Song Wang

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.

The Ebao Basin, which locates along the northwest segment of the Qilian‐Haiyuan fault, has experienced several destructive earthquakes in past decades. A 10 km long distributed acoustic sensing (DAS) array was deployed with an existing telecom fiber‐optic cable after the 2022 Mw6.6 Menyuan earthquake, which destroyed high‐speed railways and highways in this region. The DAS array continuously recorded ambient noise and earthquake signals during the 5‐day deployment period. Noise cross‐correlation functions (NCFs) were calculated, and the Rayleigh wave signal clearly emerged on the NCFs. The phase velocities of the fundamental mode between 2.5 and 17 Hz were measured with the modified Frequency‐Bessel transform method. The S‐wave velocity structure along the cable, extending to a depth of 200 m, was constructed using the surface wave tomography method. It consists of three blocks, with velocity variations of up to 12%. P‐wave delay times of regional earthquakes support the lateral variation among the three blocks. Both Vs30 and site amplification predicted with our S‐wave velocity model correlate well with the ground motion induced by local earthquakes. Precursor and coda waves on the NCFs reveal four possible faults, and fault zone scattered waves are also observed on the record of local earthquakes.