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1.
融合多源数据的高精度、高分辨率的局部重力场建模是物理大地测量学的前沿和热点问题.本文研究了基于径向基函数融合多源数据的局部重力场建模方法,利用Monte-Carlo方差分量估计实现了不同类型的观测数据的合理定权,引入了最小标准差法确定基函数的适宜网络,分析了地形因素对于基函数网络确定及局部重力场建模精度的影响.以泊松小波基函数为构造基函数,结合残差地形模型,融合实测的陆地重力异常、船载重力异常及航空重力扰动数据构建了局部区域陆海统一的似大地水准面模型.研究结果表明:引入残差地形模型平滑了地形质量引入的高频扰动信号,简化了基函数的网络设计;并提高了重力似大地水准面的精度,平原地区其精度提高了4mm,地形起伏较大的山区其精度提高了约5cm.总体而言,基于"三步法"构建的局部重力似大地水准面在荷兰、比利时及德国相关区域,其精度分别达到1.12cm、2.80cm以及2.92cm. 相似文献
2.
This paper focuses on one particular way of linear filtering the gravity data to facilitate gravity inversion or interpretation. With the use of integral transforms the gravity anomalies are transformed into new quantities that allow an easier interpretation with the help of pattern recognition. As the integral transforms are in fact filters, and as the regions of integration are caps with a variable radius, which can be systematically changed as a free parameter, we refer to such methodology as the truncation filtering. Such filters may be understood as weighted spherical windows moving over the surface, on which the gravity anomaly is defined, the kernel of the transform being the weight function. The objective of this paper is to define and deploy the truncation filtering for a planar model, i.e. for a homogenous horizontally infinite layer with embedded anomalous masses, and for a spherical model, i.e., for a homogenous massive sphere with embedded anomalous masses. Instead of the original gravity anomaly, the quantities resulting from the truncation filtering are interpreted/inverted. As we shall see, this approach has certain benefits. The fundamental concept of the truncation filtering methodology is demonstrated here in terms of the model consisting of one point mass anomaly.The relationship between the depth of the point mass and the instant of the onset of the dimple pattern observed in sequences produced by truncation filtering the synthetic gravity data generated by point masses is, for both the planar and spherical models, compiled by computer simulations, as well as derived analytically. It is shown, that the dimple pattern is a consequence of truncating the domain of the filter and is free of the choice of the kernel of the filter. It is shown, that in terms of the mean earth and depths of point masses no greater than some 100 km the spherical model may be replaced by a planar model from the perspective of the truncation filtering methodology. It is also shown, that from the viewpoint of the truncation filtering methodology the rigorous gravity anomaly may be approximated by the vertical component of the gravity disturbance. The relationship between the instant of the dimple onset and the depth of the point mass thus becomes linear and independent of the magnitude (mass) of the point mass. 相似文献
3.
The choice of the optimal spherical radial basis function (SRBF) in local gravity field modelling from terrestrial gravity
data is investigated. Various types of SRBFs are considered: the point-mass kernel, radial multipoles, Poisson wavelets, and
the Poisson kernel. The analytical expressions for the Poisson kernel, the point-mass kernel and the radial multipoles are
well known, while for the Poisson wavelet new closed analytical expressions are derived for arbitrary orders using recursions.
The performance of each SRBF in local gravity field modelling is analyzed using real data. A penalized least-squares technique
is applied to estimate the gravity field parameters. As follows from the analysis, almost the same accuracy of gravity field
modelling can be achieved for different types of the SRBFs, provided that the depth of the SRBFs is chosen properly. Generalized
cross validation is shown to be a suitable technique for the choice of the depth. As a good alternative to generalized cross
validation, we propose the minimization of the RMS differences between predicted and observed values at a set of control points.
