共查询到20条相似文献，搜索用时 15 毫秒
1.
Global ellipsoid-referenced topographic,bathymetric and stripping corrections to gravity disturbance
This paper revisits several aspects of defining and computing the anomalous gravity data for purposes of gravimetric inversion/interpretation.
Attention is paid to evaluation of a refined global topographic correction to the gravity disturbance based on the reference
ellipsoid (RE) and constant reference density for solid topography onshore and sea water density for liquid topography offshore.
The global bathymetric correction is discussed. Two issues associated with compilation and inversion of bathymetrically and
topographically corrected gravity disturbances in regions of negative ellipsoidal (geodetic) heights are pointed out: the
evaluation of normal gravity and the harmonic continuation of the gravity data. Stripping, the removal of an effect of a known
density contrast, is considered also for additional geological elements such as lakes, glaciers, sedimentary basins, isostatic
mountain roots, etc. The stripping corrections are discussed in the context of the gravimetric inverse problem. 相似文献
2.
The eigenvalue decomposition technique is used for analysis of conditionality of two alternative solutions for a determination
of the geoid from local gravity data. The first solution is based on the standard two-step approach utilising the inverse
of the Abel-Poisson integral equation (downward continuation) and consequently the Stokes/Hotine integration (gravity inversion).
The second solution is based on a single integral that combines the downward continuation and the gravity inversion in one
integral equation. Extreme eigenvalues and corresponding condition numbers of matrix operators are investigated to compare
the stability of inverse problems of the above-mentioned computational models. To preserve a dominantly diagonal structure
of the matrices for inverse solutions, the horizontal positions of the parameterised solution on the geoid and of data points
are identical. The numerical experiments using real data reveal that the direct gravity inversion is numerically more stable
than the downward continuation procedure in the two-step approach. 相似文献
3.
JIANG Tao LI JianCheng DANG YaMin ZHANG ChuanYin WANG ZhengTao KE BaoGui 《中国科学:地球科学(英文版)》2014,57(7):1637-1644
Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy,and can provide fundamental information for geophysics,geodynamics,seismology,and mineral exploration.Rectangular harmonic analysis(RHA)is proposed for regional gravity field modeling in this paper.By solving the Laplace’s equation of gravitational potential in local Cartesian coordinate system,the rectangular harmonic expansions of disturbing potential,gravity anomaly,gravity disturbance,geoid undulation and deflection of the vertical are derived,and so are the formula for signal degree variance and error degree variance of the rectangular harmonic coefficients(RHC).We also present the mathematical model and detailed algorithm for the solution of RHC using RHA from gravity observations.In order to reduce the edge effects caused by periodic continuation in RHA,we propose the strategy of extending the size of computation domain.The RHA-based modeling method is validated by conducting numerical experiments based on simulated ground and airborne gravity data that are generated from geopotential model EGM2008 and contaminated by Gauss white noise with standard deviation of 2 mGal.The accuracy of the 2.5′×2.5′geoid undulations computed from ground and airborne gravity data is 1 and 1.4cm,respectively.The standard error of the gravity disturbances that downward continued from the flight height of 4 km to the geoid is only 3.1 mGal.Numerical results confirm that RHA is able to provide a reliable and accurate regional gravity field model,which may be a new option for the representation of the fine structure of regional gravity field. 相似文献
4.
通过联合全球重力位模型(EGM2008)、航空重力扰动数据和剩余地形模型(RTM)数据,基于频谱域(二维FFT变换)和空间域(Stokes数值积分)算法对毛乌素测区GT-2A航空重力测量系统采集的空中测线后处理重力扰动数据进行解算,构建了该地区的航空重力梯度扰动全张量.(1)残余航空重力扰动延拓结果表明:残余航空重力扰动经向下延拓至大地水准面,再向上延拓至航空高度后与原数据差值的标准差为1.0078 mGal,考虑边缘效应后,内缩计算范围得到的差值标准差减小至0.1269 mGal.(2)基于残余重力扰动数据(原航空高度数据及向下延拓数据),通过不同方案解算得到的梯度扰动结果表明:两种方案得到的研究区域重力梯度扰动各分量之差的最大标准差为6.4798E(Γ_(yz)分量),最小标准差为2.6968E(Γ_(xy)分量),内缩计算范围后得到的差值标准差最大值为1.8307E(Γ_(zz)分量),最小值为0.7223E(Γ_(yz)分量).本文的思路和方法可为未来我国自主构建航空重力梯度标定场提供参考. 相似文献
5.
