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ＴｈｅｏｂｓｅｒｖａｔｉｏｎａｎｄｉｎｔｅｒｐｒｅｔａｔｉｏｎｏｆｇｅｏｍａｇｎｅｔｉｃｖａｒｉａｔｉｏｎｓｉｎａｓｍａｌａｒｅａｏｆＨａｉｎａｎＰｒｏｖｉｎｃｅ，ＣｈｉｎａＧＵＯＨＵＡＦＡＮ１）（范国华）ＴＯＮＧＱＩＹＡＯ１）（姚同起）ＺＵＯ... 相似文献
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GUO HUA FAN TONG QI YAO KE LI HAN KE JIA ZHU ZUO WEN GU Institute of Geophysics China Seismological Bureau Beijing China 《地震学报(英文版)》1998,11(6):719-727
ｎｔｒｏｄｕｃｔｉｏｎＴｈｅｖａｒｉａｔｉｏｎｍａｇｎｅｔｉｃｆｉｅｌｄｏｆｔｈｅＥａｒｔｈｃｏｎｔａｉｎｓａｂｕｎｄａｎｔｉｎｆｏｒｍａｔｉｏｎ,ｓｕｃｈａｓｔｈｅｉｎｆｏｒｍａｔｉｏｎｒｅｌａｔｉｖｅｔｏｓｏｌａｒａｃｔｉｖｉｔｙ,ｓｏｌａｒｔｅ... 相似文献
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地磁测深研究的周期范围通常为10~5~10~7s,缺少反映浅部电性结构的短周期信息,而C-响应受浅部电阻率影响明显,因此本文提出在反演中增加浅部(约200 km)电阻率约束以提高深部反演的稳定性和可靠性.在磁层环状电流满足P_1~0假设的条件下,球坐标系中一维导电薄球层状地球的C-响应和电导率分布关系由边界条件通过递推的方法计算得到.反演采用有限内存拟牛顿(L-BFGS)法;浅部电阻率约束通过将目标函数对模型参数的梯度设为零来实现;通过置信区间分析评价约束反演结果的可靠性.合成数据的无约束反演虽然最终的拟合效果很好,但浅部电阻率受初始模型影响,差异较大;采用浅部约束后,反演结果对初始模型依赖性明显减小,同时还能显著提高200~600 km范围内反演结果的准确性.对全球近地轨道卫星观测的C-响应数据约束反演后结果与前人一致,表现为地幔电导率整体上随着深度的增加而增加.参数置信区间分析表明,由于约束反演加入了浅部信息,电阻率的变化范围更加紧致,说明反演结果更加可靠.因此,有必要通过其他地球物理方法,如长周期大地电磁测深等获得浅部电阻率分布,作为先验信息参加反演,进行浅部约束的C-响应反演,获得更可靠的一维全深度电性结构,为地磁测深数据解释奠定基础. 相似文献
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Ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ａｎｄ ａｎａｌｙｓｉｓ ｏｆ ｔｈｅ ｇｅｏｍａｇｎｅｔｉｃ ｖａｒｉａｔｉｏｎｓ ｉｎ ｒｅｇｉｏｎｓ ａｒｏｕｎｄ ｔｈｅ Ｑｉｏｎｇｚｈｏｕ Ｓｔｒａｉｔ（范国华）（姚同起）（顾左文）（朱克佳）（陈伯舫）（冯戬... 相似文献
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The specific features of the spatial structure and time dynamics of the main geomagnetic field during the 20th century, proceeding
from the present-day concepts of geomagnetic jerks have been studied. The variations, caused by global dissipation of the
geomagnetic field dipole part, have been separated from the regional variations, described by nondipole spatial harmonics
of the spherical harmonic expansion series. It has been indicated that the geomagnetic field westward drift manifests itself
in a limited region of the Earth’s surface, forming the known Brazil anomaly. However, the drift component in the variations
in the geomagnetic field morphological structures is globally found out during the considered almost 100-year period along
the narrow belt around the geomagnetic axis. However, this drift is northwestward in the Northern Hemisphere, and the structures
drift southeastward in the Southern Hemisphere. The detected variations of the drift nature are reflected in the variations
in the integral geomagnetic characteristic, when changes in the position of the Earth’s magnetic center are considered. The
direct correlation between the global geomagnetic variations of the drift nature and the trend variations in the orientation
of the vector of the Earth daily rotation velocity has been detected. 相似文献
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DEEP STRUCTURE OF NORTHERN HENAN PROVINCE AND ADJACENT AREAS DERIVED FROM GRAVITY AND SEISMIC SOUNDING DATA IN RELATION TO DISTRIBUTION OF EARTHQUAKES 
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下载免费PDF全文 We conduct the wave field separation of the gravity field for northern Henan Province and adjacent areas by the wavelet multi-scale decomposition method, and obtain multi-order gravity wavelet details and regional gravity field information. Then the Parker density surface inversion is used to invert the Moho interface. Based on the analysis of wavelet details in different orders and results of three seismic sounding profiles available in this area, we attempt to reveal the deep crustal structure of the study area. Research results show that the crustal structure is dominated by uneven density distribution accompanied by uplifts and depressions in the region with obvious heterogeneities of the density in horizontal and vertical directions. The gravity field characteristics in the middle-upper crust correspond to the surface topography, the lower crust is dominated by the large-scale high-low gravity anomalies, and several major depression basins show the characteristics of low velocity and low density. At the same time, the depth of the Moho interface changes greatly, which forms the block structure pattern of the regional crustal thickness. Among