Application of high-precision LiDAR technology in research on active fault-induced offset geomorphic features - A case study of the Juxian-Tancheng segment of the Yishu fault zone

The Tancheng-Lujiang fault zone (also referred to as the TanLu fault zone), one of the most significant large-scale active faults in eastern China, has great seismogenic potential while passing through several cities with the activities and accumulation of human beings. To investigate the geometric distribution and activity characteristics of the TanLu fault zone, this study focused on the Juxian-Tancheng segment of the Yishu fault zone—a part of the TanLu fault zone. Given the vegetation coverage in eastern China, airborne light detection and ranging (LiDAR) and terrestrial laser scanning were employed to collect high-precision topographic data of the Zuoshan (Yibujian), Zhonghuashan, Jishan, and Maolingshan segments of the Yishu fault zone, as well as the Jiangjialing area. Based on these data, this study analyzed the slip distribution of the faults. The measured point cloud data were processed through point cloud matching, mosaic, vegetation filtering, and triangulated irregular network (TIN)-based modeling. As a result, a digital elevation model (DEM) with a spatial resolution of 0.1 m was obtained. This model allowed for a high-definition three-dimensional reconstruction of the microgeomorphic features of faults. Furthermore, this study extracted the dextral horizontal offset amount of fault-controlled gullies and the vertical offset amount of fault scarps. Based on these data, as well as the validation and comparison with the paleo-earthquake events revealed by geological mapping and trenches, this study conducted a quantitative analysis of the fault activity characteristics in the Juxian-Tancheng segment of the Yishu fault zone. The results indicate that the horizontal and vertical offset amount along the Zuoshan (Yibujian), Zhonghuashan, Jishan, and Maolingshan segments of the Yishu fault zone exhibit grading characteristics, suggesting multi-phase (3‒5 times) activities and multiple paleo-earthquake events since the Late Quaternary. The findings of this study will provide an important basis for further research on the kinematics and geometry of the Tan-Lu fault zone. They also demonstrate the wide application prospects of terrestrial laser scanning and airborne LiDAR in research on active faults.