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The mechanisms of tectonic transfer and strain partitioning at the eastern termination of the Kunlun fault system, particularly the role of the relatively strong Ruoergai Subblock, remain unclear. In this work, we used the finite element method to determine how the Ruoergai Subblock affects regional deformation. The results show that the Ruoergai Subblock is moving to the east or northeast in a manner that differs from the motion of the Bayan Har Block in the eastward extrusion process and thus accounts for the formation and behavior of the Awancang and Longriba faults. In addition, strain partitioning on the eastern margin of the Tibetan Plateau is progressively transferring from the Awancang fault, Ruoergai Subblock, and Longriba fault to the Longmenshan thrust. In this study, a block-controlled pattern is proposed that accounts for the distribution and behavior of most of the faults on the northern and eastern margins of the Tibetan Plateau. Our study has played a certain reference role in the consideration of railway fracture resistance parameters in the area of the southern section of the Longmenshan fault and the Xianshuihe fault during construction of the Tibet Railway. • Influence of Subblock in the consideration of Tibet railway fracture resistance parameters. • Tectonic partitioning near the eastern margin of the Tibetan Plateau. • Influence of the Ruoergai Subblock's physical properties on tectonics. • Strong block control on fault formation and behavior. [ABSTRACT FROM AUTHOR]

The Sichuan-Tibet Railway in eastern Tibet runs across numerous seismogenic faults with high seismic risks. The Lancangjiang fault (LCJF), one of the essential strike-slip faults within the Qiangtang block, traverses the railway. However, the geometry and late Quaternary activities of the LCJF remain unclear, limiting the assessment of seismic hazards on the Sichuan-Tibet Railway and the understanding of kinematic patterns in eastern Tibet. Based on the interpretation of high-resolution satellite imagery, field observations, and shallow geophysical exploration, we first mapped the detailed geometry of the northern LCJF. It consists of two branches: Yangda-Yaxu fault (YYF) and Baqing-Leiwuqi fault (BLF), which merge eastwards onto the main LCJF. Displaced landforms and multiple numerical dating techniques reveal that the YYF is a mainly sinistral fault with a late Quaternary slip rate of ~2.2 + 0.6/−0.5 mm/yr and a minor vertical component (~0.1 mm/yr). The BLF undergoes an oblique motion with a left-lateral slip rate of ~1.2 + 0.5/−0.3 mm/yr and a northeast-vergent reverse rate of ~1.2 + 0.4/−0.2 mm/yr in the Holocene. Vector analysis of slip rates suggests that the LCJF has a sinistral rate of ~3.5 + 1.1/−0.8 mm/yr with a reverse component of ~1.6 + 0.4/−0.3 mm/yr, displaying an essential role in strain partitioning of eastern Tibet. Together with slip rates of other intra-block faults, the kinematic pattern of eastern Tibet probably applies to the sub-block model. Offset geologic units yield a total displacement of ~10–11 km for the YYF. Using the slip rate of the YYF, the LCJF was initiated at ~5.9–3.9 Ma, probably related to the establishment of the present-day strain pattern and the onset of crustal thickening in eastern Tibet during the late Miocene. In addition, the active YYF and BLF across the Sichuan-Tibet Railway have a seismic potential of Mw ~7.2–7.3 that will produce a ~ 1.8–2.0 m sinistral slip on the YYF, and a ~ 2.0 m horizontal, and ~ 1.1–1.3 m reverse motion on the BLF. They will pose a high seismic hazard potential on the railway. This study provides quantitative data for regional seismic hazard analysis and shows insights into the deformation mechanism of the plateau. • The geometry of the northern LCJF is first mapped. • The northern LCJF has a late Quaternary ~3.5 mm/yr sinistral and ~ 1.6 mm/yr reverse rate. • The seismic potential of the northern LCJF on the Sichuan-Tibet Railway is estimated. • The LCJF takes an important role in strain partitioning in eastern Tibet. • The initiation of the LCJF is related to the late-Miocene tectonic event in eastern Tibet. [ABSTRACT FROM AUTHOR]