共查询到20条相似文献，搜索用时 734 毫秒
1.
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2017,10(15):337
A new approach is proposed to interpret magnetic anomalies caused by isolated thin dike-like causative targets. The approach is essentially based on utilizing artificial neural network (ANN) inversion for estimating the problem parameters. Particularly, the modular neural network (MNN) is used for the inversion process in order to quantitatively interpret the magnetic anomalies. The MNN inversion has been first tested on a synthetic data with and without random white Gaussian noise. The effect of random noise has been clearly investigated where it showed that the approach provided satisfactory results. Furthermore, three field examples have been inverted in order to investigate the applicability of the proposed approach. The results showed good agreement with the techniques that have been stated in the literatures. 相似文献
2.
Inversion of residual gravity anomalies using neural network 总被引：1，自引：1，他引：0
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2013,6(5):1509-1516
A new approach is presented in order to interpret residual gravity anomalies from simple geometrically shaped bodies such as horizontal cylinder, vertical cylinder, and sphere. This approach is mainly based on using modular neural network (MNN) inversion for estimating the shape factor, the depth, and the amplitude coefficient. The sigmoid function has been used as an activation function in the MNN inversion. The new approach has been tested first on synthetic data from different models using only one well-trained network. The results of this approach show that the parameter values estimated by the modular inversion are almost identical to the true parameters. Furthermore, the noise analysis has been examined where the results of the inversion produce satisfactory results up to 10% of white Gaussian noise. The reliability of this approach is demonstrated through two published real gravity field anomalies taken over a chromite deposit in Camaguey province, Cuba and over sulfide ore body, Nornada, Quebec, Canada. A comparable and acceptable agreement is obtained between the results derived by the MNN inversion method and those deduced by other interpretation methods. Furthermore, the depth obtained by the proposed technique is found to be very close to that obtained by drilling information. 相似文献
3.
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2009,2(2):175-184
Magnetic surveys have been used for mineral exploration where different data processing techniques were used to derive the parameters of causative targets. In this respect, the neural network (NN) technique was used to estimate the magnetic causative target parameters. Examples of NN inversion have been tested on synthetic examples where the NN was trained well using forward models of the vertical magnetic effect of a vertical sheet and a horizontal circular cylinder. Specifically, modular neural network (MNN) inversion has been used for the parameter estimation of the causative targets, where the sigmoid function was used as the activation function. The effect of random noise and the error estimation of the horizontal location have been analyzed. When NN is applied to real data, it estimates successfully the parameters of the causative targets such as burial depths, magnetic constants, and angle of polarization. Hilbert transform has been used to locate the source origin, which is important for the NN inversion. This approach has more advantages than the conventional data inversions in terms of its efficiency and flexibility. It also gives fast solutions. The MNN approach has been applied to the Kursk and Manjampalli anomalies, where the results were shown to be in good agreement with the other techniques published in the literature. 相似文献
4.
A method coupled with a GUI based code in JAVA is developed in the space domain to simultaneously estimate the structures of strike limited listric fault sources and regional gravity background from a set of observed Bouguer gravity anomalies. The density contrast within the hanging wall of the structure is assumed to be varying continuously with depth based on a parabolic equation. The limiting surface of the fault plane is described with an exponential function. This method is automatic in the sense that it initializes both parameters of a strike limited listric fault source and regional gravity background from a set of observed Bouguer gravity anomalies and improves them iteratively until the modeled gravity anomalies fit the observed anomalies within the specified convergence criteria. The advantage of the code is that besides generating output in both ASCII and graphical forms it displays the animated versions of (i) the changes in model geometry, (ii) variation of each model parameter and misfit with iteration number, (iii) improvements in modeled gravity anomalies, and (iv) variation of density contrast with depth. The applicability of the code is demonstrated on both synthetic and real field gravity anomalies. In case of synthetic example pseudorandom noise is added to the residual gravity anomalies of the structure prior to inversion. The noisy anomalies are then inverted for the unknown parameters presuming (i) an ideal listric fault structure bounded by an exponential limiting surface with perfect flat top and bottom surfaces, (ii) non-ideal structure with uneven top and bottom surfaces with imperfect exponential limiting surface. Further, the robustness of the algorithm is exemplified by adding both regional gravity background and pseudorandom noise to the anomalies of the structure before inversion. In all cases, the interpreted parameters of the structure closely mimic the assumed parameters. The interpretation of gravity anomalies across the master fault of the Chintalpudi sub-basin in India has yielded information that is consistent with both DSS results and drilling information. The highlight of the code is that it can be used to interpret the gravity anomalies of listric fault sources even when the profile along which the interpretation is intended fails to bisect the strike length of the structure. 相似文献
5.
