Measurements of the Natural Remanent Magnetism and Anisotropy of Susceptibility of some Swedish Glacial Silts

Summary. This paper describes the results of measurements of the magnetic remanence and anisotropy of susceptibility of some Swedish varved silts. An attempt has been made to observe in nature the effects, which have been demonstrated in the laboratory, of water currents on these properties and to obtain new data on the effects of slopes on the direction of remanence.
It was not possible to obtain quantitative confirmation of the effects of water currents though it is shown that the field results fit qualitatively with those from the laboratory and that the effects of currents may in favourable circumstances be neglected or corrected for. By combining the new data on the effects of slopes with those previously published it has been found possible to demonstrate the importance of grain size in determining the magnitude of the bedding error correction and an expression has been found which gives this correction to an accuracy comparable with the error of measurement of remanence direction.
It is concluded that, since all known systematic deviations of the remanence direction may now be corrected for, it should be possible, in suitable circumstances, to obtain reliable estimates of field directions over the last 10,000 years from measurements on the Swedish varves.     

基于地形动力学的海滩裂流安全性评价 ——以三亚大东海为例

文章基于海滩地形动力学模型建立了海滩安全性评价方法,认为低潮沙坝/裂流海滩类和沙坝类海滩出现裂流概率最大,沙坝消散类和有裂流的低潮台地类海滩裂流风险中等,没有裂流的低潮台地海滩、没有沙坝的消散海滩、超消散型、完全反射型海滩裂流风险很小。以三亚大东海为例,利用该评价方法分析了海滩溺水事故频发的原因,结果显示：1）该海滩状态以沙坝型和低潮沙坝/裂流海滩型为主,属于高风险海滩,此结论与当地救生实践吻合;2）该海滩溺水事故发生的根本原因为裂流危险性高,故容易发生溺水事故。     

Tidal tilt at Llanrwst, North Wales: tidal loading and Earth structure

Summary. Tidal tilt measurements in a disused lead mine at Llanrwst, North Wales, are used to examine the magnitudes of the local strain—tilt coupling perturbations that can be expected in mine and tunnel installations. From the spatial variability of the tilt signal and comparisons with tidal loading calculations on radially stratified Earth models, it is concluded that typical strain—tilt coupling perturbations are at the ± 10 per cent level. The general problem of using tidal loading tilt and strain measurements to investigate the elastic parameters of layered models of the crust and upper mantle is studied by examining the sensitivities of the load Green's functions to these parameters. It is shown that the load tilt essentially gives information on Young's modulus whereas the load strain, although more sensitive to the structure, depends on both Young's modulus and Poisson's ratio. These investigations show that, if load tilt or load strain can be measured to an accuracy of 1 or 2 per cent, then they can be used to improve models of the crust and upper mantle. It is concluded that due to the local strain—tilt coupling perturbations this accuracy cannot be achieved in mines or tunnels and that future measurements should be made in boreholes or near surface trenches. The tidal loading models are also used to examine the spatial variation of the M² loading tilt in Europe.     

BP神经网络和SVM在矿山环境评价中的应用分析

矿山环境的影响因素多样,定量评价过程易受人为因素干预。BP神经网络与SVM算法能够自动模拟各因子间的非线性关系。首次将其引入到矿山环境评价中,选取160个单元作为训练样本,以自然地理、基础地质、开发占地及地质环境等4个大类的14个变量指标为输入向量,以单元评价得分为输出向量,分别建立BP神经网络与SVM矿山环境评价模型。结果表明：两种模型均能满足矿山环境评价的精度要求;SVM模型收敛速度较BP神经网络快,MSE小于BP神经网络,更适合矿山环境评价工作;将定量模型应用于研究区,评价得分划分为4个级别,与定性评价结果一致,为矿山环境评价工作提供了新思路。     

The Sq current system during the International Geophysical Year

Summary. The daily variation for the mean of the eight most quiet days of the IGY is represented as a function of latitude, longitude and UT by means of a spherical harmonic model. The most appropriate choice of Sq baseline is investigated, on the assumption that the external electric currents deduced from the model should be negligible at local midnight. The properties of the final model are discussed, particularly with regard to the external current foci, and are compared with those of previous models.     

