Activities and geomorphic deformation of the fault belt on the southern margin of Wuwei Basin, Gansu Province during the Late Quaternary

The fault belt on the southern margin of Wuwei Basin is located in the front of the northeastern margin of the Qinghai-Tibet Plateau, and its spacial distribution and activity in the Late Quaternary are still not very clear.In additon, the magnitude 8.0 Gulang eurthquake in 1927 also caused some surface reptures on the fault zone.Based on the principles of tectonic geology and geomorphology and the method of chronological test, the relevant investigation and research were carried out.The results show that the fault belt on the southern margin of the Wuwei Basin extends strikes NWW to SEE in a right-step oblique array.From west to east, the overall behavior of the fault belt during the Late Quaternary was mainly thrusting and gradually transformed to thrusting and strike-slip or strike-slipping.The vertical activity intensity was generally weak in the west and strong in the east.Moreover, middle part exhibited strongest activity, and the horizontal left-lateral slip component was great.Its activity has obvious segmentation, that is, the latest activity of the western section is generally earlier than the regional T1 terrace, and the middle-eastern section cuts the ground of the T1 terrace, which reflects the trend of eastward migration of its latest activity.Combined with the surface rupture relics caused by the 1927 M8.0 Gulang earthquake, the latest activity in its middle-eastern section occurred at the end of the Holocene.According to the Late Quaternary activity pattern of the fault belt, face scratches, the kinematic characteristics of shear joints developed in the Late Cenozoic strata, and conjugate tension joints, the horizontal direction of the maximum principal compressive stress field during the late Quaternary was the NNE-SSW, and the orientation of the stress field changed slightly from west to east.These insights provide important basis for exploring the Late Cenozoic tectonic evolution of the three-dimensional deformation of Wuwei Basin, the strata growth and tectonic geomorphic deformation process in the northeastern margin of the Qinghai-Tibet Plateau, the rupture mechanism of the Gulang earthquake, and climate and environment changes.