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Parallel folds commonly form by a deformation mechanism called flexural slip, where folding is accommodated by motions on minor faults that occur along some mechanical layering — usually bedding. Flexural-slip surfaces, which can be observed in core or outcrop, may vary in spacing from a few millimeters to several tens of meters in spacing.
 
Parallel folds commonly form by a deformation mechanism called flexural slip, where folding is accommodated by motions on minor faults that occur along some mechanical layering — usually bedding. Flexural-slip surfaces, which can be observed in core or outcrop, may vary in spacing from a few millimeters to several tens of meters in spacing.
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==Shortcomings in seismic images of folds==
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Folds can be distorted or only partially imaged in seismic sections.
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<gallery mode=packed heights=200px widths=200px>
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File:ST53_Part01_Pg06A.jpg
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</gallery>
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==Locating axial surfaces in seismic sections==
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Migration moves dipping reflections upward and laterally to properly image the fold geometry, but reflections on non-migrated or under-migrated sections do not accurately represent fold shape. However, axial surfaces can be inferred on these sections by mapping the truncations of horizontal reflections.
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<gallery mode=packed heights=200px widths=200px>
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File:ST53_Part01_Pg06B.jpg
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</gallery>

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