Bimodal electromagnetic induction in non-uniform thin sheets with an application to the northern Pyrenean induction anomaly

In order to handle the distortion of large-scale induced electric currents by local conductivity anomalies, the problem of electromagnetic induction in non-uniform thin sheets has been reformulated in terms of an integral equation over the anomalous domain. This formulation considers in the layered substratum in addition to toroidal currents also the poloidal current mode (vertical current loops), at the expense that two scalar functions have to be determined. Simple formulas for the required kernels are derived. The algorithm is applied to model the gross features of the northern Pyrenean induction anomaly. It is suggested that this pronounced anomaly results from a conductive channel between the Atlantic Ocean and the Mediterranean Sea.     

Deep Schlumberger sounding and the crustal resistivity structure of central Australia

Summary. Three 200 km Schlumberger resistivity soundings have been conducted over the central Australian shield, using telephone lines to obtain the large electrode spacings. These represent the first crustal scale controlled source electrical study to be carried out in this continent. A computer controlled data acquisition system was used which allowed precise measurements to be made with only modest emission currents (0.1–0.5 A).
The three soundings, centred on the towns of Renner Springs, Wauchope and Aileron, showed the southern part of the study area (the Arunta Block) to be an order of magnitude more resistive than the more northerly section (the Tennant Creek Block). This difference correlates with the higher heat flow of the Tennant Creek Block. A lowering of apparent resistivity at large electrode spacings for one sounding (Wauchope) is taken to indicate the presence of a low resistivity layer in the middle crust, at a depth less than 20 km. However, the effect of the highly conductive overburden characteristic of inland Australia, combined with the large transverse resistance of the crust, prevented the other two soundings from detecting such a layer. Without support from these two soundings, it is impossible to be sure that the lowered resistivity at Wauchope is not caused merely by lateral variations in near-surface resistivity.
The data also show that crustal resistivities are much lower than the expected values for dry rock, whether or not a low resistivity layer is included in the model. This implies a widespread occurrence of free water in the crust, with greater amounts occurring at depth if the low resistivity zone exists.     

Use of magnetic hysteresis properties and electron spin resonance spectroscopy for the identification of volcanic ash: a preliminary study

This initial study investigates the possible use of hysteresis parameters and electron spin resonance (ESR) spectroscopy to identify and correlate volcanic ash. ESR and hysteresis properties are sensitive to characteristics such as the chemical composition, mineralogy, and grain size and shape. These characteristics are determined by the tectonic setting of the volcano and by the magmatic and eruptive history of the volcanic ash. Hysteresis properties and ESR spectra, therefore, should be distinct for each ash eruption and may help to identify the eruptive source of the ash and to correlate ash from unknown sources. We conducted ESR spectroscopy at room temperature and magnetic hysteresis measurements on 19 samples of a single ash, the 1974 October 14 eruption of the Fuego volcano, Guatemala, and on single samples of ash obtained from eight different volcanoes. The Fuego ash samples were obtained at increasing distances from the volcano. For the single Fuego ash, ESR spectra and hysteresis parameters become increasingly similar as the distance from the volcano increases. At distances greater than 30 km, ESR spectra and hysteresis properties are uniform. The variability of magnetic and ESR properties with distance from Fuego is due to the preferential fall-out of phenocrysts closer to the volcano. At large distances, the ash is more uniform, containing more glass and microcrystals. All eight ash samples from the different volcanoes can be distinguished from the distal Fuego 1974 October 14 ash using ESR spectra and hysteresis parameters. These results suggest that ESR and hysteresis measurements have a potential to be used as tools to identify distal ash when used in conjunction with geochemical, mineralogical and/or other types of data.     

