A hybrid refraction algorithm

Diggins, Chuck; Carvill, Charles; Daly, Cathal

doi:10.1190/1.1892453

Cited by 3 publications

(3 citation statements)

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“…It is sometimes appropriate to use more than one method to analyze the refraction data (e.g., Laidley and Mills, 1986;Beattie and Wardell, 1987;Diggins et al, 1988;Zanzi, 1990). For example, the high-and low-spatial-frequency components can be estimated indepen-dently.…”

Section: Applicability and Choice Of Refraction Interpretation Methodsmentioning

confidence: 99%

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5. Refraction Surveys

Cox¹

1999

Static Corrections for Seismic Reflection Surveys

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Refraction SurveysDownloaded 10/09/15 to 129.78.139.28. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/ c c c c c or t z V x z V z V Downloaded 10/09/15 to 129.78.139.28. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/ Downloaded 10/09/15 to 129.78.139.28. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/ Downloaded 10/09/15 to 129.78.139.28. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/Fig. 5-20. Refraction arrival picking using a peak-trough ratio technique: (a) seismic data after removal of the refractor moveout or stepout; (b) display of all peaks and troughs, with the maximum ratio between successive events (the preferred pick) indicated by a thicker line (Chun and Jacewitz, 1981; preprint).

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Section: Applicability and Choice Of Refraction Interpretation Methodsmentioning

confidence: 99%

“…Diggins et al (1988) proposed a multistage procedure with the objective of minimizing long-wavelength errors introduced in a decomposition approach from possible errors in the refractor velocity (see also Archer and Heathcote, 1985). More than one value is often present in the data.…”

Section: Applicability and Choice Of Refraction Interpretation Methodsmentioning

confidence: 99%

5. Refraction Surveys

Cox¹

1999

Static Corrections for Seismic Reflection Surveys

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“…Several attempts have been introduced to get a unified interpretation technique for shallow refraction seismic data. Diggins et al () presented a hybrid refraction algorithm in which refractor velocity independent and refractor velocity dependent methods were used. Taner et al () introduced a tomographical approach by solving a set of generalized surface delay‐time equations using the method of weighted least squares and conjugate gradient.…”

Section: Introductionmentioning

confidence: 99%

Migration and interpretation of first arrival inflection points due to lateral variations

Seisa¹

2009

Near Surface Geophysics

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The majority of shallow refraction seismic algorithms work well only in cases of a horizontal plane or inclined refractors. In case of piecewise lateral variation either in dip angle and/or in velocity along the refracting interfaces, the applications of these conventional methods are usually problematic. This is because of the existence of two different inflection points along the first arrival travel‐time curve. The first inflection point corresponds to the crossover point while the later inflection points are due to these lateral variations. The terms true and apparent inflection points will be used in this study to refer to inflection points corresponding to crossover points and those due to lateral variations, respectively. The intersection of the backward extrapolation from inflection points with the time axes will give true intercept times from true inflection points and apparent intercept times from apparent inflection points. Migration of apparent inflection points aims to remove the distortion due to lateral variations of refracted rays from the first arrival traveltime curves by moving them to their proper locations. After the migration of the apparent inflection points, the intercept time technique can be applied in a conventional way to map shallow subsurface refracting interfaces with piecewise lateral variations. The common traveltime elements recorded from the same refracting interfaces and the layer reciprocal time are required for this migration process. This algorithm will be generalized after the removal of the effects due to the apparent inflection points and calculation of the corresponding migrated traveltime elements. Each pair of the common migrated traveltime elements from forward and reverse directions will represent a simple traveltime curve of two planes. Therefore, most shallow refraction algorithms can be applied to this simple traveltime curve using their own equations to map refracting interfaces recorded from media with piecewise lateral variations.

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Practical 3D refraction statics

Dent¹

1989

Explor. Geophys.

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Analysis of refracted first breaks has traditionally assumed that the data have been collected using special geometries that enhance the results, e.g. reversed profiles with regularly spaced geophones in-line between two shots. The geometries used to collect most 3D reflection data are quite different. Thus refraction analysis to obtain statics using traditional methods requires both approximations and selection of a subset of the data. The surface-consistent method allows use of nearly all the data, thus providing the high redundancy required for statistical robustness. A large survey incorporating both a new 3D survey and older 2D lines yielded refraction statics that greatly improved the final results.The surface-consistent method assumes that the refractor can be approximated by a horizontal plane under each station. When the refracting surface is steeply dipping, this assumption may break down. The Generalized Reciprocal Method is a traditional refraction analysis technique that gives improved results for steeply-dipping refracting surfaces. The surface-consistent method can also be made less sensitive to dip by a generalization, i.e. assume a dipping plane under each station. The refracting surface between the stations can be approximated by interpolation of these planes using the "linear projection" technique. A comparison of results using the two surface-consistent methods on synthetic data generated from a model of a buried, steep-walled valley shows the superior results obtainable.

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A hybrid refraction algorithm

Cited by 3 publications

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5. Refraction Surveys

5. Refraction Surveys

Migration and interpretation of first arrival inflection points due to lateral variations

Practical 3D refraction statics

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