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Yu. P. Tsvetkov O. M. Brekhov S. V. Filippov T. N. Bondar A. A. Ivanov A. V. Krapivnyi N. S. Nikolaev 《Geomagnetism and Aeronomy》2007,47(4):510-514
The errors of measurements of vertical geomagnetic gradients at altitudes of 20–40 km, using a balloon magnetic gradiometer with a 6-km-long measuring base oriented along gravity, have been studied in the work. The errors related to the deviation of the measuring base position relative to the vertical have been studied during the real balloon flight with the help of the navigation GPS receivers. The deviations of the measuring base within 5°, which can sometimes reach 15°, have been obtained. This results in a decrease in the magnetic gradient measurement accuracy due to the errors introduced in the specification of the normal magnetic field used to detect magnetic anomalies. To eliminate this error, a GPS receiver was built in each magnetometer in order to observe magnetometers during synchronous measurements and to correct the measurements for the normal magnetic field. It has been indicated that the effect of deviations of the measuring base position on the results is not more than 2% of the measured value at such organization of a gradiometer. 相似文献
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The feasibility of electromagnetic gradiometer measurements 总被引：1，自引：0，他引：1
The quantities measured in transient electromagnetic (TEM) surveys are usually either magnetic field components or their time derivatives. Alternatively it might be advantageous to measure the spatial derivatives of these quantities. Such gradiometer measurements are expected to have lower noise levels due to the negative interference of ambient noise recorded by the two receiver coils. Error propagation models are used to compare quantitatively the noise sensitivities of conventional and gradiometer TEM data. To achieve this, eigenvalue decomposition is applied on synthetic data to derive the parameter uncertainties of layered-earth models. The results indicate that near-surface gradient measurements give a superior definition of the shallow conductivity structure, provided noise levels are 20–40 times smaller than those recorded by conventional EM instruments. For a fixed-wing towed-bird gradiometer system to be feasible, a noise reduction factor of at least 50–100 is required. One field test showed that noise reduction factors in excess of 60 are achievable with gradiometer measurements. However, other collected data indicate that the effectiveness of noise reduction can be hampered by the spatial variability of noise such as that encountered in built-up areas. Synthetic data calculated for a vertical plate model confirm the limited depth of detection of vertical gradient data but also indicate some spatial derivatives which offer better lateral resolution than conventional EM data. This high sensitivity to the near-surface conductivity structure suggests the application of EM gradiometers in areas such as environmental and archaeological mapping. 相似文献
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Application of Hilbert‐like transforms for enhanced processing of full tensor magnetic gradient data 
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下载免费PDF全文 M. Schiffler M. Queitsch R. Stolz H.‐G. Meyer N. Kukowski 《Geophysical Prospecting》2017,65(Z1):68-81
Commonly, geomagnetic prospection is performed via scalar magnetometers that measure values of the total magnetic intensity. Recent developments of superconducting quantum interference devices have led to their integration in full tensor magnetic gradiometry systems consisting of planar‐type first‐order gradiometers and magnetometers fabricated in thin‐film technology. With these systems measuring directly the magnetic gradient tensor and field vector, a significantly higher magnetic and spatial resolution of the magnetic maps is yield than those produced via conventional magnetometers. In order to preserve the high data quality in this work, we develop a workflow containing all the necessary steps for generating the gradient tensor and field vector quantities from the raw measurement data up to their integration into highresolution, lownoise, and artefactless two‐dimensional maps of the magnetic field vector. The gradient tensor components are processed by superposition of the balanced gradiometer signals and rotation into an Earth‐centred Earth‐fixed coordinate frame. As the magnetometers have sensitivity lower than that of gradiometers and the total magnetic intensity is not directly recorded, we employ Hilbert‐like transforms, e.g., integration of the gradient tensor components or the conversion of the total magnetic intensity derived by calibrated magnetometer readings to obtain these values. This can lead to a better interpretation of the measured magnetic anomalies of the Earth's magnetic field that is possible from scalar total magnetic intensity measurements. Our conclusions are drawn from the application of these algorithms on a survey acquired in South Africa containing full tensor magnetic gradiometry data. 相似文献
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A method is proposed to detect buried magnetite concentrations within river sediments. Model studies show that relatively small (thickness 1 m, width 10 m) plate-shaped volumes with magnetite contents of 0.5% within a non-magnetic matrix can be detected by a detailed ground magnetic survey using a sensitive (0.1 nT) magnetometer. Tests along lines perpendicular to the river but at a different angle to the bedrock trend (or the aeromagnetic anomaly trend) reveal that essentially all total field and vertical’gradient’anomalies detected in the profiles are elongated in the river and/or valley direction. This shows that the anomaly sources are (buried) volumes of higher magnetite content within the river sediments. Further evidence for this is (1) that higher intensity total field and vertical’gradient’anomalies occur in an area where the river cuts through strongly magnetic serpentinites, (2) the absence of high frequency anomalies over unsorted glacial till, and (3) some features on power spectra. Relatively large volumes of high magnetite concentrations within the river sediments may well contain the highest concentration of heavy economic minerals such as gold. Consequently, the areas of greatest interest in the exploitation of buried placers may be selected from maps obtained by detailed magnetic surveys either on the ground or at low altitude by helicopter. 相似文献
6.