On the location of the ionospheric current systems responsible for the lunar and solar magnetic variations

b
From a study of the sunspot cycle influence on the lunar ( L ) and solar ( S ) daily geomagnetic variations, Malin, Cecere & Palumbo have suggested that the electric currents responsible for these variations do not flow in the E -region as has hitherto been accepted. Indeed they suggested that the L current may even flow in the F 2 region. The consequences of such a suggestion are considered and it is shown that an L current in the F -region is highly unlikely from the dynamical point of view. The evidence for E -region currents is presented and it is suggested that the variation of E -region electron density used by Malin et al . to indicate conductivity changes in that region may not be a reliable indicator of such changes.     

重力测量在老挝万象盆地固体钾盐矿勘查中的有效性分析

老挝万象盆地钾盐矿赋矿地层为古近系古新统塔贡组下岩段,为隐伏矿层,分布面积广,厚度大,品位高。由于受钾盐矿层沉积基底地形差异及矿层的后期改造,钾盐矿层局部缺失。在钻探揭露控制矿层前预测矿体的赋存位置,可有效节约探矿成本。根据万象盆地古近系古新统塔贡组石盐岩、钾镁岩矿与泥岩之间存在密度差,认为重力测量能够有效区分盐类矿层的埋深、厚度,而钾盐矿层往往赋存于古近系古新统塔贡组巨厚层石盐矿层上部,重力负异常与钾盐矿层的对应性好,是钻探验证首选区域和万象盆地钾盐矿勘查较为有效的物探方法。     

山东莱州浅滩的沉积动态与地貌演变

在野外观测和历史地貌调查的基础上，利用地理信息系统和遥感技术，研究了现代莱州浅滩的地貌演变规律和人类活动对浅滩地貌冲淤动态的影响。结果表明，受其特有的沉积动力过程控制，莱州浅滩不断淤高并向东北迁移、西北延伸。1958年以来由于修建水库、码头和海底采沙等人类活动导致泥沙亏损，浅滩在继续向东北迁移、西北延伸的同时，总体上处于侵蚀、解体状态，在中部和近岸部分之间、近岸部分和刁龙嘴海岸之间先后形成了贯通的潮流槽，不同地貌部位冲淤状态存在差异。     

雷州半岛灯楼角沙岬的形成

沙岬(沙嘴)是一种海岸动力地貌类型。通过区域地貌背景、海底地貌-浅地层、海洋动力条件、相关的海岸沙坝和现代海滩的分析,认为灯楼角沙岬是来自琼州海峡的东向波浪和来自北部湾的西向波浪两种相向波浪动力平衡、灯楼角东沿岸存在逆时针环流和灯楼角西沿岸存在顺时针环流两者于此辐合,并把带来的砂子沉积下来的结果。     

The complex-image method for calculating the magnetic and electric fields produced at the surface of the Earth by the auroral electrojet

For studying the auroral electrojet and for examining the effects it can produce in power systems on the ground, it is useful to be able to calculate the magnetic and electric fields that the electrojet produces at the surface of the Earth. Including the effects of currents induced in the Earth leads to a set of integral expressions, the numerical computation of which is complicated and demanding of computer resources. An approximate solution can be achieved by representing the induced currents by an image current at a complex depth. We present a simple derivation of the complex-image expressions and use them to calculate the fields produced by the auroral electrojet at the surface of an earth represented by layered conductivity models. Comparison of these results with ones obtained using the exact integral solution show that the errors introduced are insignificant compared to the uncertainties in the parameters used. The complex-image method thus provides a simple, fast and accurate means of calculating the magnetic and electric fields.     

The in the Guliya shallow ice core during the prevailing summer monsoons and sea-air interactions