The optimal regularization parameter is determined using variance component estimation techniques. The relation between the
depth and the correlation length of the SRBFs is established. It is shown that the optimal depth depends on the type of the
SRBF. However, the gravity field solution does not change significantly if the depth is changed by several km. The size of
the data area (which is always larger than the target area) depends on the type of the SRBF. The point-mass kernel requires
the largest data area. 相似文献
4.
本文介绍一个把小波多尺度分析、表面刻痕分析以及位场频率域解释理论和反演方法结合起来的数据处理、反演解释和信息提取的方法系统.这一方法系统简称为区域重力场多尺度刻痕分析方法,应用于刻画地壳分层的三维密度结构、地壳变形带分布和构造单元分区.多尺度刻痕分析包含频率域重力场场源分层、重力场小波变换多尺度分解、场源分层深度及密度扰动反演、分层刻痕分析和构造边界定位四个子系统.文中扼要地介绍这四个子系统基本原理、方法技术及应用效果.从地球物理探测到大地构造学发现,是一个多学科综合研究的探索过程.要取得重大研究成果,必须研发和组合来自不同学科的多个新方法技术,使多学科综合研究有宽厚的理论支撑.本文介绍的四个子系统组合的理论支撑分别来自应用数学、地球物理学和信息科学. 相似文献
5.
Mohammad A. Sharifi Mohsen Romeshkani Robert Tenzer 《Studia Geophysica et Geodaetica》2017,61(3):453-468
A regional recovery of the Earth’s gravity field from satellite observables has become particularly important in various geoscience studies in order to better localize stochastic properties of observed data, while allowing the inversion of a large amount of data, collected with a high spatial resolution only over the area of interest. One way of doing this is to use observables, which have a more localized support. As acquired in recent studies related to a regional inversion of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) data, the satellite gravity-gradient observables have a more localized support than the gravity observations. Following this principle, we compare here the performance of the second- and third-order derivatives of the gravitational potential in context of a regional gravity modeling, namely estimating the gravity anomalies. A functional relation between these two types of observables and the gravity anomalies is formulated by means of the extended Stokes’ integral formula (or more explicitly its second- and third-order derivatives) while the inverse solution is carried out by applying a least-squares technique and the ill-posed inverse problem is stabilized by applying Tikhonov’s regularization. Our results reveal that the third-order radial derivatives of the gravitational potential are the most suitable among investigated input data types for a regional gravity recovery, because these observables preserve more information on a higher-frequency part of the gravitational spectrum compared to the vertical gravitational gradients. We also demonstrate that the higher-order horizontal derivatives of the gravitational potential do not necessary improve the results. We explain this by the fact that most of the gravity signal is comprised in its radial component, while the horizontal components are considerably less sensitive to spatial variations of the gravity field. 相似文献
6.
密度界面反演作为了解地球内部结构的一种重要方法,长期以来都是重力学研究的主要内容.本文结合抛物线密度模型及频率域算法的优点,将抛物线密度函数应用于Parker-Oldenburg算法,经过理论推导得到了抛物线密度模型的频率域公式,从而建立了基于抛物线密度模型的三维密度界面重力异常正反演的算法和流程.理论模型数据试验表明本方法快速、有效,适用于大多数浅部比深部增加更快的实际地壳密度.研究中还利用该方法对川滇地区重力异常进行了反演,获得了该区的莫霍面深度分布,并与接收函数研究结果进行对比分析,进一步验证了本文方法的正确性和有效性. 相似文献
7.
本文研究了基于泊松小波径向基函数融合多代卫星测高及多源重力数据精化大地水准面模型的方法.分别以沿轨垂线偏差和大地水准面高高差作为卫星测高观测量,研究了使用不同类型测高数据对于大地水准面建模精度的影响.针对全球潮汐模型在浅水区域及部分开阔海域精度较低的问题,引入局部潮汐模型研究了不同潮汐模型对于大地水准面的影响.数值分析表明:相比于使用沿轨垂线偏差作为测高观测量,基于沿轨大地水准面高高差解算得到的大地水准面模型的精度更高,特别是在海域区域,其精度提高了2.3cm.由于使用沿轨大地水准面高高差作为测高观测量削弱了潮汐模型长波误差的影响,采用不同潮汐模型对大地水准面解算的影响较小.总体而言,船载重力及测高观测数据在海洋重力场的确定中呈现互补性关系,联合两类重力场观测量可以提高局部重力场的建模精度. 相似文献
8.
