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1.
Anomalous induction across Europe 总被引：1，自引：0，他引：1
Summary Using real induction vector data, collected at 958 European observation sites, together with our data from the Bohemian Massif and the West Carpathians, we have generated a contour map of the transfer function TF1 (corresponding to transfer function A in Wiese's relation). Only the zero contour is retained and shown on the map. It clearly marks the main anomalous induction zones, related to internal structural inhomogeneities, across Europe. 相似文献
2.
A summary of experiments and analyses concerning electromagnetic induction in the Moon and other extraterrestrial bodies is presented. Magnetic step-transient measurements made on the lunar dark side show the eddy current response to be the dominant induction mode of the Moon. Analysis of the poloidal field decay of the eddy currents has yielded a range of monotonic conductivity profiles for the lunar interior: the conductivity rises from 3·10?4 mho/m at a depth of 170 km to 10?2 mho/m at 1000 km depth. The static magnetization field induction has been measured and the whole-Moon relative magnetic permeability has been calculated to be . The remanent magnetic fields, measured at Apollo landing sites, range from 3 to 327 γ. Simultaneous magnetometer and solar wind spectrometer measurements show that the 38-γ remanent field at the Apollo 12 site is compressed to 54 γ by a solar wind pressure increase of 7·10?8 dyn/cm2. The solar wind confines the induced lunar poloidal field; the field is compressed to the surface on the lunar subsolar side and extends out into a cylindrical cavity on the lunar antisolar side. This solar wind confinement is modeled in the laboratory by a magnetic dipole enclosed in a superconducting lead cylinder; results show that the induced poloidal field geometry is modified in a manner similar to that measured on the Moon. Induction concepts developed for the Moon are extended to estimate the electromagnetic response of other bodies in the solar system. 相似文献
3.
Crossing Honghe fracture in Yunnan Province two measuring profiles were set up, each measuring profile consisted of 8 observing
sites. Three component geomagnetic variation observations were carried out continuously and simultaneously along each profile.
Induction arrows were calculated for the periods from 8 min to 60 min. There exists a reversal axis of induction arrow between
Eryuan, Xiaguan, Weishan, Mejiang and Yongping, Yunxian, Lincang, Simao. The real arrows reverse from one side of the axis
to another side and the magnitude of the real induction arrows attenuates with increase in distance from the axis, the attenuation
in northeast side of the axis is slightly less than that in southwest side. The real induction arrows of shorter periods are
greater than those of longer periods at most of the observing sites. According to the features of the real induction arrows
and by use of numerical calculation we tried to look for the restriction which was to be attached to the possible high conductivity
zone in the area under investigation. It shows that there is a high conductivity belt west of Honghe fracture which tilts
northeastward and there is a high conductor cover over the high conductivity belt beneath most of the observing sites
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 201–210, 1992. 相似文献
4.
The extent of data uncertainty of surface-wave measurements may have significant consequences on 1D seismic response analysis and it may lead to inaccurate estimate of design ground motion. In this paper, an attempt has been made to quantify the data measurement uncertainty from a large repetition of the field data at two test sites and to determine bounds of data uncertainty. In the inversion with neighborhood algorithm, we generated profiles below the misfit value calculated from the uncertainty bound. Equivalent profiles have been selected covering the whole misfit value range and these profiles are subjected to equivalent linear 1D ground response analysis. The results of seismic response analysis are presented in the form of amplification spectra and response spectra which show remarkable variations. Significant variation is observed in peak frequency and peak amplification and it differs from one site to the other based on their measured data uncertainty bound. Peak Ground Acceleration (PGA) and peak spectral acceleration at both the sites reflect very high Coefficient of Variation (COV). 相似文献
5.
F.E.M. Lilley 《Physics of the Earth and Planetary Interiors》1974,8(4):301-316
The geomagnetic induction tensor is a means of summarizing the response of the earth at a given observing site to a geomagnetic variation source field. In this paper the characteristics of the tensor elements are examined, both generally and for the special cases of one-dimensional and two-dimensional geologic structure. The first-order model is taken of uniform source fields originating external to a semi-infinite half-space. Graphical ways of presenting the information contained in an induction tensor are explored, including ellipses of rotation, polar diagrams, and diagrams analogous to the Mohr circles of elasticity theory. Criteria to distinguish “two-dimensional” data from “three-dimensional” data are established. The advantages of simultaneously recording “normal” and “anomalous” variations are demonstrated in terms of the extra tensor elements which may then be estimated. The most practical way of presenting information from many stations on a map may be by drawing, for each site, arrows which summarize the response in the vertical field and quadrics which summarize the response in the horizontal field. 相似文献
6.
