共查询到20条相似文献，搜索用时 250 毫秒
1.
N. A. Chujkova L. P. Nasonova T. G. Maximova 《Izvestiya Physics of the Solid Earth》2014,50(3):427-443
The formulas that allow, within the quadratic approximation, for the contribution of the anomalous masses, distributed along the height relative to the reference ellipsoid, in the Stokes parameters are derived. It is shown that the contribution of the quadratic terms is largest and commensurate, by the order of magnitude, with the linear contribution if the anomalous masses have a dipole distribution along the height. The quadratic contribution is particularly significant for Mars, where the span of relative variations in the surface topography is by an order of magnitude larger than in the Earth. The problem is solved and the method is developed for finding the depths of compensation for the topographical harmonics of different order and degree. The most probable levels of compensation for topographic irregularities are determined by the analysis of the distribution histograms for the depths of compensation. The maps of lateral distributions of the compensating masses at the selected levels are calculated. It is shown that the observed anomalous structures generate the anomalies in the internal gravity field, which may serve as a cause for the convective motion in the mantle and core of the planet. Besides, the probable nonisostatic vertical stresses in the crust and mantle of the Earth and Mars are calculated. 相似文献
2.
气体是识别构造带展布和活动的敏感组分。 对唐山断裂带高空间分辨率气体地球化学测量数据进行了变异函数计算, 分析了断裂带活动性与断裂带气体浓度的定量关系。 结果表明, 断裂带本身结构特性是控制断裂带气体空间分布的主要因素, 高倾角断裂在地表以狭长条带状为主要特征, 分布气体浓度高值异常, 交会处气体浓度高值异常以环带形式围绕断裂分布。 沿断裂带走向, 各气体浓度呈高值分布, 利用变异函数计算, 确定各气体组分在测量区域内气体浓度与构造相关的空间范围, 据此确定了唐山断裂各段构造敏感气体组分, 在断裂带周边圈定出断裂带活动性重点监测区域。 断裂带气体浓度克里金插值分析结果表明, 唐山地区滦县—乐亭断裂带活动性较强, 唐山断裂带次之, 蓟运河断裂带活动性最弱。 断裂带交会处, 浓度高值异常分布更加明显。 相似文献
3.
本文通过概率成像法、α中心法、遗传算法的有机结合, 实现了2-D电阻率层析成像非线性反演.首先,根据概率成像结果指示出的2-D地质异常体的相对电性和大致分布范围,合理地确定出α中心的位置与强度系数的变化范围.其次,以α中心法作为2-D地电结构的正演手段,采用遗传算法反演出各α中心的强度系数.在此基础上, 应用α中心法重新构建出地下介质电阻率的分布.通过对均匀半空间中赋存2-D地质异常体模型的反演试验, 获得了令人满意的结果. 相似文献
4.
利用地下水位预报地震的新思路与新方法 总被引：3，自引：1，他引：3
根据井孔水位的不同反应，分别采用不同方法对水位进行含水层应力的演和异常信息的提取，并分别给出了对应地震的概率。对含水层应力异常展开了时空演化和频次分析，从而提出了大同地震是区域应力场演化的结果，在这一演化过程中，井孔含水 应力异常具有异常空间分布的区域性、异常时间分布的阶段性和异常时空转移特征，以及异常频次与震中的一致性。 相似文献
5.
The high-precision air navigation tools developed in recent decades enable airborne gravity measurements that are suitable for solving many problems of geophysical exploration. In Russia, experiments along these lines were initiated in 1997–1998. Profile and areal surveys of a rather complex gravity field could be carried out with an accuracy of about 1 mGal. Knowledge of the plumb line declination (PLD) is needed in various areas of geophysics and geodesy. On the basis of airborne gravity observations, it is possible to use gravity data for calculating PLDs in both plain and mountainous regions. In the latter case, a correction for the effect of topographic masses is introduced into calculation formulas. With the use of the S-approximation method, based on the representation of harmonic functions as the sum of the potentials of simple and double layers on a certain carrier (in particular, on a horizontal plane), the gravity field was reconstructed from measurements at any point of space (at any altitude of measurement), in particular, on the surface of a geoid. A software package was specially developed for the PLD calculation by the Vening Meinesz formulas (the PLD calculation in a zeroth approximation) and methods of reconstructing anomalous fields on basis of S-approximations. Results of real-data calculations for one area of Russia are presented. 相似文献
6.
