Fault breccia is a type of rock formed within a fault zone, composed of angular fragments of rock that have been crushed and broken by fault movement. These fragments are typically cemented together by finer materials. Fault breccia is significant in the study of fault mechanics, rock deformation, and the interpretation of past seismic activity.
Reference: Sibson, R. H. (1977). Fault Rocks and Fault Mechanisms. Journal of the Geological Society.