Stretching faults

An unfamiliar class of faults in flowing rock bodies has wall rocks that lengthen or shorten in the slip direction while slip accumulates. Such faults may be anticipated in metamorphic or sedimentary flow environments, where rheological and frictional properties or fluid pressures permit, on scales ranging from microscopic to regional. Large-scale structures of this kind may be important tectonic elements below levels in the crust to which faults with more rigid wall rocks extend.