Fault mechanism in active creeping Chihshang fault, Taiwan

Exploration of fault mechanisms is the key for understanding the earthquake nucleation and rupture, as mechanisms have been proposed for fault mechanics but which remains few in nature. By delicate microanalysis, here we investigate an active creeping fault zone, Chihshang fault in Taiwan accommodating a slip rate of 3 cm/year on average. Microstructural observations show that nanoparticles and amorphous materials occur at shallow crustal depths, resembling those on experimentally deformed products. In addition, compared to adjacent footwall conglomerate, fault gouge shows the combination of enrichment of smectite and networks of scaly clay fabrics. Because amorphous materials are kinetically unstable and easily transferred to smectite underground, we presume the enrichment of smectite was derived from the transformation of amorphous materials. We propose this mechanism is one of fault mechanisms in active creeping fault.