利用Radon变换进行三度体重磁异常反演   总被引：5，自引：0，他引：5       下载免费PDF全文

孟小红  王霞 《地球科学》1995,20(5):594-598

从Ｒａｄｏｎ变换角度分析解释了重磁三度体异常和二度体异常之间的等价关系，提出了利用Ｒａｄｏｎ正变换将三度体异常转化为二度体异常，对二度体异常做一维反演，然后将反演结果通过反Ｒａｄｏｎ变换实现三维场源图象重建的思想，并付诸实施，在微机上通过模型检验，证明该方法实用、可行。  相似文献   

元素迁移的分维结构、级序路径及共轭地球化学异常存在的理论依据   总被引：5，自引：0，他引：5  

周永章  卢焕章 《地球化学》1995,24(1):9-75

微量元素在矿源岩（层）中迁移遵循严格的级序路径，并且存在两种迁移倾向。迁移的结果图象是一分维结构。两种共轭地球化学异常出现的有利环境是温度高度反差地区和大断裂系及其附近。  相似文献   

地电前兆异常特征及澜沧—耿马7.6级等地震预报问题     

汪志亮  王志贤 《地震》1995,(3):240-245

深入研究了全国地电台网内M_s≥5.0的45次地电前兆震例,用统计方法按大震、强震、中强地震分别研究其地电前兆特征。 通过研究得到:大震地电阻率异常范围,其半径超过200km,在700km以内,异常时间在12—20个月内发震的概率最高,为97.8％;强震地电阻率异常范围大多在300km以内,趋势异常的时间在12个月以内发震的概率最高,为86.5％;中强地震地电阻率异常范围,半径一般在200km以内,趋势异常时间在180天之内发震的概率最高,为95.0％。大震、强震、中强地震地电趋势异常时间似乎存在着20个月、12个月、6个月三个不同的异常时间段。 临震异常类型一般可分为加速型、转向型和波动型三类。对7级和7级以上大震能观测到临震异常前兆的震例只有33.3％、强震和中强地震能观测到临震异常前兆的震例均为50.0％。出现临震异常后1—20天发震的概率最高,达94.4％。 1988年11月以来,西部地区先后发生澜沧-耿马7.6、巴塘6.7、天祝6.2级地震。震前都曾依据地电前兆短临异常特征,作过某种程度的监测预报工作,取得了较好的短临预报效果。  相似文献   

Analysis of a large extent aeromagnetic survey near the geomagnetic equator (Minas Gerais,Brazil)     

M. S. M. Mantovani  W. Shukowsky 《Pure and Applied Geophysics》1982,120(4):784-794

A large extent aeromagnetic survey, covering a 9°×9° degree of a Precambrian shield area in SE Brazil, was used to analyse long wavelength magnetic anomalies with the purpose of determining the magnetic structure of the lithosphere.Data analysis based on a novel approach to the estimation of the parameters in the statistical model ofSpector andGrant (1970), reveals a highly magnetized lower crust, bounded by an essentially non-magnetic upper mantle. The highly magnetized layer can be associated with a higher density lower crust model, derived from gravity and seismic data available in the area, suggesting a compositional transition from upper to lower crust.It was also verified that the operation of reduction to the pole, which is singular at the geomagnetic equator, performs quite satisfactorily at the low geomagnetic inclination of the area, bringing into accordance the long wavelength anomalies with the structural trends.  相似文献   

A Fourier transform method for the interpretation of self-potential anomalies due to two-dimensional inclined sheets of finite depth extent     

D. Atchuta Rao  H. V. Ram Babu  G. D. J. Sivakumar Sinha 《Pure and Applied Geophysics》1982,120(2):365-374

The self-potential anomaly due to a two-dimensional inclined sheets of finite depth extent has been analysed in the frequency domain using the Fourier transform. Expression for the Fourier amplitude and phase spectra are derived. The Fourier amplitude and phase spectra are analysed so as to evaluate the parameters of the sheet. Application of this method on two anomalies (synthetic and field data) has given good results.  相似文献   

