Movie A-2. Shortening experiment

Movie showing the cross-sectional evolution of structures in the brittle-viscous domain. In contrast to the brittle domain, the thrust belt in the brittle-viscous domain is wider and lower. Viscous material is advected along forward thrusts with progressive deformation. Each section represents a 2 mm thick X-ray computed tomography (CT) slice parallel to the shortening direction. Initial width of the model was 27 cm; initial height was 3 cm. Shortening increment between frames is 1 cm. Viscous polydimethylsiloxane (PDMS) = dark grey, quartz sand = medium grey, corundum sand = light grey.