Surface Rupture of the 1985 Wuqia Earthquake Sourced by a Structural Wedge in the Pamir‐Southern Tian Shan Convergence Zone

Abstract Through integrated analyses of pre‐ and post‐earthquake satellite images, field mapping and trenching data, as well as prior mapping data, we reexamine the spatial extent, morphology, slip distribution and slip kinematics of the surface rupture produced by the 1985 M w 6.9 Wuqia earthquake, one of the strongest events ever recorded within the Pamir‐Southern Tian Shan convergence zone. Our study reveals that (a) the 22‐km‐long surface rupture has vertical offsets of 0.2–3.3 m and very locally dextral offsets of 0.5–1.6 m; (b) the eastern rupture segment is characterized by sinuous trace shape and diverse morphology and slip kinematics, contrasting to the linear reverse fault scarps and bedding‐parallel slip geometry of the western segment, which can be attributed to the varying development of preexisting bedding‐parallel weakness along the two segments. These results, combining with known earthquake source parameters and subsurface structural geometry, support the interpretation of Ainscoe (2018) that the Wuqia earthquake rupture involves two faults of a structural wedge. The mainshock slip was generated by a NE‐dipping transpressional blind fault within the crystalline basement, while the surface rupture was likely formed predominantly by postseismic slip along a SW‐dipping thrust fault within the sedimentary cover. This study enhances our understanding of the earthquake fault interaction at different depth levels and highlights the role of structural inheritance on the formation of surface rupture in collisional tectonic settings.