以河北省流动重力测点覆盖区域内邢台地区4条断裂为例,将卫星布格重力异常与实测布格重力异常进行对比,发现流动重力资料可更为详细地反映测点周围构造的空间分布特征,为精细刻画华北平原地区深部构造背景提供可靠资料。采用向上延拓方法,对实测布格重力异常进行处理,获得不同上延高度的布格重力异常图像,结合当地地震地质与构造资料进行分析,并对流动重力资料在构造解释上的应用前景进行展望,认为该方法可提高现有资料的利用价值,适合在流动重力测量地区推广。 相似文献
6.
GOCE Data Processing: The Spherical Cap Regularization Approach 总被引：3，自引：0，他引：3
Due to the sun-synchronous orbit of the satellite gravity gradiometry mission GOCE, the measurements will not be globally
available. As a consequence, using a set of base functions with global support such as spherical harmonics, the matrix of
normal equations tends to be ill-conditioned, leading to weakly determined low-order spherical harmonic coefficients. The
corresponding geopotential strongly oscillates at the poles.
Considering the special configuration of the GOCE mission, in order to stabilize the normal equations matrix, the Spherical
Cap Regularization Approach (SCRA) has been developed. In this approach the geopotential function at the poles is predescribed
by an analytical continuous function, which is defined solely in the spatially restricted polar regions. This function could
either be based on an existing gravity field model or, alternatively, a low-degree gravity field solution which is adjusted
from GOCE observations. Consequently the inversion process is stabilized.
The feasibility of the SCRA is evaluated based on a numerical closed-loop simulation, using a realistic GOCE mission scenario.
Compared with standard methods such as Kaula and Tikhonov regularization, the SCRA shows a considerably improved performance. 相似文献
7.
重力反演方法是研究地壳结构和物性界面起伏的有效地球物理手段之一.本文收集了南北地震带南段67个已有的固定台站接收函数反演的Moho面深度结果,并使用基于EGM2008重力异常模型计算的布格重力异常,验证了本文提出的重震联合密度界面反演方法的有效性.利用接收函数对台站下方Moho面深度估计作为先验约束,定义了一类评价函数,通过对重力反演算法中尺度因子,平移因子和稳定性因子的最优选择,最小化重力反演结果与接收函数模型之间的差异.结果表明,本文提出的方法,可以有效地同化不同地球物理方法获得的反演模型,且通过重震联合反演可以改进由于对空间分布不均匀的接收函数结果插值可能而引起的误差.本文还通过引入Crust1.0的Moho面深度为初值,同时考虑地壳密度的横向不均匀分布,通过模型之间的联合反演有效改善了地球物理反演模型间的不一致性问题.本文反演得到的最优化Moho面深度模型与已知67个台站位置接收函数模型之间的标准差约1.9km,小于Crust1.0与接收函数结果模型之间标准差为3.73km的统计结果.本文研究结果对于同化重震反演结果、精化地壳密度界面模型,都具有十分重要的参考意义. 相似文献
8.
利用卫星重力测量手段监测全球质量变化取得了巨大成功,本文基于牛顿万有引力定律在三维空间直角坐标系中导出利用重力卫星观测数据监测全球质量变化的三维点质量模型法,该方法可直接利用重力卫星的轨道和星间观测数据或时变重力场模型计算全球质量变化,由于利用卫星观测数据计算地表质量变化的向下延拓过程以及观测数据噪声的影响,需要采用合适的空间约束方程或正则化技术对解算结果进行约束或平滑处理.利用合成全球质量变化模型模拟一个月的GRACE双星轨道和星间距离变率数据计算全球质量变化,对三维点质量模型法进行分析验证,采用零阶Tikhonov正则化技术处理病态问题.结果表明,三维点质量模型法可有效用于重力卫星观测数据监测全球质量变化,为利用重力卫星观测数据监测全球质量变化提供一种可选的途径. 相似文献
9.
利用兰州地震台及高台地震台连续重力资料,分析研究了2016年1月21日门源地震前连续重力变化特征。对震前5 d及震后2 d秒采样数据使用快速傅里叶变换（FFT）变换方法进行功率谱分析,发现其频率幅度持续增大,临震前一天减小到正常值后发生地震,同时对震前6 d秒采样数据进行滤波处理,发现在临震前48 h观测到重力扰动信号,周期为4~8 s。门源地震前观测到的频率特征及重力扰动信号分析,可能反映了门源地震前孕震的一个整体过程,这为揭示门源地震产生机理提供了参考。 相似文献
10.
