全球地幔密度异常及其构造意义

利用扣除地形、莫霍面和核幔边界起伏影响的中长波大地水准面异常和全球地震层析成像资料,采用阻尼最小二乘方法反演计算了全球地幔6个不同层面上的密度异常分布。分析了全球密度异常与板块构造的关系,探讨了全球密度异常分布对板块运动的作用。全球地幔密度异常结果表明存在两个主要的密度异常中心：一个位于东经80°,北纬0°;另一个位于东经240°,北纬10°附近。     

大地构造是从顶部向下驱动的吗?

目前存在两种相互对立的地幔对流模型。第一种模型对地幔进行了分层,分出两个或更多的独立对流区。第二种模型则把整个地幔对流看成一个统一单元。最近在板块构造学、地震学、固态物理学和地幔对流方面取得的进展,对分层对流提供了有力的支持。其成果可以帮助解释板块构造与地幔对流的关系。上地幔对流可能是由板块构造驱     

青藏高原及邻区地幔对流应力场及地球动力学含义

基于改进的Runcorn模型 ,利用布格重力异常计算了青藏高原及邻区地幔对流应力场。数值结果显示 ,青藏高原中部、北部和天山为应力发散区 ,对应地幔上升流 ,而塔里木、柴达木、四川盆地等地区则为应力汇聚区 ,对应下降区。地幔对流形态与地表特征之间的相关性表明 ,青藏高原下小尺度地幔对流可能是控制该区区域性构造过程的重要因素之一     

利用卫星重力数据计算地幔对流应力场

针对我国东南边缘及其邻近区域地幔对流应力场分布形态与地表构造活动特征的相关性问题,提出利用Runcorn模型及高阶卫星重力球谐系数计算欧亚板块与菲律宾板块复合接触带及其邻近区域的地幔对流应力场。结果显示,地幔对流应力矢量特征与地震应力场分布具有较好的一致性。在两大板块的接触部位均出现了显著的应力增强与汇聚趋势,同时在琉球海沟的弧后扩张带上出现的较强的地幔对流应力发散带。而在各板块相对稳定的内部区域存在微弱的地幔发散流。通过计算和分析得出,该区域下地壳小尺度的地幔对流可能是控制这一区域型构造过程的重要因素之一。     

利用重力数据反演中国东海海域莫霍面深度

莫霍面是地壳与上地幔的分界面,莫霍面的研究有助于认识地球深部构造及演化。在以往的研究中,由于重力反演方法、使用资料不同,中国东海海域莫霍面深度反演结果有较大不确定性。通过收集中国东海海域高精度地形和自由空气重力异常数据,计算了布格重力异常并分析了其构造特征。提取了中国福建省大田至中国台湾省花莲剖面和中国东海陆架盆地至菲律宾海盆剖面的重力异常数据,采用人机交互正演、反演拟合技术得到了这两条剖面的地壳密度与莫霍面深度。通过向上延拓的方法提取了莫霍面所引起的重力异常,在两条剖面反演结果和地震探测结果的约束下进行Parker-Oldenburg界面反演,得到了该地区的莫霍面深度。反演结果显示,中国东海海域莫霍面深度的变化范围为-34.4~-8.8 km,其结构呈两凹两凸的特征。     

卡尔曼滤波在山西省西山煤田地面沉降GNSS监测中的应用

本文以山西省西山煤田某一工作面为试验区,在分析地面沉降全球卫星导航系统（GNSS）监测数据特征的基础上,利用两种卡尔曼滤波方法（普通和总体卡尔曼滤波）对矿区地面沉降GNSS监测数据进行了处理与评价,同时对比了两种卡尔曼滤波方法的均方根误差分布情况。试验结果表明,两种滤波方法的滤波结果与观测值趋势大致相同,但存在少数异常点。下沉量越大的监测点,滤波结果与观测值的差异越大,但总体卡尔曼滤波的差异明显小于普通卡尔曼滤波,特别是对于下沉量较大的监测点。下沉量越大的监测点,其均方根误差越大,总体卡尔曼滤增大的速度远小于普通卡尔曼滤波,总体卡尔曼滤波均方根误差的最大值小于0.1 m,普通卡尔曼滤波的则接近0.4 m。     

