Evaluating the Potentiality of Using Control-free Images from a Mini Unmanned Aerial Vehicle (UAV) and Structure-from-Motion (SfM) Photogrammetry to Measure Paleoseismic Offsets

Abstract

ABSTRACT Paleoseismic offsets are important parameters for evaluating fault activity. With the development and popularization of unmanned aerial vehicles (UAVs) and structure-from-motion (SfM) photogrammetry, more and more low-cost mini-UAVs have been used for geoscience studies like active faults and paleoearthquakes. In this study, we take the Gebi ridge in the middle of the Altyn Tagh fault (ATF) in western China as an example of using the control-free images acquired by a mini-UAV and SfM to measure paleoseismic offsets. The measurement accuracies of the control-free images acquired by a mini-UAV were evaluated, and then the horizontal offsets of the land surface caused by paleoearthquakes were measured. After comparing the total number and anomalies of paleoearthquake events identified by UAV-based photos with those revealed by geological trenches nearby, the following conclusions can be drawn. (1) Although the absolute positioning accuracy of the control-free image from the mini-UAV and SfM is poor, the accuracy of relative horizontal measurement is acceptable. (2) Without the help of ground control points (GCPs), the accuracy of relative vertical measurement for aerial images is not sufficient to measure vertical offset. (3) Oblique photography can improve not only the accuracy of paleoseismic landform mapping but also flight safety. (4) Up to 11 paleoearthquakes have been identified through paleoseismic offset measurements using control-free images in the study area. And both the total number and the anomalies of paleoearthquakes are consistent with the geological evidence in nearby geological trenches. By taking into account the above factors, it can be concluded that it is feasible to measure the horizontal offset of the land surface caused by paleoearthquakes using control-free images from mini-UAVs and SfM.