Clay-clast aggregates in fault gouge: An unequivocal indicator of seismic faulting at shallow depths?

▸ Formation conditions of clay-clast aggregates (CCAs) were revisited. ▸ CCAs form in room-dry gouges even at subseismic slip rates (5 × 10−4 m/s). ▸ Granular flow in gouges may be important for the formation of CCAs. ▸ CCAs in gouges at shallow depths are not an unequivocal indicator of seismic slip.