7.
本文提出了磁总场异常垂直梯度三维相关成像方法,用于成像地下等效磁源分布.它首先将地下待成像空间划分为三维规则网格,然后直接计算每个网格节点磁偶板子在观测面理论磁总场异常垂直梯度与实测磁总场异常垂直梯度的互相关,其相关系数值表征等效磁偶极子分布(即磁偶极子发生的概率).理论长方体组合模型数据和实际某矿区磁测资料试验结果表明本文方法计算得到的相关系数值能基本反映地下的磁源分布,且分辨率明显高于磁总场异常三维相关成像的分辨率,也高于基于熵滤波分离异常的磁总场异常三维相关成像的分辨率. 相似文献
8.
大足石刻是中国现存的重要石质文物之一,具有重要的历史和文化价值,其中有的石刻造像曾被列为国家石质文物保护“一号工程”;最近,文物保护部门又启动了对危岩体的加固和防渗工程。为确定大足石刻宝顶山大佛湾岩体中破碎带发育情况,应用跨孔弹性波CT技术对指定位置的工程岩体进行了探测。CT探测得到的岩体弹性波速成像清楚地揭示了两个钻孔之间岩体中破碎带的规模和产状,与岩体所在的区域地质构造应力场作用协调一致,证明了探测成像结果的可靠性,为大佛湾岩体的渗流和稳定性评估提供了依据。 相似文献
9.
根据2003年中国地磁观测数据（包括135年地磁测点和35个地磁台）以及我国邻近地区38个IGRF计算点的地磁数据,计算中国地磁异常场的分布。选取两种地磁场模型作为地磁正常场,一是国际参考地磁场的球谐模型,二是中国地磁场泰勒多项式模型。根据各个测点的地磁异常值（观测值减去模型计算值）,用球冠谐分析方法计算地磁异常场的球冠谐模型,并绘制2003年中国地磁异常（△D,△I,△F,△X,△Y,△Z）。分析和讨论了中国地磁异常场。 相似文献
10.
The Laboratory of Geophysics of the University of Arizona was presented with an exploration problem by Falconbridge, Ltd. of Canada. Massive mineralized hemispherical “pods” are in the vicinity of a tuff layer of high conductivity and induced polarization response, covered by large thicknesses of resistive volcanics. The initial approach was to utilize electrolytic tank modeling. The extreme resistivity and IP contrasts proved to be difficult to recreate. Two dimensional modeling was attempted next with conductive paper, using copper and silver paint for anomalous masses. This method also proved inadequate. Finally, mathematical equations were solved which could model any arbitrary anomalous body in any steady state electrical field. Plane waves as well as point current sources producing non-plane waves are possible. Finite difference equations were derived for the non-linear partial differential equations under consideration. The equations were solved using a digital computer. Initially, the boundary conditions had to be satisfied at the boundaries of resistivity changes, severely restricting possible geometric shapes for anomalous bodies. The final and successful solution was to apply numerical techniques to obtain solutions of equations which require only that the relative resistivities through the area be specified. The Falconbridge problem and its solution are analyzed. 相似文献
11.