V Chakravarthi M Pramod Kumar B Ramamma S Rajeswara Sastry 《Arabian Journal of Geosciences》2017,10(3):64
Boundary faults associated with thick sedimentary basins are more often curved in cross section rather than planar. We develop a space domain-based automatic gravity inversion technique to quantify such listric fault sources from a set of observed gravity anomalies. The density contrast within the hanging wall of fault morphology is presumed to be known according to a prescribed exponential law. Furthermore, the fault plane is described by a polynomial function of arbitrary but specific degree, whose coefficients become the unknown parameters to be estimated from a set of observed gravity anomalies in addition to the thickness of the fault structure. Using a set of characteristic anomalies, the present inversion identifies approximate parameters pertaining to the origin of fault plane and depth to decollement horizon. Based on the errors between the observed and model gravity anomalies of the structure, the algorithm constructs and solves a system of normal equations to estimate the improvements in depth and coefficients of the polynomial in an iterative approach until one of the specified convergence criteria is fulfilled. The efficacy of the algorithm is shown with the analysis of gravity anomalies attributable to a synthetic model of a listric fault source in the presence of pseudorandom noise. Application of the proposed inversion technique on the observed gravity anomalies of the Ahri-Cherla master fault of the Godavari subbasin in India using the derived exponential density contrast model has yielded an interpretation that is consistent with the available/reported information. 相似文献
6.
BP神经网络方法在二维密度界面的反演中取得了较好的效果,但在反演三维界面时,由于模型更复杂、参数更多,BP神经网络的收敛速度和反演精度都有一定程度的下降。为了改善反演效果,本文利用遗传算法对BP神经网络的权值、阈值选择过程进行优化,获得了更好的网络模型;并将此模型应用于密度界面模型的反演中,预测误差从上百米减小到数十米,同时迭代计算步数减少了近2/3,有效减少了计算时间,反演结果更准确。利用基于遗传算法优化的BP神经网络反演了法国某地区莫霍面深度,预测相对误差仅为1.8%,取得了较好的应用效果。基于遗传算法优化的BP神经网络在密度界面的反演中具有良好的应用价值和研究前景。 相似文献
7.
时间域航空电磁系统采样密集,数据量大,所以在该领域较为实用的数据处理方法主要为一维反演和电阻率成像法。笔者从成像问题出发,建立了庞大的数据模型训练集,研究并分析了不同结构的神经网络的成像精度。通过对比分析测试结果,获得了在一定条件下适用于航空电磁成像的最优网络模型结构,包含其神经元个数和层数等信息。本文采用早停法训练神经网络,压制数据中噪声对成像结果的影响。 相似文献
8.
A direct inversion scheme for deep resistivity sounding data using artificial neural networks 总被引：1，自引：0，他引：1
Initialization of model parameters is crucial in the conventional 1D inversion of DC electrical data, since a poor guess may
result in undesired parameter estimations. In the present work, we investigate the performance of neural networks in the direct
inversion of DC sounding data, without the need ofa priori information. We introduce a two-step network approach where the first network identifies the curve type, followed by the
model parameter estimation using the second network. This approach provides the flexibility to accommodate all the characteristic
sounding curve types with a wide range of resistivity and thickness. Here we realize a three layer feed-forward neural network
with fast back propagation learning algorithms performing well. The basic data sets for training and testing were simulated
on the basis of available deep resistivity sounding (DRS) data from the crystalline terrains of south India. The optimum network
parameters and performance were decided as a function of the testing error convergence with respect to the network training
error. On adequate training, the final weights simulate faithfully to recover resistivity and thickness on new data. The small
discrepancies noticed, however, are well within the resolvability of resistivity sounding curve interpretations. 相似文献
9.
A new approach is developed to determine the model parameters of a two-dimensional inclined sheet from self-potential anomaly. In this method, the numerical horizontal self-potential gradient obtained from self-potential anomaly is convolved using Hilbert transform to obtain the vertical self-potential gradient. The complex gradient is the sum of horizontal and vertical gradient anomalies. The horizontal and vertical gradients are plotted in one graph to form the complex gradient graph. By defining few characteristic points and distances along the complex gradient profile, procedures are then formulated using the analytical functions of the complex gradients to obtain the model parameters of sheet-like structures. The validity of the new proposed method has been tested on synthetic data with and without random noise. The obtained parameters are in congruence with the model parameters when using noise-free synthetic data. After adding 10% random error in the synthetic data, the maximum error in model parameters is 11.8%. Moreover, the method have been applied to analyze and interpret the self-potential anomaly measured on a graphite ore body at southern Bavarian woods, Germany to prove its efficiency where an acceptable agreement has been noticed between the obtained results and the other published results. 相似文献
10.