E. S. Sampaio 《Pure and Applied Geophysics》1976,114(6):1009-1020
The presence of lateral contrasts of electrical conductivity modifies the original pattern of electromagnetic fields radiated from remote sources. A magnetic transverse plane wave field, interacting with a vertical conductive and outcropping dike placed between two quarter-spaces of unequal electrical conductivities, creates an anomalous vertical component of the magnetic field. This anomalous field has been analysed by computation, and drafting of master curves. Two case histories are presented to illustrate the application and the effectiveness of the solution. It is concluded that: (i) the response is higher for intermediate values of the conducting body induction number; (ii) the curves can be used for the inter-pretation of magnetotelluric, AFMAG, and VLF exploration data; (iii) it is necessary to develop solutions taking into account the vertical as well as the lateral variation of conductivity. 相似文献
7.
Induction, adaptation and recovery of biological responses: implications for environmental monitoring 总被引：3，自引：0，他引：3
A wide range of biological responses have been used to identify exposure to contaminants, monitor spatial and temporal changes in contamination levels, provide early warning of environmental deterioration and indicate occurrences of adverse ecological consequences. To be useful in environmental monitoring, a biological response must reflect the environmental stress over time in a quantitative way. We here argue that the time required for initial induction, maximum induction, adaptation and recovery of these stress responses must first be fully understood and considered before they can be used in environmental monitoring, or else erroneous conclusions (both false-negative and false-positive) may be drawn when interpreting results. In this study, data on initial induction, maximum induction, adaptation and recovery of stress responses at various biological hierarchies (i.e., molecular, biochemical, physiological, behavioral, cytological, population and community responses) upon exposure to environmentally relevant levels of contaminants (i.e., metals, oil, polycyclic aromatic hydrocarbons (PAHs), organochlorines, organophosphates, endocrine disruptors) were extracted from 922 papers in the biomarker literature and analyzed. Statistical analyses showed that: (a) many stress responses may decline with time after induction (i.e., adaptation), even if the level of stress remains constant; (b) times for maximum induction and recovery of biochemical responses are positively related; (c) there is no evidence to support the general belief that time for induction of responses at a lower biological hierarchy (i.e., molecular responses and biochemical responses) is shorter than that at higher hierarchy (i.e., physiological, cytological and behavioral responses), although longer recovery time is found for population and community responses; (d) there are significant differences in times required for induction and adaptation of biological responses caused by different types of contaminants; (e) times required for initial and maximum induction of physiological responses in fish are significantly longer than those in crustaceans; and (f) there is a paucity of data on adaptation and recovery of responses, especially those at population and community levels. The above analyses highlight: (1) the limitations and possible erroneous conclusions in the present use of biomarkers in biomonitoring programs, (2) the importance of understanding the details of temporal changes of biological responses before employing them in environmental management, and (3) the suitability of using specific animal groups as bioindicator species. 相似文献
8.
C.P. Sonett 《Physics of the Earth and Planetary Interiors》1975,10(3):313-322
A summary review of electromagnetic induction driven in the Moon by the interplanetary magnetic field is given. The point of view developed centers on inversion of Fourier transforms of the magnetic field in the free-stream solar wind (forcing function) and the response on the lunar surface measured by Lunar Surface Magnetometers. Conductivity profiles are shown to depend upon the central angle between the magnetometer given by local time and the incident wave-normal direction. The induction excites at least magnetic dipole and quadrupole “radiation”, but any scattered field is confined to the Moon's interior, save for propagation down the cavity where a TE-mode surface wave is generated. Confinement of the induced field on the sunward hemisphere and near the subsolar point is nearly complete, decreasing to the limbs, while in the diamagnetic cavity downstream of the Moon, partial confinement takes place. Both time and spatial multipoles of the induced field are present in the lunar interior complicating inversion into conductivity profiles. Profiles are reviewed and resolution limits are given and compared to those obtained from transient analysis. Finally a qualitative comparison to conductivity in the Earth is given. 相似文献
9.
