Flexural slip

Relative movement parallel to bedding during folding, allowing layers at different radii of curvature to accommodate different arc lengths. For two layer surfaces separated by thickness $h$ through bend angle $\theta$, their arc-length difference is approximately $h\theta$. Bedding-parallel slip can accommodate that mismatch without requiring each layer to stretch by the same amount. Shallow flexural slip can produce surface breaks above a blind reverse fault.