Control of Multiple Detachments on Structural Development in the Southern Junggar Fold‐and‐Thrust Belt, Northern Tian Shan: Implications for Seismic Hazard Assessment.

As large earthquakes in contractional fold‐and‐thrust belts are usually associated with complex ruptures along multiple faults or fault splays, the evaluation of potential rupture extent and relevant hazards continues to be challenging. We present a case study on the geometry and kinematic evolution of the southern Junggar fold‐and‐thrust belt, northern Tian Shan, where the 1906 M 8 Manas earthquake occurred. Our interpretations of seismic reflection profiles acquired during oil and gas exploration demonstrate that multiple detachments played significant roles in controlling the structural segmentation. We speculate that seismic potential in active fold‐and‐thrust belts can be under‐estimated by relying on the mapped surface fault traces. Structural analysis of subsurface images in sufficient detail may provide important insights into seismic hazard evaluation and hence complement traditional paleo‐seismic studies, particularly in densely populated regions such as the city of Urumqi. Key Points: Hutubi anticline is a pure shear‐dominated detachment fold, which has experienced multi‐stage tectonic shortening since the Late JurassicMultiple detachments have predominantly controlled the structural segmentation in the southern Junggar fold‐and‐thrust beltLateral structural variations and kinematic evolution also need to be considered in seismic hazard assessment [ABSTRACT FROM AUTHOR]