Electromagnetic induction in the Vancouver Island region for a uniform inducing source field for 300 s period is investigated with the aid of three-dimensional (3-D) numerical and analogue model results and field site measurements. The thin sheet numerical model, based on the subducting Juan de Fuca plate analogue model ofDosso
et al., consists of a 5km thick non-uniform thin sheet (comprising the lateral conductivity contrasts arising from the land, the varying depth ocean, and the sediment) underlain by a four-layer conductive structure. The four-layer conductive structure beneath the non-uniform thin sheet simulates the effect of the Juan de Fuca plate subducting Vancouver Island. To examine the effects of the ocean channel depth between Vancouver Island and the British Columbia (Canada) mainland, numerical results were obtained for two channel depths (0 and 600 m). The results indicate that the channel plays an important role in the geomagnetic response in the central and inner coastal regions of Vancouver Island. The general agreement of the 3-D numerical model induction arrows with the analogue model and field site induction arrows for 300 s supports the premise of a layered conductive substructure dipping at a small angle, at most, beneath Vancouver Island.Lithoprobe Publication No. 311. 相似文献
10.
Deep observation boreholes in the vicinity of active production wells in Honolulu, Hawaii, exhibit the anomalous condition that fluid-column electrical conductivity logs and apparent profiles of pore-water electrical conductivity derived from induction conductivity logs are nearly identical if a formation factor of 12.5 is assumed. This condition is documented in three boreholes where fluid-column logs clearly indicate the presence of strong borehole flow induced by withdrawal from partially penetrating water-supply wells. This result appears to contradict the basic principles of conductivity-log interpretation. Flow conditions in one of these boreholes was investigated in detail by obtaining flow profiles under two water production conditions using the electromagnetic flowmeter. The flow-log interpretation demonstrates that the fluid-column log resembles the induction log because the amount of inflow to the borehole increases systematically upward through the transition zone between deeper salt water and shallower fresh water. This condition allows the properties of the fluid column to approximate the properties of water entering the borehole as soon as the upflow stream encounters that producing zone. Because this condition occurs in all three boreholes investigated, the similarity of induction and fluid-column logs is probably not a coincidence, and may relate to aquifer response under the influence of pumping from production wells. 相似文献
11.
为研究双轴各向异性介质多分量感应测井响应特征,本文基于三重傅里叶变换,推导任意方向偶极子源的谱域电磁场解析式;采用围线积分方法,自适应截断积分区间,结合谱域电磁场周期特性,实现三重傅里叶变换的精确快速积分;进而,针对双轴各向异性倾斜地层,模拟研究不同纵横向各向异性条件多分量感应测井响应特征.结果表明:利用谱域内电磁场在周向的周期特性简化解析式,可将计算速度提高4倍;自适应截断积分区间方法保证了计算精度,并极大地减少了积分节点数.对于倾斜双轴各向异性介质,倾角较大时,共面分量可反映地层横向各向异性,同轴分量可反映地层纵向各向异性;倾角较小时,同轴分量可反映地层横向各向异性,共面分量可反映地层纵向各向异性. 相似文献
12.
本文介绍了基于月尘扬起机制的"动态喷泉模型",分析了月尘扬起的过程;最后提出了"带电月尘活动电磁感应模型",计算得到月面明暗交界处带电月尘活动产生的感应磁场强度小于0.0064nT.本文证明带电月尘的活动对月球磁场的影响微小,可以忽略. 相似文献
13.
Sundt RC Ruus A Jonsson H Skarphéðinsdóttir H Meier S Grung M Beyer J Pampanin DM 《Marine pollution bulletin》2012,64(1):144-152
Biological markers of produced water (PW) exposure were studied in Atlantic cod (Gadus morhua) in both laboratory and field experiments, using authentic PW from a North Sea oil field. In the laboratory study, the PW exposure yielded significantly elevated levels of metabolites of polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs) in bile even at the lowest exposure dose (0.125% PW). Other biomarkers (hepatic CYP1A induction and DNA adduct formation) responded at 0.25% and 0.5% PW concentrations. In the field study, bile metabolite markers and hepatic CYP1A were clearly increased in fish caged close to the PW outfall. Induction of plasma vitellogenin was not found in laboratory or field exposures, suggesting that the levels of oestrogen agonists (such as APs) might not have been sufficient to elicit induction, under the present conditions. The applicability of the biomarkers for use in water column biomonitoring programs is discussed. 相似文献
14.
