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Earth and Space Sciences · 术语表

什么是 Section restoration, pin line, kink-band method？

又称： section restoration · pin line · kink-band method

Definition 8.11 University Earth and Space Sciences — Year 3 · 第 8 章 — Structural Analysis

Section restoration undoes, on a cross-section drawn parallel to the direction of tectonic transport, the deformation it shows, event by event in the reverse order, keeping the lengths of the beds and the areas of the units in the plane of the section. A pin line is a line across the beds, placed where they did not slip along each other (in the undeformed foreland, or on the axial surface of a symmetric fold), which is taken to be perpendicular to the beds in the restored section; lengths are measured from it. In the kink-band method the folds are drawn as straight limbs of constant bed thickness joined at sharp hinges, whose axial surfaces bisect the angle between the limbs; each bed is then a broken line, whose length is the sum of its straight segments.

Restoring a kink-band fold, drawn to balance with limbs at 50. (a) Two competent layers folded into straight limbs of constant thickness over a weak layer that thickens into the core, between two pin lines on the axial surfaces of the synclines, which stayed at the original level. (b) The restored section: each bed laid straight with its length measured along the limbs, L_0, longer than the deformed section by the shortening S. The hatched area A, by which the top layer stands above its original level, equals S times its height h above the detachment; the weak layer has the same area in both panels.
Restoring a kink-band fold, drawn to balance with limbs at 50∘50{}^{\circ}. (a) Two competent layers folded into straight limbs of constant thickness over a weak layer that thickens into the core, between two pin lines on the axial surfaces of the synclines, which stayed at the original level. (b) The restored section: each bed laid straight with its length measured along the limbs, L0L_0, longer than the deformed section by the shortening SS. The hatched area AA, by which the top layer stands above its original level, equals SS times its height hh above the detachment; the weak layer has the same area in both panels.
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