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题名	地球自由振荡和极潮的小波分析
作者	徐华君
学位类别	博士
答辩日期	2008-06
授予单位	中国科学院测量与地球物理研究所
授予地点	武汉
导师	柳林涛
关键词	地球重力场 标准Morlet 小波变换 Daubechies 小波 长周期球形地球自由振荡 重力
学位专业	大地测量学与测量工程
中文摘要	地球的重力场是地球内部质量分布的表现, 是地球的重要物理属性, 表征了地球内部、表面或外部各点所受地球重力作用的空间。它直接反映地球内部的密度分布, 从地幔产生的长波信号, 到大陆岩石圈和海底地壳的局部特征等, 都反映在地球重力场中。因此, 地球重力变化的观测是大地测量学和地球物理学的一项重要内容。超导重力仪能够观测到周期变化从几秒到一年以上的重力场的微弱变化, 其观测精度达到ngal (10-11m/s2)级, 是观测重力变化的理想仪器。然而, 由于地球本身时刻都在做着复杂的运动, 以及受到外力的影响, 地球重力场会随着时间的变化而变化, 这种变化是非常复杂的过程, 需要尝试各种方法来分析。本文研究的主要目标是将小波分析方法运用到具体的地球重力信号分析中, 用连续小波变换检测并提取长周期球形地球自由振荡信号, 运用离散小波变换对重力极潮进行分析和研究, 初步获得了一些有意义的研究结果。首先利用标准Morlet 小波变换(Normal Morlet Wavelet Transform, NMWT)分析长周期自由振荡信号。NMWT 修正了原始Morlet 小波变换测不准频率的缺点, 且具有变换尺度直接表征信号周期以及无需重构就能提取准调和信号的两大优势。运用NMWT 对GGP (Global Geodynamic Project)多台超导重力仪记录的2004 年苏门答腊大地震的观测数据进行分析, 检测到了频率在1mHz 下的大部分球形自由振荡简正模, 以及由于地球形状与自转引起的谱裂, 并能提取出这些模及谱裂的时域波形, 从而精确确定各个简正模的周期, 并能在时域中精密确定各模或每个谱裂的衰减系数Q。我们给出的一些长周期自由振荡的 Q 值精度较经典Q 值的精度提高近2－3 个量级。并且在国际上首次给出了0S4, 0S5, 3S1, 1S3 等简正模谱裂的Q 值。其次, 采用紧支撑Daubechies 小波构造出不同长度的滤波器组, 详细分析了重力极潮的两个主要频率成分(Chandler 与周年项)的长期变化趋势, 计算了GGP 5 个台站重力极潮的潮汐因子与相位延迟。针对极潮的周期会随着时间和地点的不同发生变化, 提出了最小标准差方法来确定它们的周期。同时本文也关注了地球的固体潮汐的基本理论与方法, 并用计算机技术进行仿真, 动态展示了固体潮随时间及空间的变化规律
英文摘要	The Earth’s gravity field, one of important physics properties of the Earth, is characterized by the gravity role in points on the Earth's interior, or the external surface. It reflects density distribution in Earth's interior. Gravity signal contains a wealth of information about the Earth, from mantle’s long waves to continental lithosphere and harbor crust local features, etc. Therefore, observation of changes in the Earth's gravity is an important work in Geodesy and Geophysics. Superconducting gravimeter, which can observe weak gravity field changes with period from a few seconds to more than one year and observation accuracy achieving ngal (10-11m/s2) level. Therefore, it is an ideal instrument for observing gravity changes. However, due to the Earth’s complex movements, as well as the impact of external forces, the Earth’s gravity field will change with the time, which is a very complex process and needs careful analysis through various methods. The major objective of this thesis is to analysis gravity signal by using wavelet transform. That is, long period Earth spherical free oscillations signals detection and extraction with continuous wavelets, as well as secular changes in gravity pole tide analysis and study with discrete wavelets. Some valuable results are preliminarily obtained. We do time-frequency analysis of the Earth's spherical free oscillations signals by using the NMWT. According to the characters of gravity signals, we constructed Morlet wavelet to Normal Morlet wavelet, namely, NMW. It has two advantages: transform scale equals to signal’s period and the time domain signal extracted without inverse transform. In this thesis, we processed the high quality SG records from observation network of the Global Geodynamics Project (GGP) after the great Sumatra earthquake occurred in Dec. 26, 2004 with NMWT, detected spherical modes below 1mHz and also splitting singlets of these overtones. The fact that NMWT can extract the signal in time domain help us to determine period of each mode and their attenuation coefficients Q. NMWT can improve the relative accuracy of Q from 10% to 0.1-0.01%. And Q of 0S4, 0S5, 3S1 and 1S3 are caluculated for the first time. Then we estimated tide factor and phase delay of Chandler and Annual terms, which are the main frequencies in gravity pole tide, using the filter bank constructed from Daubechies wavelet. The data also come from GGP. In this processing, we proposed least standard method to determine the changing periods of gravity pole tide. And we also explore the theory and method of solid earth tides, and simulate this phenomenon with computer technology. It can display solid earth tides changes within time and space dynamically
语种	中文
公开日期	2013-01-17
内容类型	学位论文
源URL	[http://ir.whigg.ac.cn//handle/342008/3687]
专题	测量与地球物理研究所_学生论文_学位论文
推荐引用方式 GB/T 7714	徐华君. 地球自由振荡和极潮的小波分析[D]. 武汉. 中国科学院测量与地球物理研究所. 2008.

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