Arkoprovo Biswas 《Journal of the Geological Society of India》2016,88(4):493-502
Inversion of self-potential anomaly for 2-D inclined sheets of infinite horizontal extent has been studied. Least-square inversion and very fast simulated annealing global optimization has been used to model the five parameters of self potential anomaly. The method of least square and very fast simulated annealing global optimization method is compared and analyzed. Very fast simulated annealing can model the noisy and field data of self potential anomaly very precisely than linear inversion technique. However, time taken by very fast simulated annealing inversion is larger than linearized inversion. The comparative analysis has been done on synthetic data (noise free and noisy) and two field data from Bavarian woods anomaly, Germany and Surda anomaly, India to show the efficacy of both the methods. The estimated parameters were compared with those from previous studies using various global optimization algorithms, mainly neural network, genetic algorithm and particle swarm optimization on the same field data sets. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from least-square methods. The present global optimization method is in good agreement with the other global optimization methods in terms of results and computation time. 相似文献
11.
The problem of seismic tomography, in its linearized statement, is characterized by models consisting of many parameters for
velocity structures and hypocenters. The standard approach solves this problem by simultaneously finding both seismic parameters.
In the present communication, we present evidence that the velocity structure can be determined at fixed values of the earthquake
hypocenter parameters. Instead of the standard approach, we use differential one, which allows us to built inversion solutions
stable in relation to significant noise, including errors in the hypocenter parameters as well. We conclude that the greater
the number of hypocenters involved in inversion, the better the tomography result. This conclusion is proved by testing the
Tjornes fault zone in the northeast of Iceland. 相似文献
12.
13.
反转构造在我国含油气盆地中广泛发育,对于油气勘探具有重要意义.本文采用离散元颗粒流方法研究了先存正断层的陡缓程度、倾向组合关系和距离挤压端的远近等因素对断层的反转构造发育及其反转量的影响.模拟结果显示,先存断层的产状及其距离挤压端的远近会影响先存断层的反转次序、反转量,进而影响盖层内反转构造的发育.当先存正断层倾向指向... 相似文献
14.
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2018,11(6):138
Gravity anomalies caused by a thin infinite sheet are interpreted quantitatively based on an integral transform approach which is elegant and simple. The proposed technique depends on the modified Hilbert transform which is called “Sundararajan transform.” The amplitudes of the well-known Hilbert transform and Sundararajan transform are exactly the same but with a phase difference of 270° between them. The interpretation of gravity anomalies due to a thin infinite sheet has been implemented using the Sundararajan transform rather than the well-known Hilbert transform, yielding a straightforward solution. Parameters such as the depth to the top of the sheet (z), the inclination angle (θ), and the amplitude coefficient (K) have been analytically determined using simple mathematical equations. The origin of the causative target can be determined by the intersection point between Hilbert and Sundararajan transforms as well as the intersection point of the amplitudes of the analytic signal of the two transforms. The proposed technique has been first applied to synthetic data where the procedures are clearly illustrated. The effect of noise on the interpretation procedures of the proposed technique has been investigated, showing in general satisfactory results especially depth estimation. However, the most sensitive parameter to noise is the dipping angle, which can be misleading in high level of noise, whereas the least sensitive parameter is the depth. Strictly speaking, the noise does not significantly distort the depth estimation obtained with this proposed technique. Finally, the interpretation of the gravity anomaly across the Mobrun ore body, Noranda, Quebec, Canada, has been carried out using the proposed technique where the parameters are estimated and compared to the results that have been published in literatures using different techniques. 相似文献
15.