these features, the area with relatively large variations of the Moho is located in the transition zone of the basin to the Taihang Mountains, or exactly the Moho mutation belt. The Moho interface of the basin area as a whole is dominated by the uplift intertwined with local variations, of which the least and largest depths are 31km and 37km, respectively. Due to the gravity isostasy, the crustal thickness is larger(about 41km)in the northwest of the Taihang Mountains, with less average crustal density. In the study area, earthquakes tend to occur around the transition zone with density changes where the Moho is locally convex. The seismogenic mechanism may be associated with upwelling of upper mantle materials, low-velocity and low-density structures in the middle-lower crust and connection of deep large faults. Moreover, the deep large faults play a controlling role in the distribution of regional earthquakes. 相似文献
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Global electromagnetic induction 总被引：1，自引：0，他引：1
R. G. Roberts 《Surveys in Geophysics》1986,8(3):339-374
Methods of analysis of long period geomagnetic variations (periods over a few hours), the available electromagnetic response function estimates, and the effect of lateral inhomogeneity within the Earth are reviewed. Recent advances in the inversion of response function data to produce conductivitydepth profiles are mentioned, and aspects of the inverse problem specific to global (spherical Earth) induction are discussed.There is a rapid rise in electrical conductivity between about 400 km and 800 km, but whether this is a gradual change or consists of one or several steps is not resolvable with the presently available data and naive inversion algorithm used here. At the greatest depths to which presently analysed variations penetrate (1000–1500 km), available data have some difficulty in resolving finer structure, but there are indications that the electrical structure of the continents becomes more laterally homogeneous as depth increases. Previously published inversions see lateral variations in electrical structure down to at least 500 km, and at shallower depths these variations are unambiguously resolved. 相似文献
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安徽贵池矿集区是长江中下游成矿带中重要的铜多金属矿集区,随着浅表找矿难度的加大,急需了解矿集区深部结构为深部找矿提供深部找矿提供指示.为揭示贵池矿集区深部地壳结构格架、控岩、控矿构造和岩浆系统的空间结构,深化对成矿作用的认识,在该区实施了两条长度各约60km垂直于构造走向的反射地震和MT探测剖面,通过对MT数据有针对性的去噪和反演,获得了研究区10km以浅的地电结构;通过对反射数据的层析反演静校正、叠前保幅多域去噪、精细速度分析和叠前时间偏移等处理,获取了该地区地壳结构的地震成像剖面.结合区域地质构造背景和针对性处理的区域重磁数据,对两条综合探测剖面的反演处理结果进行了分析与解释,研究发现了本区地层的构造反射特征、地壳结构特征和Moho特征,厘定了盖层与基底之间的区域滑脱面、中下地壳滑脱面和Moho面的深度和形态.发现了地壳上冲和俯冲的反射特征,可能是华夏块体与扬子块体晋宁期发生板内碰撞的痕迹.高坦断裂是一个深达地壳级的断裂,其南北两侧具有不同的重磁特征、电性结构特征和地震反射特征,该断裂可能是深部流体上涌的通道,岩浆和地幔热液沿断裂上涌并沿地层和裂隙侵入中上地壳,形成岩基或岩体,或与围岩发生强烈矿化作用形成贵池矿集区多金属矿床. 相似文献
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S. V. Starchenko 《Geomagnetism and Aeronomy》2011,51(3):409-414
The large-scale harmonic magnetic-convective sources of the main geomagnetic field in the Earth’s core have been determined
for the first time. The determination is based on a complete system of eigenfunctions of the magnetic diffusion equation in
a homogeneously conducting sphere, which is surrounded by an insulator. The sources of the main geomagnetic field observed,
which is responsible for the distribution of the electric currents generating this field in the core, are expressed in terms
of large-scale eigenfunctions. In this case, the dipole sources are directly related to the observed geomagnetic dipole, whereas
the quadrupole sources are related to the quadrupole, etc. The time variations in the obtained sources are responsible for
individual spatiotemporal features in the generation or suppression of each Gaussian component of the observed geomagnetic
field. When the commonly accepted observational international geomagnetic reference field (IGRF) models were used to partially
reveal these time variations, it became possible to specify the estimate of the Earth’s core conductivity and determine the
minimum period that can separate us from the commencement of further inversion or excursion. 相似文献
11.
