Deriving effects of pressure depletion on elastic framework moduli from sonic logs     

Anne-Kari Furre  Mona Andersen  Anita Smalø Moen  Randi Kristin Tønnessen 《Geophysical Prospecting》2009,57(3):427-437

We have developed a method to determine the effect of pore pressure depletion on elastic framework moduli, by utilizing sonic logs from wells drilled at different locations through a reservoir at varying depletion stages. This is done by first inverting the sonic logs for elastic framework bulk and shear moduli, thus carefully removing pressure dependent fluid effects. By crossplotting these elastic framework moduli against an increase in net stress (which is directly related to depletion), we derive the stress sensitivity of the elastic framework moduli. We found that the observed stress sensitivity was consistent with time-lapse seismic results and that the sensitivity derived from the sonic logs was much smaller than predicted by hydrostatic measurements on core samples. This method is applicable to depletion scenarios in mature fields and can be used both for modelling and inverting time-lapse seismic data for effects of pore pressure depletion on seismic data.  相似文献   

Retention of mercury in sediments of the Baltic Sea near Oulu,Finland     

Kimmo Tolonen  Erkki Alasaarela  Anita Liehu 《Journal of Paleolimnology》1988,1(2):133-140

Several cores were compared to elucidate the grade of mercury retention in sediments of the Baltic Sea near Oulu, Finland. The known history of the mercury discharge to waste water from a chlor-alkali plant, the primary pollution source, was compared to that in the sedimentary record. One core was dated by lead-210 and varve counts. During the past thirty years, the rate of sedimentation was up to 10 mm per year corresponding to a dry matter accumulation rate of about 3 kg m^–2a^–1. Under these conditions, most of the mercury reaching the sediment was retained. Correspondingly, the mercury levels in fish were considerably lower, with a delay of some five years.The present mercury content of the upper layers is some 1/4 or 1/5 that of the late 1970's, but it is still some twentyfold compared to levels at the beginning of the century. The extent to which the present mercury level in the sediment represents the various phases of industrial emission remains unsolved due to the origin of mercury in this sea area from several other sources and due to difficulties in exact core correlations from different years.  相似文献   

Spectroscopic diagnostics for N III ion     

B. N. Dwivedi  Anita Mohan  A. K. Gupta 《Astrophysics and Space Science》1996,243(1):163-163

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Line diagnostics for Ne V and Mg V solar ions     

B. N. Dwivedi  Anita Mohan 《Solar physics》1995,158(2):237-248

Spectroscopic diagnostics for the Nev and Mgv solar ions have been investigated. The theoretical forbidden line ratios from these ions are presented for estimating the Ne/Mg variation in different solar structures. Calculations for density and temperature line diagnostics of these ions are given for the several spectral line ratios and their applications are discussed with the help of available solar observations in space. Future observations from the CDS and the SUMER experiments aboard the SOHO satellite are also discussed.  相似文献   

Trend removal in spatially correlated datasets     

Anita Singh  Ashok K. Singh 《Mathematical Geology》1996,28(1):111-132

Typically, datasets originated from mining exploration sites, industrially polluted and hazardous waste sites are correlated spatially over the region under investigation. Ordinary kriging (OK) is a well-established geostatistical tool used for predicting variables, such as precious metal contents, biomass, species counts, and environmental pollutants at unsampled spatial locations based on data collected from the neighboring sampled locations at these sites. One of the assumptions required to perform OK is that the mean of the characteristic of concern is constant for the entire region under consideration (e.g., there is no spatial trend present in the contaminant distribution across the site). This assumption may be violated by dalasets obtained from environmental applications. The occurrence of spatial trend in a dataset collected from a polluted site is an indication of the presence of two or more statistical populations (strata) with significantly different mean concentrations. Use of OK in these situations can result in inaccurate kriging estimates with higher SDs which, in turn, can lead to incorrect decisions regarding all subsequent environmental monitoring and remediation activities. A univariate and a multivariate approach have been described to identify spatial trend that may be present at the site. The trend then is removed by subtracting the respective means from the corresponding populations. The results of OK before and after trend removal are being compared. Using a real dataset, it is shown that standard deviations (SDs) of the kriging estimates obtained after trend removal are uniformly smaller than the corresponding SDs of the estimates obtained without the trend removal.  相似文献   