小波分析在重力界面反演中的应用

基于Parker-Oldenburg反演方法，分析了低通滤波器B（K）的不同阈值对位场分离的影响。分别采用小波变换和低通滤波对青藏高原地区布格重力异常进行了位场分解和莫霍面反演，并将反演结果与地震资料作比较。结果表明，在重力位场分解中小波多尺度分解可以代替低通滤波器B（K），避免了闻值的选取。     

水下定位声线扰动分析与分段指数权函数设计

声速误差是水下声学定位的重要误差来源,主要包括声速测量本身的不确定性及声速时空变化误差.本文基于常梯度声线跟踪模型,导出入射角、声速梯度及深度变化产生的声线扰动数学模型.已有研究表明,对于相同的水深和声速梯度,入射角越大其扰动对声线影响越大,声线弯曲影响越明显.依据导出的入射角扰动对声线扰动的函数响应关系,构建了入射角相关的水下定位分段指数函数随机模型.试验结果表明:分段指数函数随机模型的定位结果相较于等权模型、指数模型有明显改善,与分段余弦随机模型定位结果相当,但本文随机模型会保留更多观测信息.     

小尺度地幔对流与海底地形抬升

根据建立的垂直于大洋中脊的二维热对流有限元数值模型，采用常粘性以及与温度相关的粘性两种粘性结构对小尺度地幔对流对海底地形的影响进行了重新研究。该模型的主要特点是采用开放边界条件，从而可以避免原有封闭模型因回流问题而产生的复杂效应。数据结果显示，在常粘性模型中，小尺度地幔对流可造成海底地形抬升；但对与温度相关的粘性模型，小尺度对流对地形几乎不产生影响。     

内核的转速和倾角对ICW与FICN的影响:Mathews理论

研究了内核幌动（ICW）自由内核章动（FICN）。为了给出解析结果，采纳了一个简单地球模型。与以往的研究相比，本文的新结果包括了内核相对地幔的转速和倾角的影响。     

地球及其形状非对称性的重力学研究

依据卫星重力、大地水准面观测结果,对表示地球形状的大地水准面异常进行了不同阶次的球谐函数计算和分析,发现2~6阶大地水准面异常表现出了地球双重非对称的基本形状,而高于6阶的大地水准面异常只表示了地球形态的局部变化特征。另外,采用阻尼最小二乘方法,利用全球地震层析成像资料和大地水准面异常资料联合反演了三维全球地幔密度异常。结果显示了地幔密度异常不仅在横向上,而且在纵向上也存在着明显的不均匀性。对比分析低阶大地水准面异常和地幔密度异常结果表明,地球形状非对称性主要是由下地幔的物质密度不均匀引起的。     

The Bruns formula in three dimensions

The Bruns formula is generalized to three dimensions with the derivation of equations expressing the height anomaly vector or the geoid undulation vector as a function of the disturbing gravity potential and its spatial derivatives. It is shown that the usual scalar Bruns formula provides not the separation along the normal to the reference ellipsoid but the component of the relevant spatial separation along the local direction of normal gravity. The above results which hold for any type of normal potential are specialized for the usual Somigliana-Pizzetti normal field so that the components of the geoid undulation vector are expressed as functions of the parameters of the reference ellipsoid, the disturbing potential and its spatial derivatives with respect to three types of curvilinear coordinates, ellipsoidal, geodetic and spherical. Finally the components of the geoid undulation vector are related to the deflections of the vertical in a spherical approximation.     

