Fault slip behavior and segmentation revealed by geomorphic offset clusters: An example from the middle Riganpei Co fault, central Tibet

Abstract

High-resolution topographic datasets are useful for revealing offset features of fault geomorphology and are thus important for reconstructing the evolution history of faults. The Riganpei Co fault, located in the central Tibetan Plateau, is an important active fault on the northern boundary of the Bangong-Nujiang suture zone. In this study, WorldView-2 stereo images were used to generate high-resolution topographic data in a 1 km range on both flanks of the middle section of the Riganpei Co fault. We interpreted the tectonic geomorphology along the fault, classified it into distinct units, and measured the horizontal displacement of each unit. Within approximately 70 km along the fault, we obtained 396 displacement measurements ranging from 0 to 60 m. Given the evident uneven distribution of displacement, the fault was divided into four segments. In each fault segment, the reconstructed slip distributions revealed a tendency of larger displacements in the center and smaller displacements toward the ends. The cumulative offset probability distribution (COPD) of displacements displays 4–5 offset clusters in the range of 0–30 m for each segment, suggesting that at least four large earthquakes ruptured this fault. The binned COPD demonstrated that there are differences in the displacement accumulation modes among these fault segments, where the middle segment follows a characteristic slip accumulation mode. Reconstructed cumulative slip profiles revealed a complex pattern of strong earthquake activities along the Riganpei Co fault.