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Detection and interpretation of the Earth's free oscillations excited by the great Sumatra-Andaman earthquake with GGP station data

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Earthquake Science 2011年第2期24卷 151-162页

作者： houtse hsu Institute of Geodesy and Geophysics Chinese Academy of Sciences

The mode serials of the Earth’s free oscillation provide some important information on the Earth’s deep structure and superconducting gravimeters （SG） can investigate the phenomena of the Earth’s free oscillations with high accuracy. The great Sumatra-Andaman earthquake fully excited the Earth’s free oscillations and these signals were perfectly recorded by five superconducting gravimeters in the globe. After the pre-treatment and spectral analysis on the SG observation data, we obtained the experimented mode serials of the Earth’s free oscillations consisting of 147 modes with GGP station data. These observed modes were themselves some new important data for the study of the Earth’s deep structure. On the basis of the discussions on some checked inner-core-sensitive modes, we distinguished three layers from the inner core, and the boundary of the upper layer was compatible with the formerly known transition zone in the inner core based on seismic body waves and supported that there were the hemispherical variation and very lower shear velocity zone in the lower inner core.

关键词： Sumatra-Andaman earthquake GGP station data Earth’s free oscillation Earth’s inner core core sensitive mode

Three-dimensional crustal density distribution beneath North China by sequential inversion of local earthquake traveltimes and gravity anomaly

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Earthquake Science 2011年第2期24卷 135-141页

作者： Xinsheng Wang Jian Fang houtse hsu Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China

A three-dimensional crustal density model beneath North China is determined using P-wave traveltimes and gravity datum by sequential inversion method in this paper. To improve the uniqueness of the solution, we used a linear relationship between velocity and density to achieve mutual conversions and constraints between velocity difference and density difference. Algebraic reconstruction technique （ART） was used in density inversion, which highly improved the calculation speed comparing with common least squares method. The inversion results indicate that the crustal density beneath North China is extremely inhomogeneous with its distribution coherent with regional tectonics. The lower crust of Taihang mountain tectonic zone shows an obvious low density characteristic. We proposed that it may be an indicator of upwelling of mantle materials or partial melting of lowermost crust.

关键词： density distribution sequential inversion ART seismic tomography

Antarctic-wide annual ice flow maps from Landsat 8 imagery between 2013 and 2019

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International Journal of Digital Earth 2021年第5期14卷 597-618页

作者： Qiang Shen Hansheng Wang C.K.Shum Liming Jiang houtse hsu Fan Gao Yingli Zhao State Key Laboratory of Geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanPeople’s Republic of China Division of Geodetic Science School of Earth SciencesThe Ohio State UniversityColumbusOhioUSA College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingPeople’s Republic of China

Ice velocity constitutes a key parameter for quantifying ice-sheet discharge rates and is thus crucial for improving the coupled models of the Antarctic ice sheet towards accurately predict its contribution to future global sea-level ***,in Antarctica,high-resolution and continuous ice velocity estimates remain elusive,which is key to unravel Antarctica’s present-day ice mass balance ***,we present a suite of newly estimated Antarctic-wide,annually-sampled ice velocity products at 105-m grid-spacing observed by Landsat 8 optical images *** first describe a procedure that can automatically calibrate and integrate ice displacement maps to generate Antarcticwide seamless ice velocity *** annual ice velocity mosaics are assembled using a total of 250,000 displacement maps inferred from more than 80,000 Landsat 8 images acquired between December 2013 and April *** new annual Antarctic ice velocity data product exhibits an improved quantification of near-decadal Antarctic-wide ice flow,and an opportunity to investigate ice dynamics at a higher spatial resolution and annual sampling,as compared to existing data *** studies confirmed improved accuracy and consistency of this new data product,when compared with independently estimated optical and radar ice velocity data products,as well as in situ data.

关键词： Antarctica ice velocity Landsat 8

Check of Earth's free oscillations excited by Sumatra-Andaman Large Earthquake and discussions on the anisotropy of inner core

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Science China Earth Sciences 2007年第6期50卷 909-917页

作者： hsu houtse Key Laboratory of Dynamic Geodesy Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhan 430077China

Sumatra-Andaman Large Earthquake on Dec. 26,2004 generated not only the Indian Ocean Tsunami but also the Earth's free oscillations (EFO). The signals of Earth's free oscillations were perfectly re-corded by the superconducting gravimeter C0-32 at Wuhan station in China. After the pre-treatment and spectral analysis on the observational data from Wuhan station,we obtained more than ninety EFO modes including 42 fundamental modes,2 radial modes and 49 harmonic modes. On the basis of the discussions on some observed harmonic modes and abnormal splitting phenomena,we considered that the real rigidity might be lower than the theoretical prediction of PREM model in the inner core and however the anisotropy of compressive wave was brightly higher than the present estimations in the inner core. This suggested that the anisotropy of the inner core could be much more complicated than our present understanding,and there might be some new geophysical phenomena in the formation process of the inner core.

