Gravity and magnetic field interpretation based on transformations of horizontal gradients in the VECTOR system

A method of potential field processing based on the transformation of vectors of the total horizontal gradient in windows of various sizes is considered. The gradients are calculated at the centers of triangles, whose vertices are points of observations, as a rule, of gravity and magnetic fields. Averaging of horizontal gradients of the field rather than initial values of the field is the main distinction of this approach from the known methods. This procedure, referred to in this paper as vector scanning of the field, makes it possible to obtain layer distributions of field sources in a 3-D diagram that is a quasi-density model of the study medium within the framework of certain model concepts. The paper presents a model example demonstrating the possibility of separating the fields produced by two sources located on a vertical line and an example illustrating the application of this method to the interpretation of the gravity field in the zone of the geodynamic influence of the Urals.     

Modelling the hydrological response of mediterranean catchments,Prades, Catalonia. The use of distributed models as aids to hypothesis formulation

This paper attempts to extend the physical arguments underlying the distributed TOPMODEL concepts in an application to the strongly seasonal contributing area responses in two adjacent small mediterranean catchments in the Prades region of Catalonia, Spain. A perceptual model of hydrological response in these catchments is used to suggest possible modifications of the model in a hypothesis testing framework, including an attempt to modify the topographic index approach to reflect the expansion of the effective area of subsurface flow during the wetting-up sequence. It is found that slight improvements in modelling efficiency are possible but that different model parameter distributions are appropriate for different parts of the record. The model was much more successful for the catchment producing the higher runoff volumes. © 1997 John Wiley & Sons, Ltd.     

The application of satellite systems for crustal deformation studies

Measurements of crustal deformations provide important quantitative data for use in the study of the properties of materials and processes in the Earth's interior, and also for the purposes of delineation of active faults by which oil and gas deposits might be confined.Only the usage of satellite systems makes it possible to conduct deformometric studies over large areas and to accomplish measurements within reasonable time periods. The satellite system discussed here is based on the following concepts: pairs of satellites exchange phase information as the result of which the paired satellites emit coherent signal observed at ground sites by the interferometric method. In this process, the measured value is an increment of the difference of distances from the ground site to the two satellites.     

Identifiability analysis: towards constrained equifinality and reduced uncertainty in a conceptual model

Abstract

Different sets of parameters and conceptualizations of a basin can give equally good results in terms of predefined objective functions. Therefore, a need exists to tackle equifinality and quantify the uncertainty bands of a model. In this paper we use the concepts of equifinality, identifiability and uncertainty to propose a simple method aimed at constraining the equifinal parameters and reducing the uncertainty bands of model outputs, and obtaining physically possible and reasonable models. Additionally, the uncertainty of equifinal solutions is quantified to estimate the amount by which output uncertainty can be reduced by knowing how to discard most of the equifinal solutions of a model. As a study case, a conceptual model of the Chillán basin in Chile is carried out. From the study it is concluded that using identifiability analysis makes it possible to constrain equifinal solutions with reduced uncertainty and realistic models, resulting in a framework that can be recommended to practitioners, especially due to the simplicity of the method.     

地震破裂的方向性效应相关概念综述

地震断层破裂的方向性会造成在地震动记录和地震动分布场中出现一些典型的特征,分析方向性效应的特点以及方向性效应产生的原因对于揭示近场地震动的特征有重要的意义.文中以诸多研究文献为基础,从方向性效应的研究回顾开始,分析了方向性效应的概念,并重点论述了方向性效应对地震动影响的特点、方向性效应的产生原因及其影响因素.为了阐明与...     

Vertical structure of the midlatitude winter <Emphasis Type="Italic">F</Emphasis> region of the ionosphere during postmidnight enhancements in <Emphasis Type="Italic">NmF</Emphasis>2

The behavior of the vertical structure of the ionospheric F2 layer, including the variations in the heights of the maximum and bottom of the layer, its half-thickness, and electron content at some fixed heights during postmidnight enhancements in the electron density at the F2 layer maximum (NmF2), has been studied based on the data of the ionospheric vertical sounding, conducted in Alma-Ata (76°55′ E, 43°15′ N) in 2005–2006. The analysis of the amplitude and phase relationships between the measured parameters of the layer made it possible to qualitatively complete the existing concepts of the mechanisms by which the discussed effect is maintained. It is shown that the accelerated decrease in the electron density of the layer within a short time interval preceding the beginning of the postmidnight increase in NmF2 is governed not only by recombination processes but also by the plasma redistribution over the increasing thickness of the layer. The regularly observed effect of the delay in the moment of reversal in the motion direction of the layer bottom relative to the corresponding moment for the layer maximum made it possible to conclude that the meridional wind asynchronously reverses its direction from the poleward daytime to the equatorward nighttime in the entire layer: the direction changes later with decreasing height.     

