Influence of Pre‐Existing Strength Discontinuities on Cenozoic Evolution of the Altyn Tagh Fault System, Northern Tibetan Plateau: Insights From Physical Analog Modeling

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Abstract The ∼1,600 km‐long, left‐lateral strike‐slip Altyn Tagh fault system defines the northern margin of the Tibetan Plateau, accommodating the India‐Eurasia convergence. While this important fault system has generally been considered to develop along several pre‐existing lithospheric strength discontinuities, its evolution needs further exploration. This study investigates the structural evolution of the Altyn Tagh fault system through physical analog modeling under both normal and hyper gravity conditions, employing four distinct models (M1, M2, M3, and M4) that incorporate various geometries of pre‐existing strength discontinuities. Each model exhibits unique development of fault networks, illustrating the complexity of fault behaviors under different conditions. Model M3, featuring a Z‐shaped pre‐existing strength discontinuity between the hard and soft domains (representing the Tarim—Alxa blocks and the Tibetan Plateau, respectively), effectively replicates key characteristics of the Altyn Tagh fault system, including two prominent sinistral strike‐slip faults (the Altyn Tagh fault and the North Altyn fault), the triangle‐shaped Altyn Shan, and a suite of E‐W striking transpressional faults that have been widely observed on the southern side of the fault system. Our analysis suggests that the Altyn Tagh fault system evolved along complex lithospheric strength discontinuities, resulting in an complex tectonic history characterized by the early activation of the North Altyn fault and subsequent strike‐slip motion along the younger Altyn Tagh Fault. This tectonic reorganization aligns with recent geological findings, underscoring the significant influence of ancient structural configurations on Cenozoic tectonic processes.

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