3-D fault architecture in Pengxian thrust, eastern of the Longman Shan Range, China

The internal architecture of fault damage zones may control the fluid flow in the upper crust, which remains unknown due to limited data in the subsurface. Here we investigated the damage zone of a thrust fault using a 3-D seismic reflection dataset in the eastern margin of the Longmen Shan Range, Sichuan, China. We applied the seismic attributes of variance, curvature and dip azimuth and the results indicate several geometrical features of the Pengxian fault (PXF): (1) the PXF is a 55-km-long, intra-basin, frontal thrust fault with dip angle between 50o-60o; (2) the thicknesses of the damage zones range from 1.0 km to lager than 2 km, varying along the fault strike and between the lithologies; (3) the damage zones terminate against the Middle-Lower Triassic detachment from above and below. The architecture of the PXF presents segmented and km-scale damage zones within carbonate that is possibly correlated with the displacements of the fault. We anticipated that such damage zones are formed in a mature stage with composite slip surfaces evolved from immature faults with one slip surface. This study provides a comprehensive method in identifying the architecture of buried faults in carbonate sediments, and would be helpful in evaluating the fault behavior in the upper crust.