very long base interference (VLBI) gravity tide resonance of the earth's liquid core amplitude and phase frequency parameter amplitude and phase frequency spectrum extend range of amplitude frequency parameter FCN paramet

Study of the Earth's free core nutation by tidal gravity data recorded with international superconducting gravimeters

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Science China Earth Sciences 2002年第4期45卷 337-347页

作者：徐建桥孙和平罗少聪 laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China

By stacking high-precision tidal gravity observations obtained with superconducting gravimeters at six stations in China, Japan, Belgium, France, Germany and Finland, the local systematical discrepancies in the parameter fitting, caused by atmospheric, oceanic tidal loading and the other local environmental perturbations, are eliminated effectively. As a result, the resonance parameters of the Earth's free core nutation are accurately determined. In this study, the eigenperiod of free core nutation is given as 429.0 sidereal days, which is in agreement with those published in the previous studies. It is about 30 sidereal days less than those calculated in theoretical models (about 460 sidereal days), which confirms the real ellipticity of the fluid core of the Earth to be about 5% larger than the one expected in assumption of hydrostatic equilibrium. The quality factor (Q value) of free core nutation is given as about 9543, which, compared with those determined before based on the body tide observations, is much larger, but more close to those obtained using the VLBI observations. The complex resonance strength is also determined as (?6.10(10?4, ?0.01(10?4)(/h, which can principally describe the deformation characteristics of an anelastic mantle.

关键词： superconducting gravimeters, stacking, free core nutation, resonance parameters.

Monitoring of reclamation-induced ground subsidence in Macao (China) using PSInSAR technique

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Journal of Central South University 2013年第4期20卷 1039-1046页

作者：胡波汪汉胜江利明 State Key laboratory of Dynamical geodesy (Institute of geodesy and geophysics Chinese Academy of Sciences)

The long-term reclamation-induced ground subsidence in Macao, a coastal city of southern China was investigated. Persistent scatterer interferometry (PSI) technique was applied to retrieve the deformation rate in Macao during the period from April 2003 to August 2010 with a total of 41 scenes of descending ASAR data sets. The PSI-retrieved results show a relatively stable pattern in Macao Peninsula, Taipa Island and Coloane Island, with an average subsidence velocity of -3 mm/a. In contrast, relatively large subsidence rates are highlighted in Cotai area, a new reclamation land in 1990s, in which an average subsidence velocity is about -10 mm/a. A consistent relationship between the PSI results and the leveling measurements indicate that this PSI technique is an effective tool to monitor the reclamation-induced ground subsidence with a high accuracy and adequate spatial details. Accordingly, the valuable ground subsidence results generated by PSI can be used not only for early detection and remedial activities of potential settlement of building, but also for helping the local government to formulate regional sustainable development planning and decision-making in disaster prevention and mitigation.

关键词： persistent scatterer interferometry (PSI) Macao reclamation land ground subsidence

Detection of spheriodal free oscillation excited by Peru 8.2 M_(s) earthquake with five international superconducting gravimeter data

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Science China Earth Sciences 2005年第1期48卷 123-133页

作者： LEI Xiang'e XU Houze SUN Heping Key laboratory of Dynamic geodesy Institute of Geodesy and Geophysics. Chinese Academy of Sciences Wuhan 430077 China Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics. Chinese Academy of Sciences Wuhan 430077 China Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics. Chinese Academy of Sciences Wuhan 430077 China

In this paper, authors obtain the spectral peaks of the earth free oscillation and check all normal modes from 0S0 to 0S48 accurately, with the Fourier analysis and the maximum entropy spectrum method dealing jointly with six groups of the observational residual data from five international superconducting gravimeter stations. By comparing the observational results in this paper with three former groups of observations or models, authors notice an extra discrepancy between two observational 0S2 modes excited separately by Peru earthquake and Alaska earthquake, which probably mirrors the anisotropy of the Earth's inner core. The analysis on the splitting 1S2 mode shows that the asymmetric factor of rotationwise spectral splitting is possible to be different from that of anti-rotationwise spectral splitting.