Limnologische Transport- und Nährstoffmodelle

Physical as well as biochemical processes have a significant influence on the material balance of a lake. Mathematical concepts are developed to treat transport phenomena with which a comparison of different lakes under certain systematic aspects becomes possible. A two-box model consisting of the subsystems epilimnion and hypolimnion, for lakes with one specific limiting nutrient factor (e.g., phosphorus) is employed to evaluate eutrophication processes. In particular, a theoretical basis forVollenweider's [3] empirical relation between specific phosphorus loading and the trophic state is presented. Finally, the inhomogeneous O₂-consumption in the deep part of the lake during summer stagnation is calculated with diffusion theory.      

Evaluation of Combined Direct-Push Methods Used for Aquifer Model Generation

Most established methods to characterize aquifer structure and hydraulic conductivities of hydrostratigraphical units are not capable of delivering sufficient information in the spatial resolution that is desired for sophisticated numerical contaminant transport modeling and adapted remediation design. With hydraulic investigation methods based on the direct-push (DP) technology such as DP slug tests, DP injection logging, and the hydraulic profiling tool, it is possible to rapidly delineate hydrogeological structures and estimate their hydraulic conductivity in shallow unconsolidated aquifers without the need for wells. A combined application of these tools was used for the investigation of a contaminated German refinery site and for the setup of hydraulic aquifer models. The quality of DP investigation and the models was evaluated by comparisons of tracer transport simulations using these models and measured breakthroughs of two natural gradient tracer tests. Model scenarios considering the information of all tools together showed good reproduction of the measured breakthroughs, indicating the suitability of the approach and a minor impact of potential technical limitations. Using the DP slug tests alone yielded significantly higher deviations for the determined hydraulic conductivities compared to considering two or three of the tools. Realistic aquifer models developed on basis of such combined DP investigation approaches can help optimize remediation concepts or identify flow regimes for aquifers with a complex structure.     

The value of climate forecasting

A short survey is given of the concepts associated with meteorological forecast verification and value. Apart from matters of mathematical detail the field has not advanced greatly over the last thirty years. If significant skill develops in long-range (i.e. climate) forecasting, it will be more than ever necessary for the general user to understand the possible consequences—in particular that there can be many circumstances where some forecast skill is worse than none at all. Some highly idealized agricultural examples are used to illustrate the point. It is emphasized that some numerical measure of confidence will have to be associated with (or be built into) probability precasts of climate.     

Seismicity in the far Arctic areas: Severnaya Zemlya and the Taimyr Peninsula

Journal of Seismology - A permanent seismic station was for the first time installed on Severnaya Zemlya in the Russian Arctic. This made it possible to record low-magnitude earthquakes occurring...     

A Bayesian approach for estimating extreme flood probabilities with upper-bounded distribution functions

Some recent research on fluvial processes suggests the idea that some hydrological variables, such as flood flows, are upper-bounded. However, most probability distributions that are currently employed in flood frequency analysis are unbounded to the right. This paper describes an exploratory study on the joint use of an upper-bounded probability distribution and non-systematic flood information, within a Bayesian framework. Accordingly, the current PMF maximum discharge appears as a reference value and a reasonable estimate of the upper-bound for maximum flows, despite the fact that PMF determination is not unequivocal and depends strongly on the available data. In the Bayesian context, the uncertainty on the PMF can be included into the analysis by considering an appropriate prior distribution for the maximum flows. In the sequence, systematic flood records, historical floods, and paleofloods can be included into a compound likelihood function which is then used to update the prior information on the upper-bound. By combining a prior distribution describing the uncertainties of PMF estimates along with various sources of flood data into a unified Bayesian approach, the expectation is to obtain improved estimates of the upper-bound. The application example was conducted with flood data from the American river basin, near the Folsom reservoir, in California, USA. The results show that it is possible to put together concepts that appear to be incompatible: the deterministic estimate of PMF, taken as a theoretical limit for floods, and the frequency analysis of maximum flows, with the inclusion of non-systematic data. As compared to conventional analysis, the combination of these two concepts within the logical context of Bayesian theory, contributes an advance towards more reliable estimates of extreme floods.     

