Quaternary Tectonic Deformation and Geomorphic Evidence from the Yi Ong–Zayu Segment of the Jiali Fault Zone, Southeastern Tibetan Plateau

The Jiali Fault Zone is one of the key active tectonic structures along the southeastern margin of the Tibetan Plateau and has been widely regarded as the southern boundary structure accommodating the lateral extrusion and eastward escape of the Qiangtang and Sichuan–Yunnan blocks. Assessing its Quaternary activity is important for understanding the tectonic evolution and deformation partitioning of southeastern Tibet. This study focuses on the Yi ong–Zayu segment of the Jiali Fault Zone, using high-resolution stereo imagery from the GF-7 satellite. The ERDAS dense image matching method was applied to generate a dense point cloud and a 0.8 m high-resolution digital surface model. Combining regional remote sensing image interpretation with field surveys, we characterize the geomorphic expression and Quaternary deformation of the Yi ong–Zayu segment. The results show no significant surface displacement along the fault. The alluvial fans are largely preserved, and there are no continuous, co-directional offsets along the tributary channels or river systems. In particular, clear evidence for Quaternary right-lateral strike-slip displacement is absent. Instead, localized normal faults with NW–SE to approximately E–W strikes occur in limited areas. This study focuses on the Yi ong–Zayu segment of the Jiali Fault Zone, using high-resolution stereo imagery from the GF-7 satellite. The ERDAS dense image matching method was applied to generate a dense point cloud and a 0.8 m high-resolution digital surface model. Combining regional remote sensing image interpretation with field surveys, we characterize the geomorphic expression and Qua-ternary deformation of the Yi ong–Zayu segment. The results show no significant surface displacement along the fault. The alluvial fans are largely preserved, and there are no continuous, co-directional offsets along the tributary channels or river systems. In particular, clear evidence for Quaternary right-lateral strike-slip displacement is absent. Instead, localized normal faults with NW–SE to approximately E–W strikes occur in limited areas. These findings indicate that the Yi ong–Zayu segment experienced limited Quaternary deformation and has not functioned as a major boundary strike-slip fault since the Quaternary. Instead, it has been influenced by the rotational extrusion of the southeastern Tibetan Plateau, exhibiting characteristics of regional extensional tectonic activity. The present-day deformation is consistent with a rotation–extrusion model, in which crustal material undergoes clockwise rotation around the eastern Himalayan syntaxis and gradually transfers southeastward toward the Sichuan–Yunnan region due to the obstruction of the rigid Sichuan Basin.