H. LINSSER 《Geophysical Prospecting》1971,19(2):243-252
The considerable increase of sensitivity of new magnetometers allows the elaboration of magnetometric maps with contour intervals of fractions of one gamma. On these maps, small anomalies appear which had never been visible before. They are caused by susceptibility contrasts within the sediments. The areal distribution of these small undulations of the magnetic field depends on tectonics, therefore their analysis can give useful information about the tectonic pattern of the sediments. This paper discusses the automatic transformation of these small anomalies into tectonic units. The problem is solved by a method called Digital Template Analysis which has already yielded very useful results in gravity interpretation. The application of the method described is restricted to surveys executed by high sensitivity magnetometers. Therefore it is supposed that in most oil exploration problems these magnetometers will replace instruments with lower sensitivity. The improved magnetometer surveys in combination with the interpretation method described represent a most efficient, fast and unexpensive reconnaissance method. 相似文献
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A triple axis borehole magnetometer is described that consists of a Förster-probe (fluxgate) triplet (sensitivity 1 n T), a Förster-probe gradiometer (sensitivity 2 nT/40 cm), a gyro unit (mean angular drift approx. 0.5°/h) which is equipped with accelerometers (sensitivity 1/100°), and a data transmission unit (with multiplexer and 16-bit AD converter). The sensitive fluxgate-magnetometer can detect weakly magnetic or small source bodies. Data from the gyro and the accelerometers allow the 3-component magnetic field values to be transformed to north, east and vertical components. Since they do not rely on magnetically-determined directional data, the results are not disturbed by local anomalies of the magnetic declination. Furthermore, the magnetometer can also be used in vertical boreholes. 3-component measurements are carried out at discrete points in the neighbourhood of a source body to locate its position, and within the source body to determine the direction of magnetization. The strength of magnetization and information on magnetic classification are obtained by continuous measurement of one or more components within the source body. Calculation algorithms and computer programs are available to simplify data processing and interpretation. Survey examples are discussed. 相似文献
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重、磁勘探具有效率高、成本低、工作范围广等优点,已在地球物理勘探中得到了广泛应用.前人大多在不考虑重、磁勘探观测精度的条件下进行了垂向识别能力的研究,但在考虑重、磁观测精度条件下,重力（重力异常、重力张量）与磁力（磁力异常、磁力三分量、磁力张量）对孤立异常的垂向识别能力如何则需要进行深入的理论研究.本文从重、磁场正演理论出发,以球体（点源模型）和无限延伸水平圆柱体（线源模型）为例,考虑给定观测精度条件下,以重力和磁力幅值大小与观测精度的关系来研究垂向识别能力,从而消除了背景场的影响,提高了研究结果的可靠度.通过研究表明,对于孤立异常,重力张量在浅部一定深度内比重力异常的垂向识别能力强,该深度与重力异常和重力张量观测精度的比值成正比;垂直磁化磁力张量在浅部一定深度内比化极磁力异常的垂向识别能力强,该深度与磁力异常与磁力张量观测精度的比值成正比;磁力在浅部一定深度内比重力的垂向识别能力强,该深度与地质体的磁化强度和剩余密度比值、重力观测精度和磁力观测精度比值成正比.通过重力和磁力垂向识别能力的研究将为重、磁勘探的实际应用起到指导作用. 相似文献
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瞬变电磁法(TEM)作为地球物理非地震探勘主要电磁方法之一,广泛应用于油气、矿产等地下资源探测.本文分析TEM磁场传感器频率响应特点,采用欠阻尼匹配拓展传感器线性响应频率范围;分析磁传感器各类噪声源分布,提出不同频段上影响磁传感器性能的主要因素.最终研制一款高磁导率磁芯的TEM感应式磁场传感器,工作频段为10 mHz~1 kHz,等效输入噪声水平为4pT/√Hz@1Hz, 15fT/√Hz@200 Hz,传感器直径为50 mm,长度800 mm,重量3.2 kg,相比现有TEM接收磁场传感器,体积小、重量轻、工作频段低.实验测试与生产作业表明:最新研制的高灵敏度TEM磁场传感器更加适合大深度、3D阵列电磁勘探. 相似文献
10.
