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李忠平 《物探化探计算技术》2009,31(5):434-436
通过收集某地区地磁台记录的磁场,和当天另一地区地磁日变场数据,以某地的地磁台记录磁场作为参考地磁场,以另一地当天地磁日变场作为主要地磁场,采用傅立叶变换对时变地磁异常进行频谱分析。计算出二地的地磁场水平导数和某地磁响应参数及视电阻率,并对其进行了一维电磁测深反演,与在同一测深剖面施测的可控源音频大地电磁测深（CSAMT）反演结果对比分析,效果基本一致。采取这种计算方法,可有效地提取磁异常深部信息,为危机矿山深部找矿增加一种新的解释手段。 相似文献
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高精度磁测在云南省德宏州某地区的应用,取得了较好的效果。采用规范的地面高精度磁测方法,取得可靠的磁测数据,圈定出磁异常。经过对资料处理与定性分析解释,推断出磁异常的成因,为开展下一步地质工作和找矿远景预测,提供了有效的地球物理依据。 相似文献
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提高磁测日变改正精度的方法 总被引：7，自引：0，他引：7
在利用高精度磁测方法进行间接寻找砂金、岩金的研究中,需探测10nT左右的弱磁异常。这对日变改正精度提出了更高要求。针对这一需要,编制了软件,适用于IGS-2／MP-4与ENVIMAG两种型号的质子磁力仪,使其能同时投入工作做日变改正。采用一个完整的地磁平静日的日变观测数据,用分时区加权平均来确定日变改正基值。对每天测定的日变曲线先进行圆滑,降低仪器噪声对日变观测结果的影响后,再对当天各测点上的磁测值进行日变改正。这样既提高了日变改正精度,又实现了对两种型号磁力仪间观测数据的日变改正处理。 相似文献
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地磁场模型的计算和评述 总被引：1，自引：0，他引：1
评述了计算地磁场区域模型的各种数学方法,如:利用多项式方法可以计算地磁场的Taylor多项式模型和Legendre多项式模型,利用球冠谐和分析方法可以计算出磁场的冠谐模型。本文指出了建立区域模型各种方法的优缺点,指出球冠谐和分析方法是计算地磁场三维模型的好方法。 相似文献
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《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(5):445-448
On the territory of Bohemia and Moravia the measurements of the vector of geomagnetic field (declination, inclination and total intensity) were carried out at 199 points of the first order in 1994–1996. All values were reduced to the epoch 1995.5 and magnetic maps were derived by means of standard computer software. A comparison of recent measurements with IGRF has shown that, in the first approximation, IGRF can be used on this territory as a reference magnetic field. 相似文献
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在研究磁异常时,习惯将正常地磁场从测得的地磁场值中消除,以便突出上地幔和地壳内的各种磁异常。正常地磁场的选择正确与否,直接影响到人们对磁异常的认识及地质现象的研究。对于大面积的航空磁测编图,正常地磁场的选择尤为重要。 相似文献
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《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(5):433-438
The area of the Ionian sea, between Albania and the Southern Italian Peninsula, has been taken into account for the production of geomagnetic component maps. Data from the national Albanian and Italian magnetic repeat station networks have been merged, and normal reference fields in latitude and longitude, have been computed. Data processing, reduction procedures and comparisons with IGRF are presented. 相似文献
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《International Geology Review》2012,54(4):624-632
Results of regional geophysical work in the U.S.S.R. allow a measure of correlation between the known structural features of the crust and those of the geomagnetic field. The “normal” magnetic field used for identifying magnetic anomalies is obtained by graphic smoothing of isolines of total intensity T. Detailed analysis of data obtained in aeromagnetic and gravity surveys throughout the U. S. S. R. leads to the conclusion that the cause of the observed regional magnetic and gravity anomalies lies in the same associated geologic objects located at the same level - that of a magnetoactive interval of the crystalline envelope of the earth. The conclusions that can be drawn from existing data are: 1) the existence of “continental” anomalies of the geomagnetic field cannot be explained as an effect of the crust; 2) the basaltic layer does not affect the distribution of the geomagnetic field; 3) the anomalies in the basic (normal) geomagnetic field are caused by the presence of thermomagnetic geologic bodies in the granitic layer; accordingly, it is theoretically possible to determine the thickness of the continental layer from magnetometric data. A table showing correlative depths of the basaltic layer, its thickness, and anomalous magnetic field, as well as magnetic profiles is included.--C. E. Sears. 相似文献
