Issues During the Inversion of Crosshole Radar Data: Can We Have Confidence in the Outcome?

Clement, William P.

doi:10.2113/jeeg11.4.269

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…Figures (b) and (d) display the ray coverage (i.e., hit counts per model cell) for the final velocity models. For typical cross‐hole surveying geometries, we know that ray coverage plots are structurally comparable to resolution plots as derived from the resolution matrix in weighted, damped, least squares inversion approaches (e.g., Clement ). Better resolved regions tend to correspond to higher ray coverage.…”

Section: Inversion Resultsmentioning

confidence: 99%

Integrated analysis and interpretation of cross‐hole P‐ and S‐wave tomograms: a case study

Dietrich

Tronicke

2008

Near Surface Geophysics

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We present cross-hole P-and S-wave seismic experiments that have been performed along a ~100 m long transect for the detailed characterization of a contaminated sedimentary site (Bitterfeld research test site, Germany). We invert the corresponding first break arrival times for the P-and S-wave velocity structure and compare two different strategies to interpret these models in terms of pertinent lithological and geotechnical parameter variations. The first (common) approach is based on directly translating the tomographic velocity models into the parameters of interest (e.g., elastic moduli). The second (zonal) approach first reduces the tomographic parameter information to a limited number of characteristic velocity combinations via k-means cluster analysis. Then, for each zone (cluster) further parameters including uncertainties can be estimated. In the presented case study, our results indicate that the zonal approach provides an effective means for the integrated interpretation of different co-located data.rial at a site located in the New Madrid Seismic Zone, Missouri, USA. In another recent example, Daley et al. (2004) performed cross-hole P-and S-wave tomography to characterize fractured basalt at the Idaho National Engineering and Environmental Laboratory, USA. However, the number of published case studies illustrating the benefit of combining P-and S-wave cross-hole data is limited and further experience is needed to establish this combined approach for a variety of near-surface applications.Commonly, tomographic parameter fields (such as P-and S-wave velocity models) are interpreted manually by delineating regions characterized by similar parameter ranges. Such an interpretation is usually focused on outlining subsurface structures or zones which, then, can eventually be further interpreted, e.g., in terms of lithology by comparing the tomographic images to corresponding borehole records. In addition, we usually can estimate further petrophysical parameter models by directly translating the tomographic models using adequate petrophysical translations or by establishing statistical relations between borehole data and the tomographic parameters in the vicinity of the borehole (e.g., Yamamoto 1994;Angioni et al. 2003). However, the outcome of these common approaches often depends on the experience and preconceptions of the interpreter and the validity and applicability of the petrophysical model used.In this paper, we present the results of P-and S-wave crosshole seismic experiments performed to characterize a contaminated sedimentary site in Bitterfeld, Germany. After providing background information on the field site and the experiments, we present the inverted P-and S-wave velocity models and compare

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Section: Inversion Resultsmentioning

confidence: 99%

Integrated analysis and interpretation of cross‐hole P‐ and S‐wave tomograms: a case study

Dietrich

Tronicke

2008

Near Surface Geophysics

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Imaging weak zones in the foundation using frequency domain attenuation tomography

Balasubramaniam

Jha²,

Chandrasekhar

et al. 2013

Journal of Applied Geophysics

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A Comparison of Two Travel-time Tomography Schemes for Crosshole Radar Data: Eikonal-equation-based Inversion Versus Ray-based Inversion

Balkaya

Akçiğ

Göktürkler

2010

JEEG

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Some test studies were performed for comparison of two travel-time inversion schemes for tomographic evaluation of crosshole ground-penetrating radar (GPR) data. The first scheme was a linearized inversion based on Tikhonov regularization (Method 1). In this scheme, ray tracing was not a part of the inversion algorithm and the Jacobian matrix was calculated by numerical differentiation. Travel-time calculations were performed by a finite-difference eikonal equation solver. Model velocity fields were updated by matrix inversion techniques using iterative conjugate gradient solvers. The inversion process was stabilized by a smoothness-constrained regularization. The second scheme was based on a ray tracing algorithm (Method 2) and velocities were updated by a simultaneous iterative reconstruction technique (SIRT) using both straight- and curved-ray approximations. The test studies included synthetic travel-time data sets generated from the models with various velocity distributions. Broyden’s update was implemented within Method 1 to expedite the calculation of the Jacobian matrix, and this greatly improved the computational performance. In the tests, the effect of the regularization parameter on the models from Method 1 was examined. Also, how the straight-ray and curved-ray assumptions affected the solutions from Method 2 was illustrated. The effect of the initial velocity distribution on the resulting tomograms was exemplified by the solutions from both Method 1 and Method 2. The velocity tomograms from Method 1 were characterized by smaller travel-time residuals, Euclidean distances and lower errors in the velocity of cells. Also, the convergence rates of the solutions from Method 1 were faster than those from Method 2. Method 1 better imaged the zones with the high velocity contrast than Method 2, and both methods produced similar velocity distributions within the zones with low velocity contrast. Overall, Method 1 yielded better solutions compared to Method 2, and the curved-ray inversion generated relatively better results than the straight-ray inversion.

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Issues During the Inversion of Crosshole Radar Data: Can We Have Confidence in the Outcome?

Cited by 3 publications

References 23 publications

Integrated analysis and interpretation of cross‐hole P‐ and S‐wave tomograms: a case study

Integrated analysis and interpretation of cross‐hole P‐ and S‐wave tomograms: a case study

Imaging weak zones in the foundation using frequency domain attenuation tomography

A Comparison of Two Travel-time Tomography Schemes for Crosshole Radar Data: Eikonal-equation-based Inversion Versus Ray-based Inversion

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