C. R. COLLIN A. SALVI D. LEMERCIER P. LEMERCIER F. ROBACH 《Geophysical Prospecting》1973,21(4):704-715
The aim of this article is to describe the double resonance magnetometer system designed and built by the Division de Magnétométrie of the C.E.N. Grenoble, and used by the Département des Recherches Minières du CE.A. For the measurement of magnetic anomalies of geological origin it is necessary to make differential measurements between a mobile instrument which scans the region of interest and a fixed compensatory instrument. The apparatus described here features the following main characteristics: — it gives a direct numerical measurement of the differential magnetic field between the two instruments with an accuracy of 0.01 gamma (10-7 Oe). — it is designed to be easily operated in geological field work (light weight, low power, possibility to make continuous measurements along a given profile, the measuring signals being radio-linked there are no wires connecting the instruments). Firstly we describe the components of the magnetometer itself namely: double resonance magnetometer heads and differential numerical magnetometer. Secondly we describe the measuring technique. 相似文献
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D. G. Taimazov 《Seismic Instruments》2009,45(1):115-118
A vertical gravimetric gradient meter is described that is presented by the author and uses large hydrostatic forces with metacenters dispersed along the vertical coordinate and a weak-loaded string converter for actuating on test object in opposite directions. The calculating accuracy of the gradiometer is about ±0.10 E. The possibility of using the gradient meter for precision gravimetric experiments is shown. 相似文献
13.
激发极化法探测油气田——异常成因及其与油气藏关系的探讨 总被引：8，自引：0，他引：8
根据1982年以来在华北、西南、西北、华东等地大小20余个油田上进行激电找油的研究工作,特别对西北K区等油田进行的异常成因机制的剖析工作:激电测井、井中取样分析鉴定、扫描电镜观察、物性测定、数字模拟及同位素分析等,以充分论据证实了引起激电异常的主要地质因素是油藏上方浅部地层中的次生黄铁矿化分布。论述了黄铁矿化与烃类扩迁的密切关系。并对西北K区等油藏上方地层的垂向物质变异的规律,结合实际资料,从理论上进行了分析和解释。最后提出了油藏上覆地层垂向变化的地质-地球化学-地球物理综合参考模型。 相似文献
14.
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
15.
介绍了大连九龙地磁监测中心建设过程中场地磁场梯度的跟踪测量情况。根据中国“地震及前兆数字观测技术规范”电磁部分的要求,在地磁台站建筑施工过程中,需要用质子旋进式磁力仪在施工现场对场地磁场背景进行监测。 相似文献
16.
Robert H. Gilkeson Paul C. Heigold Douglas E. Laymon 《Ground Water Monitoring & Remediation》1986,6(1):54-61
Wastes were to be exhumed and removed from a hazardous and chemical waste disposal site. The major disposal practice was shallow burial of wastes in metal drums in parallel trenches. The actual boundaries of the trenches beneath the landscaped cover were not accurately known.
Theoretical two-dimensional models were used to evaluate the application of magnetic methods to define trench boundaries on the disposal site. The models predicted that both the total field and the vertical component anomalies were diagnostic; however, the vertical component anomaly was more focused on the trench boundaries.