关键词： 8.2 Ms Peru earthquake, detection of Earth free oscillation, observation of superconducting gravimeter,anisotropy of earth's inner core.

Towards combining multiple geophysical datasets to determine earthquake source parameters in China

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Science China Earth Sciences 2016年第11期59卷 2260-2262页

作者： ZHENG Yong LIU ChengLi State Key laboratory of geodesy and Earth's Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences

*** of conventional seismic studies on earthquake source parameters Earthquake source parameters,including magnitude,location,focal mechanism,rupture process are key factors for understanding seismogenic environment,mitigating seismic hazards,estimating earthquake triggering,and tectonic ***,source parameters are determined by seismological *** example,Fang L H et al.（2014）relocated the 2012 Ms6.6 Xinjiang Xinyuan earthquake sequence using local seismograms based on the double difference method,

关键词： geophysical tectonic rupture triggering magnitude estimating moderate epicenter constrain spatially

The nonlinear fixed gravimetric boundary value problem

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Science China Chemistry 1995年第5期38卷 596-605页

作者：于锦海朱灼文 laboratory of Dynamical geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuchang 430077 China laboratory of Dynamical geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuchang 430077 China)

The properly-posedness of the nonlinear fixed gravimetric boundary value problem is shown with the help of nonlinear functional analysis and a new iterative method to solve the problem is also given, where each step of the iterative program is reduced to solving one and the same kind of oblique derivative boundary value problem with the same type. Furthermore, the convergence of the iterative program is proved with Schauder estimate of elliptic differential equation.

关键词： nonlinear fixed gravimetric boundary value problem properly-posedness iterative program obliquederivative boundary vlaue problem convergence.

Wavelet approach to the determination of gravity tide parameters

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Science China Earth Sciences 2000年第2期43卷 158-165页

作者：柳林涛许摩泽孙和平郝兴华 Open laboratory of Dynamic geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China

A new approach is proposed for the determination of gravity tide parameters. Three pairs of compactly supported wavelet filters are introduced in the approach. They can efficiently extract the objective tides from the gravity observation series. The new approach guarantees a direct and precise analysis on the tidal gravity records of any sampling length. The new approach is applied to the harmonic analysis on Wuhan superconducting gravimeter records. The results clearly show the resonant effects of the Earth Nearly Diurnal Free Wobble (NDFW).

关键词： gravity wavelet filter tide parameters superconducting gravimeter.

Focal Mechanism and Rupture Process of the 2012 M_w 7.0 Santa Isabel, Mexico Earthquake Inverted by Teleseismic Data

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Journal of Earth Science 2015年第3期26卷 384-390页

作者： Chengli Liu Yong Zheng Xiong Xiong State Key laboratory of geodesy and Earth's Dynamic Institute of Geodesy and Geophysics Chinese Academy of Sciences

The point source parameters of the April 12, 2012 Mw 7.0 Santa Isabel, Mexico, earthquake indicated by teleseismic P and SH waveforms obtained by a means of traditional cut and paste（CAP） method show that the best double-couple solution of this event is： 37°/127°, 90°/81° and-9°/-180° for strike, dip and rake, respectively. Its centroid depth is 13 km. Global teleseismic waveform data exhibit that the rupture of the earthquake initiated at a focal depth of 13 km and propagated southeastward with a relatively slow rupture velocity（about 1.8 km/s on average）. The maximum slip occurred at 30 km southeast of the hypocenter, with the peak slip of 3.57 m and total seismic moment of whole fault up to 3.98×1019 N·m. These observations provide some insight into properties, co- or post-seismic deformation and coulomb stress changes of future earthquake in this area.

关键词： Mexico Earthquake rupture velocity focal mechanism slip history