The correlations of the δ18Omax in the shallow ice core from the Guliya ice cap on the Tibetan Plateau with the global sea surface temperatures (SST) and height at the 500 hPa over the Northern Hemisphere were analyzed. The correlated regions on oceans that have a significant influence on the δ18Omax in the Guliya ice core are all located in ocean currents, or convergent regions of currents. They are the eastern Equatorial Pacific, the Northern Pacific Current, the Hot Pool in the eastern Indian Ocean, the Mozambique Current, the Northern Atlantic Current, the Canary Current and the Atlantic Equatorial Current. The δ18Omax in the Guliya ice core has negative correlations with the SST located in the lower latitudes, and positive correlations with the SST in the middle latitudes. The correlated areas at the 500 hPa that have a great impact on the δ8Omax are located in the subtropical highs over the mid-low-latitude oceans and the long-wave trough area over Balkhash Lake, where there are marked negative correlations between the heights in those areas and the δ18Omax. The influencing mechanism is displayed by the diversity of the vapor origins transported to the Guliya region. The strengths of the European ridge and the ridge over Baikal Lake have notable positive correlations with the 8180max. The two systems indirectly influence the vapor transportation towards the Guliya region by the adjustment of long-wave trough and ridge.     

Volume, heat and salt transport by the West Spitsbergen Current

During the summer of 2000 (June-July) 14 CTD and ADCP transects perpendicular to the West Spitsbergen Current and along the western border of the Barents Sea were made. The measurements covered the area between 69° 43'and 80° N and 01° and 20° E. The main purpose was to follow changes in volume, heat and salt content of Atlantic Water (AW) on its way north. The strongest and most stable flow of AW was located along the continental slope where northward flowing currents exceeding 40 cm/sec were measured. A few weaker northward branches were also found to the west of the slope. South-directed currents were recorded between them and eddy-like mesoscale structures were commonly observed. Measured by vessel-mounted acoustic Doppler current profiler (VM-ADCP), the net northward transport of AW volume in the upper 136 m layer decreased from nearly 6 Sv at the southernmost transect to below 1 Sv at a latitude of 78° 50'N. Similarly, heat transport drops from about 173 TW to about 9 TW and relative salt transport (over 34.92 psu) from 980 × 10³ kg/sec to 14 × 10³ kg/sec. Transport in the southern direction prevails at the transect located between 79° 07'and 79° 30'N. The calculated baroclinic geostrophic transport of AW volume, heat and salt in the upper 1000 m layer behaves similarly. East-directed transport dominates at the Barents Sea boundary while westward flow prevails on the western side of the West Spitsbergen Current.     

盐酸-硫酸镍混合溶液热力学性质

在HCl-NiSO4-H2 O混合溶液中 ,以标准氢电极和银—氯化银电极组成无液接电池 ,恒定溶液总离子强度I和NiSO4在溶液中的离子强度分数yB 的条件下 ,在 2 78 1 5～ 3 2 3 1 5K温度范围内测定下列电池的电动势Pt,H2 ( 1 0 1 3 2 5kPa) |HCl(mA) ,NiSO4(mB) ,H2 O|AgCl-Ag由于体系存在硫酸的二级解离 ,应用数学迭代方法确定平衡体系氢离子的浓度 ,计算了混合溶液中HCl的活度系数γA,结果表明 ,在溶液总离子强度保持恒定时 ,HCl的活度系数服从Harned规则。在溶液组成恒定时 ,盐酸的活度系数logγA 对热力学温度l/T作图 ,是一条直线     

Inference of the Lateral Heterogeneity of the Earth from the Eigenfrequency Spectrum: a Linear Inverse Problem

Summary
We consider the problem of inferring information about the lateral heterogeneity of the Earth's physical properties given certain measurements of the eigenfrequency splitting of the elastic-gravitational normal mode multiplets. We show that this problem can be formulated as a series of exactly linear inverse problems; the data which are relevant to at least the first two of these linear inversions can be measured without having to resolve fully the normal mode multiplets.     