A survey with a vertical component fluxgate magnetometer was successful in defining trench boundaries. Observations made along traverses that trended perpendicular to the long axis of the parallel trenches indicated vertical magnetic intensity values with a cyclical pattern of large positive values over trenches and large negative values over intertrench corridors. Vertical magnetic intensity values determined with theoretical two-dimensional models compared favorably to the observed vertical magnetic values. The models were used to constrain the interpretation of the field observations to define trench boundaries; the magnetic survey defined trench boundaries with an accuracy within ± 2 feet. 相似文献
Theoretical two-dimensional models were used to evaluate the application of magnetic methods to define trench boundaries on the disposal site. The models predicted that both the total field and the vertical component anomalies were diagnostic; however, the vertical component anomaly was more focused on the trench boundaries.
A survey with a vertical component fluxgate magnetometer was successful in defining trench boundaries. Observations made along traverses that trended perpendicular to the long axis of the parallel trenches indicated vertical magnetic intensity values with a cyclical pattern of large positive values over trenches and large negative values over intertrench corridors. Vertical magnetic intensity values determined with theoretical two-dimensional models compared favorably to the observed vertical magnetic values. The models were used to constrain the interpretation of the field observations to define trench boundaries; the magnetic survey defined trench boundaries with an accuracy within ± 2 feet. 相似文献
17.
J. Bitterly J. M. Cantin R. Schlich J. Folques D. Gilbert 《Surveys in Geophysics》1984,6(3-4):233-239
A new portable magnetometer theodolite with fluxgate sensor has been developed for measuring the components of the earth's magnetic field. With this instrument, used as a null detector, it is possible to make absolute measurements of declination (D) and inclination (I). The compensation of the main magnetic field allows direct intensity measurements (H, X, Y, Z components); in this case the calibration is made by reference to a proton magnetometer.The observation procedure is particularly easy and quick. The accuracy is better than 5 sec of arc forD andI and better than 1 nT for direct intensity measurements. 相似文献
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D. H. QUICK 《Geophysical Prospecting》1974,22(4):736-746
Empirical equalities derived from time domain induced polarization scale modelling with the gradient array over simple geometries, and from the potential field functions for equivalent simple charge configurations are similar. The function for the dyke like body is analogous to the magnetic case allowing both total and vertical magnetic field interpretation techniques to be applied to gradient array chargeability anomalies. 相似文献
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卫星重力梯度测量与地球引力场的精度研究 总被引：1，自引：0，他引：1
本文根据地球引力位的球谐函数展开式,利用重力梯度张量各分量导出了位系数模型的精度估计公式.从三方面进行了研究:假定卫星重力梯度仪测量精度,探讨用重力梯度数据确定地球重力场模型的精度;求出位系数模型和大气阻力引起的重力梯度卫星的轨道误差;最后,反求轨道误差和位系数误差对重力梯度测量值的影响.数值计算表明,与地面技术和常规卫星方法相比,卫星梯度测量可使重力场模型的精度至少提高3-5倍;利用重力梯度张量全分量求得的重力值精度比单用径向分量Vrr的结果提高40％以上;若仅顾及位系数模型和大气阻力误差,则轨道误差对梯度测量值的影响△Vi3（i=3,2,1）至少可分别在1/4和1/3弧圈内达到△Vi3≤σ（仪器精度）. 相似文献
20.
基于磁通门秒值数据的地震ULF磁场可靠信息提取研究 总被引：2，自引：0，他引：2
利用磁通门观测数据进行分析,结果表明与周期在几分钟到几小时的极化值一样,5~100 s的磁场极化值Yzh同样具有年变化规律,因此简单的依据极化值Yzh由低值向高值的变化判断是否存在震前电磁辐射异常存在很大的风险。为此,分析了采用富氏拟合技术消除半年以上变化周期的Yzh与台站周边地区地震的关系,表明极化值Yzh高值与其后2个月内台站周边地区地震有很好的对应关系,且大部分地震都发生在1个月内。分析还表明Yzh高值异常持续时间一般为3~5 d,与外空磁场剧烈活动没有关系;单纯采用夜间观测数据不及采用全天观测数据的效果。 相似文献