二维层状介质中衍射波的计算

本文讨论了衍射波的计算,它是文献[5]的继续和发展,是为了应用射线法解决二维地震人机联作工作的一部分。根据波的物理性质,引入了等效炮点、等效检波点和等效界面等概念,将Berryhill导出的衍射波计算公式推广到倾斜界面和楔形结构等情形。这一工作与文献[1-3]中的工作相结合,在实用上解决了二维地震人机联作解释中的正演计算方法问题。     

New methods for measuring the permeability of rock samples for a single-phase fluid

A complex of methodology, instrumentation, and software tools is worked out, which makes it possible to accomplish high-precision measurements of permeability for a single-phase fluid and its anisotropy within a wide range of values both under the normal conditions and high temperature and pressure.The transient method, modified with allowance for the dependence of the properties of a percolating gas on the parameters of its state, enables one to simultaneously determine, from the data of a single experiment, the permeability values for a sample of condensed fluid and the Klinkenberg constant, which characterizes the pore space of rock. This approach made it possible to substantially increase the accuracy of measurements, reducing their labor-intensiveness.The method of varying the flow shape makes it possible to simultaneously determine, in the course of a single experiment, the axial and radial components of the permeability tensor of anisotropic rocks with layered structure. The instrumentation and software implementing these new methodologies are developed and thoroughly tested.     

Parameters influencing the growth and decay of the regular part of the AE index

The statistical behavior of the AE index, which describes the intensity of auroral electrojets, has been studied using hourly data. It has been shown that the AE index depends on the solar wind parameters as well as on its own value in the preceding hour. This makes it possible to describe the AE index behavior by the first-order inhomogeneous differential equation. The index growth rate is proportional mainly to the southward component of the interplanetary magnetic field (IMF). The timescale of the breakup of the currents responsible for the index is approximately 2 h. A similarity in the time variations in the AE and Dst indices has been referred to. The empirical formulas, which make it possible to restore the missing values of the IMF southward component from the available AE or Dst indices, have been proposed.     

Method of monitoring atomic oxygen and molecular nitrogen composition in the upper atmosphere on XUV images of the Sun

A method for determining the basic atmosphere O/N₂ based on the solar observations is described. It is shown that, on XUV images of the Sun received by transillumination of the atmosphere, it is possible to observe its state controlling the O/N₂ ratio. The method allows local inhomogeneities of the upper atmosphere to be studied. Its abilities were demonstrated according to the SPIRIT complex on board the Coronas-F satellite.     

A stability analysis of the geostatistical approach to aquifer transmissivity identification

In recent years, geostatistical concepts have been applied to the inverse problem of transmissivity estimation from piezometric head data. It has been claimed that such methods overcome various difficulties encountered in other approaches. However, the reconstruction of transmissivity from head measurements is ill-posed as it depends on derivatives of the head field. Consequently, any accurate method for its solution is likely to encounter numerically ill-conditioned systems. This paper reviews the geostatistical approach, and uses the stability analyses of linear algebra to show that, as the amount of available data increases and the discretization of the system is refined, both a numerically ill-conditioned parameter estimation problem and ill-conditioned cokriging equations may appear. Therefore, while the geostatistical approach does have conceptual appeal, it does not avoid the fundamental difficulties arising out of the ill-posed nature of transmissivity identification. Instead, the method is likely to be quite sensitive to these difficulties, so care must be taken in its formulation to minimize their effects. A means to stabilize the geostatistical method is suggested and numerical experiments that highlight key points of our analysis are given.     

Environmental Risk and Environmental Damage to Surface Water Quality: Topicality,Terminology, Quantitative Estimates

The concepts of environmental risk and environmental hazard to surface water quality are discussed. The interpretation of these concepts in different countries is analyzed and a list of more exact terms and definitions regarding these concepts is proposed. A method for estimating the environmental risk and environmental damage to surface water quality is developed. Possible applications of the estimated environmental risk and environmental hazard for surface water quality management are discussed.     

Modeling the Spectral Features of Acoustic Noise Produced by Gas Flow in Rock Samples Based on the Theory of Ensemble of Interconnected Pore Resonators

Izvestiya, Physics of the Solid Earth - A new model describing the pore space as an ensemble of interconnected Helmholtz resonators is proposed. This model makes it possible to improve the...     

Coupled motions of the inner core and possible geomagnetic implications

As the inner core is a good electrical conductor any ambient magnetic field would diffuse into it on a time scale long compared to several thousand years, and conversely be frozen there on shorter time scales. From the observations that the dipole component of the Earth's magnetic field has been inclined persistently to the spin axis over hundreds of thousands of years, and that the dipole drifts and decays significantly more slowly than the nondipole field, it is suggested that the external dipole is simply a manifestation of a field frozen in an inclined inner core. It is shown that the much neglected gravitational restoring torque can be significant for an inclined inner core, so much so that its motion is in the main determined by gravity, with electromagnetic and inertial coupling effects being of secondary importance. A regular precession of the inner core is shown to be possible where its spin axis drifts westward relative to the mantle with a period of ～ 7000 y. Some preliminary calculations of the possible motions of a gravitationally coupled mantle-inner core system are shown.