Explicit formula for the geoid-quasigeoid separation 总被引：1，自引：0，他引：1
The explicit formula for the geoid-to-quasigeoid correction is derived in this paper. On comparing the geoidal height and
height anomaly, this correction is found to be a function of the mean value of gravity disturbance along the plumbline within
the topography. To evaluate the mean gravity disturbance, the gravity field of the Earth is decomposed into components generated
by masses within the geoid, topography and atmosphere. Newton’s integration is then used for the computation of topography-and
atmosphere-generated components of the mean gravity, while the combined solution for the downward continuation of gravity
anomalies and Stokes’ boundary-value problem is utilized in computing the component of mean gravity disturbance generated
by mass irregularities within the geoid. On application of this explicit formulism a theoretical accuracy of a few millimetres
can be achieved in evaluation of the geoid-to-quasigeoid correction. However, the real accuracy could be lower due to deficiencies
within the numerical methods and to errors within the input data (digital terrain and density models and gravity observations). 相似文献
11.
12.
Robert Tenzer Pavel Novák Ilya Prutkin Artu Ellmann Peter Vajda 《Studia Geophysica et Geodaetica》2009,53(2):157-167
To reduce the numerical complexity of inverse solutions to large systems of discretised integral equations in gravimetric
geoid/quasigeoid modelling, the surface domain of Green’s integrals is subdivided into the near-zone and far-zone integration
sub-domains. The inversion is performed for the near zone using regional detailed gravity data. The farzone contributions
to the gravity field quantities are estimated from an available global geopotential model using techniques for a spherical
harmonic analysis of the gravity field. For computing the far-zone contributions by means of Green’s integrals, truncation
coefficients are applied. Different forms of truncation coefficients have been derived depending on a type of integrals in
solving various geodetic boundary-value problems. In this study, we utilise Molodensky’s truncation coefficients to Green’s
integrals for computing the far-zone contributions to the disturbing potential, the gravity disturbance, and the gravity anomaly.
We also demonstrate that Molodensky’s truncation coefficients can be uniformly applied to all types of Green’s integrals used
in solving the boundaryvalue problems. The numerical example of the far-zone contributions to the gravity field quantities
is given over the area of study which comprises the Canadian Rocky Mountains. The coefficients of a global geopotential model
and a detailed digital terrain model are used as input data. 相似文献
13.
A geoid solution for airborne gravity data 总被引：2，自引：0，他引：2
Airborne gravity data is usually attached with satellite positioning of data points, which allow for the direct determination
of the gravity disturbance at flight level. Assuming a suitable gridding of such data, Hotine’s modified integral formula
can be combined with an Earth Gravity Model for the computation of the disturbing potential (T) at flight level. Based on
T and the gravity disturbance data, we directly downward continue T to the geoid, and we present the final solution for the
geoid height, including topographic corrections. It can be proved that the Taylor expansion of T converges if the flight level
is at least twice the height of the topography, and the terrain potential will not contribute to the topographic correction.
Hence, the simple topographic bias of the Bouguer shell yields the only topographic correction. Some numerical results demonstrate
the technique used for downward continuation and topographic correction. 相似文献
14.
15.
Determination of the degree 120 time-variable gravity field in the Sichuan-Yunnan region using Slepian functions and terrestrial measurements 
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下载免费PDF全文 The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust. These gravity data have many applications, such as surface deformation, groundwater storage changes, and mass migration before and after earthquakes. Based on repeated terrestrial gravity measurements at 198 gravity stations in the Sichuan-Yunnan region (SYR) from 2015 to 2017, we determine a time series of degree 120 gravity fields using the localized spherical harmonic (Slepian) basis functions. Our results show that adopting the first 6 Slepian basis functions is sufficient for effective localized Slepian modeling in the SYR. The differences between two gravity campaigns at the same time of year show an obvious correlation with tectonic features. The degree 120 timevariable gravity models presented in this paper will benefit the study of the regional mass migration inside the crust of the SYR and supplement the existing geophysical models for the China Seismic Experimental Site. 相似文献
16.
Atmospheric masses play an important role in precise downward continuation and validation of satellite gravity gradiometry data. In this paper we present two alternative ways to formulate the atmospheric potential. Two density models for the atmosphere are proposed and used to formulate the external and internal atmospheric potentials in spherical harmonics. Based on the derived harmonic coefficients, the direct atmospheric effects on the satellite gravity gradiometry data are investigated and presented in the orbital frame over Fennoscandia. The formulas of the indirect atmospheric effects on gravity anomaly and geoid (downward continued quantities) are also derived using the proposed density models. The numerical results show that the atmospheric effect can only be significant for precise validation or inversion of the GOCE gradiometric data at the mE level. 相似文献
17.