A numerical method is used to calculate the electromagnetic fields associated with a three-dimensional conductivity anomaly. The source field is due to horizontal magnetic dipoles placed at two different positions with respect to the conductivity anomaly. The transfer functions and related perturbation and induction arrows associated with the fields are calculated and compared with the arrows obtained from a uniform source calculation. The results show the source effect on the induction arrows and indicate that the perturbation arrows provide a method of outlining the spatial extent of the anomaly. The transfer function calculations are made for both exact and approximate normal fields. In the transfer function calculation the anomalous fields are correlated with a normal field as suggested by Schmucker (1970) and Cochrane and Hyndman (1970). 相似文献
15.
本文是“地震的感应磁效应（一）--三维电磁感应的数值理论”一文的继续。首先从理论和实际计算两个方面证明了三维电磁感应数值方程解的唯一性、收敛性和稳定性,从而充实了作为研究地壳、上地幔电性结构横向不均匀性理论基础的“三维数值方法”。作为这一理论方法的实际应用,文中对不同源场周期和具有不同埋藏深度的三维电导率异常体进行了模拟计算,以研究地震感应磁效应的大小、空间分布特征和频率特性。模拟计算结果表明,对于周期从数秒到数分钟的地磁短周期变化,若电导率异常体的线度与5至7级地震的震源体积大体相当,其电导率较原背景电导率高近一个量级,其感应磁效应主要特征为:在异常体正上方,地面磁场的水平分量变化最大,相对变化量约30％;在异常体于源场方向一致的两侧,垂直分量变化最大,相对变化量约40-50％。因此,观测短周期地磁场的异常变化,有可能是监测地震孕育过程地下电性变化的一种试验途径。但由于上述异常强度在空间上衰减迅速,所以观测必须接近震源区,这对测点的选择是个不利的因素。 相似文献
16.
J.T. Weaver 《Physics of the Earth and Planetary Interiors》1973,7(3):266-281
A review of electromagnetic induction in a multi-layered earth is built around a development of the general theory from first principles. Induction by transient and periodic fields and by dipole and electrojet sources are discussed and the method of complex images is briefly described. The review concludes with a discussion of induction by elementary harmonic sources whose non-uniformity is characterised by Price's ν-parameter and which include the uniform source field (ν=0) as a special case. The conditions under which the source may be assumed uniform for computing the surface impedance and other ratios of field components are examined. 相似文献
17.
利用数值模式匹配技术,研究并建立层状各向异性倾斜地层中多分量感应测井响应的快速数值模拟算法.首先将位于井轴上的三个相互正交磁偶极子转化成关于极角θ的三个谐变分量的叠加,以便将三个正交磁偶极子电磁场的正演问题完全简化成三个谐变分量电磁场的轴对称定解问题,并给出电磁场各个谐变分量在井轴上满足的边界条件,保证电磁场在井轴附近仍然可解.然后利用数值模式匹配技术建立电磁场各个谐变分量的正演过程,得到层状各向异性地层中磁流源并矢Green函数的半解析表达式,给出计算层状各向异性倾斜地层中多分量感应测井响应的具体方法,最后通过数值计算结果证明该算法的有效性并考察几种不同情况下多分量感应测井响应特征. 相似文献
18.
A. V. Kuvshinov 《Surveys in Geophysics》2008,29(2):139-186
Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields.
The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability
in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes:
(a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main
magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these
sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans,
crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling
studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced
by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric
currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling
studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly
(in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral
equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations
both on the ground and at satellite altitudes.
On leave from Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences, 142190
Troitsk, Moscow region, Russia. 相似文献
19.
A. B. Raevskii 《Izvestiya Physics of the Solid Earth》2008,44(7):548-554
An iterative algorithm is proposed for magnetic induction modulus inversion. The iterative process is based on a recurrence relation for the squared induction modulus, which can be represented at each iteration step by a system of linear algebraic equations for components of the magnetization vector. Formulas for the calculation of matrix elements of this system and the determination of the magnetization at the next iteration step are given. Model and practical examples illustrating the reconstruction of magnetization and anomalous field components are presented. 相似文献
20.
阵列感应测井分辨率匹配方法及应用 总被引：2，自引：1，他引：1
测井曲线高分辨率处理对薄层测井评价意义重大。俄罗斯感应测井（HIL）仪器已经在中国应用,存在的主要问题之一是4种探测深度曲线分辨率不匹配。本文基于感应测井的信息补偿原理,在分析HIL仪器探测特性的基础上,研究了针对该仪器的分辨率匹配方法和处理技术,处理了假设模型资料和实际资料,初步验证了方法的正确性和处理实际资料的可行性。 相似文献