用变密度模型反演青藏高原的莫霍面深度

采用密度随深度呈指数变化的变密度模型来反演莫霍面深度，给出了利用指数密度模型在波数域中计算重力异常的正演公式压界面深度的反演公式。结果表明，青藏高原莫霍面呈现出边缘浅、中部深，边缘变化快、梯度大，中间变化梯度趋缓的特点。通过对常密度模型、变密度模型及地震反演得到的莫霍面的比较，证实变密度模型更适合于莫霍面结构的反演。     

Vening Meinesz inverse isostatic problem with local and global Bouguer anomalies

Inverse problems in isostasy will consist in making the isostatic anomalies to be zero under a certain isostatic hypothesis. In the case of the Vening Meinesz isostatic hypothesis, the density contrast is constant, while the Moho depth (depth of the Mohorovičić discontinuity) is variable. Hence, the Vening Meinesz inverse isostatic problem aims to determine a suitable variable Moho depth for a prescribed constant density contrast. The main idea is easy but the theoretical analysis is somewhat difficult. Moreover, the practical determination of the variable Moho depths based on the Vening Meinesz inverse problem is a laborious and time-consuming task. The formulas used for computing the inverse Vening Meinesz Moho depths are derived. The computational tricks essentially needed for computing the inverse Vening Meinesz Moho depths from a set of local and global Bouguer anomalies are described. The Moho depths for a test area are computed based on the inverse Vening Meinesz isostatic problem. These Moho depths fit the Moho depths derived from seismic observations with a good accuracy, in which the parameters used for the fitting agree well with those determined geophysically. Received: 4 February 1999 / Accepted: 4 October 1999     

结合现代大地测量成果探讨中国东部构造运动的力源问题

对中国东部所处的构造环境进行了分析和研究 ,结合现代大地测量成果 ,指出中国东部地壳运动主要是受陆陆碰撞 ,大洋板块俯冲及由二者引起的地幔对流三种主要因素控制 ,其中以印度板块与欧亚大陆的碰撞和菲律宾海板块向欧亚大陆的俯冲对中国东部的水平地壳运动及地幔对流对中国东部地壳垂直运动的影响占主导地位。在水平方向上 ,中国东部地壳的主应力方向为近东西向的压应力 ,但总体上是向东推移的。在垂直方向上 ,表现为南部隆升 ,北部沉陷。     

Forward simulation of gravity for crustal structure of Xiachayu-Gonghe profile in eastern Tibetan plateau

The crustal structure of Xiachayu-Gonghe geophysical profile in eastern Tibetan plateau is simulated with Bouguer anomaly corrected for sediments and lithosphere. The forward simulation shows that the thickness of upper crust in eastern Tibetan plateau is about 20 km, and the density is 2.78×103kg/m3. The bottom interface of middle crust changes from 30 km to 40 km, the density of middle crust is 2.89×103kg/m3. The materials with low density of 2.78 ×103kg/m3 exist in middle crust, and those with high density of 3.33 ×103kg/m3 exist at the bottom of middle crust between Wenquan and Tanggemu. The density is 3.10 ×103kg/m3 in lower crust. The shallowest depth of Moho interface is about 56 km, and the deepest one is about 74 km, the undulation of interface is large, the deep Moho is located in Xiachayu, Chayu, Nujiang, and Wenquan. The crustal density of eastern Tibetan plateau is larger than that of central section; the low velocity layers are located in middle crust and bottom in eastern Tibetan plateau and at the bottom of the upper crust in the central plateau.     

Forward simulation of gravity for crustal structure of Xiachayu-Gonghe profile in eastern Tibetan plateau

The crustal structure of Xiachayu-Gonghe geophysical profile in eastern Tibetan plateau is simulated with Bouguer anomaly corrected for sediments and lithosphere.The forward simulation shows that the thickness of upper crust in eastern Tibetan plateau is about 20 km,and the density is 2.78 3 3 × 10 kg/m.The bottom interface of middle crust changes from 30 km to 40 km,the density of middle crust is 2.89 3 3 × 10 kg/m.The materials with low density of 2.78 3 3 × 10 kg/mexist in middle crust,and those with hig...     

A theoretical random-error-propagation model for weakly constrained angular networks

Summary Idealized angular networks are considered which cover a two dimensional plane area. The networks consist of a multitude of identical elementary figures for which complete angular information can be deduced from the observations. Rather particular assumption have been made concerning the shape of the elementary figures and the covariance pattern of the observations. It is however believed that varying these assumptions would not alter the qualitative behavior of the theoretically derived error bounds. As the number n of points in such a network increases, the worst point error grows not less than a constant times √n. An upper bound for its growth is given by a constant times ℚnℓn(n). These results hold for completely free networks as well as in the case of a small number of fixed points.