The determination of the local gravity field by means of the point mass inversion method can be performed as an alternative to conventional numerical methods, such as the least-squares collocation. Based on the first derivative of the inverse-distance Newtonian potential for the representation of the gravity anomaly data, it is possible to compute any wavelength component of the geoid in planar approximation with sufficient accuracy. In order to exemplify the theoretical concept, two applications are presented of the computation of two different wavelength components of the geoid, the long wavelength component in a local solution and the short wavelength component in a regional solution. The results are compared with corresponding least-squares collocation solutions, using a global geopotential model to remove and to restore the long wavelength component. 相似文献
9.
Hasan Yildiz 《Studia Geophysica et Geodaetica》2012,56(1):171-184
Gravity field and steady-state Ocean Circulation Explorer (GOCE) is the first satellite mission that observes gravity gradients
from the space, to be primarily used for the determination of high precision global gravity field models. However, the GOCE
gradients, having a dense data distribution, may potentially provide better predictions of the regional gravity field than
those obtained using a spherical harmonic Earth Geopotential Model (EGM). This is investigated in Auvergne test area using
Least Squares Collocation (LSC) with GOCE vertical gravity gradient anomalies (Tzz), removing the long wavelength part from EGM2008 and the short wavelength part by residual terrain modelling (RTM). The results
show that terrain effects on the vertical gravity gradient are significant at satellite altitude, reaching a level of 0.11
E?tv?s unit (E.U.) in the mountainous areas. Removing the RTM effects from GOCE Tzz leads to significant improvements on the LSC predictions of surface gravity anomalies and quasigeoid heights. Comparison
with ground truth data shows that using LSC surface free air gravity anomalies and quasi-geoid heights are recovered from
GOCE Tzz with standard deviations of 11 mGal and 18 cm, which is better than those obtained by using GOCE EGMs, demonstrating that
information beyond the maximal degree of the GOCE EGMs is present. Investigation of using covariance functions created separately
from GOCE Tzz and terrestrial free air gravity anomalies, suggests that both covariance functions give almost identical predictions. However,
using covariance function obtained from GOCE Tzz has the effect that the predicted formal average error estimates are considerably larger than the standard deviations of
predicted minus observed gravity anomalies. Therefore, GOCE Tzz should be used with caution to determine the covariance functions in areas where surface gravity anomalies are not available,
if error estimates are needed. 相似文献
10.
Transformation between gravimetric and GPS/levelling-derived geoids using additional gravity information 总被引：1，自引：0，他引：1
The transformation from the gravimetric to the GPS/levelling-derived geoid using additional gravity information for the covariance function of geoid height differences has been investigated in a test area in south-western Canada. A “corrector surface” model, which accounts for datum inconsistencies, long-wavelength geoid errors, vertical network distortions and GPS errors, has been constructed using least-squares collocation. The local covariance function of geoid height differences is usually obtained from residual values between the GPS/levelling and gravimetric geoid heights after the elimination of all known systematic distortions. If additional gravity data (in the form of gravity anomalies) are available, the covariance function of geoid height differences can be determined by the following steps: (1) transforming the GPS/levelling-derived geoid heights into gravity anomalies; (2) forming differences between the computed in step 1 and given gravity anomalies; (3) determining the parameters of the local covariance function of the gravity anomaly differences; (4) constructing an analytical covariance model for the geoid height differences from the covariance function of the gravity anomaly differences using the parameters derived in step 3. The advantage of the proposed method stems from the great number of gravity data used to derive the empirical covariance function. A comparison with the least-squares adjustment shows that the standard deviation of the residuals of the predicted geoid height differences with respect to the control point values decreases by 2.4 cm. 相似文献
11.