关键词： Sumatra-Andaman Large Earthquake Earth’s free oscillations superconducting gravimeter abnormal spectral splitting anisotropy of inner core

THINNING OF THE THICKENED LITHOSPHERE AND ITS GEODYNAMIC CONSEQUENCE: APPLICATION FOR TIBETAN PLATEAU

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地学前缘 2000年第S1期7卷 368-369页

作者： Xiong Xiong,houtse hsu (Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China)

As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarify the evolution of the plateau. While many studies are often restricted to crustal units, the important role of the mantle part of the lithosphere (mantle lithosphere) during and after the collision process has not been appreciated widely. The purpose of the paper is to investigate the dynamic process of the thinning (delamination and convective removal) of the thickened lithosphere and its influence upon the uplift of the plateau.1\ Thickened lithosphere root\;Parsons and McKenzie (1978) proposed that the continental lithosphere could be thought of as consisting of two distinct parts: the mechanical and thermal boundary layers. The lower, and hotter, part is the thermal boundary layer. Its viscosity is sufficiently low that the force of gravity acting on density contrasts between the thermal boundary layer and the underlying mantle lead to the episodic sinking of the thermal boundary layer and its replacement by hot asthenosphere. When continental crust shortens and thickens, the mantle directly beneath it must also be displaced downward. In other words, mountain building process shortens horizontally and thickens vertically the mechanical boundary layer, and presumably the thermal boundary layer. And the process stretches the isotherms vertically, thus reducing the geothermal gradient. Houseman’s numerical experiments (1981) show that thickening of the thermal boundary layer enhances the density contrasts between it and the underlying asthenosphere, and so leads to its removal and replacement with hot asthenosphere. This phenomenon is called the instability of the thickened lithosphere.

关键词： thinning thickened lithosphere Tibetan Plateau uplift

Effect of different inter-satellite range on measurement precision of Earth’s gravitational field from GRACE

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Geodesy and Geodynamics 2012年第1期3卷 44-51页

作者： Zheng Wei hsu houtse Zhong Min Yun Meijuan Zhou Xuhua State Key Laboratory of Geodesy and Earth＇ s Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Disaster Prevention Research Institute Kyoto University Uji Kyoto 611-001l Japan Department of Applied Physics Wuhan University of Science and Technology Wuhan 430081 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

The precision of Earth＇s gravitational field from GRACE up to degree and order 120 was studied for different inter-satellite ranges using the improved energy conservation principle. Our simulated result shows that： For long wavelength （L≤20） at degree 20, the cumulative geoid-height error gradually decreased with increasing range, from 0. 052 cm for 110 km to 1. 156 times and 1. 209 times as large for 220 km and 330 kin, respectively. For medium-wavelength （ 100 ≤ L ≤ 120） at degree 120, the cumulative geoid-height error de- creased from 13. 052 cm for 110 km, to 1. 327 times and 1. 970 times as large for the ranges of 220 km and 330 km, respectively; By adopting an optimal range of 220 ± 50 km, we can suppress considerably the loss of precision in the measurement of the Earth＇ s long-wavelength and medium-wavelength gravitational field.

关键词： GRACE inter-satellite range colored noise Earth' s gravitational field energy conservation principle

地幔岩石圈热结构差异与中国大陆岩石圈均衡分析

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地球物理学报 2008年第4期51卷 1058-1065页

作者：单斌熊熊郑勇许厚泽中国科学院测量与地球物理研究所中国地震局地球物理研究所北京100081

观测表明,大陆地区存在很多传统均衡模型无法解释的现象,其根本原因在于传统均衡理论中没有考虑地幔岩石圈部分由于热结构差异导致密度差异的影响.本文基于岩石圈尺度的质量平衡模型研究了中国大陆20个构造单元地壳及地幔岩石圈对地形... 详细信息

