X-ray CT scan of experimentally deformed travertine block (24 x 11 x 15 cm) showing a continuous fault core that was developed during shear. The fault core consists of thick layer of cataclastic gouge (fault core) and damage zone. The image shows both the gouge and damage zones in red shades mainly due to their compacted porosity compared to their original matrix (in blue). The structure of the fault core varies from a few thin patches to a fully developed zone of about 6 mm in thickness. (See Giwelli et al. 2017, Petroleum Geoscience, 23, 92–103).