The use of equivalent current systems in the interpretation of Geomagnetic Deep Sounding data

Summary. Many geomagnetic variation anomalies are probably caused by the channelling, through small-scale bodies, of electric currents induced in much larger conductors elsewhere. Consequently, the direct interpretation of anomalous magnetic fields by modelling the electromagnetic response of conductive structures may give misleading results. It is suggested that, rather than attempting to proceed directly from the electromagnetic fields to conductivity models, we should instead take the intermediate step of determining the distribution of anomalous current flow.
Maps of the anomalous fields over a conductive structure can be generated from inter-station transfer functions. If it is assumed that the internal currents are concentrated in a thin sheet at a specified depth, the equivalent current system in the sheet can be computed directly from the vertical magnetic field. The most straightforward method of performing this calculation is to compute the Fast Fourier Transform of the magnetic field data, and then to apply a wavenumber filter.
The presence of any vertical currents invalidates the thin sheet model. However, if the spatial distribution of a horizontal component of the anomalous magnetic field is also known, the presence of any vertical currents can be detected directly, and their position determined. The value of the methods is illustrated by applying them to the interpretation of a Geomagnetic Deep Sounding survey of the Kenya rift valley.     

Mineral magnetic properties of mixtures of environmental and synthetic materials: linear additivity and interaction effects

Mineral magnetic properties have been used recently to classify and to attempt to quantify the sources of sediments through environmental systems. Linear modelling techniques could be used with a wide range of concentration-dependent magnetic measurements to quantify the sources of sediments. To investigate wider application of linear modelling techniques using mineral magnetic properties, research has been conducted using laboratory mixtures of up to six source materials, including both natural environmental materials and synthetic compounds. While six sources may seem ambitious, this figure was used as an absolute upper limit rather than giving a real prospect of mathematically unmixing six sources. It has been found that even with the most magnetically differentiable materials, large errors are encountered when modelling the sources of the mixtures. This paper investigates the causes of 'non-additivity' of certain magnetic measurements and the failure of the linear modelling of the sources of the mixtures. Possible reasons for this failure include source homogeneity, calibration and linearity of equipment, magnetic viscosity of materials and/or the changing physical characteristics of the source materials once mixed together (interaction effects). In testing linear additivity, low-frequency susceptibility is the most reliable mineral magnetic measurement, while remanence measurements suffer from a systematic error in the expected results. Results have shown that in the best controlled conditions where the sources are identified and are artificially mixed together, the results of linear modelling are quite poor and at best four sources can be 'unmixed' with reasonable success. It is suggested that interaction within the mixtures, especially when containing highly ferrimagnetic burnt environmental materials, causes some of the non-additivity phenomena.     

Effects of mining on testate amoebae in a Finnish lake

Sediment geochemistry and testate amoebae (thecamoebians) were used to track the spatial extent and temporal evolution of mine loading and its impact on aquatic biota in Lake Pyh?j?rvi, central Finland. Pyh?salmi is an operating Zn-Cu–S mine, located by Lake Pyh?j?rvi. Mine loading to the lake comes mainly from wastewater. Highest metal loading occurred in the 1970s and 1980s. Present loading consists mainly of Ca and S that nearly saturate dense wastewaters with gypsum. This affects oxygen concentration in the lake’s northern basin, where effluent is presently discharged. Of 25 short sediment cores retrieved from Lake Pyh?j?rvi, 10 came from sites ‘downstream’ and 15 from ‘upstream’ of the mine. Three sample levels from each core were selected for further investigation after exploratory XRF metal analysis. Samples were chosen to represent lake conditions before the mine impact, during the peak impact phase, and at present. Results from pre-disturbance deposits show that the two lake basins are naturally different. The ‘downstream’ basin (Junttiselk?) has lower oxygen and a higher sedimentation rate, which was revealed by concentrations of redox-sensitive and clastic-related elements, as well as faunal distributions. The peak mine impact is reflected in the high concentration of S and metals Cu, Zn, Cd, Pb, which spread widely in the lake and increased > 100% at sites near the tailings area. These concentrations have since decreased, but not to pre-disturbance levels. The faunal response to peak metal concentrations was weak, spatially limited and masked by larger responses to other environmental factors, including eutrophication, oxygen concentration, and increased clastic input generated by land-use changes. These environmental factors and changes in mine water composition probably account for the reason that faunal assemblages did not return to the pre-mine situation. Instead, the modern fauna reflects a third assemblage type that developed after the peak-loading phase. Geochemical and thecamoebian analyses show that the mine has affected the two basins of the lake differently during the lake history. Results suggest that mining impacts could be mitigated with good planning and management.