We present a geoid model for the area of Lake Vostok, Antarctica, from a combination of local airborne gravity, ice-surface and ice-thickness data and a lake bathymetry model. The topography data are used for residual terrain modeling (RTM) in a remove–restore approach together with GOCE satellite data. The quasigeoid is predicted by least-squares collocation (LSC) and subsequently converted to geoid heights. Special aspects of that method in presence of an ice sheet are discussed.It is well known that a body freely floating in water is in a state of hydrostatic equilibrium (HE). This usually applies, e.g., to ice shelves or sea ice. However, it has been shown that this is valid also for the ice sheet covering the subglacial Lake Vostok. Thus, we demonstrate the use of such a refined regional geoid model for glaciological and geophysical applications by means of the HE surface of that lake. The mean quadratic residual geoid signal (0.56 m) w.r.t. the GOCE background model exceeds the residual variations of the estimated apparent lake level (ALL) (0.26 m) within the central part of the lake. An approach considering the actual geopotential at the ALL has been derived and subsequently applied. In this context, downward continuation of the potential field within the ice sheet as well as the latitudinal tilt of off-geoid equipotential surfaces are discussed. In view of the accuracy of the ice-thickness measurements that dominate the total error budget of the estimated ALL these effects are negligible. Thus, the HE surface of subglacial lakes may safely be described by a constant height bias in small-scale regional applications. However, field continuation is significant with respect to the formal uncertainty of the quasigeoid, which is at the level of 5 cm given that accurate airborne gravity data (±2 mGal) are available. 相似文献
12.
The need to obtain more reliable Earth structures has been the impetus for conducting joint inversions of disparate geophysical datasets. For seismic arrival time tomography, joint inversion of arrival time and gravity data has become an important way to investigate velocity structure of the crust and upper mantle. However, the absence of an efficient approach for modeling gravity effects in spherical coordinates limits the joint tomographic analysis to only local scales. In order to extend the joint tomographic inversion into spherical coordinates, and enable it to be feasible for regional studies, we develop an efficient and adaptive approach for modeling gravity effects in spherical coordinates based on the longitudinal/latitudinal grid spacing. The complete gravity effects of spherical prisms, including gravitational potential, gravity vector and tensor gradients, are calculated by numerical integration of the Gauss–Legendre quadrature (GLQ). To ensure the efficiency of the gravity modeling, spherical prisms are recursively subdivided into smaller units according to their distances to the observation point. This approach is compatible with the parameterization of regional arrival time tomography for large areas, in which both the near- and far-field effects of the Earth's curvature cannot be ignored. Therefore, this approach can be implemented into the joint tomographic inversion of arrival time and gravity data conveniently. As practical applications, the complete gravity effects of a single anomalous density body have been calculated, and the gravity anomalies of two tomographic models in the Taiwan region have also been obtained using empirical relationships between P-wave velocity and density. 相似文献
13.
14.
Vertical gravity gradient anomalies from the Gravity and steady-state Ocean Circulation Explorer (GOCE) DIR-3 model have been used to determine gravity anomalies in mid-west Greenland by using Least-Squares Collocation (LSC) and the Reduced Point Mass (RPM) method. The two methods give nearly identical results. However, compared to LSC, the RPM method needs less computational time as the number of equations to be solved in LSC equals the number of observations. The advantage of the LSC, however, is the acquired error estimates. The observation periods are winter 2009 and summer 2012. In order to enhance the accuracy of the calculated gravity anomalies, ground gravity data from West Greenland is used over locations where the gravity change resulting from ice mass changes is negligible, i.e. over solid rock. In the period considered, the gravity anomaly change due to changes in ice mass varies from ?5 mGal to 4 mGal. It is negative over the outlet glacier Jacobshavn Isbræ, where the mass loss corresponds to a gravity change of approximately ?4 mGal. When using only GOCE vertical gravity gradients, the error estimates range from 5 mGal at the coast to 17 mGal over the ice sheet. Introducing the ground gravity data from West Greenland in the prediction reduces the errors to range from 2 to 10 mGal. 相似文献
15.