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基于我国大陆最新观测所得的1 302个地磁测点和32个地磁台站磁偏角D、磁倾角I、总强度F的1 334组准确数据,并结合地壳磁异常能谱变化特征,对增强地磁模型(EMM2010)在我国大陆的精度及其适用性进行了定量分析。结果表明：EMM2010模型(D、I、F)在我国大陆的总体精度分别为10.45′、8.08′、112.85 nT ;东北、华北与新疆地区模型的精度为13.07′、8.90′、130.89 nT ;华南、青藏高原及其东缘地区模型的精度为7.07′、6.65′、81.84 nT;其精度是受模型有限的截断阶数、各区域的磁异常状况和磁测数据的误差等因素共同影响的。EMM2010模型的精度在我国大陆表现出显著的地域分布特征,与磁异常的分布形态及其复杂程度、梯度密切相关,异常越突出,形态越复杂,模型的精度越低。与世界地磁模型(WMM2010)、第11代国际参考地磁场(IGRF11)相比,EMM2010模型在我国大陆的总体精度平均提高了50%,主要原因是模型不仅包含了地球主磁场,同时还包含了地壳磁场。EMM2010模型应用于我国大陆的实例及精度分析表明,模型具有一定的适用性,但有其局限性,不能准确反映出我国大陆的地磁场信息,鉴于模型的精度,建议在EMM2010模型基础上,结合我国最新的各部门的高精度磁测数据,构建我国高精度的地磁场模型。 相似文献
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We have obtained formulas to calculate the field components of an eccentric dipole (ED) with an arbitrarily directed moment from specified coordinates of the dipole center and from its moment vector. With these formulas, the model dipole position was fitted to the observed geomagnetic field, and the approximation accuracy was estimated according to the standard deviation from IGRF along the X, Y, and Z components; the fitting procedure was checked in several tests.We computed the ED parameters (position and moment orientation) and harmonic coefficients of the ED field for 50 years using surface IGRF components, discovered some changes, and compared them with those according to the Schmidt eccentric dipole model. It was found that the nondipolar contributions to the geomagnetic field increase as the dipole field decays with time, and the dipole center drifts northand eastward away from the Earth's gravity center.The main contribution of the dipole part in the Gaussian spherical harmonic expansion of the geomagnetic field turned out to come from the terms with n of 1 to 5 rather than from two first terms, and the contribution of higher harmonics increases with time. Therefore, the Schmidt ED approximation based on the first eight Gauss coefficients (n ≤ 2) must have only relative significance indicating changes of the parameters. On the other hand, world magnetic anomalies (WMA) show up already in two first Gauss terms rather than since the third term as it has been commonly assumed. 相似文献
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根据汤普森（Thompson）地磁场模型和第 8代IGRF模型，计算了1600-2000年期间的偶极子磁场、非偶极子磁场、西向漂移和地磁功率谱等反映主磁场变化的主要参数，分析了各个参数的长期变化特征。主要结果是：400年来地磁场的偶极子磁矩持续减小，1800年以来磁心的位置快速离开地心向太平洋方向移动了291km；西向漂移有大约30年左右的周期；非偶极子磁场异常中，南大西洋正磁异常、非洲负磁异常和大洋洲负磁异常是1600年以来一直存在的 3个大型磁异常，东亚正磁异常和北美正磁异常是1700年后逐渐形成的，17世纪北太平洋地区存在强的正磁异常。 相似文献
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《Russian Geology and Geophysics》2015,56(3):476-486
Chromite mineralization in metamorphosed dunites from the southern Klyuchevskoy dunite-harzburgite ultramafic complex (Central Urals) has been investigated using geomagnetic surveys along with laboratory studies of ore-forming and accessory spinels of the same genetic type. Magnetization in the study area is carried mainly by accessory Fe-Cr-spinel of a variable Fe2 +(Cr2 -xFex3 +)O4 composition. Metamorphism caused changes in element contents and in both crystal and magnetic structure of the primary nonmagnetic accessory spinel, unlike the almost fresh ore-forming spinel. Thus, ore bodies stand against their host rocks, which is a prerequisite for the use of geomagnetic surveys for exploration of podiform chromite deposits in dunite-harzburgite complexes. Ground magnetic surveys at a test site composed of faulted rocks bearing disseminated chromite mineralization in metamorphosed dunites resolved a chromite ore zone and a fault block boundary showing up as geomagnetic anomalies. Laboratory studies using high technologies (thermomagnetic analysis at 4 to 1000 K, as well as magnetic resonance and magnetic force spectroscopy) revealed, for the first time, magnetic clusters (superparamagnetic phases) in primary nonmagnetic accessory spinel, which are responsible for the magnetic properties of the host rocks. Microscale variations in Cr-spinel correlate with the geomagnetic anomalies recorded by field surveys at the test site.© 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. 相似文献