Geological interpretation based on gravity gradiometry data constitutes a very challenging problem. Rigorous 3D inversion is the main technique used in quantitative interpretation of the gravity gradiometry data. An alternative approach to the quantitative analysis of the gravity gradiometry data is based on 3D smooth potential field migration. This rapid imaging approach, however, has the shortcomings of providing smooth images since it is based on direct integral transformation of the observed gravity tensor data. Another limitation of migration transformation is related to the fact that, in a general case, the gravity data generated by the migration image do not fit the observed data well. In this paper, we describe a new approach to rapid imaging that allows us to produce the density distribution which adequately describes the observed data and, at the same time, images the structures with anomalous densities having sharp boundaries. This approach is based on the basic theory of potential field migration with a focusing stabilizer in the framework of regularized scheme, which iteratively transfers the observed gravity tensor field into an image of the density distribution in the subsurface formations. The results of gravity migration can also be considered as an a priori model for conventional inversion subsequently. We demonstrate the practical application of migration imaging using both synthetic and real gravity gradiometry data sets acquired for the Nordkapp Basin in the Barents Sea. 相似文献
12.
13.
Following the probability tomography principles previously introduced to image the sources of electric and electromagnetic anomalies, we demonstrate that a similar approach can be used to analyse gravity data. First, we give a coherent derivation of the Bouguer anomaly concept as a Newtonian-type integral for an arbitrary mass distribution buried below a non-flat topography. A discretized solution of this integral is then derived as a sum of elementary contributions, which are cross-correlated with the gravity data function in the expression for the total power associated with the Bouguer anomaly. To image the mass distribution underground we introduce a mass contrast occurrence probability function using the cross-correlation product of the observed Bouguer anomaly and the synthetic field due to an elementary mass contrast source. The tomographic procedure consists of scanning the subsurface with the elementary source and calculating the occurrence probability function at the nodes of a regular grid. The complete set of grid values is used to highlight the zones of highest probability of mass contrast concentrations. Some synthetic and field examples demonstrate the reliability and resolution of the new gravity tomographic approach. 相似文献
14.
Domenico Patella 《Geophysical Prospecting》1997,45(4):653-681
A new approach to self-potential (SP) data interpretation for the recognition of a buried causative SP source system is presented. The general model considered is characterized by the presence of primary electric sources or sinks, located within any complex resistivity structure with a flat air-earth boundary. First, using physical considerations of the nature of the electric potential generated by any arbitrary distribution of primary source charges and the related secondary induced charges over the buried resistivity discontinuity planes, a general formula is derived for the potential and the electric field component along any fixed direction on the ground surface. The total effect is written as a sum of elementary contributions, all of the same simple mathematical form. It is then demonstrated that the total electric power associated with the standing natural electric field component can be written in the space domain as a sum of cross-correlation integrals between the observed component of the total electric field and the component of the field due to each single constitutive elementary charge. By means of the cross-correlation bounding inequality, the concept of a scanning function is introduced as the key to the new interpretation procedure. In the space domain, the scanning function is the unit strength electric field component generated by an elementary positive charge. Next, the concept of charge occurrence probability is introduced as a suitable function for the tomographic imaging of the charge distribution geometry underground. This function is defined as the cross-correlation product of the total observed electric field component and the scanning function, divided by the square root of the product of the respective variances. Using this physical scheme, the tomographic procedure is described. It consists of scanning the section, through any SP survey profile, by the unit strength elementary charge, which is given a regular grid of space coordinates within the section, at each point of which the charge occurrence probability function is calculated. The complete set of calculated grid values can be used to draw contour lines in order to single out the zones of highest probability of concentrations of polarized, primary and secondary electric charges. An extension to the wavenumber domain and to three-dimensional tomography is also presented and discussed. A few simple synthetic examples are given to demonstrate the resolution power of the new SP inversion procedure. 相似文献
15.
