2. Study area
In this study, we selected Wolong (WL) region, an area of Tibet where ideal geological conditions exist, to investigate the relationship between faulting and the spatial geometrical and mechanical characteristics of a rock mass controlled by faulting (Fig. 1). In the WL region, Yarlung Tsangpo (YLZP) River turns abruptly to the northwest, providing excellent exposures of structures and rocks along the YLZP Fault. The area is affected by the YLZP Fault that belongs to a south-dipping thrust system composed of at least five south dipping thrust faults (Heim & Gansser, 1939; Yin et al., 1999; Murphy & Yin, 2003). YLZP suture zone between the Indian and the Eurasian plates has been reactivated by northward back thrusting and dextral strike-slip movement (Burg & Chen, 1984) with an underthrusting rate of 21.3 mm/yr of the Indian Shield (Murphy & Yin, 2003) and a right-lateral slip rate of 2.6±0.7 mm/yr (Chen et al., 2004). The nearly E–W trending suture zone extends for more than 2000 km in southern Tibet, whose deformation along the multiple fault planes of suture zone is complex and shows variations from place to place, depending mainly on its orientation (Aitchison et al., 2011; Yin et al., 1994; Xu et al., 2015). For the geological description of the area we relied on Quidelleur et al. (1997), Chen et al. (2004) and Xu et al. (2015). The lithology of the area is mainly diorite and granite with a small component of gneiss.