A number of lines of evidence suggest that some crustal faults are weak compared to laboratory measurements of frictional strength; however, a satisfactory explanation for this weakness has remained elusive. Laboratory evidence is now provided for a brittle, frictional weakening mechanism based on common fault zone fabrics. Fault samples with well-developed foliation are shown to be extremely weak compared to their powdered equivalents.
- Cristiano Collettini
- André Niemeijer
- Chris Marone