Improved magnetic anomalies of the Antarctic lithosphere from satellite and near-surface data     

Hyung Rae Kim  Ralph R. B. von Frese  Patrick T. Taylor  Alexander V. Golynsky  Luis R. Gaya-Piqué  Fausto Ferraccioli 《Geophysical Journal International》2007,171(1):119-126

The Antarctic magnetic anomaly map compiled marine and airborne surveys collected south of 60°S through 1999 and used Magsat data to help fill in the regional gaps between the surveys. Ørsted and CHAMP satellite magnetic observations with greatly improved measurement accuracies and temporal and spatial coverage of the Antarctic, have now supplanted the Magsat data. We combined the new satellite observations with the near-surface survey data for an improved magnetic anomaly map of the Antarctic lithosphere. Specifically, we separated the crustal from the core and external field components in the satellite data using crustal thickness variations estimated from the terrain and the satellite-derived free-air gravity observations. Regional gaps in the near-surface surveys were then filled with predictions from crustal magnetization models that jointly satisfied the near-surface and satellite crustal anomalies. Comparisons in some of the regional gaps that also considered newly acquired aeromagnetic data demonstrated the enhanced anomaly estimation capabilities of the predictions over those from conventional minimum curvature and spherical harmonic geomagnetic field models. We also noted that the growing number of regional and world magnetic survey compilations involve coverage gaps where these procedures can contribute effective near-surface crustal anomaly estimates.  相似文献   

Source, path and receiver effects on seismic surface waves     

Ana M. G. Ferreira  John H. Woodhouse 《Geophysical Journal International》2007,168(1):109-132

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Geomorphic constraints on the active tectonics of southern Taiwan     

Lucy A. Ramsey  Richard T. Walker  James Jackson 《Geophysical Journal International》2007,170(3):1357-1372

Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world.  相似文献   

Interpretation of Gravity Anomalies with the Normalized Full Gradient (NFG) Method and an Example     

Ali Aydin 《Pure and Applied Geophysics》2007,164(11):2329-2344

The Normalized Full Gradient (NFG) method which was put forward about 50 years ago has been used for downward continuation of gravity potential data, especially in the former Union of Soviet Socialist Republics. This method nullifies perturbations due to the passage of mass depth during downward continuation. The method depends on the downwards analytical continuation of normalized full gradient values of gravity data. Analytical continuation discriminates certain structural anomalies which cannot be distinguished in the observed gravity field. This method has been used in various petroleum and tectonic studies. The Trapeze method was used for the determination of Fourier coefficients during the application of this method. No other techniques for calculating these coefficients have been used. However, the Filon method was used for the determination of Fourier coefficients during the application of the NFG method in this work. This method, rather than the Trapeze method, should be preferred for indicating abnormal mass resources at the lower harmonics. In this study, the NFG method using the Filon method has been applied the first time to theoretical models of gravity profiles as example field at the Hasankale-Horasan petroleum exploration province where successful results were achieved. Hydrocarbon presence was shown on the NFG sections by the application of NFG downward continuation operations on theoretical models. Important signs of hydrocarbon structure on the NFG section for field and model data at low harmonics are obtained more effectively using this method.  相似文献   

对重力势二阶垂直偏导数的一种新的取样方法     

AHMED  A.  KHAMIES  许军才 《火山地质与矿产》2007,28(4):242-248

从目前的研究来看，二阶垂直导数（X和Y两个方向）的求解方法较简单，它采用的五个因子的数字滤波的最小二乘法来优化数据。但是在较小区域面积时（对工程和环境应用中的重力数据），重力异常很容易放大和被区域重力场掩盖，我们认为产生的缘由是表示重力场的x和y方向上的二次多项式引起的。因此，为了逼近重力水平方向的偏导可以设计一个好的滤波器来拟合在xy平面的重力场值，再得出想要的重力垂直方向偏导，文中最后对提出的方法在前人经典模型上和野外实践进行了验证。  相似文献