Wallace H. Campbell 《Surveys in Geophysics》1986,8(3):239-259
Electric currents in long pipelines can contribute to corrosion effects that limit the pipe's lifetime. One cause of such electric currents is the geomagnetic field variations that have sources in the Earth's upper atmosphere. Knowledge of the general behavior of the sources allows a prediction of the occurrence times, favorable locations for the pipeline effects, and long-term projections of corrosion contributions. The source spectral characteristics, the Earth's conductivity profile, and a corrosion-frequency dependence limit the period range of the natural field changes that affect the pipe. The corrosion contribution by induced currents from geomagnetic sources should be evaluated for pipelines that are located at high and at equatorial latitudes. At midlatitude locations, the times of these natural current maxima should be avoided for the necessary accurate monitoring of the pipe-to-soil potential. 相似文献
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Changes in total geomagnetic field intensity, of 2–3 nT, were observed prior to the 1995 Hyogo-ken Nanbu (Kobe) earthquake at the Amagase (AMG) site, located approximately 70 km from the epicenter. We examined whether the observed variations are local signals arising from the Earth's crust, or global variations that are unlikely to originate from the crust. To remove global-scale variations in total geomagnetic intensity data, we employed a regional geomagnetic field model. Using data recorded at five reference sites in Japan, we estimated global-scale variations in total geomagnetic intensity, and removed them from the observed total geomagnetic intensity at the AMG site. The reminder still showed variations during the period prior to the Kobe earthquake. In addition, these pre-seismic variations include two of the largest shifts recorded during the entire observation period at the AMG site, raising the possibility that these variations were indeed related to the earthquake. These variations cannot be interpreted as signals arising from the area close to the seismic source because of the large distance between the epicenter and the site. Therefore, our results raise the possibility that the physical state of the Earth's crust shows marked changes over a wide region in the lead-up to a seismic event. 相似文献
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Synchronous annual variations in the geoelectric and geomagnetic field are studied on the basis of long-term electromagnetic monitoring. It is shown that the annual geoelectric variations have intraterrestrial origin and are not related to the annual geomagnetic variations. Temporal variations in the magnetotelluric impedance and magnetic tipper, which characterize the electrical conductivity of the geological environment, are analyzed. It is established that annual variations in the magnetotelluric impedance mainly describe the variations in the electrical conductivity of surface crustal layers and are less sensitive to the deep electrical conductivity of the Earth. The annual variations in the imaginary magnetic tipper at the periods of 1000–3000 s probably reflect the changes in conductivity of a deep transversal low-resistive zone (the fault). It is suggested that annual variations in the geoelectrical and geomagnetic fields, as well as in the electrical conductivity of the geological environment, arise as a response to the changes in the geodynamical processes caused by the revolution of the Earth around the Sun.
相似文献15.
本文利用大地电磁测深数据,对穿过兰坪—思茅地块和川滇菱形地块以及进入扬子地块的云南兰坪—贵州贵阳大地电磁测深剖面展开了深部电性结构研究.采用大地电磁数据处理分析以及反演技术,对观测资料进行了由定性到定量全面地分析,通过二维非线性共轭梯度反演得到了沿剖面的较为详细的地壳上地幔电性结构,结合其他地质和地球物理资料的分析,对该剖面的二维电性结构进行解释,确定了主要断裂带和边界带的位置以及深部延伸情况,同时确定了壳内低阻层的分布位置,最后进行了区域动力学和孕震构造环境的探讨.研究表明:剖面壳幔电性结构分块性特征与区域地质构造分布特征基本一致,不同地块的电性结构存在显著差异,其中川滇菱形地块的结构相对复杂,上地壳的电性结构为高低阻相间分布特征,电阻率的突变带与地表断裂具有很好的对应关系;兰坪—思茅地块存在中上地壳低阻层,川滇菱形地块中西部存在下地壳低阻层,川滇菱形地块东部和华南地块西部存在中上地壳的低阻层;川滇菱形地块中部攀枝花附近的低阻层埋深最深,而华南地块西部会泽附近的低阻层埋深则最浅;兰坪—思茅地块和川滇菱形地块的中下地壳的低阻层可能与青藏高原物质的东南逃逸有关;华南块体的宣威以东的下地壳不存在低阻层,华南块体下地壳和上地幔的电阻率较高;攀枝花附近的高阻体可能是峨眉山玄武岩喷发导致底侵作用及幔源物质上侵的结果. 相似文献
16.