观测表明,大陆地区存在很多传统均衡模型无法解释的现象,其根本原因在于传统均衡理论中没有考虑地幔岩石圈部分由于热结构差异导致密度差异的影响.本文基于岩石圈尺度的质量平衡模型研究了中国大陆20个构造单元地壳及地幔岩石圈对地形海拔的贡献,以及各块体的均衡状态.计算结果表明,在一些地区,如塔里木盆地、北山和柴达木盆地,尽管岩石圈均衡模型和Airy模型得到了一致的海拔值,但岩石圈均衡模型更能体现均衡过程的物理本质;除青藏高原造山带外的多数块体,岩石圈均衡模型的计算结果更接近观测海拔和地表垂直运动状态;总体上,考虑地幔岩石圈热结构影响后,中国大陆各地区的均衡结果普遍优于传统的均衡模型.通过对均衡状态分析.我们得到以下主要结论:(1)构造稳定地区均衡程度较高;(2)青藏高原及周边造山带现今地壳运动主要为区域构造过程及深部动力学过程所控制。均衡调整过程不是主要控制因素;(3)现今地壳垂直运动比较明显的块体处于均衡调整阶段,地表垂直运动的大小反映了该区所受的均衡力作用的程度;(4)构造稳定地区基于岩石层均衡的理论计算海拔与观测海拔之差值和现今地壳垂直运动速率有较好的相关性,据此我们可以通过均衡分析研究构造块体的运动趋势和动力学性质;(5)地幔热结构对现今地形、海拔及地壳垂直运动有显著影响,在处理均衡问题时,地幔岩石圈热结构是我们必须考虑的重要因素.

关键词：地幔岩石圈均衡质量平衡模型海拔垂直形变

Simulation of the Earth' s gravitational field recovery from GRACE using the energy balance approach

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Progress in Natural Science:Materials International 2005年第7期15卷 596-601页

作者： ZHENG Wei, LU Xiaolei, hsu houtse, SHAO Chenggang, LUO Jun and WANG Nengchao ( Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China Department of Mathematics, Huazhong University of Science and Technology, Wuhan 430074, China) Department of Physics Huazhong University of Science and Technology Wuhan 430074 China Department of Mathematics Huazhong University of Science and Technology Wuhan 430074 China Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China

Based on the measurement principles of GRACE satellites, the observation equations are set up using the energy balance approach. The Earth's gravitational field complete up to degree and order 120 is recovered applying the preconditioning conjugate gradient iterative approach by numerical simulation. Assuming an accuracy of 1 μm/s in range-rate measurements of the K-band microwave ranging system, the matching relationships of accuracies of K-band microwave ranging system, SuperSTAR Accelerometer, position vector and velocity vector measurements are investigated.

关键词： the Earth’s gravitational field GRACE satellites energy balance approach preconditioning conjugate gradient method.

A robust vector tracking loop structure based on potential bias analysis

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Chinese Journal of Aeronautics 2024年第4期37卷 405-420页

作者： Qiongqiong JIA Yiran LUO Bing XU Li-Ta hsu Renbiao WU Tianjin Key Lab for Advanced Signal Processing Civil Aviation University of ChinaTianjin 300300China Interdisciplinary Division of Aeronautical and Aviation Engineering The Hong Kong Polytechnic University999077Hong KongChina Department of Geomatics Engineering University of CalgaryCalgary T2N1N4Canada

This paper proposes a robust vector tracking loop structure based on potential bias analysis. The influence of four kinds of biases on the existing two implementations of Vector Tracking Loops(VTLs) is illustrated by theoretical analysis and numerical simulations, and the following findings are obtained. Firstly, the initial user state bias leads to steady navigation solution bias in the relative VTL, while new measurements can eliminate it in the absolute VTL. Secondly, the initial code phase bias is transferred to the following navigation solutions in the relative VTL, while new measurements can eliminate it in the absolute VTL. Thirdly, the user state bias induced by erroneous navigation solution of VTLs can be eliminated by both of the two VTLs. Fourthly,the multipath/NLOS likely affects the two VTLs, and the induced tracking bias in the duration of the multipath/NLOS would decrease the performance of VTLs. Based on the above analysis,a robust VTL structure is proposed, where the absolute VTL is selected for its robustness to the two kinds of initialization biases;meanwhile, the instant bias detection and correction method is used to improve the performance of VTLs in the duration of the multipath/NLOS. Numerical simulations and experimental results verify the effectiveness of the proposed robust VTL structure.

关键词： Global Navigation Satellite System(GNSS) Vector Tracking Loop(VTL) Multipath Non-Line-of-Sight(NLOS) Tracking bias propagation Least Absolute Shrinkage and Selection Operator(LASSO)