三维密度反演已经成为重力数据定量解释的常规方法,但由于重力数据本身并没有深度分辨率,为了减少由此引起的重力反演的非唯一性,常用的手段是引入额外的先验信息.本文提出了一种重力三维稀疏反演（以下简称稀疏反演）方法,该方法通过求解物性上下界约束时的Lp范数（0 ≤ p ≤ 1）稀疏优化问题,来获得具有尖锐边界的解.与传统的L2范数反演方法相比,稀疏反演方法可以更加有效地利用已知的物性信息,获得深度分辨率更高的反演结果.此外,我们也分析了稀疏反演方法与二值、三值反演算法的等价性以及在实际应用中需要注意的问题.最后,通过模型试验以及矿区实测数据反演验证了稀疏反演方法的有效性. 相似文献
18.
We investigate the roughness of and the correlation with topography of the observed, topographically corrected (T), and bathymetrically
and topographically corrected (BT) gravity disturbances. The numerical investigation is carried out for the gravity disturbances
at the Earth’s surface and for the upward continued gravity disturbances at different altitudes. The area of study comprises
a rough part of the Canadian Rockies surrounded by flat regions. The smoothest at the Earth’s surface are the BT gravity disturbances.
The evolution of roughness with altitude shows an interesting phenomenon, diverse for the three types of gravity disturbances.
The correlation with topography over the study area of the observed gravity disturbances is bellow 0.6, and of the BT gravity
disturbances approximately −0.6. The largest absolute value, of about −0.75, is found between the topography and the T gravity
disturbances. This large negative correlation indicates a presence of the isostatic compensation in mountainous regions of
the Canadian west coast. 相似文献
19.
本文利用GRACE(Gravity Recovery And Climate Experiment)level 1b数据和径向基函数RBF(radial basis function)方法解算了全球时变地球重力场.RBF基函数相比传统球谐(spherical harmonic)基函数,其高度的空域局部特性使得正则化过程易于添加先验协方差信息,从而可能揭示更加准确的重力场信号.本文研究表明,RBF基函数算法在精化现有的GRACE全球时变重力场模型,如提升部分区域信号幅度等方面具有一定优势.本文通过将RBF的尺度因子作为待解参数,基于GRACE卫星的Level 1b数据和变分方程法,成功获取了2009-2010年90阶无约束全球时变重力场RBF模型Hust-IGG03,以及正则化全球时变重力场RBF模型Hust-IGG04.通过与GRACE官方数据处理中心GFZ发布的最新90阶球谐基时变模型RL05a进行对比,结果表明:(1)无约束RBF模型Hust-IGG03和GFZ RL05a在空域和频域表现基本一致;(2)正则化RBF模型Hust-IGG04无需进行后处理滤波已经显示较高信噪比,噪音水平接近于球谐基模型GFZ RL05a经400 km高斯滤波后的效果;(3)HustIGG04相比400 km高斯滤波GFZ RL05a在周年振幅图和趋势图上显示出更多的细节信息,并且呈现出更强的信号幅度,如在格陵兰冰川融化趋势估计上Hust-IGG04比GFZ RL05a提高了24.2%.以上结果均显示RBF方法有助于进一步挖掘GRACE观测值所包含的时变重力场信息. 相似文献
20.
重力卫星可以在相同误差尺度下对全球质量变化进行连续重复观测,并在近十余年来取得了巨大成功,探索重力卫星数据精化处理方法和相关应用研究具有重要意义.本文基于三维加速度点质量模型法的基本原理,进一步发展建立了时变重力场模型球谐位系数的变化和地面点质量变化的关系,可有效考虑地表质量变化导致的负荷形变的影响;引入等权形式、线性形式、指数形式和高斯形式的空间约束方法处理南北条带噪声和向下延拓导致的病态问题,并与零阶Tikhonov正则化方法进行对比分析.采用模拟数据和一个月的实测GRACE时变重力场模型计算全球质量变化,对三维加速度点质量模型法和几种空间约束方法进行对比分析验证.计算结果表明,对于3°等面积的全球格网质量点,高斯和指数形式空间约束方法的最优相关距离约为500km,等权和线性形式空间约束方法的最优相关距离约为600km,各方法均可有效处理条带噪声的影响,四种空间约束方法的计算效果优于零阶Tikhonov正则化方法,本文的相关方法为进一步利用三维加速度点质量模型法监测全球质量变化提供了借鉴. 相似文献