Seismic and electromagnetic controlled-source interferometry in dissipative media   总被引：3，自引：1，他引：2  

Kees Wapenaar  Evert Slob  Roel Snieder 《Geophysical Prospecting》2008,56(3):419-434

Seismic interferometry deals with the generation of new seismic responses by crosscorrelating existing ones. One of the main assumptions underlying most interferometry methods is that the medium is lossless. We develop an ‘interferometry‐by‐deconvolution’ approach which circumvents this assumption. The proposed method applies not only to seismic waves, but to any type of diffusion and/or wave field in a dissipative medium. This opens the way to applying interferometry to controlled‐source electromagnetic (CSEM) data. Interferometry‐by‐deconvolution replaces the overburden by a homogeneous half space, thereby solving the shallow sea problem for CSEM applications. We demonstrate this at the hand of numerically modeled CSEM data.  相似文献   

Using multicomponent GPR to monitor cracks in a historical building     

Luciana Orlando  Evert Slob   《Journal of Applied Geophysics》2009,67(4):327

We tested the usefulness of acquiring multicomponent GPR data to detect cracks in a historical building, and to monitor their dynamics, caused by a slowly and irregularly moving landslide. We used 2 GHz bipolar antennas in a configuration that allows for acquiring the in-line and cross-line electric field components with x- and y-directed antennas. The 2 × 2 data matrix was collected on a floor in the building along transects at four different times over a period of one year. The data were processed with a standard 2D scalar algorithm and with the latest 3D single component vector algorithm that corrects for antenna effects. We have implemented a 3D single component vector migration algorithm in a 2.5D sense to produce 2D slices of a 3D vector migration image by applying the algorithm on line data. This procedure allows for migrating single component line data taking into account all vector effects as well as three-dimensional wave propagation. We show that the 2.5D vector migration images have a much better in-line resolution than the migration images obtained by applying a standard 2D scalar migration algorithm.The GPR profiles agree with the a priori information about the structure of the floor. In particular, we detected two different types of anomalies, only a few of which can be due to utilities and to metallic mesh. Some shallower anomalies agree well with the cracks visible on the tiling, suggesting that some cracks can be directly detected using GPR. Visually there were no changes in the cracks on the floor and no clear changes in the GPR data could be attributed to possible subsurface changes in the cracks. The variations in the GPR images seemed primarily caused by changes in the coupling of the antennas with the investigated structure (floor) depending on the season when the measurements were made. For this reason the monitoring aspect of the survey is not successful.  相似文献   

Equipartitioning is not sufficient for Green's function extraction          下载免费PDF全文

Roel Snieder  Yuanzhong Fan  Evert Slob  Kees Wapenaar 《地震科学（英文版）》2010,23(5):403-415

The extraction of the Earth's Green's function from field fluctuations is a rapidly growing area of research.The principle of Green's function extraction is often related to the requirement of equipartitioning,which stipulates that the energy of field fluctuations is distributed evenly in some sense.We show the meaning of equipartitioning for a variety of different formulations for Green's function retrieval.We show that equipartitioning is not a sufficient condition,and provide several examples that illustrate this point.We discuss the implications of lack of equipartitioning for various schemes for the reconstruction of the Green's function in seismology.The theory for Green's function extraction is usually based on a statistical theory that relies on ensemble averages.Since there is only one Earth,one usually replaces the ensemble average with a time average.We show that such a replacement only makes sense when attenuation is taken into account,and show how the theory for Green's function extraction for oscillating systems can be extended to incorporate attenuation.  相似文献   

Measurements of Aitken nuclei,cloud nuclei,and ice nuclei in precipitation at the Jungfraujoch,Switzerland     

Mr. W. H. Slob  W. P. A. G. Ottevanger 《Theoretical and Applied Climatology》1973,21(4):349-363

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Linking dynamic elastic parameters to static state of stress: toward an integrated approach to subsurface stress analysis   总被引：1，自引：0，他引：1  

S. Tirek  E.C. Slob  M.W.P Dillen  S.A.P.L. Cloetingh  J.T. Fokkema 《Tectonophysics》2005,397(1-2):167

Stress is the most important parameter to understand basin dynamics and the evolution of hydrocarbon systems. The state of stress can be quantified by numerical geo-mechanical modelling techniques. These techniques require static elastic parameters of the rocks as input, while tectonic and gravitational forces are given as explicit boundary conditions to compute the local state of stress at different scales. We developed a technique to determine the density and elastic constants at seismic frequencies using full Zoeppritz inversion on angle-dependent seismic reflection data. The dynamic elastic parameters as obtained from seismic data differ from their static equivalents, which are necessary to determine the static state of stress. The dynamic elastic parameters are related to their static equivalents through experimentally obtained relations. In these rock-physics experiments, the static and dynamic elastic parameters are measured simultaneously during different external loading conditions. The experiments used here are all carried out in a tri-axial pressure machine under equal axial stresses. Then pre-stack seismic data analysis in combination with the relation between the static and dynamic elastic parameters, from the rock-physics experiments, provides the input parameters for geo-mechanical modelling.  相似文献   

The long-term fate of Cu, Zn, and Pb adsorption complexes at the calcite surface: An X-ray absorption spectroscopy study     

Evert J. Elzinga  Ashaki A. Rouff  Richard J. Reeder 《Geochimica et cosmochimica acta》2006,70(11):2715-2725

In this study, the speciation of Zn²⁺, Pb²⁺, and Cu²⁺ ions sorbed at the calcite surface was monitored during a 2.5-year reaction period, using extended X-ray absorption spectroscopy to characterize metal speciation on the molecular scale. Experiments were performed using pre-equilibrated calcite-water suspensions of pH 8.3, at metal concentrations below the solubility of metal hydroxide and carbonate precipitates, and at constant metal surface loadings. The EXAFS results indicate that all three metals remained coordinated at the calcite surface as inner-sphere adsorption complexes during the 2.5-year ageing period, with no evidence to suggest slow formation of dilute metal-calcite solid solutions under the reaction conditions employed. All three divalent metals were found to form non-octahedral complexes upon coordination to the calcite surface, with Zn²⁺ adsorbing as a tetrahedral complex, Cu²⁺ as a Jahn-Teller distorted octahedral complex, and Pb²⁺ coordinating as a trigonal- or square-pyramidal surface complex. The non-octahedral configurations of these surface complexes may have hindered metal transfer from the calcite surface into the bulk, where Ca²⁺ is in octahedral coordination with respect to first-shell O. The use of pre-equilibrated calcite suspensions, with no net calcite dissolution or precipitation, likely prevented metal incorporation into the lattice as a result of surface recrystallization. The results from this study imply that ageing alone does not increase the stability of Zn²⁺, Pb²⁺, and Cu²⁺ partitioning to calcite if equilibrium with the solution is maintained during reaction; under these conditions, these metals are likely to remain available for exchange even after extended sorption times.  相似文献   

The Third GABLS Intercomparison Case for Evaluation Studies of Boundary-Layer Models. Part A: Case Selection and Set-Up     

Fred C. Bosveld  Peter Baas  Erik van Meijgaard  Evert I. F. de Bruijn  Gert-Jan Steeneveld  Albert A. M. Holtslag 《Boundary-Layer Meteorology》2014,152(2):133-156

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Effect of Ni2+, Zn2+, and Co2+ on green rust transformation to magnetite     

Farr  Orion  Elzinga  Evert J.  Yee  Nathan 《Geochemical transactions》2022,23(1):1-25

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