A. G. Grigorian 《Izvestiya Physics of the Solid Earth》2007,43(6):524-531
A method is proposed for studying variations in the local geomagnetic field of external origin that are associated with variations in the electrical conductivity at various depths of the Earth’s crust and upper mantle. The application of the method is illustrated with the example of study of time series of geomagnetic data obtained in Armenia during 1986–1992. The method is effective for identifying the geodynamically most active areas in regions studied. 相似文献
17.
台站资料在我国地磁学基础研究中的应用 总被引：3，自引：1，他引：3
台站观测资料包含了上至太阳活动、星际空间、磁层、电离层活动，下至地壳构造、地震活动、地球深部导电特征，乃至地核活动的各种丰富的信息。中国学者利用台站资料广泛开展地磁学的基础研究，在研制中国地磁场模型，研究地磁场长期变化规律、地下的导电率结构及震磁关系等方面取得了许多成果。文章介绍了台站资料在中国地磁学基础研究中的应用。 相似文献
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Magnetic variation data recorded at 143 sites in the period range of 1000–6000 seconds were used to model the conductance distribution in the eastern part of the Bohemian Massif (BM) and the West Carpathians (WCP). The region represents a contact zone of the Palaeozoic Hercynian and Tertiary Carpathian orogenic systems. Two anomalies in the distribution of the electrical conductivity were found. One with a simple two-dimensional feature is located approximately near the boundary of the Inner and Outer West Carpathians, but the other of a complicated three-dimensional character is at the eastern margin of the BM. We inverted the observed geomagnetic data for the conductance in a unimodal thin sheet embedded at a specific depth. The inversion algorithm minimises the parametric functional that sums the squared norm of the misfit and the stabilising functional, and employs conjugate gradient optimisation. To express the sharp tectonic boundaries, we employed a minimum gradient support functional, which is applied in areas with strong variations of the model parameters. The inversion results confirmed a quasi-linear character of the regional anomaly distinguishing the Carpathian plate and led to new insight into the anomaly over the eastern margin of the BM. According to the results of the modelling the anomaly is formed by several conductive belts intersecting the anomalous zone. These belts follow important faults, dividing the transition zone between the BM and the WCP into individual blocks. 相似文献
19.
为了研究1976年唐山地震的磁效应,本文在文献[1]的基础上,利用北京测区六年(1975——1981)的磁测资料,分析了北京地区地磁场长期变化的局部差异,正常(无强震)时期地磁统计量的变化特性,以及长期变化局部差异对地磁统计量的影响.正常时期与地震前后地磁统计量的对比分析表明,唐山地震对北京地区地磁场总强度统计量的影响是显著的.通过不同区域测点、测线的各种组合,计算了地震前后统计量的空间分布,以确定测区信息最强的区域.唐山地震在北京地区所产生的磁效应的统计性质如下:1.异常信息不是短期的波动,而是呈趋势性变化,其持续时间至少一年;2.离震中较近的 S 区异常显著,其主要根据是,地磁统计量 Smj,bsn和Fk2在 S 区变化显著.特别是统计信息的局部差异与长期变化明显不同,前者呈东西分布,后者主要呈北南走向;3.趋势性异常变化的平均空间差异随时间的变化在测区总体并不显著,但在 S 区这种差异的时间变化,在震前1976年3——6月却是显著的. 相似文献
20.
《Earth and Planetary Science Letters》2006,241(3-4):603-616
Long period magnetotelluric soundings are available in a 180-km long WSW–ENE profile across the Alto Paranaíba igneous province, a complex Cretaceous alkaline province situated mostly in the southern Neoproterozoic Brasília fold and thrust belt in central Brazil. The data indicate 3D complexity at upper and mid-crust and a simpler 2D regional structure at lower crustal and upper mantle depths. A 2D inversion emphasizing long period data identifies a highly resistive block at the uppermost mantle below the central part of the profile, surrounded by a rapid decrease in resistivity with depth. Resistivities at the block are typical of dry olivine under upper mantle conditions and a deep cratonic lithosphere is defined for this region. It is proposed that the resistive block is a rheologically enduring structure preserved within a southwestward extension of the pericratonic lithosphere of the Archean–Early Proterozoic São Francisco craton that lies beneath the nappes of the Brasília belt. Lower resistivities at shallower upper mantle depths beneath the Sanfranciscana basin at the northeastern end of the profile can be interpreted either as an increased conductivity within the lithosphere or as a localized thinned out lithosphere. The conductivity enhancement possibly arises from the addition of small amounts of water to mantle anhydrous minerals during previous metasomatic percolations. 相似文献