Asymmetries during the maximum phase of solar cycle 22     

Anita Joshi 《Solar physics》1995,157(1-2):315-324

This paper presents the results of studies of the asymmetries (N-S and E-W) for different manifestations of solar activity events (sunspot groups, H flares and active prominences/filaments) during the maximum-phase (1989–1991) of solar cycle 22. During the period considered, the results obtained show the existence of a real N-S asymmetry, whereas the E-W asymmetry may exist only for H flares. There is no definite relationship between the asymmetries and the occurrence of events; however, around low activity sometimes we find enhanced asymmetry, and low asymmetry around high activity. Our study suggests a good agreement with similar studies made by others.  相似文献   

Editorial          下载免费PDF全文

Streck  Martin J.; Grunder  Anita L. 《Journal of Petrology》1997,38(1):133-163

The Rattlesnake Tuff of eastern Oregon comprises >99% ofhigh-silica rhyolite glass shards and pumices representing 280km³ of magma. Glassy, crystal-poor, high-silica rhyolite pumicesand glass shards cluster in five chemical groups that rangein color from white to dark gray with increasing Fe concentration.Compositional clusters are defined by Fe, Ti, LREE, Ba, Eu,Rb, Zr, Hf, Ta, and Th. Progressive changes with increasingdegree of evolution of the magma occur in modal mineralogy,mineral composition, and partition coefficients. Partition coefficientsare reported for alkali feldspar, clinopyroxene, and titanomagnetite.Models of modal crystal fractionation, assimilation, successivepartial melting, and mixing of end members cannot account forthe chemical variations among rhyolite compositions. On theother hand, 50% fractionation of observed phenocryst compositionsin non-modal proportions agrees with chemical variations amongrhyolite compositions. Such non-modal fractionation might occuralong the roof and margins of a magma chamber and would yieldcompositions of removed solids ranging from syenitic to granitic.A differentiation sequence is proposed by which each more evolvedcomposition is derived from the previous, less evolved liquidby fractionation and accumulation, occurring mainly along theroof of a slab-like magma chamber. As a layer of derivativemagma reaches a critical thickness, a new layer is formed, generatinga compositionally and density stratified magma chamber. KEY WORDS: high-silica rhyolite; partition coefficients; differentiation; zoned ash-flow tuff; layered convection  相似文献   

Dredging for edible cockles (Cerastoderma edule) on intertidal flats: short-term consequences of fisher patch-choice decisions for target and non-target benthic fauna     

Kraan  Casper; Piersma  Theunis; Dekinga  Anne; Koolhaas  Anita; van der Meer  Jaap 《ICES Journal of Marine Science》2007,64(9):1735-1742

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A review of: “Quantitative hydrogeology—groundwater hydrology for engineers”     

Reimer Herrmann 《地球物理与天体物理流体动力学》2013,107(4):351-352

Abstract

by Ghislain de Marsily, Academic Press, vii+440 pp. U.S. $29.95 (ISBN 0-12-208916-2) 1986.  相似文献   

Public climate-change skepticism,energy preferences and political participation     

Anita Engels  Otto Hüther  Mike Schäfer  Hermann Held 《Global Environmental Change》2013,23(5):1018-1027

Many studies have shown a general decline of public concern about climate change or vice versa a rise in public climate-change skepticism, in particular in the U.S. and other Anglo-Saxon countries. There is a vivid debate on whether this is a global phenomenon, on which factors explain the decline, and on the broader societal implications of these trends in the context of the transformation toward a low-carbon society. We add to this literature by presenting the results of a recent general population survey in Germany in which we looked for systematic linkages between public climate-change skepticism on one hand, and energy preferences and political participation on the other. Germany is an interesting testbed as it is currently involved in a large-scale restructuring of its system of energy supply toward renewable energy sources (the “Energiewende”). Our results indicate that climate-change skepticism has not diffused widely in Germany, but that it correlates with less support of renewable energy sources. However, skepticism correlates negatively with political participation, and there is no strong political outlet for public climate-change skepticism in Germany. Alternative potential barriers for the successful implementation of the “Energiewende” are also discussed.  相似文献