Strike-slip faulting drives asymmetric drainage evolution of rivers draining along the fault

Rivers draining across strike-slip faults have been the focus for analyzing strike-slip deformation through channel bends, while tectonic effects on those flowing along strike-slip faults as frequently observed are seldom studied. Recent advances in drainage-divide stability analysis offer a robust tool for studying drainage-basin evolution. Here, we investigate the Zemu and Karaxingar Rivers in western China to examine how rivers flowing along strike-slip faults evolve in response to strike-slip displacements. We assess the drainage-divide stability using χ plots and Gilbert metrics. The results reveal that sinistral strike-slip faulting in the Zemu River basin facilitates expansion of left-flank tributaries of the main trunk channel (viewed upstream) and shrinkage of right-flank tributaries (leftward divide migration at each flank), whereas dextral faulting in the Karaxingar River basin induces the opposite pattern. We suggest that the base-level changes induced by strike-slip faulting drive the observed characteristic divide migration. This study not only advances the understanding of the influence of strike-slip faulting on drainage-basin evolution but also provides a novel geomorphic indicator for detecting the offset direction of strike-slip faults.