Thrust Fault Damage Zones in Eastern Longmen Shan Range, China

We analyze here the subsurface damage zone of a thrust fault, named the Pengxian fault (PXF), at the eastern margin of the Longmen Shan Range, Sichuan, China. By using a 3-D seismic reflection survey and the seismic attributes, we find: (1) The PXF is ~55 km long, intra-basinal, frontal thrust fault that dips 40°–50° with a displacement of 100–800 m; (2) The thickness of the composite damage zones varies along the fault, and it ranges from 1 km to more than 2 km; (3) The PXF is segmented, and its damage zones terminate against the Triassic detachment zone from above and below. The thickness of PXF damage zones and their internal structure are interrelated to the local displacement and the regional carbonate lithology. We argue that the observed composite damage zones increased in thickness during the evolution from the fault's initial stage to its current mature state. This study presents the methodology for identifying the fault damage zones in carbonate sequences.