Geophysics

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Shallow-structure characterization by 2D elastic full-waveform inversion
Geophysics - Tập 76 Số 3 - Trang R81-R93 - 2011
Anouar Romdhane, Gilles Grandjean, Romain Brossier, Fayçal Réjiba, S. Operto, J. Virieux
Assessing the effectiveness of elastic full-waveform-inversion (FWI) algorithms when applied to shallow 2D structures in the presence of a complex topography is critically important. By using FWI, we overcome inherent limitations of conventional seismic methods used for near-surface prospecting (acoustic tomography and multichannel spectral analysis of surface waves). The elastic forward ...... hiện toàn bộ
Permeability prediction based on fractal pore‐space geometry
Geophysics - Tập 64 Số 5 - Trang 1447-1460 - 1999
H. Pape, Christoph Clauser, Joachim Iffland
Estimating permeability from grain‐size distributions or from well logs is attractive but difficult. In this paper we present a new, generally applicable, and relatively inexpensive approach which yields permeability information on the scale of core samples and boreholes. The approach is theoretically based on a fractal model for the internal structure of a porous medium. It yields a gener...... hiện toàn bộ
Inversion of the geophysical inverse problem for n layers with nonuniqueness reduced to n cases
Geophysics - Tập 44 Số 4 - Trang 801-819 - 1979
Barry Thornton
A new method is described for reducing nonuniqueness in the geophysical inverse problem for n layers to n cases, provided the ratio of characteristic impedances of sequential layers is of the order of unity and upper and lower layer boundary conditions are known. The method is based on impedance concepts which allow application to a number of different electromagnetic or acoustic experime...... hiện toàn bộ
On the relationship between iron concentration and induced polarization in marsh soils
Geophysics - Tập 72 Số 1 - Trang A1-A5 - 2007
Nasser M. Mansoor, Lee Slater
Induced polarization (IP) measurements [Formula: see text] were conducted on seventeen clay and peat marsh soils that were subsequently analyzed for heavy metal concentrations, moisture content, organic matter, porosity, specific surface area, and pore fluid conductivity. A Cole-Cole model was fit to each sample and model parameters analyzed in terms of physicochemical properties. We foun...... hiện toàn bộ
Electrical properties of iron-sand columns: Implications for induced polarization investigation and performance monitoring of iron-wall barriers
Geophysics - Tập 70 Số 4 - Trang G87-G94 - 2005
Lee Slater, Jaeyoung Choi, Yuxin Wu
We investigate the electrical response (0.1–1000 Hz) of reactive iron barriers by making measurements on zero valent iron ([Formula: see text])-sand columns under the following conditions: (1) variable [Formula: see text] surface area (0.1–100% by volume [Formula: see text] under constant electrolyte chemistry; (2) variable electrolyte activity (0.01–1 mol/liter), valence (mono trivalent)...... hiện toàn bộ
Relationship between low-frequency electrical properties and hydraulic permeability of low-permeability sandstones
Geophysics - Tập 75 Số 3 - Trang E131-E141 - 2010
Norbert Zisser, Andreas Kemna, G. Nover
The relationship between low-frequency electrical properties and hydraulic permeability of rocks has been the focus of geophysical investigations for a long time because it offers a possibility for an in situ and noninvasive permeability estimation of rocks. We examined the hydraulic and low-frequency [Formula: see text] electrical properties as well as the anisotropic properties of low-p...... hiện toàn bộ
Crosshole IP imaging for engineering and environmental applications
Geophysics - Tập 69 Số 1 - Trang 97-107 - 2004
Andreas Kemna, Andrew Binley, Lee Slater
Induced polarization (IP) imaging is a promising tool in engineering and environmental studies. Application of this technique for near‐surface investigations has previously been limited by incomplete understanding of the physicochemical controls on the IP response, together with a lack of appropriate methods for data inversion. As laboratory studies have shown, description of IP in terms o...... hiện toàn bộ
Induced polarization of shaly sands
Geophysics - Tập 49 Số 8 - Trang 1267-1287 - 1984
Harold J Vinegar, M. H. Waxman
Equations have been developed that relate induced polarization (IP) in shaly sands to measurable petrophysical parameters. The induced‐polarization process has been modeled in terms of two mechanisms: clay counterion displacement and membrane blockage. The resulting equations can be used to determine shaliness, brine conductivity, and oil saturation from in‐phase and out‐of‐phase conducti...... hiện toàn bộ
Chirp subbottom profiler for quantitative sediment analysis
Geophysics - Tập 54 Số 4 - Trang 445-450 - 1989
Steven G. Schock, Lester R. LeBlanc, Larry A. Mayer
A wide‐band, frequency‐modulated, subbottom profiling system (the chirp sonar) can remotely determine the acoustic attenuation of ocean sediments and produce artifact‐free sediment profiles in real time. The chirp sonar is controlled by a minicomputer which performs analog‐to‐digital and digital‐to‐analog conversion, correlation processing, and attenuation estimation in real time. The min...... hiện toàn bộ
Sinkhole detection with 3D full seismic waveform tomography
Geophysics - Tập 85 Số 5 - Trang B169-B179 - 2020
Majid Mirzanejad, Khiem T. Tran, Michael McVay, David Horhota, Scott J. Wasman
Sinkhole collapse may result in significant property damage and even loss of life. Early detection of sinkhole attributes (buried voids, raveling zones) is critical to limit the cost of remediation. One of the most promising ways to obtain subsurface imaging is 3D seismic full-waveform inversion. For demonstration, a recently developed 3D Gauss-Newton full-waveform inversion (3D GN-FWI) m...... hiện toàn bộ
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