A new approach to evaluate the extreme value distribution （EVD） of the response and reliability of general multi-DOF nonlinear stochastic structures is proposed. The approach is based on the recently developed probability density evolution method, which enables the instantaneous probability density functions of the stochastic responses to be captured. In the proposed method, a virtual stochastic process is first constructed to satisfy the condition that the extreme value of the response equals the value of the constructed process at a certain instant of time. The probability density evolution method is then applied to evaluate the instantaneous probability density function of the response, yielding the EVD. The reliability is therefore available through a simple integration over the safe domain. A numerical algorithm is developed using the Number Theoretical Method to select the discretized representative points. Further, a hyper-ball is imposed to sieve the points from the preceding point set in the hypercube. In the numerical examples, the EVD of random variables is evaluated and compared with the analytical solution. A frame structure is analyzed to capture the EVD of the response and the dynamic reliability. The investigations indicate that the proposed approach provides reasonable accuracy and efficiency. 相似文献
16.
Time domain electromagnetic (TDEM) response is usually associated with eddy currents in conductive bodies, since this is the dominant effect. However, other effects, such as displacement currents from dielectric processes and magnetic fields associated with rock magnetization, can contribute to TDEM response. In this paper we analyze the effect of magnetization on TDEM data. We use a 3-D code based on finite-difference method, developed by Wang and Hohmann [Geophysics 58 (1993) 797], to study transient electromagnetic field propagation through a medium containing bodies with both anomalous conductivity and anomalous magnetic permeability. The remarkable result is that the combination of anomalous conductivity and permeability within the same body could increase significantly the anomalous TDEM response in comparison with purely conductive or purely magnetic anomalies. This effect has to be taken into account in interpretation of TDEM data over electrical inhomogeneous structures with potentially anomalous magnetic permeability. 相似文献
17.
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
18.
The deep learning method has made nurnerials achievements regarding anomaly detection in the field of time series. We introduce the speech production model in the field of artificial intelligence, changing the convolution layer of the general convolution neural network to the residual element structure by adding identity mapping, and expanding the receptive domain of the model by using the dilated causal convolution. Based on the dilated causal convolution network and the method of log probability density function, the anomalous events are detected according to the anomaly scores. The validity of the method is verified by the simulation data, which is applied to the actual observed data on the observation staion of Pingliang geoeletric field in Gansu Province. The results show that one month before the Wenchuan MS8.0, Lushan MS7.0 and Minxian-Zhangxian MS6.6 earthquakes, the daily cumulative error of log probability density of the predicted results in Pingliang Station suddenly decreases, which is consistent with the actual earthquake anomalies in a certain time range. After analyzing the combined factors including the spatial electromagnetic environment and the variation of micro fissures before the earthquake, we explain the possible causes of the anomalies in the geoelectric field of before the earthquake. The successful application of deep learning in observed data of the geoelectric field may behefit for improving the ultilization rate both the data and the efficiency of detection. Besides, it may provide technical support for more seismic research. 相似文献
19.
使用相关方法和welch法计算功率谱密度研究汶川地震前后GPS TEC在时域和频域上的变化,并进一步分析NmF2空间分布变化.得出主要结论, 震前5月9日开始TEC平常具有良好的相关性被打破,24 h全日波、12 h半日波成分功率谱密度幅度值变化明显.5月12日至6月11日NmF2变化幅度明显增大.研究结果显示,TEC和NmF2时空分布变化存在电离层震前扰动和同震响应, 并且TEC震后的异常变化相比震前更加显著.表明使用的方法可以有效检测到地震发生前后电离层异常扰动信号. 相似文献
20.
The depth determination from the gravity data in frequency domain is carried out using the classical fast Fourier transform
(FFT) method utilizing scaling properties of ensemble of anomalous source. The problem of calculating power spectrum from
the FFT is well described in the literature. Here, the application of other high-resolution methods of power spectrum calculation,
such as maximum entropy method (MEM) and multi-taper method (MTM) are explored to estimate depth to anomalous sources. At
the outset, the FFT, the MEM and the MTM are tested on synthetic gravity data, generated for different types of synthetic
models and then all these methods are applied to the field gravity data of the Bengal basin. The MTM with scaling is found
to be superior for providing the detailed subsurface information rather than the MEM and the FFT methods in the case of synthetic
as well as field examples. 相似文献