The approach, fundamentally different from the known ones, to estimating the spatial location of the domain filled with the disturbing masses based on the gravity field measurement data is suggested. The main idea of the approach is, using the set of the probable variants of the interpretation, to construct the distribution of a certain parameter associated with the estimate of probability of detecting the sources of the field in any point of the studied geological medium and then to apply this distribution to each domain eligible for being the true carrier of the anomalous masses. These constructions yield the generalized admissible solutions of the inverse problem with ranking the separate fragments of the model carrier in terms of the probability of detecting anomalous masses in them. 相似文献
16.
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
17.
The most common approach for the processing of data of gravity field satellite missions is the so-called time-wise approach. In this approach satellite data are considered as a time series and processed by a standard least-squares approach. This approach has a very strong flexibility but it is computationally very demanding. To improve the computational efficiency and numerical stability, the so-called torus and Rosborough approaches have been developed. So far, these approaches have been applied only for global gravity field determinations, based on spherical harmonics as basis functions. For regional applications basis functions with a local support are superior to spherical harmonics, because they provide the same approximation quality with much less parameters. So far, torus and Rosborough approach have been developed for spherical harmonics only. Therefore, the paper aims at the development and testing of the torus and Rosborough approach for regional gravity field improvements, based on radial basis functions as basis functions. The developed regional Rosborough approach is tested against a changing gravity field produced by simulated ice-mass changes over Greenland. With only 350 parameters a recovery of the simulated mass changes with a relative accuracy of 5% is possible. 相似文献
18.
HUALIN ZENG 《Geophysical Prospecting》1989,37(8):959-973
A method for estimating the degree of polynomial fitted to gravity anomalies to evaluate the regional anomaly is presented. The anomaly can be fitted by polynomials of different degrees with the least-squares method and the optimum degree of the polynomial evaluating this anomaly can be estimated from the point of discontinuity of the gradient on a graph of variance against the polynomial degree. The Bouguer gravity is initially separated by upward continuation to a proper height and then the degree of regional polynomial to fit the Bouguer anomaly can be estimated. Theoretical and field examples show the effectiveness of the method. 相似文献
19.
A new interpretative approach is proposed to interpret residual gravity anomaly profiles in order to determine the depth, the amplitude coefficient and the geometric shape factor of simple spherical and cylindrical buried structures. This new approach is based on both Fair function minimization and on stochastic optimization modeling. The validity of this interpretative approach is demonstrated through studying and analyzing two synthetic gravity anomalies, using simulated data generated from a known model with different random noises components and a known statistical distribution. Being theoretically proven, this new approach has been applied on three real field gravity anomalies from Sweden, Senegal and the United States. The agreement between the results obtained by the proposed method and those obtained by other interpretation methods is good and comparable. 相似文献
20.
流动重力测量作为地震前兆监测手段之一, 所得到的区域重力场微变化信号反映地壳内部密度变化、 地壳变形、 流体运移等信息。 采用定量化和模型化方法研究与地震孕育相关的重力场变化信号时空特征, 对于构建地震预报定量化指标体系具有重要意义。 通过设定场源参数构建了数值模型, 正演得到了多组不同场源条件下的重力场变化模型; 通过模型对比, 分析了重力变化与重力梯度变化对不同类型场源参数的关系。 研究结果表明: 重力垂直梯度变化对异常体边界比较敏感, 特对浅部异常更为敏感, 适用于圈定异常体范围。 以此为基础提出了观测系统的优化测量方案, 以及对观测精度的需求。 研究结果对于构建地震预报指标参数, 优化流动重力观测系统具有一定参考意义。 相似文献