Using UAV photogrammetry technology to extract the quantitative parameters of earthquake surface rupture zone：A case study of the southern Zhongwei M7½ earthquake in 1709

This paper firstly introduces the operation flow for obtaining digital elevation model （DEM） and geomorphic data （digital orthophoto map） by unmanned aerial vehicle （UAV）photogrammetry technology, and compares and analyzes the differences in horizontal position and elevation of DEM generated by three kinds of dense point clouds with different masses. Then, the vertical and horizontal displacements of seismic faults on the main surface rupture zone of the south of Zhongwei M7½ earthquake in 1709 were extracted. The results showed that, as for the DEM generated by dense point cloud of high quality, its resolution was in centimeters, and the processing time was not too long. Compared with DEM generated from the other two kinds of dense point clouds, the difference in horizontal position and elevation is less than 0.100 m. Based on high quality dense point cloud we can generate the DEMs with resolution of 6.33 cm/pix, extract the vertical dislocation of the fault on the surface rupture of 1709 earthquake as long as （0.704±0.293） m, horizontal displacement of 5.1 m, which was consistent with previous studies and therfore represented the co-seismic slip of the 1709 earthquake. This suggests that by the UAV photogrammetry technology we can obtain high resolution topography data of typical sites on the earthquake surface rupture zone, and seismic fault quantitative parameters can be further extracted based on the generated DEM.