地面核磁共振正则化反演方法研究 总被引：2，自引：1，他引：1
不同的模型约束对基于正则化反演技术的地面核磁共振测深数据反演影响很大。利用理论数据讨论了平坦模型和光滑模型约束及与之相关的正则化参数对反演结果的影响规律。模拟表明,无论是高信噪比数据,还是低信噪比数据,反演的含水量在小正则化参数时,对模型约束的依赖性不大,主要受正则化参数影响。大正则化参数时反演分辨率低,而小正则化参数在保证数据拟合精度提高的同时,增加了模型的分辨率,能获得更可靠的含水量分布。 相似文献
16.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(4):365-373
A three-dimensional interpretation of the newly compiled Bouguer anomaly map of the Main Ethiopian Rift is discussed. Then, the crustal thickness distribution beneath the Main Ethiopian Rift is confirmed using a — dimensional inverse approach to gravity data interpretation. The depths to the crust-upper mantle interface form the inversion parameters. Both approaches are constrained with the results of the seismic refraction experiments of the region. The degree of ambiguity of the final model parameters is then quantified.The Bouguer anomalies along the axial portion of the rift floor, as deduced from the results of the regional and residual separation, are mainly caused by deep-seated structures. The high resolution 3-D forward modeling reveals a possible crustal thickness and density distribution beneath the graben.The results of the inversion confirm a strong crustal attenuation zone (≤ 31 km) closely associated with the rifting of the graben and an abrupt fall of the Moho interface on either side of the rift (up to 51 km) related to the formation of the western and southeastern plateaus. However, no indication of crustal separation is observed.The ambiguity analysis reveals that greater ambiguity of the model parameters exists in the southeastern plateau. There, these model parameters represent the depths to the Moho interface where the seismic control is relatively less. 相似文献
17.
18.
ZHANG Letian YE Gaofeng JIN Sheng WEI Wenbo Martyn UNSWORTH Alan G. JONES JING Jianen DONG Hao XIE Chengliang Florian LE PAPE Jan VOZAR 《《地质学报》英文版》2015,89(1):90-104
Project INDEPTH (InterNational DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric (MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-profile conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized. 相似文献
19.
V. Chakravarthi S. Rajeswara Sastry M. Pramod Kumar 《Journal of the Geological Society of India》2014,83(5):577-585
A method coupled with a GUI based computer program, FRGMLSTRK, coded in JAVA, has been developed to interactively model the gravity anomalies of strike-limited listric fault sources where the detached hanging wall of the structure consists of several geologic formations that have different densities and thicknesses. The program is simple and user friendly in the sense that it allows interactive model construction and modification, the display of fault geometry, depth and the densities of various sub-surface formations, and real-time computation of the gravity anomalies arising from the model. The non-planar fault planes are analytically constructed by fitting a polynomial function of arbitrary but specific degree to a set of points selected on the fault plane by means of a few mouse clicks in the structure panel of the graphical layout. Further, input parameters pertaining to depths and densities of formations can be specified by means of mouse clicks in respective panels. Subsequent changes in these parameters can be realized by simple drag and drop mouse operations. The modeled gravity anomalies are automatically updated and displayed whenever changes are made to: (i) the geometry of the fault plane; (ii) depths of density interfaces; and (iii) densities of formations. These changes can be made either independently or in combination. In addition to displaying the results in graphical form, the code also generates the output in ASCII format. The applicability of the code is demonstrated with both a simple synthetic model and real-world gravity anomalies from the margin of the Chintalpudi sub-basin in India. 相似文献
20.
覆盖区地质填图是新时期地质填图的重要方向.音频大地电磁法（AMT）是覆盖区地质填图的重要地球物理方法之一,可以为地层和基岩面的刻画提供电性参数的约束.然而,常规的AMT反演无法精确刻画电性异常体的边界,且当缺乏其他地质与地球物理资料约束时,难以进行地质解译.针对此问题,基于数值模拟结果的可行性,利用哈密烟墩戈壁覆盖区的4条实测AMT剖面探讨了AMT约束反演在地层识别中的应用效果.相位张量分析指示研究区浅部（> 1 Hz）电性结构表现为二维特征,深部受三维结构影响;浅部为低阻,深部电阻率逐渐升高.采用不加约束二维反演获得了4条剖面的地下（< 3 km）电性结构.基于研究区的重力异常、地震解译结果、物性和钻孔资料,在二维反演结果上初步划分了渐新统-中新统和侏罗系地层的底界面;进而以这两个界面建立先验模型,并根据物性资料设置电阻率变化范围,进行AMT约束反演,获得了更优化的反演结果以及清晰可靠的渐新统-中新统和侏罗系的底界面.结果显示,研究区渐新统-中新统地层电阻率值略小于10 Ω?m,其底界面平均埋深为120 m;侏罗系电阻率值为10~100Ω?m,其底界面最深可达2 km.基岩面（侏罗系底界面）埋深整体上呈现为东南深、西北浅,这指示哈密烟墩地区中生代以来的沉积中心在东南部;此外,侏罗系地层与下伏的古生界地层存在角度不整合.研究表明,哈密烟墩地区新生代以来可能受到了近南北向应力挤压,在研究区中部形成近东西或北东东向的侏罗系隆凹相间的构造地貌格局.而渐新统-中新统地层底部的不整合面可能反映了后期褶皱构造的影响,这种隆凹作用相伴的褶皱构造可能具有同沉积性质. 相似文献